Suppression of Autophagy-Related Gene Expression Following Chronic Endurance Training in Tumors of Breast Cancer-Bearing BALB/c Mice

Autophagy is lysosomal degradation pathway that contributes to tumor development through metabolic support, especially at final stages. The purpose of this study was to evaluate the effect of 12 weeks endurance training on autophagy-related gene expression levels in tumors of breast cancer-bearing BALB/c mice.

Twenty-two female BALB/c mice were randomly divided into control (n= 11) and experimental (n= 11) groups. Breast cancer was induced by injecting MC4-L2 cancer cells into the right dorsal mammary fat pad. The experimental group underwent training protocol for 12 weeks. Expression levels of autophagy-related genes were measured by real-time PCR and quantified bymethod. Data analysis was done applying Student t-test.

Endurance training led to significant decrease in tumor weight (P= 0.038) and volume (P= 0.043) in experimental group compared to the control group. Expression levels of Beclin1 (11%), Atg7 (53%), p62 (37%), gabarapl (76%), LC3-I (35%), and LC3-II (62%) in tumors of experimental group were lower compared to the controls. In addition, training protocol resulted in a decrease in LC3-II/LC3-I ratio (42%) and increase in p62 expression level (157%) (all P< 0.05).

Endurance training-induced reduction in tumor weight and volume was coincided with substantial reduction in expression levels of autophagy-related genes. This may suggest that beneficial effects of endurance training in breast cancer, at least in part, could be mediated through suppression of autophagy process in solid tumors.