Abstract: Objective To explore the inhibition effect and mechanism of miR-146a-5p on proliferation and invasion of prostate cancer (PCa) cell line PC-3 by targeting SMAD4. Methods RT-qPCR was used to detect the expression of miR-146a-5p in PCa tissues and cell lines. The relevance of miR-146a-5p expression with Gleason score was also analyzed. MTT, BrdU experiment, cell colony formation experiment, scratch experiment, Transwell assay and nude mouse xenograft model experiment were conducted to detect the effect of miR-146a-5p on cell proliferation, tumorigenicity, migration and invasion. The expression of SMAD4 in PCa tissues was detected by RT-qPCR, and the targeting relationship of SMAD4 and miR-146a-5p was confirmed by double luciferase reporter gene assay and rescue experiment. Western blot was used to detect the expression of SMAD2/SMAD3 complex in nucleus affected by miR-146a-5p and SMAD4. Finally, double luciferase reporter gene assay and ChIP experiment were performed to examine the targeting regulation of TIM3 by miR-146a-5p/SMAD4/SMAD2/SMAD3 signaling axis. Results miR-146a-5p was low expressed in PCa tissues and cell lines; its expression was negatively correlated to Gleason score and had the lowest expression in PC-3 cells. miR-146a-5p inhibited the proliferation and invasion of PC-3 cells by targeting SMAD4. SMAD2/SMAD3/TIM3 axis seemed to be the downstream mechanism of miR-146a-5p/SMAD4 signaling pathway. Conclusions miR-146a-5p can inhibit the proliferation and invasion of PC-3 cells by targeting SMAD4, and the downstream mechanism might be related to the SMAD2/SMAD3/TIM3 signaling pathway.

Key words: prostate cancer, miR-146a-5p, SMAD4, TIM3