In cancers of various origins, calcitriol exerts an anti-angiogenic effect via the down-regulation of major promoters of angiogenesis both at protein and transcriptional levels, such as hypoxia-inducible factor 1α (HIF-1α), a key transcription factor under hypoxia, vascular endothelial growth factor (VEGF-A), angiopoietin-1, and platelet-derived growth factor (PDGF). Here, HIF1A is linked to cancer.