Circadian rhythms control not only sleep but also hormonal balance, tissue repair, and the immune system. When this delicate mechanism is disrupted, the body's natural defenses begin to fail. In this situation, cancer exploits the disruption of the biological clock to its advantage.
The experiment involved two groups of mice genetically predisposed to aggressive breast cancer. One group was kept under normal light conditions, while the other was kept under artificially disrupted light conditions. In the second group, tumors appeared significantly earlier—around 18 weeks instead of 22—and were also more likely to metastasize to the lungs.
In addition to accelerated tumor growth, the researchers also documented a suppressed immune response. Long-term disruption of circadian rhythms altered even healthy breast tissue, making it more vulnerable to cancer development. This suggests that the risk begins long before the tumor itself appears.
To understand how circadian rhythm disruptions affect healthy breast tissue and weaken immune defenses, scientists analyzed the internal structure of tumors. They focused on the LILRB4 receptor, a kind of immune system "switch." Under normal conditions, it prevents excessive inflammation and protects tissue, but during cancer development, it begins to act against the body. The study showed that targeting LILRB4 can reduce tumor growth and metastasis, even in the presence of disrupted biological clocks.
These findings are particularly relevant for people with disrupted sleep patterns, such as night shift workers, flight attendants, and those who frequently travel across time zones. In a world where up to a third of people work irregular hours, understanding the connection between the internal clock and cancer could play a key role in disease prevention and treatment.
