Patent Application
20050272696
1. Field of the Invention
The present invention relates to methodology for the use of defined, specific glycosaminoglycan molecules in the treatment of specific diseases and conditions, wherein the defined, specific glycosaminoglycan molecules exhibit differential effects in treatment of different diseases and conditions.
2. Description of the Related Art
Polysaccharides are large carbohydrate molecules comprising from about 25 sugar units to thousands of sugar units. Oligosaccharides are smaller carbohydrate molecules comprising less than about 25 sugar units. Animals, plants, fungi and bacteria produce an enormous variety of polysaccharide structures that are involved in numerous important biological functions such as structural elements, energy storage, and cellular interaction mediation. Often, the polysaccharide's biological function is due to the interaction of the polysaccharide with proteins such as receptors and growth factors. The glycosaminoglycan class of polysaccharides and oligosaccharides, which includes heparin, chondroitin, dermatan, keratan, and hyaluronic acid, plays major roles in determining cellular behavior (e.g., migration, adhesion) as well as the rate of cell proliferation in mammals. These polysaccharides and oligosaccharides are, therefore, essential for the correct formation and maintenance of the organs of the human body.
Several species of pathogenic bacteria and fungi also take advantage of the polysaccharide's role in cellular communication. These pathogenic microbes form polysaccharide surface coatings or capsules that are identical or chemically similar to host molecules. For instance, Group A & C Streptococcus and Type A Pasteurella multocida produce authentic hyaluronic acid capsules, and other Pasteurella multocida (Type F and D) and pathogenic Escherichia coli (K4 and K5) are known to make capsules composed of polymers very similar to chondroitin and heparin. The pathogenic microbes form the polysaccharide surface coatings or capsules because such a coating is nonimmunogenic and protects the bacteria from host defenses, thereby providing the equivalent of molecular camouflage.
Enzymes alternatively called synthases, synthetases, or transferases, catalyze the polymerization of polysaccharides found in living organisms. Many of the known enzymes also polymerize activated sugar nucleotides. The most prevalent sugar donors contain UDP, but ADP, GDP, and CMP are also used depending on (1) the particular sugar to be transferred and (2) the organism. Many types of polysaccharides are found at, or outside of, the cell surface. Accordingly, most of the synthase activity is typically associated with either the plasma membrane on the cell periphery or the Golgi apparatus membranes that are involved in secretion. In general, these membrane-bound synthase proteins are difficult to manipulate by typical procedures, and only a few enzymes have been identified after biochemical purification.
A larger number of synthases have been cloned and sequenced at the nucleotide level using “reverse genetic” approaches in which the gene or the complementary DNA (cDNA) was obtained before the protein was characterized. Despite this sequence information, the molecular details concerning the three-dimensional native structures, the active sites, and the mechanisms of catalytic action of the polysaccharide synthases, in general, are very limited or absent.
Some of the current methods for designing and constructing carbohydrate polymers in vitro utilize: (i) difficult, multistep sugar chemistry, or (ii) reactions driven by transferase enzymes involved in biosynthesis, or (iii) reactions harnessing carbohydrate degrading enzymes catalyzing transglycosylation or hydrolysis. The latter two methods are often restricted by the specificity and the properties of the available naturally occurring enzymes. Many of these enzymes are neither particularly abundant nor stable but are almost always expensive. Overall, the procedures currently employed yield polymers containing between 2 and about 12 sugars. Unfortunately, many of the physical and biological properties of polysaccharides do not become apparent until the polymer contains 25, 100, or even thousands of monomers.
As stated above, polysaccharides are the most abundant biomaterials on earth, yet many of the molecular details of their biosynthesis and function are not clear. Hyaluronic acid or “HA” is a linear polysaccharide of the glycosaminoglycan class and is composed of up to thousands of β(1,4)GlcUA-β(1,3)GlcNAc repeats. In vertebrates, HA is a major structural element of the extracellular matrix and plays roles in adhesion and recognition. HA has a high negative charge density and numerous hydroxyl groups; therefore, the molecule assumes an extended and hydrated conformation in solution. The viscoelastic properties of cartilage and synovial fluid are, in part, the result of the physical properties of the HA polysaccharide. HA also interacts with proteins such as CD44, RHAMM, and fibrinogen, thereby influencing many natural processes such as, but not limited to, angiogenesis, cancer, cell motility, wound healing, and cell adhesion.
HA is also made by certain microbes that cause disease in humans and animals. Some bacterial pathogens, namely Gram-negative Pasteurella multocida Type A and Gram-positive Streptococcus Group A and C, produce an extracellular HA capsule which protects the microbes from host defenses such as phagocytosis. Mutant bacteria that do not produce HA capsules are 102- and 103-fold less virulent in comparison to the encapsulated strains. Furthermore, the Paramecium bursaria Chlorella virus (PBCV-1) directs the algal host cells to produce a HA surface coating early in infection.
The various HA synthases (“HAS”), the enzymes that polymerize HA, utilize UDP-GlcUA and UDP-GlcNAc sugar nucleotide precursors in the presence of a divalent Mn, Mg, or Co ion to polymerize long chains of HA. The HA chains can be quite large (n=102 to 104). In particular, the HASs are membrane proteins localized to the lipid bilayer at the cell surface. During HA biosynthesis, the HA polymer is transported across the bilayer into the extracellular space. In all HASs, a single species of polypeptide catalyzes the transfer of two distinct sugars. In contrast, the vast majority of other known glycosyltransferases transfer only one monosaccharide.
Recombinant PmHAS, PmCS, PmHS1, and PmHS2 elongate exogenous functional oligosaccharide acceptors to form long or short polymers in vitro; thus far no other Class I HA synthase has displayed this capability. The directionality of synthesis was established definitively by testing the ability of PmHAS and PmCS and PmHS1 and PmHS2 to elongate defined oligosaccharide derivatives. The non-reducing end sugar addition allows the reducing end to be modified for other purposes; the addition of GAG chains to small molecules, polymers, or surfaces is thus readily performed. Analysis of the initial stages of synthesis demonstrated that PmHAS and PmCS and PmHS1 and PmHS2 added single monosaccharide units sequentially. Apparently the fidelity of the individual sugar transfer reactions is sufficient to generate the authentic repeating structure of HA or chondroitin or heparin. Therefore, simultaneous addition of disaccharide block units is not required as hypothesized in some recent models of polysaccharide biosynthesis. PmHAS and PmCS and PmHS1 and PmHS2 appear distinct from most other known HA and chondroitin and heparin synthases based on differences in sequence, topology in the membrane, and/or putative reaction mechanism.
As mentioned previously, PmHAS, the 972-residue membrane-associated hyaluronan synthase, catalyzes the transfer of both GlcNAc and GlcUA to form an HA polymer. In order to define the catalytic and membrane-associated domains, PmHAS and PmCS mutants have been analyzed. PmHAS1-703 is a soluble, active HA synthase suggesting that the carboxyl-terminus is involved in membrane association of the native enzyme. PmHAS1-650 is inactive as a HA synthase, but retains GlcNAc-transferase activity. Within the PmHAS sequence, there is a duplicated domain containing a short motif, DGS or Asp-Gly-Ser, that is conserved among many glycosyltransferases. Changing this aspartate in either domain to asparagine, glutamate, or lysine reduced the HA synthase activity to low levels. The mutants substituted at residue 196 possessed GlcUA-transferase activity while those substituted at residue 477 possessed GlcNAc-transferase activity. The Michaelis constants of the functional transferase activity of the various mutants, a measure of the apparent affinity of the enzymes for the precursors, were similar to wild-type values. Furthermore, mixing D196N and D477K mutant proteins in the same reaction allowed HA polymerization at levels similar to the wild-type enzyme. These results provide the first direct evidence that the synthase polypeptide utilizes two separate glycosyltransferase sites. Likewise, PmCS mutants were made and tested having the same functionality (except GalNAc transferase activity) and sequence similarity to the mutants created for PmHAS. The same concept applies to PmHS1 and PmHS2, but different mutations must be made to produce the α4GlcNAc and β4 GlcA transferase activities.
The size of the HA polysaccharide dictates its biological effect in many cellular and tissue systems based on many reports in the literature. However, no source of very defined, uniform HA polymers with sizes greater than 5 kDa is currently available. This situation is complicated by the observation that long and short HA polymers appear to have antagonistic or inverse effects on some biological systems. Therefore, HA preparations containing a mixture of both size populations may yield contradictory or paradoxical results. Thus, one of the objects of the present invention is to provide a method to produce HA with very narrow, substantially monodisperse size distributions that overcomes the disadvantages and defects of the prior art.
The disease cancer has many potential clinical presentations and variables due to a combination of factors, including but not limited to: (1) the wide variety of tissues/organs of origin; (2) the biochemical differences in mutation site or physiological perturbations; and/or (3) the differences in the genetic makeup of patients. Therefore, the severity and the treatment of the disease will also vary. With respect to the use of novel glycomedicines such as GAG oligosaccharides, it is expected that not all disease states will be equal. However, there is no facile way to predict the outcome or the efficacy of any particular therapeutic molecule short of empirical testing.
Previously, other investigators have reported that mixtures of HA oligosaccharides have anticancer effects (Zeng et al., 1998). However, the most active components, as well as any inactive or inhibitory components, were not identified; thus, these formulations are not optimal and are not directly useful for treatment of mammals and humans.
Rapid blood vessel growth into the newly formed bone tissue is of paramount importance (Mowlem, 1963; Boume, 1972). Absence of adequate nutrient nourishment of the cells residing at the interior of large scaffolds after been implanted to a bone defect site will result in the death of the implanted cells and consequently the severe decrease of the possibility of bone regeneration. Apart from providing nutrients, rapid vascularization of bone grafts assists in the recruitment of osteoprogenitor and osteoclastic cells from the host tissue that will initiate the bone regeneration and remodeling cascade. The degradation products of hyaluronic acid (HA), oligoHA, are also known to stimulate endothelial-cell proliferation and to promote neovascularization associated with angiogenesis (West et al., 1985; Slevin et al., 2002).
Partial degradation products of sodium hyaluronate produced by the action of testicular hyaluronidase induced an angiogenic response (formation of new blood vessels) on the chick chorioallantoic membrane. Neither macromolecular hyaluronate nor exhaustively digested material had any angiogenic potential. Fractionation of the digestion products established that the activity was restricted to hyaluronate fragments between 4 and 25 disaccharides in length (West et al., 1985).
A delayed revascularization model was used previously to assess the angiogenic activity of hyaluronan fragments on impaired wound healing (Lees et al., 1995). 1- to 4-kDa hyaluronan fragments increased blood flow and increased graft vessel growth, whereas 33-kDa fragments had no such effect on graft blood flow or vessel growth.
Different cells in different tissues have different signalling pathways (due to varied levels and/or components that make each cell type distinct); thus, the effect of HA and oligosaccharides cannot be predicted. Empirical testing for each tissue is thus indicated. In addition, prior to the present invention, there was not a reliable supply of individual nanoHA sizes for investigating their effects.
Parent application U.S. Ser. No. 10/642,248, filed Aug. 15, 2003, the contents of which have been previously incorporated herein by reference, discloses and claims methods for the production of glycosaminoglycans of HA, chondroitin, and chimeric or hybrid molecules incorporating both HA and chondroitin, wherein the glycosaminoglycans are substantially monodisperse and thus have a defined size distribution.
The present invention discloses studies with the defined, specific GAG molecules disclosed and claimed in U.S. Ser. No. 10/642,248, and the presently disclosed and claimed invention demonstrates that these defined, specific GAG molecules have discerned differential effects. Briefly, the presently disclosed and claimed invention demonstrates that different types of cancers are prevented from proliferating and/or killed (or induced to undergo programmed suicide or apoptosis) by oligosaccharides of different sizes; one size sugar does not treat all cancers effectively. Likewise, the effects of GAG molecules on vascularization and angiogenesis are also size dependent. Therefore, the presently disclosed and claimed invention is directed to methods of “personalized medicine”, in which customized defined, specific GAG molecules are administered to a patient, wherein the defined, specific GAG molecules are chosen based on the specific ailment from which the patient is suffering and/or the response of in vitro testing of the ability of the defined, specific GAG molecules to treat, inhibit and/or prevent the ailment in a sample (i.e., biopsy) from the patient.
The present invention is related to a method of inhibiting or preventing a disease or condition in a patient. The method includes identifying a disease or condition in a patient, such as cancer or a disease associated with abnormal levels of angiogenesis, and selecting a glycosaminoglycan polymer having a specific size distribution, wherein the glycosaminoglycan polymer having the specific size distribution is effective in inhibiting the disease or condition. A composition is then provided which comprises recombinantly-produced defined glycosaminoglycan polymers having the desired specific size distribution such that the glycosaminoglycan polymers are substantially monodisperse in size, wherein at least 95% of the composition comprises the defined glycosaminoglycan polymers having the desired specific size distribution and less than 5% of the composition comprises glycosaminoglycan polymers of a different size distribution. The composition is then administered to the patient in an amount effective to inhibit the disease or condition.
In one embodiment, the desired size distribution may be obtained by controlling a stoichiometric ratio of UDP-sugar to functional acceptor in the recombinant production thereof.
The substantially monodisperse glycosaminoglycan polymers may have a molecular weight in a range of from about 600 Da to about 3.5 kDa and a polydispersity value in a range of from about 1.0 to about 1.1, such as in a range of from about 1.0 to about 1.05. The defined glycosaminoglycan polymers may be defined hyaluronan polymers having a size distribution in a range of from HA10 to HA25, such as HA10, HA12, HA20 or HA22. Optionally, the glycosaminoglycan polymers may be chimeric or hybrid glycosaminoglycans having a non-natural structure.
Optionally, when the desired size distribution is obtained by controlling a stoichiometric ratio of UDP-sugar to functional acceptor in the recombinant production thereof, the substantially monodisperse glycosaminoglycan polymers may have a molecular weight in a range of from about 3.5 kDa to about 0.5 MDa, or a molecular weight in a range of from about 0.5 MDa to about 4.5 Mda. The substantially monodisperse glycosaminoglycan polymers may have a polydispersity value in a range of from about 1.0 to about 1.1, such as a range of from about 1.0 to about 1.05.
In one embodiment, the disease or condition is a first type of cancer, and the desired size distribution of the glycosaminoglycan polymer is effective in inhibiting the first type of cancer, but is not effective in inhibiting a second type of cancer.
The defined glycosaminoglycan polymer may be produced by a method that includes providing at least one functional acceptor, wherein the functional acceptor has at least two sugar units selected from the group consisting of uronic acid, hexosamine, structural variants and derivatives thereof, a hyaluronan polymer, a chondroitin polymer, a chondroitin sulfate polymer, a heparosan-like polymer, a heparinoid, mixed GAG chains, analog containing chains, and combinations thereof, providing at least one recombinant glycosaminoglycan transferase capable of elongating the at least one functional acceptor in at least one of a controlled fashion and a repetitive fashion to form extended glycosaminoglycan-like molecules, and providing at least one UDP-sugar selected from the group consisting of UDP-GlcUA, UDP-GlcNAc, UDP-Glc, UDP-GalNAc, UDP-GlcN, UDP-GalN and structural variants or derivatives thereof in a stoichiometric ratio to the at least one functional acceptor such that the at least one recombinant glycosaminoglycan transferase elongates the at least one functional acceptor to provide glycosaminoglycan polymers wherein the glycosaminoglycan polymers have a desired size distribution such that the glycosaminoglycan polymers are substantially monodisperse in size.
In the method described above, uronic acid may further be defined as a uronic acid selected from the group consisting of GlcUA, IdoUA, GalUA, and structural variants or derivatives thereof, and hexosamine may further be defined as a hexosamine selected from the group consisting of GlcNAc, GalNAc, GlcN, GalN, and structural variants or derivatives thereof. The at least one functional acceptor may be selected from the group consisting of a chondroitin oligosaccharide comprising at least about three sugar units, a chondroitin polymer, a chondroitin sulfate polymer, a heparosan-like polymer, a heparinoid, and an extended acceptor selected from the group consisting of HA chains, chondroitin chains, heparosan chains, mixed glycosaminoglycan chains, analog containing chains, a sulfated functional acceptor, a modified oligosaccharide, and combinations thereof. The at least one recombinant glycosaminoglycan transferase may be selected from the group consisting of a recombinant hyaluronan synthase or active fragment or mutant thereof; a recombinant chondroitin synthase or active fragment or mutant thereof; a recombinant heparosan synthase or active fragment or mutant thereof; a recombinant single action glycosyltransferase capable of adding only one of GlcUA, GlcNAc, GlcN, GalNAc, GlcN, GalN or a structural variant or derivative thereof; a recombinant synthetic chimeric glycosaminoglycan transferase capable of adding two or more of GlcUA, GlcNAc, GlcN, GalNAc, GlcN, GalN or a structural variant or derivative thereof; and combinations thereof. The method may further comprise at least one of: (A) the at least one functional acceptor is a plurality of functional acceptors immobilized on a substrate; (B) the at least one functional acceptor is a plurality of functional acceptors in a liquid phase; (C) the at least one recombinant glycosaminoglycan transferase is immobilized and the at least one functional acceptor and the at least one of UDP-GlcUA, UDP-GlcNAc, UDP-Glc, UDP-GalNAc, UDP-GlcN, UDP-GalN and a structural variant or derivative thereof are in a liquid phase; and (D) the at least one functional acceptor is immobilized and the at least one UDP-sugar are in a liquid phase.
The method may further include the step of providing a divalent metal ion, wherein the divalent metal ion is selected from the group consisting of manganese, magnesium, cobalt, nickel and combinations thereof, and the method may occur in a buffer having a pH from about 6 to about 8. The at least one recombinant glycosaminoglycan transferase may be selected from the group consisting of: (A) a recombinant glycosaminoglycan transferase having an amino acid sequence encoded by a nucleotide sequence capable of hybridizing under standard stringent, moderately stringent, or less stringent hybridization conditions to a nucleotide sequence selected from the group consisting of SEQ ID NOS:1, 3, 5, 7, 9 or 11; (B) a recombinant glycosaminoglycan transferase having an amino acid sequence essentially as set forth in SEQ ID NO:2, 4, 6, 8, 10, 12-22 or 25; (C) a recombinant glycosaminoglycan transferase encoded by a nucleotide sequence essentially as set forth in SEQ ID NO:1, 3, 5, 7, 9 or 11; and (D) a recombinant glycosaminoglycan transferase having at least one motif selected from the group consisting of SEQ ID NOS:23 and 24. The at least one functional acceptor may comprise a moiety selected from the group consisting of a fluorescent tag, a radioactive tag, an affinity tag, a detection probe, a medicant, and combinations thereof. Optionally, the at least one UDP-sugar may be radioactively labeled.
The present invention is also directed to a kit that includes at least two compositions comprising recombinantly-produced defined glycosaminoglycan polymers having desired specific size distributions such that the glycosaminoglycan polymers of each composition are substantially monodisperse in size, as described herein above. The kit also includes means for testing the ability of each of the defined glycosaminoglycan polymers to inhibit or prevent a disease or condition (such as cancer or a disease or condition associated with abnormal levels of angiogenesis) in a sample from a patient, such as a biopsy. One desired size distribution of the glycosaminoglycan polymer may be effective in inhibiting or preventing the disease or condition, while a different size distribution of the glycosaminoglycan polymer is not effective in inhibiting or preventing the disease or condition. The kit may be a catalog available on the World Wide Web.
The present invention is also related to a method of inhibiting or preventing a disease or condition in a patient that includes providing at least two compositions comprising recombinantly-produced defined glycosaminoglycan polymers having desired specific size distributions such that the glycosaminoglycan polymers of each composition are substantially monodisperse in size, as described herein above. A sample (such as a biopsy) from a patient suffering from or predisposed for a disease or condition is provided, and each of the at least two defined glycosaminoglycan polymer compositions is reacted with a portion of the sample from the patient. At least one defined glycosaminoglycan polymer composition that inhibits or prevents the disease or condition in the sample is identified, and the patient is administered an effective amount of the defined glycosaminoglycan polymer composition that inhibited or prevented the disease or condition in the sample, thus inhibiting or preventing the disease or condition in the patient. One desired size distribution of the glycosaminoglycan polymer may be effective in inhibiting or preventing the disease or condition, while a different size distribution of the glycosaminoglycan polymer is not effective in inhibiting or preventing the disease or condition.
Other objects, features and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings and appended claims.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for purpose of description and should not be regarded as limiting.
Glycosaminoglycans (“GAGs”) are linear polysaccharides composed of repeating disaccharide units containing a derivative of an amino sugar (either glucosamine or galactosamine). Hyaluronan [HA], chondroitin, and heparan sulfate/heparin contain a uronic acid as the other component of the disaccharide repeat while keratan contains a galactose. The GAGs are summarized in Table I.
GAGs and their derivatives are currently used in the medical field as ophthalmic and viscoelastic supplements, adhesion surgical aids to prevent post-operative adhesions, catheter and device coatings, and anticoagulants. Other current or promising future applications include anti-cancer medications, tissue engineering matrices, immune and neural cell modulators, and drug targeting agents.
Complex carbohydrates, such as GAGs, are information rich molecules. A major purpose of the sugars that make up GAGs is to allow communication between cells and extracellular components of multicellular organisms. Typically, certain proteins bind to particular sugar chains in a very selective fashion. A protein may simply adhere to the sugar, but quite often the protein's intrinsic activity may be altered and/or the protein transmits a signal to the cell to modulate its behavior. For example, in the blood coagulation cascade, heparin binding to inhibitory proteins helps shuts down the clotting response. In another case, HA binds to cells via the CD44 receptor that stimulates the cells to migrate and to proliferate. Even though long GAG polymers (i.e., >102 Da) are found naturally in the body, typically the protein's binding site interacts with a stretch of 4 to 10 monosaccharides. Therefore, oligosaccharides can be used to either (a) substitute for the polymer or (b) to inhibit the polymer's action depending on the particular system.
HA polysaccharide plays structural roles in the eye, skin, and joint synovium. Large HA polymers (˜106 Da) also stimulate cell motility and proliferation. On the other hand, shorter HA polymers (˜104 Da) often have the opposite effect. HA-oligosaccharides composed of about 10 to 25 sugars [HA10-25] have promise for inhibition of cancer cell growth and metastasis. For example, in an in vivo assay, mice injected with various invasive and virulent tumor cell lines (melanoma, glioma, carcinomas from lung, breast and ovary) develop a number of large tumors and die within weeks. Treatment with HA oligosaccharides greatly reduced the number and the size of tumors (Zeng et al., 1998). Metastasis, the escape of cancer cells throughout the body, is one of the biggest fears of both the ailing patient and the physician. HA or HA-like oligosaccharides appear to serve as a supplemental treatment to inhibit cancer growth and metatasis.
The preliminary mode of action of the HA-oligosaccharide sugars is thought to be mediated by binding or interacting with one of several important HA-binding proteins (probably CD44 or RHAM) in the mammalian body. One proposed scenario for the anticancer action of HA-oligosaccharides is that multiple CD44 protein molecules in a cancer cell can bind simultaneously to a long HA polymer (
It has also been shown that treatment with certain anti-CD44 antibodies or CD44-antisense nucleic acid prevents the growth and metastasis of cancer cells in a fashion similar to HA-oligosaccharides; in comparison to the sugars, however, these protein-based and nucleic acid-based reagents are somewhat difficult to deliver in the body and/or may have long-term negative effects. A very desirable attribute of HA-oligosaccharides for therapeutics is that these sugar molecules are natural by-products that can occur in small amounts in the healthy human body during the degradation of HA polymer; no untoward innate toxicity, antigenicity, or allergenic concerns are obvious.
Other emerging areas for the potential therapeutic use of HA oligosaccharides are the stimulation of blood vessel formation and the stimulation of dendritic cell maturation. Enhancement of wound-healing and resupplying cardiac oxygenation may be additional applications that harness the ability of HA oligosaccharides to cause endothelial cells to form tubes and sprout new vessels. Dendritic cells possess adjuvant activity in stimulating specific CD4 and CD8 T cell responses. Therefore, dendritic cells are targets in vaccine development strategies for the prevention and treatment of infections, allograft reactions, allergic and autoimmune diseases, and cancer.
Heparin interacts with many proteins in the body, but two extremely interesting classes are coagulation cascade proteins and growth factors. Antithrombin III [ATIII] and certain other hemostasis proteins are 100,000-fold more potent inhibitors of blood clotting when complexed with heparin. Indeed, heparin is so potent it must be used in a hospital setting and require careful monitoring in order to avoid hemorrhage. Newer, processed lower molecular weight forms of heparin are safer, but this material is still a complex mixture. It has been shown that a particular pentasaccharide (5 sugars long) found in heparin is responsible for the ATIII-anticoagulant effect. But since heparin is a very heterogeneous polymer, it is difficult to isolate the pentasaccharide (5 sugars long) in a pure state. The pentasaccharide can also be prepared in a conventional chemical synthesis involving ˜50 to 60 steps. However, altering the synthesis or preparing an assortment of analogs in parallel is not always feasible—either chemically or financially.
Many growth factors, including VEGF (vascular endothelial growth factor), HBEGF (heparin-binding epidermal growth factor), and FGF (fibroblast growth factor), bind to cells by interacting simultaneously with the growth factor receptor and a cell-surface heparin proteoglycan; without the heparin moiety, the potency of the growth factor plummets. Cell proliferation is modulated in part by heparin; therefore, diseases such as cancer and atherosclerosis are potential targets. Abnormal or unwanted proliferation would be curtailed if the growth factor was prevented from stimulating target disease-state cells by interacting with a heparin-like oligosaccharide analog instead of a surface-bound receptor. Alternatively, in certain cases, the heparin oligosaccharides alone have been shown to have stimulatory effects.
Chondroitin is the most abundant GAG in the human body, but all of its specific biological roles are not yet clear. Phenomenon such as neural cell outgrowth appear to be modulated by chondroitin. Both stimulatory and inhibitory effects have been noted depending on the chondroitin form and the cell type. Therefore, chondroitin or similar molecules are of utility in re-wiring synaptic connections after degenerative diseases (e.g., Alzheimer's) or paralytic trauma. The epimerized form of chondroitin (GlcUA converted to the C5 isomer, iduronic acid or IdoUA), dermatan, selectively inhibits certain coagulation proteins such as heparin cofactor II. By modulating this protein in the coagulation pathway instead of ATIII, dermatan appears to allow for a larger safety margin than heparin treatment for reduction of thrombi or clots that provoke strokes and heart attacks.
Many details of GAG/protein interactions are not yet clear due to (a) the heterogeneity of GAGs (in part due to their biosynthesis pathway) and (b) the difficulty in analyzing long polysaccharides and membrane receptor proteins at the molecular level. Fortunately, many short oligosaccharides have biological activities that serve to assist research pursuits as well as to treat disease in the near future. Conventional chemical synthesis of short GAG oligosaccharides is possible, but the list of roadblocks includes: (i) difficult multi-step syntheses that employ toxic catalysts, (ii) very low yield or high failure rates with products longer than ˜6 monosaccharides, (iii) imperfect control of stereoselectivity (e.g., wrong anomer) and regioselectivity (e.g., wrong attachment site), and (iv) the possibility for residual protection groups (non-carbohydrate moieties) in the final product.
It is well established that the large array of functions that a tumor cell has to fulfill to settle as a metastasis in a distant organ requires cooperative activities between the tumor and the surrounding tissue and that several classes of molecules are involved, such as cell-cell and cell-matrix adhesion molecules and matrix degrading enzymes, to name only a few. Furthermore, metastasis formation requires concerted activities between tumor cells and surrounding cells as well as matrix elements and possibly concerted activities between individual molecules of the tumour cell itself. CD44 transmembrane glycoproteins belong to the families of adhesion molecules and have originally been described to mediate lymphocyte homing to peripheral lymphoid tissues. It was soon recognized that the molecules, under selective conditions, may suffice to initiate metastatic spread of tumor cells (Marhaba et al., 2004). CD44 variant isoforms have been implicated in many biological processes, such as cell adhesion, cell substrate, cell to cell interactions, including lymphocyte homing haemopoiesis, cell migration and metastasis. These abilities are of great importance in chronic inflammation and in cancer. CD44 has shown the ability to recruit leucocytes to vascular endothelium at sites of inflammation, which is one of the first steps in the inflammatory response. In cancer, deregulation of the adhesion mechanisms increases the ability of tumor cells to metastasis. This behavior seems to be explained by the existing relationship between hyaluronan and CD44, which is its major cell surface receptor. There are CD44 variant isoforms (i.e., similar, but not functionally equivalent) which are expressed on different types of normal cells. In addition some isoforms are overexpressed on tumor cells including breast, cervical, endometrial and ovarian cancer (Makrydimas et al., 2003). This property seems to be correlated with the metastatic potential of these cells. Depending on the CD44 isoform and the cell background, various phenomena are possible. Therefore, HA interactions and signaling may differ among cancer types.
Adhesion is by no means a passive task. Rather, ligand binding, as exemplified for CD44 and other similar adhesion molecules, initiates a cascade of events that can be started by adherence to the extracellular matrix. This leads to activation of the molecule itself, binding to additional ligands, such as growth factors and matrix degrading enzymes, complex formation with additional transmembrane molecules and association with cytoskeletal elements and signal transducing molecules. Thus, through the interplay of CD44 with its ligands and associating molecules CD44 modulates adhesiveness, motility, matrix degradation, proliferation and cell survival, features that together may well allow a tumor cell to proceed through all steps of the metastatic cascade (Marhaba et al., 2004).
The interaction of CD44 with fragmented hyaluronan on rheumatoid synovial cells induces expression of VCAM-1 and Fas on the cells, which leads to Fas-mediated apoptosis of synovial cells by the interaction of T cells bearing FasL. On the other hand, engagement of CD44 on tumor cells derived from lung cancer reduces Fas expression and Fas-mediated apoptosis, resulting in less susceptibility of the cells to CTL-mediated cytotoxicity through Fas-FasL pathway (Yasuda et al., 2002). Therefore, the response to HA or its fragments cannot always be predicted. Patients may differ in their responses.
Versican is a large chondroitin sulfate proteoglycan produced by several tumor cell types, including malignant melanoma. The expression of increased amounts of versican in the extracellular matrix may play a role in tumor cell growth, adhesion and migration. V3 acts by altering the hyaluronan-CD44 interaction (Serra et al., 2005). In addition, multiple myeloma (MM) plasma cells express the receptor for hyaluronan-mediated motility (RHAMM), a hyaluronan-binding, cytoskeleton and centrosome protein. Expression and splicing of RHAMM are important molecular determinants of the disease severity of MM (Maxwell et al., 2004).
However, prior to the present invention, there was not a reliable supply of individual nanoHA sizes for investigating their effects on particular types of cancer.
Rapid blood vessel growth into the newly formed bone tissue is of paramount importance (Mowlem, 1963; Boume, 1972). Absence of adequate nutrient nourishment of the cells residing at the interior of large scaffolds after been implanted to a bone defect site will result in the death of the implanted cells and consequently the severe decrease of the possibility of bone regeneration. Apart from providing nutrients, rapid vascularization of bone grafts assists in the recruitment of osteoprogenitor and osteoclastic cells from the host tissue that will initiate the bone regeneration and remodeling cascade. The degradation products of hyaluronic acid (HA), oligoHA, are also known to stimulate endothelial-cell proliferation and to promote neovascularization associated with angiogenesis (West et al., 1985; Slevin et al., 2002).
Partial degradation products of sodium hyaluronate produced by the action of testicular hyaluronidase induced an angiogenic response (formation of new blood vessels) on the chick chorioallantoic membrane. Neither macromolecular hyaluronate nor exhaustively digested material had any angiogenic potential. Fractionation of the digestion products established that the activity was restricted to hyaluronate fragments between 4 and 25 disaccharides in length (West et al., 1985).
A delayed revascularization model was used previously to assess the angiogenic activity of hyaluronan fragments on impaired wound healing (Lees et al., 1995). 1- to 4-kDa hyaluronan fragments increased blood flow and increased graft vessel growth, whereas 33-kDa fragments had no such effect on graft blood flow or vessel growth.
In addition, Slevin et al. (2002) disclosed that angiogenic oligosacharides of hyaluronan induced multiple signaling pathways affecting vascular endothelial cell mitogenic and wound healing responses. Treatment of bovine aortic endothelial cells with oligosaccharides of hyaluronan (o-HA) resulted in rapid tyrosine phosphorylation and plasma membrane translocation of phospholipase Cγ1 (PLCγ1). Cytoplasmic loading with inhibitory antibodies to PLCγ1, Gβ, and Gα(i/o/t/z) inhibited activation of extracellular-regulated kinase 1/2 (ERK1/2). Treatment with the Gα(i/o) inhibitor, pertussis toxin, reduced o-HA-induced PLCγ1 tyrosine phosphorylation, protein kinase C (PKC) α and β1/2 membrane translocation, ERK1/2 activation, mitogenesis, and wound recovery, suggesting a mechanism for o-HA-induced angiogenesis through G-proteins, PLCγ1, and PKC. The work of Slevin et al. (2002) demonstrated a possible role for PKCα in mitogenesis and PKCβ1/2 in wound recovery, and that o-HA-induced bovine aortic endothelial cell proliferation, wound recovery, and ERK1/2 activation were also partially dependent on Ras activation.
Different cells in different tissues have different signalling pathways (due to varied levels and/or components that make each cell type distinct); thus, the effect of HA and oligosaccharides cannot be predicted. Empirical testing for each tissue is thus indicated. In addition, prior to the present invention, there was not a reliable supply of individual nanoHA sizes for investigating their effects.
Chemoenzymatic synthesis, however, employing catalytic glycosyltransferases with exquisite control and superb efficiency is currently being developed by several universities and companies. A major obstacle is the production of useful catalyst because the vast majority of glycosyltransferases are rare membrane proteins that are not particularly robust. In the copending applications referenced herein and in the presently claimed and disclosed invention, several practical catalysts from Pasteurella bacteria that allow for the synthesis of the three most important human GAGs (i.e., the three known acidic GAGs) are described and enabled (e.g., HA, chondroitin, and heparin).
All of the known HA, chondroitin and heparan sulfate/heparin glycosyltransferase enzymes that synthesize the alternating sugar repeat backbones in microbes and in vertebrates utilize UDP-sugar precursors and divalent metal cofactors (e.g., magnesium, cobalt, and/or manganese ion) near neutral pH according to the overall reaction:
nUDP-GlcUA+nUDP-HexNAc→2nUDP+[GlcUA-HexNAc]n
where HexNAc=GlcNAc or GalNAc. Depending on the specific GAG and the particular organism or tissue examined, the degree of polymerization, n, ranges from about 25 to about 10,000. If the GAG is polymerized by a single polypeptide, the enzyme is called a synthase or co-polymerase.
As outlined in copending and incorporated by reference in the “Cross-Reference” section of this application hereinabove, the present applicant(s) have discovered four new dual-action enzyme catalysts from distinct isolates of the Gram-negative bacterium Pasteurella multocida using various molecular biology strategies. P. multocida infects fowl, swine, and cattle as well as many wildlife species. The enzymes are: a HA synthase, or pmHAS; a chondroitin synthase, or pmCS; and two heparosan synthases, or pmHS1 and pmHS2. To date, no keratan synthase from any source has been identified or reported in the literature.
In copending U.S. Ser. No. 10/217,613, filed Aug. 12, 2002, the contents of which are hereby expressly incorporated herein by reference in their entirety, the molecular directionality of pmHAS synthesis was disclosed and claimed. pmHAS is unique in comparison to all other existing HA synthases of Streptococcus bacteria, humans and an algal virus. Specifically, recombinant pmHAS can readily elongate exogeneously-supplied short HA chains (e.g., 2-4 sugars) into longer HA chains (e.g., 3 to 150 sugars). The pmHAS synthase has been shown to add monosaccharides one at a time in a step-wise fashion to the growing chain (
The explanation for the step-wise addition of sugars to the GAG chain during biosynthesis was determined by analyzing mutants of the pmHAS enzyme. pmHAS possesses two independent catalytic sites in one polypeptide (
The naturally occuring Pasteurella GAG synthases are very specific glycosyltransferases with respect to the sugar transfer reaction; only the correct monosaccharide from the authentic UDP-sugar is added onto acceptors. The epimers or other closely structurally related precursor molecules (e.g., UDP-glucose) are not utilized. The GAG synthases do, however, utilize certain heterologous acceptor sugars. For example, pmHAS will elongate short chondroitin acceptors with long HA chains. pmHS1 will also add long heparosan chains onto HA acceptor oligosaccharides as well as heparin oligosaccharides (see parent application U.S. Ser. No. 10/642,248). Therefore, the presently claimed and disclosed invention encompasses a wide range of hybrid or chimeric GAG oligosaccharides prepared utilizing these P. multocida GAG catalysts.
As used herein, the term “nucleic acid segment” and “DNA segment” are used interchangeably and refer to a DNA molecule which has been isolated free of total genomic DNA of a particular species. Therefore, a “purified” DNA or nucleic acid segment as used herein, refers to a DNA segment which contains a Hyaluronate Synthase (“HAS”) coding sequence or Chondroitin Synthase (“CS”) coding sequence or Heparin/Heparosan Synthase (“HS”) coding sequence yet is isolated away from, or purified free from, unrelated genomic DNA, for example, total Pasteurella multocida. Included within the term “DNA segment”, are DNA segments and smaller fragments of such segments, and also recombinant vectors, including, for example, plasmids, cosmids, phage, viruses, and the like.
Similarly, a DNA segment comprising an isolated or purified pmHAS or pmCS or pmHS1 or PmHS2 gene refers to a DNA segment including HAS or CS or HS coding sequences isolated substantially away from other naturally occurring genes or protein encoding sequences. In this respect, the term “gene” is used for simplicity to refer to a functional protein-, polypeptide- or peptide-encoding unit. As will be understood by those in the art, this functional term includes genomic sequences, cDNA sequences or combinations thereof. “Isolated substantially away from other coding sequences” means that the gene of interest, in this case pmHAS or pmCS or pmHS1 or PmHS2 forms the significant part of the coding region of the DNA segment, and that the DNA segment does not contain other non-relevant large portions of naturally-occurring coding DNA, such as large chromosomal fragments or other functional genes or DNA coding regions. Of course, this refers to the DNA segment as originally isolated, and does not exclude genes or coding regions later added to, or intentionally left in, the segment by the hand of man.
Due to certain advantages associated with the use of prokaryotic sources, one will likely realize the most advantages upon isolation of the HAS or CS or HS gene from the prokaryote P. multocida. One such advantage is that, typically, eukaryotic genes may require significant post-transcriptional modifications that can only be achieved in a eukaryotic host. This will tend to limit the applicability of any eukaryotic HAS or CS or HS gene that is obtained. Moreover, those of ordinary skill in the art will likely realize additional advantages in terms of time and ease of genetic manipulation where a prokaryotic enzyme gene is sought to be employed. These additional advantages include (a) the ease of isolation of a prokaryotic gene because of the relatively small size of the genome and, therefore, the reduced amount of screening of the corresponding genomic library and (b) the ease of manipulation because the overall size of the coding region of a prokaryotic gene is significantly smaller due to the absence of introns. Furthermore, if the product of the pmHAS or pmCS or pmHS1 or PmHS2 gene (i.e., the enzyme) requires posttranslational modifications, these would best be achieved in a similar prokaryotic cellular environment (host) from which the gene was derived.
Preferably, DNA sequences in accordance with the present invention will further include genetic control regions which allow the expression of the sequence in a selected recombinant host. The genetic control region may be native to the cell from which the gene was isolated, or may be native to the recombinant host cell, or may be an exaggerous segment that is compatible with and recognized by the transcriptional machinery of the selected recbominant host cell. Of course, the nature of the control region employed will generally vary depending on the particular use (e.g., cloning host) envisioned.
Particular sequences that may be utilized in accordance with the presently claimed and disclosed invention were originally disclosed in detail in parent application U.S. Ser. No. 10/642,248. The individual sequences and their corresponding SEQ ID NO's are listed in Table II. The numbering, mutations and nomenclature used in Table II to describe each of the sequences is defined in detail in the parent application, which has previously been incorporated by reference.
In particular embodiments, the invention concerns utilizes DNA segments and recombinant vectors incorporating DNA sequences which encode a pmHAS or pmCS or pmHS1 or PmHS2 gene, that includes within its amino acid sequence an amino acid sequence in accordance with SEQ ID NO:2,4,6,8,10,12-22 or 25, respectively. Moreover, in other particular embodiments, the invention concerns isolated DNA segments and recombinant vectors incorporating DNA sequences which encode a gene that includes within its nucleic acid sequence an amino acid sequence encoding HAS or CS or HS pepetides or peptide fragment thereof, and in particular to a HAS or CS or HS peptide or peptide fragment thereof, corresponding to Pasteurella multocida HAS or CS or HS. For example, where the DNA segment or vector encodes a full length HAS or CS or HS protein, or is intended for use in expressing the HAS or CS or HS protein, preferred sequences are those which are essentially as set forth in SEQ ID NO:1, 3, 5, 7, 9, or 11, respectively.
Truncated pmHAS gene (such as, but not limited to, pmHAS1-703, SEQ ID NO:11) also falls within the definition of preferred sequences as set forth above. For instance, at the carboxyl terminus, approximately 270-272 amino acids may be removed from the sequence and still have a functioning HAS. Those of ordinary skill in the art would appreciate that simple amino acid removal from either end of the pmHAS sequence can be accomplished. The truncated versions
of the sequence (as disclosed hereinafter) simply have to be checked for HAS activity in order to determine if such a truncated sequence is still capable of producing HA. The other GAG synthases disclosed and claimed herein are also amenable to truncation or alteration with preservation of activity and such truncated or alternated GAG synthases also fall within the scope of the present invention.
Nucleic acid segments having HAS or CS or HS activity may be isolated by the methods described herein. The term “a sequence essentially as set forth in SEQ ID NO:X” means that the sequence substantially corresponds to a portion of SEQ ID NO:X and has relatively few amino acids or codons encoding amino acids which are not identical to, or a biologically functional equivalent of, the amino acids or codons encoding amino acids of SEQ ID NO:X. The term “biologically functional equivalent” is well understood in the art and is further defined in detail herein, as a gene having a sequence essentially as set forth in SEQ ID NO:X, and that is associated with the ability of prokaryotes to produce HA or a hyaluronic acid or chondroitin or heparin polymer in vitro or in vivo. In the above examples “X” refers to either SEQ ID NO: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 or any additional sequences set forth herein, such as the truncated or mutated versions of pmHAS1-703 that are contained generally in SEQ ID NOS:13-22.
The art is replete with examples of practitioner's ability to make structural changes to a nucleic acid segment (i.e., encoding conserved or semi-conserved amino acid substitutions) and still preserve its enzymatic or functional activity when expressed. See for special example of literature attesting to such: (1) Risler et al. “Amino Acid Substitutions in Structurally Related Proteins. A Pattern Recognition Approach.” J. Mol. Biol. 204:1019-1029 (1988) [“ . . . according to the observed exchangeability of amino acid side chains, only four groups could be delineated; (I) Ile and Val; (ii) Leu and Met, (iii) Lys, Arg, and Gln, and (iv) Tyr and Phe.”]; (2) Niefind et al. “Amino Acid Similarity Coefficients for Protein Modeling and Sequence Alignment Derived from Main-Chain Folding Anoles.” J. Mol. Biol. 219:481-497 (1991) [similarity parameters allow amino acid substitutions to be designed]; and (3) Overington et al. “Environment-Specific Amino Acid Substitution Tables: Tertiary Templates and Prediction of Protein Folds,” Protein Science 1:216-226 (1992) [“Analysis of the pattern of observed substitutions as a function of local environment shows that there are distinct patterns . . . ” Compatible changes can be made.]
These references and countless others indicate that one of ordinary skill in the art, given a nucleic acid sequence or an amino acid, could make substitutions and changes to the nucleic acid sequence without changing its functionality (specific examples of such changes are given hereinafter and are generally set forth in SEQ ID NOS:13-22). Also, a substituted nucleic acid segment may be highly identical and retain its enzymatic activity with regard to its unadulterated parent, and yet still fail to hybridize thereto. Additionally, the present application discloses 4 enzymes and numerous mutants of these enzymes that still retain at least 50% of the enzymatic activity of the unmutated parent enzyme—i.e., 1/2 of the dual action transferase activity of the unadulterated parent. As such, variations of the sequences and enzymes that fall within the above-defined functional limitations have been disclosed and enabled. One of ordinary skill in the art, given the present specification, would be able to identify, isolate, create, and test DNA sequences and/or enzymes that produce natural or chimeric or hybrid GAG molecules. As such, the presently claimed and disclosed invention should not be regarded as being solely limited to the specific sequences disclosed herein.
The present invention utilizes nucleic acid segments encoding an enzymatically active HAS or CS or HS from P. multocida—pmHAS, pmCS, pmHS1, and PmHS2, respectively. One of ordinary skill in the art would appreciate that substitutions can be made to the pmHAS or pmCS or pmHS1 or PmHS2 nucleic acid segments listed in SEQ ID NO: 1, 3, 5, 7, 9, and 11, respectively, without deviating outside the scope and claims of the present invention. Indeed, such changes have been made and are described in detail in the parent application U.S. Ser. No. 10/642,248 with respect to the mutants produced. Standardized and accepted functionally equivalent amino acid substitutions are presented in Table III. In addition, other analogous or homologous enzymes that are functionally equivalent to the disclosed synthase sequences would also be appreciated by those skilled in the art to be similarly useful in the methods of the present invention, that is, a new method to control precisely the size distribution of polysaccharides, namely glycosaminoglycans.
Another preferred embodiment of the present invention includes the use of a purified nucleic acid segment that encodes a protein in accordance with SEQ ID NO:1 or 3 or 5 or 7 or 9 or 11, respectively, further defined as a recombinant vector. As used herein, the term “recombinant vector” refers to a vector that has been modified to contain a nucleic acid segment that encodes an HAS or CS or HS protein, or fragment thereof. The recombinant vector may be further defined as an expression vector comprising a promoter operatively linked to said HAS- or CS- or HS-encoding nucleic acid segment.
A further preferred embodiment of the present invention includes the use of a host cell, made recombinant with a recombinant vector comprising an HAS or CS or HS gene. The preferred recombinant host cell may be a prokaryotic cell. In another embodiment, the recombinant host cell is an eukaryotic cell. As used herein, the term “engineered” or “recombinant” cell is intended to refer to a cell into which a recombinant gene, such as a gene encoding HAS or CS or HS, has been introduced mechanically or by the hand of man. Therefore, engineered cells are distinguishable from naturally occurring cells which do not contain a recombinantly introduced gene. Engineered cells are thus cells having a gene or genes introduced through the hand of man. Recombinantly introduced genes will either be in the form of a cDNA gene, a copy of a genomic gene, or will include genes positioned adjacent to a promoter associated or not naturally associated with the particular introduced gene.
In preferred embodiments, the HAS- or CS- or HS-encoding DNA segments further include DNA sequences, known in the art functionally as origins of replication or “replicons”, which allow replication of contiguous sequences by the particular host. Such origins allow the preparation of extrachromosomally localized and replicating chimeric or hybrid segments or plasmids, to which HAS- or CS- or HS-encoding DNA sequences are ligated. In more preferred instances, the employed origin is one capable of replication in bacterial hosts suitable for biotechnology applications. However, for more versatility of cloned DNA segments, it may be desirable to alternatively or even additionally employ origins recognized by other host systems whose use is contemplated (such as in a shuttle vector).
The isolation and use of other replication origins such as the SV40, polyoma or bovine papilloma virus origins, which may be employed for cloning or expression in a number of higher organisms, are well known to those of ordinary skill in the art. In certain embodiments, the invention may thus be defined in terms of a recombinant transformation vector which includes the HAS- or CS- or HS-coding gene sequence together with an appropriate replication origin and under the control of selected control regions.
Thus, it will be appreciated by those of skill in the art that other means may be used to obtain the HAS or CS or HS gene or cDNA, in light of the present disclosure. For example, polymerase chain reaction or RT-PCR produced DNA fragments may be obtained which contain full complements of genes or cDNAs from a number of sources, including other strains of Pasteurella or from a prokaryot with similar glycosyltransferases or from eukaryotic sources, such as cDNA libraries. Virtually any molecular cloning approach may be employed for the generation of DNA fragments in accordance with the present invention. Thus, the only limitation generally on the particular method employed for DNA isolation is that the isolated nucleic acids should encode a biologically functional equivalent HAS or CS or HS.
Once the DNA has been isolated, it is ligated together with a selected vector. Virtually any cloning vector can be employed to realize advantages in accordance with the invention. Typical useful vectors include plasmids and phages for use in prokaryotic organisms and even viral vectors for use in eukaryotic organisms. Examples include pKK223-3, pSA3, recombinant lambda, SV40, polyoma, adenovirus, bovine papilloma virus and retroviruses. However, it is believed that particular advantages will ultimately be realized where vectors capable of replication in both biotechnologically useful Gram-positive or Gram-negative bacteria (e.g., Bacillus, Lactococcus, or E. coli) are employed.
Vectors such as these, exemplified by the pSA3 vector of Dao and Ferretti or the pAT19 vector of Trieu-Cuot, et al., allow one to perform clonal colony selection in an easily manipulated host such as E. coli, followed by subsequent transfer back into a food grade Lactococcus or Bacillus strain for production of hyaluronan or chondroitin or heparin polymer. In another embodiment, the recombinant vector is employed to make the functional GAG synthase for in vitro use. These are benign and well studied organisms used in the production of certain foods and biotechnology products and are recognized as GRAS (generally recognized as safe) organisms. These are advantageous in that one can augment the Lactococcus or Bacillus strain's ability to synthesize HA or chondroitin or heparin through gene dosaging (i.e., providing extra copies of the HAS or CS or HS gene by amplification) and/or inclusion of additional genes to increase the availability of HA or chondroitin or heparin precursors. The inherent ability of a bacterium to synthesize HA or chondroitin or heparin can also be augmented through the formation of extra copies, or amplification, of the plasmid that carries the HAS or CS or HS gene. This amplification can account for up to a 10-fold increase in plasmid copy number and, therefore, the HAS or CS or HS gene copy number.
Another procedure to further augment HAS or CS or HS gene copy number is the insertion of multiple copies of the gene into the plasmid. Another technique would include integrating at least one copy of the HAS or CS or HS gene into chromosomal DNA. This extra amplification would be especially feasible, since the bacterial HAS or CS or HS gene size is small. In some scenarios, the chromosomal DNA-ligated vector is employed to transfect the host that is selected for clonal screening purposes such as E. coli, through the use of a vector that is capable of expressing the inserted DNA in the chosen host.
In certain other embodiments, the invention concerns the use of isolated DNA segments and recombinant vectors that include within their sequence a nucleic acid sequence essentially as set forth in SEQ ID NO:1, 3, 5, 7, 9, or 11. The term “essentially as set forth” in SEQ ID NO: 1, 3, 5, 7, 9, or 11 is used in the same sense as described above and means that the nucleic acid sequence substantially corresponds to a portion of SEQ ID NO: 1, 3, 5, 7, 9, or 11 and has relatively few codons which are not identical, or functionally equivalent, to the codons of SEQ ID NO: 1, 3, 5, 7, 9, or 11. The term “functionally equivalent codon” is used herein to refer to codons that encode the same amino acid, such as the six codons for arginine or serine, and also refers to codons that encode biologically equivalent amino acids, as set forth in Table III.
It will also be understood that amino acid and nucleic acid sequences may include additional residues, such as additional N- or C-terminal amino acids or 5′ or 3′ nucleic acid sequences, and yet still be essentially as set forth in one of the sequences disclosed herein, so long as the sequence meets the criteria set forth above, including the maintenance of biological protein activity where protein expression and enzyme activity is concerned. The addition of terminal sequences particularly applies to nucleic acid sequences which may, for example, include various non-coding sequences flanking either of the 5′ or 3′ portions of the coding region or may include various internal sequences, which are known to occur within genes. Furthermore, residues may be removed from the N- or C-terminal amino acids and yet still be essentially as set forth in one of the sequences disclosed herein, so long as the sequence meets the criteria set forth above, as well.
Allowing for the degeneracy of the genetic code as well as conserved and semi-conserved substitutions, sequences which have between about 40% and about 99%; or more preferably, between about 80% and about 90%; or even more preferably, between about 90% and about 99% identity to the nucleotides of SEQ ID NO: 1, 3, 5, 7, 9, or 11 will be sequences which are “essentially as set forth” in SEQ ID NO: 1, 3, 5, 7, 9, or 11. Sequences which are essentially the same as those set forth in SEQ ID NO: 1, 3, 5, 7, 9, or 11 may also be functionally defined as sequences which are capable of hybridizing to a nucleic acid segment containing the complement of SEQ ID NO: 1, 3, 5, 7, 9, or 11 under “standard stringent hybridization conditions”, “moderately stringent hybridization conditions,” “less stringent hybridization conditions,” or “low stringency hybridization conditions.” Suitable “standard” or “less stringent” hybridization conditions will be well known to those of skill in the art and are clearly set forth hereinbelow. In a preferred embodiment, standard stringent hybridization conditions or less stringent hybridization conditions are utilized.
The terms “standard stringent hybridization conditions,” “moderately stringent conditions,” and “less stringent hybridization conditions” or “low stringency hybridization conditions” are used herein, describe those conditions under which substantially complementary nucleic acid segments will form standard Watson-Crick base-pairing and thus “hybridize” to one another. A number of factors are known that determine the specificity of binding or hybridization, such as pH; temperature; salt concentration; the presence of agents, such as formamide and dimethyl sulfoxide; the length of the segments that are hybridizing; and the like. There are various protocols for standard hybridization experiments. Depending on the relative similarity of the target DNA and the probe or query DNA, then the hybridization is performed under stringent, moderate, or under low or less stringent conditions.
The hybridizing portion of the hybridizing nucleic acids is typically at least about 14 nucleotides in length, and preferably between about 14 and about 100 nucleotides in length. The hybridizing portion of the hybridizing nucleic acid is at least about 60%, e.g., at least about 80% or at least about 90%, identical to a portion or all of a nucleic acid sequence encoding a HAS or chondroitin or heparin synthase or its complement, such as SEQ ID NO: 1, 3, 5, 7, 9, or 11 or the complement thereof. Hybridization of the oligonucleotide probe to a nucleic acid sample typically is performed under standard or stringent hybridization conditions. Nucleic acid duplex or hybrid stability is expressed as the melting temperature or Tm, which is the temperature at which a probe nucleic acid sequence dissociates from a target DNA. This melting temperature is used to define the required stringency conditions. If sequences are to be identified that are related and substantially identical to the probe, rather than identical, then it is useful to first establish the lowest temperature at which only homologous hybridization occurs with a particular concentration of salt (e.g., SSC, SSPE, or HPB). Then, assuming that 1% mismatching results in a 1 EC decrease in the Tm, the temperature of the final wash in the hybridization reaction is reduced accordingly (for example, if sequences having >95% identity with the probe are sought, the final wash temperature is decreased by about 5EC). In practice, the change in Tm can be between about 0.5EC and about 1.5EC per 1% mismatch. Examples of standard stringent hybridization conditions include hybridizing at about 68EC in 5×SSC/5× Denhardt's solution/1.0% SDS, followed with washing in 0.2×SSC/0.1% SDS at room temperature or hybridizing in 1.8×HPB at about 30EC to about 45EC followed by washing a 0.2-0.5×HPB at about 45EC. Moderately stringent conditions include hybridizing as described above in 5×SSC\5× Denhardt's solution 1% SDS washing in 3×SSC at 42EC. The parameters of salt concentration and temperature can be varied to achieve the optimal level of identity between the probe and the target nucleic acid. Additional guidance regarding such conditions is readily available in the art, for example, by Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, (Cold Spring Harbor Press, N.Y.); and Ausubel et al. (eds.), 1995, Current Protocols in Molecular Biology, (John Wiley & Sons, N.Y.). Several examples of low stringency protocols include: (A) hybridizing in 5×SSC, 5× Denhardts reagent, 30% formamide at about 30° C. for about 20 hours followed by washing twice in 2×SSC, 0.1% SDS at about 30° C. for about 15 min followed by 0.5×SSC, 0.1% SDS at about 30° C. for about 30 min (FEMS Microbiology Letters, 2000, vol. 193, p. 99-103); (B) hybridizing in 5×SSC at about 45° C. overnight followed by washing with 2×SSC, then by 0.7×SSC at about 55° C. (J. Viological Methods, 1990, vol. 30, p. 141-150); or (C) hybridizing in 1.8×HPB at about 30° C. to about 45° C.; followed by washing in 1×HPB at 23° C.
Naturally, the present invention also encompasses the use of DNA segments which are complementary, or essentially complementary, to the sequences set forth in SEQ ID NO:1 or 3 or 5 or 7 or 9 or 11. Nucleic acid sequences which are “complementary” are those which are capable of base-pairing according to the standard Watson-Crick complementarity rules. For example, the sequence 5′-ATAGCG-3′ is complementary to the sequence 5′-CGCTAT-3″ because when the two sequences are aligned, each “T” is able to base-pair with an “A”, which each “G” is able to base pair with a “C”. As used herein, the term “complementary sequences” means nucleic acid sequences which are substantially complementary, as may be assessed by the nucleotide comparison set forth above, or as defined as being capable of hybridizing to the nucleic acid segment of SEQ ID NO: 1, 3, 5, 7, or 9, or 11 under standard stringent, moderately stringent, or less stringent hybridizing conditions.
The nucleic acid segments utilized in the methods of the present invention, regardless of the length of the coding sequence itself, may be combined with other DNA sequences, such as promoters, polyadenylation signals, additional restriction enzyme sites, multiple cloning sites, epitope tags, polyhistidine regions, other coding segments, and the like, such that their overall length may vary considerably. It is therefore contemplated that a nucleic acid fragment of almost any length may be employed, with the total length preferably being limited by the ease of preparation and use in the intended recombinant DNA protocol.
Naturally, it will also be understood that this invention is not limited to the use of the particular amino acid and nucleic acid sequences of any of SEQ ID NOS:1-25. Recombinant vectors and isolated DNA segments may therefore variously include the HAS or CS or HS coding regions themselves, coding regions bearing selected alterations or modifications in the basic coding region, or they may encode larger polypeptides which nevertheless include HAS or CS or HS coding regions or may encode biologically functional equivalent proteins or peptides which have variant amino acid sequences.
The DNA segments utilized in accordance with the present invention encompass DNA segments encoding biologically functional equivalent HAS or CS or HS proteins and peptides. Such sequences may arise as a consequence of codon redundancy and functional equivalency which are known to occur naturally within nucleic acid sequences and the proteins thus encoded. Alternatively, functionally equivalent proteins or peptides may be created via the application of recombinant DNA technology, in which changes in the protein structure may be engineered, based on considerations of the properties of the amino acids being exchanged. Changes designed by man may be introduced through the application of site-directed mutagenesis techniques, e.g., to introduce improvements to the enzyme activity or to antigenicity of the HAS or CS or HS protein or to test HAS or CS or HS mutants in order to examine HAS or CS or HS activity at the molecular level or to produce HAS or CS or HS mutants having changed or novel enzymatic activity and/or sugar substrate specificity.
Traditionally, chemical or physical treatments of polysaccharides were required to join two dissimilar materials. For example, a reactive nucleophile group of one polymer or surface was exposed to an activated acceptor group of the other material. Two main problems exist with this approach, however. First, the control of the chemical reaction cannot be refined, and differences in temperature and level of activation often result in a distribution of several final products that vary from lot to lot preparation. For instance, several chains may be cross-linked in a few random, ill-defined areas, and the resulting sample is not homogenous. Second, the use of chemical reactions to join molecules often leaves an unnatural or nonbiological residue at the junction of biomaterials. For example, the use of an amine and an activated carboxyl group would result in an amide linkage. This inappropriate residue buried in a carbohydrate may pose problems with biological systems such as the subsequent production of degradation products which accumulate to toxic levels or the triggering of an immune response.
The methods for enzymatically producing defined glycosaminoglycan polymers utilized in the present invention involves providing at least one functional acceptor and at least one recombinant glycosaminoglycan transferase capable of elongating the functional acceptor in a controlled or repetitive fashion to form extended glycosaminoglycan-like molecules. At least one of UDP-GlcUA, UDP-GalUA UDP-GlcNAc, UDP-Glc, UDP-GalNAc, UDP-GlcN, UDP-GalN and a structural variant or derivative thereof is added in a stoichiometric ratio to the functional acceptor to provide glycosaminoglycan polymers that are substantially monodisperse in size.
The term “substantially monodisperse in size” as used herein will be understood to refer to defined glycoasminoglycan polymers that have a very narrow size distribution. For example, substantially monodisperse glycosaminoglycan polymers having a molecular weight in a range of from about 3.5 kDa to about 0.5 MDa will have a polydispersity value (i.e., Mw/Mn, where Mw is the average molecular weight and Mn is the number average molecular weight) in a range of from about 1.0 to about 1.1, and preferably in a range from about 1.0 to about 1.05. In yet another example, substantially monodisperse glycosaminoglycan polymers having a molecular weight in a range of from about 0.5 MDa to about 4.5 MDa will have a polydispersity value in a range of from about 1.0 to about 1.5, and preferably in a range from about 1.0 to about 1.2. For small sugar chains, oligosaccharides, the molecule can be exactly described structurally; these single molecular entities have a precise molecular weight, composition, and sugar linkages, and are thus considered “defined”.
Therefore, the term “defined” as used herein will be understood to refer to a single molecular entity having a precise molecular weight, composition and sugar linkages, and which is substantially free of other molecular entities having different molecular weights, compositions and sugar linkages.
The synthesis methods of the present invention allow natural and artificial oligosaccharides to be synthesized in a pure and defined state. In particular, immobilized mutatnt enzymes are very useful for step-wise synthesis. For example, the schemes of the presently disclosed and claimed invention can produce, for example but not by way of limitation, the defined oligosaccharides HA13, HA14 or HA20 with molecular weights of 2494 Da, 2670 Da, or 3808 Da, respectively (see
The functional acceptor utilized in accordance with the present invention will have at least two sugar units of uronic acid and/or hexosamine, wherein the uronic acid may be GlcUA, IdoUA or GalUA, and the hexosamine may be GlcNAc, GalNAc, GlcN or GalN. In one embodiment, the functional acceptor may be an HA oligosaccharide of about 3 sugar units to about 4.2 kDa, or an HA polymer having a mass of about 3.5 kDa to about 2MDa. In another embodiment, the functional acceptor may be a chondroitin oligosaccharide or polymer, a chondroitin sulfate oligosaccharide or polymer, or a heparosan-like polymer. In yet another embodiment, the functional acceptor may be an extended acceptor such as HA chains, chondroitin chains, heparosan chains, mixed glycosaminoglycan chains, analog containing chains or any combination thereof.
Any recombinant glycosaminoglycan transferase described or incorporated by reference herein may be utilized in the methods of the present invention. For example, the recombinant glycosaminoglycan transferase utilized in accordance with the present invention may be a recombinant hyaluronan synthase, a recombinant chondroitin synthase, a recombinant heparosan synthase, or any active fragment or mutant thereof. The recombinant glycosaminglycan transferase may be capable of adding only one UDP-sugar described herein above or may be capable of adding two or more UDP-sugars described herein above.
Metastasis, the escape of cancer cells throughout the body, is one of the biggest fears of both the ailing patient and the physician, and this area is a well studied application with respect to HA involvement. The present invention is directed to the use of defined, specific GAG molecules as a supplemental treatment to inhibit cancer growth and metatasis in conjunction with existing cancer therapies.
HA oligosaccharide treatment of cancer cell lines in culture reduced their rate of proliferation (Zeng et al., 1998). HA oligosaccharides were also very promising in an in vivo assay for tumor growth and metastasis (Zeng et al., 1998). In this assay, mice were injected with an invasive and virulent tumor cell line, and the progression of disease (e.g., general health, number of tumors, size of tumors) was monitored at a 10 day timepoint. Treatment with HA oligosaccharides greatly reduced the number and the size of tumors. Untreated animals would need to be euthanized within 2-4 weeks because of tremendous tumor growth. Various cancer cell lines, including melanoma, glioma, carcinomas from lung, breast and ovary, are susceptible to the therapeutic action of HA oligosaccharides.
The putative mode of action of the HA-oligosaccharide sugars is thought to be mediated by binding or interacting with one of several important HA-binding proteins (probably CD44 or RHAMM) in the mammalian body (Zeng et al., 1998; Yu et al., 1997; Bartolazzi et al., 1994; Zawadzki et al., 1998; Lesley et al., 2000; Radotra et al., 1997; Ahrens et al., 2001; Harada et al., 2001; Zhang et al., 1995; and Tan et al., 2001). However, the molecular details are lacking at this time, but there are several hypotheses. One attractive scenario for the anticancer action of HA-oligosaccharide is that multiple CD44 protein molecules in a cancer cell can bind simultaneously to a long HA polymer (Zeng et al., 1998; Yu et al., 1997; Bartolazzi et al., 1994; and Tan et al., 2001). This multivalent HA binding causes CD44 activation (perhaps mediated by dimerization or a receptor patching event) that triggers cancer cell activation and migration (FIG. 1). However, if the cancer cell is flooded with small HA-oligosaccharides, then each CD44 molecule individually binds a different HA molecule in a monovalent manner so that no dimerization/patching event occurs. Thus no activation or migration signal is transmitted to the cell.
It has been also shown that treatment with certain anti-CD44 antibodies (Yu et al., 1997; Bartolazzi et al., 1994; and Zawadzki et al., 1998) or CD44-antisense nucleic acid (Harada et al., 2001) prevents the growth and metastasis of cancer cells in a fashion similar to HA-oligosaccharides; in comparison to the sugars, however, these protein-based and nucleic acid-based reagents are somewhat difficult to deliver in the body and/or may have long-term negative effects. The optimal HA-sugar size was thought to be 10 to 14 sugars; molecules less than 8 sugars long do not have detectable biological activity (Zeng et al., 1998; and Tammi et al., 1998). A very desirable attribute of HA-oligosaccharides for therapeutics is that these sugar molecules are natural by-products that occur in small amounts in the healthy human body during the degradation of HA polymer; no untoward innate toxicity, antigenicity, or allergenic concerns are obvious (Zeng et al., 1998). The major current problem facing the development of the HA-based sugar therapeutics is that only very small amounts can be prepared by the current technology of the prior art.
The size of the hyaluronan (HA) polysaccharide dictates its biological effect in many cellular and tissue systems based on many reports in the literature. However, no source of very defined, uniform HA polymers with sizes greater than 5 kDa is currently available. This situation is complicated by the observation that long and short HA polymers appear to have antagonistic or inverse effects on some biological systems. Therefore, HA preparations containing a mixture of both size populations may yield contradictory or paradoxical results. One embodiment of the novel method of the present invention produces HA with very narrow, monodisperse size distributions that are referred to herein as “selectHA.”
The Pasteurella bacterial HA synthase enzyme, pmHAS, catalyzes the synthesis of HA polymers utilizing monosaccharides from UDP-sugar precursors in vivo and in vitro. pmHAS will also elongate exogenously supplied HA oligosaccharide acceptors in vitro; in fact, HA oligosaccharides substantially boost the overall incorporation rate. A purified, recombinant pmHAS derivative was employed herein to produce either native composition HA or derivatized HA.
HA polymers of a desired size were constructed by controlling stoichiometry (i.e., ratio of precursors and acceptor molecules). The polymerization process is synchronized in the presence of acceptor, thus all polymer products are very similar (see
The use of a modified acceptor allows the synthesis of selectHA polymers containing radioactive (e.g., 3H, 125I), fluorescent (e.g., fluorescein, rhodamine), detection (i.e., NMR or X-ray), affinity (e.g., biotin) or medicant tags (see
Overall, the selectHA reagents should assist in the elucidation of the numerous roles of HA in health and disease due to their monodisperse size distributions and defined compositions. It must be emphasized that unpredicted kinetic properties of the Pasteurella GAG synthases in a recombinant virgin state in the presence of defined, unnatural reaction conditions facilitates targeted size range production of monodisperse polymers that are not synthesizable by previously reported methods (
The methods of the presently disclosed and claimed invention are novel and powerful, as the availability of gram quantities of these well-defined oligosaccharides is an important step in the development of small sugars as a new class of drugs for treatment of cancer metastasis. In addition to the anticancer effects, HA-based molecules promise to be useful for other areas as well, including but not limited to, stimulation of blood vessel growth (Rahmanian et al., 1997; and Lees et al., 1995) and stimulation of the immune system (Termeer et al., 2000; and Termeer et al., 2002).
The most promising initial target oligosaccharides for inhibition of cancer metastasis are HA chains composed of 10 to 14 sugars. The two current prior art techniques for creating the desired HA-oligosaccharides are extremely limited and will not allow the medical potential of the sugars to be achieved (see
method is difficult to control, inefficient, costly, and is in a relatively stagnant development stage. For example, the enzyme wants to degrade the polymer to the 4 sugar end stage product, but this sugar is inactive. The use of acid hydrolysis also removes a fraction of the acetyl groups from the GlcNAc groups, thereby introducing a positive charge into an otherwise anionic molecule. The latter method, chemical synthesis, involves steps with low to moderate repetitive yield and has never been reported for a HA-oligosacchride longer than 6 sugars in length (Halkes et al., 1998). Also, racemization (e.g., production of the wrong isomer) during chemical synthesis may create inactive or harmful molecules. The inclusion of the wrong isomer in a therapeutic preparation in the past can have tragic consequences as evidenced by the birth defects spawned by the drug, Thalidomide. As sugars contain many similar reactive hydroxyl groups, in order to effect proper coupling between two sugars in a chemical synthesis, most hydroxyl groups must be blocked or protected. At the conclusion of the reaction, all of the protecting groups must be removed, but this process is not perfect; as a result, a fraction of the product molecules retain these unnatural moieties. The issues of racemization and side-products from chemical synthesis are not problems for the high-fidelity enzyme catalysts of the present invention.
The partial depolymerization method only yields fragments of the original HA polymer and is essentially useless for creating novel sugars beyond simple derivatizations (e.g., esterifying some fraction of GlcUA residues in an indiscriminate fashion). Chemical synthesis (
As described herein earlier, the present inventor has discovered the four Pasteurella glycosaminoglycan synthases. A novel strategy was used to isolate the gene for a HA synthase, pmHAS, as described in U.S. Ser. No. 10/217,613, filed Aug. 12, 2002, and this unique enzyme does not closely resemble the known HA synthases of Streptococcus bacteria, man or an algal virus. The chondroitin synthase, pmCS, was the first known enzyme to polymerize chondroitin (see U.S. Ser. No. 09/842,484, filed Apr. 25, 2002). The present inventor has demonstrated the molecular directionality of pmHAS synthesis, and it was observed that acceptor sugars were elongated by pmHAS if supplied with the appropriate UDP-sugar (
The pmHAS polypeptide contains duplicated sequence elements that were considered to be sugar-transfer sites; one site would transfer a GlcNAc sugar and the other site would transfer a GlcUA sugar to form the alternating HA polymer backbone (
Further mutagenesis transformed the low expression level (˜0.1% of protein) pmHAS membrane protein found in nature to a high expression level (˜10% of protein) soluble protein (see parent application U.S. Ser. No. 10/642,248). This alteration of pmHAS allows both (i) the generation of more catalyst and (ii) the purification of catalyst by standard chromatographic means. Several strategies were developed to purify milligram-level quantities of pmHAS mutant proteins by conventional protein chromatography. 90-100% pure enzyme is obtained in one or two steps by the methods of the present invention (
It has been shown that the pmHAS1-703 enzyme responds very favorably with a linear increase in reaction rate when tested with high UDP-sugar concentrations (10-15 mM) predicted to be useful for “industrial” scale synthesis; the presence of two similar UDP-sugars simultaneously does not cause cross-inhibition (see DeAngelis et al., 2003). A property of many enzymes is that their reaction products or downstream metabolites often regulate the catalysis rate. In the live cell, this control makes sense because if sufficient product is made, then it is not logical to consume more starting materials. In biotechnology, however, this feedback inhibition prematurely shuts the enzyme system down, thereby reducing yields. HA synthases from both Streptococcus bacteria and man are turned off or inhibited by low levels of the unavoidable by-product of HA synthesis, UDP (0-5% activity at 0.1-0.4 mM). On the other hand, pmHAS1-703 is not very susceptible to UDP inhibition (Table V). This fortunate circumstance allows higher production yields because UDP does not need to be vigorously removed during the reaction.
Large-scale synthesis mediated by catalysts can be performed in a variety of formats. Perhaps the most useful and advantageous method is the catalytic bioreactor format (
with catalyst. This column serves to hold or to immobilize the catalyst (often an extremely expensive material) so that it can contact all of the starting material in a serial fashion. After the reaction occurs in the column bed, the product exits the column. A good column (i.e., one that does not lose the catalyst or allow the catalyst to fail) allows repetitive (multiple use allows cost-savings) or continuous reactions to occur.
In designing the biocatalytic system for sugar synthesis of the present invention, it was first tested if the pmHAS enzyme and its mutant derivatives could be immobilized to a bead suitable for use in a column. Chemistry that will allow virtually 100% of the purified enzyme to be attached to a bead with minimal loss of catalytic activity (data not shown) was identified. The beads with wild-type dual-action pmHAS made long HA polymer chains. The mutant versions of pmHAS possessing only a single functional transfer site transferred only one type of sugar (see
Laboratory-Scale Pilot Synthesis with Bioreactors. Two bioreactors with immobilized mutant pmHAS enzymes were prepared (described above). One column only transferred GlcNAc while the other column transferred only GlcUA. As an easily monitorable test, a series of fluorescent HA oligosaccharides were prepared with these bioreactors. As a feedstock, a fluorescent HA4 (F-HA4) acceptor was first made in a two-step chemical synthesis. This acceptor and the two required UDP-sugars, UDP-GlcNAc and UDP-GlcUA (0.8 mM each), together in a suitable reaction buffer (1 M ethylene glycol, 10 mM MnCl2, 50 mM Tris, pH 7.2) were applied to the two enzyme columns in a repetitive fashion 8 times (4 cycles each column). Samples of the reaction mixture were analyzed by thin layer chromatography at every step. It was observed that larger oligosaccharides were made as expected. A desirable nanoHA molecule, a F-HA12 sugar, was produced in a single afternoon. The identity of the product was verified by the most rigorous analytical method, mass spectrometry (
In addition to being a sensitive test molecule for the synthesis process of the present invention, this fluorescent reagent has an added bonus for use as a probe. The fluorescent tag allows sensitive visualization of the location and the fate (e.g., stick to cell surface, internalized, etc.) of nanoHA on live cancer cells. The reagent also demonstrates that a drug can be coupled to HA oligosaccharides by the methods of the present invention.
Microarrays are emerging as powerful, high-throughput tools in genomics and proteomics research. Sugar-based microarrays can be generated by the methods of the present invention to test a wide variety of novel oligosaccharides for interaction with proteins essential for tissue integrity or recognition/signaling events. Information from screening microarrays allows for production of GAGs with increased potency and/or increased selectivity that can also be synthesized in the bioreactor. As shown in
Acceptor-mediated Synchronization of Reaction Yields Monodisperse HA Products—Recombinant pmHAS synthesizes HA chains in vitro if supplied with both required UDP-sugars (DeAngelis et al., 1998) according to the equation:
nUDP-GlcUA+nUDP-GlcNAc→2nUDP+[GlcUA-GlcNAc]n
However, if a HA-like oligosaccharide ([GlcUA-GlcNAc]x) is also supplied in vitro, then the overall incorporation rate was elevated up to ˜50- to 100-fold (DeAngelis, 1999). It was suggested that the rate of initiation of a new HA chain de novo was slower than the subsequent elongation (i.e., repetitive addition of sugars to a nascent HA molecule). The observed stimulation of synthesis by exogenous acceptor appears to operate by bypassing the kinetically slower initiation step allowing the elongation reaction to predominate as in the following equation:
nUDP-GlcUA+nUDP-GlcNAc+[GlcUA-GlcNAc]x→2nUDP+[GlcUA-GlcNAc]x+n
HA polymerization reactions were performed with purified pmHAS and UDP-sugar precursors under various conditions and analyzed the reaction products by agarose gel electrophoresis and/or size exclusion chromatography with MALLS. It was observed that the size distribution of HA products obtained was quite different depending on the presence or the absence of the HA4 acceptor; in summary, reactions with acceptor produced smaller HA chains with a more narrow size distribution. An example is depicted in
To verify whether pmHAS can utilize HA acceptors of various sizes, parallel assays were set up using the same starting conditions, and at various times additional UDP-sugars were added to the reaction. The result indicated that intermediate products were utilized as starting material for later chain elongation by pmHAS. (
To explain the findings above, it was hypothesized that polymerization by pmHAS in the presence of an HA acceptor is a synchronized process. Reactions without acceptor exhibit a lag period interspersed with numerous, out of step initiation events that yield a short HA oligosaccharide (
Stoichiometric Control of HA Product Size—The two enzymological properties of recombinant pmHAS described above also allow for the control of HA polymer size in chemoenzymatic syntheses. First, as noted above, the rate-limiting step in vitro appears to be chain initiation. Therefore, pmHAS will transfer monosaccharides onto the existing HA acceptor chains before substantial de novo synthesis. Second, the enzyme polymerizes HA in a rapid nonprocessive fashion in vitro (Jing et al., 2000; and DeAngelis et al., 2003). Therefore, the amount of HA4 should affect the final size of the HA product when a finite amount of UDP-sugar is present. The synthase will add all available UDP-sugar precursors to the nonreducing termini of acceptors as in the equation:
nUDP-GlcUA+nUDP-GlcNAc+z[GlcUA-GlcNAc]x→2nUDP+z[GlcUA-GlcNAc]x+(n/z)
If there are many termini (i.e., z is large), then a limited amount of UDP-sugars will be distributed among many molecules and thus result in many short polymer chain extensions (
To test this speculation, a series of assays were performed utilizing various levels of HA4 with a fixed amount of UDP-sugar and pmHAS (
Interestingly, if an intermediate-sized molecular mass HA chain is prepared by this method, then the chain may be elongated by simply adding more UDP-sugars to the reaction mixture provided that active catalyst is present. The resulting polymers migrate as tight bands on gels and appear quite monodisperse throughout the entire reaction time course even after multiple additions of UDP-sugars. The resulting bands with steadily increasing molecular weights indicated that HA polymers larger than oligosaccharides (˜20 kDa to 1.3 MDa) may also be utilized as starting material for chain elongation by pmHAS (
In vitro synthesis of tagged or labeled HA—The technology of the present invention for the production of monodisperse polymers also allows the use of a modified acceptor to synthesize HA polymers containing various types of foreign moieties. The pmHAS adds monosaccharides to the nonreducing terminus of the acceptor chain (DeAngelis, 1999), thus the aldehyde functionality of the reducing end is available for reaction by numerous chemical schemes. An example is shown using fluorescent HA4 acceptor to produce fluorescent monodisperse HA of various sizes (
Alternatively, substitution of all or a portion of the unlabeled UDP-sugars in a chemoenzymatic synthesis reaction with a radioactive precursor (e.g., UDP-[3H]GlcUA) is a very useful method to produce labeled HA probes (data not shown). The advantage of this method is that the radioactive HA does not contain any foreign, non-sugar moieties that might interfere with biological function or cause mistargeting.
Utility of synthetic HA—The molecular weights of most commercially available HA preparations is usually in the 105-106 Da range (Laurent et al., 1992). For research requiring smaller HA polymers, degradation via enzymatic (e.g., hyaluronidase digestion) or chemical (e.g., radicals or oxidation) or physical (e.g., ultrasonication) methods are usually employed. However, this process is not always satisfactory because it is time-consuming, the final yield of the targeted HA size is low, and at least one demanding chromatographic step is usually required. The methods of the present invention can generate HA as small as ˜15 kDa with polydispersity (Mw/Mn) around 1.001 with the current synchronized stoichiometrically-controlled synthesis technique. If the synthesis of smaller monodisperse HA oligosaccharides (less than 25 monosaccharides long or ˜5 kDa) is required, then it is preferable to utilize a pair of reactors with immobilized mutant pmHAS enzymes (a GlcUA-transferase and a GlcNAc-transferase) operating in an alternating, repetitive fashion (DeAngelis et al., 2003).
High molecular weight HA preparations are commercially available from animal or bacterial sources, but inherent problems including possible contaminants and broad size distributions complicate research. Polydispersities of commercially available HA polymers are commonly higher than 1.5. Indeed, there exists a substantial need for uniform HA in biomedical studies (Uebelhart et al., 1999). The present invention has demonstrated that narrow size distribution, high molecular weight HA (˜1-2 MDa) is also readily prepared by synchronized, stoichiometrically-controlled reactions (
To determine the exact average molecular mass of large polymers of HA (>10 kDa), MALLS is usually the choice. Yet many researchers need to quickly estimate the molecular mass and lack the required instrumentation. The correlation of HA migration on agarose gels with DNA (Lee et al., 1994) is often used for this purpose. Drawbacks of this method include (i) the original “calibration standard” HA samples were not uniform or monodisperse, and (ii) the migration of HA and DNA on agarose gels changes differentially with alteration of the agarose concentration. Ladders comprised of an assortment of synthetic HA polymers with defined, narrow size distributions (
In general, the unique technology platform of the presently disclosed and claimed invention allows the generation of a variety of improved synthetic HA tools with narrow size distributions and defined compositions for elucidating the numerous roles of HA in health and disease. Similar synchronized, stoichiometrically-controlled reactions utilizing the other Pasteurella glycosaminoglycan synthases (DeAngelis, 2002) is also within the scope of the presently disclosed and claimed invention, and allows the chemoenzymatic synthesis of monodisperse chondroitin and heparosan polymers.
In addition to the small sugar chains (e.g., tetrasaccharide HA4), larger HA polymers can be used as starting acceptor for pmHAS; the enzyme will elongate existing chains with more sugars. Experiments were performed using 575 kDa HA and 970 kDa HA (synthesized in vitro with pmHAS and HA4 as acceptor, using the previously described methods) and a commercially available HA sample (˜2 MDa; Genzyme) as acceptors. The results indicate that the existing HA chains were further elongated (
The molecular weights of naturally existing HA polymers usually range from hundreds of thousands up to several millions of Daltons. For research requiring smaller HA polymers, enzymatic degradation is usually the first choice. However, this process is not satisfactory because it is time-consuming and the final yield of the targeted HA size fraction is low, and demanding chromatography is required. With the in vitro synthesis techniques of the present invention, HA as small as 10 kDa can be generated with polydispersity around 1.001.
High molecular HAs are commercially available from animal or bacterial sources. Problems with those include possible contaminants leading to immunological responses as well as broad size distribution (Soltes etc, 2002). Polydispersities (Mw/Mn) are commonly higher than 1.5. Conclusions drawing from experimental data during biological research with these HA could be misleading. Thus there exists a need for uniform HA to perform biological study, as agreed by Uebelhart and Williams (1999).
In general, the unique technologies of the present invention allow the generation of a variety of defined, monodisperse HA tools for elucidating the numerous roles of HA in health and disease due to their monodisperse size distributions and defined compositions.
In addition to making HA polymers, the relaxed acceptor specificity of pmHAS allows the use of various chondroitin acceptors. This allows the production of monodisperse hybrid GAGs that have utility in medicine including tissue engineering and surgical aids. In particular, new protein-free proteoglycans are now possible that do not have antigenicity or allergenicity concerns compared to animal-derived products.
In
In
In addition to extension with a HA synthase, other GAG synthases may be used in the methods of the present invention. For example, a chondroitin synthase such as but not limited to pmCS can be used to elongate an existing chondroitin sulfate polymer or HA polymer to produce defined hybrid GAG molecules of various structures. Again, these molecules may have use as surgical aids or tissue engineering scaffolds.
In
In
In
Generation of Immobilized Enzyme-Reactors —As mentioned previously, the good solubility and higher yields of pmHAS1-703 compared to wild-type pmHAS allow for the purification of active HA synthase. Mutation of a predicted UDP-sugar substrate-binding amino acid motif, DXD (Jing et al., 2003), in either of the two enzyme active sites into NXN converts the dual-action HA synthase into essentially a single-action glycosyltransferase. Mutation of the A1 domain yields a β4GlcUA-Tase, while mutation of the A2 domain yields a β3GlcNAc-Tase (
Each of the pmHAS NXN mutant enzymes were purified and immobilized covalently onto activated agarose beads in a functional state. The solid-phase catalyst facilitates (a) recirculation of the reaction mixture to assure quantitative sugar addition at every step, (b) simplified recovery of the oligosaccharide product, and (c) preservation of the catalyst for subsequent steps. The enzyme immobilized on beads was also more stable than free soluble enzyme over time or heat challenge (data not shown).
Chemoenzymatic Synthesis—In the typical oligosaccharide synthesis, 1 equivalent of the tetrasaccharide HA4 (β4GlcUA-β3GlcNAc)2 acceptor and 1.2 to 1.5 equivalents of UDP-sugar in reaction buffer were circulated over an enzyme reactor at room temperature (
The crude reaction mixtures were judged to contain >95-97% of the target product oligosaccharide by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) (not shown) and polyacrylamide gel electrophoresis (
The only final purification required was gel filtration chromatography to remove low molecular weight salts, unincorporated precursor sugar, and UDP byproduct from the target oligosaccharide. For the larger HA molecules, simple dialysis or ultrafiltration for desalting would suffice. All of the oligosaccharides had the expected masses as measured by MALDI-TOF MS (
The recombinant Pasteurella enzyme, designated a Class II HA synthase, has several unique intrinsic properties that allow chemoenzymatic synthesis of desirable short oligosaccharides. In contrast, all the known Class I HA synthases (streptococcal, viral, and vertebrate) are relatively unsuitable for this synthetic task. Only pmHAS will readily elongate in vitro exogenously supplied oligosaccharides (e.g., HA4). The Class I HAS are not as well understood as pmHAS and the two component sugar transferase activities have not been separated in a practical fashion by molecular genetic means.
In the dual enzyme reactor strategy of the present invention, the final size of the oligosaccharide depends on the number of sugar addition steps employed. Substantial benefits of this scheme are that purification of intermediates is not needed after every step and that high stepwise yields are possible by recirculating the reaction mixture over a given enzyme-reactor. An added benefit of utilizing pmHAS derivatives for multistep syntheses is that these enzymes are relatively insensitive to the UDP byproduct of the transferase reaction (˜60% inhibition at 15 mM UDP with 1 mM substrates; Table V). In contrast, the class I HAS enzymes are greatly inhibited by relatively low concentrations of UDP (>90% inhibition at 0.5 mM UDP with 1 mM substrates). Indeed, the pmHAS mutants are efficient catalysts as judged by swift reaction times utilizing only 1.2 to 1.5 molar equivalents of UDP-sugar per sugar addition step.
Other methods for production of HA oligosaccharides have been reported, but they have shortcomings. Chemical synthesis of carbohydrates is difficult due to the demands of stereoselective (i.e., a versus b glycosidic linkages) and regioselective (i.e., only one of the multiple functionalities per sugar ring) coupling of sugars. State of the art synthetic strategies utilize multiple protection/deprotection cycles in a variety of toxic and/or flammable solvents with often less than quantitative yields (
The cost of UDP-sugars used in chemoenzymatic synthesis, a once ominous barrier, has been significantly lowered recently. Recombinant permeabilized bacterial systems for the production of kilogram quantities of nucleotide-sugars are becoming available (Koizumi et al., 1998). Even though the costs of these fine biochemicals may be higher than simpler organic chemicals and synthetic reagents, the reduced number of reaction steps, the higher overall yields, and the avoidance of toxic materials lowers the overall economic differential between a ‘standard’ and a chemoenzymatic carbohydrate synthesis.
As noted earlier, the initial discovery experiments implicating that small HA chains had interesting biological properties utilized mixtures of oligosaccharides prepared by partial digestion of high molecular weight HA polysaccharide with degradative enzymes. Such protocols typically suffer from poor reproducibility and low yields of the target species (e.g., one length in range of HA10 to HA20). Some HA chains are cleaved too much (the limit digest is HA4) resulting in inactive fragments while other HA chains are not sufficiently fragmented resulting in longer molecules which will possibly counteract the desirable effect of the shorter target HA oligosaccharides. Recently, two groups have reported anion-exchange chromatography purification schemes to separate desirable HA oligosaccharides from partial digests (Tawada et al., 2002; and Mahoney et al., 2001). However, in these reports only HA-derived materials were isolated (i.e., no novel sugars), and the processes rely on chromatographic separations which may be difficult to scale up.
In addition to being an advance in carbohydrate synthesis, the presently disclosed and claimed invention also yields basic science knowledge with respect to elucidating the mechanism of GAG synthesis in Pasteurella. Two modes of polymer synthesis are possible: (a) processive (i.e., nascent polymer is retained by the glycosyltransferase until the chain is completed) or (b) non-processive (i.e., nascent polymer is repetitively bound and released by the glycosyltransferase). In our immobilized reactor format, the HA oligosaccharide must be bound transiently to a mutant synthase, extended by one sugar, and released before the oligosaccharide is acted on by a second mutant synthase. The rapidity and the efficiency of our chemoenzymatic synthesis implies that the pmHAS catalyst elongates the HA polymer in a non-processive fashion. To form the long HA polysaccharide chains (˜1×103 sugars) observed in the Pasteurella bacterial capsule, other proteins or components of the polymer transport apparatus probably assist in vivo with chain retention because this property does not appear to be an intrinsic characteristic of pmHAS.
Previously, the present inventor has demonstrated that reactions containing a mixture of two mutant enzymes (i.e., a GlcNAc-Tase and a GlcUA-Tase) formed HA polymers relatively efficiently in comparison to wild-type (Jing et al., 2000; and Jing et al., 2003). One explanation for this observation is that two pmHAS monomers actually form the active catalytic species and the two polypeptides cooperate to perform the reaction; a lesion in any one site would be compensated by employing a pair of molecules. However, based on the success of the reactor synthesis, pmHAS must act as a monomer because the two mutant enzymes are immobilized in separate locations that cannot physically interact.
The chemoenzymatic route disclosed herein also allows the use of modified acceptor molecules. For example, previously the present inventor has elongated radiolabeled acceptor (HA4 reduced with borotritide) into longer HA chains (DeAngelis, 1999), but the foreign moiety at the reducing terminus of the HA polymer could instead be a drug or another polymer to enhance therapeutic effect. The pmHAS wild-type enzyme and pmHAS-based transferases described here only transfer authentic HA monosaccharides from UDP-sugars; the C4 epimer analogs (i.e., galactose-based) and UDP-glucose do not substitute (DeAngelis et al., 1998). Thus, the present invention also includes mutant enzymes suitable for reactors developed to catalyze the incorporation of unnatural sugars to form new molecules with altered biological activity and/or useful chemical properties Overall, the chemoenzymatic synthesis platform of the present invention opens up a wide spectrum of new biomedical applications, and is not limited simply to the creation of single molecular entities, such as HA12 through HA20.
It is well established that the large array of functions that a tumor cell has to fulfill to settle as a metastasis in a distant organ requires cooperative activities between the tumor and the surrounding tissue and that several classes of molecules are involved, such as cell-cell and cell-matrix adhesion molecules and matrix degrading enzymes, to name only a few. Furthermore, metastasis formation requires concerted activities between tumor cells and surrounding cells as well as matrix elements and possibly concerted activities between individual molecules of the tumour cell itself. CD44 transmembrane glycoproteins belong to the families of adhesion molecules and have originally been described to mediate lymphocyte homing to peripheral lymphoid tissues. It was soon recognized that the molecules, under selective conditions, may suffice to initiate metastatic spread of tumor cells (Marhaba et al., 2004). CD44 variant isoforms have been implicated in many biological processes, such as cell adhesion, cell substrate, cell to cell interactions, including lymphocyte homing haemopoiesis, cell migration and metastasis. These abilities are of great importance in chronic inflammation and in cancer. CD44 has shown the ability to recruit leucocytes to vascular endothelium at sites of inflammation, which is one of the first steps in the inflammatory response. In cancer, deregulation of the adhesion mechanisms increases the ability of tumor cells to metastasis. This behavior seems to be explained by the existing relationship between hyaluronan and CD44, which is its major cell surface receptor. There are CD44 variant isoforms (i.e., similar, but not functionally equivalent) which are expressed on different types of normal cells. In addition some isoforms are overexpressed on tumor cells including breast, cervical, endometrial and ovarian cancer (Makrydimas et al., 2003). This property seems to be correlated with the metastatic potential of these cells. Depending on the CD44 isoform and the cell background, various phenomena are possible. Therefore, HA interactions and signaling may differ among cancer types.
Adhesion is by no means a passive task. Rather, ligand binding, as exemplified for CD44 and other similar adhesion molecules, initiates a cascade of events that can be started by adherence to the extracellular matrix. This leads to activation of the molecule itself, binding to additional ligands, such as growth factors and matrix degrading enzymes, complex formation with additional transmembrane molecules and association with cytoskeletal elements and signal transducing molecules. Thus, through the interplay of CD44 with its ligands and associating molecules CD44 modulates adhesiveness, motility, matrix degradation, proliferation and cell survival, features that together may well allow a tumor cell to proceed through all steps of the metastatic cascade (Marhaba et al., 2004).
The interaction of CD44 with fragmented hyaluronan on rheumatoid synovial cells induces expression of VCAM-1 and Fas on the cells, which leads to Fas-mediated apoptosis of synovial cells by the interaction of T cells bearing FasL. On the other hand, engagement of CD44 on tumor cells derived from lung cancer reduces Fas expression and Fas-mediated apoptosis, resulting in less susceptibility of the cells to CTL-mediated cytotoxicity through Fas-FasL pathway (Yasuda et al., 2002). Therefore, the response to HA or its fragments cannot always be predicted. Patients may differ in their responses.
Versican is a large chondroitin sulfate proteoglycan produced by several tumor cell types, including malignant melanoma. The expression of increased amounts of versican in the extracellular matrix may play a role in tumor cell growth, adhesion and migration. V3 acts by altering the hyaluronan-CD44 interaction (Serra et al., 2005). In addition, multiple myeloma (MM) plasma cells express the receptor for hyaluronan-mediated motility (RHAMM), a hyaluronan-binding, cytoskeleton and centrosome protein. Expression and splicing of RHAMM are important molecular determinants of the disease severity of MM (Maxwell et al., 2004).
However, prior to the present invention, there was not a reliable supply of individual nanoHA sizes for investigating their effects on particular types of cancer. Therefore, the effects of different HA sizes on tumor cell growth was investigated. Anchorage independent growth, such as growth in soft agar, is a hallmark of transformation for those mammalian cells that usually require a substrate to which adhere in order to proliferate. Therefore, an inhibition of colony formation of a cancer cell line growing in soft agar is a direct measurement of the ability of a substance to inhibit cancer growth. Paclitaxel or nanoHA were used in standard soft agar growth test assays with two different cell lines: drug-resistance human uterine sarcoma MES-SA/Dx5 (
Rapid blood vessel growth into the newly formed bone tissue is of paramount importance (Mowlem, 1963; Boume, 1972). Absence of adequate nutrient nourishment of the cells residing at the interior of large scaffolds after been implanted to a bone defect site will result in the death of the implanted cells and consequently the severe decrease of the possibility of bone regeneration. Apart from providing nutrients, rapid vascularization of bone grafts assists in the recruitment of osteoprogenitor and osteoclastic cells from the host tissue that will initiate the bone regeneration and remodeling cascade. The degradation products of hyaluronic acid (HA), oligoHA, are also known to stimulate endothelial-cell proliferation and to promote neovascularization associated with angiogenesis (West et al., 1985; Slevin et al., 2002).
Partial degradation products of sodium hyaluronate produced by the action of testicular hyaluronidase induced an angiogenic response (formation of new blood vessels) on the chick chorioallantoic membrane. Neither macromolecular hyaluronate nor exhaustively digested material had any angiogenic potential. Fractionation of the digestion products established that the activity was restricted to hyaluronate fragments between 4 and 25 disaccharides in length (West et al., 1985).
A delayed revascularization model was used previously to assess the angiogenic activity of hyaluronan fragments on impaired wound healing (Lees et al., 1995). 1- to 4-kDa hyaluronan fragments increased blood flow and increased graft vessel growth, whereas 33-kDa fragments had no such effect on graft blood flow or vessel growth.
In addition, Slevin et al. (2002) disclosed that angiogenic oligosacharides of hyaluronan induced multiple signaling pathways affecting vascular endothelial cell mitogenic and wound healing responses. Treatment of bovine aortic endothelial cells with oligosaccharides of hyaluronan (o-HA) resulted in rapid tyrosine phosphorylation and plasma membrane translocation of phospholipase Cγ1 (PLCγ1). Cytoplasmic loading with inhibitory antibodies to PLCγ1, Gβ, and Gα(i/o/t/z) inhibited activation of extracellular-regulated kinase 1/2 (ERK1/2). Treatment with the Gα(i/o) inhibitor, pertussis toxin, reduced o-HA-induced PLCγ1 tyrosine phosphorylation, protein kinase C (PKC) α and β1/2 membrane translocation, ERK1/2 activation, mitogenesis, and wound recovery, suggesting a mechanism for o-HA-induced angiogenesis through G-proteins, PLCγ1, and PKC. The work of Slevin et al. (2002) demonstrated a possible role for PKCa in mitogenesis and PKCβ1/2 in wound recovery, and that o-HA-induced bovine aortic endothelial cell proliferation, wound recovery, and ERK1/2 activation were also partially dependent on Ras activation.
Different cells in different tissues have different signalling pathways (due to varied levels and/or components that make each cell type distinct); thus, the effect of HA and oligosaccharides cannot be predicted. Empirical testing for each tissue is thus indicated.
The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane that is commonly used in vivo to study both new vessel formation and its inhibition in response to tissues, cells, or soluble factors (see Storgard et al., 2005). Quantitative or semiquantitative methods may be used to evaluate the amount of angiogenesis and anti-angiogenesis. Thanks to the CAM system, angiogenesis could be investigated in association with normal, inflammatory and tumor tissues, and soluble factors inducing angiogenic or anti-angiogenic effects could be identified.
The avian chorioallantoic membrane (CAM) is a useful model to study angiogenesis and its regulation in vivo (Ribatti et al., 1996). Even though this model is based on avian systems, thus phylogenetically distant from mammals, it has been proven to be one of the most frequently successfully used models. Briefly, the HA oligosaccharides were applied to the CAM, the eggs were incubated for several days, and the blood vessel growth was monitored by light microscopy. The HA samples were compared to water as negative controls. The number of vessels (
Tables VI and VII list the effects of different size HA on cell behavior and physiology. These tables clearly demonstrate the importance of HA size in treating certain conditions, as one HA size may cause one biological result, while another HA size may cause the exact opposite biological result in another system. In addition, it is also evident from these tables that a single HA size range may cause one biological result in one cell type (i.e., one type of cancer) and the opposite biological result in another cell type (i.e., another type of cancer or a healthy cell). For example, an HA size of 103 causes increased metastasis in human chondrosarcoma cells and decreased metastasis in mouse mammary carcinoma, human colon carcinoma, and rat glioma cells. These results clearly demonstrate the need for the “personalized medicine” approach of the present invention, in which customized defined, specific GAG molecules are administered to a patient, wherein the defined, specific GAG molecules are chosen based on the specific ailment from which the patient is suffering and/or the response of in vitro testing of the ability of the defined, specific GAG molecules to treat, inhibit and/or prevent the ailment in a sample (i.e., biopsy) from the patient.
One strategy for patient treatment according to the methods of the presently disclosed and claimed invention would include the harvest and use of a sample from a patient (such as a biopsy or tissue) in an in vitro test to monitor reduction of a disease state (e.g., the cancer state or the modulation of angiogenesis). This test may be performed by contacting the patient sample with various sizes of GAGs and various compositions of GAGs, and assessing the optimal effective size and composition of GAG based on the consideration for healthy tissue effects. Alternatively, the GAG may be in a probe state (i.e., radioactive, fluorescent, NMR-active or other state disclosed herein or known in the art) and/or medicant state which is administered for localization and/or treatment of diseased tissue for potential subsequent or concurrent surgical, radiological or chemical modalities.
Methods were performed as described in parent application U.S. Ser. No. 10/642,248, which has previously been incorporated herein by reference, except as described herein below.
Acceptor Preparation—All reagents were the highest grade available from either Sigma or Fisher unless otherwise noted. The tetrasaccharide HA4, the starting acceptor for the synthesis of longer polymers, was generated by exhaustive degradation of streptococcal HA polymer with ovine testicular hyaluronidase Type V and purified by extensive chloroform extraction, ultrafiltration, and size exclusion chromatography. The HA4 molecule was converted into a fluorescent derivative in two steps. First, an amino-HA4 derivative was prepared by reductive amination of HA4 (12 mM) with sodium cyanoborohydride (70 mM) and excess diaminoethane (200 mM) in 0.1 M borate buffer, pH 8.5, 1 mM CuCl2 at 37° C. for 2 days. The amino-HA4 product was purified on P2 resin. Second, a fluorescent acceptor was prepared by derivatizing amino-HA4 with the N-hydroxysuccinimide ester of Oregon Green™ 488 (3-fold molar excess; Molecular Probes, Eugene, Oreg.) in 50% dimethylsulfoxide, 100 mM Hepes buffer, pH 8.5. The major isomer of fluor-HA4 was purified by preparative normal-phase thin layer chromatography (2:1:1 n-butanol/acetic acid/water and silica, Whatman). The identities of HA4, amino-HA4, and fluor-HA4 were verified by virtue of the agreement of their expected and experimental masses (775 Da, 819 Da, and 1213 Da, respectively) as assessed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry in negative mode (DeAngelis et al., 2003).
Catalyst preparation and in vitro synthesis—The catalysts, pmHAS1-703, and pmCS1-704, are soluble purified Escherichia coli-derived recombinant proteins (Jing et al., 2000). The enzymes in the octyl-thioglucoside cell extracts were purified by chromatography on Toyopearl Red AF resin (Tosoh) using salt elution (50 mM HEPES, pH 7.2, 1 M ethylene glycol (an enzyme stabilizer) with 0 to 1.5 M NaCl gradient in 1 hour) (DeAngelis et al., 2003). The fractions containing the target protein (≧90% pure by SDS-PAGE/Coomassie-staining) were concentrated and exchanged into 1 M ethylene glycol, 50 mM Tris, pH 7.2, by ultrafiltration with an Amicon spin unit (Millipore). The selectHA monodispserse syntheses in general contained pmHAS1-703, UDP-GlcNAc, UDP-GlcUA, 5 mM MnCl2, 1 M ethylene glycol, 50 mM Tris, pH 7.2, and a sugar acceptor. Reactions were incubated at 30° C. for 2 to 72 hrs. The soluble, truncated dual-action wild-type pmHAS1-703 enzyme was mutated with the QuickChange system (Stratagene) to produce a pair of single-action enzymes: the GlcNAc-Tase pmHAS1-703 (D527N, D529N) and the GlcUA-Tase pmHAS1-703 (D247N, D249N). The mutant enzymes in the bacterial lysates (Jing et al., 2000) were purified by chromatography on Toyopearl Red AF resin (Tosoh), and the fractions containing the mutant protein were immobilized via their free amino groups to N-hydroxysuccinimide agarose beads (Sigma). Typically, ˜95% of the protein was coupled to the beads after mixing for 4-6 hours at 4° C. Residual activated esters were quenched with 50 mM Tris, pH 7.2, 1 M ethylene glycol buffer (TEG) for 2 hours at 4° C. before washing the beads extensively with more TEG. The enzyme reactors (˜18 mg protein on 4 ml of packed beads in a small glass column) were catalytically active for at least 8 months with storage at 4° C. in TEG buffer with 0.05% sodium azide preservative.
Analysis of in vitro synthesized HA—The size of HA was analyzed on agarose gels (0.7-1.2%; 1×TAE buffer (40 mM Tris acetate, 2 mM EDTA); 40V) stained with Stains-All dye (0.005% w/v in ethanol) (Lee et al., 1994). Approximately 0.5-5 μg of HA was loaded per lane. For smaller HA polymers (<40 kDa), HA was also analyzed on polyacrylamide gels (15-20%) with acridine orange staining (Ikegami-Kawai et al., 2002). To purify HA for later analysis, pmHAS was removed by chloroform extraction and the HA product was precipitated with three volumes of ethanol and the pellets were redissolved in water. Alternatively, the unincorporated precursor sugars were removed by ultrafiltration (Microcon units, Millipore). The HA concentration was determined by the carbazole assay using a glucuronic acid standard (Bitter et al., 1962).
Size exclusion chromatography/multi-angle laser light scattering (SEC-MALLS) analysis was employed to determine the absolute molecular masses of HA products. Polymers (2.5 to 12 μg mass; 50 μl injection) were separated on Polymer Laboratories PL aquagel-OH 30 (8 μm), —OH 40, —OH 50, —OH 60 (15 μm) columns (7.5×300 mm, Polymer Laboratories, Amherst, Mass.) in tandem or alone as required by the size range of the polymers to be analyzed. The columns were eluted with 50 mM sodium phosphate, 150 mM NaCl, pH 7 at 0.5 ml/min. MALLS analysis of the eluant was performed by a DAWN DSP Laser Photometer in series with an OPTILAB DSP Interferometric Refractometer (632.8 nm; Wyatt Technology, Santa Barbara, Calif.). The ASTRA software package was used to determine the absolute average molecular mass using a dn/dc coefficient of 0.153 determined by Wyatt Technology. The Mw and polydispersity values are the average of data from at least two SEC-MALLS runs.
Chemoenzymatic Synthesis—In the typical oligosaccharide synthesis, 90 μmoles of acceptor oligosaccharide and 110-135 μmoles (1.2 to 1.5 equivalents) of UDP-sugar (˜15 mM final) in reaction buffer (TEG plus 17 mM MnCl2) were circulated over an enzyme reactor at room temperature. The tetrasaccharide HA4, the starting acceptor for the synthesis of longer oligosaccharides, was generated by exhaustive degradation of streptococcal HA polymer (Sigma) with ovine testicular hyaluronidase Type V (Sigma) and purified by extensive chloroform extraction, ultrafiltration, and gel filtration chromatography on P2 (BioRad) resin. For converting HA4 starting material (with a GlcUA at the nonreducing terminus) into the pentasaccharide HAS, the GlcNAc from UDP-GlcNAc was transferred with the GlcNAc-Tase reactor.
The reactions were monitored by TLC (silica plates developed with n-butanol/acetic acid/H2O, 1.5:1:1 for HA4 to HA8 or 1:1:1 for HA8 to HA14) and napthoresorcinol staining (dipped in 0.2% w/v reagent in 96% ethanol/4% sulfuric acid, followed by heating at 100° C.). Typically, each step of the 90-μmole scale reactions were judged to be complete by TLC within 1 or 2 passes of the mixture through the reactor (˜5 to 10 min contact time), but the reaction mixture was further recirculated for a total of 12 passes (˜1 to 2 hours) to insure virtually complete oligosaccharide conversion. After the reaction mixture was harvested, the enzyme reactor was washed with a column volume of TEG buffer and this washing was added to the reaction mixture. A small amount of MnCl2 was added to compensate for the volume increase due to the wash step (final 17 mM).
The next UDP-sugar (in this specific case, UDP-GlcUA) was added to the reaction mixture and then applied to the next reactor (converting HA5 into the hexasaccharide HA6 with immobilized GlcUA-Tase). This repetitive synthesis was continued by adding the next appropriate UDP-sugar and switching enzyme reactors. Between each step, the reactors were washed extensively with TEG to remove any residual reaction products retained on the column from the previous step.
At the end of the desired synthesis, the reaction mixtures were lyophilized and the oligosaccharides were desalted by gel filtration on P4 (BioRad) resin eluted with 0.2 M ammonium formate. The major sugar peak was harvested and the volatile residual salts were removed by lyophilization from water three times.
HA20 was prepared starting with purified HA13 from the synthesis above. In this synthesis, for proof of principle and for convenience, all of the required UDP-sugars for the complete synthesis were added at the first step.
Oligosaccharide Analyses—For MALDI-TOF MS, the matrix solution (50 mg/ml 6-aza-2-thiothymine in 50% acetonitrile, 49.9% water, 0.1% trifluoroacetic acid, 10 mM ammonium citrate) was mixed 1:1 with the samples containing ˜0.1 μg/μl oligosaccharide in water, spotted onto the target plate, and vacuum dried. The samples were analyzed in the negative ion, reflectron mode on a Voyager Elite DE mass spectrometer (20 kV acceleration, low mass gate 800 Da, delayed extraction 180 ns). The oligosaccharides were also analyzed by 20% polyacrylamide gel electrophoresis with acridine orange staining as described previously (Ikegami-Kawai et al., 2002).
Soft agar assays were performed as described in Chapter 5, Growth Interactions in Cancer Metastasis, of Laboratory Techniques in Biochemistry and Molecular Biology (2000; Pillai and Van Der Vliet, eds.), and as described in Hamburger et al. (1980), all of which are incorporated herein by reference.
The chick embryo chorioallantoic membrane assays were performed as described in Chapter 9, Angiogenesis and Metastasis, of Laboratory Techniques in Biochemistry and Molecular Biology (2000; Pillai and Van Der Vliet, eds.), and as described in Ribatti et al. (1996) and Ribatti et al. (1997), all of which are incorporated herein by reference.
Although the foregoing invention has been described in detail by way of illustration and example for purposes of clarity of understanding, it will be obvious to those skilled in the art that certain changes and modifications may be practiced without departing from the spirit and scope thereof, as described in this specification and as defined in the appended claims below.
The following references, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference in their entirety as though set forth herein particular.
This application claims benefit under 35 U.S.C. 119(e) of provisional application U.S. Ser. No. 60/584,442, filed Jun. 30, 2004, the contents of which are hereby expressly incorporated herein by reference in their entirety. This application is also a continuation-in-part of U.S. Ser. No. 10/642,248, filed Aug. 15, 2003; which claims benefit under 35 U.S.C. 119(e) of provisional applications U.S. Ser. No. 60/404,356, filed Aug. 16, 2002; U.S. Ser. No. 60/479,432, filed Jun. 18, 2003; and U.S. Ser. No. 60/491,362, filed Jul. 31, 2003; the contents of each of which are expressly incorporated herein by reference in their entirety. Said application U.S. Ser. No. 10/642,248 is also a continuation-in-part of copending U.S. Ser. No. 10/195,908, filed Jul. 15, 2002; which is a continuation-in-part of U.S. Ser. No. 09/437,277, filed Nov. 11, 1999, now U.S. Pat. No. 6,444,447, issued Sep. 3, 2002; which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional No. 60/107,929, filed Nov. 11, 1998, the contents of both of which are expressly incorporated herein in their entirety by reference. Said U.S. Ser. No. 10/195,908 is also a continuation-in-part of U.S. Ser. No. 09/283,402, filed Apr. 1, 1999, now abandoned; which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional No. 60/080,414, filed Apr. 2, 1998, the contents of both of which are expressly incorporated herein in their entirety by reference. Said U.S. Ser. No. 10/195,908 is also a continuation-in-part of U.S. Ser. No. 09/842,484, filed Apr. 25, 2001, now abandoned; which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional No. 60/199,538, filed Apr. 25, 2000, the contents of both of which are expressly incorporated herein in their entirety by reference. Said U.S. Ser. No. 10/195,908 is also a continuation-in-part of U.S. Ser. No. 10/142,143, filed May 8, 2002; which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional No. 60/289,554, filed May 8, 2001, the contents of both of which are expressly incorporated herein in their entirety by reference.
This application was supported in part by National Research Grant C2163601 from the National Science Foundation. The United States Government may have rights in and to this application by virtue of this funding.
| Number | Date | Country | |
|---|---|---|---|
| 60584442 | Jun 2004 | US | |
| 60404356 | Aug 2002 | US | |
| 60479432 | Jun 2003 | US | |
| 60491362 | Jul 2003 | US | |
| 60107929 | Nov 1998 | US | |
| 60080414 | Apr 1998 | US | |
| 60199538 | Apr 2000 | US | |
| 60289554 | May 2001 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10642248 | Aug 2003 | US |
| Child | 11172145 | Jun 2005 | US |
| Parent | 10195908 | Jul 2002 | US |
| Child | 11172145 | Jun 2005 | US |
| Parent | 09437277 | Nov 1999 | US |
| Child | 10195908 | Jul 2002 | US |
| Parent | 09283402 | Apr 1999 | US |
| Child | 10195908 | US | |
| Parent | 09842484 | Apr 2001 | US |
| Child | 10195908 | US | |
| Parent | 10142143 | May 2002 | US |
| Child | 10195908 | US |
