Background: Diffusely infiltrating astrocytomas are the most common primary brain tumours and most malignant of all brain tumours. These malignant gliomas are classified to WHO grades II to IV. Grade IV glioblastoma represents a devastating tumour type with a 5-year survival rate below 10%. The best treatment option available today, that is surgery possibly combined with radiation- and/or chemotherapy, is insufficient. Therefore, brain tumour research has focused on understanding of the pathogenesis, and accordingly, has aimed to develop better methods for cancer diagnostics and treatment. Carbonic anhydrases (CAs), investigated in this study, have previously been linked to carcinogenic processes of several malignancies, and are proposed to represent an attaractive target for cancer therapy.

Aims: The purpose of this study is to describe the expression of CAs in astrocytic gliomas and study their relationship to clinicopathological features, especially the proliferation of cancer cells measured by Ki-67 / MIB-1. Another aim is to develop methods for improved diagnostics and to predict more accurately survival of patients with astrocytic gliomas. The additional objective of this study is to characterize possible targets for future therapeutic interventions of gliomas.

Results: In the first study, a new method is introduced for intraoperative immunohistochemical staining of a proliferation marker, Ki-67 (Ultrarapid-Ki67®). This method was practical to perform and morphologically and quantitatively indistinguishable from the conventional Ki-67 / MIB-1 staining. In the following three studies, the expression of CAs II, IX, and XII is described in a large series of diffusely infiltrating astrocytomas for the first time. By immunohistochemistry, CA II was detected in the neovessels of high-grade gliomas, whereas CA IX and CA XII were mainly located in cancer cells. A short isoform of CA XII by alternative splicing was also introduced into gliomas. None of the CAs correlated to tumour cell proliferation by Ki-67 / MIB-1, whereas CA IX was associated with necrotic tumour regions. The expression of all CAs was significantly associated with higher WHO grade. Most importantly, the expression of all CAs predicted poor survival of patients in univariate analysis, and CA IX and CA XII were significant predictors of survival even in multivariate analysis.

Conclusions: CA II, IX, and XII are expressed in astrocytic gliomas and the expression increases within increasing WHO grade. Being involved in carcinogenesis, CAs could be used in predicting poor survival of patients. CAs seem to be potential target molecules for therapy in gliomas, which should be evaluated in clinical trials. CAs were not associated with tumour cell proliferation as evaluated by Ki-67 / MIB-1 staining. In addition, Ultrarapid-Ki67® immunostaining, as a fast and reliable method for proliferation estimation, could be used in routine intraoperative diagnosis of gliomas.