Measuring NQO1 Bioactivation Using [(2)H(7)]Glucose

SIMPLE SUMMARY: Cancer is often characterized by profound changes in metabolism, some of which are appropriate targets for therapeutic intervention. Many cancers overexpress the two-electron reductase NQO1, which can bioactivate the drug β-lapachone, inducing a futile redox cycle that liberates large amounts of reactive oxygen species and results in subsequent cell death. However, β-lapachone has off-target toxicities in red blood cells, which makes minimal dosing for chemotherapeutic response desirable. Here, we show that magnetic resonance-based detection of [(2)H(7)]glucose metabolism provides a robust metric of NQO1 activation, as the redox perturbation causes downregulation of glycolytic flux that is detectable in the HDO and lactate signals. Imaging of either metabolic product could provide constraints for a continual reassessment model for controlling therapeutic dosing levels. ABSTRACT: Treatment of cancers with β-lapachone causes NAD(P)H: quinone oxidoreductase 1 (NQO1) to generate an unstable hydroquinone that regenerates itself in a futile cycle while producing reactive oxygen species (ROS) in the form of superoxide and subsequently hydrogen peroxide. Rapid accumulation of ROS damages DNA, hyperactivates poly-ADP-ribose polymerase-I, causes massive depletion of NAD(+)/ATP, and hampers glycolysis. Cells overexpressing NQO1 subsequently die rapidly through an NAD(+)-keresis mechanism. Assessing changes in glycolytic rates caused by NQO1 bioactivation would provide a means of assessing treatment efficacy, potentially lowering the chemotherapeutic dosage, and reducing off-target toxicities. NQO1-mediated changes in glycolytic flux were readily detected in A549 (lung), MiaPaCa2 (pancreatic), and HCT-116 (colon) cancer cell lines by (2)H-NMR after administration of [(2)H(7)]glucose. The deuterated metabolic products (2)H-lactate and HDO were quantified, and linear relationships with glucose consumption for both products were observed. The higher concentration of HDO compared to (2)H-lactate allows for more sensitive measurement of the glycolytic flux in cancer. Gas chromatography-mass spectrometry analysis agreed with the NMR results and confirmed downregulated energy metabolism in NQO1(+) cells after β-lapachone treatment. The demonstrated method is ideal for measuring glycolytic rates, the effects of chemotherapeutics that target glycolysis, and has the potential for in vivo translation.