When you sleep, cancer cells are “suddenly” metastasizing. Not long ago, this rumor spread all over the Internet, cancer cells are so hard to prevent? Is this rumor true? Does Sleeping in Cancer Patients Really Promote Metastasis? 
cancer cells are secretly transferred while you sleep , from a study in the top scientific journal Nature[1] : Nicola Aceto‘s team at the Swiss Federal Institute of Technology measured 30 breast cancer patients during sleep(4am)and after waking span>(10:00 am)the number of circulating tumor cells(CTC) in the blood, it was found that both early and advanced patients, On average, the number of CTCs in the blood during sleep was more than 3 times higher than when awake. In subsequent mouse model studies, the researchers also found a similar phenomenon, 87%~99.2% of CTCs came frommice During sleep. Compared with awake, in the blood of sleeping mice, the CTCs in the free state of single cells increased by 6-88 times, the CTC clusters in a group increased by 12-278 times, and the CTC-leukocytes hugged together with immune cells. The clusters increased 8 to 34 times. Furthermore, after forcibly changing the work and rest cycle of mice by changing the light cycle, injecting melatonin, etc., the changes in the level of CTC in the blood also changed, and they were always sleeping. reached its peak. CTCs generated during sleep have stronger transfer ability than those generated during wakefulness. 
More CTCs released by the tumor during sleep at night< span>In this way, it seems that not sleeping can really prevent cancer. Not to mention that the body of patients who don’t sleep can’t stand it, and the movement of cancer cells at night is just a manifestation of the circadian rhythm. Just like Americans work while Chinese sleep, not because Americans are more industrious, but because of jet lag. Other tissues and organs in the human body also have their own circadian rhythms. Take the immune system that loves and kills cancer cells as an example, the main anti-cancer T cells are also a “night owl”< span lang="EN-US">[2]. When you are asleep and cancer cells are roaming around in the body, T cells are also dispatched in large numbers to chase and kill cancer cells. Perhaps the decline in the number of CTCs during the day is the result of T cells chasing and killing them at night. You can sleep soundly, thanks to T cells.
lymphocytes in large numbers at night >Although it is not reliable to fight cancer without sleeping, the circadian rhythm of cancer cells and various tissues and organs of the human body can indeed be used in the treatment of diseases, for example:
The feature that cancer cells come out to metastasize at night may also help scientists find the best time to treat breast cancer.
References:[1]. Diamantopoulou
Z, Castro-Giner F, Schwab F D, et al. The metastatic spread of breast cancer
accelerates during sleep[J]. Nature, 2022: 1-7.[2]. Kirsch S,
Thijssen S, Alarcon Salvador S, et al. T-cell numbers and antigen-specific
T-cell function follow different circadian rhythms[J]. Journal of clinical
immunology, 2012, 32(6): 1381-1389.[3]. Hermida R C,
Crespo J J, Domínguez-Sardiña M, et al. Bedtime hypertension treatment improves
cardiovascular risk reduction: the Hygia Chronotherapy Trial[J]. European heart
journal, 2020, 41(48): 4565-4576.[4]. Damato A R, Luo
J, Katumba R G N, et al. Temozolomide chronotherapy in patients with
glioblastoma: a retrospective single-institute study[J]. Neuro-Oncology
Advances, 2021, 3(1): vdab041.[5]. Qian D C, Kleber
T, Brammer B, et al. Effect of immunotherapy time-of-day infusion on overall
survival among patients with advanced melanoma in the USA (MEMOIR): A
propensity score-matched analysis of a single-centre, longitudinal study[J].
The Lancet Oncology, 2021, 22(12): 1777-1786.