Cyclin-dependent kinase 4 is a novel target in micoRNA-195-mediated cell cycle arrest in bladder cancer cells.

miRNAs are a class of small-noncoding RNAs capable of negatively regulating gene expression. Here, we found that miR-195 is down-regulated in human bladder cancer tissue versus normal adjacent tissue. To better characterize the role of miR-195 in bladder cancer, we conducted gain of function analysis by transfecting bladder cancer cell line T24 with chemically synthesized miR-195 mimic. We identified CDK4, an early G1 cell cycle regulator, as a novel target of miR-195. Selective over-expression of miR-195 could induce G1-phase arrest in T24 cells, and subsequently inhibit T24 cell growth. These findings indicate that miR-195 could be a potential tumor suppressor in bladder cancer.