A new study just released in the Cancer Research journal, states that poor-quality sleep marked by frequent awakenings can spread cancer growth, increase tumor aggressiveness and dampen the immune systems ability to control or eradicate early cancers. The study points to a biological mechanism that could serve as a potential target for therapy. It is the first study to demonstrate in an animal model the direct effects of fragmented sleep on tumor growth and invasiveness.
The study conducted by researchers from the University of Louisville and the University of Chicago came up with a series of experiments to measure the effects of disrupted sleep on cancer. Mice housed in small groups were evaluated after four weeks for tumors. One group of mice was not disturbed during sleep while a motorized brush moved through the cages of the other group every two minutes, forcing the mice to awake and go back to sleep.
After seven days both groups of mice were injected with cells from one of two tumor types TC-1 or 3LLC. The study found that all the mice developed palpable tumors within nine to 12 days. After four weeks all the tumors were evaluated.
Tumors from mice with fragmented sleep were twice as large for both tumor types compared to the mice that 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 difference appeared to be driven by cells from the immune system tumor-associated macrophages which cluster at the site of tumors.
Well-rested mice primarily had M-1-type TAMs concentrated in the core of the tumors while sleep-fragmented mice had primarily MS-type TAMs abundant especially around the periphery of the tumors. TAMs are a hallmark of the immune systems response to cancer, but they can respond in a variety of ways depending on the chemical signals they receive. Those labeled M1 promote a strong immune response and can eliminate tumor cells. M2s suppress the immune response and instead promote the growth of new blood vessels, which encourages tumor growth.
The sleep-disrupted mice also had high levels of toll-like receptor 4 (TLR4).
Three key molecules are part of the signaling pathway that appeared to be tilting macrophages toward M2 - TLR4 and two downstream signals called MYD88 and TRIF. Because of this the researchers injected tumor cells into a series of mice that were unable to produce one of these three proteins and then subjected them to fragmented sleep. Tumor growth was slightly reduced in mice lacking MYD88 or TRIF, but in mice lacking TLR4, tumor growth was no greater than in mice with undisturbed sleep. Taking TLR4 out of the picture resulted in a major curtailment of tumor growth.
When we injected tumor cells into mice that lacked TLR4, the differences between undisturbed and sleep-fragmented mice disappeared, study director David Gozal, MD said. The study offers biological plausibility to the epidemiological associations between perturbed sleep and cancer outcomes. The take home message is to take care of your sleep quality and quantity like you take care of your bank account.
Its not the tumor, its the immune system, Gozal continued. 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. 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.
Tips For A Good Nights Sleep
Wake Forest Baptist Medical Centers Sleep Center recently released information backing the belief that proper sleep is a key contributor to health and well-being and that getting a good nights sleep means more than you probably think.
Sleep is more than simple rest. Proper sleep contributes significantly to feeling better and functioning better when awake. During sleep the brain and body perform important tasks that promote mental and physical health such as producing hormones that help repair cells and fight off illness.
Beauty sleep is not a myth. According to a 2011 Swedish study, sleep-deprived people appear less healthy, less attractive and more tired compared to when they are well rested.
Inadequate sleep affects many things. Inadequate sleep can cause people to be irritable, have slower response times, make unwise decisions, have trouble with relationships, perform poorly at work or school, become depressed more easily as well as increase the risk for high blood pressure, heart disease, diabetes, obesity, cognitive difficulties, and other medical problems.
The Centers for Disease Control and Prevention even call insufficient sleep a public health epidemic, citing societal factors such as round-the-clock access to technology and the incidence of disorders such as insomnia and sleep apnea.
The amount of sleep a person needs depends on their age: newborns - 16 to 18 hours nightly; preschoolers 11 to 12 hours; school-age children and teenagers at least 10 hours; and adults including seniors seven or eight hours.
There are some individuals whom we call short sleepers, who probably will do okay with maybe only six hours, and at the other extreme are long sleepers, who require nine or 10 hours, but the percentage of these extremes are very small, says Dr. Sandhya Kumar, assistant professor of neurology at Wake Forest Baptist Medical Center and medical director of its Sleep Center.
Most of us, after adolescence, really need seven or eight hours of sleep and on a regular basis. But its not just the amount of time spent sleeping that counts. Theres a quality factor too, she continued. There are people who, for example, say that they can drink coffee and dont have trouble sleeping, but thats not true. They may not have trouble falling asleep but the quality of the sleep isnt good, so youre probably not going to feel rested at all the next day.