Breakthrough study reveals how exercise helps immune cells kill cancer
We know exercise is good for the mind and body, and for years researchers have seen a distinct correlation between physical exercise and lower rates of cancer incidence. But exactly how exercise could be directly helping the body fight cancer has been unclear. Now, a study led by researchers from Sweden’s Karolinska Institutet has discovered how exercise can bolster the cancer-killing ability of certain immune cells.
A large and robust 2016 study offered some of the most convincing evidence to date affirming the association between lower incidences of cancer and physical activity. The research pooled data from more than one million adults to find higher levels of exercise correlated with lower rates of 13 common types of cancer.
The following year a massive systematic review of 100 published studies found cancer patients who exercised had significantly better outcomes than those who didn’t. The implications of these findings were that exercise can not only prevent the onset of some cancers, but possibly help the body fight back more effectively.
But a big question remained … How could exercise be improving the body’s ability to hunt down and destroy cancer cells?
This new study focused on a particular immune cell called a cytotoxic T cell. Also known as killer T cells, these are the body’s cancer-killing agents. The hypothesis underpinning the research was that exercise produces certain metabolites that enhance the function of these cancer-killing cells.
Through a series of animal tests the new study reveals these killer T cells are indeed positively influenced by exercise. One experiment even transferred T cells from exercising mice to untrained mice and saw improved tumor reduction responses.
The next step was to investigate how exercise alters the behavior of T cells. The researchers homed in on a number of metabolites produced by muscles during exercise and released into the bloodstream. These metabolites subsequently were found to significantly influence T cell activity.
Lactate in particular was seen to notably bolster T cell activity. A small experiment directly administering sodium L-lactate to mice resulted in heightened T cell activity and greater decreases in tumor growth. However, the study is cautious to note the metabolic influence of exercise on cancer is due to more factors than just the release of lactate.
“These findings indicate that lactate infusion mimics some of the effects of exercise, but that exercise has additional, integrative, components beyond merely increased levels of lactate,” the researchers write in the study.
Helene Rundqvist, first author on the new study, suggests these findings offer key insights into the mechanisms underpinning the cancer-killing benefits of exercise. And while these findings are certainly academically interesting, they also offer researchers rich new investigative pathways. Developing novel immunotherapies that harness this exercise-induced T cell activity could present new and powerful treatments for cancer patients in the future.
"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 Rundqvist. "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 new study was published in the journal eLife.
Source: Karolinska Institutet