The present invention generally relates to a new method for inhibiting and preventing survival, tumorigenesis and metastasis of cancer cells and/or tumor initiation or cancer stem cells (TICs or CSCs) in a subject. In particular, the present invention provides a use of Collagen XVII (Col XVII) inhibitor to TICs in inhibiting and preventing survival, tumorigenesis and metastasis of said tumor initiation or cancer stem cells.
The discovery of tumor initiation or cancer stem cells (TICs) as cancer initiating components has provided an attractive approach to treating cancers. TICs make up a minor population of cancer cells, which possess stem cell properties, such as self-renewal and multi-potency for differentiation. Deregulation of TIC self-renewal is a possible requirement for the development of cancer, and survival of TICs may be responsible for the resistance to cancer therapies and recurrence of tumors. Since TICs are responsible for tumor initiation and treatment resistance, uncovering new characteristics of TICs and inhibiting the signal pathways have rapidly become a novel therapeutic strategy for treating cancer.
Highly pure populations of TICs have been identified in the subpopulations of cells positive for certain distinct surface markers, such as CD133, EpCAM, CD44, CD166 (O'Brien CA, Pollett A, Gallinger S, Dick J E (2007) A human colon cancer cell capable of initiating tumour growth in immunodeficient mice. Nature 445: 106-110; Ricci-Vitiani L, Lombardi D G, Pilozzi E, Biffoni M, Todaro M, Peschle C, De Maria R (2007) Identification and expansion of human colon-cancer-initiating cells. Nature 445: 111-115), or obtained by spheroid condition, a suspension culture in a serum-free medium (Dalerba P, Dylla S J, Park I K, Liu R, Wang X, Cho R W, Hoey T, Gurney A, Huang E H, Simeone D M et al (2007) Phenotypic characterization of human colorectal cancer stem cells. Proc Natl Acad Sci USA 104: 10158-10163). Cancer cells proliferate/differentiate in anchorage-independent conditions, giving rise to clonal spheroids, which can in part recapitulate the primary tumor expression profile (Lee J, Kotliarova S, Kotliarov Y, Li A, Su Q, Donin N M, Pastorino S, Purow B W, Christopher N, Zhang W et al (2006) Tumor stem cells derived from glioblastomas cultured in bFGF and EGF more closely mirror the phenotype and genotype of primary tumors than do serum-cultured cell lines. Cancer Cell 9: 391-403). Contrary to the dogma that epithelial cell survival is anchorage-dependent, previous reports have demonstrated that a small population of normal neural or mammary stem cells when cultured in suspension condition can generate floating spherical colonies (Dontu G, Abdallah W M, Foley J M, Jackson K W, Clarke M F, Kawamura M J, Wicha M S (2003) In vitro propagation and transcriptional profiling of human mammary stem/progenitor cells. Genes Dev 17: 1253-1270; Reynolds B A, Weiss S (1996) Clonal and population analyses demonstrate that an EGF-responsive mammalian embryonic CNS precursor is a stem cell. Dev Biol 175: 1-13; Weiss S, Reynolds B A, Vescovi A L, Morshead C, Craig CG, van der Kooy D (1996) Is there a neural stem cell in the mammalian forebrain? Trends Neurosci 19: 387-393). Although these data together strongly implicate that TICs or normal stem cells may have better suspension survival ability than other cells, there are few, if any, studies investigating specifically whether these cells increased in suspension survival ability and elucidating the underlying mechanisms.
This invention is based on the unexpected finding that Collagen XVII (Col XVII) serves as downstream target of S727-phosphorylated STAT3 (S727STAT3) and mediates suspension survival ability via the formation of hemidesmosome structure in cancer stem cells (CSCs).
Accordingly, in one aspect, the present invention provides a method for inhibiting and preventing survival, tumorigenesis and metastasis of cancer cells and/or cancer stem cells (CSCs) in a subject comprising administering the subject with a pharmaceutical composition comprising Collagen XVII (Col XVII) inhibitor to CSCs in an amount effective in inhibiting and preventing the formation of hemidesmosome structures, and the survival, tumorigenesis and metastasis of said cancer stem cells.
In another aspect, the invention provides a use of Col XVII) inhibitor to CSCs for the manufacture of a medicament for inhibiting and preventing the formation of hemidesmosome structures, and the survival, tumorigenesis and cancer cells and/or CSCs.
In the present invention, the Col XVII inhibitor is a component capable of blocking PP2A-S727STAT3-Col XVII pathway, a component capable of inhibiting Col XVII itself, or a component capable of inhibiting S727STAT3-Col XVII-laminin 5-FAK pathway whereby mediating the formation of hemidesmosome structures, suspension survival and tumor initiation in CSCs. In one embodiment of the present invention, the Col XVII inhibitor is selected from the group consisting of a microRNA (miRNA), a small interfering RNA (siRNA), a chemical agent, an antibody, an inhibitor of enzyme existing in PP2A-S727STAT3-Col XVII pathway, and an inhibitor of enzyme existing in S727STAT3-Col XVII-laminin 5-FAR pathway.
In further aspect, the present invention also provides a pharmaceutical composition for inhibiting and preventing the formation of hemidesmosome structures, and the survival, tumorigenesis and metastasis of cancer cells and/or cancer stem cells, comprising an effective amount of Col XVII inhibitor.
In still further aspect, the present invention also provides a use of a CSC surface protein or extracellular protein for the manufacture of a kit for preventing tumorigenicity and treating cancer, wherein the CSC surface protein or extracellular protein is Col XVII.
These and other aspects will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.
The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawing. In the drawings:
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art to which this invention belongs.
As used herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a sample” includes a plurality of such samples and equivalents thereof known to those skilled in the art.
The term “inhibiting” refers to the ability of a compound, agent, or method to prevent the onset of the symptoms, alleviating the symptoms, or eliminating the disease, condition or disorder.
As used herein, the terms “prevent”, “preventing”, “prevention” and the like refer to reducing the probability of developing a disorder or condition in a subject, who does not have, but is at risk of or susceptible to developing a disorder or condition.
The term “tumorigenesis” refers to initiation of primary or metastatic tumor growth, and the promotion of invasive growth.
The term “metastasis” as used herein refers to the spread of cancer cells, or cancer stem cells from one organ or part to another non-adjacent organ or part.
The term “cancer stem cells (CSCs)” as used herein refers to cancer cells (found within tumors or hematological cancers) that possess characteristics associated with normal stem cells, specifically the ability to give rise to all cell types found in a particular cancer sample. CSCs are therefore tumorigenic (tumor-forming), at much lower cell numbers than commonly used cell cultures grown in fetal calf serum containing medium. CSCs may generate tumors through the stem cell processes of self-renewal and differentiation into multiple cell types. The terms “tumor stem-like cells” or “tumor initiating cells” are essentially synonymous to the term “cancer stem cells.”
The term “therapeutically effective amount” or “effective amount” refers to a predetermined amount calculated to achieve the desired effect, i.e., to inhibit, block, or reverse the activation, migration, or proliferation of cells.
As used herein, the term “chemical agent” encompasses any chemical molecule or chemical element, or combination of chemical molecules and/or chemical elements. For example, the term “chemical agent” encompasses proteins and peptides.
The term “antibody” relates to derivatives or functional fragments thereof which still retain the binding specificity.
The present invention unexpectedly found that TICs increase phosphorylation of S727STAT3 by inactivating PP2A, leading to up-regulation of Collagen XVII (Col XVII), which stabilizes laminin 5 to form hemidesmosome-like structures. Targeting PP2A-S727STAT3-Col XVII in TICs blocks their suspension survival and tumour initiation. In contrast, up-regulation of Col XVII, enhancing S727STAT3 phosphorylation or suppressing PP2A in bulk cancer cells increases their suspension survival and tumour initiation. The S727STAT3 phosphorylation and Col XVII expression in colorectal cancer samples correlated inversely with patient prognosis and survival. Moreover, targeting TICs through the current pathway in a subcutaneous xenograft model and a malignant pleural effusion model confirms the TIC suspension survival-related pathway is a potential target for curing cancer.
In one aspect, the present invention provides a method for inhibiting and preventing survival, tumorigenesis and metastasis of cancer cells and/or cancer stem cells (CSCs) in a subject comprising administering the subject with a pharmaceutical composition comprising Collagen XVII (Col XVII) inhibitor to CSCs in an amount effective in inhibiting and preventing survival, tumorigenesis and metastasis of said cancer stem cells. In other words, the present invention provides a use of Collagen XVII (Col XVII) inhibitor to cancer stem cells (CSCs) for the manufacture of a medicament for inhibiting and preventing survival, tumorigenesis and metastasis of cancer cells and/or CSCs.
In one embodiment of the invention, the Col XVII is a target of S727-phosphorylated STAT3 (S727STAT3) and responsible for suspension survival and tumor initiation via the activation of the laminin 5-FAK pathway in CSCs.
In the present invention, the Col XVII inhibitor is a component capable of blocking PP2A-S727STAT3-Col XVII pathway, a component capable of inhibiting Col XVII itself, or a component capable of inhibiting S727STAT3-Col XVII-laminin 5-FAK pathway whereby mediating suspension survival and tumor initiation in CSCs. In one embodiment of the present invention, the Col XVII inhibitor is selected from the group consisting of a microRNA (miRNA), a small interfering RNA (siRNA), a chemical agent, an antibody, an inhibitor of enzyme existing in PP2A-S727STAT3-Col XVII pathway, and an inhibitor of enzyme existing in S727STAT3-Col XVII-laminin 5-FAK pathway. In one specific embodiment, the chemical agent is PP2A activator or STAT3 inhibitor. In particularly, the PP2A activator is forskolin, 1,9-dideoxy-forskolin, or FTY720, and the STAT3 inhibitor is selected from the group consisting of PY*LKTK, SS 610, 53I-M2001, STA-21, S3I-201, Stattic, IS3 295, CPA-1, CPA-7, Galiellalactone, Peptide aptamers, Decoy ODN, G-quartet ODN, and Peptides. In one another specific embodiment, the antibody is anti-Col XVII monoclonal or polyclonal antibody, or anti-laminin 5 monoclonal or polyclonal antibody.
In another aspect, the present invention also provides a pharmaceutical composition for inhibiting and preventing survival ability, tumorigenesis and metastasis of cancer cells and/or cancer stem cells, comprising an effective amount of Col XVII inhibitor.
In the present invention, the composition in the present invention comprises a Col XVII inhibitor, wherein the Col XVII inhibitor is a component capable of blocking PP2A-S727STAT3-Col XVII pathway, a component capable of inhibiting Col XVII itself, or a component capable of inhibiting S727STAT3-Col XVII-laminin 5-FAK pathway whereby mediating suspension survival and tumor initiation in CSCs. In one embodiment of the present invention, the Col XVII inhibitor is selected from the group consisting of a microRNA (miRNA), a small interfering RNA (siRNA), a chemical agent, an antibody, an inhibitor of enzyme existing in PP2A-S727STAT3-Col XVII pathway, and an inhibitor of enzyme existing in S727STAT3-Col XVII-laminin 5-FAK pathway.
In one aspect, the present invention provides use of a CSC surface protein or extracellular protein for the manufacture of a kit for preventing tumorigenicity or treating cancer, wherein the CSC surface protein or extracellular protein is Col XVII.
The present invention is further illustrated by the following examples, which are provided for the purpose of demonstration rather than limitation.
I. Materials and Methods
1. Reagents
Treatment reagents included MG132 (Merk, Schwalbach, Germany), Calyculin A (Cell Signaling Technologies, Beverly, Mass.), Okadaic acid (Merk), Ceramide C6 (Santa Cruz Biotechnology Inc., Santa Cruz, Calif.), Cyclohexamide (Merk), and S3I-201 (Merk).
2. Primary Cells and Cell Lines
All human materials such as fresh human tumour samples or tissue blocks used in this study were approved by Institutional Review Board (IRB) of Taipei Veterans General Hospital (Taipei, Taiwan). The CCS and HCW primary cancer cells, provided by Dr. Wen K. Yang (China Medical University Hospital, Taichung, Taiwan), were isolated from a primary tumour of a 63 y/o female with colorectal adenocarcinoma and from a liver metastasis of a male with colorectal adenocarcinoma, respectively. HT29 (human colorectal cancer cell line) was obtained from the American Type Culture Collection (ATCC). All of CCS, HCW and HT29 cancer cells were grown in DMEM-HG (Gibco, Grand Island, N.Y.) containing 10% fetal bovine serum (FBS; Gibco). A549 (human lung cancer cell line) was obtained from the ATCC and grown in Han's F12 (Gibco) containing 10% FBS. MCF7 (human breast cancer cell line) was obtained from the ATCC and grown in DMEM/F12 (Gibco) containing 10% FBS. HTB186 (human medulloblastoma cell line) was obtained from the ATCC and grown in MEM (Gibco) containing 10% FBS. For spheroid culture, cells were grown in serum-free DMEM-F12 (Gibco) containing 20 ng/mL EGF (Peprotech, Rocky Hill, N.J.), 10 ng/mL bFGF (Peprotech), and N2-supplement (Gibco), with or without PKH26 viable dye labeling (Sigma-Aldrich, St. Louis, Mo.). For PKH26 labeling, cells were labeled with 1:1 mix of 2× Dye for 10 min. For differentiation culture, the spheres after 15 days of spheroid culture were mixed with growth factor-reduced matrigel (Becton Dickinson, San Jose, Calif.) and cultured in growth medium with 15% FBS for one month. Cells were then recovered by commercial solution (Becton Dickinson) for the subsequent experiments.
2. Tissue Collection and Flow Cytometry Cell Sorting
The tissue collection was approved by the Institutional Ethics Committee/Institutional Review Board of the Taipei Veterans General Hospital. Colorectal cancer specimens with disease grade 3 to 4 were collected during surgery and immersed in normal saline, brought to the laboratory within 1 hour, and washed 5 times with phosphate-buffered saline containing 500 U/mL penicillin and 500 g/mL streptomycin (Gibco). Sample were minced into small fragments (2 mm) and resuspended in DMEM-HG (Gibco) containing 1 mg/mL type I Colase (Sigma-Aldrich) for enzymatic dissociation at 37° C. for 2 hour. Released cell samples were subjected to fluorescence-activated cell sorter.
3. Flow Cytometric Analysis and MACS-Separation
Single cell suspension from spheres was incubated with PE-conjugated monoclonal antibodies against human CD133 (MACS; Miltenyi Biotec Ltd., Surrey, UK) for 30 min at 4° C., washed twice with PBS and analyzed with FACScan flow cytometer (Becton Dickinson). The isolation of cells with high Aldehyde Dehydrogenase (ALDH) enzymatic activity was performed by using ALDEFLUOR kit (StemCell Technologies, Durham, N.C.). Briefly, single cells were suspended in ALDEFLUOR assay buffer containing ALDH substrate and then incubated for 30 min at 37° C. without or with a specific ALDH inhibitor, diethylaminobenzaldehyde (DEAB), as a control. Stained cells were sorted on a FACSAria flow cytometer (Becton Dickinson). Magnetic cell separation (MACS) of CD133+ cells was performed (Auto-Macs; Miltenyi Biotec Ltd.).
4. Xenograft Transplantation and In Vivo Suspension Experiment
The protocols were approved by the Institutional Animal Committee of Taipei Veterans General Hospital. The athymic nude mice (BALB/cAnN.Cg-Foxnlnu/CrlNarl, National Laboratory Animal Center) were maintained in specific pathogen-free conditions. The mice used for the experiments were 6 to 8 weeks of age. Tumour cells were injected subcutaneously (s.c.) and tumour growth was monitored every week for up to 3 months. For the in vivo suspension experiment, aliquots of 104 cells which delivered in 0.5% methylcellulose without or with matrigel (5%) were loaded to Directed in vivo Angiogenesis Assay (DIVAA) angioreactors (Trevigen, Gaithersburg, Md.) and implanted beneath the skin of nude mice. After 24 hours, cells were recovered from the tubes and processed for TUNEL assay.
5. TUNEL Assay
Detection of apoptosis was performed (Roche Molecular Biochemicals, Indianapolis, Ind.). Cells were fixed with 4% paraformaldehyde, and rinsed with PBS, then incubated with blocking solution (3% H2O2 in methanol) for 10 min. The cells were rinsed with PBS, and permeabilized by 0.1% Triton X-100 in 0.1% sodium citrate for 2 min at 4° C., then incubated with reaction mixture for 60 min at 37° C. in the dark. The mixture was rinsed with PBS, and counterstained with DAPI. Immunofluorescence is observed with fluorescence microscope.
6. Quantitative Real-Time PCR (Quantitative RT-PCR)
TRIzol reagent (Invitrogen, Carlsbad, Calif.) was employed to extract total RNA, and RNA was reversely transcribed using Superscript III RT Kit (Invitrogen). The quantitative real-time PCR was performed using FastStart SYBR Green Master (Roche Applied Science, Mannheim, Germany) and ABI Step One Real-Time PCR System machine. The sequences of primer sets are listed in Table 1.
7. Western Blot Analysis
Cells were lysed and protein was extracted using M-PER (Pierce, Rockford, Ill.) plus protease inhibitor cocktail (Pierce), and the protein concentrations were determined by the BCA assay (Pierce). Aliquots of protein lysates were separated on SDS-10% polyacrylamide gels and transferred onto poly-vinylidenedifluoride (PVDF) membrane, which was blocked with 5% milk (Bio-Rad, Richmond, Calif.) in TBST. The membrane was then hybridized with primary antibodies followed by corresponding secondary antibodies, and then detected using a chemiluminescence assay (Millipore, Billerica, Mass.). Membranes were exposed to X-ray film to visualize the bands (Amersham Pharmacia Biotech, Piscataway, N.J.). Antibodies against pSTAT3 (S727) (1:1000), pSTAT3 (Y705) (1:1000), STAT3 (1:2000), PP2A C subunit (1:2000), pAkt (S473) (1:1000), β-tubulin (1:2000), Flag (1:2000), pAkt (T308) (1:1000), Akt (1:2000), ERK (1:2000), pP38 (T180 and Y182) (1:1000), P38 (1:2000), pJNK (1:1000), and pmTOR (S2448) (1:1000) were purchased from Cell Signaling Technologies. Antibodies against pPP2A (Y307) (1:2000), Oct4 (1:500), Nanog (1:500), Histone H1 (1:1000), and Sox2 (1:500) were purchased from Santa Cruz Biotechnology Inc. Antibodies against pFAK (Y397) (1:1000) were purchased from GeneTex (San Antonio, Tex.). Antibody against Col17a1 was purchased from Abcam. Antibody against Laminin y2 (1:1000) was purchased from Chemicon (Temecula, Calif.). Antibody against cleaved-caspase 3 (1:1000) was purchased from Epitomics (Burlingame, Calif.). Antibody against pERK (1:1000) was purchased from Biosource (Camerillo, Calif.).
8. Immunoprecipitation
Cell extracts were incubated with antibodies against PP2A (Cell Signaling Technologies) and STAT3 (Cell Signaling Technologies) overnight at 4° C. with gentle rotation. The immune complexes were collected by adding protein G beads (Millipore) and incubated for 1 hour at 4° C. with gentle rotation followed by centrifugation. Precipitates were washed with ice-cold PBS. The precipitates were suspended in SDS sample buffer and analyzed by SDS-polyacrylamide gel. Immunoblotting was performed by antibodies against PP2A, and STAT3.
9. Immunofluorescence
Cells were fixed with 4% paraformaldehyde, and reacted with primary antibodies against human CDX2 (Chemicon) (1:200), pSTAT3 (S727) (1:10), cleaved-caspase3 (1:100), β-tubulin (1:10), Col17a1 (1:50), Laminin y2 (1:50), and pPP2A (Y307) (1:50). The cells were washed with PBS containing 0.1% Triton X-100, reacted with corresponding DyLight™ 488, DyLight™649 or DyLight™594-conjugated secondary antibodies (Jackson ImmunoResearch Laboratories, West Grove, Pa.), and counterstained with DAPI. Immunofluorescence was observed with a fluorescence microscope or a confocal fluorescence microscope.
10. Tissue Microarray Slides and Immunohistochemistry
The use of human tissues or tumour specimen samples was approved by the Institutional Review Board of Taipei Veterans General Hospital (Taipei, Taiwan). For immunohistochemical staining, paraffin-embedded sections were deparaffinized and rehydrated, with antigen retrieved by placing sections in Declere working solution (Cell Marque, Austin, Tex.) in 95° C. water for 30 min. Endogenous peroxidase activity was blocked by 3% hydrogen peroxide. Residual enzymatic activity was removed by washes in PBS, and non-specific staining was blocked with Ultra V Block for 5 min (Thermo Fisher Scientific, Fremont, Calif.). Then the sections were reacted with primary antibodies: pS727-STAT3 (1:25) and Col17a1 (1:50) followed by corresponding biotinylated secondary antibodies (Vector Laboratories, Burlingame, Calif.), treated with streptavidin-peroxidase (LSAB Kit; Dako, Carpinteria, Calif.), and followed by diaminobenzidine staining. Counterstaining was performed with Mayer's hematoxylin and photographed with Zeiss Axiolmager Z1 microscope system (Wetzlar, Germany) and an automated acquisition system (TissueGnostics, Vienna, Austria). Pictures were acquired using Tissue-Faxs software (TissueGnostics). The percentage of positively stained cells was determined using HistoQuest software (TissueGnostics).
11. Plasmid Reconstruction
The pHM6-CMV-PP2A (WT and H59K) plasmids were provided by Dr. CW Chiang in Chang-Gung University (Taipei, Taiwan). The pHM6-CMV-PP2A (WT and H59K) plasmids were subcloned into PCDNA3 plasmids. The pXJ40-CMV-STAT3 (S727A and Y705F) plasmids were obtained from Dr. Steven Plelech in Brain Research Center and Department of Medicine, University of British Columbia. The lentiviral-based expression plasmids for S727A (SA), S727E (SE), and Y705F+S727E (YFSE) point-mutated STAT3 were generated by subcloning pXJ40-CMV-STAT3 (S727A and Y705F) plasmid into pLKO-AS2.puro plasmids, followed by site-directed mutagenesis PCR.
12. Lentiviral Vector Production and Cell Infection
The shRNA expression plasmids and the bacteria clones for STAT3 (TRCN-00000020840, TRCN-0000020843) or Col17a1 (TRCN-0000118937, TRCN-0000118940) were provided by the RNAi core of the National Science Council in Taiwan. Lentiviral production for shRNA and point-mutated STAT3 over-expression were performed by transfection of 293T cells using Lipofectamine 2000 (LF2000; Invitrogen, Carlsbad, Calif.). Cells were infected in the presence of 8 μg/mL polybrene (Sigma-Aldrich) and selected with puromycin (1 g/mL).
13. Anchorage-Independent Growth Assay
Agarose culture medium (1%) containing 10% FBS was employed to coat the bottom of culture plates. After hardening, 500, 1000, and 2500 cells were suspended in agarose culture medium (0.8%) containing 10% FBS and plated onto the bottom layer. Colonies formed in the soft agarose culture were stained with crystal violet and counted 2 weeks after inoculation.
14. Gene Expression Profiling
Total RNA was isolated using the Qiagen RNeasy kit. The generation of labeled cRNA and its hybridization to Human U133 Plus 2 GeneChip arrays (Affymetrix) were done at the genomic core facilities in National Yang-Ming University (Taipei, Taiwan). Functional annotation and identification of overrepresented functional themes were done using Ingenuity Pathway Analysis (IPA) web tool developed by Ingenuity Co. All data were deposited in the Gene Expression Omnibus (GEO) database with an accession number of GSE43576.
15. ChIP Assay
Chromatin immunoprecipitation (ChIP) assay was performed by a commercial kit (Upstate Biotechnology). HT29 cells with stably overexpressed S727E-mutated STAT3 were fixed with 1% formaldehyde for 20 min at 37° C., and lysed on ice for 10 min in lysis buffer. DNA-protein complexes were sonicated to 200 and 600 base pairs. One aliquot of chromatin was stored for use as input DNA, and the remainder was diluted in immunoprecipitation (IP) buffer, and incubated overnight (4° C.) with anti-Flag antibody (Sigma-Aldrich). DNA-protein complexes were isolated on salmon sperm DNA/protein A agarose beads and then eluted. Cross-linking was reversed by incubation at 65° C. for 4 hours. Proteins were removed with proteinase K. DNA was extracted with phenol/chloroform, and PCR-amplified with specific primer for conserved STAT3 binding sequence.
16. Luciferase Reporter Assay
Luciferase assay was performed by the Secrete-Pair Dual Luminescence Assay kit (GeneCopoeia, Rockville, Md.). All transfections were performed by Nucleofector technology (AMAXA Biosystems, Cologne, Germany). Wild-type and mutated Col17a1 promoters were cloned in pEZX-PG04 reporter plasmid (GeneCopoeia).
17. Ultrastructural Analysis
Spheres were fixed in 2.5% glutaraldehyde (phosphate buffer) overnight at 4° C. and postfixed in 2% osmium tetroxide (Millonigs buffer) for 90 min at 4° C. after washing with phosphate buffer. Specimens were dehydrated through a graded series of ethanol and embedded in Epon 812-equivalent (TAAB Lab). Semi-thin sections (1 nm) were stained with toluidine blue for light microscopy analysis. Ultra-thin sections (40-90 nm) were cut, stained with uranyl acetate and lead citrate and examined with a Hitachi H7600 transmission electron microscope. For pretreatment of spheres with enzymes, spheres were incubated with chymotrypsin (25 ng/μl) and trypsin (25 ng/μl) in medium for 5 min, followed by washing with PBS twice and subject to suspension culture for 24 hours.
18. Isolation of Cancer Cells from Malignant Pleural Effusion
Malignant pleural effusion obtained aseptically in heparinized (10 U/ml) bottles were centrifuged at 200 g for 20 min at room temperature and cell pellet was resuspended in 30 ml of cold 1% BSA/2 mM EDTA/PBS. After counting by Trypan Blue exclusion method, cell suspension was layered on Ficoll gradient solution and centrifuged at 800 g for 30 min at room temperature. After centrifugation, cells contained in the upper gradient were washed once with 1% BSA/2 mM EDTA/PBS and plated in spheroid medium at a concentration of 105 cells/ml in ultralow attachment plates (Corning). Half volume of spheroid medium was added every 3 days.
19. Mouse Model of Malignant Pleural Effusion
Animal model of malignant pleural effusion was developed by using male athymic nude mice according to protocols modified from Stathopoulos et al (Stathopoulos et al., Current opinion in pulmonary medicine 15, 343-352, 2009). In brief, the animals were anesthetized with 2% Rompun (Bayer Pharma, Puteaux, France) at 5 mg/kg and Zoletil 100 (VirbacR, Carros, France) at 30 mg/kg, and administered intraperitoneally (i.p.). Tumour cells were implanted through the chest wall into the left pleural space of mice (i.p.) in a volume of 200 μl using a 26 gauge needle. The depth of needle penetration through the intercostal muscles was controlled to avoid lung injury and hemorrhage into the pleural space. Prior to being returned to their cages, mice were placed until recovery under a heat lamp to maintain body temperature.
Statistical Analysis
Comparisons between two groups were analyzed by Student's t-test. Comparisons within three groups were analyzed by ANOVA test. Comparison of patient survival curve was analyzed by Log-rank test. Comparison of in vivo tumourigeneicity was analyzed by Fisher's exact test. A value of P<0.05 was considered statistically significant.
II. Results
1. TICs show suspension survival ability
To avoid the unreliability of the isolation TICs by putative surface markers and the selection of cells preferred to survive suspension in ultralow dishes, TICs were enriched by the spheroid culture both in ultralow (
The enriched TICs of CCS and HT29 showed less apoptosis than their bulk cancer cells at 24 hours of suspension with serum deprivation (
To demonstrate that TICs also increased suspension survival in vivo, the nude mice subcutaneously implanted with silica tubes containing methylcellulose-delivered cells. Transplants recovered 24 hours later revealed survival of the majority of enriched TICs from CCS, while bulk cancer cells underwent apoptosis, which can be prevented by adding ECM in methylcellulose (
2. Phosphorylation of STAT3 at S727 Mediates Suspension Survival in TICs
Anoikis is the apoptosis induced by loss of cell adhesion, and is associated with the state of cell differentiation. Immunoblotting analysis revealed no differences in the activation of anoikis-related pathways between TICs and bulk cancer cells under suspension (
3. Col XVII serves as downstream target of S727-phosphorylated STAT3 and mediates suspension survival in TICs
Through Gene Ontology analysis of genes up-regulated along with the increase of spheroid culture time (
Chromatin immunoprecipitation (ChIP) assay of the Col17a1 promoter (
4. Suspension survival mediated by Col XVII depends on laminin 5
Previous report demonstrates that Col XVII and laminin 5 are components of hemidesmosome for mediating cell adhesion. Moreover, laminin 5 was reported to regulate anchorage-independent survival through downstream signaling, such as FAK. The present invention showed the increase in protein level of laminin 5 in TICs but not in bulk cancer cells (
These data suggest that Col XVII mediates suspension survival through maintaining the stability of laminin 5.
5. Col XVII and laminin 5 form organized structure to support suspension survival
To exclude the possibility that suspension survival by TICs in spheres was mediated by merely cell aggregation, we demonstrated the expression of Col XVII and laminin 5 and the existence of hemidesmosome-like plaques, an organized ECM ultrastructure in the basal lamina of skin epidermis and normal mucosa, in spheres but not in the aggregates of bulk cancer cells formed by hanging drop culture (
6. PP2A serves as upstream regulator of STAT3 activation at S727 and mediates suspension survival in TICs
PP2A phosphatase has been reported to inactivate STAT3 via dephosphorylating S727. The phosphorylation of Y307PP2A, which was associated with suppressed PP2A activity, was higher in both enriched TICs (
TICs enriched by spheroid culture from A549 lung cancer cells, HTB186 brain cancer cells, and MCF7 breast cancer cells showed increased expression of Oct4, Nanog and Sox2 (
7. Suspension survival in TICs determines tumour initiation ability and corresponds to clinical tumour staging and survival
To demonstrate the increased suspension survival ability is essential for tumour formation of TICs and has clinical relevance, the present invention firstly showed that blocking the PP2A-S727STAT3-Col XVII pathway inhibited tumour initiation by TICs (
We then examined specimens from 150 colorectal cancer patients and showed increase in phosphorylation at S727 of STAT3 and Col17a1 expression in correspondence with tumour stages (
8. Increase in suspension survival and related pathway in TICs of malignant pleural effusion
Malignant pleural effusion of lung cancer is a genuine suspension condition in patients' bodies and contains CD44+ TICs. After isolation of cancer cells from cytology-confirmed malignant pleural effusion by use of density gradient centrifugation, viable CD44+ cells clustering as spheres were observed and could be maintained in spheroid culture (
I. Materials and Methods
1. Cell line culture and reagents
The lung cancer cell lines A549 and CL1-1 were obtained from the American Type Culture Collection. Cells were grown in Dulbecco's Modified Eagle Medium (DMEM) (Gibco, Grand Island, N.Y.) containing 10 units/ml penicillin, 10 μg/ml streptomycin, 2 mM glutamine, and 10% fetal bovine serum (FBS; Gibco), in a 37° C. humidified atmosphere with 5% CO2. For enrichment of cancer stem-like cells (CSCs) in spheroid culture, lung cancer cells were suspended in tumor sphere medium consisting of serum-free DMEM/F12 (Gibco), N2 supplement (Gibco), human recombinant epidermal growth factor (EGF) (20 ng/ml, PeproTech, Rocky Hill, N.J.), and basic fibroblastic growth factor (bFGF) (10 ng/ml, PeproTech). Cell colonies >100 μm in diameter and >50% in area showing 3-dimensional structure and blurred cell margins were defined as spheres. Sphere numbers were counted at day 12 of culture. Cells were harvested and protein lysates were collected for further experiments. Treatment reagents included FAK inhibitor (20 μM) (Calbiochem, San Diego, Calif.; Merk, Schwalbach, Germany), LY294002 (10 μM) (Calbiochem), 1,10-phenanthroline (20 μM) (Sigma-Aldrich; St. Louis, Mo.), PMA (100 nM) (Sigma-Aldrich) and Cyclohexamide (50 μg/ml) (Calbiochem).
2. Antibodies
Antibodies against ADAM9, phospho-AKT (Ser473), β-actin, phospho-FAK (Tyr397), ubiquitin and phospho-GSK3b (Ser9) were purchased from Cell Signaling (Boston, Mass.). Antibodies against laminin-5 (γ72 chain), Sox2, Oct-3/4, Nanog and E-cadherin were from Santa Cruz Biotechnology, Inc. (Santa Cruz, Calif.). Antibodies against fibronectin, vimentin and N-cadherin were purchased from GeneTex (San Antonio, Tex.). Antibodies against Col XVII, Col XVII (NC16A-3) and Snail were purchased from Abcam (Cambridge, Mass.). Antibodies against ADAM10 were from Millipore (Amersham Pharmacia Biotech, Piscataway, N.J.). Antibodies against phospho-Snail (Ser246) were from OriGene Technologies, Inc. (Rockville, Md.).
3. Western Blot Analysis
Cell extracts were prepared with M-PER (Pierce, Rockford, Ill.) plus protease inhibitor cocktail (Halt™; Pierce) and protein concentrations were determined using the bicinchoninic acid (BCA) assay (Pierce). Aliquots of protein lysates were separated on SDS-10% polyacrylamide gels and transferred to PVDF membrane filters, followed by blocking with 5% blotting grade milk (Bio-Rad, Hercules, Calif.) in TBST (20 mM Tris-HCl [pH 7.6], 137 mM NaCl, 1% Tween 20). Membranes were then probed with the indicated primary antibodies, reacted with the corresponding secondary antibodies, and results detected using a chemiluminescence assay (Millipore, Billerica, Mass.). Membranes were exposed to X-ray film to visualize the bands (Amersham Pharmacia Biotech, Piscataway, N.J.).
4. Lentiviral Vector Production and Cell Infection
The shRNA expression plasmids and the bacteria clones for ADAM9 (TRCN46978, TRCN46980), ADAM10 (TRCN6674, TRCN6675), Col XVIIa1 (TRCN118937, TRCN118941) and laminin-5 (TRCN119152, TRCN119156) were provided by the RNAi Core Facility, Academia Sinica (Taipei, Taiwan). Subconfluent tumor cells were infected with lentivirus in the presence of 8 μg/ml polybrene (Sigma-Aldrich). At 24 hours post-infection, media were removed and replaced with fresh growth media containing puromycin (4 μg/ml) to select for infected cells after 48 hours of infection.
5. Migration Assay
Cell migration assay was performed using Boyden chambers. At the end of the assay, cells in the upper chamber and on the upper filter surface were removed, whereas cells on the lower filter surface were fixed with ethanol and stained with Giemsa (Sigma-Aldrich). The number of migrating cells was determined by counting cells in 10 random fields/filter at 200× magnification. Data were calculated as a percentage of migrated cells in the absence of chemoattractant or adherent culture, which was considered as 100%. All experiments were performed in triplicate.
6. Invasion Assay
Cell invasion assays were performed using 24-well BD Biocoat Matrigel Invasion Chambers (Becton, Dickinson and Company, San Jose, Calif.) according to the manufacturer's instructions. In brief, cells were seeded into upper inserts (2.5×104 cells/insert) in DMEM supplemented with 0.1% bovine serum albumin (BSA). Outer wells were filled with DMEM containing 10% FBS as the chemoattractant. After 24 hours of incubation, the membranes with invaded cells were stained with Giemsa (Sigma), washed and mounted on slides. The entire membrane with invading cells was counted by light microscopy. Data are expressed as the number of invaded cells/well. Each assay was performed in triplicate and repeated at least twice.
7. Wound Healing Assay
An in vitro model of the ability of A549 and CL1-1 lung cancer cells to migrate in a monolayer culture was used to measure wound healing ability. Lung cancer cells were seeded into 6-well plates and incubated overnight. The cells were disrupted by scraping them with a 200 IA pipette tip. Migration of cells into wounded areas of the plate was observed at 24 hours. The percent of wounded area filled was calculated as follows: [(mean wound width-mean remaining width)/mean wound width]×100(%).
8. Microarray and Data Analysis
We compared the gene expression pattern after 12 days of A549 lung cancer cells cultured in a spheroid (3D) culture and in a traditional monolayer (2D) culture. Total RNA was isolated with TRIzol reagent (Invitrogen, Carlsbad, Calif.) according to the protocol of the manufacturer. Each sample was processed and analyzed using the Affymetrix Human U133 plus 2.0 array chip (Affymetrix, Santa Clara, Calif.) at the National Microarray and Gene Expression Analysis Core Facility (National Research Program for Genomic Medicine, Taipei, Taiwan). The array data were analyzed using GeneSpring GX v12 software (Agilent Technologies, Santa Clara, Calif.) and classified using Gene Ontology terms.
9. Quantitative Real-Time Polymerase Chain Reaction (PCR)
Total RNA was extracted using TRIzol reagent (Invitrogen, Carlsbad, Calif.) and RNA was reverse-transcribed using Superscript II (Invitrogen) according to the manufacturer's instructions. The samples were analyzed with SYBR Green Master (GeneMark, Georgia Institute of Technology, Atlanta, Ga.) and ABI Step one Real-Time PCR System machine (Applied Biosystems, Carlsbad, Calif.). Specific primers used for PCR are as follows: Col XVIIA1 (forward, 5′-AAAGGACCAATGGGACCACC-3′; reverse, 5′-TTCACCTCTTGGGCCTTGGT-3′).
10. Immunoprecipitation Assay
Aliquots of 500 μg cell lysate were incubated with 2 μg antibody in 500 μl IP Lysis/Wash Buffer (Pierce/Thermo Scientific), with gentle rocking overnight at 4° C., then 25 μl Protein A/G Magnetic beads (Pierce/Thermo Scientific) were added and incubation was continued with gentle rocking for another 2 hours at 4° C. Then, the beads were collected with a magnetic stand and the unbound sample was discarded. The precipitate was washed 2-3 times by adding 500 μl Lysis/Wash Buffer (Pierce/Thermo Scientific), followed by replacement with 500 IA of ultra-pure water. The beads were gently mixed and collected on a magnetic stand, followed by removal of the supernatant and dilution with 50 μl sample buffer. After adequate vortex, the sample was denatured at 100° C. for 10 minutes. The beads were magnetically separated and the supernatant was saved in a new microcentrifuge tube. Immunoblotting was performed with appropriate antibodies.
11. Animal Model of Lung Metastasis
Male Balb/C nude mice were used in the study and maintained as a colony in specific pathogen-free conditions. The mice were used for experiments at 7 weeks of age. Tumor cells A549 (spheroid or non-spheroid culture) without/with Collagen XVII or laminin-5 knockdown (siRNA) (3×105, 5 groups, 4-5 mice in each group) were injected in the tail vein for evaluation of lung metastasis 12 weeks later. The lung tissue of mice was embedded in paraffin and sequentially stained with HE.
12. Patients and Immunohistochemistry
Patients
Ninety-eight patients who underwent surgical resection for lung cancer in Taipei Veterans General Hospital (Taipei, Taiwan) were enrolled in this study. None of these patients received neoadjuvant chemotherapy or radiotherapy. The clinical data including the sex, age, TNM Classification of Malignant Tumors (TNM) status and disease-specific survival were reviewed and calculated. The Institutional Review Board of Taipei Veterans General Hospital approved the protocol for this study (2013-10-030CC).
Immunohistochemistry
Immunohistochemical analysis was performed of Col XVII and laminin-5 in the resected tumor tissues. Paraffin blocks of tumors were cut into 4 μm slices and then processed using standard deparaffinization and rehydration techniques. Anti-Col XVII antibody (1:50) and anti-laminin-5 polycloncal antibody (1:50) were used as the primary antibodies to detect the protein expression Col XVII and laminin-5, respectively. For Col XVII and laminin-5 immunostaining, positive expression was defined as detectable immunoreaction in perinuclear and other cytoplasmic regions of >25% of the cancer cells.
13. Statistical Analysis
Values are shown as the mean (±standard error or deviation) of measurements of at least three independently performed experiments to minimize variation between cell cultures. Student's t-test or one-way ANOVA was employed. Survival curves were calculated using the Kaplan-Meier method and comparisons were performed using the log-rank test. P<0.05 was considered to be statistically significant.
II. Results
1. Lung Cancer Cells in Spheroid Culture have CSC Features and Upregulation of EMT Markers
Lung adenocarcinoma A549 and CL1-1 cells cultured in serum-free medium supplemented with EGF and bFGF grew in suspension and started to form spheres in 5 days, and the spheres grew slowly for at least 12 days (
2. Col XVII Upregulated in the Lung Cancer Spheroid Culture is Required for the Maintenance of EMT Phenotypes
To identify genes responsible for EMT, we performed microarray analysis to establish and compare the expression profiles of lung cancer cells grown in spheroid culture and in monolayer for 12 days. The gene-ontology (GO) analysis revealed that the genes differentially expressed in the spheroid culture were mainly involved in cell adhesion, biological adhesion, cell-cell adhesion, cell-substrate adhesion, cell-matrix adhesion, single-organism cellular process and leukocyte migration (
3. Laminin-5 May Work Together with Collagen XVII to Support the EMT Phenotypes in the Spheroid Culture of Lung Cancer Cells
Col XVII has been shown to interact with laminin-5 and, together, participate in cell/matrix interaction. We next examined the involvement of laminin-5 in Col XVII-regulated EMT maintenance in CSCs. We first showed that laminin 5 was upregulated in spheroid culture of A549 and CL1-1 cells as compared to the cells in monolayer (
4. Shedding of Collagen XVII is Required to Maintain Laminin-5 Expression and EMT Phenotypes in Spheroid Culture of Lung Cancer Cells
Col XVII has been demonstrated to undergo proteolytic cleavage and the resultant ectodomain of Col XVII was shown to promote keratinocyte motility. We therefore examined whether shedding of Col XVII took place in the spheroid culture. Western blot analysis showed that cells of spheroid culture gave rise to both the full-length Col XVII (180 kDa) and the proteolytic ectodomain fragment (120 kDa) (
5. Spheroid Culture of Lung CSC Metastasize to the Lung in Nude Mice which is Blocked by Depleting the Expression of Col XVII or Laminin-5
To demonstrate the importance of Col XVII/laminin 5-mediated effect in facilitating EMT phenotypes in spheroid culture of lung cancer cells, we performed the experimental metastasis assay by xenografting the spheroid and monolayer cells into nude mice through tail vein injection. Macro- and microscopic analyses of the lung were performed to assess the formation of metastatic tumors in the lung. s metastasizing to the lung were recorded according to the gross morphology and microscopic analysis of HE stain of the lung sections. As shown in
6. Expression of Col XVII and Laminin-5 Predicts Poorer Prognosis in Patients with Resectable Lung Cancer
We next investigated the clinical significance of Col XVII and laminin-5 expression by immunohistochemical analysis of Col XVII and laminin-5 expression in tumor specimens from a cohort of 98 patients who received lung resection for lung cancer (
7. Col XVII/Laminin 5 Promotes EMT Phenotypes in Spheroid Culture of Lung Cancer Cells Via FAK/AKT/GSK3β Pathway
We next explored the mechanism underlying Col XVII/laminin 5-mediated maintenance of EMT phenotypes in CSCs. Snail has been shown as a highly labile protein which undergoes GSK3-regulated phosphorylation and ubiquitin-mediated degradation. We examined whether AKT/GSK3 pathway was involved in Col XVII/laminin 5-mediated Snail upregulation. Western blot analysis showed increased levels of phospho-AKT and phospho-GSK3 in spheroid culture of A549 and CL1-1 cells compared to the monolayer cells (
8. Col XVII and Laminin 5 Form Organized Structure to Support Suspension Survival.
Previous report demonstrates that Col XVII and laminin 5 are components of hemidesmosome for mediating cell adhesion. To exclude the possibility that suspension survival by TICs in spheres was mediated by merely cell aggregation, we demonstrated the expression of Col XVII and laminin 5 (
It is believed that a person of ordinary knowledge in the art where the present invention belongs can utilize the present invention to its broadest scope based on the descriptions herein with no need of further illustration. Therefore, the descriptions and claims as provided should be understood as of demonstrative purpose instead of limitative in any way to the scope of the present invention.
Filing Document | Filing Date | Country | Kind |
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PCT/CN2015/091452 | 10/8/2015 | WO | 00 |
Number | Date | Country | |
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62061278 | Oct 2014 | US |