Pharmacologic ascorbate induces neuroblastoma cell death by hydrogen peroxide mediated DNA damage and reduction in cancer cell glycolysis

摘要

Abstract An ascorbate-mediated production of oxidative stress has been shown to retard tumor growth. Subsequent glycolysis inhibition has been suggested. Here, we further define the mechanisms relevant to this observation. Ascorbate was cytotoxic to human neuroblastoma cells through the production of H 2 O 2 , which led to ATP depletion, inhibited GAPDH, and non-apoptotic and non-autophagic cell death. The mechanism of cytotoxicity is different when PARP-dependent DNA repair machinery is active or inhibited. Ascorbate-generated H 2 O 2 damaged DNA, activated PARP, depleted NAD+, and reduced glycolysis flux. NAD+ supplementation prevented ATP depletion and cell death, while treatment with a PARP inhibitor, olaparib, preserved NAD+ and ATP levels but led to increased DNA double-strand breakage and did not prevent ascorbate-induced cell death. These data indicate that in cells with an intact PARP-associated DNA repair system, ascorbate-induced cell death is caused by NAD+ and ATP depletion, while in the absence of PARP activation ascorbate-induced cell death still occurs but is a consequence of ROS-induced DNA damage. In a mouse xenograft model, intraperitoneal ascorbate inhibited neuroblastoma tumor growth and prolonged survival. Collectively, these data suggest that ascorbate could be effective in the treatment of glycolysis-dependent tumors. Also, in cancers that use alternative energy metabolism pathways, combining a PARP inhibitor with ascorbate treatment could be useful. Graphical abstract Pharmacologic ascorbate forms H 2 O 2 , damages DNA and activates PARP. Activated PARP depletes NAD+, and therefore inhibited GAPDH activity, and ATP is depleted in neuroblastoma cells, leading to cell death. In the absence of PARP activation, fatal DNA damage accumulates and leads to cell death. Display Omitted Highlights ? Ascorbate induces neuroblastoma cell death and inhibited tumor growth in mice. ? Ascorbate-generated H 2 O 2 damages DNA, activates PARP, depletes NAD+ and ATP. ? In the absence of PARP activation, cell death is mediated by ROS-induced DNA damage. ? Translational studies are warranted using ascorbate in high-risk neuroblastoma.