# Gene expression patterns of breast carcinomas distinguish tumor subclasses with clinical implications

Source: https://onco.cc/key-papers/paper-sorlie-breast-carcinoma-subclasses-pnas-2001/  
OnCo record `paper-sorlie-breast-carcinoma-subclasses-pnas-2001` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The 2001 follow-up showing that the gene-expression groups of breast cancer predict how patients fare, with the basal-like group doing worst; it made the subtypes clinical rather than descriptive.

## Summary

Sørlie, Perou, Tibshirani, Aas and colleagues analysed 85 cDNA microarray experiments representing 78 cancers, three fibroadenomas and four normal breast tissues by hierarchical clustering. As reported earlier, the cancers separated into a basal epithelial-like group, an ERBB2-overexpressing group and a normal breast-like group; the luminal, oestrogen receptor-positive group divided into at least two subgroups with distinct profiles. The subtypes were robust to two gene sets (456 intrinsic clones and an outcome-correlated set). In a subcohort of locally advanced cancers treated uniformly in a prospective study, outcomes differed significantly by group, with a poor prognosis for the basal-like subtype and a difference between the two oestrogen receptor-positive groups.

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Tags: tnbc-evidence
- Journal: Proceedings of the National Academy of Sciences
- Year: 2001
- DOI: 10.1073/pnas.191367098
- Authors: Sørlie T, Perou CM, Tibshirani R, et al.
- Findings: 78 cancers clustered into basal-like, ERBB2-overexpressing, normal-like and at least two luminal subgroups.; Significantly different outcomes by subtype in uniformly treated locally advanced disease; basal-like had a poor prognosis.
- What it means: The first evidence that the basal-like group is not just biologically distinct but clinically dangerous, the observation that triple-negative outcome studies of 2007 confirmed in the clinic.
- Caveats: Survival analysis on a subcohort of locally advanced disease.; Microarray platforms of the period; subtype calls were later standardised as PAM50.

## Sources

- Proc Natl Acad Sci 2001: https://doi.org/10.1073/pnas.191367098
- PubMed: https://pubmed.ncbi.nlm.nih.gov/11553815/

## Connected records

- key papers: [Molecular portraits of human breast tumours](https://onco.cc/key-papers/paper-perou-molecular-portraits-breast-tumours-nature-2000/)
- cancers: [HER2-positive breast cancer](https://onco.cc/cancers/breast-her2-positive/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- terms: [PAM50 / intrinsic subtypes](https://onco.cc/terms/pam50/)
- people: [Charles M. Perou](https://onco.cc/people/charles-perou/)
- journals: [Proceedings of the National Academy of Sciences](https://onco.cc/journals/pnas/)
- roadmaps: [Triple-negative breast cancer roadmap: from a remainder defined by three negative tests to immunotherapy, antibody-drug conjugates and the residual disease problem](https://onco.cc/roadmaps/tnbc-roadmap/)

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