PRF1 and neoplasm: -Immunosurveillance of tumor-Immature NK cells have antitumor activities-Differentiated NK cells with PD‐1 receptor exhibit protumor activities-Destruction of cancer cells exhibiting MHC-I expressive profile-Release of perforin and granzymes that induce cancer cell apoptosis-Secretion of pro-inflammatory cytokines and chemokines (GM-CSF, CCL5, TNF, IFN-γ, IL-6)