Current therapies for the treatment of malignant gliomas are not very effective and patient outlook remains unfavorable. Malignant tumors have been characterized by their increased rate of glucose utilization compared to corresponding normal tissues. The level of glucose uptake correlates with the degree of malignancy, treatment resistance and poor prognosis. The use of glucose analogs to inhibit glucose metabolism and proliferation in cancer cells has demonstrated promising results. One of the most effective glucose analogs investigated is 2-deoxy-D-glucose (2-DG), which has been reported to accelerate cancer cell death by inhibiting glycolysis and ATP production. Additionally, 2-DG has been evaluated as a modulator of radiosensitivity in malignant tumors. The combination of 2-DG with radiation reduced the rate of DNA repair, enhanced cytogenetic damage and cell death. Ongoing clinical trials in glioblastoma patients treated with 2-DG in combination with radiotherapy indicate improved survival and quality of life. Since alterations in signal transduction pathways plays an important role in the cellular responses to stress caused by radiation and metabolic inhibitors like 2-DG, we are investigating the effects of 2-DG and radiation on the expression of genes in an attempt to elucidate the molecular mechanisms underlying the radiosensitization by 2-DG. Exponentially growing U87 cells were exposed to (a) 10 mM 2-DG, (b) 5 Gy X-rays, or (c) 2-DG + X-rays and total RNA was isolated after four hours. Biotin labeled cRNA probes were prepared from the RNA samples and hybridized on Affymetrix GeneChips (U95Aver2). Changes in gene expression between the treatment groups were elucidated using Affymetrix DMT software. Cells exposed to 2-DG + X-rays induced 253 genes while 2-DG alone induced 157 genes and X-rays alone induced only 32 genes. Furthermore, analysis of the data showed a greater correlation in gene expression profiles between 2-DG treated cells and 2-DG + X-rays than profiles of cells exposed to X-rays alone, suggesting that 2-DG is responsible for causing the majority of alterations in gene expression. The genes with the greatest induction appear to suggest an endoplasmic reticulum stress response (CHOP/GADD-153, ATF3). Changes in oncogenes (c-MYC, c-JUN) and transcription factors were also observed suggesting modulation of signal transduction pathways. We have initiated studies to validate the GeneChip results for the genes of interest. Results from real-time PCR and western blotting for GADD-45 and GADD-153 demonstrate a high correlation with the GeneChip data. Taken together, these results suggest that radiosensitization of U-87 cells by 2-DG involves alterations in signaling pathways and induction of ER stress leading to cell death, besides inhibition of repair processes.

[Proc Amer Assoc Cancer Res, Volume 45, 2004]