Activation of microRNA-596 induced by DNA demethylation and interferon in malignant melanoma cells

Dysregulation of microRNA has been implicated in melanoma, although the mechanism is not fully understood. We aimed to examine the epigenetically silenced miRNAs and its involvement in the antitumor effect of DNA demethylation and interferon in melanoma. Growth suppressive effects of 5-aza-2’deoxycytidine plus interferon-β were assessed in 20 melanoma cell lines, and the highest effect was observed in TXM18 cells. A screen for miRNAs induced by 5-aza-2’deoxycytidine plus IFN-β in TXM18 cells identifi ed a set of miRNAs including miR-7, miR-203, miR-215 and miR-596. The CpG island of the miR-596 gene was highly methylated in all melanoma cell lines tested (n = 20) whereas levels of methylation were limited in normal melanocytes. Methylation levels of miR-596 were signifi cantly higher in clinical specimens of melanoma than in benign melanocytic nevi (40.6% vs. 30.1%, P= 0.018). Furthermore, transfection of a precursor of miR-596 into melanoma cells induced growth suppression, indicating that the effect of 5-aza-2’deoxycytidine plus interferon-β is in part due to induction of miR-596. Our data suggest that miR-596 is a novel tumor suppressor frequently silenced by DNA methylation in melanoma; that modulation of miRNAs may be involved in the antitumor effect of DNA demethylation plus interferon in melanoma.