HIF-1α inhibition by siRNA or chetomin in human malignant glioma cells: effects on hypoxic radioresistance and monitoring via CA9 expression

• Published in: BMC cancer Vol. 10; no. 1; p. 605
• Main Authors: Kessler, Jacqueline, Hahnel, Antje, Wichmann, Henri, Rot, Swetlana, Kappler, Matthias, Bache, Matthias, Vordermark, Dirk
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 04-11-2010; BioMed Central; BMC
• Subjects: Antigens, Neoplasm - biosynthesis; Antineoplastic Agents - pharmacology; Apoptosis; Carbonic Anhydrase IX; Carbonic Anhydrases - biosynthesis; Cell Line, Tumor; Cell Survival; Disease Progression; Disulfides - pharmacology; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Glioma - metabolism; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Indole Alkaloids - pharmacology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering - metabolism
• ISSN: 1471-2407; 1471-2407
• DOI: 10.1186/1471-2407-10-605

Hypoxia induces activation of the HIF-1 pathway and is an essential characteristic of malignant gliomas. Hypoxia has been linked to tumor progression, therapy resistance and poor prognosis. However, little is known about the impact of HIF-1α inhibition on radioresistance of malignant glioma.
In this study, we investigated the effects of the inhibition of HIF-1α on cell survival and radiosensitivity in U251MG and U343MG glioma cells, using two different strategies. HIF-1α inhibition was achieved by siRNA targeting of HIF-1α or via chetomin, a disruptor of interactions between HIF-1α and p300. The inhibition of the HIF-1 pathway was monitored by quantitative real-time PCR and Western blot analyses of the expression levels of HIF-1α and CA9. CA9 expression was investigated as a potential indicator of the efficacy of HIF-1 inhibition and the resulting radiosensitivity of malignant glioma cell lines was determined by clonogenic assay after irradiation under normoxic (2-10 Gy) or hypoxic (2-15 Gy) conditions.
Although siRNA and chetomin show distinct modes of action, both attenuated the hypoxia-induced radioresistance of malignant glioma cell lines U251MG (DMF10: 1.35 and 1.18) and U343MG (DMF10: 1.78 and 1.48). However, siRNA and chetomin showed diverse effects on radiosensitivity under normoxic conditions in U251MG (DMF10: 0.86 and 1.35) and U343MG (DMF10: 1.33 and 1.02) cells.
Results from this in vitro study suggest that inhibition of HIF-1α is a promising strategy to sensitize human malignant gliomas to radiotherapy and that CA9 could serve as an indicator of effective HIF-1-related radiosensitization.