Androgen receptor up-regulates insulin-like growth factor binding protein-5 (IGFBP-5) expression in a human prostate cancer xenograft

Insulin-like growth factor binding protein 5: Diverse roles in cancer

Insulin-like growth factor binding proteins (IGFBPs) and the associated signaling components in the insulin-like growth factor (IGF) pathway regulate cell differentiation, proliferation, apoptosis, and adhesion. Of the IGFBPs, insulin-like growth factor binding protein 5 (IGFBP5) is the most evolutionarily conserved with a dynamic range of IGF-dependent and -independent functions, and studies on the actions of IGFBP5 in cancer have been somewhat paradoxical. In cancer, the IGFBPs respond to external stimuli to modulate disease progression and therapeutic responsiveness in a context specific manner. This review discusses the different roles of IGF signaling and IGFBP5 in disease with an emphasis on discoveries within the last twenty years, which underscore a need to clarify the IGF-independent actions of IGFBP5, the impact of its subcellular localization, the differential activities of each of the subdomains, and the response to elements of the tumor microenvironment (TME). Additionally, recent advances addressing the role of IGFBP5 in resistance to cancer therapeutics will be discussed. A better understanding of the contexts in which IGFBP5 functions will facilitate the discovery of new mechanisms of cancer progression that may lead to novel therapeutic opportunities.

Identification of Impacted Pathways and Transcriptomic Markers as Potential Mediators of Pulmonary Fibrosis in Transgenic Mice Expressing Human IGFBP5

Pulmonary fibrosis is a serious disease characterized by extracellular matrix (ECM) component overproduction and remodeling. Insulin-like growth factor-binding protein 5 (IGFBP5) is a conserved member of the IGFBP family of proteins that is overexpressed in fibrotic tissues and promotes fibrosis. We used RNA sequencing (RNAseq) to identify differentially expressed genes (DEGs) between primary lung fibroblasts (pFBs) of homozygous (HOMO) transgenic mice expressing human IGFBP5 (hIGFBP5) and wild type mice (WT). The results of the differential expression analysis showed 2819 DEGs in hIGFBP5 pFBs. Functional enrichment analysis confirmed the pro-fibrotic character of IGFBP5 and revealed its impact on fundamental signaling pathways, including cytokine–cytokine receptor interaction, focal adhesion, AGE-RAGE signaling, calcium signaling, and neuroactive ligand-receptor interactions, to name a few. Noticeably, 7% of the DEGs in hIGFBP5-expressing pFBs are receptors and integrins. Furthermore, hub gene analysis revealed 12 hub genes including Fpr1, Bdkrb2, Mchr1, Nmur1, Cnr2, P2ry14, and Ptger3. Validation assays were performed to complement the RNAseq data. They confirmed significant differences in the levels of the corresponding proteins in cultured pFBs. Our study provides new insights into the molecular mechanism(s) of IGFBP5-associated pulmonary fibrosis through possible receptor interactions that drive fibrosis and tissue remodeling.

Quercetin-Resveratrol Combination for Prostate Cancer Management in TRAMP Mice

Prostate Cancer (PCa) is a leading cause of cancer-related morbidity and mortality in men. Therefore, novel mechanistically-driven approaches are needed for PCa management. Here, we determined the effects of grape antioxidants quercetin and/or resveratrol (60 and 600 mg/kg, respectively, in diet) against PCa in Transgenic Adenocarcinoma of Mouse Prostate (TRAMP)-model in prevention and intervention settings. We found resveratrol alone and in combination significantly inhibited prostate tumorigenesis in prevention setting, while the same was seen only in combination after intervention. The observed effects were associated with marked inhibition in proliferation, oxidative stress, and tumor survival markers, and induced apoptosis markers. Utilizing PCa PCR array analysis with prevention tumor tissues, we identified that quercetin-resveratrol modulates genes involved in promoter methylation, cell cycle, apoptosis, fatty acid metabolism, transcription factors, androgen response, PI3K/AKT and PTEN signaling. Ingenuity Pathway Analysis (IPA) identified IGF1 and BCL2 as central players in two gene networks. Functional annotation predicted increased apoptosis and inhibited cell viability/proliferation, hyperplasia, vasculogenesis, and angiogenesis with dual treatment. Furthermore, IPA predicted upstream inhibition of major PCa signaling VEGF, Ca2+, PI3K, CSF2, PTH). Based on PCR array, we identified decreased levels of EGFR, EGR3, and IL6, and increased levels of IGFBP7 and NKX3.1, overall supporting anti-PCa effects of quercetin-resveratrol.

Human placental androgen receptor variants: Potential regulators of male fetal growth

INTRODUCTION

Numerous studies show that males have increased intrauterine growth compared to females, and that pregnancy complications may further these growth differences, but the regulatory mechanisms underlying these differences remain unknown. We propose that these growth outcomes may be due to sex-specific differences in androgen sensitivity - giving rise to altered growth signalling pathways - mediated by the differential expression of placental androgen receptor (AR) variants.

METHODS

Placental protein and mRNA were used to identify AR protein variant levels and AR-downstream target gene expression, and were then analysed against neonatal measurements. Dihydrotestosterone (DHT)-induced AR protein variant expression and downstream growth factors were examined in vitro.

RESULTS

Four known AR variants (AR-FL, AR-V1, AR-V7, and AR-45), and three unknown proteins (120, 90 and 55 kDa) immunoreactive to the anti-AR antibody were identified in human placentae. Male placentae from controlled asthmatic pregnancies had increased AR-45 and decreased AR-V1 and AR-V7 nuclear expression. Increased nuclear AR-45 expression was associated with increased insulin-like growth factor 1 (IGF-1), IGF-1 receptor (IGF-1R), and IGF-binding protein 5 (IGFBP-5) mRNA expression and normal male growth. AR-45 mRNA and protein did not change in the presence of uncontrolled maternal asthma and associated with an increase in small for gestational (SGA) male fetuses. In vitro DHT stimulation increased AR-45 protein and IGF-1R and IGFBP-5 mRNA expression.

CONCLUSIONS

Collectively, our data shows altered AR protein expression and downstream signalling targets may contribute to sex-specific fetal growth outcomes in response to an adverse environment, and that AR-45 appears central in mediating these changes.

Molecular basis for prostate cancer racial disparities

Prostate cancer (PCa) remains the most common cancer in American men. African-American (AA) men continue to have higher PCa prevalence and mortality rates compared to men in other populations. In addition to socioeconomic factors and lifestyle differences, molecular alterations contribute to this discrepancy. We summarize molecular genetics research results interrelated with the biology of PCa racial disparity. Androgen and androgen receptor (AR) pathways have long been associated with prostate growth. Racial differences have also been found among variants of genes of the enzymes involved in androgen biosynthesis and metabolism. Growth factors and their receptors are a potential cause of the disparity in PCa. Recent molecular and biotechnological approaches in the field of proteomics and genomics will greatly aid the advancement of translational research on racial disparity in PCa, which may help, in finding new prognostic markers and novel therapeutic approaches for the treatment of PCa in AA.

The C-terminus of IGFBP-5 suppresses tumor growth by inhibiting angiogenesis

Insulin-like growth factor-binding protein 5 (IGFBP-5) plays a role in cell growth, differentiation, and apoptosis. In this study, we found that IGFBP5 was markedly downregulated in ovarian cancer tissue. We investigated the functional significance of IGFBP-5 as a tumor suppressor. To determine functional regions of IGFBP-5, truncation mutants were prepared and were studied the effect on tumor growth. Expression of C-terminal region of IGFBP-5 significantly decreased tumor growth in an ovarian cancer xenograft. A peptide derived from the C-terminus of IGFBP-5 (BP5-C) was synthesized to evaluate the minimal amino acid motif that retained anti-tumorigenic activity and its effect on angiogenesis was studied. BP5-C peptide decreased the expression of VEGF-A and MMP-9, phosphorylation of Akt and ERK, and NF-kB activity, and inhibited angiogenesis in in vitro and ex vivo systems. Furthermore, BP5-C peptide significantly decreased tumor weight and angiogenesis in both ovarian cancer orthotopic xenograft and patient-derived xenograft mice. These results suggest that the C-terminus of IGFBP-5 exerts anti-cancer activity by inhibiting angiogenesis via regulation of the Akt/ERK and NF-kB–VEGF/MMP-9 signaling pathway, and might be considered as a novel angiogenesis inhibitor for the treatment of ovarian cancer.

microRNA -140-5p inhibits colorectal cancer invasion and metastasis by targeting ADAMTS5 and IGFBP5

Background

Colorectal cancer (CRC) is one of the most common malignancies in the world. microRNA-140-5p (miR-140) has been shown to be involved in cartilage development and osteoarthritis (OA) pathogenesis. Some contradictions still exist concerning the role of miR-140 in tumor progression and metastasis, and the underlying mechanism is uncertain.

Methods

Immunohistochemistry was performed to determine the expressions of ADAMTS5 and IGFBP5 in CRC tissues. Human CRC cell lines HCT116 and RKO were transfected with miR-140 mimic, inhibitor, or small interfering RNA (siRNA) against ADAMTS5 or IGFBP5, respectively, using oligofectamine or lipofectamine 2000. Scratch-wound assay and transwell migration and invasion assays were used to evaluate the effects of miR-140 on the capabilities of migration and invasion. The levels of miR-140 and ADAMTS5 and IGFBP5 mRNA were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to examine the expression of ADAMTS5 and IGFBP5 proteins.

Results

miR-140 was significantly reduced, whereas ADAMTS5 and IGFBP5 were upregulated, in the human CRC tissues compared to the corresponding normal colorectal mucosa. miR-140 downregulation and ADAMTS5 or IGFBP5 overexpression were associated with the advanced TNM stage and distant metastasis of CRC. There was a reverse correlation between miR-140 levels and ADAMTS5 and IGFBP5 expression in CRC tissues. ADAMTS5 and IGFBP5 were downregulated by miR-140 at both the protein and mRNA levels in the CRC cell lines. The gain-of- and loss-of-function studies showed that miR-140 inhibited CRC cell migratory and invasive capacities at least partially via downregulating the expression of ADAMTS5 and IGFBP5.

Conclusions

These findings suggest that miR-140 suppresses CRC progression and metastasis, possibly through downregulating ADAMTS5 and IGFBP5. miR-140 might be a potential therapeutic candidate for the treatment of CRC.

Roles for the backdoor pathway of androgen metabolism in prostate cancer response to castration and drug treatment

Almost all men who present with advanced prostate cancer (CaP) and many men who fail potentially curative therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. The goal of this review is to describe the evolution of adrenal androgen blockade, how new androgen measurement methods have furthered understanding of androgen metabolism, and how further understanding of the backdoor pathway of androgen metabolism may lead to interventions that extend survival even more.

The Lsktm1 locus modulates lung and skin tumorigenesis in the mouse

Alleles derived from skin tumor−resistant Car-R mice provide resistance to both skin and lung tumorigenesis over the susceptibility of the SWR/J strain. In an effort to map tumor modifier loci affecting both tumor types, we carried out a genetic linkage analysis in backcross SWR/J x (SWR/J x Car-R) mice and identified a locus (Lsktm1) on chromosome 1 linked to both skin (LOD score = 3.93) and lung (LOD score = 8.74) tumorigenesis. Two genes, Igfbp5 and Igfbp2, residing in this locus and belonging to the insulin-like growth factor binding protein family were expressed at significantly greater levels in normal lung tissue from cancer-resistant Car-R mice than in cancer-susceptible SWR/J mice. Overexpression of the recombinant Igfbp5 and Igfbp2 genes in two lung cancer cell lines significantly inhibited clonogenicity (P < 0.0001). Collectively, we have identified a single polymorphic locus that affects skin and lung tumorigenesis and identify Igfbp5 and Igfbp2 as candidate modifier genes of lung tumorigenesis.

ERK regulates calpain 2-induced androgen receptor proteolysis in CWR22 relapsed prostate tumor cell lines

Androgen ablation therapy is effective in treating androgen-dependent prostate tumors; however, tumors that can proliferate in castrate levels of androgen eventually arise. We previously reported that in CWR22Rv1 (Rv1) cells, the protease calpain 2 can cleave the androgen receptor (AR) into a constitutively active approximately 80,000 low molecular weight (LMW) form. In this study, we further dissect the mechanisms that produce the AR LMW forms using Rv1 cells and the related CWR22-R1 (R1) cells. The 39-amino acid insertional mutation in the Rv1-AR (E3DM-AR) sensitizes this AR to calpain 2 proteolysis. R1 cells encode the same AR molecule as the parental CWR22 xenograft. Using calpain 2 small interfering RNA and calpeptin, we find that calpain 2 plays a role in the generation of the LMW-AR in R1 cells. Furthermore, LMW-AR expression is regulated by the activation of calpain 2 by ERK 1 and 2. Inhibition of ERK phosphorylation or small interfering RNA-mediated decrease of ERK expression reduces LMW-AR levels in R1 cells. Conversely, activation of the MAPK pathway results in increased ERK phosphorylation and increased levels of LMW-AR. Finally, analyses of human tumor samples found that LMW-AR levels are higher in tumors that have an increased calpain/calpastatin ratio and/or increased levels of phospho-ERK (pERK). This suggests that a higher calpain/calpastatin ratio collaborates with activated ERK to promote the generation of the LMW-AR.

The impact of diabetes type 2 in the pathogenesis of benign prostatic hyperplasia: a review

Introduction. Clinical observation of larger prostate glands in men with diabetes mellitus type 2 led some investigators to hypothesize that an association between these two conditions exists. In fact, both diseases are very common in men as they age and seem to be sharing similar epidemiologic features. Several studies examining the above hypothesis were yielded. Aim. The purpose of this paper is to summarize the existing literature focusing on the coexistence of BPH and diabetes mellitus type 2 and to elucidate whether or not an association among these conditions exists. Methods. We identified studies published from 1990 onwards by searching the MEDLINE database of the National Library of Medicine. Initial search terms were benign prostatic hyperplasia, epidemiology, and risk factor, combined with diet hyperinsulinemia, and diabetes mellitus type 2. Results. Diabetes mellitus type 2 and hyperinsulinemia are quite common conditions and often coexist with BPH. There are several studies (observational, epidemiological, and experimental) examining the association between them in literature. Conclusion. Evidence suggests that an association between BPH and diabetes through a common pathogenic mechanism is possible. The specific pathway interfering in the development of both conditions is still poorly investigated; thus, the exact relationship of BPH to diabetes remains unclear.

Oncogenic activation of androgen receptor

BACKGROUND

There is considerable evidence implicating the aberrant activation or "reactivation" of androgen receptor in the course of androgen-ablation therapy as a potential cause for the development of castration-resistant prostate cancer. Several non-mutually exclusive mechanisms including the inappropriate activation of androgen receptor (AR) by non-steroids have been postulated. The present work is aimed to understand the role of neuropeptides released by neuroendocrine transdifferentiated prostate cancer cells in the aberrant activation of AR.

OBJECTIVES

The study was designed to study how neuropeptides such as gastrin-releasing peptide activate AR and to define the crucial signal pathways involved, in the hope to identify therapeutic targets.

METHODS AND MATERIALS

Androgen-dependent LNCaP cell line was used to study the effects of bombesin/gastrin-releasing peptide on the growth of the cell line and the transactivation of AR. The neuropeptide was either added to the media or introduced as a transgene in LNCaP cells to study its paracrine or autocrine effect on LNCaP growth under androgen-deprived conditions. The activation of AR was monitored by reporter assay, chromatin immunoprecipitation (ChIP) of AR, translocation into the nucleus and cDNA microarray of the AR response genes.

RESULTS

Bombesin/gastrin releasing peptides induce androgen-independent growth of LNCaP in vitro and in vivo. It does so by activating AR, which is accompanied by the activation of Src tyrosine kinase and its target c-myc oncogene. The bombesin or Src-activated AR induces an overlapping set of AR response genes as androgen, but they also a unique set of genes. Intriguingly, the Src-activated and androgen-bound ARs differ in their binding specificity toward AR response elements, indicating the receptors activated by these 2 mechanisms are not conformationally identical. Finally, Src inhibitor was shown to effectively block the activation of AR and the growth effects induced by bombesin.

CONCLUSION

The results showed that AR can be activated by neuropeptide, a ligand for G-protein coupled receptor, in the absence of androgen. The activation goes through Src-tyrosine kinase pathway, and tyrosine kinase inhibitor is a potentially useful adjunctive therapy during androgen ablation.

Phthoxazolin A inhibits prostate cancer growth by modulating tumor-stromal cell interactions

Because stroma in tumor tissues can promote prostate cancer development, modulation of tumor-stromal cell interactions may represent an attractive new strategy for cancer treatment. Here, we report that phthoxazolin A and its analog inthomycin B inhibit the growth of human prostate cancer DU-145 cells by modulating tumor-stromal cell interactions. Using an in vitro coculture system, in which prostate cancer cell growth is upregulated by prostate stromal cells (PrSC), we found that phthoxazolin A and inthomycin B strongly inhibited the growth of DU-145 cells when in coculture with PrSC compared to DU-145 cells cultured alone. Although PrSC consist of both fibroblasts and myofibroblasts, phthoxazolin A and inthomycin B inhibited the expression of smooth muscle alpha-actin, a myofibroblast marker, without affecting vimentin and beta-actin expression. Because myofibroblasts secrete various factors that can promote tumor cell growth, we examined whether the inhibitory compounds affected the secretion of such factors from PrSC. Proteomic analysis and reverse transcription-polymerase chain reaction revealed that phthoxazolin A and inthomycin B inhibited the expression of several insulin-like growth factor binding proteins and insulin-like growth factor (IGF)-I by PrSC. Transforming growth factor-beta1 increased myofibroblast numbers and IGF-I levels in PrSC. Phthoxazolin A inhibited transforming growth factor-beta1 activity without altering phosphorylation of the downstream molecule smad2. Furthermore, conditioned medium from phthoxazolin A-treated PrSC failed to increase the phosphorylation of IGF-IR and Akt in DU-145 cells. Taken together, our results suggested that phthoxazolin A acts as a small-molecule modulator of tumor-stromal cell interactions that can indirectly suppress prostate cancer cell growth through inhibition of IGF-I production by PrSC.

Multifunctional roles of insulin-like growth factor binding protein 5 in breast cancer

The insulin-like growth factor axis, which has been shown to protect cells from apoptosis, plays an essential role in normal cell physiology and in cancer development. The family of insulin-like growth factor binding proteins (IGFBPs) has been shown to have a diverse spectrum of functions in cell growth, death, motility, and tissue remodeling. Among the six IGFBP family members, IGFBP-5 has recently been shown to play an important role in the biology of breast cancer, especially in breast cancer metastasis; however, the exact mechanisms of action remain obscure and sometimes paradoxical. An in-depth understanding of IGFBP-5 would shed light on its potential role as a target for breast cancer therapeutics.

Regulation of global gene expression in the bone marrow microenvironment by androgen: androgen ablation increases insulin-like growth factor binding protein-5 expression

BACKGROUND

Prostate cancer frequently metastasizes to bone. Androgen suppression treatment is initially highly effective, but eventually results in resistant cancer cells. This study evaluates the effects of androgen suppression on the bone and bone marrow (BM). In particular we questioned whether the androgen therapy could adversely facilitate prostate cancer progression through an increase growth factor secretion by the bone microenvironment.

METHODS

Global gene expression is analyzed on mPEDB DNA microarrays. Insulin-like growth factor binding protein-5 (IGFBP5) is detected by immunohistochemistry in mouse tissues and its regulation measured by qPCR and Western blotting in human BM stromal cells. Effects of extracellular matrix-associated IGFBP5 on human prostate epithelial cells are tested in an MTS cell-growth assay.

RESULTS

Castration increases expression of 159 genes (including 4 secreted cytokines) and suppresses expression of 84 genes. IGFBP5 is most consistently increased and the increase in expression is reversed by testosterone administration. IGFBP5 protein is detected in vivo in osteoblasts, BM stromal cells, and endothelial cells. Primary human stromal cell cultures secrete IGFBP5. In vitro, treatment of immortalized human marrow stromal cells with charcoal-stripped serum increases IGFBP5 mRNA expression, which is reversed by androgen supplementation. IGFBP5 is incorporated into the extracellular matrix. Further, IGFBP5 immobilized on extracellular matrices of stromal cells enhances the growth of immortalized prostate epithelial cells.

CONCLUSIONS

Androgen suppressive therapy increases IGFBP5 in the BM microenvironment and thereby may facilitate the progression of prostate cancer.

Feasibility of constructing tissue microarrays from diagnostic prostate biopsies

OBJECTIVES

The ability to construct prostate tissue microarrays (TMAs) using prostate needle biopsies could allow high throughput molecular profiling to search for prostate cancer prognostic biomarkers.

MATERIALS AND METHODS

Diagnostic prostate biopsies from 13 patients (diagnosed 1996-2000) were obtained from the University of North Carolina (UNC) to construct one prostate TMA under uniform conditions. A second prostate TMA was attempted using diagnostic prostate biopsies from 45 patients (diagnosed 2004) obtained from the North Carolina-Louisiana Prostate Cancer Project (PCaP).

RESULTS

Eleven men had sufficient prostate cancer in their diagnostic prostate biopsy blocks to construct a UNC TMA that yielded six-micron sections that provided an average of 76% of cores (maximum 99%) to a depth of 360 microm. Diagnostic prostate biopsy blocks from 35 PCaP research subjects were unsuitable for TMA construction as a result of no remaining prostate cancer in 4, insufficient prostate cancer in 9, and insufficient prostate tissue in 22. The PCaP TMA constructed from 10 men yielded an average of 37%, and a maximum of 45%, of cores when sectioned to a depth of 360 microm.

CONCLUSIONS

TMAs may be constructed from diagnostic prostate biopsies obtained at an academic center under uniform conditions. However, excessive facing of blocks and the large number of re-cuts ordered by many community pathology laboratories deplete diagnostic prostate biopsy tissue. The experience of a population-based study of men with newly diagnosed prostate cancer in Louisiana and North Carolina suggests that TMAs may not be constructed using diagnostic prostate biopsies from men diagnosed with prostate cancer throughout the United States.

Clinical implications of neuroendocrine differentiation in prostate cancer

The cellular signaling pathways of the prostate play a central role in the induction, maintenance, and progression of prostate cancer (CaP). Neuroendocrine (NE) cells demonstrate attributes that suggest they are an integral part of these signaling cascades. We summarize what is known regarding NE cells in CaP focusing on NE cellular transdifferentiation. This significant event in CaP progression appears to be accelerated by androgen deprivation (AD) treatment. We examine biochemical pathways that may impact NE differentiation in a chronological manner focusing on AD therapy (ADT) as a central event in inducing androgen-independent CaP. Our analysis is limited to the common adenocarcinoma pattern of CaP and excludes small-cell and carcinoid prostatic variants. In conclusion, we speculate on the future of treatment and research in this area.

Regulation of multiple insulin-like growth factor binding protein genes by 1alpha,25-dihydroxyvitamin D3

Recently, insulin-like growth factor binding proteins (IGFBPs) have been found to be primary mediators of the anti-proliferative actions of the nuclear hormone 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3], but dependent on cellular context IGFBPs can also have a mitogenic effect. In this study, we performed expression profiling of all six human IGFBP genes in prostate and bone cancer cells and demonstrated that IGFBP1, 3 and 5 are primary 1alpha,25(OH)2D3 target genes. In silico screening of the 174 kb of genomic sequence surrounding all six IGFBP genes identified 15 candidate vitamin D response elements (VDREs) close to or in IGFBP1, 2, 3 and 5 but not in the IGFBP4 and 6 genes. The putative VDREs were evaluated in vitro by gelshift assays and in living cells by reporter gene and chromatin immuno-precipitation (ChIP) assays. Of these 10 VDREs appear to be functional. ChIP assays demonstrated for each of these an individual, stimulation time-dependent association profile not only with the vitamin D receptor, but also with first heterodimeric partner the retinoid X receptor, other regulatory complex components and phosphorylated RNA polymerase II. Some of the VDREs are located distantly from the transcription start sites of IGFBP1, 3 and 5, but all 10 VDREs seem to contribute to the regulation of the genes by 1alpha,25(OH)2D3. In conclusion, IGFBP1, 3 and 5 are primary 1alpha,25(OH)2D3 target genes that in intact cells are each under the control of multiple VDREs.

Comparative effects of DHEA vs. testosterone, dihydrotestosterone, and estradiol on proliferation and gene expression in human LNCaP prostate cancer cells

Serum levels of the adrenal androgen dehydroepiandrosterone (DHEA) peak in men and women in the third decade of life and decrease progressively with age. Increasing numbers of middle-aged and older individuals consume over-the-counter preparations of DHEA, hoping it will retard aging by increasing muscle and bone mass and strength, decreasing fat, and improving immunologic and neurobehavioral functions. Because DHEA can serve as a precursor to more potent androgens and estrogens, like testosterone (T), dihydrotestosterone (DHT), and 17beta-estradiol (E2), supplemental DHEA use may pose a cancer risk in patients with nascent or occult prostate cancer. The steroid-responsive human LNCaP prostate cancer cells, containing a functional but mutated androgen receptor (AR), were used to compare effects of DHEA with those of T, DHT, and E2 on cell proliferation and protein and/or gene expression of AR, prostate-specific antigen (PSA), IGF-I, IGF-I receptor (IGF-IR), IGF-II, IGF-binding proteins-2, -3, and -5, (IGFBPs-2, -3, and -5), and estrogen receptor-beta (ERbeta). Cell proliferation assays revealed significant stimulation by all four steroids. DHEA- and E2-induced responses were similar but delayed and reduced compared with that of T and DHT. All four hormones increased gene and/or protein expression of PSA, IGF-IR, IGF-I, and IGFBP-2 and decreased that of AR, ERbeta, IGF-II, and IGFBP-3. There were no significant effects of hormone treatment on IGFBP-5 mRNA. DHEA and E2 responses were similar, and distinct from those of DHT and T, in time- and dose-dependent studies. Further studies of the mechanisms of DHEA effects on prostate cancer epithelial cells of varying AR status, as well as on prostate stromal cells, will be required to discern the implications of DHEA supplementation on prostatic health.

CELL LINES USED IN PROSTATE CANCER RESEARCH: A COMPENDIUM OF OLD AND NEW LINES—PART 2

PURPOSE

This is part 2 of a 2-part review. Research into the molecular mechanisms underlying the various aspects of prostate cancer (PCa) requires the use of in vivo and in vitro model systems. In the last few years many new cell lines have been established by investigators from primary tissue sources and clonal derivatives of previously established lines. Therefore, the purpose of this 2-part review is to catalogue the current human cell lines developed for PCa research, as reported in the literature. Part 2 describes tissue culture cell lines derived by the insertion of transgenes, including human telomerase reverse transcriptase, SV40 T antigen and human papillomavirus genes. Part 2 also includes xenograft lines that require propagation and passage in vivo in mice.

MATERIALS AND METHODS

Prostate cell lines included in this review were identified by extensive searching of the literature using several strategies, including PubMed searches and book chapter reviews.

RESULTS

In total we describe the derivation, phenotype, genotype and characterization of molecular markers expressed by approximately 200 lines and sublines used in PCa research, including ones derived from primary tumors, metastases and normal prostate tissue. We paid particular attention to the expression of prostate specific antigen, androgen receptor, cytokeratins and other molecular markers used to indicate the status of PCa and the prostatic lineage of a given line. In an attempt to provide PCa researchers with a resource of information regarding new and established cell lines we have also created an online database of these PCa cell lines freely accessible via the World Wide Web at http://www.CaPCellLines.com. The web based interface allows researchers to peruse and print information regarding cell lines, add new cell lines and update or add new information regarding established cell lines.

CONCLUSIONS

This compendium of cell lines currently used in PCa research combined with access to our on-line database provides researchers with a continually updated and valuable resource for investigating the molecular mechanisms of PCa.

Insulin-like growth factor-binding protein-5 induces a gender-related decrease in bone mineral density in transgenic mice

IGF-binding protein-5 (IGFBP-5) is abundant in serum and bone during normal skeletal development, but levels decrease in osteoporosis. Studies have shown that IGFBP-5 stimulates markers of bone formation by potentiating IGF actions and by IGF-independent actions. To test the hypothesis that IGFBP-5 promotes the acquisition of bone mineral density (BMD), we generated transgenic (Tg) mice overexpressing Igfbp5 using a cytomegalovirus enhancer and beta-actin promoter (CMV/betaA). Tg animals showed an increase in serum IGFBP-5 concentrations by 7.7- to 3.5-fold at 3-8 wk of age, respectively. Concentrations were 6-49% higher for males compared with females in both wild-type and Tg mice. Surprisingly, BMD decreased in a gender-dependent manner, with Tg male adults affected more severely than Tg females (31.3% vs. 19.2% reduction, respectively, compared with wild-type mice, assessed by dual energy x-ray absorptiometry). Significant gender differences in BMD were confirmed by peripheral quantitative computed tomography. Histomorphometry revealed that although the bone formation rate and mineralizing surface at the periosteum decreased in Tg mice, they increased at the endosteum, suggesting opposing effects of IGFBP-5 on periosteal and endosteal osteoblasts (by altering proliferation or survival). These findings differ from previous observations in Igf1- and Igf2-null animals. In conclusion, IGFBP-5 has a significant influence on BMD acquisition and maintenance that is dependent on gender and age. The phenotype of Igfbp5 mice cannot be explained solely by IGF inhibition; thus, this study provides the first in vivo evidence, by genetic manipulation, for IGF-independent actions of IGFBP-5 in bone function. These findings have implications for the gender-biased progression of osteoporosis.

The androgen axis in recurrent prostate cancer

PURPOSE

Prostate cancer that recurs during androgen deprivation therapy is referred to as androgen-independent. High levels of expression of androgen receptor and androgen receptor-regulated genes in recurrent prostate cancer suggest a role for androgen receptor and its ligands in prostate cancer recurrence.

EXPERIMENTAL DESIGN

Recurrent prostate cancer specimens from 22 men whose prostate cancer recurred locally during androgen deprivation therapy and benign prostate specimens from 48 men who had received no prior treatment were studied. Androgen receptor expression was measured using monoclonal antibody and automated digital video image analysis. Tissue androgens were measured using radioimmunoassay.

RESULTS

Epithelial nuclei androgen receptor immunostaining in recurrent prostate cancer (mean optical density, 0.284 +/- SD 0.115 and percentage positive nuclei, 83.7 +/- 11.6) was similar to benign prostate (mean optical density, 0.315 +/- 0.044 and percentage positive nuclei, 77.3 +/- 13.0). Tissue levels of testosterone were similar in recurrent prostate cancer (2.78 +/- 2.34 pmol/g tissue) and benign prostate (3.26 +/- 2.66 pmol/g tissue). Tissue levels of dihydrotestosterone, dehydroepiandrosterone, and androstenedione were lower (Wilcoxon, P = 0.0000068, 0.00093, and 0.0089, respectively) in recurrent prostate cancer than in benign prostate, and mean dihydrotestosterone levels, although reduced, remained 1.45 nM. Androgen receptor activation in recurrent prostate cancer was suggested by the androgen-regulated gene product, prostate-specific antigen, at 8.80 +/- 10.80 nmol/g tissue.

CONCLUSIONS

Testosterone and dihydrotestosterone occur in recurrent prostate cancer tissue at levels sufficient to activate androgen receptor. Novel therapies for recurrent prostate cancer should target androgen receptor directly and prevent the formation of androgens within prostate cancer tissue.

Protein kinase Cepsilon interacts with Bax and promotes survival of human prostate cancer cells

Prostatic glandular epithelial cells express protein kinase Cepsilon (PKCepsilon ), an oncoprotein that coordinately disrupts the reactivation of the tumor suppressor Rb, derepressess transcriptional elongation of the c-myc oncogene, and propagates survival signals in LNCaP cells. Since the activation of such a program may contribute to the progression of human prostate cancer, a proteomic analysis was performed to gain a more global perspective on the signaling network that PKCepsilon might be capable of engaging in prostate cancer cells. Using CWR22 xenografts, we identified at least 18 different structural, signaling, and stress-related proteins that associated with PKCepsilon, including an interaction with the proapoptotic protein Bax that was novel to recurrent CWR22 tumors. An investigation into the biological significance of the PKCepsilon association with Bax provided the first evidence of an inverse relationship between endogenous levels of PKCepsilon and susceptibility of prostate cancer cells to the apoptotic effects of phorbol esters. Western blot and antisense experiments demonstrated that CWR-R1 cells expressed moderate levels of PKCepsilon and relied on this protein to survive in the presence of phorbol esters, while the apoptosis normally induced by phorbol esters in PKCepsilon -deficient LNCaP cells was dependent on the presence of Bax. Forced expression of PKCepsilon in LNCaP cells was sufficient to confer a significant resistance to phorbol esters and this resistance was associated with an inhibition of phorbol ester-induced Bax conformational rearrangements that are important for Bax oligomerization, mitochondrial integration, and cytochrome c release. Considered in their entirety, our data suggest that an association of PKCepsilon with Bax may neutralize apoptotic signals propagated through a mitochondrial death-signaling pathway.

Identification of differentially expressed genes associated with androgen-independent growth of prostate cancer

BACKGROUND

The human prostate cancer xenograft, CWR22, similar to most human prostate cancers, regresses after castration and recurs several months after the removal of androgen. Genes uniquely associated with proliferation were identified by comparison of tumors that exist in androgen absence but differ in proliferative capacity.

METHODS

cDNA libraries from CWR22 tumors from 20-day castrate mice (proliferation undetectable) and recurrent CWR22 tumors (proliferation rate similar to androgen-dependent CWR22) were compared to evaluate the possibility that proliferation is triggered by either gain of function or loss of suppression. Differentially expressed genes were evaluated further for their temporal association with the onset of cellular proliferation using northern and western analysis and immunohistochemistry of a series of CWR22 tumors that spanned the transition from androgen-dependent to recurrent growth.

RESULTS

Subtractive hybridization identified 11 candidate genes from among 1,057 clones examined. Northern analysis confirmed differential expression of 8 genes. Western analysis revealed an association between tomoregulin, translation elongation factor-1 alpha (EF-1 alpha), Mxi-1, and thioredoxin-binding protein 2/vitamin D up-regulated protein, and the onset of recurrent growth. Immunohistochemistry revealed expression of tomoregulin, EF-1 alpha, Mxi-1, and thioredoxin reductase-1 coincidental with the onset of cellular proliferation on day 120 after castration.

CONCLUSIONS

One or more of these genes may represent an appropriate target to prevent, delay or treat recurrent prostate cancer.

Neuroendocrine pathogenesis in adenocarcinoma of the prostate

BACKGROUND

In the prostate, the importance of sex hormones for its normal development and function is well known. However, it has been proposed that various neuroendocrine (NE) hormones and growth factors may be involved in the pathogenesis of prostatic carcinoma (CaP). Neuroendocrine differentiation appears to be associated with tumour progression and the androgen-independent state, for which there is currently no successful therapy. Therefore, we need to improve our understanding of NE cells, their regulatory products and influence on the prostate gland. Finally, new therapeutic protocols need to be developed.

METHODS

Information is presented on prostatic NE cells and neuroendocrine differentiation (NED) in prostatic carcinoma. Neuroendocrine secretory products and interactions with epithelial prostate cells are investigated in order to understand their significance for the pathogenesis of the prostate gland, prognosis and therapy.

RESULTS

Recent research suggests that NE-secreted products. such as serotonin, somatostatin and bombesin, may influence growth, invasiveness, metastatic processes and angiogenesis in CaP. During recent years. new experimental models for NED have been developed to provide evidence that NE products may promote proliferation and confer antiapoptotic capabilities on non-neuroendocrine cells in close proximity to NE cells. Cancerous epithelial cells may become more responsive to NE factors by upregulation of receptors for neuropeptides, or may induce NE cells to upregulate the secretion and synthesis of NE factors. In the androgen independent state, neuropeptides and their intracellular signals may activate the androgen receptor. Furthermore, androgen ablation may lead to downregulation of neural endopeptidase 24.11 (a zinc-dependent metalloproteinase) and PSA, which would lead to increased levels of NE products becoming available. These studies confirm that NE cells and NED may have a significant impact on prostate cancer, especially in the androgen independent state.

CONCLUSIONS

Recent developments in molecular biology and pathophysiology of prostate cancer have increased our understanding of the NE regulatory mechanisms. Hopefully, this will lead to the development of entirely new therapeutic modalities. For example, somatostatin agonists may suppress angiogenesis and proliferation, and simultaneously promote apoptosis in prostate cancer cells. Somatostatin may thus have an important role in tumour biology, and in the future there may be a potential role for somatostatin analogues in the treatment of prostate cancer, but also for serotonin and bombesin receptor antagonists. However, a review of the accumulated knowledge in this field suggests that we still need to improve our understanding of NE cells and their regulatory products and influence on the prostate gland. and that clinical trials are needed, to test drugs based on neuroendocrine hormones and their agonists/antagonists.

Androgen receptor expression and cellular proliferation during transition from androgen-dependent to recurrent growth after castration in the CWR22 prostate cancer xenograft

Androgen receptor expression was analyzed in the CWR22 human prostate cancer xenograft model to better understand its role in prostate cancer recurrence after castration. In androgen-dependent tumors, 98.5% of tumor cell nuclei expressed androgen receptor with a mean optical density of 0.26 +/- 0.01. On day 2 after castration androgen deprivation decreased immunostained cells to 2% that stained weakly (mean optical density, 0.16 +/- 0.08). Cellular proliferation measured using Ki-67 revealed <1% immunostained cells on day 6. Androgen receptor immunostained cells increased to 63% on day 6 and 84% on day 32 although immunostaining remained weak. Cellular proliferation was undetectable beyond day 6 after castration until multiple foci of 5 to 20 proliferating cells became apparent on day 120. These foci expressed increased levels of prostate-specific antigen, an androgen receptor-regulated gene product. In tumors recurrent 150 days after castration androgen receptor-immunostaining intensity was similar to CWR22 tumors from intact mice although the percentage of cells immunostained was more variable. The appearance of proliferating tumor cells that expressed androgen receptor and prostate-specific antigen 120 days after castration suggests that these cells represent the origin of recurrent tumors.

Insulin-like growth factor-binding protein-5 inhibits growth and induces differentiation of mouse osteosarcoma cells

The precise role of insulin-like growth factor-binding protein-5 (IGFBP-5) in regulating the growth of tumor cells, especially of bone-derived malignant cells, is not well understood. We have investigated the biological activity of IGFBP-5 by transfecting OS/50-K8 mouse osteosarcoma cells with an expression vector containing the osteocalcin promoter and the complete mouse IGFBP-5 cDNA (OC-IGFBP-5). Overexpression of IGFBP-5 mRNA and secretion of increased amounts of bioactive protein in conditioned media were demonstrated in different clones. For the analysis of cell proliferation, three clones exhibiting high levels of IGFBP-5 expression were selected and compared to a mock clone and to nontransfected parental cells. IGFBP-5-secreting clones displayed reduced proliferation under both anchorage-dependent and -independent conditions (P < 0.05). The increase in proliferation observed in IGFBP-5-secreting clones after addition of exogenous IGF was significantly lower than that observed in mock-transfected or parental cells. A similar result was obtained with long[R3]IGF-I which has a low affinity for all IGFBPs, suggesting that the inhibitory effect of IGFBP-5 is only partially IGF-dependent. OC-IGFBP-5-transfected clones expressed significantly higher amounts of osteocalcin mRNA (P < 0.05) and secreted more osteocalcin protein than a mock clone or parental OS-50/K8 cells. Thus, part of the growth-inhibiting effect of IGFBP-5 may be due to an induction of differentiation in these cells.

An 800-kb region of deletion at 13q14 in human prostate and other carcinomas

Deletions of regions at 13q14 have been detected by various genetic approaches in human cancers including prostate cancer. Several studies have defined one region of loss of heterozygosity (LOH) at 13q14 that seems to reside in a DNA segment of 7.1 cM between genetic markers D13S263 and D13S153. To define the smallest region of overlap (SRO) for deletion at 13q14, we first applied tissue microdissection and multiplex PCR to detect homozygous deletion and/or hemizygous deletion at 13q14 in 134 prostate cancer specimens from 114 patients. We detected deletions at markers D13S1227, D13S1272, and A005O48 in 13 (10%) of these tumor specimens. Of the 13 tumors with deletions, 12 were either poorly differentiated primary tumors or metastases of prostate cancer. To fine-map the deletion region, we then constructed a high-resolution YAC/BAC/STS/EST physical map based on experimental and database analyses. Several markers encompassing the deletion region were analyzed for homozygous deletion and/or hemizygous deletion in 61 cell lines/xenografts derived from human cancers of the prostate, breast, ovary, endometrium, cervix, and bladder, and a region of deletion was defined by duplex PCR assay between markers A005X38 and WI-7773. We also analyzed LOH at 13q14 in the 61 cell lines/xenografts using the homozygosity mapping of deletion approach and 26 microsatellite markers. We found 24 (39%) of the cell lines/xenografts to show LOH at 13q14 and defined a region of LOH by markers M1 and M5. Combination of homozygous or hemizygous deletion and LOH results defined the SRO for deletion to be an 800-kb DNA interval between A005X38 and M5. There are six known genes located in or close to the SRO for deletion. This region of deletion is at least 2 Mb centromeric to the RB1 tumor-suppressor gene and the leukemia-associated genes 1 and 2, each of which is located at 13q14. These data suggest that the 800-kb DNA segment with deletion contains a gene whose deletion may be important for the development of prostate and other cancers. This study also provides a framework for the fine-mapping, cloning, and identification of a novel tumor-suppressor gene at 13q14.

Primate epididymis-specific proteins: characterization of ESC42, a novel protein containing a trefoil-like motif in monkey and human

Epididymal secreted proteins promote sperm maturation and fertilizing capacity by interacting with sperm during passage through the epididymis. Here we investigate the molecular basis of sperm maturation by isolating cDNA clones for novel epididymis-specific expressed sequences. Thirty-six novel cDNAs were isolated and sequenced from a subtracted Macaca mulatta epididymis library. The clones encode proteins with a range of motifs characteristic of protein-modifying enzymes, protease inhibitors, hydrophobic ligand-binding and transport proteins, extracellular matrix-interacting proteins, and transcription regulatory factors. The full length coding sequences were obtained for 11 clones representing a range of abundance levels. Expression of each is regionally localized and androgen regulated. The most abundant, ESC42, contains a cysteine-rich region similar to the signature binding domain of the trefoil family of motogenic wound repair proteins. The monkey and human proteins are nearly 90% identical. Immunohistochemical staining revealed that the protein is most abundant in the epithelium of the caput and is also present in the lumen and bound to sperm. The ESC42 gene, located on chromosome 20q11, contains two exons encoding two nearly identical predicted signal peptides and a third exon encoding the rest of the protein.

Insulin-like growth factor binding protein 5 and type-1 insulin-like growth factor receptor are differentially regulated during apoptosis in cerebellar granule cells

Neuronal apoptosis is considered to play a significant role in several neuropathological conditions. However, the molecular mechanisms underlying neuronal apoptosis are poorly understood. Insulin-like growth factor (IGF) signalling is considered to be an important regulator of neuronal differentiation, survival and apoptosis. We have examined the expression of two members of the IGF system, insulin-like growth factor binding protein 5 (IGFBP-5) and the type-1 IGF receptor (IGF1R), during apoptosis of rat cerebellar granule cells (CGCs) in vitro. We describe a prominent downregulation of IGFBP-5 mRNA and protein expression. We also show that IGF-I increases IGFBP-5 expression in CGCs and that the downregulation of IGFBP-5 mRNA can be suppressed by inhibiting mRNA synthesis with actinomycin D. The expression of IGF1R mRNA showed a transient upregulation during potassium chloride (KCl) deprivation induced apoptosis, in contrast to the IGF1R protein level, which was downregulated during KCl deprivation. Our results provide insight into the expression of IGF-related genes during neuronal apoptosis, and indicate that they mediate a protective response to the withdrawal of trophic stimulation. It seems that the expression of IGFBP-5 and IGF1R is regulated to maximize the availability of IGF and the activity of IGF-triggered survival signalling.

Expression and function of androgen receptor in carcinoma of the prostate

This article reviews recent findings on androgen receptor expression, structure, and function in carcinoma of the prostate. In this decade, it became clear that androgen-resistant prostate cancers contain androgen receptors and, therefore, regulation of androgen receptor expression and function receives considerable attention. The article summarizes findings on regulation of androgen receptor expression by androgens, growth factors, and protein kinase A activators. In addition, modulation of function of the wild-type and mutant AR is discussed. Androgen receptor functional activity is up-regulated by androgens and nonsteroidal activators, which influence transcription of androgen receptor-regulated genes in a cell type-dependent manner. This study also contains a chapter on androgen receptor-associated proteins, coactivators, and coreppressors and their possible role in pathological situations.

Thyroid receptor activator molecule, TRAM-1, is an androgen receptor coactivator

An androgen receptor (AR) interacting protein was isolated from a HeLa cell complementary DNA library by two-hybrid screening in yeast using the AR DNA and ligand binding domains [amino acids (aa) 481-919] as bait. AR binding of the protein in yeast was dependent on the presence of testosterone or dihydrotestosterone (DHT). The isolated protein is identical to thyroid receptor activator molecule TRAM-1 but lacking aa 1-458. TRAM-1 is a steroid receptor coactivator-3 (SRC-3) subtype. In affinity matrix assays, 35S-labeled TRAM-1 bound the GST-AR ligand binding domain (aa 624-919) and GST-AR N-terminal and DNA binding domains (aa 1-660), but not the GST-AR DNA binding domain (aa 544-634) alone. Coexpression of TRAM-1 increased DHT-dependent AR transactivation 5-fold and constitutive activity of AR (aa 1-660) N-terminal and DNA-binding domains increased 9-fold. Full-length TRAM-1 (aa 1-1424) and the partial (aa 459-1424) were AR and GR coactivators as was SRC-1. In human testis, immunostaining of SRC-3 colocalized with AR in nuclei of Sertoli cells and peritubular myoid cells, indicating it could function as an AR coactivator in these cells. SRC-3 was also present in nuclei of spermatogenic cells where AR was not expressed, suggesting it might also be a coactivator with other nuclear receptors that regulate spermatogenesis.

Overexpression of insulin-like growth factor binding protein-5 helps accelerate progression to androgen-independence in the human prostate LNCaP tumor model through activation of phosphatidylinositol 3'-kinase pathway

Although insulin-like growth factor (IGF) binding protein-5 (IGFBP-5) is highly up-regulated in normal and malignant prostate tissues after androgen withdrawal, its functional role in castration-induced apoptosis and androgen-independent progression remains undefined. To analyze the functional significance of IGFBP-5 overexpression in IGF-I-mediated mitogenesis and progression to androgen-independence, IGFBP-5-overexpressing human androgen-dependent LNCaP prostate cancer cells were generated by stable transfection. The growth rates of IGFBP-5-transfected LNCaP cells were significantly faster, compared with either the parental or vector-only transfected LNCaP cells in both the presence and absence ofdihydrotestosterone. IGFBP-5-induced increases in LNCaP cell proliferation occurs through both IGF-I-dependent and -independent pathways, with corresponding increases in the cyclin D1 messenger RNA expression and the fraction of cells in S + G2/M phases of the cell cycle. Changes in Akt/protein kinase B, a downstream component of phosphatidylinositol 3'-kinase (PI3K) pathway, in the LNCaP sublines also paralleled changes in their growth rates. Although treatment with a PI3K inhibitor induced apoptosis in both control and IGFBP-5-overexpressing LNCaP cells, this PI3K inhibitor-induced apoptosis was prevented by exogenous IGF-I treatment only in IGFBP-5 transfectants, suggesting that IGFBP-5 overexpression can potentiate the antiapoptotic effects of IGF-I. Furthermore, tumor growth and serum prostate-specific antigen levels increased several fold faster in mice bearing IGFBP-5-transfected LNCaP tumors after castration, despite having similar tumor incidence and tumor growth rates with controls when grown in intact mice before castration. Collectively, these data suggest that IGFBP-5 overexpression in prostate cancer cells after castration is an adaptive cell survival mechanism that helps potentiate the antiapoptotic and mitogenic effects of IGF-I, thereby accelerating progression to androgen independence through activation of the PI3K-Akt/ protein kinase B signaling pathway.