In order to investigate the role of melatonin over the effectiveness of tamoxifen, a breast cancer drug widely used to fight against human breast cancer cells; investigators and co-leaders of Tulane's Circadian Cancer Biology Group, Steven Hill and David Blask, and rest of the team members Robert Dauchy and Shulin Xiang, implanted them in rats.
Through an exciting finding it was observed that exposure to light at night shuts down nighttime production of a hormone called melatonin which in turn causes the development of temoxifen resistant breast cancer.
The report got published in the journal of Cancer Research.
“According to Science Daily, in the first phase of the study, we kept animals in a daily light/dark cycle of 12 hours of light followed by 12 hours of total darkness (melatonin is elevated during the dark phase) for several weeks. In the second study, we exposed them to the same daily light/dark cycle; however, during the 12 hour dark phase, animals were exposed to extremely dim light at night (melatonin levels are suppressed), roughly equivalent to faint light coming under a door, explained Hill”
It was found that Melatonin caused delaying of tumour formation and also was capable of bringing along significant slowdown of their growth but the use of tamoxifen led to a huge regression of tumours in rats with either high night time levels of melatonin during absolute darkness or in the rats who were on melatonin supplementation during dim light at night exposure.
The researchers believe these results have immense implications for women who while being treated with tamoxifen are regularly exposed to light at night because of insomnia, irregular working hours. Even exposure to light from computer or TV screen should not be allowed with them.
"High melatonin levels at night put breast cancer cells to 'sleep' by turning off key growth mechanisms. These cells are vulnerable to tamoxifen. But when the lights are on and melatonin is suppressed, breast cancer cells 'wake up' and ignore tamoxifen," Blask was quoted saying.
This study in the future can successfully announce light at night as a new and serious risk factor for developing resistance to tamoxifen and other anticancer drugs as well.
It will most likely also be possible to make use of melatonin in combination with tamoxifen, administered at the optimal time of day or night as a standard treatment for innumerable breast cancer patients.