Their study, published September 28 in the journal Science Advances, could not only further the understanding of how circadian rhythms impact cancer, but also potentially provide a preventative way of protecting vulnerable groups who are at risk.

"There has always been a lot of evidence that shift workers and others with disrupted sleep schedules have higher rates of cancer, and our mission for this study was to figure out why," senior author Katja Lamia, PhD, associate professor in SRI's Department of Molecular Medicine, said in a statement.

The study confirmed that chronic circadian disruption significantly increased lung cancer growth in animal models. Mice that were exposed to irregular, shifting light patterns had an increased tumor burden of 68%, according to the results.

However, when researchers used RNA sequencing to determine the different genes involved in the cancer growth, they were surprised to find that a collection in the heat shock factor 1 (HSF1) family of proteins was the main culprit. The scientists suspect that HSF1 activity is increased in response to circadian disruption because changes in sleep cycles disturb the daily rhythms of body temperature.

"Normally, our body temperature changes by one or two degrees while we're sleeping. If shift workers don't experience that normal drop, it could interfere with how the HSF1 pathway normally operates -- and ultimately lead to more dysregulation in the body," Lamia said.

Researchers believe their study's findings could help develop more targeted cancer treatments and result in better monitoring of high-risk groups such as shift workers.