PRF1 and melanoma: To confirm that NK cells were responsible for melanoma target cell death, in the context of PBMCs, we have shown that (1) depletion of NK cells from PBMCs significantly reduced killing of MEL888 cells (Figure S1A) and (2) that killing was mediated by perforin and granzyme (pivotal components of NK cell cytotoxic granules) because cell lysis was abrogated by EGTA, a calcium chelator that prevents the activity of calcium-dependent perforin (Figure S1B).