Institute of Nuclear Medicine and Allied Sciences, Defence Research & Development Organization, Delhi, India.
Free Radic Res. 2012 Dec;46(12):1446-57. doi: 10.3109/10715762.2012.724771. Epub 2012 Oct 1.
Enhanced level of nuclear erythroid-related factor-2 (Nrf2) has been associated with cancer chemo/radioresistance. Therefore, the role of Nrf2 in radiosensitization of malignant cells induced by a combination of 2-deoxy-D-Glucose (2-DG) and 6-aminonicotinamide (6-AN) was investigated. Two established human malignant cells lines namely KB (head and neck squamous carcinoma) and BMG-1 (cerebral glioma) were used. Following treatment with a combination of 2-DG (5 mM) and 6-AN (5 μM), irradiated (2Gy) KB and BMG-1 cells were assessed for protein level of Nrf2, Keap1 and γ-glutamylcysteine synthetase (γ-GCS) by western blotting and mRNA expression of γ-GCS, glutathione reductase (GR) and glutathione peroxidase (GPx1) by RT-PCR at 24 hours post treatment. A significant decrease in the level of Nrf2 with a concomitant increase in Keap1 was observed in both the irradiated malignant cells at 24 hours following treatment with combination (2-DG + 6-AN). Down regulation of γ-GCS, GR and GPx1 at 24 hours following treatment with combination (2-DG + 6-AN) resulted in abrogation of glutathione (GSH)-mediated defense in both the irradiated malignant cells. Eventual accumulation of ROS led to radiosensitization of both the malignant cells. These results indicate that deregulated Nrf2-Keap1 signalling leads to the radiosensitization of malignant cells due to abrogated glutathione defense. Metabolic modification-mediated down regulation of Nfr2 and its downstream signalling may have a potential of improving tumour radiotherapy.
核红细胞相关因子-2（Nrf2）水平升高与癌症的化疗/放疗抵抗有关。因此，研究了 2-脱氧-D-葡萄糖（2-DG）和 6-氨基烟酰胺（6-AN）联合应用诱导恶性细胞放射增敏过程中 Nrf2 的作用。使用了两种已建立的人恶性细胞系，即 KB（头颈部鳞状细胞癌）和 BMG-1（脑胶质瘤）。用 2-DG（5mM）和 6-AN（5μM）联合处理后，用 Western blot 检测照射（2Gy）的 KB 和 BMG-1 细胞中 Nrf2、Keap1 和γ-谷氨酰半胱氨酸合成酶（γ-GCS）的蛋白水平，并用 RT-PCR 检测γ-GCS、谷胱甘肽还原酶（GR）和谷胱甘肽过氧化物酶（GPx1）的 mRNA 表达，在处理后 24 小时进行。在联合处理（2-DG+6-AN）后 24 小时，照射的恶性细胞中 Nrf2 水平显著下降，同时 Keap1 水平升高。联合处理（2-DG+6-AN）后 24 小时，γ-GCS、GR 和 GPx1 的下调导致照射的恶性细胞中谷胱甘肽（GSH）介导的防御作用被阻断。ROS 的最终积累导致两种恶性细胞的放射增敏。这些结果表明，Nrf2-Keap1 信号的失调导致恶性细胞的放射增敏，因为 GSH 防御被阻断。Nfr2 及其下游信号的代谢修饰介导下调可能有改善肿瘤放疗的潜力。
