According to a recent study conducted by experts from ETH Zurich, the University Hospital Basel, and the University of Basel, circulating cancer cells that later become metastases arise largely during the sleep phase of affected persons.
The study’s findings were published in the journal ‘Nature.’
According to the World Health Organization, breast cancer is one of the most common types of cancer (WHO). Around 2.3 million people globally acquire the disease each year. Patients usually respond favourably to treatment if doctors find breast cancer early enough.
However, if the cancer has already spread, things become much more difficult. When circulating cancer cells separate from the initial tumour, they travel across the body via blood arteries and establish new tumours in other organs.
To date, cancer research has given little attention to when tumours discharge metastatic cells. Previously, researchers considered that tumours continuously released such cells.
“When the patient is sleeping, the tumour awakens,” says study leader Nicola Aceto, Professor of Molecular Oncology at ETH Zurich. The researchers discovered that the tumour develops more circulating cells when the body is asleep during their investigation, which involved 30 female cancer patients and mice models. Cells that leave the tumour at night divide faster and so have a greater potential to produce metastases than circulating cells that leave the tumor during the day.
“Our findings suggest that hormones like melatonin, which regulate our circadian rhythms, affect the escape of circulating cancer cells from the primary tumour,” explains Zoi Diamantopoulou, the study’s lead author and a postdoctoral researcher at ETH Zurich.
Adapting treatments to the tumour
Furthermore, the study suggests that the timing of tumour or blood sample collection for diagnosis may alter oncologists’ conclusions. An unintentional discovery along these lines set the researchers on the right route in the first place. “Some of my coworkers work early in the morning or late in the evening; they’ll also analyse blood at odd hours,” Aceto explains with a smile.
The researchers were caught aback when they discovered that samples collected at different times of the day showed extremely variable quantities of circulating cancer cells.
Another hint was the very high quantity of cancer cells detected in mice per unit of blood when compared to humans. Because mice are nocturnal animals, they sleep throughout the day, which is when scientists gather the majority of their samples.
“In our opinion, these data suggest that healthcare providers should systematically record the time at which they do biopsies,” Aceto added. “It could aid in making the data genuinely comparable.”
The researchers’ next step will be to figure out how to incorporate these discoveries into existing cancer treatments in order to optimise remedies. Professor Nicola Aceto of ETH wants to examine whether different types of cancer behave similarly to breast cancer and whether existing medicines might be made more effective if individuals are treated at different times.
