MicroRNA-221/222 Negatively Regulates Estrogen Receptorα and Is Associated with Tamoxifen Resistance in Breast Cancer*

A search for regulators of estrogen receptor α (ERα) expression has yielded a set of microRNAs (miRNAs) for which expression is specifically elevated in ERα-negative breast cancer. Here we show distinct expression of a panel of miRNAs between ERα-positive and ERα-negative breast cancer cell lines and primary tumors. Of the elevated miRNAs in ERα-negative cells, miR-221 and miR-222 directly interact with the 3′-untranslated region of ERα. Ectopic expression of miR-221 and miR-222 in MCF-7 and T47D cells resulted in a decrease in expression of ERα protein but not mRNA, whereas knockdown of miR-221 and miR-222 partially restored ERα in ERα protein-negative/mRNA-positive cells. Notably, miR-221- and/or miR-222-transfected MCF-7 and T47D cells became resistant to tamoxifen compared with vector-treated cells. Furthermore, knockdown of miR-221 and/or miR-222 sensitized MDA-MB-468 cells to tamoxifen-induced cell growth arrest and apoptosis. These findings indicate that miR-221 and miR-222 play a significant role in the regulation of ERα expression at the protein level and could be potential targets for restoring ERα expression and responding to antiestrogen therapy in a subset of breast cancers.

[1]  V. Ambros,et al.  The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14 , 1993, Cell.

[2]  M. Duffy,et al.  Studies on oestrogen receptor-α and -β mRNA in breast cancer , 2001 .

[3]  I. Poola,et al.  Estrogen receptor alpha (ERα) mRNA copy numbers in immunohistochemically ERα-positive-, and negative breast cancer tissues , 2007, BMC Cancer.

[4]  Xu Ma,et al.  Genome-wide microRNA profiling in human fetal nervous tissues by oligonucleotide microarray , 2006, Child's Nervous System.

[5]  Christopher P Evans,et al.  An androgen-regulated miRNA suppresses Bak1 expression and induces androgen-independent growth of prostate cancer cells , 2007, Proceedings of the National Academy of Sciences.

[6]  Huan Yang,et al.  MicroRNA expression profiling in human ovarian cancer: miR-214 induces cell survival and cisplatin resistance by targeting PTEN. , 2008, Cancer research.

[7]  C. Croce,et al.  MicroRNA gene expression deregulation in human breast cancer. , 2005, Cancer research.

[8]  B. Reinhart,et al.  The 21-nucleotide let-7 RNA regulates developmental timing in Caenorhabditis elegans , 2000, Nature.

[9]  J. Cheng,et al.  A simple method for profiling miRNA expression. , 2008, Methods in molecular biology.

[10]  S. K. Zaidi,et al.  MicroRNAs 221 and 222 bypass quiescence and compromise cell survival. , 2008, Cancer research.

[11]  A. Giordano,et al.  Epigenetic information and estrogen receptor alpha expression in breast cancer. , 2006, The oncologist.

[12]  Giovanni Vanni Frajese,et al.  miR-221 and miR-222 Expression Affects the Proliferation Potential of Human Prostate Carcinoma Cell Lines by Targeting p27Kip1* , 2007, Journal of Biological Chemistry.

[13]  Xu Ma,et al.  Retinoic acid downregulates microRNAs to induce abnormal development of spinal cord in spina bifida rat model , 2008, Child's Nervous System.

[14]  C. Croce,et al.  MicroRNAs 221 and 222 inhibit normal erythropoiesis and erythroleukemic cell growth via kit receptor down-modulation. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[15]  J. Herman,et al.  Specific Inhibition of DNMT1 by Antisense Oligonucleotides Induces Re-expression of Estrogen Receptor a (ER) in ER-negative Human Breast Cancer Cell Lines , 2003, Cancer biology & therapy.

[16]  F. Le Provost,et al.  MicroRNA involvement in mammary gland development and breast cancer. , 2006, Reproduction, nutrition, development.

[17]  B. White,et al.  The Micro-Ribonucleic Acid (miRNA) miR-206 Targets the Human Estrogen Receptor-α (ERα) and Represses ERα Messenger RNA and Protein Expression in Breast Cancer Cell Lines , 2007 .

[18]  Reuven Agami,et al.  Regulation of the p27Kip1 tumor suppressor by miR‐221 and miR‐222 promotes cancer cell proliferation , 2007 .

[19]  R. Weinberg,et al.  Tumour invasion and metastasis initiated by microRNA-10b in breast cancer , 2007, Nature.

[20]  J. Herman,et al.  Synergistic activation of functional estrogen receptor (ER)-α by DNA methyltransferase and histone deacetylase inhibition in human ER-α-negative breast cancer cells , 2001 .

[21]  Mauro Biffoni,et al.  The promyelocytic leukemia zinc finger-microRNA-221/-222 pathway controls melanoma progression through multiple oncogenic mechanisms. , 2008, Cancer research.

[22]  K. Nicholas,et al.  Identification and transcript analysis of a novel wallaby (Macropus eugenii) basal-like breast cancer cell line , 2008, Molecular Cancer.

[23]  V. Ambros.  microRNAs Tiny Regulators with Great Potential , 2001, Cell.

[24]  C. Croce,et al.  MicroRNAs (miR)-221 and miR-222, both overexpressed in human thyroid papillary carcinomas, regulate p27Kip1 protein levels and cell cycle. , 2007, Endocrine-related cancer.

[25]  S. Wołczyński,et al.  Distinct mRNA, protein expression patterns and distribution of oestrogen receptors alpha and beta in human primary breast cancer: correlation with proliferation marker Ki-67 and clinicopathological factors. , 2005, European journal of cancer.

[26]  P. Adams,et al.  Induction of the Estrogen Receptor by Ablation of DNMT1 in ER-Negative Breast Cancer Cells , 2003, Cancer biology & therapy.

[27]  J E Paciga,et al.  Phosphatidylinositol-3-OH Kinase (PI3K)/AKT2, activated in breast cancer, regulates and is induced by estrogen receptor alpha (ERalpha) via interaction between ERalpha and PI3K. , 2001, Cancer research.

[28]  S. Baylin,et al.  Methylation of the oestrogen receptor CpG island links ageing and neoplasia in human colon , 1994, Nature Genetics.

[29]  W. Gerald,et al.  Endogenous human microRNAs that suppress breast cancer metastasis , 2008, Nature.

[30]  B. Reinhart,et al.  Conservation of the sequence and temporal expression of let-7 heterochronic regulatory RNA , 2000, Nature.