The circadian rhythm (the alternation between sleep and wakefulness), plays a decisive role in the dissemination of tumor cells, according to a new study by Swiss researchers that could have great implications and influence the time of day in which some treatments are administered.
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The researchers claim to have found a surprising and unexpected boss” in the generation of circulating tumor cells (CTC), clones of cancer cells with the ability to travel through the bloodstream after detaching from the original tumor that can lodge in other organs of the body and trigger a new tumor process.
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Until now, it was thought that CTCs were constantly detached, regardless of the time of day or night, from the original growing tumor (called the primary) or due to certain mechanical insults.
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“We have found that in both breast cancer patients and mouse models, CTC generation is highly restricted to the resting phase, and that resting-phase CTCs are endowed with a much higher metastatic proclivity compared to CTCs. CTCs in the active phase”, point out the authors of the study, published Wednesday in the magazine Nature.
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Researchers have found that CTCs that are generated during wakefulness are less likely to metastasize than the same cells when produced in the resting phase. They have also determined that it is during sleep hours when these tumor cells enter the bloodstream spontaneously.
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Link Between Circadian Rhythm and Cancer
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This research also clarifies the role of hormones that regulate the circadian rhythm, such as melatonin, as they “dictate” how CTCs are generated. And it is another hormone, insulin, which directly promotes the proliferation of tumor cells.
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To carry out this study, the researchers took two blood samples from 30 women with breast cancer with and without metastases, one during the day and the other at night. The results show that the levels of tumor cells in the blood are much higher at night, and that these cells are also much more aggressive.
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The researchers completed the research with mice. Also in these animals, the tumor cells were much more active during rest periods (in their case during the day, since the mice are more active at night).
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In 2014, a team from the Weizmann Institute in Israel demonstrated a connection between the hormones of rest and the spread of cancer, according to the Spanish newspaper El País. The researchers demonstrated with their work with laboratory mice that administering the same cancer drug reduced tumors more or less depending on whether it was administered during the day or at night.
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The specific mechanisms that explain these observations are still unknown. However, an emerging discipline, called chronotherapy, studies the confluence of the disease, the therapies applied and the time of day and night.
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