[Role of androgen receptors in hormone-refractory prostate cancer: molecular basics and experimental therapy approaches]. / Die Rolle des Androgenrezeptors im hormonrefraktären Prostatakarzinom : Molekulare Grundlagen und experimentelle Therapieansätze.

The development of hormone-refractory prostate cancer cells is one of the major causes for the progression and high mortality rates in advanced prostate cancer (PCA). While the loss of the androgen receptor (AR) is the predominant mechanism for development of a hormone-insensitive disease in vitro, the first in vivo studies showed that the AR is still expressed or is even overexpressed in hormone-refractory PCA. In view of the increasing cases of PCA in the industrialized Western countries, a series of cell and molecular biological studies has led to the identification of various new factors and mechanisms that play a role during the development of hormone-refractory tumors. These findings should lead to the development of new therapeutic strategies.

Genital skin fibroblasts (GF) of patients with androgen insensitivity syndrome express higher insulin-like growth factor binding protein (IGFBP)-2, -3 and -5 than GF of normally virilized males.

BACKGROUND: We investigated the effects of androgens, estradiol (E2) and insulin-like growth factor (IGF)-I on IGF-II, insulin-like growth factor binding protein (IGFBP)-2, -3 and -5 and mRNA in genital fibroblasts (GF) from patients with complete androgen insensitivity (CAIS) and normally virilized males (C). METHODS: Proteins were measured by specific RIA and Western ligand blot, and specific mRNA levels by RT-PCR normalized by GAPDH levels. RESULTS: Secretion of IGF-II was lowered in CAIS (p<0.001) GF and by testosterone + IGF-I in C GF. Secretion of IGFBP-2 was higher (p<0.001) in CAIS GF and IGFBP-2 mRNA levels were increased by E2 in C GF (p<0.05). E2 stimulated IGFBP-2, -3 and -5 expression in CAIS GF. CAIS GF also secreted more IGFBP-3 (p<0.001) and accumulated 3-5 times more IGFBP-5 mRNA than C GF (p<0.001). CONCLUSION: In contrast to C GF, the availability of IGF-II in CAIS GF is apparently decreased by two facts: by the decreased expression and by increased expression of IGFBP-2, -3 and -5. Furthermore, E2 and IGF-I modulate the expression of IGF-II and IGFBP in GF. This may play a role in the failure to develop male external genitals in CAIS patients.

Decreased expression of IGF-II and its binding protein, IGF-binding protein-2, in genital skin fibroblasts of patients with complete androgen insensitivity syndrome compared with normally virilized males.

The action of androgen by way of the AR is required for the development of male gonads and external genitalia. The interplay between androgens and the somatotropic axis, in particular the IGFs in sexual development, is currently under thorough investigation. The IGF system is thought to mediate the androgen action in androgen-responsive cells. To investigate the interaction of androgens with the IGF system, we compared the expression of IGFs and IGF-binding proteins in cultured genital skin fibroblasts from nine patients with the syndrome of complete androgen insensitivity with that in genital skin fibroblasts from 10 normally virilized males. Mutations in the AR gene and/or abnormalities of the AR protein in the immunoblot were detected in all complete androgen insensitivity genital skin fibroblast strains. They caused a complete failure of DHT binding. RIA and RT-PCR demonstrated that the genital skin fibroblast strains expressed IGF-II, IGF-binding protein-2, and IGF-binding protein-3, but no IGF-I. Most strikingly, complete androgen insensitivity genital skin fibroblast strains produced significantly lower IGF-II (P < 0.001; 42.2 +/- 9.7 vs. 106.9 +/- 11.8 ng/mg protein) and IGF-II mRNA (P < 0.01, by RT-PCR) than control genital skin fibroblast strains. The production of IGF-binding protein-2 was also decreased (P < 0.03) in complete androgen insensitivity genital skin fibroblasts, whereas that of IGF-binding protein-3 did not differ. Furthermore, high levels of IGF-binding protein-5 mRNA were detected in all genital skin fibroblast strains, whereby the 28-kDa band in the ligand blot, probably representing IGF-binding protein-5, was more abundant in complete androgen insensitivity genital skin fibroblasts. Exposure of the genital skin fibroblasts to T (5 x 10(-8) M) had only weak effects on the expression of IGFs and IGF-binding proteins. In conclusion, although the mechanism underlying these differences requires further study, it is conceivable that in addition to the endocrine actions of IGF-I, IGF-II and IGF-binding protein-2, as local growth factors, are involved in the mediation of androgen action and growth of genital tissues.

Effect of testosterone on plaque development and androgen receptor expression in the arterial vessel wall.

BACKGROUND: -Recent studies have suggested that testosterone has a protective effect in the arterial vascular system. However, little is known about the molecular aspects of the mechanism(s) involved in these processes. The aim of the present study was to investigate the effect of testosterone on neointimal plaque development and on the expression of the vascular androgen receptor. Methods and Results-Neointimal plaque formation was induced by endothelial denudation in the aortas of male New Zealand White rabbits. Aortic ring segments were cultured for 21 days after endothelial denudation. Testosterone was applied to the culture medium in different doses. Compared with the non-hormone-treated control group, a significant inhibition of neointimal plaque development (expressed as the intima/media ratio) was found at testosterone concentrations of 10 ng/mL (P:=0.037) and 100 ng/mL (P:=0.012; intima/media ratios: median of controls, 0.25; median of 10 ng/mL testosterone group, 0.15; median of 100 ng/mL testosterone group, 0.16). Associated with this inhibitory effect on plaque size was a 50% increase of the amount of androgen receptor mRNA in the arterial segments treated with testosterone. CONCLUSION: -The beneficial effects of testosterone on postinjury plaque development underlines, at least in males, the important role of androgens in the vascular system. As our data suggest, the vascular androgen receptor is probably involved in these processes. Further studies are required to characterize the androgen receptor-dependent pathways in the vascular system.

Cracks in the beta-can: fluorescent proteins from Anemonia sulcata (Anthozoa, Actinaria).

We characterize two green fluorescent proteins (GFPs), an orange fluorescent protein, and a nonfluorescent red protein isolated from the sea anemone Anemonia sulcata. The orange fluorescent protein and the red protein seem to represent two different states of the same protein. Furthermore, we describe the cloning of a GFP and a nonfluorescent red protein. Both proteins are homologous to the GFP from Aequorea victoria. The red protein is significantly smaller than other GFP homologues, and the formation of a closed GFP-like beta-can is not possible. Nevertheless, the primary structure of the red protein carries all features necessary for orange fluorescence. We discuss a type of beta-can that could be formed in a multimerization process.

A cDNA encoding a chitinase from the epithelial cell line of chironomus tentans (Insecta, diptera) and its functional expression.

A cDNA coding for chitinase was isolated from Chironomus cells, which possesses conserved regions I and II characteristic for family 18 chitinases, a C-terminus enriched in Glu and Pro without the typical "PEST-region," putative glycosylation sites, a reduced number of C-terminal cysteines, and no typical chitin binding domain. Northern blots revealed one specific signal with an apparent size of 2.3 kb. The cDNA was expressed in the baculovirus/Spodoptera system as a His-tag fusion protein, which was secreted as a functionally active enzyme into the medium and could be separated from endogenous viral and Spodoptera-specific chitinases.

DNA-binding properties of the ecdysteroid receptor-complex (EcR/USP) of the epithelial cell line from Chironomus tentans.

DNA-binding features of EcR and USP were investigated using a 0.4 M NaCl extract of the epithelial cell line of Chironomus tentans by means of electrophoretic mobility shift assays (EMSAs). It is shown that the DNA-binding is enhanced by hormone administration and that in the hormone dependent shift, both EcR and USP, are present. Furthermore, we demonstrate that under these conditions, EcR/USP form a unique complex on inverted repeat elements (PAL1 and hsp27-EcRE), while on direct repeat elements (DR1-5), a second complex with higher mobility is formed. In this second complex, neither EcR nor USP are present. Thus, an additional difference between PAL1 and DR-elements is the competition of other factors for DR-elements, modulating its function as an EcRE. A competition EMSA, using PAL1 as radiolabeled probe, reveals the following order of binding strength: PAL1>DR4/5>DR1>DR2/3/hsp27. Surprisingly, using DR1 as radiolabeled probe, shows a different order of binding strength: DR1>DR2>DR3/4/5/PAL1>hsp27. This indicates that the complexes formed on PAL1 are not identical to the ones formed on DR1 and that both are not easily convertible. Furthermore, the affinity of the EcR/USP complex may be altered under various conditions or by interaction with cofactors. Upon hormone administration, DNA binding of the receptor complex is enhanced, but the difference to hormone-free binding reactions decreases in course of time, indicating an additional hormone independent activation. Arch.

Hormonal regulation of actin and tubulin in an epithelial cell line from Chironomus tentans.

The morphogenetic changes in an epithelial cell line from Chironomus tentans that are evoked by molting hormones and molting hormone agonists are accompanied by transient changes in the concentration of actin and beta-tubulin protein and mRNA. As compared to controls, actin protein and mRNA concentrations increase by about 50%, whereas tubulin reaches maxima of 100% increase. The proportion between globular and filamentous actin remains constant after hormone treatment.

Complete androgen insensitivity caused by a new frameshift deletion of two base pairs in exon 1 of the human androgen receptor gene.

We describe a novel mutation in exon 1 of the androgen receptor gene in a patient with complete androgen insensitivity (CAIS). Endocrine findings were typical for androgen insensitivity (testosterone serum levels in the upper limit of normal males and increased LH serum concentrations). Biochemical investigations in cultured genital skin fibroblasts of the patient showed a normal 5alpha-reductase activity but a complete absence of androgen binding. Western blot analysis revealed no detectable protein product. Sequence analysis of the entire coding region of the androgen receptor gene resulted in the identification of a 2-bp deletion in codon 472, causing frameshift and introduction of a premature stop codon 27 codons downstream of the mutation.

An androgen receptor mutation in the direct vicinity of the proposed C-terminal alpha-helix of the ligand binding domain containing the AF-2 transcriptional activating function core is associated with complete androgen insensitivity.

Subjects with androgen insensitivity syndromes (AIS) are characterized by a 46, XY karyotype, presence of testes, normal or elevated androgen levels in blood, and impairment of the usual response to androgens associated with various aberrations of male differentiation and virilization ranging from slightly undervirilized men to phenotypic females. Here we describe a novel proline to serine mutation in codon 892 (exon 8) of the androgen receptor in a patient with complete androgen insensitivity. The mutation is located in the direct vicinity of the proposed C-terminal alpha-helix of the ligand binding domain containing the AF-2 transcriptional activating function core. Investigation of androgen binding in cultured testicular fibroblasts of the patient revealed a reduced AR binding capacity (11 fmol/mg protein) and a highly elevated Kd value (3.1 nM) in comparison to control genital skin fibroblasts. Cotransfection studies with an androgen-responsive reporter gene revealed a diminished transactivation property of the mutant androgen receptor.

Inhibitors of chitinases.

In this review we describe inhibition of chitinases from bacteria, fungi, plants and animals by allosamidin and its derivatives, cyclic peptides, styloguanidin and divalent cations. Most information is available for allosamidin, whose important structural features necessary for inhibition are known. At least one N-acetylallosamine sugar must be present, and the spatial arrangement of the allosamizoline moiety are important for inhibition. Less complex compounds are therefore possible as lead structures for the development of agents interfering with chitinase. There is a pronounced species specificity in chitinase inhibition by allosamidin: half-maximal values are often in the range of 0.1-1 microM (e.g. in all arthropods), being lower in nematodes (0.048, 0.0002 microM, respectively) and amoeba (0.002-0.01 microM) and quite divergent in fungi (0.01-70 microM). These differences cannot be caused by the catalytic centers of family 18 and 19 chitinases.

Synthesis and action of the cyclic AMP antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), in Dictyostelium discoideum.

The cyclic AMP antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), is synthesized from prostaglandin E (PGE) and activated inositol phosphate (n-IP) in the presence of ATP by an enzyme of rat liver plasma membranes. Extracts of the slime mould Dictyostelium discoideum contain this activated inositol phosphate and D. discoideum cells convert [3H]PGE1 to [3H]cyclic PIP. This extracted polar [3H]product co-chromatographed with cyclic PIP from rat liver on gel filtration, anion exchange- and adsorption chromatography. Starving D. discoideum cells show cyclic AMP-induced oscillations, which can be inhibited by cyclic PIP (0.4 x 10(-7) M), but not by its phosphomonoester prostaglandylinositol phosphate (PIP) (1.4 x 10(-7) M). AMP and ADP at much higher concentrations (1 mM) antagonized these oscillations. The time needed for aggregation and fruiting body formation of starving D. discoideum cells is extended by cyclic PIP (1.4 x 10(-7) M) up to 3-fold, whereas its phosphomonoester (1.9 x 10(-7) M) showed a 9-fold weaker effect, and AMP and ADP even at 1 mM concentration showed no effect.

Ecdysteroid receptor and ultraspiracle from Chironomus tentans (Insecta) are phosphoproteins and are regulated differently by molting hormone.

Three different isotypes of the ecdysteroid receptor (cEcR) (66, 68 and 70 kDa) and several molecular variants of the dimerization partner "ultraspiracle" (cUSP) (58-77 kDa) can be separated electrophoretically in homogenates of the epithelial cell line from Chironomus tentans. After phosphatase treatment the bands with the lowest electrophoretic mobility disappear in both cases. Phosphorylation occurs exclusively at ser/thr in EcR and USP. Binding studies with 3H-ponasterone A using 0.4 M NaCl extracts revealed two classes of high-affinity binding (KD1 = 0.47 and KD2 = 7.2 nM) competable either with 20-OH-ecdysone or muristerone A. At least KD2 and Bmax2 are unchanged after dephosphorylation. In hormonally naive cells a considerable part of EcR and USP is already present in nuclei. The phosphorylation pattern of both transcription factors is the same in cytosol and nuclear fractions. Incubation with 20-OH-ecdysone (1 microM, up to 4 days) does not alter the extent and mode of phosphorylation of EcR, although EcR concentration increases. In contrast USP concentration remains constant but phosphorylation is enhanced.

Immunohistochemical localization of ecdysteroid receptor and ultraspiracle in the epithelial cell line from Chironomus tentans (Insecta, Diptera).

Ecdysteroid receptor (EcR) and its heterodimerization partner, ultraspiracle (USP), were demonstrated in the epithelial cell line from Chironomus tentans by immunohistochemistry. In untreated cells both proteins are present in nuclei as well as in granular compartments of the cytosol. At 1 day after addition of 1-microM 20-OH-ecdysone (20E) total immunofluorescence had increased in the nuclei, whereas the cytoplasmic staining had disappeared. At the 2nd and 3rd days all cells within a vesicle appear identical according to morphological criteria, but the EcR and USP immunoreactivity becomes restricted into patches of neighbouring cells. The hormonally induced changes in the pattern of localization of functional ecdysteroid receptor, the heterodimer of EcR and USP, are discussed in relation to similar effects of 20E on acetylcholinesterase and muscarinic acetylcholine receptor distribution in this cell line.

Ecdysteroid resistant subclones of the epithelial cell line from Chironomus tentans (Insecta, Diptera). I. Selection and characterization of resistant clones.

Chironomus tentans cells were cultured in the presence of gradually increasing concentrations of 20-OH-ecdysone or a nonsteroidal molting hormone agonist, the benzoylhydrazine RH 5992, for a period of about 2 yr. From these cultures, subclones were selected, which are resistant to up to 25 microM 20-OH-ecdysone according to morphological (changes in cell shape and cell arrangement) and physiological criteria (acetylcholinesterase induction, secretion of chitinolytic enzymes, thymidine incorporation). Some subclones, selected in the presence of 20-OH-ecdysone, are resistant only to molting hormone, but still respond to RH 5992 morphologically and biochemically, whereas subclones selected in the presence of the benzoylhydrazine showed no reaction neither to 20-OH-ecdysone nor to the hormone agonist. Hormone resistance is stable; 3 mo. after hormone withdrawal, resistant clones still do not respond to renewed exposure to 20-OH-ecdysone or RH 5992, respectively. Because in all resistant subclones tested so far all hormonally regulated responses known from sensitive cells were no longer detectable, it is assumed that the hormone signaling pathway itself is interrupted. Possible mechanisms of hormone resistance were discussed.

Response to androgen treatment in a patient with partial androgen insensitivity and a mutation in the deoxyribonucleic acid-binding domain of the androgen receptor.

Supplemental androgen therapy has enhanced virilization in only a few patients with partial androgen insensitivity (PAIS). We herein report on virilization in a patient with PAIS and a point mutation in the DNA-binding domain of the androgen receptor. At the age of 19 yr, the patient sought medical attention because of undervirilization. Endocrine findings were typical for androgen insensitivity, but 5alpha-reductase activity and androgen binding characteristics in fibroblasts cultured from genital skin were normal. In an attempt to improve virilization, high dose testosterone enanthate treatment (250 mg by i.m. injection once a week) was begun. After 3.5 yr of this treatment, marked promotion of virilization was achieved, i.e. lowering of voice, male pattern secondary hair distribution, marked growth of beard and coarse body hair, increase in phallic size, increase in bone mineral density, and decrease in mammary gland size. In addition, serum lipid levels were not affected. To our knowledge this is the first documentation of successful treatment in a patient with PAIS and a point mutation in the DNA-binding domain of the androgen receptor.

Point mutations of the human parathyroid calcium receptor gene are not responsible for non-suppressible renal hyperparathyroidism.

The calcium-dependent secretion of parathyroid hormone (PTH) is mediated through an extracellular G protein-coupled calcium receptor (CaR). Inactivating point mutations of this receptor have been found in familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. These diseases feature a decreased calcium sensitivity of the parathyroid glands, resulting in a rightward shift of the Ca2(+)-PTH relationship. Severe non-suppressible renal hyperparathyroidism (rHPT) is often characterized by similar setpoint shifts to the right. Thus, point mutations of the CaR gene could contribute to non-suppressible rHPT. We examined genomic DNA of hyperplastic or mainly nodular tissues of 39 parathyroids from 25 rHPT-patients with resistance to calcitriol therapy. Amplification of the six exons of the CaR gene was followed by single-strand conformation polymorphism (SSCP) analysis. DNA sequencing was performed where band shifts were observed. No point mutations in the coding sequence of the CaR gene were detected using the PCR-SSCP strategy. Point mutations in the coding regions of the CaR gene probably play no role in the evolution of renal HPT and are not responsible for the calcitriol resistance of PTH secretion.

Interactions between steroid hormones and the nervous system.

After a short description of the endocrine and nervous system and their similarities and differences, interactions between both parts are mainly dealt with in this brief review. This is especially exemplified by the modulation of receptors for neurotransmitters, of ion channels and other membrane components by neurosteroids and steroid hormones and the physiological significance of this regulation. Both classes of hormones can act via nongenomic and genomic actions. As biological responses to neurosteroids and steroid hormones in the nervous system exocytosis of peptide hormones and neurosteroids, regulation of neurotransmitter release, sexual brain development and male behavior and cell death are described. Neurotransmitters and their receptors are also modulated in their expression and biological activity by steroid hormones and neurosteroids in non-neuronal tissues, as demonstrated for GABA-receptors in the uterus and the embryonic cholinergic system. Because of the close links between endocrine and nervous system agents toxic for one component may also interfere with the other one.

Effect of demethylation on the chitinase inhibitory activity of allosamidin.

Removal of a methyl group of the allosamizoline moiety of allosamidin decreases the inhibitory effect on family 18 chitinases from three different species (a bacterium, Serratia marcescens, a crustacean, Artemia salina, and an insect cell line, Chironomus tentans). Loss of a second methyl group weakens enzyme inhibition further. This is in agreement with the highly conserved catalytic centre of these enzymes.

A muscarinic acetylcholine receptor, present in the epithelial cell line from Chironomus tentans.

A muscarinic cholinergic receptor (mAchR) is present in the non-neuronal epithelial cell line from Chironomus tentans. Scatchard plot analysis (KD = 1.4 nM) using the non-selective antagonist quinuclidinylbenzilate (QNB), as well as kinetic data (KD = 1.7 nM), reveals one class of high affinity binding sites. About 2000 binding sites/cell are present. The receptor concentration (54.5 +/- 7.5 fmol/mg protein) is comparable to the values reported from insect brain. The receptor interacts only with muscarinic ligands; nicotinergic acetylcholine receptors are not present. Binding properties are not comparable to any of the muscarinic subtypes known from vertebrate tissues. The rank order of competition of radiolabelled QNB is: QNB > atropine > PrBCM > oxotremorine, pirenzepine > methoctramine. The competition curve obtained with carbamylcholine is shifted to higher ligand concentrations in the presence of Gpp(NH)p and to lower carbamylcholine concentrations by 1 mM NEM. With antibodies against muscarinic receptor from calf brain one band with a molecular weight of about 80 kDa is detected on Western blots. The moulting hormone 20-OH-ecdysone transiently increases the concentration of muscarinic receptor.