The effect of physical training on the N-methyl-N-nitrosourea-induced mammary carcinogenesis of Sprague–Dawley rats

Abstract

The impact of physical activity on carcinogenesis has been demonstrated in many studies. Taking into account the discrepant results of physical exercise on the cell proliferation and apoptosis of breast cancer, we aimed to examine the impact of physical training on N-methyl-N-nitrosourea-(MNU)-induced mammary carcinogenesis. Fifty female rats were divided into four groups according to the intensity of physical activity they undertook. The number of developed tumors, tumor volume, and histopathological diagnoses were noted. Apoptosis and cell proliferation were studied by the number of TUNEL-positive and Ki-67-expressing cells. We demonstrated a statistically significant decrease in the tumor number between all trained groups and the control group. The results were most pronounced in the group with a moderate intensity of training. Moreover, we showed a decrease in tumor volume as training intensity increased, though the differences were not statistically significant. The mean number of TUNEL-positive cancer cells was significantly higher in the training groups than in the control group. These data suggest that physical training, especially of moderate intensity, may alleviate MNU-induced mammary carcinogenesis. The results could suggest that physical exercise-induced apoptosis may be a protective mechanism.

The Impact of Exercise Training on Breast Cancer

“…The results related to the primary prevention were presented in Malicka et al (4). In the present paper, the results related to the secondary prevention model will be provided.…”

“…Fifty female Sprague-Dawley rats (Medical University of Silesia, Katowice, Poland) were used in the experiment. All the conducted procedures were described in Malicka et al (4). They were consistent with the European Union standards and the consent was issued by the Bioethics Committee of the Institute of Immunology and Experimental Therapy of the Polish Academy of Sciences (consent no 37/2010).…”

“…Animals at 1 month of age were intraperitoneally injected with 180 mg/kg N-methyl-N-nitrosourea (MNU) (Sigma-Aldrich, Darmstadt, Germany) as previously described (4,28).…”

“…However, the results are not conclusive (2)(3)(4)(5)(6)(7)(8)(9). Westerlind et al found that in girls aged 10-15 who were more active than their peers with a sedentary lifestyle the risk for developing breast cancer decreased by 30-50% (2).…”

“…Studies on animal models also confirm this thesis. Malicka et al demonstrated that moderate intensity training reduced the number of induced tumors in rats (4). Other studies showed that in animals physically active at puberty (rodent treadmill, tunnels and ladders), the risk of developing the disease is decreased, the possible tumor development is delayed and smaller-sized tumors are observed (5)(6)(7)(8)(9)(10)(11).…”