Arginase 1 Suppression Makes Exercise Effective Against Prostate Cancer

Exercise has consistently been linked to improved outcomes in prostate cancer, but the mechanisms behind this effect have remained unclear. A recent preclinical study provides a compelling explanation, identifying suppression of arginase 1 (Arg1) and modulation of arginine metabolism as key drivers of exercise-induced tumor control.

Using a prostate-specific Pten-knockout mouse model, researchers observed that voluntary exercise significantly reduced tumor burden. Prostate weight was lower and tumor cell proliferation, measured by Ki-67, was reduced by more than half in exercising mice, despite no differences in body weight. This suggests the anti-tumor effect was not simply due to systemic metabolic changes such as weight loss.

Molecular analyses revealed that exercise downregulated pathways involved in arginine metabolism, with a marked reduction in Arg1 expression at both the mRNA and protein levels. Arg1 plays a central role in the tumor microenvironment by converting arginine into ornithine, effectively depleting arginine, a critical nutrient for T-cell function. Elevated Arg1 activity is known to promote immune suppression and tumor growth, partly through supporting polyamine synthesis.

To test causality, the researchers administered an arginase inhibitor. This intervention reduced tumor growth to a similar extent as exercise. Importantly, combining exercise with arginase inhibition did not produce additional benefit, indicating that both act through the same pathway. These findings strongly support the conclusion that suppression of Arg1 is a primary mechanism by which exercise inhibits prostate cancer progression.

This study highlights arginine metabolism as a key link between physical activity and tumor biology. By preserving arginine availability and potentially restoring anti-tumor immune responses, exercise may function as a physiological modulator of the tumor microenvironment. While translation to humans requires further validation, the results provide a mechanistic foundation for integrating structured exercise into prostate cancer management and for exploring synergy with emerging therapies targeting arginine metabolism.

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