Writing in PLoS One, the early stage research suggests that the hormone melatonin - which is also approved for use as a nutritional supplement in some areas - could reduce the risk of developing certain types of cancer by blocking the growth of tumours and new blood vessels that support tumour growth.
Led by Adarsh Shankar and his colleagues from Henry Ford Hospital in Detroit, USA, and the Foundation for Research Support of the State of São Paulo, Brazil, the team noted that melatonin's suspected antioxidant properties, have led some to believe it may suppress the growth of certain types of cancer cells - especially when combined with certain anti-cancer drugs.
"These early stage research results with the melatonin drug in a triple-negative breast cancer animal models achieved in our lab has not been seen anywhere else," said Shankar.
"The key finding of the study is that we now know that we can trace this ... and its effect on tumour growth, which opens the door for more research on this topic."
To determine the effectiveness of melatonin at reducing tumour growth, the team evaluated the action of melatonin on angiogenesis in ER-negative breast cancer in vitro and in vivo using cell and mouse models respectively.
Mice were randomly assigned to either melatonin or control groups. The melatonin group received supplementation each night for 21 days, with melatonin administered at pharmacologic concentrations one hour before room lighting was switched off.
At the end of the 21-day study, researchers used single photon emission computed tomography (SPECT) to determine whether the melatonin had effectively decreased the size of implanted human triple negative breast cancer in the mouse models - and if there was any sign of changes in the formation of new blood vessels.
Additionally, tumour volume was measured each week and tumour tissue was analyzed at the end of treatment.
Shankar and his colleagues revealed that none of the mice given melatonin showed any loss of weight and lethargy during the 21-day treatment; instead, most showed excessive movement but no irritability or aggressive behaviour.
Those recieving melatonin also showed significantly smaller tumours after 21 days while the mean tumour volume increased significantly in the control group. In addition, there was less vascular growth in the tumours of the melatonin group.
Shankar and his team concluded that their results suggest that melatonin has the potential as a therapeutic agent for breast cancer, and may reduce the risk of cancer development.
However, they cautioned that the research is still in its very early stages and results are not yet ready to be translated in to humans.
Source: PLoS One
Published online ahead of print, doi: 10.1371/journal.pone.0085311
"Effect of Melatonin on Tumor Growth and Angiogenesis in Xenograft Model of Breast Cancer"
Authors: Bruna Victorasso Jardim-Perassi, Ali S. Arbab