Exposure to light at night makes breast cancer completely resistant to drug

Exposure to light at night makes breast cancer completely resistant to drug -

Exposure to light at night, which stops the nocturnal production of hormone melatonin, makes breast cancer completely resistant to the drug tamoxifen against breast cancer widely used, according to a new study by researchers at the school of the Tulane University medical cancer. The study "circadian disruption and melatonin by light exposure at night Drives intrinsic resistance to tamoxifen therapy in breast cancer," published in the journal Cancer Research , is the first to show that melatonin is critical to the success of tamoxifen in breast cancer treatment.

principal investigators and co-managers of Circadian Biology Group of the Tulane Cancer, Steven Hill and David Blask, as well as team members Robert Dauchy and Shulin Xiang, studied the role of melatonin on the effectiveness of tamoxifen in the fight against human breast cancer cells implanted in rats.

"in the first phase of the study, we kept the animals in a daily light day / night cycle of 12 hours of light followed by 12 hours of total darkness (melatonin is high in of the dark phase) for several weeks, "says Hill." in the second study, we exposed them to the same daily light day / night cycle, but during the 12-hour dark phase, animals were exposed to extremely low light at night (melatonin levels are deleted), roughly equivalent to low light under a door. "

melatonin by itself delayed tumor formation and significantly slowed their growth, but tamoxifen caused a significant regression of tumors in animals with either high levels of melatonin at night in complete darkness or those receiving melatonin supplementation during dim light in the night show.

These findings have potentially huge implications for women being treated with tamoxifen and also regularly exposed to light at night because of sleep problems, night work or exposed to light of the screens computer and television.

"high levels of melatonin at night to breast cancer cells to" sleep "by turning off growth mechanisms. These cells are vulnerable to tamoxifen. But when the lights are on and the melatonin is suppressed to awaken "the breast cancer cells and ignore tamoxifen," said Blask.

The study could shed light night a new and serious risk factor to develop resistance to tamoxifen and other anti-cancer drugs and make the use of melatonin in combination with tamoxifen, administered optimal time of day or night, the standard treatment for patients with breast cancer.