Poor-quality sleep marked by frequent awakenings can speed cancer growth, increase tumor aggressiveness and dampen the immune system's ability to control or eradicate early cancers, according to a new study published online January 21, 2014, in the journal Cancer Research.
The study is the first to demonstrate, in an animal model, the direct effects of fragmented sleep on tumor growth and invasiveness, and it points to a biological mechanism that could serve as a potential target for therapy.
"It's not the tumor, it's the immune system," said study director David Gozal, MD, chairman of pediatrics at the University of Chicago Comer Children's Hospital. "Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive."
"Fortunately, our study also points to a potential drug target," he said. "Toll-like receptor 4, a biological messenger, helps control activation of the innate immune system. It appears to be a lynchpin for the cancer-promoting effects of sleep loss. The effects of fragmented sleep that we focused on were not seen in mice that lacked this protein."
Gozal, an authority on the consequences of sleep apnea, was struck by two recent studies linking apnea to increased cancer mortality. So he and colleagues from the University of Chicago and the University of Louisville devised a series of experiments to measure the effects of disrupted sleep on cancer.
They used mice, housed in small groups. During the daywhen mice normally sleepa quiet, motorized brush moved through half of the cages every two minutes, forcing those mice to wake up and then go back to sleep. The rest of the mice were not disturbed.
After seven days in this setting, both groups of mice were injected with cells from one of two tumor types (TC-1 or 3LLC). All mice developed palpable tumors within 9 to 12 days. Four weeks after inoculation the researchers evaluated the tumors.<
|Contact: John Easton|
University of Chicago Medical Center