In a study, biologists showed mice that maximized time on a running wheel were able to shrink tumors to a far greater extent than a relatively inactive control group. The difference in tumor size reduction was around 50 percent.
The theory that underpins this is adrenaline, a hormone produced in far higher quantities in response to exercise. The presence of adrenaline appears to aid cancer-killing immune ‘natural killer‘ (NK) cells in their transition towards tumors. This happens through an immune signaling molecule called IL-6, which is mobilized by the adrenaline. NK cells are lymphocytes.
Higher levels of the NK cells were found through testing samples of blood taken from the mice. Levels of the NK cells at the site of the tumor were assessed. Mice were engineered to have a variety of different tumors (of lung, liver, or skin.) A similar level of reduction was found, in relation to exercise, irrespective of the tumor location.
As a further control, a group of mice were taken and the ability to block adrenaline was engineered. Here it was shown that exercise alone was of no benefit — the hormone was needed.
Speaking with Bioscience Technology, lead researcher Pernille Hojman, who is based at the University of Copenhagen, stated: “It is known that infiltration of natural killer (NK) immune cells can control and regulate the size of tumors, but nobody had looked at how exercise regulates the system.”
The implications are that exercise may assist cancer medicines in tackling tumors. It should be noted that a study on mice does not necessarily mean the same effects would be seen with people. Further research is required.
The results are published in the journal Cell Metabolism. The research paper is titled “Voluntary Running Suppresses Tumor Growth through Epinephrine- and IL-6-Dependent NK Cell Mobilization and Redistribution.”