In human studies of TILs, metformin triggered reduced CD8+ effector T cells and FoxP3+ Tregs in head and neck squamous cell carcinoma [78], CD3+ CD8+ TILs in colorectal cancer in patients with T2D [79], CD8+ TILs and tumor-suppressive CD11c+ macrophages in human esophageal cancer [80], and memory stem and central memory CD8+ T cells [81]. This evidence concerns the gene CD8A and type 2 diabetes mellitus.