PDCD1 and cancer: In mouse KP1233 (KP) tumor cells, CAR-T cells targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1) cannot effectively invade tumors and are dysfunctional, while anti-PD-1 / PD-L1 can enhance CAR-T cell efficacy in cyclophosphamide (Ox) / oxaliplatin (Cy)-treated cancers [36].