posters International Association for Breast Cancer Research 2014

Identifying downstream targets of the transcription factor ELF5 that mediate anti-oestrogen resistance in breast cancer (#200)

Stephanie Allerdice 1 , Maria Kalyuga 1 , David Gallego-Ortega 1 , Heather J. Lee 1 , Daniel L. Roden 1 , Mark J. Cowley 1 2 , C.Elizabeth Caldon 1 , Andrew Stone 1 , Fatima Valdes-Mora 1 , Rosalind Launchbury 1 , Aaron L. Statham 1 , Nicola Armstrong 1 3 , M.Chehani Alles 1 , Adelaide Young 1 , Andrea Egger 1 , Wendy Au 1 , Catherine L. Piggin 1 , Cara J. Evans 1 , Anita Ledger 1 , Tilman Brummer 1 , Samantha R. Oakes 1 , Warren Kaplan 2 4 , Julia M.W. Gee 1 , Robert I. Nicholson 5 , Robert L. Sutherland 1 4 , Alexander Swarbrick 1 4 , Matthew J. Naylor 1 4 6 , Susan J. Clark 1 4 , Jason S. Carroll 7 , Christopher J. Ormandy 1 4
  1. Cancer Research Program and The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  2. Peter Wills Bioinformatics Centre, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  3. School of Mathematics and Statistics, and Prince of Wales Clinical School, University of New South Wales, Kensington, NSW, Australia
  4. St Vincent’s Clinical School, St Vincent’s Hospital and University of New South Wales, Darlinghurst, NSW, Australia
  5. Breast Cancer (Molecular Pharmacology) Group, Cardiff School of Pharmacy and Pharmaceutical Science, Cardiff University, Cardiff, Wales, United Kingdom
  6. Discipline of Physiology & Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
  7. Cancer Research UK, Cambridge Research Institute, Cambridge, United Kingdom

Rationale: The transcription factor elf5 is crucial for mammary gland development, and we have shown that it predicts breast cancer subtype. Forced expression of elf5 in luminal breast cancer cells has previously shown elf5 to decrease EGFR, IGFR and FGFR due to transcription modulation. In aggressive, basal-like breast cancers elf5 expression is higher compared to endocrine-treatment responsive, oestrogen receptor positive (ER+) luminal breast cancer. Around 40% of women receiving the anti-oestrogen therapy tamoxifen will acquire resistance. In this study we use the ER+ breast cancer cell line MCF-7, as well as a model of acquired tamoxifen resistance (TamR), an MCF-7 derived cell line, which displays higher levels of elf5, and is dependent upon elf5 for their proliferation.

Objective: To determine the significance and role of increased elf5 in anti-endocrine resistant breast cancer

Methods and Results: We have generated stable cell lines containing a doxycycline inducible overexpression vector with V5 tagged elf5 into the MCF-7 and TamR cell lines. Confirming previous results, overexpression of elf5 in the ER+ MCF-7 cell line resulted in a decrease in proliferation, however, despite high endogenous levels of elf5, overexpression of elf5 also resulted in a decrease in proliferation in the TamRs. In order to discover how elf5 mediates anti-estrogen resistance, we will use a triple-pronged approach. We will use stable isotope labelling by amino acids in cell culture (SILAC) in order to determine the effect of elf5 on the whole proteome of these cells. In addition, to explore the possible protein-protein interactions of this transcription factor, we will use an immunoprecipitation approach coupled with mass spectrometry to identify possible binding partners.

Conclusions: Elf5 is an important transcription factor in breast cancer and is important for acquired anti-oestergen resistance. This method will allow us to pinpoint targets that are responsible for anti-estrogen resistance downstream of elf5.