In this study, we reported Apoe-/- mice to exhibit higher resistance toward the development of three types of carcinomas including gastric carcinoma (GC), colorectal carcinoma (CRC), and hepatocellular carcinoma (HCC) as compared with mice with wild type (WT) and to have greater responses to αPD-1 (anti-PD-1) immunotherapy. This evidence concerns the gene APOE and colorectal carcinoma.