@article{pittir20431,
          volume = {309},
          number = {1},
           month = {April},
          author = {Y Han and H Shen and BI Carr and P Wipf and JS Lazo and SS Pan},
           title = {NAD(P)H:Quinone Oxidoreductase-1-Dependent and -Independent Cytotoxicity of Potent Quinone Cdc25 Phosphatase Inhibitors},
         journal = {Journal of Pharmacology and Experimental Therapeutics},
           pages = {64 -- 70},
            year = {2004},
             url = {http://d-scholarship-dev.library.pitt.edu/20431/},
        abstract = {Cdc25 dual-specificity phosphatases coordinate cell cycle progression and cellular signaling. Consequently, Cdc25 inhibitors represent potential anticancer agents. We evaluated {\ensuremath{>}}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-ylethylamino)quinoline-5,8-dione (NSC 663284). Each inhibitor was reduced by human NQO1 (Km of 0.3-0.5 {\ensuremath{\mu}}M) 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 b5 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 IC50 of 1.3 {$\pm$} 0.3 and 2.6 {$\pm$} 0.4 {\ensuremath{\mu}}M, 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.}
}