Patent Application
20090075272
CD40 promotes survival, proliferation, and differentiation of normal B-cells, but can cause activation-induced cell death in malignant B-lymphocytes. CD40 ligand and anti-CD40 antibodies have been used successfully to induce apoptosis in lymphoma lines both in vitro and in xenograft tumor models. While this makes CD40 an attractive target for anti-tumor therapies, the response of malignant B-cells to CD40 signaling is variable and CD40 stimulation can enhance proliferation and increase chemoresistance in some cell lines.
CD40 is first expressed prior to the rearrangement of immunoglobulin heavy chain genes in early B-cell development; its expression is maintained through all subsequent stages of B-cell development and is not lost during malignant transformation (2). Malignant B-lymphocytes and other CD40-positive tumor cells differ from normal B-cells in that they undergo apoptosis following CD40 stimulation (3). CD40 stimulation shows promise as an anti-tumor therapy in murine models of B-cell lymphoma and breast cancer (4, 5). CD40 ligand has also been tested in phase I clinical trials (6); however, the use of CD40-directed therapy remains controversial because CD40 signaling can enhance cell proliferation and survival as well as induce resistance to chemotherapeutic agents in some B-cell malignancies (7, 8). Consequently, elucidation of the mechanisms involved in CD40-mediated apoptosis may help to identify markers for susceptibility to CD40-mediated cell death and reveal proteins that specifically control the apoptotic arm of CD40 signaling. It would be useful to have a method to use to predict whether a specific cell line or tumor will undergo apoptosis when stimulated with CD40, and to identify targets downstream of CD40 which affect only the apoptotic arm of CD40 signaling.
In one embodiment, the invention is a method of determining whether first cells respond to CD40 stimulation by undergoing apoptosis, said method comprising testing said first cells for their profile of gene expression, and comparing said profile with a second profile of gene expression of second cells known to respond to CD40 stimulation by undergoing apoptosis. If the profile of gene expression of the first cells shows expression levels of genes characteristic of the second profile, said first cells respond to CD40 stimulation by undergoing apoptosis. The method can be performed by analyzing RNA from the first cells and the second cells on one or more arrays prepared for detection and/or quantitation of RNA purified or partially purified from cells.
In another embodiment, the invention is a method of determining whether first cells respond to CD40 stimulation by undergoing apoptosis, said method comprising testing said first cells for levels of expression of one or more genes, and comparing a first set of levels of expression of said one or more genes to a second set of levels of expression of said one or more genes in second cells known to respond to CD40 stimulation by undergoing apoptosis; wherein, if the first set of levels of expression of said one or more genes in said first cells is characteristic of said second set of levels of the second cells, said first cells respond to CD40 stimulation by undergoing apoptosis.
Methods for quantitating levels of gene expression and/or providing means to compare levels of expression of selected genes are known in the art, and any such method previously described can be used where a step of a method requires such quantitation and/or comparison. Methods that rely on nucleic acid hybridization or hybridizable analogs thereof are particularly useful. They can include, for example, analysis by oligonucleotide (or hybridizable analogs thereof) arrays or microarrays, commercially available or custom-made. Other methods that can be used for quantitating and comparing gene expression are RT-PCR, western blotting or immunostaining methods.
In a further embodiment, the invention is a method for determining whether a population of cells is CD40-sensitive, said method comprising quantitating expression of one or more genes in a sample of cells from the population, wherein said one or more genes in diffuse large-cell B-lymphoma (DLCBL) cell lines are differentially regulated between CD40-sensitive DLCBL cell lines and CD40-resistant DLCBL cell lines, and comparing quantities of expression of said one or more genes in said sample to quantities of expression of said one or more genes in CD40-resistant DLCBL cell lines, wherein if said one or more genes are differentially regulated between the cells in the sample and the CD40-resistant DLCBL cell lines, then the population of cells is CD40-sensitive.
The genes to be examined for gene expression can be one or more of any of a number of genes described herein that were found to be expressed constitutively at significantly different levels in CD40-resistant cells as compared to expression of those genes in CD40-sensitive cells. The genes can be one or any number of genes selected from B-cell maturation specific genes and members of the CD40/BCR signaling pathway (see Tables 7A, 7B, 10A and 10B). Preferred genes to examine are RAG1, RAG2, IGLL1, CD9, VPREB1, CD22, CD38, Bruton's tyrosine kinase, VAV1, LYN, LCK and MEK1/MAP2K1. In other methods, the gene to be examined can be RAG1 or VAV1 or both.
Methods to quantitate gene expression are known by persons of skill in the art. One such suitable method is reverse transcription polymerase chain reaction (RT-PCR). Another method that allows quantitating gene expression and comparing levels of expression among or between genes is analysis on arrays. A further method to quantitate expression of a gene is immunohistochemistry, which employs antibodies that can be added to a sample of cells prepared for immunohistochemical testing. The antibodies bind specifically to the protein product of the gene.
Yet another embodiment of the invention is a method for determining whether a population of cells is CD40-sensitive or CD40-resistant, said method comprising testing a sample of cells from said population for the presence or absence of phosphorylated ERK, whereby, if phosphorylated ERK is present, the population of cells is CD40-sensitive, and if phosphorylated ERK is absent, population of cells is CD40-resistant. The method can be carried out by testing the sample of cells by immunohistochemical methods, such as immunoblot of non-denatured lysates from the sample of cells using anti-phospho-ERK antibodies, or immunostaining with immunofluorescent labeled anti-phospho-ERK antibodies or with anti-phospho-ERK antibodies conjugated to a reactive label that can be readily visualized, for example.
Any of the above methods can be carried out on a sample of cells wherein the sample is a tissue biopsy or a fluid sample from a human or animal. Any of the methods can be carried out on a population of cells or a portion of a population of cells wherein the population of cells is a primary culture of cells from a human or animal, or the population of cells is a cell line. The population of cells can comprise B-cell lymphoma cells, diffuse large-cell B-lymphoma cells, cancer cells, for example cancer cells derived from endothelial cells, epithelial cells, fibroblasts, or breast cancer cells, prostate cancer cells, lung cancer cells, or colon cancer cells, for instance.
A further method can be used to identify CD40-sensitive cells, performed by treating said cells to activate CD40, and testing said cells for an increase in the quantity of phosphorylated ERK, whereby if an increase in the quantity of phosphorylated ERK is observed, said cells are CD40-sensitive cells.
Cells in a population of cells, following one or more generations of cell divisions, may change in phenotype and/or genotype relative to the original population of cells. Cells may have been grown in culture for one or more generations or they may have undergone mutation(s) at their normal site in a human or animal. Cancer cells are widely recognized as cells that have undergone genotypic and phenotypic changes so that they differ from their cell of origin. Cells that are derived from a specific cell type means that the original population of cells some generations ago were of that cell type.
Arrays or microarrays for detection and quantitation of RNA are not limited to the use of oligonucleotides as probes. Arrays can include as probes oligonucleotides, peptide nucleic acids, locked nucleic acids, phosphorothioate analogs of oligonucleotides and other analogs or mimics of oligonucleotides that can hybridize to RNA. Such probes can also be used in other methods based on hybridization.
Differences in the effects elicited by CD40 stimulation in B-cell lines suggest that different signal transduction pathways may be expressed in CD40-sensitive and CD40-resistant cells. To assess this, expression microarray studies were performed on CD40-sensitive and CD40-resistant DLCBL cell lines. The data showing that CD40-sensitive and resistant cells display different gene expression profiles suggests that these lines may be derived from two distinct B-cell populations. CD40-sensitive cells overexpressed CD22 and CD38, which are found on mature, activated B-cells (35). CD40-resistant cells expressed high levels of CD9, the recombination activating genes RAG1 and RAG2, and the pre-B cell receptor genes IGLL1 and VPREB1, which are characteristic of pre-B cells at the stage of immunoglobulin rearrangement (36-39), and have also been detected in B-lymphocytes in germinal centers (40). This suggests that the CD40-sensitive OCI-Ly7 and Su-DHL4 cell lines may be derived from mature, activated B-cells whereas the CD40-resistant OCI-Ly1 and OCI-Ly8 lines resemble immature B-cells. Expression of members of the CD40 signaling pathway was investigated to determine the underlying mechanism of CD40-mediated cell death. Failure of OCI-Ly1 and OCI-Ly8 cells to undergo apoptosis upon CD40 stimulation may be the result of defects in the CD40 signal transduction pathway. These two cell lines showed reduced expression of several genes involved in CD40 signaling, including LCK, VAV, and MEK1. Analysis of LCK by RT-PCR and Western blot revealed that although RNA levels differed among CD40-sensitive and CD40-resistant lines, all four cell lines expressed significant amounts of active LCK. This suggests that differences in LCK mRNA levels may not have any functional consequences. However, differences in VAV, a phosphorylation target of LCK, were striking, with strong mRNA expression in CD40-sensitive lines and undetectable levels in CD40-resistant lines. LCK and VAV have been previously shown to maintain constitutive activation of ERK via stimulation of the RAS pathway (31) which is consistent with our observation that ERK was constitutively phosphorylated in CD40-sensitive DLCBL cell lines but permanently inactive in VAV-deficient CD40-resistant lines. Although all four cell lines expressed active LCK, the SRC family inhibitor PP1 was more effective at reducing proliferation of OCI-Ly7 and Su-DHL4 cells. Differential sensitivity to PP1 could result from inhibition of other SRC family kinases or from the differential function of downstream effectors such as VAV, RAS, and ERK. Lack of VAV and inactive ERK in OCI-Ly1 and OCI-Ly8 cells is consistent with a dead-end in the SRC signal transduction pathway. This could render the cells resistant to SRC family kinase inhibitors even if the targeted kinase itself is active.
ERK activation has often been reported to be anti-apoptotic in both lymphoid and non-lymphoid malignancies (34, 41); however, the effect of ERK phosphorylation varies, even among different stimuli in the same cell line (12). Two different ERK inhibitors did not affect the growth of DLCBL cell lines containing activated ERK, which suggests that these lines are not dependent on ERK signaling for survival or proliferation. Addition of ERK inhibitors prior to CD40 stimulation blocked activation-induced cell death, which indicates that overexpression or aberrant activation of a protein in the ERK signaling cascade may sensitize DLCBL cell lines to CD40. The observation reported herein that ERK is constitutively active in these cell lines suggests that the actual death signal must be initiated by a second pathway when CD40 signaling occurs. ERK has been implicated in apoptosis in other systems of activation-induced cell death, both directly and as a predisposing factor. TCR-mediated activation-induced cell death in a TCR hybridoma cell line was shown to be mediated by activation of VAV and ERK (42). Transfection of RAT-1 fibroblasts or MCF-7 human breast cancer cells with the ERK-regulated transcription factor elk-1 did not induce apoptosis directly, but rendered the cells susceptible to killing by a calcium ionophore (38). ERK may function in a similar way in DLCBL cell lines, rendering cells susceptible to a second signal caused by CD40 stimulation. However, the signal is unlikely to be calcium-mediated, as treatment of the cells with the calcium ionophore ionomycin induced cell death in Su-DHL4 but not OCI-Ly7 cells.
The observations herein on two pairs of cell lines are insufficient to determine whether differential expression of maturation-specific genes outside of the LCK-ERK pathway plays a role in determining susceptibility to CD40-mediated cell death; however, they are consistent with a previous report that B-cells at different stages of development differ in the protein phosphorylation patterns elicited by CD40 stimulation (43). As CD40 signaling can promote proliferation and resistance to apoptosis in normal B-cells (44), it is possible that constitutive activation of this pathway in a tumor may lead to a more aggressive phenotype. DLCBL has been shown to segregate into two subtypes with distinct gene expression patterns, one resembling germinal center cells (germinal center type) and the other similar to mature B-cells that have been subjected to CD40 and B-cell receptor stimulation (activated B-cell type) (45). The prognosis was shown to differ significantly, with five-year survival being 76% for germinal center and 34% for activated type DLCBL (46). Neither the prevalence of constitutive ERK activation in either subtype of DLCBL nor correlation with CD40 sensitivity has yet been investigated in tumor tissue. This area may be fruitful for future investigation based not only on our observations, but also on recent development of inhibitors which modulate relevant signal transduction pathways. The SRC-VAV-ERK signal transduction pathway is activated by both CD40 and B-cell receptor signaling (12), and been implicated in proliferation of B-cell malignancies (41). Several proteins in this pathway, including CD40, SRC family kinases, RAS, and MEK are being investigated as targets for anti-tumor therapies (47-50).
The studies herein show that increased expression of genes involved CD40/BCR signal transduction coincided with constitutive ERK activation and susceptibility to CD40-mediated cell death in DLCBL cell lines. A constitutively active phenotype has previously been associated with reduced survival in DLCBL (45). This raises the question whether the poor prognosis of activated type DLCBL may be the result of one or more overactive proteins in the CD40 signal transduction pathway. An interesting but as yet untested hypothesis is that the mechanism underlying the aggressive nature of activated DLCBL may also be its Achilles heel, leaving it vulnerable to therapies targeting the CD40 signal transduction pathway.
Diffuse large-cell lymphoma lines OCI-Ly1, OCI-Ly7, OCI-Ly8, and Su-DHL4 (13, 14) were provided by Dr. Neil Berinstein, Ontario Cancer Institute, Toronto, ON, Canada. A hybridoma line producing anti-human CD40 (clone G28.5) (15) was provided by Dr. Bruce Mazer, McGill University, Montreal, PQ, Canada. The cell lines were maintained in RPMI1640 medium (Sigma, Oakville, ON, Canada) supplemented with 10% bovine growth serum (VWR Canlab, Montreal, PQ, Canada), 0.2 mM glutamine, 0.05 mM β-mercaptoethanol, 100 U/mL penicillin and 100 μg/mL streptomycin in a 5% CO2 atmosphere at 37° C. Antibodies against human CD40 (clone G28.5) and murine IgG (clone HB58) were purified from hybridoma supernatants with a Protein G sepharose column as described by the manufacturer (Amersham, Baie d'Urfe, PQ, Canada).
Cells were resuspended at 1×105 cells/mL in RPMI 1640 medium supplemented as described above. Anti-CD40 antibody G28.5 and secondary crosslinking antibody HB58 were added to a final concentration of 10 μg/mL each, and the cells were incubated at 37° C. At 24 hour intervals aliquots of cells were harvested by centrifugation, washed once in phosphate buffered saline, and resuspended in FACS buffer. Non-permeabilized cells were stained by addition of 1 μg/mL propidium iodide, and the density of viable cells was determined using a FACScan flow cytometer and CellQuest software (Becton Dickinson, Mississauga, ON, Canada) set to count for a fixed 30-second time interval. To determine the fraction of cells that had undergone apoptosis, total intracellular DNA content was measured by propidium iodide staining of ethanol-permeabilized cells as previously described (16). Expression of CD40 on the cell surface was confirmed by staining non-permeabilized cells with a phycoerythrin-linked anti-CD40 antibody (clone 5C3, Becton-Dickinson) as per the manufacturer's directions, followed by flow cytometry.
The src family kinase inhibitor PP1 and the MEK inhibitor U0126 were purchased from Biomol (Plymouth Meeting, Pa., USA), and from Cell Signaling Technology (Beverly, Mass., USA) respectively. Kinase inhibition assays were performed using cells seeded at a density of 5×104 per mL in 96-well plates, to which kinase inhibitors were added to final concentrations of 10−4 to 10−8 M. The treated cells were incubated at 37° C. for 96 hours and cell viability was quantitated by MTT assay as previously described (17). For inhibition of CD40-mediated apoptosis, the MEK inhibitors U0126 (10 μM) and PD98059 (50 μM) as well as the p38 inhibitor SB203580 (10 μM) (Cell Signaling Technologies) were added 30 minutes prior to CD40 stimulation. The dose of kinase inhibitors used in this study have been previously shown to mediate target-specific effects in lymphocytes (18).
Cells were permeabilized in Cytofix/Cytoperm (Becton-Dickinson) for 20 minutes, and stained with anti-phospho-ERK antibody (Cell Signaling Technology #9101) and FITC-conjugated anti-rabbit secondary antibody (Cedarlane Laboratories, Hornby, ON, CA) following the manufacturers' instructions. The stained cells were analyzed by flow cytometry with a FACScan flow cytometer and CellQuest software.
Nondenatured whole cell lysates were prepared by sonicating cells in nondenaturing lysis buffer (20 mM Tris pH 7.5, 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% Triton-X 100, 1 mM Na3VO4) containing a protease inhibitor cocktail (Roche Diagnostics, Laval, PQ, Canada). Cytoplasmic-enriched extracts were prepared by lysing cells in hypotonic lysis buffer (10 mM Hepes pH 7.9, 1.5 mM MgCl2, 100 mM KCl, 1 mM DTT, 1% protease inhibitor cocktail (Sigma, P8340)) followed by shearing through a 23 G needle to release the nuclei. The nuclei were pelleted at 450×g and the supernatant (cytoplasmic-enriched cell extract) was removed and stored at −80° C. Protein concentration was determined using the BCA protein assay (Pierce, Rockford, Ill., USA).
LCK was immunoprecipitated from nondenatured cell lysate with a polyclonal rabbit antibody (Cell Signaling Technology #2752) as recommended by the manufacturer. Proteins were separated by SDS-PAGE on a 14% polyacrylamide gel at 180V for 1 h and transferred to a nitrocellulose membrane by electrophoretic transfer at 100V for 1 h. Western blots were performed as previously described (16). Primary antibodies against total and phosphorylated ERK, JNK, and p38 (Cell Signaling Technology #9101, #9102, #9151, #9152, #9211 and #9212) were used at a dilution of 1:100, primary antibodies against LCK and activated src family kinases (Cell Signaling Technology #2752 and #2101) were diluted 1:500, and peroxidase-conjugated goat anti-mouse or donkey anti-rabbit secondary antibodies (BioCan Scientific, Mississauga, ON, Canada) were used at a dilution of 1:10000. The compositions of blocking and antibody dilution solutions were as specified by the manufacturer. Blots were immersed in Femto West ECL staining solution (Pierce) for 30 seconds and photographed with a Syngene chemiluminescence imaging system and GeneSnap software. Image size and contrast was adjusted using Canvas software.
Total RNA was prepared from cultured cells using Trizol reagent according to the manufacturer's instructions (Invitrogen, Carlsbad, Calif.). The integrity of the purified RNA was verified using an Agilent 2100 Bioanalyzer (Agilent Technologies, Palo Alto, Calif.). Probes for microarray analysis were prepared using 10 micrograms of total RNA and hybridized to Affymetrix HG-U113A Gene Chips (Affymetrix, Santa Clara, Calif.) as previously described (19). In order to minimize technical variability, RNA processing steps (RNA extraction, probe labeling and chip hybridization) were performed in parallel for each set of four RNA samples.
The hybridized arrays were scanned and raw data extracted using the Microarray Analysis Suite 5.0 (MAS5, Affymetrix, Santa Clara, Calif.). The raw data were normalized using RMAExpress (20) (http://stat-www.berkeley.edu/users/bolstad/RMAExpress/RMAExpress.html) and filtered to exclude genes that MAS5 did not identify as “Present” in any expression profile. Differentially expressed genes were identified by performing a t-test between each pair of CD40-sensitive and CD40-resistant lines. False positive error correction was performed to maintain a 10% false discovery rate (FDR) (21). Genes whose expression differed significantly and showed the same direction of change in all four comparisons were considered to be differentially regulated between sensitive and resistant lines. Functional assessment of these expression differences was performed using contingency table analysis, based on hand-curated lists of NFκB targets ((22) and references obtained from http://people.bu.edu/gilmore/nf-kb)) genes involved in CD40 and BCR signal transduction, B-cell maturation markers and the Gene Ontology classification of proteins implicated in apoptosis (Affymetrix, Santa Clara, Calif.). See Tables 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A and 10B.
RNA isolation and cDNA synthesis was performed as for the microarray analyses. Primers were designed to span introns to ensure specificity for cDNA as opposed to genomic DNA sequences. Intron/exon junctions were identified by use of the UCSC genome browser (http://www.genome.ucsc.edu) (24). Primers were designed using Primer3 software (http://frodo.wi.mit.edu/cgi-bin/primer3/primer3_www.cgi) (25) and their specificity was verified by performing a BLAST search (http://www.ncbi.nlm.nih.gov/BLAST/) of the NCBI “nr” nucleotide sequence database (26). The following primer pairs were used:
PCR amplification was performed with 0.01 U/μL Taq DNA polymerase (Sigma) in PCR buffer (Sigma) containing 2 mM MgCl2, 0.25 μg/μL bovine serum albumin (New England Biolabs), and 0.1 mM each dATP, DCTP, dGTP, and dTTP (Amersham). Amplification was performed with 25 cycles (GAPDH, BTK) or 35 cycles (all other primers) of 30 seconds each at 95° C., 58° C., and 72° C. PCR products were detected by gel electrophoresis and ethidium bromide staining. Images were acquired with a Syngene gel documentation system and GeneSnap software. Gene expression was quantitated with GeneTools software, using PCR products amplified from a cDNA dilution series as a standard curve. Images were transferred to Canvas software for adjustment of contrast and image size.
Diffuse large-cell B-lymphoma cell lines were screened for susceptibility to CD40-mediated cell death. The number of viable OCI-Ly7 and Su-DHL4 cells was reduced after 72 hours of exposure to crosslinked anti-CD40 antibody, whereas the viability of OCI-Ly1 and OCI-Ly8 cells was unaffected (
To identify pre-existing gene expression patterns that may predict susceptibility to CD40-mediated cell death, RNA from unstimulated OCI-Ly1, OCI-Ly8, OCI-Ly7, and Su-DHL4 cells was analyzed on Affymetrix U133A oligonucleotide arrays. In total, 304 genes were differentially expressed among CD40-sensitive and CD40-resistant cells (
Homo sapiens cDNA: FLJ22642 fis, clone
Homo sapiens cDNA FLJ26296 fis, clone
Homo sapiens cDNA FLJ39619 fis, clone
Homo sapiens immunoglobulin kappa light
Homo sapiens cDNA FLJ40384 fis, clone
Homo sapiens clone 23718 mRNA sequence
Homo sapiens cDNA clone IMAGE: 4446165,
Homo sapiens partial mRNA for IgM
Homo sapiens cDNA FLJ26905 fis, clone
Homo sapiens, clone IMAGE: 5728597,
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Homo sapiens, clone IMAGE: 5728597,
Homo sapiens clone 23718 mRNA sequence
Homo sapiens transcribed sequence with
Homo sapiens, clone IMAGE: 4816940,
FDR (false discovery rate) cutoffs are the same for Tables 5B and 6B. FDR cutoffs are the same for Tables 7B, 8B, 9B and 10B.
In lymphoma cells, CD40 signaling is mediated by three interacting pathways. Current evidence suggests that the NFκB pathway is the most important of these pathways for controlling cell survival. Microarray studies showed that CD40 sensitivity was not associated with differences in expression of transcripts encoding members of this pathway, but rather with changes in the expression level of LCK and VAV1, which activate the RAS-RAF-ERK pathway. To further characterize the association between the MAPK pathway and CD40 sensitivity, we investigated activation of LCK (which activates VAV1) and MAP kinases (which are activated by VAV1). LCK is a member of the src protein family of kinases, which can be phosphorylated at two sites, one of which activates the kinase, whereas the other is inhibitory. Western blots showed that activated LCK was present in all four cell lines in the absence of CD40 stimulation (
LCK transgenic mice have been shown to develop thymic lymphomas containing constitutively activated VAV and ERK, and cell lines derived from such tumors were dependent on tyrosine phosphorylation and raf-dependent ERK activation for survival (31). CD40-sensitive but not CD40-resistant cell lines express VAV, a central part of the LCK-ERK signal transduction pathway; therefore, we would expect growth of CD40-sensitive but not CD40-resistant cells would be expected to be inhibited by blocking LCK or ERK activity. Cells were exposed to a range of concentrations of the src family kinase inhibitor PP1 (32). As predicted, growth of CD40-sensitive OCI-Ly7 and Su-DHL4 cells was inhibited by PP1 more efficiently than growth of CD40-resistant OCI-Ly1 and OCI-Ly8 cells (
CD40 stimulation has been shown to activate both ERK and p38; however, inhibition of ERK, but not p38 phosphorylation, has been reported to enhance CD40-mediated apoptosis in a carcinoma cell line (34). We therefore determined the effect of CD40 stimulation on ERK activation by Western blotting for phosphorylated and total ERK. ERK was constitutively phosphorylated in OCI-Ly7 and Su-DHL4 cells, and not phosphorylated before or after CD40 ligation in OCI-1 and OCI-Ly8 cells (
To determine if variations in ERK signaling exist in human tumors, immunohistochemical staining for phosphorylated SRC family kinases (p-SRC), VAV, and p-ERK was performed. An initial set of 25 blocks was pre-screened for expression of the B-cell markers CD20 and CD79a. Twenty samples were found to be positive and stained with antibodies to p-SRC, VAV, and p-ERK. Staining intensity was scored using the H-score system, which combines the percentage of positive cells with an intensity grade to yield a final range of 0 (negative staining) to 300 (all cells strongly positive).
The following correlations were observed. All six samples lacking phosphorylated ERK were also p-SRC negative. The four p-ERK positive samples lacking p-SRC had very high levels of VAV expression, suggesting that constitutive activation of VAV may abrogate the need for active SRC family kinases. Where VAV expression was moderate, staining intensity of p-ERK correlated with intensity of p-SRC.
The tumor samples were from biopsies performed at the Montreal General and Royal Victoria Hospitals in Montreal between 1991 and 1993. All samples had been classified as diffuse large B-cell lymphoma at diagnosis. This was confirmed by staining for expression of CD20 with an antibody from DAKO. CD20 is the standard marker for B-cells. Dr. Rene Michel of McGill University is kindly thanked for his assistance in these immunohistochemical studies on tumor samples.
Antibodies for staining of VAV, phospho-ERK, and phospho-SRC family were from Cell Signaling Technology, Danvers, Mass., USA (www.cellsignal.com). The VAV antibody was #2502. The presence of VAV has been associated with increased NFκB activity. The phospho-ERK antibody #4376 detects specifically the active form of ERK, the form that is required for CD40-mediated cell death. The phospho-SRC family #2101 detects SRC as well as the related kinases Lyn, Fyn, Lck, Yes and Hck in the active form. These kinases are part of a signaling pathway that can activate ERK.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
This application claims the benefit of U.S. Provisional Application No. 60/760,648, filed on Jan. 20, 2006. The entire teachings of the above application are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2007/000073 | 1/18/2007 | WO | 00 | 9/24/2008 |
