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 Sciences.
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.