Biomedical subjects

E R Barrack

Publications and source records attributed to E R Barrack.

At least 19 recordsLinked to original sources

PubMed1997

TGF beta in prostate cancer: a growth inhibitor that can enhance tumorigenicity.

A common feature of cancer cells is the autocrine production of growth promoters and the loss of function of tumor suppressors. In our search for such features of prostate cancer, we discovered that transforming growth factor beta 1 (TGF beta 1) levels are higher in prostate cancer than in normal prostate, and prostate cancer cells can activate endogenously-produced latent TGF beta to a bioactive form. Because TGF beta 1 is a potent growth inhibitor of epithelial cells, it seems paradoxical that malignant epithelial cells make high levels of a growth inhibitor. Even prostate cancer cells can be growth-inhibited by TGF beta 1, but only under specific conditions in vitro (plating at low cell density in serum-free medium), and this response is readily disrupted by growth factors, serum, and extracellular matrix, to all of which the cells are exposed in vivo. This explains why prostate cancer cells are resistant to the growth-inhibitory effect of TGF beta in vivo. In vivo, TGF beta 1 actually enhances prostate tumor growth and metastasis, but not by affecting tumor cell proliferation directly. One possibility is that TGF beta affects the host to allow increased numbers of tumor cells to survive and produce progeny. In addition, since prostate cancer cells can still respond to TGF beta, e.g., by increased cell motility, even under conditions that prevent growth inhibition, the ability of TGF beta to enhance tumorigenicity in vivo might also occur via direct effects on the tumor cells themselves. I will discuss new developments in our understanding of TGF beta action, which provide a framework for elucidating the mechanism by which prostate cancer cells have devised a way to protect themselves from being growth-inhibited by TGF beta 1 in vivo. Since the cells retain the ability to be growth-inhibited by TGF beta, indicating that the TGF beta receptors and signaling pathways for growth inhibition are intact, albeit inactive, it might be possible to reactivate this pathway to achieve a therapeutic benefit in vivo.

Animals↗

PubMed1997

Androgen receptor variants with short glutamine or glycine repeats may identify unique subpopulations of men with prostate cancer.

The androgen receptor (AR) contains glutamine (CAG) and glycine (GGC) repeats that are each polymorphic in length. We screened clinically localized prostate cancers for somatic mutations in the length of the CAG and GGC repeats in the AR gene and characterized the length of these repeats in the germ-line AR gene. Somatic mutations were rare, and the range of germ-line repeat lengths in men with prostate cancer was within the range of normal in the general population. Most allele frequencies in Caucasian men with clinical prostate cancer were remarkably comparable to those in the general Caucasian population. However, a subpopulation of the men with clinical prostate cancer had a substantially higher frequency of AR alleles with 16 or 17 CAGs (6 of 59 men, 10%) than did the general population (6 of 370 alleles, 1.6%), and a different subpopulation of the men with prostate cancer had a higher frequency of AR alleles with 12 or 13 GGCs (7 of 54 men, 13%) than did the general population (1 of 110 alleles, 0.9%). Of the men with prostate cancer who had an AR gene with 16 or 17 CAGs, 83% had lymph node-positive disease, despite the lack of clinical evidence of metastatic spread. This suggests that a short AR CAG allele may be a risk factor for the development of clinically unsuspected lymph node-positive prostate cancer among men undergoing radical prostatectomy and raises the question of whether this short repeat length played an active role in the development of aggressive prostate cancer. The odds of having a germ-line AR gene with a short CAG repeat (</=17 CAGs) were substantially higher in Caucasian men with lymph node-positive prostate cancer than in Caucasian men with lymph node-negative disease or in the general Caucasian population. The odds of having a short germ-line AR CAG were the same for men with lymph node-negative prostate cancer as for the general Caucasian population. The odds of having a germ-line AR gene with a short glycine repeat (</=14 GGCs) were substantially higher in men with prostate cancer than in the general population, but the frequency of alleles with a short GGC repeat was the same in men with lymph node-positive versus lymph node-negative disease. This suggests that a short GGC repeat may be a risk factor for the development of clinical prostate cancer, a hypothesis that needs to be tested in cohort and case-control studies.

Adenocarcinoma↗

PubMed1996

Androgen-receptor gene structure and function in prostate cancer.

Androgen-receptor (AR) gene mutations have been found in clinical prostate cancer, both prior to hormonal therapy and in hormone-refractory disease that persists despite androgen-ablative therapy. Thus, mutations that are present in late-stage disease might arise prior to therapy rather than as a result of therapy. A common feature of mutations in untreated prostate cancer and in hormone-refractory prostate cancer is that the AR retains activity as a ligand-dependent transcription factor. Some AR mutations in prostate cancer show broadened ligand specificity, such that the transcription-factor activity of the AR can be stimulated not just by dihydrotestosterone (DHT) but also by estradiol and other androgen metabolites that have a low affinity for the AR. The activation of mutant AR by estrogen and weak androgens could confer on prostate cancer cells an ability to survive testicular androgen ablation by allowing activation of the AR by adrenal androgens or exogenous estrogen. Such mutations might confer an advantage even prior to androgen ablation, since prostate cancer has lower levels of 5 alpha-reductase and, therefore, of DHT, than normal. Thus, AR mutations that occur prior to therapy may characterize a more aggressive disease. A large percentage of tumors appear to have no AR gene mutation. In tumors without an AR gene mutation, AR function might be affected via other mechanisms (e.g., AR gene amplification, which could increase the amount of AR activity at a given DHT level). Importantly, the apparent absence of AR gene mutations in the majority of earlystage tumors indicates that the role of androgen in the development of clinical prostate cancer is mediated predominantly by a normal AR gene. There are actually multiple alleles of the normal AR gene; these allelic variants differ in glutamine and glycine repeat length in the transactivation domain of the protein, and they may differ in signal-transducing activity. The glutamine and glycine repeat length may thereby modulate the effect of androgen on tumor-cell proliferation that occurs during clonal expansion.

Alleles↗

PubMed1995

Modulation of transforming growth factor beta 1 effects on prostate cancer cell proliferation by growth factors and extracellular matrix.

Poorly differentiated MATLyLu rat prostate cancer cells are resistant to the growth inhibitory effect of transforming growth factor (TGF) beta 1 in vivo, but are inhibited by TGF-beta 1 in vitro. However, TGF-beta 1 inhibited proliferation only when the cells were plated at low density in serum-free medium (concentration for 50% of maximum inhibition, 0.1 ng/ml). TGF-beta 1 was not growth inhibitory when cells were plated at high density, or at low density in 0.5% serum. At low cell density in serum-free medium, 0.5 ng/ml TGF-beta 1 caused maximum inhibition. In the presence of basic fibroblast growth factor (10 ng/ml), TGF-beta 1 did not inhibit proliferation. In the presence of epidermal growth factor (50 ng/ml), TGF-beta 1 inhibited proliferation by only 18%. Growth inhibition by TGF-beta 1 was less effective on extracellular matrix than on plastic. The ability of high cell density, serum, growth factors, or extracellular matrix to prevent or blunt the growth inhibitory effect of TGF-beta 1 in vitro probably explains why TGF-beta 1 does not inhibit tumor growth in vivo. Thus, prostate cancer cells express high levels of TGF-beta and retain exquisite sensitivity to the growth inhibitory effect of TGF-beta, but have devised a way to protect themselves from growth inhibition by TGF-beta in vivo. TGF-beta 1 stimulated MATLyLu cell motility even at high cell density, suggesting that TGF-beta 1 might affect motility even in vivo and contribute to the aggressiveness of the tumor, without affecting proliferation.

Adenocarcinoma↗

PubMed1994

Microsatellite mutation (CAG24-->18) in the androgen receptor gene in human prostate cancer.

The androgen receptor (AR) gene contains a polymorphic CAG microsatellite that codes for a variable length of glutamine repeats in the AR protein. Microsatellite DNA sequences may be potential sites of genetic instability. Using the polymerase chain reaction (PCR), we screened 40 human prostate cancer specimens for expansions or deletions of this microsatellite. In one patient, nontumor DNA yielded a single PCR product, as expected for the AR, but the tumor DNA yielded two discrete products, one identical to normal, and a second smaller one. Direct sequencing revealed that the nontumor tissue contained 24 CAGs, whereas the tumor contained one fragment with 24 CAGs (wild-type) and a second fragment with 18 CAGs (mutant), representing a somatic contraction of the AR CAG repeat (CAG24-->CAG18) in the tumor. Interestingly, this patient manifested a paradoxical agonistic response to hormonal therapy with the antiandrogen flutamide.

Adenocarcinoma↗

PubMed1994

Expression of transforming growth factor-beta 1 in prostate cancer.

Transforming growth factor-beta 1 (TGF beta 1) is a potent modulator of cell proliferation, differentiation, angiogenesis, and the immune system. TGF beta 1 messenger RNA (mRNA) levels were much higher in several rat prostate adenocarcinomas (Dunning R3327 MATLyLu, AT2, G, HI, and H sublines) than in normal prostate. Normal prostate and the well differentiated H and HI tumors produced two TGF beta 1 mRNA transcripts, 2.4 kilobases (major) and 1.6 kilobases (minor). The poorly differentiated MATLyLu and AT2 sublines produced these plus additional TGF beta 1 mRNA transcripts that were present in the primary tumors, metastases, and cultured cell lines. TGF beta 1 mRNA levels were unchanged 2 weeks after castration. Immunohistochemical staining of TGF beta 1 protein was more prominent and more extensive in prostate cancer than in normal prostate. Only extracellular TGF beta 1 staining was detected. In normal prostate and in well differentiated tumors (H and HI), extracellular TGF beta 1 staining was located in the interacinar stroma, suggesting that it may be produced there. In contrast, in the poorly differentiated tumors (MATLyLu, AT2, and G) that contain sheets of epithelial cells, extracellular TGF beta 1 staining was present throughout the tumor, suggesting that TGF beta 1 may be made and secreted by the tumor epithelial cells. MATLyLu, AT2, and G tumor cells were cultured in vitro, and the conditioned medium was analyzed for the presence of TGF beta using a bioassay. TGF beta 1 is produced and secreted as an inactive latent precursor and must be activated to release bioactive TGF beta 1. Cells secreted about 100-500 pg TGF beta/10(6) cells.24 h and were able to activate about 50% of the total TGF beta secreted. Because TGF beta 1 mRNA and protein expression are higher in cancerous than normal tissue and because prostate cancer cells themselves can activate latent TGF beta 1 to a bioactive form, TGF beta 1 produced endogenously by prostate cancer has the potential to affect tumor behavior in vivo. Therefore, TGF beta 1 may represent a new therapeutic target in prostate cancer.

Adenocarcinoma↗

PubMed1994

Effects of transforming growth factor beta 1 on the adenylyl cyclase-cAMP pathway in prostate cancer.

We reported previously that MATLyLu rat prostate cancer cells engineered to overproduce transforming growth factor beta 1 (TGF beta 1) produce larger, more metastatic tumors in vivo. We recognized that this ability of TGF beta 1 to act as a positive modulator of prostate tumor behavior might be due to effects of TGF beta 1 on the host and/or on the tumor cells. In this study we demonstrated that the cells themselves respond to endogenously produced TGF beta 1, and that the adenylyl cyclase (AC)-cAMP pathway is affected. TGF beta 1-overproducing cells had lower membrane AC activity, lower intracellular cAMP content, and a lower Gs alpha protein level than did control cells. Prostate cancer cells were growth inhibited by 8-bromo-cAMP or forskolin, agents that elevate intracellular cAMP. Thus, TGF beta 1 overproduction affects the phenotype of the tumor cells, deliberate activation of endogenously produced latent TGF beta 1 is not required (indicating that the cells themselves are capable of activating latent TGF beta 1), and TGF beta 1 overproduction lowers the cellular concentration of the growth inhibitor cAMP. Therefore, TGF beta 1 overproduction could affect tumor behavior in vivo in part via a direct effect on the tumor cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1993

Image analysis of androgen receptor immunostaining in metastatic prostate cancer. Heterogeneity as a predictor of response to hormonal therapy.

BACKGROUND: Reliable predictors of the response of prostate cancer to androgen ablation therapy are lacking. The goals of this study were to determine whether nuclear androgen receptor (AR) concentrations in metastatic prostate cancer varied within and between specimens and to correlate this information with the response to therapy. METHODS: AR concentration was evaluated by computer-assisted image analysis of immunohistochemical staining intensity in 200 malignant epithelial nuclei of each of 17 specimens of Stage D2 prostate cancer obtained before hormonal therapy. The data were correlated with the time to tumor progression (relapse) after hormonal therapy. RESULTS: AR staining intensity varied within specimens, and the variance of staining intensity was significantly greater (P = 0.03) in the poor responders (n = 8; time to progression, < 20 months) than in the good responders (n = 9; time to progression, > or = 20 months). The kurtosis was significantly lower in poor responders (P = 0.04). However, the mean AR staining intensity was not significantly different among patients. The frequency distribution plots of good responders were generally uniform and unimodal, but those of poor responders were flattened (more platykurtic), dispersed, and highly variable. Thus, the AR concentration per cell was significantly more heterogeneous in poor responders. Variance was a significant predictor of response. Five of 6 patients with a high variance (defined as variance greater than the mean) were poor responders, whereas 8 of 11 patients with a low variance were good responders (an overall classification accuracy of 13 of 17, 76%). CONCLUSIONS: The greater AR heterogeneity in poor responders may reflect a greater genetic instability in tumors that have progressed further toward androgen independence and may be a valuable predictor of progression.

Antibodies, Neoplasm↗

PubMed1993

Sexually dimorphic expression of estrogen receptors, but not of androgen receptors in human fetal external genitalia.

Using immunohistochemistry, we investigated the distribution of androgen receptors (AR) and estrogen receptors (ER) in the external genitalia of human male and female fetuses at 18-22 weeks gestation. In the male, the corpus cavernosum, and the stroma of the inner prepuce, scrotum, and periphery of the glans were AR rich. The corpus spongiosum, a well defined structure that surrounds the penile urethra in the neonate, was not yet developed at this fetal age, but the periurethral mesenchyme (presumably the primordium of the corpus spongiosum) was intensely AR positive. In contrast, the epithelium of the preputial skin, penile shaft skin, and scrotal skin were AR negative. The urethral plate in the distal glans was nonpatent and was filled with a meshwork of AR-negative epithelial cells. Canalization of the AR-negative urethral plate was observed to begin where it joined the patent distal penile urethra, which was AR positive. Male external genitalia lacked ER, ruling out a direct influence of maternal estrogen on male genital development. Interestingly, female external genital structures contained AR, and the distribution of AR and staining intensity were strikingly similar to that in the male. The distribution of AR in the female provides a mechanism to explain how female external genitalia become masculinized if exposed to elevated androgen levels in the first trimester. Moreover, it implies that in the male, these AR indeed mediate androgen-dependent male external genital development. Female fetal external genitalia were also intensely ER positive in the stroma of the labia minora and in the periphery of the glans and inner prepuce. The presence of ER suggests that maternal estrogen may play a direct role in female external genital development, challenging the widely held view that female external genital development is passive because it can occur in the absence of fetal gonadal hormones.

Epithelium↗

PubMed1992

Androgen receptor gene mutations in human prostate cancer.

We screened human prostate cancer tissues for the presence of somatic mutations in the hormone binding domain of the androgen receptor (AR) gene. Exons E-H were amplified from genomic DNA using the polymerase chain reaction and analyzed by denaturing gradient gel electrophoresis (DGGE), which separates DNA fragments that differ by only a single base. We detected a mutation in exon E of the hormone binding domain in 1 of 26 specimens of untreated organ-confined stage B prostate cancer. The mutation was not detectable in peripheral blood lymphocyte DNA. Lymphocyte DNA (wild-type AR) migrated in DGGE as a single band. The tumor DNA migrated in DGGE as four bands, consistent with the presence of cells with mutant AR plus cells with wild-type AR and indicating that the tumor contained a somatic mutation. To our knowledge, a somatic AR gene mutation has not been reported previously. Sequencing revealed a G----A substitution in codon 730, changing valine to methionine. Codon 730 is in a region highly conserved among all steroid receptors. The abundance of the mutated fragment (about 50% of the DNA in the specimen) indicates its presence in cells with a growth advantage. A somatic mutation could be detected by DGGE if it represented at least 10% of the sample. Failure to detect mutations in other specimens analyzed may be due to this limit of sensitivity, the presence of mutations in other parts of the AR, or a low frequency of mutations in early stage disease.

Amino Acid Sequence↗

PubMed1992

Transforming growth factor-beta 1 overproduction in prostate cancer: effects on growth in vivo and in vitro.

We found previously that transforming growth factor-beta 1 (TGF beta 1) mRNA levels are markedly elevated in rat prostate cancer (Dunning R3327 sublines) compared to levels in normal prostate. Our goal was to determine whether elevated expression of TGF beta 1 is biologically relevant to prostate cancer growth in vivo. We chose as our model the R3327-MATLyLu prostate cancer epithelial cell line, which produces metastatic anaplastic tumors when reinoculated in vivo. Our approach was to stably transfect MATLyLu cells with an expression vector that codes for latent TGF beta 1 and to isolate subclones of cells that over-expressed TGF beta 1 mRNA. We also isolated a subclone of MATLyLu cells transfected with a control vector lacking the TGF beta 1 cDNA insert. We then studied the growth of these cells in vivo and in vitro. Twenty days after sc inoculation of 10(6) cells in vivo, TGF beta 1-overproducing MATLyLu tumors were 50% larger, markedly less necrotic, and produced more extensive metastatic disease (lung metastases in 73% of all lobes and lymph node metastases in 88% of animals) compared to control MATLyLu tumors (lung metastases, 21%; lymph node metastases, 7%). Thus, TGF beta 1 produced in vivo is biologically active and can promote prostate cancer growth, viability, and aggressiveness, perhaps via effects on the host and/or on the tumor cells themselves. When followed in vitro, TGF beta 1-overproducing cells became growth inhibited, but this effect was transient as cells subsequently resumed proliferating. Growth inhibition was due to TGF beta, because it could be prevented by TGF beta-neutralizing antibody. Therefore, prostate cancer cells can activate and respond to secreted latent TGF beta 1, and although the cells are transiently inhibited in vitro, there is no net inhibition of growth. The ability of the cells to respond to endogenously produced TGF beta 1 suggests that TGF beta 1 overexpression enhances tumor growth in vivo at least in part via an effect of TGF beta 1 on the tumor cells themselves.

Animals↗

PubMed1991

Immunohistochemical study of androgen receptors in metastatic prostate cancer. Comparison of receptor content and response to hormonal therapy.

A longstanding goal has been to determine whether androgen receptor (AR) levels could be used to predict the clinical response of metastatic prostate cancer to androgen withdrawal therapy. A major limitation of previous studies was the use of homogenized tissue, which yields an average AR content for all cells. By AR immunohistochemical study using an antibody specific for AR the authors assessed nuclear AR content specifically in the malignant epithelial cells of prostate needle biopsy specimens of 17 patients with Stage D prostate cancer. The authors found that prostate cancer contains AR-positive and AR-negative malignant cells before androgen withdrawal therapy, but the percentage of AR-positive cells did not predict the time to tumor progression after therapy. There was no significant correlation between the percentage of AR-positive malignant cells and the time to tumor progression. When patients were divided into two groups based on the median time to progression, the percentage of AR-positive nuclei was not significantly different in poor responders versus good responders. When patients were divided into two groups based on the median percentage of receptor-positive nuclei, Kaplan-Meier estimates of the progression-free interval revealed no significant difference between the group of patients with AR-poor tumors and patients with AR-rich tumors. Potential explanations for these results are discussed. The authors conclude that the percentage of AR-positive nuclei is not a sufficient criterion to predict tumor behavior.

Adenocarcinoma↗

PubMed1991

Determination of growth fraction in advanced prostate cancer by Ki-67 immunostaining and its relationship to the time to tumor progression after hormonal therapy.

Reliable predictors of response for prostate cancer patients undergoing hormonal therapy are lacking. This study investigates the possibility that tumor proliferation rates might predict tumor behavior for these patients. The growth fraction of metastatic prostate cancer biopsy specimens obtained before androgen withdrawal therapy was evaluated by Ki-67 antibody immunohistochemical study to determine whether a higher tumor growth fraction was associated with a shorter time to tumor progression after therapy. The percentage of Ki-67-positive malignant epithelial nuclei in the primary tumors of 17 patients ranged from 1.7% to 7.5% (median, 2.5%). When patients were divided into two response groups according to the median time to progression, poor responders (time to progression less than 20 months) and good responders (greater than or equal to 20 months) had similar growth fractions (3.5 +/- 0.5% versus 3.1 +/- 0.6% Ki-67-positive nuclei, respectively). However, when patients were divided into two groups based on the median growth fraction, patients with a high growth fraction (greater than 2.5% Ki-67-positive nuclei) tended to have a shorter time to progression (median, 10 months) than patients with a low (less than 2.5%) growth fraction (median time to progression, 25 months), although statistical significance was not reached. Despite this interesting trend, Ki-67 immunostaining was not accurate to predict the time to progression in individual patients undergoing hormonal therapy. Reliable prediction of growth rates may require measurement of both cell proliferation and cell death rates.

Aged↗

PubMed1991

Androgen receptors and growth fraction in metastatic prostate cancer as predictors of time to tumour progression after hormonal therapy.

Reliable predictors of response for prostate cancer patients undergoing hormone therapy are lacking. Since 80-90% of such patients do respond but the time between therapy and relapse (progression) is variable, our goal has been to predict the time to tumour progression after therapy rather than merely to predict whether a patient would respond. We investigated AR positivity and Ki-67 growth fraction of malignant epithelial cells as potential predictors of the time to progression; these studies are summarized in this chapter. The percentage of AR positive nuclei has no predictive value; however, the variance of AR immunostaining intensity within a certain specimen is an important discriminator between good responders (patients with a prolonged interval between initiation of therapy and relapse) and poor responders (short time to relapse). There is a trend towards a higher growth fraction in poor responders, but statistical significance is borderline at best. Growth fraction measurement might be more useful as a predictor if the rate of cell death could also be evaluated or if analysis could be limited to the androgen independent cells that continue to proliferate after hormone therapy and that ultimately are responsible for the clinical manifestation of tumour progression and relapse.

Autoradiography↗

PubMed1987

DNA synthesis in the canine prostate: effects of androgen and estrogen treatment.

Canine prostatic DNA synthesis was evaluated by measuring [3H]thymidine incorporation into DNA of tissue slices in vitro. Among untreated beagles, prostatic DNA synthesis rates in young dogs with normal prostates, young dogs with spontaneous benign prostatic hyperplasia (BPH), and old dogs with BPH were 676 +/- 186, 1,220 +/- 156, and 641 +/- 88 cpm/100 micrograms DNA/hr, respectively. Among 81 young beagles (intact or castrated) that had been treated for 4 months with various steroids, rates of DNA synthesis varied according to the type of hormonal treatment. Prostatic DNA synthesis (cpm/100 micrograms DNA/hr) was significantly different (P less than 0.001) for dogs treated with estradiol alone (1,658 +/- 221 cpm/100 micrograms DNA/hr; n = 10 dogs), androgen alone (testosterone, 5 alpha-dihydrotestosterone, or 5 alpha-androstane-3 alpha,17 beta-diol; 1,000 +/- 61 cpm/100 micrograms DNA/hr; n = 31 dogs). However, there was no correlation between prostate size and rate of DNA synthesis (cpm/100 micrograms DNA/hr). Although treatment with estrogen alone resulted in the highest rate of DNA synthesis, it produced squamous metaplasia and the smallest prostates; these results are indicative of a high rate of cell turnover. Comparing prostates that reached the same size following 4 months of treatment with androgen alone or androgen plus estrogen, the rate of prostatic cell turnover was lower in the androgen plus estrogen group. These results are interpreted to indicate an inhibitory effect of estradiol on the rate of cell death in the presence of androgens.

Androgens↗

PubMed1987

Immunocytochemical localization of estrogen receptors in spontaneous and experimentally induced canine benign prostatic hyperplasia.

Estrogens are believed to play a critical role in the etiology of canine benign prostatic hyperplasia (BPH); however, the mechanism has not been elucidated. To gain insight into this problem, we investigated the immunocytochemical localization of estrogen receptors (ER) in normal prostates, spontaneous BPH, and experimentally induced BPH by using a monoclonal ER antibody (H222). In all canine prostates the majority of ER was localized in nuclei of the same histological components: (1) transitional epithelium and subjacent stroma of the prostatic urethra, (2) periurethral prostatic ductal epithelium, and (3) prostatic stroma. ER content in the stroma was highest in the periurethral region of the prostate. Among the different groups of dogs, differences in ER location were seen only in the glandular epithelium. No ER was found in the glandular epithelium of normal prostates of young untreated dogs. In striking contrast, glandular epithelium of spontaneous BPH contained specific nuclear ER staining, though this staining was heterogeneous and was observed in only a minority (less than 10%) of the acinar epithelial cells. ER-positive acini in BPH were located predominantly in the periurethral region. These data demonstrate anatomical and biochemical heterogeneity of prostatic components and indicate that the estrogen sensitivity of prostatic cells is heterogeneous. If estrogen does play a role in BPH, it appears to act selectively rather than uniformly throughout the prostate. We reasoned that if glandular epithelial ER are involved in the development of spontaneous BPH, one might expect to find the same location of ER in BPH that was induced experimentally by specific types of treatment with androgens +/- estradiol. However, among hormone-treated dogs the presence of ER-positive prostatic glandular epithelium varied with the type of hormonal treatment but did not correlate with the experimental induction of glandular BPH. Some treatment groups with induced BPH had ER-positive prostatic glandular epithelial nuclei (with the same extent and pattern of ER localization as in spontaneous BPH); however, other treatment groups with induced BPH had ER-negative glandular epithelium. These data indicate either that glandular epithelial ER may not be involved in the pathogenesis of canine BPH or that there may be different types of BPH that have different etiologies. Possible mechanisms by which estrogen may affect the canine prostate are discussed in light of these new data on ER location.

Androgens↗

PubMed1987

Steroid hormone receptor localization in the nuclear matrix: interaction with acceptor sites.

The nuclear matrix is a conceptually attractive candidate for the site in the nucleus where steroid hormone-receptor complexes might interact to modulate DNA structure and function. We have demonstrated that in sex steroid target tissues a major proportion (50-100%) of the high affinity and steroid-specific receptors that become associated with the nucleus following hormonal stimulation are localized in the nuclear matrix. Direct cell-free binding assays confirm that this localization is due to the presence of specific acceptor sites in the matrix to which steroid-receptor complexes bind with high affinity and tissue specificity, and is not the result of spurious binding. The nuclear matrix appears to be a major site of hormone receptor binding in the nucleus, and this situation is consistent with the known ability of steroid hormones to stimulate gene transcription, a process which also appears to occur in association with the nuclear matrix.

Animals↗

PubMed1987

Androgen receptor localization in the human prostate: demonstration of heterogeneity using a new method of steroid receptor autoradiography.

We have used a novel receptor labeling and autoradiographic technique to identify the cell types in human benign prostatic hyperplasia (BPH) that contain androgen receptors, and we have found that androgen receptor localization is heterogeneous. Prostatic androgen receptors were labeled by incubating slide-mounted frozen tissue sections (10 micron thickness) with [3H]R1881 in vitro. Tissue sections labeled in this way were subjected to concurrent biochemical and autoradiographic analysis. Some of the sections were wiped from the slides for scintillation counting to validate that the procedure indeed measures total cellular androgen receptors of appropriate high affinity and androgen steroid specificity. Replicate labeled slide-mounted tissue sections were dried rapidly, apposed to dry emulsion-coated coverslips, and exposed in the dark for autoradiography. Autoradiograms were developed, fixed, and stained; silver grains were counted over nuclei or cytoplasm of epithelium or stroma to evaluate specific androgen receptor location. Autoradiographic analysis of human glandular BPH demonstrated androgen receptor localization almost exclusively in the epithelial nuclei, with little or none in the stroma. We anticipate that data obtained using this new method of steroid receptor autoradiography may provide fresh insight into the mechanism of hormonal regulation of the prostate.

Autoradiography↗