Heme oxygenase (HO) isoforms in experimental C6 glioma: an immunocytochemical study

Because of their potential to regulate tumoural blood flow and interactions with nitric oxide the expression of the type 1 and 2 isoforms of heme oxyg enase (HO-1 and HO-2) were evaluated in implanted C6 striatal gliomas. Immu nocytochemistry using antibodies specific for HO-1 and HO-2 were used in 20 C6 glioma tumours. The bulk of the tumour parenchyma and endothelium was n egative for both HO isoforms. Isolated, but weak staining for HO-1 was seen in most tumours with focally increased expression in perinecrotic regions. Cells morphologically resembling macrophages stained with both HO-1 and HO -2, but were not numerous. These findings suggest that carbon monoxide, unl ike nitric oxide, does not have a major role in regulating tumoural blood f low in this experimental glioma model. These findings once again demonstrat e the differences between human malignant glioma and experimental implantat ion glioma models.