This is the main conclusion of a study involving 30 patients and mouse models published in the journal Nature, conducted by researchers from the Swiss Federal Institute of Technology (ETH) in Zurich, the University Hospital of Basel and the University of Basel.
Breast cancer is one of the most common forms of cancer, according to the World Health Organization (WHO). Each year, approximately 2.3 million people contract the disease worldwide.
If doctors find the cancer in time, patients usually respond well to treatment. However, things become much more difficult if the cancer has already metastasized, reminds ETH.
Metastasis occurs when circulating cancer cells break away from the original tumor, travel through the body through blood vessels, and form new tumors in other organs.
According to those responsible for the work, until now, cancer research has not paid much attention to this question of when tumors release metastatic cells.
This new study led to “a surprising conclusion”: circulating cancer cells that later metastasize mainly occur during the sleep phase.
Hormones regulated by the circadian rhythm control metastasis.
“When the affected person sleeps, the tumor wakes up”, summarizes the head of the study Nicola Aceto, professor of molecular oncology at ETH Zurich.
During the study, which involved 30 cancer patients and mice, the researchers found that the tumor generates circulating malignant cells when the body is asleep.
Cells that leave the tumor at night also divide faster and therefore have a greater potential for metastasis than cells that leave the tumor during the day.
“Our research demonstrates that the release of circulating cancer cells from the original tumor is controlled by hormones such as melatonin, which determine our daytime and nighttime rhythms,” added Zoi Diamantopoulou.
Additionally, the study indicates that the time at which tumor or blood samples are taken for diagnosis may influence oncologists’ conclusions.
According to the Swiss center, it was an accidental discovery in this sense that put the investigators on the right track for the first time.
The scientists were surprised to find that samples taken at different times of the day had vastly different levels of cancer cells.
“In our opinion, these results may indicate the need for healthcare professionals to systematically record the time at which they perform biopsies,” says Aceto, noting, “This can help make the data really comparable.”
The researchers’ next step will be to find out how these findings can be incorporated into existing cancer treatments to optimize therapies.
Aceto wants to study whether different types of cancer behave in the same way as breast cancer and whether existing therapies might be more effective if patients are treated at different times.