[Inhibitory effects of melatonin on breast cancer].

Melatonin has a significant inhibitory effect on various cancers, especially on breast cancer. In estrogen receptor (ER)-positive human breast cancer, anti-cancer effects of melatonin on breast cancer cells and transplanted tumors mainly achieve by suppressing ER mRNA expression and ER transcriptional activity via the MT1 receptor. In addition, melatonin regulates the transactivation of other members of the nuclear receptor super-family, estrogen metabolizing enzymes, and the expression of related genes. Furthermore, melatonin also suppresses tumor aerobic metabolism, critical cell-signaling pathways relevant to cell proliferation, survival, metastasis, and drug resistance. Melatonin demonstrates both cytostatic and cytotoxic activity in breast cancer cells that appears to be cell-type specific. Studies on animal and human models indicate that disruption of the circadian nocturnal melatonin signal promotes the growth, metabolism, and signaling of human breast cancer, resulting in invalid hormone therapy and chemotherapeutic resistance in breast tumors.