Physical activity and breast cancer.

There is strong evidence that physical activity profoundly protects against several types of cancer.

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Exercise can suppress signaling within breast cancer cells, which can reduce tumor growth and even kill cancer cells, according to a recently published study (Davis AM et al. — Texas A&M University, October 2022). This reduction in tumor growth was concomitant with increased DEPTOR protein levels and reduced mTOR kinase activity.

It is worth noting that cancer in general is the second cause of death in the United States, with a frequency very close to that of heart disease (National Vital Statistics Reports, Vol. 68, №9, 24 June 2019). Breast cancer is the most common malignancy in women, and the American Cancer Society reported 276,480 new cases and more than 42,170 deaths in 2020 alone (Siegel et al., 2020).

Regular exercise has been noted as a key factor in reducing tumor growth in numerous studies. Habitual physical activity decreases the risk of developing breast cancer and improves survival after cancer diagnosis. Previous studies have attributed these benefits to improvements in systemic factors such as improved body composition, reductions in inflammatory markers, or stabilization of circulating hormones.

These events are undoubtedly important for overall homeostasis and health; however, the identification of myokines, compounds released from skeletal muscle, has led to a new appreciation of the role of muscle in mediating the metabolism and function of numerous cells and tissues in the body.

Convincing evidence suggests that during exercise, contracting skeletal muscle functions as an endocrine-like organ that can regulate the activity of other tissues, including malignant tumors, by releasing pharmacologically active signaling molecules into the circulation.

Indeed, the benefits of mTOR inhibition have been demonstrated in the clinical treatment of breast cancer, indicating the importance of this inhibition in preventing and fighting cancer.

The ability of myokines released during muscle contraction to reduce mTOR activity has also been demonstrated in other types of cancer. The results of the study by Davis and colleagues conclusively demonstrate that signaling factors released in skeletal muscle contraction reduce growth and anabolism in breast cancer cells; this process is mediated by suppression of mTOR activity and due, at least in part, to increased levels of DEPTOR.

Breast cancer is one of the leading causes of morbidity and mortality and there is an urgent need to identify prevention and treatment routes for these deadly tumors. Regular physical exercise, as part of a healthy lifestyle, is effective in combating many chronic diseases, including the development and recurrence of cancer. While exercise certainly has systemic benefits that are beneficial to overall health; the results of the study by Davies and colleagues confirm the findings of other studies that suggest that skeletal muscle contraction can regulate the metabolism of cancer cells.

In current investigation, it has been identified pharmacologically active factors that are released during skeletal muscle contraction, and that these compounds have demonstrable effects on growth and metabolism in cultured breast cancer cells. Myokines released during muscle contraction induce apoptosis (cell death) and suppress protein synthesis in cancer cells, both in vitro and in vivo.

The results of the study by Davis and colleagues indicate that skeletal muscle is capable of altering the behavior of extramuscular tissues and that the act of exercising can, by itself, provide demonstrable benefits in the fight against breast neoplasms.

In summary, during muscle contractions, the muscle releases some factors into the bloodstream that may play a role in the fight against breast cancer: these factors kill, or at least slow down, the growth of these neoplastic cells.

Simple activities like walking or dancing can release these factors to fight cancer.

Why does the risk of cancer decrease with exercise?

Exercise, as we have seen, slows down the growth of abnormal cells, and pre-cancerous cells can be destroyed by our bodies before they begin to develop. Regular exercise can interrupt communication in cancer cells and consequently stops the growth of these cells; thus, factors released by exercise may play a role in preventing the development of breast cancer.

But beware cancer prevention cannot be 100% guaranteed by exercise. Diagnosis of cancer can occur in people who exercise regularly, as many factors can contribute to a person’s risk of developing cancer, such as smoking, age, genetics, and comorbidities. Thus, looking for your doctor, participating in campaigns, and carrying out tests for cancer prevention cannot be neglected.

According to studies by the National Cancer Institute (INCA — Brazil), physical activity promotes balance in hormone levels, reduces gastrointestinal transit time, strengthens the body’s defenses, and helps maintain adequate body weight.

So, the good news, physical activity not only contributes to preventing breast cancer but also to the prevention of bowel (colon) and endometrial (uterine body) cancer.

Performing physical activities is the beginning of a story of quality of life and good health. Although even people who practice regular activities are susceptible to having the disease due to genetic factors, not doing physical activity can be very harmful.

It is worth remembering that, until recently, cancer prevention strategies in general, and colorectal cancer in particular were primarily focused on diet. The harmful effects of excessive consumption of industrialized products, particularly sausages, and foods loaded with dyes and preservatives for health, were already well known and commented on. But some more recent research indicates that physical exercise at adequate intensity is just as important as healthy eating.

Combining a healthy diet with exercise is not only important for the prevention of cancer in general and colorectal cancer in particular, but it can also improve the effectiveness of the treatment of the disease as well as prevent recurrence.

Some additional data show the importance of physical activity even for those women already undergoing treatment for breast cancer: Lyra VB et al (2021) demonstrated that the significant decrease in the regular practice of physical activity caused by the social isolation imposed by the recent pandemic ( COVID-19), given the imminent danger of contagion, seems to have contributed to the exacerbation of the clinical and physical symptoms of breast cancer, such as the perceived increase in lymphedema and pain, especially in the arm corresponding to the oncological surgery.

There has been evidence since the 1990s that physical activity has an impact on reducing the risk of cancer and the data collected even allow quantifying how much it is possible to reduce. For breast cancer, it is estimated that the reduction is 40%. A sedentary lifestyle can increase the risk for the evolution and development of the disease by up to 104%.

The sedentary lifestyle must decrease, for example, by reducing the time we remain seated. If possible, the activity should be done standing up and introducing more activity into your daily life.

And as for physical activity, doing little is better than not doing it.

References

• Davies AR e al — Frontiers in Physiology, October 2022.
• Ortega E et al — Rev Bras Med Esport, Vol 4, número 3.
• Lyra VB et al — Rev Bras Oncol 2021, 67(2):e-111291