They emerge at night, while we sleep unaware, growing and spreading out as quickly as they can. And they are deadly.
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It turns out tumors spread faster at night time, Weizmann Institute of Science researchers showed in findings recently published in Nature Communications, suggesting that it would be better to deliver cancer treatments in the wee hours of the night.
“It seems to be an issue of timing,” says Prof. Yosef Yarden of Weizmann's Biological Regulation Department. “Cancer treatments are often administered in the daytime, just when the patient’s body is suppressing the spread of the cancer on its own. What we propose is not a new treatment, but rather a new treatment schedule for some of the current drugs.”
The scientists investigated the relationships between different receptors, protein molecules that reside on the cell's surface or within cells, which take in biochemical messages secreted by other cells and pass them on into the cell’s interior.
The team was led by Dr. Mattia Lauriola, a postdoctoral fellow in Prof. Yarden's research group, working together with Prof. Eytan Domany of the Physics of Complex Systems Department.
Lauriola and Yarden found that cell migration – the activity promoted by the epidermal growth factor receptor, which promotes the growth and migration of cells, including cancer cells – is suppressed when the glucocorticoid receptor is bound to its steroid messenger.
Glucocorticoids play a role in maintaining the body’s energy levels during the day, as well as the metabolic exchange of materials. It is often called the stress hormone because its levels rise in stressful situations, rapidly bringing the body to a state of full alert.
Since the steroid levels peak during waking hours and drop off during sleep, the scientists asked how this might affect the second receptor – epidermal growth factor receptor. Checking the levels of this activity in mice, they found that there was a significant difference: This receptor is much more active during sleep and quiescent during waking hours.
This discovery led the scientists to check the efficacy of delivering cancer drugs at different times of the day. The scientists gave a drug used to treat breast cancer to mice at various hours and discovered that the size of tumors in the different groups of mice varied significantly, depending on whether they had been given the drug during sleep or waking hours.
"The experimental findings suggest that it is indeed the rise and fall in the levels of the GC steroids over the course of 24 hours that hinder or enable the growth of the cancer," stated the Weizmann Institute.
The conclusion, say the scientists, is that it could be more efficient to administer certain anticancer drugs at night.