VHL and neoplasm: HIF‐1α is constitutively expressed under normoxic conditions, but post‐translationally modified by a class of 2‐oxoglutarate‐dependent and Fe2+‐dependent prolyl hydroxylases (PHDs) at prolines 402 and 564; the modified protein is degraded after ubiquitination by von Hippel Lindau (pVHL), a tumour suppressor 33, 34.