Daily stretching reduces tumor growth and improves the immune and inflammatory responses in mice with breast cancer, according to researchers.
Their study, “Stretching Reduces Tumor Growth in a Mouse Breast Cancer Model,” was published in the journal Scientific Reports.
Increasing evidence suggests that exercise can reduce the risk of developing breast cancer or of breast cancer relapse (recurrence) in cancer survivors.
It has also been suggested as a method to ease treatment side effects and improve quality of life.
However, preclinical results are heterogeneous and inconsistent, and the type, duration, intensity, and frequency of exercise that could potentially prevent and control breast cancer remains unclear.
Yoga, tai chi, and qi gong are mind-body practices frequently used and well-tolerated among cancer patients to manage symptoms and improve mobility and well-being.
Stretching is a common component among these gentle movement-based exercises, and 10 minutes of stretching per day has been shown to reduce local inflammation and scarring — biological processes associated with cancer.
Researchers at Brigham and Women’s Hospital, in collaboration with colleagues at Dana-Farber Cancer Institute, both in Boston, evaluated whether daily stretching could affect tumor growth in mice with breast cancer.
Researchers injected breast cancer cells into the breast tissue of 66 female mice, which were then randomized to receive 10 minutes of daily stretching for four weeks. Mice received no other form of treatment during the study.
The team used a well-established stretching technique, in which mice are held by the base of the tail and gently lifted, with their front paws grasping a bar. With minimal training, mice can comfortably hold this position for 10 minutes without struggling.
Tumor growth between weeks two and four was significantly slower in the stretched mice, compared with those that did not stretch.
Also, after four weeks, the tumor volume of mice receiving daily stretching was 52% smaller than those of mice in the no-stretch group.
To better understand the mechanisms behind the beneficial effects of stretching, researchers analyzed the levels of molecules involved in immune and inflammatory responses.
Stretched mice showed a significant reduction in the levels of PD-1 — a protein known to suppress the activity of T-cells, a type of white blood cell that fights cancer — suggesting that stretching could potentially restore or activate this T-cell-based immune response.
Because chronic uncontrolled inflammation in the tumor microenvironment can promote tumor growth, researchers also evaluated the levels of RvD1 and RvD2, molecules that promote the natural resolution of inflammation and have been shown to suppress tumor growth in mice. Their levels were significantly higher in mice that stretched compared with mice that did not stretch.
These findings suggested that the resolution of inflammation and increased immune response may work together to reduce tumor growth as a result of stretching.
“These results open myriad new avenues of research,” Jean J. Zhao, the study’s co-corresponding author, said in a press release. “Understanding [how stretching reduces tumor growth] could help us develop more effective therapies against breast cancer and potentially other cancer types.”
Researchers said the “potential clinical significance of our results lies in the possibility of developing a method of gentle stretching that could be well tolerated and testable in humans for primary or secondary cancer prevention, or in conjunction with cancer treatment.”
The authors noted that their results do not suggest in any way that cancer patients should stretch instead of receiving standard cancer treatment, and that more research is needed to confirm the therapeutic benefits of stretching in humans.
For now, they plan to evaluate whether stretching may affect the spread of more advanced cancer in mice.