Anti-PD-L1 monoclonal antibody labeled with 131I (131I-PD-L1-Mab), and in vitro binding assays were used to evaluate the affinity of 131I-PD-L1-Mab to PD-L1 and their binding level to different colorectal cancer cells, and compared with flow cytometry, Western blot analysis, and immunofluorescence staining. This evidence concerns the gene CD274 and colorectal cancer.