BioEd Online

Fat could send the wrong signals to sick cells.

In studies with mice, shedding a bit of weight acted as a preventative against cancers. And they didn't even have to exercise to get the benefit: the mouse equivalent of liposuction did the trick.

Allan Conney and his colleagues at Rutgers University in New Jersey chopped the excess fat from some mice and exposed them to UV light, damaging some of their skin cells and inducing sunburn. The fat reduction boosted the rate of helpful cell suicide, called apoptosis, in skin tumour cells: cancerous cells died twice as fast in the slimmed-down mice as in the fat ones, they report in Proceedings of the National Academy of Sciences¹.

Mice kept slim by regular exercise also felt a benefit. The team saw no effect on non-cancerous cells in any of the mice.

"Fat tissue may be preventing the death of damaged cells," says Conney. He and his team suggest that fat cells might be secreting proteins called cytokines, which usually act as cellular messengers and could send signals to tumour cells telling them to interrupt apoptosis. They also implicate another molecule called insulin-like growth factor 1 (IGF-1), known to have a similar anti-suicide effect on cells. But these are speculations that the group has yet to test.

Gross statistics

"The findings are certainly interesting and novel," says Simon Cook, an apoptosis expert at the Babraham Institute in Cambridge, UK. Anything that can tell us more about the mechanism, he adds, is valuable given the current rise in obesity.

According to the US National Cancer Institute, about 3% of all new cancers in the United States are linked to obesity. Being overweight has been linked to an increase in many types of cancer, though it is unclear why: changing levels of hormones (including IGF-1) and steroids have been suggested.

There's also evidence that keeping trim can cut cancer risk. In one study, when people with a history of skin cancer halved their fat intake, they also slashed the chance of developing tumours by two-thirds².

The team haven't yet tested whether a bout of exercise or liposuction can help after a cancer has already gained a hold. "We do plan to take a look at animals that already have tumours, and then see what happens if you given them voluntary exercise," Conney says.

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