Question: Does the body naturally kill cancer cells?
Answer: Yes, especially if the immune system gets by with a little help from exercise.

A multinational team may have decoded a mysterious link between exercise and one of the body’s own resources for destroying cancer cells. In October, 2020, Rundqvist, et al. published “Cytotoxic T-cells mediate exercise-induced reductions in tumor growth.”^[i] The authors’ opening sentence says it all: “Exercise affects almost all tissues in the body, and scientists have found that being physically active can reduce the risk of several types of cancer as well as improving outcomes for cancer patients.”

The many benefits of exercise include heart health, weight control, uplifted mood, better sleep that supports brain health, and reduced inflammation—a known precursor for cancer and even diabetes.

Before delving more deeply into their paper, our own blog deserves a pat on the back for our topical articles going back to 2014. For example, a 2015 blog summarized three recent studies covered exercise as preventing prostate cancer (PCa), facilitating more robust recovery from prostatectomy, and boosting long-term health-related quality of life in older PCa survivors. The following year, I reported that vigorous aerobic walking seemed to lower the risk of recurrence after prostate cancer (PCa) treatment, noting a relationship between exercise, the shape of blood vessels, and reduced PCa mortality. Most recently, on the heels of the first wave of the coronavirus pandemic, I explained a study on exercise, free radicals, and protecting your life during the pandemic as well as PCa.

To return to the Rundqvist paper, the authors investigated the influence exercise on the immune system’s cellular components. They note that cancer has tactics for evading detection, thus keeping the cytotoxic (killer) T-cells from doing their work of assassinating cancer cells. As one reporter describes it, “Researchers have known for some time that different types of immune cells tend to target different types of cancer. But little has been known about if and how exercise affects any of these immune cells and if those changes might somehow be contributing to exercise’s cancer-blunting effects.”^[ii]

Running as an immune system activator

The subjects in Rundqvist team’s experiments were mice. They compared groups of running mice vs. non-running mice before and after tumor cells were implanted in them. Based on observations of different tumor growth rates, as well as analysis of blood and tissue, a process of elimination led them to focus on a specific type of immune cell called CD8+ T-cells.

They observed that when they blocked the action of CD8+ T-cells in some mice who were runners, they formed tumors quickly compared with other active mice whose CD8+ T-cell function was normal. This meant that they had indeed isolated these particular T-cells as tumor fighting agents. This was an encouraging discovery, but it still did not answer the question: what is it about exercise that exactly fosters these cells’ activity?

They turned to sophisticated lab analysis tests to examine blood cell components at the molecular level, then conduct cell experiments in lab dishes. A key ingredient was lactate, a substance that muscles produce in abundance when put to sustained effort. Did you ever experience a burning sensation in your muscles during prolonged activity such as running further than usual, or doing more reps than usual when working with free weights? What’s causing that burn is lactic acid, or lactate, because you’re calling upon the muscles for more exertion than they’re used to. An article from WebMD offers a simple explanation: “When you exercise, your body uses oxygen to break down glucose for energy. During intense exercise, there may not be enough oxygen available to complete the process, so a substance called lactate is made. Your body can convert this lactate to energy without using oxygen.”

Apparently, lactate does more than fuel your muscles. In the lab experiments, the researchers found that when they bathed the CD8+ T-cells in lactate, then exposed them to cancer cells, they were much more active in fighting the malignant cells.

To review, there are a number of mechanisms by which exercise supports overall wellness, and specifically acts as a deterrent to tumor formation. Ample evidence from studies in the lab, with animals and with humans support the interconnectedness of reducing inflammation, controlling weight, boosting metabolic and hormone functions, and altering blood vessels in the direction of healthy shape demonstrate that exercise causes “…increases in circulating numbers of immune cells…and enhance vaccination response.” The authors conclude:

[W]e have shown that the antitumoral effects of exercise depend on CD8+ T-cells, and that intense exertion can alter the intrinsic metabolism and antitumoral effector function of cytotoxic T-cells…. This indicates that the adaptive immune system is a key component of exercise-induced suppression of tumorigenesis.^[iii]

Of course, these results were gained from studies with mice, but why wait until a human clinical trial? I can confidently say, based on a wide range of data, if you want to lower your risk of PCa—or any cancer, for that matter—embrace the exercise program of your choice and JUST DO IT!

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Rundqvist H, Veliça P, Barbieri L, Gameiro PA et al. Cytotoxic T-cells mediate exercise-induced reductions in tumor growth. Elife. 2020 Oct 23;9:e59996. doi: 10.7554/eLife.59996.
[ii] Reynolds, Gretchen. “How Exercise Might Affect Immunity to Lower Cancer Risk.” New York Times, Nov. 11, 2020. https://www.nytimes.com/2020/11/11/well/move/how-exercise-might-affect-immunity-to-lower-cancer-risk.html?referringSource=articleShare
[iii] Rundqvist et al, ibid.