PRF1 and neoplasm: DAC/IL-33 and PD-1 mAb strongly synergized to increase tumor-infiltrating immune effector cells (i.e., CD4 T cells, CD8 T cells and eosinophils) and intratumoral expression of effector molecules (i.e., IFN-γ, granzyme B, perforin and TNF-α) which may account for therapeutic efficacy.