Age dependency of androgen and estrogen effects on incorporation of (3H)-thymidine by rat prostates in organ culture

Clinical Usefulness of the Histoculture Drug Response Assay for Prostate Cancer and Benign Prostate Hypertrophy (BPH)

The histoculture drug response assay (HDRA) has been adapted to determine androgen sensitivity in Gelfoam histoculture of human benign prostatic tissue as well as prostate cancer. Gelfoam histoculture was used to measure androgen-independent and androgen-dependent growth of benign and malignant prostate tissue. The androgen-sensitivity index was significantly higher in 23 paired specimens of prostate cancer compared to benign prostate hypertrophy (BPH). Genistein decreased the androgen-sensitivity index of BPH and prostate cancer in Gelfoam^® histoculture in a dose-dependent manner.

A role for estrogen receptor beta in the regulation of growth of the ventral prostate

In normal rats and mice, immunostaining with specific antibodies revealed that nuclei of most prostatic epithelial cells harbor estrogen receptor beta (ERbeta). In rat ventral prostate, 530- and 549-aa isoforms of the receptor were identified. These sediment in the 4S region of low-salt sucrose gradients, indicating that prostatic ERbeta does not contain the same protein chaperones that are associated with ERalpha. Estradiol (E(2)) binding and ERbeta immunoreactivity coincide on the gradient, with no indication of ERalpha. In prostates from mice in which the ERbeta gene has been inactivated (BERKO), androgen receptor (AR) levels are elevated, and the tissue contains multiple hyperplastic foci. Most epithelial cells express the proliferation antigen Ki-67. In contrast, prostatic epithelium from wild-type littermates is single layered with no hyperplasia, and very few cells express Ki-67. Rat ventral prostate contains an estrogenic component, which comigrates on HPLC with the testosterone metabolite 5alpha-androstane-3beta,17beta-diol (3betaAdiol). This compound, which competes with E(2) for binding to ERbeta and elicits an estrogenic response in the aorta but not in the pituitary, decreases the AR content in prostates of wild-type mice but does not affect the elevated levels seen in ERbeta knockout (BERKO) mice. Thus ERbeta, probably as a complex with 3betaAdiol, is involved in regulating the AR content of the rodent prostate and in restraining epithelial growth. These findings suggest that ligands specific for ERbeta may be useful in the prevention and/or clinical management of prostatic hyperplasia and neoplasia.

Comparison of androgen-independent growth and androgen-dependent growth in BPH and cancer tissue from the same radical prostatectomies in sponge-gel matrix histoculture

BACKGROUND

In order to determine androgen sensitivities of prostate cancer and benign prostatic hypertrophy (BPH) tissues from the same patient in vitro, we used a histoculture technique to measure androgen-independent and androgen-dependent growth and compared them in paired specimens of BPH and prostate cancer from 23 radical prostatectomies. Both androgen-independent growth and androgen-dependent growth are measures of important biological characteristics of benign and malignant prostate tissue.

METHODS

The effect of hydroxyflutamide and antiandrogens on dihydrotestosterone (DHT)-stimulated incorporation of 3H-thymidine into both paired specimens of BPH and cancer was utilized to measure androgen-independent and androgen-dependent growth. The percentage decrease in 3H-thymidine incorporation/microgram protein in the flutamide-treated specimen compared to the DHT-treated specimen represented androgen-dependent growth. Residual 3H-thymidine incorporation/microgram protein during hydroxyflutamide administration represented androgen-independent growth.

RESULTS

Androgen-independent growth was significantly greater (P = 0.015) in the BPH compared to the cancer paired tissue. Androgen-dependent growth was significantly higher in 23 paired specimens of cancer compared to BPH (P < 0.03).

CONCLUSIONS

In paired specimens of BPH and prostate cancer from the same radical prostatectomy specimen, androgen-independent growth appeared greater in BPH compared to cancer specimens; androgen-dependent growth, however, was greater in prostate cancer than in BPH. There was no correlation of either growth parameter with Gleason tumor grade. Future clinical correlations will indicate whether either growth parameter represents an important prognostic factor for prostate cancer aggressiveness stimulated 3H-thymidine incorporation into DNA.

Analysis of cell death and cell proliferation in embryonic stages, normal adult, and aging prostates in human and animals

Homeostasis in the prostate is recognized to be maintained by a complex interplay between the opposing actions of cell proliferation and cell death. Growth regulatory factors that promote or inhibit cell proliferation and promote cellular death have been identified in the prostate. The integration of these forces involves cellular cooperation between the prostatic stroma and epithelium. Hormone-regulated production of growth regulatory factors by one cell type may determine growth stimulation, inhibition, or cell death in a reciprocal cell partner. Imbalance between net cell proliferation and net cell death rates may result in abnormal growth leading to BPH. Additional study of the growth regulatory factors associated with distal vs. proximal epithelial cells and stroma and comparison of growth factor expression by the neonatal, postnatal growing, adult quiescent, and aging prostates will likely provide further insight into the regulation of prostate cell division and death.

Antiandrogens inhibit human androgen receptor-dependent gene transcription activation in the human prostate cancer cells LNCaP

Human androgen receptor (hAR) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. Transfection studies in the human prostate cancer cell line LNCaP examine the ability of dihydrotestosterone (DHT), hydroxyflutamide (HO-FLU), cyproterone acetate (Cypro.A), and RU 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (MMTV-CAT). DHT stimulated transcription activation of MMTV-CAT gene in LNCaP cells in a dose-dependent manner. HO-FLU, Cypro.A, and RU 23908-10, though only partially, also stimulated the transcription activation of MMTV-CAT. Despite this, 100- to 1,000-fold molar excess of all antiandrogens inhibited the agonistic activity of 10 nM DHT in this system. Receptor binding assays confirmed that HO-FLU, Cypro.A, and RU 23908-10 competed with DHT for AR binding in LNCaP cells. Western blot analysis using AR antipeptide antibodies raised in rabbits revealed the presence of two AR protein bands in LNCaP cells, following treatment with antiandrogens. Increasing doses of HO-FLU stimulated the expression of the 114-kDa AR by 2.5-fold, but did not affect the 108-kDa AR. Increasing doses of Cypro.A and RU 23908-10 decreased the levels of both the 114-kDa and the 108-kDa AR. Although the exact nature of 108-kDa and 114-kDa AR in LNCaP cells is still unknown, these data suggest that the regulatory actions of each individual antiandrogen on AR expression in LNCaP cells may be different.

Interaction of antiandrogen-androgen receptor complexes with DNA and transcription activation

Human androgen receptor (hAR) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. Transfection studies in receptor deficient monkey kidney cells CV-1 in culture examine the ability of dihydrotestosterone (DHT) and of the antiandrogens hydroxylflutamide (HO-FLU), cyproterone acetate (Cypro.A) and RU 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (MMTV-CAT). CV-1 cells cotransfected with wild type hAR (hAR1-910) and MMTV-CAT, were treated with varying concentrations of DHT. DHT stimulated transcription activation of MMTV-CAT gene in a dose-dependent fashion. Cypro.A though only partially, also stimulated the transcription activation of MMTV-CAT. In the absence of steroids, HO-FLU induced the MMTV-CAT transcription in transfectants only 4% above the basal level. RU 23908-10 revealed the least agonistic activity at concentrations between 10 nM and 1 microM. Despite this, 100- to 1000-fold molar excess of all antiandrogens inhibited the agonistic activity of 10 nM DHT in this system. Receptor binding assays confirmed that HO-FLU, Cypro.A and RU 23908-10 competed with [3H]DHT for AR binding with hAR expressed in CV-1 cells. Western blot analysis using AR antipeptide antibodies raised in rabbits revealed the presence of two AR protein bands in extracts prepared from hAR1-910 transfected CV-1 cells. Incubation of labeled synthetic palindromic androgen responsive element (ARE) with the hAR containing CV-1 cell extracts followed by u.v. cross-linking demonstrated the specificity of AR-DNA interaction. Analysis by gel mobility shift assays showed that the interaction of AR-antiandrogen complexes with labeled ARE was specific.

Transdermal dihydrotestosterone treatment of 'andropause'

Male ageing coincides on average with progressive impairment of testicular function. The most striking plasma changes are an increase in sex hormone binding globulin (SHBG) and a decrease in non SHBG-bound testosterone, which is the only testosterone subfraction effectively bioavailable for target tissues. In healthy subjects the bioavailable testosterone declines by approximately 1% per year between 40 and 70 years but a more pronounced decline has been observed in non-healthy groups, especially in high cardiovascular risks groups. Relative androgen deficiency is likely to have unfavourable consequences on muscle, adipose tissue, bone, haematopoiesis, fibrinolysis, insulin sensitivity, central nervous system, mood and sexual function and might be treated by an appropriate androgen supplementation. The potential risk for prostate has been the main reason for limiting indications of such treatment. Testosterone (T) and dihydrotestosterone (DHT) are two potent androgens which have opposite effects regarding aromatase activity, an enzyme present in prostate stroma and suspected to have a pathogenic influence through local oestradiol synthesis. T is the main substrate for aromatase and oestradiol synthesis while DHT is not aromatizable and, at sufficient concentration, decreases T and oestradiol levels. A 1.8 years survey of 37 men aged 55-70 years treated with daily percutaneous DHT treatment suggested that high plasma levels of DHT (> 8.5 nmol/l) effectively induced clinical benefits while slightly but significantly reducing prostate size. Early stages of prostate hypertrophy require synergic stimulation by both DHT and oestradiol, and suppressing oestradiol instead of DHT seems easier and better adapted to the specific situation of aged hypogonadic men.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of androgen sensitivity in the human prostate in in vitro three-dimensional histoculture

We have adopted an in vitro three-dimensional histoculture technique for assay of androgen sensitivity in explants of human benign prostatic tissue. The assay is based on the uptake of 3H-thymidine/micrograms protein in explants of prostate incubated in parallel with dihydrotestosterone (DHT) and hydroxyflutamide (HF) controls. The ratio of 3H-thymidine/micrograms protein in DHT treated samples per 3H-thymidine/micrograms protein in HF treated samples provides an index of androgen sensitivity. The DHT/HF index measured in 24 BPH specimens averaged 3.6. To determine the specificity of the HF effect, we measured the DHT/HF index in a single prostate at different concentrations of HF in the presence of fixed concentrations of DHT (2 x 10(-8) M) and noted a dose-response relationship. In addition we noted no effects of HF on 3H-thymidine incorporation over a range of 2 x 10(-4)M compared to 2 x 10(-7)M, except at the highest concentration. Of surprise was the finding of an average DHT/HF index in 5 different nonprostate tissues, including breast, uterus, colon, kidney, and thyroid, that was similar to the index found in prostates. We plan to adapt this androgen sensitivity assay to measure the DHT/HF index in biopsy-size samples of prostate, since such an assay could then be utilized to determine androgen sensitivity in individual patients with prostate cancer.

Prostatein C3-mRNA: a sensitive marker of androgen-responsiveness in prostate explant cultures

Prostatein is an androgen-dependent protein which is secreted by the rat ventral prostate. To determine if prostatein or its mRNA were responsive to androgen in vitro, prostate explants were cultured in media containing 0 or 25 nM dihydrotestosterone (DHT), estradiol (E2), or cortisol (F). Prostatein concentrations in medium were measured by radioimmunoassay at 2 and 4 days and in homogenates at 4 days. They were not changed significantly by any of these steroids. The concentration of the mRNA for the C3-subunit of prostatein was determined by dot hybridization at 0, 2, 4, 6, and 8 days. It was decreased significantly by 2 days when compared with explants cultured in the presence of DHT and significant differences persisted through 8 days. In conclusion, quantitation of the mRNA for the C3-subunit of prostatein in short-term cultures of ventral prostate explants appears to be more sensitive to changes in androgen concentration than does measurement of prostatein, per se. Prostatein C3-mRNA may be a useful marker for in vitro studies of androgen agonists and antagonists.

Aberrant response in vitro of hormone-responsive prostate cancer cells to antiandrogens

Antiandrogens are in use alone and in combination with other agents as hormonal therapy for prostate cancer. We conducted studies on the androgen-responsive human prostate cancer cell line LNCaP to determine the direct effects of three antiandrogens (hydroxyflutamide, RU23908, and cyproterone acetate) on hormone-responsive human prostate cancer cells in culture. Dihydrotestosterone (DHT) stimulated the growth of LNCaP cells in a dose-dependent fashion. These cells contained approximately 31,000 high-affinity (Kd = 9 x 10(-10) M) androgen binding sites per cell. In the absence of any androgenic stimulation, all three antiandrogens tested showed agonistic properties by increasing the cell number and uptake of [3H]-thymidine. Competitive uptake studies using [3H]-R1881, a nonmetabolized androgen, showed that the three antiandrogens inhibited specific R1881 uptake with IC50s of 0.9 x 10(-7) M for hydroxyflutamide, 2 x 10(-7) M for RU23908, and 1 x 10(-7) M for cyproterone acetate. It is not known whether these unexpected agonistic effects are due to an altered receptor, previously unmasked agonistic properties of the antiandrogens, or emergence of a hypersensitive clone of cells.

Effect of cyproterone acetate in comparison to flutamide and megestrol acetate on the ventral prostate, seminal vesicle, and adrenal glands of adult male rats

Cyproterone acetate (CPA) has a stronger inhibitory effect than megestrol acetate (MGA) and flutamide (FL) on the prostate and seminal vesicle of intact adult rats. Only in the clinically irrelevant regimen of castration and simultaneous androgen substitution is FL as a competitive androgen antagonist more potent than CPA and MGA. The latter inhibit complete involution of the ventral prostate but not of the seminal vesicle of castrated adult rats. This effect is very small in magnitude, cannot be increased by the use of higher doses, and is only reduced but not blocked by simultaneous treatment with high doses of FL. Further, CPA is unable to stimulate proliferation or restore the function of the involuted rat prostate. CPA and MGA inhibit adrenal weight in rats, thus indicating a glucocorticoidlike activity in this species. A critical review of all available data on the antiandrogenic, glucocorticoidlike, and possible paradoxical androgenlike activities of CPA in different animal experiments has no important bearing on the clinical effectiveness of CPA in the treatment of prostatic cancer.

Interaction of male and female sex hormones in cultured rat prostate

The organ culture of the rat ventral prostate was chosen as a model to determine whether any of the estrogen effects in vivo on the prostate are direct and expressed at the hormone concentrations normally found in the male. During 2 weeks of culture, estradiol at the high concentration of 10(-5) M blocked the androgenic activation of [3H]thymidine incorporation into DNA. The inhibition was localized in epithelium. Protein content of testosterone-treated explants and the accumulation of prostatein in the medium were considerably decreased, indicating inhibition of secretion. Antiandrogenic effects were not seen in morphology of estrogen-treated explants. The lower concentrations (from 10(-9) M to 10(-6) M) of estradiol increased the volume density of epithelium from day 7 onwards. The height of epithelium was concomitantly increased. The volume density of epithelium as well as the percentage of acini with metaplastic changes were significantly increased. These epithelial changes were less pronounced in the presence of androgen, suggesting that physiological concentrations of androgen prevent the expression of estrogen action in the morphology of the prostate. A change in staining with peanut (PNA)- and wheat germ agglutinin (WGA)-lectins indicated defective secretory capacity in metaplastic epithelium. In spite of the increased protein content in the explants, no constant pattern of the changes in prostatein accumulation could be recorded. Although the concentrations of estrogen required to induce squamous metaplasia were still unphysiological, the occurrence of this abnormal differentiation of the prostatic epithelium suggests that the cooperative action of estrogen is involved in androgen-dependent normal epithelial growth and possibly also in promoting growth of prostatic neoplasia.

Acid phosphatase activity: a marker of androgen action in prostate explant cultures

Acid phosphatase activity in rat ventral prostate explants has been assayed to determine if this parameter could serve as a specific and quantitative marker of androgen action in this in vitro model. Dihydrotestosterone (10 nM) caused an absolute increase in both total (42.5 +/- 2.9 vs control 27.1 +/- 4.0 nmoles p-nitrophenol generated in 30 min/micrograms DNA, P less than .01) and tartrate-resistant acid phosphatase activity (34.1 +/- 1.5 vs control 17.2 +/- 2.8 U/micrograms DNA, P less than .05), and this effect was maximal on the 4th day of culture. This was the time when explant weight and DNA content tended to fall or only to be maintained by androgen. Similar changes were observed with the potent synthetic androgen, mibolerone. The addition of either the antiandrogen cyproterone acetate or flutamide in a 100-fold excess to that of androgen caused significant inhibition in acid phosphatase activity. No significant change was observed at low concentrations of estradiol or progesterone, and only minimal and inconsistent increases in activity were noted at high concentrations. No increase was noted when cortisol, cyproterone acetate, or flutamide was added to the media. We conclude that measurement of acid phosphatase activity in cultured explants of rat ventral prostate provides a biochemical marker of androgenicity that is more specific than measurement of [3H]-thymidine incorporation.