PRF1 and neoplasm: The function of NK cells against tumor cells is through various mechanisms including releasing cytoplasmic granules (such as Perforin and Granzyme), secretion of various cytokines (such as IFN-γ and TNF-α), triggering death receptor-mediated apoptosis (such as FasL or TRAIL), ADCC by CD16 antigen expression on the NK cells, and also indirectly via interaction with other immune cells (Cheng et al., 2013).