GPX1 and glioblastoma: GPx1 expression was positively correlated with tumor grade, expression of HIF-1α (hypoxia-inducible factor-1α), HIF-1α target genes, and tetraspanin exosomal marker genes (CD9, CD63, CD81)-conversely, it was inversely correlated with the overall survival outcome in human glioblastoma specimens [69].