To ensure normal growth and avoid tumour formation, cell division must be tightly regulated. Remarkably, many cells from species as diverse as single celled organisms and humans only divide at certain times of the day, suggesting that division is under the control of a circadian clock. The evolutionary explanation put forward for this is a selective advantage for organisms with cells that divide at night when the mutational effects of ultraviolet light are lowest.
It has been proposed that the uncontrolled growth shown by tumour cells is caused by fault in the biological clock but a study by researchers at Vanderbilt University has now shown that although immortalised rat fibroblasts have functioning clocks, the clocks don’t control the rate at which the cells divide and grow. Similar results were seen in preliminary experiments with lung cancer cells. If follow-up studies confirm that control of cell cycle by circadian rhythm has been lost in immortalised cells, the research may suggest new targets for cancer therapy.
The study is published in PNAS.