Cancer tumours: Cancer may interfere with the body’s natural day–night hormone cycle, and restoring that rhythm could help the immune system push back against tumours, according to a new mouse study.
Researchers studying mice with induced breast cancer found that tumours quickly dulled the normal daily rise-and-fall pattern of corticosterone, a stress hormone that typically follows a circadian rhythm. The shift appeared early, even before tumours could be felt. Within about three days of inducing cancer, the hormone rhythm was blunted by roughly 40–50%, the team reported.
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The work focuses on the body’s internal timing system, which is regulated in part by the hypothalamus, pituitary gland and adrenal glands, together known as the HPA axis. When the researchers examined the hypothalamus in tumour-bearing mice, they observed that certain key neurons were stuck in an unusual state: highly active, but producing low output.
Instead of giving anti-cancer drugs, the team used a technique to stimulate specific hypothalamic neurons in a way that mimicked the normal day–night cycle. When the stimulation was applied at the right time of day, just before the transition from light to dark, corticosterone rhythms returned, more anti-cancer immune cells moved into tumours, and tumour growth dropped significantly.
Timing turned out to be crucial. The same stimulation delivered at the wrong time of day did not produce the tumour-slowing effect, suggesting the benefit depends on restoring the rhythm in sync with the body’s clock.
Lead author Jeremy Borniger, an assistant professor at Cold Spring Harbor Laboratory, said the goal is not to replace existing therapies but to strengthen the body’s baseline physiology, potentially making standard treatments work better and reducing side effects in the future.
The researchers are now investigating how tumours disrupt healthy circadian rhythms in the first place, and whether similar clock-focused approaches could eventually support cancer care in people through improved “chronotherapy,” which times treatment to the body’s biological rhythms.
