Purpose Cancer cells (relative to normal cells) demonstrate increased steady-state levels of hydroperoxides that are compensated for by increased glucose and hydroperoxide metabolism. The current study determined if inhibitors of glucose and hydroperoxide metabolism could induce chemo-radio-sensitization by enhancing oxidative stress in lung cancer cells. Experimental Design A549 and NCI-H292 human lung carcinoma cells were treated with 2-Deoxy-D-glucose (2DG) combined with carboplatin (carbo) + ionizing radiation (IR). Lung cancer cells were further sensitized with inhibitors of glutathione- and thioredoxin-dependent metabolism [buthionine sulfoximine (BSO) and auranofin (Au), respectively] in vitro and in vivo. Results When 2DG was combined with carbo+IR, clonogenic cell killing was enhanced in A549 and NCI-H292 cells and this combination was more effective than paclitaxel+carbo+IR. The thiol antioxidant (N-acetylcysteine, NAC) was capable of protecting cancer cells from 2DG+carbo-induced cell killing. Simultaneous treatment of cancer cells with BSO and Au, at doses that were not toxic as single agents also enhanced lung cancer cell killing and sensitivity to 2DG+carbo. This treatment combination also increased both glutathione and thioredoxin oxidation which were inhibited by NAC. Mice treated with Au+BSO showed no alterations in circulating leukocytes or red blood cells. Xenograft lung tumor growth in mice was more effectively inhibited by treatment with Au+BSO+carbo when compared to animals treated with carbo or Au+BSO alone. Conclusions These results show in vitro and in vivo that simultaneous inhibition of glutathione and thioredoxin metabolism can effectively inhibit lung cancer cell growth and induce chemo-sensitization by a mechanism that involves thiol mediated oxidative stress.

The current study determined if depletion of glutathione (GSH) and inhibition of thioredoxin reductase (TR) activity could enhance radiation responses in human breast cancer stem cells by a mechanism involving thiol dependent oxidative stress. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor; sulfasalazine (SSZ), an inhibitor of xc- cysteine/glutamate antiporter; auranofin (Au), a thioredoxin reductase inhibitor; or 2AAPA, a GSH-reductase inhibitor, were used to inhibit GSH- and thioredoxin (Trx)-metabolism. Clonogenic survival, Matrigel assays, flow cytometry cancer stem cell assays (CD44+CD24-ESA+ or ALDH1), and human tumor xenograft models were used to determine the antitumor activity of drug and radiation combinations. Combined inhibition of GSH and Trx-metabolism enhanced cancer cell clonogenic killing and radiation responses in human breast and pancreatic cancer cells via a mechanism that could be inhibited by N-acetylcysteine (NAC). Au, BSO, and radiation also significantly decreased breast cancer cell migration and invasion in a thiol dependent fashion that could be inhibited by NAC. In addition pre-treating cells with Au sensitized breast cancer stem cell populations to radiation in vitro as determined by CD44+CD24-ESA+ or ALDH1. Combined administration of Au and BSO, given prior to radiation significantly increased the survival of mice with human breast cancer xenografts as well as decreasing the number of ALDH1 positive cancer stem cells. These results indicate that combined inhibition of GSH- and Trx-dependent thiol metabolism using pharmacologically relevant agents can enhance responses of human breast cancer stem cells to radiation both in vitro and in vivo.

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<div>Abstract<p><b>Purpose:</b> Cancer cells (relative to normal cells) show increased steady-state levels of hydroperoxides that are compensated by increased glucose and hydroperoxide metabolism. The current study determined whether inhibitors of glucose and hydroperoxide metabolism could induce chemoradiosensitization by enhancing oxidative stress in lung cancer cells.</p><p><b>Experimental Design:</b> A549 and NCI-H292 human lung carcinoma cells were treated with 2-deoxy-d-glucose (2DG) combined with carboplatin + ionizing radiation (IR). Lung cancer cells were further sensitized with inhibitors of glutathione (GSH)- and thioredoxin (Trx)-dependent metabolism [buthionine sulfoximine (BSO) and auranofin, respectively] <i>in vitro</i> and <i>in vivo</i>.</p><p><b>Results:</b> When 2DG was combined with carboplatin + IR, clonogenic cell killing was enhanced in A549 and NCI-H292 cells, and this combination was more effective than paclitaxel + carboplatin + IR. The thiol antioxidant (<i>N</i>-acetylcysteine, NAC) was capable of protecting cancer cells from 2DG + carboplatin -induced cell killing. Simultaneous treatment of cancer cells with BSO and auranofin, at doses that were not toxic as single agents, also enhanced lung cancer cell killing and sensitivity to 2DG + carboplatin. This treatment combination also increased oxidation of both GSH and Trx, which were inhibited by NAC. Mice treated with auranofin + BSO showed no alterations in circulating leukocytes or red blood cells. Xenograft lung tumor growth in mice was more effectively inhibited by treatment with auranofin + BSO + carboplatin than animals treated with carboplatin or auranofin + BSO alone.</p><p><b>Conclusions:</b> These results show <i>in vitro</i> and <i>in vivo</i> that simultaneous inhibition of GSH and Trx metabolism can effectively inhibit lung cancer cell growth and induce chemosensitization by a mechanism that involves thiol-mediated oxidative stress. <i>Clin Cancer Res; 17(19); 6206–17. ©2011 AACR</i>.</p></div>

<p>PDF file - 72K</p>

<div>Abstract<p><b>Purpose:</b> Cancer cells (relative to normal cells) show increased steady-state levels of hydroperoxides that are compensated by increased glucose and hydroperoxide metabolism. The current study determined whether inhibitors of glucose and hydroperoxide metabolism could induce chemoradiosensitization by enhancing oxidative stress in lung cancer cells.</p><p><b>Experimental Design:</b> A549 and NCI-H292 human lung carcinoma cells were treated with 2-deoxy-d-glucose (2DG) combined with carboplatin + ionizing radiation (IR). Lung cancer cells were further sensitized with inhibitors of glutathione (GSH)- and thioredoxin (Trx)-dependent metabolism [buthionine sulfoximine (BSO) and auranofin, respectively] <i>in vitro</i> and <i>in vivo</i>.</p><p><b>Results:</b> When 2DG was combined with carboplatin + IR, clonogenic cell killing was enhanced in A549 and NCI-H292 cells, and this combination was more effective than paclitaxel + carboplatin + IR. The thiol antioxidant (<i>N</i>-acetylcysteine, NAC) was capable of protecting cancer cells from 2DG + carboplatin -induced cell killing. Simultaneous treatment of cancer cells with BSO and auranofin, at doses that were not toxic as single agents, also enhanced lung cancer cell killing and sensitivity to 2DG + carboplatin. This treatment combination also increased oxidation of both GSH and Trx, which were inhibited by NAC. Mice treated with auranofin + BSO showed no alterations in circulating leukocytes or red blood cells. Xenograft lung tumor growth in mice was more effectively inhibited by treatment with auranofin + BSO + carboplatin than animals treated with carboplatin or auranofin + BSO alone.</p><p><b>Conclusions:</b> These results show <i>in vitro</i> and <i>in vivo</i> that simultaneous inhibition of GSH and Trx metabolism can effectively inhibit lung cancer cell growth and induce chemosensitization by a mechanism that involves thiol-mediated oxidative stress. <i>Clin Cancer Res; 17(19); 6206–17. ©2011 AACR</i>.</p></div>