Breast cancer: melatonin could reduce cancer

Melatonin, the hormone involved in regulating circadian rhythms, could slow the growth of breast cancer of the estrogen-insensitive type. The 'antitumor action would be due to the molecule's ability to block the formation of blood vessels, which are necessary for cancer cell proliferation and metastasis formation.

This is the discovery made by researchers at the Faculdade de Medicina de São José do Rio Preto in São Paulo, Brazil, and Henry Ford Hospital in Detroit, USA, and published in the prestigious journal PLoS One.

The antitumor role of melatonin

Melatonin is a molecule produced by the pituitary gland, a gland that reacts to the light-dark alternation. Its production follows a circadian rhythm, that is, over the 24 hours, with a minimum during the daylight hours and a peak during the nighttime hours between 2 a.m. and 4 a.m. Melatonin regulates the dream-wake rhythm but also appears to have other properties including antioxidant and anticancer properties. 

Several studies, in fact, suggest that melatonin may slow the growth of certain types of cancer such as prostate and breast cancer. This effect would be due to its ability to block angiogenesis, which is the formation of new blood vessels necessary for the tumor to grow and form metastases. Some research has shown that the substance may have an antiproliferative effect against ER- positive type breast cancers, that is, those that express the receptor for estrogen on the cell surface and respond positively to treatment with these hormones.

In contrast, triple-negative tumors, about 20 percent of all breast cancers, are so named because they do not express receptors for estrogen (ER), progesterone (PgR) and epidermal growth factor (HER 2) hormones. This characteristic of theirs makes them untreatable with some common therapies, which act on these very receptors.

Melatonin slows tumor progression in mice

During the study, the effect of melatonin was studied in laboratory mice in which triple-negative tumors were implanted. The 33 animals were divided into two groups: one receiving melatonin treatment and the other receiving a control solution. The treatment lasted 3 weeks, with administrations 5 days a week. After 21 days, tumor volume, tumor cell motility and the amount of blood vessels in the tumor were measured. The results showed that the melatonin-treated mice had maintained smaller tumor sizes than the controls and, in one case, one tumor had even regressed. In addition, compared with the control group, the density of blood vessels formed was lower in the mice treated with the hormone.

The inhibition of angiogenesis

These results suggest, for the first time, that melatonin can inhibit tumor growth, cell proliferation, and block angiogenesis, in animal models of triple-negative breast cancer. The treatment did not cause toxicity, suggesting the conduct of further studies that may ascertain the therapeutic role of melatonin, including for other types of cancer. To stay up-to-date with the latest news from Omega-3 scientific research, subscribe to our newsletter.

Source: Bruna Victorasso Jardim-Perassi, Ali S. Arbab, Lívia Carvalho Ferreira, Thaiz Ferraz Borin, Nadimpalli R. S. Varma, A. S. M. Iskander, Adarsh Shankar,Meser M. Ali,Debora Aparecida Pires de Campos Zuccari "Effect of Melatonin on Tumor Growth and Angiogenesis in Xenograft Model of Breast Cancer" Published: January 09, 2014 DOI: 10.1371/journal.pone.0085311