NADH: ubiquinone oxidoreductase inhibitors block induction of ornithine decarboxylase activity in MCF-7 human breast cancer cells.

J C Rowlands, J E Casida

Index: Pharmacol. Toxicol. 83(5) , 214-9, (1998)

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Abstract

Rotenone is the classical inhibitor of NADH: ubiquinone oxidoreductase and its analogue deguelin is a potent inhibitor of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ornithine decarboxylase mRNA steady state level and enzyme activity in mouse 308 cells (Gerhäuser et al. 1995). In MCF-7 human breast cancer cells, rotenone, deguelin and two structurally-unrelated miticides (pyridaben and fenazaquin) inhibit not only NADH: ubiquinone oxidoreductase but also induced ornithine decarboxylase activity with IC50 values of < 1 to 70 nM. Rotenone inhibits ornithine decarboxylase activity equally well as induced by TPA, insulin-like growth factor I and 17 beta-oestradiol. Pyridaben is the most potent of the four inhibitors not only for NADH: ubiquinone oxidoreductase activity (bovine heart enzyme) and TPA-induced ornithine decarboxylase activity and mRNA steady state level but also for TPA-induced reactive oxygen species. It is therefore proposed that NADH: ubiquinone oxidoreductase inhibitors block multiple and possibly reactive oxygen species-modulated pathways which regulate ornithine decarboxylase activity.