To identify the mechanism of how NK cells kill melanoma cells, NK cells were incubated with an inhibiting anti-TRAIL antibody for 1 h prior to co-culture with melanoma cells; similarly, to investigate the role of the FASL/FAS pathway in NK cell-mediated cytotoxicity, melanoma cells were pre-incubated with an FAS-blocking antibody for 1 h before co-culture with NK cells. Here, FAS is linked to melanoma.