Steady-state levels of ascorbate are maintained by the NADH-dependent cytochrome b5 reductase 3 (Cyb5R3) [54,55], and they are significantly higher in cancer cells compared to normal cells due to overexpression of vitamin C transporters (glucose transporter 1 (GLUT1) and sodium-dependent vitamin C transporters 1 and 2 (SVCT1, SVCT2)) [56]. Here, SLC23A1 is linked to cancer.