PTEN and neoplasm: Moreover, a number of studies have reported on pseudohypoxic tumor phenotypes that occur due to specific mutations that upregulate HIF-1α and prevent its degradation, e.g., mutations in isocitrate dehydrogenase (IDH) [11], (PTEN), von Hippel–Lindau protein (pVHL), p53, epidermal growth factor (EGF), and mutant Ras and Src [13,14].