With both the immunotherapy-sensitive MC38 colon cancer model and the less immunotherapy-sensitive B16-OVA melanoma model, a MAOAI (PLZ) effectively inhibited tumor growth similarly to anti-PD-1 therapy, and subsequent combinations of PLZ and anti-PD-1 therapy produced better efficacy and completely inhibited tumor growth. The gene discussed is PDCD1; the disease is colonic neoplasm.