Androgen-regulated expression of secretory protein synthesis in mouse ventral prostate

WNT5A selectively inhibits mouse ventral prostate development

The establishment of prostatic budding patterns occurs early in prostate development but mechanisms responsible for this event are poorly understood. We investigated the role of WNT5A in patterning prostatic buds as they emerge from the fetal mouse urogenital sinus (UGS). Wnt5a mRNA was expressed in UGS mesenchyme during budding and was focally up-regulated as buds emerged from the anterior, dorsolateral, and ventral UGS regions. We observed abnormal UGS morphology and prostatic bud patterns in Wnt5a null male fetuses, demonstrated that prostatic bud number was decreased by recombinant mouse WNT5A protein during wild type UGS morphogenesis in vitro, and showed that ventral prostate development was selectively impaired when these WNT5A-treated UGSs were grafted under under kidney capsules of immunodeficient mice and grown for 28 d. Moreover, a WNT5A inhibitory antibody, added to UGS organ culture media, rescued prostatic budding from inhibition by a ventral prostatic bud inhibitor, 2,3,8,7-tetrachlorodibenzo-p-dioxin, and restored ventral prostate morphogenesis when these tissues were grafted under immunodeficient mouse kidney capsules and grown for 28 d. These results suggest that WNT5A participates in prostatic bud patterning by restricting mouse ventral prostate development.

Noggin is required for normal lobe patterning and ductal budding in the mouse prostate

Mesenchymal expression of the BMP antagonist NOGGIN during prostate development plays a critical role in pre-natal ventral prostate development and opposes BMP4-mediated inhibition of cell proliferation during postnatal ductal development. Morphologic examination of newborn Noggin-/- male fetuses revealed genitourinary anomalies including cryptorchidism, incomplete separation of the hindgut from the urogenital sinus (UGS), absence of the ventral mesenchymal pad, and a complete loss of ventral prostate (VP) budding. Examination of lobe-specific marker expression in the E14 Noggin-/- UGS rescued by transplantation under the renal capsule of a male nude mouse confirmed a complete loss of VP determination. More modest effects were observed in the other lobes, including decreased number of ductal buds in the dorsal and lateral prostates of newborn Noggin-/- males. BMP4 and BMP7 have been shown to inhibit ductal budding and outgrowth by negatively regulating epithelial cell proliferation. We show here that NOGGIN can neutralize budding inhibition by BMP4 and rescues branching morphogenesis of BMP4-exposed UGS in organ culture and show that the effects of BMP4 and NOGGIN activities converge on P63+ epithelial cells located at nascent duct tips. Together, these studies show that the BMP-NOGGIN axis regulates patterning of the ventral prostate, regulates ductal budding, and controls proliferation of P63+ epithelial cells in the nascent ducts of developing mouse prostate.

Epitope topology and removal of mouse acrosomal plasma membrane by P12-targeted immunoaggregation

P12 is a Kazal-type trypsin inhibitor that has been purified from mouse seminal vesicle secretion. We observed a slight impact of P12 on sperm capacitation, and demonstrated the removal of plasma membrane overlaying the acrosome region by immunoaggregation of P12 on mouse sperm. Further, we compared the immunoreactivity of P12 antibody to ten P12 variants, including six single-site mutated mutants (R19L, Y21V, D22G, R43G, K44S, and R45T), two multisite mutated mutants (R43G/K44S/R45T and L50H/R52G/K53A), and two deletion mutants (Nd10 and Cd8) in which 10 and 8 residues were deleted from the N- and C-terminals, respectively. We found that the N-terminal region, 43RKR45, and the C-terminal region, but not R19, Y21, and D22, are involved in the three epitopes that reside on one side and are three-dimensionally distant from R19, Y21, and D22 on the P12 molecule. Based on the epitope topology, we elucidated the structural basis by which P12 antibody immunoaggregated P12 on sperm head.

Altered Prostatic Epithelial Proliferation and Apoptosis, Prostatic Development, and Serum Testosterone in Mice Lacking Cyclin-Dependent Kinase Inhibitors1

Normal prostatic development and some prostatic diseases involve altered expression of the cell-cycle regulators p27 and p21 (also known as CDKN1B and CDKN1A, respectively). To determine the role of these proteins in the prostate, we examined prostatic phenotype and development in mice lacking p27 and/or p21. In p27-knockout (p27KO) mice, epithelial proliferation was increased 2- and 3.8-fold in the ventral and dorsolateral prostate, respectively, versus wild-type (WT) mice, although prostatic weights were not different. Epithelial apoptosis was increased in p27KO mice and may account for the lack of a concurrent increase in weight. Testosterone deficiency observed in this group was not the cause of this increase, because vehicle- and testosterone-treated p27KO mice had similar percentages of apoptotic cells. Also observed was a trend toward a decreased functional epithelial cytodifferentiation, indicating a potential role of p27 in this process. Conversely, dorsolateral prostate and seminal vesicle (SV) of p21-knockout (p21KO) mice, and all prostatic lobes and SV of p21/p27 double-knockout mice, weighed significantly less compared to the WT mice, and their epithelial proliferation was normal. Decreased testosterone concentrations may contribute to the decreased prostatic weights. However, other factors may be involved, because testosterone replacement only partially restored prostatic weights. We conclude that loss of p27 increases prostatic epithelial proliferation and alters differentiation but does not result in prostatic hyperplasia because of increased epithelial cell loss. The p21KO mice showed phenotypes distinctly different from those of p27KO mice, suggesting nonredundant roles of p21 and p27 in prostatic development. Loss of p27 or of both p21 and p27 results in serum testosterone deficiency, complicating analysis of the prostatic effects of these cell-cycle regulators.

Negative acting HLH proteins Id 1, Id 2, Id 3, and Id 4 are expressed in prostate epithelial cells

BACKGROUND

The four known Id proteins, Id 1, Id 2, Id 3, and Id 4 are largely considered as dominant negative helix-loop-helix (HLH) proteins. They can dimerize with basic helix loop proteins (bHLH) but the dimers fail to bind the consensus E box response element (CANNTG). Alternatively, members of the Id family, for example, Id 2 can also bind to non-bHLH proteins such as retinoblastoma (Rb) and ETS-TCF to modulate their activities. Consistent with their role as promoters of proliferation, subset of Id genes for example, Id 1 and Id 2 are expressed in many cancers including that of the prostate. However, their expression and function in the normal prostate is unknown.

METHODS

The present study was designed to evaluate the expression profile and functional significance of all Id isoforms in normal rat prostate epithelial cells. The data suggests that all four Id isoforms are expressed in normal cells, albeit at different levels.

RESULTS

Agents that promote growth, for example, serum increase the levels of Id 1, Id 2, and Id 3. The hormones and mitogens such as testosterone and hepatocyte growth factor (HGF) that promote prostate epithelial cell differentiation stimulate Id 4 and Id 2, respectively.

CONCLUSIONS

In prostate epithelial cells, Id 1 may be specifically involved in promoting proliferation whereas Id 4 and Id 2 may have defined roles in regulating differentiated functions in response to androgens and local paracrine factors such as HGF.

Expression signature of the mouse prostate

Genetically engineered mice are being used increasingly for delineating the molecular mechanisms of prostate cancer development. Epithelium-stroma interactions play a critical role in prostate development and tumorigenesis. To better understand gene expression patterns in the normal sexually mature mouse prostate, epithelium and stroma were laser-capture microdissected from ventral, dorsolateral, and anterior prostate lobes. Genome-wide expression was measured by DNA microarrays. Our analysis indicated that the gene expression pattern in the mouse dorsolateral lobe was closest to that of the human prostate peripheral zone, supporting the hypothesis that these prostate compartments are functionally equivalent. Stroma from a given lobe had closer gene expression patterns with stroma from other lobes than epithelium from the same lobe. Stroma appeared to have higher expression complexity than epithelium. Specifically, stromal cells had higher expression levels of genes implicated in cell adhesion, muscle development, and contraction, in structural constituents of cytoskeleton and actin binding, and in components such as sarcomere and extracellular matrix collagen. Among the genes that were enriched in the epithelium were secretory proteins, including seminal vesicle protein secretion 2 and 5. Surprisingly, prostate stroma expressed many osteogenic molecules, as confirmed by immunohistochemistry. A "bone-like" environment in the prostate may predispose prostate cells for survival in the bone. Chemokine Cxcl12 but not its receptor, Cxcr4, was expressed in normal prostate. In prostate tumors, interestingly, Cxcl12 was up-regulated in epithelial cells with a concomitant expression of Cxcr4. Expression of both the receptor and ligand may provide an autocrine mechanism for tumor cell migration and invasion.

In utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure: effects on the prostate and its response to castration in senescent C57BL/6J mice

In utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure inhibits ventral, dorsolateral, and anterior prostate development in C57BL/6 mice. To determine if prostatic abnormalities persist into senescence, mice born to dams given TCDD (5 mug/kg, po) or vehicle on gestation day 13 were examined at 100 and 510 days of age. Half the mice were castrated ten days prior to necropsy in order to assess androgen dependence, while the remaining mice were sham castrated. Effects of TCDD on the dorsolateral and anterior prostate of senescent sham-castrated mice were relatively subtle, whereas the ventral prostate was rudimentary or absent. Castration of vehicle-exposed mice caused far greater reductions in prostate lobe weights, epithelial cell height, and androgen-dependent gene expression (MP25 and probasin) in young mice than in senescent ones, while cell proliferation was decreased by castration in young mice and increased in senescence. Responses to castration were similar at 100 days of age in vehicle- and TCDD-exposed mice. At 510 days, however, TCDD-exposed mice were substantially more responsive to castration by most indices than vehicle-exposed mice. These results demonstrate that prostatic androgen dependence in mice declines substantially with age in several key ways, and that in utero and lactational TCDD exposure protects against this decline. Surprisingly, TCDD increased the incidence of cribriform structures in dorsolateral prostate ducts, from 2-3% in vehicle-exposed senescent mice to 16% in sham-castrated and to 7% in castrated senescent mice. Collectively, these results demonstrate that effects of in utero and lactational TCDD exposure on the prostate persist into senescence, and suggest that in utero and lactational TCDD exposure retards the aging process in the prostate. However, because cribriform structures are often considered to be associated with prostate carcinogenesis, these results also suggest that TCDD exposure early in development may increase susceptibility to prostate cancer.

Hoxb13 is required for normal differentiation and secretory function of the ventral prostate

The murine prostate is a structure that is made up of four distinct lobes; the dorsal and lateral prostates (often grouped together as the dorsolateral prostate), the anterior (coagulating gland) and the ventral prostate. Previous work has implicated Hox genes in the development of these structures, but how each lobe acquires unique identities for specific functions has not been addressed. In this study, the ventral prostate-specific function of Hoxb13 is described. Mice lacking Hoxb13 function show normal numbers of duct tips, but mice mutant for both Hoxb13 and Hoxd13 exhibit severe hypoplasia of the duct tips, revealing a role for Hoxb13 in ventral prostate morphogenesis. Additionally, a ventral lobe-specific defect was identified in Hoxb13 mutants wherein the epithelium is composed of simple cuboidal cells rather than of tall columnar cells. Ventral prostate ducts appear devoid of contents and do not express the ventral prostate-specific secretory proteins p12, a kazal-type protease inhibitor and p25, a spermine binding protein. These defects are not due to reduction of Nkx3.1 expression or to a global effect on androgen receptor signaling. These results suggest a specific role for Hoxb13 in a differentiation pathway that gives the ventral prostate epithelium a unique identity, as well as a more general role in ventral prostate morphogenesis that is redundant with other Hox13 paralogs.

Hormonal, cellular, and molecular control of prostatic development

The prostate is a male accessory sex gland found only in mammals that functions to produce a major fraction of seminal fluid. Interest in understanding the biology of the prostate is driven both by the fascinating nature of the developmental processes that give rise to the prostate and by the high incidence in humans of prostatic diseases, including prostatic adenocarcinoma and benign prostatic hyperplasia. This review summarizes the current state of knowledge of the cellular and molecular processes that control prostatic development. Insight into the mechanisms that control prostatic development has come from experimental embryological work as well as from the study of mice and humans harboring mutations that alter prostatic development. These studies have demonstrated a requirement for androgens throughout prostatic development and have revealed a series of reciprocal paracrine signals between the developing prostatic epithelium and prostatic mesenchyme. Finally, these studies have identified several specific gene products that are required for prostatic development. While research in recent years has greatly enhanced our understanding of the molecular control of prostatic development, known genes cannot yet explain in molecular terms the complex biological interactions that descriptive and experimental embryological studies have elucidated in the control of prostatic development.

Roles for Nkx3.1 in prostate development and cancer

In aging men, the prostate gland becomes hyperproliferative and displays a propensity toward carcinoma. Although this hyperproliferative process has been proposed to represent an inappropriate reactivation of an embryonic differentiation program, the regulatory genes responsible for normal prostate development and function are largely undefined. Here we show that the murine Nkx3.1 homeobox gene is the earliest known marker of prostate epithelium during embryogenesis and is subsequently expressed at all stages of prostate differentiation in vivo as well as in tissue recombinants. A null mutation for Nkx3.1 obtained by targeted gene disruption results in defects in prostate ductal morphogenesis and secretory protein production. Notably, Nkx3.1 mutant mice display prostatic epithelial hyperplasia and dysplasia that increases in severity with age. This epithelial hyperplasia and dysplasia also occurs in heterozygous mice, indicating haploinsufficiency for this phenotype. Because human NKX3.1 is known to map to a prostate cancer hot spot, we propose that NKX3.1 is a prostate-specific tumor suppressor gene and that loss of a single allele may predispose to prostate carcinogenesis. The Nkx3.1 mutant mice provide a unique animal model for examining the relationship between normal prostate differentiation and early stages of prostate carcinogenesis.

Developmental profile of a caltrin-like protease inhibitor, P12, in mouse seminal vesicle and characterization of its binding sites on sperm surface

We examined the developmental profile of a kazal-type trypsin inhibitor (P12) of Mr 6126 in mouse seminal vesicle, characterized its binding sites on the surface of sperm, and assessed its effect on Ca2+ uptake by spermatozoa. Among the genital tracts of adult mice, P12 was found only in the male accessory glands including seminal vesicle, coagulating gland, and prostate. It was immunolocalized on the luminal epithelium of the primary and secondary folds in both the seminal vesicle and coagulating gland, and on the folds projecting into the lumen of the glandular alveolus in the prostate. The protein and its RNA message in seminal vesicle did not appear in the prepubertal period, but expression coincided with maturation. Castration of adult mice resulted in cessation of P12 expression. Treatment of the castrated mice with testosterone propionate in corn oil restored the protein expression in the seminal vesicle. Spermatozoa collected from caudal epididymis were devoid of P12. Cytochemical study illustrated a P12-binding region on the anterior acrosomes of cells preincubated with P12. Analysis of equilibrium data from the binding assay using 125I-P12 with a Scatchard plot showed a single type of P12-binding sites on sperm, with an apparent dissociation constant of 70.15 +/- 5.25 nM and the capacity of 1.49 +/- 0.06 x 10(6) binding sites/cell. The protein could serve as a calcium transport inhibitor to suppress a great extent of Ca2+ uptake by spermatozoa. The immunohistochemical staining patterns of testis revealed that the P12-binding sites appeared on postmeiotic cells such as spermatids and spermatozoa, but were absent in Leydig cells, Sertoli cells, spermatogonia, and spermatocytes in seminiferous tubules.

Enlargement of the ampullary gland and seminal vesicle, but not the prostate in int-2/Fgf-3 transgenic mice

Expression of the int2/Fgf-3 gene occurs during normal embryonic development and is associated with mammary cancer in mice. Overexpression of this gene under the control of the mouse mammary tumor virus long terminal repeat (MMTV-LTR) in males was reported to result in prostatic enlargement. In this report male Fgf-3-overexpressing mice were shown to have enlarged ampullary glands, seminal vesicles, and ductus deferens; there was extensive epithelial hyperplasia in the ampullary glands and seminal vesicles. The prostates of these animals were of normal size and histology. The transgene was expressed in all of the enlarged organs, which are derived exclusively from the Wolffian duct. Male secondary sex organs derived from the urogenital sinus, e.g., the ventral prostate, coagulating gland, and bulbourethral glands, were normal and did not express the MMTV-LTR-driven Fgf-3 transgene. A dorsolateral prostate was also morphologically normal but did express the transgene. This study underscores the importance of careful organ identification in transgenic models in which gross organ enlargement or distortion occurs. It also highlights the heterogeneity of the response to Fgf-3 among the secondary sex organs and even within the prostate itself.

Ductal heterogeneity in rat dorsal-lateral prostate

Given the lobar complexity of the rat prostate at the morphological level, differences in secretory protein expression were investigated in individual prostatic ducts that constitute the subdivisions of the dorsal-lateral prostate, ie., the dorsal prostate, lateral prostate type 1 and lateral prostate type 2. For this purpose, individual prostatic ducts were microdissected from these prostatic lobes, photographed, and secretions subsequently collected from individual prostatic ducts and analyzed by Western blot for the expression of DP-1 and probasin, two major proteins expressed in rat the dorsal-lateral prostate. Many individual glands constituting the dorsal prostate, lateral prostate type 1 and lateral prostate type 2 co-express DP-1 and probasin, but at vastly different levels. DP-1 is a major secretory protein of the dorsal prostate and lateral prostate type 1, while probasin is the major secretory protein of the lateral prostate type 2. A small percentage of individual ducts of the dorsal prostate, lateral prostate type 1 and lateral prostate type 2 express either DP-1 or probasin. However, most of the individual prostatic ducts constituting the dorsal prostate and lateral prostate type 1 express DP-1 at high levels and probasin at low levels. Conversely, most of the individual prostatic glands that constitute the lateral prostate type 2 express probasin at high levels and DP-1 at low levels. This study emphasizes the morphological and functional heterogeneity within the prostate gland.

Photoperiod-induced changes in the proteins secreted by the male genital tract of the rodent Octodon degus

The proteins secreted by the male genital tract were analyzed in the seasonally breeding rodent Octodon degus. The protein patterns from the fluids collected from sexually active animals were compared with those from animals in resting period, with others which were previously castrated, and with castrated animals which received testosterone replacement treatment. Fluids from cauda epididymides (CE), seminal vesicles (SV) and prostate glands (PG) were collected, and analyzed by polyacrylamide gel electrophoresis followed by different staining methods and densitometry. Modifications were detected in the protein patterns of resting or castrated animals. In CE fluid, the decrease of one protein band (45 Kda) and the uprising of another (210 Kda) were recognized after castration. In animals during resting period the changes were not as marked as in castrated animals. SV secretion demonstrated a similar response to resting phase and castration, because Protein SVS I (200 Kda) decreased or were not observed when these conditions occurred. PG fluid proteins were also modified after castration. In general, the more severe changes in the protein spectrum were induced by castration, despite radioimmunoassay showing that testosterone fall is even higher in resting period animals than in those castrated. Testosterone replacement resulted in recovery of a protein profile which is very similar to that of sexually active males. Results suggest that the androgenic control of male tract secretions would be rather different in this seasonal hystrichomorph when compared to the regulation system described for myomorph rodents.

Induction of prostatic morphology and secretion in urothelium by seminal vesicle mesenchyme

Mesenchymal-epithelial interactions are essential for the development of the male reproductive tract. Tissue recombination experiments have been used to define the characteristics of these interactions. When mesenchyme, embryonic connective tissue, is recombined with epithelium from another organ an instructive induction may occur in which the developmental fate of the epithelium is altered. Instructive inductions are most common when the epithelium that is removed from the mesenchyme and the epithelium that is recombined with the mesenchyme are from the same germ layer. All of the mesenchyme of the male reproductive tract is of mesodermal origin. The epithelia of these organs are derived from either the mesodermal Wolffian duct epithelium or the endodermal urogenital sinus epithelium. Urogenital sinus mesenchyme can instructively induce bladder and urethral epithelium to form prostate (Donjacour, A. A. and Cunha, G. R. (1993) Endocrinol. 132, 2342–2350) and seminal vesicle mesenchyme can instructively induce epithelium from the ductus deferens and ureter (Cunha, G. R., Young, P., Higgins, S. J. and Cooke, P. S. (1991) Development 111, 145–158) to form seminal vesicle. To see whether inductive interactions could occur across germ layers in this system, seminal vesicle mesenchyme, normally associated with a mesodermal epithelium, was recombined with epithelium from neonatal or adult bladder or urethra, which are of endodermal origin. The resulting tissue recombinants were analyzed histologically and by immunocytochemistry and western blotting with antibodies to prostatic and seminal vesicle secretory proteins. Full prostatic differentiation was observed in tissue recombinants made with seminal vesicle mesenchyme plus either adult or neonatal bladder or urethral epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Transgenic models for the study of prostate cancer

Transgenic model systems provide tools for obtaining information that clarifies important relationships between genetic alterations and carcinogenesis. One such relationship is the induction of specific growth factor activities by dominantly acting oncogenes. Using a "transgenic organ" model referred to as mouse prostate reconstitution (MPR) under conditions where the ras and myc oncogenes were introduced using a recombinant retrovirus into both the mesenchymal and epithelial compartments of the urogenital sinus, poorly differentiated prostate cancer (PC) was produced with high frequency (> 90%) in inbred C57BL/6 mice. Time-course studies using northern blotting and immunohistochemical analysis showed that the transition from benign to malignant status invariably was associated with the induction of elevated transforming growth factor-beta 1 (TGF-beta 1) expression. Additional immunohistochemical analysis of TGF-beta 1 in human PC and benign prostatic hyperplasia (BPH) showed that positive extracellular staining was significantly more extensive in PC compared with BPH. This differential staining pattern was evident in focal areas of PC adjacent to BPH. These findings in both the MPR model system and human PC suggest that elevated TGF-beta 1 expression is involved in the progression to malignancy and that its pattern of expression may become a useful marker of PC. Additional studies using transgenic animal models will continue to provide important clinically useful information about PC in man.

Transcription of the mouse secretory protease inhibitor p12 gene is activated by the developmentally regulated positive transcription factor Sp1

We have previously shown that a trans-acting protein produced in some tissue culture cells positively control the transcriptional activity directed by the mouse p12 promoter. This nuclear protein exerts its positive activity by interacting with a regulatory sequence designated p12.A and located between the TATA and CCAAT box elements on the p12 gene promoter. Using DNase I and dimethyl sulfate methylation interference footprinting techniques coupled with gel retardation assays, we found evidence that the protein which binds to the p12.A element is the well-known transcription factor Sp1. Mutational analysis in transient transfection assays confirmed the positive activity exerted by this protein in every cell line tested. In agreement with this observation, we detected a p12.A-Sp1 binding activity in nuclear extracts prepared from all cell lines used. However, a similar binding activity could not be detected in a number of nuclear extracts prepared from normal mouse tissues. In this report, we provide the evidence that the lack of Sp1-binding activity results from the degradation of Sp1 in the kidney, liver, and pancreas of the mouse.

Androgen sensitivity and gene expression in ras + myc-induced mouse prostate carcinomas

We established an androgen-sensitive cell line (BR31-5) from a ras + myc-induced mouse prostate carcinoma and used this cell line together with a previously reported transplantable androgen-independent mouse prostate carcinoma to investigate patterns of expression for apoptosis-related genes in an androgen-deprived environment. Single cell suspensions derived from the BR31-5 cell line were inoculated into the flank of intact or castrated adult male C57BL/6 mice and tumors were harvested 12 days post-inoculation for Northern blotting. A transplantable androgen-independent prostate cancer was also inoculated into intact or castrated mice and tumors harvested 21 days later. Tumor volume analyses showed that BR31-5 carcinomas were androgen-sensitive. Northern blotting showed that mRNA levels for two apoptosis-related genes, transforming growth factor-beta 1 and c-myc, were significantly elevated to a similar extent in carcinomas grown in castrated hosts compared to intact hosts for both the androgen-sensitive BR31-5 and androgen-independent carcinomas. Levels of mRNA for tissue type plasminogen activator, shown previously to be elevated in androgen-independent carcinomas following growth in castrates, were also increased in BR31-5 carcinomas under similar androgen-deprived conditions but to a lesser extent. Interestingly, testosterone repressed prostate mRNA No. 2 levels shown previously to be similar in both the intact and castrated groups for androgen-independent carcinomas were significantly increased in the castrated group compared to the intact group for BR31-5 carcinomas. Therefore, specific patterns of expression for apoptosis-related genes may be able to discriminate androgen-sensitive and androgen-independent prostate cancer under androgen-deprived conditions.

Transcription of the mouse secretory protease inhibitor p12 gene is activated by the developmentally regulated positive transcription factor Sp1

We have previously shown that a trans-acting protein produced in some tissue culture cells positively control the transcriptional activity directed by the mouse p12 promoter. This nuclear protein exerts its positive activity by interacting with a regulatory sequence designated p12.A and located between the TATA and CCAAT box elements on the p12 gene promoter. Using DNase I and dimethyl sulfate methylation interference footprinting techniques coupled with gel retardation assays, we found evidence that the protein which binds to the p12.A element is the well-known transcription factor Sp1. Mutational analysis in transient transfection assays confirmed the positive activity exerted by this protein in every cell line tested. In agreement with this observation, we detected a p12.A-Sp1 binding activity in nuclear extracts prepared from all cell lines used. However, a similar binding activity could not be detected in a number of nuclear extracts prepared from normal mouse tissues. In this report, we provide the evidence that the lack of Sp1-binding activity results from the degradation of Sp1 in the kidney, liver, and pancreas of the mouse.

The response of female urogenital tract epithelia to mesenchymal inductors is restricted by the germ layer origin of the epithelium: prostatic inductions

The epithelium of the mammalian vagina arises from two distinct germ layers, endoderm from the urogenital sinus and mesoderm from the Müllerian ducts. While neonatal vaginal epithelium can be induced to form prostate which is normally an endodermal derivative, it has not been determined whether this ability to form prostate is shared by both mesoderm- and endoderm-derived vaginal epithelia. To test the competence of vaginal epithelia we have isolated sinus-derived and Müllerian-derived vaginal epithelia from newborn mice, combined them with rat urogenital sinus mesenchyme, and grown the tissue recombinants for 4 weeks in male athymic nude mice. Endoderm-derived sinus vaginal epithelium was induced to form prostatic tissue which expressed prostate-specific secretory proteins in 21 of 23 tissue recombinants. Müllerian-derived vaginal epithelium formed small ducts and cysts lined by a simple epithelium. These latter tissue recombinants lacked any evidence of prostatic secretory proteins. Similarly, endoderm-derived urethral epithelium was induced to form prostate (17 of 17 cases), while mesoderm-derived uterine epithelium was not (0 of 13 cases). Therefore, the ability to form prostatic epithelium was limited to endodermal derivatives of the urogenital tract.

Purification and characterization of a trypsin inhibitor from mouse seminal vesicle secretion

A Kazal-type trypsin inhibitor in mouse seminal vesicle secretion was purified to homogeneity via a series of purification steps including ammonium sulfate fractionation, affinity chromatography on a trypsin Affi-Gel 10 column, and HPLC on a reverse phase C4 column. It was shown to be a weak basic protein with an isoelectric point of 8.7 and to contain no carbohydrate. The protein had a specific activity of 184 U/mg protein in the inhibitory effect on the trypsin digestion of N-benzoyl-Pro-Phe-Arg-p-nitroanilide. Analysis of the kinetic data for the trypsin digestion of N-benzoyl-Phe-Val-Arg 7-amido-4-methylcoumarin revealed that the protein was a competitive inhibitor with an inhibitory constant (Ki) of 0.15 nM. The molecular mass of the protein was determined to be 7 kDa by both gel chromatography and electrophoresis. Results of direct amino acid determinations indicated that this protein corresponded to the reading frame of MP12 cDNA identified from mouse prostate. We found that cleavage only at the reactive site of this protein (Arg19-Ile20) resulted in its denaturation.

Multistage carcinogenesis induced by ras and myc oncogenes in a reconstituted organ

ras and myc oncogenes were able to induce distinct phenotypic alterations, resembling different types of premalignant lesions, when introduced into approximately 0.1% of the cells used to reconstitute the mouse prostate gland. While ras induced dysplasia in combination with angiogenesis, myc induced a hyperplasia of the otherwise normally developed organ. ras and myc together induced primarily carcinomas. However, tumor progression was also associated with additional genetic alterations involving gene amplification. Our data indicate that specific types of benign premalignant lesions may reflect the activation of different single oncogenes, and that the consecutive activation of multiple oncogenes could be a causal event in the step-like progression of tumorigenesis.

Analysis of regulatory sequences in androgen-responsive genes

We have analysed the effect of androgens on the activity of promoters from MMTV, and the rat prostate C3(1) and mouse secretory protease inhibitor genes. MMTV promoter activity was stimulated by testosterone as well as progesterone and dexamethasone but not by oestradiol. Deletion analysis indicated that the three steroids acted through DNA sequences between nucleotides -201 and -69 upstream of the MMTV cap site. In contrast, the promoters for the C3(1) gene and the protease inhibitor gene were unaffected by testosterone in a number of cell types, including prostate cells, despite the fact that the MMTV promoter was stimulated in such cells.