London, Feb 17 (IANS): Mice that spent their free time on a running wheel were better able to shrink tumour size by nearly 50 percent as compared to their less active counterparts, a study shows.

A surge in adrenaline that comes with a high-intensity workout helped to move cancer-killing immune (NK) cells toward lung, liver, or skin tumours, implanted into the mice, the research elicited.

An immune signalling molecule called IL-6 was discovered to be the link between adrenaline-dependent mobilisation of NK cells and tumour infiltration.

The adrenaline specifically hails IL-6 sensitive NK cells and the IL-6 molecules helps in guiding the immune cells to the tumours.

"In this study, we show that the exercise-induced IL-6 seems to play a role in homing of NK cells to the tumour and also in the activation of those NK cells," said Pernille Hojman from the University of Copenhagen in Denmark.

Even with exercise and a full suite of other immune cells, without the NK cells the mice experienced the normal rate of cancer growth, the findings, detailed in the journal Cell Metabolism, revealed.

The study is hopeful for patients looking for inexpensive ways to manage their cancer.

However, more needs to be learned about the effects of exercise on metastasis and longevity, as well as if the observations hold true in humans, the researchers said.

The scientists injected mice with adrenaline to mimic this increase seen during exercise. It resulted in NK cells mobilising into the bloodstream, to find the tumour.

They next used mice depleted of NK cells to show that the increase in number of NK cells at the site of the tumour was directly contributing to the reduction in size.