Mice that take exercise have fewer tumours than those that do not — thanks to more cancer-fighting immune cells finding their way into tumours.

Studies in humans have linked the effects of taking regular exercise to a reduced risk of developing cancer. To investigate the underlying molecular mechanisms, Pernille Hojman of the University of Copenhagen in Denmark and her colleagues compared tumour growth in sedentary mice and in those that had access to an exercise wheel over four weeks.

Animals that ran had about 60% fewer tumours, which were also smaller in size. Exercise was associated with an increase in the number of a particular type of immune cell — the natural killer cell — found in the tumours. An exercise-induced surge in the hormone adrenaline mobilized these cells.

Cell Metab. http://doi.org/bcnk (2016)