Are cancer cells mainly active at night?


Metastases are usually more dangerous than the primary tumor. According to a Swiss study, these cancer cells behave differently depending on the time of day. But there are still many ambiguities.

< p>Metastases: The “Deadly Daughters” of Cancer

Tumor cells are most active during human sleep phases. This is the result of researchers at the Swiss Federal Institute of Technology in Zurich, ETH. 30 breast cancer patients were observed for the study, which was published in the journal “Nature”. In addition, studies were carried out on mice. The study was relatively small, but according to the researchers, it still came to results that could definitely have an impact on the diagnosis and treatment of breast cancer

Breast cancer is one of the most common forms of cancer. According to the World Health Organization (WHO), around 2.3 million women worldwide contract it every year. Detected early enough, the chances of recovery are great. It becomes difficult when metastases have formed. The WHO estimates that the so-called “deadly daughters” lead to death in 90 percent of all cancers. Research on metastases is correspondingly important, why and how they develop and – according to the results of the Swiss study – also when.

Watch video 04:27

How cancer changes life< /h2>

More of a chance find?

The assumption that metastases in breast cancer are very active at night is due to the fact that employees at the ETH molecular biology laboratory have different working hours and therefore took blood samples from the patients at different times and examined them. The team found that the number of tumor cells circulating in the blood (CTC – circulating tumor cells) was significantly higher at night than during the day.

Nadia Harbeck, head of the breast center and the oncological day clinic of the women's clinic at the Ludwig Maximilian University of Munich (LMU) sees a practical problem with the results of the study. “This is very interesting basic work, which is worth investigating further and, above all, working out the clinical significance of,” says Harbeck. “Because it should be confirmed that certain tumor cells form primarily at night when we sleep , that would initially be difficult with a view to the treatment in everyday clinical practice.” After all, patients do not come for treatment and blood tests at night, but during the day. 

The Swiss researchers observed that more cells or entire clumps of cells detached themselves from the actual tumor at night and then spread through the blood in the body. If it is confirmed that certain circulating cancer cells do in fact have a circadian rhythm, i.e. have a biological rhythm that determines how aggressive the cancer cells are, this can be an indicator both for the diagnosis and for a possible therapy. < /p>

“One might ask, for example, whether blood draws for CTCs in our cancer patients shouldn't always be done early in the morning,” says Harbeck. “So far, there is no uniform regulation for this. But it would be even more interesting to know which growth factors exactly determine the dynamics of the CTCs. Because advising patients not to sleep anymore is unrealistic. I would be interested in the details of which ones mechanism during our sleep causes the CTCs to become more aggressive. Answering this question would then be of great importance for cancer therapy.”

Does the time of day really matter?

The findings seem rather random at first. Therefore, breast cancer patients were also examined at the University Hospital Basel. The blood samples were taken at different times of the day: at 10:00 a.m. and at 4:00 p.m. The study confirmed the observations of the researchers from Zurich: the samples from the night contained significantly more cancer cells circulating freely in the blood. There were 80 percent more, almost twice as many.

The more often cancer cells divide, the more dangerous it is becomes the disease

Tanja Fehm, director of the women's clinic at the Düsseldorf University Hospital, is rather critical of the study and the corresponding results. “Due to the fact that many cells in the body and their activities – for example immune cells – are subject to a circadian rhythm, we can assume that there are daily differences and short-term fluctuations in the number of CTCs. This suggests that metastasis through the circadian rhythm could be regulated.” 

But, according to Fehm, overall this phenomenon and thus the results of the Swiss findings must be confirmed in a larger cohort of patients in a multi-centre study with independent people. “Only then will one be able to foresee whether this will affect future treatment methods.”

Another critical aspect is that a non-standard method was used in detecting the tumor cells circulating in the blood. “It is therefore difficult to assess to what extent [in the case of] breast cancer patients it was actually tumor cells and not false-positive white blood cells, which are also subject to circadian rhythms,” Fehm continued. p>

Breast cancer often metastasizes to the bones and lymph nodes. Feeling your own breasts can help to discover the disease as early as possible.

Opposite results in the mouse model

The experiments that the researchers also carried out on laboratory mice came to the opposite conclusion. Here, the number of metastasizing cancer cells was significantly higher during the day than in samples that had been taken and examined at night. Cells from breast cancer patients had previously been implanted in some mice. Others had developed the form of cancer on their own.

In the mice examined, the researchers found 90 times more metastatic cancer cells during the day than at night. Mice are nocturnal, so they sleep during the day. These results suggested that hormones play an essential role in the development of metastases. The hormone melatonin is responsible for our sleep rhythm. 

“The in-vivo studies in the mouse models raise exciting questions, the relevance of which will have to be investigated in patients in further studies,” says Fehm.  

So far, the time of day for blood collection and blood analysis has hardly been the focus. That could change in the future.  However, further, large-scale studies are still required for valid results to track down the activity of cancer cells in the formation of the “deadly daughters”. 

  • Avoiding cancer instead of curing it

    Fate is in your hand

    A cancer diagnosis is always hard and unexpected. Almost half of all cancer cases could be avoided. Smoking is to blame for about every fifth tumor. The toxic tobacco smoke not only causes lung cancer, but also many other types of tumours. Smoking is the most common self-inflicted cause of cancer – but not the only one.

  • Avoiding cancer instead of curing it

    Being fat can be deadly

    The second most common cause of cancer: obesity. High insulin levels are to blame. They increase the risk of almost all types of cancer, especially kidney, gallbladder and esophageal cancer. Overweight women also produce more female sex hormones in adipose tissue and are therefore more likely to develop uterine and breast cancer.

  • Avoiding cancer instead of curing it

    Get off the sofa!

    People who hardly move are particularly likely to get cancer. Long-term studies show: Sport prevents tumors. Physical activity lowers insulin levels and also prevents you from getting fat. And it doesn't have to be a high-level sport: just a little walk or bike ride makes a big difference.

  • Avoiding cancer instead of curing it

    Cancer for the good!

    Alcohol is carcinogenic. It primarily promotes tumors in the oral cavity, the pharynx and the esophagus. The combination of smoking and alcohol is particularly dangerous: This increases your risk of cancer a hundredfold. However, a glass of wine a day is healthy because it supports the cardiovascular system. Anything beyond that should be avoided.

  • Avoiding cancer instead of curing it

    Unhealthy things from animals

    Red meat can cause colon cancer. The exact reason has not yet been clarified, but long-term studies show a clear connection. Beef is particularly dangerous, and to a lesser extent, pork. Consumption increases the risk of cancer by a factor of one and a half. Fish, on the other hand, prevents cancer.

  • Prevent cancer instead of curing it < h2>Danger from the charcoal grill?

    Carcinogenic substances such as polycyclic aromatic hydrocarbons are produced when meat is grilled. In animal experiments, these chemical compounds trigger tumors. This has not yet been clearly proven in long-term studies on humans. It's possible that eating the meat is the bad thing, not the way it's cooked.

  • Avoiding cancer instead of curing it

    Avoid fast food

    A diet high in fruits, vegetables, and fiber helps prevent cancer. In long-term studies, however, researchers have seen that a healthy diet has less of an impact on the risk of cancer than originally thought: it only reduces the risk slightly, by no more than ten percent.

  • < img src="" /> Avoiding cancer instead of curing it

    A lot of sun is bad for you

    UV radiation in sunlight penetrates the genome and changes it. The result: black or white skin cancer. Sunscreen protects against sunburn – but as soon as the skin tans, it has already received too much radiation.

  • Preventing cancer instead of curing it

    Cancer through modern medicine

    X-rays damage the genetic material. With an ordinary X-ray, however, the exposure is low. Completely different with a computed tomography: You should only undergo it if there are good reasons. Magnetic resonance imaging, on the other hand, is harmless. By the way: You are also exposed to carcinogenic radiation when you fly.

  • Avoiding cancer instead of curing it

    Cancer through infections

    Human papillomavirus can cause cervical cancer. Hepatitis B and C viruses can cause liver cells to degenerate. The bacterium Helicobacter pylori (photo) nests in the stomach and can be the cause of stomach cancer. You can get vaccinated against many of the pathogens, and antibiotics help against Helicobacter pylori.

  • Preventing cancer instead of curing it

    Better than its reputation

    Although the contraceptive pill slightly increases the risk of developing breast cancer, it also greatly reduces the risk of ovarian cancer. Overall, the pill protects more than it harms – at least as far as cancer is concerned.

  • Avoiding cancer instead of curing it

    A true stroke of fate

    But even if you do everything right – you are never completely immune to cancer. Half of all cancer cases are caused solely by the wrong genes – or simply by age. Brain tumors in particular often develop without external intervention.

    Author: Brigitte Osterath