Date of Degree
PhD (Doctor of Philosophy)
Molecular Physiology and Biophysics
Michael E. Wright
First Committee Member
Robert C Piper
Second Committee Member
Michael D Henry
Third Committee Member
Thomas J Schmidt
Fourth Committee Member
David M Lubaroff
Fifth Committee Member
Mark A Stamnes
Aberrant androgen receptor (AR) activity plays a critical role in the development and progression of both early-staged organ-confined and late-staged metastatic human prostate cancer. Recent large-scale genomic sequencing studies showed that ~50% of organ-confined prostate cancer patients have genetic rearrangements that placed the ETS transcription factors (e.g. ERG, ETV1) under the control of androgen-regulated gene promoters such as TMPRSS2. This results in the upregulation of the ETS transcription factors’ expressions in the presence of androgens. The aberrant overexpression of the ETS transcription factors are shown to induce the expression of genes that promote the cellular motility and invasive potential of prostate-tumor cells. Moreover, the improved therapeutic outcome of the second-generation anti-androgen therapies (e.g. abiraterone and enzalutamide) are encouraging, and prove that aberrant AR activity still drives the progression of metastatic prostate cancer. Although these treatments are initially effective, these cancer cells eventually develop resistance to these AR-targeted therapies termed castration-resistant prostate cancer (CRPC). Since the molecular steps involved in AR activation is still not clearly defined, it is critical to define the interactions required for AR activation prostate cancer cells, which will provide a framework for establishing more effective treatments to inhibit aberrant AR activity in human prostate cancer cells.
Here, I developed a cellular system to isolate ligand-dependent interactions of AR in prostate-tumor cells. A siRNA luciferase screen was also developed and identified novel modulators of AR-mediated transcription selected from the proteomic dataset. Further biochemical studies showed that AR is associated with the Golgi membrane in a ligand-sensitive manner. And that the nuclear localization of ARA160, an AR coactivator, is regulated by the COPI retrograde trafficking machinery. Collectively, these results support the use of this cellular system to decipher the known AR-interacting proteins and novel components involved in AR signaling in prostate-tumor cells.
I next investigated the androgen-sensitive AR transcriptional complexes and androgen-sensitive microsomes isolated from LNCaP prostate-tumor cells. Both studies yielded results that would further strengthen the diverse AR actions mediated within the cell. These results further support the notion that there is significant crosstalk amongst different cell surface receptor signaling pathways with AR. An extension of the androgen-sensitive microsome findings also led us to study the androgen-sensitive G-protein coupled receptor, CXCR7. I showed that androgens regulate the expressions of CXCR7 and CXCR4 and in turn modulated CXCL12-mediated motility in prostate tumor cells.
Lastly, biochemical strategies were developed to detect differences in glycoprotein expression of frozen prostate cancer tissues isolated from human patients. I showed that the workflow successfully solubilized and isolated N- and O-linked glycoproteins from the frozen tissue samples and can be analyzed by quantitative mass spectrometry. This workflow would thus facilitate future biomarker studies. In summary, these data demonstrate the utility of developing methods for the comprehensive mapping of AR-mediated signaling in prostate cancer cells, and thus provide novel target candidates for the therapeutic treatment of metastatic or CRPC.
Metastatic prostate cancer is an incurable disease that is dependent on androgen receptor (AR) activity. Current research has been focused on developing drugs targeting the receptor directly. Here, alternative strategies were presented to discover determinants of AR activity from a global perspective. The goal was to comprehensively define how AR works by understanding what protein interactions facilitate AR activation in prostate cancer cells. By defining the critical components required for AR activity, this information can be used to develop new therapeutic strategies to inhibit aberrant AR activity in prostate cancer cells. For my thesis project, I have laid the groundwork by developing new methods and utilizing new technologies that will advance our understanding of how AR works in prostate cancer cells. The initial data were encouraging and validated our experimental approach. Future studies will be required to obtain a greater understanding of all the components involved in AR activation, which will contribute to the development of better therapeutic treatments for patients afflicted with prostate cancer.
Androgen, Androgen receptor, Mass Spectrometry, Protein complexes, Proteomics, Steroid hormone receptor
xvi, 269 pages
Includes bibliographical references (pages 249-269).
Copyright © 2015 Jordy Jame Hsiao
Hsiao, Jordy Jame. "Quantitative proteomics of androgen receptor-mediated signaling networks in prostate tumor cells." PhD (Doctor of Philosophy) thesis, University of Iowa, 2015.