Circadian rhythms are the body’s natural 24-hour clock and they regulate sleep, hormones, tissue repair and immune surveillance. New work from a team at Texas A&M University shows that repeated disruption of this clock changes healthy breast tissue and weakens immune defenses, which together speed breast cancer in experimental models.
The researchers, led by Tapasree Roy Sarkar, used genetically engineered models that develop aggressive breast cancer. One group lived on a normal light–dark cycle and another on a disrupted cycle that disturbed internal clocks. Compared with the normal group, the disrupted animals developed signs of cancer earlier and their tumors were more aggressive and more likely to spread to the lungs.
At the molecular level the team identified LILRB4, a receptor that normally limits inflammation. In the tumors it acted like an immune checkpoint and helped suppress immune attack. When researchers targeted LILRB4, the tumor environment became less immunosuppressive and showed reduced metastasis and tumor growth, even with circadian disruption. The team plans further work on reversing these effects in people who work irregular hours.
Difficult words
- circadian rhythm — Body's internal 24-hour timing systemCircadian rhythms
- disruption — An event that breaks normal functioning
- immune surveillance — Body processes that detect and fight threats
- receptor — Protein on a cell that receives signals
- inflammation — Body reaction causing redness and swelling
- metastasis — When cancer spreads to another body part
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Discussion questions
- Do you think people who work at night should change their light exposure to protect their health? Why or why not?
- What changes to daily life could help keep a regular circadian rhythm? Give one or two examples.
- How might a weaker immune system affect a person's chance of getting or spreading cancer?
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