Artikel
Expression of the hypoxia marker carbonic anhydrase IX (CA IX) in human malignant glioma in vitro and in vivo
Expression des Hypoxiemarkers CA-IX in humanen malignen Gliomen In-vitro und In-vivo
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Autoren
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H.M. Said
- Department of Radiation Oncology, University of Wuerzburg, Germany
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C. Hagemann
- Department of Neurosurgery, University of Wuerzburg, Germany
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B. Schoemig
- Department of Neurosurgery, University of Wuerzburg, Germany
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G. H. Vince
- Department of Neurosurgery, University of Wuerzburg, Germany
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M. Flentje
- Department of Radiation Oncology, University of Wuerzburg, Germany
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D. Vordermark
- Department of Radiation Oncology, University of Wuerzburg, Germany
| Veröffentlicht: | 30. Mai 2008 |
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Gliederung
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Objective: The hypoxia-inducible enzyme carbonic anhydrase IX (CA IX) has recently been discussed as a surrogate marker of tumor hypoxia, an indicator of prognosis and a potential therapeutic target in malignant glioma.
Methods: To characterize patterns of expression of CA IX in human malignant glioma cells, we studied CA IX protein, CA9 mRNA and hypoxia-inducible factor-1α (HIF-1α) protein levels in U87-MG, U251, U373 and GaMG cells exposed to in vitro hypoxia (1, 6 or 24 h at 5%, 1% or 0.1% O2). Also CA9 mRNA and protein expression were examined in two groups of tumor patient specimens, namely low-grade astrocytoma (LGA; n=15) and glioblastoma (GBM; n=15) and compared to a negative control group of normal brain samples (n=3). CA9 and HIF-1α protein expression were detected via Western blot while CA9 and HIF-1α mRNA expression detection was via Northern blot or semi quantitative RT-PCR, respectively.
Results: In the series of in vitro experiments, all cell lines displayed a strong hypoxic induction of CA9 mRNA in response to prolonged severe hypoxia with cell-line specific patterns at moderate to mild hypoxia and shorter treatment times. Only U87-MG exhibited a strong constitutive, normoxic expression of CA IX protein without a detectable change under hypoxia. In U251 and GaMG cell lines, a marked induction of CA IX protein in response to severe hypoxia was seen. CA IX changes under severe hypoxia and the inhibitory effect of the glycolysis inhibitor iodoacetate (IAA, 50 µM) on hypoxic CA IX overexpression were paralleled by the results for HIF-1α protein. In the patient tumor specimens, CA IX protein was only overexpressed in (GBM). CA9 mRNA was predominantly overexpressed in GBM (12/15) patients compared to LGA patients (3/15).
Conclusions: Immunohistochemical CA IX staining in human malignant glioma specimens can result from low oxygen concentrations or constitutive, oncogene-related, overexpression both of which may be prognostically relevant. CA9 expression in (GBM) tumors occurs at a higher frequency, both on protein or mRNA levels, rendering CA9 as a suitable hypoxia-related diagnostic marker or target for therapeutic approaches.
