The Anti-tumor Role And Mechanism Of MiR-195in Bladder Cancer

Urinary bladder cancer ranks ninth in worldwide cancer incidence, and it has been listed as the most common genitourinary tract malignancy in China. It is believed that tumorigenesis and progression of bladder cancer would involve various factor, including genetic changes. microRNA are a class of small-noncoding RNA capable of negatively regulating the gene expression. Accumulating evidences indicate that aberrant expression of microRNA can contribute to bladder tumorigenesis.Our research focused on discussing the anti-tumor role and mechanism of miR-195in bladder cancer. The main investigations and results are as follows:1) miR-195was quantified in human bladder cancer tissue by qPCR. Out of16paired bladder cancer tissues and adjacent non-tumorous bladder mucosal tissues,15(93.75%) cancer tissues presented with miR-195in down-regulated pattern while comparing with normal adjacent tissue. The mean miR-195expression level in cancer tissues was about1/4of that in normal adjacent tissue. However, no difference was detected when the bladder caner cases were stratified by histological stage or grade.2) To better characterize the role of miR-195in bladder cancer, we conducted gain of function analysis by transfecting bladder cancer cell line T24with chemically synthesized miR-195mimic. We found that over expression of miR-195could induce G1-phase arrest in T24cells, and subsequently inhibit T24cells growth and colony formation. Notably,50nM miR-195mimic demonstrated a potent inhibitory effect at72h after transfection. It could reduce cell viability by37%. Also, the colony formation ability was impared after miR-195mimic treatment, with a9%drop in in vitro colony formation rates and retardation in vivo tumor growth. However, no effect on cell apoptosis was detected. The cell migration and invasion were undisturbed either.3) We explored the possible targets of miR-195involved in T24cell cycle arrest. We identified that Cyclin D1, CDK4, CDK6and E2F3could be down-regulated by miR-195. Moreover, as a novel target, CDK4was verified as one of the key mediator of miR-195induced Gl-phase arrest in T24cells. Further qPCR analysis and luciferase assay confirmed that miR-195transcriptionally repressed CDK4by interatcting with the essential binding sequence located in3'-UTR of CDK4.In conclusion, we identified that miR-195was novel tumor suppressor microRNA in bladder cancer. It could suppress bladder caner cell growth via cell cycle arrest induction. CDK4was a novel direct target of miR-195, and it played an important role in the anti-tumor mechanism of miR-195...