Body fat blocks cancer-killing pathway in mice
US scientists have made a discovery that might explain why overweight or obese people are more prone to certain cancers.
Many studies have suggested a link between body fat and some forms of cancer, but working out the biological reasons for this has proved to be challenging.
The new finding, from a team at Rutgers University, New Jersey, came from studies on skin cancer in laboratory mice.
The team divided a group of mice in two, and allowed one group to use an exercise wheel, resulting in them having a much lower bodyweight.
After two weeks, all the mice were exposed to UV light, causing skin damage and cancer.
The mice that had been allowed to exercise had much lower levels of skin damage and cancer.
Further analysis revealed that this was because the body's natural mechanism of destroying damaged cells, called apoptosis, was not working as well in the overweight rats.
In a second experiment, another group of mice had pads of fatty tissue removed by surgery.
When they were exposed to UV light, they also had lower levels of cell damage and skin cancer compared to a group that had not had any surgery.
This proved that it was the body fat, and not the lack of exercise, that was inhibiting the destruction of the damaged cells.
The team believes that fatty cells secrete some factor or factors that blocks apoptosis and plan to identify the substances involved.
The researchers said that the results would have to be replicated in humans before they were able to make any firm connection with body fat and skin cancer in people, however. Several large studies on skin cancer rates and body weight have proved inconclusive.
Cancer Research UK pointed out that the best way to reduce the risk of skin cancer was to avoid strong sunlight, but that maintaining a healthy body weight was a proven way to reduce the risk of several other cancers.
The study is published in the Proceedings of the National Academy of Sciences.