Abstract 5305: Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, suppresses tumor growth and β-catenin activity

Introduction: African American (AA) men have the highest prostate cancer incidence and mortality rates in the US. The biological contribution to this disparity, however, is not well understood. LSAMP inactivation has been implicated in several cancers, and was recently identified in prostate cancer. A higher frequency of LSAMP inactivation has been observed in AA prostate cancer, and this aberration has been associated with a significantly greater risk of disease progression. In the characterization of LSAMP in prostate cancer cells lines, we found the copy number to be variable and the expression to be low or undetectable. LNCaP, MDA PCa 2B, and DU 145 prostate cancer cell lines were stably transduced to express LSAMP in an inducible or constitutive manner. LSAMP expression in these cell lines resulted in reduced cell proliferation, and induced a reversion to indolent cell-cell, and cell-extra-cellular-matrix adhesion characteristics, consistent with its tumor suppressive role. LSAMP expression also resulted in the down-regulation of receptor tyrosine kinases EPHA3, FGFR2, and FGFR4, and reduced activation of their downstream ERK and AKT pathways. Several Integrins were also up-regulated upon LSAMP expression. Additionally, β-catenin localization was altered, suggesting a potential reduction in transcriptional activity. We assessed the tumor suppressive function of LSAMP further, using in vitro assays and in vivo mouse models.

Methods: LSAMP expressing and control DU 145 cells were used to investigate the tumor suppressive function of LSAMP in vivo. Athymic nude mice were injected either subcutaneously, to determine effect of LSAMP expression on prostate tumor growth rates, or intravenously, to determine effect of LSAMP expression on tumor formation. We performed the TOPflash/FOPflash luciferase reporter assay to determine whether LSAMP expression modulates transcriptional activity of β-catenin in vitro.

Results: LSAMP expression resulted in a significant inhibition of tumor growth in the subcutaneous xenograft model. In the intravenous xenograft model, LSAMP expression resulted in a reduced incidence of distant metastases. Consistent with the negative modulation of signal transduction, and β-catenin localization previously observed, LSAMP expression resulted in a reduction of β-catenin transcriptional activity in vitro.

Conclusion: These studies provide in vivo evidence of the suppressive function of LSAMP in prostate tumors, corroborating previous in vitro and clinical findings. LSAMP expression reduced tumor growth rates, and incidence of distant metastases. LSAMP expression also reduced β-catenin transcriptional activity in vitro. These findings provide further support for a biological mechanism underlying the aggressive prostate cancer phenotype observed with LSAMP inactivation.

Citation Format: Kevin Babcock, Taduru Sreenath, Charles P. Xavier, Inger L. Rosner, Shiv Srivastava, Albert Dobi, Shyh-Han Tan. Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, suppresses tumor growth and β-catenin activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5305.

Abstract 2797: Synthesis and evaluation of derivatives of selective inhibitor ERGi USU, for ERG-positive prostate cancer cells

Introduction and objectives:

Prostate cancer is the most frequently diagnosed non-skin malignancy and third leading cause of cancer related deaths among men in the United States. Currently, early detected organ confined prostate cancer (CaP) is managed by active surveillance, surgery or radiation therapy. A significant subset of patients (20% to 40%) experience biochemical recurrence after definitive treatment. New AR axis inhibitors (abiraterone and enzalutamide) are leading to significant improvements in treatment of late stages of CaP. However, sustained therapeutic response remains a challenge due to high mutation load at late stages of the disease. Thus, there is an urgent need for evaluating new therapeutic targets for early stages of CaP. ERG oncoprotein and ERG dependent pathways are promising targets for early stage cancer therapy. Previously identified ERGi-USU from our laboratory, demonstrated remarkable exclusivity for inhibiting ERG protein and cell growth of ERG positive tumor cells in both in vitro and in vivo. With comprehensive structure activity relationship (SAR) studies, we generated new derivatives with substituents around the core structure to further enhance efficacy.

Methods: Cell growth inhibition of small molecules was validated with established prostate cancer cell lines and normal prostate/endothelial derived cell panel. Preferential species-specific binding of ERGi-USU to human RIOK2 was confirmed by tryptophan fluorescence quenching assay.

Result: Based on SAR of the parental ERGi-USU, 90 new ERGi-USU derivatives were designed using structure based predictions. Of these, 37 compounds were prioritized for chemical synthesis and biological evaluations using assays that were developed earlier in our laboratory. We completed primary screen of these compounds in cell culture models. Among these one compound (ERGi-USU-6) inhibited the growth of ERG positive prostate cancer cells with remarkable improvement IC50=70 nM. This value is in the range of current FDA approved drugs. The result also confirmed the high selectivity of ERGi-USU-6 for the inhibition of ERG positive cancer cell growth. Further, mechanistic studies revealed ERGi-USU binding and disruption of the atypical RIOK2 kinase basic function of ribosome biogenesis, due to initiation of ribosomal stress, cell cycle arrest and apoptosis in ERG positive VCaP cells. We also demonstarte preferential binding of ERGi-USU to human RIOK2 by tryptophan fluorescence quenching assay.

Conclusion: The ERGi-USU-6, derivative of ERGi-USU showed improved efficacy in selectively inhibiting the growth of ERG positive cancer cells. Since ERG is a prostate cancer causing oncogene that affects approximately one third of CaP patients world-wide, early therapeutic intervention with ERGi-USU derivatives may prevent the development of late stage disease in prostate cancer patients.

Citation Format: Charles Peter Xavier, Ahmed A. Mohamed, Nishat Seraj, Vineet Kumar, Taduru Sreenath, Inger L. Rosner, Gyorgy Petrovics, Meera Srivastava, Clifton L. Dalgard, Sanjay V. Malhotra, Nicole A. LaRonde, Albert Dobi, Shiv Srivastava. Synthesis and evaluation of derivatives of selective inhibitor ERGi USU, for ERG-positive prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2797.

Identification of a Small Molecule That Selectively Inhibits ERG-Positive Cancer Cell Growth

Oncogenic activation of the ETS-related gene (ERG) by recurrent gene fusions (predominantly TMPRSS2-ERG) is one of the most validated and prevalent genomic alterations present in early stages of prostate cancer. In this study, we screened small-molecule libraries for inhibition of ERG protein in TMPRSS2-ERG harboring VCaP prostate cancer cells using an In-Cell Western Assay with the highly specific ERG-MAb (9FY). Among a subset of promising candidates, 1-[2-Thiazolylazo]-2-naphthol (NSC139021, hereafter ERGi-USU) was identified and further characterized. ERGi-USU selectively inhibited growth of ERG-positive cancer cell lines with minimal effect on normal prostate or endothelial cells or ERG-negative tumor cell lines. Combination of ERGi-USU with enzalutamide showed additive effects in inhibiting growth of VCaP cells. A screen of kinases revealed that ERGi-USU directly bound the ribosomal biogenesis regulator atypical kinase RIOK2 and induced ribosomal stress signature. In vivo, ERGi-USU treatment inhibited growth of ERG-positive VCaP tumor xenografts with no apparent toxicity. Structure-activity-based derivatives of ERGi-USU recapitulated the ERG-selective activity of the parental compound. Taken together, ERGi-USU acts as a highly selective inhibitor for the growth of ERG-positive cancer cells and has potential for further development of ERG-targeted therapy of prostate cancer and other malignancies.Significance: A highly selective small-molecule inhibitor of ERG, a critical driver of early stages of prostate cancer, will be imperative for prostate cancer therapy. Cancer Res; 78(13); 3659-71. ©2018 AACR.

Abstract 1854: Generation and characterization of mouse model of Pmepa1 conditional knockout in prostate epithelia

Introduction and Objectives: Prostate cancer (CaP) is the most common non-skin malignancy diagnosed in American men and desfunctions of androgen receptor (AR) plays an essential role in prostate tumorigenesis. PMEPA1 is an androgen and TGF-β -induced gene abundant in prostate, which was identified to degrade AR protein via NEDD4 E3 ligase mediated pathway. Reduced or loss of PMEPA1 expression, commonly detected in prostate tumors, led to increased AR protein and activated AR signaling. PMEPA1 inhibited TGF-β receptor 1 meditated signaling by a negative feedback loop. It was reported that loss of PMEPA1 facilitates bone metastasis of CaP through blocking TGF-β signaling. To further investigating the biological function of PMEP1 gene in CaP tumorigenesis, particularly via AR and TGF-β, we generated Pmepa1 prostate conditional knockout mouse model.

Methods: C57BL/6 mice were utilized for generation of Pmepa1 conditional knockout model. Pmepa1 gene was conditionally deleted in mouse prostate epithelium by ARR2PB-Cre-Lox system. Male mice of genotypes of wild-type, Pmepa1 flox/wild-type-ARR2PB-Cre, Pmepa1 flox/flox-ARR2PB-Cre were euthanized at the age of 3 months for analysis. The prostate tissue was collected for frozen and formalin fixation for histology analysis, and other major organs including heart, lung, liver, spleen, bladder and testis were also collected for control. The tissue were sectioned and stained with Hematoxylin & Erosin (H&E). Total RNA and protein were harvested by homogenizing tissue. The protein levels of Pmepa1, Ar and Nkx3.1 were analyzed by immunohistochemistry (IHC) and immunoblotting, and the transcript levels of these genes were evaluated by in situ hybridization (ISH) and quantitative-PCR (Q-PCR).

Results: The expression of Pmepa1 protein was found to focus on lateral lobe, consistent with Ar protein expression pattern. The data of Q-PCR and ISH showed that transcript level of Pmepa1 was dramatically suppressed in Pmepa1 flox/flox and flox/wild-type ARR2PB-Cre mice. Compared to wild-type ones, Pmepa1 protein was shown significantly decreased in heterozygous and homozygous knockout mice by immunoblotting and IHC staining. And the protein level of Ar was stronger in Pmepa1 conditional deleted mouse. There was no dramatic morphology change in mouse prostate gland by H&E staining.

Conclusions: Conditional deletion of Pmepa1 gene in mouse prostate epithelium led to enhanced Ar protein and activating Ar signaling. The effects of Pmepa1 gene loss in mouse prostate gland on other signaling such as TGF-β and prostate tumorigenesis are needed to be further evaluated.

Funding: This study was supported by CPDR, USUHS, HU0001-10-2-0002 to DGM.

Citation Format: Hua Li, Shashwat Sharad, Talai Barbiev, Yingjie Song, Denise Young, Taduru Sreenath, Albert Dobi, Shiv Srivastava. Generation and characterization of mouse model of Pmepa1 conditional knockout in prostate epithelia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1854. doi:10.1158/1538-7445.AM2017-1854

Abstract 1183: Structure-activity studies and biological evaluations of ERGi-USU, a highly selective inhibitor for ERG-positive prostate cancer cells

Introduction and objectives: While new prostate cancer (CaP) treatments (Abiraterone and Enzalutamide) have improved survival in castration-resistant prostate cancer (CRPC), their benefits are short-lived and drug resistance develops likely due to numerous adaptive mutations. Therefore it is a critical to develop effective novel inhibitors to target other signaling pathways that promote or contribute to prostate tumorigenesis. Accumulating evidence has established the androgen regulated TMPRSS2-ERG fusion as a common oncogenic driver that contributes to the early development and progression of over half of CaP. Therefore, ERG oncoprotein and ERG dependent pathways are promising targets for CaP therapy in early stages when cancer is most responsive to treatment. We previously identified a small molecule inhibitor, ERGi-USU, which selectively inhibits ERG protein and cell growth in ERG positive tumor cell lines and mouse xenograft models. In an effort to further develop ERGi-USU with enhanced efficacy we performed detailed structure-activity relationship (SAR) evaluation of ERGi-USU core structure and developed new derivatives.

Methods: Based on SAR of the core structure of ERGi-USU, 48 new derivatives were designed and synthesized by substitutions with alkyl, alkoxy, cycloalkyl, heterocycloalkyl, aryl, heteroaryl or hydroxyl groups. The new ERGi-USU derivatives were evaluated for inhibition of cell growth and ERG protein levels in the TMPRSS2-ERG fusion harboring CaP cell line, VCaP. Four of these compounds have been selected for evaluation of ERG selectivity by defining IC50 in ERG positive malignant cells (VCaP, KG1, MOLT-4 and COLO320), ERG negative CaP cell line (LNCaP) or ERG positive normal primary endothelium-derived cells (HUVEC).

Result: Like parental compound, four new ERGi-USU derivatives exhibited inhibition of cell growth and ERG protein levels in ERG positive VCaP, KG1, MOLT-4 and COLO320 cell lines, with no or minimal effects on LNCaP and HUVEC cells. One of the new derivatives (ERGi-USU#6) showed increased efficacy for cell growth inhibition (IC50=0.074µM) compared to the parental ERGi-USU (IC50=0.200µM). Other three new compounds showed similar IC50 as the ERGi-USU.

Conclusion: Comprehensive evaluation of ERGi-USU derivatives along with parental compound has continued to underscore selective inhibition of ERG positive tumor cells by these small molecules.

Citation Format: Ahmed A. Mohamed, Charles P. Xavier, Gauthaman Sukumar, Samuel D. Banister, Vineet Kumar, Shyh-Han Tan, Shilpa Katta, Lakshmi Ravindranath, Muhammad Jamal, Taduru Sreenath, David G. McLeod, Gyorgy Petrovics, Albert Dobi, Meera Srivastava, Sanjay Malhotra, Clifton Dalgard, Shiv Srivastava. Structure-activity studies and biological evaluations of ERGi-USU, a highly selective inhibitor for ERG-positive prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1183. doi:10.1158/1538-7445.AM2017-1183

Silencing of PMEPA1 accelerates the growth of prostate cancer cells through AR, NEDD4 and PTEN

Androgen Receptor (AR) is the male hormone receptor and a nuclear transcription factor which plays a central role in the growth of normal and malignant prostate gland. Our earlier studies defined a mechanistic model for male hormone dependent regulation of AR protein levels in prostate cancer (CaP) cells through a negative feed-back loop between AR and PMEPA1, an androgen induced NEDD4 E3 ubiquitin ligase binding protein. This report focuses on the impact of PMEPA1 silencing on CaP biology. PMEPA1 knockdown accelerated the growth of CaP tumor cells in athymic nude mice. In cell culture models knockdown of PMEPA1 resulted in resistance to AR inhibitors enzalutamide and bicalutamide. While, AR protein down regulation by NEDD4 was PMEPA1 dependent, we also noted a PMEPA1 independent downregulation of PTEN by NEDD4. In a subset of human CaP, decreased PMEPA1 mRNA expression significantly correlated with increased levels of AR transcription target PSA, as a surrogate for elevated AR. This study highlights that silencing of PMEPA1 accelerates the growth of CaP cells through AR, NEDD4 and PTEN. Thus, the therapeutic restoration of PMEPA1 represents a promising complementary strategy correcting for AR and PTEN defects in CaP. Statement of significance: Here we define that silencing of PMEPA1 facilitates the growth of CaP cells and modulates AR through NEDD4 and PTEN. The restoration of PMEPA1 represents a promising complementary therapeutic strategy correcting for AR and PTEN defects.

Abstract 5058: Silencing of NOTCH signaling enhances the sensitivity of ERG positive prostate cancer cells to AR inhibitors

Introduction: Androgen receptor (AR) signaling plays a critical role in all the stages of prostate cancer (CaP) ranging from organ confined to castration-resistant (CRPC) phases. Although androgen deprivation therapy (ADT) remains the mainstay treatment for advanced CaP, the inevitable transition from androgen- sensitive to CRCP presents the most significant challenge in CaP therapy. Androgen dependent expression of oncogenic ETS related gene (ERG) in half of all CaP in western countries plays critical role in the tumorigenesis of CaP through regulation of cancer specific signaling pathways. We found that NOTCH transcription factors are common targets of ERG in ERG positive cancer cells. NOTCH signaling pathway is an important signaling pathway in the development of drug-resistant tumor growth. In the current study we evaluated the combinatorial effects of NOTCH and AR inhibitors in the context of ERG positive prostate cancer cells.

Methods: ERG, NOTCH1, NOTCH2 and downstream targets of NOTCH transcription factors were analyzed by Western blot assays. Dose and time kinetics of combining NOTCH inhibitor (γ-Secretase inhibitor 1, GSI-1) and AR inhibitors (Bicalutamide, Enzalutamide, and Abiraterone) were assessed in a panel of ERG positive or ERG negative CaP cells. Trypan blue exclusion, methylthiazole tetrazolium (MTT), or ApoTox-Glo™ Triplex assays were used to asses cell proliferation, apoptosis and drug cytotoxicity.

Results: Prostate cancer cell lines with endogenous or ectopic expression of ERG showed upregulation of NOTCH1 and NOTCH2. The NOTCH inhibitor, GSI-1 conferred an increased sensitivity to all tested AR inhibitors (Bicalutamide, Enzalutamide, and Abiraterone) with bicalutamide showing the most robust inhibition of AR, ERG, NOTCH1, NOTCH2, PSA, decreased cell growth and enhanced apoptosis in ERG positive VCaP cells. This observation was not seen in ERG negative LNCaP cells or in ERG positive primary endothelial cells.

Conclusions: NOTCH inhibitor enhanced sensitivity of AR inhibitors in ERG positive VCaP cells growth. The combination of the GSI-1 with AR inhibitors has shown synergistic effect when compared to single agent treatment. Taken together, our study suggests that NOTCH inhibitors may enhance the actions of AR inhibitors in the treatment of ERG positive prostate cancers. Inhibition of AR and NOTCH signaling may offer new opportunities in assessing ERG targeted therapy for prostate cancer.

Citation Format: Ahmed A. Mohamed, Shyh-Han Tan, Shilpa Katta, Charles P. Xavier, Lakshmi Ravindranath, Wei Huang, Hua Li, Meera Srivastava, Shashwat Sharad, Taduru Sreenath, Gyorgy Petrovics, Albert Dobi, Shiv Srivastava. Silencing of NOTCH signaling enhances the sensitivity of ERG positive prostate cancer cells to AR inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5058. doi:10.1158/1538-7445.AM2015-5058

Abstract 4679: Silencing of PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein, stabilizes androgen receptor and confers resistance to AR inhibitors

INTRODUCTION: The androgen receptor (AR) dysfunctions contribute to prostate cancer (CaP) development and progression. Earlier we defined the regulation of AR protein levels by a negative feed-back loop between AR and the androgen regulated PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein. Our data also revealed decreased or absent PMEPA1 transcripts in 65% prostate tumors. This study focuses on the relationship of PMEPA1 protein with AR and its transcriptional targets (PSA) in human CaP, as well as the impact of PMEPA1 silencing on growth of PMEPA1-shRNA LNCaP cells derived tumors in naïve and castrated nude mice.

METHODS: Ten weeks old athymic Ncr-nu/nu mice were evaluated for the growth of tumor xenografts derived from PMPEA1-shRNA LNCaP (N = 20) and control-shRNA LNCaP cells (N = 20). Each mouse received 4×106 cells by subcutaneous injection to right flank side. The mice with tumors were castrated at 9th week post-injection. The tumor sizes were monitored twice per week until 16th week post-injection. The xenograft tissues were assayed by immunohistochemical (IHC) staining for PMEPA1, AR and PSA protein levels. The AR, PMEPA1 and PSA expressions in whole mount human prostate specimens were evaluated by IHC staining and QRT-PCR.

RESULTS: The PMEPA1 shRNA-LNCaP and control shRNA-LNCaP cells started to form subcutaneous tumors at 4 weeks after injections. However, the growth rate of PMEPA1 shRNA-LNCaP derived tumors was significantly faster than control derived tumors (P<0.05). PMEPA1 shRNA-LNCaP tumors expressed higher levels of AR and PSA proteins as assessed by IHC. At 7 weeks after castration the tumor sizes increased by 69% in the control group in contrast to 304% in the PMEPA1-shRNA harboring xenografts (P<0.05). In human CaP, decreased PMEPA1 mRNA expression significantly correlated with increased levels of AR transcription target PSA, as a surrogate for elevated AR. Focally increased PSA and AR protein levels were detected in a subset of low PMEPA1 expressing tumors.CONCLUSIONS: PMEPA1 silencing in CaP cells leads to gain of AR, increased tumor growth with potential to induce resistance to AR inhibition targeted therapy. Decreased PMEPA1 in human CaP correlated with increased AR activity. Thus, monitoring PMEPA1 expression in CaP cells offers new opportunities in therapeutic stratification of CaP. Further, restoring PMEPA1 in CaP cells may provide a new strategy for AR degradation focused therapy.

Citation Format: Hua Li, Elizabeth Umeda, Yingjie Song, Denise Young, Lakshmi Ravindranath, Ahmed Mohamed, Shashwat Sharad, Gyorgy Petrovics, David McLeod, Isabell Sesterhenn, Taduru Sreenath, Albert Dobi, Shiv Srivastava. Silencing of PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein, stabilizes androgen receptor and confers resistance to AR inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4679. doi:10.1158/1538-7445.AM2015-4679

ERG oncoprotein inhibits ANXA2 expression and function in prostate cancer

Overexpression of ERG in the prostate epithelium, due to chromosomal translocations, contributes to prostate tumorigenesis. Here, genomic analysis of ERG siRNA-treated prostate cells harboring the endogenous TMPRSS2-ERG fusion revealed an inverse relationship between ERG and Annexin A2 (ANXA2) expression at both the RNA and protein level. ANXA2, a Ca(2+)-dependent and phospholipid-binding protein, is involved in various cellular functions, including maintenance of epithelial cell polarity. Mechanistic studies defined the prostate-specific transcription start site of ANXA2 and showed that the recruitment of ERG to the ANXA2 promoter is required for transcriptional repression by ERG. Knockdown of ERG enhanced the apical localization of ANXA2, the bundling of actin filaments at cell-cell junctions and formation of a polarized epithelial phenotype. ERG overexpression disrupted ANXA2-mediated cell polarity and promoted epithelial-mesenchymal transition (EMT) by inhibiting CDC42 and RHOA, and by activating cofilin. Immunohistochemistry demonstrated a reciprocal relationship of ANXA2 and ERG expression in a large fraction of primary prostate cancer clinical specimens. ANXA2 was absent or markedly reduced in ERG(+) tumors, which were mostly well differentiated. ERG(-) tumors, meanwhile, expressed moderate to high levels of ANXA2, and were either poorly differentiated or displayed subsets of poorly differentiated cells. Taken together, the transcriptional repression of ANXA2 by ERG in prostate epithelial cells plays a critical role in abrogating differentiation, promoting EMT, and in the reciprocal correlation of ERG and ANXA2 expression observed in human prostate cancer.

IMPLICATIONS

ANXA2 is a new component of the ERG network with potential to enhance biologic stratification and therapeutic targeting of ERG-stratified prostate cancers.

Functional antagonism of TMPRSS2-ERG splice variants in prostate cancer

The fusion between ERG coding sequences and the TMPRSS2 promoter is the most prevalent in prostate cancer (CaP). The presence of two main types of TMPRSS2-ERG fusion transcripts in CaP specimens, Type I and Type II, prompted us to hypothesize that the cumulative actions of different ERG variants may impact CaP development/progression. Using TMPRSS2-ERG3 (Type I) and TMPRSS2-ERG8 (Type II) expression vectors, we determined that the TMPRSS2- ERG8 encoded protein is deficient in transcriptional regulation compared to TMPRSS2-ERG3. Co-transfection of vectors resulted in decreased transcriptional regulation compared to TMPRSS2-ERG3 alone, suggesting transdominance of ERG8. Expression of exogenous ERG8 protein resulted in a decrease in endogenous ERG3 protein levels in TMPRSS2-ERG positive VCaP cells, with a concomitant decrease in C-MYC. Further, we showed a physical association between ERG3 and ERG8 in live cells by the bimolecular fluorescence complementation assay, providing a basis for the observed effects. Inhibitory effects of TMPRSS2-ERG8 on TMPRSS2- ERG3 were also corroborated by gene expression data from human prostate cancers, which showed a positive correlation between C-MYC expression and TMPRSS2-ERG3/TMPRSS2- ERG8 ratio. We propose that an elevated TMPRSS2-ERG3/TMPRSS2-ERG8 ratio results in elevated C-MYC in CaP, providing a strong rationale for the biomarker and therapeutic utility of ERG splice variants, along with C-MYC.

Evaluation of ERG responsive proteome in prostate cancer

BACKGROUND

Gene fusion between TMPRSS2 promoter and the ERG proto-oncogene is a major genomic alteration found in over half of prostate cancers (CaP), which leads to aberrant androgen dependent ERG expression. Despite extensive analysis for the biological functions of ERG in CaP, there is no systematic evaluation of the ERG responsive proteome (ERP). ERP has the potential to define new biomarkers and therapeutic targets for prostate tumors stratified by ERG expression.

METHODS

Global proteome analysis was performed by using ERG (+) and ERG (-) CaP cells isolated by ERG immunohistochemistry defined laser capture microdissection and by using TMPRSS2-ERG positive VCaP cells treated with ERG and control siRNA.

RESULTS

We identified 1,196 and 2,190 unique proteins stratified by ERG status from prostate tumors and VCaP cells, respectively. Comparative analysis of these two proteomes identified 330 concordantly regulated proteins characterizing enrichment of pathways modulating cytoskeletal and actin reorganization, cell migration, protein biosynthesis, and proteasome and ER-associated protein degradation. ERPs unique for ERG (+) tumors reveal enrichment for cell growth and survival pathways while proteasome and redox function pathways were enriched in ERPs unique for ERG (-) tumors. Meta-analysis of ERPs against CaP gene expression data revealed that Myosin VI and Monoamine oxidase A were positively and negatively correlated to ERG expression, respectively.

CONCLUSIONS

This study delineates the global proteome for prostate tumors stratified by ERG expression status. The ERP data confirm the functions of ERG in inhibiting cell differentiation and activating cell growth, and identify potentially novel biomarkers and therapeutic targets.

Abstract 3004: Functional analysis of ERG splice variants and their effect on c-myc expression in prostate cancer

Introduction and Objectives: The oncogenic activation of ERG in prostate cancer has been well established in recent years. Towards understanding the functional role of ERG, our laboratory previously identified two major types of ERG splice variants in human prostate tumors: Type I, which encodes a full length prototypical ERG protein, and Type II, which encodes a truncated protein lacking the ETS DNA-binding domain. Analysis of clinico-pathologic data from patients and ratios of Type I/Type II ERG revealed that an increased ratio correlated with a higher Gleason sum and poorly differentiated phenotype. However, the functional significance of the ERG splice variants is not clearly understood. Studying the function and interaction of the individual splice variants can further enhance our understanding of ERG, and advance efforts towards its clinical utility in the treatment of prostate cancer.

Methods: Exogenous Type II ERG was expressed in TMPRSS2-ERG fusion harboring VCaP cells and endogenous levels of Type I ERG and C-MYC proteins were evaluated. Type I and Type II ERG were also co-transfected in various cell lines to examine interaction among splice variants and regulatory efficiency with luciferase reporter constructs. In addition, quantitative RNA expression data of C-MYC and Type I/Type II ERG ratio were assessed by correlation analysis in patient samples.

Results: Expression of exogenous Type II ERG resulted in a decrease in endogenous Type I ERG protein expression in VCaP cells in a dose dependent manner, with a concomitant decrease in C-MYC. This decrease was not observed in the other cell lines. Decreased regulatory efficiency of Type I ERG, by addition of Type II ERG, was also observed. Patient data analysis also revealed a positive correlation between C-MYC expression and increased Type I/Type II ratio.

Conclusions: Decreased Type I/Type II ratios in VCaP cells showed decreases in C-MYC, suggesting that modulation of Type II ERG alters Type I ERG and thus its regulation of C-MYC. This interference was not observed in other cell lines, indicating the interaction is context dependent. While Type I ERG positively regulated downstream targets, addition of Type II ERG decreased their expression, implying an interaction between splice variants. Analysis of patient data affirmed in vitro results, thus we propose that modulation of Type I/Type II ratio may regulate downstream targets including oncogenic C-MYC in prostate cancer, providing a strong rationale for the biomarker and therapeutic utility of ERG splice variants.

Funding source: DoD/CDMRP (PC073614) grant to S.S.

Citation Format: Anshu Rastogi, Shyh-Han Tan, Gyorgy Petrovics, Yongmei Chen, Taduru Sreenath, David G. McLeod, Shiv Srivastava, Albert Dobi. Functional analysis of ERG splice variants and their effect on c-myc expression in prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3004. doi:10.1158/1538-7445.AM2013-3004

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract A30: ERG protein expression and genomic rearrangement status in primary and metastatic prostate cancer a comparative study of two monoclonal antibodies

Introduction and Objective: Overexpression of the ERG protein is highly prevalent in prostate cancer (PCa) and most commonly results from gene fusions involving the ERG gene. Recently, an N-terminal epitope targeted mouse and a C-terminal epitope targeted rabbit monoclonal anti-ERG antibody have been introduced for the detection of the ERG protein. Independent studies reported that immunohistochemical (IHC) stains with both monoclonal anti-ERG antibodies (ERG-MAbs) highly correlate with the underlying ERG gene rearrangement status. However, a comparative study of both antibodies has not been provided so far. Here, we are the first to compare the mouse ERG-MAb to the rabbit ERG-MAb for their concordance on the same PCa cohort. Furthermore, we assessed if the ERG protein expression is conserved in lymph node and distant PCa metastases, of which a subset underwent decalcification.

Methods: We evaluated tissue microarrays of 278 specimens containing 265 localized PCa, 29 lymph node, 30 distant metastases, and 13 normal prostatic tissues. We correlated the ERG protein expression with the ERG rearrangement status using an ERG break-apart fluorescence in-situ hybridization (FISH) assay and IHC of both ERG antibodies.

Results: ERG protein expression and ERG rearrangement status were highly concordant regardless of whether the mouse or rabbit ERG-MAb was used (97.8% versus 98.6%, respectively). Of interest, both ERG antibodies reliably detected the ERG expression in lymph node and distant PCa metastases, of which a subset underwent decalcification. If an ERG protein expression was present in localized PCa, we observed the same pattern in the corresponding lymph node metastases.

Conclusions: This is the first study to comprehensively compare the two available ERG-MAbs. By demonstrating a broad applicability of IHC to study ERG protein expression using either antibody, this study adds an important step towards a facilitated routine clinical application. Further, we demonstrate that the clonal nature of the ERG rearrangement is not restricted to the genomic level, but proceeds in the proteome. Together, our results simplify future efforts to further elucidate the biological role of ERG in PCa.

Citation Format: Taduru Sreenath, Falko Fend, Nicolas Wernert, Glen Kristiansen, Sven Perner, Shyh-Han Tan, Sr., Martin Braun, Diane Goltz, Zaki Shaikibrahim, Wenzel Vogel, Diana Boehm, Veit Scheble, Albert Dobi. ERG protein expression and genomic rearrangement status in primary and metastatic prostate cancer a comparative study of two monoclonal antibodies [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A30.

Abstract 4287: Ets-related gene (Erg) expression in developing and adult mouse tissues

Oncogenic activation of the ETS Related Gene (ERG) in human neoplasms was originally identified in subsets of Ewing sarcomas, myeloid leukemias and, recently, in the majority of prostate cancers. Expression of human ERG protein and consequently its functions in normal and disease states needs to be better understood in light of its suggested role in cell differentiation and proliferation.

In this study, we analyzed temporal and spatial expression of the Erg protein by immunohistochemical analysis during mouse embryonic and adult organogenesis using a highly specific ERG monoclonal antibody (CPDR ERG-MAb) developed by our group. Initially, we evaluated the specificity of three recently available ERG monoclonal antibodies (Epitomics EPR 3864 and EPR 3863, and CPDR ERG-MAb) using ERG expressing MOLT4, KG1, COLO 320, VCaP tumor cell lines and LNCaP, MCF7, Jurkat cell lines that do not express ERG. Unlike, rabbit monoclonal antibodies to ERG obtained from Epitomics, the ERG MAb did not show cross reactivity to FLI-1 or to the other ETS related proteins. Our comprehensive evaluation of mouse tissues established a widespread immunolocalization of Erg protein in endothelial cells and restricted expression in precartilage and hematopoietic tissues. Intriguingly, Erg is not expressed in any epithelial tissue including prostate epithelium, a common site of tumors with ERG rearrangements and unscheduled ERG expression. Further, use of two different monoclonal antibodies revealed that infiltrating lymphocytes that are occasionally seen in the prostate environment were positive for Fli-1, did not exhibit any Erg expression.

These findings will further aid in investigations of Erg functions in normal and disease conditions.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4287. doi:10.1158/1538-7445.AM2011-4287

Abstract 4007: Defining the role of ERG-mediated repression of HPGD in prostate tumorigenesis

Activation of the ETS Related Gene (ERG) was originally identified in subsets of Ewing sarcomas, myeloid leukemias and, recently, in the majority of prostate cancers (CaP). Emerging studies in experimental models underscore functions of ERG in prostate tumorigenesis. However, biological functions of ERG in CaP remains to be better understood. Evaluation of ERG downstream targets identified 15-hydroxyprostaglandin dehydrogenase gene (HPGD) in response to ERG knockdown. Several recent studies have indicated that HPGD, the main catabolizing enzyme of prostaglandins and lipoxins and a tumor suppressor, is down-regulated in a majority of lung, colon, breast, and bladder cancers. However, the regulation of HPGD within the biological context of ERG expressing prostate tumors remains to be defined. The objective of this study was to evaluate the effects of ERG on the prostaglandin signaling pathway in prostate cancer.

Correlation between HPGD and ERG expression was evaluated at the mRNA and protein levels in prostate cancer specimens and cell lines by Western blot, QRT-PCR, and immunofluorescence assays. Small interference RNA against human ERG and HPGD were used to knock-down their respective expressions. Functional consequences of ERG and HPGD knockdown in VCaP cells harboring TMPRSS2-ERG fusions were assessed by ChIP and BrdU cell proliferation assays.

The experiments showed that loss of ERG expression leads to a robust overexpression of HPGD in prostate cancer cells. Furthermore, we observed altered PGE2 production, decreased expression of prostaglandin E2 receptor 4 (EP4), and inhibition of prostaglandin E2 induced cell growth. Chromatin immunoprecipitation experiments revealed direct binding of ERG protein to the HPGD core promoter. Comparison of HPGD expression in TMPRSS2-ERG positive and negative prostate tumors indicated a trend towards decreased HPGD expression.

In conclusion ERG activation, as a consequence of TMPRSS2-ERG fusions, may influence the components of the prostaglandin signaling pathway in prostate tumorigenesis disrupting the tumor suppressor functions of HPGD. These findings suggests for a new biological role of ERG in CaP that may be further evaluated as a target for prevention, as well as early therapeutic intervention in CaP.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4007. doi:10.1158/1538-7445.AM2011-4007

ERG oncogene modulates prostaglandin signaling in prostate cancer cells

Androgen dependent induction of the ETS related gene (ERG) expression in more than half of all prostate cancers results from gene fusions involving regulatory sequence of androgen regulated genes (i.e. TMPRSS2, SLC45A3 and NDRG1) and protein coding sequence of the ERG. Emerging studies in experimental models underscore the functions of ERG in prostate tumorigenesis. However, biological and biochemical functions of ERG in prostate cancer (CaP) remain to be elucidated. This study suggests that ERG activation plays a role in prostaglandin signaling because knockdown of ERG expression in TMPRSS2-ERG fusion containing CaP cells leads to altered levels of the 15-hydroxy-prostaglandin dehydrogenase (HPGD), a tumor suppressor and prostaglandin catabolizing enzyme, and prostaglandin E2 (PGE2) . We demonstrate that HPGD expression is regulated by the binding of the ERG protein to the core promoter of this gene. Moreover, prostaglandin E2 dependent cell growth and urokinase-type plasminogen activator (uPA) expression are also affected by ERG knockdown. Together, these data imply that the ERG oncoprotein in CaP cells positively influence prostaglandin mediated signaling, which may contribute to tumor progression.

ERG oncoprotein expression in prostate cancer: clonal progression of ERG-positive tumor cells and potential for ERG-based stratification

Gene fusions prevalent in prostate cancer (CaP) lead to the elevated expression of the ERG proto-oncogene. ERG activation present in 50–70% of prostate tumors underscores one of the most common oncogenic alterations in CaP. Despite numerous reports of gene fusions and mRNA expression, ERG oncoprotein status in CaP still remains to be defined. Furthermore, development of ERG protein-based assays may provide a new dimension to evaluation of gene fusions involving diverse androgen-regulated promoters and the ERG protein-coding sequence. Through exhaustive evaluations of 132 whole-mount prostates (261 tumor foci and over 200 000 benign glands) for the ERG oncoprotein nuclear expression, we demonstrated 99.9% specificity for detecting prostate tumor cells using a highly specific anti-ERG monoclonal antibody. The ERG oncoprotein expression correlated well with fusion transcript or gene fusion in randomly selected specimens. Strong concordance of ERG-positive foci of prostatic intraepithelial neoplasia (PIN) with ERG-positive carcinoma (82 out of 85 sections with PIN, 96.5%) affirms the biological role of ERG in clonal selection of prostate tumors in 65% (86 out of 132) of patients. Conversely, ERG negative PINs were associated with ERG-negative carcinoma. Taken together, the homogeneous and strong ERG expression detected in individual tumors establishes the potential for ERG oncoprotein-based stratification of CaP.

Abstract 30: ERG oncoprotein expression in prostate cancer: Potential for ERG-based stratification

Introduction: Prevalent gene fusions involving regulatory sequences of the androgen receptor (AR) regulated prostate associated genes (predominantly TMPRSS2) and protein coding sequences of nuclear transcription factors in the ETS gene family (primarily ERG), result in frequent overexpression of ERG in prostate tumors. Emerging studies suggest oncogenic functions of ERG in prostate cancer (CaP). Despite numerous reports of gene fusions and mRNA expression, ERG oncoprotein in CaP still remains to be defined. Using an anti-ERG monoclonal antibody (ERG-MAb) developed by our group, a global view of ERG oncoprotein expression has been established in the context of multi-focal CaP.

Experimental procedures: Specificity of the ERG MAb was established using wt ERG and TMPRRSS2-ERG encoded proteins expressed in HEK 293 cells and ERG si RNA treated VCaP cells harboring TMPRRSS2-ERG fusion. ERG expression in formalin fixed paraffin embedded (FFPE), whole mount-prostate specimens was optimized by immuno-histochemistry assay. TMPRSS2-ERG fusion status in representative specimens was analyzed by b-DNA assay or fluorescent in situ hybridization (FISH).

Results: Through exhaustive evaluations of 132 whole-mount prostates (227 tumor foci and over 200,000 benign glands), we demonstrate 99.9 % specificity of an anti-ERG monoclonal antibody. Specimens from over 60% patients had one or more ERG positive tumor focus. Over 80% concordance was noted between the presence of ERG protein and the common TMPRSS2-ERG fusion (A type) transcript in representative specimens from 35 pateints.

Conclusions: Unequivocal association of focally ERG positive PIN lesions with ERG positive carcinoma (80 out of 80 specimens) and vice versa (52 out of 52 specimens) strongly affirms biological role of ERG in clonal progression of prostate tumors. Taken together, the homogeneous and strong ERG expression in individual tumors establishes the potential for ERG based stratification of prostate cancers.

Funding sources: NIH Grants RO1 DK065977 and Center for Prostate Disease Research Program HU001-04-C-1502

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 30.

Abstract 4920: Effects of PMEPA1 in prostate tumor cell growth and tumor formation

Introduction: PMEPA1 is an androgen-induced gene. We have shown that androgen receptor transcriptionally activates PMEPA1 and PMEPA1 negatively regulates androgen receptor by recruiting the E3 ubiquitinatin ligase NEDD4 to AR, therefore promoting proteasome-dependent AR degradation, thus, forming a remarkably tight feedback loop between AR and PMEPA1. Moreover, PMEPA1 mRNA was found in decreased amounts in prostate carcinoma. Previous data in cell culture models of prostate cancer have shown that DNA Methylation of the PMEPA1 gene may play a role in decreased PMEPA1 expression in human prostate cancer cells.

Experimental procedures: We generated stable PMEPA1 shRNA expressing LNCaP cells and analyzed this cell line by cancer biological assays including cell counting, soft agar and cell invasive assays. To evaluate the Methylation status of PMEPA1 promoter genomic DNA from primary human prostate tumors was examined by Methylation sensitive PCR method.

Results: PMEPA1 is successfully knocked down in the PMEPA1 shRNA expressing LNCaP cell line as detected at the mRNA and protein levels. The PMEPA1 knockdown cell line expressed AR protein at elevated levels and consistent elevation of AR signaling was evident in the study. Interestingly, the size of PMEPA1 knockdown cell showed altered morphology when compared to stale transfectant non-targeted shRNA LNCaP cells. In the PMEPA1 knockdown cell line we found higher number of cells in the S phase of the cell cycle compared with the control. In agreement with this observation the cellular proliferations were also enhanced under both androgen dependent and independent conditions. Moreover, the PMEPA1 knockdown cells have stronger invasive activity compared to control cells. The promoter methylation study of human prostate tumor derived genomic DNA revealed DNA Methylation within the PMEPA1 promoter downstream region in 20% of the examined samples.

Conclusions: PMEPA1 knockdown may enhance proliferation and invasiveness of prostate cancer cell by the elevation of AR levels. Thus PMEPA1 gene may act as a tumor suppressor gene in human prostate cancer cells. DNA methylation may play a role in silencing PMEPA1 gene expression in a subset of patients with lost or decreased PMEPA1 expression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4920.

Abstract 4962: ERG expression levels in prostate tumors reflect functional status of the androgen receptor as a consequence of fusion of ERG with AR regulated gene promoters

Background: Androgen dependent overexpression of the TMPRSS2:ERG fusion is the most prevalent chromosomal rearrangement in prostate cancer. During our recent evaluations of the ERG downstream transcriptional targets, we identified 15-Hydroxyprostaglandin Dehydrogenase gene (HPGD) in response to ERG knock-down. HPGD is an enzyme that catalyzes the oxidation of prostaglandins and lipoxins by converting them into inactive keto-metabolites, and physiologically antagonizes COX-2, a prostaglandin-synthesizing enzyme. HPGD also behaves as a tumor suppressor in many cancers as overexpression of HPGD resulted in marked inhibition of cell growth. The objective of this study was to evaluate potential connection between ERG overexpression and prostaglandin signaling.

Experimental procedures: Small interference RNA (siRNA) oligo duplex was used to knock-down endogenous ERG and HPGD expressions. Western blot assay and Immunofluorescence was used to detect protein expressions. QT-PCR (normalized to GAPDH) was used for transcriptome analysis. GeneChip, Chromatin immunoprecipitation assays and cell proliferation assay were utilized for functional analysis.

Results: ERG knock-down in VCaP prostate tumor cells results in overexpression of HPGD, down regulation of the prostaglandin E2 receptor 4 (EP4), and inhibition of prostaglandin E2 induced Urokinase Plasminogen Activator (uPA) expression and cell growth. Comparison of HPGD between TMPRSS2:ERG positive and negative prostate tumors revealed a trend towards decreased HPGD expression in fusion positive tumors.

Conclusions: Taken together, these data suggest that ERG over-expression in CaP cells may positively influence prostaglandin mediated signaling. Funding sources: NIH Grants RO1 DK065977

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4962.

Dentin sialoprotein and dentin phosphoprotein have distinct roles in dentin mineralization

Dentin sialophosphoprotein (DSPP), a major non-collagenous matrix protein of odontoblasts, is proteolytically cleaved into dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). Our previous studies revealed that DSPP null mice display a phenotype similar to human autosomal dominant dentinogenesis imperfecta, in which teeth have widened predentin and irregular dentin mineralization resulting in sporadic unmineralized areas in dentin and frequent pulp exposure. Earlier in vitro studies suggested that DPP, but not DSP, plays a significant role in initiation and maturation of dentin mineralization. However, the precise in vivo roles of DSP and DPP are far from clear. Here we report the generation of DPPcKO mice, in which only DSP is expressed in a DSPP null background, resulting in a conditional DPP knockout. DPPcKO teeth show a partial rescue of the DSPP null phenotype with the restored predentin width, an absence of irregular unmineralized areas in dentin, and less frequent pulp exposure. Micro-computed tomography (micro-CT) analysis of DPPcKO molars further confirmed this partial rescue with a significant recovery in the dentin volume, but not in the dentin mineral density. These results indicate distinct roles of DSP and DPP in dentin mineralization, with DSP regulating initiation of dentin mineralization, and DPP being involved in the maturation of mineralized dentin.

DSPP effects on in vivo bone mineralization

Dentin sialophosphoprotein has been implicated in the mineralization process based on the defective dentin formation in Dspp null mice (Dspp-/-). Dspp is expressed at low levels in bone and Dspp-/- femurs assessed by quantitative micro-computed tomography (micro-CT) and Fourier transform infrared spectroscopic imaging (FTIRI) exhibit some mineral and matrix property differences from wildtype femurs in both developing and mature mice. Compared to wildtype, Dspp-/- mice initially (5 weeks) and at 7 months had significantly higher trabecular bone volume fractions and lower trabecular separation, while at 9 months, bone volume fraction and trabecular number were lower. Cortical bone mineral density, area, and moments of inertia in Dspp-/- were reduced at 9 months. By FTIRI, Dspp-/- animals initially (5 months) contained more stoichiometric bone apatite with higher crystallinity (crystal size/perfection) and lower carbonate substitution. This difference progressively reversed with age (significantly decreased crystallinity and increased acid phosphate content in Dspp-/- cortical bone by 9 months of age). Mineral density as determined in 3D micro-CT and mineral-to-matrix ratios as determined by 2D FTIRI in individual cortical and trabecular bones were correlated (r(2)=0.6, p<0.04). From the matrix analysis, the collagen maturity of both cortical and trabecular bones was greater in Dspp-/- than controls at 5 weeks; by 9 months this difference in cross-linking pattern did not exist. Variations in mineral and matrix properties observed at different ages are attributable, in part, to the ability of the Dspp gene products to regulate both initial mineralization and remodeling, implying an effect of Dspp on bone turnover.

Delineation of TMPRSS2-ERG splice variants in prostate cancer

PURPOSE

The expression of the ETS-related gene (ERG) is low or undetectable in benign prostate epithelial cells. High prevalence of ERG overexpression in prostate cancer cells due to TMPRSS2-ERG fusions suggest for causal roles of ERG protein in the neoplastic process. TMPRSS2-ERG fusion junctions have been extensively studied in prostate cancer. However, virtually nothing is known about the nature of full-length transcripts and encoded proteins. This study focuses on qualitative and quantitative features of full-length TMPRSS2-ERG transcripts in prostate cancer.

EXPERIMENTAL DESIGN

Full-length TMPRSS2-ERG transcripts were cloned and sequenced from a cDNA library generated from pooled RNA of six TMPRSS2-ERG fusion-positive prostate tumors. The encoded ERG proteins were analyzed in HEK293 cells. Copy numbers of TMPRSS2-ERG splice variants were determined by quantitative reverse transcription-PCR in laser capture microdissected prostate cancer cells.

RESULTS

Two types of TMPRSS2-ERG cDNAs were identified: type I, which encodes full-length prototypical ERG protein (ERG1, ERG2, ERG3), and type II, encoding truncated ERG proteins lacking the ETS domain (ERG8 and a new variant, TEPC). In microdissected prostate tumor cells from 122 patients, relative abundance of these variants was in the following order: ERG8 > TEPC > ERG 3 > ERG1/2 with combined overexpression rate of 62.3% in prostate cancer. Increased ratio of type I over type II splice forms showed a trend of correlation with less favorable pathology and outcome.

CONCLUSIONS

Qualitative and quantitative features of specific ERG splice variants defined here promise to enhance the utility of ERG as a biomarker and therapeutic target in prostate cancer.

Female mice are more susceptible to developing inflammatory disorders due to impaired transforming growth factor β signaling in salivary glands

OBJECTIVE

Transforming growth factor beta (TGFbeta) plays a key role in the onset and resolution of autoimmune diseases and chronic inflammation. The aim of this study was to delineate the precise function of TGFbeta signaling in salivary gland inflammation.

METHODS

We impaired TGFbeta signaling in mouse salivary glands by conditionally inactivating expression of TGFbeta receptor type I (TGFbetaRI), either by using mouse mammary tumor virus-Cre mice or by delivering adenoviral vector containing Cre to mouse salivary glands via retrograde infusion of the cannulated main excretory ducts of submandibular glands.

RESULTS

TGFbetaRI-conditional knockout (TGFbetaRI-coko) mice were born normal; however, female TGFbetaRI-coko mice developed severe multifocal inflammation in salivary and mammary glands and in the heart. The inflammatory disorder affected normal growth and resulted in the death of the mice at ages 4-5 weeks. Interestingly, male TGFbetaRI-coko mice did not exhibit any signs of inflammation. The female TGFbetaRI-coko mice also showed an increase in Th1 proinflammatory cytokines in salivary glands and exhibited an up-regulation of peripheral T cells. In addition, these mice showed an atypical distribution of aquaporin 5 in their salivary glands, suggesting likely secretory impairment. Administration of an adenoviral vector encoding Cre recombinase into the salivary glands resulted in inflammatory foci only in the glands of female TGFbetaRI-loxP-flanked (floxed) mice (TGFbetaRI-f/f mice), but not in those of male and female wild-type mice or male TGFbetaRI-f/f mice.

CONCLUSION

These results suggest that female mice are uniquely more susceptible to developing inflammatory disorders due to impaired TGFbeta signaling in their salivary glands.

Amelogenin-mediated regulation of osteoclastogenesis, and periodontal cell proliferation and migration

We previously reported that amelogenin isoforms M180 and leucine-rich amelogenin peptide (LRAP) are expressed in the periodontal region, and that their absence is associated with increased cementum defects in amelogenin-knockout (KO) mice. The aim of the present study was to characterize the functions of these isoforms in osteoclastogenesis and in the proliferation and migration of cementoblast/periodontal ligament cells. The co-cultures of wild-type (WT) osteoclast progenitor and KO cementoblast/periodontal ligament cells displayed more tartrate-resistant acid phosphatase (TRAP)-positive cells than the co-cultures of WT cells. The addition of LRAP to both co-cultures significantly reduced RANKL expression and the TRAP-positive cells. Proliferation and migration rates of the KO cementoblast/periodontal ligament cells were lower than those of WT cells and increased with the addition of either LRAP or P172 (a porcine homolog of mouse M180). Thus, we demonstrate the regulation of osteoclastogenesis by LRAP, and the proliferation and migration of cementoblast/periodontal ligament cells by LRAP and P172.

Dph3, a small protein required for diphthamide biosynthesis, is essential in mouse development

The translation elongation factor 2 in eukaryotes (eEF-2) contains a unique posttranslationally modified histidine residue, termed diphthamide, which serves as the only target for diphtheria toxin and Pseudomonas aeruginosa exotoxin A. Diphthamide biosynthesis is carried out by five highly conserved proteins, Dph1 to Dph5, and an as-yet-unidentified amidating enzyme. The evolutionary conservation of the complex diphthamide biosynthesis pathway throughout eukaryotes implies a key role for diphthamide in normal cellular physiology. Of the proteins required for diphthamide synthesis, Dph3 is the smallest, containing only 82 residues. In addition to having a role in diphthamide biosynthesis, Dph3 is also involved in modulating the functions of the Elongator complex in yeast. To explore the physiological roles of Dph3 and to begin to investigate the function of diphthamide, we generated dph3 knockout mice and showed that dph3+/- mice are phenotypically normal, whereas dph3-/- mice, which lack the diphthamide modification on eEF-2, are embryonic lethal. Loss of both dph3 alleles causes a general delay in embryonic development accompanied by lack of allantois fusion to the chorion and increased degeneration and necrosis in neural tubes and is not compatible with life beyond embryonic day 11.5. The dph3-/- placentas also developed abnormally, showing a thinner labyrinth lacking embryonic erythrocytes and blood vessels. These results attest to the physiological importance of Dph3 in development. The biological roles of Dph3 are also discussed.

Increased activity of cyclin-dependent kinase 5 leads to attenuation of cocaine-mediated dopamine signaling

Cocaine, a drug of abuse, increases synaptic dopamine levels in the striatum by blocking dopamine reuptake at axon terminals. Cyclin-dependent kinase 5 (Cdk5) and its activator p35, proteins involved in phosphorylation of substrates in postmitotic neurons, have been found to be up-regulated after chronic exposure to cocaine. To further examine the effects of Cdk5 and p35 induction on striatal dopamine signaling, we generated two independent transgenic mouse lines in which Cdk5 or p35 was overexpressed specifically in neurons. We report here that increased Cdk5 activity, as a result of p35 but not of Cdk5 overexpression, leads to attenuation of cocaine-mediated dopamine signaling. Increased Cdk5-mediated phosphorylation of dopamine and cAMP-regulated phosphoprotein, molecular mass 32 kDa (DARPP-32) at Thr-75, was accompanied by decreased phosphorylation of DARPP-32 at Thr-34. Increased Cdk5-mediated phosphorylation of extracellular signal-regulated kinase kinase 1 at Thr-286 was accompanied by decreased activation of extracellular signal-regulated kinase 1/2. These effects contributed to attenuation of cocaine-induced phosphorylation of cAMP response element-binding protein as well as a lesser induction of c-fos in the striatum. These results support the idea that Cdk5 activity is involved in altered gene expression after chronic exposure to cocaine and hence impacts the long-lasting changes in neuronal function underlying cocaine addiction.

Transgenic mouse model of early-onset DYT1 dystonia

Early-onset dystonia is an autosomal dominant movement disorder associated with deletion of a glutamic acid residue in torsinA. We generated four independent lines of transgenic mice by overexpressing human DeltaE-torsinA using a neuron specific enolase promoter. The transgenic mice developed abnormal involuntary movements with dystonic-appearing, self-clasping of limbs, as early as 3 weeks after birth. Animals also showed hyperkinesia and rapid bi-directional circling. Approximately 40% of transgenic mice from each line demonstrated these severe behavioral abnormalities. Neurochemical analyses revealed decreases in striatal dopamine in affected transgenic mice, although levels were increased in those that had no behavioral changes. Immunohistochemistry demonstrated perinuclear inclusions and aggregates that stained positively for ubiquitin, torsinA and lamin, a marker of the nuclear envelope. Inclusions were detected in neurons of the pedunculopontine nucleus and in other brain stem regions in a pattern similar to what has been described in DYT1 patients. This transgenic mouse model demonstrates behavioral and pathologic features similar to patients with early-onset dystonia and may help to better understand the pathophysiology of this disorder and to develop more effective therapies.

Is the lingual forming part of the incisor a structural entity? Evidences from the fragilitas ossium (fro/fro) mouse mutation and the TGFbeta1 overexpressing transgenic strain

Our objective was to study the teeth of a mutant mice fro/fro that display severe forms of osteogenesis imperfecta. One day and 8 week-old fro/fro and +/fro heterozygote mice (wild type, WT) were processed for light and scanning electron microscopy. The genetic defect, shown to be located on chromosome 8, induced alveolar bone and teeth hypomineralisation. Due to defective cell proliferation in the fro/fro, the distal growth of the mandibular incisors was impaired. Immunolabelling revealed an increase of chondroitin/dermatan sulphate, whereas no difference was detected in dental tissues for decorin and biglycan. Amelogenin expression was decreased in the incisor and enhanced in the molar. Dentin sialoprotein was below the level of detection in the fro/fro, whereas osteonectin and osteopontin were unchanged. The main target of the mutation was seen in the lingual part of the incisor near the apex where dentine formation was delayed. In the molars, bulbous roots with obliteration of the pulp chamber were seen. In the TGFbeta1 overexpressing mice, the lingual root-analogue part of the incisor was missing. In the molar, short roots, circumpulpal dentine of the osteodentine type and pulp obliteration were seen. It may be noted that, although the mutant and transgenic strains mutations are two different genetic alterations not related to the same defective gene, in both cases the expression of the dentin sialoprotein is altered. Altogether, the present data suggest that the lingual forming part of the incisor seems to be an anatomical entity bearing its own biological specificities.

Molecular cloning, characterization, and distribution of the gerbil angiotensin II AT2 receptor

We isolated a cDNA clone encoding the gerbil AT2 receptor (gAT2) gene from a gerbil adrenal gland cDNA library. The full-length cDNA contains a 1,089-bp open reading frame encoding 363 amino acid residues with 90.9, 96.1, and 95.6% identity with the human (hAT2), rat (rAT2), and mouse AT2 (mAT2) receptors, respectively. There are at least seven nonconserved amino acids in the NH2-terminal domain and in positions Val196, Val217, and Met293, important for angiotensin (ANG) II but not for CGP-42112 binding. Displacement studies in adrenal sections revealed that affinity of the gAT2 receptor was 10-20 times lower for ANG II, ANG III, and PD-123319 than was affinity of the rAT2 receptor. The affinity of each receptor remained the same for CGP-42112. When transfected into COS-7 cells, the gAT2 receptor shows affinity for ANG II that is three times lower than that shown by the hAT2 receptor, whereas affinities for ANG III and the AT2 receptor ligands CGP-42112 and PD-123319 were similar. Autoradiography in sections of the gerbil head showed higher binding in muscles, retina, skin, and molars at embryonic day 19 than at 1 wk of age. In situ hybridization and emulsion autoradiography revealed that at embryonic day 19 the gAT2 receptor mRNA was highly localized to the base of the dental papilla of maxillary and mandibular molars. Our results suggest selective growth-related functions in late gestation and early postnatal periods for the gAT2 receptor and provide an essential basis for future mutagenesis studies to further define structural requirements for agonist binding.

The receptor activator of nuclear factor-kappa B ligand-mediated osteoclastogenic pathway is elevated in amelogenin-null mice

Amelogenins, major components of developing enamel, are predominantly involved in the formation of tooth enamel. Although amelogenins are also implicated in cementogenesis, their precise spatial expression pattern and molecular role are not clearly understood. Here, we report for the first time the expression of two alternate splice forms of amelogenins, M180 and the leucine-rich amelogenin peptide (LRAP), in the periodontal region of mouse tooth roots. Lack of M180 and LRAP mRNA expression correlated with cementum defects observed in the amelogenin-null mice. The cementum defects were characterized by an increased presence of multinucleated cells, osteoclasts, and cementicles. These defects were associated with an increased expression of the receptor activator of the nuclear factor-kappa B ligand (RANKL), a critical regulator of osteoclastogenesis. These findings indicate that the amelogenin splice variants, M180 and LRAP, are critical in preventing abnormal resorption of cementum.

Dentin sialophosphoprotein knockout mouse teeth display widened predentin zone and develop defective dentin mineralization similar to human dentinogenesis imperfecta type III

Dentin sialophosphoprotein (Dspp) is mainly expressed in teeth by the odontoblasts and preameloblasts. The Dspp mRNA is translated into a single protein, Dspp, and cleaved into two peptides, dentin sialoprotein and dentin phosphoprotein, that are localized within the dentin matrix. Recently, mutations in this gene were identified in human dentinogenesis imperfecta II (Online Mendelian Inheritance in Man (OMIM) accession number 125490) and in dentin dysplasia II (OMIM accession number 125420) syndromes. Herein, we report the generation of Dspp-null mice that develop tooth defects similar to human dentinogenesis imperfecta III with enlarged pulp chambers, increased width of predentin zone, hypomineralization, and pulp exposure. Electron microscopy revealed an irregular mineralization front and a lack of calcospherites coalescence in the dentin. Interestingly, the levels of biglycan and decorin, small leucine-rich proteoglycans, were increased in the widened predentin zone and in void spaces among the calcospherites in the dentin of null teeth. These enhanced levels correlate well with the defective regions in mineralization and further indicate that these molecules may adversely affect the dentin mineralization process by interfering with coalescence of calcospherites. Overall, our results identify a crucial role for Dspp in orchestrating the events essential during dentin mineralization, including potential regulation of proteoglycan levels.

Spatial expression of Cbfa1/Runx2 isoforms in teeth and characterization of binding sites in the DSPP gene

Cbfa1/Runx2 is an essential transcription factor for osteoblast and odontoblast differentiation. Heterogeneous mutations of Cbfa1 gene result in cleidocranial dysplasia, an autosomal dominant syndrome, characterized by abnormal skeletal genesis and dental disorders. Recently three Cbfa1/Runx isoforms (Pebp2 alpha A/type I, til-1/type II, and Osf2/type III) have been identified that differ in their amino-terminal sequences. The precise roles of Cbfa1/Runx2 isoforms in odontoblast development are not known. The purpose of this study was to determine and compare expression patterns of the three Cbfa1/Runx2 isoforms in newborn tooth organs. Toward this aim, we developed three probes: type I and type II, which specifically hybridize with Pebp2 alpha A and til-1, respectively, and type II/III, which hybridizes with osf2 and partially with til-1. In addition, Cbfa1/Runx2 binding sites were identified in the regulatory elements of mouse dentin sialophosphoprotein (mDSPP) gene, which encodes a matrix protein expressed during odontogenesis. In situ hybridization performed with the specific Cbfa1/Runx2 isoform probes demonstrated that all isoforms are expressed in teeth and bone. The type I isoform was expressed at higher levels than isoforms type II and type II/III in developing newborn mouse incisors. Genomic mDSPP clones were isolated and characterized containing approximately 2.6 kb of the promoter region. Computer analysis of the promoter segment and intron 1 revealed a number of potential transcriptional factor binding sites including five Cbfa1/Runx2 binding sites, three in the promoter region and two within intron 1. DNA-protein assay and antibody supershift experiments showed that these binding sites interact with nuclear extracts isolated from the mouse odontoblast cell line MO6-G3. Further characterization of the functional role of Cbfa1/Runx2 in the regulation of the mDSPP gene expression is being investigated.

Amelogenin-deficient mice display an amelogenesis imperfecta phenotype

Dental enamel is the hardest tissue in the body and cannot be replaced or repaired, because the enamel secreting cells are lost at tooth eruption. X-linked amelogenesis imperfecta (MIM 301200), a phenotypically diverse hereditary disorder affecting enamel development, is caused by deletions or point mutations in the human X-chromosomal amelogenin gene. Although the precise functions of the amelogenin proteins in enamel formation are not well defined, these proteins constitute 90% of the enamel organic matrix. We have disrupted the amelogenin locus to generate amelogenin null mice, which display distinctly abnormal teeth as early as 2 weeks of age with chalky-white discoloration. Microradiography revealed broken tips of incisors and molars and scanning electron microscopy analysis indicated disorganized hypoplastic enamel. The amelogenin null phenotype reveals that the amelogenins are apparently not required for initiation of mineral crystal formation but rather for the organization of crystal pattern and regulation of enamel thickness. These null mice will be useful for understanding the functions of amelogenin proteins during enamel formation and for developing therapeutic approaches for treating this developmental defect that affects the enamel.

Neuron-specific expression of Cre recombinase during the late phase of brain development

Gene targeting to disrupt gene expression in a temporal and spatial manner in a specific tissue using Cre recombinase-mediated gene inactivation has been proven to be useful to study in vivo gene function. To delete genes specifically in neurons during the late phase of brain development, we have generated transgenic mouse lines that express Cre recombinase under the control of the murine neurofilament-H (mNF-H) gene promoter. In this study, we report that one of these mouse lines expresses Cre recombinase specifically in the neurons of the brain and spinal cord during the late stage of their development. The transgenic line displays specific excision of the loxP-flanked gene in the neurons just after embryonic day 18.5 (E.18.5), which coincides with the later phase of brain maturation including spinal cord and olfactory bulb area. This mNF-H-cre transgenic mouse line will be valuable for studying in vivo functions of neuron-specific genes, particularly, defining their precise roles in the mature nervous system using conditional gene targeting strategies.

Reduced expression of dentin sialophosphoprotein is associated with dysplastic dentin in mice overexpressing transforming growth factor-beta 1 in teeth

Transforming growth factor (TGF)-beta1 is expressed in developing tooth from the initiation stage through adulthood. Odontoblast-specific expression of TGF-beta1 in the tooth continues throughout life; however, the precise biological functions of this growth factor in the odontoblasts are not clearly understood. Herein, we describe the generation of transgenic mice that overexpress active TGF-beta1 predominantly in the odontoblasts. Teeth of these mice show a significant reduction in the tooth mineralization, defective dentin formation, and a relatively high branching of dentinal tubules. Dentin extracellular matrix components such as type I and III collagens are increased and deposited abnormally in the dental pulp, similar to the hereditary human tooth disorders such as dentin dysplasia and dentinogenesis imperfecta. Calcium, one of the crucial inorganic components of mineralization, is also apparently increased in the transgenic mouse teeth. Most importantly, the expression of dentin sialophosphoprotein (dspp), a candidate gene implicated in dentinogenesis imperfecta II (MIM 125420), is significantly down-regulated in the transgenic teeth. Our results provide in vivo evidence suggesting that TGF-beta1 mediated expression of dspp is crucial for dentin mineralization. These findings also provide for the first time a direct experimental evidence indicating that decreased dspp gene expression along with the other cellular changes in odontoblasts may result in human hereditary dental disorders like dentinogenesis imperfecta II (MIM 125420) and dentin dysplasia (MIM 125400 and 125420).

Neuronal cyclin-dependent kinase 5 activity is critical for survival

Cyclin-dependent kinase 5 (Cdk5) null mice exhibit a unique phenotype characterized by perinatal mortality, disrupted cerebral cortical layering attributable to abnormal neuronal migration, lack of cerebellar foliation, and chromatolytic changes of neurons in the brainstem and the spinal cord. Because Cdk5 is expressed in both neurons and astrocytes, it has been unclear whether this phenotype is primarily attributable to defects in neurons or in astrocytes. Herein we report reconstitution of Cdk5 expression in neurons in Cdk5 null mice and its effect on the null phenotype. Unlike the Cdk5 null mice, the reconstituted Cdk5 null mice that express the Cdk5 transgene under the p35 promoter (TgKO mice) were viable and fertile. Because Cdk5 expression is mainly limited to neurons in these mice and rescues the defects in the nervous system of the Cdk5 null phenotype, it clearly demonstrates that Cdk5 activity is necessary for normal development and survival of p35-expressing neurons.

Androgen-independent expression of hoxb-13 in the mouse prostate

BACKGROUND

Hox genes encode transcriptional regulatory proteins that are largely responsible for establishing the body plan of all metazoan organisms. A subset of Hox genes is expressed during the period of organogenesis and into adulthood. hoxb-13 is a recently-described member of the Hox gene family that is expressed in the spinal cord, hindgut, and urogenital sinus during embryogenesis.

METHODS

Northern blot and in situ hybridization analyses of hoxb-13 expression in adult mouse tissues were performed.

RESULTS

hoxb-13 mRNA is restricted to the prostate gland and distal colon in adult animals. In situ hybridization of mouse prostate tissue demonstrated that hoxb-13 is expressed in the epithelial cells of the ventral, dorsal, lateral, and anterior prostate lobes. Accumulation of hoxb-13 mRNA is not diminished following castration.

CONCLUSIONS

These data demonstrate that hoxb-13 expression is androgen-independent in mouse prostate glands. The identification of hoxb-13 as an androgen-independent gene expressed in adult mouse prostate epithelial cells provides a new potential target for developing therapeutics to treat advanced prostate cancer.

Expression pattern of macrophage migration inhibitory factor during embryogenesis

Although macrophage migration inhibitory factor (MIF) was originally identified as a lymphokine that inhibits the migration of macrophages, its ubiquitous expression suggests it may have a role beyond the immune system. Here we report a detailed characterization of MIF expression during mouse embryogenesis. The MIF expression pattern was found to parallel tissues specification and organogenesis.

Gain of function mutations for paralogous Hox genes: implications for the evolution of Hox gene function

To investigate the functions of paralogous Hox genes, we compared the phenotypic consequences of altering the embryonic patterns of expression of Hoxb-8 and Hoxc-8 in transgenic mice. A comparison of the phenotypic consequences of altered expression of the two paralogs in the axial skeletons of newborns revealed an array of common transformations as well as morphological changes unique to each gene. Divergence of function of the two paralogs was clearly evident in costal derivatives, where increased expression of the two genes affected opposite ends of the ribs. Many of the morphological consequences of expanding the mesodermal domain and magnitude of expression of either gene were atavistic, inducing the transformation of axial skeletal structures from a modern to an earlier evolutionary form. We propose that regional specialization of the vertebral column has been driven by regionalization of Hox gene function and that a major aspect of this evolutionary progression may have been restriction of Hox gene expression.