New Insights into How Exercise Can Help Slow Cancer Progression.

Exercise has the potential to slow tumor development in mice by altering metabolic pathways, enabling muscle cells to absorb glucose instead of cancer cells for growth. This may also occur in humans.

While it’s established that exercise lowers cancer risk and healthier individuals generally have better cancer survival rates, the underlying mechanisms are still being explored. Notably, some benefits of exercise appear linked to changes in gut microbiota and the immune system.

To examine another possible pathway, Rachel Perry and her colleagues at Yale University School of Medicine conducted an experiment on 18 mice injected with breast cancer cells. Twelve of these mice were given an obesity-inducing diet, known to accelerate various cancers. Half of the group was also equipped with a running wheel to exercise as desired.

After four weeks, tumors in the exercising obese mice were found to be 60% smaller compared to their non-exercising counterparts, and were slightly smaller than tumors in sedentary mice fed a standard diet. The study revealed that just 30 minutes of exercise led to an increase in oxygen and glucose uptake in skeletal and cardiac muscles, with a corresponding decrease in glucose assimilation by tumors.

“This research demonstrates that aerobic fitness significantly alters the metabolic rivalry between muscle and tumor,” states Perry. “Crucially, the exercise was voluntary—these mice weren’t being forced to run like marathon athletes; they exercised as per their preference.”

The scientists evaluated gene expression and identified changes in 417 genes associated with vital metabolic pathways in mice due to exercise. This indicates that muscle tissue utilizes more glucose while tumor tissue absorbs less.

Specifically, a reduction in mTOR, a protein pivotal for cancer cell proliferation, shows potential for limiting tumor expansion, according to the researchers.

Perry anticipates that these metabolic patterns, which are similar across mammals, may extend to humans, even those without obesity. In fact, analogous gene activity shifts during exercise have been documented in cancer patients.

“This points to another mechanism illustrating how exercise fosters a cancer-suppressive environment,” mentions Rob Newton from Edith Cowan University in Perth, Australia. “We need to conduct clinical trials in humans, as there’s no clear reason to suspect it wouldn’t produce similar outcomes.”

Perry emphasizes that metabolism encompasses all tissues and is influenced by both the microbiome and immune responses. “These metabolic adaptations may bridge the connections between exercise, the microbiome, the immune system, and tumor progression,” she explains. “However, I’d be surprised if the positive implications of exercise stemmed from a single mechanism.”

This discussion also sheds light on why lower muscle mass heightens cancer mortality risk, as observed by Newton. “If your muscles preferentially absorb glucose, increasing muscle mass and regularly activating your muscles could yield significant advantages.”

He believes it’s crucial to view exercise not just as a lifestyle change but as an adjunctive anti-cancer intervention alongside other treatments. “Identifying primary environmental contributors to cancer is key, and we must formulate specific strategies to address them,” Newton concludes. “While enhancing cardiorespiratory fitness is beneficial, if a patient presents with notably low muscle mass, that should be prioritized with strength training.”