Effects of aerobic physical training on blood circulation and skeletal muscle myomiRs expression in a experimental breast cancer model

Abstract

Cancer is a set of diseases characterized by uncontrolled cell growth that target tissues and organs and can spread to different parts of the body. This process called metastasis invasion is extremely harmful because the cancer cells can be very aggressive, uncontrolled and a high-speed cell division. These cells do not resemble the original tissue and cause various deleterious changes in the organ of origin and also systemics changes. And so, the cancer has a progressive and degenerative character and is one of major cause of deaths in the world (INCA, 2014). Breast cancer is the second most common form of cancer and one of the cancer types that cause the most death worldwide (WHO, 2014). The major causes of deaths from this cancer are due to metastasis. However, breast cancer also has a deleterious systemic effects and causes many changes in the body. (NEILSON et al., 2009). Recently a new class of molecules has been investigated to be related to many physiological and pathological factors. These molecules are called microRNAs. It is known that miRNAs control the expression of many RNAs and thereby regulate cellular protein expression, and biological processes. Therefore, a change in the expression of microRNAs can result in an imbalance in the regulation of the molecular mechanisms and cellular phenotype (AMBROS, 2001). Recent findings show that microRNAs are altered in patients with breast cancer. These changes in the expression of miRNAs are found in the blood circulation to the tumor and in some tissues such as skeletal and cardiac muscle. Uncontrolled expression of these microRNAs in circulation causes aggression to other tissues. In tumor stimulates the growth and skeletal and cardiac muscle imbalance generates losses in the balance of synthesis and protein degradation (Chen et al., 2014). Moreover, evidence accumulated in recent years show that exercise causes extensive adjustments skeletal muscle, including pathological conditions. One of the most striking is the normalization of the balance between the synthesis and degradation of proteins in skeletal myocyte (Cunha et al, 2012). Also, exercise plays an important role in regulating the expression of many microRNAs. And due to its restorative action in the expression of several altered microRNAs present in different diseases, it has therapeutic potential (Fernandes et al., 2011). This knowledge gives support for this proposal in which we intend to answer the following questions: 1) circulating miRNAs expressed in breast cancer influence the skeletal muscle phenotype?; 2) the physical training alters the expression of circulating microRNAs that are expressed in breast cancer? (AU)