APLN and neoplasm: In the search for new pathways involved in GBM pathology, the mRNA of the angiogenic factor Apelin (APLN) and its G-protein coupled receptor, Apelin receptor (APLNR) were found to be upregulated in GBM-associated vascular proliferations as well as in hypoxic tumor regions [14], where co-expression with VEGFA was observed [14,15].