In general, metformin may exert its anticancer effect through the inhibition of tumor angiogenesis [30], suppressing cancer cell metabolism [31], activation of apoptosis and autophagy [32], inhibition of mammalian target of rapamycin (mTOR) [33], immunomodulation by increasing the number of CD8+ tumor-infiltrating lymphocytes [34], and impairing one-carbon metabolism acting like an antifolate drug [35]. Here, CD8A is linked to cancer.