How does exercise protect against cancer?

CANCER DIGEST – Nov. 9, 2020 – It has long been known that exercise provides a protective effect against a number of illnesses including cancer, but exactly what the biological mechanism is that underpins that effect has not been identified.

In new research in the journal eLife, Swedish researchers have shown that exercise stimulates certain metabolites that increase T cell activity, which could explain the protective effect of exercise.
"Our research shows that exercise affects the production of several molecules and metabolites that activate cancer-fighting immune cells and thereby inhibit cancer growth," study author Helene Rundqvist, senior researcher at the Department of Laboratory Medicine, Karolinska Institutet said in a press release. "We hope these results may contribute to a deeper understanding of how our lifestyle impacts our immune system and inform the development of new immunotherapies against cancer."

Starting in mice the researchers compared two groups of mice with cancer. One group had access to a spinning wheel and the other group did not. Over time the mice with the spinning wheel survived the cancer longer than the mice that remained sedentary.

The researchers then examined the importance of T cells on cancer survival. They injected antibodies that removed T cells in both the sedentary mice and the spinning wheel mice. In both cases tumor growth increased and survival decreased. The researchers say this shows the importance of T cells for exercise-induced cancer suppression.

The researchers then examined the effect of exercise on T cells and found that the spinning wheel mice excreted much higher levels of metabolites, such as lactate, into the blood, which in turn increased T cell activity, showing the the exercise-induced metabolites were linked to T cell activity.

To see if the same chain of effects occur in humans, the researchers looked at the same metabolites in 8 men after 30 minutes of intense cycling. They found that the same training-induced metabolites were released in the humans.

To see if this exercise effect is what affords protection against illness and cancer, will require larger studies, and this small study provides the basis for that further research.

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Sources: Karolinska Institutet press release and the journal eLife