Login to Access Video or Poster Abstract: MP44-14
Sources of Funding: none

Introduction

Chemoresistance to cisplatin (CDDP) is one of the major clinical issues in bladder cancer (BCa) treatment. MicroRNAs (miRNA) are noncoding RNAs that are potentially involved in chemoresistance in various cancers. We therefore aimed to determine the roles of miRNAs in the CDDP-resistance in BCa.

Methods

We established 2 CDDP-resistant BCa cell lines (T24RC and EJ138RC) by continuously treating parental T24 and EJ138 cells. Profiles of miRNA expression in BCa cells were assessed by TaqMan arrays (Applied Biosystems). BCa cells were transfected with a mimic or an inhibitor of miR-200b (Ambion), after which the sensitivities to CDDP were evaluated via cell viability assays. Methylation of a CpG island of the miR200b gene was assessed by bisulfite-pyrosequencing. BCa cells were treated with the DNA demethylating agent 5-aza-2’-deoxycytidine (5-aza-dC) to restore the expression of miR-200b.

Results

Of the 754 miRNAs analyzed, miR-200b was downregulated in CDDP-resistant BCa cells (Figure 1). Induction of miR-200b in T24RC cells restored the CDDP sensitivity (Figure 2a). In contrast, inhibition of miR-200b increased CDDP resistance in T24 and EJ138 cells (Figure 2b and 2c). The levels of methylation in the CpG islands of miR-200b were significantly increased in T24RC and EJ138RC as compared to their parental cells (T24RC, 83.3%; T24, 53.3%; EJ138RC, 77.0%; EJ138, 62.6%; P < 0.01, Student t test), and treatment with 5-aza-dC restored the miR-200b expression in resistant cells (Figure 3a and 3b). Moreover, treatment with CDDP and 5-aza-dC synergistically inhibited the growth of T24RC cells (Figure 3c).

Conclusions

Our results suggest that epigenetic downregulation of miR-200b may be causally related to the CDDP-resistance in BCa, and that it could be a potential therapeutic target.

Funding

none