Tumor cell circadian clock genes are rhythmically expressed in coordination with rhythmic circadian growth and thereby may represent new therapeutic targets: Abstract 698
Recent research suggests that at least eight central 'clock' genes coordinate many basic functions such as cell proliferation and apoptosis in circadian time, or within each day, according to researchers from the Dorn Veterans Administration Medical Center and the University of South Carolina. Shaojin You, M.D., Ph.D., assistant professor, and his colleagues undertook the first study to establish a relationship between circadian clock gene expression and the growth rate of tumors.
"These results demonstrate that tumor growth itself, as well as cellular and molecular measures of cancer growth, are organized within circadian time," said Dr. You. "Taken in the context of other recent studies, this work indicates that circadian clock genes and their products potentially represent novel targets for the control of cancer growth."
In these studies, some 30 female mice kept on an alternating 12-hour light and 12-hour dark schedule were injected with tumor cells; the rate of tumor growth was subsequently measured to determine the impact of circadian rhythms.
The results showed that "tumors grew on average twice as fast in the 'daily activity/dark circadian phase' than during the 'sleep/light phase' of the [24 hour] circadian cycle," the team reported. The tumor mitotic index, a measure of the proportion of cancer cells actively dividing,
Contact: Warren Froelich
American Association for Cancer Research