Early castration reduces prostatic carcinogenesis in transgenic mice

In vivo magnetic resonance imaging of orthotopic prostate cancer

Methods for imaging orthotopic prostate tumors within the prostate or small tumors with extension outside the prostate are needed to more closely model human prostate tumors, which are most commonly located within the gland or may extend just through the gland. By comparing MR sequences, we found that the T2-based Dixon 'water only' sequence best visualized tumors within the prostate of mouse models in both young and old mice and that tumor weight derived from this sequence correlated highly with ex vivo tumor weight (r² = 0.98, p < 0.001, n = 12). This should aid tumor detection, margin delineation and evaluation of tumor burden to enable studies including, but not limited to, evaluating the natural history of the disease, the mechanisms of action and the efficacy of therapeutic interventions.

Intracellular CD24 disrupts the ARF-NPM interaction and enables mutational and viral oncogene-mediated p53 inactivation

CD24 is overexpressed in nearly 70% human cancers, whereas TP53 is the most frequently mutated tumour-suppressor gene that functions in a context-dependent manner. Here we show that both targeted mutation and short hairpin RNA (shRNA) silencing of CD24 retard the growth, progression and metastasis of prostate cancer. CD24 competitively inhibits ARF binding to NPM, resulting in decreased ARF, increase MDM2 and decrease levels of p53 and the p53 target p21/CDKN1A. CD24 silencing prevents functional inactivation of p53 by both somatic mutation and viral oncogenes, including the SV40 large T antigen and human papilloma virus 16 E6-antigen. In support of the functional interaction between CD24 and p53, in silico analyses reveal that TP53 mutates at a higher rate among glioma and prostate cancer samples with higher CD24 mRNA levels. These data provide a general mechanism for functional inactivation of ARF and reveal an important cellular context for genetic and viral inactivation of TP53.

P53 is a tumour suppressor that is frequently mutated or downregulated in cancer. Here, Wang et al. show that CD24, a molecule frequently overexpressed in cancer, promotes p53 degradation by disrupting a regulatory ARF–MDM2 interaction, and silencing CD24 prevents the downregulation of p53.

Ultra-early versus early salvage androgen deprivation therapy for post-prostatectomy biochemical recurrence in pT2-4N0M0 prostate cancer

BACKGROUND

The optimal timing of salvage androgen deprivation therapy (ADT) for biochemical recurrence after radical prostatectomy is controversial. We compared the outcomes of ultra-early versus early salvage ADT.

METHODS

Among 855 patients undergoing radical prostatectomy at our institution between 2000 and 2012, we identified 121 with adjuvant-treatment-naïve pT2-4N0M0 prostate cancer who received salvage ADT for biochemical recurrence. These patients were divided into an ultra-early salvage ADT group (n = 51), who started salvage ADT before meeting the standardized definition of biochemical recurrence in Japan (two consecutive prostate-specific antigen [PSA] values ≥0.2 ng/ml), and an early salvage ADT group (n = 70) who started salvage ADT when they met the definition. The ultra-early ADT group consisted of those who started salvage ADT with a single PSA value ≥0.2 ng/ml (n = 30) or with two consecutive PSA values >0.1 ng/ml and rising (n = 21). The primary endpoint was biochemical recurrence after salvage ADT, defined as a single PSA value ≥0.2 ng/ml after PSA nadir following salvage ADT. Secondary endpoints were clinical metastasis and cancer-specific survival. A Cox proportional hazards model was used for multivariate analysis. The median follow-up was 65.5 months.

RESULTS

Biochemical recurrence occurred in one patient (2.0%) in the ultra-early group and in 12 (17.1%) in the early salvage ADT group. Multivariate analysis identified ultra-early salvage ADT and preoperative Gleason score ≤7 as independent negative predictors of biochemical recurrence after salvage ADT. Only one patient in the early salvage ADT group developed clinical metastasis to a left supraclavicular lymph node, and no patient died from prostate cancer during follow-up. The major limitations of this study were its retrospective design, selection bias, and the possibility that the ultra-early salvage ADT group may have included patients without biochemical recurrence.

CONCLUSIONS

Ultra-early salvage ADT was an independent negative predictor of biochemical recurrence after salvage ADT in post-prostatectomy patients. Further consideration should be given to the use of salvage ADT before meeting the current definition of biochemical recurrence.

Dietary tomato and lycopene impact androgen signaling- and carcinogenesis-related gene expression during early TRAMP prostate carcinogenesis

Consumption of tomato products containing the carotenoid lycopene is associated with a reduced risk of prostate cancer. To identify gene expression patterns associated with early testosterone-driven prostate carcinogenesis, which are impacted by dietary tomato and lycopene, wild-type (WT) and transgenic adenocarcinoma of the mouse prostate (TRAMP) mice were fed control or tomato- or lycopene-containing diets from 4 to 10 weeks of age. Eight-week-old mice underwent sham surgery, castration, or castration followed by testosterone repletion (2.5 mg/kg/d initiated 1 week after castration). Ten-week-old intact TRAMP mice exhibit early multifocal prostatic intraepithelial neoplasia. Of the 200 prostate cancer-related genes measured by quantitative NanoString, 189 are detectable, 164 significantly differ by genotype, 179 by testosterone status, and 30 by diet type (P < 0.05). In TRAMP, expression of Birc5, Mki67, Aurkb, Ccnb2, Foxm1, and Ccne2 is greater compared with WT and is decreased by castration. In parallel, castration reduces Ki67-positive staining (P < 0.0001) compared with intact and testosterone-repleted TRAMP mice. Expression of genes involved in androgen metabolism/signaling pathways is reduced by lycopene feeding (Srd5a1) and by tomato feeding (Srd5a2, Pxn, and Srebf1). In addition, tomato feeding significantly reduced expression of genes associated with stem cell features, Aldh1a and Ly6a, whereas lycopene feeding significantly reduced expression of neuroendocrine differentiation-related genes, Ngfr and Syp. Collectively, these studies demonstrate a profile of testosterone-regulated genes associated with early prostate carcinogenesis that are potential mechanistic targets of dietary tomato components. Future studies on androgen signaling/metabolism, stem cell features, and neuroendocrine differentiation pathways may elucidate the mechanisms by which dietary tomato and lycopene impact prostate cancer risk.

Longitudinal anatomical and metabolic MRI characterization of orthotopic xenograft prostate tumors in nude mice

PURPOSE

To assess anatomic and functional magnetic resonance imaging (MRI) for monitoring of tumor volume and metabolism of orthotopic xenograft prostate cancer tumors.

MATERIALS AND METHODS

Human-derived PC-3M cells were implanted into the prostate in 22 nude mice. Tumor volume and MRI appearance were monitored for up to 29 days. Histology was performed to detect metastases. Hyperpolarized [1-(13) C]pyruvate MRI was used to measure tumor metabolism on day 22.

RESULTS

Tumors were visible by MRI 9 days after tumor cell implantation. Tumor volume increased to 720 ± 190 mm(3) on day 29 of imaging. Metastasis was seen in the iliac lymph nodes at all timepoints, and in more distant lymph nodes at later timepoints, but was not detectable by MRI. Regions with low pyruvate uptake corresponded to regions with necrosis and had a higher lactate/pyruvate ratio (0.98 ± 0.4 vs. 1.6 ± 1.1).

CONCLUSION

MRI using the balanced steady-state free precession (bSSFP) sequence can be used to monitor tumor growth in orthotopic PC-3M tumors as early as 9 days post-injection. Hyperpolarized pyruvate MRI has potential to assess tumor metabolism and necrosis.

Optimization of the balanced steady state free precession (bSSFP) pulse sequence for magnetic resonance imaging of the mouse prostate at 3T

INTRODUCTION

MRI can be used to non-invasively monitor tumour growth and response to treatment in mouse models of prostate cancer, particularly for longitudinal studies of orthotopically-implanted models. We have optimized the balanced steady-state free precession (bSSFP) pulse sequence for mouse prostate imaging.

METHODS

Phase cycling, excitations, flip angle and receiver bandwidth parameters were optimized for signal to noise ratio and contrast to noise ratio of the prostate. The optimized bSSFP sequence was compared to T1- and T2-weighted spin echo sequences.

RESULTS

SNR and CNR increased with flip angle. As bandwidth increased, SNR, CNR and artifacts such as chemical shift decreased. The final optimized sequence was 4 PC, 2 NEX, FA 50°, BW ±62.5 kHz and took 14-26 minutes with 200 µm isotropic resolution. The SNR efficiency of the bSSFP images was higher than for T1WSE and T2WSE. CNR was highest for T1WSE, followed closely by bSSFP, with the T2WSE having the lowest CNR. With the bSSFP images the whole body and organs of interest including renal, iliac, inguinal and popliteal lymph nodes were visible.

CONCLUSION

We were able to obtain fast, high-resolution, high CNR images of the healthy mouse prostate with an optimized bSSFP sequence.

Indoleamine 2,3-dioxygenase (IDO) activity influence tumor growth in the TRAMP prostate cancer model

BACKGROUND

Indoleamine 2,3-dioxygenase (IDO) activity has been shown to be expressed in local lymph nodes and induce immune suppression of tumor immunity. Here we analyze the effect of IDO expression on prostate tumor growth using the transgenic adenocarcinoma of mouse prostate (TRAMP) animal model.

METHODS

Mice deficient in IDO expression were crossed to TRAMP mice and the time to the appearance of palpable tumors were measured. Immune histology was used to analyze the IDO expressing cells in tumors and in local lymph nodes. The levels of the substrate for IDO (tryptophane) and its product (kynurenine) was measured by HPLC.

RESULTS

We found that systemic IDO activity, determined as the kynurenine/tryptophan ratio in serum, correlated with the presence of palpable tumor. Immunohistological analysis showed increased numbers of IDO expressing cells in local lymph nodes. In tumors, IDO expression could be detected in the tumor stroma by both CD31+ and CD31(-) cells. Essentially no CD45+, IDO expressing cells could be detected in the tumors. The influence of IDO activity on tumor progression was analyzed by back-crossing TRAMP mice with IDO(-/-) animals and J-chain negative (J(-/-)) mice that have perturbed IDO activity. In both crosses a delayed tumor incidence was observed.

CONCLUSION

Our results argue for a role for IDO mediated immune suppression in the early stages of prostate cancer progression. However, since the intra-tumor IDO expression in J(-/-) mice was indistinguishable from that of C57BL/6 animals the IDO expression in the tumor tissue appears to be irrelevant for TRAMP tumor incidence.

Androgen ablation augments human HLA2.1-restricted T cell responses to PSA self-antigen in transgenic mice

BACKGROUND

In recent years, there has been an increasing interest in targeting human prostate tumor-associated antigens (TAAs) for prostate cancer immunotherapy as an alternative to other therapeutic modalities. However, immunologic tolerance to TAA poses a significant obstacle to effective, TAA-targeted immunotherapy. We sought to investigate whether androgen deprivation would result in circumventing immune tolerance to prostate TAA by impacting CD8 cell responses.

METHODS

To this end, we generated a transgenic mouse that expresses the human prostate-specific antigen (PSA) specifically in the prostate, and crossed it to the HLA-A2.1 transgenic mouse to evaluate how androgen deprivation affects human HLA A2.1-resticted T cell responses following immunization of PSA-expressing mice by vaccinia-PSA (PROSTVAC).

RESULTS

Our PSA transgenic mouse showed restricted expression of PSA in the prostate and detectable circulating PSA levels. Additionally, PSA expression was androgen-dependent with reduced PSA expression in the prostate within 1 week of castration, and undetectable PSA by day 42 after castration as evaluated by ELISA. Castration of the PSA/A2.1 hybrid mouse prior to immunization with a PSA-expressing recombinant vaccinia virus resulted in a significant augmentation of PSA-specific cytotoxic lymphocytes.

CONCLUSIONS

This humanized hybrid mouse model provides a well-defined system to gain additional insight into the mechanisms of immune tolerance to PSA and to test novel strategies aiming at circumventing immune tolerance to PSA and other TAA for targeted prostate cancer immunotherapy.

Plant-derived alternative treatments for the aging male: facts and myths

Soy- or red clover- derived products containing isoflavones have been amply studied in climacteric and postmenopausal women, and confusing contradicting results have been published. The beneficial effects on climacteric complaints, cholesterol and the development of osteoporosis are marginally at best and there are no uterine and mammary safety studies. In males, however, isoflavones may protect the prostate to make them less prone to develop cancer. Cell biological and animal experimental data support this notion. Clinical data about possible beneficial effects on cholesterol or in the bone are largely missing. Hence, soy or red clover products containing the mild estrogenic isoflavones with a slightly higher affinity to the estrogen receptor of the beta in comparison to the alpha subtype may prove to have some beneficial effects in males.

Targeting lymphotoxin-mediated negative selection to prevent prostate cancer in mice with genetic predisposition

The identification of individuals genetically susceptible to cancer calls for preventive measures to minimize the cancer risk in these high-risk populations. Immune prevention is made necessary by the anticipated health threat, but lack of enough high-affinity T cells against tumor-associated antigens and the unpredictability of tumor antigens make antigen-based immune prevention untenable for cancer. To address this issue, we explored a non-antigen-based cancer immune prevention strategy using the transgenic adenocarcinoma of mouse prostate model that spontaneously develops prostate cancer with 100% penetrance. We show that targeted mutation of the lymphotoxin alpha (LTalpha) gene efficiently rescued tumor-reactive T cells, drastically reduced cancer incidence, and almost completely ablated metastasis. Remarkably, short-term treatments with the fusion protein consisting of constant region of IgG and extracellular domain of lymphotoxin beta receptor (LTbetaRIg) interrupted clonal deletion, reduced the size of the primary cancer, and completely prevented metastasis later in life. Our data demonstrated the value of non-antigen-based immune prevention for those with a genetic predisposition to cancer.

Proteomics of rat prostate lobes treated with 2-N-hydroxylamino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 5alpha-dihydrotestosterone, individually and in combination

Epidemiological and preclinical studies suggest that environmental factors, hormonal responses and lifestyle, including diet and physical inactivity, are likely contributors to the initiation and progression of prostate cancer in humans. Although the effects of the food derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and/or testosterone (T) in the development of prostate cancer in the rat have been reported, the extent to which such compounds impact cancer related proteins is not clear. Knowledge of cancer-related proteins impacted by PhIP and/or T is prerequisite to developing novel strategies to early-detect prostate cancer. Male F344 rats were sacrificed, the prostate tissue isolated and separated into dorsolateral, ventral, and anterior lobes. The lobes were cultured and treated with 10(-3) M NHPhIP and/or 10(-7) M DT for 24 h. NHPhIP is the genotoxic form of PhIP and DT is the more proliferative form of T. We used 2D-DIGE and LC/MS/MS technologies to study the proteome of the prostate lobes to determine if the compounds will trigger detectable changes in expression of cancer-related proteins. Analysis of the signals from 2D-DIGE revealed that about 10% of proteins were differentially expressed in the NHPhIP and/or DT treatments compared to controls. Eight candidate protein spots detected by 2D-DIGE in at least two out of three lobes showed > or =2-fold difference between treated and control samples. Five out of the eight spots contained single proteins; including, phospholipase Calpha (PLP-Calpha), Rab7, SAR1a, ribosomal protein S7 (RPS7), and nucleoside diphosphate kinase (NDPK). A survey of the literature shows that NDPK expression is altered in human cancers, including prostate cancer. Thus, we validated the altered expression of NDPK by Western blot analysis. The concordance between 2D-DIGE and Western blot analysis was 80%. The results of this study demonstrate, for the first time, that the combination of 2D-DIGE and LC/MS/MS is a powerful tool for identification of proteins in the prostate tissue that are altered by environmental carcinogens and/or hormones.

B7 blockade alters the balance between regulatory T cells and tumor-reactive T cells for immunotherapy of cancer

PURPOSE

In prostate cancer-bearing host, regulatory T (Treg) cells restrain activity of tumor antigen-specific T cells. Because B7:CD28 interactions are needed for both function of CD4+CD25+ Treg cells and CD8+ effective T cells, targeting this pathway may help to overcome the immunotherapy barriers.

EXPERIMENTAL DESIGN

The anti-B7-1/B7-2 monoclonal antibodies were administered to a transgenic mouse model of prostate cancer (TRAMP) ectopically expressing SV40 large T antigen in different tumor development stages for prevention and therapy of prostate cancer. The treatment was also tested in treating transplanted MC38 colon adenocarcinoma in mice.

RESULTS

Here, we showed that short-term administration of anti-B7-1/B7-2 monoclonal antibodies in TRAMP mice leads to significant inhibited primary tumor growth and the size of metastatic lesions. The treatment is effective to inhibit MC38 colon cancer growth. Correspondingly, this treatment results in a transient reduction of Treg in both thymus and the periphery. In vivo cytotoxicity assay revealed T antigen-specific CTL effectors in anti-B7-treated but not control IgG-treated TRAMP mice.

CONCLUSIONS

Transient blockade of B7-1/B7-2 alters the balance between Treg and cancer-reactive T cells to enhance cancer immunotherapy.

Endocrine therapy for prostate cancer

Endocrine therapy of prostate cancer has mostly been reserved to patients with advanced stages of the disease. The principle for endocrine treatment of prostate cancer is elimination of stimulatory effects of testicular androgens on the prostate tumour cells. This can be achieved by surgical removal of the testes, by inhibition of pituitary gonadotrohin secretion by GnRH-angonsists or antagonists, by oestrogens or by non-steroidal antiandrogens. Since non-steroidal antiandrogens have fewer side-effects than castrational therapies, there is an increased interest for using endocrine treatment as adjuvant therapy after localized treatment. At least in certain stages of the disease, early hormonal treatment may have survival benefits. The timing of endocrine therapy, the usage of combined androgen blockade and intermittent endocrine therapy will be discussed in this overview.

Early and delayed castrations confer a similar survival advantage in TRAMP mice

The most appropriate time to introduce androgen deprivation therapy for prostate cancer remains controversial. Our aim was to evaluate the effects of early versus delayed surgical castration on prostate cancer progression and survival in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. TRAMP mice were randomly divided into three groups: the early castration group (on which castration was performed at the age of 4 weeks), the delayed castration group (on which castration was performed when abdominal tumours could be palpated), and the sham-castrated group. Mice were monitored daily throughout their lives until cancer-related death or the development of an obviously moribund appearance, at which time the individual mouse was killed. Androgen receptor expression in prostate tumours was also evaluated. The results shows that the average lifespan in early castration, delayed castration and sham-castrated groups were 54.1 weeks, 59.9 weeks and 39.1 weeks, respectively. Both early castration and delayed castration conferred a statistically significant survival advantage when compared with the sham-castrated group (P<0.001). However, the difference in lifespan between the early castration group and the delayed castration group was not statistically significant (P=0.85). The increase in lifespan in the TRAMP mice that received either early or delayed castration correlated with lower G/B value (genitourinary tract weight/body weight) at death than the sham-castrated mice. In conclusion, early and delayed castrations in TRAMP mice prolonged survival to a similar extent. This finding may provide a guide for clinical practice in prostate cancer therapy.

Characterization of SV-40 Tag rats as a model to study prostate cancer

Background

Prostate cancer is the second most frequently diagnosed cancer in men. Animal models that closely mimic clinical disease in humans are invaluable tools in the fight against prostate cancer. Recently, a Simian Virus-40 T-antigen (SV-40 Tag) targeted probasin promoter rat model was developed. This model, however, has not been extensively characterized; hence we have investigated the ontogeny of prostate cancer and determined the role of sex steroid receptor and insulin-like growth factor-1 (IGF-1) signaling proteins in the novel SV-40 Tag rat.

Methods

The SV-40 Tag rat was histopathologically characterized for time to tumor development, incidence and multiplicity and in the ventral, dorsal, lateral and anterior lobes of the prostate. Immunoassay techniques were employed to measure cell proliferation, apoptosis, and sex steroid receptor and growth factor signaling-related proteins. Steroid hormone concentrations were measured via coated well enzyme linked immunosorbent assay (ELISA) kits.

Results

Prostatic intraepithelial neoplasia (PIN) and well-differentiated prostate cancer developed as early as 2 and 10 weeks of age, respectively in the ventral prostate (VP) followed by in the dorsolateral (DLP). At 8 weeks of age, testosterone and dihydrotestosterone (DHT) concentrations in SV-40 Tag rats were increased when compared to non-transgenic rats. High cell proliferation and apoptotic indices were found in VP and DLP of transgenic rats. Furthermore, we observed increased protein expression of androgen receptor, IGF-1, IGF-1 receptor, and extracellular signal-regulated kinases in the prostates of SV-40 Tag rats.

Conclusion

The rapid development of PIN and prostate cancer in conjunction with the large prostate size makes the SV-40 Tag rat a useful model for studying prostate cancer. This study provides evidence of the role of sex steroid and growth factor proteins in prostate cancer development and defines appropriate windows of opportunity for preclinical trials and aids in the rational design of chemoprevention, intervention, regression, and therapeutic studies using prostate cancer rodent models.

Divergent effects of castration on prostate cancer in TRAMP mice: possible implications for therapy

PURPOSE

Divergent responses to androgen deprivation have been found in patients and in animal models of prostate cancer. The molecular basis for these different outcomes is unknown. Our aim was to identify the molecular responses of prostate cancer with divergent outcomes to androgen deprivation in TRAMP mice.

EXPERIMENTAL DESIGN

Castrated and noncastrated B6xFVB TRAMP mice were evaluated for survival, tumor development, pathology, and expressions of specific proteins at different time points.

RESULTS

TRAMP mice responded differentially to androgen deprivation. In the majority, primary tumors regressed after castration (positive response), whereas in others the tumors grew even more aggressively than in the noncastrated mice (negative response). Mice with regressed tumors had the highest survival rates. Androgen receptor was elevated in all tumors from castrated mice despite significant differences in tumor sizes. In positively responding tumors, expressions of Bcl-2 and Grp78 were greatly increased by 10 weeks after castration, whereas expressions of Bax, Bcl-xl, SV40 T antigen, and c-myc were lower. These tumors also showed a reduction in proliferating cells compared with noncastrates and negatively responding tumors. Most of these changes disappeared 20 weeks after castration, by which time there was an increase in the size of primary tumors as well as in distant metastasis.

CONCLUSIONS

In TRAMP prostate cancer that responded positively to castration, different expression patterns of proteins involved in cellular apoptosis, stress, and proliferation occur approximately 10 weeks after castration. This may be an optimal time for targeting Bcl-2, and perhaps Grp78, to enhance the antitumor effects of androgen deprivation.

Phenotype-specific CpG island methylation events in a murine model of prostate cancer

Aberrant DNA methylation plays a significant role in nearly all human cancers and may contribute to disease progression to advanced phenotypes. Study of advanced prostate cancer phenotypes in the human disease is hampered by limited availability of tissues. We therefore took advantage of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model to study whether three different phenotypes of TRAMP tumors (PRIM, late-stage primary tumors; AIP, androgen-independent primary tumors; and MET, metastases) displayed specific patterns of CpG island hypermethylation using Restriction Landmark Genomic Scanning. Each tumor phenotype displayed numerous hypermethylation events, with the most homogeneous methylation pattern in AIP and the most heterogeneous pattern in MET. Several loci displayed a phenotype-specific methylation pattern; the most striking pattern being loci methylated at high frequency in PRIM and AIP but rarely in MET. Examination of the mRNA expression of three genes, BC058385, Goosecoid, and Neurexin 2, which exhibited nonpromoter methylation, revealed increased expression associated with downstream methylation. Only methylated samples showed mRNA expression, in which tumor phenotype was a key factor determining the level of expression. The CpG island in the human orthologue of BC058385 was methylated in human AIP but not in primary androgen-stimulated prostate cancer or benign prostate. The clinical data show a proof-of-principle that the TRAMP model can be used to identify targets of aberrant CpG island methylation relevant to human disease. In conclusion, phenotype-specific hypermethylation events were associated with the overexpression of different genes and may provide new markers of prostate tumorigenesis.

Effects of castration on the development of prostate adenocarcinoma from its precursor HGPIN and on the occurrence of androgen-independent, poorly differentiated carcinoma in TRAMP mice

Androgen ablation is thought to exert selective pressure for the development of androgen-independent forms of prostate cancer. This study was set up to investigate the effects of surgical castration on the development of prostate adenocarcinoma (ADC) from its precursor (high-grade prostate intraepithelial neoplasia (HGPIN)) and on the occurrence of androgen-independent, poorly differentiated carcinoma (PDC) in (C57Bl/6 transgenic adenocarcinoma of mouse prostate) TRAMP mice. It was found that castration cures HGPIN and ADC and prevents their further occurrence and growth, but has no effect on PDC. This indicates that in this model, PDC is not the progression of ADC favoured by androgen ablation and that its initiating cells are different from those of HGPIN and ADC.

Origin of androgen-insensitive poorly differentiated tumors in the transgenic adenocarcinoma of mouse prostate model

Following castration, the transgenic adenocarcinoma of mouse prostate (TRAMP) model demonstrates rapid development of SV40-Tag-driven poorly differentiated tumors that express neuroendocrine cell markers. The cell population dynamics within the prostates of castrated TRAMP mice were characterized by analyzing the incorporation of 5-bromodeoxyuridine (BrdUrd) and the expression of SV40-Tag, synaptophysin, and androgen receptor (AR). Fourteen days postcastration, the remaining epithelial cells and adenocarcinoma cells were nonproliferative and lacked detectable SV40-Tag or synaptophysin expression. In contrast, morphologically distinct intraglandular foci were identified which expressed SV40-Tag, synaptophysin, and Ki67, but that lacked AR expression. These proliferative SV40-Tag and synaptophysin-expressing intraglandular foci were associated with the rare BrdUrd-retaining cells. These foci expanded rapidly in the postcastration prostate environment, in contrast to the AR- and SV40-Tag-expressing adenocarcinoma cells that lost SV40-Tag expression and underwent apoptosis after castration. Intraglandular foci of synaptophysin-expressing cells were also observed in the prostates of intact TRAMP mice at a comparable frequency; however, they did not progress to rapidly expanding tumors until much later in the life of the mice. This suggests that the foci of neuroendocrine-like cells that express SV40-Tag and synaptophysin, but lack AR, arise independent of androgen-deprivation and represent the source of the poorly differentiated tumors that are the lethal phenotype in the TRAMP model.

Protein Kinase Cε Interacts with Signal Transducers and Activators of Transcription 3 (Stat3), Phosphorylates Stat3Ser727, and Regulates Its Constitutive Activation in Prostate Cancer

Prostate cancer is the most common type of cancer in men and ranks second only to lung cancer in cancer-related deaths. The management of locally advanced prostate cancer is difficult because the cancer often becomes hormone insensitive and unresponsive to current chemotherapeutic agents. Knowledge about the regulatory molecules involved in the transformation to androgen-independent prostate cancer is essential for the rational design of agents to prevent and treat prostate cancer. Protein kinase Cepsilon (PKCepsilon), a member of the novel PKC subfamily, is linked to the development of androgen-independent prostate cancer. PKCepsilon expression levels, as determined by immunohistochemistry of human prostate cancer tissue microarrays, correlated with the aggressiveness of prostate cancer. The mechanism by which PKCepsilon mediates progression to prostate cancer remains elusive. We present here for the first time that signal transducers and activators of transcription 3 (Stat3), which is constitutively activated in a wide variety of human cancers, including prostate cancer, interacts with PKCepsilon. The interaction of PKCepsilon with Stat3 was observed in human prostate cancer, human prostate cancer cell lines (LNCaP, DU145, PC3, and CW22rv1), and prostate cancer that developed in transgenic adenocarcinoma of mouse prostate mice. In reciprocal immunoprecipitation/blotting experiments, prostatic Stat3 coimmunoprecipitated with PKCepsilon. Localization of PKCepsilon with Stat3 was confirmed by double immunofluorescence staining. The interaction of PKCepsilon with Stat3 was PKCepsilon isoform specific. Inhibition of PKCepsilon protein expression in DU145 cells using specific PKCepsilon small interfering RNA (a) inhibited Stat3Ser727 phosphorylation, (b) decreased both Stat3 DNA-binding and transcriptional activity, and (c) decreased DU145 cell invasion. These results indicate that PKCepsilon activation is essential for constitutive activation of Stat3 and prostate cancer progression.

In vivo MRI volumetric measurement of prostate regression and growth in mice

Background

Mouse models for treatment of late-stage prostate cancer are valuable tools, but assessing the extent of growth of the prostate and particularly its regression due to therapeutic intervention or castration is difficult due to the location, small size and interdigitated anatomy of the prostate gland in situ. Temporal monitoring of mouse prostate regression requires multiple animals and examination of histological sections.

Magnetic resonance imaging and histopathological characterization of prostate tumors in TRAMP mice as model for pre-clinical trials

BACKGROUND

The Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) develops progressive forms of prostate cancer. Due to the lack of a validated non-invasive methodology, pathology has been so far the most common parameter evaluated in efficacy studies.

METHODS

We studied by magnetic resonance imaging (MRI) 210 mice that were repeatedly measured up to 33 weeks of age in order to stage prostate tumors and follow pathological progression in single animals. A pre-clinical trial with doxorubicin was also performed.

RESULTS

Progressive forms of cancer (well and poorly differentiated (PD) adenocarcinomas) were easily recognized on MR images and MRI findings were validated against histopathological analysis. Age at tumor onset was different for the two tumoral forms. Doxorubicin treatment caused a strong reduction in tumor volume.

CONCLUSIONS

Prostate cancer in TRAMP mice is multifocal and heterogeneous: a non-invasive methodology such as MRI facilitates the rational design of translational pre-clinical trials in this widely used animal model.

Immediate versus deferred androgen deprivation treatment in patients with node-positive prostate cancer after radical prostatectomy and pelvic lymphadenectomy

BACKGROUND

Appropriate timing of androgen deprivation treatment (ADT) for prostate cancer is controversial. Our aim was to determine whether immediate ADT extends survival in men with node-positive prostate cancer who have undergone radical prostatectomy and pelvic lymphadenectomy compared with those who received ADT only once disease progressed.

METHODS

Eligible patients from 36 institutes in the USA were randomly assigned in 1988-93 to receive immediate ADT (n=47) or to be observed (n=51), with ADT to be given on detection of distant metastases or symptomatic recurrences. Patients were followed up every 3 months for the first year and every 6 months thereafter. The primary endpoint was progression-free survival; secondary endpoints were overall and disease-specific survival. Analysis was by intention to treat. To ensure that the treatment groups were comparable, we did a retrospective central pathology review of slides and regraded the Gleason scores for available samples. This trial predates the requirement for clinical trial registration.

FINDINGS

At median follow-up of 11.9 years (range 9.7-14.5 for surviving patients), men assigned immediate ADT had a significant improvement in overall survival (hazard ratio 1.84 [95% CI 1.01-3.35], p=0.04), prostate-cancer-specific survival (4.09 [1.76-9.49], p=0.0004), and progression-free survival (3.42 [1.96-5.98], p<0.0001). Of 49 histopathology slides received (19 immediate ADT, 30 observation), 16 were downgraded from the original Gleason score (between groups < or = 6, 7, and > or = 8) and five were upgraded. We recorded similar proportions of score changes in each group (p=0.68), and no difference in score distribution by treatment (p=0.38). After adjustment for score, associations were still significant between treatment and survival (overall, p=0.02; disease-specific, p=0.002; progression-free survival, p<0.0001).

INTERPRETATION

Early ADT benefits patients with nodal metastases who have undergone prostatectomy and lymphadenectomy, compared with those who receive deferred treatment. The beneficial effects of early ADT, rather than an imbalance in risk factors, are likely to explain the differences in outcomes between treatments.

In vivo magnetic resonance volumetric and spectroscopic analysis of mouse prostate cancer models

BACKGROUND

Mouse prostate cancer modeling presents unique obstacles to the study of spontaneous tumor initiation and progression due to the anatomical location of the tissue.

RESULTS

High resolution (130 microm(x) x 130 microm(y) x 300 microm(z)), three-dimensional MRI allowed for the visualization, segmentation, and volumetric measurement of the prostate from normal and genetically engineered animals, in vivo. Additionally, MRS performed on the prostate epithelia of probasin-ErbB-2Delta x Pten(+/-) mice identified changes in the relative concentrations of the metabolites choline and citrate, which was not observed in TRAMP mice.

METHODS

T1-weighted MRI was performed on normal, TRAMP, probasin-ErbB-2/Her2/Neu (probasin-ErbB-2Delta), and probasin-ErbB-2Delta in the context of decreased Pten activity (probasin-ErbB-2Delta x Pten(+/-)) mice. Volume-localized single-voxel proton magnetic resonance spectroscopy (SVS (1)H MRS) was also performed.

CONCLUSIONS

The data presented supports the use of combined MRI and MRS for the measurement of biochemical and morphometric alterations in mouse models of prostate cancer.

Androgens regulate the immune/inflammatory response and cell survival pathways in rat ventral prostate epithelial cells

A major hurdle in understanding the role of androgens is the heterogeneity of androgen receptor (AR) expression in the prostate. Because the majority of prostate cancer arises from the AR-positive secretory luminal epithelial cells, identifying the androgen-mediated pathways in the prostate epithelium is of great significance to understanding their role in prostate pathogenesis. To meet this objective, the current study was designed to identify immediate-early genes expressed in response to the synthetic androgen R1881 in cultured rat ventral prostate epithelial cells. Rat ventral prostate epithelial cells, purified from 20-d-old rats, were cultured, and the presence of AR and the response to androgen were established. The cells were then treated with R1881 for 2 and 12 h to capture immediate-early genes in an Affymetrix-based gene chip platform. A total of 66 nonredundant genes were identified that were responsive to R1881. The functional androgen response elements were identified in the proximal promoter to determine possible molecular mechanism. Cluster analysis identified five distinct signatures of R1881-induced genes. Pathway analysis suggested that R1881 primarily influences cell proliferation/differentiation and inflammatory/immune response pathways. Androgens appear to regulate cell renewal by regulating differentiation, cell proliferation, and apoptosis. Two mutually exclusive inflammatory response pathways were observed. The interferon pathway was up-regulated, and the ILs were down-regulated. The data identified novel androgen-regulated genes (e.g. Id1, Id3, IL-6, IGF-binding protein-2 and -3, and JunB). The loss of androgen regulation of these genes can have important consequences for cellular transformation and transition to androgen-independent growth and survival.

Reduced risk of prostate cancer in men who are childless as compared to those who have fathered a child: a population based case-control study

Androgens are believed to play a major role in the etiology of prostate cancer, but studies of sex-hormone exposure in relation to risk for prostate cancer have been inconclusive. Male fertility may be an indicator of long-term androgen status. To study the role of testicular function in prostate cancer development, we have assessed number of biological children in relation to risk for this malignancy. We carried out a population-based case-control study with retrospective ascertainment of cases occurring in Sweden between 1958-98. In total, 48,850 cases of prostate cancer were identified through the nation-wide Cancer Registry. For each case, one control, matched by year of birth, was randomly selected from the Swedish population. Information on offspring was obtained from the Swedish Multi-Generation Registry. We estimated odds ratios (OR) and 95% confidence intervals (CI) for the association between number of offspring and risk for subsequent prostate cancer. Being childless or having fathered one child only were associated with reduced risks for prostate cancer compared to having fathered 2 or more children (OR = 0.83; 95% CI = 0.81-0.86 and OR = 0.93; 95% CI = 0.90-0.96, respectively). There was no further change in risk associated with fathering of more than 2 children. The risk for prostate cancer is reduced among childless men. A dysfunctioning reproductive apparatus fueling to a lesser extent prostatic growth, could be a plausible mechanism of this association.

Regression of mouse prostatic intraepithelial neoplasia by nonsteroidal anti-inflammatory drugs in the transgenic adenocarcinoma mouse prostate model

PURPOSE

Epidemiologic studies have revealed a decreased risk of colon cancer among people who have regularly taken cyclooxygenase (COX)-2 inhibitors such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Whereas the selective COX-2 inhibitor celecoxib and exisulind, a metabolic product of sulindac, have gained increasing attention as efficacious chemopreventive agents against colon and prostate cancer, not much is known about the underlying molecular targets and mechanisms. Moreover, the side effects of NSAIDs are a major obstacle for large-scale application to the prevention of cancer in humans; for example, in the United States in 1998, there were 16,550 deaths from NSAID-induced gastrointestinal complications. The toxicity associated with these compounds is raising concerns, and more needs to be known about their mode of action and molecular targets.

EXPERIMENTAL DESIGN

We used the transgenic mouse prostate (TRAMP) model, which exhibits similarities with human prostate cancer, including epithelial origin, progression from the PIN stage to adenocarcinoma, and metastasis by a transgene that is hormonally regulated by androgens. In addition to histologically analyzing the PIN lesions of the dorsolateral prostate from TRAMP mice, we delineated the molecular targets and mechanisms of celecoxib and exisulind against mouse PIN lesions. We performed Western blot analysis of the total protein lysate from the tissues of mouse PIN lesions to measure the level of expression of androgen receptor, vascular endothelial growth factor, nuclear factor-kappaB p65, BclII, AKT (total and phosphorylated Ser473), p53, cyclin-dependent kinase inhibitor p21WAF1/CIP1, p27, BAX, and caspase-3 to demonstrate the COX-2-independent mechanism involved in the inhibition of PIN lesions of the dorsolateral prostate by both celecoxib and exisulind.

RESULTS

We found for the first time that (a) both celecoxib and exisulind as dietary supplements induce strong inhibitory effects against prostate cancer at doses of 800 and 500 ppm, respectively, after 16 weeks; (b) the histologic analysis of the dorsolateral prostate after 2 weeks of treatment indicated a reduction of PIN lesions from 75% to 19% with celecoxib and to 16% with exisulind; (c) more importantly, those few PINs and adenocarcinomas in the groups treated with celecoxib or exisulind showed more apoptotic cells, lower levels of proliferating cell nuclear antigen, and a lower number of mitotic cells. To understand the molecular mechanisms involved in the inhibition of PIN lesions, first, we examined the expression of molecular targets involved in angiogenesis and inflammatory processes. It was clearly evident from Western blot analysis of the total protein lysate derived from the dorsolateral prostate tissues with PIN lesions that expression of androgen receptor, vascular endothelial growth factor, nuclear factor-kappaB p65, and BclII is down-regulated more effectively by celecoxib. Down-regulation of AKT protein (total and phosphorylated at Ser473) signaling by celecoxib clearly indicates an inhibition of the survival gene and the pathological process that could otherwise lead to adenocarcinoma.

CONCLUSIONS

Overall, the findings from this study clearly show the effectiveness of celecoxib and exisulind in reducing the PIN lesions by modulating a cascade of molecular targets involved in COX-2-dependent and -independent mechanisms. Whereas these agents are already in clinical trial or in use as chemopreventive agents, findings from this study demonstrate the difference in their mode of action, thus helping us to understand the side effects.

Androgen ablation mitigates tolerance to a prostate/prostate cancer-restricted antigen

To understand the T cell response to prostate cancer, we created transgenic mice that express a model antigen in a prostate-restricted pattern and crossed these animals to TRAMP mice that develop spontaneous prostate cancer. Adoptive transfer of prostate-specific CD4 T cells shows that, in the absence of prostate cancer, the prostate gland is mostly ignored. Tumorigenesis allows T cell recognition of the prostate gland--but this recognition is tolerogenic, resulting in abortive proliferation and ultimately in hyporesponsiveness at the systemic level. Androgen ablation (the most common treatment for metastatic prostate cancer) was able to mitigate this tolerance--allowing prostate-specific T cells to expand and develop effector function after vaccination. These results suggest that immunotherapy for prostate cancer may be most efficacious when administered after androgen ablation.

Gene expression profiling identifies a unique androgen-mediated inflammatory/immune signature and a PTEN (phosphatase and tensin homolog deleted on chromosome 10)-mediated apoptotic response specific to the rat ventral prostate

Understanding androgen regulation of gene expression is critical for deciphering mechanisms responsible for the transition from androgen-responsive (AR) to androgen-independent (AI) prostate cancer (PCa). To identify genes differentially regulated by androgens in each prostate lobe, the rat castration model was used. Microarray analysis was performed to compare dorsolateral (DLP) and ventral prostate (VP) samples from sham-castrated, castrated, and testosterone-replenished castrated rats. Our data demonstrate that, after castration, the VP and the DLP differed in the number of genes with altered expression (1496 in VP vs. 256 in DLP) and the nature of pathways modulated. Gene signatures related to apoptosis and immune response specific to the ventral prostate were identified. Microarray and RT-PCR analyses demonstrated the androgen repression of IGF binding protein-3 and -5, CCAAT-enhancer binding protein-delta, and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) genes, previously implicated in apoptosis. We show that PTEN protein was increased only in the luminal epithelial cells of the VP, suggesting that it may be a key mediator of VP apoptosis in the absence of androgens. The castration-induced immune/inflammatory gene cluster observed specifically in the VP included IL-15 and IL-18. Immunostaining of the VP, but not the DLP, showed an influx of T cells, macrophages, and mast cells, suggesting that these cells may be the source of the immune signature genes. Interestingly, IL-18 was localized mainly to the basal epithelial cells and the infiltrating macrophages in the regressing VP, whereas IL-15 was induced in the luminal epithelium. The VP castration model exhibits immune cell infiltration and loss of PTEN that is often observed in progressive PCa, thereby making this model useful for further delineation of androgen-regulated gene expression with relevance to PCa.

Early versus late hormonal therapy for prostate cancer

Hormonal therapy remains the critical therapeutic option for men with advanced prostate cancer. However, considerable uncertainty remains regarding the appropriate choice/timing and actual benefits of hormonal therapy in various situations. This article reviews the relevant studies of immediate versus deferred hormonal therapy in patients with prostate cancer. The evidence from the data supports that early treatment is beneficial to many patients. Significant survival benefit of early hormonal therapy has been observed among patients with asymptomatic metastatic disease, node-positive but clinically localized disease after radical prostatectomy and lymphadenectomy, and advanced local/regional disease during and after radiotherapy.

Genetically modified mice and their use in developing therapeutic strategies for prostate cancer

PURPOSE

At the National Cancer Institute a comprehensive program has been developed for accelerating prostate cancer research, especially in the area of mouse models for human cancers. This review focuses on transgenic mouse models for elucidating the molecular and cellular processes that lead to prostate cancer initiation, progression and metastasis, and on their suitability for therapeutic and chemopreventive trials.

MATERIALS AND METHODS

Published data from MEDLINE, http://emice.nci.nih.gov/, our laboratory and other investigators are reviewed.

RESULTS

Currently no 1 mouse model displays the entire continuum of human prostate cancer initiation, development and metastasis. The loss or over expression of a single gene results primarily in epithelial hyperplasia, prostatic intraepithelial neoplasia or more aggressive localized adenocarcinoma. To date the only models that develop lung, liver and occasionally bone metastasis are those that express SV40 large T antigen. A number of models have been used to investigate the efficacy of androgen deprivation, lovastatin, vitamin D, the anti-inflammatory drug E-7869, genistein and (-)-epigallocatechin-3-gallate as therapeutic or chemopreventive agents. Noninvasive optical imaging technologies facilitate the detection of metastatic lesions and the effects of therapeutic agents on tumor regression.

CONCLUSIONS

Integrating mouse studies with human clinical trials would ensure that mechanisms that promote prostate cancer are identified and potential therapeutic targets are validated.

Decreasing mortality rates for prostate cancer: possible role of hormonal therapy?

Within the last decade prostate cancer mortality rates have started to decrease in some countries. Although it is tempting to assume that these trends are a result of earlier diagnosis and aggressive therapeutic intervention, as a consequence of prostate-specific antigen screening, definitive results from randomized trials of screening will not be available for several years. Moreover, there is mounting evidence that the effects of screening cannot be entirely responsible for this reduction in mortality rates. This review explores the possibility that other factors, particularly the increased uptake of early hormonal therapy, are contributing to the observed changes in mortality.

Effect of time of castration and tumour volume on time to androgen-independent recurrence in Shionogi tumours

OBJECTIVE

To use the androgen-dependent Shionogi tumour model in mice to help define the effects of the timing of androgen ablation on the development of androgen resistance in prostate cancer, as the timing of androgen ablation remains controversial.

MATERIALS AND METHODS

Groups of nine mice were castrated at 1, 3, 6, 10 and 14 days after tumour inoculation, with a similar-sized group of mice castrated before tumour inoculation serving as a control. The time of first palpable tumour recurrence and tumour volume was monitored after castration.

RESULTS

All mice were observed for > or = 80 days after castration. Only mice castrated at 10 and 14 days had palpable tumour at the time of castration. Mice castrated at 14 days had the highest rate of early tumour recurrence (all nine) while mice castrated before inoculation or at 1 and 3 days afterward had a significantly lower rate of tumour recurrence (four of nine; P < 0.01). Mice castrated at 14 and 10 days had tumour recurrence significantly earlier than mice in the other groups. When calcium-channel blockers were administered to inhibit apoptosis, all mice had a similar time to recurrence and time to death regardless of the time of castration.

CONCLUSIONS

Large tumour volume and corresponding delay in castration reduced the time to androgen-independent tumour recurrence and survival. Earlier androgen ablation, at the time of subclinical (impalpable) disease, significantly delayed the rate and time to androgen-independent recurrence compared with delayed therapy when the tumour burden was high.

Immunization against luteinizing hormone-releasing hormone fusion proteins does not decrease prostate cancer in the transgenic adenocarcinoma mouse prostate model

This study was undertaken to test the effect of immunization against luteinizing hormone-releasing hormone (LHRH) fusion proteins on the development and progression of prostate cancer in the transgenic adenocarcinoma mouse prostate (TRAMP) model. Two LHRH fusion proteins, ovalbumin with seven LHRH peptides (OV-LHRH-7), and thioredoxin with seven LHRH peptides (TH-LHRH-7) were used in a cocktail vaccine. Two groups of male TRAMP mice were immunized with the cocktail. Primary immunizations were at either 4 or 8 weeks of age. LHRH immunized mice (n=19) were compared with castrated (n=19) and intact mice (n=18) for testosterone concentration, tumor weight, and lifespan. Immunization against LHRH in the TRAMP mice resulted in significant production of antibodies to LHRH compared with surgically castrated and intact control mice. Testicular weight was significantly reduced in the LHRH immunized groups compared with intact control mice. Serum testosterone was reduced (P<0.05) in the immunized mice compared with intact control mice and was not different from that of castrated mice (P>0.05). Tumor weight was variable and inconsistent throughout all treatment groups. Lifespan was not increased by immunization against LHRH or castration. Intact control mice (lived the longest (227+/-11 days), whereas immunized mice lived 206+/-11 days and castrated mice lived 213+/-13 days. Tumors from immunized TRAMP mice appeared more aggressive than tumors of castrated and intact mice, as demonstrated by 35% expression of gross lung tumors in the immunized mice whereas none were observed in the castrated or intact TRAMP mice. Prostate cancer is initially dependent upon androgens for growth and development, but cells have the ability to escape androgen dependence and progress to an androgen independent state, which was evident in this study. The TRAMP mouse model immunized against LHRH may have utility in future studies and treatments of the androgen independent prostate cancer.

The timing of hormone therapy for men with asymptomatic advanced prostate cancer

The most appropriate time to introduce hormonal therapy for patients with advanced prostate cancer is a contentious issue. Recent prospective studies comparing immediate and deferred hormonal therapy (medical or surgical castration) on survival outcome are reviewed with the aim of redefining the most appropriate time to initiate hormonal therapy for individual patients. The evidence supports the use of immediate hormonal therapy in previously untreated patients with advanced disease (M1) and also the use of adjuvant hormonal therapy after radical prostatectomy and lymphadenectomy for node-positive (but clinically localized) disease. Immediate hormonal therapy may also be advantageous in advanced local/regional disease when it is the primary treatment contemplated (i.e., without any definitive curative therapy to the prostate), although not all studies show this. Adjuvant hormonal therapy has significantly improved survival in some studies in the radiotherapy setting; the lack of statistically significant benefits in other studies may be a result of the timing of hormonal therapy in relation to the administration of external beam irradiation. Decisions on the immediate initiation of hormonal therapy should also take into account the patient's life expectancy and the side effects and long-term complications of androgen deprivation therapy. Recent epidemiological studies indicate that prostate cancer mortality has fallen in the USA. This decline in prostate cancer mortality is likely to be multifactorial with early application of hormonal therapy being one potential contributory factor. It is recommended that after an assessment of their disease risk, patients should be informed about the benefits and side effects of all potential treatment options and allowed to make an informed choice about their treatment.

A grading scheme for the assessment of proliferative lesions of the mouse prostate in the TRAMP model

To improve the precision and consistency of experimental results, we have developed a scoring system for proliferative epithelial lesions in the mouse prostate based on histological growth patterns observed in individual lobes. Severity of proliferative lesions was divided into 6 categories; the grade of the most advanced lesion was identified for each lobe and its distribution estimated semiquantitatively. A numerical score combining grade and distribution of the most advanced lesion in each lobe was assigned and termed the "distribution-adjusted lesion grade"; the mean of these scores was calculated for each treatment group. Using this grading scheme, we assessed lesion development in ad libitum-fed and 20%-diet-restricted groups of TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice that were started on study at 7 weeks of age and sacrificed when 11 and 20 weeks old. The anterior, dorsal, lateral, and ventral prostate lobes showed clear reductions in lesion severity in diet-restricted TRAMPS at 11 and 20 weeks. This method for scoring the epithelial pathology of the prostate in the TRAMP model with minimal to severe proliferative lesions utilizes the natural history of lesion development for assessing the effects of chemical and dietary interventions.

Flt3 ligand expands dendritic cell numbers in normal and malignant murine prostate

We have developed a murine model that facilitates the structural and functional analysis in vivo of dendritic cell (DC)-mediated phagocytosis of prostate epithelial cells. Recombinant human Flt3 ligand (rhFL) expands the number of dendritic cells in lymphoid and non-lymphoid tissues of mice. We show that rhFL also induced the ingress of dendritic cells into murine prostate, which involutes via epithelial apoptosis after surgical castration. Intact or castrated C57BL/6 and syngeneic transgenic adenocarcinoma of mouse prostate (TRAMP) mice were treated with rhFL or PBS control. Prostate and spleen were then studied by flow cytometry and immunohistochemistry. The number of prostatic CD11c+ and CD11b+ dendritic cells increased significantly in rhFL-treated mice compared with PBS-treated control mice and this effect was greatly augmented by castration of the mice. The immunophenotype of rhFL-mobilized prostatic cells was consistent with that of Langerhans cells (MHC class II+, CD11c+,CD11b+, DEC-205+, CD8 alpha-).MHC class II+ and CD11c+ dendritic cells that were present in the prostate glands of rhFL-treated and castrated C57BL/6 mice were intimately associated with TUNEL+ inclusions, which suggests that Langerhans-type dendritic cells in prostate participated in the clearance of apoptotic cells. Expression of MHC class II, CD54, CD80 and CD86 by prostatic dendritic cells was not up-regulated after castration and freshly isolated rhFL-induced prostate cells were unable to prime allogeneicT cells unless they were activated by culture either on plastic or with recombinant soluble CD40 ligand. Our data suggest that rhFL-mobilized prostatic dendritic cells resemble the functionally immature dendritic cells, which reside in peripheral tissues and contribute to the maintenance of peripheral tolerance.

Derivation of MPR and TRAMP models of prostate cancer and prostate cancer metastasis for evaluation of therapeutic strategies

Pre-clinical models of primary and metastatic prostate cancer are increasingly needed to evaluate efficacy of the new therapeutic strategies currently under investigation. The androgen-independent RM1 and androgen-dependent TR cell lines derived from transgenic mouse models of prostate cancer were examined in this regard. Following implantation in immune competent mice, the RM1 cell line was able to generate extremely fast growing s.c. and iprost tumors and metastatic lung lesions providing a time period of approximately 14-17 days from the time of tumor establishment to animal sacrifice to assess therapies. Implantation of TR cell lines resulted in more slowly growing s.c. and iprost tumors and metastatic lung lesions that exhibited highly variable incidence and growth. These models represent the best available means to evaluate therapeutics in primary and metastatic prostate cancer variants in an intact immune system.

Timing hormonal therapy in prostate cancer

The history of the use of hormonal therapy to treat prostrate cancer is outlined, focusing on such treatments and disease scenarios as diethylstilboestrol therapy, androgen ablation alone or in conjunction with radiation, and the treatment of minimal disease burdens. Studies have pointed to the benefits of initiating androgen ablation therapy earlier in the treatment of prostate cancer; the greatest benefits of anti-androgen therapy may be gained when only tiny amounts of prostate cancer are present.

Autochthonous mouse models for prostate cancer: past, present and future

Prostate cancer continues to be the second leading cancer related death among men. In order to more fully develop effective prevention and intervention strategies for this prevalent disease, the underlying molecular mechanisms of initiation, progression and metastatic spread must be understood. To this end mouse models have an essential role in prostate cancer research in that they can closely mimic the pathological and biochemical features of the disease. In this review we discuss the history of autochthonous murine models of prostate cancer, the essentials of the idealized mouse model for prostate cancer and speculate on approaches towards this goal.

Bcl-2 accelerates multistep prostate carcinogenesis in vivo

The impact of bcl-2 proto-oncogene expression on the pathogenesis and progression of prostate cancer was examined in a transgenic mouse model. Probasin-bcl-2 transgenic mice were crossed with TRAMP (TRansgenic Adenocarcinoma Mouse Prostate) mice that express the SV40 early genes (T/t antigens) under probasin control. Prostate size, cell proliferation, apoptosis, and the incidence and latency of tumor formation were evaluated. The double transgenic, probasin-bcl-2 X TRAMP F1 (BxT) mice exhibited an increase in the wet weight of the prostate. This was associated with an increase in proliferation, attributable to T/t antigens, and a decrease in apoptosis attributable to bcl-2. The latency to tumor formation was also decreased in the BxT mice compared to the TRAMP mice. The incidence of metastases was identical in both the TRAMP and BxT mice. Lastly, the incidence of hormone-independent prostate cancer was reduced in the BxT mice compared to the TRAMP mice. Together, these results demonstrate that bcl-2 can facilitate multistep prostate carcinogenesis in vivo.

The timing of hormonal treatment for prostate cancer

This article reviews publications investigating the optimal timing of androgen ablative therapy for prostate cancer. We regard with some concern retrospective series, the use of endpoints other than overall survival, the presentation of actuarial and not actual survival, and the omission of appropriate controls. Treatment of minimal residual disease and other clinical scenarios are explored.