miR-20b regulates expression of proteinase-activated receptor-1 (PAR-1) thrombin receptor in melanoma cells.

The proteinase-activated receptor 1 (PAR-1) plays a central role in melanoma progression and its expression level is believed to correlate with the degree of cancer invasiveness. Here, we show that PAR-1 is post-transcriptionally regulated by miR-20b microRNA in human melanoma cells. PAR-1 was found to be expressed in metastatic melanoma cells but was barely detectable in primary melanoma. By transducing primary melanoma cells with a lentivirus containing a 3'-UTR construct of PAR-1 mRNA, we could show that endogenous melanoma microRNAs interacted with PAR-1 3'-UTR and silenced a fused luciferase reporter. Transfection of an inhibitor against miR-20b into primary melanoma cells reversed this process. Finally, transfection of miR-20b mimic into metastatic melanoma cells caused downregulation of the luciferase reporter. We conclude that miR-20b regulates expression of melanoma PAR-1 receptor, which may explain the differential expression of PAR-1 observed in human melanoma.