GZMB and neoplasm: Since the amount of effector T cells and cytolytic NK cells, being the two major sources of IFN-γ, granzyme B and perforin, were correlated with the production of GM-CSF by NK cells used for adoptive transfer therapies, we hypothesized that the levels of these cytokines would also be associated with the level of NK-derived GM-CSF in the tumor microenvironment.