Invasion is a defining hallmark of glioblastoma (GBM) and its infiltrative capacity is supported by the presence of tumor cells at a distance greater than 4 cm from the tumor margin. Several studies have suggested that the space demanding growth, the production of soluble factors and the peculiar vasculature of GBM induce changes in surroundings. We previously reported that the presence of activated MAP kinases and stem cell marker nestin in peritumor tissue of GBM, even in the absence of tumor cells, carries a prognostic significance, and that neoangiogenesis occurs in peritumor areas. GD3 ganglioside is linked with malignant transformation that promotes migration, invasion and neoangiogenesis. Neuro-glial proteoglycan 2 (NG2) is also involved in invasion and angiogenesis; it is expressed by pericytes that have multipotent stem cell properties. Both markers are present in several precursor cells. To gain a deeper insight into the characteristics of GBM peritumor tissue, we investigated GD3 and NG2 expression in peritumor areas compared to the enhanced lesion. Patients (n=40) recruited in this study had a supratentorial GBM and underwent “en bloc” surgery. Tissue samples from the enhanced lesion (1st area), white matter at a distance <1 cm (2nd area) and between 1 and 3.5 cm from the tumor margin (3rd area) were obtained using adopted surgical technique. Immunohistochemical analysis using anti-GD3 (n=40) monoclonal and anti-NG2 (n=15) polyclonal antibody was performed in paraffin-embedded sections and frozen sections, respectively. Results showed cell membrane and cytoplasmic GD3 and NG2 expression in both GBM and peritumor tissue. Specifically, GD3 was expressed in tumor and endothelial cells; it was present in reactive astrocytes and in apparently normal cells in peritumor areas. Percentage of GD3 positive cells was higher in GBM than in 2nd and 3rd areas (P< 0.001); GD3 was higher in peritumor areas when tumor cells were present (P< 0.005). NG2 was expressed in GBM and in cells of various morphology in peritumor tissue. Double labelled confocal microscopy analysis showed that NG2 was co-expressed with alpha-smooth muscle actin in pericytes while CD105 was present in endothelium of the vessel walls in tumor and peritumor tissue. Percentage of NG2 positive cells was higher in GBM than in peritumor areas (P< 0.001), and was lower in the 3rd compared to the 2nd area (P< 0.05). Our findings confirm that peritumor tissue undergoes a significant transformation. Apparently normal glial cells expressing GD3 and NG2 might represent precursor cells in peritumor tissue. Marker expression in both these cells and pericytes may indicate the acquisition of properties linked to proliferation, motility and neovascularization contributing to tumor progression. Importantly, our results provide a useful tool to develop informed and unified approaches to diagnosis and therapy of GBM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4676.