Biomedical subjects

B A Foster

Publications and source records attributed to B A Foster.

At least 19 recordsLinked to original sources

PubMed2001

Adenovirus-mediated transfer of inducible caspases: a novel "death switch" gene therapeutic approach to prostate cancer.

In patients with localized prostate cancer, radical prostatectomy and radiation therapy, although effective in controlling localized disease, are often associated with significant side effects attributable to injury of adjacent tissues. Moreover, patients with metastatic disease eventually fail systemic hormonal or chemotherapy because of the development of progressive, refractory disease. In this study, we evaluated the safety and efficacy of a novel suicide gene therapy that could potentially spare normal tissue while bypassing molecular mechanisms of apoptosis resistance by using chemically inducible effector caspases to trigger apoptosis in prostate cancer cells. Initially, we compared the ability of a panel of inducible Fas signaling intermediates to kill human and murine prostate cancer cell lines. On the basis of the superior killing by downstream caspase-1 and caspase-3, replication-deficient adenoviral vectors expressing conditional caspase-1 (Ad-G/iCasp1) or caspase-3 (Ad-G/iCasp3), regulated by nontoxic, lipid-permeable, chemical inducers of dimerization (CID), were constructed. Upon vector transduction followed by CID administration, aggregation and activation of these recombinant caspases occur, leading to rapid apoptosis. In vitro, both human (LNCaP and PC-3) and murine (TRAMP-C2 and TRAMP-C2G) prostate cancer cell lines were efficiently transduced and killed in a CID-dependent fashion. In vivo, direct injection of Ad-G/iCasp1 into s.c. TRAMP-C2 tumors caused focal but extensive apoptosis without evidence for a bystander effect at the maximal viral dose (i.e., 2.5 x 10(10) viral particles/25 microl) in host animals that also received CID compared with control animals. Treatment with Ad-G/iCasp1 plus CID resulted in a transient, yet significant, reduction both in tumor growth and volume compared with tumors treated with vector but not CID (P < 0.035) or vector-diluent plus CID (P < 0.022), both of which grew more rapidly. These results demonstrate that CID-regulated, caspase-based suicide gene therapy is safe and can inhibit the growth of experimental prostate cancer in vitro and in vivo through potent induction of apoptosis, providing a rationale for further development.

Adenocarcinoma↗

PubMed2000

Hormone status selects for spontaneous somatic androgen receptor variants that demonstrate specific ligand and cofactor dependent activities in autochthonous prostate cancer.

We have used the autochthonous transgenic adenocarcinoma of mouse prostate (TRAMP) model to investigate the relationship between somatic mutation in the androgen receptor (AR) and the emergence of androgen-independent prostate cancer. Here we report the identification, isolation, and characterization of distinct classes of AR variants from spontaneous prostate tumors in the TRAMP model. Using cDNA cloning, single stranded conformation polymorphism and sequencing strategies, 15 unique somatic mutations in the AR were identified in prostate tumors obtained from eight TRAMP mice between 24 and 29 weeks of age. At least one mutation was isolated from each mouse. All mutations were single base substitutions, 10 were missense and 5 were silent. Nine mutations in the AR were identified in tumors of four mice that were castrated at 12 weeks of age. Interestingly, the majority of mutations (seven out of nine, 78%) identified in the androgen-independent tumors colocalized in the AR transactivation domain. The remaining mutations colocalized in the AR ligand binding domain. In general, the AR variants demonstrated promoter-, cell-, and cofactor-specific activities in response to various hormones. All AR variants isolated in this study maintained strong sensitivity for androgens, and four AR variants isolated from castrated mice demonstrated increased activities in the absence of ligand. The K638M and F677S variants demonstrated increased activities in response to androgen, and K638M also demonstrated increased response to estradiol. In the presence of AR coactivator ARA70 the E231G variant demonstrated increased activity in response to both androgen and estradiol. However, in the presence of AR coactivator ARA160 the E231G variant was selectively responsive to androgen. Collectively these analyses not only indicate that somatic mutations in the AR gene occur spontaneously in TRAMP tumors but also how changes in the hormonal environment may drive the selection of spontaneous somatic mutations that provide a growth advantage.

Animals↗

PubMed2000

Combination immunotherapy of primary prostate cancer in a transgenic mouse model using CTLA-4 blockade.

We have previously shown that antibodies to CTLA-4, an inhibitory receptor on T cells, can be effective at inducing regression of transplantable murine tumors. In this study, we demonstrate that an effective immune response against primary prostate tumors in transgenic (TRAMP) mice can be elicited using a strategy that combines CTLA-4 blockade and an irradiated tumor cell vaccine. Treatment of TRAMP mice at 14 weeks of age resulted in a significant reduction in tumor incidence (15% versus control, 75%), as assessed 2 months after treatment. Histopathological analysis revealed that treated mice had a lower tumor grade with significant accumulation of inflammatory cells in interductal spaces when treated with anti-CTLA-4 and a granulocyte-macrophage colony-stimulating factor-expressing vaccine. Vaccination of nontransgenic mice with this regimen resulted in marked prostatitis accompanied by destruction of epithelium, indicating that the immune response was, at least in part, directed against normal prostate antigens. These findings demonstrate that this combinatorial treatment can elicit a potent antiprostate response and suggest potential of this approach for treatment of prostate cancer.

Abatacept↗

PubMed1999

Pharmacological rescue of mutant p53 conformation and function.

Compounds that stabilize the DNA binding domain of p53 in the active conformation were identified. These small synthetic molecules not only promoted the stability of wild-type p53 but also allowed mutant p53 to maintain an active conformation. A prototype compound caused the accumulation of conformationally active p53 in cells with mutant p53, enabling it to activate transcription and to slow tumor growth in mice. With further work aimed at improving potency, this class of compounds may be developed into anticancer drugs of broad utility.

Animals↗

PubMed1999

Elimination of residual metastatic prostate cancer after surgery and adjunctive cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade immunotherapy.

Cancer relapse after surgery is a common occurrence, most frequently resulting from the outgrowth of minimal residual disease in the form of metastases. We examined the effectiveness of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade as an adjunctive immunotherapy to reduce metastatic relapse after primary prostate tumor resection. For these studies, we developed a murine model in which overt metastatic outgrowth of TRAMP-C2 (C2) prostate cancer ensues after complete primary tumor resection. Metastatic relapse in this model occurs reliably and principally within the draining lymph nodes in close proximity to the primary tumor, arising from established metastases present at the time of surgery. Using this model, we demonstrate that adjunctive CTLA-4 blockade administered immediately after primary tumor resection reduces metastatic relapse from 97.4 to 44%. Consistent with this, lymph nodes obtained 2 weeks after treatment reveal marked destruction or complete elimination of C2 metastases in 60% of mice receiving adjunctive anti-CTLA-4 whereas 100% of control antibody-treated mice demonstrate progressive C2 lymph node replacement. Our study demonstrates the potential of adjunctive CTLA-4 blockade immunotherapy to reduce cancer relapse emanating from minimal residual metastatic disease and may have broader implications for improving the capability of immunotherapy by combining such forms of therapy with other cytoreductive measures including surgery.

Abatacept↗

PubMed1999

Role of RhoA activation in the growth and morphology of a murine prostate tumor cell line.

Prostate cancer cells derived from transgenic mice with adenocarcinoma of the prostate (TRAMP cells) were treated with the HMG-CoA reductase inhibitor, lovastatin. This caused inactivation of the small GTPase RhoA, actin stress fiber disassembly, cell rounding, growth arrest in the G1 phase of the cell cycle, cell detachment and apoptosis. Addition of geranylgeraniol (GGOL) in the presence of lovastatin, to stimulate protein geranylgeranylation, prevented lovastatin's effects. That is, RhoA was activated, actin stress fibers were assembled, the cells assumed a flat morphology and cell growth resumed. The following observations support an essential role for RhoA in TRAMP cell growth: (1) TRAMP cells expressing dominant-negative RhoA (T19N) mutant protein displayed few actin stress fibers and grew at a slower rate than controls (35 h doubling time for cells expressing RhoA (T19N) vs 20 h for untransfected cells); (2) TRAMP cells expressing constitutively active RhoA (Q63L) mutant protein displayed a contractile phenotype and grew faster than controls (13 h doubling time). Interestingly, addition of farnesol (FOL) with lovastatin, to stimulate protein farnesylation, prevented lovastatin-induced cell rounding, cell detachment and apoptosis, and stimulated cell spreading to a spindle shaped morphology. However, RhoA remained inactive and growth arrest persisted. The morphological effects of FOL addition were prevented in TRAMP cells expressing dominant-negative H-Ras (T17N) mutant protein. Thus, it appears that H-Ras is capable of inducing cell spreading, but incapable of supporting cell proliferation, in the absence of geranylgeranylated proteins like RhoA.

Actin Cytoskeleton↗

PubMed1999

The insulin-like growth factor axis and prostate cancer: lessons from the transgenic adenocarcinoma of mouse prostate (TRAMP) model.

We have characterized the temporal expression of the insulin-like growth factor (IGF) axis in the transgenic adenocarcinoma of mouse prostate (TRAMP) model as prostate cancer progression in this model closely mimics that observed in the human disease, and the model provides samples representing the earliest stages of prostate cancer that are clinically the most difficult to obtain. We report that prostate-specific IGF-I mRNA expression increased during prostate cancer progression in TRAMP mice and was elevated in the accompanying metastatic lesions, whereas prostatic IGF-I mRNA remained at nontransgenic levels in androgen-independent disease. Expression of IGF-II mRNA, however, was reduced in primary prostate cancer, metastatic lesions, and androgen-independent disease. Expression of type-1 IGF receptor (IGF1R) mRNA, encoding the cognate receptor for both IGF-I and IGF-II, as well as type-2 IGF receptor (IGF2R) mRNA was not found to be altered during primary prostate cancer progression in intact TRAMP mice but was dramatically reduced in metastatic lesions and in androgen-independent disease. Similar to reports from clinical disease, serum IGF-I levels were observed to increase precociously in TRAMP mice early in disease progression but remained at nontransgenic levels after castration. Elevated serum levels of IGF-binding protein 2 were observed to correlate with advanced prostate cancer in the TRAMP model. Together these observations implicate IGF-I as an important factor during the initiation and progression of primary prostate cancer and provide evidence that there is a strong selection against expression of IGF1R and IGF2R in metastatic and androgen-independent disease.

Adenocarcinoma↗

PubMed1999

Pathologic progression of autochthonous prostate cancer in the TRAMP model.

The ability to manipulate gene expression in specific cell types at specific times utilizing transgenic technology has allowed the development of novel mouse model systems that can mimic human disease. We have previously established the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model for prostate cancer using the rat probasin promoter to direct expression of the SV40 early genes to prostate epithelium. Male TRAMP mice exhibit consistent prostate-specific patterns of expression and develop prostatic intraepithelial neoplasia that will become invasive and metastasize primarily to the lymph nodes and lungs. In this paper we report our continued experience with this model and present a standardized histologic grading system to designate low and high grade prostatic intraepithelial neoplasia and well, moderate, and poorly differentiated prostate adenocarcinoma. In addition, we demonstrate the persistence of androgen receptor expression during pathologic progression and characterize heterogeneous cytokeratin expression in localized and metastatic prostate cancer. Finally, we report on our observations that phenotypic variability in tumor and pathologic progression in TRAMP occurs as a function of genetic background.

Journal Article↗

PubMed1999

Characterization of the FGF axis and identification of a novel FGFR1iiic isoform during prostate cancer progression in the TRAMP model.

Expression of the fibroblast growth factor (FGF) axis was examined during prostate cancer progression in the autochthonous Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model, including TRAMP derived cell lines. Transcripts for FGF-7 and FGF-10 that are normally expressed by the stroma were detected in all samples, including the epithelial cell lines, suggesting that elaboration of these factors by the epithelium may be an essential event during transformation. Interestingly FGFR2iiib, the FGF-7 and FGF-10 receptor, was downregulated during tumor progression whereas a novel FGFR1iiic (Phi) inframe splice form was found to be expressed. These observations support the hypothesis that specific changes in FGF axis correlate with, and probably facilitate, tumor progression.

Journal Article↗

PubMed1999

Efficacy of various natural and synthetic androgens to induce ductal branching morphogenesis in the developing anterior rat prostate.

The studies presented herein quantitated ductal branching morphogenesis in the anterior prostate (AP) of the newborn rat. Four parameters were measured: epithelial area, epithelial perimeter, node number, and form factor. Nine natural and synthetic androgens were tested for their effectiveness in inducing postnatal prostatic development using 808 newborn rat APs in 68 dose-response experiments. Based on these studies it was shown that testosterone (T) was slightly more effective than dihydrotestosterone (DHT) in supporting ductal branching morphogenesis in the developing rat AP. Furthermore, the activity of T could not be accounted for simply by conversion of T to DHT. Synthetic androgens, 7alpha-methyl-19-nortestosterone and methyltrienolone (R1881), which cannot be 5alpha-reduced to DHT, also induced extensive ductal branching and elicited responses less than those to T and not statistically different from those to DHT. This suggests that although DHT is sufficient for prostatic development, it is not necessary for postnatal ductal branching morphogenesis and growth of the prostate. 5Alpha-androstan-3alpha,17beta-diol was particularly potent in inducing ductal branching, eliciting a response greater than or comparable to those of T and DHT. Androsterone, androstanedione, 5alpha-androstan-3beta,17beta-diol and 5beta-androstan-3alpha,17beta-diol induced ductal branching, but to a lesser extent than either T or DHT. These studies challenge the assumption that DHT is essential for prostatic development, specifically during ductal branching morphogenesis of the neonatal rat prostate.

Androgens↗

PubMed1997

Characterization of prostatic epithelial cell lines derived from transgenic adenocarcinoma of the mouse prostate (TRAMP) model.

To develop a syngeneic transplantable system to study immunotherapeutic approaches for the treatment of prostate cancer, three cell lines were established from a heterogeneous 32 week tumor of the transgenic adenocarcinoma mouse prostate (TRAMP) model. TRAMP is a transgenic line of C57BL/6 mice harboring a construct comprised of the minimal -426/+28 rat probasin promoter driving prostate-specific epithelial expression of the SV40 large T antigen. TRAMP males develop histological prostatic intraepithelial neoplasia by 8-12 weeks of age that progress to adenocarcinoma with distant metastases by 24-30 weeks of age. The three cell lines (TRAMP-C1, TRAMP-C2, and TRAMP-C3) express cytokeratin, E-cadherin, and androgen receptor by immunohistochemical analysis and do not appear to have a mutated p53. Although TRAMP-C1 and TRAMP-C2 are tumorigenic when grafted into syngeneic C57BL/6 hosts, TRAMP-C3 grows readily in vitro but does not form tumors. The T antigen oncoprotein is not expressed by the cell lines in vitro or in vivo. The rationale for establishing multiple cell lines was to isolate cells representing various stages of cellular transformation and progression to androgen-independent metastatic disease that could be manipulated in vitro and, in combination with the TRAMP model, provide a system to investigate therapeutic interventions, such as immunotherapy prior to clinical trials.

Adenocarcinoma↗

PubMed1997

Manipulation of T cell costimulatory and inhibitory signals for immunotherapy of prostate cancer.

The identification of potentially useful immune-based treatments for prostate cancer has been severely constrained by the scarcity of relevant animal research models for this disease. Moreover, some of the most critical mechanisms involved in complete and proper antitumoral T cell activation have only recently been identified for experimental manipulation, namely, components involved in the costimulatory pathway for T cell activation. Thus, we have established a novel syngeneic murine prostate cancer model that permits us to examine two distinct manipulations intended to elicit an antiprostate cancer response through enhanced T cell costimulation: (i) provision of direct costimulation by prostate cancer cells transduced to express the B7.1 ligand and (ii) in vivo antibody-mediated blockade of the T cell CTLA-4, which prevents T cell down-regulation. In the present study we found that a tumorigenic prostate cancer cell line, TRAMPC1 (pTC1), derived from transgenic mice, is rejected by syngeneic C57BL/6 mice, but not athymic mice, after this cell line is transduced to express the costimulatory ligand B7.1. Also, we demonstrated that in vivo antibody-mediated blockade of CTLA-4 enhances antiprostate cancer immune responses. The response raised by anti-CTLA-4 administration ranges from marked reductions in wild-type pTC1 growth to complete rejection of these cells. Collectively, these experiments suggest that appropriate manipulation of T cell costimulatory and inhibitory signals may provide a fundamental and highly adaptable basis for prostate cancer immunotherapy. Additionally, the syngeneic murine model that we introduce provides a comprehensive system for further testing of immune-based treatments for prostate cancer.

Abatacept↗

PubMed1997

Differentiation of rat neonatal ventral prostates grown in a serum-free organ culture system.

BACKGROUND: Organ culture methods have long been used in the study of the prostate because effects of drugs and hormones can be examined in the absence of systemic effects. METHODS: Neonatal rat ventral prostates (VP) were grown on Millipore filters floating on fluid medium composed of Dulbecco's modified Eagle's medium/Ham's F-12 supplemented with insulin, transferrin, and hydrocortisone, and in the presence or absence of testosterone (T, 10(-8)M). RESULTS: In the presence of T, ductal lumen formation occurred, ductal branching was extensive, and basal and luminal epithelial cells were identified by immunocytochemistry based on their distinctive cytokeratin profile. In the absence of T, ductal lumen formation did not occur, basal and luminal epithelial cells failed to differentiate, and there was a marked decrease in prostatic organ size relative to glands grown with T. Interestingly, DNA synthesis, as measured by counts per min (CPM) for 3H-thymidine incorporation, showed that DNA synthesis per microgram DNA at 7 days of organ culture was not inhibited by lack of T. Androgen receptor expression is another marker of prostatic epithelial differentiation, and it occurred in both the presence and absence of T. CONCLUSIONS: Growth and differentiation of the neonatal rat prostate in vitro occur in a manner similar to that of the developing prostate in vivo, demonstrating that organ cultures of neonatal rat ventral prostates provide a faithful model for studying rat prostatic development and differentiation under serum-free conditions.

Animals↗

PubMed1997

Analysis of growth factor and receptor mRNA levels during development of the rat seminal vesicle and prostate.

Development of the mammalian male accessory sexual organs requires both androgens and mesenchymal/epithelial interactions. Paracrine acting factors whose expression is mesenchymal and androgen dependent have been proposed to regulate development of these organs, although the identity of these paracrine mediators is unknown. Keratinocyte growth factor (Kgf) has been shown to play an important role in the development of the mouse seminal vesicle and rat ventral prostate. Also, Kgf is expressed in mesenchymal cells and has been shown to be regulated by androgens in prostatic cells grown in vitro. Thus Kgf has been proposed as a mediator of androgen action. We have investigated the expression of Kgf mRNA during development of the rat seminal vesicle and prostate, both in vitro and in vivo. Additionally we have examined mRNAs for Kgf receptor (KgfR), transforming growth factor alpha (Tgf alpha), epidermal growth factor receptor (EgfR) and cytokeratin 19 (CK19). The levels of growth factor and receptor mRNAs fluctuated during androgen-regulated development; however, these changes reflected variations in the mesenchymal/epithelial ratio rather than regulation by testosterone. Expression of Kgf is mesenchymal, while KgfR is epithelial and Tgf alpha is predominantly epithelial. The changes in the levels of mRNAs for these factors correlated well with changes in the level of an epithelial marker, CK19, suggesting they were due to alterations in the relative abundance of tissue compartments in which they were expressed. Kgf has been shown to mimic androgen action in explant cultures of seminal vesicle and prostate. We demonstrate here that anti-androgens are able to block Kgf stimulated development, suggesting that Kgf and androgen receptor signalling pathways may interact. Taken together our data suggest that, in vivo, Kgf may interact with androgen receptor signalling but it is not a direct target of androgen action.

Actins↗

PubMed1996

Smooth muscle-epithelial interactions in normal and neoplastic prostatic development.

A hypothesis is proposed that unifies prostatic developmental biology and carcinogenesis. The foundation of this hypothesis is the reciprocal interaction of epithelium and mesenchyme during prostatic development followed thereafter by a reciprocal homeostatic interaction of epithelium and smooth muscle in adulthood. This smooth muscle-epithelial cell interaction is perturbed during prostatic carcinogenesis with adverse sequelae for both epithelium and smooth muscle. The following sequence of events is proposed to occur: (1) Under the influence of androgens, urogenital sinus mesenchyme (UGM) induces urogenital sinus epithelium to undergo prostatic ductal morphogenesis and differentiation. (2) As prostatic epithelium differentiates, it in turn signals the UGM to differentiate into smooth muscle cells that closely surround the epithelial ducts. Differentiation of prostatic smooth muscle requires both an inductive signal from epithelium and androgens. (3) Once formed, prostatic smooth muscle participates in reciprocal homeostatic interactions. We propose that prostatic smooth muscle under the influence of androgens signals to prostatic epithelium to maintain epithelial differentiation and to repress epithelial proliferation, while prostatic epithelium signals to prostatic smooth muscle to maintain smooth muscle differentiation. In adulthood, homeostasis is maintained through reciprocal interactions between smooth muscle and epithelial cells with minimal proliferation of either cell type. Prostatic carcinogenesis, which is initiated following genetic damage to prostatic epithelium, is surmised to involve a sequential disruption in these reciprocal homeostatic interactions with ensuing dedifferentiation of both the emerging prostatic carcinoma cells and smooth muscle. Thus, following genetic insult to prostatic epithelium the epithelium fails to signal appropriately to the smooth muscle, which then begins to dedifferentiate. As smooth muscle differentiation begins to deviate, signaling from prostatic smooth muscle to prostatic epithelium becomes anomalous resulting in progressive loss of control over epithelial differentiation and proliferation. During progression of prostatic carcinogenesis a vicious cycle is established in which both prostatic epithelium and smooth muscle dedifferentiate. This hypothesis is based on the ontogeny of prostatic smooth muscle differentiation during development and by the fact that the amount of smooth muscle progressively diminishes in human prostatic adenocarcinomas during progression from low- to high-grade cancers. Finally, in experimental tissue recombinants in which various normal or neoplastic prostatic epithelia were grown in combination with embryonic rat UGM, only normal (non-neoplastic) epithelia were capable of inducing differentiation of prostatic smooth muscle in UGM. Based on several lines of evidence, it is now apparent that smooth muscle-epithelial interactions are the operative cell-cell interaction in the postnatal prostate which plays a key role in regulating epithelial differentiation, proliferation and carcinogenesis.

Animals↗

PubMed1996

Epithelial development in the rat ventral prostate, anterior prostate and seminal vesicle.

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. The epithelial cells of these glands produce the bulk of the seminal secretions. The objective of the present study was to examine the ontogeny of cytokeratin and androgen receptor (AR) expression in the rat SV, anterior prostate (AP) and ventral prostate (VP). The study utilized organ culture to examine the effects of androgens on the development of these markers and castration of adult rats to examine androgenic effects on their maintenance. Tissues were examined from 14 days of gestation to adulthood. The SV was a tubular organ from its inception while the prostate formed from solid epithelial cords. These prostatic buds canalized in a proximal to distal manner starting at day 1 postnatal in the VP and day 5 in the AP. The expression of cytokeratins and AR was visualized by immunocytochemistry. In all three glands keratins 5, 7, 8, 14, 18 and 19 were initially uniformly expressed in all epithelial cells. In the SV, segregation of cytokeratins between the luminal and basal cell types started at 4 days postnatally with keratin 7 localizing to basal cells. Five days after birth, keratins 5 and 14 were also localized to the basal epithelium, while keratins 8 and 18 were only expressed by luminal cells, Keratin 19 was expressed in all epithelial cells throughout development and into adulthood. In the VP and AP the same pattern of cytokeratin segregation occurred as in the SV. Epithelial differentiation occurred in a proximal to distal fashion in the prostate. In the proximal VP ducts keratins 7 and 14 were basally localized by 2 days postnatally, while keratin 5 did not clearly segregate to basal cells until day 9 after birth. In the AP keratin 14 was basally localized by 1 day postnatal but keratin 5 and 7 did not colocalize to the basal cells until days 9 and 12, respectively. AR were expressed in the epithelium of the urogenital sinus from 19 days of gestation. At 19 and 20 days of embryonic development AR-negative prostatic buds were seen emerging from the AR-positive urogenital sinus epithelium. By birth AR were detectable in the epithelium of both prostatic lobes and the SV. The role of androgens in the development of the prostatic and SV epithelium was investigated in a serum-free organ culture system. These experiments showed that differentiation of prostatic and SV luminal and basal epithelial cell types was accelerated as compared to the in vivo situation in the presence of androgens, and did not occur in their absence. Following castration of adult animals the prostate and SV regressed with preferential loss of luminal epithelium. The relative numbers of basal cells was increased, though some flattened cells expressing a luminal cell pattern of cytokeratins were still observed. AR were detected in the prostatic and SV epithelium of long-term castrated animals. In summary, the rat prostate was found to be derived from undifferentiated solid epithelial cords. Canalization occurred concurrent with the differentiation of clear epithelial subtypes. Epithelial AR were expressed from around the time of birth and expression levels increased with age. The SV was canalized from its inception but likewise was derived from an undifferentiated epithelial precursor.

Age Factors↗

PubMed1996

Stromal development in the ventral prostate, anterior prostate and seminal vesicle of the rat.

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. They produce the bulk of the seminal secretions. The object of the present study was to examine and document the ontogeny of stromal maturation in the rat anterior and ventral prostate and SV. These organs have a loosely organized cellular mesenchyme during fetal development. During prostatic development the mesenchyme condensed to form smooth muscle sheaths immediately surrounding the epithelium, with looser connective tissue between individual ducts. In the SV, a loose connective tissue layer called the lamina propria lies between the epithelium and developing muscle. Smooth muscle alpha-actin, myosin, desmin, laminin, vinculin, vimentin and androgen receptor (AR) expression were examined by immunocytochemical methods during the pre- and postnatal developmental periods. The first marker to be detected was vimentin, which was initially found throughout the mesenchyme. During development vimentin became mostly restricted to the interductal tissue of the prostate and the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proximal to distal manner along prostatic ducts, from the urethra towards the tips. Expression of alpha-actin was followed by vinculin, myosin, desmin, and laminin. These markers became localized to the developing smooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the lamina propria of the SV. Organ culture experiments demonstrated that androgens were required for the differentiation of smooth muscle sheaths. Castration of adult rats demonstrated that androgens were required to maintain smooth muscle differentiation. In castrates, the stroma was relatively thicker but less dense than in intact animals. Following castration, expression of the smooth muscle markers was lost sequentially in the reverse order of their expression during development. In long-term castrates alpha-actin, vimentin and a small amount of vinculin were detected. AR were first detected in the urogenital sinus mesenchyme immediately surrounding the epithelium at 16 days of gestation. As development progressed expression of AR became more widespread, and postnatally was found throughout the mesenchyme. As maturation of smooth muscle occurred, stromal expression of AR became localized to the muscular sheath immediately surrounding the epithelium. In the prostate the interductal connective tissue displayed very low levels of AR expression. In the SV, AR were also observed in the lamina propria. In summary, stromal differentiation and dedifferentiation in the rat prostate and SV were found to be androgen-dependent processes with ordered sequential ontogenic expression of specific markers.

Actins↗

PubMed1996

Initiation of secretory activity of rat prostatic epithelium in organ culture.

Functional differentiation of prostatic epithelium is manifested by the production of tissue specific secretory proteins. In vivo production of these proteins is dependent on the presence of serum androgens. A serum-free organ culture system was used to examine the initiation of prostatic epithelial cytodifferentiation in vitro using two rat prostate specific secretory proteins (DP-1 and probasin) as markers of epithelial cytodifferentiation. The dorsal-lateral and anterior prostatic (AP) lobes from 12-day-old rats were cultured for 6 days in serum-free medium in the presence or absence of androgens. At the start of culture, secretory proteins DP-1 and probasin were undetectable using Western blot analysis. DP-1 and probasin were produced by explants cultured in the presence of androgens but were not detected in the absence of androgens. Dose-response studies were carried out for testosterone (T), 5 alpha-dihydrotestosterone (DHT), 5 alpha-Androstan-3 alpha, 17 beta-diol (3 alpha-Adiol), and two synthetic androgens: 17 alpha-methyl-19-nortestosterone (MENT) and methyltrienolone (R1881). All androgens used were capable of inducing expression of DP-1 and probasin in vitro. T, R1881, and Ment were effective at doses of 10(-7) M to 10(-9) M, whereas both DHT and 3 alpha-Adiol were able to induce DP-1 and probasin at concentrations as low as 10(-10) M. Estrogen (17 beta-Estradiol), hydrocortisone (11 beta, 17 alpha, 21-trihydroxypregn-4-ene-3, 20-dione), and progesterone (4-pregnen-3, 20-Dione) were ineffective in inducing prostatic secretory activity. Hydroxyflutamide (alpha-alpha-alpha-trifluro-2-methyl-4'-nitro-m-lactoluidide ) blocked the induction of secretory activity elicited by T. From histological sections, it was observed that explants cultured with T exhibited tall columnar epithelial morphology with organized stromal components. Tissue sections of explants cultured without T exhibited a cuboidal to low columnar morphology with less organized stromal components when compared with glands cultured with T. A DNA synthetic index was established to measure proliferation in the explants at the end of the culture period. Explants cultured in the presence of T exhibited greater DNA synthetic activity than explants cultured in the absence of T (P < 0.05). Using this serum-free model, we can explore the mechanism for the initiation of secretory cytodifferentiation.

Androgen-Binding Protein↗