Another mechanism is based on calcitriol reducing the expression of prostaglandin E2 (PGE2) generated by cyclooxygenase-2 (COX-2); this potentially inhibits angiogenesis by decreasing the synthesis of vascular endothelial growth factor (VEGF) and impairing the HIF-1α pathway in cancer cells [230]. This evidence concerns the gene PTGS2 and cancer.