microRNA-195 inhibits cell proliferation in bladder cancer via inhibition of cell division control protein 42 homolog/signal transducer and activator of transcription-3 signaling.

microRNA (miR)-195 acts as a suppressor in multiple types of malignant tumors, including bladder cancer; however, the detailed function of miR-195 in bladder cancer remains largely unknown. The aim of the present study was to investigate the role of miR-195 in the regulation of bladder cancer cell proliferation and to determine whether cell division control protein 42 homolog (Cdc42)/signal transducer and activator of transcription-3 (STAT3) signaling acts as a downstream effector of miR-195 in bladder cancer cells. Reverse transcription-quantitative polymerase chain reaction was used to determine the expression levels of miR-195 in bladder cancer tissues and normal adjacent tissue. The results revealed that the expression of miR-195 was significantly downregulated in bladder cancer tissues compared with that in the normal adjacent tissues. A luciferase reporter assay was then conducted, which identified Cdc42 as a direct target of miR-195, and the expression of Cdc42 was significantly upregulated in bladder cancer tissues, as determined by western blotting. Furthermore, miR-195 negatively regulated the protein expression of Cdc42 in bladder cancer cells. An MTT assay was also conducted to determine the rate of cell proliferation. Upregulation of miR-195 or the inhibition of Cdc42 could inhibit bladder cancer cell proliferation, possibly through activation of STAT3 signaling. In addition, restoration of Cdc42 could reverse the inhibitory effect of miR-195 upregulation on bladder cancer cell proliferation. In conclusion, the results of the present study suggest that miR-195 plays an inhibitory role in the regulation of bladder cancer cell proliferation by directly targeting Cdc42/STAT3 signaling.