“We found that cold-activated brown adipose tissue competes against tumors for glucose and can help inhibit tumor growth in mice,” says Professor Yihai Cao at the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, and corresponding author. “Our findings suggest that cold exposure could be a promising novel approach to cancer therapy, although this needs to be validated in larger clinical studies.”
The study compared tumor growth and survival rates in mice with various types of cancer, including colorectal, breast and pancreatic cancers, when exposed to cold versus warm living conditions. Mice acclimatized to temperatures of 4 degrees Celsius had significantly slower tumor growth and lived nearly twice as long compared with mice in rooms of 30 degrees Celsius.
To find out why that is, the researchers analyzed markers in the tissue to study cellular reactions and used imaging tests to examine glucose metabolism. Cancer cells typically need large amounts of glucose, or sugar, to grow.
Activated glucose uptake in brown fat
They found that cold temperatures triggered significant glucose uptake in brown adipose tissue, also known as brown fat, a type of fat that is responsible for keeping the body warm during cold conditions. At the same time, the glucose signals were barely detectable in the tumor cells.
When the researchers removed either the brown fat or a protein crucial for its metabolism called UCP1, the beneficial effect of the cold exposure was essentially wiped out and the tumors grew at a pace on par with those that were exposed to higher temperatures. Similarly, feeding tumor-bearing mice with a high sugar drink also obliterated the effect of cold temperatures and restored tumor growth.