Melatonin: A Potential Antineoplastic Agent in Breast Cancer

Melatonin is primarily synthesized in the pineal gland under the influence of noradrenergic stimulation at night. Melatonin regulates the sleep-wake cycle, gonadal activity, redox homeostasis, immune-modulation, anti-carcinogenic effects at the normal physiological state. Melatonin uses membrane-bound G-protein coupled MT1 and MT2 receptors and intracellular factors for its actions. Circadian deregulation, exposure to light-at-night, shift works, and jet lag disrupt the melatonin rhythm. Low levels of circulatory melatonin concentration influence the development of many cancers, including breast. Melatonin acts as an anti-cancer agent in breast tissue, suppresses metabolic activity, regulates cell-signaling pathways, subsequently blocks cell proliferation, induces apoptosis, inhibits chronic inflammation and metastasis. Melatonin restricts the functions of estrogen receptor , and also inhibits aromatase activity. Melatonin is a potent antioxidant, reduces the chemo-resistance capacity of breast cancer cells. At the therapeutic levels, it has potential impacts, increases the efficacy of chemotherapeutic agents, decreases the adverse effects of the drugs during the treatment of breast cancer. The present review has focused on the anti-neoplastic activity of melatonin against breast cancer and the possibilities of its therapeutic aspects.