PRF1 and neoplasm: Furthermore, increased levels of cytotoxic granules (Granzyme B and Perforin), anti-tumor cytokines (IFN-γ and TNFα), and the apoptotic marker CHOP/GADD153 were observed in MerTK-overexpressing tumors in both ICI treatment groups (Figure 5C, Supplementary Figure S5) by IHC.