Circadian rhythms are the body’s 24-hour clock that coordinates sleep, hormone release, tissue repair and immune surveillance. New research from the Texas A&M University College of Arts and Sciences, led by Tapasree Roy Sarkar, shows that repeated disruption of this clock actively alters mammary tissue and weakens immune defenses, driving faster and more aggressive breast cancer in experimental models.
The team used genetically engineered models that develop aggressive breast cancer. One group lived on a normal light–dark cycle; the other experienced a disrupted light schedule that desynchronised internal clocks. Compared with the normal group, the disrupted group showed signs of cancer earlier (nearly 18 weeks versus the typical 22-week marker), had more aggressive tumors and a higher tendency to metastasize to the lungs — a sign of poor prognosis.
Long-term circadian disruption also changed the morphology of milk-producing tissue and suppressed immune responses. Sarkar noted the immune system was “actively restrained,” creating conditions that help cancer cells survive and spread. At the molecular level the researchers identified leukocyte immunoglobulin-like receptor B4 (LILRB4). While LILRB4 normally limits excessive inflammation, in tumors it functioned as an immune checkpoint or “off switch.” Targeting LILRB4 made the tumor environment less immunosuppressive and reduced metastasis and tumor growth, even under disrupted circadian conditions.
The study suggests disruption can drive cancer progression rather than just correlate with risk. An estimated 12 to 35% of Americans work irregular schedules, including night and rotating shifts. The research team plans to study whether and how chronic circadian disruption effects can be reversed in humans to improve health for night-shift workers, flight attendants and frequent travelers.
Difficult words
- circadian rhythm — body's internal 24-hour biological timing systemCircadian rhythms
- desynchronise — to disturb the normal timing of processesdesynchronised
- metastasize — to spread cancer cells to other organs
- morphology — shape and structure of tissues or organs
- suppress — to reduce or stop a biological responsesuppressed
- immune checkpoint — molecule or receptor that limits immune attack
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What practical measures could employers or workers use to reduce long-term circadian disruption for night-shift staff?
- What additional human studies would you want to see to decide if these experimental results apply to people like flight attendants or frequent travellers?
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