Malignant cancer tumors grow faster at night, a new research shows. The finding might help with certain treatments in time with the body's day-night cycle in order to increase their efficiency.
Researchers at the Weizmann Institute of Science in Israel assessed the functioning of two receptors on cancer cells. The two receptors are the epidermal growth factor receptor (EGFR) and the glucocorticoid receptors (GR). EGFR is known to speed up the growth and spreading of cells including cancer cells, whereas glucocorticoids are steroid hormones that preserve energy levels in the body during the day. Receptors pass on to the interior of the cell, messages received from other cells.
The receptors - protein molecules on the cell's surface or within cells - receive biochemical messages secreted by other cells and pass them on to the cell's interior. If one receptor receives a message, this might have an impact on other receptors.
The researchers noted that the when a GC hormone bound to the GC receptor, it suppressed the activity of EGFR. As GC hormone levels peak during the day, EGFR activity is limited during waking hours. It, however, functions nocturnally as GC levels taper off during night.
In order to check their theory, the researchers administered breast cancer drug Lapatinib to a group of mice during different times in a day. Lapatinib works by curtailing EGFR activity. The experiments on mice confirmed the hypothesis that changes in GC levels are crucial in preventing growth of cancer cells.
"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," said study co-leader Dr. Yosef Yarden, who is a biology professor at Weizmann Institute of Science.
The study, 'Diurnal suppression of EGFR signalling by glucocorticoids and implications for tumour progression and treatment', was published in Nature Communications.
