Thus, melatonin, through its inhibitory effect on the expression and activity of cyclooxygenases in breast cancer, decreases the production of prostaglandin E2, which reduces the levels of cAMP and indirectly decreases the activation of aromatase promoters II and I.3, decreasing aromatase expression and activity and therefore estrogen production [28]. The gene discussed is CYP19A1; the disease is breast cancer.