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.
Abstract. Background Breast cancer is still a major medical, social and economic problem due to the increasing prevalence and unsatisfactory treatment results. In 2013, nearly 235,000 new cases of breast cancer were reported in the United States, which accounted for 29% of all malignant neoplasms and was related to 14% risk of death. Based on current trends, over 23 million of new cases will be diagnosed by the year 2030 (1).Numerous scientific reports indicate the impact of physical activity on the development of breast cancer. However, the results are not conclusive (2-9). 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 (5-11). Currently, a longer survival time is observed in individuals after cancer treatment who regularly exercise (12)(13)(14)(15)(16)(17). Holmes et al. demonstrated a reduction in the risk of death due to breast cancer in women who exercised (3-5 hours per week) after treatment compared to women with a sedentary lifestyle (18). Other research groups have confirmed these results (19)(20)(21)(22). Walsh et al. and Daroux-Cole et al. suggested that exercise stimulated the immune system in cancer patients (23,24). Fairey et al. found an increase in the number of NK cells in the blood of women who trained and had previously undergone breast cancer treatment (13). It should also be noted that Demarzo and Garcia demonstrated an increase of breast tumor incidence in rats after intense exercise compared to untrained rats (25). Experiments on rats are a recognized model of experimental breast cancer research. The mammary gland model of rodents shows a significant similarity to the human mammary gland. In rodents, terminal end buds are the basic structures forming the mammary ridge while in humans it is the duct lobular unit which forms the 249 This article is freely accessible online.
Background/Aim: Breast cancer is the most common malignant tumor among women worldwide. In previous work, we presented results of physical activity in primary prevention in a model of induced mammary gland cancer. In the present study, we assessed the influence of physical activity on sex hormone levels (estradiol and progesterone) and the expression of their receptors (ER, PR), as well as the level of apoptosis of tumor cells in secondary prevention. Materials and Methods: Fifty 1-month-old female Sprague-Dawley rats received intraperitoneal injection of 180 mg/kg body weight of N-methyl-N-nitrosourea (MNU) for tumor induction. Three months after the administration of MNU, rats were divided into four groups: low-intensity, moderate-intensity, and high-intensity physical training groups (combined as PT) and a sedentary control (SC) group. Physical training was conducted 5 days per week with a threeposition treadmill according to a precisely described protocol. The entire training was completed by 32 rats from which tissue and blood were collected for further analysis. Immunohistochemistry for ER and PR expression, terminal deoxynucleotidyl transferase dUTP nick-end labeling method for detection of apoptosis, and enzyme-linked fluorescent assay for detection of plasma hormone levels (estradiol and progesterone) were performed. Statistical analysis used p<0.05 as the significance level. Results: Significantly stronger expression of ER and PR was found in the SC in comparison to the PT group (p=0.035 and p=0.036, respectively). No statistically significant differences were found in estradiol or progesterone concentrations between SC and PT groups. Apoptosis was non-significantly increased in the PT group in comparison with the SC group. Stronger apoptosis in the PT group correlated positively with the level of training intensity (r=0.35, p=0.05). Conclusion: Physical training may reduce ER and PR expression in breast cancer cells, and reduce cell sensitivity to pro-proliferative and antiapoptotic effects of estrogens, ultimately leading to apoptosis. Breast cancer is the most common malignant tumor among women worldwide (30%), being the second leading cause of cancer-related death in the United States and in Europe (14%) (1). Nearly 20% of women worldwide are diagnosed at 30-49 years of age and over 40% of women aged 65 years or over (2). Estrogens play an important role in the pathogenesis of breast cancer. Estradiol stimulates cell proliferation and differentiation by estrogen receptor (ER). Many reports indicate the relationship between exposure to estrogens and 495 This article is freely accessible online.
University (constant temperature and humidity, 12/12 h light and dark cycle, rat chow and water ad libitum), were utilized in the experiment. The study was approved by the local Ethics Committee (decision no. 37/2010). Following a two-week quarantine period, animals were intraperitoneally injected with 180 mg/kg body weight of MNU (Sigma-Aldrich, Munich, Germany) (19). Four weeks after MNU administration, the animals were monitored in accordance with a previously applied procedure (21).Physical training. The animals were divided into four groups: the sedentary control (SC; n=14), and low-(LIT; n=12), moderate-(MIT; n=12) and high-intensity (HIT; n=12) PT groups. Immediately after MNU administration, all training rats (LIT, MIT, HIT) were subjected to supervised 12-week PT (5 days a week) on a 3-position treadmill (Exer 3/6; Columbus Instruments, Columbus, OH, USA). The speed of the treadmill and training duration were gradually increased (Table I). For the LIT group, the training parameters were reduced by 20% compared to the MIT group, whereas for the HIT group, they were increased by 20% (22). After the administration of MNU, the rats from the SC group were not subjected to PT, however, they were housed for 12 weeks under the same conditions as training rats.
The aim of the study was to assess physical fitness of school-age children after cancer treatment. The study was comprised of one hundred and fifty six children—children after cancer treatment (n = 71, mean age 11.22 ± 3.11 years) vs. healthy children previously untreated for cancer (n = 85, mean age 10.71 ± 1.22 years). Physical fitness was assessed indirectly based on a ball throw (assessment of strength, coordination, and upper limb speed), long jump (assessment of jumping ability, speed, and coordination), and a 60 m run (assessment of speed). The analysis was performed based on the Student’s t-test for independent samples and the analysis of variance and the post-hoc least significant difference test (LSD test). Children from the study group threw the ball closer and had shorter long jump performance compared to the control group, i.e., 12.93 [m] vs. 19.79 [m], respectively (p < 0.001) and 2.46 [m] vs. 2.70 [m], respectively (p = 0.02). However, their mean running time was longer, i.e., 13.33 [s] vs. 11.73 [s], respectively (p = 0.01). Division according to sex showed additionally significantly shorter ball throw distance in the study group in both girls (p = 0.001) and boys (p < 0.001), significantly shorter jump length in the group of girls (p = 0.01), and significantly longer running time in the group of boys (p = 0.04). Children treated for cancer are characterized by decreased physical fitness, and motor ability is sex-dependent. Both groups showed decreased strength, coordination, and upper limb speed. Additionally, worse jumping ability was found in girls whereas decreased speed was observed in boys.
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