Prior Adjuvant Tamoxifen Treatment in Breast Cancer Is Linked to Increased AIB1 and HER2 Expression in Metachronous Contralateral Breast Cancer

PLoS One. 2016 Mar 9;11(3):e0150977. doi: 10.1371/journal.pone.0150977. eCollection 2016.

Abstract

Aim: The estrogen receptor coactivator Amplified in Breast Cancer 1 (AIB1) has been associated with an improved response to adjuvant tamoxifen in breast cancer, but also with endocrine treatment resistance. We hereby use metachronous contralateral breast cancer (CBC) developed despite prior adjuvant tamoxifen for the first tumor as an "in vivo"-model for tamoxifen resistance. AIB1-expression in the presumable resistant (CBC after prior tamoxifen) and naïve setting (CBC without prior tamoxifen) is compared and correlated to prognosis after CBC.

Methods: From a well-defined population-based cohort of CBC-patients we have constructed a unique tissue-microarray including >700 patients.

Results: CBC developed after adjuvant tamoxifen more often had a HER2-positive/triple negative-subtype and a high AIB1-expression (37% vs. 23%, p = 0.009), than if no prior endocrine treatment had been administered. In patients with an estrogen receptor (ER) positive CBC, a high AIB1-expression correlated to an inferior prognosis. However, these patients seemed to respond to tamoxifen, but only if endocrine therapy had not been administered for BC1.

Conclusions: Metachronous CBC developed after prior endocrine treatment has a decreased ER-expression and an increased HER2-expression. This is consistent with endocrine treatment escape mechanisms previously suggested, and indicates metachronous CBC to be a putative model for studies of treatment resistance "in vivo". The increased AIB1-expression in CBC developed after prior tamoxifen suggests a role of AIB1 in endocrine treatment resistance. In addition, we found indications that the response to tamoxifen in CBC with a high AIB1-expression seem to differ depending on previous exposure to this drug. A different function for AIB1 in the tamoxifen treatment naïve vs. resistant setting is suggested, and may explain previously conflicting results where a high AIB1-expression has been correlated to both a good response to adjuvant tamoxifen and tamoxifen resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents, Hormonal / therapeutic use
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism*
  • Female
  • Humans
  • In Vitro Techniques
  • Male
  • Middle Aged
  • Nuclear Receptor Coactivator 3 / metabolism*
  • Receptor, ErbB-2 / metabolism*
  • Receptors, Estrogen / metabolism
  • Tamoxifen / therapeutic use*

Substances

  • Antineoplastic Agents, Hormonal
  • Receptors, Estrogen
  • Tamoxifen
  • NCOA3 protein, human
  • Nuclear Receptor Coactivator 3
  • Receptor, ErbB-2

Grants and funding

This work was supported by the Swedish Breast Cancer Association (BRO) (2011, 2014, SA); the Skåne University Hospital foundation (2014-94413, SA); the Percy Falk Foundation (2011, SA); the Swedish Cancer Society (13 0499, MF); the Swedish Research Council (B0262601, 521-2011-3021, MF); the Gunnar Nilsson Cancer Foundation (2013, 2014, MF); the Mrs. Berta Kamprad Foundation (11/2014, MF); the Anna and Edwin Berger’s Foundation (2014, MF); Skane County Council’s Research and Development Foundation (REGSKANE-434091, 286421, SA and LR); the Swedish Cancer and Allergy Foundation (150423/2014, MF); and the Governmental Funding of Clinical Research within the National Health Service (2011-2014, MF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.