Carbonic anhydrase IX in oligodendroglial brain tumors

Background: Carbonic anhydrase IX is a hypoxia-induced enzyme that has many biologically important functions, including its role in cell adhesion and invasion. Methods: This study was set out to investigate the role of CA IX in a series of 86 oligodendroglial brain tumors (71 primary and 15 recurrent; 48 pure oligodendrogliomas and 40 mixed oligoastrocytomas). Results: 80% of the tumors showed CA IX expression by immunohistochemistry. Tumors with moderate or strong CA IX expression had decreased level of cell proliferation compared to weak or no CA IX expression ( median 2.9 vs. 5.8, p = 0.015). CA IX correlated with two antioxidative enzymes, manganese superoxide dismutase (MnSOD) and regulatory gammaglutamylcysteine synthetase (GLCL-R): CA IX expression was significantly higher in MnSOD-positive tumors ( p = 0.008) and decreased in GLCL-R-positive tumors ( p = 0.044). In Cox multivariate analysis CA IX expression, patient age and histological component ( pure oligodendroglioma vs. mixed oligoastrocytoma) showed independent prognostic values ( p = 0.009, p = 0.003 and p = 0.022, respectively), CA IX positivity predicting poorer outcome. Conclusion: CA IX was proved to be an independent prognostic indicator in oligodendroglial brain tumors, and it also correlates reversely with cell proliferation. It may have a role in the biology of oligodendrogliomas, and most interestingly, as it is mainly expressed in tumor tissue, CA IX could serve as a target molecule for anticancer treatments.