Melatonin Suppresses Growth of Breast Cancer

Melatonin, the hormone that helps regulate wake and sleep cycles, also appears to suppress the growth of breast cancer tumors.

Melatonin is made in the pineal gland of the brain, and it’s only made at night. Scientists have speculated that low levels of the hormone, partly due to sleep deprivation, could increase a woman’s risk for breast cancer.

Before the research team at Michigan State University could test its theory, the scientists had to grow tumors from stem cells, known as “mammospheres,” a method perfected in the laboratory of James Trosko at MSU.

The growth of the mammospheres was enhanced with chemicals known to fuel the growth of tumors — the natural hormone estrogen, and the estrogen-like chemical Bisphenol A, or BPA, found in many types of plastic food packages.

Treating the tumors with melatonin significantly decreased the number and size of mammospheres when compared with the control group. Furthermore, when the cells were stimulated by estrogen or BPA and treated with melatonin at the same time, there was a greater reduction in the number and size of mammospheres.

“This work establishes the principal by which cancer stem cell growth may be regulated by natural hormones, and provides an important new technique to screen chemicals for cancer-promoting effects, as well as identify potential new drugs for use in the clinic,” said Trosko.

The study was published in the journal Genes and Cancer.

Other research has also indicated that melatonin fights cancer. A study conducted at Harvard University found that men who had higher levels of melatonin were 75 percent less likely to develop advanced prostate cancer than those who had lower levels.

Additional research has suggested that melatonin may also protect the heart by increasing the normal drop in blood pressure that occurs during sleep. Italian researchers recruited healthy women and also women with high blood pressure. They were divided into two groups, and one group was given melatonin for three weeks while the other group was given a placebo.

After three weeks, the two groups switched treatments. The study, which was published in the American Journal of Hypertension, found that blood pressure dropped more at night when the women were taking melatonin, but had no effect on daytime blood pressure.