Prolonged ERK Activation of S1P on B16 Melanoma Cells

Lee, Hyun Sook; Choi, Gwang Seong; Shin, Jeong Hyun

Abstract

BACKGROUND: The bioactive sphingolipid metabolite sphingosine 1-phosphate (S1P), was reported to induce apoptosis of some cancer cells and neurons, although it is generally known to exert mitogenic and antiapoptotic effects. Recently, it was described that S1P induced time- and dose-dependent apoptosis in B16 melanoma cells, that was not associated with cell membrane receptors for S1P but ERK and caspase-3 activation.
OBJECTIVE
In this study, we aimed to investigate the exact mechanism of apoptosis by S1P using cultured B16 melanoma cells with caspase activity assay and Western blot assays for p-ERK, Fas, Bcl-2 family and cytochrome C proteins.
METHODS
We cultured B16 melanoma cells and treated S1P with various concentrations and time. Caspases (3, 8, and 9) activity assay and Western blot assays for phosphor-ERK, Fas, Bcl-2 family and cytochrome C proteins were performed.
RESULTS
We observed S1P induced caspase-3, -8, and -9 activations in our results. S1P also induced prolonged activation of ERK in 72 hours. S1P concomitantly increased Bcl-2 protein expression in the early 12 hours of the treatment. Neither fas nor cytochrome C were affected by S1P.
CONCLUSION
In conclusion, we propose that S1P may induce apoptotic signal on B16 melanoma cells by prolonged ERK activation and caspase-8, -9, -3 activations. S1P also appears to exert antiapoptotic signal by increasing Bcl-2 protein.