Abstract 5242: Effect of total saponins of Gynostemma pentaphyllum on melanogenesis and anti-melanoma effect in B16 cells.

Abstract

Abstract Melanogenesis is a physiological process of melanin production in response to UV exposure, which is modulated through multi-signaling pathways including cAMP/PKA, Wnt/β-catenin and MAPK signaling cascades. In this study, we investigated both the melanogenesis and anti-melanoma effects of total saponins of Gynostemma pentaphyllum (GpS). Our results showed that non-toxic dosages of GpS stimulated tyrosinase activity and increased melanin content in a dose-dependent manner. Western blot analysis showed that GpS treatment significantly up-regulated the expression levels of the melanogenic proteins, tyrosinase (TYR) and microphthalmia-associated transcription factor (MITF) in a dose-dependent manner. The p-CREB, which is the down-stream target of PKA is also elevated upon GpS treatment. We further observed that H89, a PKA inhibitor, attenuated the GpS induced tyrosinase activity, melanin content, and the protein expression of p-CREB and the nuclear β-catenin. To identify the active saponins, GpS was fractionated in the MCI-CHP 20P column and eluted with methanol in a gradient of 50 to 100% . The resulting ten fractions were tested for their melanogensis activities. We found that Fractions 5 to 9 showed the strongest effect in melanin synthesis in B16 cultures, while up-regulated the expression levels of TYR and MITF, while Fractions 7 to 9 increased nucleus β-catenin protein expression. Further purification of GpS is under way. Our early works showed that GpS exhibits strong anti-cancer effects in both in cellular and animal model. We were wonder whether GpS would exert anti-cancer effect against melanoma. To address this question, we tested and showed that GpS inhibited B16 cells migration in a dose-dependent manner. Meanwhile, GpS also increased G1/S ratio of the GpS-treated B16 cells, suggesting that GpS may act as G1 inhibitor. Our study seems to be in line with the recent reports that stimulation of melanogenesis might be associated with the anti-melanoma effect by decreasing proliferation and invasiveness of melanoma (Chien, et al.,2009). Based on the above results, we proposed that GpS might exert the anti-melanoma effect by stimulating the melanogenesis through the activation of cAMP/PKA and Wnt/β-catenin signaling pathways. Citation Format: Ting Fung Tsang, William Chi Shing Tai, Wendy Wen Luan Hsiao. Effect of total saponins of Gynostemma pentaphyllum on melanogenesis and anti-melanoma effect in B16 cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5242. doi:10.1158/1538-7445.AM2013-5242