GZMB and neoplasm: This has been affirmed through subsequent mechanistic studies indicating that TGFβ impedes the effector function of CTLs through the canonical SMAD pathway, leading to the transcriptional repression of functional cytokines including interferon-γ and granzyme B [141], the latter being an anti-tumor serine protease found in CTL-associated cytotoxic granules with important roles in anti-tumor immunity [142,143].