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

Alessio D’Alessio,Filippo Biamonte,Libero Lauriola,Gina Lama,Gigliola Sica,Umberto Moscato,Cristiana Angelucci,Angelo Vescovi,Gabriella Proietti,Annunziato Mangiola

doi:10.18632/oncotarget.12398

Abstract

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.

Highlights

Among different type of solid tumors, glioblastoma multiforme (GBM) is highly angiogenic and characterized by evident vascular proliferation [1]
We report here the expression of HIF1α, HIF2α, VEGF, VEGFR1 and VEGFR2 in both GBM and peritumoral tissue, indicating that both areas contain, to some extent, cells that are either responsive to angiogenic stimuli or able to trigger angiogenic response
Since the expression of HIF1α or HIF2α has been detected at higher level in tumor tissues compared to the tumor surrounding tissue, we can hypothesize that the high expression of HIF2α in peritumoral tissue might be seen as a further sign of an initial transformation

Summary

Introduction

Among different type of solid tumors, GBM is highly angiogenic and characterized by evident vascular proliferation [1]. Our group has been focusing on the potential contribution of the GBM peritumoral compartment [7,8,9,10] and its neovascularization [11] which may serve as a potential target for tumor therapy To this regard, we demonstrated the expression of phosphorylated mitogenactivated protein kinases and of the stem cell marker nestin in the peritumoral tissue of GBM, even in the absence of tumor cells. It is well known that developing tumors rapidly deplete oxygen supply, becoming hypoxic These changes, occurring in the tissue microenvironment, stimulate hypoxia inducible factor (HIF) signaling and VEGF secretion in hypoxia-sensing cells as well as in tumor-associated stromal cells [14, 15], which in turn stimulates tumor vascular growth. We investigated the capability of both GCSCs and PCSCs to modulate EC properties, such as migration and tube formation in vitro

Methods

Results

Conclusion