Tangeretin triggers melanogenesis through the activation of melanogenic signaling proteins and sustained extracellular signal- regulated kinase in B16/F10 murine melanoma cells.

In order to test the effectiveness of tangeretin at ameliorating melanoma and melanoma-associated depigmentation, western blotting was used to assess the melanin content of treated melanoma cells. Tangeretin, a 4',5,6,7,8-pentamethoxyflavone, was found to trigger intracellular melanin production in a concentration-dependent manner in B16/F10 murine melanoma cells. Melanin content increased 1.74-fold in response to treatment with 25 μM of tangeretin, compared to that in non-treated cells. Examination of melanogenic protein expression showed that tyrosinase, tyrosinase-related protein (TRP)-1, and extracellular signal-regulated kinase (ERK) 1/2 levels increased in a dose-dependent manner. Furthermore, the expression of cyclic adenosine monophosphate response element binding protein (CREB) and microphthalmia transcription factor (MITF) was increased by tangeretin in 1 h and 4 h, respectively. Tangeretin- upregulated melanogenesis was suppressed by ERK 1/2 inhibitor and not by ERK1 inhibitor. These results suggest that tangeretin has therapeutic potential for melanoma and melanoma-associated depigmentation because it can induce hyperpigmentation through the activation of melanogenic signaling proteins and initiation of sustained ERK2 expression.