Possible new mitochondrial mechanism of vitamin C anticancer activity

Abstract

The main feature of fast-growing malignant tumors is the Warburg-type metabolism, which is directly related to an extremely high quantity of hexokinase (HK) bound to the voltage-dependent anion channels (VDACs) in the mitochondrial outer membrane. Previously, we explained the Warburg type metabolism as a result of the electrical suppression of mitochondria due to the closure of free VDACs that are not bound to HK. Here, we propose a possible new mechanism of high-dose vitamin C (ascorbate) anticancer activity estimated with a simplified computational model. According to the proposed hypothesis and the model, ascorbate oxidation in mitochondria leads to the generation of the negative outer membrane potential (OMP) of opposite sign to the positive OMP generated by the VDAC-HK complexes in cancer cells. The model demonstrates that negative OMP generated by any mechanism, even of relatively low magnitudes, leads tothe reopening of the electrically closed VDACs, thus reprogramming cell energy metabolism.According to the hypothesis, redox mediators, which increase the rate of ascorbate oxidation in mitochondria, should synergistically increase anticancer effects of high-dose ascorbate in accordance with experimental data recorded in the literature. The model shows that even small changes in the VDAC-voltage sensitivity and/or quantity of the VDAC-HK complexes, known to be caused by various physiological factors, might strongly influence the proposed mitochondrial mechanism of ascorbate anticancer activity.