The role of NAD(P)H:quinone oxidoreductase (NQO1) in redox regulation of pancreatic cancer cell growth

Abstract

Background: One infrequently considered NAD(P)H-dependent source of reactive oxygen species is NAD(P)H:quinone oxidoreductase (NQO~), a homodimeric, ubiquitous, cytosolic, and membrane flavoprotein that catalyzes the two-electron reduction of quinones, including membrane ubiquinone, which can in turn redox cycle with molecular oxygen to produce superoxide (02). Aims: To determine the role of NQO~ in redox (reduction/oxidation) reactions on the malignant phenotype of pancreatic cancer cell growth. Methods: RT-PCR for NQO~ was performed in normal human pancreas and on four pancreatic cancer cell lines. MIA PaCa-2 pancreatic cancer cells were treated with a selective inhibitor of NQO1, dicumarol (50-250 I~M). Intracefiular production of 0 2 was measured by hydroethidine fluorescence. Tumor cell behavior was determined in the pancreatic cancer cell line MIA PaCa-2 by examining cell growtk, plating efficiency, and anchorage-independent growth in soft agar treated with dicumarol (0-250 I~M). Results: RT-PCR demonstrated NQOt was present in all of the pancreatic cancer cell lines. In the M1A PaCa-2 pancreatic cancer cell line, dicumarol increased hydroethidine staining twoto three-fold (P < 0,05 vs parental cell line) and this effect was blunted with transfection of an adenoviral vector containing the cDNA for manganese superoxide dismutase. Dicumarol (100-250 ~M) inhibited cell growth, plating efficiency, and growth in soft agar compared to the parental cell line (17< 0,01) Conclusions: Inhibition of NQO~ increases intracellular 02 production and inhibits m vitro cell growth characteristics of pancreatic cancer. These mechanisms suggest that altering redox regulation of pancreatic cancer cell growth may be a strategy directed against pancreatic cancer. N1H grants DK 60618 and CA 66081.