A recent study conducted by the University of Turku in Finland has revealed that just 30 minutes of exercise can significantly increase the proportion of tumour-killing white blood cells in the bloodstream of breast cancer patients. Published in the scientific journal Frontiers in Immunology, this discovery holds potential implications for cancer treatment and patient-care.
White blood cells are crucial components of the immune system, tasked with combating cancer, bacteria and viruses. However, not all white blood cells have the same function; some destroy cancer cells, while others may actually support cancer growth. The most important cancer-fighting cells are cytotoxic Tcells and natural killer cells, while regulatory Tcells and myeloid-derived suppressor cells can promote cancer progression.
“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 tumor area, the body is more capable of fighting cancer,” explained Dr Tiia Koivula, the lead author of the study from the University of Turku.
The study involved 20 breast cancer patients who had recently been diagnosed and had not yet begun any cancer treatments. Participants were asked to pedal a bicycle ergometer for 30 minutes at a self-selected resistance level. Blood samples were collected before, during and after the exercise session to measure the amounts of various white blood cell types.
Results showed that, during exercise, the number of several white blood cell types increased in the bloodstream, particularly the cancer-destroying cytotoxic Tcells and natural killer cells. Conversely, the number of cancer-promoting regulatory Tcells and myeloid-derived suppressor cells remained unchanged. Additionally, the proportion of natural killer cells relative to the total white blood cell count increased significantly, while the proportion of myeloid-derived suppressor cells decreased.
“We found that during the exercise, the number and proportion of cancer-destroying cells increase in the bloodstream, while the proportion of cancer-promoting cells either stays the same or decreases. However, it is still unclear whether these changes seen in the bloodstream also lead to changes in the white blood cell counts in the tumor area,” noted Dr Koivula.
The study also observed that the number of white blood cells returned to resting values one hour after exercise. While it is not yet clear where the white blood cells go post-exercise, pre-clinical studies have suggested that cancer-destroying cells might migrate to the tumour area.
Further analysis explored how different types of breast cancer might affect the exercise responses of white blood cells. It was found that larger tumours correlated with a smaller increase in natural killer cells and oestrogen and/or progesterone receptor-positive breast cancers showed a smaller increase in cytotoxic Tcells compared to hormone receptor-negative cancers.
“In our previous study, we found small indications that the type of breast cancer might affect the effects of exercise on white blood cells, which is why we wanted to examine it further. However, the correlations we found were not very strong and therefore, no decisive conclusions can be drawn from the results. According to current knowledge, it is beneficial for all cancer patients to exercise, and our recent study supports this notion,” Dr Koivula concluded.
This study underscores the importance of exercise for cancer patients and opens new avenues for integrating physical activity into cancer treatment regimens.
