Melatonin may be able to suppress the growth of breast cancer tumors, according to new research published in Genes and Cancer.

Mounting speculation from epidemiologists and experimentalists suggests that a lack of melatonin is the cause for greater risks of developing breast cancer. As melatonin is produced naturally in the brain only at night to regulate sleep cycles, some researchers speculate that our sleep-deprived society is the cause of a current lack of melatonin among many women; this may ultimately place women at higher risk for breast cancer. 

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To test the possible association between melatonin and breast cancer suppression, the researchers evaluated its effect on the regulation of the transcription factor Octamer Binding 4 (OCT4) by estrogen receptor alpha (Era) in breast cancer stem cells (BCSCs). The results were assessed on tumors that the researchers grew from stem cells, tumor types known as ‘mammospheres’. Three-dimensional tumor growth was performed by cell suspension and AIG.

The  mammosphere tumors were enlarged with estrogen (which can fuel tumor growth) and the estrogen-like Bisphenol A (BPA). The team found that 1mM of melatonin significantly decreased the number and size of mammospheres compared to the control group. Additionally, when the cells were stimulated by estrogen or BPA and simultaneously treated with melatonin, the size and number of mammospheres were greatly reduced.

The authors assert that their study shows, “that melatonin counteracts the effects of E2 and BPA treatment on mammosphere growth as well as the expression of ERα and the stem cell marker OCT4.”

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