Scientists discovered that just one round of exercise can change blood chemistry in breast cancer survivors, releasing proteins that help suppress tumor cell growth in laboratory experiments and pointing to exercise as a powerful, non-drug therapy.
Study: 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. Image credit: shevtsovy/Shutterstock.com
A recent study in Breast Cancer Research and Treatment assessed the impact of a single bout of high-intensity interval training (HIIT) versus resistance training (RT) on anti-cancer myokines and in vitro cancer cell suppression in breast cancer survivors, potentially contributing to a lower risk of recurrence.
Exercise and the management of breast cancer
International guidelines support the use of exercise as a therapeutic intervention in the management of breast cancer. Exercise is safe and effective both during and after treatments for breast cancer to improve various health-related cancer outcomes, such as cardiorespiratory fitness and fatigue.
Research also shows that among breast cancer patients, exercise is associated with an approximately 20% lower risk for recurrence and mortality. Physical fitness is associated with a 31 to 46% risk reduction in all-cause mortality. Furthermore, exercise poses almost negligible risk of morbidity compared to other therapeutic interventions. Further research is needed to understand the biological mechanisms underlying the relationship between exercise and improved survival.
Skeletal muscle secretes myokines, which suppress the growth of cancer cells in various cancer cell lines. In specific breast cancer subtypes, IL-6 induces apoptosis and inhibits proliferation, and decorin alters the tumor microenvironment and inhibits receptor tyrosine kinases. Studies have shown that serum collected after a single exercise bout reduces cancer cell growth in different cancer types, including breast cancer. However, the effect of different exercise modes on myokine expression and their suppressive effects on breast cancer cells have not been studied yet.
About the study
The current study assessed the effects of RT and HIIT on cancer cell suppression and myokine expression in breast cancer survivors. It also studied whether the two exercise modes induce different responses in cancer cell suppression and myokine levels. The sample comprised women with a body mass index (BMI) between 18.5 and 35 kg/m2 and had been initially diagnosed with stage I–III breast cancer. They had also completed primary treatment and been medically cleared for exercise.
Blood samples were collected at baseline (following a 2-hour fast), after an acute exercise session (0P), and half an hour after exercise (30P), and the serum levels of interleukin 6 (IL-6), decorin, oncostatin M (OSM), and secreted protein acidic and rich in cysteine (SPARC) were analyzed.
Subsequently, the negative growth of the breast cancer cell line MDA-MB-231 was examined. Cell growth was monitored every 15 minutes to calculate the area under the curve (AUC).
Study findings
A total of 32 breast cancer survivors were recruited and were randomly assigned to the RT or HIIT group in a 1:1 ratio. The mean age of the participants was 58.6 years, with a mean BMI of 27.9 kg/m². Participants were diagnosed with breast cancer on average for 29.3 months. Approximately 34%, 41% and 25% of the participants were at stage I, stage II, and stage III of breast cancer, respectively.
Significant changes were observed for RT at repeated time points for decorin, IL-6, OSM, and SPARC. Furthermore, a significant elevation in decorin by 23%, IL-6 by 9%, and SPARC by 15% was estimated at 0P. Significant increases in IL-6 and OSM were observed at 30P compared to baseline.
For HIIT, significant changes were observed at repeated time points for decorin, IL-6, and SPARC. At 0P, there were significant increases in decorin, IL-6, and SPARC. Furthermore, a significant increase in IL-6 was observed at 30P compared to baseline.
This study observed no significant adverse events during the single exercise bout. Concerning between-group changes of serum myokine levels, a statistically significant effect was only observed for IL-6 at 0P, with a greater increase in favour of HIIT.
Real-time cellular analysis revealed only a statistically significant effect for the AUC at 0P. A greater reduction was observed in favor of HIIT. For both RT and HIIT, considerable changes were found at repeated time points for the AUC. Compared to baseline, significant reductions in MDA-MB-231 cell growth were observed at 0P and 30P.
Conclusions
The current study highlighted that both RT and HIIT induce acute changes in circulating myokines and reduce cancer cell growth. Both RT and HIIT had a prominent cancer-suppressive effect on MDA-MB-231 cells.
The research findings favored HIIT compared with RT for a greater increase in IL-6 levels and the inhibitory effects on cancer cells immediately after exercise. Therefore, a single bout of exercise at moderate to high intensity could be considered an accessible, non-pharmacological intervention that may contribute to cancer control; however, the long-term effects on recurrence remain to be determined in breast cancer survivors.
In the future, more research is required to determine the long-term effects of this intervention on disease recurrence in breast cancer survivors.
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