Cancer-Fighting Exercise: Workout Reduces Tumor Cell Growth By Up To 30%

Breast cancer is the leading cause of cancer death in women, and the risk of the disease returning continues even after treatment. Research shows that physical exercise can help reduce this risk. A recent study compared the effects of a single strength training session (resistance training) and HIIT in women who survived breast cancer. The results showed that both workouts increased blood substances (myokines) that help fight cancer cells. This indicates that exercise may have a direct effect on preventing cancer recurrence.

Breast cancer is one of the diseases that most affects women's health worldwide. In 2022, more than 2 million new cases were recorded, and approximately 660,000 women died from the disease. This makes breast cancer the most common type of cancer and the leading cause of cancer death among women.

Even after treatment, many patients remain at risk of the cancer returning, in some cases, even years later. The chance of recurrence varies greatly depending on the type of tumor, the stage of the disease when it was discovered, the woman's age, and whether she has gone through menopause. Therefore, it is essential to seek new ways to prevent the disease from returning and improve current treatments.

In recent years, physical exercise has proven to be an important tool in the fight against breast cancer. In addition to traditional treatments such as surgery, chemotherapy, and radiation therapy, physical activity has been recommended by doctors and scientists worldwide.

Studies show that exercising during or after treatment can bring several benefits: it reduces fatigue, improves quality of life, strengthens muscles, helps with weight control, and improves overall health.

Furthermore, women who exercise have about a 20% lower risk of having their cancer return or dying from it. This is because exercise improves muscle strength and cardiorespiratory fitness, and these factors are linked to lower mortality in cancer patients.

An advantage of exercise compared to other treatments is that it has few or no side effects. Despite this, the mechanisms that explain how physical activity helps fight cancer are still not fully understood.

One of the most recent scientific discoveries is that muscles, when they contract during exercise, produce substances called myokines. These molecules are released into the bloodstream and can influence various organs in the body, such as bones, liver, brain, fat, and even cancer cells.

Several myokines have been studied for their anti-cancer effects, including interleukin 6 (IL-6), decorin, SPARC, and oncostatin M (OSM). These substances can act directly on breast cancer cells, helping to prevent them from growing, multiplying, or spreading to other parts of the body.

For example, IL-6 can cause cancer cell death and prevent their multiplication. Oncostatin M can keep cancer cells "dormant," meaning they cannot develop. Decorin works by blocking signals that stimulate tumor growth. SPARC hinders tumor cell migration and modifies the environment around the tumor to make it less favorable for cancer.

Laboratory studies have shown that the blood of people who have just exercised can inhibit the growth of cancer cells, including breast cancer cells. However, few studies have analyzed this effect in real patients, that is, in women who have already had breast cancer. This is important because cancer itself and treatments, such as hormone therapy, can alter the body's functioning and response to exercise.

When we talk about exercise, there are different types. Among the most studied are aerobic training (such as walking or cycling), high-intensity interval training (HIIT), and strength (or resistance) training, which includes weight training.

Previous studies have tested these types of exercise separately, but none have directly compared the impact of HIIT and strength training on the release of anticancer myokines and their effects on breast cancer cells.

Therefore, a new study investigated exactly that: comparing the effects of a single strength training session (resistance training) and HIIT on the release of these myokines and the behavior of cancer cells in the laboratory.

Thirty-two women who had already overcome breast cancer participated in the study. They were divided into two groups: one did strength training and the other did HIIT. Blood samples were collected before, immediately after, and 30 minutes after the exercises.

The scientists analyzed the levels of IL-6, decorin, SPARC, and oncostatin M and also tested this blood on breast cancer cells (MDA-MB-231 line) to see if it could inhibit cancer cell growth.

The results showed that, after exercise, myokine levels increased significantly. Substances such as IL-6, decorin, and SPARC increased by 9 to 47% immediately after training in both groups.

Myokine levels in resistance training and high-intensity interval training groups. Key: pg = picogram; ng = nanogram; BA = baseline; 0P = immediately after exercise; 30P = 30 min after exercise; RT = resistance training; HIIT = high-intensity interval training; * = p < 0.0167 compared to baseline.

IL-6 remained elevated half an hour after exercise in all participants, and oncostatin M was elevated only in the resistance training group.

Blood collected after exercise was able to reduce breast cancer cell growth by 19% to 29% in both the resistance training and HIIT groups. However, HIIT had a greater effect immediately after exercise.

These findings are important because they show that even a single exercise session can stimulate the release of cancer-fighting substances. This reinforces the role of physical exercise as an essential part of treatment and health care for women who have had breast cancer.

Strength training or HIIT can, in addition to improving overall health, help reduce the risk of cancer recurrence, with few risks and many benefits.

Results in the resistance training and high-intensity interval training groups showing significant improvements immediately after and up to 30 minutes after exercise. Legend: RT = resistance training; HIIT = high-intensity interval training; BA = baseline; 0P = immediately after exercise; 30P = 30 minutes after exercise.

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A single bout of resistance or high-intensity interval training increases anti-cancer myokines and suppresses cancer cell growth in vitro in survivors of breast cancer

Francesco Bettariga, Dennis R. Taaffe, Cristina Crespo-Garcia, Timothy D. Clay, Mauro De Santi, Giulia Baldelli, Sanjeev Adhikari, Elin S. Gray, Daniel A. Galvão, and Robert U. Newton

Breast Cancer Research and Treatment, Volume 213, pages 171–180, (2025)

DOI: 10.1007/s10549-025-07772-w

Abstract: 

Breast cancer is the leading cause of cancer-related death in women, highlighting the need for strategies to mitigate recurrence and mortality. We examined the effects of a single bout of resistance training (RT) versus high-intensity interval training (HIIT) on anti-cancer myokines and in vitro cancer cell suppression. Thirty-two survivors of breast cancer were randomly allocated to a single bout of RT (n = 16) or HIIT (n = 16). Blood was collected before, immediately post (0P) and 30 min post (30P) exercise. We measured serum levels of decorin, interleukin 6 (IL-6), secreted protein acidic and rich in cysteine (SPARC), and oncostatin M (OSM) and cell growth of MDA-MB-231 cells in vitro using real time cellular analysis at each time point. Decorin, IL-6, and SPARC significantly increased (9 to 47%, p < 0.05) from baseline to 0P in both groups. IL-6 remained elevated in both groups at 30 min post-intervention (30P), while OSM levels were elevated only in the RT group at 30P. Between groups, IL-6 was significantly increased in HIIT at 0P (p = 0.001). Cancer cell growth was significantly reduced at 0P and 30P compared to baseline in RT (20 to 21%, p < 0.05) and HIIT (19 to 29%, p < 0.05), with significantly greater effects on MDA-MB-231 cell growth reduction in favour of HIIT at 0P (p = 0.001). A single bout of RT or HIIT can increase levels of anti-cancer myokines and reduce the growth of MDA-MB-231 cells in vitro in survivors of breast cancer, potentially contributing to a lower risk of recurrence. This highlights the importance of exercise as a treatment with promising anti-cancer effects.