Let-7b and microRNA-199a inhibit the proliferation of B16F10 melanoma cells.

Cutaneous melanoma is an aggressive form of human skin cancer characterized by high metastatic potential and poor prognosis. Biomarkers of metastatic risk are critically needed to instigate new auxiliary measures in high-risk patients. In clinical specimens of skin melanoma, we previously found that let-7b, microRNA-199a and microRNA-33 were significantly associated with metastatic melanoma, and thus may be the key to melanoma treatment. In this study, we examined the effect of overexpression and inhibition of let-7b and microRNA-199a. Plasmids overexpressing these genes were transfected into B16F10 melanoma cells, and let-7b and microRNA-199a expression were evaluated at the RNA, protein and cellular level. Cyclin D1 expression was significantly higher in cells transfected with let-7b plasmid and let-7b inhibitor compared with control cells (P<0.05). In turn, Met expression in the microRNA-199a plasmid group and microRNA-199a inhibitor group was significantly higher than in the control group (P<0.05). The proliferation rate of B16F10 cells transfected with let-7b or microRNA-199a was lower than that of the control group, particularly until the third day after transfection when the proliferation rate dropped to the lowest value (P<0.05). In addition, the apoptosis rates of the let-7b plasmid group and microRNA-199a plasmid group were significantly higher compared to that of the control group (P<0.05). These results suggest that let-7b and microRNA-199a may be negative regulators of B16F10 cell proliferation.