The glycolytic inhibitor 2-deoxy-D-glucose enhances the efficacy of etoposide in Ehrlich ascites tumor-bearing mice

Earlier studies have shown that 2-deoxy-D-glucose (2-DG), a glucose analogue and inhibitor of glycolytic ATP production significantly enhances the cytotoxic effects of anti-cancer agents like topoisomerase inhibitors (etoposide and camptothecin) and a radiomimetic drug (bleomycin) in established human tumor cell lines. Therefore, combination of 2-DG and DNA damage causing cytotoxic agents could be very useful in enhancing local tumor control. The purpose of the present studies was to investigate the therapeutic effects of etoposide and 2-DG in Ehrlich ascites tumor (EAT) bearing mice, grown as solid tumor as well as in the ascites form. Cell growth, cell cycle perturbations (flow cytometry), cytogenetic damage (micronuclei assay) and apoptosis (DNA content, morphological changes) were studied as parameters of cellular response, while delay in tumor growth and cure rate (tumor free survival) were evaluated as parameters of systemic response. Body weight and general condition as well as the damage to bone marrow and spleen was monitored to evaluate normal tissue toxicity. Intraperitoneal administration of etoposide (30 mg/Kg b.w.) resulted in significant tumor growth delay and cure (∼11%) only in subcutaneous tumors leading to local tumor control. When etoposide was combined with 2-DG (2 g/Kg b.w.; i.v./i.p.; 4 h after etoposide injection), these effects were further enhanced resulting in a cure rate of ∼22% in case of subcutaneous tumors and 20% in ascites bearing mice. Analysis of cells obtained from ascitic fluid as well as solid tumors during follow up clearly showed that etoposide induced cell death was mainly due to apoptosis, which was enhanced further by 2-DG. Although, there was a significant level of toxicity revealed by reduced animal survival, decrease in body weight and damage to sensitive organ status like spleen and bone marrow at 60 mg/Kg b.w. of etoposide, it was not significant at 30 mg/Kg b.w. 2-DG, however, did not enhance the etoposide toxicity at both the doses. These results indicate that the administration of 2-DG can improve the local control of tumors without increasing normal tissue toxicity, thereby enhancing the therapeutic efficacy of topoisomerase inhibitor based anticancer drugs like etoposide.