Abstract

Glioblastoma Multiforme (GBM) is a highly infiltrative neoplasm and is characterized by a poor prognosis and a survival rate that does not exceed 15 months following surgical resection. Hypoxic niches of GBM can induce tumorigenic properties of a small cell subpopulation called Glioblastoma Stem-like Cells (GSCs), and can also increase extracellular adenosine generation which activates the A3 Adenosine Receptor (A3AR). Moreover, GSCs are responsible for several GBM hallmarks that potentiate their persistent neovascularization. In this study we evaluated the effect of A3AR on the differentiation of GCSs to Endothelial Cells (ECs) under hypoxia (0.5% O2). For this, we evaluated the expression of endothelial cell markers (CD31, CD34, CD144 and vWF) and VEGF secretion in vitro using MRS1220, a selective A3AR antagonist. To further validate our results, we generated a specific A3AR knockout in U87MG GSCs (GSCsA3-KO). The effect of MRS1220 on blood vessel formation was evaluated in vivo using a subcutaneous GSCs-tumor model. Our results showed that GSCs increased their extracellular adenosine production and A3AR expression under hypoxia. Hypoxia also increased the expression of endothelial markers and VEGF secretion, which was in turn prevented when using MRS1220 and in GSCsA3-KO. Finally, in vivo treatment with MRS1220 reduced tumor size and blood vessel formation. In conclusion, we suggest that A3AR activation promotes neovascularization and differentiation of GSCs to ECs under hypoxic conditions.