Wnt/beta-catenin signaling inhibitor ICG-001 enhances pigmentation of cultured melanoma cells

Abstract

Background: Wnt/beta-catenin signaling is important in development and differentiation of melanocytes. Objective: The object of this study was to evaluate the effects of several Wnt/beta-catenin signaling inhibitors on pigmentation using melanoma cells. Methods: Melanoma cells were treated with Wnt/beta-catenin signaling inhibitors, and then melanin content and tyrosinase activity were checked. Results: Although some inhibitors showed slight inhibition of pigmentation, we failed to observe potential inhibitory effect of those chemicals on pigmentation of HM3KO melanoma cells. Rather, one of powerful Wnt/beta-catenin signaling inhibitors, ICG-001, increased the pigmentation of HM3KO melanoma cells. Pigmentation-enhancing effect of ICG-001 was reproducible in other melanoma cell line MNT-1. Consistent with these results. ICG-001 increased the expression of pigmentation-related genes, such as MITF, tyrosinase and TRP1. When ICG-001 was treated, the phosphorylation of CREB was significantly increased. In addition, ICG-001 treatment led to quick increase of intracellular cAMP level, suggesting that ICG-001 activated PICA signaling. The blockage of PKA signaling with pharmaceutical inhibitor H89 inhibited the ICG-001-induced pigmentation significantly. Conclusions: These results suggest that PKA signaling is pivotal in pigmentation process itself, while the importance of Wnt/beta-catenin signaling should be emphasiZed in the context of development and differentiation. (C) 2016 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.