NAD(P)H:Quinone Oxidoreductase-1-Dependent and -Independent Cytotoxicity of Potent Quinone Cdc25 Phosphatase Inhibitors

• Published in: The Journal of pharmacology and experimental therapeutics 2004-04, Vol.309 (1), p.64-70
• Main Authors: Han, Yusheng, Shen, Hongmei, Carr, Brian I, Wipf, Peter, Lazo, John S, Pan, Su-shu
• Format: Article
• Language: English
• Subjects: CDC2 Protein Kinase - metabolism; cdc25 Phosphatases - antagonists & inhibitors; Cell Division - drug effects; Cell Fractionation; Cell Line; Dicumarol - pharmacology; G2 Phase - drug effects; HT29 Cells; Humans; Microsomes - metabolism; Mitosis - drug effects; NAD(P)H Dehydrogenase (Quinone) - metabolism; NAD(P)H Dehydrogenase (Quinone) - physiology; Naphthoquinones - pharmacology; Phosphorylation; Quinolones - pharmacology; Quinones - pharmacology; Recombinant Proteins - metabolism; Tumor Cells, Cultured
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.103.059477

Cdc25 dual-specificity phosphatases coordinate cell cycle progression and cellular signaling. Consequently, Cdc25 inhibitors represent potential anticancer agents. We evaluated >10,000 compounds for inhibition of human Cdc25 phosphatases and identified many potent and selective inhibitors, which all contained a quinone. Bioreductive enzymes frequently detoxify or activate quinones. Therefore, we evaluated the effect of NAD(P)H:quinone oxidoreductase-1 (NQO1) and reductase-rich microsomes on the activity of three quinone-containing Cdc25 inhibitors: 2-(2-hydroxyethylsulfanyl)-3-methyl-1,4-naphthoquinone (Cpd 5, compound 5; NSC 672121), 2,3-bis-(2-hydroxyethylsulfanyl)-1,4-naphthoquinone (NSC 95397), and 6-chloro-7-(2-morpholin-4-yl-ethylamino)quinoline-5,8-dione (NSC 663284). Each inhibitor was reduced by human NQO1 ( K m of 0.3–0.5 μM) but none by microsomes. Compounds were evaluated with six cancer cell lines containing different amounts of NQO1: HT-29 (1056 nmol/mg/min), HCT116 (660 nmol/mg/min), sublines HCT116-R30A (28 nmol/mg/min) and HCT-116R30A/NQ5 (934 nmol/mg/min), MDA-MB-231/Q2 (null NQO1), and subline MDA-MB-231/Q6 (124 nmol/mg/min) but containing similar amounts of microsomal cytochrome P450 reductase and cytochrome b 5 reductase. Growth inhibition and G2/M arrest by Cpd 5 was proportional to NQO1 levels, requiring 4- to 5-fold more Cpd 5 to inhibit HCT-116 or HCT-116R30A/NQ5 compared with HCT-116R30A. In contrast, in all tested cell lines irrespective of NQO1 level, growth inhibition and G2/M arrest by NSC 95375 and NSC 663284 were similar (average IC 50 of 1.3 ± 0.3 and 2.6 ± 0.4 μM, respectively). NSC 95375 and NSC 663284 also caused similar Cdk1 hyperphosphorylation, indicating similar Cdc25 inhibition. However, lower Cpd 5 concentrations were needed to produce Cdk1 hyperphosphorylation in sublines with minimal NQO1. Thus, NQO1 detoxified Cpd 5, probably by reducing it to a less active hydroquinone, whereas NSC 95397- and NSC 663284-generated cytotoxicity was unaffected by NQO1.