Left out in the cold: Moving beyond hormonal therapy for the treatment of immunologically cold prostate cancer with CAR T cell immunotherapies.

Prostate cancer is primarily hormone-dependent, and medical treatments have focused on inhibiting androgen biosynthesis or signaling through various approaches. Despite significant advances with the introduction of androgen receptor signalling inhibitors (ARSIs), patients continue to progress to castration-resistant prostate cancer (CRPC), highlighting the need for targeted therapies that extend beyond hormonal blockade. Chimeric Antigen Receptor (CAR) T cells and other engineered immune cells represent a new generation of adoptive cellular therapies. While these therapies have significantly enhanced outcomes for patients with hematological malignancies, ongoing research is exploring the broader use of CAR T therapy in solid tumors, including advanced prostate cancer. In general, CAR T cell therapies are less effective against solid cancers with the immunosuppressive tumor microenvironment hindering T cell infiltration, activation and cytotoxicity following antigen recognition. In addition, inherent tumor heterogeneity exists in patients with advanced prostate cancer that may prevent durable therapeutic responses using single-target agents. These barriers must be overcome to inform clinical trial design and improve treatment efficacy. In this review, we discuss the innovative and rationally designed strategies under investigation to improve the clinical translation of cellular immunotherapy in prostate cancer and maximise therapeutic outcomes for these patients.

Low-dose carboplatin modifies the tumor microenvironment to augment CAR T cell efficacy in human prostate cancer models.

Chimeric antigen receptor (CAR) T cells have transformed the treatment landscape for hematological malignancies. However, CAR T cells are less efficient against solid tumors, largely due to poor infiltration resulting from the immunosuppressive nature of the tumor microenvironment (TME). Here, we assessed the efficacy of Lewis Y antigen (LeY)-specific CAR T cells in patient-derived xenograft (PDX) models of prostate cancer. In vitro, LeY CAR T cells directly killed organoids derived from androgen receptor (AR)-positive or AR-null PDXs. In vivo, although LeY CAR T cells alone did not reduce tumor growth, a single prior dose of carboplatin reduced tumor burden. Carboplatin had a pro-inflammatory effect on the TME that facilitated early and durable CAR T cell infiltration, including an altered cancer-associated fibroblast phenotype, enhanced extracellular matrix degradation and re-oriented M1 macrophage differentiation. In a PDX less sensitive to carboplatin, CAR T cell infiltration was dampened; however, a reduction in tumor burden was still observed with increased T cell activation. These findings indicate that carboplatin improves the efficacy of CAR T cell treatment, with the extent of the response dependent on changes induced within the TME.

Prostate-regenerating capacity of cultured human adult prostate epithelial cells.

Experimentation with the progenitor/stem cells in adult prostate epithelium can be inconvenient due to a tight time line from tissue acquisition to cell isolation and to downstream experiments. To circumvent this inconvenience, we developed a simple technical procedure for culturing epithelial cells derived from human prostate tissue. In this study, benign prostate tissue was enzymatically digested and fractionated into epithelium and stroma, which were then cultured in the medium designed for prostate epithelial and stromal cells, respectively. The cultured cells were analyzed by immunocytochemical staining and flow cytometry. Prostate tissue-regenerating capacity of cultured cells in vitro was determined by co-culturing epithelial and stromal cells in dihydrotestosterone-containing RPMI. Cell lineages in formed acini-like structures were determined by immunohistochemistry. The culture of epithelial cells mainly consisted of basal cells. A minor population was negative for known lineage markers and positive for CD133. The culture also contained cells with high activity of aldehyde dehydrogenase. After co-culturing with stromal cells, the epithelial cells were able to form acini-like structures containing multiple cell lineages. Thus, the established culture of prostate epithelial cells provides an alternative source for studying progenitor/stem cells of prostate epithelium.

Cancer-associated fibroblasts of the prostate promote a compliant and more invasive phenotype in benign prostate epithelial cells.

Reciprocal interactions between prostate epithelial cells and their adjacent stromal microenvironment not only are essential for tissue homeostasis but also play a key role in tumor development and progression. Malignant transformation is associated with the formation of a reactive stroma where cancer-associated fibroblasts (CAFs) induce matrix remodeling and thereby provide atypical biochemical and biomechanical signals to epithelial cells. Previous work has been focused on the cellular and molecular phenotype as well as on matrix stiffness and remodeling, providing potential targets for cancer therapeutics. So far, biomechanical changes in CAFs and adjacent epithelial cells of the prostate have not been explored. Here, we compared the mechanical properties of primary prostatic CAFs and patient-matched non-malignant prostate tissue fibroblasts (NPFs) using atomic force microscopy (AFM) and real-time deformability cytometry (RT-FDC). It was found that CAFs exhibit an increased apparent Young's modulus, coinciding with an altered architecture of the cytoskeleton compared with NPFs. In contrast, co-cultures of benign prostate epithelial (BPH-1) cells with CAFs resulted in a decreased stiffness of the epithelial cells, as well as an elongated morphological phenotype, when compared with co-cultures with NPFs. Moreover, the presence of CAFs increased proliferation and invasion of epithelial cells, features typically associated with tumor progression. Altogether, this study provides novel insights into the mechanical interactions between epithelial cells with the malignant prostate microenvironment, which could potentially be explored for new diagnostic approaches.

Elevated level of inhibin-alpha subunit is pro-tumourigenic and pro-metastatic and associated with extracapsular spread in advanced prostate cancer.

The biological function of inhibin-alpha subunit (INH alpha) in prostate cancer (PCa) is currently unclear. A recent study associated elevated levels of INH alpha in PCa patients with a higher risk of recurrence. This prompted us to use clinical specimens and functional studies to investigate the pro-tumourigenic and pro-metastatic function of INH alpha. We conducted a cross-sectional study to determine a link between INH alpha expression and a number of clinicopathological parameters including Gleason score, surgical margin, extracapsular spread, lymph node status and vascular endothelial growth factor receptor-3 expression, which are well-established prognostic factors of PCa. In addition, using two human PCa cell lines (LNCaP and PC3) representing androgen-dependent and -independent PCa respectively, we investigated the biological function of elevated levels of INH alpha in advanced cancer. Elevated expression of INH alpha in primary PCa tissues showed a higher risk of PCa patients being positive for clinicopathological parameters outlined above. Over-expressing INH alpha in LNCaP and PC3 cells demonstrated two different and cell-type-specific responses. INH alpha-positive LNCaP demonstrated reduced tumour growth whereas INH alpha-positive PC3 cells demonstrated increased tumour growth and metastasis through the process of lymphangiogenesis. This study is the first to demonstrate a pro-tumourigenic and pro-metastatic function for INH alpha associated with androgen-independent stage of metastatic prostate disease. Our results also suggest that INH alpha expression in the primary prostate tumour can be used as a predictive factor for prognosis of PCa.

Inhibition of compensatory renal growth by the N-terminus of a sheep-derived peptide.

The N-terminal sequence of a novel sheep-derived peptide with growth inhibitory activity has been obtained. The N-terminal fragment was chemically synthesised and designated EPL001. The kidney was chosen as the first mammalian system in which to study EPL001 since kidney growth can be accurately quantified following a surgical reduction in renal mass. Cell proliferation was measured in mouse collecting duct kidney (MCDK) cells stimulated with insulin-like growth factor I (IGF-I). Compensatory renal growth (CRG) was induced in Wistar rats and either EPL001 or an EPL001 antibody delivered by continuous renal tissue infusion. Mouse monoclonal antibodies to EPL001 were generated for immunoneutralisation, rabbit polyclonal antibodies were generated for immunohistochemistry. EPL001 had no apparent effect on IGF-I stimulated cell proliferation in MCDK cells in vitro, yet provoked a dose-dependent inhibition of CRG in vivo. An EPL001 antibody potentiated CRG, in the absence of exogenous EPL001, consistent with an inhibitory role in kidney growth for an endogenous peptide containing the EPL001 sequence. Tubular staining for epitopes to the EPL001 sequence was detected in normal human kidney sections and enhanced in renal cell carcinoma. Results support the presence of growth inhibitory activity in the N-terminus of a sheep-derived peptide with evidence for both its presence and endogenous activity in the kidney. Attempts to further characterise its structure and activity are ongoing.

Activins and inhibins in endocrine and other tumors.

Inhibin and activin are members of the TGF beta superfamily of growth and differentiation factors. They were first identified as gonadal-derived regulators of pituitary FSH and were subsequently assigned multiple actions in a wide range of tissues. More recently, the inhibin alpha subunit was considered as a tumor suppressor based on functional studies employing transgenic mouse models. This review evaluates the functional and molecular evidence that the inhibin alpha subunit is a tumor suppressor in endocrine cancers. The evaluation highlights the discrepant results from the human and mouse studies, as well as the differences between endocrine tumor types. In addition, we examine the evidence that the activin-signaling pathway is tumor suppressive and identify organ-specific differences in the actions and putative roles of this pathway in endocrine tumors. In summary, there is a considerable body of evidence to support the role of inhibins and activins in endocrine-related tumors. Future studies will define the mechanisms by which inhibins and activins contribute to the process of initiation, promotion, or progression of endocrine-related cancers.

Differences in proteins synthesized by fibroblasts from normal individuals and patients with complete testicular feminization.

Patterns of protein synthesis by genital skin fibroblasts from three unrelated normal individuals and three unrelated patients with complete testicular feminization were compared to two-dimensional gel electrophoresis. cell lines were maintained in monolayer culture and pulse labeled with [35S]methionine. Cells were lysed in 9 M urea, and aliquots of 20 microliters subjected to isoelectric focussing and polyacrylamide gel electrophoresis followed by autoradiography. Gels of control fibroblasts showed two proteins (mol wt approximately 45,000, approximately 85,000; pKi approximately 5.0) markedly more prominent than on gels from affected fibroblasts. This pattern was unaltered by prior exposure to dihydrotestosterone, suggesting differences in constitutive proteins of the fibroblast cells. Parallel studies demonstrated a marked reduction in the ability of fibroblasts from patients with complete testicular feminization to bind androgens in vitro compared with those of normal individuals. The relationship between these proteins, androgen receptors, and androgen insensitivity requires further investigation.

17beta-estradiol induces apoptosis in the developing rodent prostate independently of ERalpha or ERbeta.

Estrogens induce both proliferative and antiproliferative responses in the prostate gland. To date, antiproliferative effects of estrogens are generally considered to be due to systemic antiandrogenic actions. However, estrogen action mediated through estrogen receptor (ER) beta was recently suggested as another mechanism of induction of apoptosis in the prostate. This study aimed to explore the hypothesis that the antiproliferative effects of estrogen are directly mediated through ERbeta using a prostate organ culture system. We previously reported effects of 17beta-estradiol (E2) using rat ventral prostate (VP) tissues, and adapted the system for culturing mouse tissues. In both rat and mouse models, estrogen-induced apoptosis was detected that was spatially and regionally localized to the epithelium of the distal tips. Using organ cultures of alphaER knockout (alphaERKO) and betaERKO prostates, we failed to demonstrate that apoptosis induced by E2 was mediated through either receptor subtype. Activation of ER-selective ligands (ERalpha, propyl pyrazole triol, ERbeta, diaryl-proprionitrile, and 5alpha-androstane-3beta,17beta-diol) in organ culture experiments failed to induce apoptosis, as did the membrane impermeable conjugate E2:BSA, discounting the possibility of nongenomic effects. Consequently, E2 regulation of androgen receptor (AR) expression was examined and, in the presence of nanomolar testosterone levels, E2 caused a specific reduction in AR protein expression in wild-type, alphaERKO, and betaERKO mice, particularly in the distal region where apoptosis was detected. This down-regulation of AR protein provides a possible mechanism for the proapoptotic action of E2 that is independent of ERs or nongenomic effects.

Aromatase and prostate cancer.

The normal growth and development of the prostate requires the presence and action of androgens, which are also known risk factors in the origins of benign and malignant prostate disease. Paradoxically, the incidence of prostate disease increases with age when serum androgen levels are in decline and emerging evidence suggests that estrogens may also be important in the normal prostate, as well as in the etiology of prostate disease. Both estrogen receptor subtypes are present in the prostate, demonstrating that the gland responds directly to estrogens. Recent data suggests that estrogens play a role in prostate disease and has demonstrated that high doses of estrogens induce premalignant dysplasia and in combination with high doses of androgens, malignancy. The production of estrogens from androgens is mediated by the aromatase enzyme, the aberrant expression of which plays a critical role in the disease process in other tissues, most notably the breast. The prostate expresses aromatase within the stroma of benign tissue, while in malignancy there is an induction of epithelial expression with altered promoter utilisation. Although the presence of aromatase in the prostate and its aberrant expression in prostate cancer is significant, its role and contribution to prostate carcinogenesis remains unclear. Transgenic mouse models lacking aromatase (ArKO) and over-expressing aromatase (AROM+) have provided an ideal means to examine aromatase expression in the prostate. Studies using these animals may lead to a better understanding of the role that aromatase--and therefore estrogen--plays in the development and progression of prostate disease.

betaA- and betaC-activin, follistatin, activin receptor mRNA and betaC-activin peptide expression during rat liver regeneration.

The mRNA expression of two activin growth factor subunits (betaA- and betaC-activin), activin receptor subunits (ActRIIA, ActRIIB) and the activin-binding protein follistatin, and peptide expression of betaA-activin and betaC-activin subunits, were examined in regenerating rat liver after partial hepatectomy (PHx). Liver samples were collected from adult, male Sprague-Dawley rats, 12-240 h (n=3-5 rats per time point) after PHx or from sham-operated controls at the same time points. Hepatocyte mitosis and apoptosis were assessed histologically and by in situ cell death detection. RT and PCR were used to assess relative gene expression. betaA- and betaC-activin peptide immunoreactivity was assessed in liver and serum samples by western blotting, whereas cellular expression was investigated by immunohistochemistry, using specific monoclonal antibodies. betaA- and betaC-activin mRNA dropped to < 50% of sham control values 12 h after PHx and remained at this level until 168 h post-PHx, when betaA-activin expression increased to three times sham control values and betaC-activin mRNA returned to pre-PHx levels. A peak in follistatin expression was observed 24-48 h post-PHx, coincident with an increase in hepatocyte mitosis. No changes were observed in ActRIIA mRNA, whereas ActRIIB expression paralleled that of betaA-activin mRNA. betaC-activin immunoreactive homo- and heterodimers were observed in regenerating liver and serum. Mitotic hepatocytes frequently contained betaC-activin immunoreactivity, whereas apoptotic hepatocytes were often immunoreactive for betaA-activin. We conclude that betaA- and betaC-activin subunit proteins are autocrine growth regulators in regenerating liver and when expressed independently lead to hepatocyte apoptosis or mitosis in a subset of hepatocytes.

The role of inhibins and activins in prostate cancer pathogenesis.

Successful prostate cancer diagnosis and management continue to provide challenges for the clinician. While interventions aimed at the containment of both early and late disease continue to fail in a significant number of patients, the search for answers must incorporate an analysis of the processes of normal and aberrant growth and development within the gland itself. Inhibin and its structurally related protein, activin, are members of the transforming-growth-factor beta (TGFbeta) superfamily. Originally identified as regulators of FSH, these proteins are now recognised to have widespread biological functions. This might be expected of proteins that are structurally homologous to TGFbeta itself, which is recognised to have regulatory roles in both normal and malignant prostate tissue. The aim of this review is to examine the relationship between inhibins, activins and their related proteins and the development of prostate cancer. The homology with TGF, the pluripotent effects of activin on various tissues and the roles for inhibins in ovarian cancer make activins and inhibins candidate growth factors for involvement at multiple sites in the progression from benign disease to cancer. In compiling this review, we aim to delineate the changes in inhibins and activins in this pathway and in doing so implicate their potential roles in the progression of carcinogenesis. We will compare the changes in inhibin and its related proteins in prostate cancer to those that are known in ovarian cancer. We will discuss the similarities and differences between the putative role of activins and TGFbeta in prostate carcinogenesis. The importance of this review lies in demonstrating that inhibin, an endocrine hormone, and its related proteins may contribute to endocrine-related cancers, such as that of the prostate gland.

Oestrogens and prostate cancer.

Androgens are essential for stimulating normal development, growth and secretory activities of the prostate whereas oestrogens are generally regarded as inhibitors of growth. Evidence for the local synthesis of oestrogens includes the detection of aromatase mRNA and protein in the stroma of human non-malignant tissues and in malignant tissue, where it is detected in epithelial tumour cells. As well, aromatase activity was measured by biochemical assay and protein was detected in prostatic non-malignant and tumour cell lines. Taken together with the identification of direct oestrogenic actions on the prostate, these results suggest that alterations in local oestrogen synthesis may have significant consequences in malignancy of these organs. Genetically modified mouse models were studied in order to evaluate the action of oestrogens alone or in combination with androgens on the prostate gland. Hypogonadal (hpg) mice are deficient in gonadotrophins and androgens but showed direct proliferative responses to oestradiol. The responses were characterised by discrete lobe-specific changes including smooth-muscle regression, fibroblast proliferation, inflammation, and basal epithelial cell proliferation and metaplasia. The aromatase knockout (ArKO) mouse, deficient in oestrogens due to a non-functional aromatase enzyme, developed prostatic hyperplasia during the lifelong exposure to elevated androgens, however, no malignant changes were detected in the prostate at any time. In contrast, combined androgen and oestrogen treatment has been shown to induce prostatic dysplasia and adenocarcinoma. These results demonstrate that malignant changes to the prostate gland are dependent upon both androgenic and oestrogenic responses and that neither hormone alone is sufficient to evoke aberrant patterns of growth, resulting in malignancy.

The effect of testicular macrophages and interleukin-1 on testosterone production by purified adult rat Leydig cells cultured under in vitro maintenance conditions.

A functional interaction between testicular macrophages and Leydig cells has been suggested. The present study attempts to clarify the interaction between purified Leydig cells and macrophages from adult male rats in coculture, employing culture conditions that maintain Leydig cell steroidogenic responsiveness in vitro. Basal Leydig cell testosterone production over 24 h was not significantly affected by coculture with macrophages, but an inhibitory effect of testicular macrophages on testosterone production by Leydig cells over 24 h was observed in the presence of increasing doses of LH from 0.125 ng/ml up to a maximally stimulating dose of 8 ng/ml. A consistent inhibitory effect was observed over a range of Leydig cell-testicular macrophage coculture ratios from 0.5:1 to 4:1 in the presence of LH (8 ng/ml). A similar inhibitory effect on maximal LH-stimulated Leydig cell testosterone production over 24 h was observed when Leydig cells were cocultured with peritoneal macrophages. Conditioned medium collected from testicular or peritoneal macrophage cultured for 24 h also inhibited LH-stimulated Leydig cell testosterone production, indicating that the effect of the macrophages was mediated by a secreted product. Inhibition of LH-stimulated testosterone production was observed also when Leydig cells were cultured in the presence of testicular macrophages for 24 h before maximal LH stimulation (8 ng/ml) for a further 24 h. Human recombinant interleukin-1 alpha and interleukin-1 beta (0.5-10 U/ml) did not significantly alter basal or LH-stimulated Leydig cell testosterone production at 24, 48, or 72 h of culture. The specific binding of 125I-human CG to Leydig cells was not affected by testicular macrophage-conditioned medium. These data demonstrate that testicular and peritoneal macrophages inhibit LH-stimulated Leydig cell testosterone production in coculture through secreted factors, acting distal to the LH receptor, and provide further support for paracrine interactions between these cell types.

In vivo and in vitro production of inhibin by cryptorchid testes from adult rats.

Adult male rats were made bilaterally cryptorchid for 3, 7, 10, and 14 days, and the peripheral serum, testicular vein serum, and interstitial fluid levels of inhibin were measured by RIA, and compared with values obtained in intact animals. The levels of inhibin in peripheral serum, testicular vein, and interstitial fluid were significantly elevated (P less than 0.01) after 3 days of cryptorchidism but declined significantly thereafter. The secretion of inhibin was also studied in vitro using isolated segments of seminiferous tubules from scrotal and abdominal testis in adult rats made unilaterally cryptorchid for 3, 6, and 12 days. The basal inhibin secretion by 3-day cryptorchid seminiferous tubules incubated at 37 C was significantly greater when compared with the scrotal seminiferous tubules at 32 C. If seminiferous tubules from scrotal testes were incubated at 37 C, the secretion of inhibin was greatly increased to similar levels observed by the 3-day abdominal seminiferous tubule cultures. In addition inhibin secretion was significantly higher when tubules from 5-week hypophysectomized rats were cultured at 37 C compared to 32 C. The inhibin secretion by seminiferous tubules from 6-day abdominal testes had returned to scrotal seminiferous tubule levels but then decreased below scrotal seminiferous tubule levels after 12 days of cryptorchidism. Seminiferous tubules from cryptorchid testes remain responsive to FSH stimulation (500 ng/ml) up to 12 days of cryptorchidism. FSH-stimulated inhibin production was increased at 3 and 12 days after cryptorchidism, but similar at 6 days after cryptorchidism, compared to the response of tubules obtained from scrotal testes. Furthermore, using seminiferous tubules from normal adult rats, FSH-stimulated inhibin production was increased by raising the incubation temperature from 32 C to 37 C. These in vivo and in vitro data suggest a dual stimulatory and inhibitory effect of higher temperature on inhibin production with an initial rise in basal and FSH-stimulated inhibin secretion by the cryptorchid testis which seems to be due to a direct effect of temperature on Sertoli cells. The subsequent decline in inhibin secretion could be due to the disruption of the seminiferous epithelium.

The involvement of Leydig cells in the regulation of inhibin secretion by the testis.

The stimulation of Leydig cells by the administration of a single injection of 100 IU human CG (hCG) to adult male rats caused a significant biphasic stimulation of serum testosterone levels at 2 h and 3 days after injection. Serum immunoreactive (IR)-inhibin levels were elevated by 6 h and peaked at 24 h after hCG, then progressively declined thereafter. The removal of Leydig cells in vivo by the injection of the cytotoxic drug ethane dimethane sulfonate (EDS) causes a significant decrease in serum testosterone levels within 4 days, which is sustained 1 and 2 weeks after EDS. Serum IR-inhibin levels, however, rise significantly 2 and 4 weeks after injection of EDS. An injection of 100 IU hCG, 4 days after EDS (when no Leydig cells were present in vivo), failed to provoke an elevation of either testosterone or IR-inhibin levels in serum. But 2 or 4 weeks after administration of EDS, as a new population of Leydig cells develops in the interstitium, an injection of 100 IU hCG provokes a significant increase in serum testosterone and IR-inhibin levels. The possibility that the failure of IR-inhibin levels to rise after EDS and hCG treatment could be due to changes in the seminiferous epithelium, caused by testosterone deprivation induced by Leydig cell destruction after EDS, was examined by administering high doses of testosterone known to maintain spermatogenesis. Under such conditions, hCG failed to induce a rise of IR-inhibin after EDS treatment had destroyed the Leydig cells. These data strongly support the concept that the Leydig cells are involved in the regulation of IR-inhibin secretion in vivo through factors other than testosterone.

The effects of chronic human chorionic gonadotropin treatment on Leydig cell function.

The purpose of this study was to examine the effect of chronic daily hCG treatment on interstitial cell function in the rat, as judged by plasma testosterone levels, the testicular binding of labeled hCG, and the capacity of the testis to respond to gonadotropin stimulation by the production of testosterone in vitro. TWenty-four hours after the first injection of 100 IU hCG there was a significant decline in hCG binding to testis homogenates and an inability to respond to hCG stimulation in vitro, After 7 days of daily injections of 10 IU or 100 IU hCG, the loss of hCG binding was maintained. However, despite the marked decline in hCG binding, there was an enhanced testosterone response to hCG stimulation in vitro, and plasma testosterone levels were significantly elevated. With continued injections of hCG for 14 or 21 days, the testes remained hyperresponsive to hCG stimulation in vitro, but hCG binding returned to control levels, and plasma testosterone concentrations declined and were not statistically different from controls. The latter changes probably result from the formation of specific hCG antibodies (Kd at 4 C, 7.8 +/- 4.5 X 10(-10) M) that were detected in plasma from rats treated for 14 or mopre days with hCG. The formation and levels of the hCG antibodies in these animals were sufficient to neutralize the effects of the exogenous hCG, thereby returning plasma testosterone levels to normal and restoring the complement of hCG receptors.

The metaplastic effects of estrogen on mouse prostate epithelium: proliferation of cells with basal cell phenotype.

The exogenous administration of estrogens to male mice alters the hypothalamic-pituitary-gonadal axis and reduces androgen levels, leading to a regression of the prostatic epithelium. As well, a specific direct response to estrogens is the induction of epithelial squamous metaplasia. The aims of this study were to identify the process by which the prostatic epithelium is transformed in intact adult male mice using the synthetic estrogen, diethylstilbestrol. A comparison of the effects of diethylstilbestrol in the three lobes revealed a hierarchy of response, with the anterior lobe being the most responsive, the dorsolateral lobe less responsive, and the ventral lobe the least responsive. The effect of castration was used to distinguish between the epithelial responses to estrogen administration and androgen deprivation. The results demonstrate that transformation of the epithelium involved proliferation of cells with a basal cell phenotype, the onset of cytokeratin 10 expression, up-regulation of progesterone receptor expression, and loss of the cell cycle inhibitor, p27(Kip1) expression; none of these changes was observed after castration. Mice lacking functional estrogen receptor alpha failed to respond, demonstrating a requirement for estrogen receptor alpha in the epithelium and/or stroma to mediate the proliferative response to estrogen in the prostate gland.

An assessment of Leydig cell function after bilateral or unilateral efferent duct ligation: further evidence for local control of Leydig cell function.

Leydig cell function was examined in adult male rats at 2 and 4 weeks after bilateral or unilateral efferent duct ligation. Bilateral efferent duct ligation resulted in significantly elevated serum LH levels, an increased size of Leydig cells and an enhanced testosterone response to gonadotropin stimulation in vitro despite a marked loss of LH-hCG receptors. After unilateral ligation of the vasa efferentia, the parameters of Leydig cell function in the ligated testes showed identical changes to those seen after bilateral ligation, whereas such changes were minor or absent in the unligated contralateral testes of the same animals. These results demonstrate that the modifications of Leydig cell function after efferent duct ligation are mainly due to local changes within the testes providing further evidence for an intratesticular control of Leydig cell function.

Differential localization of inhibin subunit proteins in the ovine testis during fetal gonadal development.

Inhibins and activins are dimeric proteins that are involved in cell proliferation, apoptosis, and differentiation in a number of systems and have previously been detected in fetal testes of many species. This study used immunohistochemistry to examine the localization of inhibin alpha-, betaA-, and betaB- subunits during ovine testicular development from days 40-135 of gestation. Localization of inhibin betaA- and betaB-subunit messenger RNAs was confirmed by in situ hybridization. The results showed that there was differential localization of inhibin alpha-, betaA-, and betaB-subunits to specific cells in the ovine fetal testis from 40 days of gestation. All three inhibin subunits were present in Sertoli cells throughout gestation, whereas the rete epithelium and gonocytes did not express inhibin alpha-subunit. These data suggest that the fetal Sertoli cells have the capacity to produce all forms of inhibins and activins, i.e. inhibin A and B, and activins A, AB, and B, whereas the rete testis epithelial cells can only synthesize activin A. In the interstitium, the fetal Leydig cells expressed all three inhibin subunits, but this was restricted to the period between 40 and 90 days of gestation. Thereafter, inhibin alpha-subunit immunoreactivity was not observed in fetal Leydig cells, which suggests that only activin ligands are produced by Leydig cells during late gestation. Collectively, the data demonstrate that fetal ovine testes have the potential to produce the full repertoire of inhibins and activins from very early in testicular differentiation. The distinct and restricted localization of the various subunits to specific cells suggests that specific dimeric proteins have particular roles in the development and function of the fetal testis.