Relative influence of testosterone and insulin in the regulation of prostatic cell proliferation and growth

Prostatic hyperplasia is a common problem of the aged men population. Recent experimental and clinical studies provide sufficient evidence that apart from androgens, insulin also plays an important role in the pathogenesis of prostatic hyperplasia. The present study was aimed to investigate the relative influence of testosterone and insulin on the cellular proliferation and prostatic growth. Effect of testosterone on the prostate of hypoinsulinemic, and glandular injection of insulin-receptor antagonist S961 on the prostate of castrated Sprague-Dawley rat (220 ± 10 g) was examined. Significant decrease in the weight of the ventral prostate was observed in the streptozotocin-induced hypoinsulinemic rats (∼6 fold), which is restored by the intervention of testosterone. Although, glandular injection of S961 did not led to any change in the frequency of proliferating cell nuclear antigen (PCNA) positive cells in normal rats, significant decrease was observed in the castrated rats. Castration led to increase in the frequency of the caspase-3 and the TUNEL positive cells in the ventral prostate. Further, long-term (6 weeks) administration of S961 induced significant decrease in the weight of the ventral prostate. Results of the present study provide that both testosterone and insulin promote prostatic cell proliferation and change in the level of either of the hormone results in the destabilization of cellular equilibrium, and modulation of the insulin-receptor signaling in the prostate may provide an alternative strategy for the treatment of prostatic enlargement. Further, studies are required to better understand the interplay between these hormones in the regulation of prostatic growth.     

Hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development

This review on normal and neoplastic growth of the prostate emphasizes the importance of epithelial-mesenchymal/stromal interactions. Accordingly, during prostatic development urogenital sinus mesenchyme (a) specifies prostatic epithelial identity, (b) induces epithelial bud formation, (c) elicits prostatic bud growth and regulates ductal branching, (d) promotes differentiation of a secretory epithelium, and (e) specifies the types of secretory proteins expressed. In reciprocal fashion, prostatic epithelium induces smooth muscle differentiation in the mesenchyme. Epithelial-mesenchymal interactions during development continue postnatally into adulthood as stromal-epithelial interactions which play a homeostatic role and in so doing reciprocally maintain epithelial and stromal differentiation and growth-quiescence. Prostatic carcinogenesis involves perturbation of these reciprocal homeostatic cell-cell interactions. The central role of mesenchyme in prostatic epithelial development has been firmly established through analysis of tissue recombinants composed of androgen-receptor-positive wild-type mesenchyme and androgen-receptor-negative epithelium. These studies revealed that at the very least ductal morphogenesis, epithelial cytodifferentiation, epithelial apoptosis and epithelial proliferation are regulated by stromal and not epithelial androgen receptors. Likewise, progression from non-tumorigenesis to tumorigenesis elicited by testosterone plus estradiol proceeds via paracrine mechanisms. Thus, stromal-epithelial interactions play critical roles in the hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development.     

Early prostate development and its association with late-life prostate disease

The development of the prostate is an emerging priority area for prostate biologists. Early changes in prostate development permanently alter prostate morphology and function and an understanding of the permanent nature of early events that may influence the onset of late-life disease is vital. Two of the inherent problems involve associating exposure in early life with outcome in late life or maturity and accounting for the influence of genetic, environmental, dietary or metabolic factors during the intervening period. Any one of these factors, alone or in combination, might lead to an explanation of the discrepancies found in the literature regarding the influence of early changes to the prostate in later life. Therefore, it is important to establish a causal link between the hormonal changes that occur during the fetal/neonatal period and that imprint the gland and the onset of late-life pathology. In order to achieve this goal, several technical challenges need to be overcome to permit the objective assessment of prostate branching morphogenesis. Stereological techniques now allow the quantification of several parameters of branching morphogenesis and the identification of specific early changes that are permanent and irreversible with a late-life outcome. This methodology provides the means to determine the action of a range of genes or hormone/growth factors that have been implicated in prostate development and disease. This study is supported by an NH&MRC program grant number 973218.     

Sonic hedgehog regulates prostatic growth and epithelial differentiation

The Sonic hedgehog (SHH)-signalling pathway mediates epithelial-mesenchymal interactions in several tissues during development and disease, and we have investigated its role in rat ventral prostate (VP) development. We have demonstrated that Shh and Ptc expression correlates with growth and development of the prostate and that their expression is not regulated by androgens in the VP. Prostatic budding was induced in response to testosterone in Shh null mouse urogenital sinus (UGS) explants grown in vitro and in rat UGS explants cultured with cyclopamine, suggesting that SHH-signalling is not critical for prostatic induction. SHH-signalling was disrupted at later stages of VP development (in vitro), resulting in a reduction in organ size, an increase in ductal tip number, and reduced proliferation of ductal tip epithelia. The addition of recombinant SHH to VPs grown in vitro caused a decrease in ductal tip number and expansion of the mesenchyme. In the presence of testosterone, inhibition of SHH-signalling accelerated the canalisation of prostatic epithelial ducts and resulted in ducts that showed morphological similarities to cribiform prostatic intraepithelial neoplasia (PIN). The epithelia of these ducts also demonstrated precocious and aberrant differentiation, when examined by immunohistochemistry for p63 and cytokeratin 14. In conclusion, we show that SHH-signalling is not essential for prostatic induction, but is important for prostatic growth, branching, and proliferation, and that androgen-stimulated growth in the absence of signalling from the SHH pathway results in aberrant epithelial differentiation.     

Human salivary gland branching morphogenesis: morphological localization of claudins and its parallel relation with developmental stages revealed by expression of cytoskeleton and secretion markers

Development of salivary glands is a highly complex and dynamic process termed branching morphogenesis, where branched structures differentiate into mature glands. Tight junctions (TJ) are thought to play critical roles in physiological functions of tubular organs, contributing to cell polarity and preventing lateral movement of membrane proteins. Evidence demonstrated that claudins are directly involved in TJ formation and function. Using immunohistochemistry and immunofluorescence we have mapped the distribution of claudins-1, 2, 3, 4, 5, 7 and 11 and compared it with the expression of differentiation markers in human salivary glands obtained from foetuses ranging from weeks 4 to 24 of gestation. Expression of all claudins, except claudin-2 was detected in the various phases of human salivary gland development, up to fully mature salivary gland. The expression of all claudins increased according to the progression of salivary gland maturation evidenced by the classical markers-cytokeratin 14, cytokeratin low molecular weight, smooth muscle actin and human secretory component. Tight junction proteins-claudins appear to be important in the final shape and physiological functions of human salivary glands and are parallel related with markers of salivary gland differentiation.     

The hormonal control of begging and early aggressive behavior: experiments in black-headed gull chicks

The hormonal control of begging and sibling competition is largely unknown, but recent evidence suggests a role for steroid hormones. We tested the influence of the aromatizable androgen testosterone (T), the non-aromatizable androgen 5alpha-dihydrotestosterone (DHT), and 17beta-estradiol (E) on both begging behavior and aggressive behavior in black-headed gull chicks (Larus ridibundus). Chicks of this species have a conspicuous begging display, while their frequently performed early aggressive behavior is facilitated by testosterone and important for territorial defense. Hormone treatment was applied by implants between days 6 and 16 after hatching. Behavior was tested by means of standard stimulus tests. The results were validated in a second experiment under semi-natural conditions. Begging was suppressed by T and DHT and not affected by E. Aggressive Pecking was strongly facilitated by T. The erect threat posture, characteristic for older chicks, was facilitated by T, DHT, and E and the nest-oriented threat display, typical for young chicks, only by T and DHT. Growth was suppressed in the T group. The results indicate that androgen production, needed for territorial defense, has costs in terms of a suppression of begging and growth. It is discussed to what extent older chicks may avoid these costs by converting testosterone to estrogen and why pre-natal and post-natal exposure to androgens differ in their effect on begging behavior.     

Sox2 is important for two crucial processes in lung development: branching morphogenesis and epithelial cell differentiation

The primary lung bud originates from the foregut and develops into the bronchial tree by repetitive branching and outgrowing of the airway. The Sry related HMG box protein Sox2 is expressed in a cyclic manner during initiation and branching morphogenesis of the lung. It is highly expressed in non-branching regions and absent from branching regions, suggesting that downregulation of Sox2 is mandatory for airway epithelium to respond to branch inducing signals. Therefore, we developed transgenic mice that express a doxycycline inducible Sox2 in the airway epithelium. Continuous expression of Sox2 hampers the branching process resulting in a severe reduction of the number of airways. In addition, the bronchioli transiently go over into enlarged, alveolar-like airspaces, a pathology described as bronchiolization of alveoli. Furthermore, a substantial increase was observed of cGRP positive neuroendocrine cells and ΔNp63 isoform expressing (pre-) basal cells, which are both committed precursor-like cells. Thus, Sox2 prevents airways from branching and prematurely drives cells into committed progenitors, apparently rendering these committed progenitors unresponsive to branch inducing signals. However, Sox2 overexpression does not lead to a complete abrogation of the epithelial differentiation program.     

Hormonal and local control of mammary branching morphogenesis

Unlike other branched organs, the mammary gland undergoes most of its branching during adolescent rather than embryonic development. Its morphogenesis begins in utero, pauses between birth and puberty, and resumes in response to ovarian estrogens to form an open ductal tree that eventually fills the entire mammary fat pad of the young female adult. Importantly, this "open" architecture leaves room during pregnancy for the organ to develop milk-producing alveoli like leaves on otherwise bare branches. Thereafter, the ducts serve to deliver the milk that is produced throughout lactation. The hormonal cues that elicit these various phases of mammary development utilize local signaling cascades and reciprocal stromal-epithelial interactions to orchestrate the tissue reorganization, differentiation and specific activities that define each phase. Fortunately, the mammary gland is rather amenable to experimental inquiry and, as a result, we have a fair, although incomplete, understanding of the mechanisms that control its development. This review discusses our current sense and understanding of those mechanisms as they pertain to mammary branching, with the caveat that many more aspects are still waiting to be solved.     

Role of stromal tenascin-C in mouse prostatic development and epithelial cell differentiation

Deregulation of epithelial-stromal interactions is considered to play a critical role in the initiation and promotion of benign prostatic hyperplasia (BPH) and prostate carcinoma (PCa). Expression of tenascin-C (TN-C), an extracellular matrix (ECM) glycoprotein, is reportedly higher in BPH and PCa as compared with normal prostate. Remodeling of the ECM alters the homeostatic balance between epithelium and stroma, resulting in physiological changes in cellular functions. To investigate the role of TN-C in prostatic development and differentiation, we evaluated the morphological phenotype of TN-C knockout (KO) mouse prostate (ventral: VP, dorsolateral: DLP, and anterior: AP) and examined tissue recombinants composed of adult mouse DLP epithelium and fetal TN-C KO urogenital sinus mesenchyme (UGM). Histological analysis showed epithelial cell clusters protruding into the ductal lumens in TN-C KO AP and DLP. Interestingly, binucleated cells appeared in epithelium of TN-C KO DLP at 8 weeks. Simultaneously, androgen receptor (AR)-positive cells were decreased in TN-C KO epithelia. Similar to the TN-C KO phenotype, protruded epithelial clusters, binucleated cells, and AR-negative nuclei were induced in DLP epithelium by recombining with TN-C KO UGM. Our results suggest that stromal TN-C might be involved in maintaining epithelial cytodifferentiation, morphogenesis, and androgen receptor expression of normal prostate glands in adult mice.     

Organogenesis in plants: the molecular and genetic control of ovule development

The ovule is the site of megagametogenesis and fertilization and hence is of central importance to sexual reproduction in seed plants. In recent years, the ovule has become established as an excellent model system in which to study organogenesis. Progress has been made in several aspects of ovule development: the control of ovule identity, the mechanism of primordium outgrowth, early pattern formation and the regulation of integument morphogenesis.     

Developmental control of imprinted expression by macro non-coding RNAs

Genomic imprinting is a developmentally regulated epigenetic phenomenon. The majority of imprinted genes only show parent-of-origin specific expression in a subset of tissues or at defined developmental stages. In some cases, imprinted expression is controlled by an imprinted macro non-coding RNA (ncRNA) whose expression pattern and repressive activity does not necessarily correlate with that of the genes whose imprinted expression it controls. This suggests that developmentally regulated factors other than the macro ncRNA are involved in establishing or maintaining imprinted expression. Here, we review how macro ncRNAs control imprinted expression during development and differentiation and consider how this impacts on target choice in epigenetic therapy.     

Secreted frizzled related protein 1 is a paracrine modulator of epithelial branching morphogenesis, proliferation, and secretory gene expression in the prostate

Previous in vitro studies identified secreted frizzled related protein 1 (SFRP1) as a candidate pro-proliferative signal during prostatic development and cancer progression. This study determined the in vivo roles of SFRP1 in the prostate using expression studies in mice and by creating loss- and gain-of-function mouse genetic models. Expression studies using an Sfrp1^lacZ knock-in allele showed that Sfrp1 is expressed in the developing mesenchyme/stroma of the prostate. Nevertheless, Sfrp1 null prostates exhibited multiple prostatic developmental defects in the epithelium including reduced branching morphogenesis, delayed proliferation, and increased expression of genes encoding prostate-specific secretory proteins. Interestingly, over-expression of SFRP1 in the adult prostates of transgenic mice yielded opposite effects including prolonged epithelial proliferation and decreased expression of genes encoding secretory proteins. These data demonstrated a previously unrecognized role for Sfrp1 as a stromal-to-epithelial paracrine modulator of epithelial growth, branching morphogenesis, and epithelial gene expression. To clarify the mechanism of SFRP1 action in the prostate, the response of WNT signaling pathways to SFRP1 was examined. Forced expression of SFRP1 in prostatic epithelial cells did not alter canonical WNT/β-catenin signaling or the activation of CamKII. However, forced expression of SFRP1 led to sustained activation of JNK, and inhibition of JNK activity blocked the SFRP1-induced proliferation of prostatic epithelial cells, suggesting that SFRP1 acts through the non-canonical WNT/JNK pathway in the prostate.     

Hormonal and behavioral correlates of morphological variation in an Amazonian electric fish (Sternarchogiton nattereri: Apteronotidae)

The weakly electric fish from the main channel of the Amazon river, Sternarchogiton nattereri, offers a striking case of morphological variation. Females and most males are toothless, or present only few minute teeth on the mandible, whereas some males exhibit exaggerated, spike-like teeth that project externally from the snout and chin. Androgens are known to influence the expression of sexually dimorphic traits, and might be involved in tooth emergence. In this study we assess the relationship in S. nattereri between morphological variation, 11 ketotestosterone (11-KT) and testosterone (T). We also examine relationships of morphology and androgen levels with electric organ discharge (EOD) frequency, reproductive condition, and seasonality. Our main finding is that male morph categories differed significantly in plasma concentrations of 11-KT, with toothed males showing higher levels of 11-KT than toothless males. By contrast, we did not detect statistical differences in T levels among male morph categories. Reproductive condition, as measured by gonadosomatic indexes (GSI), differed across two sample years, increased as the season progressed, and was higher in toothed males than in non-toothed males. EOD frequency was higher in toothed males than in either toothless males or females. Taken together, our findings suggest that S. nattereri male sexual characters are regulated by 11-KT levels, and that both morphology and androgens interact with reproductive condition and EOD frequency in ways that vary within and across reproductive seasons.     

Intrahippocampal administration of an androgen receptor antagonist, flutamide, can increase anxiety-like behavior in intact and DHT-replaced male rats

Testosterone (T) and its 5alpha-reduced metabolite, dihydrotestosterone (DHT), can decrease anxiety-like behavior; however, the mechanisms underlying these effects have not been established. First, we hypothesized that if T reduces anxiety-like behavior through actions of its 5alpha-reduced metabolite, DHT, then gonadectomy (GDX) would increase anxiety-like behavior, an effect which would be reversed by systemic administration of DHT. Second, we hypothesized that if T and DHT reduce anxiety-like behavior in part through actions at intracellular androgen receptors in the hippocampus, then administration of an androgen receptor antagonist, flutamide, directly to the hippocampus should increase anxiety-like behavior of intact and DHT-replaced, but not GDX, male rats. Inserts that were empty or contained flutamide were applied directly to the dorsal hippocampus of intact, GDX, or GDX and DHT-replaced rats 2 h prior to testing in the open field, elevated plus maze, or defensive freezing tasks. GDX rats exhibited significantly more anxiety-like behaviors than intact or DHT-replaced rats. Intact and DHT-replaced rats administered flutamide to the hippocampus showed significantly more anxiety-like behavior than did intact and DHT-replaced controls. However, flutamide alone did not increase anxiety-like behavior of GDX rats. Together, these findings suggest that androgens can decrease anxiety-like behavior of male rats in part through DHT's actions at androgen receptors in the hippocampus.     

Book lung development in the embryo,postembryo and first instar of the cobweb spider,Parasteatoda tepidariorum C. L Koch, 1841 (Araneomorphae,Theridiidae)

Light and electron microscopy were used to compare spider book lung development with earlier studies of the development of horseshoe crab book gills and scorpion book lungs. Histological studies at the beginning of the 20th century provided evidence that spider and scorpion book lungs begin with outgrowth of a few primary lamellae (respiratory furrows, saccules) from the posterior surface of opisthosomal limb buds, reminiscent of the formation of book gills in the horseshoe crab. In spider embryos, light micrographs herein also show small primary lamellae formed at the posterior surface of opisthosomal limb buds. Later, more prominent primary lamellae extend into each book lung sinus from the inner wall of the book lung operculum formed from the limb bud. It appears most primary lamellae continue developing and become part of later book lungs, but there is variation in the rate and sequence of development. Electron micrographs show the process of air channel formation from parallel rows of precursor cells: mode I (cord hollowing), release of secretory vesicles into the extracellular space and mode II (cell hollowing), alignment and fusion of intracellular vesicles. Cell death (cavitation) is much less common but occurs in some places. Results herein support the early 20th century hypotheses that 1) book lungs are derived from book gills and 2) book lungs are an early step in the evolution of spider tracheae.     

Hormonal control of the development of tryptophan oxygenase in primary cultures of young rat hepatocytes

Developmental increase of tryptophan oxygenase (L--tryptophan: oxygen 2,3-oxidoreductase (decyclizing), EC 1.13.11.11) was studied using hepatocytes of neonatal rats in primary culture. Hepatocytes from rats of 2–30-days-old were isolated and cultured for 2 days. In cultured hepatocytes of 2-day-old rats, tryptophan (2.5 mM), dexamethasone (1.10^?5 M) and glucagon (1.10^?7 M) did not cause the appearance of tryptophan oxygenase. But the enzyme activity became detectable, when heptocytes from 5-day-old rats were incubated wiht tryptophan, the oxygenase could be induced precociously by dexamethasone, but not by glucagon. The effect of glucagon was first seen 2 weeks after birth. However, in hepatocytes of 9-day-old rats glucagon stimulated formation of cyclic AMP and protein kinase activity (EC 2.7.1.37) and also induced tyrosine aminotransferase (EC 2.6.1.5). When heptocytes of 9-day-old rats were cultured for 4 days, their tryptophan oxygenase became inducible by glucagon. Insulin almost completely inhibited precocious appearance of the enzyme activity evoked by tryptophan plus dexamethasone in hepatocytes of 9-day-old rats. These results suggest that the appearance of tryptophan oxygenase in rat liver during development is due to first the onset of gene coding for tryptophan oxygenase and then stimulation by the sequential of glucocorticoid and glucagon.     

Function of Focal Adhesion Kinase Scaffolding to Mediate Endophilin A2 Phosphorylation Promotes Epithelial-Mesenchymal Transition and Mammary Cancer Stem Cell Activities in Vivo

Tyrosine kinases have been shown to play critical roles in cancer development and progression, and their inhibitors hold the potential as effective targeted therapies for breast and other cancers. However, some of these kinases like focal adhesion kinase (FAK) also possess scaffolding functions in intracellular signaling, but such kinase-independent functions of FAK or other kinases have not been examined in cancer directly in vivo. Here, we report that disruption of the function of FAK scaffolding through its Pro-878/881 motif suppressed mammary tumor growth and metastasis in a well characterized murine model of human breast cancer. P878A/P881A mutation in the endogenous FAK gene decreased the expression of markers for epithelial-mesenchymal transition (EMT) and mammary cancer stem cell (MaCSC) activities in tumors derived from mutant mice. This mutation disrupted the function of FAK scaffolding to mediate endophilin A2 phosphorylation at Tyr-315 by Src, leading to the decreased surface expression of MT1-MMP, as observed previously in transformed fibroblasts in vitro. Inhibition of the downstream components of this FAK scaffolding function by Y315F endophilin A2 mutant or MT1-MMP knockdown reduced markers for EMT and MaCSC activities. Conversely, bypass of the scaffolding function using the phosphorylation mimic mutant Y315E endophilin A2 or endophilin A2 knockdown rescued the decreased markers for EMT and MaCSCs as well as surface expression of MT1-MMP in tumor cells harboring the P878A/P881A mutation. Together, these results identify a novel role of FAK scaffolding function in breast cancer, which could serve as a new target in combination with kinase inhibition for more effective treatment strategies.     

A multiscale analysis of early flower development in Arabidopsis provides an integrated view of molecular regulation and growth control

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