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Researchers Discover The Reason Why Exercise Stalls Cancer Growth

by DailyHealthPost Editorial

There’s no denying it. Exercise is something we should all strive to do everyday. Not every workout session has to be intense. You could go for a walk, swim or even cycle around your neighborhood. Truth is, just being more active in general is good for our bodies. This is especially true for our immune system because even people diagnosed with cancer who exercise generally have a better prognosis than inactive patients.

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A study published in the journal of eLife has found one plausible reason as to why exercise can help slow down cancer growth in mice: Physical activity changes the metabolism of the immune system’s cytotoxic T cells and thereby improves their ability to attack cancer cells, which helps prevent and inhibit cancer growth.

“The biology behind the positive effects of exercise can provide new insights into how the body maintains health as well as help us design and improve treatments against cancer,” says Randall Johnson, professor at the Department of Cell and Molecular Biology, Karolinska Institutet.

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In this study, researchers at Karolinska Institutet in Sweden expanded on this hypothesis by examining how the immune system’s T-cells, which are basically white blood cells specialized in killing cancer cells, respond to exercise.

Cancer growth is slowed down by exercise

They divided mice with cancer into two groups and let one group exercise regularly in a spinning wheel while the other remained inactive. The result showed that cancer growth slowed and mortality decreased in the trained animals compared with the untrained.

Next, the researchers injected antibodies to remove the T cells in both trained and untrained mice. As a result, the antibodies cancelled out the benefits of exercise on both cancer growth and survival, which according to the researchers show how important T cells are for suppressing cancer growth through exercise.

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The researchers also transferred T cells from trained to untrained mice with tumors, which improved their prospects compared with those who got cells from untrained animals.

Exercise supercharges T cell metabolism

To examine how exercise influenced cancer growth, the researchers isolated T cells, blood and tissue samples after training sessions and measured levels of common metabolites that are produced in muscle and excreted into plasma at high levels during exertion. Some of these metabolites, such as lactate, altered the metabolism of the T cells and increased their activity. The researchers also found that T cells isolated from an exercised animal showed an altered metabolism compared to T cells from inactive animals.

In addition, the researchers examined how these metabolites change in response to exercise in humans. They took blood samples from eight healthy men after 30 minutes of intense cycling and noticed that the same training-induced metabolites were released in humans.

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“Our research shows that exercise affects the production of several molecules and metabolites that activate cancer-fighting immune cells and thereby inhibit cancer growth,” says Helene Rundqvist, senior researcher at the Department of Laboratory Medicine, Karolinska Institutet, and the study’s first author. “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.”

The ability of T cells to identify and eliminate cancer cells is essential to avoid tumor growth, and is one of the foundations of current immune therapy treatments. Exercise could improve the outcome of these treatments by increasing the activation of the immune system, making tumor-fighting cells more effective.

How much, and what type of exercise, is needed?

According to a paper published in Medicine & Science in Sports & Exercise, conducted by an international group of experts led by the University of British Columbia, cancer survivors are recommended to perform aerobic and resistance training for approximately 30 minutes per session, three times a week.

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“Exercise has been regarded as a safe and helpful way for cancer survivors to lessen the impact of cancer treatment on their physical and mental health, but the precise type and amount of exercise to treat the many different health outcomes related to cancer treatment hasn’t been clear,” says the paper’s lead author, Dr. Kristin Campbell, associate professor at UBC’s department of physical therapy. “In the absence of this information, cancer survivors were advised to strive toward meeting the general public health guidelines for all Americans — an amount of physical activity that may be difficult for people to achieve during or following cancer treatment.”

These recommendations are based on more than 2,500 published randomized controlled exercise trials in cancer survivors.

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