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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Radiotherapy, Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, Ernst-Grube-Straße 40, 06097 Halle, Saale, Germany. jacqueline.kessler@medizin.uni-halle.de
Jacqueline
J
Kessler
Antje
A
Hahnel
Henri
H
Wichmann
Swetlana
S
Rot
Matthias
M
Kappler
Matthias
M
Bache
Dirk
D
Vordermark
D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D002470:Cell Survival; D018450:Disease Progression; D004220:Disulfides / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D026121:Indole Alkaloids / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D004220:Disulfides; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D026121:Indole Alkaloids; D034741:RNA, Small Interfering; C001598:chetomin; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases