Serine palmitoyltransferase inhibitor myriocin induces growth inhibition of B16F10 melanoma cells through G2/M phase arrest

Objectives: Melanoma is the most aggressive form of skin cancer, and it resists chemotherapy. Candidate drugs for effective anti-cancer treatment have been sought from natural resources. Here, we have investigated anti-proliferative activity of myriocin, serine palmitoyltransferase inhibitor, in the de novo sphingolipid pathway, and its mechanism in B16F10 melanoma cells. Material and methods: We assessed cell population growth by measuring cell numbers, DNA synthesis, cell cycle progression, and expression of cell cycle regulatory proteins. Ceramide, sphingomyelin, sphingosine and sphingosine-1-phosphate levels were analysed by HPLC. Results: Myriocin inhibited proliferation of melanoma cells and induced cell cycle arrest in the G(2)/M phase. Expressions of cdc25C, cyclin B1 and cdc2 were decreased in the cells after exposure to myriocin, while expression of p53 and p21(waf1cip1) was increased. Levels of ceramide, sphingomyelin, sphingosine and sphingosine-1-phosphate in myriocin-treated cells after 24 h were reduced by approximately 86%, 57%, 75% and 38%, respectively, compared to levels in control cells. Conclusions: Our results suggest that inhibition of sphingolipid synthesis by myriocin in melanoma cells may inhibit expression of cdc25C or activate expression of p53 and p21(waf1/cip1), followed by inhibition of cyclin B1 and cdc2, resulting in G(2)/M arrest of the cell cycle and cell population growth inhibition. Thus, modulation of sphingolipid metabolism by myriocin may be a potential target of mechanism-based therapy for this type of skin cancer.