Abstract: Objective To investigate the role and mechanism of miR-491-5p on 5-fluorouracil (5-FU) sensitivity in human bladder cancer cell line EJ. Methods The expressions of miR-491-5p in chemotherapy-sensitive and resistant tissues were detected by RT-qPCR. The 5-FU resistant EJ/5-FU cell line was constructed, the miR-491-5p expression and phosphorylation of AKT and STAT3 were detected by RT-qPCR and Western blot, respectively. After miR-491-5p inhibitor was transfected into EJ cells or miR-491-5p mimic was transfected into EJ/5-FU cells, the cell viability, apoptosis, wound healing, migration, invasion, AKT and STAT3 phosphorylation levels were detected by CCK-8 assay, Annexin V-FITC/PI staining, scratch assay and Transwell assay and Western blot under the condition of 5-FU, respectively. Results The expression of miR-491-5p was significantly decreased in chemotherapy-resistant tissues and EJ/5-FU cell line(P＜0.01). After down-regulation of miR-491-5p in EJ cells, the inhibition of 5-FU on cell viability, wound healing, migration and invasion, and the promotion of apoptosis were significantly reduced (P＜0.01). After up-regulation of miR-491-5p in EJ/5-FU cell line, the inhibition of 5-FU on cell viability, wound healing, migration and invasion, and the promotion of apoptosis were significantly increased(P＜0.01). The phosphorylation of AKT and STAT3 was significantly increased in EJ/5-FU cell line(P＜0.01); the phosphorylation of AKT and STAT3 in cell line EJ was significantly increased after the down-regulation of miR-491-5p (P＜0.01), and the phosphorylation of AKT and STAT3 in EJ/5-FU cell line was significantly decreased after the up-regulation of miR-491-5p (P＜0.01). Conclusions Down-regulation of miR-491-5p reduces the sensitivity of cell line EJ to 5-FU, while up-regulation of miR-491-5p inhibits 5-FU resistance in EJ/5-FU cell line. miR-491-5p in regulation of 5-FU resistance of cell line EJ is accompanied by changes of AKT and STAT3 phosphorylation.

Key words: miR-491-5p, bladder cancer, 5-fluorouracil