Breast Cancer (BC) is the most common type of malignant neoplasm among women and although death from this disease has decreased with new alternatives for diagnosis and treatment, it is still one of the biggest health problems in the world. The therapeutic decision for the management of patients with MC is based not only on the evaluation of prognostic factors, such as Estrogen Receptors (ER), Progesterone Receptors (PR) and Epidermal Growth Factor Receptor 2 (HER2), but also on the evaluation of clinical and pathological parameters. However, although this has been a successful approach, some patients relapse or eventually develop resistance to treatment. Taking into account the high frequency of patients who do not respond to therapy or who develop resistance to it over time, and the role played by the GLI1, ZNF217 and KI67 genes, the evaluation of the expression of these genes in MC cell lines treated with different drugs, this in order to understand the role that these genes play in therapy and as possible biomarkers in the development of new personalized therapeutic strategies. The results of this study show that the expression of these genes is modified depending on the state of RE and HER2 in tumor cells. For example, in RE + / RP + / HER2- cells, the GLI1 gene could be considered as a biomarker of response to treatment, either individually or in combination. On the contrary, it is observed that in RE- / RP- / HER2- cells, where the GLI1, ZNF217 and KI67 genes could be considered as biomarkers of resistance independent of whether the treatment is individual or combined. Regarding RE- / RP- / HER2 + cells, these genes respond in different ways to each of the treatments, which translates into a more complex response.
