Laurencia okamurai extract containing laurinterol induces apoptosis in melanoma cells

Laurinterol is a marine sesquiterpene that has been known to have antimicrobial activity. The purpose of this study is to investigate the effect of Laurencia okamurai extract containing laurinterol (LOEL) on induction of apoptosis in melanoma cells (B16F1). Anticancer activity of LOEL against melanoma cells was shown in a dose-dependent manner by the 1-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. It was for the first time found that LOEL exhibited an excellent effect on the induction of apoptosis as determined by DNA fragmentation, terminal deoxynucleotidyl transferase-mediated dUTP in situ nick-end labeling assay, cell cycle analysis, and measurement of activities of several caspases in melanoma cells. It was also demonstrated that transcriptional activation of p53, a tumor suppressor gene, and activation of p21 promoter by LOEL were involved in the induction of apoptosis by reporter gene assay. In particular, western blot analysis confirmed that LOEL above 5 mu g/mL significantly increased the expression level of phospho-p53, the active form. These results indicate that LOEL can induce apoptosis through a p53-dependent pathway in melanoma cells.