Epithelial ovarian cancer is the most lethal gynecological malignancy in the Western world. A major impediment for the successful treatment is the development of drug resistance. The molecular processes that contribute to resistance have been extensively studied; however, there is not much known about regulation by microRNAs (miRNAs). We compared miRNA expression profiles of an isogenic cisplatin-sensitive and -resistant ovarian cancer cell line pair (A2780/A2780 DDP) and found 27 miRNAs to be differentially expressed (≥2-fold). Five of these, including the family members miR-141/200c, showed a correlation with cisplatin sensitivity in the NCI-60 panel. Overexpression of miR-141 resulted in enhanced resistance to cisplatin in ovarian cancer cell lines. We next correlated the expression level of miR-141 in 132 primary ovarian tumors (108 serous and 24 non-serous) with response to platinum-based chemotherapy. Although no differences were observed in the serous tumors, miR-141 levels were higher in non-serous ovarian tumors that did not respond well to therapy (platinum-free interval <6 months). We demonstrate that miR-141 directly targets KEAP1, and that downregulation of KEAP1 induces cisplatin resistance. Conversely, overexpression of KEAP1 significantly enhanced cisplatin sensitivity. Expression of KEAP1 with its 3′-UTR, and a 3′-UTR in which the miR-141 target site has been mutated, revealed that miR-141 regulates KEAP1 upon exposure to cisplatin. Finally, we show that the NF-κB pathway, which can be regulated by KEAP1, is activated upon miR-141 overexpression, and that inhibition of this pathway partially reverses miR-141-mediated cisplatin resistance. These findings demonstrate that the miR-141-mediated regulation of KEAP1 has a crucial role in the cellular response to cisplatin.

cisplatin, drug resistance, KEAP1, miR-141, ovarian cancer
dx.doi.org/10.1038/onc.2012.433, hdl.handle.net/1765/66728
Oncogene: including Oncogene Reviews
Erasmus MC: University Medical Center Rotterdam

van Jaarsveld, M.T.M, Helleman, J, Boersma, A.W.M, van Kuijk, P.F, van IJcken, W.F.J, Despierre, E, … Wiemer, E.A.C. (2013). miR-141 regulates KEAP1 and modulates cisplatin sensitivity in ovarian cancer cells. Oncogene: including Oncogene Reviews, 32(36), 4284–4293. doi:10.1038/onc.2012.433