MiR-181c sensitizes ovarian cancer cells to paclitaxel by targeting GRP78 through the PI3K/Akt pathway.

Primary cytoreductive surgery with platinum-taxane-based chemotherapy is the standard treatment for ovarian cancer (OC) patients; however, resistance to chemotherapy is a contributing factor to OC mortality. Paclitaxel (PTX), the most widely used taxane, has become the first-line drug against OC. The molecular mechanism of PTX resistance is different from that of platinum-based agents and is still not completely elucidated. Our previous study showed that glucose-regulated protein 78 (GRP78) is involved in the resistance of OC cells to PTX. However, little is known regarding endogenous inhibitors of this gene. MicroRNAs (miRNAs) play critical roles in the regulation of gene expression; therefore, we sought to identify miRNA(s) with potential to target GRP78 under the hypothesis that miRNA(s) could serve as potential therapeutic targets. Here, we show that miR-181c, predicted to target GRP78, was downregulated in PTX-resistant OC cells and tissues. MiR-181c downregulated GRP78 expression and induced apoptosis by directly targeting its 3'-untranslated region (UTR). Overexpression of miR-181c sensitized resistant OC to PTX by inhibiting the PI3K/Akt pathway in vitro and in vivo. Taken together, our findings indicate that the delivery of miR-181c can efficiently suppress GRP78 expression and GRP78-mediated PTX resistance in OC and suggest that this strategy has therapeutic potential.