The ethnic and regional variations reported in the incidence of breast cancer, as well as the sustained increase in the number of cases that this disease has since the 80's to date, are some topics that can not be explained solely in function of inherited or acquired mutations in high penetrance genes. Epidemiological studies have reported a positive correlation between increased risk of breast cancer and the growing consumption of high-fat foods, ethanol and tobacco by current women [1, 2]. This has prompted a further research of the molecular mechanisms underlying the appearance of breast cancer by some habits that women have been adopting their lifestyl.The oncogenic pathologies are currently considered the result of the loss of cell identity caused by the disturbance in expression of proteins associated with the cell differentiation. Among the multiple factors that can alter gene expression programs, the high penetrance mutations, inherited or acquired, are the most easily detectable cause. However, the percentage of breast cancer cases etiologically associated with this type of mutations does not exceed 10% [3,4]. The high probability of developing cancer from these mutations is explained by the fact that the affected genes, encode proteins involved in cellular processes such as: DNA repair, cell cycle regulation and protection against xenobiotics and free radicals, which are essential functions for maintaining the fidelity and integrity of the genome [4]. In the case of breast cancer, genetic linkage analysis and next generation sequencing studies have found that higher penetrance mutations occur mainly in the genes encoding: breast cancer 1 (BRCA1), tumor protein p53 (TP53), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), retinoblastoma 1 (RB1), phosphatase and tensin homolog,(PTEN), GATA binding protein 3 (GATA-3) and mitogen-activated protein kinase kinase kinase 1 (MAP3K1) [5-7]. Such modifications commonly alter the open reading frame of the gene, resulting in the loss or gain of function in the encoded proteins [4]. However, the involvement of mutations in regions of gene transcriptional regulation, and its association in the development of breast cancer needs further investigation. On the other hand, the association that the epidemiology studies have found between the process of cell malignancy and some lifestyle factors such as smoking, diet, alcoholism and obesity; has prompted a further research on the role of alterations produced by these factors in the mechanisms of gene expression regulation [1]. Although there are several regulation levels for the gene expression, the transcriptional regulation mechanisms are considered the fundamental system whereby the cells can modulate, halt or activate the expression of a given gene [8]. So that any malfunction or modification in the expression of the proteins involved in these mechanisms could have important consequences in the cell protein expression