Study shows how exercise stalls cancer growth through immune system

A recent study suggested that people with cancer who exercise generally have a better

prognosis than inactive patients. Now, scientists explain 'Why?'

The study is published in the journal eLife.

Researchers at Karolinska Institutet in Sweden have found a likely explanation of why exercise

helps 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.

"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," said Randall

Johnson, professor at the Department of Cell and Molecular Biology, Karolinska Institutet, and

the study's corresponding author.

Prior research has shown that physical activity can prevent the health condition as well as

improve the prognosis of several diseases including various forms of cancer. Exactly how

exercise exerts its protective effects against cancer is, however, still unknown, especially when

it comes to the biological mechanisms. One plausible explanation is that physical activity

activates the immune system and thereby bolsters the body's ability to prevent and inhibit

cancer growth.

In this study, researchers expanded on this hypothesis by examining how the immune system's

cytotoxic T cells, that is white blood cells specialized in killing cancer cells, respond to

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 examined the importance of cytotoxic T cells by injecting antibodies that

remove these T cells in both trained and untrained mice. The antibodies knocked out the

positive effect of exercise on both cancer growth and survival, which according to the

researchers demonstrates the significance of these T cells for exercise-induced suppression of

cancer.

The researchers also transferred cytotoxic T cells from trained to untrained mice with tumours,

which improved their prospects compared with those who got cells from untrained animals.

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 resting 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.

"Our research shows that exercise affects the production of several molecules and metabolites

that activate cancer-fighting immune cells and thereby inhibit cancer growth," said Helene

Rundqvist, senior researcher at the Department of Laboratory Medicine at the 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."

Source: https://www.newkerala.com/news/2020/188243.htm