Thomas C. Case

Prostate epithelial cell fate.

Androgen receptor (AR) within prostatic mesenchymal cells, with the absence of AR in the epithelium, is still sufficient to induce prostate development. AR in the luminal epithelium is required to express the secretory markers associated with differentiation. Nkx3.1 is expressed in the epithelium in early prostatic embryonic development and expression is maintained in the adult. Induction of the mouse prostate gland by the embryonic mesenchymal cells results in the organization of a sparse basal layer below the luminal epithelium with rare neuroendocrine cells that are interdispersed within this basal layer. The human prostate shows similar glandular organization; however, the basal layer is continuous. The strong inductive nature of embryonic prostatic and bladder mesenchymal cells is demonstrated in grafts where embryonic stem (ES) cells are induced to differentiate and organize as a prostate and bladder, respectively. Further, the ES cells can be driven by the correct embryonic mesenchymal cells to form epithelium that differentiates into secretory prostate glands and differentiated bladders that produce uroplakin. This requires the ES cells to mature into endoderm that gives rise to differentiated epithelium. This process is control by transcription factors in both the inductive mesenchymal cells (AR) and the responding epithelium (FoxA1 and Nkx3.1) that allows for organ development and differentiation. In this review, we explore a molecular mechanism where the pattern of transcription factor expression controls cell determination, where the cell is assigned a developmental fate and subsequently cell differentiation, and where the assigned cell now emerges with its own unique character.

Hepsin cooperates with MYC in the progression of adenocarcinoma in a prostate cancer mouse model.

Hepsin is a cell surface protease that is over‐expressed in more than 90% of human prostate cancer cases. The previously developed Probasin‐hepsin/Large Probasin‐T antigen (PB‐hepsin/LPB‐Tag) bigenic mouse model of prostate cancer demonstrates that hepsin promotes primary tumors that are a mixture of adenocarcinoma and neuroendocrine (NE) lesions, and metastases that are NE in nature. However, since the majority of human prostate tumors are adenocarcinomas, the contribution of hepsin in the progression of adenocarcinoma requires further investigation.

SPARCL1 suppresses metastasis in prostate cancer.

Metastasis, the main cause of death from cancer, remains poorly understood at the molecular level.

Characterization of cis elements of the probasin promoter necessary for prostate-specific gene expression.

The androgen‐regulated probasin (PB) promoter has been used extensively to target transgenes to the prostate in transgenic mice; however, limited data exist on the mechanism that dictates prostate‐specific gene expression. Tissue‐specific gene expression involves synergistic effects among transcription factors associated in a complex bound to cis‐acting DNA elements.

Candidate metastasis suppressor genes uncovered by array comparative genomic hybridization in a mouse allograft model of prostate cancer

BackgroundThe purpose of this study was to identify candidate metastasis suppressor genes from a mouse allograft model of prostate cancer (NE-10). This allograft model originally developed metastases by twelve weeks after implantation in male athymic nude mice, but lost the ability to metastasize after a number of in vivo passages. We performed high resolution array comparative genomic hybridization on the metastasizing and non-metastasizing allografts to identify chromosome imbalances that differed between the two groups of tumors.ResultsThis analysis uncovered a deletion on chromosome 2 that differed between the metastasizing and non-metastasizing tumors. Bioinformatics filters were employed to mine this region of the genome for candidate metastasis suppressor genes. Of the 146 known genes that reside within the region of interest on mouse chromosome 2, four candidate metastasis suppressor genes (Slc27a2, Mall, Snrpb, and Rassf2) were identified. Quantitative expression analysis confirmed decreased expression of these genes in the metastasizing compared to non-metastasizing tumors.ConclusionThis study presents combined genomics and bioinformatics approaches for identifying potential metastasis suppressor genes. The genes identified here are candidates for further studies to determine their functional role in inhibiting metastases in the NE-10 allograft model and human prostate cancer.

Transgenic Mouse Models of Prostate Cancer

The reproductive organs are not required for an individual’s survival but are required for survival of the species. As the individual approaches adulthood, the prostate undergoes developmental changes, resulting in maturation of this gland at puberty. At this stage, the prostate becomes a differentiated gland that produces proteins and other substances fundamental for reproduction and survival of the species. By the age of 50, as many as 30% of all men will harbor microscopic foci of prostate adenocarcinoma (CaP), and the incidence increases with age. In the United States, CaP is clinically diagnosed in approx 10% of men during their lifetime (189,000/yr), where it will claim 31,900 lives each year (13% of male cancer deaths) (1). The recent rising incidence of CaP (2) has plateaued (3), but the high prevalence of this disease and the aging of the US population still makes this a cancer that demands prompt attention.

Human homolog of Drosophila Hairy and enhancer of split 1, Hes1, negatively regulates δ-catenin (CTNND2) expression in cooperation with E2F1 in prostate cancer

BackgroundNeuronal synaptic junction protein δ-catenin (CTNND2) is often overexpressed in prostatic adenocarcinomas but the mechanisms of its activation are unknown. To address this question, we studied the hypothesis that Hes1, human homolog of DrosophilaH airy and e nhancer of s plit (Hes) 1, is a transcriptional repressor of δ-catenin expression and plays an important role in molecular carcinogenesis.ResultsWe identified that, using a δ-catenin promoter reporter assay, Hes1, but not its inactive mutant, significantly repressed the upregulation of δ-catenin-luciferase activities induced by E2F1. Hes1 binds directly to the E-boxes on δ-catenin promoter and can reduce the expression of δ-catenin in prostate cancer cells. In prostate cancer CWR22-Rv1 and PC3 cell lines, which showed distinct δ-catenin overexpression, E2F1 and Hes1 expression pattern was altered. The suppression of Hes1 expression, either by γ-secretase inhibitors or by siRNA against Hes1, increased δ-catenin expression. γ-Secretase inhibition delayed S/G2-phase transition during cell cycle progression and induced cell shape changes to extend cellular processes in prostate cancer cells. In neuroendocrine prostate cancer mouse model derived allograft NE-10 tumors, δ-catenin showed an increased expression while Hes1 expression was diminished. Furthermore, E2F1 transcription was very high in subgroup of NE-10 tumors in which Hes1 still displayed residual expression, while its expression was only moderately increased in NE-10 tumors where Hes1 expression was completely suppressed.ConclusionThese studies support coordinated regulation of δ-catenin expression by both the activating transcription factor E2F1 and repressive transcription factor Hes1 in prostate cancer progression.

Inhibition of Stathmin1 Accelerates the Metastatic Process

The oncoprotein stathmin 1 (STMN1) is upregulated in most, if not all, cancers of epithelial cell origin; therefore STMN1 is considered a target for cancer therapy. However, its role during metastasis has not been investigated. Here, we report for the first time that STMN1 strongly inhibits metastatic behavior in both normal epithelial and cancerous epithelial cells. Initially, loss-of-STMN1 compromises cell-cell adhesion. This is followed by epithelial-to-mesenchymal transition (EMT), increased cell migration, and metastasis via cooperative activation of p38 and through TGF-β-independent and -dependent mechanisms. In contrast, expressing STMN1 restores cell-cell adhesion and reverses the metastatic cascade. Primary prostate epithelial cell cultures from benign to undifferentiated adenocarcinoma (UA) clinical biopsies show that EMT-like cells arise while the cancer is still organ-confined and that their emergence is tumor-stage specific. Furthermore, primary EMT-like cells exhibit metastatic behavior both in vitro and in vivo as compared with their non-EMT counterpart. These observations predict that using STMN1 as a generic therapeutic target might accelerate metastasis. Instead, there may be a tumor stage-specific window-of-opportunity in which conserving STMN1 expression is required to inhibit emergence of metastatic disease.

Human homolog of airy and nhancer of plit 1, Hes1, negatively regulates δ-catenin () expression in cooperation with E2F1 in prostate cancer

BackgroundNeuronal synaptic junction protein δ-catenin (CTNND2) is often overexpressed in prostatic adenocarcinomas but the mechanisms of its activation are unknown. To address this question, we studied the hypothesis that Hes1, human homolog of DrosophilaH airy and e nhancer of s plit (Hes) 1, is a transcriptional repressor of δ-catenin expression and plays an important role in molecular carcinogenesis.ResultsWe identified that, using a δ-catenin promoter reporter assay, Hes1, but not its inactive mutant, significantly repressed the upregulation of δ-catenin-luciferase activities induced by E2F1. Hes1 binds directly to the E-boxes on δ-catenin promoter and can reduce the expression of δ-catenin in prostate cancer cells. In prostate cancer CWR22-Rv1 and PC3 cell lines, which showed distinct δ-catenin overexpression, E2F1 and Hes1 expression pattern was altered. The suppression of Hes1 expression, either by γ-secretase inhibitors or by siRNA against Hes1, increased δ-catenin expression. γ-Secretase inhibition delayed S/G2-phase transition during cell cycle progression and induced cell shape changes to extend cellular processes in prostate cancer cells. In neuroendocrine prostate cancer mouse model derived allograft NE-10 tumors, δ-catenin showed an increased expression while Hes1 expression was diminished. Furthermore, E2F1 transcription was very high in subgroup of NE-10 tumors in which Hes1 still displayed residual expression, while its expression was only moderately increased in NE-10 tumors where Hes1 expression was completely suppressed.ConclusionThese studies support coordinated regulation of δ-catenin expression by both the activating transcription factor E2F1 and repressive transcription factor Hes1 in prostate cancer progression.

The Role of Foxa Proteins in the Regulation of Androgen Receptor Activity

Activation of the androgen receptor is required for normal prostate physiology and in controlling the growth prostate cancer. However, the fact that multiple target organs express androgen receptor and are exposed to circulating androgens, yet fail to express prostate-specific markers and fail to develop androgen-dependent cancers, indicates that androgen receptor alone is not sufficient to dictate normal function and progression to cancer. Therefore, androgen action can be restricted in a given tissue by transcription factors that serve as co-regulators of androgen receptor. How androgen signaling acts in concert with other transcription factors, resulting in tissue-specific gene expression needs to be understood. The establishment of unique transcription factor regulatory networks is responsible, at least in part, to control androgen receptor action (1) in tissue-specific gene expression; (2) organ determination; and (3) cell differentiation. The identification of TF networks involved in these disparate events will allow researchers to elucidate the mechanisms that control prostate development, function, and pathology. Experimental evidence generated by our laboratory and others indicates that members of the Foxa subfamily of transcription factors play an important role in (1) normal prostate development; (2) the determination of prostatic cell fate; and (3) specific types of prostate pathology. This chapter reviews evidence generated by our laboratory and others regarding the important role of the Foxa transcription factors in the regulation of prostate-specific gene regulatory networks.