WASHINGTON, April 30 (Xinhua) -- A study published on Tuesday in the journal PLOS Biology showed that a disruption of normal circadian rhythms could promote tumor growth and suppress the effects of a tumor-fighting drug.
Disruption of circadian rhythms, due to jet travel, shift work or sleep disturbances, is a known risk factor for several types of cancer, but the underlying mechanism has not been clear.
The researchers from the University of Pennsylvania used the hormone dexamethasone to chronically advance daily rhythms in cultured cells and they found that the hormone altered expression of multiple genes, especially those involved in regulating the cell cycle.
Circadian rhythm disruption increased cell proliferation and cell division, which are tightly linked to tumor. Many cancer treatments seek to arrest progression through the cell cycle.
The researchers found that the tumor-fighting ability of one drug that arrests cell cycle progression varied with time-of-day.
The treatment in the morning is more effective than treatment at night and its efficacy was reduced in both cells and mice when their circadian rhythms were disrupted, according to the study.
"Better understanding the molecular effects of jet lag, shift work, and other sources of chronic disruption may lead to strategies to minimize the increased cancer risk associated with these behaviors, and to better treatment strategies," said the paper's co-author Amita Sehgal, a neuroscience professor with the university.
