Melatonin in human cancer: Therapeutic possibilities

Abstract

The recent discovery in the neuropsychoimmunology of tumors has demonstrated that human body may produce not only pro-tumoral hormones such as estrogens, androgens, and perhaps GH itself but also antitumor endocrine molecules, the most important of them represented by pineal hormones, melatonin as the most investigated of them. The antitumor activity of melatonin has been demonstrated by a great number of experimental studies, and it has been proven to be able to exert the overall potential antitumor mechanisms, commonly used by the conventional clinical oncology, including (1) antiproliferative cytotoxic action, mainly on melatonin receptor-expressing tumor cells; (2) inhibition of growth factor receptor activation; (3) inhibitory effect on tumor angiogenesis; (4) inhibition of tumor growth factor secretion; and (5) stimulation of the antitumor immunity, namely, by stimulating IL-2 secretion by T helper lymphocytes and IL-12 production by dendritic cells. In addition, melatonin could reserve interesting therapeutic results in the palliative therapy of cancer, particularly by counteracting the onset of the neoplastic cachexia by inhibiting the TNF-alpha secretion. Unfortunately, despite the great number of the experimental evidences, very few clinical studies with melatonin have been carried up to now in the treatment of human neoplasms, at least from a palliative point of view, to improve the quality of life.