Effect of 2-deoxyglucose on prostate cell viability is independent of Bcl-2 expression

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Advanced Prostate Cancer is only temporarily controlled with androgen ablation therapy or chemotherapy, secondary to the development of molecular mechanisms of resistance. Although abrogating the anti-apoptotic protein Bcl-2 is one promising therapeutic approach, efforts to simultaneously target additional pathways are warranted. Initial studies by Warburg et al. demonstrated dependence of tumor cells on the glycolytic pathway, and more recent studies demonstrated increased dependence on glycolysis with the development of molecular mechanisms of tumor resistance, such as the overexpression of Bcl-2. We hypothesized that inhibition of glycolysis with 2-deoxyglucose (2DG) would be cytotoxic to prostate cancer cells independent of bcl-2 over-expression, which has been demonstrated to increase resistance to most chemotherapeutic agents. To determine the effect of 2DG on prostate cancer cell viability, we first treated LNCaP cells with 2DG and assessed by tetrazolium assay (MTT). We found an IC-50 of 250uM, which is well below levels achievable in humans with this agent. To determine the effect of Bcl-2 on 2DG induced cytotoxicity, we used rat prostate epithelial cells transformed with E1A (RP) and transfected with a human Bcl-2 expression vector (RP-B) or vector control (RP-V). The effect of 2DG on RP cell cytotoxicity was similar in RP-B and RP-V cells. Using MTT assay the IC-50 for RP-V and RP-B cells was found to be 1mM (cell viability decreased by 51.6% in RP-V and 51.0% in RP-B cell lines). To determine the effect of 2DG on protein expression, LNCaP cells were treated with 2DG and assessed using 2-Dimensional Poly Acrylamide Gel Electrophoresis (using 11 cm strips, pH 3-10 IEF and 10% polyacrylamide gels) and were stained with SYPRO Ruby Protein gel stain. The proteomic profile from the scanned images were compared and analysed by PDQuest software (Bio-Rad Laboratories, Hercules, CA) and found to have decreased expression of multiple glycolytic enzymes. These data, therefore, demonstrate that 2DG is cytotoxic in prostate cells independent of overexpression of Bcl-2. Inhibition of glycolysis, and the assessment of glycolytic enzymes as markers of drug effect, warrants further study in the laboratory and clinic.