title: Epigenetic silencing of microRNA-199b-5p is associated with acquired chemoresistance via activation of JAG1-Notch1 signaling in ovarian cancer.
abstract: Epithelial ovarian cancer is a highly lethal and aggressive gynecological malignancy. The high mortality rate is due in part to the fact that many advanced cancer patients become refractory to current chemotherapeutic agents, leading to tumor recurrence and death. However, the underlying mechanisms leading to chemoresistance remain obscure. Here, we report that the loss of miR-199b-5p due to progressive epigenetic silencing leads to the activation of the JAG1-mediated Notch1 signaling cascade, thereby leading to the development of acquired chemoresistance in ovarian cancer. Using miRCURY LNA™ microRNA array and Q-PCR analyses of two pairs of cisplatin-sensitive and -resistant ovarian cancer cell lines, we identified miR-199b-5p as significantly down-regulated in cisplatin-resistant ovarian cancer cells and confirmed that miR-199b-5p is clinically associated with advanced and poor survival ovarian cancers. Interestingly, the loss of miR-199b-5p could be restored by 5-Aza-dC-mediated demethylation, and methylated specific PCR (MS-PCR), bisulfite-sequencing and pyrosequencing revealed that the promoter region of miR-199b-5p was hypermethylated. Computational and mechanistic analyses identified JAG1 as a primary target of miR-199b-5p. Notably, the reduced expression of miR-199b-5p was found to be inversely correlated with the increased expression of JAG1 using an ovarian cancer tissue array. Enforced expression of miR-199b-5p sensitized ovarian cancer cells to cisplatin-induced cytotoxicity both in vitro and in vivo. Conversely, re-expression of miR-199b-5p and siRNA-mediated JAG1 knockdown or treatment with Notch specific inhibitor γ-secretase (GSI) attenuated JAG1-Notch1 signaling activity, thereby enhancing cisplatin-mediated cell cytotoxicity. Taken together, our study suggests that the epigenetic silencing of miR-199b-5p during tumor progression is significantly associated with acquired chemoresistance in ovarian cancer through the activation of JAG1-Notch1 signaling.
authors.affiliation: Department of Obstetrics and Gynaecology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, P.R.China.
authors.forename: Michelle X
authors.initials: MX
authors.lastname: Liu
authors.forename: Michelle K Y
authors.initials: MK
authors.lastname: Siu
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Liu
authors.forename: Judy W P
authors.initials: JW
authors.lastname: Yam
authors.forename: Hextan Y S
authors.initials: HY
authors.lastname: Ngan
authors.forename: David W
authors.initials: DW
authors.lastname: Chan
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000077216:Carcinoma, Ovarian Epithelial; D002945:Cisplatin / Q000494:pharmacology; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D044127:Epigenesis, Genetic; D057890:Epigenomics; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000072100:Jagged-1 Protein; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D035683:MicroRNAs / Q000235:genetics*; D009375:Neoplasms, Glandular and Epithelial / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D002135:Calcium-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; C000606273:JAG1 protein, human; C000606274:Jag1 protein, mouse; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; D035683:MicroRNAs; C497761:NOTCH1 protein, human; D051881:Receptor, Notch1; D000072099:Serrate-Jagged Proteins; C531408:mirn199 microRNA, human; D002945:Cisplatin