Of note, Apolipoprotein E (APOE) has been strongly associated with a number of cancers, such as lung cancer, hepatocellular carcinoma, and pancreatic ductal adenocarcinoma.[42–44] It has been shown in animal studies that elevated APOE levels are associated with immunosuppression, and higher serum APOE levels are associated with lower patient survival.[44] Studies in mouse models of pancreatic ductal adenocarcinoma have further demonstrated that APOE -/- mice have elevated levels of intratumor CD8 + T cells compared to wild-type mice. This evidence concerns the gene CD8A and lung cancer.