Abstract P055: 2-Deoxy-Glucose Reduces Doxorubicin Cardiotoxicity in Tumor-Bearing Mice

Abstract

Doxorubicin (DOX) is a potent, commonly used anthracycline antibiotic for a wide range of cancers, but its dose is limited by its strong cardiotoxic effects. The glucose analog 2-deoxy-D-glucose (2-DG) has been shown to enhance the antitumor efficacy of DOX in tumor cell lines and in animals. However, the cardiac effects of 2-DG in these experiments were not determined. In the current study, we examined whether 2-DG could protect from DOX cardiotoxicity in a BALB/c mouse breast cancer model. A total of 32 mice were injected with 10 5 4T1 mouse mammary epithelial tumor cells in the right hind leg. The tumor was allowed to progress for 1 week before dividing the mice into four groups: saline, 2-DG, DOX, and 2-DG with DOX treatment. 2-DG was given 150 mg/kg i.p. Monday through Friday; DOX was given 5 mg/kg i.p. Wednesday. The study was conducted for 3 weeks and echocardiography was performed the day before sacrifice. Two of the eight mice in the DOX group died before echocardiography, while none died in the 2-DG with DOX group. Echocardiography indicated similar cardiac function between saline and 2-DG groups as measured by fractional shortening (36.3±1.31% vs 37.7±0.942%, p>0.05). DOX markedly reduced cardiac function, which was almost completely recovered by 2-DG (25.1±1.06% vs 36.7±1.76%, p<0.01). Serum CK-MB content, a common clinical marker for heart damage, was increased ~6 fold in the DOX group (67.5±19.4 vs 400±145, p<0.023). 2-DG tended to reduce DOX-triggered CK-MB release, but it did not reach significant levels likely due to the small sample size and high variation (279±68.7 vs 400±145, p>0.05). Nonetheless, 2-DG largely eliminated DOX-induced apoptosis in the heart as shown by a DNA laddering assay. 2-DG or DOX alone increased cardiac autophagic flux as measured by the difference in LC3-II protein levels in the absence and presence of the lysosomal inhibitor, bafilomycin A1. Paradoxically, autophagic flux was not notably elevated when mice were treated with 2-DG and DOX simultaneously. These results demonstrate the ability of 2-DG to reduce DOX cardiotoxicity without affecting its antitumor activity, suggesting that 2-DG can improve the therapeutic window for DOX, allowing greater flexibility in designing different regimens for treating cancers.