Prostatic Dysplasia Research Articles

Dietary Soybean may be Antiestrogenic in Male Mice

We tested whether dietary soybeans alter prostatic growth and development of prostatic dysplasia in mice that were treated with a synthetic nonsteroidal estrogen, diethylstilbestrol during the first 3 d after birth. Soybeans were chosen because they contain substantial amounts of isoflavonic estrogens. The presence of estrogenic isoflavonoids in soybean-containing feed was confirmed by measuring the excretion of seven different plant estrogens in the urine of normal adult male mice. Estrogenicity of dietary soybean was confirmed by the growth response in uteruses of immature mice. In addition to their estrogenic effect, antiestrogenic properties of soybeans on uterine growth were observed in the presence of a more potent estrogenic growth stimulator, diethylstilbestrol in feed. In neonatally estrogenized male mice, soybean feeding reduced the prostatic growth inhibition due to diethylstilbestrol and, in preliminary experiments, delayed the development of dysplastic changes in the prostate. The number of animals showing severe dysplasia in prostatic epithelium was significantly lower in 9-mo-old animals given soybean-containing feed from fertilization onwards, but in 12 mo-old animals the difference was less obvious and was not significant. Our findings suggest an antiestrogenic action for dietary soybean in male mice, which may be important for the hormonal regulation of normal as well as neoplastic prostatic growth.

Role of Estrogen in Androgen-Induced Prostate Carcinogenesis in NBL Rats.

Androgens are thought to cause prostate cancer, but the underlying mechanisms are unclear. Data from animal studies suggest that for androgens to cause prostate cancer, they must be aromatized to estrogen and act in concert with estrogen metabolites. We tested the hypothesis that androgen-receptor and estrogen receptor-mediated effects of androgen and estrogen are necessary, as well as genotoxicity of estrogen metabolites. NBL rats were treated with androgenic and estrogenic compounds for 16-75weeks through slow-release silastic implants or pellets. Testosterone alone induced cancer in the prostate of 37% of rats. 5α-Dihydrotestosterone, which cannot be converted to estradiol or testosterone, did not cause a significant prostate cancer incidence (4%). Addition of estradiol to 5α-dihydrotestosterone treatment did not markedly enhance prostate cancer incidence (14%), unlike adding estradiol to testosterone treatment which induced a 100% tumor incidence. Testosterone plus estradiol treatment induced a DNA adduct detectable by 32P-postlabeling, oxidative DNA damage (8-hydroxyguanosine), and lipid peroxidation at the site within the prostate where this treatment causes cancers, preceding later cancer formation. The non-estrogenic 4-hydroxy metabolite of estradiol, when combined with testosterone, induced prostatic dysplasia within 16weeks and, after long-term treatment, a very low incidence of prostate cancer (21%). When an estrogen that cannot be hydroxylated (2-fluoroestradiol) was added to this combined treatment with testosterone and 4-hydroxyestradiol, dysplasia frequency after 16weeks was doubled. These results strongly support the hypothesis, but additional definitive studies are needed which may identify new targets to interfere with these mechanisms that are clinically feasible in humans.

Abstract 1382: Developmental exposure to BPA increases the prostate cancer susceptibility via reprogramming of androgen-responsive genes via increased H3K4me3 methylation

Abstract Background: Early life exposure to endocrine disrupting compounds (EDCs) during critical developmental periods increases susceptibility to cancer and other diseases in adulthood. Because EDC exposures cause life-long changes in gene expression of target tissues, identification of gene targets for developmental reprogramming holds promise for both understanding the etiology of environmental causes of cancer and development of biomarkers of EDC exposure. Aim: Our goal was to identify targets for developmental reprogramming in the prostate using a rat model for development of hormone-dependent early prostate (PIN) lesions induced by the EDC bisphenol A (BPA). Methods: Rats were exposed neonatally to vehicle or BPA and assessed at 12 months for development of hormone-dependent prostate lesions. Epigenetic status and gene expression were profiled in the at-risk (d70) adult prostate using CHIP- and RNA-seq, with qRT-PCR and ChIP used to confirm changes in gene expression and histone methylation (respectively). Results: As expected, BPA exposure significantly increased PIN lesions and the dysplasia score in 12 mo rats. CHIP-seq in adult rats (day 70) prior to lesion development showed a significant increase in histone H3, lysine 4 trimethylation (H3K4me3) levels in prostate cancer-associated KEGG pathway genes of rats exposed to BPA neonatally. Changes reflective of both increased basal, as well as hormone-induced, KEGG pathway gene expression were observed in BPA exposed animals at increased risk for development of PIN lesions. Conclusion: Neonatal BPA exposure reprograms the developing prostate to alter gene expression in adulthood and increase incidence and severity of prostatic dysplasia. Several KEGG-pathway prostate cancer pathway genes were identified as targets for epigenetic reprogramming, providing new tools for future studies to understand gene-environment interactions as determinants of prostate cancer risk. Citation Format: Quan Wang, Rebecca Lee Yean Wong, Donna F. Kusewitt, Maarten C. Bosland, Jing Chen, Mario Medvedovic, Gail S. Prins, Kurunthachalam Kannan, Shuk-Mei Ho, Cheryl Lyn Walker. Developmental exposure to BPA increases the prostate cancer susceptibility via reprogramming of androgen-responsive genes via increased H3K4me3 methylation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1382. doi:10.1158/1538-7445.AM2014-1382

The influence of growth hormone/insulin-like growth factor deficiency on prostatic dysplasia in pbARR2-Cre, PTEN knockout mice

Elevated insulin-like growth factor-I (IGF-I) serum levels and phosphatase and tensin homolog (PTEN) loss are prostate cancer (PCa) risk factors that enhance androgen-responsive and castration-resistant PCa xenografts growth. The impact of suppressed growth hormone (GH)/IGF-I levels on neoplastic initiation of PTEN-deficient prostate epithelia was assessed histologically and by epithelial-to-mesenchymal marker expression in Ghrhr D60G homozygous (lit/lit) and heterozygous (lit/+) pbARR2-Cre, PTEN(fl/fl) (PTEN-/-) mice. How suppressed GH/IGF-I levels impacted growth of PTEN-/- mouse-derived prostate cells (MPPK) was examined by growth and survival signaling of cells cultured in lit/+ or lit/lit serum. Body weight, prostate weight and serum GH and IGF-I levels were reduced in lit/lit relative to lit/+ PTEN-/- littermates. While the anterior lobes of lit/+ PTEN-/- prostates consistently presented swollen, indicative of ductal blockage, the degree of prostatic dysplasia in 15- and 20-week-old lit/lit and lit/+ PTEN-/- mice was indistinguishable as measured by normalized prostatic weight, tissue histology, or probasin, PSP94, E-cadherin, N-cadherin and vimentin expression. However, growth and AKT activation of MPPK cells was decreased when cultured in lit/lit serum as compared with lit/+ serum and restored in lit/lit serum supplemented with IGF-I and, to a lesser extent, GH. These results suggest that initiation of prostate carcinogenesis by loss of PTEN is not influenced by germline variation of genes encoding signaling molecules in the GH/IGF-I axis, but suggests that these factors may affect the progression of dysplastic phenotype and supports previous studies, indicating that the GH/IGF milieu does impact the growth of PTEN-deficient dysplastic prostatic cells once transformed.

Urologic Cancer Risks For Veterans Exposed To Agent Orange

Agent Orange, an herbicide widely used during the Vietnam War, has been linked to various health risks, including urologic malignancy. Exposed veterans are at risk for prostate cancer and may be entitled to compensation if diagnosed with prostate cancer. Current research studies are aimed at mitigating prostate dysplasia and prostate cancer

Abstract 3429: AKAP12/SSeCKS inhibits peritoneal metastasis by regulating chemokine production

Abstract AKAP12/SSeCKS/Gravin (AKAP12) is thought to act as a metastasis suppressor through its direct scaffolding of major signaling proteins such as PKC, PKA and Src, in a spatiotemporal manner (1). For example, AKAP12 inhibition of Src-mediated oncogenic signaling, including induction of VEGF secretion by tumor cells, correlates with inhibition of neovascularization at metastatic sites (2). We have established AKAP12-null (KO) mice and demonstrated that they are cancer-prone in regards to the formation of spontaneous prostatic dysplasia and to carcinogen-induced skin cancer formation (3, 4). However, the role of AKAP12 in host microenvironment in regards to tumor or metastasis control has yet to be elucidated. In this study, we utilized an orthotropic, subcutaneous injection model of B16F10 melanoma to address whether the loss of AKAP12 in the host facilitates metastasis. Although the size of the primary tumors was similar in WT vs. KO mice, KO mice exhibited increased rates of peritoneal metastasis. The peritoneal fluid (PF) of KO mice was more potent than WT-PF in inducing in vitro chemotaxis. Comparison of the cytokines/chemokines using antibody arrays showed a severe upregulation of multiple potential chemoattractants in the KO-PF, including CXCL9/10/11, known ligands for CXCR3, a chemokine receptor upregulated 12-fold in B16F10 versus the low-metastatic B16F0 variant. Pre-injection of KO-PF, but not WT-PF, into WT mice was sufficient to induce high levels of peritoneal metastasis from subcutaneous sites. Taken together, our study suggests that AKAP12 controls metastasis by regulating the production of chemoattractants in the peritoneum, produced either by local microenvironmental cells or by recruited inflammatory cells.

The influence of growth hormone/insulin-like growth factor deficiency on prostatic dysplasia in pbARR2-cre PTEN knockout mice.

66 Background: Signaling through GH/IGF-I axis has been linked to PCa risk. The GH/IGF-I axis is an important regulator of growth, survival, and metastatic potential in a variety of malignancies and is strongly implicated in PCa etiology. A range of therapeutic approaches including reducing ligand availability by GH antagonist, IGF-I antibodies, and recombinant IGFBPs, reducing IGF-1R expression by antisense and RNA interference, or inhibiting of IGF-1R signaling by IGF-1R antibodies and small molecule tyrosine kinase inhibitors are under investigation in PCa. Methods: To investigate the role of GH/IGF-I axis on in vivo prostate carcinogenesis and neoplastic progression, we crossed pbARR2-Cre, PTEN(fl/fl) mice (PTEN-/-) with IGF-I deficient lit mice, and produced lit/lit and lit/+ PTEN-/- mice. To complement the in vivo experiments, in vitro growth and growth factor signaling of murine PTEN-/- cells derived from the prostate (MPPK) using serum from lit/lit or lit/+ mice was examined. Results: No obvious differences in prostatic dysplasia were observed in lit/lit mice at 15 and 20 weeks of age when compared to lit/+ littermates measured as normalized prostatic wet weight or for expression of the murine prostatic differentiation markers, probasin and PSP94. However the rate of decreased expression of E-cadherin and increased expression of N-cadherin was slightly delayed in PTEN-/- prostates from lit/lit mice as compare to lit/+ mice. In vitro, growth of MPPK cells was decreased when cultured in serum from lit/lit mice as compared with serum from lit/+ mice. Suppressed growth of MPPK cells in lit/lit serum could be restored by addition of IGF-I, and to a lesser extent, GH. Addition of GH or IGF-I to lit/lit serum increased steady-state activation of AKT without affecting ERK1/2 activation. Conclusions: Our data suggest that initiation of prostate carcinogenesis by loss of PTEN is not influenced by germ line variation of genes encoding signaling molecules in the GH/IGF-I axis, but suggests that such factors may affect the progression of dysplasic phenotype.

The effects of XMRV gene expression on the mouse prostate

Xenotropic murine leukemia virus related virus (XMRV) has been the subject of intense investigation since its discovery and initial characterization in human prostate carcinoma. Notwithstanding the important and ongoing controversies surrounding detection methods, seroprevalence, disease association, or viral origin, we sought to determine whether XMRV gene expression was sufficient to promote prostate pathology in a transgenic mouse model. Using the probasin promoter to drive prostate specific expression of XMRV genes in a transgenic mouse (PRO-XMRV) in vivo, we compared prostates of age matched male littermates over time. Using immunohistochemistry to stain envelope proteins we have been able to detect XMRV gene expression in the prostate of 3 of 3, 11-15 month old mice with the highest levels found in the lateral lobes. The lateral lobes also exhibit thickened layers of glandular epithelia that contain elevated numbers of bromodeoxyuridine retaining cells. While this model produces wild-type particles that can be detected in the urine by RT-PCR, infection is not thought to be occurring due to the absence of the receptor, XPR-1, in mouse cells. To determine if viral infection and integration is required for XMRV-related prostate pathology, we have also created a transgenic strain in which XPR-1 is expressed in the mouse prostate (PRO-XPR1). Breeding PRO-XMRV mice with PRO-XPR1 mice will allow us to test whether XMRV integration or gene expression can cause more advanced prostate pathology in vivo. With these XMRV mouse models we seek to address the question that remains unanswered to date as to whether XMRV is capable of causing prostate dysplasia or cancer in vivo.

Gene Expression Profiling Identifies Lobe-Specific and Common Disruptions of Multiple Gene Networks in Testosterone-Supported, 17β-Estradiol- or Diethylstilbestrol-Induced Prostate Dysplasia in Noble Rats

The xenoestrogen diethylstilbestrol (DES) is commonly believed to mimic the action of the natural estrogen 17beta-estradiol (E2). To determine if these two estrogens exert similar actions in prostate carcinogenesis, we elevated circulating levels of estrogen in Noble (NBL) rats with E(2/DES-filled implants, while maintaining physiological levels of testosterone (T) in the animals with T-filled implants. The two estrogens induced dysplasia in a lobe-specific manner, with E2 targeting only the lateral prostate (LP) and DES impacting only the ventral prostate (VP). Gene expression profiling identified distinct and common E2-disrupted versus DES-disrupted gene networks in each lobe. More importantly, hierarchical clustering analyses revealed that T + E2 treatment primarily affected the gene expression pattern in the LP, whereas T + DES treatment primarily affected the gene expression profile in the VP. Gene ontology analyses and pathway mapping suggest that the two hormone treatments disrupt unique and/or common cellular processes, including cell development, proliferation, motility, apoptosis, and estrogen signaling, which may be linked to dysplasia development in the rat prostate. These findings suggest that the effects of xenoestrogens and natural estrogens on the rat prostate are more divergent than previously suspected and that these differences may explain the lobe-specific carcinogenic actions of the hormones.

CYR61, a cellular proliferation marker in dogs with prostatic disease

The life expectancy of dogs is increasing and is associated with a greater frequency of age-related disease, including that of the prostate gland. A marker of cell proliferation, CYR61, may be detected in a number of conditions in humans, including hyperplasia and neoplasia. The objective of the present study was to investigate the degree of CYR61 expression in a number of different prostate diseases in dogs in order to understand the potential of this marker for diagnosis of prostatic disease. Immunohistochemistry with a CYR61 antibody was performed on prostatic tissue from 22 dogs with different diseases. Intense stromal staining was observed in cases of prostatic dysplasia and benign prostate hyperplasia. In contrast, CYR61 staining was very intense in alveolar epithelial cells in cases of epithelial benign prostate hyperplasia and one case of adenocarcinoma. An obvious CYR61 staining pattern was absent in cases of prostatitis. In conclusion, CYR61 may be a useful marker of cell proliferation in a number of prostatic pathologies, although further studies of normal tissue are warranted.

COX-1 and -2 Expressions in Sex-Related Organs of Neonatally Estrogen-Treated Rats and in Activated and Nonactivated Macrophage RAW264.7 Cells with Phytoestrogen

Cyclooxygenase (COX)-2 is an inducible isoform, expressed in inflamed leukocytes and cancer cells. It is known that estrogen causes prostate dysplasia, but little is known about COX-2 expression and its influence on male reproductivity. In this study, we show that COX-2 was abolished in the distal end of the vas deferens in neonatally estrogenized (diethylstilbestrol, NeoDES) Sprague-Dawley (SD) rats at age of 15 mo, but the control normal rats were found to remain constitutive expression at the same age, while the levels of COX-1 in these rats remained intact. Furthermore, BAX, an indicator of sperm quality, was observed in the endothelium of vas deferens and sperm of the aged rats. However, COX-2 was not detected in the inflamed lesions of NeoDES rat's prostate by immunohistochemistry. In addition to estrogen, hydroxymatairesinol (HMR), a phytoestrogen, was analyzed in vitro for possible regulation on COX-2. Through Western blot analysis, HMR was shown to have no inhibitory affect on COX-2 expression. These results indicated that estrogen treatment strongly influences the expression of COX-2 that is associated with fertility, but no induction of COX-2 by estrogen may not exclude COX-2's role in prostatitis, and the anti-tumor mechanism of HMR largely remains elusive.

Altered Immunity Accompanies Disease Progression in a Mouse Model of Prostate Dysplasia

Increasing evidence suggests that altered immune function accompanies, and indeed may facilitate, cancer progression. In this study, we sought to determine the nature of, and cellular mechanisms underlying, changes in immune status during disease progression in a transgenic mouse model of prostate dysplasia. Immune cells in the tumor microenvironment, as well as in the secondary lymphoid tissues, displayed altered phenotypes. Although evidence of antitumor immunity was detected, there was a paradoxical decrease in the ability of T cells to proliferate in vitro at later stages of disease progression. Detailed analysis of the draining lumbar lymph nodes revealed an increased frequency and number of CD4(+)CD25(+) T cells and an enhanced production of inhibitory cytokines, which correlated with impaired T-cell function. Functional studies confirmed a role for CD4(+)CD25(+) regulatory T cells in suppressing T-cell proliferation as well as regulating the growth of transplanted prostate tumor cells. In addition, our studies show for the first time that anti-CD25 antibody treatment reduces, but does not prevent, tumor growth in a transgenic mouse model of prostate dysplasia. Taken together, this work provides compelling evidence that prostate tumor progression is accompanied by altered immune function and, moreover, that regulatory T cells play an important role in this process. These studies thus provide the impetus for development of specific and effective strategies to deplete regulatory T cells, or suppress their function, as an alternative or adjunct strategy for reducing tumor growth.

Deletion, Methylation, and Expression of the NKX3.1 Suppressor Gene in Primary Human Prostate Cancer

NKX3.1 is a prostate-specific homeoprotein and tumor suppressor that is affected by the loss of 8p21 in prostate cancer. In mice, Nkx3.1 haploinsufficiency results in prostatic dysplasia and complements cancer formation induced by loss of other suppressor genes. However, NKX3.1 expression can be immunohistochemically detected in most primary prostate cancers. We examined the relationship between suppressor gene haploinsufficiency, methylation, and quantitative NKX3.1 expression levels in primary prostate cancer. NKX3.1 gene copy number was assessed by microsatellite analysis, fluorescence in situ hybridization, and quantitative PCR. NKX3.1 gene methylation was determined in prostate cancer cell lines and we thereby identified potential CpG methylation sites for methylation-specific PCR analysis in tissues. We validated and then applied an internally controlled fluorescence immunomicroscopic assay for NKX3.1 protein expression in 48 primary prostate cancer specimens from radical prostatectomies. NKX3.1 loss of heterozygosity was found in 27 of 43 tissues tested. Classic CpG island methylation of the NKX3.1 gene was not found in either prostate cancer cell lines or tissues. However, in 33 of 40 samples tested, CpG sites at -921, -903, and -47 were methylated to a greater degree in malignant than in adjacent normal cells. In 43 of 48 samples, NKX3.1 protein expression was reduced from 0.34 to 0.90 compared with adjacent normal luminal epithelium (mean of all samples, 0.68; 95% confidence interval, 0.05). In 12 cases that also had high-grade prostatic intraepithelial neoplasia, NKX3.1 expression levels were similar in preinvasive and invasive cancer cells and significantly lower than adjacent normal cells. Even in the presence of allelic loss, NKX3.1 expression is reduced over a wide range in prostate cancer at the time of prostatectomy, suggesting that diverse factors influence expression. Samples with protein expression below the median level in cancer cells had both NKX3.1 deletion and selective CpG methylation.

Oestrogens and prostate cancer.

Androgens are essential for stimulating normal development, growth and secretory activities of the prostate whereas oestrogens are generally regarded as inhibitors of growth. Evidence for the local synthesis of oestrogens includes the detection of aromatase mRNA and protein in the stroma of human non-malignant tissues and in malignant tissue, where it is detected in epithelial tumour cells. As well, aromatase activity was measured by biochemical assay and protein was detected in prostatic non-malignant and tumour cell lines. Taken together with the identification of direct oestrogenic actions on the prostate, these results suggest that alterations in local oestrogen synthesis may have significant consequences in malignancy of these organs. Genetically modified mouse models were studied in order to evaluate the action of oestrogens alone or in combination with androgens on the prostate gland. Hypogonadal (hpg) mice are deficient in gonadotrophins and androgens but showed direct proliferative responses to oestradiol. The responses were characterised by discrete lobe-specific changes including smooth-muscle regression, fibroblast proliferation, inflammation, and basal epithelial cell proliferation and metaplasia. The aromatase knockout (ArKO) mouse, deficient in oestrogens due to a non-functional aromatase enzyme, developed prostatic hyperplasia during the lifelong exposure to elevated androgens, however, no malignant changes were detected in the prostate at any time. In contrast, combined androgen and oestrogen treatment has been shown to induce prostatic dysplasia and adenocarcinoma. These results demonstrate that malignant changes to the prostate gland are dependent upon both androgenic and oestrogenic responses and that neither hormone alone is sufficient to evoke aberrant patterns of growth, resulting in malignancy.

Antiestrogens and selective estrogen receptor modulators reduce prostate cancer risk.

The development of chemoprevention strategies against prostate cancer would have the greatest overall impact both medically and economically against prostate cancer. Estrogens are required for prostate carcinogenesis. Estrogenic stimulation through estrogen receptor alpha in a milieu of decreasing androgens contributes significantly to the genesis of benign prostatic hyperplasia, prostate dysplasia, and prostate cancer. The ability of antiestrogens and selective estrogen receptor modulators (SERMs) to delay and to suppress prostate carcinogenesis is supported by preclinical, clinical, and epidemiological studies. SERMs have many features that make them attractive candidates for prostate cancer chemoprevention including their favorable safety profile and efficacy in preclinical prostate cancer models. The true clinical benefits of SERMs for chemoprevention to prevent prostate cancer, however, should continue to be investigated through human clinical trials. A phase IIb/III human clinical trial is currently evaluating safety and efficacy of toremifene, a SERM, in men who have high-grade prostatic intraepithelial neoplasia.

Gene expression profiling of testosterone and estradiol-17 beta-induced prostatic dysplasia in Noble rats and response to the antiestrogen ICI 182,780.

We previously demonstrated that 1) treatment of Noble rats for 16 wk with testosterone (T) and estradiol-17 beta (E2) led to 100% incidence of dorsolateral prostate (DLP) dysplasia and hyperprolactinemia and 2) blockade of PRL release with bromocriptine cotreatment significantly lowered the incidence of DLP dysplasia. In the current study, we sought to determine whether E2 exerts direct effects, independent of PRL, in this model system. The pure antiestrogen ICI 182,780 (ICI), reported to have no effect on PRL release in female rats, was administered biweekly to T + E2-treated rats at 3 mg/kg body weight. ICI cotreatment completely prevented DLP dysplasia development but it also blocked hyperprolactinemia in the dual hormone-treated rats. Gene profiling with an 1185 gene rat cDNA array identified approximately 100 genes displaying > or = 3-fold changes in rat lateral prostates (LPs) following T + E2 treatment. Significantly more genes were up-regulated (77) than down-regulated (14), reflecting cellular/molecular changes associated with enhanced cell proliferation, DNA damage, heightened protein and RNA synthesis, increased energy metabolism, and activation of several proto-oncogenes and intracellular signaling pathways. Post hoc analyses, using quantitative real-time RT-PCR, corroborated differential expression of eight genes, exhibiting three different patterns of altered expression. Genes encoding the early growth response protein 1 and metalloendopeptidase meprin beta-subunit were similarly altered in T + E2- and T + E2 + ICI-treated animals when compared with untreated controls. In contrast, transcripts of fos-related antigen-2, growth arrest and DNA damage-inducible protein-45, and signal transducer and activator of transcription-3 were significantly increased in the LPs of T + E2-treated animals, but the increases were reversed by cotreatment with ICI. Differential expression of fos-related antigen-2 and growth arrest and DNA damage-inducible protein-45 were further confirmed at the protein level by immunohistochemistry. Lastly, levels of A-RAF, VIP-1 receptor, and calpastatin mRNA were distinctly lessen in rat LPs under T + E2 influence, but rebound with ICI cotreatment. In conclusion, our findings further implicated pituitary PRL in the induction of dysplasia in rat LP. Gene profiling provided clues that molecular events related to enhancement of cell proliferation, DNA damage, and activation of proto-oncogenes and transforming factors may be causally linked to the genesis of LP dysplasia in this rat model.

Gene Expression Profiling of Testosterone and Estradiol-17 -Induced Prostatic Dysplasia in Noble Rats and Response to the Antiestrogen ICI 182,780

Gene Expression Profiling of Testosterone and Estradiol-17 -Induced Prostatic Dysplasia in Noble Rats and Response to the Antiestrogen ICI 182,780

Aberrant expression of hepatocyte growth factor and its receptor, c-Met, during sex hormone-induced prostatic carcinogenesis in the Noble rat.

Hepatocyte growth factor (HGF) is a multifunctional cytokine which acts as a mitogen, motogen, morphogen and angiogenic factor of epithelial cells. HGF receptor is encoded by a proto-oncogene, c-met, which is overexpressed in various cancers. The role of HGF and c-Met in prostate carcinogenesis, especially in the early stages, is undefined. In this study, prostatic dysplasia and carcinomas were induced by testosterone propionate and 17 beta-estradiol in Noble rats. The expression of HGF and c-Met was assessed at a protein level by immunohistochemistry and western blot analysis. Intense immunostaining for HGF alpha and c-Met beta-chain was co-localized in dysplastic lesions and in primary and metastatic cancer cells. The levels of HGF alpha expression were similar among normal control, dysplastic and cancerous prostate tissues, as determined by western blot analysis. Immunoblot study for c-Met under reducing conditions identified two bands at 145 kDa (beta-subunit of c-Met) and 170 kDa (precursor form of c-Met) in rat liver extracts. However, two bands at approximately 220 and 245 kDa were detected in hormone-treated dysplastic prostate tissues and primary tumors. Overexpression of the 220 kDa band was observed in long-term (10-12 months) hormone-treated prostate and primary tumor extracts. Metastatic tumors consistently exhibited up-regulation of a single 245 kDa band. Under non-reducing conditions, however, protein bands of 220, 280 or 300 kDa were seen in the blots. The hormone-treated prostate tissues and metastatic tumors expressed the 220 and 300 kDa proteins, respectively. The majority of primary tumors expressed the 280 kDa protein. In summary, HGF and its receptor, c-Met, were co-expressed in dysplastic and tumor cells, suggesting that an autocrine mode of action may be involved in prostate carcinogenesis. The close correlation of expression of the high-molecular-weight isoforms of c-Met with different stages of carcinogenesis implicates that they might play differential roles in the onset, progression, growth and metastasis in prostate cancer.

Differential expression of PSP94 in rat prostate lobes as demonstrated by an antibody against recombinant GST-PSP94

Prostate secretory protein (PSP94, 94 amino acids) is one of the most abundant proteins secreted from the prostate. Its biological role is unknown and still controversial, although it is assumed to have the potential to be a biomarker and a suppressor of prostate cancer. In order to establish an animal model to further elucidate its biological role, we expressed the mature form of rat PSP94 in Escherichia coli, using a glutathione S-transferase (GST) fusion expression vector; we generated a polyclonal rabbit antibody against the recombinant protein. The antibody specifically recognized recombinant rat PSP94 and cross-reacted only very weakly with its human homologue. Using the characterized anti-rat PSP94 antibody, we found that PSP94 was located primarily in rat prostate. Furthermore, PSP94 is present at different levels in different lobes of rat prostate, with significant levels detectable only in the lateral lobe (LP). In addition, the most abundant PSP94 expression was found in the prostate lobe secretions, and PSP94 levels in LP secretions were at least seven times higher than in secretions from the dorsal prostate (DP). The rat ventral prostate (VP) and other regions of the male accessory glands were found to be almost completely devoid of PSP94. Since most rat prostate dysplasia induced by steroid hormone treatment occurs only in dorsolateral prostate, prostate tissue-specific expression and the expression of PSP94 in dorsolateral, but not other, lobes of the prostate suggest a potential role in prostate targeting and prostate cancer development.

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.