Most medical procedures are planned around the availability of the doctor rather than the patient's biological clock. That could soon change, according to new findings suggest that the molecular clock directs cell division. Coordinate cancer therapies to accommodate the biological clock could lead to faster healing after surgery, more effective targeting of tumor cells, and fewer side effects.
Many aspects of our physiology, such as blood pressure and body temperature, the cycle on a 24-hour rhythm called the circadian clock. This system keeps the body in synchronization with the light-dark cycle of the Earth and is based on multiple interacting genes. Last year, researchers reported that mice with a mutation in one of these clock genes develop cancer more easily than normal mice, suggesting that the clock may influence cell division. They found that monitoring clock cyclic gene expression of several proteins important for cell division.
To further examine the relationship between the clock and cell division of circadian rhythms, molecular neurobiologist Hitoshi Okamura of Kobe University, Japan, and his colleagues studied cell division after surgery liver in mice. Liver part withdrawal stimulates cell proliferation such as organ regrows, making it easy for researchers to locate and examine actively dividing cells. They found that cell division started at the same time of day, regardless of when the transaction occurred: In mice operated at dawn, most cells divided at dawn two days later, but if the surgery took place 8 hours after first light, cell division reached its peak at the dawn of the second day. Probing deeper, scientists have discovered three genes involved in cell division, whose activity reflects the circadian time. These genes appeared to direct the cells to begin dividing. In mice engineered to lack timekeeping genes, cells do not regrow and liver slowed significantly.
Cheng Chi Lee molecular geneticist at Baylor College of Medicine in Houston, Texas, said the study reinforces previous work and provides "a wonderful demonstration of the relative molecular mechanism of the clock for the cycle of cell division . " Using the activity of the genes of the cell cycle as a time indicator of the body clock, Lee said, doctors could surgery a calendar day when the cells divide to maximize tissue regeneration for healing, or deliver chemotherapy when normal cells are at rest, strengthening the attack on cancer cells and minimizing side effects.
Related Sites
Background on circadian rhythms
homepage Cheng Chi Lee
international research consortium Chronobiology and cancer
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