Breast Cancer: Melatonin May Reduce Tumor Growth

Melatonin, the hormone involved in regulating circadian rhythms, may slow the growth of estrogen receptor-negative breast cancer tumors. Its anti-cancer action appears to be due to its ability to block the formation of blood vessels necessary for cancer cell proliferation and metastasis formation.

This discovery was made by researchers from 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 Anti-Tumor Role of Melatonin

Melatonin is a molecule produced by the pituitary gland, which responds to the light-dark cycle. Its production follows a circadian rhythm over 24 hours, with a minimum during daylight hours and a peak during the night between 2 and 4 AM. Melatonin regulates the sleep-wake cycle but also appears to have other properties, including antioxidant and anti-cancer effects. 

Numerous studies suggest that melatonin may slow the growth of some cancers, such as prostate and breast cancer. This effect is thought to be due to its ability to block angiogenesis, the formation of new blood vessels needed by tumors to grow and metastasize. Some studies have shown that melatonin may have an antiproliferative effect on ER-positive breast cancers, which express estrogen receptors on the cell surface and respond to hormone treatments. 

Conversely, triple-negative tumors, about 20% of all breast carcinomas, are called so because they do not express receptors for estrogen (ER), progesterone (PgR), or the epidermal growth factor receptor (HER2). This characteristic makes them unresponsive to some common therapies that target these receptors.

Melatonin Slows Tumor Progression in Mice

The study examined the effect of melatonin in laboratory mice implanted with triple-negative tumors. The 33 animals were divided into two groups: one received melatonin treatment, the other a control solution. The treatment lasted 3 weeks with dosing 5 days a week. After 21 days, tumor volume, tumor cell motility, and the number of blood vessels in the tumors were measured. Results showed that mice treated with melatonin had smaller tumors than controls, and in one case, a tumor even regressed.  Furthermore, compared to the control group, the density of blood vessels formed was lower in the melatonin-treated mice.

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 caused no toxicity, suggesting further studies to confirm melatonin’s therapeutic role, including for other cancer types. To stay updated on the latest scientific research on Omega-3, 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