Up-regulation of miR-21 by HER2/neu Signaling Promotes Cell Invasion

Abstract

The cell surface receptor tyrosine kinase HER2/neu enhances tumor metastasis. Recent studies suggest that deregulated microRNA (miRNA) expression promotes invasion and metastasis of cancer cells; we therefore explored the possibility that HER2/neu signaling induces the expression of specific miRNAs involved in this process. We identified a putative oncogenic miRNA, miR-21, whose expression is correlated with HER2/neu up-regulation and is functionally involved in HER2/neu-induced cell invasion. We show that miR-21 is up-regulated via the MAPK (ERK1/2) pathway upon stimulation of HER2/neu signaling in breast cancer cells, and overexpression of other ERK1/2 activators such as RASV12 or ID-1 is sufficient to induce miR-21 up-regulation in HER2/neu-negative breast cancer cells. Furthermore, the metastasis suppressor protein PDCD4 (programmedcell death 4) is down-regulated by miR-21 in breast cancer cells expressing HER2/neu. Our data reveal a mechanism for HER2/neu-induced cancer cell invasion via miRNA deregulation. In addition, our results identify miR-21 as a potential therapeutic target for the prevention of breast cancer invasion and metastasis. The cell surface receptor tyrosine kinase HER2/neu enhances tumor metastasis. Recent studies suggest that deregulated microRNA (miRNA) expression promotes invasion and metastasis of cancer cells; we therefore explored the possibility that HER2/neu signaling induces the expression of specific miRNAs involved in this process. We identified a putative oncogenic miRNA, miR-21, whose expression is correlated with HER2/neu up-regulation and is functionally involved in HER2/neu-induced cell invasion. We show that miR-21 is up-regulated via the MAPK (ERK1/2) pathway upon stimulation of HER2/neu signaling in breast cancer cells, and overexpression of other ERK1/2 activators such as RASV12 or ID-1 is sufficient to induce miR-21 up-regulation in HER2/neu-negative breast cancer cells. Furthermore, the metastasis suppressor protein PDCD4 (programmedcell death 4) is down-regulated by miR-21 in breast cancer cells expressing HER2/neu. Our data reveal a mechanism for HER2/neu-induced cancer cell invasion via miRNA deregulation. In addition, our results identify miR-21 as a potential therapeutic target for the prevention of breast cancer invasion and metastasis. The HER2/neu (c-erbB-2) proto-oncogene encodes a transmembrane protein-tyrosine kinase growth factor receptor, p185HER2, which is a member of the human epidermal growth factor receptor family. HER2/neu overexpression is found in about 30% of human breast cancers and several other cancer types. HER2/neu overexpression is associated with a poor clinical outcome, including a positive correlation with metastasis (1.Slamon D.J. Godolphin W. Jones L.A. Holt J.A. Wong S.G. Keith D.E. Levin W.J. Stuart S.G. Udove J. Ullrich A. Science. 1989; 244: 707-712Crossref PubMed Scopus (6289) Google Scholar, 2.Yu D. Hung M.C. Oncogene. 2000; 19: 6115-6121Crossref PubMed Scopus (353) Google Scholar). The involvement of HER2/neu in metastasis is supported by studies demonstrating that HER2/neu increases the metastatic potential of human and murine cancer cell lines (3.Tan M. Yao J. Yu D. Cancer Res. 1997; 57: 1199-1205PubMed Google Scholar) and induces lung metastasis in transgenic animal models (4.Guy C.T. Webster M.A. Schaller M. Parsons T.J. Cardiff R.D. Muller W.J. Proc. Natl. Acad. Sci. U.S.A. 1992; 89: 10578-10582Crossref PubMed Scopus (1025) Google Scholar). Additionally, HER2/neu signaling up-regulates genes that play important roles in cell invasion and metastasis, such as cyclooxygenase-2, CXCR4, and matrix metalloproteinases (5.Subbaramaiah K. Norton L. Gerald W. Dannenberg A.J. J. Biol. Chem. 2002; 277: 18649-18657Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar, 6.Li Y.M. Pan Y. Wei Y. Cheng X. Zhou B.P. Tan M. Zhou X. Xia W. Hortobagyi G.N. Yu D. Hung M.C. Cancer Cell. 2004; 6: 459-469Abstract Full Text Full Text PDF PubMed Scopus (457) Google Scholar, 7.Bosc D.G. Goueli B.S. Janknecht R. Oncogene. 2001; 20: 6215-6224Crossref PubMed Scopus (97) Google Scholar). Given the complex signaling network initiated by HER2/neu overexpression in cancer cells, it is likely that HER2/neu regulates additional unidentified players involved in these processes. miRNAs 4The abbreviations used are: miRNAmicroRNAMAPKmitogen-activated protein kinaseERKextracellular signal-regulated kinaseMEKMAPK/ERK kinaseGFPgreen fluorescent proteinqRTquantitative real timeScFVsingle chain FvTNFtumor necrosis factorRTKreceptor tyrosine kinase. constitute a class of 21 or 22 nucleotides noncoding RNAs that play an important role in development and cellular processes. Aberrant expression of miRNAs is associated with cancer (8.He L. Thomson J.M. Hemann M.T. Hernando-Monge E. Mu D. Goodson S. Powers S. Cordon-Cardo C. Lowe S.W. Hannon G.J. Hammond S.M. Nature. 2005; 435: 828-833Crossref PubMed Scopus (3155) Google Scholar), suggesting that some miRNAs can function as tumor suppressor genes or oncogenes. miRNAs may also cooperate with the loss of tumor suppressors or overexpression oncogenes in cancer cells to contribute to a fully malignant phenotype. Up-regulation of several miRNAs in breast cancer cells, such as miR-21 and miR-10b, can increase cell invasion and metastasis (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, 10.Ma L. Teruya-Feldstein J. Weinberg R.A. Nature. 2007; 449: 682-688Crossref PubMed Scopus (2236) Google Scholar). HER2/neu signaling activates a variety of transcription factors, such as AP-1, Myc, and NF-κB that alter miR-21 and other miRNA transcription (8.He L. Thomson J.M. Hemann M.T. Hernando-Monge E. Mu D. Goodson S. Powers S. Cordon-Cardo C. Lowe S.W. Hannon G.J. Hammond S.M. Nature. 2005; 435: 828-833Crossref PubMed Scopus (3155) Google Scholar, 11.Fujita S. Ito T. Mizutani T. Minoguchi S. Yamamichi N. Sakurai K. Iba H. J. Mol. Biol. 2008; 378: 492-504Crossref PubMed Scopus (367) Google Scholar, 12.Taganov K.D. Boldin M.P. Chang K.J. Baltimore D. Proc. Natl. Acad. Sci. U.S.A. 2006; 103: 12481-12486Crossref PubMed Scopus (3569) Google Scholar). We therefore hypothesize that HER2/neu signaling may induce the expression of specific miRNAs, which contribute to the increased metastatic potential of HER2/neu-overexpressing cancer cells. microRNA mitogen-activated protein kinase extracellular signal-regulated kinase MAPK/ERK kinase green fluorescent protein quantitative real time single chain Fv tumor necrosis factor receptor tyrosine kinase. Here we describe a putative oncogenic miRNA, miR-21, whose expression is correlated with HER2/neu up-regulation. We found that HER2/neu signaling up-regulates miR-21 via the MAPK (ERK1/2) pathway and that its increased expression promotes cell invasion. Furthermore, miR-21 suppressed expression of the metastasis suppressor PDCD4 in HER2/neu-expressing breast cancer cells. Our data show a new mechanism by which HER2/neu induces cell invasion via miR-21 deregulation in breast cancer cells. This raises the possibility that anti-miR-21 therapies might exhibit a synergistic effect with other anti-HER2/neu therapeutics, for example Herceptin, in treating HER2/neu-associated breast cancers. Human breast cancer cell line SKBR3 (ATCC) was cultured in McCoy's 5A medium with 10% fetal bovine serum. BT-474 (ATCC) was cultured in RPMI 1640 with 10% fetal bovine serum. The HeLa (ATCC) cell line and its HER2/neu transfectant were maintained in Dulbecco's modified Eagle's medium with 10% fetal bovine serum. The human breast cancer cell line MDA-MB-435 transfected with a neo vector or a HER2-expressing vector were gifts from Dr. Mien-Chie Hung (M. D. Anderson Cancer Center, Houston, TX) and have been characterized and described previously (6.Li Y.M. Pan Y. Wei Y. Cheng X. Zhou B.P. Tan M. Zhou X. Xia W. Hortobagyi G.N. Yu D. Hung M.C. Cancer Cell. 2004; 6: 459-469Abstract Full Text Full Text PDF PubMed Scopus (457) Google Scholar). These cells were maintained in Dulbecco's modified Eagle's medium/F-12 supplemented with 10% fetal bovine serum and 400 μg/ml geneticin (Invitrogen). pEBS7 and pEBS7-HER2/neu vectors were gifts from Dr. Mikala Egeblad (13.Egeblad M. Jäättelä M. Int. J. Cancer. 2000; 86: 617-625Crossref PubMed Scopus (28) Google Scholar). Ets-1 small hairpin RNA-expressing vector was obtained from SuperArray Bioscience Corp. (Frederick, MD). Replication-defective mouse stem cell (MSCV-IRES-GFP) retrovirus encoding control vector, activated H-Ras (G12V), activated myristoylated AKT, Myc, or ID-1 were prepared as previously described (14.Goga A. Yang D. Tward A.D. Morgan D.O. Bishop J.M. Nat. Med. 2007; 13: 820-827Crossref PubMed Scopus (248) Google Scholar). Nontransformed human MCF10A breast epithelial cells were infected with each of the recombinant retrovirus to generate stable cell populations. Greater than 80% of MCF10A stable cell populations expressed cis-linked GFP fluorescence marker as judged by fluorescence microscopy. The wild type ERK2 and dominant negative ERK2 were gift from Dr. Mien-Chie Hung (M. D. Anderson Cancer Center) and have been characterized and described previously (15.Yang J.Y. Zong C.S. Xia W. Yamaguchi H. Ding Q. Xie X. J.Y. Chang H. Cheng X. Chang K.J. Muller W.J. Yu D. Hortobagyi G.N. Hung M.C. Nat. Cell Biol. 2008; PubMed Scopus Google Scholar). the miR-21 and the GFP in the vector A. A. M. L. R. T. Proc. Natl. Acad. Sci. U.S.A. 2004; PubMed Scopus Google Scholar) was with the the and The with or were the the and to the miR-21 vector and the vector, the miR-21 expression vector, including the miR-21 was by from human with the and the The was a vector to the The vector was and with and to the which was a modified vector from the GFP modified with were in a Science. 1997; PubMed Scopus Google Scholar). The were of S. S. A. A.J. Res. 2006; PubMed Scopus Google Scholar) and miRNAs E. J. E. E. Cell. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar), with some to in the were and were miRNA were as described J.M. J. Hammond S.M. Nat. 2004; PubMed Scopus Google Scholar) with the was with to the of was to a of or of and was to with were and with was in of and for a The were and a The data were and was The data were in to the for each of in each The data the results from in which of each was with a each as to The fluorescence for each from the was to the fluorescence for each the the to human miRNAs HER2/neu was obtained from AKT, and from Cell is from is from is from HER2/neu for is from The HER2/neu anti-HER2/neu was a gift from Dr. and been characterized and described previously J. 2006; PubMed Scopus Google Scholar). The and ERK1/2 were obtained from Cell real time of miR-21 and was prepared the miRNA TX) and by transcription was with a for real time (Invitrogen). time was real time The was the and the and the of the was previously D. K. C. J. R. M. C. K. H. F. 2007; PubMed Scopus Google Scholar). The human Ets-1 was the and the The was the and the which was previously J. K. F. N. A. F. Biol. 2002; PubMed Google Scholar) and as an control the and Ets-1 The was with the and was in these of miR-21 and other was by the miRNA as described previously C. A.J. Zhou M. K.J. K.J. Res. 2005; PubMed Scopus Google Scholar). The results were with as an control and expressed as expression with of HER2/neu the cells were with for and with a of the cells were with the of miR-21 by was by the to the (Invitrogen). of was a 10% was to a by a The was to the by was by to the The was to the of miR-21 and was with the were of PDCD4 expression was as previously described S. Wu H. Mo Y.Y. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). In the protein was by protein and the were in with a the was with with was with the and associated expression of PDCD4 was the control of MDA-MB-435 and BT-474 cells with anti-miR-21 or a control was the small to the of HeLa cells and BT-474 cells with was to the (Invitrogen). were as previously described A. A. M. L. R. T. Proc. Natl. Acad. Sci. U.S.A. 2004; PubMed Scopus Google Scholar). of vector and of a of vectors were in cells The were a and used to cancer cells. The potential of cells was in invasion the the cells were for in a with the cells that the surface of the were by cells were and in in the of each fluorescence medium or the effect of HER2/neu the miR-21 target PDCD4 expression the cellular cells were with cells were transfected with or cells were transfected with miR-21 expression vector, by with The transfected cells were and with as described previously F. S. Mo Y.Y. Mol. Cancer 2007; 6: PubMed Scopus Google Scholar). with PDCD4 with was used to reveal PDCD4 The were a fluorescent of HER2/neu enhances tumor invasion and lung metastasis of breast cancer cells (4.Guy C.T. Webster M.A. Schaller M. Parsons T.J. Cardiff R.D. Muller W.J. Proc. Natl. Acad. Sci. U.S.A. 1992; 89: 10578-10582Crossref PubMed Scopus (1025) Google Scholar). miR-21 and other have been to increase the metastatic potential of breast cancers (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, 10.Ma L. Teruya-Feldstein J. Weinberg R.A. Nature. 2007; 449: 682-688Crossref PubMed Scopus (2236) Google Scholar), and HER2/neu signaling activates several transcription that have been to miR-21 expression in cancer cell lines S. Ito T. Mizutani T. Minoguchi S. Yamamichi N. Sakurai K. Iba H. J. Mol. Biol. 2008; 378: 492-504Crossref PubMed Scopus (367) Google Scholar, D. K. C. J. R. M. C. K. H. F. 2007; PubMed Scopus Google Scholar). We therefore explored the possibility that HER2/neu signaling induces the expression of miR-21 other which in contribute to the increased metastatic potential of these cancer cells. We miR-21 is up-regulated in the MDA-MB-435 human breast cancer cell overexpression of HER2/neu enhances invasion and metastasis in this cell line its cell growth and other of potential (3.Tan M. Yao J. Yu D. Cancer Res. 1997; 57: 1199-1205PubMed Google Scholar). We that HER2/neu expression was sufficient to miR-21 in MDA-MB-435 cells that HER2/neu is sufficient to induce miR-21 up-regulation in other cancer cells and identify other we the in miRNA expression in the cells with vector control cells by miRNA We HeLa cells of the that some HER2/neu A. A. T. M. L. S. A. Cancer. 2004; PubMed Scopus Google Scholar), and the of HER2/neu expression vector is and in this cell HeLa cell line was that HER2/neu and a single from the was in the the miR-21 miRNA This was which that miR-21 expression in cells was increased with control cells these a up-regulation of miR-21 expression Our results that HER2/neu overexpression up-regulated miR-21 in MDA-MB-435 and HeLa cells. HER2/neu overexpression may the miR-21 in breast cancer cells, in miR-21 with control cells. HER2/neu signaling is to induce miR-21 we the of miR-21 by the of its and upon HER2/neu signaling in cancer cells. HER2/neu was used to induce HER2/neu signaling in HER2/neu-expressing cells lines J. 2006; PubMed Scopus Google Scholar). is a specific for human HER2/neu to a with This HER2/neu previously been to a via the of the and is therefore to HER2/neu the tyrosine of HER2/neu receptor and the and MAPK signaling J. 2006; PubMed Scopus Google Scholar). HER2/neu a and up-regulation in SKBR3 and BT-474 cells and the of of In the of miR-21 in these cells is HER2/neu of cells for a up-regulation of miR-21 expression as with cells. In miR-21 up-regulation was in vector control cells with the HER2/neu as with cells In to cells, up-regulation of miR-21 was in the HER2/neu-overexpressing breast cancer cell lines SKBR3 and BT-474 miR-21 was increased and in SKBR3 and BT-474 cells, with HER2/neu for These results suggest that HER2/neu signaling induces transcription of to miR-21 is in SKBR3 and BT-474 breast cancer cells. it been that the expression of is in several C. S. C. Biol. 2007; PubMed Scopus Google Scholar), which may the in increased miR-21 expression in SKBR3 and BT-474 cells. Given the of miR-21 we to a in miR-21 expression a in target the potential of miR-21 up-regulation in to HER2/neu we of a encoding a fluorescent in its miR-21 with was used as a control vector in to HER2/neu expression SKBR3 cells infected with the that the is or in HER2/neu-overexpressing breast cancer cells with the HER2/neu the a increase of the of the of transcription by HER2/neu In SKBR3 cells infected with the miR-21 a that the is by miR-21 expression in these cells with HER2/neu the miR-21 an of the that the miR-21 expression by the HER2/neu signaling is sufficient to target expression and may therefore have a in cancer cells by target The and signaling of activated HER2/neu. which pathway is for the miR-21 we HER2/neu-overexpressing cells BT-474 with an of ERK1/2 or and these cells for with HER2/neu cells up-regulated miR-21 by the ERK1/2 miR-21 by the HER2/neu in a In the miR-21 up-regulation We also that with the ERK1/2 the miR-21 by HER2/neu in SKBR3 cells and HER2/neu transfected HeLa cells miR-21 increased in cells transfected with a wild type ERK2 30% in cells transfected with a dominant negative ERK2 These that ERK1/2 is a for the miR-21 up-regulation and that this mechanism is several cell types. We which transcription miR-21 The miR-21 a in which and can induce miR-21 expression via in cells D. K. C. J. R. M. C. K. H. F. 2007; PubMed Scopus Google Scholar). putative for have also been identified in the miR-21 which can miR-21 transcription in HeLa cells with S. Ito T. Mizutani T. Minoguchi S. Yamamichi N. Sakurai K. Iba H. J. Mol. Biol. 2008; 378: 492-504Crossref PubMed Scopus (367) Google Scholar). In to and AP-1, we also found this is to an transcription factor R. D. S. C. S. Oncogene. 2002; PubMed Scopus Google Scholar), we the protein is involved in HER2/neu-associated miR-21 transcription in breast cancer cells. Ets-1 by transcription by than in HER2/neu-overexpressing BT-474 cells suggesting that Ets-1 is involved in the miR-21 with these of a single Ets-1 miR-21 by than in HeLa cells with S. Ito T. Mizutani T. Minoguchi S. Yamamichi N. Sakurai K. Iba H. J. Mol. Biol. 2008; 378: 492-504Crossref PubMed Scopus (367) Google Scholar). our data that transcription can miR-21 or in to to that the is the pathway for miR-21 we the pathway activators or ID-1 Int. J. Cancer. PubMed Scopus Google Scholar, M.T. X. K. S.W. Wong Oncogene. 2002; PubMed Scopus Google Scholar) in HER2/neu-negative MCF10A breast cancer cells. of H-Ras or ID-1 miR-21 by and In overexpression of other oncogenes such as activated or that the pathway miR-21 up-regulation and of and signaling in human breast cancers K. K. M. S. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar) and may the increase of miR-21 expression in cells that activated our results suggest that the pathway regulates miR-21 expression in breast cancer cells and that miR-21 may functionally involved in the H-Ras and oncogenic of HER2/neu been to invasion and metastasis in MDA-MB-435 cells other (3.Tan M. Yao J. Yu D. Cancer Res. 1997; 57: 1199-1205PubMed Google Scholar). some in other cancer cell lines from increased cell growth and we that a MDA-MB-435 cell line an to the mechanism of cell invasion Given that miR-21 is up-regulated by HER2/neu in this cell line and that miR-21 been to cell invasion and metastasis in breast cancer (3.Tan M. Yao J. Yu D. Cancer Res. 1997; 57: 1199-1205PubMed Google Scholar, S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar), we were to miR-21 function to the of miR-21 in cell invasion in MDA-MB-435 cells, we expressed the the miR-21 and of the miR-21 hairpin in MDA-MB-435 cells a vector, and we a increase in miR-21 in cells The cells a increased to as with control cells in a This that miR-21 up-regulation to the of MDA-MB-435 cells in Furthermore, of miR-21 by a miR-21 or the in cells, the in cells transfected with a control These results that miR-21 is a in cancer cell invasion and that expression may in a the role of miR-21 in cell invasion in a we in BT-474 cells, which of HER2/neu and miR-21 We HER2/neu expression with the miR-21 in BT-474 cells. of these cells with the HER2/neu or the HER2/neu kinase the miR-21 and These results that HER2/neu signaling is for the miR-21 in BT-474 cells. the was in BT-474 cells transfected with miR-21 suggesting that HER2/neu-induced miR-21 up-regulation is for the of BT-474 cells. with the in cells, these results suggest that miR-21 a role in in cancer cells. We and other have previously that a for breast cancer cell invasion R. Cancer Res. PubMed Scopus Google Scholar), is a target for miR-21 (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, S. H. Oncogene. 2008; PubMed Scopus Google Scholar, A. M. A. J. Biol. Chem. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). we found that expression of PDCD4 the of cells suggesting that the PDCD4 can the of this cell HER2/neu miR-21 up-regulation in MDA-MB-435 cells, we HER2/neu can PDCD4 via miR-21 in this cell PDCD4 is a protein M. K. A. R. Oncogene. PubMed Scopus Google Scholar), we therefore the PDCD4 expression an that the PDCD4 was in cells than in vector control cells We also a and the PDCD4 expression in cell and the PDCD4 expression was in the in cells with vector control cells the effect of miR-21 we expressed miR-21 in cells. miR-21 expression vector was with the overexpression of we a of in miR-21 overexpression cells with cells In the vector control have such an effect PDCD4 expression we transfected cells with specific to miR-21 with in and anti-miR-21 were in the the effect PDCD4 anti-miR-21 up-regulated PDCD4 these results suggest that HER2/neu signaling can PDCD4 expression via of miR-21 In addition, of PDCD4 by miR-21 may contribute to the cell invasion and metastasis in breast cancer cells miRNA expression can (8.He L. Thomson J.M. Hemann M.T. Hernando-Monge E. Mu D. Goodson S. Powers S. Cordon-Cardo C. Lowe S.W. Hannon G.J. Hammond S.M. Nature. 2005; 435: 828-833Crossref PubMed Scopus (3155) Google Scholar) and contribute to cancer including invasion and metastasis (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, 10.Ma L. Teruya-Feldstein J. Weinberg R.A. Nature. 2007; 449: 682-688Crossref PubMed Scopus (2236) Google specific oncogenic miRNA expression in cancer cells is In the we have that an oncogenic receptor tyrosine kinase can signaling that results in miR-21 up-regulation in cancer cells. of an oncogenic microRNA in A. L. A. J. D. R. T. Cell. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar), in an oncogenic microRNA can in and C. L. J. J.M. K. Nat. 2008; PubMed Scopus Google Scholar). Our data show that a of miR-21 up-regulation by HER2/neu is sufficient to increase the of cancer cells. our this is the to that HER2/neu signaling can induce the expression of specific miRNAs, which in play roles in the of cancer cells. the signaling by other for example and with by and overexpression of these is also associated with tumor R. Cancer Res. 2002; Google Scholar, F. A. F. Cancer Res. 2005; PubMed Scopus Google Scholar). to other miRNA expression and miR-21 overexpression is a of miR-21 been to exhibit oncogenic in cell miR-21 as an factor in human cell lines J.A. Cancer Res. 2005; PubMed Scopus Google Scholar) and enhances the of breast cancer cells S. Wu H. Wu F. Mo Y.Y. Oncogene. 2007; PubMed Scopus Google Scholar) and cancer cell lines F. R. H. K. T. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). Additionally, miR-21 promotes cell invasion and metastasis of and breast cancer cell lines (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, S. H. Oncogene. 2008; PubMed Scopus Google Scholar). miRNAs function via of target and miR-21 a variety of including and (9.Zhu S. Wu H. Wu F. Nie D. Sheng S. Mo Y.Y. Cell Res. 2008; 18: 350-359Crossref PubMed Scopus (990) Google Scholar, S. Wu H. Mo Y.Y. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar, S. H. Oncogene. 2008; PubMed Scopus Google Scholar, F. R. H. K. T. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar) that have been in cell it is likely that miR-21 roles the of the miR-21 in a cell Our supported this we found that miR-21 down-regulated PDCD4 other miR-21 in MDA-MB-435 breast cancer cells and expression of miR-21 MDA-MB-435 cell The miR-21, and the expression of the HER2/neu-induced oncogenic in cancer cells. a miR-21 target expression may as a marker for the of the HER2/neu-overexpressing cancers in a clinical In the we that miR-21 is via the pathway of HER2/neu. We pathway activated (G12V), and found that it also increased miR-21 in HER2/neu-negative breast cancer cells our results suggest that miR-21 is an important involved in the signaling associated with In to H-Ras (G12V), an of transcription factors, promotes the development of breast cancer N. J. Mol. Cell. Biol. 18: PubMed Scopus Google Scholar), and of ID-1 expression the and metastasis of breast cancer cells S. Y. T. J. Y. Proc. Natl. Acad. Sci. U.S.A. PubMed Scopus Google Scholar). the mechanism by which the pathway activates ID-1 in our studies we found that overexpression of ID-1 the miR-21 up-regulation of the oncogenes we up-regulation of miR-21 is associated with cell it is that miR-21 is for the metastasis in breast cancer cells. miR-21 overexpression may a of signaling associated with pathway Here we show that HER2/neu can induce miR-21 up-regulation in a variety of cancer cell miR-21 been previously to up-regulated in human breast cancer and breast cancer cell lines of HER2/neu expression S. Y. T. J. Y. Proc. Natl. Acad. Sci. U.S.A. PubMed Scopus Google Scholar, M. A. M. W. S. Cancer Res. 2007; PubMed Scopus Google Scholar). miR-21 is via the it is likely that miR-21 is up-regulated in breast cancer cells oncogenes or that this expression of of the epidermal growth factor receptor or is in breast cancer cells, and these have been to the pathway J.A. Mol. 2000; PubMed Google Scholar, A. D. M. A. M. W. M. F. J. PubMed Scopus Google Scholar). This may miR-21 is up-regulated in breast cancer cells. This also raises the possibility that miR-21 expression as a may of in HER2/neu-overexpressing also in a of In the of HER2/neu-induced miR-21 new HER2/neu overexpression promotes invasion and metastasis in cancers. We Dr. Mien-Chie Hung (M. D. Anderson Cancer Center) for the and for this We also and for MCF10A cells expressing the receptor, Dr. for the of MCF10A cells expressing and Dr. of for for this with