Gastric cancer remains the second leading cause of cancer deaths worldwide. Resistance to chemotherapy is a significant barrier for effective cancer treatment. Here, we identified miR-185 to be a contributor to chemosensitivity in gastric cancer. We observed low levels of miR-185 in gastric cancer cell lines and clinical tissues, compared with gastric epithelium cell line and noncancerous tissues. Furthermore, enforced expression of miR-185 increased the sensitivity of gastric cancer cells to low-dose chemotherapeutic agents, which alone cannot trigger significant apoptosis. Conversely, knockdown of endogenous miR-185 prevented high-dose chemotherapy-induced apoptosis. In elucidating the molecular mechanism by which miR-185 participated in the regulation of chemosensitivity in gastric cancer, we discovered that apoptosis repressor with caspase recruitment domain (ARC) is a direct target of miR-185. The role of miR-185 was confirmed in gastric tumor xenograft model. The growth of established tumors was suppressed by a combination therapy using enforced miR-185 expression and a low dose of anticancer drugs. Finally, we found that RUNX3 (Runt-related transcription factor) was involved in the activation of miR-185 at the transcriptional level. Taken together, our results reveal that RUNX3, miR-185 and ARC regulate the sensitivity of gastric cancer cells to chemotherapy.

The results suggest a distinctly different mutation spectrum of MMR genes between northern and southern Chinese populations and call for a systematic, nationwide study to facilitate the design of a MMR gene mutation detection strategy tailored for individual populations in China.

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