Hifs are primed for degradation by Egln1, 2, and 3 hydroxylases (also termed prolyl-hydroxylase domain enzymes, PHD) that act upon specific proline residues in an O2-dependent manner and thereby target Hif-α subunits for ubiquitination by von Hippel-Lindau tumor suppressor and proteasomal-degradation [8], [23], [24]. This evidence concerns the gene EGLN1 and neoplasm.