Growth factors as mediators of androgen action during the development of the male urogenital tract

Heat Shock Proteins in Benign Prostatic Hyperplasia and Prostate Cancer

Two out of three diseases of the prostate gland affect aging men worldwide. Benign prostatic hyperplasia (BPH) is a noncancerous enlargement affecting millions of men. Prostate cancer (PCa) in turn is the second leading cause of cancer death. The factors influencing the occurrence of BPH and PCa are different; however, in the course of these two diseases, the overexpression of heat shock proteins is observed. Heat shock proteins (HSPs), chaperone proteins, are known to be one of the main proteins playing a role in maintaining cell homeostasis. HSPs take part in the process of the proper folding of newly formed proteins, and participate in the renaturation of damaged proteins. In addition, they are involved in the transport of specific proteins to the appropriate cell organelles and directing damaged proteins to proteasomes or lysosomes. Their function is to protect the proteins against degradation factors that are produced during cellular stress. HSPs are also involved in modulating the immune response and the process of apoptosis. One well-known factor affecting HSPs is the androgen receptor (AR)—a main player involved in the development of BPH and the progression of prostate cancer. HSPs play a cytoprotective role and determine the survival of cancer cells. These chaperones are often upregulated in malignancies and play an indispensable role in tumor progression. Therefore, HSPs are considered as one of the therapeutic targets in anti-cancer therapies. In this review article, we discuss the role of different HSPs in prostate diseases, and their potential as therapeutic targets.

Predicting the tumorigenic phenotype of human bladder cancer cells by combining with fetal rat mesenchyme

BACKGROUND

In nonmuscle invasive bladder cancer patients, prediction of pTa and pT1 bladder cancer recurrence and progression must be established. Micropapillary structures have been defined as small clusters of invasive cancer cells having features of the epithelial-mesenchymal transition. Since the stromal microenvironment helps to induce the epithelial-mesenchymal transition, interactions between cancer cells and stroma should be closely examined to predict the tumorigenic phenotype of human bladder cancer cells.

MATERIALS AND METHODS

To investigate differences in the responsiveness of cancer cells to stroma, we combined 3 established human bladder cancer cell lines (high-grade T24 and UM-UC-3 cells, and low-grade papillary RT4 cells) with fetal rat mesenchyme.

RESULTS

Among 3 bladder cancer cell lines, the expression profiles of p63 isoforms were distinct, i.e., p63γ in T24 cells, p63β in UM-UC-3 cells, and p63α in RT4 cells. Tumors formed by T24 cells combined with fetal mesenchyme formed micropapillary-like structures, whereas those formed by T24 cells alone did not. T24 cells combined with fetal mesenchyme showed poor differentiation, e.g., innumerable chromatic atypia in the nuclei, higher levels of chromatic condensation, and increased nucleoli. In contrast, both UM-UC-3 and RT4 cells combined with fetal mesenchyme did not form micropapillary-like structures. Ki-67 and p63 labeling indices were significantly elevated by combining fetal mesenchyme with T24 cells but not with the others.

CONCLUSIONS

By mixing cancer cells with fetal mesenchyme, our data demonstrated that formation of micropapillary-like structures may predict the tumorigenic phenotype of invasive bladder cancer cells. Taken together, distinct expression profiles of p63 isoforms may predict poor outcomes in invasive bladder cancer.

Protective effect of resveratrol on urogenital sinus and prostate development in rats exposed in utero to TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)

This study evaluated the protective effects of resveratrol on the prostate development of rats exposed to TCDD. Pregnant rats received TCDD (1 μg/kg) at GD15 and/or RES (20 mg/kg/day) from GD10 to PND21. Newborn and adult males from Control, TCDD, TCDD + RES and RES groups were euthanized and the prostate was excised. On PND1, there was a reduction in the number of prostatic buds, AR-positive mesenchymal cells and proliferation index in epithelial and mesenchymal cells in TCDD group, but restored by RES. AhR immunoreactivity was greater in TCDD group than the other groups. On PND90, there was higher frequency of functional hyperplasia in the distal area of the prostate acini in TCDD group, but restored by RES. AhRR expression was higher in the TCDD while NRF2 was higher in the TCDD + RES compared to the other groups. Resveratrol was able to reduce the adverse effects of TCDD on prostate development and its long-term repercussions.

Androgen receptor dysfunction as a prevalent manifestation in young male carriers of a FLNA gene mutation

Androgenic actions require the proper signal transmission by the androgen receptor (AR), a nuclear transcription factor. This is initially located in the cell cytoplasm and should translocates to the nucleus to interact with DNA. AR functional impairment causes diverse blockage degrees of androgenic steroid action, known as androgen insensitivity syndromes. Filamin A, a protein coded by the FLNA gene, is a co-activator of various cytoplasmic factors, including AR. The mutational inactivation of the FLNA gene induces insufficiency of translocation and activation of AR. Consequently, it causes a developmental disorder of the male gonad and hypogonadism, similar to those observed in partial androgen insensitivity. We report two brothers carrying a loss-of-function mutation of FNLA with gonadal differentiation disorder and hypospadias. Specific staining for AR shows almost an absolute absence of these receptors in the testicular tissue. This association recommends investigating a possible mutational inactivation of the FLNA gene in patients with cryptorchidism and epididymo-testicular dissociation. The study is especially indicated when the family history, more often that of the mother, is suggestive. Likewise, growth and gonadal development of all male patients carrying this genetic trait should be monitored since childhood.

Gestational protein restriction delays prostate morphogenesis in male rats

Maternal malnutrition due to a low-protein diet is associated with functional disorders in adulthood, which may be related to embryonic development failures. The effects of gestational protein restriction on prostate morphogenesis in male offspring were investigated. Pregnant rat dams were divided into normoprotein (NP; fed a normal diet containing 17% protein) and hypoprotein (LP; fed a diet containing 6% protein) groups. On the day of birth (PND1), anogenital distance and bodyweight were measured in male pups. Seven males per experimental group (one male per litter) were killed, and the pelvic urethra was evaluated. LP offspring showed a significant reduction in bodyweight and anogenital distance on PND1. On three-dimensional reconstruction of the prostate, the number of prostatic buds was lower in LP than in NP males. Mesenchymal cells surrounding the buds were androgen-receptor positive, and the quantity and intensity of nucleus immunoreactivity was decreased in LP. The proliferation index was lower in LP than in NP prostatic buds. Immunoreactivity for α-actin in mesenchymal cells and that for epidermal growth factor receptor in epithelial cells was higher in NP than in LP. Our findings demonstrate that maternal protein restriction delays prostatic morphogenesis, probably because of considerable disruption in the epithelium–mesenchyme interaction.

Formation of human prostate epithelium using tissue recombination of rodent urogenital sinus mesenchyme and human stem cells

Progress in prostate cancer research is severely limited by the availability of human-derived and hormone-naïve model systems, which limit our ability to understand genetic and molecular events underlying prostate disease initiation. Toward developing better model systems for studying human prostate carcinogenesis, we and others have taken advantage of the unique pro-prostatic inductive potential of embryonic rodent prostate stroma, termed urogenital sinus mesenchyme (UGSM). When recombined with certain pluripotent cell populations such as embryonic stem cells, UGSM induces the formation of normal human prostate epithelia in a testosterone-dependent manner. Such a human model system can be used to investigate and experimentally test the ability of candidate prostate cancer susceptibility genes at an accelerated pace compared to typical rodent transgenic studies. Since Human embryonic stem cells (hESCs) can be genetically modified in culture using inducible gene expression or siRNA knock-down vectors prior to tissue recombination, such a model facilitates testing the functional consequences of genes, or combinations of genes, which are thought to promote or prevent carcinogenesis. The technique of isolating pure populations of UGSM cells, however, is challenging and learning often requires someone with previous expertise to personally teach. Moreover, inoculation of cell mixtures under the renal capsule of an immunocompromised host can be technically challenging. Here we outline and illustrate proper isolation of UGSM from rodent embryos and renal capsule implantation of tissue mixtures to form human prostate epithelium. Such an approach, at its current stage, requires in vivo xenografting of embryonic stem cells; future applications could potentially include in vitro gland formation or the use of induced pluripotent stem cell populations (iPSCs).

Mechanisms of prostate cancer initiation and progression

Prostate cancer is a major health problem as it continues to be the most frequently diagnosed cancer in men in the Western world. While improved early detection significantly decreased mortality, prostate cancer still remains the second leading cause of cancer-related death in Western men. Understanding the mechanisms of prostate cancer initiation and progression should have a significant impact on development of novel therapeutic approaches that can help to combat this disease. The recent explosion of novel high-throughput genetic technologies together with studies in animal models and human tissues allowed a comprehensive analysis and functional validation of the molecular changes. This chapter will summarize and discuss recently identified critical genetic and epigenetic changes that drive prostate cancer initiation and progression. These discoveries should help concentrate the efforts of drug development on key pathways and molecules, and finally translate the knowledge that is gained from mechanistic studies into effective treatments.

Matched pairs of human prostate stromal cells display differential tropic effects on LNCaP prostate cancer cells

Prostate stromal cells may play binary roles in the process of prostate cancer development. As the first to be encountered by infiltrating prostate cancer cells, prostate stromal cells form the first defense line against prostate cancer progression and metastasis. However, interaction between prostate cancer and stromal cells may facilitate the formation of a tumor microenvironment favoring cancer cell growth and survival. To establish an experimental system for studying the interaction between cancer and stromal cells, we isolated three matched pairs of normal and cancer-associated human prostate stromal clones. In this report, we describe the morphologic and behavioral characteristics of these cells and their effect on LNCaP prostate cancer cells in co-culture. Unlike LNCaP prostate cancer cells, the isolated prostate stromal clones are large fibroblast-like cells with a slow proliferation rate. Growth and survival of these clones are not affected by androgens. The stromal cells display high resistance to serum starvation, while cancer-associated stromal clones have differentiated survival ability. In co-culture experiments, the stromal cells protected some LNCaP prostate cancer cells from death by serum starvation, and cancer-associated stromal clones showed more protection. This work thus established a panel of valuable human prostate stromal cell lines, which could be used in co-culture to study the interaction between prostate cancer and prostate stromal cells.

Lineage enforcement by inductive mesenchyme on adult epithelial stem cells across developmental germ layers

During development, cell differentiation is accompanied by the progressive loss of pluripotent gene expression and developmental potential, although de-differentiation in specialized cells can be induced by reprogramming strategies, indicating that transdifferentiation potential is retained in adult cells. The stromal niche provides differentiating cues to epithelial stem cells (SCs), but current evidence is restricted to tissue types within the same developmental germ layer lineage. Anticipating the use of adult SCs for tissue regeneration, we examined if stroma can enforce lineage commitment across germ layer boundaries and promote transdifferentiation of adult epithelial SCs. Here, we report tissue-specific mesenchyme instructing epithelial cells from a different germ layer origin to express dual phenotypes. Prostatic stroma induced mammary epithelia (or enriched Lin(-)CD29(HI)CD24(+/MOD) mammary SCs) to generate glandular epithelia expressing both prostatic and mammary markers such as steroid hormone receptors and transcription factors including Foxa1, Nkx3.1, and GATA-3. Array data implicated Hh and Wnt pathways in mediating stromal-epithelial interactions (validated by increased Cyclin D1 expression). Other recombinants of prostatic mesenchyme and skin epithelia, or preputial gland mesenchyme and bladder or esophageal epithelia, showed foci expressing new markers adjacent to the original epithelial differentiation (e.g., sebaceous cells within bladder urothelium), confirming altered lineage specification induced by stroma and evidence of cross-germ layer transdifferentiation. Thus, stromal cell niche is critical in maintaining (or redirecting) differentiation in adult epithelia. In order to use adult epithelial SCs in regenerative medicine, we must additionally regulate their intrinsic properties to prevent (or enable) transdifferentiation in specified SC niches.

Dual-label centromere and telomere FISH identifies human, rat, and mouse cell contribution to Multispecies recombinant urogenital sinus xenografts

BACKGROUND

Recombinant xenografts of human cells growing in immunocompromised rodents are widely used for studying stem cell biology, tumor biology, and epithelial to mesenchyme transitions. Of critical importance is the correct interpretation of the cellular composition of such xenografts.

METHODS

Here we present a rapid and robust method employing protein nucleic acid (PNA) FISH probes to dual-label centromeres and telomeres (Cen/Tel FISH). Such labeling allows unambiguous discrimination between human, mouse, and rat cells in paraffin-embedded tissue sections, providing significant advantages over current methods used to discern human versus rodent cell types.

RESULTS

Using an in vivo prostatic developmental system where rat embryonic urogenital sinus mesenchyme is recombined with human prostate epithelial organoids and grown in an immunocompromised mouse, Cen/Tel FISH documents that all three species contribute to the development of glandular structures.

CONCLUSIONS

The method is an indispensable tool to analyze xenograft/host interactions and prevent misinterpretation of data using tissue recombination approaches.

The diverse and contrasting effects of using human prostate cancer cell lines to study androgen receptor roles in prostate cancer

The androgen receptor (AR) plays an important role in the development and progression of prostate cancer (PCa). Androgen deprivation therapy is initially effective in blocking tumor growth, but it eventually leads to the hormone-refractory state. The detailed mechanisms of the conversion from androgen dependence to androgen independence remain unclear. Several PCa cell lines were established to study the role of AR in PCa, but the results were often inconsistent or contrasting in different cell lines, or in the same cell line grown under different conditions. The cellular and molecular alteration of epithelial cells and their microenvironments are complicated, and it is difficult to use a single cell line to address this important issue and also to study the pathophysiological effects of AR. In this paper, we summarize the different effects of AR on multiple cell lines and show the disadvantages of using a single human PCa cell line to study AR effects on PCa. We also discuss the advantages of widely used epithelium-stroma co-culture systems, xenograft mouse models, and genetically engineered PCa mouse models. The combination of in vitro cell line studies and in vivo mouse models might lead to more credible results and better strategies for the study of AR roles in PCa.

Improvement in predicting tumorigenic phenotype of androgen-insensitive human LNCaP prostatic cancer cell subline in recombination with rat urogenital sinus mesenchyme

Hormone-refractory prostate cancer, a heterogeneous disease, has varying degrees of androgen sensitivity. To understand the physiological changes in the hormone-refractory state, the present study used a lineage-derived androgen receptor (AR)-positive, androgen-insensitive prostate cancer cell line and evaluated the tumorigenic phenotype, focusing on tumor-stromal interactions in vivo. First, tumorigenic differences of cancer cells alone were examined in an androgen-insensitive AR-positive LNCaP subline, AIDL, compared with those of the androgen-sensitive AR-positive parental LNCaP and the androgen-insensitive AR-negative PC-3 cells transplanted into subcutaneous, sub-renal and prostatic orthotopic graft sites. Next, cancer cells were recombined with rat urogenital sinus mesenchyme (rUGM) to simulate the tumor-stromal microenvironment. Tumors of AIDL and LNCaP without stromal components both formed well-defined globular tumors and contained large blood-filled areas, with no significant difference in tumor growth or histopathology regardless of the cell line's androgen sensitivity or graft site. In contrast, tumors of AIDL and LNCaP recombined with rUGM both showed reduction of blood-filled areas in the tumors and increased tumor growth compared with cancer cells alone. Tumors of AIDL + rUGM recombinants were approximately three times as large as those of LNCaP + rUGM recombinants, whereas tumors of AIDL and LNCaP without rUGM were not different in size. In addition to the tumor size, cell proliferation (Ki-67 labeling index) in tumors of AIDL + rUGM recombinants was significantly higher than that in tumors of LNCaP + rUGM recombinants. Immunoreactivities of AR, E-cadherin and beta-catenin were decreased in AIDL + rUGM recombinants relative to AIDL alone and LNCaP + rUGM recombinants. These results demonstrated that tumorigenic features of androgen-insensitive AR-positive prostate cancer cells could be significantly influenced by rUGM. Therefore, this in vivo recombination model with rUGM may be useful in developing new treatment strategies.

Urothelial transdifferentiation to prostate epithelia is mediated by paracrine TGF-beta signaling

The embryonic urogenital sinus mesenchyme (UGM) induces prostate epithelial morphogenesis in development. The molecular signals that drive UGM-mediated prostatic induction have not been defined. We hypothesized that the TGF-beta signaling directed the prostatic induction. UGM from TGF-beta type II receptor stromal conditional knockout mice (Tgfbr2(fspKO)) or control mice (Tgfbr2(floxE2/floxE2)) was recombined with wild-type adult mice bladder urothelial cells. The resulting urothelium associated with Tgfbr2(floxE2/floxE2) UGM was instructively differentiated into prostatic epithelium, as expected. In contrast, the urothelium associated with Tgfbr2(fspKO) UGM permissively maintained the phenotype of bladder epithelial cells. Microarray analysis of UGM tissues suggested the down-regulation of multiple Wnt ligands and the up-regulation of the Wnt antagonist, Wif 1, by the Tgfbr2(fspKO) UGM compared with Tgfbr2(floxE2/floxE2) UGM. The overexpression of Wif-1 by wild-type UGM resulted in the inhibition of prostatic induction. These data suggest that the stromal TGF-beta activity mediated by paracrine Wnt is necessary for the induction of prostatic differentiation. As Wnt ligands mediate differentiation and maintain the stem cell phenotype, the contribution of mouse stem cells and somatic cells to prostatic epithelium in the tissue recombination models was tested. The directed differentiation of mouse embryonic stem cells by UGM is suggested by a threshold number of mouse stem cells required in prostatic differentiation. To determine the contribution of somatic cells, the adult bladder epithelial compartment was labeled with green-fluorescent vital dye (CMFDA) and the stem-like cells marked by bromodeoxyuridine (BrdU) label-retention. The resulting prostatic epithelia of the tissue recombinants maintained the CMFDA dye, suggesting minimal cell division. Thus, the UGM can induce endoderm-derived epithelia and stem cells to form prostate through a transdifferentiation mechanism that requires stromal TGF-beta signaling to mediate epithelial Wnt activity.

Estrogen receptor-alpha signaling in growth of the ventral prostate: comparison of neonatal growth and postcastration regrowth

A role for estrogen receptor (ER)-alpha in branching morphogenesis in the ventral prostate (VP) has previously been demonstrated; in the VP of ERalpha(-/-) mice, there are fewer side branches than in wild-type littermates. In the present study, we show that in the postnatal VP, fibroblast growth factor 10 (FGF10) is expressed in wild-type mice but not in ERalpha(-/-) mice, and because branching involves proliferation pathways also used in malignant growth, we investigated whether branching during regrowth of the VP after castration involves ERalpha and FGF10. ERalpha was not detectable in the prostates of sham-operated or castrated mice but was expressed in the prostatic epithelium between d 3 and 5 after testosterone replacement. Blocking either ERalpha or ERbeta with ICI 182,780 had no detectable effects on epithelial cell proliferation during regrowth by testosterone. The ERalpha agonist, propylpyrazoletriol, did not induce regrowth by itself, but exposure to propylpyrazoletriol on d 3-5 of testosterone replacement resulted in cyclin D1-positive cells in the ductal epithelium, invasion of FGF10-positive immune cells in the regrowing prostate, and budding 14 d later. Testosterone replacement alone did not induce cyclin D1, FGF10, or bud formation. These results indicate that stimulation of ERalpha is essential for ductal branching during postnatal prostate growth. During regrowth after castration, there is a window in time when selective stimulation of ERalpha can also induce ductal branching. The FGF10 for this growth comes from the immune system, not from the prostatic mesenchyme.

Prostate development: a historical perspective

The regional anatomy of the human prostate has been debated periodically over the last century with various levels of controversy and agreement, beginning with the concept of lobes and replaced by the current model of zones. During this period a variety of classifications have been proposed, based upon the studies of glandular morphogenesis, responses to hormones or histopathology. The current paradigm suggests that the regional differences seen in the prostate of both animal models and the human are a consequence of specific epithelial-mesenchymal interactions along the cranial-caudal axis of the urogenital sinus. The distinctive regional patterns seen in the rodent prostate and the histological heterogeneity of the human adult gland all point to the modification of the distal portion of the ducts, while the proximal segments retain their spatial relationship to the urethra that was formed during fetal development. This suggests that the early epithelial budding that occurs in utero represents a common, fairly symmetrical pattern of growth in many species, while the regional differences in branching morphogenesis and cytodifferentiation are controlled by the instructional influences of mesenchyme and temporal expression of growth factors. Perturbation of the normal processes involved during critical periods of fetal development during reproductive organ development may also play a role in the susceptibility of the prostate to disease in adulthood. Past descriptions of detailed anatomical studies, which span over a century, have provided much insight into the architecture and processes that form a complex tubulo-alveolar gland. New insights into the ductal detail and the advent of sophisticated analyses of cell-cell interactions and molecular mechanisms controlling pathways of cellular growth, differentiation, and apoptosis will likely lead to new approaches for prevention and therapy of prostatic diseases.

Tumor-stroma interactions of metastatic prostate cancer cell lines: analyses using microarrays

Tumor-stroma interactions are of great importance not only for the development and progression of primary prostate carcinoma but probably also for the establishment of metastasis. Fibroblasts are an important stromal cell type encountered by metastatic tumor cells at different sites. In previous investigations, we had found that media conditioned by three metastatic prostate cancer cell lines (LNCaP, PC-3, and DU-145) induced cultured nonprostatic fibroblasts to proliferate or to express matrix-metalloproteinase-1 considered important for tumor invasion. Fibroblast-conditioned media in turn stimulate proliferation of DU-145 cells and migration of PC-3 cells. Both tumor cells and fibroblasts secrete VEGF suggesting that not only metastatic but also stromal cells at metastatic sites contribute to the vascularization of metastasis necessary for continuous growth. In order to better understand the reciprocal tumor-stroma cross-talk in molecular terms we used the mRNA extracted from stimulated and unstimulated neoplastic and fibroblastic stromal cells for cDNA array hybridization using Affymetrix chips. The three prostate cell lines influenced the fibroblasts nearly in the same manner. In particular proteins involved in cell adhesion, cell-cell contact, and cell cycle regulation were downregulated in stimulated fibroblasts. In contrast, fibroblasts affected every prostate cancer cell line in different ways, which may be because of the different origin of the metastatic prostate cancer cell lines.

Mullerian Inhibiting Substance Regulates Androgen-Induced Gene Expression and Growth in Prostate Cancer Cells through a Nuclear Factor-κB-Dependent Smad-Independent Mechanism

Mullerian inhibiting substance (MIS), a member of the TGFβ superfamily, causes regression of the Mullerian duct in male embryos. The presence of MIS type II and type I receptors in tissues and cell lines derived from the prostate suggests that prostate is a likely target for MIS. In this report, we demonstrate that MIS inhibits androgen-stimulated growth of LNCaP cells and decreases their survival in androgen-deprived medium by preventing cell cycle progression and inducing apoptosis. Expression of dominant-negative Smad1 reversed the ability of MIS to decrease LNCaP cell survival in androgen-deprived medium but not androgen-stimulated growth, whereas abrogation of nuclear factor-κB (NFκB) activation ablated the suppressive effects of MIS on both androgen-stimulated growth and androgen-independent survival. The effect of MIS on androgen-induced growth was not due to changes in androgen receptor expression. However, MIS suppressed androgen-stimulated transcription of prostate-specific antigen; ablation of NFκB activation reversed MIS-mediated suppression of prostate-specific antigen. These observations suggest that MIS regulates androgen-induced gene expression and growth in prostate cancer cells through a NFκB-dependent but Smad1-independent mechanism. Thus, MIS, in addition to potentially regulating prostate growth indirectly by suppressing testicular testosterone synthesis, may also be a direct regulator of androgen-induced gene expression and growth in the prostate at the cellular level.

The role of androgens in sertoli cell proliferation and functional maturation: studies in mice with total or Sertoli cell-selective ablation of the androgen receptor

The role of androgens in the proliferation and maturation of Sertoli cells (SC) and the development of their capacity to support spermatogenesis remains poorly understood. We evaluated these functions in complete androgen receptor knockout (ARKO) and SC-selective androgen receptor knockout (SCARKO) mice. Compared with controls, ARKO mice exhibited a progressive reduction in SC number/testis, whereas SCARKOs showed minor changes, suggesting that androgen effects on SC number are not mediated via direct action on SCs. Immunoexpression of anti-Mullerian hormone (AMH), p27(kip1), GATA-1, and sulfated glycoprotein-2, which changes according to SC maturational status, occurred normally in ARKOs and SCARKOs. Functional capacity of SCs to support spermatogonia was similar in SCARKOs and controls, whereas ARKOs showed reduced capacity with age. SC capacity to support total germ cells revealed major deficits in ARKO and SCARKO adults, particularly with respect to postmeiotic germ cells. Using quantitative RT-PCR, the expression of SC markers was compared in d 50 testes. In ARKOs, expression of Pem, fatty acid binding protein, platelet-derived growth factor-A, and transferrin were all significantly reduced, whereas FSH receptor and AMH were increased. In SCARKOs, there were modest reductions in expression of cystatin-related gene highly expressed in testis and epididymis (cystatin-TE) and claudin-11, whereas expression of Pem, fatty acid binding protein, and platelet-derived growth factor-A was markedly reduced, highlighting these as potentially androgen-regulated SC genes that merit further study. In conclusion, androgen action is not required for maturation-dependent changes in immunoexpression of the SC markers AMH, p27(kip1), GATA-1, and sulfated glycoprotein-2 but is essential for expression of other SC genes, the attainment of normal SC number, and the support of meiotic and postmeiotic germ cell development.

Identification of genetic pathways activated by the androgen receptor during the induction of proliferation in the ventral prostate gland

The androgen receptor (AR), when complexed with 5alpha-dihydrotestosterone (DHT), supports the survival and proliferation of prostate cells, a process critical for normal development, benign prostatic hypertrophy, and tumorigenesis. However, the androgen-responsive genetic pathways that control prostate cell division and differentiation are largely unknown. To identify such pathways, we examined gene expression in the ventral prostate 6 and 24 h after DHT administration to androgen-depleted rats. 234 transcripts were expressed significantly differently from controls (p < 0.05) at both time points and were subjected to extensive data mining. Functional clustering of the data reveals that the majority of these genes can be classified as participating in induction of secretory activity, metabolic activation, and intracellular signaling/signal transduction, indicating that AR rapidly modulates the expression of genes involved in proliferation and differentiation in the prostate. Notably AR represses the expression of several key cell cycle inhibitors, while modulating members of the wnt and notch signaling pathways, multiple growth factors, and peptide hormone signaling systems, and genes involved in MAP kinase and calcium signaling. Analysis of these data also suggested that p53 activity is negatively regulated by AR activation even though p53 RNA was unchanged. Experiments in LNCaP prostate cancer cells reveal that AR inhibits p53 protein accumulation in the nucleus, providing a post-transcriptional mechanism by which androgens control prostate cell growth and survival. In summary these data provide a comprehensive view of the earliest events in AR-mediated prostate cell proliferation in vivo, and suggest that nuclear exclusion of p53 is a critical step in prostate growth.

New perspectives on growth factor-sex steroid interaction in the prostate

Many organs respond to both sex steroids and growth factors. Regulation of these pathways is integral to cell-cell communications during development and aberrant changes cause disease pathogenesis. Traditionally, paracrine and endocrine actions of growth factors and steroid hormones are considered independently. Recently, new data indicated that activin/TGFbeta and sex steroid signalling are linked; explicitly, that the pathways cross-talk intracellularly. Here we present new perspectives on these interactions, using examples predominantly from the prostate, as it is a well-characterised organ in this context. While this information provides insight to the potential mechanisms behind these interactions, it also presents a new challenge; the action of any of these factors cannot be considered exclusively without considering the impact on the other biological pathways.

Dedifferentiation of stromal smooth muscle as a factor in prostate carcinogenesis

We had earlier established an animal model of prostate carcinogenesis using a combination of testosterone (T) and 17beta-estradiol benzoate (E2) on Noble rats (Wang and Wong, 1998). In the present study we examined the changes in a number of smooth muscle differentiation markers including smooth muscle alpha-actin and myosin, vinculin, desmin, laminin and vimentin as well as changes in fine structure by electron microscopy. Our immunohistochemical (IHC) studies revealed that smooth muscle cells (SMCs) subjacent to dysplastic (precancerous) sites and carcinoma usually exhibited a preferential loss of myosin, desmin and laminin. However, the expression of alpha-actin and vinculin appeared to be more persistent in most dysplastic or neoplastic sites. The study reaffirmed our earlier observation that there was a concurrent dedifferentiation of surrounding SMCs during the development and progression of prostate carcinogenesis. The structural study revealed that SMC subjacent to epithelial dysplasia displayed a spectrum of derangements. These included the loosening of muscular layers with SMC characterized by their highly irregular external contours with numerous spine-like cytoplasmic projections. There was also a reduction in density of myofilaments and presence of many enlarged caveolae in muscle cells. Additionally, focal discontinuity or disruptions of muscular layer were often observed together with an increase in abundance of fibrous connective tissue. Moreover, the amount of smooth muscle appeared to be inversely correlated with the histologic grade of prostate tumors. In most instances, SMCs were totally absent in the moderately or poorly differentiated tumors and in metastatic tumors in the lung and the small intestine. Stromal muscular deformity was associated with concurrent changes in epithelial cells. Dysplastic epithelial cells were characterized by a reduction in abundance of secretory organelles such as reduction in size of Golgi apparatus, paucity of granular endoplasmic reticulum and secretory vesicles. The nuclei showed typical deformity characterized by deep nuclear membrane foldings. The basal lamina of dysplastic or tumor cells was present although focal structural abnormalities such as reduplication, disruption and smearing were sometimes observed. The present data indicate that derangements of epithelial cells during prostate carcinogenesis are associated with a reduction or dedifferentiation of stromal SMCs. Our results lend support to the hypothesis that transformed epithelium is incapable of maintaining normal differentiation of adjacent muscle. In turn, abnormal stromal, resulting from dedifferentiation or reduction of SMC, may lead to loss of stromal control over epithelial proliferation and differentiation. Consequently, a loss of differentiation in both epithelium and stromal SMCs may be critically involved in hormone-induced prostate carcinogenesis.

Regulation of the expression of protein kinase C isoenzymes in rat ventral prostate: effects of age, castration and flutamide treatment

Protein kinase C (PKC) isoenzymes are involved in cell function, growth, apoptosis and neoplastic transformation in the prostate gland. We detected by means of Western blot the expression of the classical alpha and beta1, the novel epsilon and the atypical zeta isoforms of PKC in ventral prostates from rats with different extents of plasma testosterone levels and/or androgen imprinting on the gland. The expression of the four isoforms decreased in 5-day castrated rats showing apoptotical regression of the gland and a drastic reduction of circulating testosterone. However, the expression of PKC isoenzymes (alpha, beta1, epsilon ) increased in prostates from pubertal (35-days old) rats that are characterized by relatively low but extremely bioactive testosterone plasma levels. Treatment of adult rats for 14 days with flutamide (daily s.c. injection of 15 mg/Kg B.W.) resulted in increased expression of the four isoenzymes; it occurred in the presence of increased (normal rats) or drastically reduced (rats castrated after 9 days of flutamide administration) levels of plasma testosterone conceivably through a direct effect of this nonsteroidal antiandrogen on prostate cells. Measurements of PKC(alpha) activity were in agreement with the observations on protein expression and showed that flutamide (that is extensively used in the treatment of advanced prostate cancer) elicits some impairment in the mechanisms of translocation of this isoform from the cytosol to the membrane. Thus, in addition to the possibility of direct effects of flutamide upon the rat prostate, we present evidence that the levels of circulating androgens and/or their bioactivity in the gland regulate the expression of various important PKC isoforms.

Insulin-like growth factor binding protein-3 induces early apoptosis in malignant prostate cancer cells and inhibits tumor formation in vivo

BACKGROUND

Insulin-like growth factor binding protein (IGFBP-3) levels are significantly reduced in malignant prostate epithelial cells. In this study, we evaluated the role of endogenous IGFBP-3 on prostate cancer cell growth and tumorigenesis.

METHODS

IGFBP-3 was re-expressed by stable transfection of human IGFBP-3 cDNA in a model of human prostate cancer, M12, a malignant subline in which IGFBP-3 levels are undetectable in comparison to the parent epithelial cell, P69. Effect of IGFBP-3 re-expression (M12-BP-3) on growth kinetics, morphology, propensity to apoptosis, and in vivo tumor formation were studied.

RESULTS

M12-BP-3 cells secreted IGFBP-3 and growth arrested at a cell density that was threefold lower than control cells and this was associated with marked alteration in cell morphology. Control cells when grown in conditioned media secreted by M12-BP-3 also showed altered morphology compared to when cultured in IGFBP-3-immunodepleted conditioned media. The M12-BP-3 clones showed altered mitochondrial membrane potential, increased PARP cleavage, increase in sub-G1 peak, decreased levels of neuron specific enolase, and decreased tumor formation in athymic, nude mice.

CONCLUSIONS

These data suggest that IGFBP-3 induces early apoptosis and has potential tumor suppressive effect in prostate cancer. Prostate 51: 141-152, 2002.

Effects of aging on growth factors gene and protein expression in the dorsal and ventral lobes of rat prostate

We hypothesize that various growth factors and their receptors gene and protein are modulated in dorsal and ventral lobes of aging prostate. To test this hypothesis, TGFbeta1, TGFbeta2 TGFbeta3, TGFbetaR-I, TGFbetaR-II, TGFalpha, EGF, EGFR, KGF and KGFR gene and protein expression were analyzed in dorsal and ventral lobes of aging rat prostates (1, 3, 6, 9, 12, 18, 24, and 28/30 months). KGF gene expression was very weak or absent in 1, 3, and 6 month old rat dorsal and ventral lobes of prostate whereas it re-expressed in 9, 12, 18, 24 and 30 month old rat prostate. All growth factors and their receptors expect KGF and EGFR were mainly localized in epithelium of ventral and dorsal lobes of aging rat prostates. EGF, TGFalpha, TGFbeta1, and TGFbetaR-I protein expression was lacking in stroma of dorsal and ventral lobes of 1, 3, 6, 9, 12/18 months old rat prostates. However, EGF, TGFbeta1 and TGFbetaR-I proteins re-expressed in stroma of 24 and 28 months old rat prostates. KGF protein expression was lacking in epithelium of dorsal and ventral lobes of all aging rat prostates. This is the first report to demonstrate differential gene and protein expression of growth factors in dorsal and ventral lobes is associated with aging rat prostate, suggesting their role in pathogenesis of prostatic diseases with aging.

Chronic treatment with epidermal growth factor induces growth of the rat ventral prostate

OBJECTIVE

The epidermal growth factor (EGF) system is expressed in the rat prostate, and growth factors from this system induce proliferation in prostate epithelial and stromal cell cultures. The aim of the study was to investigate the possible growth-promoting effects of the system during the hyperplastic growth phase of the prostate in newborn rats.

MATERIAL AND METHODS

Newborn rats were treated for 8 weeks with EGF (150 microg/kg body weight per day), administered as daily subcutaneous injections. Sections of the prostate tissue were examined by a stereological technique to determine tissue composition.

RESULTS

Treatment with EGF increased the weight of the ventral prostate, relative to body weight, by 50% compared with placebo (p < 0.005). Neither the dorsolateral prostate, seminal vesicles nor coagulating glands were affected by EGF. Prostate tissue showed a significant increase in the volume of the prostate epithelium, the stroma and the lumen following EGF treatment, in a pattern resembling physiological growth of the ventral prostate. A significant correlation (r = 0.78, p < 0.0001) of the volume fraction of the lumen with the glandular weight of the ventral prostate was seen. Serum testosterone was not affected by chronic EGF administration.

CONCLUSIONS

EGF selectively induces growth of the ventral lobe of the prostate in newborn rats, in a pattern comparable to normal physiological growth. It may be hypothesized that the physiological growth of the prostate is directly correlated to endogenous activity of the EGF system in the rat prostate gland.

Activins as regulators of branching morphogenesis

Development of glandular organs such as the kidney, lung, and prostate involves the process of branching morphogenesis. The developing organ begins as an epithelial bud that invades the surrounding mesenchyme, projecting dividing epithelial cords or tubes away from the site of initiation. This is a tightly regulated process that requires complex epithelial-mesenchymal interactions, resulting in a three-dimensional treelike structure. We propose that activins are key growth and differentiation factors during this process. The purpose of this review is to examine the direct, indirect, and correlative lines of evidence to support this hypothesis. The expression of activins is reviewed together with the effect of activins and follistatins in the development of branched organs. We demonstrate that activin has both negative and positive effects on cell growth during branching morphogenesis, highlighting the complex nature of activin in the regulation of proliferation and differentiation. We propose potential mechanisms for the way in which activins modify branching and address the issue of whether activin is a regulator of branching morphogenesis.

Regulation of prostate branching morphogenesis by activin A and follistatin

Ventral prostate development occurs by branching morphogenesis and is an androgen-dependent process modulated by growth factors. Many growth factors have been implicated in branching morphogenesis including activins (dimers of beta(A) and beta(B) subunits); activin A inhibited branching of lung and kidney in vitro. Our aim was to examine the role of activins on prostatic development in vitro and their localization in vivo. Organ culture of day 0 rat ventral prostates for 6 days with activin A (+/- testosterone) inhibited prostatic branching and growth without increasing apoptosis. The activin-binding protein follistatin increased branching in vitro in the absence (but not presence) of testosterone, suggesting endogenous activins may reduce prostatic branching morphogenesis. In vivo, inhibin alpha subunit was not expressed until puberty, therefore inhibins (dimers of alpha and beta subunits) are not involved in prostatic development. Activin beta(A) was immunolocalized to developing prostatic epithelium and mesenchymal aggregates at ductal tips. Activin beta(B) immunoreactivity was weak during development, but was upregulated in prostatic epithelium during puberty. Activin receptors were expressed throughout the prostatic epithelium. Follistatin mRNA and protein were expressed throughout the prostatic epithelium. The in vitro evidence that activin and follistatin have opposing effects on ductal branching suggests a role for activin as a negative regulator of prostatic ductal branching morphogenesis.

Growth factors: roles in andrology

Mesenchymal-epithelial interactions are extremely important during growth and development and in the functional cytodifferentiation of male sex accessory organs. Interactions between mesenchyme and epithelium occur mainly through a paracrine action that is mediated by various growth factors. The role of androgens is very important for these organs and the androgenic effect is mediated by paracrine interactions. A number of growth factors have been studied in prostate and seminal vesicles from mice, rats, and humans because they are potent mediators of cellular proliferation, differentiation, and death. This review provides an overview of current knowledge about growth factors involved in the development of male sex accessory organs, with particular emphasis on the prostate.

Growth factors and epithelial-stromal interactions in prostate cancer development

Epithelial-stromal interactions are important not only in growth, development, and functional cytodifferentiation of the prostate but also in derangements of prostate gland such as BPH and prostate carcinoma. This chapter explores the roles of epithelium and stroma during this delicate process and highlights the role and mutual influence of each on the other. It also examines the importance of ECM in mediating the effects of androgens and drawn attention to estrogen and genetic factors in the process. During this process of epithelial-stromal interaction, growth factors play a central role in mediating the interactions. This chapter focuses on the role of several growth factors including epidermal growth factor, fibroblast growth factor, transforming growth factor alpha, transforming growth factor beta, insulin-like growth factor-1, vascular endothelial growth factor, nerve growth factor, platelet-derived growth factor, and hepatocyte growth factor. This chapter emphasizes the importance of epithelial-stromal interactions in tumorigenesis and highlights the switch of paracrine to autocrine mode during the process of carcinogenesis.

Prostatic ductal system in rats: changes in regional distribution of extracellular matrix proteins during castration-induced regression

BACKGROUND

The extracellular matrix (ECM) is an intricate network composed of an array of molecules that play an integral role in the regulation of cell function, differentiation, and tissue-specific gene expression in various epithelia. In the present study, we examined the distribution of collagen type IV and laminin along the rat ventral prostatic duct before and after castration.

METHODS

Mature Sprague-Dawley rats were castrated and their prostates processed for immunocytochemistry of ECM proteins, laminin, and collagen type IV. Tissue sections were also processed for apoptosis staining, using the 3' end-labeling technique. To examine the effect of ECM proteins on epithelial growth, rat ventral epithelial cells were cultured on ECM-coated surfaces.

RESULTS

In the intact rat, laminin was localized in the basement membrane along all regions of the ventral prostate ductal system. Collagen type IV was found to be distributed evenly in the basement membrane of the distal and intermediate regions but was absent or poorly organized in the proximal region, where apoptosis in the epithelium occurs at a high rate. In the regressing prostate after castration, there was a shift in apoptosis from the proximal region to the distal intermediate regions of the prostatic duct. Associated with the shift was a remodeling of basement membrane proteins due to the specific loss of collagen type IV in the distal and intermediate regions. Collagen type IV reappeared underneath the epithelium 7 days after castration, when apoptosis in the epithelium stopped. In vitro, collagen type IV enhanced the growth of ventral prostatic epithelial cells, as assessed by cell number.

CONCLUSIONS

Collagen basement membrane type IV mediates growth of rat ventral prostate epithelium, and its loss during tissue remodeling after castration is associated with cell death.

Involvement of heparin affin regulatory peptide in human prostate cancer

BACKGROUND

Heparin affin regulatory peptide (HARP) composes, together with midkine (MK), a new family of heparin-binding growth/differentiation factors. Recently, HARP was incriminated in cancer progression, as an angiogenic factor and as a tumor growth factor. In this study, we analyzed the possible involvement of HARP in human prostate cancer (Pca).

METHODS

The localization of HARP protein and its mRNAs in normal prostate (n = 5), benign prostate hyperplasia (BPH) (n = 7), and prostate cancer (Pca) (n = 9) was analyzed by immunohistochemistry and in situ hybridization. The mitogenic activity of this growth factor for prostate epithelial cells was determined with a thymidine incorporation assay. HARP cDNA was transfected into normal prostate epithelial (PNT-1A) cells, and their growth was evaluated by soft-agar growth assay.

RESULTS

We found HARP protein associated with epithelial cells in PCa but not in normal prostate or BPH, while the corresponding mRNAs were located in the stromal compartment. Furthermore, HARP is mitogenic for PNT-1A, LNCaP, and DU-145 cells. Overexpression of the human HARP in PNT-1A transfected cells induced both anchorage-independent growth and growth at low serum concentrations.

CONCLUSIONS

Our results suggest that HARP may act in a paracrine manner from mesenchymal to tumoral epithelial cells, and may play a role in the molecular mechanisms that regulate prostate tumor cell growth.

Interactive effects of TCDD and p,p'-DDE on male reproductive tract development in in utero and lactationally exposed rats

The developing male rat reproductive system is highly sensitive to low doses of TCDD and p,p'-DDE (DDE), which exert antiandrogenic effects via different mechanisms. This study investigates the interactive effects of in utero and lactational exposure to a mixture of these compounds. Pregnant Holtzman rats received one of the following: vehicle on gestation day (GD) 14-18, 0.25 microgram/kg TCDD on GD15, 100 mg/kg DDE on GD 14-18, or 0.25 microgram/kg TCDD on GD15 and 100 mg/kg DDE on GD 14-18. Male offspring were euthanized on postnatal day (PND) 21 (weaning), PND 32 (prepuberty), PND 49 (puberty), and PND 63 (postpuberty). Coadministration of these doses of TCDD and DDE appeared to potentiate their individual actions on prostate weight on PND 21, while immunostaining for the prostatic androgen receptor exhibited patterns characteristic of the effects of both compounds individually. Cauda epididymal sperm number was reduced by each compound but was not further reduced by exposure to TCDD and DDE in combination. Anogenital distance, age at onset of puberty, daily sperm production, testicular and accessory sex organ weight (nonprostate), and levels of prostatic androgen-regulated gene transcripts are affected at higher doses of both compounds, but not at the doses used in the present study. Only DDE-treated animals retained nipples on PND 13. Serum androgen levels did not differ between treatment groups. In conclusion, the developing rat prostate is uniquely sensitive to the effects of TCDD and DDE, which may augment one another's effects in this organ.

Regional expression of transforming growth factor-alpha in rat ventral prostate during postnatal development, after androgen ablation, and after androgen replacement

The prostate is a highly heterogeneous organ, composed of different types of epithelial and stromal cells organized regionally along the ductal network. Although androgen-stimulated growth and maintenance of the prostate gland primarily involve epithelial cells, it is unclear whether all epithelial cells are androgen dependent. Moreover, the actions of androgens may not be direct; a number of polypeptide growth factors, including transforming growth factor-alpha (TGFalpha), are postulated to mediate androgen action in the rat prostate. In this investigation, using an immunohistochemical technique, we examined the cellular and regional expression of TGFalpha in the rat ventral prostate during postnatal development to adulthood. TGFalpha-immunopositive cells were located throughout the ductal epithelium from postnatal days 5-20. By day 45 and thereafter, regional variation in TGFalpha expression became apparent; epithelial cells in the proximal segment exhibited intense staining, whereas those in the distal segment exhibited negligible staining. These observations were coincident with increased serum testosterone concentrations at puberty. To understand the role of androgen in the expression of TGFalpha in the epithelial cells of the distal and proximal segments of the adult rat ventral prostate, androgen was withdrawn by castration, and testosterone subsequently was administered. Androgen receptor protein expression decreased after castration and reappeared after androgen replacement in both the distal and proximal segments. TGFalpha staining was negligible in epithelial cells of the distal segment of intact adult rats, became prominent by 7 days after castration, but then diminished after the administration of testosterone. Western blot analyses revealed the presence of a specific 30-kDa immunoreactive form of TGFalpha in rat ventral prostate, and its quantity reflected the staining intensities observed in the immunohistochemical studies. These results suggest that TGFalpha expression is negatively regulated by androgen in epithelial cells of the distal segment. In contrast, staining for TGFalpha in epithelial cells of the proximal segment did not change with castration or testosterone administration, suggesting that TGFalpha is not regulated by androgen in this region of the ventral prostate. In summary, TGFalpha expression is differentially regulated among epithelial cells localized in two different regions of the ventral prostate. We hypothesize that TGFalpha may function as a survival factor for epithelial cells which, as a consequence of its expression, become androgen independent and thus escape apoptotic cell death after androgen ablation.

Epidermal growth factor in the rat prostate: production, tissue content and molecular forms in the different prostatic lobes

BACKGROUND

Epidermal growth factor (EGF) induces proliferation in prostate epithelial and stromal cells in primary culture. This investigation was set up to characterize the time and spatial expression of EGF in the rat prostate.

METHODS

The expression of EGF was characterized in the distinct lobes of the rat prostate by means of ELISA, gel filtration, immunohistochemistry, and in situ hybridization.

RESULTS

Local synthesis of EGF by the luminal epithelium was demonstrated by in situ hybridization in the dorsal lobe only. This lobe contained the major part of the prostatic EGF with a sixfold higher concentration than measured in the lateral lobe, and 300-fold higher than in the ventral lobe. Rat prostatic EGF was found to consist of at least two high-molecular-weight forms, as well as a 6-kDa form. The high-molecular-weight forms made up approximately 40% of the EGF measured in the dorsal rat prostate. At 8-12 weeks of age, the concentration of EGF in the dorsal lobe was doubled, with no further increase up to 16 weeks.

CONCLUSIONS

We report a 300-fold difference in the lobar content of EGF in the rat prostate, and a doubling of the concentration at 8-12 weeks of age.

Ontogenic development of the adenylyl cyclase enzyme and the alpha s, alpha i1 and alpha i2 G-protein regulatory subunits from rat prostate

The expression of alpha s, alpha i1 and alpha i2 G-protein subunits measured by immunoblot increased in the rat prostate during sexual maturation, supporting their involvement in proliferation/differentiation. Northern blotting gave transcripts of 1.8 and 4 kb for alpha s, 1.4 and 4.5 kb (mainly) for alpha i1, and 2.4 kb for alpha i2 with levels suggesting a differential regulation (at transcription or post-transcription for alpha s, transcription for alpha i1, and translation for alpha i2). The stimulatory effects of forskolin, vasoactive intestinal peptide (VIP) and isoproterenol on adenylyl cyclase activity increased between 0.5-3 mo, remained constant up to 12 mo and decreased thereafter, conceivably following the expression of VIP and beta-adrenergic receptors. However, G-protein activation of adenylyl cyclase (by GTP and Gpp[NH]p) was maximal at 0.5 mo and then decreased as it occurred with toxin-catalyzed ADP-ribose incorporation to alpha subunits suggesting that other factors are also involved in the regulation of G-protein activity during rat prostatic development.

Development and regenerative ability of bladder in the transgenic epidermal growth factor receptor gene knockout mouse

PURPOSE

During embryogenesis we have previously shown that urothelium is essential for normal bladder growth and development. Urothelial growth may be mediated by peptides of the epidermal growth factor family, since the epidermal growth factor receptor is expressed in bladder urothelium and epidermal growth factor has been shown to induce deoxyribonucleic acid synthesis and migration of urothelial cells in vitro. Bladders from transgenic mice in which the epidermal growth factor receptor gene has been knocked out were used to examine the possible role of epidermal growth factor in bladder growth and development, detrusor neoformation and bladder regeneration.

MATERIALS AND METHODS

Whole bladders from transgenic knockout mice 0 to 10 days old were surgically implanted into the "subdetrusor" space of adult athymic nude rat hosts. After 10 days the dome of the host rat bladder was resected with the distal half of the transplanted knockout mouse bladder. Augmentation cystoplasty was then performed on the host rat bladder using acellular tissue matrix with a portion of the acellular matrix sutured directly to the transplanted knockout mouse bladder. The animals were sacrificed 2 or 3 weeks postoperatively. To test the ability of knockout bladder tissue to regenerate into the transplanted matrix species specific Hoechst dye was used to determine whether the cells within the acellular matrix were of host (rat) or transplant (knockout mouse) origin. Immunocytochemical analysis was used to assess muscle neoformation. Controls consisted of wild-type mouse bladders from the same litter. Since epidermal growth factor receptor knockout mice usually die in the neonatal period, the role of the epidermal growth factor receptor signaling pathway in long-term muscle development was evaluated by transplanting knockout and wild-type control bladders under the renal capsule of athymic nude mouse hosts. These mice were sacrificed 30 days later and muscle development was assessed using immunocytochemical analysis.

RESULTS

Histologically the transplanted acellular tissue matrix in the experimental and control animals appeared the same, containing well differentiated urothelial and smooth muscle cells that had migrated into the transplanted matrix. Staining with species specific Hoechst dye revealed that urothelial and smooth muscle cells transplanted from the knockout and wild-type mouse bladders invaded and regenerated in the transplanted matrix. There was no apparent difference in the amount of knockout or control mouse tissue in the transplanted matrix. Also, the long-term renal capsule transplants revealed no difference in the amount of smooth muscle in the epidermal growth factor receptor knockout and wild-type bladders.

CONCLUSIONS

Signaling through the epidermal growth factor receptor pathway is not necessary for normal bladder development or bladder regeneration after injury.

Change in morphological and functional cytodifferentiation induced by seminal vesicle mesenchyme in cell suspensions of rat Dunning prostatic adenocarcinoma cells

Previous experiments have shown that seminal vesicle mesenchyme (SVM) can induce small 0.5 mm fragments of the rat Dunning tumor (DT) to undergo secretory differentiation with a concomitant reduction in tumorigenesis. In the present experiments Dunning tumor epithelial cells (DTE) were purified from DT cell suspensions by Percoll gradient centrifugation and recombined with neonatal rat SVM. The resultant tissue recombinants (SVM + DTE) were grafted under the renal capsule of male athymic mice and grown for 2 months. Under these conditions SVM induced the DTE to exhibit a highly differentiated secretory phenotype by forming ducts lined with tall columnar epithelial cells or large clear cells with pale cytoplasm. Undifferentiated epithelial cells of the parental DT were rarely observed in these tissue recombinants. The loss of tumorigenicity in SVM + DTE recombinants was associated with a striking reduction of epithelial 3H-thymidine labeling index in SVM + DTE recombinants (DT = 8.31%; SVM + DTE recombinants = 1.10%). Differences in putative secretory proteins were also observed by SDS-PAGE in SVM + DTE recombinants in comparison with DT. Testosterone metabolism was examined in epithelial cells recovered from grafts of DT vs. SVM + DTE tissue recombinants by thin layer chromatography and revealed that the major metabolite produced by DTE was androstenedione, whereas in epithelium isolated from SVM + DTE tissue recombinants the major androgen metabolite was 5alpha-DHT. Thus, after induction by SVM the DTE metabolized androgens in a pattern similar to the normal rat dorsal prostate. The SVM-induced changes in DTE suggest the possibility that emerging or established carcinomas might be regulated at least in part by their connective tissue microenvironment.