Mirna21 Expression in the Breast Cancer Tumor Tissue is Independent of Neoadjuvant Chemotherapy

MicroRNA-21 (miRNA-21) has been described as one of the most significantly upregulated miRNAs in human breast cancer. However, limited knowledge exists on miRNA-21 expression in breast cancer tissue after neoadjuvant chemotherapy (NAC). The aim of this study was to assess miRNA-21 expression in the tumor tissues of Brazilian patients with breast cancer who underwent NAC and its correlation with clinicopathological variables. Utilizing qRT-PCR, miRNA-21 expression in tumor tissue was measured in a cohort of female patients with breast cancer who underwent NAC. The correlation of miRNA-21 expression with breast cancer molecular subtypes and other clinicopathological variables was also assessed. A total of 55 patients were included in the study, and 28 (50.9%) underwent NAC. miRNA-21 was upregulated in patients with breast cancer, regardless of previous exposure to chemotherapy, molecular subtypes, tumor-node-metastasis (TNM) staging and lymph node status of the axilla. miRNA-21 expression did not differ between patients with breast cancer who achieved a pathologic complete response after NAC and healthy controls. miRNA-21 was upregulated in the tumor tissue of Brazilian patients with breast cancer regardless of NAC treatment, which reinforces its role as an "oncomiR" and a potential biomarker.