Induction of pigmentation by a small molecule tyrosine kinase inhibitor nilotinib.

Skin color is determined by the melanin pigments that are produced in melanocytes then transferred to surrounding keratinocytes. Despite the growing number of commercial products claiming the pigmentation-regulatory effects, there is still a demand for the development of new materials that are safe and more efficacious. We tried to screen the pigmentation-regulatory materials using a commercially available drugs, and found that nilotinib could induce pigmentation in melanoma cells. When HM3KO melanoma cells were treated with nilotinib, melanin content was increased together with increase of tyrosinase activity. Nilotinib increased the expression of pigmentation-related genes such as MITF, tyrosinase and TRP1. Consistent with these results, the protein level for MITF, tyrosinase, and TRP1 was significantly increased by nilotinib. To delineate the action mechanism of nilotinib, we investigated the effects of nilotinib on intracellular signaling. As a result, nilotinib decreased the phosphorylation of AKT, while increased the phosphorylation of CREB. The pretreatment of PKA inhibitor H89 markedly blocked the nilotinib-induced phosphorylation of CREB. In accordance with, pretreatment of H89 significantly inhibited the nilotinib-induced pigmentation, indicating that nilotinib induces pigmentation via the activation of PKA signaling. Together, our data suggest that nilotinib can be developed for the treatment of hypopigmentary disorder such as vitiligo.