This integrin is expressed on T cells residing in tissue microenvironments, where TGF-β is abundant, such as mucosal CD8+ T lymphocytes and, mainly, IEL [53], but it is also expressed on CD4+ and CD8+ regulatory T (Treg) cells [54, 55] and on a large proportion of CD8+ effector T cells infiltrating epithelial tumors, including bladder [56], pancreatic [57], colorectal [28], ovarian [26] and lung cancers [27, 38, 58, 59]. This evidence concerns the gene CD8A and lung cancer.