Obesity is a contributor to cancer. Work in mice now reveals the mechanism by which obesity enhances inflammation and tumour growth in the liver.
Michael Karin and his co-workers at the University of California, San Diego, found that both mice eating a high-fat diet and those genetically engineered to be obese had higher incidences of liver cancer and had larger and more numerous tumours than normal mice when given a known carcinogen.
Obese animals had higher levels of activated STAT3, a known cancer-promoting protein. Obese mice also had elevated levels of IL-6, an immune-modulating and tumour-promoting protein, and TNF, a proinflammatory protein. The team found that both IL-6 and TNF, which activate STAT3, are required for obese mice to develop inflamed livers, which are at greater risk of becoming cancerous.