Salvianolic acid B can directly bind to ubiquitin carboxyl-terminal hydrolase 2 (USP2) and inhibit its deubiquitinating activity in colon cancer cells RKO, thus promoting the ubiquitin–proteasome pathway degradation of programmed cell death ligand 1 (PD-L1) proteins and enhancing the killing activity of T cells against tumor cells, eventually exerting antitumor effects. The gene discussed is CD274; the disease is malignant colon neoplasm.