The VEGF/VEGFR2 signaling between endothelial cells and tumor cells is one of the most representative systems for tumor-associated angiogenesis [51]; long-term melatonin therapy significantly attenuated this signaling in OC, possibly indicating a dual function of melatonin in inhibiting paracrine pathways created between tumor cells and the vessel endothelium. This evidence concerns the gene KDR and neoplasm.