Analysis of angiogenesis related factors in glioblastoma, peritumoral tissue and their derived cancer stem cells

The formation of new blood vessels represents a crucial event under both physiological and pathological circumstances. In this study, we evaluated by immunohistochemistry, and/or Western blotting and/or quantitative real time-PCR the expression of HIF1α, HIF2α, VEGF, VEGFR1 and VEGFR2 in surgical glioblastoma multiforme (GBM) and peritumoral tissue samples obtained from 50 patients as well as in cancer stem cells (CSCs) isolated from GBM (GCSCs) and peritumoral tissue (PCSCs) of 5 patients. We also investigated the contribution of both GCSCs and PCSCs on the behavior of endothelial cells (ECs) in vitro. Immunohistochemistry demonstrated the expression of angiogenesis markers in both GBM and peritumoral tissue. In addition, in vitro tube formation assay indicated that both GCSCs and PCSCs stimulate EC proliferation as well as tube-like vessel formation. An increased migration aptitude was mainly observed when ECs were cultured in the presence of GCSCs rather than in the presence of PCSCs. These findings suggest that relevant neoangiogenetic events may occur in GBM. In particular, VEGF/VEGFR co-expression in PCSCs leads to hypothesize the involvement of an autocrine signaling. Moreover, our results suggest that both GCSCs and PCSCs own the skill of activating the "angiogenic switch" and the capability of modulating EC behavior, indicating that both cell types are either responsive to angiogenic stimuli or able to trigger angiogenic response. Together with our previous findings, this study adds a further piece to the challenging puzzle of the characterization of peritumoral tissue and of the definition of its real role in GBM pathophysiology.