BRCA1-Mutated Estrogen Receptor-Positive Breast Cancer Shows BRCAness, Suggesting Sensitivity to Drugs Targeting Homologous Recombination Deficiency

Clin Cancer Res. 2017 Mar 1;23(5):1236-1241. doi: 10.1158/1078-0432.CCR-16-0198. Epub 2016 Sep 12.

Abstract

Purpose: As estrogen receptor-positive (ER+) breast cancer in BRCA1 mutation carriers arises at an older age with less aggressive tumor characteristics than ER-negative (ER-) BRCA1-mutated breast cancer, it has been suggested that these tumors are "sporadic" and not BRCA1 driven. With the introduction of targeted treatments specific for tumors with a nonfunctioning BRCA1 or BRCA2 gene, the question whether the BRCA genes are impaired in the tumor is highly relevant. Therefore, we performed genomic profiling of BRCA1-mutated ER+ tumors.Experimental Design: Genomic profiling, BRCA1 promoter methylation assessment, and loss of heterozygosity analysis were done on 16 BRCA1-mutated ER+ tumors. Results were compared with 57 BRCA1-mutated ER- tumors, 36 BRCA2-mutated ER+-associated tumors, and 182 sporadic ER+ tumors.Results: The genomic profile of BRCA1-mutated ER+ tumors was different from BRCA1-mutated ER- breast tumors, but highly similar to BRCA2-mutated ER+ tumors. In 83% of the BRCA1-mutated ER+ tumors, loss of the wild-type BRCA1 allele was observed. In addition, clinicopathologic variables in BRCA1-mutated ER+ cancer were also more similar to BRCA2-mutated ER+ and sporadic ER+ breast cancer than to BRCA1-mutated ER- cancers.Conclusions: As BRCA1-mutated ER+ tumors show a BRCAness copy number profile and LOH, it is likely that the loss of a functional BRCA1 protein plays a role in tumorigenesis in BRCA1-mutated ER+ tumors. Therefore, we hypothesize that these tumors are sensitive to drugs targeting the BRCA1 gene defect, providing new targeted treatment modalities for advanced BRCA-deficient, ER+ breast cancer. Clin Cancer Res; 23(5); 1236-41. ©2016 AACR.

MeSH terms

  • Adult
  • Aged
  • BRCA1 Protein / genetics*
  • BRCA2 Protein / genetics
  • Biomarkers, Tumor / genetics*
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology
  • Carcinogenesis / genetics
  • DNA Copy Number Variations / genetics
  • Female
  • Homologous Recombination / genetics
  • Humans
  • Loss of Heterozygosity / genetics
  • Middle Aged
  • Mutation
  • Receptors, Estrogen / genetics*

Substances

  • BRCA1 Protein
  • BRCA1 protein, human
  • BRCA2 Protein
  • Biomarkers, Tumor
  • Receptors, Estrogen