Breast cancer spreads while people sleep, scientists have discovered in a breakthrough that could lead to night-time biopsies and treatments.
Researchers in Switzerland made the discovery while working late in their laboratories and noticed that cancer cells which break away from the original tumour and travel elsewhere ramp up activity during the sleep phase of affected individuals.
Until now, little attention has been paid to whether cancer acts differently depending on the time of day or night, with scientists assuming that tumours release metastasising – or spreading – cells continuously.
But the findings suggest they operate on a circadian rhythm, controlled by night-time hormones such as melatonin, which aids their spread.
Cells that leave the tumour at night also divide more quickly and therefore have a higher potential to spread, compared with circulating cells that leave the tumour during the day.
Researchers believe the findings could significantly change the way cancer is diagnosed and treated in the future.
Nicola Aceto, an associate professor of molecular oncology at ETH Zurich, who led the study, said: “Some of my colleagues work early in the morning or late in the evening and sometimes they’ll also analyse blood at unusual hours.
“They found that when the affected person is asleep, the tumour awakens. In our view, these findings may indicate the need for healthcare professionals to systematically record the time at which they perform biopsies.”
Breast cancer is the most common cancer in Britain, accounting for 15 per cent of all new cases, with around 55,900 people diagnosed with the condition each year.
‘Controlled by hormones such as melatonin’
Screening programmes have helped improve survival rates in recent years, with 85 per cent of women still alive five years after diagnosis.
Researchers studied the tumour activity of 30 breast cancer patients as well as corroborating their findings in mice.
They found that tumours generated more circulating cells during the hours of sleep. The findings also help explain why circulating tumour cells are higher in mice than humans during the day, because the animals are nocturnal.
Zoi Diamantopoulou, the study’s lead author and a postdoctoral researcher at ETH Zurich, said: “Our research shows that the escape of circulating cancer cells from the original tumour is controlled by hormones such as melatonin, which determine our rhythms of day and night.”
The team wants to investigate how the findings can be incorporated into existing cancer treatments to optimise therapies.
As part of further studies with patients, Prof Aceto wants to investigate whether different types of cancer behave similarly and determine whether existing therapies could be more successful if patients are treated at different times.
The results were published in the journal Nature.