GZMB and neoplasm: CTLs partially mediate their cytotoxic effects on tumor cells by secreting the serine protease granzyme B (GZMB), which cleaves and activates the initiator caspases 8 and 10 (Afonina et al, 2010) and the pro-apoptotic protein Bid to trigger apoptosis (Kaloni et al, 2023).