EPAS1 and neoplasm: Also illustrated in Fig. 6 is that increased HIF-1α levels in hypoxic lungs correlate with macrophage infiltration; this has been shown to promote tumour growth and metastasis22,27; our results suggest that prolonged exposure to hypoxia allows vascular regeneration, in agreement with previous reports that this is a process dependent on HIF-2α activation4,7,28,61.