Transgenic Adenocarcinoma Mouse Prostate Mice Research Articles

A null-mutation in the Znt7 gene accelerates prostate tumor formation in a transgenic adenocarcinoma mouse prostate model

Decrease of cellular zinc in the epithelium of the prostate has been implicated in the development of prostate cancer. To investigate whether ZnT7, a zinc transporter involved in intracellular zinc accumulation, played a role in prostate cancer development, we generated and characterized a transgenic adenocarcinoma mouse prostate (TRAMP) model with a Znt7-null genetic background. TRAMP mice (TRAMP/ Znt7 −/− and TRAMP/ Znt7 +/+) were euthanized at 6, 8, 16, and 28 weeks of age for histopathological analysis of the prostates and for the presence of prostate tumors and metastasis. At 6 and 8 weeks of age, TRAMP/ Znt7 −/− mice displayed higher frequencies of low grade prostatic intraepithelial neoplasia (PIN) and high grade PIN, respectively, in the prostates than the age-matched TRAMP/ Znt7 +/+ mice. At 16 weeks of age, 33% TRAMP/ Znt7 −/− mice had prostate tumors and one half of the mice with prostate tumors had tumor metastasized to the draining lymph nodes while no prostate tumor was detected in the control TRAMP mice. By 28 weeks, 67% TRAMP/ Znt7 −/− mice developed prostate tumors while only 22% control TRAMP mice had prostate tumors. Furthermore, apoptosis was reduced in the prostates of TRAMP/ Znt7 −/− mice. In conclusion, a null-mutation of the Znt7 gene accelerates prostate tumor formation in TRAMP mice.

Disruption of cellular zinc homeostasis in transgenic adenocarcinoma mouse prostate (TRAMP) mice leads to an early onset of prostate cancer and metastasis

Decrease of cellular zinc in the epithelium of the prostate has been implicated in the development of prostate cancer. To investigate whether ZnT7, a zinc transporter involved in intracellular zinc accumulation, played a role in prostate cancer development, we generated and characterized a transgenic adenocarcinoma mouse prostate (TRAMP) model with a Znt7-null genetic background. Four week old male TRAMP mice (TRAMP/Znt7−/− and TRAMP/Znt7+/+) were fed a semi-purified diet containing 15 mg zinc/kg diet for 2–24 weeks. Mice were euthanized at 6, 8, 16, and 28 weeks for histopathological analysis of the prostates and for the presence of prostate tumors and metastasis. At 6 and 8 weeks of age, TRAMP/Znt7−/− mice displayed higher frequencies of low grade prostatic intraepithelial neoplasia (PIN) and high grade PIN, respectively, in the prostates compared to the age-matched TRAMP/Znt7−/− mice. At 16 weeks of age, 33% TRAMP/Znt7−/− mice had prostate tumors and one half of the mice with prostate tumors had tumor metastasized to the draining lymph nodes while no prostate tumor was detected in the control TRAMP mice. By 28 weeks, 67% TRAMP/Znt7−/− mice developed prostate tumors while only 22% control TRAMP mice had prostate tumors. Furthermore, apoptosis was reduced in the prostates of TRAMP/Znt7−/− mice. In conclusion, disruption of cellular zinc homeostasis caused by the Znt7 knockout leads to an early onset of prostate cancer and metastasis in TRAMP mice. This work was supported by the United States Department of Agriculture, ARS projects 5306-515-30-014-00D and 5306-515-20-007-00D.

3,3′-diindolylmethane inhibits prostate cancer development in the transgenic adenocarcinoma mouse prostate model

3,3'-Diindolylmethane (DIM) is a major in vivo derivative of indole-3-carbinol, which is present in cruciferous vegetables and has been reported to possess anti-carcinogenic properties. In the present study, we examined whether DIM inhibits the development of prostate cancer using the transgenic adenocarcinoma mouse prostate (TRAMP) model. DIM feeding inhibited prostate carcinogenesis in TRAMP mice, reduced the number of cells expressing the SV40 large tumor antigen and proliferating cell nuclear antigen, and increased the number of terminal dUTP nick-end labeling-positive cells in the dorsolateral lobes of the prostate. Additionally, DIM feeding reduced the expression of cyclin A, cyclin-dependent kinase (CDK)2, CDK4, and Bcl-xL, and increased p27 and Bax expression. To assess the mechanisms by which DIM induces apoptosis, LNCaP and DU145 human prostate cancer cells were cultured with various concentrations of DIM. DIM induced a substantial reduction in the numbers of viable cells and induced apoptosis in LNCaP and DU145 cells. DIM increased the cleavage of caspase-9, -7, -3, and poly (ADP-ribose) polymerase (PARP). DIM increased mitochondrial membrane permeability and the translocation of cytochrome c and Smac/Diablo from the mitochondria. Additionally, DIM induced increases in the levels of cleaved caspase-8, truncated Bid, Fas, and Fas ligand, and the caspase-8 inhibitor Z-IETD-FMK was shown to mitigate DIM-induced apoptosis and the cleavage of caspase-3, PARP, and Bid. These results indicate that DIM inhibits prostate carcinogenesis via induction of apoptosis and inhibition of cell cycle progression. DIM induces apoptosis in prostate cancer cells via the mitochondria- and death receptor-mediated pathways.

Proteomic Profiling of Potential Molecular Targets of Methyl-Selenium Compounds in the Transgenic Adenocarcinoma of Mouse Prostate Model

Because the Selenium (Se) and Vitamin E Cancer Prevention Trial (SELECT) failed to show the efficacy of selenomethionine for prostate cancer prevention, there is a critical need to identify safe and efficacious Se forms for future trials. We have recently shown significant preventive benefit of methylseleninic acid (MSeA) and Se-methylselenocysteine (MSeC) in the transgenic adenocarcinoma mouse prostate (TRAMP) model by oral administration. The present work applied iTRAQ proteomic approach to profile protein changes of the TRAMP prostate and to characterize their modulation by MSeA and MSeC to identify their potential molecular targets. Dorsolateral prostates from wild-type mice at 18 weeks of age and TRAMP mice treated with water (control), MSeA, or MSeC (3 mg Se/kg) from 8 to 18 weeks of age were pooled (9-10 mice per group) and subjected to protein extraction, followed by protein denaturation, reduction, and alkylation. After tryptic digestion, the peptides were labeled with iTRAQ reagents, mixed together, and analyzed by two-dimensional liquid chromatography/tandem mass spectrometry. Of 342 proteins identified with >95% confidence, the expression of 75 proteins was significantly different between TRAMP and wild-type mice. MSeA mainly affected proteins related to prostate functional differentiation, androgen receptor signaling, protein (mis)folding, and endoplasmic reticulum-stress responses, whereas MSeC affected proteins involved in phase II detoxification or cytoprotection, and in stromal cells. Although MSeA and MSeC are presumed precursors of methylselenol and were equally effective against the TRAMP model, their distinct affected protein profiles suggest biological differences in their molecular targets outweigh similarities.

Mixed Tocotrienols Inhibit Prostate Carcinogenesis in TRAMP Mice

The biological activities of tocotrienols are receiving increasing attention. Herein, we report the efficacy of a mixed-tocotrienol diet against prostate tumorigenesis in the transgenic adenocarcinoma mouse prostate (TRAMP) mouse model. Male TRAMP mice, 8 wk old, were fed 0.1%, 0.3%, or 1% mixed tocotrienols in AIN-76A diet up to 24 wk old. Likewise, a positive control group consisting of male TRAMP mice and a negative control group consisting of wild-type nontransgenic mice were fed regular AIN-76A diet up to 24 wk old. Our results show that mixed-tocotrienol-fed groups had a lower incidence of tumor formation along with a significant reduction in the average wet weight of genitourinary apparatus. Furthermore, mixed tocotrienols significantly reduced the levels of high-grade neoplastic lesions as compared to the positive controls. This decrease in levels of high-grade neoplastic lesions was found to be associated with increased expression of proapoptotic proteins BAD (Bcl2 antagonist of cell death) and cleaved caspase-3 and cell cycle regulatory proteins cyclin dependent kinase inhibitors p21 and p27. In contrast, the expression of cyclins A and E were found to be decreased in mixed-tocotrienol groups. Taken together, our results show that by modulating cell cycle regulatory proteins and increasing expression of proapoptotic proteins, mixed tocotrienols suppress prostate tumorigenesis in the TRAMP mice.

Abstract 2876: 3,3’-Diindolylmethane inhibits prostate cancer development in the transgenic adenocarcinoma mouse prostate model

Abstract 3,3’-Diindolymethane (DIM) is a major in vivo derivative of indole-3-carbinol, which is present in cruciferous vegetables and has been reported to evidence anti-carcinogenic properties. In the present study, we attempted to determine whether DIM inhibits the development of prostate cancer using the transgenic adenocarcinoma mouse prostate (TRAMP) model. DIM feeding inhibited prostate carcinogenesis in TRAMP mice, reduced the number of cells expressing the SV40 large tumor antigen and proliferating cell nuclear antigen, and increased the number of terminal dUTP nick-end labeling (TUNEL)-positive cells in the dorsolateral lobes of the prostate. Additionally, DIM feeding reduced the expression of cyclin A, cyclin-dependent kinase (CDK)2, and CDK4, and increased Bax expression. To assess the mechanisms by which DIM induces apoptosis, LNCaP and DU145 human prostate cancer cells were cultured with various concentrations (0 – 30 μmol/L) of DIM. DIM induced a substantial reduction in the numbers of viable cells and induced apoptosis in LNCaP and DU145 cells. DIM increased the cleavage of caspase-9, −7, −3, and poly (ADP-ribose) polymerase (PARP). DIM increased mitochondrial membrane permeability and the translocation of cytochrome c and Smac/Diablo from the mitochondria. Additionally, DIM induced increases in the levels of cleaved caspase-8, truncated Bid, Fas, and Fas ligand, and the caspase-8 inhibitor z-IETD-FMK was shown to mitigate DIM-induced apoptosis and the cleavage of caspase-3, PARP, and Bid. These results indicate that DIM inhibits prostate carcinogenesis via induction of apoptosis and inhibition of cell cycle progression. DIM induces apoptosis in prostate cancer cells via the mitochondria- and death receptor-mediated pathways. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2876.

Chinese medicinal herb Scutellaria barbata modulates apoptosis and cell survival in murine and human prostate cancer cells and tumor development in TRAMP mice

Scutellaria barbata (SB) has been used in Chinese medicine to treat various cancers. This study investigated the effects of SB on prostate cancer prevention. Male TRansgenic Adenocarcinoma Mouse Prostate (TRAMP) mice at 9 weeks were randomly divided into four groups and given daily oral feedings of 8, 16, or 32 mg SB or sterilized water. In the control group, palpable tumors initially appeared at 19 weeks of age and were present in all mice by 32 weeks. In the respective treatment groups, palpable tumor development was delayed by 2, 4, and 7 weeks and 22, 30, and 38% of the mice were free of palpable tumors. Palpable tumor development in 50% of the mice occurred at 25 weeks in the placebo group, 29 weeks in the low-dose and mid-dose treatment groups, and 33 weeks in the high-dose group (log rank, P = 0.0211). Histological assessment further showed that the SB treatment (32 mg) delayed prostate tumor progression in the TRAMP mice. Caspase 3 activation was observed in SB-treated prostate tissue. Positive TUNEL assay results were detected in TRAMP-C1 and LNCaP cells treated with SB (1 mg/ml), which indicated significant apoptosis induction. Western blotting of SB-treated LNCaP cells also showed elevated expression of Bax, p53, Akt, and JNK. In-vivo data showed that the SB delayed tumor development in TRAMP mice. Complementary in-vitro data indicated that SB might exert this function by upregulating the apoptotic pathway and downregulating the survival pathway in prostate cancer cells, thus suggesting that SB possesses chemopreventive properties and has potential for cancer treatment.

Retinoid metabolism and ALDH1A2 (RALDH2) expression are altered in the transgenic adenocarcinoma mouse prostate model

Retinoids, which include vitamin A (retinol) and metabolites such as retinoic acid, can inhibit tumor growth and reverse carcinogenesis in animal models of prostate cancer. We analyzed retinoid signaling and metabolism in the TRAMP (transgenic adenocarcinoma mouse prostate) model. We detected increased retinol and retinyl esters in prostates pooled from 24 to 36 week TRAMP transgenic positive mice compared to nontransgenic littermates by HPLC. We used quantitative RT-PCR to measure transcripts for genes involved in retinoid signaling and metabolism, including ALDH1A1, ALDH1A2, ALDH1A3, CYP26A1, LRAT, and RARβ 2, in prostate tissue from TRAMP positive (+) and age-matched littermate control mice ranging from 18 to 36 weeks. Transcript levels of ALDH1A1, a putative stem cell marker, were decreased in ventral and lateral lobes of prostates from TRAMP mice compared to age-matched, nontransgenic mice. ALDH1A2 (RALDH2) mRNA levels in dorsal and anterior lobes of TRAMP+ mice were lower than in age-matched (24 week) nontransgenic mice. We detected lower RARβ 2 mRNA levels in dorsal prostate lobes of 36 week TRAMP mice relative to nontransgenic mice. We detected high levels of ALDH1A2 protein in the cytoplasm and nucleus in nontransgenic murine prostate paraffin sections, and lower ALDH1A2 protein levels in all prostate lobes of TRAMP mice compared to nontransgenic mice by immunohistochemistry. We also detected much lower cytoplasmic ALDH1A2 protein levels in all human prostate cancer paraffin sections stained (19 total) relative to normal human prostate tissue on the same sections. Our data indicate that this reduction in ALDH1A2 protein is an early event in human prostate cancer.

Methyl-Selenium Compounds Inhibit Prostate Carcinogenesis in the Transgenic Adenocarcinoma of Mouse Prostate Model with Survival Benefit

Chemoprevention of prostate cancer by second-generation selenium compounds in reference to selenomethionine holds strong promise to deal with the disease at the root. Here we used the transgenic adenocarcinoma mouse prostate (TRAMP) model to establish the efficacy of methylseleninic acid (MSeA) and methylselenocysteine (MSeC) against prostate carcinogenesis and to characterize potential mechanisms. Eight-week-old male TRAMP mice (C57B/6 background) were given a daily oral dose of water, MSeA, or MSeC at 3 mg Se/kg body weight and were euthanized at either 18 or 26 weeks of age. By 18 weeks of age, the genitourinary tract and dorsolateral prostate weights for the MSeA- and MSeC-treated groups were lower than for the control (P < 0.01). At 26 weeks, 4 of 10 control mice had genitourinary weight >2 g, and only 1 of 10 in each of the Se groups did. The efficacy was accompanied by delayed lesion progression, increased apoptosis, and decreased proliferation without appreciable changes of T-antigen expression in the dorsolateral prostate of Se-treated mice and decreased serum insulin-like growth factor I when compared with control mice. In another experiment, giving MSeA to TRAMP mice from 10 or 16 weeks of age increased their survival to 50 weeks of age, and delayed the death due to synaptophysin-positive neuroendocrine carcinomas and synaptophysin-negative prostate lesions and seminal vesicle hypertrophy. Wild-type mice receiving MSeA from 10 weeks did not exhibit decreased body weight or genitourinary weight or increased serum alanine aminotransferase compared with the control mice. Therefore, these selenium compounds may effectively inhibit this model of prostate cancer carcinogenesis.

Involvement of FLIP in 2-Methoxyestradiol–Induced Tumor Regression in Transgenic Adenocarcinoma of Mouse Prostate Model

The purpose of this study is to investigate whether Fas-associated death domain interleukin-1 converting enzyme like inhibitory protein (FLIP) inhibition is a therapeutic target associated with 2-methoxyestradiol (2-ME2)-mediated tumor regression. Expression and levels of FLIP were analyzed using (a) real-time PCR and immunoblot analysis in androgen-independent PC-3 cells treated with the newly formulated 2-ME2 and (b) immunohistochemistry in different Gleason pattern human prostate tumors. Transient transfections and chromatin immunoprecipitation (ChIP) assays were used to identify the transcription factors that regulate FLIP. Involvement of FLIP in 2-ME2-induced tumor regression was evaluated in transgenic adenocarcinoma mouse prostate (TRAMP) mice. High Gleason pattern (5+5) human prostate tumors exhibit significant increase in FLIP compared with low Gleason pattern 3+3 (P=or<0.04). 2-ME2 reduced the levels and promoter activity of FLIP (P=0.001) in PC-3 cells. Transient expression assays show sequences between -503/+242 being sufficient for 2-ME2-induced inhibition of FLIP promoter activity. Cotransfection experiments show that overexpression of Sp1 activated, whereas Sp3 inhibited, Sp1 transactivation of FLIP promoter activity (P=0.0001). 2-ME2 treatment reduced binding of Sp1 to the FLIP promoter as evidenced by ChIP. Further, levels of FLIP associated with Fas or FADD decreased, whereas cleavage of caspase-8, levels of Bid, and apoptosis increased in response to 2-ME2 treatment in PC-3 cells. Administration of 2-ME2 regressed established prostate tumors in TRAMP mice that were associated with reduced expression of FLIP and Sp1. Targeting Sp1-mediated FLIP signaling pathway may provide a novel approach for prostate cancer management.

Targeted Deletion of Hepatic Igf1 in TRAMP Mice Leads to Dramatic Alterations in the Circulating Insulin-Like Growth Factor Axis but Does Not Reduce Tumor Progression

The role of systemic and local insulin-like growth factor I (IGF-I) in the development of prostate cancer is still controversial. Transgenic adenocarcinoma mouse prostate (TRAMP) mice express the SV40 T-antigen under the control of the probasin promoter, and spontaneously develop prostate cancer. We crossed TRAMP mice with liver IGF-deficient (LID) mice to produce LID-TRAMP mice, a mouse model of prostate cancer with low serum IGF-I, to allow us to study the effect of circulatory IGF-I levels on the development of prostate cancer. LID mice have a targeted deletion of the hepatic Igf1 gene but retain normal expression of Igf1 in extrahepatic tissues. Serum IGF-I and IGFBP-3 levels in LID and LID-TRAMP mice were measured using novel assays, which showed that they are approximately 10% and 60% of control L/L- mice, respectively. Serum growth hormone (GH) levels of LID-TRAMP mice were 3.5-fold elevated relative to L/L-TRAMP mice (P < 0.001), but IGFBP-2 levels were not different. Surprisingly, rates of survival, metastasis, and the ratio of genitourinary tissue weight to body weight were not significantly different between LID-TRAMP and L/L-TRAMP mice. There was also no difference in the pathologic stage of the prostate cancer between the two groups at 9 to 19 weeks of age. LID-TRAMP tumors displayed increased levels of GH receptors and increased Akt phosphorylation. These results are in striking contrast with the published model of the GH-deficient lit/lit-TRAMP, which has smaller tumors and improved survival, and indicate that the reduction in systemic IGF-I is not sufficient to inhibit prostate cancer tumor progression in the TRAMP model, which may require a reduction of GH levels as well.

Prostate Stem Cell Antigen Vaccination Induces a Long-term Protective Immune Response against Prostate Cancer in the Absence of Autoimmunity

Prostate stem cell antigen (PSCA) is an attractive antigen to target using therapeutic vaccines because of its overexpression in prostate cancer, especially in metastatic tissues, and its limited expression in other organs. Our studies offer the first evidence that a PSCA-based vaccine can induce long-term protection against prostate cancer development in prostate cancer-prone transgenic adenocarcinoma mouse prostate (TRAMP) mice. Eight-week-old TRAMP mice displaying prostate intraepithelial neoplasia were vaccinated with a heterologous prime/boost strategy consisting of gene gun-delivered PSCA-cDNA followed by Venezuelan equine encephalitis virus replicons encoding PSCA. Our results show the induction of an immune response against a newly defined PSCA epitope that is mediated primarily by CD8 T cells. The prostates of PSCA-vaccinated mice were infiltrated by CD4-positive, CD8-positive, CD11b-positive, and CD11c-positive cells. Vaccination induced MHC class I expression and cytokine production [IFN-gamma, tumor necrosis factor-alpha, interleukin 2 (IL-2), IL-4, and IL-5] within prostate tumors. This tumor microenvironment correlated with low Gleason scores and weak PSCA staining on tumor cells present in hyperplastic zones and in areas that contained focal and well-differentiated adenocarcinomas. PSCA-vaccinated TRAMP mice had a 90% survival rate at 12 months of age. In contrast, all control mice had succumbed to prostate cancer or had heavy tumor loads. Crucially, this long-term protective immune response was not associated with any measurable induction of autoimmunity. The possibility of inducing long-term protection against prostate cancer by vaccination at the earliest signs of its development has the potential to cause a dramatic paradigm shift in the treatment of this disease.

The resistance to the tumor suppressive effects of COX inhibitors and COX-2 gene disruption in TRAMP mice is associated with the loss of COX expression in prostate tissue

Over-expression of cyclooxygenase-2 (COX-2) and prostaglandin E(2) has been demonstrated to play a significant role in the tumorigenesis of colon, lung, breast, bladder and skin. However, inconsistent and controversial reports on the expression and activity of COX-2 in prostate cancer raised the question of whether COX-2 plays a pivotal role in prostate carcinogenesis. To address this question, we examined the effects of COX-2 inhibition on prostate tumorigenesis in the transgenic adenocarcinoma mouse prostate (TRAMP) model. Three-week-old TRAMP mice were fed control, celecoxib- or indomethacin-supplemented diets for 27 weeks. A TRAMP/COX-2 knockout mouse model was also generated to determine the effects of the loss of the COX-2 gene on prostate tumorigenesis in TRAMP mice. These studies demonstrated that neither non-steroidal anti-inflammatory drugs (NSAIDs) nor genetic disruption of COX-2 was inhibitory in terms of tumor and metastases incidence, lobe weight or types of pathological lesions. A careful analysis of wild-type and TRAMP tissues was undertaken for the expression of cyclooxygenase-1 (COX-1) and COX-2 using immunoblotting, quantitative real time polymerase chain reaction (qRT-PCR) and immunohistochemistry approaches in TRAMP dorsal prostate tissue from 10- and 16-week-old, as well as tumor from 30-week-old mice. We found that the expression of COX-1 and COX-2 dramatically decreased during TRAMP carcinogenesis. Using the probasin promoter, a COX-2 over-expressing mouse model was also generated but failed to show any pathology in any of the prostate lobes. Collectively, our results suggest that COX-2 may not play a tumorigenic role during prostate carcinogenesis in the TRAMP model.

Epigallocatechin‐3‐Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: Mechanisms of action

Prostate cancer (PCa) is the second leading cause of cancer-related death in men in the United States. Many men have implemented purported chemopreventive agents into their daily diet in an attempt to delay the early onset of a PCa. Green tea polyphenols, one such agent, has been shown to be chemopreventive in skin, breast, and prostate cancers. We hypothesized that Epigallocatechin-3-Gallate (EGCG), the major polyphenol found in green tea, will exert its chemopreventive effect in the prostate via regulation of sex steroid receptor, growth factor-signaling, and inflammatory pathways. Five-week-old male TRAMP (Transgenic Adenocarcinoma Mouse Prostate) offspring were fed AIN-76A diet and 0.06% EGCG in tap water. Animals were sacrificed at 28 weeks of age and the entire prostates were scored histopathologically. In addition, animals were sacrificed at 12 weeks of age and ventral (VP) and dorsolateral (DLP) prostates were removed for histopathological evaluation and immunoblot analyses or ELISA. EGCG, inhibited early but not late stage PCa in the current study. In the VP, EGCG significantly reduced cell proliferation, induced apoptosis, and decreased androgen receptor (AR), insulin-like growth factor-1 (IGF-1), IGF-1 receptor (IGF-1R), phospho-extracellular signal-regulated kinases 1 and 2 (phospho-ERKs 1 and 2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). The attenuation of the AR, the down-regulation of potent growth factor IGF-1, modulation of inflammation biomarkers, and decrease in the MAPK signaling may contribute to the reduction in cell proliferation and induction of apoptosis and hence provide a biochemical basis for EGCG suppressing PCa without toxicity.

Genistein chemoprevention of prostate cancer in TRAMP mice.

Epidemiological studies suggest an inverse association between soy intake and prostate cancer risk. Genistein, the predominant phytoestrogen in soy food, has been proposed as a potential chemopreventive agent due to its anti-estrogen and tyrosine kinase inhibitory effects. To determine the most effective period for genistein chemoprevention, the Transgenic adenocarcinoma mouse prostate (TRAMP) model was used. The treatments were 250 mg genistein/kg AIN-76A diet 1) prepubertally only, 2) in adulthood only or 3) through out life. Controls received AIN-76A diet. By 28 weeks of age, 100% TRAMP mice fed control diet developed prostatic intraepithelial neoplasia (PIN) or adenocarcinomas with 6%, 16%, 44% and 34% developing high grade PIN, well differentiated, moderately differentiated and poorly differentiated prostatic adenocarcinomas, respectively. Prepubertal only (1–35 days postpartum) and adult only genistein treatments (12 – 28 weeks) resulted in 6% and 29% decreases in poorly-differentiated cancerous lesions compared with controls, respectively. The most significant effect was seen in the TRAMP mice exposed to genistein throughout life (1–28 weeks) with a 50% decrease in poorly-differentiated cancerous lesions. In a separate experiment in castrated TRAMP mice, dietary genistein suppressed the development of advanced prostate cancer by 35% compared with controls. Of the tumors that developed in castrated TRAMP mice, 100% were poorly-differentiated in contrast to the 37% of noncastrated TRAMP mice that developed poorly-differentiated tumors. ICI 182,780 (ICI), genistein and estrogen down-regulated androgen receptor (AR), estrogen receptor alpha (ER-α) and progesterone receptor (PR) in the prostates of C57BL/6 mice, and act independently of ER. Our data obtained in intact and castrated transgenic mice suggest that genistein may be a promising chemopreventive agent against androgen-dependent and independent prostate cancers.

Epithelial-Stromal Tumor of the Seminal Vesicles in the Transgenic Adenocarcinoma Mouse Prostate Model

The transgenic adenocarcinoma mouse prostate (TRAMP) model, designed for researching human prostatic cancer, was genetically engineered to harbor a transgene composed of the simian virus 40 Large-T/small-t antigen promoted by the rat probasin gene. In addition to prostatic neoplasms, the TRAMP mouse develops tumors in the seminal vesicles. This study was conducted to evaluate the pathology and histogenesis of TRAMP seminal vesicle neoplasms. Tissues of accessory sex organs harvested from 72 TRAMP mice of various ages (11-40 weeks of age) were fixed in neutral buffered formalin and stained with hematoxylin and eosin, desmin, 5-bromo-2'-deoxyuridine (BrdU, treated animals only), and SV40 Large-T antigen (SV40-Tag). In the seminal vesicles, we found neoplastic stromal cells that emerged multicentrically just beneath the epithelium, densely packed between the epithelium and the smooth muscle layer. These stromal cells frequently exhibited mitotic figures and showed BrdU incorporation and SV40-Tag protein expression in the nuclei and immunopositivity for desmin. The proliferative mesenchymal cells were lined by cuboidal to columnar epithelium. Some of the larger papillary, polypoid lesions exhibited a phyllodes pattern resembling that seen in mixed epithelial-stromal tumors of the breast, prostate, and seminal vesicles of humans. Although the epithelium was negative for SV40-Tag and showed only occasional incorporation of BrdU, it clearly participated in the biphasic proliferation, forming papillary, cystic, and tubuloglandular structures. No conclusive evidence of malignancy (invasion or metastasis) was identified. Our recommended diagnosis of this lesion in the seminal vesicles is epithelial-stromal tumor.

INCREASED EXPRESSION OF MUC18 CORRELATES WITH THE METASTATIC PROGRESSION OF MOUSE PROSTATE ADENOCARCINOMA IN THE TRAMP MODEL

The transgenic adenocarcinoma mouse prostate (TRAMP) model is a paradigm that closely mimics the progression of clinical prostate cancer. We have previously reported that MUC18, a cell adhesion molecule in the Ig gene superfamily, is a marker as well as an important mediator for the metastatic potential of human prostate cancer cells. In this study we investigated the possible correlation of increased MUC18 expression with the malignant progression of prostate cancer in the TRAMP model. We used immunohistochemistry, Western blot and reverse transcriptase-polymerase chain reaction analyses to determine MUC18 expression in the prostate gland of 178 to 282-day-old TRAMP positive males with a prostate tumor size of 0.4 to 12.7 gm. Eight normal prostates, 10 prostates with high grade prostatic intraepithelial neoplasia (PIN), 24 prostates with primary prostate cancer, 10 metastatic lesions from 50 pure C57BL/6 TRAMP mice (Wu colony) and 2 normal prostates, 2 prostates with high grade PIN, 6 prostates with primary prostate cancer and 4 metastatic lesions from 10 [C57BL/6 TRAMP x FVB] F1 mice (NMG colony) were used. We found that mouse MUC18 was expressed in all (100%) high grade PIN, adenocarcinomas and metastatic lesions. All mice bearing primary prostate tumors had prostate cancer metastatic to the peri-aortic lymph nodes and some had it to other organs (liver, lung, kidney, testes, seminal vesicles and abdominal cavity). In contrast, prostates from 10 nontransgenic littermates did not have detectable MUC18 expression. MUC18 expression is up-regulated in the TRAMP model and it correlates with the malignant progression of mouse prostate adenocarcinoma in this transgenic model. This further strengthens the hypothesis that MUC18 has an important role in increasing the metastatic potential of prostate cancer cells.

Evidence for downregulation of calcium signaling proteins in advanced mouse adenocarcinoma

Prostate cancer (PCa) is the leading cancer related death in America. Gleason grading is currently the predominant method for prediction, with only few biomarkers available. More biomarkers, especially as they relate to cancer progression are desirable. The abundance of several important proteins in prostate tissue was compared between wild-type mouse dorsal prostate and well-differentiated transgenic adenocarcinoma mouse prostate (TRAMP) mouse dorsal prostates, and between wild-type mouse dorsal prostate and poorly-differentiated TRAMP mouse tumor tissue. 2DIGE method in conjunction with MALDI-ToF and Western blots was used to determine differential expression. In TRAMP dorsal prostates with well-differentiated adenocarcinoma, there were few significant changes in the protein abundances compared to wild-type dorsal prostates, with the exception of increases in proliferating cell nuclear antigen (PCNA) and beta tubulin, two proteins implicated in cell proliferation, and a more than 2-fold increase in Hsp60, a protein involved in the suppression of apoptosis. In the poorly-differentiated tumors, the changes in protein abundance were substantial. While some of those changes could be related to the disappearance of stromal tissue or the appearance of epithelial tissue, other changes in protein abundance were more significant to the cancer development itself. Most notable was the overall decrease in calcium homeostasis proteins with a 10-fold decrease in calreticulin and Hsp70 and a 40-fold decrease in creatine kinase bb in the cancerous tissue. Proteomics of TRAMP mice provide an excellent method to observe changes in protein abundance, revealing changes in pathways during cancer progression.

The chemopreventive action of catechins in the TRAMP mouse model of prostate carcinogenesis is accompanied by clusterin over-expression.

Clusterin (CLU) protein is widely distributed in animal tissues and is involved in many different processes, including apoptosis and neoplastic transformation. Green tea catechins (GTC) are known to exert chemopreventive effects in many cancer models, including transgenic adenocarcinoma mouse prostate (TRAMP) mice that spontaneously develop prostate cancer (CaP). We report here that growth of SV40-immortalized human prostate epithelial cells (PNT1A) as well as tumorigenic, poorly differentiated prostate cancer cells (PC-3) was potently inhibited by EGCG, the major green tea catechin, while normal human prostate epithelial cells were not significantly affected. IC(50) doses of EGCG for 24 h caused caspase cascade activation and CLU protein accumulation in both cells lines but not in normal cells, in which CLU remained undetectable. While 100% of TRAMP mice developed CaP, only 20% of those receiving 0.3% GTC in drinking water developed the neoplasm. In TRAMP mice, the CLU gene was dramatically down-regulated during onset and progression of CaP. In GTC-treated TRAMP mice in which tumor progression was chemoprevented, CLU mRNA and protein progressively accumulated in the prostate gland. CLU dropped again to undetectable levels in animals in which GTC chemoprevention failed and CaP developed. Up-regulation of histone H3 and down-regulation of growth arrest-specific gene 1 (Gas1) mRNAs in CaP-developing TRAMP mice demonstrated a high proliferation rate in tumors, while the opposite occurred in the glands of GTC chemoprevented animals. Failure of GTC chemoprevention caused induction of both histone H3 and Gas1 and down-regulation of CLU. Immunohistochemistry experiments confirmed CLU down-regulation during CaP onset and progression, and CLU sustained expression in chemoprevented TRAMP mice. A possible role for CLU as a novel tumor-suppressor gene in the prostate is thus suggested.

Effect of flaxseed supplementation on prostatic carcinoma in transgenic mice

Objectives To investigate the effects of flaxseed supplementation on prostatic neoplasia in the transgenic adenocarcinoma mouse prostate (TRAMP) model. Methods A total of 135 male TRAMP mice 5 to 6 weeks old were randomized to a control group (AIN-76A diet) or an experimental group (AIN-76A diet plus 5% flaxseed by weight). One half of the mice in each group were treated for 20 weeks and the remainder for 30 weeks. At autopsy, urogenital tissues (four prostatic lobes, seminal vesicles, and emptied bladder), lungs, lymph nodes, and grossly abnormal tissues were collected for histologic evaluation. Results Of the control mice, 100% developed prostate cancer versus 97% of the mice in the flaxseed group. The tumor/urogenital weight was 3.6 ± 0.4 g in the controls versus 1.9 ± 0.2 g in the flaxseed-treated mice ( P = 0.0005). At 20 weeks, no significant difference in tumor grade was seen between the two groups; however, at 30 weeks, the flaxseed-treated mice had significantly less aggressive tumors than did the controls ( P = 0.01). The prevalence of lung and lymph node metastases was 13% and 16%, respectively, in the control mice versus 5% and 12%, respectively, in the experimental group (difference not significant). After 20 weeks of treatment, cellular proliferation (Ki-67) differed significantly between the control and experimental groups (38.1 ± 2.03 versus 26.2 ± 2.03; P <0.0001), and the apoptotic index (deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling) was 1.45 ± 0.14 versus 3.3 ± 0.31 ( P <0.0001). Similar differences were seen after 30 weeks of treatment. Conclusions A diet supplemented with 5% flaxseed inhibits the growth and development of prostate cancer in the TRAMP model.