RESUMEN
BACKGROUND: MicroRNAs (miRNAs) are involved in the regulation of genes with important roles in cancer. Therefore, they represent interesting targets as biomarkers for early detection, follow-up, and prognosis of the disease. CONTEXT: In early stages of breast cancer, differences in the expression of miR-148b-3p, miR-145-5p and miR-133a-3p have been reported. AIMS: To compare the expression of miR-148b-3p, miR-145-5p and miR-133a-3p in serum samples from female patients with and without breast cancer. SETTING AND DESIGN: Case control study. MATERIALS AND METHODS: We quantified the expression by real-time polymerase chain reaction of miR-148b-3p, miR-145-5p, and miR-133a-3p in serum samples from 27 breast cancer (BC) and 17 benign breast tumor patients. STATISTICAL ANALYSIS USED: Comparison between groups with categorical variables was made using the Pearson's Chi-square test. Comparative analysis for continuous variables between two groups was performed using the Student's t-test. One-way analysis of variance (ANOVA) was used for multigroup comparison, followed by Tukey HSD analysis. RESULTS: The use of contraceptives and a high number of births were identified as risk factors for BC. We observed that miR-145-5p expresses in low levels in BC and positively diagnosed Her2 patients. In addition, BC patients with either ductal carcinoma or positive molecular diagnosis for estrogen receptor, progesterone receptor, luminal A, or Her2 negative, presented a decreased expression of miR-133a-3p. CONCLUSIONS: We observed an existing association between the molecular characteristics of BC and levels of circulating miR-133a-3p and miR-145-5p, proving the potential role of miRNAs as biomarkers for BC.