CD274 and metastatic malignant neoplasm: Considering all the above advantages of CIK cells and the synergistic effects led by PD-L1/PD-1 blockade, combined therapy of simultaneous CIK infusion and PD-L1/PD-1 signaling blockade should be put forward as a novel promising candidate for clinical trial, especially in the setting of unresectable metastatic cancers.