Ascorbate potentiates the cytotoxicity of menadione leading to an oxidative stress that kills cancer cells by a non-apoptotic caspase-3 independent form of cell death.
Hepatocarcinoma cells (TLT) were incubated in the presence of ascorbate and menadione, either alone or in combination. Cell death was only observed when such compounds were added simultaneously, most probably due to hydrogen peroxide (H2O2) generated by ascorbate-driven menadione redox cycling. TLT cells were particularly sensitive to such an oxidative stress due to its poor antioxidant status. DNA strand breaks were induced by this association but this process did not correspond to oligosomal DNA fragmentation (a hallmark of cell death by apoptosis). Neither caspase-3-like DEVDase activity, nor processing of procaspase-3 and cleavage of poly(ADP-ribose) polymerase (PARP) were observed in the presence of ascorbate and menadione. Cell death induced by such an association was actively dependent on protein phosphorylation since it was totally prevented by preincubating cells with sodium orthovanadate, a tyrosine phosphatase inhibitor. Finally, while H2O2, when administered as a bolus, strongly enhances a constitutive basal NF-kappaB activity in TLT cells, their incubation in the presence of ascorbate and menadione results in a total abolition of such a constitutive activity.
Unité de Pharmacocinétique, Métabolisme, Nutrition et Toxicologie, Département des Sciences Pharmaceutiques, Université Catholique de Louvain, Belgium.
Julien
J
Verrax
Julie
J
Cadrobbi
Carole
C
Marques
Henryk
H
Taper
Yvette
Y
Habraken
Jacques
J
Piette
Pedro Buc
PB
Calderon
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D008113:Liver Neoplasms / Q000378:metabolism; D051379:Mice; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology*; D013997:Time Factors; D024483:Vitamin K 3 / Q000378:metabolism* / Q000633:toxicity
D000975:Antioxidants; D024483:Vitamin K 3; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D001205:Ascorbic Acid