Nighttime Dim-Light Exposure Might Cause Breast Cancer to Travel into Bones

Researchers have shown that exposure to dim light at night time causes breast cancer to spread into the bones.

“To date, no one has reported that exposure to dim light at night induces circadian disruption, which then increases the formation of bone metastatic breast cancer,” said an assistant professor at Tulane University, Dr. Muralidharan Anbalagan. “This is important, as many patients with breast cancer are likely exposed to light at night as a result of lack of sleep, stress, excess light in the bedroom from mobile devices and other sources, or night shift work.”

In this study, a mouse model that suffered from bone metastatic breast cancer was created by the researchers. The researchers injected in mice some human estrogen receptor-positive cells of breast cancer that have a very low tendency to grow into the bones. The mice that were used, produced a strong circadian melatonin signal at nighttime, just like in humans. This nighttime melatonin signal has been shown to produce strong anti-cancer actions and also promotes sleep.

All the mice were held in reserve for 12 hours every day in the light. One of the groups of 3 mice was exposed to the dark for the other 12 hours, which helped in the production of high levels of endogenous melatonin. Another group was exposed for 12 hours in the light and then followed by twelve hours in dim light at night time. Dr. Anbalagan said that the dim light was 0.2 lux.

He reported that the X-ray images had proved that those mice who were exposed to dim light cycle had much greater tumors and damages to bones than the mice present in a standard light cycle.

Dr. Anbalagan said, “Our research identified the importance of an intact nocturnal circadian melatonin anti-cancer signal in suppressing bone-metastatic breast tumor growth,”

He further said that finding a way to stop or at least suppress the spreading of Breast Cancer into bones was their ultimate goal.