Expression of angiogenesis markers in cancer stem cells derived from glioblastoma and peritumor tissue

The process of angiogenesis is essential for tumor growth and invasion. Glioblastoma (GBM) is a lethal cancer characterized by florid vascularization and aberrantly elevated VEGF. Antiangiogenic therapy with VEGF antibody reduces GBM tumor growth. However, the clinical benefits are transient and invariably followed by tumor recurrence. Recently, it has been demonstrated that in glioblastoma (GBM), cancer stem cells (CSCs) are responsible for either tumorigenesis or neoangiogenesis. In particular, a fraction of CSCs includes a population of endothelial progenitors (1). In our previous study we showed the presence of nestin+ cell and nestin+ and endoglin (CD105) + vasculature , not only in the GBM but also in the tissue surrounding the tumor. This suggests that the endothelial differentiation of GSCs may be the reason why nestin+ cells were found in the blood vessels wall. In this study, with the aim to understand CSCs involvement in angiogenic drive we investigated, the expression of angiogenesis markers (VEGF, VEGFR1, VEGFR2, HIF1α and HIF2α) by immunocytochemistry, western blot or RT- PCR, in CSCs derived from glioblastoma (GCSC) and peritumor tissue (PCSC) of 4 patients. Both GCSC and PCSC were immunopositive for HIF1α and HIF2α, (molecules necessary for the promotion of angiogenesis),VEGF and its receptors VEGFR1 and VEGFR2 underline the presence of autocrine and paracrine growth factor loops. Moreover, we evaluated the expression of VEGFR1 and VEGFR2 in both GCSCs and PCSCs, by means of real time PCR analysis. Our results showed that both receptors were expressed at low level in both cell types. However, we found that although the expression of VEGFR2 was comparable, the expression of VEGFR1 resulted down regulated in PCSCs. These results show the presence of all angiogenic markers in PCSCs suggesting their involvement in the GBM local recurrence underling that the inhibition of multiple angiogenic pathways may be a new line of attack on this deadly cancer.