Is Cancer Growth Nocturnal?

They emerge at night, while we sleep unaware, growing and spreading out as quickly as they can - and they are deadly. No, I am not talking about werewolves or zombies. According to a new study, it turns out that tumors may grow faster at night, suggesting that cancer growth might be a nocturnal mechanism.

Scientists hope that their findings provide evidence that administering certain treatments in time with the body's day-night cycle could boost their efficiency.

"It seems to be an issue of timing," Professor Yosef Yarden of the Weizmann Institute of Science, one of the study's researchers, said in a statement.

Published in the journal Nature Communications, scientists came to this conclusion by looking into the relationships between different receptors in the cell. Receptors - protein molecules on the cell's surface or within cells - take in biochemical messages secreted by other cells and pass them on into the cell's interior. The Weizmann team focused on two receptors in particular: epidermal growth factor receptor, EGFR, and one that binds to the steroid hormone glucocorticoid (GC).

EGFR promotes the growth and migration of cells, including cancer cells, while the GC receptor plays a role in maintaining the body's energy levels during the day as well as the metabolic exchange of materials.

Since cells have multiple receptors, they receive multiple messages at once, though some take priority over others. During the study, Yarden and co-author Dr. Mattia Lauriola found that the GC receptor, when bound to its steroid messenger, takes precedence over cell migration, or EGFR.

Interestingly, steroid levels are at their highest during the day, and drop off at night. To find out how this relates to cancers, especially those that use the EGF receptors to grow and spread, researchers gave Lapatinib - one of the new generation of cancer drugs - to mouse models of cancer. This drug is designed to inhibit EGFR, and thus prevent the growth and migration of the cancer cells.

After administering the drug to the mice at different times of the day, the findings showed that the size of the cancer tumors were significantly different depending on whether they had been given the drug during sleep or waking hours.

Yarden and Lauriola suggest then that the rise and fall in the levels of the GC steroids over the course of 24 hours either hinder or enable the growth of the cancer, and that certain anticancer drugs would be more efficient at night.

"Cancer treatments are often administered in the daytime, just when the patient's body is suppressing the spread of the cancer on its own," Yarden added. "What we propose is not a new treatment, but rather a new treatment schedule for some of the current drugs."