Researchers say that the hormone melatonin appears to suppress the growth of breast cancer tumors. Although treatments based on this key discovery are still years away, the results offer an avenue for future research.

The brain manufactures melatonin only at night to regulate sleep cycles. Epidemiologists and experimentalists have speculated that the lack of melatonin, due in part to our sleep-deprived modern society, puts women at higher risk for breast cancer.

This new study shows that melatonin suppresses the growth of breast cancer stem cells, providing scientific proof to support the growing body of anecdotal evidence on sleep deprivation.

Co-author David Arnosti, a biochemistry professor and director of the Gene Expression in Development and Disease Initiative at Michigan State University, said:

“You can watch bears in the zoo, but you only understand bear behavior by seeing them in the wild. Similarly, understanding the expression of genes in their natural environment reveals how they interact in disease settings.”


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

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

Melatonin treatment 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,” Trosko says.

Juliana  Lopes, David  Arnosti, James E. Trosko, Mei-Hui  Tai, and Debora  Zuccari Melatonin decreases estrogen receptor binding to estrogen response elements sites on the OCT4 gene in human breast cancer stem cells Genes And Cancer DOI: 10.18632/genesandcancer.107

Image: Michael Reuter/Flickr

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