“Fragmented sleep changes how the immune system deals with cancer in ways that make the disease more aggressive,” study director David Gozal, MD, chairman of pediatrics at the University of Chicago Comer Children’s Hospital, said.
The researcher said that 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 researchers used mice, housed in small groups. During the day—when mice normally sleep—a 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.
They found that tumors from mice with fragmented sleep were twice as large, for both tumor types, as those from mice that had slept normally.
A follow-up experiment found that when tumor cells were implanted in the thigh muscle, which should help contain growth, the tumors were much more aggressive and invaded surrounding tissues in mice with disrupted sleep. The study was published in the journal Cancer Research.