Objective: Exercise has been reported to suppress colorectal cancer; however, the mechanism of suppression by exercise and its effect on the Wnt pathway, which is particularly involved in the early stage of carcinogenesis, remain unclear. In this study, we subjected ApcMin/+ mice to exercise by shaking stimuli to investigate the mechanisms of suppressing colorectal cancer, and focused on the Ca2+ pathway, which is one of the β-catenin-independent Wnt signaling pathways that suppress the accumulation of β-catenin.
Methods: Mice in the exercise group were subjected to exercise by shaking stimuli for 30 min/session, 6 sessions/ week, for a total of 11 weeks. The number and diameter of intestinal polyps were calculated. Expression analysis of β-catenin and Pak1 from the intestinal tract and Wnt5a-Pan and Wnt5a-Long from the gastrocnemius muscle was performed by western blotting. The expression of β-catenin and Wnt5a-Pan was observed by immunohistochemical staining.
Result: The levels of expression of β-catenin and Pak1 in the small intestine were low in the exercise group, indicating that exercise suppressed the accumulation of β-catenin. In the gastrocnemius muscle, the levels of expression of Wnt5a-Pan and Wnt5a-Long were significantly higher in the exercise group (p < 0.05). Histological analysis revealed that the percentage of large polyps was significantly lower in the exercise group than in the control group (p < 0.01), revealing that exercise suppressed the growth of polyps. In addition, the villi/crypt ratio (V/C ratio) was significantly higher in the exercise group, suggesting the suppression of exercise-induced local inflammation in the small intestine.
Conclusion: We believe that the mechanism of polyp growth suppression is related to the inflammatory and not the Wnt pathway. This study clarified the growth-suppressing effect of a novel exercise method on cancer. We believe that its development and clinical application might open new possibilities for the prevention treatment of colorectal cancer.
Keywords: Exercise Therapy; colorectal cancer; myokine; shaking and vibration.