| Popis: |
The clinical potential of pharmacologic ascorbate (P-AscH−; intravenous delivery achieving mmol/L concentrations in blood) as an adjuvant in cancer therapy is being reevaluated. At mmol/L concentrations, P-AscH− is thought to exhibit anticancer activity via generation of a flux of H2O2 in tumors, which leads to oxidative distress. Here, we use cell culture models of pancreatic cancer to examine the effects of P-AscH− on DNA damage, and downstream consequences, including changes in bioenergetics. We have found that the high flux of H2O2 produced by P-AscH− induces DNA damage. In response to this DNA damage, we observed that PARP1 is hyperactivated. Using our unique absolute quantitation, we found that P-AscH− mediated the overactivation of PARP1, which results in consumption of NAD+, and subsequently depletion of ATP leading to mitotic cell death. We have also found that Chk1 plays a major role in the maintenance of genomic integrity following treatment with P-AscH−. Hyperactivation of PARP1 and DNA repair are ATP-consuming processes. Using a Seahorse XF96 analyzer, we demonstrated that the severe decrease in ATP after challenging with P-AscH− is because of increased demand, not changes in the rate of production. Genetic deletion and pharmacologic inhibition of PARP1 preserved both NAD+ and ATP; however, the toxicity of P-AscH− remained. These data indicate that disruption of bioenergetics is a secondary factor in the toxicity of P-AscH−; damage to DNA appears to be the primary factor.Implications:Efforts to leverage P-AscH− in cancer therapy should first focus on DNA damage. |
