BRCA1 regulation of epidermal growth factor receptor (EGFR) expression in human breast cancer cells involves microRNA-146a and is critical for its tumor suppressor function

Oncogene. 2015 Aug 13;34(33):4333-46. doi: 10.1038/onc.2014.363. Epub 2014 Nov 24.

Abstract

Breast cancer 1 (BRCA1)-associated breast cancers are mostly basal-like high-grade ductal carcinomas that frequently overexpress epidermal growth factor receptor (EGFR). Aberrant EGFR expression is correlated with disease progression, resistance to radiation and chemotherapy, and poor clinical prognosis. Although BRCA1 is involved in multiple cellular processes, its functional role in EGFR regulation remains enigmatic. Here, we report a previously unrecognized posttranscriptional mechanism by which BRCA1 regulates EGFR expression through the induction of miR-146a. We demonstrate that EGFR expression correlates negatively with BRCA1, whereas miR-146a levels increase with BRCA1. We show that BRCA1 binds to MIR146A promoter and activates transcription, which in turn attenuates EGFR expression. Knockdown of miR-146a in BRCA1-overexpressing cells negated this effect and suppressed its ability to inhibit proliferation and transformation. In archived triple-negative breast cancer samples, we show a strong positive correlation between BRCA1 and miR-146a expression. We also show that low expression of miR-146a strongly predicts positive lymph node status and is associated with distinctively poor overall survival of patients. Together, these observations provide an insight into a novel BRCA1miR-146aEGFR paradigm by which BRCA1 carries out an aspect of tumor suppressor function that is potentially amenable to therapeutic intervention.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • BRCA1 Protein / genetics*
  • Cell Line, Tumor
  • Cell Proliferation / genetics
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / pathology
  • ErbB Receptors / genetics*
  • Female
  • Humans
  • Lymph Nodes / pathology
  • MicroRNAs / genetics*
  • Promoter Regions, Genetic / genetics
  • RNA Processing, Post-Transcriptional / genetics
  • Transcriptional Activation / genetics
  • Triple Negative Breast Neoplasms / genetics*
  • Triple Negative Breast Neoplasms / pathology
  • Tumor Suppressor Proteins / genetics

Substances

  • BRCA1 Protein
  • MIRN146 microRNA, human
  • MicroRNAs
  • Tumor Suppressor Proteins
  • EGFR protein, human
  • ErbB Receptors