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Åke Borg

Åke Borg

Principal investigator

Åke Borg

Genomic subtypes of breast cancer identified by array-comparative genomic hybridization display distinct molecular and clinical characteristics

Author

  • Göran B Jönsson
  • Johan Staaf
  • Johan Vallon-Christersson
  • Markus Ringnér
  • Karolina Holm
  • Cecilia Hegardt
  • Haukur Gunnarsson
  • Rainer Fagerholm
  • Carina Forsare
  • Bjarni A. Agnarsson
  • Outi Kilpivaara
  • Lena Luts
  • Paivi Heikkila
  • Kristiina Aittomaki
  • Carl Blomqvist
  • Niklas Loman
  • Per Malmström
  • Håkan Olsson
  • Oskar Th Johannsson
  • Adalgeir Arason
  • Heli Nevanlinna
  • Rosa B. Barkardottir
  • Åke Borg
Show all

Summary, in English

Introduction: Breast cancer is a profoundly heterogeneous disease with respect to biologic and clinical behavior. Gene-expression profiling has been used to dissect this complexity and to stratify tumors into intrinsic gene-expression subtypes, associated with distinct biology, patient outcome, and genomic alterations. Additionally, breast tumors occurring in individuals with germline BRCA1 or BRCA2 mutations typically fall into distinct subtypes. Methods: We applied global DNA copy number and gene-expression profiling in 359 breast tumors. All tumors were classified according to intrinsic gene-expression subtypes and included cases from genetically predisposed women. The Genomic Identification of Significant Targets in Cancer (GISTIC) algorithm was used to identify significant DNA copy-number aberrations and genomic subgroups of breast cancer. Results: We identified 31 genomic regions that were highly amplified in > 1% of the 359 breast tumors. Several amplicons were found to co-occur, the 8p12 and 11q13.3 regions being the most frequent combination besides amplicons on the same chromosomal arm. Unsupervised hierarchical clustering with 133 significant GISTIC regions revealed six genomic subtypes, termed 17q12, basal-complex, luminal-simple, luminal-complex, amplifier, and mixed subtypes. Four of them had striking similarity to intrinsic gene-expression subtypes and showed associations to conventional tumor biomarkers and clinical outcome. However, luminal A-classified tumors were distributed in two main genomic subtypes, luminal-simple and luminal-complex, the former group having a better prognosis, whereas the latter group included also luminal B and the majority of BRCA2-mutated tumors. The basal-complex subtype displayed extensive genomic homogeneity and harbored the majority of BRCA1-mutated tumors. The 17q12 subtype comprised mostly HER2-amplified and HER2-enriched subtype tumors and had the worst prognosis. The amplifier and mixed subtypes contained tumors from all gene-expression subtypes, the former being enriched for 8p12-amplified cases, whereas the mixed subtype included many tumors with predominantly DNA copy-number losses and poor prognosis. Conclusions: Global DNA copy-number analysis integrated with gene-expression data can be used to dissect the complexity of breast cancer. This revealed six genomic subtypes with different clinical behavior and a striking concordance to the intrinsic subtypes. These genomic subtypes may prove useful for understanding the mechanisms of tumor development and for prognostic and treatment prediction purposes.

Department/s

  • Breastcancer-genetics
  • Pathology, Malmö
  • EpiHealth: Epidemiology for Health

Publishing year

2010

Language

English

Publication/Series

Breast Cancer Research

Volume

12

Issue

3

Document type

Journal article

Publisher

BioMed Central (BMC)

Topic

  • Cancer and Oncology

Status

Published

Research group

  • Pathology, Malmö

ISBN/ISSN/Other

  • ISSN: 1465-5411