Exercise is a critical component of public health recommendations to prevent cancer. A growing body of scientific research demonstrates that engaging in exercise after a cancer diagnosis can improve outcomes, but the mechanisms that mediate these effects are not fully characterized. Findings from a new study demonstrate that exercise alters the metabolism of cytotoxic T cells to improve their ability to attack cancer cells.

Cytotoxic T cells play key roles in the body’s immune response. They destroy malignant cells by triggering apoptosis – a type of cellular self-destruct mechanism that rids the body of damaged or aged cells.

The authors of the study placed mice with cancer into one of two groups. Half of the mice exercised on a treadmill, but the other half remained inactive. They transferred cytotoxic T cells from the mice that exercised into the inactive mice. Then they isolated T cells, blood, and tissues from the exercising mice. Finally, the authors injected both groups of mice with antibodies that would destroy the animals' cytotoxic T cells.

The mice that exercise exhibited slower cancer growth and reduced death rates than those that remained inactive. The inactive mice that received the cytotoxic T cells from exercised mice showed marked improvements in their disease status. The exercising mice had high blood levels of lactate, which altered the T cells' metabolism and increased the cells' activity. Destroying the animals' cytotoxic T cells negated the beneficial effects that the exercise had in terms of cancer growth and survival.

Taken together, these findings suggest that exercise alters cytotoxic T cells to mediate exercise-induced cancer suppression. Treatment protocols that incorporate exercise might improve outcomes by activating the immune system.

• Link to full study.