RERG Is a Novel ras-related, Estrogen-regulated and Growth-inhibitory Gene in Breast Cancer

Using microarray analysis, we identified a unique ras superfamily gene, termed RERG (r as-related andestrogen-regulated growth inhibitor), whose expression was decreased or lost in a significant percentage of primary human breast tumors that show a poor clinical prognosis. Importantly, high RERG expression correlated with expression of a set of genes that define a breast tumor subtype that is estrogen receptor-positive and associated with a slow rate of tumor cell proliferation and a favorable prognosis for these cancer patients. RERG mRNA expression was induced rapidly in MCF-7 cells stimulated by β-estradiol and repressed by tamoxifen treatment. Like Ras, RERG protein exhibited intrinsic GDP/GTP binding and GTP hydrolysis activity. Unlike Ras proteins, RERG lacks a known recognition signal for COOH-terminal prenylation and was localized primarily in the cytoplasm. Expression of RERG protein in MCF-7 breast carcinoma cells resulted in a significant inhibition of both anchorage-dependent and anchorage-independent growth in vitro and inhibited tumor formation in nude mice. These features of RERG are strikingly different from most Ras superfamily GTP-binding pro-teins and suggest that the loss of RERG expression may contribute to breast tumorigenesis. Using microarray analysis, we identified a unique ras superfamily gene, termed RERG (r as-related andestrogen-regulated growth inhibitor), whose expression was decreased or lost in a significant percentage of primary human breast tumors that show a poor clinical prognosis. Importantly, high RERG expression correlated with expression of a set of genes that define a breast tumor subtype that is estrogen receptor-positive and associated with a slow rate of tumor cell proliferation and a favorable prognosis for these cancer patients. RERG mRNA expression was induced rapidly in MCF-7 cells stimulated by β-estradiol and repressed by tamoxifen treatment. Like Ras, RERG protein exhibited intrinsic GDP/GTP binding and GTP hydrolysis activity. Unlike Ras proteins, RERG lacks a known recognition signal for COOH-terminal prenylation and was localized primarily in the cytoplasm. Expression of RERG protein in MCF-7 breast carcinoma cells resulted in a significant inhibition of both anchorage-dependent and anchorage-independent growth in vitro and inhibited tumor formation in nude mice. These features of RERG are strikingly different from most Ras superfamily GTP-binding pro-teins and suggest that the loss of RERG expression may contribute to breast tumorigenesis. estrogen receptor hemagglutinin antigen guanosine 5′-o-(3-thiotriphosphate) Raf proto-oncogene serine/threonine protein kinase Ric (Drosophila)-like, expressed in neurons green fluorescent Protein Microarray analysis of primary human tumors has led to the identification of novel tumors subtypes that were not identified previously and to the discovery of new genes that may be involved in the disease process. When using hierarchical clustering to classify breast tumors based upon variations in gene expression patterns, ∼4–5 distinct breast tumor subtypes were identified (1Perou C.M. Sørlie T. Eisen M.B. van de Rijn M. Jeffrey S.S. Rees C.A. Pollack J.R. Ross D.T. Johnsen H. Akslen L.A. Fluge Ø. Pergamenschikov A. Williams C. Zhu S.X. Lønning P.E. Børresen-Dale A.-L. Brown P.O. Botstein D. Nature. 2000; 406: 747-752Crossref PubMed Scopus (11349) Google Scholar, 2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar). In addition, it has been shown that these tumor subtypes were predictive of disease outcome (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar); in the extended study of Sørlie et al. (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar), the breast tumor data was statistically analyzed to identify genes whose expression patterns correlated with overall patient survival (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar). In the present study, we focus on one of the genes whose high expression correlated with a favorable patient outcome and whose expression pattern helped to define a breast tumor subtype that also expressed the estrogen receptor (ER).1 This gene encodes a novel member of the Ras superfamily of small GTPases that we have designated RERG. The mammalian Ras superfamily members serve as molecular switches to regulate a diverse array of cellular functions. These include control of cellular proliferation, differentiation, regulation of the actin cytoskeleton, membrane trafficking, and nuclear transport (3Macara I.G. Lounsbury K.M. Richards S.A. McKiernan C. Bar-Sagi D. FASEB J. 1996; 10: 625-630Crossref PubMed Scopus (209) Google Scholar, 4Campbell S.L. Khosravi-Far R. Rossman K.L. Clark G.J. Der C.J. Oncogene. 1998; 17: 1395-1413Crossref PubMed Scopus (918) Google Scholar, 5Malumbres M. Pellicer A. Front. Biosci. 1998; 3: 887-912Crossref PubMed Scopus (10) Google Scholar, 6Hall A. Science. 1998; 280: 2074-2075Crossref PubMed Scopus (164) Google Scholar). Despite sequence differences between subfamily members, all Ras-related GTPases contain five highly conserved domains (G1-G5) and function as guanine nucleotide-dependent molecular switches. For example, the prototypic Ras proteins transduce signals for growth and differentiation by alternating between active guanosine triphosphate (GTP)-bound and inactive guanosine diphosphate (GDP)-bound conformational states (7Bourne H.R. Sanders D.A. McCormick F. Nature. 1991; 349: 117-127Crossref PubMed Scopus (2655) Google Scholar). When in their active GTP-bound state, Ras-related proteins interact through their effector domain with a variety of cellular targets to elicit their biological effects. Recently, several novel Ras-related GTPases have been identified that exhibit amino acid sequence features that distinguish them from Ras proteins (reviewed in Ref. 8Reuther G.W. Der C.J. Curr. Opin. Cell Biol. 2000; 12: 157-165Crossref PubMed Scopus (345) Google Scholar). The Rheb GTPases are conserved from human to yeast and are subject to regulated expression in response to a number of stimuli (9Urano J. Tabancay A.P. Yang W. Tamanoi F. J. Biol. Chem. 2000; 275: 11198-11206Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar, 10Yamagata K. Sanders L.K. Kaufmann W.E. Yee W. Barnes C.A. Nathans D. Worley P.F. J. Biol. Chem. 1994; 269: 16333-16339Abstract Full Text PDF PubMed Google Scholar). Although the function of Rheb in mammalian cells is unclear, the yeast Rheb homologue appears to have the ability to regulate cell cycle progression and arginine uptake. The strong amino acid identity of Rin and Rit proteins with Ras, particularly within their effector domains, suggest that Rit and Rin may share partially overlapping functions with Ras (11Wes P.D., Yu, M. Montell C. EMBO J. 1996; 15: 5839-5848Crossref PubMed Scopus (72) Google Scholar, 12Lee C.H. Della N.G. Chew C.E. Zack D.J. J. Neurosci. 1996; 16: 6784-6794Crossref PubMed Google Scholar, 13Shao H. Kadono-Okuda K. Finlin B.S. Andres D.A. Arch. Biochem. Biophys. 1999; 371: 207-219Crossref PubMed Scopus (58) Google Scholar). Finally,ARHI is an imprinted tumor suppressor gene in breast and ovarian carcinomas; expression of ARHI in cancer cells inhibited cell growth and was associated with down-regulation of cyclin D1 promoter activity and induction of p21WAF1/CIP1 (14Yu Y. Xu F. Peng H. Fang X. Zhao S. Li Y. Cuevas B. Kuo W.L. Gray J.W. Siciliano M. Mills Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar). of these members has of the of GTP-binding proteins in cell and that are to serve as distinct of as to be we the identification of a novel member of the Ras superfamily of GTP-binding proteins that was through microarray of human breast it is to Ras and regulated in an we have termed gene as-related andestrogen-regulated growth RERG has of the Ras an intrinsic ability to and of RERG in a rate of proliferation and a significant inhibition of both anchorage-dependent and anchorage-independent were and as in Perou et al. (1Perou C.M. Sørlie T. Eisen M.B. van de Rijn M. Jeffrey S.S. Rees C.A. Pollack J.R. Ross D.T. Johnsen H. Akslen L.A. Fluge Ø. Pergamenschikov A. Williams C. Zhu S.X. Lønning P.E. Børresen-Dale A.-L. Brown P.O. Botstein D. Nature. 2000; 406: 747-752Crossref PubMed Scopus (11349) Google Scholar, C.M. Jeffrey S.S. van de Rijn M. Rees C.A. Eisen M.B. Ross D.T. Pergamenschikov A. Williams Zhu S.X. J.C. D. D. Brown P.O. Botstein D. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar). For the MCF-7 estrogen the MCF-7 control cell was to in the cells were to that for of these cells were in for and For the of in were with or for mRNA was from using a mRNA and on or (1Perou C.M. Sørlie T. Eisen M.B. van de Rijn M. Jeffrey S.S. Rees C.A. Pollack J.R. Ross D.T. Johnsen H. Akslen L.A. Fluge Ø. Pergamenschikov A. Williams C. Zhu S.X. Lønning P.E. Børresen-Dale A.-L. Brown P.O. Botstein D. Nature. 2000; 406: 747-752Crossref PubMed Scopus (11349) Google Scholar). In the of the the control cells were with and with the that were with for the estrogen the was with and with the were in with MCF-7 human breast carcinoma cells in RERG were in with MCF-7 cells RERG or or were by cells with or MCF-7 were for to and were using were using breast cell in the were from The RERG gene sequence was number The RERG gene was from using that contain and and was the of the yeast expression a hemagglutinin to was the of the human expression in RERG expression for RERG protein was using to a of the and an of the The was the and of to was to the amino acid For in RERG in was as a to for The and recognition and were of and with the green fluorescent protein of the to RERG expression in human breast cell was from cell by as PubMed Scopus Google Scholar). was on and to RERG or was with the with and to the using was to a human The was for the expression of protein as H. Andres D.A. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Google Scholar). on RERG protein was using a and in Protein were by the using as a RERG of as by H. Kadono-Okuda K. Finlin B.S. Andres D.A. Arch. Biochem. Biophys. 1999; 371: 207-219Crossref PubMed Scopus (58) Google Scholar, B.S. H. Kadono-Okuda K. Andres D.A. Biochem. J. 2000; PubMed Scopus Google Scholar). GTP binding to RERG was by a as previously B.S. H. Kadono-Okuda K. Andres D.A. Biochem. J. 2000; PubMed Scopus Google Scholar, B.S. Andres D.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). RERG or RERG for was in binding and for and the was to to for the were and through and and the of was by to the and of binding and guanine were as H. Kadono-Okuda K. Finlin B.S. Andres D.A. Arch. Biochem. Biophys. 1999; 371: 207-219Crossref PubMed Scopus (58) Google Scholar, B.S. H. Kadono-Okuda K. Andres D.A. Biochem. J. 2000; PubMed Scopus Google Scholar). GTP hydrolysis was by to and GTP H. Kadono-Okuda K. Finlin B.S. Andres D.A. Arch. Biochem. Biophys. 1999; 371: 207-219Crossref PubMed Scopus (58) Google Scholar, B.S. H. Kadono-Okuda K. Andres D.A. Biochem. J. 2000; PubMed Scopus Google Scholar). the RERG protein was to contain a was to as GTP hydrolysis were in of RERG or and or and were for the was to The were for the and were and analyzed as The data were using a The percentage of GTP hydrolysis was by the of in the by that of the of the GTP and cell were by cells to on the cells were one with and on with of and for with were for and the protein of the was by the of cell was on a and expression was analyzed by using the of and and were from of with and in a of on for were on an of the cell was a for When of the cell was it was for The was as the and the were in of The were and in of of the nuclear and were a and analysis was or cells were with of or using the in to the cells were to growth and cells were in a with a and were using expression was from of cell by with by and by were for MCF-7 cells RERG protein or as G.J. Der C.J. PubMed Scopus Google Scholar). In were in and in the growth were as previously G.J. Der C.J. PubMed Scopus Google Scholar). MCF-7 cells or RERG or were in a with were as previously G.J. Der C.J. PubMed Scopus Google Scholar), that of were the of MCF-7 cells or RERG or high and were nude formation was a and using the of the from the variations in gene expression patterns within primary human breast a new analysis of Tibshirani R. Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google was to microarray data from different human breast tumors (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar). This analysis resulted in the identification of genes whose expression correlated with overall patient survival Sørlie et al. (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar), for the survival associated were genes in high expression was associated with favorable patient and the survival of we to as the most of the genes whose high expression was associated with survival (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar); within set of genes was the a known gene and a novel that we RERG as-related andestrogen-regulated The mRNA expression pattern of RERG these breast tumors was a statistically significant of patient outcome in a analysis as be by expression it was not an of outcome in a analysis of with expression The expression pattern of RERG was in a of cell analysis RERG mRNA in all of the estrogen receptor-positive cell and not in of the cell and The RERG gene is by an mRNA that a of number The an to the and the sequence the the sequence for an M. 12: PubMed Scopus Google Scholar). The of RERG mRNA expression was by analysis and of a was in all and with the of expression in and not pattern of expression is by expression data protein that RERG is in and The RERG gene is is within overlapping and and is of the of are by a of the RERG gene sequence identified binding within the not The of RERG within a gene expression that the the high expression of RERG in breast cell and the of binding within the promoter that RERG be an we microarray analysis and RERG expression in response to β-estradiol in the MCF-7 cell for all microarray primary data MCF-7 cells in for were with β-estradiol for or mRNA and were with MCF-7 in was rapidly expressed in response to β-estradiol and that it is a of an in the as an of the regulation of the of tamoxifen in the of estrogen was on gene expression for an gene, RERG expression was repressed by tamoxifen and induced by estrogen not as as known genes and protein kinase for of known genes in these The amino acid sequence of the RERG protein is by an of that for a acid protein that is and to the and proteins and to to human and Although RERG significant sequence identity and with Ras, it also a number of unique RERG has an the to the of of with in the of Ras M. Biochem. PubMed Scopus Google Scholar). unique of RERG is that it lacks known COOH-terminal prenylation that it is not subject to prenylation J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar, Cell Biol. 1994; 10: PubMed Scopus Google Scholar). the of Ras with the and of Ras are of are in the RERG COOH-terminal These unique COOH-terminal features of RERG are to of Rit and Rin (11Wes P.D., Yu, M. Montell C. EMBO J. 1996; 15: 5839-5848Crossref PubMed Scopus (72) Google Scholar, 12Lee C.H. Della N.G. Chew C.E. Zack D.J. J. Neurosci. 1996; 16: 6784-6794Crossref PubMed Google Scholar, 13Shao H. Kadono-Okuda K. Finlin B.S. Andres D.A. Arch. Biochem. Biophys. 1999; 371: 207-219Crossref PubMed Scopus (58) Google Scholar). The GTP binding activity of RERG was using and GTP was by in RERG not RERG rapidly in a upon with the of guanine with RERG was by the of of in the with binding not The binding of both and was and The ability of to for binding to RERG was also and that RERG is a guanine an of not or for binding These GTP binding are with of Ras and all Ras superfamily The RERG a as be for a of binding The for from RERG was slow to in study RERG with a of This rate of is in to the rate of for the of Ras-related RERG was to GTP to RERG was with and the were analyzed by in RERG was of in the of an of When was with we not the of that the hydrolysis activity. that the activity is intrinsic to the RERG protein from analysis of the RERG The in Ras in a protein with decreased and is in and of Ras C.J. T. Full Text PDF PubMed Scopus Google Scholar). The of it to have guanine binding that were to the the activity of was the of we expressed a RERG protein in the MCF-7 and human breast cell and in shown in with the led to the of an as by of cells a and the cell signal in the expression pattern and was in MCF-7 cells RERG and in a of cell not cells were that exhibited a membrane of is with the of a COOH-terminal prenylation signal This is to that in cells The of RERG was using and analysis and that was present in the of MCF-7 cells that were proteins The effector domain of Ras is for Ras with Raf and effector proteins S.L. Khosravi-Far R. Rossman K.L. Clark G.J. Der C.J. Oncogene. 1998; 17: 1395-1413Crossref PubMed Scopus (918) Google Scholar). RERG identity with Ras in the that RERG may interact with of Ras we the between RERG and a of known Ras between RERG and guanine or were using a yeast not with the of of RERG with Ras RERG expression not in the of of cells in a not was for Ras-related proteins that COOH-terminal H. Andres D.A. Oncogene. 2000; 19: PubMed Scopus Google Scholar), with Raf to was we not significant of or RERG expression on the of cells by not When we the expression of RERG the breast tumors in the study by Sørlie et al. (2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google and expression pattern with the expression of the set of genes (1Perou C.M. Sørlie T. Eisen M.B. van de Rijn M. Jeffrey S.S. Rees C.A. Pollack J.R. Ross D.T. Johnsen H. Akslen L.A. Fluge Ø. Pergamenschikov A. Williams C. Zhu S.X. Lønning P.E. Børresen-Dale A.-L. Brown P.O. Botstein D. Nature. 2000; 406: 747-752Crossref PubMed Scopus (11349) Google Scholar, C.M. Jeffrey S.S. van de Rijn M. Rees C.A. Eisen M.B. Ross D.T. Pergamenschikov A. Williams Zhu S.X. J.C. D. D. Brown P.O. Botstein D. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, D.T. U. Eisen M.B. Perou C.M. Rees C. Jeffrey S.S. de Rijn M. M. Pergamenschikov A. J.C. D. D. Botstein D. Brown P.O. 2000; PubMed Scopus Google Scholar, C.M. Brown P.O. Botstein D. for 2000; Scholar), we that the tumors that most highly expressed RERG to be the and the with to to be the most The of RERG expression within breast that are highly that RERG may function as an of we MCF-7 cell RERG and the on growth in vitro and in MCF-7 cells for these were for expression and are an cell of MCF-7 cells with an expression a of RERG were cells were also as for these with expression of in with the expression in and expression in the of high RERG expression on the rate of proliferation the were on cell of cell proliferation with the control cell growth inhibition was with MCF-7 cells RERG expression was the control of an promoter not we RERG anchorage-independent growth of MCF-7 that MCF-7 cells in with the control MCF-7 cells we the in of MCF-7 cells was by RERG For these we the cell nude and estrogen for of with control MCF-7 cells with a of were also in with cells with a In with the high for an of MCF-7 cell tumor formation in nude by with estrogen were with MCF-7 cells or or formation was a from in a new with estrogen were with MCF-7 cells or or formation was a from microarray to identify genes whose expression correlated with a favorable prognosis for breast cancer patients. gene identified a novel gene that we have designated as-related andestrogen-regulated growth that RERG expression was decreased or lost in a significant percentage of primary human breast tumors that a poor clinical prognosis and was regulated by estrogen in Like Ras, RERG protein and that RERG also functions as a Unlike Ras, RERG lacks known COOH-terminal prenylation signal sequence and exhibited a membrane RERG not interact with of Ras, that RERG function is distinct from that of in to the activity associated with Ras and Ras-related proteins, RERG inhibited the growth of breast tumor cells in vitro and in When these an for the loss of RERG function in the of breast have identified a novel member of the Ras superfamily of small GTP-binding of the RERG sequence that it encodes a protein of amino with a molecular of The with between RERG and Ras members to the five of Ras involved in GTP binding (G1-G5) H.R. Sanders D.A. McCormick F. Nature. PubMed Scopus Google Scholar). The sequence of the is present in RERG an the to of Ras and the of Ras superfamily also a in Ras an of intrinsic activity and in a and Ras protein M. Biochem. PubMed Scopus Google Scholar). that RERG an intrinsic activity that was a to the the intrinsic and activity of Ras and Ras was RERG. from Ras, it is that RERG is not active and be to are guanine protein that regulate RERG function and are regulated by Although RERG strong sequence identity with the effector domain of Ras, we that RERG not to Raf and of This with the of activity in cells that RERG function is by with targets distinct from of Although Ras superfamily GTPases have been as of cell growth and differentiation G.W. Der C.J. Curr. Opin. Cell Biol. 2000; 12: 157-165Crossref PubMed Scopus (345) Google Scholar), and have been as of (14Yu Y. Xu F. Peng H. Fang X. Zhao S. Li Y. Cuevas B. Kuo W.L. Gray J.W. Siciliano M. Mills Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, H. Y. T. Y. M. Full Text PDF PubMed Scopus Google Scholar). suggest that RERG functions as a growth Ras Ras-related proteins are and membrane is both and to their biological activity Cell Biol. 1994; 10: PubMed Scopus Google Scholar, Der C.J. Biophys. PubMed Scopus Google Scholar). binding the of a COOH-terminal by a that the recognition of conserved as as J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). of the features of RERG is a unique COOH-terminal sequence that of lacks a for that RERG is localized in the expressed in a variety of cell breast cell In RERG is to the proteins, a COOH-terminal and to be localized to the B.S. H. Kadono-Okuda K. Andres D.A. Biochem. J. 2000; PubMed Scopus Google Cell 1998; PubMed Scopus Google Scholar). the of RERG protein and to identify proteins, be the of unique cellular be of study is that the expression of RERG in MCF-7 breast carcinoma cells be by estrogen and and rapidly the expression of RERG in a tamoxifen or estrogen repressed RERG expression to estrogen response were within the promoter of the RERG gene, we RERG to be an with is that RERG expression a high of with in both breast cell and primary tumors and The expression of the estrogen receptor has for the of breast with tumors that have a and overall survival with tumors that expression W.L. Google Scholar, of the Scholar). The and differences between and breast tumors have been to be to differences in gene expression between these tumor is a to identify genes within primary breast tumors and define their in tumorigenesis. These that RERG may be of biological clinical in breast cancer and suggest an for RERG in the response of breast cells to The of RERG in breast tumor growth was in several The of RERG in MCF-7 cells inhibited their anchorage-dependent growth RERG expression formation in and inhibited tumor formation in nude these suggest that loss of RERG expression may of breast be that the by of RERG in MCF-7 cells are with expression pattern the set of breast tumors in the of tumors that most highly expressed the set of genes RERG and termed subtype were on of the tumors (1Perou C.M. Sørlie T. Eisen M.B. van de Rijn M. Jeffrey S.S. Rees C.A. Pollack J.R. Ross D.T. Johnsen H. Akslen L.A. Fluge Ø. Pergamenschikov A. Williams C. Zhu S.X. Lønning P.E. Børresen-Dale A.-L. Brown P.O. Botstein D. Nature. 2000; 406: 747-752Crossref PubMed Scopus (11349) Google Scholar, 2Sørlie T. Perou C.M. Tibshirani R. Aas T. Geisler S. Johnsen H. Eisen M.B. van de Rijn M. Jeffrey S.S. Quist H. Matese J.C. Brown P.O. Botstein D. Lønning P.E. Børresen-Dale A.-L. Proc. Natl. Acad. Sci. U. S. A. 2001; 19: 10869-10874Crossref Scopus (8330) Google Scholar). These suggest that RERG may function as a growth in breast inhibition on the cellular in RERG is expressed and the identification of the signal that are to be