Laboratório de Oncogenética e Radiobiologia e Laboratório de Biologia Tumoral, Associação de Combate ao Câncer em Goiás, Goiânia-GOMicro-RNAs (miRNAs) are non-coding short RNAs that function as post-transcriptional regulators by targeting mRNAs, and either, degrading mRNA or inhibiting translation. In essence, miRNAs add an extra level of regulation to gene expression, and studies are rapidly emerging on their role in diseases, including cancer. BRCA1 is a tumor suppressor protein that plays a critical role in DNA repair, cell cycle checkpoint control, and maintenance of genomic stability. Inherited mutations in BRCA1 gene significantly increase breast cancer (BC) risk, and BRCA1 activity also seems to be important in BC prognostic. The present study aimed to evaluate the possible association between BRCA1 protein expression and miR-7 and miR-10b expression levels in BCs. The group included 36 triple negative (TN) and 56 non-triple negative (NTN) patients. Total RNA was extracted from paraffin-embedded BC tissues by using miRNeasy FFPE kit (Qiagen N.V., Hilden, Germany). RNA quality and quantity were determined by NanoDrop spectrophotometer (Thermo Scientific, Wilmington, USA). Real-time PCR was performed in a StepOne Real-time PCRs system (AppliedBiosystems™, Life Technologies, Carlsbad, USA) by using miScript SYBR® Green PCR kit (Qiagen N.V., Hilden, Germany) for hsa-miR-7 and hsa-miR-10b expression levels determination. BRCA1 protein expression was evaluated by immunohistochemistry (IHC), using BRCA1 mouse monoclonal antibody (SC-56030 BRCA1 GLK-2, Santa Cruz Biotechnology, Santa Cruz, USA). Lack of BRCA1 protein expression was observed in 26 TN patients (72.2%) and in 28 NTN (50%) (p=0.034). Expression levels of miR-7 and miR-10b were sixteen-fold and two-fold increased, respectively, in TN compared to NTN (p<0.05). Moreover, miR-7 and miR-10b were also overexpressed in BRCA1 negative BCs (p<0.05). Our preliminary results demonstrated that miR-7 and miR-10b expression levels could be associated to BRCA1 expression, especially in patients with triple negative tumors. BRCA1, micro-RNA, miR-7, miR-10b, triple-negative breast cancer.
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