title: 2-Deoxy-D-glucose and 6-aminonicotinamide-mediated Nrf2 down regulation leads to radiosensitization of malignant cells via abrogation of GSH-mediated defense.
abstract: 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.
authors.affiliation: Institute of Nuclear Medicine and Allied Sciences, Defence Research & Development Organization, Delhi, India.
authors.forename: Pradeep Kumar
authors.initials: PK
authors.lastname: Sharma
authors.forename: Rajeev
authors.initials: R
authors.lastname: Varshney
mesh_terms: D015120:6-Aminonicotinamide / Q000494:pharmacology*; D000963:Antimetabolites / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D049109:Cell Proliferation / Q000187:drug effects; D003847:Deoxyglucose / Q000494:pharmacology*; D015536:Down-Regulation; D005910:Glioma / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D005978:Glutathione / Q000378:metabolism*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D006801:Humans; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013723:Teratogens / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000963:Antimetabolites; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D017382:Reactive Oxygen Species; D013723:Teratogens; D015120:6-Aminonicotinamide; D003847:Deoxyglucose; D005978:Glutathione