ARNT and hemangioma: Hif-2α was found to mediate up-regulation of erythropoietin and multiple pro-angiogenic cytokines in these mouse models, and inactivation of Hif-2α or Hif-1β/Arnt, but not Hif-1α, rescued hemangiomas in PEPCK-Cre or Albumin-Cre driven Vhlh knockout mice [22, 24].