Lowering the temperature appears to hinder the growth of cancer cells, according to a study carried out on mice by researchers at the Karolinska Institutet in Sweden.
The study, published in Nature on Aug. 3, found that cold temperatures activate heat-producing brown fat, which consumes the sugars tumors need to grow.
Similar metabolic mechanisms were found in a cancer patient exposed to a lower ambient temperature.
“We found that cold activated brown tissue competes against tumors for glucose and can help to inhibit tumor growth in mice,” explains Yihai Cao, a professor in the Department of Microbiology, Tumor and Cell Biology.
“Our findings suggest that cold exposure may be a promising new approach to cancer therapyalthough this needs to be validated in larger clinical studies,” adds Cao.
The study compared tumor growth and survival rates in mice with various types of cancer, including colorectal, mammary and pancreatic cancers, when exposed to cold versus warm environments.
Mice acclimated to temperatures of 4 degrees Celsius had significantly slower tumor growth and lived almost twice as long, compared to mice in 30 degree Celsius rooms.
To find out why, the researchers analyzed markers in the tissue to study cellular reactions and used imaging tests to examine glucose metabolism. Cancer cells normally need large amounts of glucose, or sugar, to grow.
They found that cold temperatures triggered significant absorption of glucose in brown adipose tissue, also known as brown fat, the type of fat responsible for keeping the body warm during cold environments. At the same time, the glucose levels were barely detectable in tumor cells.
When the researchers removed the brown fat or a crucial protein for its metabolism called UCP1, the beneficial effect of the cold exposure was essentially eliminated and the tumors grew at a rate equivalent to that of those exposed to higher temperatures.
Likewise, mice with tumors ingesting a high-sugar beverage also obliterated the effect of cold temperatures, and restored tumor growth.
“Interestingly, the high-sugar drinksr appear to nullify the effect of cold temperatures on cancer cells, suggesting that limiting the supply of glucose is probably one of the most important methods for tumor suppression.” Science Daily.
To study the human relevance of the results, the researchers recruited six healthy volunteers and one cancer patient undergoing chemotherapy.
Using positron emission tomography (PET), the researchers identified a significant amount of activated brown fat on the neck, spine and chest of healthy adults in shorts and t-shirts, while exposed to a slightly cold ambient temperature of 16 degrees Celsius for up to six hours a day for two weeks.
The cancer patient wore light clothing and spent time in 22 degree Celsius rooms for a week, and then in 28 degree Celsius rooms for four days.
Previous research has shown that while there are significant individual differences, 28 degrees Celsius is generally considered a comfortable room temperature for most inactive humans.
The tests performed detected an increase in brown fat and a decrease in the tumor’s glucose uptake during the lower temperature compared to the higher one.
“These temperatures are considered tolerable by most people,” notes Cao. “We are therefore optimistic that the cold therapy and the activation of brown adipose tissue with other approaches, such as drugs, may represent another tool in cancer treatment options”, he concludes.