Admitting that EC-targeted deletion of HIF-1α or HIF-2α as published previously [45], [53] resulted in a surprisingly unremarkable phenotype, except for its profound disturbance of tumor angiogenesis, may imply that tumor vessel growth as compared to regenerative vasculogenesis (in this study) and angiogenesis [36] follow different developmental programs with a certainly underestimated impact of the perivascular compartment. The gene discussed is EPAS1; the disease is neoplasm.