Prostate androgen receptor: immunohistological localization and mRNA characterization

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies

Despite improvements in early detection and advances in treatment, patients with prostate cancer continue to die from their disease. Minimal residual disease after primary definitive treatment can lead to relapse and distant metastases, and increasing evidence suggests that circulating tumour cells (CTCs) and bone marrow-derived disseminated tumour cells (BM-DTCs) can offer clinically relevant biological insights into prostate cancer dissemination and metastasis. Using epithelial markers to accurately detect CTCs and BM-DTCs is associated with difficulties, and prostate-specific markers are needed for the detection of these cells using rare cell assays. Putative prostate-specific markers have been identified, and an optimized strategy for staining rare cancer cells from liquid biopsies using these markers is required. The ideal prostate-specific marker will be expressed on every CTC or BM-DTC throughout disease progression (giving high sensitivity) and will not be expressed on non-prostate-cancer cells in the sample (giving high specificity). Some markers might not be specific enough to the prostate to be used as individual markers of prostate cancer cells, whereas others could be truly prostate-specific and would make ideal markers for use in rare cell assays. The goal of future studies is to use sensitive and specific prostate markers to consistently and reliably identify rare cancer cells.

Diagnostic utility of androgen receptor expression in discriminating poorly differentiated urothelial and prostate carcinoma

AIMS

Pathological separation of poorly differentiated urothelial and prostate carcinoma is difficult, but imperative because of the impact on patient management. Tumour morphology, in conjunction with a panel of immunohistochemistry (IHC), such as prostate-specific antigen (PSA), prostatic acid phosphatase (PSAP), CK7, CK20, p63 and high molecular weight keratins (HMWKs) are usually employed to resolve this issue. Androgen receptor (AR) expression is maintained in high-grade, undifferentiated prostate carcinoma, and thus, could be considered as a potentially useful adjunct to the conventional panel of markers.

METHODS

We performed an institutional review of all cases from 2006 to 2012 in which AR IHC had been performed to determine its diagnostic utility in discriminating between poorly differentiated urothelial and prostate carcinoma. Of the eligible cases (n=40), there were 9 high-grade urothelial carcinomas, 27 prostate carcinomas and 4 with both prostate and bladder tumours. All diagnoses were made by integrating the clinical, radiological, morphological and IHC results.

RESULTS

In all the prostate carcinomas, there was diffuse, intense nuclear staining for AR. The urothelial tumours were either negative, had cytoplasmic staining or showed occasionally weak nuclear staining. The difference was highly significant with p<0.0001 (Mann-Whitney U test).

CONCLUSIONS

We conclude that AR is an important marker as it is best able to distinguish between poorly differentiated urothelial and prostate carcinoma. AR appears superior to PSA and PSAP, which are not consistently expressed in high-grade prostate carcinoma. Also, high-grade urothelial carcinoma may be negative for CK20, p63/HMWK and occasionally CK7. We advocate the inclusion of AR in the panel of markers to differentiate these tumours.

A role for the androgen-receptor in clinically localized and advanced prostate cancer

Earlier studies of androgen-receptor (AR) expression using frozen prostate tissue, and later studies using archived specimens, produced the consensus that ligand-stabilized AR is nuclear, AR expression is similar in benign epithelia and stroma, AR expression is greater in secretory epithelia than basal cells, and AR expression is more variable in prostate cancer (CaP) than in benign prostatic hyperplasia (BPH). Accurate measurement of AR expression remains technically challenging but necessary to evaluate the relevance of AR to clinical CaP. Recent studies demonstrated that AR expression in epithelia and stroma may be prognostic in clinically localized CaP, and AR expression may play a role in racial differences in CaP mortality and predict response to androgen deprivation therapy. High levels of AR and AR-regulated gene expression indicate a central role for AR in growth regulation of castration-recurrent CaP. New treatments for the lethal phenotype of CaP require better understanding of AR transactivation during androgen deprivation therapy.

Androgenic/estrogenic balance in the male rat cerebral circulation: metabolic enzymes and sex steroid receptors

Tissues from males can be regulated by a balance of androgenic and estrogenic effects because of local metabolism of testosterone and expression of relevant steroid hormone receptors. As a critical first step to understanding sex hormone influences in the cerebral circulation of males, we investigated the presence of enzymes that metabolize testosterone to active products and their respective receptors. We found that cerebral blood vessels from male rats express 5alpha-reductase type 2 and aromatase, enzymes responsible for conversion of testosterone into dihydrotestosterone (DHT) and 17beta-estradiol, respectively. Protein levels of these enzymes, however, were not modulated by long-term in vivo hormone treatment. We also showed the presence of receptors for both androgens (AR) and estrogens (ER) from male cerebral vessels. Western blot analysis showed bands corresponding to the full-length AR (110 kDa) and ERalpha (66 kDa). Long-term in vivo treatment of orchiectomized rats with testosterone or DHT, but not estrogen, increased AR levels in cerebral vessels. In contrast, ERalpha protein levels were increased after in vivo treatment with estrogen but not testosterone. Fluorescent immunostaining revealed ERalpha, AR, and 5alpha-reductase type 2 in both the endothelial and smooth muscle layers of cerebral arteries, whereas aromatase staining was solely localized to the endothelium. Thus, cerebral vessels from males are target tissues for both androgens and estrogen. Furthermore, local metabolism of testosterone might balance opposing androgenic and estrogenic influences on cerebrovascular as well as brain function in males.

Immunocytochemical detection of the androgen receptor in fine needle aspirates from benign and malignant human prostate

A monoclonal antibody to the androgen receptor was applied to fine needle aspirates from patients with benign and malignant prostatic disease. The series includes six patients with benign hyperplasia and 24 patients with prostatic carcinomas. The androgen receptor was detected in most nuclei of both benign and malignant epithelial cells. The intensity of immunostaining varied. No obvious relation was observed between the intensity of the staining in benign versus malignant cells. In addition no clear differences were found in the proportion of androgen receptor positive cells in benign aspirates as compared with aspirates from well differentiated or moderately well differentiated prostatic carcinomas. The relative number of androgen receptor positive cells was highest in smears from poorly differentiated prostatic carcinomas.

Androgen receptor levels are increased by interferons in human prostate stromal and epithelial cells

Proliferation of normal and malignant prostate epithelium is regulated by androgen stimulation via both the androgen receptor (AR)-positive stromal and epithelial cells. However, it is not known how AR expression is regulated in human prostate cells. We report that treatment of normal human prostate stromal cells (PrSCs) with type I IFN (alpha or beta), but not type II IFN (gamma), resulted in increased levels of AR protein. The maximal increase in AR protein levels was dependent on the dose and the duration of the IFN-alpha treatment. We found that the increase in AR protein levels was independent of de novo transcription and protein synthesis. Interestingly, the IFN-alpha treatment of PrSCs resulted in considerable nuclear accumulation of AR, stimulation of AR-mediated transcription of reporter genes, and retardation of cell proliferation. Furthermore, treatment of normal human prostate epithelial cells with IFNs (alpha, beta or gamma) also resulted in increased levels of AR protein. Together, our observations identify the androgen receptor as an IFN-regulated protein in normal human prostate stromal and epithelial cells and predict that IFN-induced levels of AR in prostate cells contribute to the regulation of androgen signaling.

Localization of androgen receptor expression in human bone marrow

Androgens have been shown to modulate the haematopoietic and immune systems and have been used clinically for stimulating haematopoiesis in bone marrow failure conditions. To identify the bone marrow cell types as potential targets of androgens, an androgen receptor (AR)-specific antibody was used to localize the AR in normal human bone marrow biopsies. The results show that AR was ubiquitously expressed in the bone marrow of both males and females. Furthermore, the AR expression pattern did not change with age. Stromal cells, macrophages, endothelial cells, myeloblasts, myelocytes, neutrophils, and megakaryocytes expressed AR. In contrast, AR was not detected in the lymphoid and erythroid cells, or in eosinophils. These results indicate that androgens may exert direct modulating effects on a wide spectrum of bone marrow cell types via AR-mediated responses.

Tubular morphogenesis and mesenchymal interactions affect renin expression and secretion in SIMS mouse submandibular cells

We have previously immortalized a mouse submandibular gland (SMG) ductal epithelial cell line, SIMS, from pubertal male mice transgenic for the SV40 large T antigen under the control of the adenovirus 5 E1A promoter. Here we demonstrate the role of the extracellular environment in directing not only the morphogenetic behavior of the cells, but also their functional differentiation in terms of renin expression and secretion. First, we measured renin activity of polarized SIMS cells. Low levels of renin are secreted from both the apical and the basolateral domains; the mechanism appears to be direct as no renin was found to be transcytosed across the cell. Second, we studied homotypic and heterotypic mesenchymal cell interactions with SIMS cells. We found that epithelial-mesenchymal coculture in collagen I gels results in branching tubular morphogenesis of SIMS cells and that significant amounts of renin are secreted, probably into the lumen, as the precursor form, prorenin. Third, we investigated the effects of the basement membrane on SIMS cell morphology and function and found that this structure alone is sufficient to allow expression and secretion of both prorenin and active renin. Finally, we established that SIMS cells can express androgen-regulated genes in a transient transfection assay. In addition, in Matrigel cultures androgen receptor expression appears to be induced, suggesting that the SIMS cell line will be useful for further studies on the molecular basis of the observed high-level expression of SMG-specific genes in male mice.

Localization of 1,25-dihydroxyvitamin D3 receptor (VDR) expression in human prostate

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been found to have a variety of physiological functions, including effects on growth and differentiation in normal and malignant cells. The antiproliferative effects of 1,25(OH)2D3 are reported to be mediated through the genomic signaling pathway by binding to a specific high affinity receptor protein, the 1,25-dihydroxyvitamin D3 receptor (VDR). VDR has been localized in a variety of tissues, but little is known about VDR distribution in human prostate. In this study, we raised an antibody against a synthetic peptide corresponding to amino acids 10-24 of human vitamin D receptor. The sequence selected for immunization is identical in human, rat and mouse VDR. Based on this antibody, we developed an immunohistochemical method suitable for studying VDR expression in paraffin-embedded tissue. The immunohistochemical staining was verified using classical target organs for vitamin D (kidney, intestine, skin). With this method, we studied VDR localization on paraffin-embedded human prostatic tissue obtained from 8 patients undergoing radical prostatectomy for urinary bladder cancer and demonstrate VDR expression in the secretory epithelial and few stromal cells of human prostate. The nuclear staining in the secretory epithelial cells was concentrated near the nuclear membrane and in discrete foci in the nucleoplasm. This suggests that effects of 1,25-dihydroxyvitamin D3 are mediated through VDR in these cells. Moreover our result indicates that there are strong variations in VDR expression between prostatic samples.

Human genital melanocytes as androgen target cells

As some parts of human skin - such as genital and areolar skin - become pigmented after puberty, melanocytes in these regions are thought to be sex hormone target cells. We immunohistochemically localized androgen receptors in the nuclei of cultured human genital melanocytes by monoclonal and polyclonal antibodies. When these cells were incubated with [1,2-3H]-testosterone, the major metabolite in the medium was dihydrotestosterone and 5alpha-reduction predominated over 17beta-oxidation. Androgen receptor and type I 5alpha-reductase mRNAs could be detected in genital melanocytes by reverse transcriptase polymerase chain reaction. The tyrosinase activity was stimulated by the addition of androgen. This stimulation was antagonized by cyproterone acetate, whereas tyrosinase mRNA expression was not affected by androgen. These results indicate that human genital melanocytes are androgen target cells, and that androgen plays a role for pigmentation in the specific regional skin after puberty.

Age-dependent expression of the androgen receptor gene in the prostate and its implication in glandular differentiation and hyperplasia

The senescence phenotype is the product of both cumulative physical damages during the life span and a species-specific genetic program. The genetic program of aging appears to have co-evolved with the sexual mode of reproduction. The same developmental processes that prepare the animal for maximum vitality and reproductive competence during young adulthood, if allowed to continue, can be detrimental during old age. Androgen receptor-mediated development and growth of the prostate gland is an example of such "antagonistic pleiotropy." The prostate gland is composed of two major groups of cells: the epithelial and stromal. Among the epithelial type, the columnar cells on the luminal surface produce the prostatic secretions, and the basal cells are presumed to serve as progenitors of the columnar cells. Within the stromal cell population, fibroblastic and smooth muscle cells are thought to produce growth factors that support the development and function of the epithelial cells. Both epithelial and stromal cells are dependent on androgens. In this study, we have examined age-dependent expression of the androgen receptor gene in the prostatic tissues of rats and dogs. Unlike the rat, in which the prostatic growth ceases after sexual maturation, the dog prostate continues to grow during aging. Similar to the dog, the antagonistic pleiotropy of the prostatic growth in the human causes the pathological condition of benign prostatic hyperplasia (BPH), the major health problem in old men. Quantitation of the androgen receptor (AR) mRNA in the total prostate extracts from young and old animals by the reverse transcriptase-polymerase chain reaction (RT-PCR) method showed about a 30% decline in AR mRNA in the 24-month-old rat prostate, as compared to the prostate of 3-month-old young adult animals. However, no significant difference in AR mRNA contents between 1-year-old and 10-year-old dog prostates was observed. In situ immunostaining for the androgen receptor protein revealed that in the case of rat, developmental maturation during the first month of life is associated with an increase in AR immunoreactivity in the luminal columnar epithelium, with a concomitant loss of immunoreactivity in the basal cells. Furthermore, with aging, there was a marked increase in the proportion of AR-negative basal cells in comparison to luminal columnar cells. Surprisingly, in both young adult (approximately 1-year-old) and old (approximately 10-year-old) dogs, most of the AR immunoreactivity was localized in the fibroblastic stromal cells rather than in the epithelial cells. Based on these observations and the existing literature, we propose that normally, in most mammalian species, an age-dependent decline in the conversion of basal to columnar epithelial cells after sexual maturation serves as a stop signal for the prostate growth. However, in certain species, such as the dog, robust AR expression in the stromal cells overrides this regulatory blockage and leads to prostatic hyperplasia in old age.

Synergistic effects of estrogen and androgen on the prostate: effects of estrogen on androgen- and estrogen-receptors, BrdU uptake, immunohistochemical study of AR, and responses to antiandrogens

To investigate the synergistic effects of estradiol (E2) and testosterone (T) on prostate growth, castrated Wistar rats were treated with 1 mg/day of T or with 1 mg/day of T and 0.01 mg/day of E2 for 6 weeks. The weight of the prostate in T + E2-treated rats was significantly higher than that in T-treated and normal rats, parallel with the bromodeoxy-uridine (BrdU) labeling index (LI). Nuclear androgen receptor (AR) content in the T + E2 group was significantly higher than that in the T group. But they were lower than that in normal rats. And there were no significant differences between the groups in nuclear estrogen receptor (ER) content. Immunohistochemical studies with the AR antibody revealed positive staining in the prostatic epithelium and stromal cells in the normal, T-treated, and T + E2-treated animals. However, castration led to loss of staining. Response to steroidal antiandrogens was also determined. Antiandrogen treatment abrogated the increases in nuclear AR content and BrdU LI, and prevented immunohistochemical staining. These results suggest that AR and ER, which were measured in this study, were not indicators of prostatic proliferation. We further need to investigate other factors, including other types of receptors, growth factors involved in epithelial-stromal interaction, and so on.

Detection of human androgen receptor mRNA in hepatocellular carcinoma by in situ hybridisation

Recent evidence suggests that anti-androgen therapy may be useful in patients with androgen receptor (AR)-positive hepatocellular carcinomas (HCC), as determined by a steroid binding assay. To evaluate the AR expression of HCC, in both histological and cytological material, we developed a non-radioisotopic in situ hybridisation (NISH) assay specific for the human AR mRNA. A synthetic oligonucleotide complementary to positions 661-695 of the human AR coding sequence was end-labelled with digoxigenin-dUTP and revealed by an alkaline phosphatase-conjugated anti-digoxigenin antibody. We analysed 22 formalin-fixed, paraffin-embedded HCC, obtained at surgery, together with the corresponding non-neoplastic liver tissues (19 cases). In six cases, cell blocks obtained by fine-needle aspiration (FNA) prior to surgery were also available. Positive controls included seminal vesicles and prostate tissues. Sixteen HCCs (73%) expressed a variable amount of AR mRNA, with the proportion of positive cells ranging from very few to more than 90%. Normal hepatocytes were stained weakly and focally in eight cases (42%). Appropriate controls, inclusive of immunohistochemical detection of the AR protein in selected cases, established the specificity of the assay. Data obtained on FNA specimens were predictive of the results on histologic material. However, in two cases the NISH assay was negative on the cytological specimen but stained rare hepatocytes within the surgically resected tumor. In conclusion, NISH is a novel procedure for rapid and specific assessment of the expression of AR in HCC tissue. Its clinical significance, in terms of predictivity of response to anti-androgen treatment, needs to be assessed in large correlative studies.

Immunocytochemical localization of androgen receptors in the scalp of the stumptail macaque monkey, a model of androgenetic alopecia

The purpose of this study was to identify the distribution of androgen receptors in the bald and hairy scalp of adult male and female stumptail macaque monkeys by light microscopic biotin-avidin immunocytochemistry with a highly purified rat monoclonal antibody against the cloned human androgen receptor. Consistent, intense nuclear and minimal cytoplasmic immunostaining was observed in several distinct cell populations of the pilosebaceous unit including the dermal papilla, hair epithelium, outer root sheath, dermal sheath, and sebaceous gland. A similar distribution of androgen receptors was found in miniaturized and terminal anagen and telogen follicles of the bald and hairy scalp, respectively. Binding of androgen receptor antibody was also detected in dermal fibroblasts, basal and intermediate layers of the interfollicular epidermis, and duct and glandular cells of eccrine sweat glands. This investigation demonstrates the presence of androgen receptors in the pilosebaceous unit of the scalp of the stumptail macaque and also shows that their distribution is comparable to that previously reported for humans.

Androgen insensitivity syndrome

In a relatively short period of time, understanding of the fundamental causes of androgen insensitivity syndromes has improved dramatically. This has been brought about by the combination of several disciplines, including endocrinology, genetics, developmental and molecular biology. Mutations can be identified in the androgen receptor gene in suspected cases of AIS, and their functional consequences examined in various in-vitro systems. This information can then be correlated with the clinical presentation of the patient, and is beginning to provide an explanation for the highly variable clinical presentation of AIS. It is to be hoped that this information will also help to predict the likely outcome of androgen therapy in infants with PAIS and an intersex phenotype. More speculatively, functional studies may also lead to novel strategies for the treatment of patients. This would then be of enormous benefit to both patient and parents. Furthermore, the identification of a mutation allows precise information for genetic counselling of families affected by AIS. However, many questions still remain to challenge clinicians and scientists alike. These include the risk of testicular malignancy in patients with AIS and currently there is no worldwide consensus on the stage at which testes should be removed from patients reared as female. There are also significant challenges in patient counselling. Although there is greater understanding of the molecular defects that cause AIS, there are several examples of patients with a similar degree of receptor dysfunction, or even the same mutation, but whose phenotypes are widely different. Other factors must therefore contribute to the clinical presentation of AIS, although these have not been identified. Finally, there are the mutations in patients with Kennedy's disease. The consequences of the mutations are unexplained and are a clear indication that there is still a great deal to discover about the function and biology of androgen receptors.

Immunohistochemistry of the androgen receptor in human benign and malignant prostate tissue

The role of the androgen receptor in the development and progression of prostatic carcinoma has not been defined. The development of androgen receptor antibodies has provided new opportunities for direct immunohistochemical analysis. We compared the androgen receptor staining characteristics of fresh human prostatic carcinoma with benign prostatic hyperplasia (BPH) using an avidin-biotin complex method. Cancer and BPH obtained from the same radical retropubic prostatectomy specimen in 10 prostate cancer patients (68.5 +/- 7.3 years old standard deviation) and BPH from 10 noncancer patients (71.5 +/- 7.7 years old) were incubated with AR52, a rabbit polyclonal antibody against a synthetic androgen receptor peptide. Nuclei within each section were graded for intensity of androgen receptor staining (0-absent, 1-weak, 2-moderate or 3-strong) and the percentage (0 to 100%) of nuclei sampled staining at each of these intensity levels was determined. A total intensity score (0 to 300) was the summation of the products of each intensity score (0 to 3) and their corresponding percentages. Cancer sections (166 +/- 69) stained less intensely and more heterogeneously than BPH in cancer patients (246 +/- 41, Student's t test p < 0.05) and noncancer patients (225 +/- 39, p < 0.05). The decreased intensity and greater heterogeneity of androgen receptor staining in cancer tissue may implicate a quantitative or functional difference in androgen receptor between prostatic carcinoma and BPH.

Immunocytochemical localization of androgen receptors in human skin using monoclonal antibodies against the androgen receptor

Androgen receptors were localized in cryostat sections of human skin using monoclonal antibodies to the human androgen receptor. Bound antibodies were detected using biotinylated rabbit anti-rat IgG, peroxidase-conjugated streptavidin, and diaminobenzidine as chromogen. In the neonatal foreskin, antibody to androgen receptor bound to keratinocytes in the epidermis and to fibroblasts and vascular endothelial cells in the dermis. Immunohistochemical staining was stronger in nuclei than in cytoplasm. This staining was specific, because there was no significant staining when antibody to the androgen receptor was replaced with IgG from nonimmunized rats or with buffer, or when antibody to androgen receptor was incubated, prior to immunostaining, with a trp E-human androgen-receptor fusion protein used as immunogen. Incubation of androgen receptor antibody with trp E alone did not affect staining. Androgen-receptor antibody also bound to keratinocytes, fibroblasts, and endothelial cells in skin from adult men and women. Skin from the scalp, nose, lip, back, and chest gave positive staining for androgen receptor. Antibody to androgen receptor also bound to the coil and ductal cells of eccrine glands, external root sheath of hair follicles, epithelium in the hair bulb, dermal papilla cells, and sebocytes. There was no significant binding to adipocytes, collagen, or stratum corneum. These results show that androgen receptor is present in cells that are known to be targets for androgens and also in cells in which the biologic effects of androgens are yet to be characterized.

Androgen receptor immunoreactivity in intact and castrate guinea pig using antipeptide antibodies

We developed and used antibodies to an androgen receptor (AR)-specific synthetic peptide (amino acids 201-222 of the human androgen receptor) to localize AR in the brain and peripheral tissues of intact and castrate adult male guinea pigs. Immunoreactivity was localized to the nucleus of epithelial and stromal cells in the prostate of intact animals. Immunostaining was abolished in the prostate 4 days following castration. Androgen receptor immunoreactivity was found in brain nuclei known to be involved in reproductive and other androgen-dependent behaviors, including the preoptic area, medial basal hypothalamus, and anterior pituitary gland. Castration had no effect on the distribution or intensity of AR immunostaining in the brain. These data indicate a differential regulation of AR in the brain compared to peripheral tissues.

Evidence for the presence of androgen receptors in the synovial tissue of rheumatoid arthritis patients and healthy controls

OBJECTIVE

To study the presence of androgen receptors in the synovial tissue of male and female patients with rheumatoid arthritis (RA) and matched healthy controls.

METHODS

Both site I (high affinity, low binding capacity) and site II (reduced affinity, higher binding capacity) androgen receptors were investigated in soluble and nuclear fractions of homogenized synovial samples, using the dextran-coated charcoal method. The finding of pure, high-affinity site I receptors in both fractions was considered indicative of androgen receptor positivity. In order to determine what type of synovial cell was positive for androgen receptors, cryosections of synovial tissues were immunostained with a specific monoclonal anti-androgen receptor antibody (MAb), using both immunofluorescence and immunoperoxidase techniques. Double immunostaining with this MAb and specific MAb directed toward different macrophage/granulocyte antigens was also performed.

RESULTS

Remarkable differences were found between male and female controls: Most males were positive for androgen receptors, and most females were negative. The fetomolar content of androgen receptor in the nuclear fraction was fairly constant, but the soluble fraction showed a higher femtomolar concentration in female RA patients than in controls of either sex, as well as in male RA patients compared with female RA patients. The androgen receptor-positive cells in both RA and control synovial cryosections were found by immunostaining to be macrophage-like synoviocytes, and were also found to be HLA-DR positive.

CONCLUSIONS

The immunosuppressive action exerted by androgens might, at least in part, be mediated through their interaction with macrophage-like synoviocytes functioning as antigen-processing and antigen-presenting cells in rheumatoid synovia.

The methyltrienolone binding protein of JEG-3 cells and human placenta is localized within the nucleus and is tightly associated with chromatin

Human placenta contains the methyltrienolone binding protein (MTBP), an androgen binding protein which is distinct from the androgen receptor. This study demonstrates that the human choriocarcinoma cell line (JEG-3) also contains the MTBP and that in both human placenta and JEG-3 cells the MTBP is located exclusively in the nucleus and in particular is associated with DNase 1 resistant chromatin.

Immunocytochemical localization of androgen receptors in the male songbird and quail brain

The distribution of androgen receptors was studied in the brain of the Japanese quail (Coturnix japonica), the zebra finch (Taeniopygia guttata), and the canary (Serinus canaria) by immunocytochemistry with a polyclonal antibody (AR32) raised in rabbit against a synthetic peptide corresponding to a sequence located at the N-terminus of the androgen receptor molecule. In quail, androgen receptor-immunoreactive cells were observed in the nucleus intercollicularis and in various nuclei of the preoptic-hypothalamic complex, namely, the nucleus preopticus medialis, the ventral part of the nucleus anterior medialis hypothalami, the nucleus paraventricularis magnocellularis, the nucleus ventromedialis hypothalami, and the tuberal hypothalamus. In the two songbird species, labeled cells were also observed in various nuclei in the preoptic-hypothalamic region, in the nucleus taeniae, and in the nucleus intercollicularis. Additional androgen receptor-immunoreactive cells were present in the androgen-sensitive telencephalic nuclei that are part of the song control system. These immunoreactive cells filled and outlined the boundaries of the hyperstriatum ventrale, pars caudalis, nucleus magnocellularis neostriatalis anterioris (both in the lateral and medial subdivisions), and nucleus robustus archistriatalis. The immunoreactive material was primarily present in cell nuclei but a low level of immunoreactivity was also clearly detected in cytoplasm in some brain areas. These studies demonstrate, for the first time, that androgen receptors can be detected by immunocytochemistry in the avian brain and the results are in general agreement with the binding data obtained by autoradiography with tritiated dihydrotestosterone. Immunocytochemical methods offer several advantages over autoradiography and their use for the study of the androgen receptor will greatly facilitate the analysis of steroid-sensitive systems in the avian brain.

Immunohistochemistry and biochemistry in detection of androgen, progesterone, and estrogen receptors in benign and malignant human prostatic tissue

The relative distribution of androgen (AR), progesterone (PR), and estrogen receptors (ER) was localized and estimated in human prostate tissue by immunohistochemistry in five normal tissue samples, in eight benign hyperplastic (BPH) samples, in nine primary cancers, and in seven prostate cancer metastases. Moreover, three prostatic cancer cell lines (LNCaP, DU 145, and PC 3) were analyzed. A comparison between the results obtained by radioligand binding assays and immunohistochemistry was performed for the AR and PR. Using immunohistochemistry, the AR was exclusively detected in the nuclei of both benign and malignant prostatic epithelial cells. The highest proportion of AR-positive cells was found in BPH and in prostate cancer metastases as compared with normal prostatic tissue. In a majority of the cases, the PR was only present in the nuclei of stromal cells. Benign hyperplastic prostates contained higher proportions of PR-positive cells as compared with primary carcinoma. PR was sparse in epithelial cells. ER-positive stromal cell nuclei were only detected in carcinomatous prostates. A few ER-positive epithelial cell nuclei were found in one sample each of a BPH and normal prostate. All cells from the androgen-dependent, LNCaP, cell line and a majority of the cells from the androgen-independent, DU 145, cell line were AR-positive. In contrast, the cells from the androgen-independent, PC 3, cell line were all AR-negative. All three cell lines were PR- and ER-negative. The radioligand binding technique detected the AR in extracts from both the cytosol and the nucleus. Again BPH contained higher amounts of AR as compared with normal prostatic tissue. The LNCaP cells contained high amounts of cytosolic AR while cells from the DU 145 and PC 3 cell lines lacked detectable AR as estimated by biochemical techniques. There seemed to be a discrepancy between biochemically measured and immunohistochemically estimated receptor content.

Steroid receptor profile and receptor stability in subfractions of human prostatic tissues. Critical aspects on microassays

Androgen (AR), progesterone (PR), and estrogen (ER) receptor contents in cytosol and salt-extractable nuclear subcompartments from 6 normal, 39 benign hyperplastic (BPH), and 7 malignant prostatic tissue specimens were analyzed by radioligand-binding assay techniques. In addition, the temperature stability of AR and PR was measured in another three BPH specimens. Five punch-needle biopsy samples from prostate cancers were also analyzed for AR and PR content. All receptor data were calculated from saturation analyses. The highest AR content was found in the cytosol and nucleic from malignant prostatic tissues. The highest PR concentrations were found in BPH cytosol, whereas nuclei of all types of tissues were negative with regard to this receptor. Markedly lower concentrations of ER were found in cytosol and nuclei from BPH as compared with malignant and normal tissues. PR was the most temperature-stable receptor; a marked receptor loss at room temperature was not registered until after 12 h. AR was stable for 4-5 h in cytosol and for 8-9 h in nuclei. Needle-biopsy specimens from prostate cancer showed highly variable and confusing results for AR and PR content, indicating that microassay studies using biochemical techniques on small tissue samples are unreliable and should not be recommended.

Evidence for the presence of androgen receptors in human Leydig cells

Localization of androgen receptors (ARs) in the human testis Leydig cells was examined with an AR assay and Northern blot analysis. Leydig cells, highly purified on a Percoll gradient, were used for the experiments. AR concentration in the total cell extract containing both the cytosol and nuclear fractions in Leydig cells was measured using [3H]methyltrienolone. ARs in Leydig cells showed a high affinity for [3H]methyltrienolone and the Kd and Bmax of the receptors were 1.24 nM and 11.7 fmol/mg protein, respectively. Northern blot analysis, using a 32P-labeled full-length human AR complementary DNA (cDNA) detected a 9.5-kb hybridizing band in the total RNA extracted from Leydig cells. These data can be interpreted as evidence of the existence of ARs in human Leydig cells.

Steroid hormone receptors

In the three decades since the original discovery of receptors for steroid hormones, much has been learned about the biochemical processes by which these regulatory agents exert their effects in target tissues. The intracellular receptor proteins are potential transcription factors, needed for optimal gene expression in hormone-dependent cells. They are present in an inactive form until association with the hormone converts them to a functional state that can react with target genes. Transformation of the receptor protein to the nuclear binding form appears to involve the removal of both macromolecular and micromolecular factors that act to keep the receptor form reacting with DNA. Much of the native receptor is present in the nucleus, loosely bound and readily extractable, but for some and possibly all steroid hormones, some receptor is in the cytoplasm, perhaps in equilibrium with a nuclear pool. Methods have been developed for the stabilization, purification, and characterization of receptor proteins, and through cloning and sequencing of their cDNAs, primary structures for these receptors are now known. This has led to the recognition of structural similarities among the family of receptors for the different steroid hormones and to the identification of regions in the protein molecule responsible for the various aspects of their function. Monoclonal antibodies recognizing specific molecular domains are available for most receptors. Despite the knowledge that has been acquired, many important questions remain unsolved. How does association with the steroid remove factors keeping the receptor protein in its native state, and how does binding of the transformed receptor to the response element in the promoter region enhance gene transcription? Once it has converted the receptor to the nuclear binding state, is there a further role for the steroid in modulating transcription? Still not entirely clear is the involvement of phosphorylation and/or dephosphorylation in hormone binding, receptor transformation, and transcriptional activation. Less vital to basic understanding but important in the overall picture is whether the native receptors for gonadal hormones are entirely confined to the nucleus or whether there is an intracellular distribution equilibrium. With the effort now being devoted to this field, and with the application of new experimental techniques, especially those of molecular biology, our understanding of receptor function is progressing rapidly. The precise mechanism of steroid hormone action should soon be completely established.

Steroid receptor profile in human prostate cancer metastases as compared with primary prostatic carcinoma

The steroid receptor profile in seven prostate cancer metastases was compared with the profile in seven primary prostate cancers. The secondaries were all lymph node metastases, obtained during pelvic lymphadenectomy, preceding radical prostatectomy or irradiation. Cytosol androgen receptor content was higher in metastases, whereas the nuclear androgen receptor content was only one-fourth that in primary cancer. Cytosol progesterone as well as estrogen receptor contents were markedly lower in metastases compared with primary cancer. The steroid receptor profile differed very little between primary cancer and normal tissue. Primary prostatic carcinoma is usually obtained at early stages of the disease, whereas metastases represent a dedifferentiated, more aggressive cell population. This may explain the low amounts of progesterone, estrogen, and nuclear androgen receptor levels. The total androgen receptor content was similar in metastatic and primary disease, however, with a shift towards a cytosolic predominance in metastases. Possibly androgen receptors in metastatic disease are "deactivated."

Localization and regulation of estrogen, progestin and androgen receptors in the seminal vesicle of the rhesus monkey

We have used monoclonal antibodies against the estrogen (E), progestin (P) and androgen (A) receptors (R) to study receptor localization and regulation in the seminal vesicles of rhesus monkeys under different hormonal conditions. The antibodies caused substantial shifts of the appropriately labeled receptors on sucrose gradients. ER levels were lower in intact males than in immature, castrate, and estrogen-treated castrates. With immunocytochemistry, ER were detectable only in stromal and smooth muscle cells, not the epithelium. The number of ER-positive stromal cells was significantly lower in intact males than in immature, castrate, and estrogen-treated castrates, and low in a DHT-treated castrate animal. Androgen receptors were localized in epithelial as well as stromal and smooth muscle cells, and the number of AR-positive stromal cells was highest in intact adults and lowest in castrated and immature animals. Estrogen treatment at the time of castration induced PR in the ER-positive stromal cells, prevented a decline in the number of AR-positive stromal cells, and caused stromal hypertrophy. In summary, in the seminal vesicle, as in the prostate, ER is restricted to the fibromuscular stroma, is suppressed by androgens, and can mediate induction of PR on estrogen treatment. Androgen receptors are present in epithelial as well as stromal and smooth muscle cells, but variations in hormonal state appear to affect regulation of AR more in the stroma than the epithelium.

Immunohistochemical study of androgen receptor in benign hyperplastic and cancerous human prostates

Androgen receptor was detected immunohistochemically in benign as well as malignant prostatic tissues by using a monoclonal rat anti-human androgen receptor antibody (AN 1-15). In both benign and malignant cells, the androgen receptor was exclusively localized in nuclei. In hyperplastic prostate, the androgen receptor was stained in the glandular and the stromal cells. In the gland, cells facing the lumen were stained more intensively than those adjacent to the basal membrane. In cancer tissue, receptor-positive and -negative cancer cells were intermingled. The percent of strongly positive cancer cells was correlated inversely with grade. Relapsed cells showed a low population of strongly positive cells irrespective of grade.