l-Theanine inhibits melanoma cell growth and migration via regulating expression of the clock gene BMAL1

Purpose l-Theanine is a unique non-protein amino acid found in green tea, which has been identified as a safe dietary supplement. It has been reported that l-theanine exerts various biological activities. In this study, we explored the anti-cancer effects of l-theanine on melanoma cells. Methods A375, B16-F10, and PIG1 cell lines were used in the present study. EdU labeling, TUNEL and Annexin V/PI staining, wound-healing, and transwell migration assay were performed to detect the effects of l-theanine on melanoma cell proliferation, apoptosis, and migration. Brain and muscle Arnt-like protein 1 (BMAL1) was knocked down in melanoma cells to evaluate if l-theanine plays the anti-cancer role through regulating circadian rhythm of melanoma cells. The western blot, qRT-PCR, and dual luciferase assay were performed to explore the mechanism involved in the effects of l-theanine on melanoma cells. Results l-Theanine apparently reduced the viability of melanoma cells. Further experiments showed that l-theanine attenuated the proliferation and migration, and promoted apoptosis of melanoma cells. l-Theanine significantly enhanced the expression of BMAL1, a clock gene in melanoma cells. Down-regulation of BMAL1 suppressed the anti-cancer effects of l-theanine on melanoma cells. Further experiments indicated that the p53 transcriptional activity raised by l-theanine was dependent on BMAL1 expression in melanoma cells. Conclusion l-Theanine exerts the anti-cancer effect on melanoma cells through attenuating the proliferation and migration, and promoting apoptosis of them, which is dependent on the regulation of the clock gene Bmal1 in melanoma cells.