Studies of the normal functions and diseases of the prostate request in vivo models that maintain the tissue architecture and the multiple-cell type compartments of human origin in order to recapitulate reliably the interactions of different cell types. Cell type-specific transcriptomes are critical to reveal the roles of each cell type in the functions and diseases of the prostate. A primary prostate tissue xenograft model was developed using fresh human prostate tissue specimens transplanted onto male mice that were castrated surgically and implanted with a device to maintain circulating testosterone levels comparable to adult human males. Endothelial cells and epithelial cells were isolated from 7 fresh human prostate tissue specimens and from primary tissue xenografts established from 9 fresh human prostate tissue specimens, using antibody-conjugated magnetic beads specific to human CD31 and human EpCAM, respectively. Transcriptomes of endothelial, epithelial and stromal cell fractions were obtained using RNA-Seq. Global and function-specific gene expression profiles were compared in inter-cell type and inter-tissue type manners. Gene expression profiles in the individual cell types isolated from xenografts were similar to those of cells isolated from fresh tissue, demonstrating the value of the primary tissue xenograft model for studies of the interrelationships between prostatic cell types and the role of such interrelationships in organ development, disease progression, and response to drug treatments.

Introduction and objectives: Androgen receptor (AR) is involved in development prostate cancer (CaP), and is a primary target for treatment of CaP. Androgen deprivation therapy (ADT) inhibits AR signaling by reducing AR ligands and/or blocking AR-ligand binding. ADT induces apoptosis of both endothelial cells and epithelial cells of human prostate, with apoptosis of endothelial cells preceding the apoptosis of epithelial cells. Further, the AR response to stimulation by androgen also differs between the 2 cell types. The current understanding of AR signaling was gained predominantly using CaP cell lines and samples prepared from whole tissue specimens. The present study sought to delineate AR signaling specifically in endothelial, epithelial, and stromal cells isolated from fresh clinical prostate tissue specimens and primary xenografts of human prostate tissue. Our results reveal the potentially different roles of AR signaling in different human prostate cell compartments, how AR regulates normal differentiated cell functions, and the biological consequences of ADT. Methods: Prostate tissue remnants were transplanted to male nude mice that were castrated and implanted with a sustained delivery device to maintain testosterone at human plasma levels. Endothelial and epithelial cells of both fresh prostate tissue and prostate tissue xenografts were isolated sequentially using magnetic beads conjugated with an antibody specific to epithelial cell or endothelial cell surface markers; the remaining cell fraction was defined as stromal cells. Transcriptomes were obtained using RNASeq, and were analyzed for differential expression of AR-regulated genes, AR co-regulators, and androgen metabolism enzymes. Results: Antibody-mediated cell type-specific enrichment isolated effectively the 3 cell types from the prostate from 16 patients. Among 1263 AR-regulated genes, 399, 313, and 223 were predominantly expressed in epithelial, endothelial or stromal cells, respectively. Among 179 AR co-regulators, 26, 26, and 18 were expressed predominantly in epithelial, endothelial or stromal cells, respectively. Among 128 potential androgen metabolic enzyme genes, 42, 15, and 12 were expressed predominantly in epithelial, endothelial or stromal cells, respectively. Conclusions: Differences in expression of genes associated with AR-mediated trans-regulation were apparent between the different cell types of prostate, whereas, the difference in expression of androgen metabolism genes was less striking. Therefore, the organ level outcome of ADT can only be understood by determining the response of the different cell types in CaP tissue. Citation Format: Nelson T. Gross, Jianming Wang, Gary Smith, Yue Wu. Molecular dissection of androgen receptor signaling in prostatic endothelial, epithelial, and stromal cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1015.

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