PDCD1 and neoplasm: The present study reports the effective killing activity of CIK cells against allogeneic gastric and colorectal cancer cell lines, and for the first time reflects the potentialities of PD-L1/PD-1 blockade to enhance tumoricidal activity of CIK cells as a promising adoptive immunotherapy, and presents crucial immunologic elements involved in the complex interactions between tumor cells and immune effectors in the preclinical model of CIK cells, with insights on their prospective for clinical translation.