Delphinidin upregulates microRNA-let-7b expression through family with sequence similarity 222 member B.

Delphinidin is a major anthocyanidin belonging to the flavonoid family with pharmacological activities against cancer, inflammation, and muscle atrophy. However, the mechanism regulating its activity is yet to be completely elucidated. The present study aimed to identify the molecules responsible for the effects of delphinidin. We investigated the effects of delphinidin on melanoma cells and observed that delphinidin upregulates the expression of let-7b, a microRNA (miRNA) that inhibits the proliferation of melanoma cells. Delphinidin-induced upregulation of let-7b led to the suppression of cyclin D1, a target gene associated with cell cycle progression. Using genetic functional screening, we identified that family with sequence similarity 222 member B (Fam222B) is an important factor behind the inhibitory effects of delphinidin against melanoma cell proliferation and that the transfection with small interfering RNA specifically targeting Fam222B altered miRNAs expression in B16 cells. In summary, delphinidin exerts antimelanoma effects by increasing let-7b expression through Fam222B, and Fam222B is involved in regulating miRNA expression.