While treatments based on this key discovery are still years away, the results can give scientists a key foundation on which to build future research.
"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. That's what is so special about this work," said co-author of the study David Arnosti, Professor at Michigan State University in the US.
Scientists have speculated that the lack of melatonin, due in part to our sleep-deprived modern society, put women at higher risk for breast cancer.
The latest study showed that melatonin suppresses the growth of breast cancer stem cells, providing scientific proof to support the growing body of anecdotal evidence on sleep deprivation.
The research team was led by Juliana Lopes, a visiting researcher from Sao Paolo, Brazil.
For their experiment, the scientists grew tumours from stem cells, known as "mammospheres".
The growth of these mammospheres was enhanced with chemicals known to fuel tumour 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 principle 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 said.
The findings appeared in the journal Genes and Cancer.
