The anti-angiogenic action of melatonin might well be related to the estrogen availability in the tumor environment, since melatonin reduced the expression and activity of both classical aromatase promoter and aromatase promoter I.7 in HUVEC cells, indicating that melatonin reduced the production of estrogens, thus preventing carcinogenesis by interrupting the feedback between endothelial and tumor cells in hormone-dependent mammary tumor [22]. This evidence concerns the gene CYP19A1 and neoplasm.