An optical proteomic profile of the HER2 family in breast tumours and the effect of exposure to tyrosine kinase inhibitors

    Student thesis: Doctoral ThesisDoctor of Philosophy


    My hypothesis is that delineation of the effects of HER2-targeted therapy with the tyrosine kinase inhibitor (TKI) lapatinib, in vitro, and elucidation of the ensuing conformational changes may help understand the molecular activity of lapatinib and elucidate mechanisms of resistance. Clinical translation of this knowledge may help to improve performance of current biopsy-derived biomarkers, bringing real patient benefits.
    HER2-targeted treatments such as the monoclonal antibody, trastuzumab and the tyrosine kinase inhibitor (TKI) lapatinib, were developed for HER2-positive breast cancer patients; a group with a poor prognosis. However trastuzumab induces response in only 40% of patients and resistance inevitably develops to both drugs. HER2:HER3 dimerisation is vital to the translation of extracellular signals, via intracellular signaling cascades, to promote cancer cell proliferation, invasion and metastasis, and is studied herein. Regulation of the amplitude and kinetics of signal transduction from the HER family is reliant upon receptor endocytosis, and sorting to recycling or degradation. As these processes are likely to play a key role in treatment of HER2-positive breast cancer and the development of resistance, they are investigated in this project.
    Within the context of this work, optical proteomics quantifies post-translational modifications and protein-protein interactions by measuring Förster resonance energy transfer (FRET). Where fluorophores are located within nanometer proximity, FRET occurs, thus allowing quantification of protein-protein interactions. This novel technology is used alongside traditional biochemical methods, to demonstrate HER2/3 dimerisation, and the effect of perturbation of this system by lapatinib.
    Treatment with lapatinib abolishes HER2 phosphorylation but stabilises the HER2:HER3 dimer. Mutation at the HER2:HER3 intracellular interface prevents HER2:HER3 dimerisation and negates the lapatinib effect. Resistance may be mediated by endocytosis of the HER2:HER3 dimer, recycling and rephosphorylation of HER3.
    Fluorophore-conjugated antibodies have been optimised in cell lines, with the development of dual antibody assays to measure HER2:HER3 dimerisation in paraffin embedded tumour tissue. A prospective clinical trial is being set up in order to validate these assays alongside clinico-pathological and genetic biomarkers for prediction of response to HER2-targeted therapy.
    Date of Award1 Jun 2013
    Original languageEnglish
    Awarding Institution
    • King's College London
    SupervisorTony Ng (Supervisor), Paul Ellis (Supervisor) & Cheryl Gillett (Supervisor)

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