In vitro cell lines:Colorectal cancer cells: RKO, HCT116 (highly expressing endogenous PD-L1), primary colorectal cancer cells;PCa cells: PC3, Du145, LNCaP;Other tumor cells: Non-small cell lung cancer A549, H1299; Triple-negative breast cancer MDA-MB-231;Human embryonic kidney cells HEK293T (for overexpression experiments)Murine models: Subcutaneous xenografts established using RM1.Clinical specimens: 81 cases of colorectal adenocarcinoma and 80 cases of adjacent normal tissues; Public databases of colon adenocarcinoma and prostate adenocarcinoma. The gene discussed is CD274; the disease is breast cancer.