Deregulation of let-7e in epithelial ovarian cancer promotes the development of resistance to cisplatin

Drug resistance remains a major clinical obstacle to successful treatment in ovarian cancer patients, and the evidence of microRNAs involvement in drug resistance has been emerging recently. In this report, we investigated the role of let-7e in the development of cisplatin-resistant ovarian cancer. On the cellular level, let-7e expression was significantly reduced in cisplatin-resistant human epithelial ovarian cancer (EOC) cell line A2780/CP compared with parental A2780 cell and decreased in a concentration-dependent manner in A2780, SKOV3 and ES2 cells treated with cisplatin. Overexpression of let-7e by transfection of agomir could resensitize A2780/CP and reduce the expression of cisplatin-resistant-related proteins enhancer of zeste 2 (EZH2) and cyclin D1 (CCND1), whereas let-7e inhibitors increased resistance to cisplatin in parental A2780 cells. Quantitative methylation-specific PCR analysis showed hypermethylation of the CpG island adjacent to let-7e in A2780/CP cells, and demethylation treatment with 5-aza-CdR or transfection of pYr-let-7e-shRNA plasmid containing unmethylated let-7e DNA sequence could restore let-7e expression and partly reduce the chemoresistance. In addition, cisplatin combined with let-7e agomirs inhibited the growth of A2780/CP xenograft more effectively than cisplatin alone. Diminished expression of EZH2 and CCND1 and higher cisplatin concentrations in tumor tissue of mice subjected to administration of let-7e agomirs in addition to cisplatin were revealed by immunohistochemistry and atomic absorption spectroscopy, respectively. Taken together, our findings suggest that let-7e may act as a promising therapeutic target for improvement of the sensibility to cisplatin in EOC.

[1]  R C Young,et al.  Characterization of a cis-diamminedichloroplatinum(II)-resistant human ovarian cancer cell line and its use in evaluation of platinum analogues. , 1987, Cancer research.

[2]  N. Dubrawsky.  Cancer statistics , 1989, CA: a cancer journal for clinicians.

[3]  H. Warenius,et al.  Sensitivity to cis‐diamminedichloroplatinum in human cancer cells is related to expression of cyclin D1 but not C‐RAF‐1 protein , 1996, International journal of cancer.

[4]  Thomas D. Schmittgen,et al.  Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. , 2001, Methods.

[5]  V. Brabec,et al.  Molecular aspects of resistance to antitumor platinum drugs. , 2002, Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy.

[6]  Myriam Rochdi,et al.  Acquisition of resistance to cisplatin is accompanied by changes in the cellular pharmacology of copper. , 2002, Cancer research.

[7]  P. Morin.  Drug resistance and the microenvironment: nature and nurture. , 2003, Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy.

[8]  Z. Siddik,et al.  Cisplatin: mode of cytotoxic action and molecular basis of resistance , 2003, Oncogene.

[9]  C. Burge,et al.  Prediction of Mammalian MicroRNA Targets , 2003, Cell.

[10]  D. Bartel.  MicroRNAs Genomics, Biogenesis, Mechanism, and Function , 2004, Cell.

[11]  J. Lamb,et al.  The activities of cyclin D1 that drive tumorigenesis. , 2004, Trends in molecular medicine.

[12]  Y. Yatabe,et al.  Reduced Expression of the let-7 MicroRNAs in Human Lung Cancers in Association with Shortened Postoperative Survival , 2004, Cancer Research.

[13]  John G Doench,et al.  Specificity of microRNA target selection in translational repression. , 2004, Genes & development.

[14]  K. Gunsalus,et al.  Combinatorial microRNA target predictions , 2005, Nature Genetics.

[15]  H. Heng,et al.  Overexpression of Cyclin D1 Promotes Tumor Cell Growth and Confers Resistance to Cisplatin-Mediated Apoptosis in an Elastase-myc Transgene–Expressing Pancreatic Tumor Cell Line , 2005, Clinical Cancer Research.

[16]  S. Howell,et al.  Contribution of the Major Copper Influx Transporter CTR1 to the Cellular Accumulation of Cisplatin, Carboplatin, and Oxaliplatin , 2006, Molecular Pharmacology.

[17]  A. Jemal,et al.  Cancer Statistics, 2007 , 2007, CA: a cancer journal for clinicians.

[18]  D. Katsaros,et al.  Hypermethylation of let-7a-3 in epithelial ovarian cancer is associated with low insulin-like growth factor-II expression and favorable prognosis. , 2007, Cancer research.

[19]  T. Patel,et al.  The MicroRNA let-7a Modulates Interleukin-6-dependent STAT-3 Survival Signaling in Malignant Human Cholangiocytes* , 2007, Journal of Biological Chemistry.

[20]  Imran Babar,et al.  MicroRNAs as potential agents to alter resistance to cytotoxic anticancer therapy. , 2007, Cancer research.

[21]  Asli Silahtaroglu,et al.  Altered MicroRNA expression confined to specific epithelial cell subpopulations in breast cancer. , 2007, Cancer research.

[22]  S. Howell,et al.  Transport of Cisplatin by the Copper Efflux Transporter ATP7B , 2008, Molecular Pharmacology.

[23]  Zhenbao Yu,et al.  Genetic variations of microRNAs in human cancer and their effects on the expression of miRNAs. , 2008, Carcinogenesis.

[24]  William C Reinhold,et al.  MicroRNAs modulate the chemosensitivity of tumor cells , 2008, Molecular Cancer Therapeutics.

[25]  Tian-Li Wang,et al.  MicroRNA Expression and Identification of Putative miRNA Targets in Ovarian Cancer , 2008, PloS one.

[26]  G. Calin,et al.  Cancer-associated genomic regions (CAGRs) and noncoding RNAs: bioinformatics and therapeutic implications , 2008, Mammalian Genome.

[27]  Tyler E. Miller,et al.  MicroRNA-221/222 Confers Tamoxifen Resistance in Breast Cancer by Targeting p27Kip1*♦ , 2008, Journal of Biological Chemistry.

[28]  C. Creighton,et al.  Widespread deregulation of microRNA expression in human prostate cancer , 2008, Oncogene.

[29]  A. Addario,et al.  Role of microRNAs in drug-resistant ovarian cancer cells. , 2008, Gynecologic oncology.

[30]  M. Toyota,et al.  Epigenetic silencing of microRNA-34b/c and B-cell translocation gene 4 is associated with CpG island methylation in colorectal cancer. , 2008, Cancer research.

[31]  A. Sood,et al.  Novel strategies for reversing platinum resistance. , 2009, Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy.

[32]  H. Verheul,et al.  Understanding the causes of multidrug resistance in cancer: a comparison of doxorubicin and sunitinib. , 2009, Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy.

[33]  Jingqin Luo,et al.  Epigenetic repression of microRNA-129-2 leads to overexpression of SOX4 oncogene in endometrial cancer. , 2009, Cancer research.

[34]  B. Blair,et al.  Copper Transporter 2 Regulates the Cellular Accumulation and Cytotoxicity of Cisplatin and Carboplatin , 2009, Clinical Cancer Research.

[35]  Zhiwei Wang,et al.  Up-regulation of miR-200 and let-7 by natural agents leads to the reversal of epithelial-to-mesenchymal transition in gemcitabine-resistant pancreatic cancer cells. , 2009, Cancer research.

[36]  D. Berney,et al.  The association of CCND1 overexpression and cisplatin resistance in testicular germ cell tumors and other cancers. , 2010, The American journal of pathology.

[37]  D. Hanahan,et al.  Enhancing tumor-specific uptake of the anticancer drug cisplatin with a copper chelator. , 2010, Cancer cell.

[38]  J Ma,et al.  MicroRNA and drug resistance , 2010, Cancer Gene Therapy.

[39]  Jing Wang,et al.  Overexpression of EZH2 contributes to acquired cisplatin resistance in ovarian cancer cells in vitro and in vivo , 2010, Cancer biology & therapy.

[40]  F. Pontén,et al.  Expression of the RNA-binding protein RBM3 is associated with a favourable prognosis and cisplatin sensitivity in epithelial ovarian cancer , 2010, Journal of Translational Medicine.

[41]  Jingde Zhu,et al.  DNA Methylation-regulated miR-193a-3p Dictates Resistance of Hepatocellular Carcinoma to 5-Fluorouracil via Repression of SRSF2 Expression* , 2011, The Journal of Biological Chemistry.

[42]  A. Chinnaiyan,et al.  Genetic and epigenetic loss of microRNA-31 leads to feed-forward expression of EZH2 in melanoma , 2012, Oncotarget.

[43]  Shadan Ali,et al.  Loss of Let-7 Up-Regulates EZH2 in Prostate Cancer Consistent with the Acquisition of Cancer Stem Cell Signatures That Are Attenuated by BR-DIM , 2012, PloS one.