Structural and expression differences between the vasculature of pilocytic astrocytomas and glioblastomas

The identification of differences in vascular architecture and utilization of angiogenic pathways is a first step for identifying specific targets for tailored antiangiogenic therapies of brain tumor patients. Here, we compared the proliferating vasculature of 2 glioma subtypes with entirely different biologic behaviors and molecular background at the immunophenotype and gene expression levels. Proliferating vessels in 13 pilocytic astrocytomas and 8 glioblastomas were compared for differences in the composition of the vascular walls using confocal microscopy for markers of endothelial cells and pericytes/mural cells. Endothelial, pericytic, and mural cells had normal-appearing arrangements in the vessels in pilocytic astrocytomas, whereas those in glioblastomas appeared to be more disorganized. In addition, differences in expression of angiogenesis-related genes were sought in the tumor specimens using RNA expression arrays. There were 114 out of 2,894 differentially expressed angiogenesis-related genes between these 2 glioma subtypes indicating differences in the utilization of various pathways. These results point to the need for detailed information on mechanisms of neoangiogenesis in tumor subtypes to facilitate the development of specific antiangiogenic strategies.