Reactive Oxygen Species Mediate Met Receptor Transactivation by G Protein-coupled Receptors and the Epidermal Growth Factor Receptor in Human Carcinoma Cells

Abstract

Cross-communication between the Met receptor tyrosine kinase and the epidermal growth factor receptor (EGFR) has been proposed to involve direct association of both receptors and EGFR kinase-dependent phosphorylation. Here, we demonstrate that in human hepatocellular and pancreatic carcinoma cells the Met receptor becomes tyrosine phosphorylated not only upon EGF stimulation but also in response to G protein-coupled receptor (GPCR) agonists. Whereas specific inhibition of the EGFR kinase activity blocked EGF- but not GPCR agonist-induced Met receptor transactivation, it was abrogated in the presence of a reducing agent or treatment of cells with a NADPH oxidase inhibitor. Both GPCR ligands and EGF are further shown to increase the level of reactive oxygen species within the cell. Interestingly, stimulation of the Met receptor by either GPCR agonists, EGF or its cognate ligand HGF, resulted in release of Met-associated β-catenin and in its Met-dependent translocation into the nucleus, as analyzed by small interfering RNA-mediated knockdown of the Met receptor. Our results provide a new molecular explanation for cell surface receptor cross-talk involving the Met receptor and thereby link the wide diversity of GPCRs and the EGFR to the oncogenic potential of Met signaling in human carcinoma cells. Cross-communication between the Met receptor tyrosine kinase and the epidermal growth factor receptor (EGFR) has been proposed to involve direct association of both receptors and EGFR kinase-dependent phosphorylation. Here, we demonstrate that in human hepatocellular and pancreatic carcinoma cells the Met receptor becomes tyrosine phosphorylated not only upon EGF stimulation but also in response to G protein-coupled receptor (GPCR) agonists. Whereas specific inhibition of the EGFR kinase activity blocked EGF- but not GPCR agonist-induced Met receptor transactivation, it was abrogated in the presence of a reducing agent or treatment of cells with a NADPH oxidase inhibitor. Both GPCR ligands and EGF are further shown to increase the level of reactive oxygen species within the cell. Interestingly, stimulation of the Met receptor by either GPCR agonists, EGF or its cognate ligand HGF, resulted in release of Met-associated β-catenin and in its Met-dependent translocation into the nucleus, as analyzed by small interfering RNA-mediated knockdown of the Met receptor. Our results provide a new molecular explanation for cell surface receptor cross-talk involving the Met receptor and thereby link the wide diversity of GPCRs and the EGFR to the oncogenic potential of Met signaling in human carcinoma cells. The proto-oncogene MET encodes the prototypic receptor tyrosine kinase (RTK) 1The abbreviations used are: RTK, receptor tyrosine kinase; HGF, hepatocyte growth factor; EGFR, epidermal growth factor receptor; ROS, reactive oxygen species; LPA, lysophosphatidic acid; EGCG, epigallocatechin gallate; DCF-DA, 2′,7′-dichlorofluorescein diacetate; PIPES, 1,4-piperazinediethanesulfonic acid; siRNA, small interfering RNA. for the scatter factor receptor family (1Giordano S. Ponzetto C. Di Renzo M.F. Cooper C.S. Comoglio P.M. Nature. 1989; 339: 155-156Crossref PubMed Scopus (424) Google Scholar). It has been originally discovered as the product of a human oncogene, tpr-met (2Cooper C.S. Park M. Blair D.G. Tainsky M.A. Huebner K. Croce C.M. Vande Woude G.F. Nature. 1984; 311: 29-33Crossref PubMed Scopus (782) Google Scholar, 3Park M. Dean M. Kaul K. Braun M.J. Gonda M.A. Vande Woude G. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6379-6383Crossref PubMed Scopus (483) Google Scholar), and since then has been recognized as a key mediator of invasive growth in both physiological but also pathophysiological signaling. Stimulation by its cognate ligand hepatocyte growth factor (HGF)/scatter factor induces various biological responses such as cell dissociation, migration, cell scattering, and invasion, but also stimulates cell proliferation or survival depending on the cellular context (4Trusolino L. Comoglio P.M. Nat. Rev. Cancer. 2002; 2: 289-300Crossref PubMed Scopus (631) Google Scholar, 5Zhang Y.W. Vande Woude G.F. J. Cell. Biochem. 2003; 88: 408-417Crossref PubMed Scopus (272) Google Scholar). Whereas Met exerts essential developmental functions (6Birchmeier C. Gherardi E. Trends Cell Biol. 1998; 8: 404-410Abstract Full Text Full Text PDF PubMed Scopus (508) Google Scholar), deregulated Met receptor signaling because of overexpression, mutation, or autocrine growth factor loops has been frequently implicated in tumor invasion and metastasis (4Trusolino L. Comoglio P.M. Nat. Rev. Cancer. 2002; 2: 289-300Crossref PubMed Scopus (631) Google Scholar) of tumor cells. The Met RTK consists of a single membrane spanning β-subunit of 145 kDa, which is linked by disulfide bridges to an extracellular α-chain of 50 kDa (1Giordano S. Ponzetto C. Di Renzo M.F. Cooper C.S. Comoglio P.M. Nature. 1989; 339: 155-156Crossref PubMed Scopus (424) Google Scholar). Upon HGF stimulation two receptor molecules dimerize and cross-phosphorylate each other, thereby creating binding sites for signaling molecules within the cell. By recruiting adaptor proteins such as Gab1 and Grb2 the Met receptor induces activation of phosphatidylinositol 3-kinase/Akt, phospholipase-γ, extracellular signal-regulated kinase 1/2, and the phosphorylation of signal transducers and activators of transcription factors. Moreover, receptor-associated β-catenin was identified as a signaling partner of the Met receptor (7Monga S.P. Mars W.M. Pediaditakis P. Bell A. Mule K. Bowen W.C. Wang X. Zarnegar R. Michalopoulos G.K. Cancer Res. 2002; 62: 2064-2071PubMed Google Scholar, 8Hiscox S. Jiang W.G. Biochem. Biophys. Res. Commun. 1999; 261: 406-411Crossref PubMed Scopus (101) Google Scholar). In the cell, β-catenin exerts a dual function: it allows tight intercellular adhesion, as a member of cell adherence junctions, linking E-cadherin to the cytoskeleton (9Conacci-Sorrell M. Zhurinsky J. Ben-Ze'ev A. J. Clin. Investig. 2002; 109: 987-991Crossref PubMed Scopus (525) Google Scholar) and it translocates into the nucleus to induce gene expression in complex with the transcription factor TCF upon activation of the Wnt-signaling pathway. Independent of Wnt signaling HGF is able to induce β-catenin phosphorylation (10Hiscox S. Jiang W.G. Anticancer Res. 1999; 19: 509-517PubMed Google Scholar, 11Shibamoto S. Hayakawa M. Takeuchi K. Hori T. Oku N. Miyazawa K. Kitamura N. Takeichi M. Ito F. Cell Adhes. Commun. 1994; 1: 295-305Crossref PubMed Scopus (403) Google Scholar), leading to dissociation of the Met-β-catenin complex, nuclear translocation of β-catenin, and concomitant induction of TCF target genes (7Monga S.P. Mars W.M. Pediaditakis P. Bell A. Mule K. Bowen W.C. Wang X. Zarnegar R. Michalopoulos G.K. Cancer Res. 2002; 62: 2064-2071PubMed Google Scholar, 12Muller T. Bain G. Wang X. Papkoff J. Exp. Cell Res. 2002; 280: 119-133Crossref PubMed Scopus (154) Google Scholar). Cross-talk between cell surface receptors can occur in several different ways. The most direct mechanism is receptor heterodimerization that is well described for members of the EGFR family (13Yarden Y. Sliwkowski M.X. Nat. Rev. Mol. Cell. Biol. 2001; 2: 127-137Crossref PubMed Scopus (5670) Google Scholar) or for Met and its relative RON (14Follenzi A. Bakovic S. Gual P. Stella M.C. Longati P. Comoglio P.M. Oncogene. 2000; 19: 3041-3049Crossref PubMed Scopus (161) Google Scholar). Also less related receptors have been shown to be able to associate such as EGFR and platelet-derived growth factor receptor (15Saito Y. Haendeler J. Hojo Y. Yamamoto K. Berk B.C. Mol. Cell. Biol. 2001; 21: 6387-6394Crossref PubMed Scopus (157) Google Scholar) or Met and semaphorin receptors (16Giordano S. Corso S. Conrotto P. Artigiani S. Gilestro G. Barberis D. Tamagnone L. Comoglio P.M. Nat. Cell Biol. 2002; 4: 720-724Crossref PubMed Scopus (364) Google Scholar). In the case of EGFR and Met receptor cross-communication has been reported to occur on different levels: EGFR signal transactivation induces metalloprotease-mediated ectodomain shedding of Met (17Nath D. Williamson N.J. Jarvis R. Murphy G. J. Cell Sci. 2001; 114: 1213-1220Crossref PubMed Google Scholar) and aberrant EGFR activation elevates Met expression and phosphorylation in thyroid carcinoma cells (18Bergstrom J.D. Westermark B. Heldin N.E. Exp. Cell Res. 2000; 259: 293-299Crossref PubMed Scopus (92) Google Scholar). Moreover, EGFR function has been implicated in HGF-induced hepatocyte proliferation (19Scheving L.A. Stevenson M.C. Taylormoore J.M. Traxler P. Russell W.E. Biochem. Biophys. Res. Commun. 2002; 290: 197-203Crossref PubMed Scopus (59) Google Scholar), and a possible heterodimer formation of both receptors has been suggested (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar, 21Pai R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar). In addition to RTK cross-talk, also completely unrelated cell surface receptors are able to communicate and influence each other. The prototype for such a pathway is the GPCR-induced EGFR signal transactivation (22Daub H. Weiss F.U. Wallasch C. Ullrich A. Nature. 1996; 379: 557-560Crossref PubMed Scopus (1329) Google Scholar). Treatment of cells with GPCR agonists induces phosphorylation of the EGFR by metalloprotease-dependent release of EGF-like ligands (23Prenzel N. Zwick E. Daub H. Leserer M. Abraham R. Wallasch C. Ullrich A. Nature. 1999; 402: 884-888Crossref PubMed Scopus (1501) Google Scholar), thereby coupling GPCRs to EGFR characteristic downstream signaling such as or the phosphatidylinositol pathway A. N. Ullrich A. Cancer Res. 2002; 62: Google Scholar). In addition to the EGFR have been shown to be in response to GPCR the growth receptor P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), receptor Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google Scholar), platelet-derived growth factor receptor J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. Daub H. A. P. Ullrich A. G. T. Proc. Natl. Acad. Sci. U. S. A. 1998; PubMed Scopus Google Scholar), and the growth factor receptor D. L. C. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). cross-talk can also occur in a involving for tyrosine such as Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google Scholar, T. Berk B.C. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). Moreover, implicated the reactive oxygen species as signaling in RTK activation E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. K. T. PubMed Scopus Google Scholar, M. L. S. Biol. 2001; 21: PubMed Scopus Google Scholar, S. Y. S. and J. Scholar, Y. Berk B.C. J. Mol. Cell 2001; Full Text PDF PubMed Scopus Google Scholar). inhibition of results in an the to the phosphorylated of the increase in has been reported not only RTK but also in response to GPCR stimulation in cells and cells C. J. P. C. C. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar). Interestingly, have been with the Cancer Res. Google Scholar). various cellular for have been described J. 2000; PubMed Google Scholar), NADPH are as the of upon growth factor or stimulation S. Y. S. and J. Scholar, J.D. 2002; PubMed Scopus Google Scholar, T. Cell Biol. 2003; PubMed Scopus Google Scholar). Whereas have been originally discovered in have also been in cells J.D. 2002; PubMed Scopus Google Scholar). of the of the NADPH oxidase was able to induce of cells B. J. X. D. J.D. Nature. 1999; PubMed Scopus Google Scholar). Moreover, of NADPH oxidase tumor formation in J. E. R. S. J.D. Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google Scholar), and and J. R. B. C. M. S. J.D. Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google Scholar) reported that by NADPH oxidase expression in a Here, we and GPCRs and EGFR the Met Our results provide that the Met receptor is by both GPCRs and EGFR in pancreatic and hepatocellular carcinoma cell transactivation the of by NADPH Interestingly, β-catenin Met receptor and translocates into the nucleus, an shown to be with TCF target gene expression and cell and The epigallocatechin and and HGF The 2′,7′-dichlorofluorescein was Cell cell The pancreatic carcinoma cell was in with and cells in essential with and and cells in with and in and for to to cells to with and agonists as in the and then for on in 50 and by for the and of for with of in for and to proteins to to The human EGFR has been (23Prenzel N. Zwick E. Daub H. Leserer M. Abraham R. Wallasch C. Ullrich A. Nature. 1999; 402: 884-888Crossref PubMed Scopus (1501) Google Scholar). Met was the was with the was with a shown are for was the of by in and for to stimulation cells with for and as for cells and in with analyzed on a was as described 1994; PubMed Scopus Google Scholar). with as in the cells in and a was a PIPES, and The was as the The was by the in PIPES, for and of the The was in PIPES, in a by and The was as the was the and of to and MET expression was by the in a the of the as described M. L. 2002; PubMed Scopus Google Scholar). a cells with a the in or an specific for cells in for and then with of proteins by in each with to human MET was used to between two are as of was GPCR and EGFR Stimulation Met we in the Met receptor can function as a downstream signaling partner of different membrane as a of for signaling we used to the phosphorylation of receptor in response to treatment with different GPCR agonists. shown in Met receptor tyrosine phosphorylation was in response to different GPCR ligands in the pancreatic carcinoma cell as well as in the hepatocellular carcinoma cell and activation within and as shown for and cells a and transactivation of the Met receptor. Interestingly, not only GPCR ligands but also EGF stimulation of the Met receptor Met phosphorylation in was in of and to that on stimulation with HGF Met transactivation is of EGFR kinase and and cells with or an of for and with EGF or HGF as for of cell with proteins with and with EGFR phosphorylation was analyzed by of cell with and with The with of was the for stimulation for inhibition GPCR-induced Met Independent EGFR receptor cross-talk mechanism is GPCR-induced EGFR signal The mechanism was shown to involve the shedding of an EGF-like ligand have described the association between Met and EGFR and the phosphorylation of Met by the EGFR (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar, 21Pai R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar), we the transactivation EGFR kinase the Met receptor as a direct signaling partner of the we used the EGFR to phosphorylation in of cells with blocked GPCR-induced EGFR signal transactivation (22Daub H. Weiss F.U. Wallasch C. Ullrich A. Nature. 1996; 379: 557-560Crossref PubMed Scopus (1329) Google Scholar, N. Zwick E. Daub H. Leserer M. Abraham R. Wallasch C. Ullrich A. Nature. 1999; 402: 884-888Crossref PubMed Scopus (1501) Google Scholar) but not GPCR agonist-induced phosphorylation of the Met receptor. that EGFR activity is for GPCR-induced Met receptor transactivation and Met transactivation by EGF was abrogated by with and as the EGFR kinase is to the of direct association or an with the Met receptor. In to the by and (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar) we to direct binding between Met and EGFR in hepatocellular and pancreatic carcinoma cells not and in Cell of tyrosine by growth of has been suggested to for the activation of E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. K. T. PubMed Scopus Google Scholar, M. L. S. Biol. 2001; 21: PubMed Scopus Google Scholar, S. Y. S. and J. Scholar, T. Cell Biol. 2003; PubMed Scopus Google Scholar). Met receptor transactivation and we Met receptor activation is by a increase of used the to is a which is the cell. of the of cells with and stimulation with EGF or the GPCR ligands and an increase of reactive oxygen species within the cell and of and cells with the reducing agent with EGF- and GPCR-induced Met receptor the of in signaling pathway. the treatment not EGFR signal transactivation and results demonstrate that are in Met receptor Met NADPH of implicated NADPH in the growth factor of in S. Y. S. and J. Scholar, T. Cell Biol. 2003; PubMed Scopus Google Scholar, and T. 2000; PubMed Scopus Google Scholar). NADPH oxidase are in Met receptor transactivation, we used the NADPH to with NADPH and analyzed Met receptor phosphorylation by shown in of NADPH oxidase function with both and Met phosphorylation in and EGFR signal transactivation by GPCRs was not by treatment and The small has been to be of the of the NADPH oxidase complex and has been implicated in the of NADPH activity M. K. T. Biochem. J. 1996; PubMed Scopus Google Scholar). Moreover, has been shown as a downstream signaling target of both GPCRs and we used the which of the and to with function G. Nat. Rev. Mol. Cell. Biol. 2001; 2: PubMed Scopus Google Scholar). with abrogated both and Met transactivation and EGFR signal transactivation was not and that NADPH oxidase activity is for Met Met of the in and has been shown to be with the Met receptor in and hepatocellular carcinoma cells S. Jiang W.G. Biochem. Biophys. Res. Commun. 1999; 261: 406-411Crossref PubMed Scopus (101) Google Scholar, R. R. Clin. Exp. 2003; PubMed Scopus Google Scholar). of Met hepatocellular carcinoma cells tyrosine phosphorylated β-catenin Stimulation of Met transactivation by both GPCR ligands and EGF the dissociation of receptor complex the translocation of β-catenin in response to Met transactivation we used the to and that stimulation of as well as cells with LPA, or HGF translocation of β-catenin the membrane to the and the increase of β-catenin in the the β-catenin translocation in response to GPCR agonists or EGF on the Met we used a to knockdown the Met receptor shown in of cells with a expression knockdown of Stimulation of cells with LPA, or HGF to induce nuclear of β-catenin Interestingly, knockdown of the Met receptor resulted in a level of nuclear β-catenin in cells with cells. Cross-talk between cell surface receptors has been recognized as a signaling mechanism to the cellular such as members of the EGFR family are of thereby downstream signaling (13Yarden Y. Sliwkowski M.X. Nat. Rev. Mol. Cell. Biol. 2001; 2: 127-137Crossref PubMed Scopus (5670) Google Scholar). further of was by the of the cross-talk mechanism with EGFR signal transactivation as the prototypic signaling pathway (22Daub H. Weiss F.U. Wallasch C. Ullrich A. Nature. 1996; 379: 557-560Crossref PubMed Scopus (1329) Google Scholar, N. Zwick E. Daub H. Leserer M. Abraham R. Wallasch C. Ullrich A. Nature. 1999; 402: 884-888Crossref PubMed Scopus (1501) Google Scholar). in addition to the involving and receptors have also been reported L. M. C. L. F. L. G. P. J. 1998; 17: PubMed Scopus Google Scholar, L. A. Comoglio P.M. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, T. K. K. H. N. M. M. M. T. H. T. Y. T. Y. T. Nature. PubMed Scopus Google Scholar), is on Here, we provide that the EGFR the Met RTK in human carcinoma cells. cross-talk between receptors on the level and Met ectodomain shedding in response to EGFR activation (17Nath D. Williamson N.J. Jarvis R. Murphy G. J. Cell Sci. 2001; 114: 1213-1220Crossref PubMed Google Scholar, J.D. Westermark B. Heldin N.E. Exp. Cell Res. 2000; 259: 293-299Crossref PubMed Scopus (92) Google Scholar). association of Met with and phosphorylation by the EGFR has been suggested as the mechanism of cross-communication (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar). EGF- and Met phosphorylation and to cells that EGFR because of gene in hepatocellular carcinoma cell of both the transactivation of Met of Met and EGFR (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar). we association of Met and EGFR in hepatocellular and pancreatic carcinoma we an mechanism heterodimerization for Met receptor a of cells with the we that reactive oxygen species are in response to EGF treatment The of in cross-talk mechanism was further by the that with the reducing agent with Met receptor transactivation Whereas different cellular for have been reported J. 2000; PubMed Google Scholar), provide for the of NADPH and and have been implicated in the and of in response to growth factor treatment S. Y. S. and J. Scholar, J. 2000; PubMed Google Scholar, T. Cell Biol. 2003; PubMed Scopus Google Scholar, T. 2000; PubMed Scopus Google Scholar). Moreover, the that inhibition of the small and by with Met transactivation also an of NADPH as has been shown to the activity of the NADPH In addition to also stimulation of cells with GPCR ligands such as LPA, or the and phosphorylation of the Met receptor In to Met transactivation we demonstrate that GPCR-induced Met phosphorylation on the of by NADPH and and and that stimulation with LPA, or EGF a with stimulation with the can be as the by in cells be in its and which are in case the In only a of the the cell can be in response to growth factor The increase in to a increase of Met receptor which is to stimulation with HGF Interestingly, the level of receptor phosphorylation is with the level of EGFR transactivation by GPCR and R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar) reported that is to induce Met receptor phosphorylation in carcinoma cells. suggested an mechanism involving the EGFR, because with the EGFR Met activation R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar). Interestingly, EGF treatment not Met phosphorylation. treatment of hepatocellular and pancreatic carcinoma cells with not Met phosphorylation in response to GPCR agonists, that GPCR-induced Met phosphorylation not on EGFR kinase activity in cellular the EGFR is able to induce E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), in cellular EGFR signal transactivation be used by GPCRs that are to the of reactive oxygen to induce Met The of in Met transactivation is by the that platelet-derived growth factor induces in cells A. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). The has been in cells in response to EGF treatment E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). in carcinoma cells that have been used in the by and R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar), of NADPH have been H. M. H. M. 2000; PubMed Scopus Google Scholar, A. L. G. J. 2003; PubMed Scopus Google Scholar), the results can provide a molecular explanation for activation of Met in response to in the cellular reported by Stolz and (20Jo M. Stolz D.B. Esplen J.E. Dorko K. Michalopoulos G.K. Strom S.C. J. Biol. Chem. 2000; 275: 8806-8811Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar) and R. Nakamura T. Moon W.S. Tarnawski A.S. FASEB J. 2003; 17: 1640-1647Crossref PubMed Scopus (161) Google Scholar). have been implicated in receptor cross-talk in in or such as EGFR transactivation M. L. S. Biol. 2001; 21: PubMed Scopus Google Scholar). Our results and demonstrate of GPCR and Met cross-talk in cells of hepatocellular and pancreatic the association between the Met receptor and β-catenin (7Monga S.P. Mars W.M. Pediaditakis P. Bell A. Mule K. Bowen W.C. Wang X. Zarnegar R. Michalopoulos G.K. Cancer Res. 2002; 62: 2064-2071PubMed Google Scholar, 8Hiscox S. Jiang W.G. Biochem. Biophys. Res. Commun. 1999; 261: 406-411Crossref PubMed Scopus (101) Google Scholar, 12Muller T. Bain G. Wang X. Papkoff J. Exp. Cell Res. 2002; 280: 119-133Crossref PubMed Scopus (154) Google Scholar). Interestingly, we that in the hepatocellular carcinoma cell and in the pancreatic carcinoma cell not only direct Met activation by HGF but also Met transactivation by GPCR agonists and EGF stimulates the nuclear translocation of β-catenin has been with transcription of TCF target genes that are in to and the of an invasive (9Conacci-Sorrell M. Zhurinsky J. Ben-Ze'ev A. J. Clin. Investig. 2002; 109: 987-991Crossref PubMed Scopus (525) Google Scholar, J. N. Y. Acad. Sci. 2000; PubMed Scopus Google Scholar, M. A. Rev. 2003; PubMed Scopus Google Scholar). The Met receptor has been shown to be to invasive growth in both the physiological and pathophysiological signaling context (4Trusolino L. Comoglio P.M. Nat. Rev. Cancer. 2002; 2: 289-300Crossref PubMed Scopus (631) Google Scholar). Interestingly, implicated of Met and EGFR in tumor and in and hepatocellular In the of both Met and the EGFR is with tumor tumor and survival M. M. J. Clin. Cancer Res. 2002; 8: Google Scholar). M. M. A. C. G. Y. M. M.F. Mol. 2003; PubMed Scopus Google Scholar) reported the presence of of for both in in and in with tumor and Y. Y. K. Biochem. Biophys. Res. Commun. 2003; PubMed Scopus Google Scholar) that the invasive activity of cells by the of The Met receptor and its ligand HGF are able to induce complex biological responses such as EGF is not able to the signaling pathway EGFR and Met receptor signaling. are two between Met receptor stimulation with its cognate ligand HGF and transactivation of HGF stimulation induces the receptor phosphorylation Met receptor transactivation by GPCRs or EGFR a different of receptor phosphorylation. Both a activity of or activation to Met stimulation with HGF the level of phosphorylation in response to Met receptor transactivation is with the phosphorylation by HGF of which are used to induce for results provide a molecular mechanism for transactivation of the Met receptor and to cross-talk involving GPCRs and to the of the Met receptor in tumor invasion, are of for the of and metastasis in response to growth factor stimulation involving the Met receptor. M. for of the