Targeting the Androgen Receptor in Breast Cancer
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Targeting the Androgen Receptor in Breast Cancer ______________________________________________________________________ Kee Ming Chia A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy Garvan Institute of Medical Research St. Vincent’s Hospital Clinical School Faculty of Medicine December 2018 iii Thesis/Dissertation Sheet Surname/Family Name : CHIA Given Name/s : KEE MING Abbreviation for degree as given in the : PhD University calendar Faculty : Medicine School : St Vincent’s Hospital Clinical School Thesis Title : Targeting AR in breast cancer Abstract Estrogen receptor positive (ER+) breast cancer constitutes 70% of all breast cancers and anti-ER therapies such as aromatase inhibitors and tamoxifen represent the main therapeutic strategies in the treatment of this disease. Unfortunately, up to 30% of all primary ER+ tumours will ultimately develop endocrine-resistance and progress on ER-targeted therapies resulting in disease-related morbidity. As a result, there is an urgent medical need for novel therapeutic strategies capable of managing endocrine-resistant breast cancer. Androgen receptor (AR) is expressed in up to 90% of ER+ breast cancers. AR functions as a tumour suppressor in primary ER+ breast cancer and high AR positivity is strongly associated with a favourable patient outcome in the ER+ setting. However, the role of AR in endocrine-resistant breast tumours is highly controversial with data supporting both oncogenic and tumour suppressive functions reported in the literature. Here I have used different modulatory approaches on in vitro and in vivo preclinical models to dissect the functions of AR and determine the best approach to target AR in endocrine-resistant breast cancer. I use an siRNA-mediated approach to knock down AR in cell line models and discover that the basal expression of AR contributes to endocrine-resistance and that loss of AR restores classical ER signalling and reverses endocrine-resistance. However, inhibiting the transcriptional activity of AR with enzalutamide does not recapitulate this effect, suggesting that it is the non-canonical activity of AR which contributes to endocrine-resistance. In contrast, I show that activation of AR by either 5-α dihydrotestosterone (DHT) or selective AR modulator enobosarm in vitro and in patient derived (PDX) models of endocrine-resistance results in significant growth suppression. Mechanistically, this growth-inhibitory effect of AR activation is associated with downregulation of ER signalling. Moreover, I identify AR-regulated genes from the global gene expression of an ER+AR+ endocrine-resistant PDX model treated with DHT and establish a highly prognostic AR gene signature based on primary ER+ patients in the METABRIC dataset. This suggests that activity of AR is tumour-suppressive independent of endocrine- sensitivity. In summary, I demonstrate that activation, not antagonism, is the optimal AR-targeted therapeutic strategy in the management of endocrine-resistant breast cancer. i Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorize University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). 18-12-2018 ….……………… …………………………………………………………… ……………………………………..……………… Date Signature Witness Signature The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE Date of completion of ONLY requirements for Award: ii Originality Statement ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed Date 18-12-18 iv COPYRIGHT STATEMENT 'I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in DissertationAbstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have apphed l apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed Date AUTHENTICITY STATEMENT 'I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my the is. No emendation of content has occurred and if there are any minor variati s in formatting, they are the result of the conversion to digital format.' Signed Date 1/t I I q INCLUSION OF PUBLICATIONS STATEMENT UNSW is supportive of candidates publishing their research results during their candidature as detailed in the UNSW Thesis Examination Procedure. Publications can be used in their thesis in lieu of a Chapter if: The student contributed greater than 50% of the content in the publication and is the “primary author”, ie. the student was responsible primarily for the planning, execution and preparation of the work for publication The student has approval to include the publication in their thesis in lieu of a Chapter from their supervisor and Postgraduate Coordinator. The publication is not subject to any obligations or contractual agreements with a third party that would constrain its inclusion in the thesis Please indicate whether this thesis contains published material or not. This thesis contains no publications, either published or submitted for publication ☐ (if this box is checked, you may delete all the material on page 2) Some of the work described in this thesis has been published and it has been ☒ documented in the relevant Chapters with acknowledgement (if this box is checked, you may delete all the material on page 2) This thesis has publications (either published or submitted for publication) ☐ incorporated into it in lieu of a chapter and the details are presented below CANDIDATE’S DECLARATION I declare that: I have complied with the Thesis Examination Procedure where I have used a publication in lieu of a Chapter, the listed publication(s) below meet(s) the requirements to be included in the thesis. Name Signature Date (dd/mm/yy) Kee Ming Chia 18-12-18 v Financial Support and Publications Financial Support NHMRC Dora Lush Scholarship Garvan Institute Postgraduate Top-up scholarship Publications arising from this thesis Hickey, T.E., Selth, L.A., Chia, K. et al, The androgen receptor is a tumour suppressor in estrogen receptor positive breast cancer. (Submitted to Nature in April, 2019). Chia, K., et al., Milioli, H., Portman, N., Laven-Law, G., Coulson, R., Yong, A., Segara, D., Parker, A., Caldon, C. E., Deng, N., Swarbrick, A., Tilley, W. D., Hickey, T. E., & Lim, E. (2019). Non-canonical AR activity facilitates endocrine resistance in breast cancer. Endocr Relat Cancer, 26(2), 251-264. doi: 10.1530/erc-18-0333 Papachristou, E. K., Kishore, K., Holding, A. N., Harvey, K., Roumeliotis, T. I., Chilamakuri, C. S. R., Omarjee, S., Chia, K., Swarbrick, A., Lim, E., Markowetz, F., Eldridge, M., Siersbaek, R., D'Santos, C. S., & Carroll, J. S. (2018). A quantitative mass spectrometry-based approach to monitor the dynamics of endogenous chromatin-associated protein complexes. Nat Commun, 9(1), 2311. doi: 10.1038/s41467-018-04619-5 Chia, K., O'Brien, M., Brown, M., & Lim, E. (2015). Targeting the androgen receptor in breast cancer. Curr Oncol Rep, 17(2), 4. doi: 10.1007/s11912-014-0427-8 vi Presentations Poster International PacRim Meeting, Adelaide Australia 2019 (Best Poster in the Junior Researcher category) San Antonio Breast Cancer Symposium, Texas USA 2018 Gordon Research Conference (Hormone-Dependent Cancers), Maine USA 2017 (Poster Prize) Lorne Cancer Conference in Victoria, Australia 2016 NSW Translational Breast Cancer Research Symposium, NSW Australia 2016 (Poster Prize) Oral