Exercise reduces risk of several cancers yet researchers are working to understand how. A new lab study now offers insight, showing that running mice have far fewer tumors than their less active counterparts and pinpointing how the adrenaline of exercise can activate cancer-fighting cells towards a tumor.
The study was published in Cell Metabolism.
Graphical abstract, Pedersen et al., 2016, Cell Metabolism 23, 554–562
AICR research shows that exercise reduces risk of colorectal, endometrial and post-menopausal breast cancers. Other research suggests that activity may also play a role in the health of cancer survivors.
This study first conducted a series of tests with wheel-running mice to observe tumor growth. Compared to inactive mice, the runners showed overall smaller and fewer tumors. In one test, for example, where the mice were given a compound that causes liver tumors, 31 percent of the running mice developed tumors compared with 75% of the inactive mice. In another test, mice that ran for a month before given tumor cells had about 60 percent fewer tumors compared to the inactive rodents.
Then the researchers analyzed what cells were activated when the mice were running, zeroing in on a group of immune cells called natural killer (NK). After six weeks of running, the mice showed higher levels of NK cells in the tumors. The more NK cells, the fewer the tumors. When running mice were stripped of their NK cells, they showed no signs of less tumor growth. More tests showed that adrenal appeared to activate NK cells. Adrenalin, also known as epinephrine, is a hormone released when exercising.
The study also observed an immune signaling molecule, which exercises releases, is involved with guiding the NK cells to the tumors.
A key action of NK cells is to deliver the initial ‘‘spark’’ that activates other cell types of the immune system, the authors write. And a they note, this is only one of several mechanisms in which exercise can play a role in cancer risk.
The study was funded by Centre of Inflammation and Metabolism (CIM) is supported the Danish National Research Foundation (DNRF55). Centre of Physical Activity Research (CFAS) is supported by TrygFonden. This study was further supported by the Danish Medical Research Council, Novo Nordic Foundation, Lundbeck Foundation, Danish Cancer Society, and Aase og Ejnar Danielsen Foundation.
Source: Source: Pedersen et al.: "Voluntary Running Suppresses Tumor Growth through Epinephrine- and IL-6-Dependent NK Cell Mobilization and Redistribution." Cell Metabolism. 2016 Mar 8;23(3):554-62. doi: 10.1016/j.cmet.2016.01.011. Epub 2016 Feb 16.
Published on May 11, 2016