Abstract: Objective To investigate the relationship between miR-135a expression and paclitaxel sensitivity in gastric cancer cells, and explore the possible mechanisms. Methods The differential microRNAs were screened using Taqman microRNA assay in the serum of gastric cancer patients with different efficacies treated with paclitaxel chemotherapy. microRNA-135a (miR-135a), which had relationship with paclitaxel sensitivity, was selected in the following study. The influence and possible mechanisms of miR-135a expression on the sensitivity of paclitaxel in gastric cancer cells were investigated by using cell proliferation curve, flow cytometry, and Western blot. Results The expression level of miR-135a in patients with progressive disease treated with paclitaxel was significantly higher than that in patients with partial response（P<0.05）, suggesting its relationship with paclitaxel resistance. miR-135a could decrease the sensitivity of paclitaxel in gastric cancer cells through inhibiting cell cycle arrest at G2 phase and cell apoptosis induced by paclitaxel（P<0.05）. Conclusions miR-135a might be a predictive marker for paclitaxel efficacy in future clinical practice.

Key words: gastric cancer, miR-135a, paclitaxel, resistance