Altered gene expression induced by ionizing radiation and glycolytic inhibitor 2-deoxy-glucose in a human glioma cell line: Implications for radio sensitization

Abstract

The glycolytic inhibitor 2-deoxy-D-glucose (2-DG) has been shown to enhance the cell death induced by radiation and other DNA damaging agents selectively in cells with high rates of glycolysis, like cancer cells. While energy linked modification of DNA and cellular repair processes have been suggested as possible mechanisms of sensitization, other effects such as global stress response cannot be excluded. In this pilot study, we have investigated the effect of 2-DG and radiation on the transcriptome in an attempt to elucidate how 2-DG impacts gene expression in undamaged verses irradiation (IR) damaged cells using a human malignant glioma cell line, U-87. Exponentially growing U-87 cells were exposed to various combinations of 2-DG and X-rays and total RNA was isolated four hours after exposure. Gene expression changes were elucidated using Affymetrix GeneChips. As expected, U-87 cells treated with 2-DG showed activation of several endoplasmic reticulum stress response genes. Selective RT-PCR and Western blotting confirmed these gene alterations. Given that glucose deprivation leads to p53 activation and 2-DG led to activation of p53 response genes in our present study (e.g., PMAIP1 and GADD45A), we examined the impact of transient p53 knockdown and observed that induction of PMAIP1 and GADD45A appear to be via p53-independent mechanisms. The majority of gene alterations seen with IR-treatment alone were consistent with previous reports. While most gene alterations seen with 2-DG and IR dual treatment were confirmed in the gene profiles seen with individual (2-DG or IR) treatments, several genes appeared differentially regulated between IR and 2-DG (e.g., DUSP8, IL8, GADD45B). Additionally, gene expression patterns suggested alterations in cell cycle regulation, apoptosis, and cytokine signaling pathways. Taken together, this study provides new insights into how the transcriptome of tumor cells are likely to be affected by a combined stress caused by IR and 2-DG.

Combined Treatment with 2-Deoxy-D-Glucose and Doxorubicin Enhances the in Vitro Efficiency of Breast Cancer Radiotherapy

“…Alterations in expression levels of many genes involved in damage response pathways including DNA repair and apoptosis, transcriptional regulators, cell signaling, besides energy metabolism have been reported that could significantly influence on the radiosensitization of tumor cells (Dwarakanath and Jain, 1987). A robust UPR was also induced by 2DG that contributes to the radiosensitization (Heminger et al, 2006). The 2DG-induced enhancement of radiation damage has been found to be directly proportional to the glucose usage, presence of hypoxia, and doses of 2DG and radiation (Dwarkanath et al, 2001;Khaitan et al, 2006), as our finding.…”

2-Deoxyglucose Induces Noxa-Dependent Apoptosis in Alveolar Rhabdomyosarcoma

“…Noxa is a well-studied BH3-only protein that has recently been described to play a role in glucose metabolism by promoting glucose uptake but directing glucose flux away from the glycolytic pathway by a yet uncharacterized mechanism (23). Noxa/ PMAIP1 mRNA had been observed to be induced in response to 2-DG (38), but its role in cell death had not been tested. In addition, Noxa has been shown to mediate death by ER stressors (22).…”

Roles of p53, Myc and HIF-1 in Regulating Glycolysis — the Seventh Hallmark of Cancer

“…3-BrPA effectively kills colon cancer cells and lymphoma cells in a hypoxic environment in which the cancer cells exhibit high glycolytic activity and decreased sensitivity to common anticancer agents [143]. 2-deoxy-Dglucose inhibits glycolytic enzymes and has also produced encouraging antineoplastic results in vitro and in vivo [141, 143 -145] as well as sensitizing cancer cells to radiation [146,147] particularly in cancer cells with high rates of glycolysis [148].…”