Localized prostate cancer can be treated surgically or by radiotherapy. However, a large percentage of men will already have metastatic disease upon initial diagnosis. The only effective systemic therapy available for metastatic prostate cancer is androgen deprivation. The inability of androgen deprivation to completely and permanently eliminate all prostate cancer cell populations is manifested by the predictable pattern of initial response and relapse with the ultimate progression to androgen independence. Androgen deprivation is associated with a gradual transition of prostate cancer cells through a spectrum of androgen dependence, androgen sensitivity and ultimately androgen independence. There is mounting evidence supporting the concept that prostate cancer progression is accompanied by a shift in reliance on endocrine controls to paracrine and eventually autocrine controls and that this complex process is the result of changes, which occur at molecular levels of cellular control. However, the molecular mechanisms involved in the development of androgen independent prostate cancer are unknown. Investigation of these molecular mechanisms has been impeded by problems related to cell heterogeneity of biopsy material and the lack of an ideal in vivo model. Available human xenograft models that progress to androgen independence after castration of the host yield tumors that are highly contaminated with host cells. Therefore, we have developed an in vivo model that encompasses the use of hollow fibers to retrieve uncontaminated packages of prostate cancer cells (tumors) that can be used for subsequent molecular biology analyses of the progression of prostate cancer to androgen independence. We propose to characterize gene expression in cells harvested from animals both prior and subsequent to the onset of androgen independent tumor progression.
Specific Aim 1 will employ serial analysis of gene expression technology (SAGE) and Affymetrix GeneChips, while in Aim 2, ICATLC/ MC/MS and two-dimensional gel electrophoresis (2D gels) will be used to identify changes in protein expression in during progression of prostate cancer cells to androgen independence. A double pronged approach is required to identify global changes in expression in the transcriptome and proteome during progression to androgen independence. The results of Aims 1 and 2 will be confirmed using in situ hybridization and/or immunohistochemistry in clinical samples from prostate cancer patients before and after xenografting into hosts. We are in a unique position, having both access to the only model available that provides uncontaminated (by host cells) sources of RNA and protein during the stages of progression of prostate cancer cells to androgen independence, proven expertise and facilities for SAGE library construction, sequencing, bioinformatic analysis, and a novel human xenograft model. The data obtained from these studies will be used to identify important pathways and molecular mechanisms involved in the progression of prostate cancer to androgen independence. Only through the identification of these pathways and mechanisms can new targets and therapeutics be developed that may potentially delay or avert the progression of prostate cancer to androgen independent disease. ? ?
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