Chemotherapy’s circadian link?
Doctors often wonder if there is a best time of day for cancer patients to receive chemotherapy. Past research suggests there probably is an optimal time based on the body’s circadian rhythms. Now a compelling new study offers some biological proof for the idea.
Researchers at the University of North Carolina have discovered that chemotherapy is probably most effective at particular times of day when an enzyme system in the body that can blunt the effect of the drugs is at its lowest levels.
The enzyme system is called nucleotide excision repair. It works to fix DNA damage from toxic substances such as chemotherapy agents, but also DNA damage from sun exposure.
The study is one of the most convincing pieces of evidence that the body’s internal time-keeping system, which resides in every cell, can affect the potency of some drugs. It reflects a growing interest among scientists in understanding the effect of circadian rhythms on human health.
The study, conducted in mice, found that the ability to repair damage was at a minimum in the early morning and reached a peak in the evening.
The researchers say their study needs to be replicated in humans and that they plan to explore whether their findings can apply to skin cancer prevention. Showing the same patterns in humans could suggest the safest time for sun exposure, the senior author of the paper, Dr. Aziz Sancar, said in a news release.
The study will be published this week in the online early edition of the Proceedings of the National Academy of Sciences.
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