Análise da expressão de miR-10b e miR-7 potencialmente associados à expressão de BRCA1 em carcinomas de mama

Abstract

Introduction: Breast cancer is the most frequent neoplasm among women worldwide and represents the leading cause of death in this population. Important biomarkers have been studied in order to better define the prognosis of patients affected by this cancer. MicroRNAs are small molecules of non-coding RNAs composed of 21 to 25 nucleotides that play an important role in the post-transcriptional regulation of several genes. Objective: The objective of this study was to evaluate the expression of microRNAs (miRNAs: hsa-miR-7 and hsa-miR-10b) and BRCA1 protein in breast cancer samples, as well as the possible associations between expression of these markers with clinicopathological and prognostic aspects. Method: The study included 92 cases of breast carcinoma from Hospital Araújo Jorge, Associação de Combate ao Câncer em Goiás. Formalin fixed paraphin embedded samples were used for the analisis. MicroRNA was extracted from the samples and used for cDNA synthesis. The cDNA samples were adjusted to the same concentration and submitted to quantitative real-time PCR (qRT-PCR). Samples were further evaluated by immunohistochemistry for BRCA1 expression. Results: From a group of 234 immunohistochemical records, 56 cases of non-triple-negative and 36 triple-negative breast carcinomas were selected. Five-year overall survival was significantly associated to triple negative phenotype (p = 0.044), advanced stages (p = 0.005), lymph node involvement (p = 0.038), presence of distant metastasis (p = 0, 0008) and absence of BRCA1 expression (p = 0.039). Significant associations were demonstrated between the absence of BRCA1 and the triple-negative phenotype (p = 0.0346), as well as the absence of estrogen receptor expression (p = 0.006) and absence of progesterone receptor expression (p = 0.0163). The analysis by qRTPCR demonstrated different levels of miR-10b and miR-7 expression in the tumors, with significant associations with triple-negative phenotype (p = 0.021, p = 0.042) and the absence of BRCA1 (p = 0.039, p = 0.006). The comparison between absence and presence of human epidermal growth factor receptor expression showed a significant difference for miR-7 (p = 0.031), and the expression of miR-10b in these cases was not statistically different (p = 0.926). Conclusion: Significant associations were demonstrated between the absence of BRCA1 and the triple-negative phenotype. Five-year overall survival was reduced for the triple-negative phenotype patients, clinical stages III and IV, the presence of lymph node metastasis, the presence of distant metastasis and the absence of BRCA1 expression. This study also demonstrated that hsa-miR-7 and hsa-miR-10b are significantly associated with the absence of BRCA1 expression and triple-negative phenotype, with poorer survival in these patient profiles. Studies with more cases and with cell lines should be performed in order to confirm the role of hsa-miR-7 and hsa-miR-10b in the modulation of BRCA1 expression.