The tumour suppressor miR-34c targets MET in prostate cancer cells

Background: The microRNA, miR-34c, is a well-established regulator of tumour suppression. It is downregulated in most forms of cancers and inhibits malignant growth by repressing genes involved in processes such as proliferation, anti-apoptosis, stemness, and migration. We have previously reported downregulation and tumour suppressive properties for miR-34c in prostate cancer (PCa). Methods: In this study, we set out to further characterize the mechanisms by which miR-34c deregulation contributes to PCa progression. The genes regulated by miR-34c in the PCa cell line PC3 were identified by microarray analyses and were found to be enriched in cell death, cell cycle, cellular growth, and cellular movement pathways. One of the identified targets was MET, a receptor tyrosine kinase activated by hepatocyte growth factor, that is crucial for metastatic progression. Results: We confirmed the inhibitory effect of miR-34c on both MET transcript and protein levels. The binding of miR-34c to two binding sites in the 3'-UTR of MET was validated using luciferase reporter assays and target site blockers. The effect of this regulation on the miR-34c inhibition of the migratory phenotype was also confirmed. In addition, a significant inverse correlation between miR-34c expression levels and MET immunostaining was found in PCa patients. Conclusion: These findings provide a novel molecular mechanism of MET regulation in PCa and contribute to the increasing evidence that miR-34c has a key tumour suppressive role in PCa.