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Sequential changes in gene expression profiles in breast cancers during treatment with the aromatase inhibitor, letrozole


The study aim was to identify early (within 14 days) and late changes (by 3 months) in breast cancer gene expression profiles associated with neoadjuvant therapy with letrozole. RNA from sequential tumour biopsies in 54 patients was analyzed on microarrays; changes were determined by frequency, magnitude and significance analyses. Substantially more genes were changed at 3 months (1503) than at 14 days (237). Early changed genes were associated with cell cycle (downregulation), blood vessel development and extracellular matrix (upregulation); late changes included ‘cellular metabolic process’, ‘generation of precursor metabolites and energy’ (decreased) and ‘cell adhesion’ ‘biological adhesion‘ (increased). A striking difference between the early and late changes was the general location of downregulated genes—nuclear structures at 14 days and mitochondria after 3 months. These changes in gene expression profiles provide a new and important database by which to understand molecular mechanisms of letrozole in breast cancers.

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Correspondence to W R Miller.

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DBE is an employee and share holder of Novartis Pharma AG. Other authors declare no conflict of interest.

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Miller, W., Larionov, A., Anderson, T. et al. Sequential changes in gene expression profiles in breast cancers during treatment with the aromatase inhibitor, letrozole. Pharmacogenomics J 12, 10–21 (2012).

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  • aromatase inhibitor
  • breast cancer
  • gene expression profiles
  • microarray analysis
  • neoadjuvant treatment

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