Interaction between the Adhesion Receptor, CD44, and the Oncogene Product, p185 , Promotes Human Ovarian Tumor Cell Activation

Abstract

In this study we have examined the interaction between CD44s (the standard form) and the p185 HER2 proto-oncogene in the ovarian carcinoma cell line. Surface biotinylation followed by wheat germ agglutinin column chromatography and anti-CD44-mediated immunoprecipitation indicate that both CD44s and p185 HER2 are expressed on the cell surface and most importantly, that these two molecules are physically linked to each other via interchain disulfide bonds. We have also determined that hyaluronic acid stimulates CD44s-associated p185 HER2 tyrosine kinase activity, leading to an increase in the ovarian carcinoma cell growth.After transfection of the ovarian carcinoma cell line with the adenovirus 5 E1A gene, which is known to repress p185 HER2 expression, we observed that both surface CD44s expression and CD44s-mediated cell adhesion to hyaluronic acid are significantly reduced in the transfectant cells compared with the control cells. These data suggest that down-regulation of p185 HER2 blocks CD44s expression and subsequent adhesion function. Our findings also indicate that the CD44s-p185 HER2 interaction is both functionally coupled and biosynthetically regulated. We believe that direct “cross-talk” between these two surface molecules (i.e. CD44s and the p185 HER2 ) may be one of the most important signaling events in human ovarian carcinoma development. In this study we have examined the interaction between CD44s (the standard form) and the p185 HER2 proto-oncogene in the ovarian carcinoma cell line. Surface biotinylation followed by wheat germ agglutinin column chromatography and anti-CD44-mediated immunoprecipitation indicate that both CD44s and p185 HER2 are expressed on the cell surface and most importantly, that these two molecules are physically linked to each other via interchain disulfide bonds. We have also determined that hyaluronic acid stimulates CD44s-associated p185 HER2 tyrosine kinase activity, leading to an increase in the ovarian carcinoma cell growth. After transfection of the ovarian carcinoma cell line with the adenovirus 5 E1A gene, which is known to repress p185 HER2 expression, we observed that both surface CD44s expression and CD44s-mediated cell adhesion to hyaluronic acid are significantly reduced in the transfectant cells compared with the control cells. These data suggest that down-regulation of p185 HER2 blocks CD44s expression and subsequent adhesion function. Our findings also indicate that the CD44s-p185 HER2 interaction is both functionally coupled and biosynthetically regulated. We believe that direct “cross-talk” between these two surface molecules (i.e. CD44s and the p185 HER2 ) may be one of the most important signaling events in human ovarian carcinoma development. CD44 is a transmembrane glycoprotein that is widely distributed in different cell types and tissues (for reviews see Refs. 1Bourguignon L.Y.W. Curr. Top. Membr. 1996; 43: 293-312Crossref Scopus (24) Google Scholar and 2Lesley J. Hyman R. Kincade P. Adv. Immunol. 1993; 54: 271-335Crossref PubMed Scopus (1025) Google Scholar). The extracellular domain of CD44 is extensively modified byN,O-glycosylation and glycosaminoglycan addition (2Lesley J. Hyman R. Kincade P. Adv. Immunol. 1993; 54: 271-335Crossref PubMed Scopus (1025) Google Scholar, 3Lokeshwar V.B. Bourguignon L.Y.W. J. Biol. Chem. 1991; 266: 17983-17989Abstract Full Text PDF PubMed Google Scholar) and is responsible for the binding of extracellular matrix materials such as hyaluronate and collagen (2Lesley J. Hyman R. Kincade P. Adv. Immunol. 1993; 54: 271-335Crossref PubMed Scopus (1025) Google Scholar, 3Lokeshwar V.B. Bourguignon L.Y.W. J. Biol. Chem. 1991; 266: 17983-17989Abstract Full Text PDF PubMed Google Scholar, 4Carter W.G. Wayner E.A. J. Biol. Chem. 1988; 263: 4193-4201Abstract Full Text PDF PubMed Google Scholar) as well as fibronectin (5Jalkanen S. Jalkanen M. J. Cell Biol. 1992; 116: 817-825Crossref PubMed Scopus (447) Google Scholar). The cytoplasmic domain of CD44 contains at least one ankyrin binding site (6Lokeshwar V.B. Fregien N. Bourguignon L.Y.W. J. Cell Biol. 1994; 126: 1099-1109Crossref PubMed Scopus (198) Google Scholar). Post-translational modification of the CD44 cytoplasmic domain by either acylation (7Bourguignon L.Y.W. Kalomiris E. Lokeshwar V.B. J. Biol. Chem. 1991; 266: 11761-11765Abstract Full Text PDF PubMed Google Scholar), protein kinase C (8Kalomiris E.L. Bourguignon L.Y.W. J. Biol. Chem. 1989; 264: 8113-8119Abstract Full Text PDF PubMed Google Scholar), or GTP binding (9Lokeshwar V.B. Bourguignon L.Y.W. J. Biol. Chem. 1992; 267: 22073-22078Abstract Full Text PDF PubMed Google Scholar) enhances the binding between CD44 and ankyrin. The transmembrane interaction between CD44 and the cytoskeleton appears to play an important role in the early signal transduction events leading to cell activation (10Bourguignon L.Y.W. Lokeshwar V.B. Chen X. Kerrick W.G.L. J. Immunol. 1993; 151: 6634-6644PubMed Google Scholar). The gene encoding the CD44 protein (located on human chromosome 11) contains 20 exons, of which only 10 are expressed in the standard form (CD44s). 1The abbreviations used are: CD44s and CD44v, standard and variant forms of CD44, respectively; RT-PCR, reverse transcription-polymerase chain reaction; PBS, phosphate-buffered saline; PAGE, polyacrylamide gel electrophoresis; HA, hyaluronic acid; E1A, adenovirus 5 gene. 1The abbreviations used are: CD44s and CD44v, standard and variant forms of CD44, respectively; RT-PCR, reverse transcription-polymerase chain reaction; PBS, phosphate-buffered saline; PAGE, polyacrylamide gel electrophoresis; HA, hyaluronic acid; E1A, adenovirus 5 gene. The remaining 10 exons are expressed in different combinations in the extracellular domain of variant isoforms of the protein (CD44v), generated by alternative splicing of the mRNA (11Screaton G.R. Bell M.V. Jackson D.G. Cornelis F.B. Gerth U. Bell J.I. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 12160-12164Crossref PubMed Scopus (974) Google Scholar, 12Gunthert U. Cancer Res. 1991; 51: 5292-5297PubMed Google Scholar). Some of these CD44v isoforms are selectively expressed on certain tumor cell surfaces during metastasis (13Bourguignon L.Y.W. Iida N. Welsh C.F. Zhu D. Krongrad A. Pasquale D. J. Neuro-Oncol. 1995; 26: 201-208Crossref PubMed Scopus (54) Google Scholar, 14Tanabe K.K. Ellis L.M. Saya H. Lancet. 1993; 341: 725-726Abstract PubMed Scopus (276) Google Scholar, 15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar). In addition, high levels of CD44s/CD44v expression have been correlated with the progression of various carcinomas (13Bourguignon L.Y.W. Iida N. Welsh C.F. Zhu D. Krongrad A. Pasquale D. J. Neuro-Oncol. 1995; 26: 201-208Crossref PubMed Scopus (54) Google Scholar, 14Tanabe K.K. Ellis L.M. Saya H. Lancet. 1993; 341: 725-726Abstract PubMed Scopus (276) Google Scholar, 15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar). At the present time, information concerning possible factors involved in triggering CD44v formation and CD44s overexpression during tumorigenesis or metastasis is very limited. Ovarian carcinoma is the most lethal tumor of the female genital tract and continues to be the major cause of mortality in female cancer patients. Ovarian cancer has a unique pattern of spreading, which is primarily by intraperitoneal seeding (16Piver M.S. Baker T.R. Piedmonte M. Sandecki A.M. Semin. Oncol. 1991; 18: 177-185PubMed Google Scholar). Recently, it has been shown that ovarian cancer cells express CD44s predominantly, which causes very strong adhesion to peritoneal mesothelium (17Cannistra S.A. Kansas G.S. Niloff J. DeFranzo B. Kim Y. Ottensmeier C. Cancer Res. 1993; 53: 3830-3838PubMed Google Scholar, 18Cannistra S.A. DeFranzo B. Niloff J. Ottensmeier C. Clin. Cancer Res. 1995; 1: 333-342PubMed Google Scholar). It has also been reported that a significant reduction in tumor implants occurred in nude mice 5 weeks after intraperitoneal injection of ovarian cancer cells incubated with anti-CD44 antibody compared with injected cells pretreated with antibodies to other cell surface proteins (17Cannistra S.A. Kansas G.S. Niloff J. DeFranzo B. Kim Y. Ottensmeier C. Cancer Res. 1993; 53: 3830-3838PubMed Google Scholar, 18Cannistra S.A. DeFranzo B. Niloff J. Ottensmeier C. Clin. Cancer Res. 1995; 1: 333-342PubMed Google Scholar). These findings suggest that CD44 plays an important role in the implantation of ovarian cancer metastasis. The HER2 oncogene (also called c-erbB-2 or neu) encodes a 185-kDa (p185 HER2 ) membrane protein that contains a single transmembrane spanning region, two cystine-rich extracellular domains and a tyrosine kinase-associated cytoplasmic domain (19Bargmann C.I. Hung M.C. Weinberg R.A. Cell. 1986; 45: 649-657Abstract Full Text PDF PubMed Scopus (806) Google Scholar). This protein belongs to the epidermal growth factor receptor subgroup of the receptor-linked tyrosine kinase superfamily (20Pele E. Yarden Y. Bioessays. 1993; 15: 815-823Crossref PubMed Scopus (260) Google Scholar). Overexpression and amplification of HER2 oncogenes have been found to correlate with poor survival of many known cancers including ovarian cancer (21Berchuck A. Kamel A. Whitaker R. Kerns B. Olt G. Kinney R. Soper J.T. Dodge R. Clarke-Pearson D.L. Marks P. McKenzie P.Yin. Bast J.R.C. Cancer Res. 1990; 50: 4087-4091PubMed Google Scholar, 22Hung M.C. Zhang X. Yen D.-H. Zhang H.-Z. He G.-P. Zhang T.-Q. Shi D.R. Cancer Lett. 1992; 61: 95-103Crossref PubMed Scopus (76) Google Scholar). Hung and co-worker (23Yu D. Wolf J.K. Scanlon M. Price J.E. Hung M.C. Cancer Res. 1993; 53: 891-898PubMed Google Scholar) have shown that the HER2 oncogene is also overexpressed in certain ovarian carcinoma cell lines, such as SKOV3.ipl, shown to display high tumorigenic and metastatic potential. Therefore, coexpression of both CD44s and p185 HER2 appears to be closely associated with ovarian cancer progression. In this study we have addressed the question of whether there is any interaction between CD44s and p185 HER2 in ovarian tumor cells using various human ovarian carcinoma cell lines including SKOV3.ipl (established from ascites of a nu/nu mouse given an intraperitoneal injection of SKOV-3 human ovarian carcinoma cell line) and derivatives (e.g. two stable transfectant cell lines designated as SKOV3.ipl.E1A (expressing E1A genes) and SKOV3.ipl.Efs (E1A frameshift mutants)) as model systems. Our results clearly indicate that these two surface molecules (i.e.CD44s and p185 HER2 ) are physically linked, functionally coupled, and biosynthetically regulated together. We proposed that the interaction between CD44s and p185 HER2 may be critically important for the onset of tumorigenesis and spreading during ovarian tumor development. The SKOV3.ipl cell line was established from ascites that developed in a nu/nu mouse given an intraperitoneal injection of SKOV-3 human ovarian carcinoma cell line (obtained from the American Type Culture Collection) as described previously (23Yu D. Wolf J.K. Scanlon M. Price J.E. Hung M.C. Cancer Res. 1993; 53: 891-898PubMed Google Scholar). Cells were grown in Dulbecco's modified Eagle's medium, F12 medium supplement (Life Technologies, Inc.) supplemented with 10% fetal bovine serum. Two stable transfectant cell lines, SKOV3.ipl.E1A transfectants (expressing E1A genes) andE1A frameshift mutants (SKOV3.ipl.Efs) were prepared as a control cell line (to make sure the changes in transformation phenotypes (if any) in ipl.E1A transfectants were not due to the selection process or to transfection of the plasmids and thepSV2-neo gene) (23Yu D. Wolf J.K. Scanlon M. Price J.E. Hung M.C. Cancer Res. 1993; 53: 891-898PubMed Google Scholar). Monoclonal rat anti-CD44 antibody (Clone 020, Isotype IgG2b; obtained from CMB-TECH, Inc., Miami, FL) used in this study recognizes a common determinant of the CD44 class of glycoproteins including CD44s and other variant isoforms (15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar) and is capable of precipitating all CD44 variants. Monoclonal mouse anti-p185 HER2 antibody (c-neu-ab-3) and anti-phosphotyrosine antibody were purchased from Oncogene Science, Inc. (Manhasset, NY) andZymed Laboratories Inc. (PY-plusTM, clone PY20, IgG2b; South San Francisco, CA), respectively. Total RNA was extracted from ≈1 g of human ovarian cells (e.g. SKOV3.ipl) and processed for RT-PCR (using specific primer pairs (e.g. exon 5 and 15 primer pairs)) and Southern blot analyses as described previously (15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar). Twenty μg of total RNA isolated from SKOV3.ipl cells was separated on a 1.2% agarose-formaldehyde gel, transferred to nylon membrane, and hybridized to the CD44s cDNA probe at 42 °C for 16 h. Human ovarian carcinoma cells (SKOV3.ipl) and derivatives (e.g. SKOV3.ipl.E1A2 and SKOV3.ipl.Efs) suspended in PBS were surface-labeled using the following biotinylation procedure. Briefly, cells (107cells/ml) were incubated with sulfosuccinimidobiotin (Pierce) (0.1 mg/ml) in labeling for at Cells were with PBS to the cells were used for anti-CD44-mediated immunoprecipitation as described cells were in PBS and in followed by wheat germ chromatography and immunoprecipitation by rat anti-CD44 antibody The was in either or and by or were transferred After with bovine the were incubated with or with anti-p185 HER2 antibody followed by an addition of The were developed using Science, Inc., to the In SKOV3.ipl cells with hyaluronic acid for or pretreated with anti-CD44 followed by for or were processed for anti-CD44-mediated immunoprecipitation to the HER2 This was by transferred to the and incubated with to CD44 anti-phosphotyrosine antibody to p185 HER2 tyrosine kinase In cells and SKOV3.ipl.Efs) were with anti-CD44 or with various such as mouse anti-p185 HER2 and followed by with at for h. After an addition of the were developed using to the After the gel that was was from the gel, and using the following biotinylation procedure. Briefly, protein was incubated with sulfosuccinimidobiotin (0.1 mg/ml) in labeling for at followed by PBS and This was by transferred to the and incubated with After an addition of the were developed using to the In the was by followed by with anti-p185 HER2 anti-CD44 antibody to the described Human ovarian carcinoma cells such as SKOV3.ipl were with PBS and by cells were incubated with rat anti-CD44 antibody and antibody to surface CD44 these cells were by and with mouse anti-p185 HER2 followed by antibody cells were incubated with mouse followed by labeling was observed in such control The and were examined with a Human ovarian carcinoma cell lines including SKOV3.ipl and derivatives and SKOV3.ipl.Efs) were with as described previously (10Bourguignon L.Y.W. Lokeshwar V.B. Chen X. Kerrick W.G.L. J. Immunol. 1993; 151: 6634-6644PubMed Google Scholar). After the cells were in PBS and incubated in PBS 5 at °C to a cells were incubated on as described (10Bourguignon L.Y.W. Lokeshwar V.B. Chen X. Kerrick W.G.L. J. Immunol. 1993; 151: 6634-6644PubMed Google Scholar) at °C for either or in the of a unique rat anti-CD44 antibody After the were in PBS, the cells were in PBS and the was determined by SKOV3.ipl cells with pretreated with anti-CD44 followed by or were in in of Dulbecco's modified Eagle's medium, F12 medium supplement either fetal bovine or for at °C in In each a total of (e.g. or anti-CD44 or was were The in growth of these cells was by in cell using the cell to the by were by a at a of The expression of CD44 is known to be closely correlated with the metastatic and of a of tumor cells including human ovarian tumor cells (13Bourguignon L.Y.W. Iida N. Welsh C.F. Zhu D. Krongrad A. Pasquale D. J. Neuro-Oncol. 1995; 26: 201-208Crossref PubMed Scopus (54) Google Scholar, 14Tanabe K.K. Ellis L.M. Saya H. Lancet. 1993; 341: 725-726Abstract PubMed Scopus (276) Google Scholar, 15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar, S.A. Kansas G.S. Niloff J. DeFranzo B. Kim Y. Ottensmeier C. Cancer Res. 1993; 53: 3830-3838PubMed Google Scholar, 18Cannistra S.A. DeFranzo B. Niloff J. Ottensmeier C. Clin. Cancer Res. 1995; 1: 333-342PubMed Google Scholar). the expression of CD44 at the mRNA total RNA from ovarian tumor cells (SKOV3.ipl) was isolated and by RT-PCR with exon 5 and 15 primer pairs to the of CD44 involved in the alternative splicing of (15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar). of followed by Southern blot we have a major of pairs that with an of CD44s (the standard form) in human ovarian tumor cells blot also a single CD44s that is expressed in these cells data that this the CD44 standard CD44s not CD44 expression at the mRNA not correlate with protein Therefore, it is important to CD44 protein expression in the human ovarian tumor cells. CD44 expression on the surface of ovarian tumor we have surface biotinylation and a specific anti-CD44 antibody that recognizes the standard form of CD44 as well as other variant isoforms (15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar). Our results indicate that a single with CD44s is expressed on the cell surface of human ovarian cells is observed in control rat is used Therefore, we believe that the major CD44 expressed on the surface of the human ovarian tumor cells (SKOV3.ipl) is These results are with findings ovarian cancer cells express CD44s (17Cannistra S.A. Kansas G.S. Niloff J. DeFranzo B. Kim Y. Ottensmeier C. Cancer Res. 1993; 53: 3830-3838PubMed Google Scholar, 18Cannistra S.A. DeFranzo B. Niloff J. Ottensmeier C. Clin. Cancer Res. 1995; 1: 333-342PubMed Google Scholar). CD44s and the p185 HER2 oncogene are overexpressed as in human tumor cells as a of gene amplification (15Iida N. Bourguignon L.Y.W. J. Cell. Physiol. 1995; 162: 127-133Crossref PubMed Scopus (127) Google Scholar, Cell 1996; Google Scholar, Zhang N. Hung M.C. Clin. Cancer Res. Google Scholar). In this study we addressed the question whether there is an interaction between CD44s and p185 HER2 in human ovarian tumor cells. the to cells followed by wheat germ column chromatography and anti-CD44-mediated we found that only one CD44s is by we have a that is with CD44s this the protein was from the gel and processed for biotinylation we found that this is reduced two proteins to p185 HER2 and the other is CD44s as by anti-p185 HER2 and respectively. data indicate that the p185 HER2 associated with the membrane of SKOV3.ipl cells is not p185 HER2 is by the for biotinylation of this This is the we the and to both p185 HER2 and CD44s In addition, we anti-p185 HER2 or followed by or anti-p185 HER2 using Our results indicate that the CD44s is in anti-p185 HER2 materials The p185 HER2 also be in the materials These findings clearly indicate that CD44s and p185 HER2 are closely associated with each other in a interchain disulfide in ovarian tumor cells. on the obtained from cDNA of the human CD44s gene, have been including at the one acid in the transmembrane region, and one acid in the cytoplasmic domain (11Screaton G.R. Bell M.V. Jackson D.G. Cornelis F.B. Gerth U. Bell J.I. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 12160-12164Crossref PubMed Scopus (974) Google Scholar). The of the at the domain of CD44s is not at the present of not of human CD44s has been reported to cause a reduction of binding D. M.S. J. 1996; PubMed Scopus Google Scholar). (e.g. the transmembrane the cytoplasmic in mouse CD44s have been shown to play an important role in signal transduction and cell these to be involved in CD44s acylation for CD44s and ankyrin interaction (7Bourguignon L.Y.W. Kalomiris E. Lokeshwar V.B. J. Biol. Chem. 1991; 266: 11761-11765Abstract Full Text PDF PubMed Google Scholar). Therefore, it is possible that of these of CD44s may also be involved in the disulfide with one or in p185 HER2 The question of which in human CD44s are responsible for disulfide with p185 HER2 is in The of p185 HER2 with other surface molecules via disulfide has been reported previously J. 1996; PubMed Google Scholar). analyses using labeling and also the that CD44s and p185 HER2 are at the of ovarian tumor cells Therefore, we believe that CD44s and p185 HER2 are physically linked in a in ovarian tumor cells such as has been shown to play an important role in important such as of and proteins in the and and cell J. 1992; PubMed Scopus Google Scholar). In addition, of are known to which cell and formation V.B. Iida N. Bourguignon L.Y.W. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar, S. D. J. The of Scholar, S. J. Cell Biol. 1992; PubMed Scopus Google Scholar). CD44 is the major cell surface receptor C. J. Cell Sci. 1992; PubMed Google Scholar) and adhesion in many different cell types L.Y.W. Curr. Top. Membr. 1996; 43: 293-312Crossref Scopus (24) Google J. Hyman R. Kincade P. Adv. Immunol. 1993; 54: 271-335Crossref PubMed Scopus (1025) Google Scholar). binding have been and in the extracellular domain of a of CD44 isoforms M.C. J. Immunol. 1995; Google Scholar). In this study we examined the of ovarian tumor cells to to Our data indicate that ovarian tumor cells display a high of cell adhesion to After with specific rat anti-CD44 the cells were from cell adhesion These results that CD44s is a receptor for cell adhesion in these ovarian adhesion cell adhesion to in SKOV3.ipl human ovarian tumor cells pretreated with anti-CD44 of E1A on cell adhesion to in various human ovarian tumor cells pretreated with anti-CD44 cells pretreated with anti-CD44 were with cells were incubated with as described and binding was determined in the of and from the total an of of at least with a in a Cells were with cells were incubated with as described and binding was determined in the of and from the total an of of at least with a 5 E1A have been shown to be involved in the expression of a of important molecules (e.g. p185 HER2 and in model D. J. Zhang H. Hung M.C. 1992; Google Scholar, A.M. A. E. 1989; PubMed Scopus Google Scholar). the as of and metastasis in p185 HER2 mouse D. J. Zhang H. Hung M.C. 1992; Google Scholar). In is involved in the expression of metastatic tumor gene) in rat A.M. A. E. 1989; PubMed Scopus Google Scholar). These results suggest that E1A play an important role in certain events leading to the metastatic it has been shown that of the E1A gene SKOV3.ipl ovarian cancer cells (e.g. results in the of p185 HER2 metastatic including tumor cell adhesion and (23Yu D. Wolf J.K. Scanlon M. Price J.E. Hung M.C. Cancer Res. 1993; 53: 891-898PubMed Google Scholar, A.M. A. E. 1989; PubMed Scopus Google Scholar). In this study we determined the of E1A on CD44s and p185 HER2 interaction in ovarian tumor cells. Our results indicate that control cells (SKOV3.ipl.Efs) express very high levels of p185 HER2 in transfectants (e.g. E1A p185 HER2 oncogene expression is significantly These results are with findings reported by Hung and M.C. Zhang X. Yen D.-H. Zhang H.-Z. He G.-P. Zhang T.-Q. Shi D.R. Cancer Lett. 1992; 61: 95-103Crossref PubMed Scopus (76) Google D. Wolf J.K. Scanlon M. Price J.E. Hung M.C. Cancer Res. 1993; 53: 891-898PubMed Google Scholar). importantly, CD44s expression in transfectants E1A is also as compared with that in the control cells Our results indicate that of p185 HER2 and CD44s CD44s-mediated cell adhesion D. Bourguignon L.Y.W. 1996; Google Scholar). The that CD44s-mediated cell adhesion to significant reduction in transfectants that down-regulation of these two molecules (e.g. CD44s and p185 HER2 ) blocks CD44s-mediated cell adhesion function. such as not any changes in the as compared with the cells This coupled interaction between CD44s and p185 HER2 may be very important for the early onset of the metastatic during ovarian is also known to be involved in a of high levels of in (e.g. and to be closely associated with tumor progression and metastasis C. D. J. The of Scholar, 1988; PubMed Scopus Google Scholar). In this we found that CD44s-associated p185 HER2 tyrosine kinase 5 and subsequent ovarian tumor cell growth are significantly by as by and an in growth 5 We believe that p185 HER2 kinase activation 5 and cell growth are control and or pretreated with anti-CD44 to binding (10Bourguignon L.Y.W. Lokeshwar V.B. Chen X. Kerrick W.G.L. J. Immunol. 1993; 151: 6634-6644PubMed Google Scholar) and followed by display very levels of CD44s and p185 HER2 tyrosine kinase 5 and and tumor cell growth and These findings clearly that both CD44s-associated p185 HER2 kinase and ovarian tumor cell growth are by Recently, we found that the formation of a HER2 p185 HER2 kinase activation and cell growth also in other ovarian tumor cells (e.g. SKOV-3 and as well as tumor cells (e.g. and Y. H. A. N. and of other molecules epidermal growth ascites a factor from bovine and factors in have been as for the activation of p185 HER2 tyrosine kinase (20Pele E. Yarden Y. Bioessays. 1993; 15: 815-823Crossref PubMed Scopus (260) Google Scholar). Therefore, we believe that the results of this study that the for HA, may also play an important role in CD44s-associated p185 HER2 kinase for the onset of tumor cell growth and spreading during ovarian tumor development. We the of J. Bourguignon in the of this