Epigenetic silencing of miR-200b is associated with cisplatin resistance in bladder cancer

// Tetsuya Shindo 1, 2 , Takeshi Niinuma 2 , Naotaka Nishiyama 1 , Nobuo Shinkai 1 , Hiroshi Kitajima 2 , Masahiro Kai 2 , Reo Maruyama 3 , Takashi Tokino 4 , Naoya Masumori 1 and Hiromu Suzuki 2 1 Department of Urology, Sapporo Medical University School of Medicine, Sapporo 060-8543, Japan 2 Department of Molecular Biology, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan 3 Project for Cancer Epigenome, The Cancer Institute, Japanese Foundation for Cancer, Koto-ku, Tokyo 135-8550, Japan 4 Medical Genome Science, Research Institute for Frontier Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan Correspondence to: Hiromu Suzuki, email: hsuzuki@sapmed.ac.jp Keywords: bladder cancer; cisplatin resistance; miRNA; DNA methylation; histone modification Abbreviations: BCa: bladder cancer; NMIBC: non-muscle invasive bladder cancer; MIBC: muscle invasive bladder cancer; CDDP: cisplatin Received: November 07, 2017      Accepted: April 17, 2018      Published: May 11, 2018 ABSTRACT In this study, we identified microRNAs (miRNAs) involved in cisplatin (CDDP) resistance in bladder cancer (BCa). After establishing CDDP-resistant BCa cell lines (T24RC and EJ138RC), TaqMan arrays revealed that members of the miR-200 family (miR-200b, miR-200a and miR-429) were downregulated in T24RC as compared to parental T24 cells. miR-200b was associated with CDDP sensitivity in BCa cells, and its downregulation was associated with CpG island hypermethylation. Pharmacological demethylation using 5-aza-2’-deoxycytidine restored miR-200b expression, and the combination of 5-aza-2’-deoxycytidine + CDDP strongly inhibited T24RC cell proliferation. Microarray analysis revealed that miR-200b + CDDP induced genes involved in CDDP sensitivity or cytotoxicity, including IGFBP3, ICAM1 and TNFSF10, in the resistant cells. Expression and DNA methylation of miR-200b were inversely associated in primary BCa, and low expression/high methylation was associated with poor overall survival. These results suggest downregulation of miR-200b is associated with CDDP resistance in BCa. Epigenetic silencing of miR-200b may be a marker of CDDP resistance and a useful therapeutic target for overcoming CDDP resistance in BCa.