Identification of a Novel Ligand-Receptor Pair Constitutively Activated by ras Oncogenes

Abstract

The Ras signaling pathway is thought to control the expression of a subset of yet to be defined genes that are crucial for cell growth and differentiation. Here we have identified by differential display a novel oncogenic Ras target, mob-5, encoding a 23-kDa cytokine-like secreted protein. Mob-5 expression could be induced by oncogenic Ha-ras and Ki-ras, but not by normal ras activation. Inhibitors of both Ha-Ras and mitogen-activated protein kinase kinase completely abolished the mob-5 expression in ras transformed cells, with concomitant loss of the transformation phenotype. Using an alkaline phosphatase-tagged Mob-5 as ligand, a putative Mob-5 receptor was identified on the cell surface of oncogenic ras transformed cells. Thus, the Mob-5/Mob-5 receptor may represent a novel putative autocrine loop coordinately activated by rasoncogenes. The Ras signaling pathway is thought to control the expression of a subset of yet to be defined genes that are crucial for cell growth and differentiation. Here we have identified by differential display a novel oncogenic Ras target, mob-5, encoding a 23-kDa cytokine-like secreted protein. Mob-5 expression could be induced by oncogenic Ha-ras and Ki-ras, but not by normal ras activation. Inhibitors of both Ha-Ras and mitogen-activated protein kinase kinase completely abolished the mob-5 expression in ras transformed cells, with concomitant loss of the transformation phenotype. Using an alkaline phosphatase-tagged Mob-5 as ligand, a putative Mob-5 receptor was identified on the cell surface of oncogenic ras transformed cells. Thus, the Mob-5/Mob-5 receptor may represent a novel putative autocrine loop coordinately activated by rasoncogenes. farnesyltransferase inhibitor mitogen-activated protein rat intestinal epithelial polymerase chain reaction base pairs isopropyl-1-thio-β-d-galactopyranoside alkaline phosphatase interleukin 10 Ras proteins are among the most important molecular switch molecules that relay mitogenic or differentiation signals from the cell surface to the nucleus where selective gene expression takes place. Oncogenic mutations lock the Ras proteins into a permanent “on” position, leading to unregulated cell proliferation, which is the hallmark of cancer (1Barbacid M. Annu. Rev. Biochem. 1987; 56: 779-827Crossref PubMed Scopus (3778) Google Scholar, 2Lowy D.R. Willumsen B.M. Annu. Rev. Biochem. 1993; 62: 851-891Crossref PubMed Scopus (1124) Google Scholar). Mutations in ras oncogenes have been detected in over 90% of pancreatic cancers and 50% of colorectal cancer (3Kiaris H. Spandidos D.A. Int. J. Oncol. 1995; 7: 413-421PubMed Google Scholar). In contrast to the extensive body of knowledge related to the genetics of ras activation (4Boguski M.S. McCormick F. Nature. 1993; 366: 643-654Crossref PubMed Scopus (1761) Google Scholar), relatively little is known of the transcriptional events triggered by Ras. Of a fewras target genes previously identified, including transin/stromelysin-1 (5Matrisian L.M. Glaichenhaus N. Gesnel M-C. Breathnach R. EMBO J. 1985; 4: 1435-1440Crossref PubMed Scopus (227) Google Scholar), glucose transporter (6Flier J. Mueckler M.M. Usher P. Lodish H.F. Science. 1987; 235: 1492-1495Crossref PubMed Scopus (688) Google Scholar, 7Godwin A. Lieberman M. Oncogene. 1990; 5: 1231-1241PubMed Google Scholar), Pai-2 (8Cohen L.R. Niclas J. Lee W.M.F. Wun T.-C. Crowley C.W. Levinson A.D. Sadler J.E. Shuman M.A. J. Biol. Chem. 1989; 264: 8375-8383Abstract Full Text PDF PubMed Google Scholar), heparin binding epidermal growth factor (9McCarthy S.A. Samuels M.L. Pritchard C.A. Abraham J.A. McMahon M. Genes Dev. 1995; 9: 1953-1964Crossref PubMed Scopus (170) Google Scholar), and mob-1/IP10 (10Liang P. Averboukh L. Zhu W. Pardee A.B. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12515-12519Crossref PubMed Scopus (59) Google Scholar,11Zhang R. Zhang H. Zhu W. Coffey R. Pardee A.B. Liang P. Oncogene. 1997; 14: 1607-1610Crossref PubMed Scopus (27) Google Scholar), nearly all were shown to be inducible in normal cells by serum growth factors, likely through the activation of endogenousras (12Dobrowolski S. Harter M. Stacey D.W. Mol. Cell. Biol. 1994; 14: 5441-5449Crossref PubMed Scopus (99) Google Scholar, 13Durkin J.P. Whitfield J.F. Mol. Cell. Biol. 1986; 6: 1386-1392Crossref PubMed Scopus (32) Google Scholar, 14Taylor S.J. Shalloway D. Curr. Biol. 1996; 6: 1621-1627Abstract Full Text Full Text PDF PubMed Scopus (352) Google Scholar). One long standing puzzle surroundingras has been that although the effects of Ras activation are very similar to those of serum growth factors,ras-transformed cells may be oncogenic, whereas the parental cells continuously exposed to serum growth factors are not. To search for additional ras target genes, especially those that may be oncogenic ras-specific, optimized differential display technology (15Liang P. Pardee A.B. Science. 1992; 257: 967-971Crossref PubMed Scopus (4700) Google Scholar, 16Liang P. Zhu W. Zhang X. Guo Z. O'Connell R. Averboukh L. Wang F. Pardee A.B. Nucleic Acids Res. 1994; 22: 5763-5764Crossref PubMed Scopus (309) Google Scholar) was employed to systematically search for such genes in comparative studies involving two carefully chosen paradigms. Since the development of the method, it has been realized that differential display, like other competitive methods such as DNA microarray, is mechanism-based, rather than function-based gene screening tool (17Liang P. Methods. 1998; 16: 361-364Crossref PubMed Scopus (26) Google Scholar). Therefore, much effort should be made to establish the comparative systems based on as direct and simple a mechanism as possible to identify the relevant genes. To this end, alteration in gene expression in Rat-1 embryo fibroblasts upon conditional expression of oncogenic Ha-ras was analyzed to identify the early ras inducible genes. In the other complementary screening, changes in gene expression was followed in the oncogenic Ha-ras transformed Rat-1 cells upon the treatment with inhibitors of either Ras farnesyltransferase (FTI)1 (18Kohl N.E. Mosser S.D. deSolms S.J. Giuliani E.A. Pompiano D.L. Graham S.L. Smith R.L. Scolnick E.M. Oliff A. Gibbs J.B. Science. 1993; 260: 1934-1937Crossref PubMed Scopus (619) Google Scholar) or MAP kinase kinase (19Pang L. Sawada T. Decker S.J. Saltiel A.R. J. Biol. Chem. 1995; 270: 13585-13588Abstract Full Text Full Text PDF PubMed Scopus (896) Google Scholar), which is one of the major Ras downstream kinases required for cell transformation. Here we describe the identification and biochemical characterization of mob-5, the only oncogenicras-specific gene identified in both paradigms. We demonstrate that mob-5 encodes a cytokine-like secreted protein, which binds specifically to its putative cell surface receptor (Mob-5R) expressed by the ras-transformed cells, but not by their normal parental controls. We propose that the coordinate activation of this novel ligand/receptor loop may play an important role inras oncogene-mediated neoplasia. All cell lines including Rat1, Rat1(ras), Rat-1:iRas (10Liang P. Averboukh L. Zhu W. Pardee A.B. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12515-12519Crossref PubMed Scopus (59) Google Scholar, 35Zhang R. Averboukh L. Zhu W. Zhang H. Jo H. Dempsey P.J. Coffey R., A. Pardee A.B. Liang P. Mol. Cell. Biol. 1998; 18: 6131-6141Crossref PubMed Scopus (131) Google Scholar), rat intestinal epithelial (RIE), RIE(Ha-ras), and RIE(Ki-ras) (Ko, 1995) were routinely grown in Dulbecco's modified Eagle's medium (Life Technologies, Inc.) with 10% bovine calf serum (HyClone, Logan, UT) and 1% penicillin-streptomycin (Life Technologies, Inc.) at 37 °C with 10% CO2. 293T cells and their derivatives were maintained under the same condition as above except 10% fetal bovine serum (HyClone, Logan, UT) was used in place of 10% bovine calf serum. Serum starvation and restimulation of the Rat-1 cells in the absence and presence of cyclohexamide (Sigma) was carried out essentially as described previously (11Zhang R. Zhang H. Zhu W. Coffey R. Pardee A.B. Liang P. Oncogene. 1997; 14: 1607-1610Crossref PubMed Scopus (27) Google Scholar). Total RNA from cells were purified using the RNApure reagent following the manufacture's instruction (GenHunter Corp., Nashville, TN). DNase I treatment of RNA prior to differential display was carried out using the MessageClean kit (GenHunter Corp., Nashville, TN). Differential display PCR reactions were setup in 96-well PCR plates (Perkin-Elmer) by the Beckman Biomek 2000 automated liquid dispensing workstation using one-base anchored oligo(dT) primers and rationally designed arbitrary 13-mers (16Liang P. Zhu W. Zhang X. Guo Z. O'Connell R. Averboukh L. Wang F. Pardee A.B. Nucleic Acids Res. 1994; 22: 5763-5764Crossref PubMed Scopus (309) Google Scholar) from the RNAimage kits (GenHunter Corp., Nashville, TN). The cDNAs were amplified in the presence of [α-33P]dATP (NEN Life Science Products) using Taq DNA polymerase (Qiagene) and separated on 6% denaturing polyacrylamide gels (National Diagnostic, Atlanta, GA). Total RNA was isolated from Ha-Ras-transformed rat embryo fibroblasts as described (16Liang P. Zhu W. Zhang X. Guo Z. O'Connell R. Averboukh L. Wang F. Pardee A.B. Nucleic Acids Res. 1994; 22: 5763-5764Crossref PubMed Scopus (309) Google Scholar) and then purified by using a The kit was used to the following the by the were for mob-5 using mob-5 from differential were as and by the molecular of the The was amplified from RNA isolated from cancer by based on the H. Z. Oncogene. 1995; Google Scholar). The was carried out in a of of and of at 37 °C for at °C to the of the reaction was used as for PCR of using of and The PCR was carried out in of PCR of and of Taq polymerase an of at of at at and at °C the at the were analyzed on a The amplified was into the and completely the rat Mob-5 its was by PCR using the Mob-5 as a The primers used were and The PCR was into the Nashville, and was then and into of the expression the expression of protein, the of the putative was amplified by PCR using primers and The PCR was into the and then as into the of The were transformed into cells to Mob-5 and with (Life the Mob-5 and were as proteins in the and purified on a under denaturing to the The purified proteins were in to the and then into to the of mob-5 was by PCR using the mob-5 as a The was the and of Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, A. P. H. H. D. Proc. Natl. Acad. Sci. U. S. A. 1993; PubMed Scopus Google Scholar) and to the the Mob-5 and including their were amplified by PCR and into the of Corp., to the of the All were to The and which the secreted P. Cell. 1990; Full Text PDF PubMed Scopus Google Scholar), were into 293T cells. The expression of the and receptor binding were essentially as described P. Cell. 1990; Full Text PDF PubMed Scopus Google Scholar). for receptor binding the cells were at in plates in cells receptor binding was carried out with of either the protein medium or medium were by the 293T cells. were into target cells by the was with at a of of of into the cells to cell was carried out essentially as described previously R. Averboukh L. Zhu W. Zhang H. Jo H. Dempsey P.J. Coffey R., A. Pardee A.B. Liang P. Mol. Cell. Biol. 1998; 18: 6131-6141Crossref PubMed Scopus (131) Google Scholar). protein expression of and the were into the 293T cells, with a at a of and were by 10 of of cell medium were separated by on a polyacrylamide (National Atlanta, and a a of either or (GenHunter Corp., Nashville, was The was with for Ras was carried out using and of protein from Rat-1:iRas cells and proteins were with an kit following the Using automated differential display screening with (16Liang P. Zhu W. Zhang X. Guo Z. O'Connell R. Averboukh L. Wang F. Pardee A.B. Nucleic Acids Res. 1994; 22: 5763-5764Crossref PubMed Scopus (309) Google Scholar), two one with Rat-1:iRas cells inducible oncogenic Ha-ras (9McCarthy S.A. Samuels M.L. Pritchard C.A. Abraham J.A. McMahon M. Genes Dev. 1995; 9: 1953-1964Crossref PubMed Scopus (170) Google Scholar, R. Zhang H. Zhu W. Coffey R. Pardee A.B. Liang P. Oncogene. 1997; 14: 1607-1610Crossref PubMed Scopus (27) Google Scholar) and the other with oncogenic Ha-ras transformed Rat-1 cells and treatment of a MAP kinase kinase inhibitor (19Pang L. Sawada T. Decker S.J. Saltiel A.R. J. Biol. Chem. 1995; 270: 13585-13588Abstract Full Text Full Text PDF PubMed Scopus (896) Google Scholar), were for the screening of oncogenic ras target genes. screening through of primers of the genes expressed in a cell P. D. Averboukh L. P. M. H. M. Pardee A.B. 1995; PubMed Scopus Google Scholar), a of inducible genes and ras genes were identified H. Zhang H. Zhang R. Liang P. Methods. 1998; 16: PubMed Scopus Google Scholar). of ras inducible genes, transin/stromelysin-1 (5Matrisian L.M. Glaichenhaus N. Gesnel M-C. Breathnach R. EMBO J. 1985; 4: 1435-1440Crossref PubMed Scopus (227) Google Scholar), A. M. Biochem. Res. PubMed Scopus Google Scholar), H. J. Liang P. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar), and Pai-2 (8Cohen L.R. Niclas J. Lee W.M.F. Wun T.-C. Crowley C.W. Levinson A.D. Sadler J.E. Shuman M.A. J. Biol. Chem. 1989; 264: 8375-8383Abstract Full Text PDF PubMed Google Scholar), were identified by other methods in studies as ras One of the ras inducible genes, mob-5, to be and the gene was identified in both using either an inducible ras or which signaling and The mob-5 was from the differential display and used as a to the Ha-ras of the gene a target previously (10Liang P. Averboukh L. Zhu W. Pardee A.B. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12515-12519Crossref PubMed Scopus (59) Google Scholar, R. Zhang H. Zhu W. Coffey R. Pardee A.B. Liang P. Oncogene. 1997; 14: 1607-1610Crossref PubMed Scopus (27) Google Scholar) was used as a control for ras The treatment of Rat-1:iRas to the of the oncogenic Ha-Ras protein with concomitant of mob-5 that mob-5 is an early target gene of oncogenic of mob-5 as an oncogenic target RNA from Rat-1:iRas cells and of Ha-ras were analyzed by using mob-5 as a ras target was analyzed as a The of oncogenic Ha-Ras protein was by as from the same cells. the of Ha-Ras and mob-5 at mob-5 expression be activated by serum growth Rat-1 cells were for serum for and then with 10% bovine calf serum in the absence or presence of protein as Total were analyzed by using the same as used in A. the of but not mob-5, by serum and protein cyclohexamide of mob-5 expression in cells by cells were with of for the and the RNA was analyzed by using mob-5 as a RNA was shown as a control for studies that ras is required for the early to growth factor and normal cell (12Dobrowolski S. Harter M. Stacey D.W. Mol. Cell. Biol. 1994; 14: 5441-5449Crossref PubMed Scopus (99) Google Scholar, 13Durkin J.P. Whitfield J.F. Mol. Cell. Biol. 1986; 6: 1386-1392Crossref PubMed Scopus (32) Google Scholar, 14Taylor S.J. Shalloway D. Curr. Biol. 1996; 6: 1621-1627Abstract Full Text Full Text PDF PubMed Scopus (352) Google Scholar). mob-5 expression was not detected in Rat-1 cells in one that it could be expressed in to serum the gene is a downstream target of the Ras signaling with this were that all of the previously identified ras target genes including (16Liang P. Zhu W. Zhang X. Guo Z. O'Connell R. Averboukh L. Wang F. Pardee A.B. Nucleic Acids Res. 1994; 22: 5763-5764Crossref PubMed Scopus (309) Google Scholar), epidermal growth factor (9McCarthy S.A. Samuels M.L. Pritchard C.A. Abraham J.A. McMahon M. Genes Dev. 1995; 9: 1953-1964Crossref PubMed Scopus (170) Google Scholar), (5Matrisian L.M. Glaichenhaus N. Gesnel M-C. Breathnach R. EMBO J. 1985; 4: 1435-1440Crossref PubMed Scopus (227) Google Scholar), A. M. Biochem. Res. PubMed Scopus Google Scholar), and glucose transporter (6Flier J. Mueckler M.M. Usher P. Lodish H.F. Science. 1987; 235: 1492-1495Crossref PubMed Scopus (688) Google Scholar) could be induced by serum growth To the serum of the mob-5 Rat-1 cells were for serum and then with 10% fetal calf serum. mob-5 expression was not detected following serum either in the presence or absence of protein inhibitor In to mob-5 expression in normal from which and not The has been shown to be to cell transformation of rat embryo fibroblasts (18Kohl N.E. Mosser S.D. deSolms S.J. Giuliani E.A. Pompiano D.L. Graham S.L. Smith R.L. Scolnick E.M. Oliff A. Gibbs J.B. Science. 1993; 260: 1934-1937Crossref PubMed Scopus (619) Google Scholar). the of Ras protein, its and mob-5 is a target gene of one that mob-5 expression in oncogenic cells. To cells were with of and the mob-5 expression and were following the mob-5 expression was essentially abolished in the cells to the transformed not Using the by differential display, the mob-5 was isolated from a of rat embryo fibroblasts (10Liang P. Averboukh L. Zhu W. Pardee A.B. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12515-12519Crossref PubMed Scopus (59) Google Scholar). The mob-5 encodes an of with an of the putative the mob-5 identified by differential display at the of the mob-5 The Mob-5 protein to a gene isolated as a differentiation gene from cells with and and The only other gene that a of to Mob-5 over most of the is interleukin 10 from both or which is a and The Mob-5 protein a at its that Mob-5 may be a secreted protein, although to demonstrate for H. Z. Oncogene. 1995; Google Scholar). of the mob-5 with in a of including Rat-1 cells, to a of Mob-5 protein with a molecular of The Mob-5 protein secreted into the medium could be detected by using the Mob-5 of Mob-5 in Rat-1 cells not to such as transformation. To the secreted Mob-5 is a signaling or a it is important to its To this end, technology P. Cell. 1990; Full Text PDF PubMed Scopus Google Scholar) was employed to a protein, which then be used as an for the receptor has been used to identify and a of important cell surface including those of M. X. N. J. R. J. S. A. E.A. C.A. Cell. 1995; Full Text PDF PubMed Scopus Google Scholar) and Z. M. Cell. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). Mob-5 was secreted at a from 293T cells with the The secreted be detected from the medium by either the alkaline phosphatase or direct using The of the protein was by using to the secreted the Mob-5 receptor Rat-1 cells and transformation by oncogenic Ha-ras were with the cell medium an of either the protein or secreted the was to be to the cell surface of the cells but not of the parental Rat-1 control mutations have been with cancers of intestinal (3Kiaris H. Spandidos D.A. Int. J. Oncol. 1995; 7: 413-421PubMed Google Scholar), cells were analyzed for the expression of was with cells and transformation by oncogenic Ha-ras and D. E.A. Oncogene. 1995; Google Scholar). with the with both oncogenic were shown to be to mob-5 expression in cells a of to Mob-5 may be the rat of this was to be in nearly all cancer on either protein, one out that Mob-5 and are related of a same gene on the of the of the gene was amplified from cancer by DNA of the a the and of the H. Z. Oncogene. 1995; Google Scholar). The protein was and expressed in 293T cells. studies on the by the of was to be secreted at a into the The secreted could be detected by both from to and direct using of the protein was by using to in Rat-1 cells, the putative Mob-5 receptor was to be expressed the normal and cells using protein as a To the could to the cell surface of cells, the receptor binding was using in place of with the not cell surface binding to the cells and transformation by To the expression of the putative was by the oncogenic the cell surface binding was carried out for the cells grown for in the absence or presence of either 10 of the MAP kinase kinase or of The that the was by the inhibitor of Ras farnesyltransferase but not that of the MAP kinase kinase One of the major of is to control of gene expression in a and in to much has been in the two the of the ras signaling little is known the downstream genes activation at the of the on cell and transformation. differential display and have the of expressed genes, the target genes of a in their or biochemical have been In this we described the that was crucial for the identification of target genes by differential The were based on activation of expression in normal cells by inducible oncogenic of expression inras cells by Ras or MAP kinase and the to be induced by serum growth factors through normal ras activation. Mob-5 the only novel target of ras oncogenes identified by using expressed genes in a The expression of mob-5 is activated by oncogenic Ha-ras in Rat-1 cells with an inducible Ha-ras The activation of mob-5 expression a MAP kinase as both inhibitors of Ha-Ras and MAP kinase kinase completely the expression of the gene in cells. One of the ras has been that although the effects of oncogenic Ras are similar to those of serum growth factors, ras-transformed cells are whereas the parental cells continuously exposed to serum factors are not. of the ras target genes previously identified were shown to be serum with the activation of the normal ras by serum growth factors and its for the cell mob-5 expression could not be detected in Rat-1 cells following serum growth factor we that mob-5 is not a the of mob-5 as a oncogenic target the of for a of by the oncogenic Ras. mob-5 to be a target of and its expression with cell expression of mob-5 in parental Rat-1 cells to by oncogenic Ha-ras in not was not as may be ras target genes, which in to the by oncogenic ras both in cell and in the that mob-5 encodes a secreted protein based on the presence of a that Mob-5 may not Mob-5 an extensive at both DNA and a protein to a gene to be induced in cells by the treatment with and which is an of protein kinase H. Z. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). was shown not to be a secreted or protein and its biochemical H. Z. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). is of to that the of to mob-5 in completely of and that mob-5 the of the from the of the Here we demonstrate that expression of the Mob-5 in either fibroblasts or epithelial cells such as 293T in of the protein. Mob-5 from oncogenic ras-transformed cells were detected by following of proteins not of alkaline phosphatase its at the of Mob-5 to the of the protein. that mob-5 encodes a secreted protein as by the presence of the an important on which the biochemical of the protein be The only gene with known that a to Mob-5 is a secreted by activated cells, cells, and P. M.L. Science. 1990; PubMed Scopus Google Scholar). known as by binding to its cell surface receptor on it a A. R. P. Annu. Rev. 1993; PubMed Scopus Google Scholar). DNA such as the its which has been shown to be important in J. 1993; PubMed Scopus Google Scholar). In of we that Mob-5 may by in an autocrine or is by that the expression of mob-5 and its putative receptor are coordinately activated by the oncogenic ras in both Rat-1 and cells. it is to that whereas both Mob-5 and are activated by the ras the signaling pathway downstream of Ras to have with Mob-5 expression and expression of MAP kinase to the previously this that both and protein are to specifically to the cell surface of cells. is possible like of the including that of may be J. 1994; Google Scholar). Mob-5 and may not be but rather related of the same gene studies on Mob-5 and to the two this important which that Mob-5 binding to ras-transformed cells is should be out that which we from cancer has a in the of the is possible that this could the the and studies on with to its to be secreted by the was identified as a gene induced by the treatment of and to cell lines as cell differentiation H. Z. Oncogene. 1995; Google Scholar), the molecular mechanism the activation and its role in cell differentiation expression of in or other of cancer cell lines to growth H. Z. Oncogene. 1995; Google Scholar, H. Z. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). were shown that was expressed in cell lines in the absence of and treatment H. Z. Oncogene. 1995; Google Scholar). should be to out the cell growth by is through the receptor one that to the medium should have a similar that mob-5 and its putative receptor were specifically activated oncogenes in both fibroblasts and intestinal epithelial cells and that was in colorectal cancer to the of H. Z. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). this was in a gene was identified by differential display to be induced in a rat and the expression of the encoding protein was to cells at the R. A. J. Cell. Biochem. PubMed Scopus Google Scholar). this gene is essentially to Thus, mob-5 may be in such as or Thus, this into the that is a that The activation of and their by ras may a molecular for such an activated by the ras could either in an autocrine to cancer cell growth in a as a to effort in studies that Mob-5 is from based on the of either to to receptor or to of cells with The molecular of the using the proteins should to establish the role of this novel putative We and Zhang for Coffey for the cell lines and and for and cell lines with and