Cancer cells travel at night

In one way or another, all our organs, tissues and cells obey daily rhythms, and malignant cells are no exception. Although in fact for a long time it was believed that the biological clock in tumors does not work – simply because they have a lot of mutations and they have long forgotten what normal, healthy molecular biology is. It is known that breakdowns in the internal clock increase the likelihood of cancer; This is also indicated by many experimental studies and clinical observations – people working in night shifts are more likely to develop malignant neoplasms. But, let us repeat once again, it was customary to think about the tumor itself that no clock affects it anymore.

However, this is not the case – in an article in Nature employees ETH Zurich and the University of Basel write that circadian rhythms affect metastasis. At first, the researchers noticed that in mice with tumors, the number of metastatic cells – that is, those that left the tumor and began to wander around the body – changed during the day. The same thing happened to happen in humans: thirty breast cancer patients were bled at 4 am and 10 am, and at 4 am the level of wandering cancer cells was noticeably higher – not always, but in 80% of cases.

Then the researchers returned to the mice: they transplanted tumor samples and again counted the number of metastatic cells at different times of the day. During the day, mice had much, much more such cells, sometimes as much as 88 times more than at night. Here we must not forget that mice are twilight and nocturnal animals, they rest during the day. That is, the result, in fact, turned out to be the same: the cells prefer to leave the tumor when, according to the daily rhythms, it is time to rest. What’s more, metastatic cells that wander around the body while resting are more likely to form a new tumor in a new location than metastatic cells that wander while awake.

Perhaps the results are not so surprising: a cancerous tumor does not exist in a vacuum, it is affected by many different molecular signals, hormones, etc. And the level of hormones and other bioactive molecules is subject to daily rhythms. Even if their clocks in cancer cells are broken, they still perceive signal molecules from the outside. Exactly which molecules these are remains to be seen, and just as it remains to be seen whether all cancers respond in a similar way to alternating sleep and wakefulness. The problem is all the more difficult because in some cases, cancer patients who sleep little die more often and faster from the disease, and knocked down biological clocks in mice not only increase the likelihood of a tumor, but also make it more aggressive. That is, the point is not to sleep less – the mechanism that links circadian rhythms and metastasis is more complex and requires further study.

Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by

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