Effect of PACAP on Hypoxia-Induced Angiogenesis and Epithelial-Mesenchymal Transition in Glioblastoma.

Grazia Maugeri,Rosario Caltabiano,Giuseppe Broggi,Concetta Federico,Daniela Maria Rasà,Agata Grazia D’Amico,Giuseppe Musumeci,Salvatore Saccone,Velia D’Agata,Salvatore Giunta

doi:10.3390/biomedicines9080965

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) exerts different effects in various human cancer. In glioblastoma (GBM), PACAP has been shown to interfere with the hypoxic micro-environment through the modulation of hypoxia-inducible factors via PI3K/AKT and MAPK/ERK pathways inhibition. Considering that hypoxic tumor micro-environment is strictly linked to angiogenesis and Epithelial–Mesenchymal transition (EMT), in the present study, we have investigated the ability of PACAP to regulate these events. Results have demonstrated that PACAP and its related receptor, PAC1R, are expressed in hypoxic area of human GBM colocalizing either in epithelial or mesenchymal cells. By using an in vitro model of GBM cells, we have observed that PACAP interferes with hypoxic/angiogenic pathway by reducing vascular-endothelial growth factor (VEGF) release and inhibiting formation of vessel-like structures in H5V endothelial cells cultured with GBM-conditioned medium. Moreover, PACAP treatment decreased the expression of mesenchymal markers such as vimentin, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) as well as CD44 in GBM cells by affecting their invasiveness. In conclusion, our study provides new insights regarding the multimodal role of PACAP in GBM malignancy.

Highlights

Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults [1]
Our results have shown that Pituitary adenylate cyclase-activating polypeptide (PACAP) decreases the production and release of vascular-endothelial growth factor (VEGF) in cells exposed to deferoxamine mesylate, a wellknown hypoxia mimetic agent
To investigate the peptide and receptor expression in the hypoxic area of the tumor, we analyzed the co-localization of PACAP or PAC1R with hypoxia-inducible factors (HIFs)-1α on human GMB sections by double-immunofluorescence analysis

Summary

Introduction

Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults [1]. GBM displays strong proliferation index, diffused infiltration, aberrant angiogenesis and poor outcome [3]. The highly malignant phenotype of this tumor as well as its resistance to chemotherapy and radiotherapy is exacerbated by the extensive hypoxic areas in the tumor bulk [5]. In these regions, low oxygen tension arises from reduced vascular perfusion or insufficient oxygen diffusion as consequence of higher metabolic demand of Biomedicines 2021, 9, 965.

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Results

Conclusion