PDCD1 and neoplasm: In general, it was reported that (i) non-responding tumors had higher HRH1 and VISTA expression on TAMs than partially responding tumors under anti programmed cell death protein 1 (PD-1) treatment, (ii) inhibition of HRH1 enhanced the anti-tumor immunity of programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) blockade, (iii) FEXO in combination with ICB (anti-PD-1/anti-CTLA-4) achieved the higher therapeutic effect compared to FEXO or ICB alone.