P04.47 Nrf2 mediates hypoxic tolerance in human glioblastoma cells. (19th September 2018)

• Record Type: Journal Article
• Authors: Lorenz, N I; Luger, A; Zeiner, P S; Engel, A L; Harter, P N; Steinbach, J P; Ronellenfitsch, M W
• Is Part Of: Neuro-oncology. Volume 20(2018)Supplement 3
• Page Start: iii289
• Page End: iii290
• Publication Date: 2018-09-19
• Subjects: Brain Neoplasms -- Periodicals; Brain -- Tumors -- Periodicals; Brain -- Cancer -- Periodicals; Nervous system -- Cancer -- Periodicals; 616.99481
• DOI: 10.1093/neuonc/noy139.281
• Languages: English
• ISSNs: 1522-8517

Abstract

Abstract: Background: Oxidative stress is one of the major challenges of glioblastoma (GB) cells in the tumor microenvironment. Induction can be triggered by both local metabolic conditions including nutrient and oxygen deprivation as well as therapeutic interventions including radio- and chemotherapy. Cancer cell survival and clonal successfulness requires adaptation and ultimately therapeutic resistance. Since multiple conditions result in induction of oxidative stress, we hypothesized that glioma cells can develop cross-tolerance to differing stress stimuli. In this concept exposure to one oxidative stressor will induce adaptive programs that will prepare GB cells to better cope with subsequent other oxidative stressors. For example a hypoxic tumor microenvironment-mediated oxidative stress might induce programs allowing better coping with subsequent oxidative stress caused e.g. by chemotherapy. One key player of the oxidative stress response is the transcription factor Nrf2, which is upregulated in many human cancers. Oxidative stress causes Nrf2 release from its cytosolic sequestor KEAP1 and nuclear activation of transcriptional programs for adaptation including transcription of heme oxygenase 1, thioredoxin 1 and NAD(P)H-quinone-oxidoreductase. In order to investigate the role of Nrf2 activation especially under hypoxic conditions in malignant glioma cells we used two selective small-molecule inhibitors of the Nrf2-Keap1-interaction, ML334 and RA839. Material and Methods: The human GB cell lines LNT-229, LN-308, T98G and the immortalized astrocyte cell line SVG were used as a representative panel. The effects of the pharmacological inhibitors of the Nrf2-Keap1 interaction, ML334 and RA839, were analyzed by measuring Nrf2 target gene expression. Furthermore the role of Nrf2 for survival under conditions of the tumor microenvironment was analyzed in a paradigm of hypoxia-induced cell death by LDH release measurement and PI staining. Glucose consumption was analyzed by an enzyme-based assay. Results: Both ML334 and RA839 caused Nrf2 activation in all tested cell lines followed by Nrf2 target gene expression. Hypoxic conditions (0.1% O2 ) similarly induced Nrf2. Pharmacological Nrf2 activation resulted in protection from hypoxia-induced cell death even though glucose consumption of the cells increased after pharmacological Nrf2 activation. Conclusion: Nrf2-dependent adaptive programs are functional in human GB as well as immortalized astrocytic cells. Activation of Nrf2 increases hypoxia tolerance under conditions of the tumor microenvironment. Nrf2 may be a therapeutic target in GB treatment. Experiments on effects of chemotherapy sensitivity are ongoing.