Prostatic ductal system in rats: regional variation in localization of an androgen-repressed gene product, sulfated glycoprotein-2

Downregulation of clusterin mediates sensitivity to protein kinase inhibitors in breast cancer cells

The efficacy of protein kinase inhibitors (PKIs) has been shown in clinical assays for cancer, but as isolated agents, they only have a modest effect. One of the most important characteristics of mitogen-activated PKIs is their ability to decrease the apoptotic threshold of cancer cells, sensitizing them to the action of other antiapoptotic agents. The secretory clusterin protein is an inhibitor of apoptosis with a cytoprotective function. We describe the use of clusterin-specific antisense oligonucleotides and siRNA to sensitize breast carcinoma cells to several PKIs. MCF-7 and MDA-MB-231 cells were treated with antisense oligonucleotide or siRNA to clusterin and the following PKIs: H-89, chelerythrine and genistein. The three inhibitors used in this study upregulated clusterin expression and treatments that included antisense oligonucleotide or siRNA to clusterin reduced the number of viable cells more effectively than did treatment with the drugs alone. Therefore, treatment with such combinations may benefit patients with breast cancer.

Role of the adjacent stroma cells in prostate cancer development and progression: synergy between TGF-β and IGF signaling

This review postulates the role of transforming growth factor-beta (TGF-β) and insulin-like growth factor (IGF-I/IGF-II) signaling in stromal cells during prostate carcinogenesis and progression. It is known that stromal cells have a reciprocal relationship to the adjacent epithelial cells in the maintenance of structural and functional integrity of the prostate. An interaction between TGF-β and IGF signaling occupies a central part in this stromal-epithelial interaction. An increase in TGF-β and IGF signaling will set off the imbalance of this relationship and will lead to cancer development. A continuous input from TGF-β and IGF in the tumor microenvironment will result in cancer progression. Understanding of these events can help prevention, diagnosis, and therapy of prostate cancer.

The role of stress proteins in prostate cancer

The development of therapeutic resistance, after hormone or chemotherapy for example, is the underlying basis for most cancer deaths. Exposure to anticancer therapies induces expression of many stress related proteins, including small heat shock proteins (HSPs). HSPs interact with various client proteins to assist in their folding and enhance the cellular recovery from stress, thus restoring protein homeostasis and promoting cell survival. The vents of cell stress and cell death are linked, as the induction of molecular chaperones appears to function at key regulatory points in the control of apoptosis. On the basis of these observations and on the role of molecular chaperones in the regulation of steroid receptors, kinases, caspases, and other protein remodelling events involved in chromosome replication and changes in cell structure, it is not surprising that molecular chaperones have been implicated in the control of cell growth and in resistance to various anticancer treatments that induce apoptosis. Recently, several molecular chaperones such as Clusterin and HSP27 have been reported to be involved in development and progression of hormone-refractory prostate cancer. In this review, we address some of the molecular and cellular events initiated by treatment induced stress, and discuss the potential role of chaperone proteins as targets for prostate cancer treatment.

The role of clusterin (CLU) in malignant transformation and drug resistance in breast carcinomas

Breast cancer is the main cause of cancer-related death among women in Western countries. Current research is focused on identifying antiapoptotic proteins which could be a possible target for novel chemotherapeutic drugs. Secretory clusterin (sCLU) is an extracellular chaperone that has been functionally implicated in DNA repair, cell-cycle regulation, apoptotic cell death and tumorigenesis. The implication of sCLU in carcinogenesis and the progression of breast carcinomas make it an interesting gene, worthy of investigation. It has been reported to present powerful antiapoptotic activity and to perform a prosurvival function with most therapeutic treatments for breast cancer. This review summarizes our current understanding of the role of CLU in tumorigenesis, progression, and response to treatment in breast carcinomas.

Matrix metalloproteinase (MMP)-2 and MMP-9 activity and localization during ventral prostate atrophy and regrowth

Matrix metalloproteinses (MMPs) are enzymes involved in prostatic development, growth, disease-induced tissue remodelling and secretory fluid. Although the prostate function depends upon androgen regulation, the relationship between MMPs and androgen has not been well established. Here, we evaluated MMP-2 and MMP-9 gelatinolytic activity in association with tissue localization during ventral prostate atrophy and regrowth induced by testosterone replacement (TR). Adult male Wistar rats were divided into three experimental groups: control, castrated (CS) and TR 21 days after castration. Ventral prostate (VP) was excised at 3, 5, 7 and 21 days after castration in CS group, and at 3, 5, 7 and 10 days after TR (4 mg/kg/day) in TR group. The VP was dissected, weighed and processed for histology, immunohistochemistry, ultrastructure and zymography analyses. Castration elicited the typical parenchymal atrophy and stromal condensation. TR induced intense epithelial growth towards the stromal space to restore the prostate histoarchitecture. MMP-2 and MMP-9 immunostaining presented intense reaction in CS and TR groups, mainly in the epithelial and endothelial cells. After TR, a strong immunoreaction for MMP-2 was observed in the activated stromal fibroblasts. Zymography showed that MMP-2 and MMP-9 activity, mainly the active form, increased after castration. In contrast, TR induced an additional increase in MMP-2 activity, but not in MMP-9. In conclusion, the overall behaviour of MMP-2 and MMP-9 within the prostate under androgen handling is highly complex, as each glandular compartment and cell type is affected differently by the androgenic status. Prostate regrowth appears to involve a more effective participation of MMP-2 in both epithelial and stromal compartments, while MMP-9 plays a major role in the late prostate atrophy and early regrowth.

Gene expression changes are age-dependent and lobe-specific in the brown Norway rat model of prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is an age-related enlargement of the prostate, characterized by increased proliferation of stromal and epithelial cells. Despite its prevalence, the etiology of BPH is unknown.

METHODS

The Brown Norway rat is a model for age-dependent, lobe-specific hyperplasia of the prostate. Histological analyses of the dorsal and lateral lobes from aged rats reveal focal areas characterized by increased numbers of luminal epithelial cells, whereas the ventral lobe is unaffected. This study examined differential gene expression by lobe and age in the Brown Norway rat prostate. The objective was to identify genes with different levels of expression in the prostate lobes from 4-month (young) and 24-month (old) animals, and to subsequently link changes in gene expression to mechanisms of prostate aging.

RESULTS

The number of age-dependent differentially expressed genes was greatest in the dorsal compared to the ventral and lateral lobes. Minimal redundancy was observed among the differentially expressed genes in the three lobes. Age-related changes in the expression levels of 14 candidate genes in the dorsal, lateral and ventral lobes were confirmed by quantitative RT-PCR. Genes that exhibited age-related differences in their expression were associated with proliferation, oxidative stress, and prostate cancer progression, including topoisomerase II alpha (Topo2a), aurora kinase B (Aurkb), stathmin 1 (Stmn1), and glutathione S-transferase pi. Immunohistochemistry for Topo2a, Aurkb, and Stmn1 confirmed age-related changes in protein localization in the lateral lobe of young and aged prostates.

CONCLUSION

These findings provide clues to the molecular events associated with aging in the prostate.

Differential age-associated regulation of clusterin expression in prostate lobes of brown Norway rats

BACKGROUND

Serum androgen concentrations decline with age in male Brown Norway rats and castration induces apoptosis of luminal secretory epithelial cells in the ventral but not in the dorsal and lateral prostate lobes. Clusterin has been described as an androgen-repressed gene and a protein with either anti- or pro-apoptotic actions.

METHODS

We measured clusterin mRNA and protein levels, the effects of aging and castration on clusterin protein levels and clusterin immunolocalization within the prostatic ductal network in the prostate lobes of young and aged rats.

RESULTS

Whereas levels of clusterin mRNA and protein expression measured by RT-PCR and Western blot, respectively, were higher in the ventral and lateral lobes of aged (24 months) compared to young (4 months) rats, no age-dependent differences were observed in the dorsal lobe. Clusterin expression was localized by immunohistochemistry exclusively to the proximal duct segment of young rats, but extended to the distal segment of the ventral and lateral lobes of aged rats. Despite an age-related decrease in serum testosterone concentration, clusterin gene expression was not altered in the dorsal lobe. After castration, levels of clusterin expression increased significantly in the ventral and lateral lobes despite the absence of epithelial cell apoptosis in the latter. In castrated rats, clusterin expression extended throughout the proximal-distal duct regions of the prostate lobes of young and aged rats.

CONCLUSION

Regulation of clusterin expression in the prostate lobes of aging rats appears complex and is neither directly repressed by androgen nor dependent on apoptotic-induced stress.

Anticlusterin treatment of breast cancer cells increases the sensitivities of chemotherapy and tamoxifen and counteracts the inhibitory action of dexamethasone on chemotherapy-induced cytotoxicity

INTRODUCTION

Overexpression of the apoptosis-related protein clusterin is associated with breast cancer development and tumor progression. We describe the use of clusterin-specific antisense oligonucleotides and antibodies to sensitize breast carcinoma cells to anticancer drugs routinely used in breast cancer therapy.

METHODS

MCF-7 and MDA-MB-231 cells were treated with the oligonucleotide or antibody, chemotherapeutic agents (doxorubicin or paclitaxel), tamoxifen, or with combinations of these.

RESULTS

Treatments that include antisense clusterin oligonucleotide or antibody to clusterin have been shown to reduce the number of viable cells more effectively than treatment with the drugs alone. We also demonstrate that dexamethasone pretreatment of breast cancer cell lines inhibits chemotherapy-induced cytotoxicity and is associated with the transcriptional induction of clusterin. However, anticlusterin treatment increases chemotherapy-induced cytotoxicity, even in the presence of glucocorticoids, suggesting a possible role for these proteins in glucocorticoid-mediated survival.

CONCLUSION

These data suggest that combined treatment with antibodies to clusterin or antisense clusterin oligodeoxynucleotides and paclitaxel, doxorubicin, or tamoxifen could be a novel and attractive strategy to inhibit the progression of breast carcinoma by regulation of the clusterin function. Moreover, glucocorticoid activation in breast cancer cells regulates survival signaling by the direct transactivation of genes like clusterin which encode proteins that decrease susceptibility to apoptosis. Given the widespread clinical administration of dexamethasone before chemotherapy, understanding glucocorticoid-induced survival mechanisms is essential for achieving optimal therapeutic responses.

Clusterin is not essential for androgen-regulated involution and regeneration of the normal mouse prostate

BACKGROUND

Inhibition of clusterin expression has been shown to enhance the sensitivity of prostate cancer cells to chemo and hormone therapy. Clusterin antisense oligonucleotides (ASOs) are currently in phase II human clinical trials for treatment of hormone refractory prostate cancer. However, the role of clusterin in androgen-regulated involution and regeneration of the normal prostate gland has not been established.

METHODS

Prostate involution and regeneration was examined in clusterin-deficient mice undergoing up to three cycles of androgen withdrawal and restoration.

RESULTS

Surprisingly, clusterin deficiency did not affect the apoptotic index, and the temporal biochemical and morphological changes associated with involution and regeneration of the normal adult prostate following multiple rounds of androgen withdrawal and replacement.

CONCLUSION

Clusterin is not critical for normal prostate development or androgen-regulated involution and regrowth of the mouse prostate gland, suggesting that clusterin may have distinct functions in malignant versus normal prostatic epithelial cells.

The potential of clusterin inhibiting antisense oligodeoxynucleotide therapy for prostate cancer

This review summarise the authors' recent experience in the development of antisense (AS) oligodeoxynucleotide (ODN) therapy that targets a cytoprotective gene, clusterin, for the treatment of prostate cancer. The acquisition of resistance to a wide variety of proapototic stimuli was initially demonstrated by introducing the clusterin gene into prostate cancer cells. Furthermore, silencing clusterin expression using AS ODN synergistically enhanced the effects of several conventional therapeutic modalities through the effective induction of apoptosis in prostate cancer xenograft models. Based on these outcomes, Phase I clinical trials were conducted using AS clusterin ODN incorporating 2'-O-(2-methoxy)ethyl-gapmer backbone (OGX-011), and the optimal dose of OGX-011 capable of inducing </= 90% suppression of clusterin in human prostate cancer tissue was determined. Collectively, these findings suggest the utility of inactivating clusterin function using AS ODN technology as a novel therapeutic strategy for prostate cancer treatment. There have been four kinds of Phase II studies that have begun to further evaluate the efficacy of OGX-011 in patients with prostate, breast and lung cancers.

Antisense oligodeoxynucleotide therapy targeting clusterin gene for prostate cancer: Vancouver experience from discovery to clinic

BACKGROUND

The objective of this study was to review our experience in the development of antisense (AS) oligodeoxynucleotide (ODN) therapy for prostate cancer targeting antiapoptotic gene, clusterin.

METHODS

We initially summarized our data demonstrating that clusterin could be an optimal therapeutic target for prostate cancer, then presented the process of developing AS ODN therapy using several preclinical animal models. Finally, the preliminary data of the recently completed phase I clinical trial using AS clusterin ODN as well as the future prospects of this therapy are discussed.

RESULTS

Expression of clusterin was highly up-regulated after androgen withdrawal and during progression to androgen-independence, but low or absent in untreated tissues in both prostate cancer animal model systems and human clinical specimens. Introduction of the clusterin gene into human prostate cancer cells confers resistance to several therapeutic stimuli, including androgen ablation, chemotherapy and radiation. AS ODN targeting the translation initiation site of the clusterin gene markedly inhibited clusterin expression in prostate cancer cells in a dose-dependent and sequence-specific manner. Systemic treatment with AS clusterin ODN enhanced the effects of several conventional therapies through the effective induction of apoptosis in prostate cancer xenograft models. Based on these findings, a phase I clinical trial was completed using AS clusterin ODN incorporating 2'-O-(2-methoxy)ethyl-gapmer backbone (OGX-011), showing up to 90% suppression of clusterin in prostate cancer.

CONCLUSIONS

The data described above identified clusterin as an antiapoptotic gene up-regulated in an adaptive cell survival manner following various cell death triggers that helps confer a phenotype resistant to therapeutic stimuli. Inhibition of clusterin expression using AS ODN technology enhances apoptosis induced by several conventional treatments, resulting in the delay of AI progression and improved survival. Clinical trials using AS ODN confirm potent suppression of clusterin expression and phase II studies will begin in early 2005.

Antisense clusterin oligodeoxynucleotides increase the response of HER-2 gene amplified breast cancer cells to Trastuzumab

Clusterin (CLU) is a heterodimeric secreted glycoprotein implicated in several physiological and pathological processes including cancer. Although recent data showed that overexpression of CLU is closely associated with disease progression in patients with breast tumor, the functional role of CLU expression in this tumor hystotype remains to be determined. The objectives in this study were to evaluate CLU expression levels after treatment with Trastuzumab, a HER2-targeted monoclonal antibody used in the clinical management of advanced breast cancer patients, and to test the usefulness of combined treatment with OGX-011, the second generation 2'-methoxyethyl gapmer oligonucleotides targeting the CLU gene, and Trastuzumab in this tumor hystotype. By using the HER-2 gene amplified-BT474 human breast cancer cells, we found Trastuzumab decreased HER-2 expression and inhibited cell proliferation without affecting apoptosis. Interestingly, Trastuzumab treatment up-regulated CLU protein expression in a dose-dependent fashion. We therefore hypothesized that the treatment with OGX-011, by blocking Trastuzumab-induced CLU expression, might potentiate the growth-inhibitory effect of Trastuzumab alone. Although OGX-011 had no effect on the behavior of the BT474 cells when used alone, it significantly enhanced the sensitivity of cells to Trastuzumab. A significant increase in the percentage of apoptotic cells, analyzed in terms of annexin V positivity and cleavage of poly(ADP-ribose) polymerase, was observed after combined treatment with OGX-011 plus Trastuzumab but not with either agent alone. Altogether our findings suggest that combined targeting of HER-2 and CLU may represent a novel, rational approach to breast cancer therapy.

Investigation on urinary proteins and renal mRNA expression in canine renal papillary necrosis induced by nefiracetam

The occurrence of renal papillary necrosis (RPN), seen only in dogs after repeated oral administration of nefiracetam, a neurotransmission enhancer, at a relatively high dose, is because of inhibition of renal prostaglandin synthesis by the nefiracetam metabolite M-18. In this study, analyses of urinary proteins and renal mRNA expression were performed to investigate the possible existence of a specific protein expressing the characteristics of RPN evoked by nefiracetam. In the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of urinary proteins from male dogs given nefiracetam at 300 mg kg(-1) day(-1) over weeks 5-11, a protein of approximately 40 kDa, which was not seen in control urine, and protein of approximately 30 kDa emerged as distinct bands. Subsequently, clusterin precursor was identified in the former band and tissue kallikrein precursor in the latter by LC-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). By quantitative real-time RT-PCR analysis with renal morphological aspects, individual findings showed that renal clusterin mRNA was increased in dogs with severe renal injury, and renal tissue kallikrein also increased, presumably related to hemodynamics. These results demonstrate that changes in renal clusterin mRNA may reflect the progression or severity of RPN, whereas upregulation of tissue kallikrein mRNA may subsequently play a compensating role in the prevention of RPN.

Therapeutic efficacy of adenoviral-mediated p53 gene transfer is synergistically enhanced by combined use of antisense oligodeoxynucleotide targeting clusterin gene in a human bladder cancer model

To establish a more effective therapeutic strategy against advanced bladder cancer, we investigated the effects of combined treatment with antisense (AS) oligodeoxynucleotide (ODN) targeting the anti-apoptotic gene clusterin and adenoviral-mediated p53 gene transfer (Ad5CMV-p53) using the human bladder cancer KoTCC-1 model. Clusterin expression in KoTCC-1 cells was highly upregulated by Ad5CMV-p53 treatment; however, AS clusterin ODN treatment further suppressed clusterin expression in KoTCC-1 cells after Ad5CMV-p53 treatment. AS clusterin ODN treatment synergistically enhanced the cytotoxic effect of Ad5CMV-p53, and DNA fragmentation characteristic of apoptosis was observed only after combined treatment with AS clusterin ODN and Ad5CMV-p53, but not after treatment with either agent alone. Administration of AS clusterin ODN and Ad5CMV-p53 into nude mice resulted in a significant inhibition of KoTCC-1 tumor growth as well as lymph node metastases compared to administration of either agent alone. Furthermore, combined treatment with AS clusterin ODN, Ad5CMV-p53, and cisplatin completely eradicated KoTCC-1 tumors and lymph node metastases in 60% and 100% of mice, respectively. These findings suggest that combined treatment with AS clusterin ODN and Ad5CMV-p53 could be a novel strategy to inhibit bladder cancer progression, and that further additional use of a chemotherapeutic agent may substantially enhance the efficacy of this combined regimen.

Synergistic antitumor effect of combined use of adenoviral-mediated p53 gene transfer and antisense oligodeoxynucleotide targeting clusterin gene in an androgen-independent human prostate cancer model

Our recent studies showed that antisense oligodeoxynucleotide targeting antiapoptotic gene, clusterin, enhanced apoptosis induced by conventional therapeutic modalities using several prostate cancer models. In this study, to establish a more effective therapeutic strategy against prostate cancer, we investigated the effect of combined treatment with antisense clusterin oligodeoxynucleotide and adenoviral-mediated p53 gene transfer (Ad5CMV-p53) in an androgen-independent human prostate PC3 tumor model. Treatment of PC3 cells with 500 nmol/L antisense clusterin oligodeoxynucleotide decreased clusterin mRNA by &gt;80% compared with that with 500 nmol/L mismatch control oligodeoxynucleotide. Clusterin mRNA expression in PC3 cells was highly up-regulated by Ad5CMV-p53 treatment; however, antisense clusterin oligodeoxynucleotide treatment further suppressed clusterin expression in PC3 cells after Ad5CMV-p53 treatment. Antisense clusterin oligodeoxynucleotide treatment significantly enhanced the sensitivity of Ad5CMV-p53 in a dose-dependent manner, reducing the IC50 of Ad5CMV-p53 by 75%. Apoptotic cell death was detected after combined treatment but not after treatment with either agent alone. In vivo administration of antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 resulted in a significant inhibition of s.c. PC3 tumor growth as well as lymph node metastases from orthotopic PC3 tumors compared with administration of either agent alone. Furthermore, combined treatment with antisense clusterin oligodeoxynucleotide, Ad5CMV-p53, and mitoxantrone completely eradicated s.c. PC3 tumors and lymph node metastases from orthotopic PC3 tumors in 60% and 100% of mice, respectively. These findings suggest that combined treatment with antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 could be a novel strategy to inhibit progression of hormone-refractory prostate cancer and that further addition of chemotherapeutic agents may help to enhance the efficacy of this combined regimen.

Emergence of metastatic hormone-refractory disease in prostate cancer after anti-androgen therapy

The anti-androgens used in prostate cancer therapy have been designed to interfere with the normal androgen receptor (AR)-mediated processes that ensure prostate cell survival, triggering tumor cells to undergo programmed cell death. While anti-androgens were originally designed to treat advanced disease, they have recently been used to debulk organ-confined prostate tumors, to improve positive margins prior to surgery, and for chemoprevention in patients at high risk for prostate cancer. However, tumors treated with anti-androgens frequently become hormone refractory and acquire a more aggressive phenotype. Progression toward metastatic hormone-refractory disease has often been regarded as the outgrowth of a small number of hormone-independent cells that emerge from a hormone-dependent tumor during anti-androgen treatment by natural selection. While a number of selective advantages have recently been identified, there is also considerable evidence suggesting that the progression toward metastatic hormone-refractory disease is an dynamic process which involves abrogation of programmed cell death as a result of the attenuation of DNA fragmentation and maintenance of mitochondrial membrane potential in tumor cells; the upregulation of stromal-mediated growth factor signaling pathways; and the upregulation of extracellular matrix (ECM) protease expression.

Nucleotide-based therapies targeting clusterin chemosensitize human lung adenocarcinoma cells both in vitro and in vivo

Introduction: Lung cancer is highly lethal and resistant to most anticancer interventions. Treatment resistance is mediated, in part, by enhanced expression of cell survival proteins that help facilitate tumor progression. Clusterin is a stress-associated cytoprotective protein up-regulated by various apoptotic triggers in many cancers and confers treatment resistance when overexpressed. The objectives in this study were to evaluate clusterin expression levels in human lung cancer tissue, and to test effects of clusterin silencing using antisense oligonucleotides (ASOs) and short interfering double-stranded RNAs (siRNAs) on chemosensitivity in human lung cancer A549 cells. Methods: Clusterin immunostaining was evaluated in a tissue microarray of 149 spotted human lung cancers. The effects of clusterin ASO or siRNA treatment on clusterin expression and chemosensitivity to paclitaxel was examined in A549 cells in vitro while the ability of clusterin ASO to chemosensitize in vivo was evaluated in immunocompromised mice bearing A549 tumors. Results: More than 80% of human non-small cell lung cancers are immunoreactive for clusterin. Clusterin ASO or siRNA decreased clusterin mRNA expression in A549 cells &gt;75% in a dose-dependent, sequence-specific manner, and significantly enhanced chemosensitivity to paclitaxel in vitro. Characteristic apoptotic DNA laddering was observed after combined treatment with ASO plus paclitaxel, but not with either agent alone. In vivo administration of clusterin ASO, compared to mismatch control oligonucleotide, synergistically enhanced the effects of paclitaxel or gemcitibine to significantly delay A549 tumor growth. Conclusion: These findings identify clusterin as a valid therapeutic target in strategies employing novel multimodality therapy for advanced lung cancer.

Clusterin as a possible predictor for biochemical recurrence of prostate cancer following radical prostatectomy with intermediate Gleason scores: a preliminary report

Disease recurrence following radical prostatectomy is a major concern in prostate cancer patients. Gleason scores are useful in predicting recurrence. Low Gleason scores are usually associated with long disease-free intervals, while high Gleason scores are suggestive of early recurrence. However, prediction of recurrence has been difficult with intermediate Gleason scores. Clusterin is a ubiquitous secretory sulfated glycoprotein. It is also an antiapoptotic mediator in prostate cancer. The objective of the present study is to determine if clusterin can serve as a predictive biomarker for recurrence of prostate cancer with intermediate Gleason scores in patients following radical prostatectomy. Prostatic specimens with Gleason score of 6 (3+3) or 7 (3+4) were obtained from the archival bank. Three groups of specimens were investigated. The first group was from nine patients who developed recurrent disease according to a persistent rise of serum PSA within 3 years following radical prostatectomy. Those in the second group and the third group were from patients who showed no evidence of disease recurrence for at least 5 y (11 patients) and 10 y (eight patients), respectively following the surgery. Histological sections were subjected to immunohistochemical staining using a monoclonal antibody specific for clusterin. The staining intensity was scored as 0, 1, 2, and 3, with 0 being no staining, 1 showing less than 25% positive staining, 2 being 25-50% positive, and 3 showing greater than 75% positive staining. One-way ANOVA with Bonferroni correction was used for statistical analysis. Evaluation of the scores of clusterin staining was carried out according to four specific areas in each specimen. They were (a) benign epithelial cells, (b) malignant epithelial cells (cancer epithelia), (c) stromal cells surrounding benign cells, and (d) stromal cells surrounding malignant cells (cancer stroma). Staining score in prostatic epithelial cells, benign as well as malignant, showed no significant relationship among the three patient groups. However, when staining scores in stromal cells were compared, there was a significant difference between patients with recurrent disease and those showed no evidence of disease recurrence for at least 10 y. Results of this preliminary study support the important role of clusterin in the stromal component for prostate cancer progression. Clusterin immunostaining may be useful to aid the prediction of chance of disease recurrence in patients with Gleason score 6 or 7 prostate cancer following radical prostatectomy. Further studies with a large number of cases are warranted to verify this preliminary finding.

Proteomic analysis of human prostasomes

BACKGROUND

Prostasomes are secretory particles in human seminal fluid. Other than a microscopic description of these secretory particles and an incomplete two-dimensional gel electrophoresis (2DE) study, little is known about the composition of proteins in prostasomes.

METHODS

We employed a direct iterative approach using Gas phase fractionation and microcapillary HPLC-tandem mass spectrometry (microLC-MS/MS) to catalogue the prostasome proteome.

RESULTS

We identified 139 proteins that can be divided into the following categories: (1). enzymes (33.8% of total), (2). transport/structural (19.4% of total), (3). GTP proteins (14.4% of total), (4). chaperone proteins (5.8% of total), (5). signal transduction proteins (17.3% of total), and (6). unannotated proteins (9.4% of total). A total of 128 of the 139 proteins have not previously been described as prostasomal.

CONCLUSIONS

The proteins identified can be used as reference dataset in future work comparing prostasome proteins between normal and pathological states such as prostate cancer, benign prostatic hyperplasia, prostatitis, and infertility.

The Nuclear Factor I (NFI) gene family in mammary gland development and function

Mammary gland development and function require the coordinated spatial and temporal expression of a large fraction of the mammalian genome. A number of site-specific transcription factors are essential to achieve the appropriate growth, branching, expansion, and involution of the mammary gland throughout early postnatal development and the lactation cycle. One family of transcription factors proposed to play a major role in the mammary gland is encoded by the Nuclear Factor I (NFI) genes. The NFI gene family is found only in multicellular animals, with single genes being present in flies and worms and four genes in vertebrates. While the NFI family expanded and diversified prior to the evolution of the mammary gland, it is clear that several mammary-gland specific genes are regulated by NFI proteins. Here we address the structure and evolution of the NFI gene family and examine the role of the NFI transcription factors in the expression of mammary-gland specific proteins, including whey acidic protein and carboxyl ester lipase. We discuss current data showing that unique NFI proteins are expressed during lactation and involution and suggest that the NFI gene family likely has multiple important functions throughout mammary gland development.

Proximal location of mouse prostate epithelial stem cells: a model of prostatic homeostasis

Stem cells are believed to regulate normal prostatic homeostasis and to play a role in the etiology of prostate cancer and benign prostatic hyperplasia. We show here that the proximal region of mouse prostatic ducts is enriched in a subpopulation of epithelial cells that exhibit three important attributes of epithelial stem cells: they are slow cycling, possess a high in vitro proliferative potential, and can reconstitute highly branched glandular ductal structures in collagen gels. We propose a model of prostatic homeostasis in which mouse prostatic epithelial stem cells are concentrated in the proximal region of prostatic ducts while the transit-amplifying cells occupy the distal region of the ducts. This model can account for many biological differences between cells of the proximal and distal regions, and has implications for prostatic disease formation.

Clusterin expression is significantly enhanced in prostate cancer cells following androgen withdrawal therapy

INTRODUCTION AND OBJECTIVES

Progression of prostate cancer to androgen independence (AI) results in part from the upregulation of anti-apoptotic genes following androgen withdrawal, and androgen-independent disease remains the primary obstacle to improved survival. Testosterone-repressed prostate message-2 (TRPM-2) encodes the anti-apoptotic protein clusterin, which is upregulated in response to cellular compromise as observed in normal and malignant tissues undergoing apoptosis. Systemic administration of antisense clusterin oligonucleotides in prostate cancer xenograft models delays progression to AI and enhances chemosensitivity. The objective of this study was to define changes in clusterin expression following neoadjuvant hormone therapy (NHT) in prostate cancer patients.

MATERIALS AND METHODS

Archival radical prostatectomy (RP) specimens were obtained for 128 patients who received either no NHT or treatment for 2-8 weeks, 3 months, or 8 months. Paired needle biopsy specimens were acquired for 30 patients and all tissues were subjected to clusterin immunohistochemistry. Western blot analysis was performed on frozen tissue from 5 untreated and 5 treated patients.

RESULTS

Clusterin expression in malignant prostatic tissue was significantly greater in patients who underwent preoperative NHT (P < 0.001). Needle biopsies obtained prior to NHT consistently demonstrated lower staining intensity than corresponding RP specimens (P < 0.001). Western blot analysis confirmed clusterin levels increased 17-fold beginning within 4 weeks after androgen withdrawal.

CONCLUSIONS

Upregulation of clusterin levels following androgen ablation therapy may represent an adaptive cell survival response following apoptotic signals like androgen withdrawal. These findings support clusterin as a valid therapeutic target in strategies employing novel multimodality therapy for advanced prostate cancer.

Acquisition of resistance to Fas-mediated apoptosis by overexpression of clusterin in human renal-cell carcinoma cells

Recent studies have shown the antiapoptotic activity of clusterin against a wide variety of stimuli; however, the functional role of clusterin in Fas-mediated apoptosis has not been well characterized. We transfected the clusterin cDNA into human renal-cell carcinoma (RCC) ACHN cells that scarcely express clusterin protein in order to examine whether overexpression of clusterin inhibits the Fas-mediated signal pathway for apoptotic cell death. No significant difference was observed in the in vitro cell growth rates between the clusterin-transfected cell line (ACHN/CL) and the vector-only-transfected control cell line (ACHN/C), whereas the colony-forming efficiency in soft agar of ACHN/CL was significantly higher than that of ACHAN/C. The anti-Fas monoclonal antibody CH11 induced apoptosis in ACHAN/C cells in a dose-dependent manner; however, the growth-inhibitory effect of CH11 on ACHN/CL cells was markedly suppressed, with corresponding increases in p53 expression and decrease in the fraction of cells in the sub-G(1) phase of the cell cycle. Furthermore, the cytotoxic effect of CH11 on ACHN/CL cells was augmented by treatment with interferon-gamma, but a corresponding effect on ACHN/C cells was not observed. These findings suggest that overexpression of clusterin may contribute to a phenotype resistant to Fas-mediated apoptosis, and that if interferon-gamma treatment is added according to the clusterin expression level, Fas-mediated therapy could be a novel approach to RCC.

Novel therapeutic strategy for advanced prostate cancer using antisense oligodeoxynucleotides targeting anti-apoptotic genes upregulated after androgen withdrawal to delay androgen-independent progression and enhance chemosensitivity

Progression to androgen-independence remains the main obstacle to improving survival for patients with advanced prostate cancer. In this review, findings are summarized that have recently been demonstrated to establish novel therapeutic strategy targeting several genes playing functionally important roles after androgen withdrawal and during androgen-independent progression. The authors initially characterized changes in gene expression after androgen withdrawal in the androgen-dependent Shionogi and LNCaP tumor models using cDNA arrays. Based on these results, they focused on genes highly upregulated after androgen ablation (i.e. bcl-2, bcl-xL, TR.PM-2, IGFBP-5), which have anti-apoptotic or mitogenic activities, and thereby confer a resistance to androgen withdrawal as well as cytotoxic chemotherapy. The authors further demonstrated the efficacy of an antisense oligodeoxynucleotide (ODN) strategy for patients with advanced prostate cancer through the inhibition of target gene expression, resulting in a delay in the progression to androgen-independence by enhancing apoptotic cell death induced by androgen ablation and chemotherapy. The authors also showed the effectiveness of combined antisense ODN therapy and cytotoxic chemotherapy by achieving additive or synergistic effects. These findings provide a basic significance for the design of clinical studies using antisense ODN either alone or in combination with chemotherapeutic agents in patients with advanced prostate cancer.

Absence of proximal duct apoptosis in the ventral prostate of transgenic mice carrying the C3(1)-TGF-beta type II dominant negative receptor

BACKGROUND

Prostatic epithelial cells are sensitive to the inhibitory effects of TGF-beta. However, TGF-beta signaling in the prostate is dependent on androgenic status. Under the in vivo conditions, it is difficult to dissociate the effect of TGF-beta from that of androgen on the prostate.

METHODS

The objective of the present study was to create and verify a transgenic mouse system in which epithelial cells of the ventral prostate are insensitive to the actions of TGF-beta. By using a modified prostate-specific promoter, C3(1), the TGF-beta dominant negative receptor is only expressed in the epithelial cells of the ventral prostate, and these cells are resistant to TGF-beta. Morphology of transgenic animal prostates was compared to wild-type animal prostates by immunohistochemistry and microscopy.

RESULTS

The prostate of transgenic mice exhibited an abnormal morphology with multiple layers of epithelial cells lining the proximal ducts, in contrast to the simple cuboidal monolayer of cells seen in the normal prostate. This observation was accompanied by a loss of apoptosis in this region, as seen by TUNEL assay. There was no significant difference in serum levels of testosterone between the wild-type and transgenic animals.

CONCLUSIONS

These results demonstrated that a loss of sensitivity to TGF-beta results in the accumulation of multiple layers of epithelial cells in the proximal region of the ventral prostate. This abnormal growth illustrates that TGF-beta plays an important role in regulating prostate growth. The current transgenic system can be used as an experimental model to study the functional role of TGF-beta in prostatic growth and function.

Castration-induced apoptotic cell death in the Brown Norway rat prostate decreases as a function of age

Growth and differentiation of the prostate gland depends upon androgens, yet overgrowth of the human prostate occurs later in life when serum levels of testosterone are declining. We have reported a similar phenomenon in the Brown Norway rat, but the age-dependent overgrowth of the prostate is confined to the dorsal and lateral lobes and, hence, is lobe specific. Because tissue growth depends upon the balance between proliferation and death of cells, the present study was designed to investigate whether cell death differed in the various prostatic lobes of Brown Norway rats as a function of age. Apoptosis of cells in the ventral, dorsal, lateral, and anterior lobes of the prostate was examined in young (4-month-old) and old (24-month-old) Brown Norway rats after castration. Whereas castration caused tissue weights of all four prostatic lobes to decrease over the course of 10 days, this occurred more rapidly and to a greater magnitude in the ventral than in the dorsal, lateral, and anterior lobes. Tissue DNA content, a measure of cell number, decreased only in the ventral lobe after castration. DNA fragmentation, indicative of apoptotic cell death, was detected by in situ labeling using the terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling method and as intranucleosomal cleavage of genomic DNA analyzed by agarose gel electrophoresis. Both methods demonstrated the correlation between loss of DNA content and apoptotic cell death in the ventral lobe, whereas only the highly sensitive terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling (TUNEL) method revealed relatively few dying cells in the dorsal, lateral, and anterior lobes after castration. Moreover, when examined as a function of age, less cell death occurred in all four lobes of old rats compared with young rats. In both young and old rat prostates, cell death was observed in epithelial and stromal cells within the ventral lobe where apoptotic cells were detected throughout the branched ductal network and were not restricted to a particular region. Taken together, these studies demonstrate the marked differences in cell death and survival between the different rat prostatic lobes in response to castration and further suggest that the androgen-sensitive apoptotic response is age dependent. Hence, the lower rates of cell death observed for the dorsal and lateral lobes, accompanied by the further decline that occurs with increasing age, are important components of the age-dependent and lobe-specific overgrowth observed for these lobes. Moreover, the age-dependent decline in apoptotic cell death observed in the prostates of old rats suggests that prostatic cells develop androgen independence as a function of age, and survival of these cells does not require androgen.

Postnatal development and regulation of proteins secreted in the boar epididymis

The number of proteins secreted by the boar epididymis increased progressively from 1 mo of age to the adult period. The first specific secretory activity was revealed at 2 mo in the distal caput (hexosaminidase, clusterin, and lactoferrin) and in the corpus (train O/HE1). Train A and glutathione peroxidase specific to the proximal caput, and trains E and M specific to the corpus, appeared at 4 mo. At 5 mo, secretion of procathepsin L occurred in the middle caput and that of mannosidase and E-RABP in the distal caput. Approximately 48% of all the proteins secreted in the adult boar epididymis were dependent on the presence of androgens, either stimulated (33.6%) or repressed (14.4%); 47% were modulated by other factors, and 5% were unregulated. In the proximal caput, 50% of the specific secreted proteins were controlled essentially by factors emanating from the testis. In more distal regions, two proteins secreted in the corpus were regulated by factors from the anterior regions. The regionalization of the secretory activity of the epididymal epithelium resulted in a specific regulation for each protein, which was modulated according to the region of expression and influenced by either testicular or epididymal factors that remain to be identified.

Expression of p190A during apoptosis in the regressing rat ventral prostate

After hormonal ablation, 90% of the secretory epithelial cells of the prostate undergo apoptosis, and the remaining cells are reorganized as the tissue is remodeled. Using differential display RT-PCR of total RNA extracted from the rat ventral prostate before and 4 days after castration, we have cloned and sequenced a number of complementary DNAs whose cognate messenger RNAs (mRNAs) may be either up- or down-regulated during prostatic regression. One sequence of particular interest, 25.2, is up-regulated after castration and is homologous to p190, a protein associated with cytoskeletal reorganization. RT-PCR has confirmed that the steady state level of p190A mRNA is increased in the rat ventral prostate after castration, and Western blot analysis indicates that the protein levels for p190A also increase. The steady state level of p190B mRNA, the second isoform of p190, does not appear to change significantly after hormone ablation. Immunohistochemical analysis demonstrates that p190A is up-regulated primarily in the columnar epithelial cells that actively undergo cell death after hormone ablation. As Rho-GAP signaling had been shown to be influenced by p190 levels, leading to the disassembly of focal adhesion contacts and the loss of cytoskeletal architecture, we also measured the changes in Rho-GAP during prostate regression. Rho-GAP levels do not change significantly, suggesting that changes in stoichiometry of the interaction between p190A and Rho-GAP may be a prerequisite for the initiation of cytoplasmic condensation. These intracellular events coupled with the proteolytic degradation of the extracellular matrix appear to be integral to the apoptotic process in glandular epithelia.

Estrogen receptor-beta: implications for the prostate gland

Estrogens can have profound effects on prostate growth and differentiation. These effects were thought to be mediated by the classical estrogen receptor; however, the discovery of a second estrogen receptor has redefined the estrogen signaling pathway and may have broad implications on estrogen-responsive tissues, including the prostate. The new estrogen receptor, named estrogen receptor-beta (ERbeta), is preferentially expressed in the prostate and maintains some characteristics that are different from ERalpha. Establishing the distribution and function of ERbeta in the various estrogen-responsive tissues is critical to defining its pharmacological and physiological impact. Differential expression of ERbeta may facilitate development of tissue-specific estrogen agonists and antagonists, a goal in the treatment of diseases in estrogen-sensitive tissues such as breast cancer. This article reviews the current knowledge on ERbeta and its potential impact on the prostate.

Imprinting by neonatal sex steroids on the structure and function of the mature mouse prostate

Perinatal sex-steroid exposure may result in permanent modifications in the structure and function of the prostate gland. The mechanism of such long-range alterations in hormonal sensitivity is not known. This study aimed to define the molecular requirements for neonatal sex-steroid imprinting and to investigate whether combined administration of neonatal androgens and estrogens had synergistic effects upon the mature mouse prostate. Since the interaction between endogenous and exogenous sex steroids in normal mice makes it difficult to dissociate direct from indirect effects, we used the hypogonadal (hpg) mouse, characterized by congenital androgen deficiency yet still fully responsive to exogenous androgens. Newborn mice (Days 1-2) were administered a single s.c. injection of androgens alone or in combination with an estrogen followed by testosterone-induced maximal prostate growth at maturity. The final effects were determined in 7-wk-old mice through study of ductal architecture in microdissected ventral prostates (VP) and quantitation of volume densities and diameters of prostate tissue components. A single neonatal dose of androgens, but not of estrogen, increased branching morphogenesis and VP weights at adulthood. These effects did not differ significantly between various androgens; in addition, combined androgen and estrogen treatment failed to demonstrate any synergistic effects on the prostate. We conclude that neonatal androgens induce long-range effects upon the mature VP structure as well as its secretory function and that this imprinting occurs via the androgen receptor without requiring aromatization of androgens. However, these conclusions, based on a specific treatment protocol, are confined only to the distal segment of VP, and effects of neonatal sex-steroid exposure in other regions or lobes of VP may differ.

Transforming growth factor-beta in benign and malignant prostate

BACKGROUND

The present review summarizes the cellular action of TGF-beta in benign and malignant growth of the prostate.

METHODS

TGF-beta is a pleiotropic growth factor. It plays an important role in the regulation of growth and differentiation in many cells. In benign prostatic epithelia, its action is mediated through a paracrine mechanism. It inhibits proliferation and induces apoptosis in prostatic epithelia. It provides a mechanism to maintain epithelial homeostasis in the prostate. In prostatic stroma, its continual action leads to smooth muscle differentiation. This effect of TGF-beta may regulate the development of prostatic smooth muscle nodules in benign prostatic hyperplasia.

RESULTS

As prostatic epithelial cells undergo malignant transformation, two major events occur regarding TGF-beta action. These include the loss of expression of functional TGF-beta receptors and overproduction of TGF-beta in malignant cells. The loss of expression of functional TGF-beta receptors provides a growth advantage to cancer cells over their benign counterparts. The overproduction of TGF-beta by cancer cells has a multitude of adverse consequences. TGF-beta can promote extracellular matrix production, induce angiogenesis, and inhibit host immune function. The biological consequence of these activities is an enhanced tumorigenicity in prostate cancer. Results of our recent studies with a rat prostate cancer model suggest that the immunosuppressive effect of TGF-beta seems to be the primary cause of tumor progression. This is because, if these cancer cells were engineered to reduce the production of TGF-beta, tumor growth was inhibited in syngeneic hosts but not in immune compromised hosts.

CONCLUSIONS

Our future research should take advantage of this knowledge to devise therapeutic strategies aimed at eradicating prostate cancer.

Clusterin in the male reproductive system: localization and possible function

Clusterin is a glycoprotein that was initially isolated from the male reproductive system. Subsequently, clusterin has been found to be widely distributed in a variety of tissues in mammals. One characteristic of the expression of clusterin is that it is induced as a result of cellular injury, death, or pathology. Despite the efforts of many laboratories working in diverse biological systems, the function of clusterin remains unknown. Recent studies have revealed a 'heat-shock element' in the promoter of the gene that may account for the inducible nature of the clusterin gene. Overall, the evidence suggests that function of clusterin is to protect surviving cells after damage. This protection may result from a detergent-like action of the protein.

Regulation of Apoptosis in the Prostate Gland by Androgenic Steroids

The prostate gland requires androgenic steroids for its appropriate embryological formation and postpubertal growth and, once at adult size, remains dependent on a continuous supply of androgens for its vitality and function. A reduction of the levels of circulating androgens will rapidly induce apoptosis of the cells of the prostate, leading to extensive glandular regression. Studies of rodent models of prostate response to castration have shown that there are some remarkable changes in the gene activity of prostate epithelial cells leading up to apoptosis. There is now evidence for a critical cell signaling pathway, regulated by c-fos expression, necessary for castration-induced apoptosis, as well as evidence that this signaling initiates an abrupt and transient alteration in the synthesis of fas antigen, p53, bax and bcl-2 proteins in the androgen receptor-expressing prostate epithelial cells, the cellular compartment that appears to be the most affected by castration. However, more recent studies suggest that these castration-induced effects on the prostate epithelial cells might be, at least in part, an indirect response to a critical reduction in blood flow to the prostate gland that precedes the onset of epithelial cell apoptosis. The castration effects on blood flow to the prostate gland seem to be related to vascular degeneration associated with apoptosis of a subset of prostate endothelial cells.

Phytoestrogens and diseases of the prostate gland

Both benign hyperplasia (BPH) and cancer of the prostate are manifest in men beyond the age of 50. Approximately 50% of men greater than 50 years of age will suffer from the symptoms associated with BPH, especially from bladder outlet obstruction. With the ever-increasing proportion of the population over 65 years of age worldwide, BPH is becoming an important medical problem as the world moves into the next millennium. Cancer of the prostate is the second most commonly diagnosed cancer after skin cancer in the male population of the United States, and the second most common cause of death from cancer after that of the lung. Overall, around the world the incidence of carcinoma of the prostate is increasing annually by 2-3%. Both race and geographical location have a profound influence of the prevalence of prostate cancer worldwide. Black men in the USA have the highest incidence, while the incidence is much lower in Asian men from China, Japan and Thailand. Although the prostate gland is androgen-dependent, it is now recognized that the biological actions of endocrine-related factors, such as androgens, oestrogens, glucocorticoids and certain dietary and environmental factors, are mediated within the gland by various growth regulatory factors. The growth regulatory factors such as epidermal growth factor (EGF), keratinocyte growth factors (KGF), fibroblast growth factors (FGFs) and insulin-like growth factors II and I are mitogenic and directly stimulate cell proliferation under the modulating influence of steroid hormones. Steroids are therefore essential but not directly responsible for cell proliferation. Certain plant compounds such as isoflavonoids, flavonoids and lignans have been proposed as cancer protective compounds in populations with low incidences of prostate diseases. In particular, soya contains the isoflavone genistein, a compound with many properties which could influence both endocrine and growth factor signalling pathways.

Lack of association between enhanced TRPM-2/clusterin expression and increased apoptotic activity in sex-hormone-induced prostatic dysplasia of the Noble rat

Although the functional role of TRPM-2/clusterin in the prostate remains controversial, it has been postulated that transcriptional activation of the gene is an important mechanism in castration-induced prostatic involution and perhaps is a means for prostatic cells to escape apoptotic induction. In the present study, we have measured expression levels of TRPM-2/clusterin and apoptotic activities in the prostates of castrated Noble (NBL) rats and those treated with testosterone (T) and estradiol-17beta (E2) for 16 weeks. We have previously shown that the combined sex hormone treatment (T+E2) induces dysplasia, a purported preneoplastic lesion, exclusively in the dorsolateral prostates (DLPs) of all treated rats. In the present study, we demonstrate that, as expected, castration readily induced enhanced TRPM-2/clusterin expression, which was accompanied by increased apoptotic activity in the epithelia of DLP and ventral prostate (VP). The increase in TRPM-2/clusterin expression appeared earlier and was more dramatic in the VP than in the DLP. In sharp contrast, treatment of rats with T+E2 for 16 weeks induced augmentation of TRPM-2/clusterin expression selectively in the dysplastic lesions of the DLP but not in the lesion-free VP. The enhanced expression of TRPM-2/clusterin in the dysplastic epithelium was, however, not attended by an increase in apoptotic activity within the lesion. Thus, the observed up-regulation of TRPM-2/clusterin expression in the dysplastic foci of T+E2-treated rats occurred in animals whose androgen status remained normal and, despite the increased level of expression of this gene, apoptotic activity in these lesions was unchanged from basal values measured in the DLPs of untreated rats. These findings suggest that TRPM-2/clusterin expression in dysplastic lesions was no longer repressed by androgen nor was it associated with apoptosis. We propose that overexpression of the gene is likely a phenotype of neoplastic transformation. In addition, we speculate that TRPM-2/clusterin may serve as a survival factor, which could favor accumulation of transformed cells in dysplastic foci and thus promote the carcinogenic process.

Regional expression of transforming growth factor-alpha in rat ventral prostate during postnatal development, after androgen ablation, and after androgen replacement

The prostate is a highly heterogeneous organ, composed of different types of epithelial and stromal cells organized regionally along the ductal network. Although androgen-stimulated growth and maintenance of the prostate gland primarily involve epithelial cells, it is unclear whether all epithelial cells are androgen dependent. Moreover, the actions of androgens may not be direct; a number of polypeptide growth factors, including transforming growth factor-alpha (TGFalpha), are postulated to mediate androgen action in the rat prostate. In this investigation, using an immunohistochemical technique, we examined the cellular and regional expression of TGFalpha in the rat ventral prostate during postnatal development to adulthood. TGFalpha-immunopositive cells were located throughout the ductal epithelium from postnatal days 5-20. By day 45 and thereafter, regional variation in TGFalpha expression became apparent; epithelial cells in the proximal segment exhibited intense staining, whereas those in the distal segment exhibited negligible staining. These observations were coincident with increased serum testosterone concentrations at puberty. To understand the role of androgen in the expression of TGFalpha in the epithelial cells of the distal and proximal segments of the adult rat ventral prostate, androgen was withdrawn by castration, and testosterone subsequently was administered. Androgen receptor protein expression decreased after castration and reappeared after androgen replacement in both the distal and proximal segments. TGFalpha staining was negligible in epithelial cells of the distal segment of intact adult rats, became prominent by 7 days after castration, but then diminished after the administration of testosterone. Western blot analyses revealed the presence of a specific 30-kDa immunoreactive form of TGFalpha in rat ventral prostate, and its quantity reflected the staining intensities observed in the immunohistochemical studies. These results suggest that TGFalpha expression is negatively regulated by androgen in epithelial cells of the distal segment. In contrast, staining for TGFalpha in epithelial cells of the proximal segment did not change with castration or testosterone administration, suggesting that TGFalpha is not regulated by androgen in this region of the ventral prostate. In summary, TGFalpha expression is differentially regulated among epithelial cells localized in two different regions of the ventral prostate. We hypothesize that TGFalpha may function as a survival factor for epithelial cells which, as a consequence of its expression, become androgen independent and thus escape apoptotic cell death after androgen ablation.

Estrogen receptor-beta messenger ribonucleic acid ontogeny in the prostate of normal and neonatally estrogenized rats

Neonatal exposure to estrogens permanently alters rat prostate growth and epithelial differentiation leading to prostatic dysplasia on aging. The effects are lobe-specific, with the greatest response observed in the ventral lobe. Recently, a novel estrogen receptor (ER) complementary DNA was cloned from the rat prostate and termed ER-beta (ER beta) due to its high homology with the classical ER alpha. The protein possesses high affinity for 17beta-estradiol, indicating that ER beta is an alternate molecule for mediating estrogenic effects. Importantly, ER beta messenger RNA (mRNA) was localized to rat prostatic epithelial cells, which contrasts with the stromal localization of ER alpha in the rat prostate. The present study was undertaken to determine the ontogeny of ER beta mRNA expression in the rat prostate lobes and to examine the effects of early estrogen exposure on prostatic ER beta expression. Male rat pups were given 25 microg estradiol or oil on days 1, 3, and 5; were killed on day 1, 3 (oils only), 6, 10, 30, or 90; and prostate lobes were frozen. Longitudinal sections were processed for in situ hybridization using an 35S-labeled antisense mRNA probe corresponding to a 400-bp EcoRI-AccI fragment in the 5' untranslated region of rat ER beta complementary DNA. Image analysis was used to quantitate silver grains. In addition, total RNA was isolated from the ventral prostate (VP) and used for semiquantitative RT-PCR. Results from in situ hybridization revealed that at birth, ER beta was equivalently expressed at low levels in both mesenchymal and epithelial cells in oil-treated rats. From day 1 onwards, expression in all stromal cells slowly and significantly declined, so that in the control adult prostate, stromal ER beta mRNA was slightly above background. In the oil-treated control rats, epithelial ER beta mRNA increased to moderate levels between days 6-10 in the VP and days 10-15 in the dorsal and lateral lobes as cells began differentiation and ducts lumenized. A further significant increase in ER beta message was observed at day 30, which indicates that full epithelial ER beta expression may require the completion of functional differentiation. By day 90, expression levels were maximal and similar between the lobes. RT-PCR substantiated this developmental increase in ER beta between days 1-90. Neonatal exposure to estrogens did not have an immediate effect on prostatic ER beta mRNA levels as determined by in situ hybridization and RT-PCR. However, the marked increase in epithelial cell expression at day 30 observed in the control VP was dampened in the VP of animals exposed neonatally to estrogens. By day 90, the VP of estrogenized rats possessed low ER beta message levels compared with the high expression in oil controls. In contrast, the dorsal and lateral lobes of neonatally estrogenized rats possessed high levels of ER beta mRNA at day 90, equivalent to controls. The present data demonstrate that ER beta mRNA expression in the rat prostate is developmentally regulated, and that neonatal estrogen can affect this expression in the adult VP. Because the effect of neonatal estrogens was not immediate, the data imply that early estrogen exposure may not directly autoregulate ER beta expression, and suggests that the adult effects on ER beta mRNA expression may be indirect. The differences in ER beta mRNA imprinting in the separate lobes may account for or reflect the lobe-specific neonatal estrogen imprints previously observed in the rat prostate.

Genes regulated by androgen in the rat ventral prostate

Genes that are regulated by androgen in the prostate were studied in the rat. Four of the less than 10 genes that are down-regulated by androgen in the ventral prostate of a 7-day castrated rat were identified; their mRNAs decayed with identical kinetics. Twenty-five of the estimated 56 genes that are up-regulated by androgen in the castrated prostate have been isolated. The up-regulated genes fall into two kinetic types. Early genes are significantly up-regulated by 6.5 hr whereas the delayed genes respond mainly after 24 hr from the time of androgen replacement. These androgen-response genes are also regulated in the prostate by castration, indicating that these genes could play important roles in androgen-induced regrowth and/or castration-induced regression of the prostate during hormonal manipulation. A survey of the tissue specificity showed that the androgen-response gene expression program in the prostate is mainly prostate-specific. Total RNA Northern blot analysis detects the expression of about 16 up-regulated genes and 3 down-regulated genes in the prostate only. Four up-regulated genes and one down-regulated gene are regulated by androgen in both the prostate and seminal vesicles but not in other organs. The expression of the remaining androgen-response genes is not limited to the prostate but is only responsive to androgen in the prostate. This survey of the androgen-response gene expression program provides insights into the molecular and cellular mechanisms of androgen action in the prostate.

Intrinsic and extrinsic factors controlling benign prostatic growth

This review will present a new concept on the etiology of the development of benign prostatic hyperplasia (BPH). Conventionally, two known etiological factors for the development of BPH have been aging and the presence of functional testes. Assignment of these two factors, although reasonable, has not been conducive to aid the research community to identify and isolate the patho-physiological agents that are directly responsible for the development of this disease. In the present review, we proposed a broadened concept of intrinsic and extrinsic factors for BPH. This concept offers identifiable research opportunities that will facilitate our quest in search for etiological agents for BPH. A brief description of various intrinsic and extrinsic factors and justifications for their selection will be discussed.

Expression of a 74-kDa nuclear factor 1 (NF1) protein is induced in mouse mammary gland involution. Involution-enhanced occupation of a twin NF1 binding element in the testosterone-repressed prostate message-2/clusterin promoter

Testosterone repressed prostate message-2 (TRPM-2)/clusterin gene expression is rapidly induced in early involution of the mouse mammary gland, after weaning, and in the rat ventral prostate, after castration. A search for involution-enhanced DNaseI footprints in the proximal mouse TRPM-2/clusterin gene promoter led to the identification and characterization (by DNase I footprinting and EMSA) of a twin nuclear factor 1 (NF1) binding element at -356/-309, relative to the proposed transcription start site; nuclear extracts from 2-day involuting mouse mammary gland showed an enhanced footprint over the proximal NF1 element; extracts from involuting prostate showed enhanced occupancy of both NF1 binding elements. Subsequent EMSA and Western analysis led to the detection of a 74-kDa NF1 protein whose expression is triggered in early involution in the mouse mammary gland; such an induced protein is not found in the involuting rat ventral prostate. This protein was not found in lactation where three other NF1 proteins of 114, 68, and 46 kDa were detected. Reiteration of the epithelial cell apoptosis associated with early mammary gland involution, in vitro, in a primary cell culture system, triggered the appearance of the 74-kDa NF1. Overlaying the cells with laminin-rich extracellular matrix suppressed the apoptosis and the expression of the 74-kDa NF1 and, in the presence of lactogenic hormones, initiated milk protein gene expression and the expression of two of the lactation-associated NF1 proteins (68 and 46 kDa). This study, thus, identifies for the first time the occurrence of a switch in expression of different members of the family of NF1 transcription factors as mammary epithelial cells move from the differentiated to the involution/apoptotic state, and it is likely that the involution-specific 74-kDa NF1 accounts for the enhanced NF1 footprint detected on the TRPM-2/clusterin promoter with extracts of mouse mammary gland.

Effects of castration on plasminogen activator activities and plasminogen activator inhibitor type 1 in the rat ventral prostate

The involution of the prostate gland after castration is an active process which requires the induction of new proteins. The plasminogen activator urokinase has been proposed to be a gene repressed by androgen which is activated upon castration and thus participating in the atrophy of the gland. However, urokinase is secreted by the ventral lobe of the rat prostate and this should be positively affected by androgens. The purpose of this study was to examine further the effects of castration upon plasminogen activator (PA) activities in the rat prostate and to determine possible explanations to this apparent dilemma. Castration of young sexually mature adult rats resulted in a substantial increase in PA activities at 4 days after castration in the ventral prostate, but then the activities returned to within the range of untreated animals with a longer duration of castration. Urokinase was the predominant molecular form of PA in the normal ventral prostate and it was the molecular form increased after castration; based upon its sensitivity to amiloride and its molecular size determined in zymograms. In contrast to the effect of castration, there was no increase in PA activities in the ventral prostate with treatment of rats with the antiandrogen flutamide, but rather a decrease when specific activity was expressed per unit DNA. In addition, the effect of castration was specific for the ventral lobe for there was no change in the PA activity in the dorsolateral prostate after androgen ablation. The diminished PA activities in the ventral prostates of rats castrated for 7 days or longer appeared to be due at least in part to an increase in plasminogen activator inhibitor type-1 (PAI-1). Immunoreactive PAI-1 was found predominantly in high molecular weight forms which indicates that the inhibitor was complexed with PA. Daily treatment of rats upon castration with agents known to retard the rate of regression of the involuting prostate gave dichotomous results. Hydrocortisone prevented the increase in PA activity, whereas treatment with actinomycin D, an inhibitor of RNA synthesis, not only did not prevent an increase in PA activity, but actually produced a superinduction in PA activity at 4 days orchiectomy. These data may be interpreted to mean that hydrocortisone stimulated PAI activity and that actinomycin D treatment blocked its induction. However, the actinomycin D data may also indicate that an increase in urokinase protein and mRNA after castration may result from some mechanism to conserve these molecules suggesting that this inhibitor of RNA synthesis prevented the transcription of messages for proteins involved in the degradation of urokinase message.

Prostatic ductal system in rats: regional variation in stromal organization

The rat prostate is composed of a complex system of branching ducts which terminate proximally at the urethra. It has been recognized that epithelial cells lining the ducts respond differently to androgen in various regions of the ducts, with responses ranging from proliferation to apoptosis, but the cellular mechanisms underlying these effects are unclear. Interaction between prostatic stroma and epithelium is essential to normal prostate growth and development, and the prostatic stroma is thought to be the first site of androgen action. Therefore we have examined the organization and distribution of stromal cell types along the rat prostatic ductal system. Using immunohistochemical techniques, we observed abundant fibrous tissue surrounding the distal region of the ducts, with a sparse, discontinuous smooth muscle layer. The intermediate region was surrounded by a continuous layers of smooth muscle one to two cells thick, which increased to greater than four layers thick at the proximal region. Fibrous tissue was located in interductal spaces and occasionally interspersed within the muscle layers in both regions. These observations indicate that regional variations in the distribution of stromal cell types exist and suggest that their corresponding secretory products could be responsible for the various effects of androgen on the epithelium in the rat prostatic ductal system.

Influence of testosterone on chondroitin sulphate proteoglycan in the rat prostate

There are recognized interactions between prostatic stromal and epithelial cells. These interactions may be influenced by the composition of the extracellular matrix, which is composed of proteins such as collagen, laminin, fibronectin, and proteoglycans (PGs) such as chondroitin sulphate proteoglycan (CSPG). In our continuing studies on prostate biology, we examined the three lobes of the normal adult rat prostate, i.e., ventral, dorsal, and lateral, for CSPG by indirect immunofluorescence, using an immunospecific monoclonal antibody (CS-56) for the chondroitin sulphate (CS) moiety of the PG. Staining of the prostate sections with CS-56 antibody followed by labelling with IgG fluorescein isothiocyanate conjugate indicated strong fluorescent signals associated with the ventral lobe basement membrane. The signal was stronger and more continuous in the distal acini than in the proximal acini. The staining of the dorsal and lateral lobes was less intense than that of the ventral lobe. Following castration of the rats, the basement membrane staining became discontinuous. Androgen replacement by administration of testosterone propionate (TP) reversed the effects of castration. Quantification of the total CS content showed decreases of about 60% in the ventral and lateral lobes after castration. TP administration for 14 days increased the total CS content several fold above the values for castrated rats in all lobes. The results demonstrated that CS content was significantly higher for TP-treated animals, suggesting that the expression of prostate CSPG is regulated by androgens. This approach should be useful in the study of the extracellular matrix in prostate biology.

Clusterin: a role in cell survival in the face of apoptosis?

Clusterin is a multifunctional glycoprotein complex found in virtually all body fluids and on the surface of cells lining body cavities. Demonstrated and proposed functions include the transport of lipoproteins, the inhibition of complement-mediated cell lysis and the modulation of cell-cell interactions. On the basis of its elevated expression in apoptotic tissues, it was originally proposed that the protein might be casually involved in apoptosis. Here, we discuss the recent data that, in contrast to the earlier notion, suggest that clusterin expression is not enhanced, but rather is down-regulated in the cells undergoing apoptosis and that its expression in the apoptotic tissue is restricted to the vital neighboring cells. These results led to the proposal that rather than being a cell death gene, clusterin is a cell survival gene, exerting a protective function on the surviving bystander cells.