Effects of oestradiol-17 beta and 5 alpha-dihydrotestosterone on guinea-pig prostate smooth muscle cell proliferation and steroid receptor expression in vitro

Importance of Estrogenic Signaling and Its Mediated Receptors in Prostate Cancer

Prostate cancer (PCa) treatment was first established by Huggins and Hodges in 1941, primarily described as androgen deprivation via interference of testicular androgen production. The disease remains incurable with relapse of hormone-refractory cancer after treatments. Epidemiological and clinical studies disclosed the importance of estrogens in PCa. Discovery of estrogen receptor ERβ prompted direct estrogenic actions, in conjunction with ERα, on PCa cells. Mechanistically, ERs upon ligand binding transactivate target genes at consensus genomic sites via interactions with various transcriptional co-regulators to mold estrogenic signaling. With animal models, Noble revealed estrogen dependencies of PCa, providing insight into potential uses of antiestrogens in the treatment. Subsequently, various clinical trials were conducted and molecular and functional consequences of antiestrogen treatment in PCa were delineated. Besides, estrogens can also trigger rapid non-genomic signaling responses initiated at the plasma membrane, at least partially via an orphan G-protein-coupled receptor GPR30. Activation of GPR30 significantly inhibited in vitro and in vivo PCa cell growth and the underlying mechanism was elucidated. Currently, molecular networks of estrogenic and antiestrogenic signaling via ERα, ERβ and GPR30 in PCa have not been fully deciphered. This crucial information could be beneficial to further developments of effective estrogen- and antiestrogen-based therapy for PCa patients.

Responsiveness of Dupuytren's disease fibroblasts to 5 alpha-dihydrotestosterone

PURPOSE

We recently showed that androgen receptors are expressed in Dupuytren's contracture. The aim of the present work was to test the responsiveness of Dupuytren's fibroblasts to 5 alpha-dihydrotestosterone (5 alpha-DHT), the active form of testosterone.

RESULTS

Cultured palmar fascia cells from 10 patients with Dupuytren's contracture and 4 normal subjects were exposed to 5 alpha-DHT (10 or 100 ng/mL) for 1, 3, 7, and 15 days. Their phenotype was analyzed immunohistochemically for alpha-smooth muscle actin and androgen receptor expression and proliferation rates were studied.

RESULTS

At 15 days the higher concentration of 5 alpha-DHT induced an increase in Dupuytren's fibroblast proliferation, whereas anti-alpha-smooth muscle actin exhibited the strongest expression. At the same time point androgen receptor expression decreased with the lower concentration and disappeared altogether with the higher dose of 5 alpha-DHT.

CONCLUSIONS

The palmar fascia is a target tissue for androgen action via androgen receptors. Further studies are required to determine whether control of androgen receptor may control the evolution of Dupuytren's disease.

Dietary supplements of soya flour lower serum testosterone concentrations and improve markers of oxidative stress in men

OBJECTIVE

We examined the effects on serum sex steroids, lipids and markers of oxidative stress of supplementing the diets of healthy male volunteers with scones made with soya flour.

DESIGN

A randomized placebo controlled cross-over trial.

SETTING

University Hospital of Wales.

SUBJECTS

Twenty volunteers recruited by advertisement.

INTERVENTIONS

Male volunteers ate three scones a day in addition to their normal diet for a period of 6 weeks. The scones were made with either wheat or soya flour (containing 120 mg/day of isoflavones). Blood was analysed for sex steroids (testosterone, dihydro-testosterone, oestradiol, oestrone, sex hormone binding globulin, albumin and the concentration of non-protein bound sex steroids were calculated), lipid profile (total cholesterol, high density lipoprotein cholesterol and triglycerides) and measures of oxidative stress (hydroperoxides, susceptibility of LDL to oxidation with copper and myeloperoxidase).

RESULTS

The volunteers' mean age was 35.6 (s.d. 11.2) y. Total serum testosterone fell in volunteers taking the soya scones (19.3-18.2 nmol/l; 95% CI 1.01, 1.12; P=0.03). No significant changes were seen in the concentrations of the other serum sex steroids, albumin or sex hormone binding globulin throughout the study. Significant improvements in two of the three markers of oxidative stress were seen in volunteers taking soya scones. Lag time for myeloperoxidase rose from 55.0 to 68.0 min (95% CI -16.0, -3.5; P=0.009) and the presence of hydroperoxides decreased from 2.69 to 2.34 micro mol/l (95% CI 0.12, 0.71; P=0.009). There were no changes seen in serum triglycerides or cholesterol.

CONCLUSIONS

We have shown that soya supplements reduce serum testosterone and improve markers of oxidative stress. These findings provide a putative mechanism by which soya supplements could protect against prostatic disease and atherosclerosis. Further dietary studies with clinical end points are warranted.

Dedifferentiation of stromal smooth muscle as a factor in prostate carcinogenesis

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

Androgen receptors in Dupuytren's contracture

Palmar fascia tissue and cultured cells from patients with Dupuytren's contracture and from normal subjects were characterized and analyzed for androgen receptor expression. Androgen receptors have never been studied in Dupuytren's myofibroblasts and may have a role in its high male predominance. Surgical samples were collected from eight patients undergoing surgery for Dupuytren's contracture and from four patients with carpal tunnel syndrome, used as control tissue. Immunohistochemical analysis was performed on tissue samples and on cell cultures with anti-androgen receptor, anti-alpha-smooth muscle actin, anti-fibronectin, and anti-type I and III collagen antibodies using the biotin avidin peroxidase method as revelatory system. Immunostaining for androgen receptors in tissue samples and cultured cells revealed nuclear reaction in many Dupuytren's myofibroblasts, but in few fibroblasts of the normal palmar fascia. In a double-labeling study, androgen receptors were seen to co-localize with alpha-actin in both cell cultures and tissue samples. We present the first evidence that the palmar fascia is a target tissue for androgen action and that the expression of androgen receptors in Dupuytren's contracture is considerably higher than in the normal palmar fascia. Further studies will need to evaluate whether the androgen-responsive state of the tissue is related to the high incidence of Dupuytren's contracture in the male sex.

Transforming growth factor-beta is an autocrine mitogen for a novel androgen-responsive murine prostatic smooth muscle cell line, PSMC1

A prostatic smooth muscle cell line (PSMC1) was established from the dorsolateral prostate of p53 null mice. The cell line is nontumorigenic when inoculated subcutaneously, under the renal capsule or intraprostatically in syngeneic mice. These cells express alpha-smooth muscle actin (alpha-SMA), indicating their smooth muscle origin, and TGF-beta significantly enhances expression of alpha-SMA. The cells express both androgen receptor (AR) mRNA and protein, and respond mitogenically to physiological concentrations of androgens. PSMC1 cells produce significant amounts of TGF-beta, which stimulates growth by an autocrine mechanism. Dihydrotestosterone (DHT) increases proliferation of PSMC1 cells by promoting TGF-beta secretion. Considering the significant inhibitory effect of TGF-beta on prostatic epithelial cells and its stimulatory effect on the PSMC1 cells, we postulate that TGF-beta produced by prostatic smooth muscle cells may have a paracrine effect on the prostatic epithelium. We also postulate that TGF-beta may be involved in the etiology of benign prostatic hyperplasia (BPH) by stimulating excessive stromal proliferation. Line PSMC1 is the first reported androgen-responsive murine smooth muscle cell line. It will be useful for in vivo and in vitro experiments to study the mechanisms of androgen action on prostatic stroma and for delineating the interactions that occur between prostatic smooth muscle and epithelium that may lead to prostatic diseases such as BPH.

Human prostatic smooth muscle cells in culture: estradiol enhances expression of smooth muscle cell-specific markers

Smooth muscle cells (SMCs) constitute a major cellular component of prostatic stroma. SMC tension plays an important role in urethral obstruction secondary to benign prostatic hyperplasia (BPH). We have developed an in vitro procedure for the propagation of human prostatic SMCs. Tissue specimens from patients undergoing radical prostatectomy or cystectomy were enzymatically disaggregated and cultured in MCDB-131 medium supplemented with horse serum, insulin, conditioned medium from the tumor cell line CRL-5813, and steroid hormones. The medium was assembled on the basis of the effects these supplements have on the growth of SMC cultures and on the expression of the two markers desmin and smooth muscle myosin. Addition of 0.1 microM of estradiol to the growth medium dramatically increased expression of these SMC-specific markers. Dihydrotestosterone (DHT) and hydrocortisone had a similar, albeit less pronounced effect. At three to five passages, about two thirds of the cells were immunohistologically positive for smooth muscle myosin or desmin. Almost all cells were positive for the myofibroblast marker smooth muscle alpha-actin throughout 10 passages and more. In SMC cultures, cells staining for smooth muscle myosin and desmin were found to seek direct contact to myofibroblasts. They grew in aggregates on a layer of myofibroblasts which adhered to the surface of the culture vessel. As revealed by transmission electron microscopy the cultured cells exhibited morphological features of myofibroblasts. Characteristics of smooth muscle cells, such as prominent bundles of microfilaments associated with dense bodies, basal laminae investing the cells, and numerous caveolae at the cell surfaces were regularly observed in cultures of low passages. After several passages, these features were markedly decreased and organelles of the biosynthetic system became more prominent. In summary, we present an in vitro model of prostatic SMCs and demonstrate that steroid hormones have characteristic effects on these cells. SMC cultures are expected to facilitate investigation of the functions and properties of human prostatic SMCs.

Androgens induce divergent proliferative responses in human breast cancer cell lines

Although the majority of primary human breast cancers express the androgen receptor (AR), the role of androgens in breast cancer growth and progression is poorly understood. We have investigated the effects of the naturally occurring androgen, dihydrotestosterone (DHT), and a synthetic non-metabolizable androgen, mibolerone, on the proliferation of six human breast cancer cell lines. The anti-proliferative and proliferative effects of androgens were only observed in cell lines that expressed the AR. Two of the AR-positive cell lines, T47-D and ZR-75-1 were growth inhibited in the presence of either DHT or mibolerone, while the proliferation of MCF-7 and MDA-MB-453 cells was increased by both androgens. Co-incubation of cultures with 1 nM DHT and a 100-fold excess of the androgen receptor antagonist, hydroxyflutamide, resulted in reversal of both inhibitory and stimulatory effects of DHT on T47-D, MCF-7 and MDA-MB-453 cell proliferation, indicating that DHT action is mediated by the AR in these lines. Hydroxyflutamide only partially reversed the DHT-induced growth inhibition of ZR-75-1 cultures, which suggests that growth inhibition of these cells may be mediated by non-AR pathways of DHT (or DHT metabolite) action. Mibolerone action on breast cancer cell growth was similar to that of DHT, with the exception that growth stimulation of MCF-7 and MDA-MB-453 cells was only partially reversed in the presence of a 100-fold excess of hydroxyflutamide. Anandron, another androgen receptor antagonist, was able to reverse all inhibitory and stimulatory actions of the androgens. AR antisense oligonucleotides reduced the level of immunoreactive AR expression in MDA-MB-453 and ZR-75-1 cells by more than 60%, but only reversed the growth inhibitory action of mibolerone in ZR-75-1 cultures. The results suggest that androgen action in breast cancer cell lines may not be solely mediated by binding of androgen to the AR. For example, metabolites of DHT with oestrogenic activity, or androgen binding to receptors other than the AR, may explain the divergent responses to androgens observed in different breast cancer cell lines.

Evidence for a novel mechanism of androgen resistance in the human prostate cancer cell line, PC-3

Progression to hormone-refractory disease is a common outcome of human prostate cancer. In this study, we have investigated the basis of androgen insensitivity in the human prostate cancer cell line, PC-3, which was derived from a bone metastasis of a hormone-refractory prostate cancer. PC-3 cells with virtually undetectable (PC-3AR-) or low (PC-3AR+) levels of androgen receptor (AR) RNA expression were examined. RNase protection assays demonstrated that the level of AR RNA in PC-3AR+ cells was similar to that in a normal androgen-responsive genital skin fibroblast cell strain. Quantitative immunocytochemical staining of AR in PC-3AR+ cells using antibodies directed against the amino and carboxyl termini of the receptor revealed staining in 30% of cells with either antibody. Furthermore, the level of AR staining in PC-3AR+ cells was higher than in the androgen-responsive breast cancer cell lines ZR-75-1, T47-D, and MCF-7. Despite the expression of AR RNA and protein, PC-3AR+ cell proliferation was unaffected by the presence of 0.1-10 nM mibolerone. Scatchard analysis demonstrated a complete absence of specific [3H]dihydrotestosterone ([3H]DHT) binding to PC-3AR+ cytosolic extracts, which could not be explained by structural alterations in the AR gene. The sizes of individual AR exons amplified from genomic DNA derived from PC-3AR+ cells were identical to those amplified from normal human cells. Furthermore, sequence analysis did not reveal a mutation in the DNA- or hormone-binding domains of the AR gene in PC-3AR+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)