title: Estrogen independent gene expression defines clinically relevant subgroups of estrogen receptor positive breast cancer.
abstract: BACKGROUND
  Human breast cancer represents a significantly heterogeneous disease. Global gene expression profiling measurements have been used to classify tumors into multiple molecular subtypes. The capacity to define subtypes of breast tumors provides a framework to enable improved understanding of the mechanisms of breast oncogenesis, as well as to provide opportunities for improved therapeutic intervention in patients.
  
  
  METHODS
  We used publicly available gene expression profiling data to identify 'estrogen independent' genes in estrogen receptor alpha (ER+) breast tumors, and subsequently identified 6 subgroups of ER+breast tumors.
  
  
  RESULTS
  Each of the 6 identified subgroups exhibited distinct clinical behaviors and biology. Patients whose tumors comprised subgroups 2,5&6 experienced excellent long-term survival, whereas those patients whose tumors belonged to subgroups 1&4 experienced much poorer survival. Breast tumor cell lines representative of the different subgroups responded to therapeutic compounds in accordance with their subgroup classification.
  
  
  CONCLUSIONS
  These data support the existence of 6 distinct subgroups of ER+breast cancer and suggest that knowledge of the ER+subgroup status of patient samples have the potential to guide therapy choice.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Hallett
authors.affiliation: Department of Biochemistry and Biomedical Sciences, Centre for Functional Genomics, McMaster University, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada. hassell@mcmaster.ca.
authors.forename: John A
authors.initials: JA
authors.lastname: Hassell
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000145:classification* / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D030541:Databases, Genetic; D019008:Drug Resistance, Neoplasm; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011960:Receptors, Estrogen / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D011960:Receptors, Estrogen