A new Finnish study from the University of Turku shows that a 30-minute exercise can increase the proportion of tumour-killing white blood cells in the bloodstream of breast cancer patients.
White blood cells are part of the body’s immune system, and they fight against cancer, bacteria, and viruses.
Not all white blood cells destroy cancer cells, and some can even promote cancer growth. The most important cell types that destroy cancer cells are cytotoxic T cells and natural killer cells. Cell types that support cancer growth include, for example, regulatory T cells and myeloid derived suppressor cells.
The balance of different types of white blood cells determines whether the immune system works to destroy cancer or to support it. If there are more cancer-destroying cells than cancer-promoting cells in the tumour area, the body is more capable of fighting cancer.
In terms of the study, twenty breast cancer patients who had just been diagnosed and therefore had not yet started their cancer treatments participated. During the study, the patients pedalled a bicycle ergometer for 30 minutes at a resistance of their own choosing. Blood samples were taken from the patients at rest before the pedalling, during the exercise, and after the exercise.
Following this, blood samples were analysed to calculate the amount of many different types of white blood cells, and the amounts measured during the exercise were compared to those at rest.
During the exercise, the amount of several different white blood cell types increased in the bloodstream. The number of cancer-destroying cytotoxic T cells and natural killer cells increased the most. On the other hand, the number of cancer-promoting regulatory T cells and myeloid derived suppressor cells did not change.
The researchers also examined the proportions of different white blood cell types relative to the total white blood cell count and found that the proportion of natural killer cells increased significantly, while the proportion of myeloid derived suppressor cells decreased.
Hence, during the exercise the number and proportion of cancer-destroying cells increases in the bloodstream, while the proportion of cancer-promoting cells either stays the same or decreases. Cancer-destroying cells have been seen to migrate into the tumour area.
The researchers also analysed whether different types of breast cancer affect the exercise responses of white blood cells. The researchers found that the larger the tumour, the less the number of natural killer cells increased, and if the breast cancer was oestrogen or progesterone receptor-positive, the number of cytotoxic T cells increased less than in hormone receptor-negative cancers.
The study appears in the journal Frontiers in Immunology, titled “The effect of exercise and disease status on mobilization of anti-tumorigenic and protumorigenic immune cells in women with breast cancer”.
