Could exercise help beat cancer? Perhaps, if you happen to be a mouse. An experiment in which mice chose to run between 4 and 7 kilometres a night has shown how exercise can boost the immune system鈥檚 attack on cancer, preventing new tumours growing, and slowing the growth of existing ones by up to 60 per cent.
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鈥淚t鈥檚 the first time we鈥檝e shown that exercise can directly control the growth rate of tumours,鈥� says Pernille Hojman of the University of Copenhagen in Denmark. Her team tested the effects of exercise on five different types of mouse cancer, including those of the skin, lung and liver.
They found that exercise prompts the release of adrenaline. This stress hormone in turn stimulates the immune system to send its cancer-fighting natural killer cells into the bloodstream. A substance called interleukin-6, which is released by exercising muscles in the mice, directs these killer cells to attack the tumours.
Missing piece of puzzle
鈥淲e already know that exercise has an impact on natural killer cell activity, but this is the first time anyone has shown it鈥檚 directly involved in helping them invade tumours,鈥� says Lee Jones of the Memorial Sloan Kettering Cancer Center in New York. 鈥淭his is a big piece of the puzzle that鈥檚 been missing,鈥� he says.
None of the mouse tumours shrank as a result of exercise, they only grew less quickly, suggesting that exercise is unlikely to reverse an existing cancer. But in some animals, running did prevent liver tumours from growing in the first place.
In people, there is some evidence that , says Hojman. Next, her team will follow cancer patients to see if their exercise patterns are associated with similar beneficial effects.
Journal reference: Cell Metabolism,
