Several studies have shown that exercise may slow the progression of cancer in mice. However, the exact mechanism behind the protective effects of exercise is still unclear. Understanding the biology behind exercise may lead to new oncology treatment approaches. Researchers at the Karolinska Institutet have identified a plausible explanation for how exercise affects the size of tumors in mice. In the study, researchers examined the immune system’s response to exercise. The researchers found that exercise reduced the number of immune suppressive cells in the spleen, the number of natural killer (NK) cells in the spleen, and the number of cancer cells in the spleen. These cells are important in the suppression of cancer. They control micrometastasis and help to prevent tumors from spreading.
In addition to reducing the number of immune suppressive cells, exercise also inhibited the growth of tumors in both the 4T1 model of human TNBC and the syngeneic B16F10 melanoma model. The researchers were able to use microarray analysis to determine the effects of exercise on the size of tumors. The size of the tumors in exercised mice was significantly reduced compared with the tumors in the control group. The difference in size was statistically significant at p 0.05.
Physical activity has also been shown to alter the metabolism of the immune system’s cytotoxic T cells. These cells are important for the exercise-induced suppression of cancer. Exercise may shift the balance of these cells by releasing common metabolites into the blood, which increase T cell activity. These metabolites are also released in humans, where they alter the metabolism of T cells. This may help explain why exercise is so effective at slowing cancer growth.
The study also showed that exercise can improve the anti-tumor effect of chemotherapy and radiotherapy. In addition to enhancing the anti-cancer response of these therapies, exercise also enhanced the ability of the immune system to respond to the PD-1 cytotoxic agent. Researchers also found that exercise had a positive effect on the survival of mice with 4T1 tumors. This is because exercise significantly reduced the development of metastatic tumors.
Researchers also found that physical activity enhanced the trafficking of natural killer (NK) cells in the body. The exercise-induced trafficking of NK cells into the spleen helped to slow the progression of the cancer in mice. The increase in NK cell activity was associated with the decrease in the size of the tumor. The number of NK cells was also significantly higher in exercised mice compared with the control group.
Researchers also found that exercise was able to reduce the number of myeloid-derived suppressor cells (MDSCs) in the spleen. The amount of MDSCs in the spleen was reduced by about a third, and was proportional to the amount of exercise done. Interestingly, the number of MDSCs was not correlated with the number of CD8+ T cells, suggesting that exercise has a role to play in the regulation of immune cells. This is important for cancer treatment, since MDSCs are a major source of resistance to chemotherapy and radiotherapy.
