Summary of Immunohistochemical Marker Expression in Prostate lesions and metastases in C57BL/6 TRAMP mice [15]
1. Introduction
Prostate cancer (PCA) is the most commonly diagnosed cancer affecting men in many countries and it has been estimated that there would be 33, 000 deaths due to PCA in the United States in 2011 alone [1]. The standard chemotherapy for metastatic castration-resistant prostate cancer (CRPC) is the taxane anticancer drug docetaxel in combination with the steroid prednisone. In the past two years, autologous immunotherapy sipuleucel-T (Provenge), the new taxane drug cabazitaxel (Jevtana) and a P450 C17 inhibitor drug abiraterone acetate (Zytiga) were also approved by the US FDA (Food and Drug Administration) [2]. Unfortunately, those drugs can only offer limited survival benefit but have significant side effects that negatively affect the quality of life of the patients.
In contrast to chemotherapy, cancer chemoprevention uses naturally occurring or synthetic chemicals to block, delay or reverse carcinogenesis, progression and metastasis and is increasingly being recognized as essential for winning the war on PCA. Animal models are essential for development of effective chemoprevention. Currently, the mouse models used for PCA research include human xenograft models in immunocompromised mice, mouse prostate reconstitution models, transgenic models and single stem cell-based prostate regeneration (see a comprehensive review by Jeet
2. TRAMP model represents at least two lineages of prostate carcinogenesis
The transgenic adenocarcinoma of mouse prostate (TRAMP) model was originally developed by Dr. Greenberg in 1995 [5]. It belongs to the first generation of models based on SV40 viral oncogenes [3]. In this TRAMP model, the rat probasin promoter (-426 to 28 bp) drives the expression of SV40 large T-antigen (T-Ag) and small t-antigen in the prostate. T-Ag abrogates P53 and Rb tumor suppressor proteins by direct binding. Simultaneously, small t-antigen interacts with protein phosphatase 2A [6] to regulate activity of the mitogen activated protein kinase activation pathway and the AP-1 transcription factor activity [7]. T-Ag and small t-antigen act spontaneously to propel the genesis of prostate epithelial lesions and malignant carcinomas and metastases. The TRAMP model is by far the most widely used PCA transgenic model for chemoprevention studies because of its simplicity in breeding compared to next generations of transgenic models based on deletions, insertions or mutations of mouse genes to mimic their changes in human PCA.
For more than one decade since its inception, the TRAMP model has been believed to represent a single lineage of epithelial lesion progression with well-defined kinetics and molecular marker alterations. The progression was thought to start from low and high grade PIN, to well-differentiated (WD) and moderately-differentiated (MD) adenocarcinoma in the dorsolateral prostate lobes (DLP) and finally by stoichastic phenotypic conversion, to poorly differentiated adenocarcinomas (PD-Ca) with lymph node and other distant metastases [8]. Many subsequent publications interpreted the histology results and molecular characterizations using such a paradigm.
However, several recent studies have suggested that the poorly-differentiated neuro-endocrine (NE)-like carcinomas (NECa) [9, 10] belonged to a distinct lineage from the epithelial lesions, which included low and high grade PIN, WD to MD “adenocarcinomas” of the original classification by Dr. Greenburg [8]. Those epithelial lesions were recently termed “atypical hyperplasias of T-Ag” (AHT) to distinguish from the human prostate cancer pathogenesis because they did not invade adjacent tissues [9]. In addition, the incidence of the NECa was found to be profoundly affected by the genetic background of the host mice [9]. In the C57BL/6 background, the lifetime incidence of NECa was estimated to be about 20% whereas in the FVB background, 87% NECa incidence was recorded by as early as 16 weeks of age and reached 100% by 20 weeks of age [9]. Furthermore, these NECa mostly arose in the ventral prostate (VP) lobes instead of the DLP in both strains [9, 10]. Tissue reconstitution experiments carried out by Chiaverotti
These findings significantly challenged the classical notion of single-lineage disease progression in the TRAMP DLP [8, 12]. Since the TRAMP model has been increasingly used for prostate cancer chemoprevention studies, it is very critical to further characterize the lobe-specificity of lesion lineages and NECa incidence in the prostate to consolidate the advantages of this model and minimize its limitations for both etiological and chemoprevention studies. To experimentally approach this, our group estimated the incidence of NECa based on 90 TRAMP mice in the C57BL/6 background spanning the age range of 16-50 weeks from several study cohorts [13-15]. We also characterized the histological features of different lineages of carcinogenesis in this model using archived tissue blocks from those studies [13-15]. In addition, by using state-of-the-art proteomics, we sought insights on mechanisms underlying carcinogenesis of different lineages and possible targets of chemopreventive reagents [15-17]. Here, we review our results as well as from other researchers’ work to provide an objective analysis of the utility of this preclinical model for cancer chemoprevention studies.
3. Histological characteristics of prostate carcinogenesis in TRAMP model
In our studies, the female heterozygous C57BL/TGN TRAMP mice (line PB Tag 8247NG) were purchased from The Jackson Laboratory (Bar Harbor, ME), and were cross-bred with non-transgenic C57BL/6 males [13-15]. H&E and immuno-histological (IHC) staining were routinely performed in our lab and the results are summarized in Table 1 [15]. Figure 1a shows the H&E staining of representative morphological features of DLP and VP with micro-NECa in TRAMP mice [15]. As can be seen in Figure 1b-1e, the AR-expressing glandular prostate epithelial lesions, which are now termed atypical hyperplasias of T-Ag (AHT), express nuclear T-Ag, epithelial membrane-staining of E-cadherin and are negative for synaptophysin (SYP), which is a neuroendocrine cell marker [15]. Staining of Ki67 (Figure1f), a proliferative index protein, showed a descending order of NE-Ca >> DLP AHT > VP epithelium. In the prostate from wild-type mice, single layer luminal epithelial cells were stained positive for nuclear AR, membrane E-cadherin with rare Ki-67 positive proliferating cells, while negative for T-Ag and SYP (Figure 2) [13-15]. In contrast, poorly-differentiated prostate carcinomas (PD) as classified by Greenberg [5] had distinct morphological features compared to AHT described above, regardless of the microscopic size found within the VP lobe (Figure 1, right panels) or those weighing over many grams [15]. Those lesions/tumors expressed strong T-Ag and SYP (except negative in trapped glandular epithelial islands), and were negative for AR and E-cadherin (except positive in the trapped glandular epithelial islands) [15].
We analyzed all tumors and prostates in our cohorts with the above panel of biomarkers. The incidence of macroscopic tumors (>1 gram) in TRAMP mice of 16-18, 22-24 and 26 weeks of age (WOA) were 10%, 20% and 30%, respectively. They were all poorly differentiated NECa expressing SYP [13, 15]. In another study, 31 C57BL/6 TRAMP mice in the control group (no chemo-preventive agents administrated) were followed up to 50 WOA. Ten large tumors traceable to the prostate were found (32.3%) and they were all SYP positive poorly differentiated NECa [13]. Overall, we observed that there was a trend for increasing detection of visible macroscopic NECa in TRAMP mice and the life-time NECa incidence rate was 1 out of 3 TRAMP mice from our experiments. This value was slightly higher than that reported by Chiaverotti (20%) [9]. The possible reason might be a smaller number of and younger C57BL/6 TRAMP mice used in their study [9].
We attempted to identify the anatomical origin of the NECa. Out of 18 NECa’s in a cohort of 90 C57BL/6 TRAMP mice of 22 to 24 WOA, 12 were traceable to the VP (66.7%), two tiny tumors were traced to DLP (11.1%), whereas 1 large tumor was found in the anterior prostate (AP) (5.6%). The other three tumors were not traceable to any lobe location due to their overwhelming large sizes. These data were consistent with two recent studies showing a preponderance of SYP positive NECa arising from VP in the TRAMP mice of both C57BL/6 and FVB backgrounds [9, 10]. In contrast, the weight of macroscopic tumor-free VP lobes was only slightly increased in TRAMP mice compared to their wild type littermates at 24 WOA (Table 2 [15]), whereas the DLP lobes underwent significant expansion (more than doubled) in the TRAMP mice in one study where these lobes were compared side by side [14, 15].
The Greenberg group had reported the prevalence of seminal vesicles (SV) problems such as papillary fibroadenoma in the TRAMP mice with C57BL/6 background shortly after the strain was established [12, 18]. Later on, several publications also described the histogenesis and pathology of SV neoplasms in the TRAMP mice [19, 20]. In one long-term survival experiment carried out by our group [13], 54.8% (17 out of 31) TRAMP mice in the control group developed tumors in their SV and SV tumor loads became significantly increased beyond 30 WOA [13, 15]. Tani
Protein Biomarker | Wild type | TRAMP | TRAMP | TRAMP Seminal vesicle |
Prostrate | AHT* | NECa/Metastasis | Epithelial-stromal tumors/Metastasis | |
T-Antigen | - | +++ | +++ | + |
Androgen Receptor | ++ | +++ | - | + |
Synaptophysin | - | - | +++ | - |
E-cadherin | +++ | +++ | - | -/+ |
Ki-67 (MIB-1) | <1% | ++ | +++ | ++ |
2/18 | 3/18 | 12/18 | 1/18 | |
11.10% | 16.70% | 66.70% | 5.60% | |
0.09 | 4.98 | 1.65 | 1.1 | |
(0.07, 0.11) | (3.44, 4.38, 7.11) | (0.02- 4.84) | ||
79.2+3.7 (n =17)** | 15.3+1.1 (n=17) ** | |||
31.7+2.9 (n=8) ** | 12.5+1.7 (n=8) ** | |||
4. Molecular changes in prostate carcinogenesis in TRAMP model
Classical methods detecting the steady levels of mRNAs and proteins, as well as “omics” approaches such as microarray, antibody array and two-dimension electrophoresis based proteomics have been used to study the molecular changes associated with TRAMP carcinogenesis using prostate or serum as starting materials. The Greenberg group reported increased expression of basic fibroblast growth factor (FGF2) in the prostates (whole prostate) of TRAMP mice ([C57BL/6 X FVB] F1) [21]. They found that the expression of the 25-kDa isoform of FGF2 was 2-fold higher in PIN and WD and MD tumors than in normal DLP and VP; the expression of the 22-kDa isoform of FGF2 was not elevated in PIN lesions, but was observed to be increased in WD, MD, PD and androgen-independent tumors. Interestingly, the 18-kDa isoform of FGF2 was only expressed in the samples representing PD and androgen-independent disease. These observations implicated specific changes in the FGF axis with the initiation and progression of PCA. The important role of FGF2 in PCA progression was further investigated in an
Considering extracellular proteolysis as an important biochemical event in the invasion and metastasis of PCA, Bok
Using Affymetrix GeneChip Mouse Genome 430 2.0 micorarrays, Haram
Therefore, it will be prudent to carefully read the descriptions of the tissue samples used in the published papers. For example, many older publications prepared lysate from the whole prostate whereas very few focused on particular lobes [24, 31, 32]. Recently, researchers started to carefully look into the molecular pathways involved in two lineages of carcinogenesis (different prostate lobes, mainly DLP and VP) in TRAMP mice after the lineage differences of the prostate carcinogenesis had been recognized [9, 13]. For instance, Slack-Davis
Our group [15] dissected prostate lobes and visible tumors separately in most of our experiments in order to assess the lobe-specific biochemical changes. Using these dissected lobes/tumors as starting materials, we studied the expression of classical biomarkers by immuno-blot. The expression patterns of proliferative cell nuclear antigen (PCNA) (Figure 3a) confirmed the Ki67 staining patterns by IHC staining described above [15]. Consistent with the lack of proliferation of normal prostate epithelium, PCNA was non-detectable in the DLP and VP in the wild type mice at 16-18 WOA, whereas significantly higher levels of PCNA were detected in the DLP and VP and NECa of TRAMP mice. Since the Ki67 proliferation index in the VP epithelium appeared to be lower than in TRAMP DLP as evidenced by IHC (Figure 1f), the higher level of PCNA in TRAMP VP (Figure 3b) than in DLP might be due to the presence of micro NECa foci in the TRAMP VP lobes (NECa has much higher Ki67 index, Figure 1f) [15]. We also confirmed the contrasting patterns of AR, SYP and E-cadherin expression patterns in the DLP AHT vs. NECa. Although the expression of AR and E-cadherin were increased in both DLP and VP in TRAMP mice at 16-18 WOA, there were more AR and E-cadherin in VP than in DLP of littermate wild type mice (Figure 3b) [15]. These patterns are in agreement with that published by the Greenberg group [8, 12] and others [9]. In addition, we found that the level of cleaved PARP (endogenous substrate for caspase 3) was higher in the NECa than in the DLPs of TRAMP and wild type mice (Figure 3a). The STAT3 level in TRAMP DLP was higher than in the wild type DLP and the NECa. However, there might be an isoform of STAT3 with higher molecular weight in the NECa, indicated by a mobility-retarded band (Figure 3a, arrow) [15]. Our observation was consistent with phosphorylative modification and activation of STAT3 in NECa, as reported by Aziz
To provide more information on potential molecular correlates of the differences in DLP and VP for epithelial lesions and NE-carcinogenesis, we compared the expression level of proteins in respective lobes of wild type vs. TRAMP mice of 18 WOA by the iTRAQ proteomic approach, as we recently reported [16, 17]. We employed two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) with iTRAQ labeling, which enables the concurrent identification and quantification of proteins through peptides generated upon tryptic digestion. The principle and advantages of the platform have been described in our previous publications [16, 17, 37]. In total, we identified 1068 proteins expressed in the DLP and VP of TRAMP mice and wild type mice. Among them, 483 and 748 proteins were identified at FDRs of 1% and 5% respectively. We found that the expression levels of 84 proteins were different between DLP and VP in wild-type mice [17]. For example, heat shock protein 5/glucose-regulated protein78 (GRP78), transglutaminase 4 (TGM4), experimental autoimmune prostatitis antigen 2 (EAPA2), probasin, beta-tropomyosin, calponin-1, as well as high mobility group box 1 & 2 were preferentially expressed in DLP, whereas there were higher levels of prostatic spermine-binding protein (SBP), serine peptidase inhibitor Kazal type 3 (SPINK3), polymeric immunoglobulin receptor (PIGR), solute carrier family 12 member 2, epidermal growth factor (EGF) and clusterin in the VP lobe. The expression pattern of GRP78 and clusterin were validated by immuno-blots [17]. The mRNA abundances of prostatic proteins in each lobe of mice or rats have been investigated by Fujimoto
To shed light on the key expression signatures or “master switches” that may not be virtually identified due to technical limitation, we analyzed the lists of differentially expressed proteins in each lobe by IPA software for pathway connections based on gene ontogeny and functionality [17]. Proteins with altered expression in DLP during carcinogenesis were preferentially clustered into Immunological Disease/Cancer/Antigen Presentation and Post-Translational Modification/Protein Folding/Cancer networks. 14-3-3 zeta/delta (YWHAZ, up-regulated only in DLP), NF-κB, epidermal growth factor (EGF, up-regulated only in DLP), ERK1/2, PKCs were identified as distinct inferred network nodes for those networks. On the other hand, proteins with altered expression in VP were mapped to Connective Tissue Disorders/Developmental Disorder/Genetic Disorder and Cancer/Cell Cycle/Cellular Development pathways with ERK1/2 and FGF2 identified as distinct network nodes in the two networks. We further used immunoblot to study the expression pattern of FGF2 proteins, which were not identified by LC-MS/MS but unraveled by IPA analysis as important proteins in the TRAMP carcinogenesis of the VP lobe. The data indicated that different isoforms of FGF2 were expressed in each lobe and FGF2 was only up-regulated in the VP lobe of TRAMP mice [17]. To our knowledge, we are the first to systematically compare the different protein profile changes between DLP and VP lobes during TRAMP carcinogenesis. Our results further support the concept that the C57BL/6 TRAMP mouse represents two lineages of prostate carcinogenesis in DLP and VP lobes. Further efforts to narrow down possible target proteins and investigation on the functional significance of those proteins will not only help understand the mechanisms of TRAMP carcinogenesis, but also facilitate the understanding and use of TRAMP model in the field of prostate cancer chemoprevention.
5. Effects of chemopreventive agents on prostate carcinogenesis in TRAMP model and possible mechanisms
Because the breeding strategy of TRAMP mice is straightforward, TRAMP mice have been widely used in evaluating potential preventive modalities by many groups in the past decade. Besides the effect of androgen deprivation therapy (ADT) on the progression of PCA by surgical castration of TRAMP mice [41, 42], the effects of many agents with chemo-preventive potential including green tea [26, 43], NSAIDs [44, 45], flutamide [46], retinoic acid [47], vitamin E analog [48], genistein [24, 49], epigallocatechin-3-gallate (EGCG) [50], silibinin [23, 51], dietary restriction [52] and immunotherapy [53, 54], have been studied using this model. While most of the publications reported anti-cancer effects of their test compounds, El Touny
The recognition of different lineages of carcinogenesis in the TRAMP prostate has important implications on the interpretation of chemoprevention data. Due to the distinct characteristics of AHT in DLP and NECa in VP, their sensitivity to different chemo-preventive agents might not be the same. Knowledge of lineage-specific effects of each agent will be essential for selecting additional models to confirm the efficacy and to ultimately benefit clinical translation studies. In addition, it can provide valuable insights into mechanism studies for molecular pathway(s) and targets specific to the particular lineage of carcinogenesis. Using this paradigm, our group evaluated the chemopreventive efficacy of next-generation selenium compounds methylseleninic acid (MSeA) and methylselenocysteine (MSeC) in TRAMP mice with C57BL/6 background [13]. In a short-term experiment, TRAMP mice of 8 WOA were given an oral dose of MSeA or MSeC at 3 mg Se/kg daily and were euthanized at either 18 or 26 WOA. By 18 WOA, the genitourinary tract and DLP weights for both treatment groups were lower than for the control (p< 0.01). At 26 weeks, 4 of 10 control mice had genitourinary weight >2 g whereas only 1 of 10 in each of the treatmente groups did. The efficacy was accompanied by delayed lesion progression, increased apoptosis, and decreased proliferation without appreciable changes of T-antigen expression in the DLP. In another experiment, giving MSeA to TRAMP mice from 10 or 16 WOA increased their survival to 50 weeks of age and delayed the death due to SYP-positive NECa, SYP-negative prostate lesions and seminal vesicle hypertrophy [13]. Interestingly, although MSeA and MSeC were considered as precursors of methylselenol, the proteins they modulated in the DLP of TRAMP mice were quite different as indicated by proteomic profiling. The data suggest that MSeA and MSeC should be developed as separate agents rather than as equal precursors of methylselenol [16]. Very recently, our group also demonstrated that oral administration of the alcoholic extract of
As mentioned above, the life-time NECa incidence has been estimated to be approximately 30% in TRAMP mice with C57BL/6 background. Rest of the mice will be free of NECa and may therefore model the epithelial lineage lesions that are more relevant to the human prostate epithelial adeno-carcinogenesis, since the majority of human PCA are adenocarcinomas.
On the other hand, NECa occurs in nearly 100% of the TRAMP mice in the FVB background and the DLP undergoes more epithelial lesion growth than does the VP [9, 12]. This might have contributed to the assumption that a single lineage of carcinogenesis progressed from DLP epithelial lesions to poorly differentiated Ca (i.e., NECa) by the Greenberg group. Based on the current information, the C57BL/6 background will be a preferred choice over the FVB background for chemoprevention studies since the former allows a clear separation of estimation of the impact of the test agents on both lineages of lesions in the prostate, provided that the studies are terminated before SV tumors in the C57BL/6 TRAMP mice become a serious complication to survival.
Since many studies had followed the Greenberg paradigm for interpretation of their results, it will be prudent to carefully look into the genetic background of TRAMP mice, the manner with which prostate/tumors were collected and the end point(s) chosen to evaluate the efficacy. Some of the studies as shown below could be questionable in term of the conclusions. In the study by Adhami
6. The concept of cancer stem cells in TRAMP model
The concept of cancer stem cells (CSC) or tumor-initiating cells assumes that cancers are mainly sustained by a small pool of neoplastic cells, which are responsible for cancer initiation and/or progression. Although currently no single protein is widely accepted as a definitive stem cell marker in the prostate, investigations using
Huss
ADT was reported to result in a state of androgen independence with more malignant behavior in TRAMP mice [41]. Whether certain types of “cancer stem cells” were activated during or after castration awaits further investigation. Recently, Tang
In one recently published paper [15], our group compared different treatment regimens with MSeA on TRAMP mice (C57BL/6) to investigate whether MSeA could irreversibly inhibit early events in TRAMP carcinogenesis (e.g. activation of “cancer stem cells”). MSeA exposure to TRAMP mice (C57BL/6) from 5 to 15 WOA was sufficient to elicit protective effects against the two lineages of carcinogenesis to the same extent as continuous MSeA exposure from 5 to 23 WOA [15]. Similar findings in a chemically-induced mammary carcinogenesis model was reported by Ip
7. Conclusion
The paradigm of distinct lineages of carcinogenesis in the TRAMP model and our data with MSeA, a sulindac derivative compound and AGN extract shed new light on the utility of this preclinical model for chemoprevention studies in spite of much concern regarding of the NE nature of the resultant carcinomas and metastasis. Future data collection and analyses should incorporate this new knowledge for efficacy assessment and for molecular target validations, avoiding ‘‘apple versus orange’’ comparisons.
References
- 1.
Siegel R Ward E Brawley O Jemal A 2011 Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths.61 4 212 236 - 2.
Logothetis C. J Efstathiou E Manuguid F Kirkpatrick P 2011 Abiraterone acetate. Nature Reviews Drug Discovery10 8 573 574 - 3.
Jeet V Russell P. J Khatri A 2010 Modeling prostate cancer: a perspective on transgenic mouse models Cancer Metastasis Reviews29 1 123 142 - 4.
Teicher B. A 2006 Tumor models for efficacy determination. 5 10 2435 2443 - 5.
Greenberg N. M Demayo F Finegold M. J Medina D Tilley W. D Aspinall J. O Cunha G. R Donjacour A. A Matusik R. J Rosen J. M 1995 Prostate cancer in a transgenic mouse. Proceedings of the National Academy of Sciences of the United States of America92 8 3439 3443 - 6.
Pallas D. C Shahrik L. K Martin B. L Jaspers S Miller T. B Brautigan D. L Roberts T. M 1990 Polyoma small and middle T antigens and SV40 small t antigen form stable complexes with protein phosphatase 2A 60 1 167 176 - 7.
Frost J. A Alberts A. S Sontag E Guan K Mumby M. C Feramisco J. R 1994 Simian virus 40 small t antigen cooperates with mitogen-activated kinases to stimulate AP-1 activity. 14 9 6244 6252 - 8.
Kaplan-lefko P. J Chen T. M Ittmann M. M Barrios R. J Ayala G. E Huss W. J Maddison L. A Foster B. A Greenberg N. M 2003 Pathobiology of autochthonous prostate cancer in a pre-clinical transgenic mouse model. Prostate55 3 219 237 - 9.
Chiaverotti T Couto S. S Donjacour A Mao J. H Nagase H Cardiff R. D Cunha G. R Balmain A 2008 Dissociation of epithelial and neuroendocrine carcinoma lineages in the transgenic adenocarcinoma of mouse prostate model of prostate cancer The American Journal of Pathology172 1 236 246 - 10.
Huss W. J Gray D. R Tavakoli K Marmillion M. E Durham L. E Johnson M. A Greenberg N. M Smith G. J 2007 Origin of androgen-insensitive poorly differentiated tumors in the transgenic adenocarcinoma of mouse prostate model. Neoplasia9 11 938 950 - 11.
Tang Y Wang L Goloubeva O Khan M. A Lee D Hussain A 2009 The relationship of neuroendocrine carcinomas to anti-tumor therapies in TRAMP mice 69 16 1763 1773 - 12.
Gingrich J. R Barrios R. J Foster B. A Greenberg N. M 1999 Pathologic progression of autochthonous prostate cancer in the TRAMP model 2 2 70 75 - 13.
Wang L Bonorden M. J Li G. X Lee H. J Hu H Zhang Y Liao J. D Cleary M. P Lu J 2009 Methyl-selenium compounds inhibit prostate carcinogenesis in the transgenic adenocarcinoma of mouse prostate model with survival benefit. Cancer Prevention Research2 5 484 495 - 14.
Zhang Y Zhang J Wang L Quealy E Gary B. D Reynolds R. C Piazza G. A Lu J 2010 A novel sulindac derivative lacking cyclooxygenase-inhibitory activities suppresses carcinogenesis in the transgenic adenocarcinoma of mouse prostate model 3 7 885 895 - 15.
Wang L Zhang J Zhang Y Nkhata K Quealy E Liao J. D Cleary M. P Lu J 2011 Lobe-specific lineages of carcinogenesis in the transgenic adenocarcinoma of mouse prostate and their responses to chemopreventive selenium. Prostate71 13 1429 1440 - 16.
Zhang J Wang L Anderson L. B Witthuhn B Xu Y Lu J 2010 Proteomic profiling of potential molecular targets of methyl-selenium compounds in the transgenic adenocarcinoma of mouse prostate model 994 EOF 1006 EOF - 17.
Zhang J Wang L Zhang Y Li L Higgins L Lu J 2011 Lobe-specific proteome changes in the dorsal-lateral and ventral prostate of TRAMP mice versus wild-type mice. 11 12 2542 2549 - 18.
Hsu C. X Ross B. D Chrisp C. E Derrow S. Z Charles L. G Pienta K. J Greenberg N. M Zeng Z Sanda M. G 1998 Longitudinal cohort analysis of lethal prostate cancer progression in transgenic mice. The Journal of Urology160 4 1500 1505 - 19.
Tani Y Suttie A Flake G. P Nyska A Maronpot R. R 2005 Epithelial-stromal tumor of the seminal vesicles in the transgenic adenocarcinoma mouse prostate model. 42 3 306 314 - 20.
Yeh I. T Reddick R. L Kumar A. P 2009 Malignancy arising in seminal vesicles in the transgenic adenocarcinoma of mouse prostate (TRAMP) model 69 7 755 760 - 21.
Huss W. J Barrios R. J Foster B. A Greenberg N. M 2003 Differential expression of specific FGF ligand and receptor isoforms during angiogenesis associated with prostate cancer progression. Prostate54 1 8 16 - 22.
Polnaszek N Kwabi-addo B Peterson L. E Ozen M Greenberg N. M Ortega S Basilico C Ittmann M 2003 Fibroblast growth factor 2 promotes tumor progressionin an autochthonous mouse model of prostate cancer. 63 18 5754 5760 - 23.
Singh R. P Raina K Sharma G Agarwal R 2008 Silibinin inhibits established prostate tumor growth, progression, invasion, and metastasis and suppresses tumor angiogenesis and epithelial-mesenchymal transition in transgenic adenocarcinoma of the mouse prostate model mice an official journal of the American Association for Cancer Research14 23 7773 7780 - 24.
Wang J Eltoum I. E Lamartiniere C. A 2004 Genistein alters growth factor signaling in transgenic prostate model (TRAMP). 171 EOF 80 EOF - 25.
Shukla S Maclennan G. T Marengo S. R Resnick M. I Gupta S 2005 Constitutive activation of Prostate 64(3):224-239.I3 K-Akt and NF-kappaB during prostate cancer progression in autochthonous transgenic mouse model. - 26.
A. (Caporali A Davalli P Astancolle S D Arca D Brausi M Bettuzzi S Corti 2004 The chemopreventive action of catechins in the TRAMP mouse model of prostate carcinogenesis is accompanied by clusterin over-expression 25 11 2217 2224 - 27.
Maddison L. A Huss W. J Barrios R. M Greenberg N. M 2004 Differential expression of cell cycle regulatory molecules and evidence for a "cyclin switch" during progression of prostate cancer. Prostate58 4 335 344 - 28.
Morey Kinney SR Smiraglia DJ, James SR, Moser MT, Foster BA, Karpf AR. (2008 Stage-specific alterations of DNA methyltransferase expression, DNA hypermethylation, and DNA hypomethylation during prostate cancer progression in the transgenic adenocarcinoma of mouse prostate model 6 8 1365 1374 - 29.
Kinney S. R Moser M. T Pascual M Greally J. M Foster B. A Karpf A. R 2010 Opposing roles of Dnmt1 in early- and late-stage murine prostate cancer 30 17 4159 4174 - 30.
Majeed N Blouin M. J Kaplan-lefko P. J Barry-shaw J Greenberg N. M Gaudreau P Bismar T. A Pollak M 2005 A germ line mutation that delays prostate cancer progression and prolongs survival in a murine prostate cancer model. 24 29 4736 4740 - 31.
Bok R. A Hansell E. J Nguyen T. P Greenberg N. M Mckerrow J. H Shuman M. A 2003 Patterns of protease production during prostate cancer progression: proteomic evidence for cascades in a transgenic model. 6 4 272 280 - 32.
Ruddat V. C Whitman S Klein R. D Fischer S. M Holman T. R 2005 Evidence for downregulation of calcium signaling proteins in advanced mouse adenocarcinoma. Prostate64 2 128 138 - 33.
Haram K. M Peltier H. J Lu B Bhasin M Otu H. H Choy B Regan M Libermann T. A Latham G. J Sanda M. G et al 2008 Gene expression profile of mouse prostate tumors reveals dysregulations in major biological processes and identifies potential murine targets for preclinical development of human cancer therapy Prostate68 14 1517 1530 - 34.
Morgenbesser S. D Mclaren R. P Richards B Zhang M Akmaev V. R Winter S. F Mineva N. D Kaplan-lefko P. J Foster B. A Cook B. P et al 2007 Identification of genes potentially involved in the acquisition of androgen-independent and metastatic tumor growth in an autochthonous genetically engineered mouse prostate cancer model. Prostate67 1 83 106 - 35.
Slack-davis J. K Hershey E. D Theodorescu D Frierson H. F Parsons J. T 2009 Differential requirement for focal adhesion kinase signaling in cancer progression in the transgenic adenocarcinoma of mouse prostate model 8 8 2470 2477 - 36.
Aziz M. H Manoharan H. T Church D. R Dreckschmidt N. E Zhong W Oberley T. D Wilding G Verma A. K 2007 Protein kinase Cepsilon interacts with signal transducers and activators of transcription 3 (Stat3), phosphorylates Stat3Ser727, and regulates its constitutive activation in prostate cancer. 67 18 8828 8838 - 37.
Zhang J Nkhata K Shaik A. A Wang L Li L Zhang Y Higgins L. A Kim K. H Liao J. D Xing C et al 2011 Mouse prostate proteome changes induced by oral pentagalloylglucose treatment suggest targets for cancer chemoprevention. Current Cancer Drug Targets11 7 787 798 - 38.
Fujimoto N Akimoto Y Suzuki T Kitamura S Ohta S 2006 Identification of prostatic-secreted proteins in mice by mass spectrometric analysis and evaluation of lobe-specific and androgen-dependent mRNA expression. 190 3 793 803 - 39.
Fujimoto N Suzuki T Ohta S Kitamura S 2009 Identification of rat prostatic secreted proteins using mass spectrometric analysis and androgen-dependent mRNA expression 30 6 669 678 - 40.
Berquin I. M Min Y Wu R Wu H Chen Y. Q 2005 Expression signature of the mouse prostate. 280 43 36442 36451 - 41.
Tang Y Wang L Goloubeva O Khan M. A Zhang B Hussain A 2008 Divergent effects of castration on prostate cancer in TRAMP mice: possible implications for therapy an official journal of the American Association for Cancer Research14 10 2936 2943 - 42.
Zhang Z. X Xu Q. Q Huang X. B Zhu J. C Wang X. F 2009 Early and delayed castrations confer a similar survival advantage in TRAMP mice 11 3 291 297 - 43.
Adhami V. M Siddiqui I. A Sarfaraz S Khwaja S. I Hafeez B. B Ahmad N Mukhtar H 2009 Effective prostate cancer chemopreventive intervention with green tea polyphenols in the TRAMP model depends on the stage of the disease. 15 6 1947 1953 - 44.
MacLennan GT, Lewin JS, Hafeli UO, Fu P, Mukhtar H. (Gupta S Adhami V. M Subbarayan M 2004 Suppression of prostate carcinogenesis by dietary supplementation of celecoxib in transgenic adenocarcinoma of the mouse prostate model. 64 9 3334 3343 - 45.
Narayanan B. A Narayanan N. K Pittman B Reddy B. S 2004 Regression of mouse prostatic intraepithelial neoplasia by nonsteroidal anti-inflammatory drugs in the transgenic adenocarcinoma mouse prostate model. 10 22 7727 7737 - 46.
Raghow S Kuliyev E Steakley M Greenberg N Steiner M. S 2000 Efficacious chemoprevention of primary prostate cancer by flutamide in an autochthonous transgenic model. 60 15 4093 4097 - 47.
Huss W. J Lai L Barrios R. J Hirschi K. K Greenberg N. M 2004 Retinoic acid slows progression and promotes apoptosis of spontaneous prostate cancer. Prostate61 2 142 152 - 48.
DiMaggio MA, Guo Y, Yeh S. (Yin Y Ni J Chen M 2007 The therapeutic and preventive effect of RRR-alpha-vitamin E succinate on prostate cancer via induction of insulin-like growth factor binding protein-3. 13 7 2271 2280 - 49.
El Touny L. H Banerjee P. P 2009 Identification of a biphasic role for genistein in the regulation of prostate cancer growth and metastasis Cancer Research69 8 3695 3703 - 50.
Harper C. E Patel B. B Wang J Eltoum I. A Lamartiniere C. A 2007 Epigallocatechin-3-Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: mechanisms of action. Prostate67 14 1576 1589 - 51.
Raina K Rajamanickam S Singh R. P Deep G Chittezhath M Agarwal R 2008 Stage-specific inhibitory effects and associated mechanisms of silibinin on tumor progression and metastasis in transgenic adenocarcinoma of the mouse prostate model 68 16 6822 6830 - 52.
Suttie A. W Dinse G. E Nyska A Moser G. J Goldsworthy T. L Maronpot R. R 2005 An investigation of the effects of late-onset dietary restriction on prostate cancer development in the TRAMP mouse 33 3 386 397 - 53.
de la Luz Garcia-Hernandez M, van West M, Kanodia S, Hubby B, KastWM. (Gray A 2009 Prostate cancer immunotherapy yields superior long-term survival in TRAMP mice when administered at an early stage of carcinogenesis prior to the establishment of tumor-associated immunosuppression at later stages Suppl 6:G52 59 - 54.
Liu Z Eltoum I. E Guo B Beck B. H Cloud G. A Lopez R. D 2008 Protective immunosurveillance and therapeutic antitumor activity of gammadelta T cells demonstrated in a mouse model of prostate cancer. Journal of Immunology180 9 6044 6053 - 55.
Lei Wang Yong Zhang, Jinhui Zhang, Katai Nkata, Emily Quealy, Li Li, Hyo-Jeong Lee, Soo-Jin Jeong, Joshua Liao, Cheng Jiang, Sung-Hoon Kim, and Junxuan Lu. (2011 Korean Angelica gigas Nakai (AGN) and Oriental herbal cocktail ka-mi-kae-kyuk-tang (KMKKT) inhibit prostate carcinogenesis in TRAMP model. Cancer Research 71(8 (Suppl)):Abstract nr 5581. - 56.
Jinhui Zhang Li Li, Yong Zhang, Lei Wang, Cheng Jiang, Sung-Hoon kim, and Junxuan Lu. (2012 Proteomic and transcriptomic profiling of effects of Angelica gigas ethanol extract on prostate neuroendocrine carcinomas of TRAMP mice. Cancer Research 72(8 (Suppl)):Abstract nr 2587. - 57.
Cheng L Ramesh A. V Flesken-nikitin A Choi J Nikitin A. Y 2010 Mouse models for cancer stem cell research 38 1 62 71 - 58.
Taylor R. A Toivanen R Risbridger G. P 2010 Stem cells in prostate cancer: treating the root of the problem R273 285 - 59.
Miki J 2010 Investigations of prostate epithelial stem cells and prostate cancer stem cells. official journal of the Japanese Urological Association17 2 139 147 - 60.
Huss W. J Gray D. R Greenberg N. M Mohler J. L Smith G. J 2005 Breast cancer resistance protein-mediated efflux of androgen in putative benign and malignant prostate stem cells. 65 15 6640 6650 - 61.
Tang Y Hamburger A. W Wang L Khan M. A Hussain A 2009 Androgen deprivation and stem cell markers in prostate cancers International Journal of Clinical and Experimental Pathology3 2 128 138 - 62.
Ip C Lisk D. J Thompson H. J 1996 Selenium-enriched garlic inhibits the early stage but not the late stage of mammary carcinogenesis. 17 9 1979 1982