Abstract 1388: Biological role of novel NQO2 inhibitors in cancer therapeutics

Abstract

Abstract Background: NRH: quinone oxidoreductase 2 (NQO2), is a cytosolic flavoprotein that catalyses the two-electron reduction of quinones into hydroquinones. The physiological role of NQO2 in cancer biology is still not well understood. Some studies have suggested that inhibiting NQO2 could have a great potential in chemoprevention. This is based on the observation that NQO2 gene knockdown promotes protection against the toxicity of quinones such as menadione. Aim: To evaluate the biological role of novel NQO2 inhibitors in cancer therapeutics. Novel inhibitors will be used as pharmacological tools to study the physiological role of NQO2 in cancer cells, and to identify the consequences of inhibiting NQO2 on the tumor microenvironment. Methods: Novel compounds with diverse structures have been tested for their inhibition of NQO2 enzymatic activity in a cell-free system using a pure enzyme assay. The functional activity of these compounds as NQO2 inhibitors in the MDA-MB 231 breast cancer cells was also assessed. The effect of these inhibitors on the cellular proliferation of MDA-MB 231 breast cancer cells was tested using an MTT assay. Off-target (DNA binding) effects were analyzed by measuring the DNA thermal temperature. Moreover, the effect of these inhibitors on modulating TNFα-mediated NF-kB transcriptional activity was tested and the mechanism behind this modulation was also examined. Results: The novel inhibitors tested resulted in the inhibition of NQO2 activity in the cell free and the cellular system at nano-molar concentrations .Inhibition of MDA-MB 231 cell proliferation was also witnessed at low micro-molar concentrations. The inhibitors also displayed no DNA binding ability. In addition, the inhibitors were able to attenuate TNFα-mediated NF-kB transcriptional activity by blocking the phosphorylation of IkBα. This has resulted in the suppression of cell growth and promotion of cell apoptosis. Conclusions: This study has demonstrated novel potent inhibitors of NQO2 that are functionally active in the cells at nano-molar concentrations. The effect of the inhibitors on TNFα-mediated NF-kB transcriptional activity raises the possibility that inhibiting NQO2 could modulate the tumor micro-environmental factors, such as metastasis and angiogenesis. Citation Format: Elham Santina, Amy Chadwick, Soraya Al Nabulsi, Sally Freeman, Constantinos Demonacos, Ian Stratford. Biological role of novel NQO2 inhibitors in cancer therapeutics. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1388. doi:10.1158/1538-7445.AM2014-1388