Differential expression of miR-124 and miR-155 in tumor tissue of breast before and after neoadjuvant chemotherapy
Summary. Recently, numerous studies have shown the important role of microRNAs in the development of cancer. They are proposed as potential biomarkers for the cancer diagnosis and therapy. We examined the potential of the tumor suppressor miR-124 and oncogen miR-155 in patients with breast cancer (BC) before and after neoadjuvant chemotherapy (NACT). The BC was characterized by decreasing of miR-124 expression level and by overexpression of miR-155. These expression violations of microRNAs mainly contribute to tumor growth. Our results have shown that the aberrant expression of miR-155 is present in the human BC. After NACT miR-124 expression was restored. This result can be characterized as positive effect, since this microRNA causes silencing of genes which are responsible for tumor growth and progression. The persistent overexpression of miR-155 after NACT may indicate necessity to test this miRNA during the treatment for understanding its role in chemoresistance. Further investigations will be required in order to examine these markers and to assess their reliability in identifying patients with the BC and in monitoring the effectiveness of the treatment.
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