Management of Advanced Prostate Cancer in the Precision Oncology Era

Prostate cancer (PC) is the second leading cause of cancer death in men in the United States. While diversified and improved treatment options for aggressive PC have improved patient outcomes, metastatic castration-resistant prostate cancer (mCRPC) remains incurable and an area of investigative therapeutic interest. This review will cover the seminal clinical data supporting the indication of new precision oncology-based therapeutics and explore their limitations, present utility, and potential in the treatment of PC. Systemic therapies for high-risk and advanced PC have experienced significant development over the past ten years. Biomarker-driven therapies have brought the field closer to the goal of being able to implement precision oncology therapy for every patient. The tumor agnostic approval of pembrolizumab (a PD-1 inhibitor) marked an important advancement in this direction. There are also several PARP inhibitors indicated for patients with DNA damage repair deficiencies. Additionally, theranostic agents for both imaging and treatment have further revolutionized the treatment landscape for PC and represent another advancement in precision medicine. Radiolabeled prostate-specific membrane antigen (PSMA) PET/CT is rapidly becoming a standard of care for diagnosis, and PSMA-targeted radioligand therapies have gained recent FDA approval for metastatic prostate cancer. These advances in precision-based oncology are detailed in this review.

Abstract 2980: MIRO2/GCN1/ATF4 retrograde signaling modulates prostate cancer growth and invasion

Our understanding of the mechanisms that drive aggressiveness of metastatic prostate cancer (mPC) are limited. In this context, we aim to identify novel targets in mPC by focusing on key mitochondrial signaling pathways exploited by mPC. Here we identify a novel mitochondrial signaling pathway centered on mitochondrial Rho GTPase 2 (MIRO2). MIRO2 mRNA is upregulated in mPC compared to localized tumors, and higher MIRO2 levels are correlated with poor patient survival. Despite this association, the importance of MIRO2 in tumor cell biology has been overlooked. To address this, we examined MIRO2’s role in tumor cell-intrinsic phenotypes of relevance to metastatic potential. Using human cell lines that represent androgen-independent and -sensitive mPC, we showed that MIRO2 depletion impaired cell growth, colony formation, tumor cell invasion and migration, and tumor growth in mice. Next we reasoned that identifying MIRO2’s protein binding partners would shed light on the molecular function of MIRO2 in mPC. Network analysis of MIRO2’s binding partners identified metabolism, cell cycle, and cellular responses to extracellular stimuli amongst the top over-represented pathways. Interestingly, the top hit on our screen was General Control Non-derepressible 1 (GCN1). GCN1 was an essential gene for 90% of the cell lines in a large pan-cancer screen for gene essentiality. GCN1 is the upstream activator of the kinase GCN2, which senses amino acid availability, actin dynamics cues in cells, and regulates cell cycle progression. Our results showed that MIRO2 is necessary for efficient GCN2 signaling, activation of the integrated stress response, and downstream translation of the transcription factor ATF4 in culture and tumors in mice. Further, exogenous expression of ATF4 restored clonogenic growth of MIRO2 depleted cells. MIRO2 and GCN1 expression were positively correlated in mPC from patient cohorts, and GCN1 was overexpressed in mPC compared to primary PC. Further, MIRO2-GCN1 interacted in mPC cell lines and in primary PC cells. We showed activated GCN2 and HIF1α were positively correlated in tumors grown in mice. Together, the data suggest our pathway is important in nutrient limited regions of tumors. In conclusion, MIRO2 belongs to a novel protein network that controls mPC cellular responses and adaptation to extracellular stimuli. Overall, we propose a new mechanism by which a mitochondrial retrograde signal can drive prostate cancer cell growth.

Citation Format: Madison Furnish, Dillon Boulton, Victoria Genther, Denisa Grofova, Mitchell L. Ellinwood, Lina Romero, M. Scott Lucia, Scott D. Cramer, M. Cecilia Caino. MIRO2/GCN1/ATF4 retrograde signaling modulates prostate cancer growth and invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2980.

MIRO2 regulates prostate cancer cell growth via GCN1-dependent stress signaling

There is a continued need to identify novel therapeutic targets to prevent the mortality associated with prostate cancer. In this context, Mitochondrial Rho GTPase 2 (MIRO2) mRNA was upregulated in metastatic prostate cancer compared to localized tumors, and higher MIRO2 levels were correlated with poor patient survival. Using human cell lines that represent androgen-independent or -sensitive prostate cancer, we showed that MIRO2 depletion impaired cell growth, colony formation and tumor growth in mice. Network analysis of MIRO2's binding partners identified metabolism and cellular responses to extracellular stimuli as top over-represented pathways. The top hit on our screen, General Control Non-derepressible 1 (GCN1), was overexpressed in prostate cancer, and interacted with MIRO2 in prostate cancer cell lines and in primary prostate cancer cells. Functional analysis of MIRO2 mutations present in prostate cancer patients led to the identification of MIRO2 159L, which increased GCN1 binding. Importantly, MIRO2 was necessary for efficient GCN1-mediated GCN2 kinase signaling and induction of the transcription factor ATF4 levels. Further, MIRO2's effect on regulating prostate cancer cell growth was mediated by ATF4. Finally, levels of activated GCN2 and ATF4 were correlated with MIRO2 expression in prostate cancer xenografts. Both MIRO2 and activated GCN2 levels were higher in hypoxic areas of prostate cancer xenografts. Overall, we propose that targeting the MIRO2-GCN1 axis may be a valuable strategy to halt prostate cancer growth. Implications: MIRO2/GCN1/GCN2 constitute a novel mitochondrial signaling pathway that controls androgen-independent and androgen-sensitive prostate cancer cell growth.

MAP3K7 Loss Drives Enhanced Androgen Signaling and Independently Confers Risk of Recurrence in Prostate Cancer with Joint Loss of CHD1

Prostate cancer genomic subtypes that stratify aggressive disease and inform treatment decisions at the primary stage are currently limited. Previously, we functionally validated an aggressive subtype present in 15% of prostate cancer characterized by dual deletion of MAP3K7 and CHD1. Recent studies in the field have focused on deletion of CHD1 and its role in androgen receptor (AR) chromatin distribution and resistance to AR-targeted therapy; however, CHD1 is rarely lost without codeletion of MAP3K7. Here, we show that in the clinically relevant context of co-loss of MAP3K7 and CHD1 there are significant, collective changes to aspects of AR signaling. Although CHD1 loss mainly impacts the expansion of the AR cistrome, loss of MAP3K7 drives increased AR target gene expression. Prostate cancer cell line models engineered to cosuppress MAP3K7 and CHD1 also demonstrated increased AR-v7 expression and resistance to the AR-targeting drug enzalutamide. Furthermore, we determined that low protein expression of both genes is significantly associated with biochemical recurrence (BCR) in a clinical cohort of radical prostatectomy specimens. Low MAP3K7 expression, however, was the strongest independent predictor for risk of BCR over all other tested clinicopathologic factors including CHD1 expression. Collectively, these findings illustrate the importance of MAP3K7 loss in a molecular subtype of prostate cancer that poses challenges to conventional therapeutic approaches. IMPLICATIONS: These findings strongly implicate MAP3K7 loss as a biomarker for aggressive prostate cancer with significant risk for recurrence that poses challenges for conventional androgen receptor-targeted therapies.

Androgen Receptor Signaling in Prostate Cancer Genomic Subtypes

While many prostate cancer (PCa) cases remain indolent and treatable, others are aggressive and progress to the metastatic stage where there are limited curative therapies. Androgen receptor (AR) signaling remains an important pathway for proliferative and survival programs in PCa, making disruption of AR signaling a viable therapy option. However, most patients develop resistance to AR-targeted therapies or inherently never respond. The field has turned to PCa genomics to aid in stratifying high risk patients, and to better understand the mechanisms driving aggressive PCa and therapy resistance. While alterations to the AR gene itself occur at later stages, genomic changes at the primary stage can affect the AR axis and impact response to AR-directed therapies. Here, we review common genomic alterations in primary PCa and their influence on AR function and activity. Through a meta-analysis of multiple independent primary PCa databases, we also identified subtypes of significantly co-occurring alterations and examined their combinatorial effects on the AR axis. Further, we discussed the subsequent implications for response to AR-targeted therapies and other treatments. We identified multiple primary PCa genomic subtypes, and given their differing effects on AR activity, patient tumor genetics may be an important stratifying factor for AR therapy resistance.

MAP3K7 and CHD1 Are Novel Mediators of Resistance to Oncolytic Vesicular Stomatitis Virus in Prostate Cancer Cells

A key principle of oncolytic viral therapy is that many cancers develop defects in their antiviral responses, making them more susceptible to virus infection. However, some cancers display resistance to viral infection. Many of these resistant cancers constitutively express interferon-stimulated genes (ISGs). The goal of these experiments was to determine the role of two tumor suppressor genes, MAP3K7 and CHD1, in viral resistance and ISG expression in PC3 prostate cancer cells resistant to oncolytic vesicular stomatitis virus (VSV). MAP3K7 and CHD1 are often co-deleted in aggressive prostate cancers. Silencing expression of MAP3K7 and CHD1 in PC3 cells increased susceptibility to the matrix (M) gene mutant M51R-VSV, as shown by increased expression of viral genes, increased yield of progeny virus, and reduction of tumor growth in nude mice. Silencing MAP3K7 alone had a greater effect on virus susceptibility than did silencing CHD1. Silencing MAP3K7 and CHD1 decreased constitutive expression of ISG mRNAs and proteins, whereas silencing MAP3K7 alone decreased expression of ISG proteins, but actually increased expression of ISG mRNAs. These results suggest a role for the protein product of MAP3K7, transforming growth factor β-activated kinase 1 (TAK1), in regulating translation of ISG mRNAs and a role of CHD1 in maintaining the transcription of ISGs.

The interplay of autophagy and non-apoptotic cell death pathways

Autophagy, the process of macromolecular degradation through the lysosome, has been extensively studied for the past decade or two. Autophagy can regulate cell death, especially apoptosis, through selective degradation of both positive and negative apoptosis regulators. However, multiple other programmed cell death pathways exist. As knowledge of these other types of cell death expand, it has been suggested that they also interact with autophagy. In this review, we discuss the molecular mechanisms that comprise three non-apoptotic forms of cell death (necroptosis, pyroptosis and ferroptosis) focusing on how the autophagy machinery regulates these different cell death mechanisms through (i) its degradative functions, i.e., true autophagy, and (ii) other non-degradative functions of the autophagy machinery such as serving as a signaling scaffold or by participating in other autophagy-independent cellular processes.

Loss of MAP3K7 Sensitizes Prostate Cancer Cells to CDK1/2 Inhibition and DNA Damage by Disrupting Homologous Recombination

The combined loss of CHD1 and MAP3K7 promotes aggressive prostate cancer by unknown mechanisms. Because both of these genes are lost genetically in prostate cancer, they cannot be directly targeted. We applied an established computational systems pharmacology approach (TRAP) to identify altered signaling pathways and associated druggable targets. We compared gene expression profiles of prostate cancer with coloss of CHD1 and MAP3K7 with prostate cancer diploid for these genes using The Cancer Genome Atlas patient samples. This analysis prioritized druggable target genes that included CDK1 and CDK2. We validated that inhibitors of these druggable target genes, including the CDK1/CDK2 inhibitor dinaciclib, had antiproliferative and cytotoxic effects selectively on mouse prostate cells with knockdown of Chd1 and Map3k7. Dinaciclib had stronger effects on prostate cells with suppression of Map3k7 independent of Chd1 and also compared with cells without loss of Map3k7. Dinaciclib treatment reduced expression of homologous recombination (HR) repair genes such as ATM, ATR, BRCA2, and RAD51, blocked BRCA1 phosphorylation, reduced RAD51 foci formation, and increased γH2AX foci selectively in prostate cells with suppression of Map3k7, thus inhibiting HR repair of chromosomal double-strand breaks. Dinaciclib-induced HR disruption was also observed in human prostate cells with knockdown of MAP3K7. Cotreatment of dinaciclib with DNA-damaging agents or PARP inhibitor resulted in a stronger cytotoxic effect on prostate cells with suppression of MAP3K7 compared with those without loss of MAP3K7, or to each single agent. IMPLICATIONS: These findings demonstrate that loss of MAP3K7 is a main contributing factor to drug response through disruption of HR in prostate cancer.

CD38 Inhibits Prostate Cancer Metabolism and Proliferation by Reducing Cellular NAD+ Pools

Tumor cells require increased rates of cell metabolism to generate the macromolecules necessary to sustain proliferation. They rely heavily on NAD⁺ as a cofactor for multiple metabolic enzymes in anabolic and catabolic reactions. NAD⁺ also serves as a substrate for PARPs, sirtuins, and cyclic ADP-ribose synthases. Dysregulation of the cyclic ADP-ribose synthase CD38, the main NAD'ase in cells, is reported in multiple cancer types. This study demonstrates a novel connection between CD38, modulation of NAD⁺, and tumor cell metabolism in prostate cancer. CD38 expression inversely correlates with prostate cancer progression. Expressing CD38 in prostate cancer cells lowered intracellular NAD⁺, resulting in cell-cycle arrest and expression of p21^Cip1 (CDKNA1). In parallel, CD38 diminishes glycolytic and mitochondrial metabolism, activates AMP-activated protein kinase (AMPK), and inhibits fatty acid and lipid synthesis. Pharmacologic inhibition of nicotinamide phosphoribosyltransferase (NAMPT) mimicked the metabolic consequences of CD38 expression, demonstrating similarity between CD38 expression and NAMPT inhibition. Modulation of NAD⁺ by CD38 also induces significant differential expression of the transcriptome, producing a gene expression signature indicative of a nonproliferative phenotype. Altogether, in the context of prostate cancer, the data establish a novel role for the CD38-NAD⁺ axis in the regulation of cell metabolism and development.Implications: This research establishes a mechanistic connection between CD38 and metabolic control. It also provides the foundation for the translation of agents that modulate NAD⁺ levels in cancer cells as therapeutics. Mol Cancer Res; 16(11); 1687-700. ©2018 AACR.

Abstract 4332: Meta-analysis of molecular features associated with aggressive prostate cancer

The TMPRSS2:ERG fusion is the most common genomic alteration in prostate cancer, occurring in 40-50% of primary tumors. The frequency of the ERG fusion remains between 40-50% in metastatic tumors, supporting previous findings that the fusion can drive tumor development, but is not sufficient to drive aggressive, lethal disease. Large -omic datasets collected over thousands of patient tumors, such as The Cancer Genome Atlas (TCGA), paired with outcomes present the raw data needed to associate genetic aberrations with markers of aggressive disease. Accordingly, we performed a meta-analysis of over 2,000 patient samples to identify combinations of -omic features associated with aggressive ERG fusion-positive and ERG fusion-negative prostate cancer. The data were collected from 8 independent, publicly available prostate cancer cohorts and cover range of disease phenotypes (e.g., neuroendocrine, castration resistance). Our analysis consisted of training univariate Cox regression models separately for single genomic or pairs of genomic features within each independent dataset. Based on the availability, we explored gene expression, mutation, and copy number alterations, all used to build separate models. We then combined models for a genomic feature across all datasets by weighting individual coefficients by the inverse of their squared error in a fixed effects model; final results are reported as corrected p-values. We compared and contrasted results from combined models within data type (i.e., only gene expression) to models integrating multiple data types. Interestingly, we find that the genomic features associated with aggressive disease differed based on ERG status. We report genomic loci that are altered in all patients, but associate with aggressive disease only in patients with an ERG fusion. We also report loci that co-occur or are mutually exclusive of the ERG fusion and associated with aggressiveness. For example, SPOP mutations are known to be mutually exclusive of ERG fusions. We report a finer stratification of patients with SPOP mutations based on biochemical relapse. Our results present a compressive meta-analysis of molecular features in prostate cancer and identify novel molecular subtypes associated with aggressive disease.

Citation Format: James C. Costello, Rani Powers, Andrew Goodspeed, Scott D. Cramer. Meta-analysis of molecular features associated with aggressive prostate cancer [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 4332.

Abstract 1580: Combined neuroendocrine differentiation and androgen receptor hyperactivity in MAP37 and CHD1 null prostate cancer

We recently functionally validated a clinically aggressive subtype of prostate cancer characterized by dual deletion of MAP3K7 and CHD1. This subtype accounts for up to 25% of prostate cancer deaths. Androgen signaling is a critical component of prostate tumorigenesis and disease progression, which is exploited in treatment of prostate cancer with androgen deprivation and anti-androgen therapies. Neuroendocrine differentiation is thought to provide a selective growth advantage of prostate cancer in androgen-depleted conditions such as surgical or chemical castration. REST is a transcriptional repressor of neuronal gene expression and has been implicated in neuroendocrine differentiation of prostate cancer. The impact of combined MAP3K7 and CHD1 loss on androgen signaling and neuroendocrine differentiation has not been determined. Here, we demonstrate that dual loss of MAP3K7 and CHD1 simultaneously stimulates enhanced androgen signaling and enhanced neuronal differentiation correlated with enhanced growth in both androgen-depleted and androgen-replete conditions. These changes occur via increased androgen receptor chromatin binding, loss of CHD1 chromatin binding, loss of REST expression, and reduced chromatin binding by REST. Suppression of CHD1 and MAP3K7 attenuates the antiproliferative activity of the anti-androgen Enzalutamide. Furthermore, we translate these findings to clinical samples and show that decreased expression of CHD1, MAP3K7, and REST is associated with previous therapeutic intervention, castrate-resistant disease, and progression to a neuroendocrine phenotype. Overall, patients with low expression of all three have poorer disease-free survival. Together these data support the lineage plasticity of prostate tumors with loss of CHD1 and MAP3K7 exhibiting both androgen-dependent and -independent phenotypes leading to poor clinical outcome, which poses challenges to conventional therapeutic approaches.

Citation Format: Leah C. Rider, Lindsey U. Rodrigues, Anis Karimpour-Fard, Lina Romero, Claire Gillette, James C. Costello, Scott D. Cramer. Combined neuroendocrine differentiation and androgen receptor hyperactivity in MAP37 and CHD1 null prostate cancer [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 1580. doi:10.1158/1538-7445.AM2017-1580

The Autophagy Machinery Controls Cell Death Switching between Apoptosis and Necroptosis

Although autophagy controls cell death and survival, underlying mechanisms are poorly understood, and it is unknown whether autophagy affects only whether or not cells die or also controls other aspects of programmed cell death. MAP3K7 is a tumor suppressor gene associated with poor disease-free survival in prostate cancer. Here, we report that Map3k7 deletion in mouse prostate cells sensitizes to cell death by TRAIL (TNF-related apoptosis-inducing ligand). Surprisingly, this death occurs primarily through necroptosis, not apoptosis, due to assembly of the necrosome in association with the autophagy machinery, mediated by p62/SQSTM1 recruitment of RIPK1. The mechanism of cell death switches to apoptosis if p62-dependent recruitment of the necrosome to the autophagy machinery is blocked. These data show that the autophagy machinery can control the mechanism of programmed cell death by serving as a scaffold rather than by degrading cargo.

SPOP the mutation

Prostate cancers with mutations to a protein called SPOP use an error-prone method to repair broken DNA strands.

Antenatal endotoxin disrupts lung vitamin D receptor and 25-hydroxyvitamin D 1α-hydroxylase expression in the developing rat

Vitamin D [vit D; 1,25-(OH)2D] treatment improves survival and lung alveolar and vascular growth in an experimental model of bronchopulmonary dysplasia (BPD) after antenatal exposure to endotoxin (ETX). However, little is known about lung-specific 1,25-(OH)2D3 regulation during development, especially regarding maturational changes in lung-specific expression of the vitamin D receptor (VDR), 1α-hydroxylase (1α-OHase), and CYP24A1 during late gestation and the effects of antenatal ETX exposure on 1,25-(OH)2D3 metabolism in the lung. We hypothesized that vit D regulatory proteins undergo maturation regulation in the late fetal and early neonatal lung and that prenatal exposure to ETX impairs lung growth partly through abnormal endogenous vit D metabolism. Normal fetal rat lungs were harvested between embryonic day 15 and postnatal day 14. Lung homogenates were assayed for VDR, 1α-OHase, and CYP24A1 protein contents by Western blot analysis. Fetal rats were injected on embryonic day 20 with intra-amniotic ETX, ETX + 1,25-(OH)2D3, or saline and delivered 2 days later. Pulmonary artery endothelial cells (PAECs) from fetal sheep were assessed for VDR, 1α-OHase, and CYP24A1 expression after treatment with 25-(OH)D3, 1,25-(OH)2D3, ETX, ETX + 25-(OH)D3, or ETX + 1,25-(OH)2D3. We found that lung VDR, 1α-OHase, and CYP2741 protein expression dramatically increase immediately before birth (P < 0.01 vs. early fetal values). Antenatal ETX increases CYP24A1 expression (P < 0.05) and decreases VDR and 1α-OHase expression at birth (P < 0.001), but these changes are prevented with concurrent vit D treatment (P < 0.001). ETX-induced reduction of fetal PAEC growth and tube formation and lung 1α-OHase expression are prevented by vit D treatment (P < 0.001). We conclude that lung VDR, 1α-OHase, and CYP24A1 protein content markedly increase before birth and that antenatal ETX disrupts lung vit D metabolism through downregulation of VDR and increased vit D catabolic enzyme expression, including changes in developing endothelium. We speculate that endogenous vitamin D metabolism modulates normal fetal lung development and that prenatal disruption of vit D signaling may contribute to impaired postnatal lung growth at least partly through altered angiogenic signaling.

Silibinin prevents prostate cancer cell-mediated differentiation of naïve fibroblasts into cancer-associated fibroblast phenotype by targeting TGF β2

Tumor microenvironment (TM) is an essential element in prostate cancer (PCA), offering unique opportunities for its prevention. TM includes naïve fibroblasts that are recruited by nascent neoplastic lesion and altered into 'cancer-associated fibroblasts' (CAFs) that promote PCA. A better understanding and targeting of interaction between PCA cells and fibroblasts and inhibiting CAF phenotype through non-toxic agents are novel approaches to prevent PCA progression. One well-studied cancer chemopreventive agent is silibinin, and thus, we examined its efficacy against PCA cells-mediated differentiation of naïve fibroblasts into a myofibroblastic-phenotype similar to that found in CAFs. Silibinin's direct inhibitory effect on the phenotype of CAFs derived directly from PCA patients was also assessed. Human prostate stromal cells (PrSCs) exposed to control conditioned media (CCM) from human PCA PC3 cells showed more invasiveness, with increased alpha-smooth muscle actin (α-SMA) and vimentin expression, and differentiation into a phenotype we identified in CAFs. Importantly, silibinin (at physiologically achievable concentrations) inhibited α-SMA expression and invasiveness in differentiated fibroblasts and prostate CAFs directly, as well as indirectly by targeting PCA cells. The observed increase in α-SMA and CAF-like phenotype was transforming growth factor (TGF) β2 dependent, which was strongly inhibited by silibinin. Furthermore, induction of α-SMA and CAF phenotype by CCM were also strongly inhibited by a TGFβ2-neutralizing antibody. The inhibitory effect of silibinin on TGFβ2 expression and CAF-like biomarkers was also observed in PC3 tumors. Together, these findings highlight the potential usefulness of silibinin in PCA prevention through targeting the CAF phenotype in the prostate TM.

Coordinate loss of MAP3K7 and CHD1 promotes aggressive prostate cancer

Prostate cancer subtypes are poorly defined and functional validation of drivers of ETS rearrangement-negative prostate cancer has not been conducted. Here, we identified an ETS(-) subtype of aggressive prostate cancer (ERG(-)MAP3K7(del)CHD1(del)) and used a novel developmental model and a cell line xenograft model to show that cosuppression of MAP3K7 and CHD1 expression promotes aggressive disease. Analyses of publicly available prostate cancer datasets revealed that MAP3K7 and CHD1 were significantly codeleted in 10% to 20% of localized tumors and combined loss correlated with poor disease-free survival. To evaluate the functional impact of dual MAP3K7-CHD1 loss, we suppressed Map3k7 and/or Chd1 expression in mouse prostate epithelial progenitor/stem cells (PrP/SC) and performed tissue recombination experiments in vivo. Dual shMap3k7-shChd1 PrP/SC recombinants displayed massive glandular atypia with regions of prostatic intraepithelial neoplasia and carcinoma apparent. Combined Map3k7-Chd1 suppression greatly disrupted normal prostatic lineage differentiation; dual recombinants displayed significant androgen receptor loss, increased neuroendocrine differentiation, and increased neural differentiation. Clinical samples with dual MAP3K7-CHD1 loss also displayed neuroendocrine and neural characteristics. In addition, dual Map3k7-Chd1 suppression promoted E-cadherin loss and mucin production in recombinants. MAP3K7 and CHD1 protein loss also correlated with Gleason grade and E-cadherin loss in clinical samples. To further validate the phenotype observed in the PrP/SC model, we suppressed MAP3K7 and/or CHD1 expression in LNCaP prostate cancer cells. Dual shMAP3K7-shCHD1 LNCaP xenografts displayed increased tumor growth and decreased survival compared with shControl, shMAP3K7, and shCHD1 xenografts. Collectively, these data identify coordinate loss of MAP3K7 and CHD1 as a unique driver of aggressive prostate cancer development.

Abstract 107: Lipid metabolism inhibitors enhance glycolysis and FDG-PET imaging of prostate cancer tumors

Introduction: Positron Emission Tomography (PET) with18F-deoxyglucose (FDG) has gained a major role in the clinical setting for detection, staging and assessment of treatment response for a number of epithelial cancers. However, staging of primary or metastatic prostate cancer with 18F-FDG-PET is suboptimal, likely due to the low glucose uptake and enhanced lipid metabolism characteristic of primary prostate tumors. The exact mechanisms of aerobic glycolysis (Warburg effect) and lipid metabolism in prostate cancer (PCa) cells remain unknown. However, 18F-FDG-PET imaging of metastatic PCa might be enhanced by altering the intrinsic energy metabolism of involved sites.

Experimental Procedures: In vitro radioactive studies were carried out to confirm the specificity of etomoxir for blocking lipid oxidation and enhancing glucose uptake at 24 hours in prostate cancer cell lines. For in vivo studies, three mouse models of PCa were used: Male nude mice with subcutaneous xenograts or orthotopic injections and TRAMP mice that develop prostate cancer with age. All mice were treated with a single dose of the lipid oxidation inhibitor etomoxir (20 mg/kg) or vehicle (saline) for 24 hours. A basal FDG-PET scan was performed before the drug treatment, followed by a second FDG-PET scan after 24 hours. Western blot analysis was used to validate the molecular mechanisms of increased FDG uptake.

Results: The clinically safe drug etomoxir blocks fat oxidation within 4 hours and increases glucose uptake in cultured PCa cells. Subcutaneous xenografts showed a significant increase in normalized FDG uptake (NUV) after a single dose of etomoxir compared to basal NUV (1.4 fold change, p =0.03). This enhancing effect was not seen in mice treated with saline (vehicle). Mice with orthotopic xenografts and 20-week old TRAMP mice showed a 2.7-fold (p=0.03) and 1.6-fold (p=0.07) increase in FDG uptake, respectively, over basal. Protein examination of the excised subcutaneous tumors showed increased hexokinase-II content and activated mTOR and p70-S6 Kinase proteins in the etomoxir-treated tumors when compared to saline-treated tumors.

Conclusion: 18F-FDG is a commercially available tracer that is widely used for standard-of-care and research-based oncologic imaging. Blocking lipid oxidation in PCa tumors has the potential to improve diagnostic imaging, since 18F-FDG that accumulates inside the cell can enhance FDG-PET imaging of prostate cancer tumors to detectable and quantifiable levels.

Citation Format: Isabel R. Schlaepfer, Colton T. Pac, Natalie J. Serkova, Gagan Deep, Rajesh Agarwal, Scott D. Cramer, Robert H. Eckel, L. Michael Glode. Lipid metabolism inhibitors enhance glycolysis and FDG-PET imaging of prostate cancer tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 107. doi:10.1158/1538-7445.AM2014-107

Lipid catabolism via CPT1 as a therapeutic target for prostate cancer

Prostate cancer is the most commonly diagnosed malignancy among Western men and accounts for the second leading cause of cancer-related deaths. Prostate cancer tends to grow slowly and recent studies suggest that it relies on lipid fuel more than on aerobic glycolysis. However, the biochemical mechanisms governing the relationships between lipid synthesis, lipid utilization, and cancer growth remain unknown. To address the role of lipid metabolism in prostate cancer, we have used etomoxir and orlistat, clinically safe drugs that block lipid oxidation and lipid synthesis/lipolysis, respectively. Etomoxir is an irreversible inhibitor of the carnitine palmitoyltransferase (CPT1) enzyme that decreases β oxidation in the mitochondria. Combinatorial treatments using etomoxir and orlistat resulted in synergistic decreased viability in LNCaP, VCaP, and patient-derived benign and prostate cancer cells. These effects were associated with decreased androgen receptor expression, decreased mTOR signaling, and increased caspase-3 activation. Knockdown of CPT1A enzyme in LNCaP cells resulted in decreased palmitate oxidation but increased sensitivity to etomoxir, with inactivation of AKT kinase and activation of caspase-3. Systemic treatment with etomoxir in nude mice resulted in decreased xenograft growth over 21 days, underscoring the therapeutic potential of blocking lipid catabolism to decrease prostate cancer tumor growth.

Influence of stromal-epithelial interactions on androgen action

Androgen receptor (AR) signaling is vital to the development and function of the prostate and is a key pathway in prostate cancer. AR is differentially expressed in the stroma and epithelium, with both paracrine and autocrine control throughout the prostate. Stromal-epithelial interactions within the prostate are commonly dependent on AR signaling and expression. Alterations in these pathways can promote tumorigenesis. AR is also expressed in normal and malignant mammary tissues. Emerging data indicate a role for AR in certain subtypes of breast cancer that has the potential to be exploited therapeutically. The aim of this review is to highlight the importance of these interactions in normal development and tumorigenesis, with a focus on the prostate and breast.

A role for interleukin-1 alpha in the 1,25 dihydroxyvitamin D3 response in mammary epithelial cells

Breast cancer is the most common non-cutaneous malignancy in American women, and better preventative strategies are needed. Epidemiological and laboratory studies point to vitamin D3 as a promising chemopreventative agent for breast cancer. Vitamin D3 metabolites induce anti-proliferative effects in breast cancer cells in vitro and in vivo, but few studies have investigated their effects in normal mammary epithelial cells. We hypothesized that 1,25(OH)2D3, the metabolically active form of vitamin D3, is growth suppressive in normal mouse mammary epithelial cells. In addition, we have previously established a role for the cytokine interleukin-1 alpha (IL1α) in the anti-proliferative effects of 1,25(OH)2D3 in normal prostate cells, and so we hypothesized that IL1α is involved in the 1,25(OH)2D3 response in mammary cells. Evaluation of cell viability, clonogenicity, senescence, and induction of cell cycle regulators p21 and p27 supported an anti-proliferative role for 1,25(OH)2D3 in mammary epithelial cells. Furthermore, 1,25(OH)2D3 increased the intracellular expression of IL1α, which was necessary for the anti-proliferative effects of 1,25(OH)2D3 in mammary cells. Together, these findings support the chemopreventative potential of vitamin D3 in the mammary gland and present a role for IL1α in regulation of mammary cell proliferation by 1,25(OH)2D3.

Genetic markers associated with early cancer-specific mortality following prostatectomy

BACKGROUND

This study sought to identify novel effectors and markers of localized but potentially life-threatening prostate cancer (PCa), by evaluating chromosomal copy number alterations (CNAs) in tumors from patients who underwent prostatectomy and correlating these with clinicopathologic features and outcome.

METHODS

CNAs in tumor DNA samples from 125 patients in the discovery cohort who underwent prostatectomy were assayed with high-resolution Affymetrix 6.0 single-nucleotide polymorphism microarrays and then analyzed using the Genomic Identification of Significant Targets in Cancer (GISTIC) algorithm.

RESULTS

The assays revealed 20 significant regions of CNAs, 4 of them novel, and identified the target genes of 4 of the alterations. By univariate analysis, 7 CNAs were significantly associated with early PCa-specific mortality. These included gains of chromosomal regions that contain the genes MYC, ADAR, or TPD52 and losses of sequences that incorporate SERPINB5, USP10, PTEN, or TP53. On multivariate analysis, only the CNAs of PTEN (phosphatase and tensin homolog) and MYC (v-myc myelocytomatosis viral oncogene homolog) contributed additional prognostic information independent of that provided by pathologic stage, Gleason score, and initial prostate-specific antigen level. Patients whose tumors had alterations of both genes had a markedly elevated risk of PCa-specific mortality (odds ratio = 53; 95% CI = 6.92-405, P = 1 × 10(-4)). Analyses of 333 tumors from 3 additional distinct patient cohorts confirmed the relationship between CNAs of PTEN and MYC and lethal PCa.

CONCLUSIONS

This study identified new CNAs and genes that likely contribute to the pathogenesis of localized PCa and suggests that patients whose tumors have acquired CNAs of PTEN, MYC, or both have an increased risk of early PCa-specific mortality.

Abstract A86: Silibinin inhibits prostate cancer and stromal cells interaction through targeting TGFβ and α-smooth muscle actin

The tumor microenvironment is now established as an integral and essential component of carcinogenesis playing a critical role in early tumor development. Therefore, targeting the interaction between a growing cancerous lesion and its microenvironment is considered an important translational cancer preventive strategy. Fibroblasts are a key cellular component of the prostate cancer (PCA) microenvironment as they have the capacity to remodel that microenvironment, promoting tumor growth, angiogenesis, invasiveness, and metastasis. Earlier studies have shown that the cancer preventive agent silibinin has broad spectrum efficacy against PCA but its effect on the PCA-fibroblast interaction remains unknown. In the present study we developed cell culture models to study the molecular interaction between PCA and fibroblasts and the effect of silibinin therein. We treated human PCA PC3 cells with DMSO or silibinin (30-60 μM dose) and collected conditioned media labeled as CCM (control conditioned media) or SBCM (silibinin treated conditioned media) respectively. Human prostate fibroblasts (PrSC) were exposed to CCM or SBCM (volume normalized with respective cell number) and we analyzed cell growth, morphology, invasiveness and molecular alterations. It was revealed that CCM exposure resulted in PrSC attaining an elongated morphology, increased invasiveness, and enhanced α-SMA (alpha-smooth muscle actin) and vimentin expression, overall transforming into a ‘myofibroblast’ phenotype permissive to prostate cancer growth and progression. In contrast, PrSC exposed to SBCM failed to manifest a myofibroblast phenotype lacking an elongated morphology, exhibiting decreased invasiveness and reduced α-SMA and vimentin expression. Analyses of CCM and SBCM revealed that the inhibitory effect of silibinin could be the result of decreasing levels of TGFβ1 secreted by PCA cells. These results are currently being validated in other PCA cells (Du145, C4-2B). To investigate the effect of silibinin directly on the fibroblasts component of PCA, we employed both PrSC treated with CCM as well as cancer-associated fibroblasts (CAFs) obtained from PCA patients. Silibinin (30-90 μM dose) exposure inhibited the invasiveness of and α-SMA expression in both CCM-treated PrSC as well as CAFs. Ongoing studies also suggest that silibinin targets CAF-induced EMT (epithelial-to-mesenchymal transition) and invasiveness of human PCA LNCaP cells. These results collectively show that silibinin could target PCA, PrSC, and CAFs as well as their cancer promoting interactions and suggest a role for silibinin in PCA prevention and intervention.

Citation Format: Harold J. Ting, Gagan Deep, Chapla Agarwal, Scott D. Cramer, Lina M. Romero, Rajesh Agarwal. Silibinin inhibits prostate cancer and stromal cells interaction through targeting TGFβ and α-smooth muscle actin. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A86.

Suppression of Tak1 promotes prostate tumorigenesis

More than 30% of primary prostate cancers contain a consensus deletion of an approximately 800 kb locus on chromosome 6q15.1. The MAP3K7 gene, which encodes TGF-β activated kinase-1 (Tak1), is a putative prostate tumor suppressor gene within this region whose precise function remains obscure. In this study, we investigated the role of Tak1 in human and murine prostate cancers. In 50 well-characterized human cancer specimens, we found that Tak1 expression was progressively lost with increasing Gleason grade, both within each cancer and across all cancers. In murine prostate stem cells and Tak1-deficient prostatic epithelial cells, Tak1 loss increased proliferation, migration, and invasion. When prostate stem cells attenuated for Tak1 were engrafted with fetal urogenital mesenchyme, the histopathology of the grafts reflected the natural history of prostate cancer leading from prostatic intraepithelial neoplasia to invasive carcinoma. In the grafts containing Tak1-suppressed prostate stem cells, p38 and c-jun-NH(2)-kinase activity was attenuated and proliferation was increased. Together, our findings functionally validate the proposed tumor suppressor role of Tak1 in prostate cancer.

Hydroxyproline metabolism in mouse models of primary hyperoxaluria

Primary hyperoxaluria type 1 (PH1) and type 2 (PH2) are rare genetic diseases that result from deficiencies in glyoxylate metabolism. The increased oxalate synthesis that occurs can lead to kidney stone formation, deposition of calcium oxalate in the kidney and other tissues, and renal failure. Hydroxyproline (Hyp) catabolism, which occurs mainly in the liver and kidney, is a prominent source of glyoxylate and could account for a significant portion of the oxalate produced in PH. To determine the sensitivity of mouse models of PH1 and PH2 to Hyp-derived oxalate, animals were fed diets containing 1% Hyp. Urinary excretions of glycolate and oxalate were used to monitor Hyp catabolism and the kidneys were examined to assess pathological changes. Both strains of knockout (KO) mice excreted more oxalate than wild-type (WT) animals with Hyp feeding. After 4 wk of Hyp feeding, all mice deficient in glyoxylate reductase/hydroxypyruvate reductase (GRHPR KO) developed severe nephrocalcinosis in contrast to animals deficient in alanine-glyoxylate aminotransferase (AGXT KO) where nephrocalcinosis was milder and with a lower frequency. Plasma cystatin C measurements over 4-wk Hyp feeding indicated no significant loss of renal function in WT and AGXT KO animals, and significant and severe loss of renal function in GRHPR KO animals after 2 and 4 wk, respectively. These data suggest that GRHPR activity may be vital in the kidney for limiting the conversion of Hyp-derived glyoxylate to oxalate. As Hyp catabolism may make a major contribution to the oxalate produced in PH patients, Hyp feeding in these mouse models should be useful in understanding the mechanisms associated with calcium oxalate deposition in the kidney.

Isolation of prostate tumor initiating cells (TICs) through their dielectrophoretic signature

In this study, the dielectrophoretic response of prostate tumor initiating cells (TICs) was investigated in a microfluidic system utilizing contactless dielectrophoresis (cDEP). The dielectrophoretic response of prostate TICs was observed to be distinctively different than that for non-TICs, enabling them to be sorted using cDEP. Culturing the sorted TICs generated spheroids, indicating that they were indeed initiating cells. This study presents the first marker-free TIC separation from non-TICs utilizing their electrical fingerprints through dielectrophoresis.

Effect of dietary polyunsaturated fatty acids on castration-resistant Pten-null prostate cancer

A common treatment of advanced prostate cancer involves the deprivation of androgens. Despite the initial response to hormonal therapy, eventually all the patients relapse. In the present study, we sought to determine whether dietary polyunsaturated fatty acid (PUFA) affects the development of castration-resistant prostate cancer. Cell culture, patient tissue microarray, allograft, xenograft, prostate-specific Pten knockout and omega-3 desaturase transgenic mouse models in conjunction with dietary manipulation, gene knockdown and knockout approaches were used to determine the effect of dietary PUFA on castration-resistant Pten-null prostate cancer. We found that deletion of Pten increased androgen receptor (AR) expression and Pten-null prostate cells were castration resistant. Omega-3 PUFA slowed down the growth of castration-resistant tumors as compared with omega-6 PUFA. Omega-3 PUFA decreased AR protein to a similar extent in tumor cell cytosolic and nuclear fractions but had no effect on AR messenger RNA level. Omega-3 PUFA treatment appeared to accelerate AR protein degradation, which could be blocked by proteasome inhibitor MG132. Knockdown of AR significantly slowed down prostate cancer cell proliferation in the absence of androgens. Our data suggest that omega-3 PUFA inhibits castration-resistant prostate cancer in part by accelerating proteasome-dependent degradation of the AR protein. Dietary omega-3 PUFA supplementation in conjunction with androgen ablation may significantly delay the development of castration-resistant prostate cancer in patients compared with androgen ablation alone.

Interleukin-1α mediates the antiproliferative effects of 1,25-dihydroxyvitamin D3 in prostate progenitor/stem cells

Vitamin D(3) is a promising preventative and therapeutic agent for prostate cancer, but its implementation is hampered by a lack of understanding about its mechanism of action. Upon treatment with 1α,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3), vitamin D(3)], the metabolically active form of vitamin D(3), adult prostate progenitor/stem cells (PrP/SC) undergo cell-cycle arrest, senescence, and differentiation to an androgen receptor-positive luminal epithelial cell fate. Microarray analyses of control- and vitamin D(3)-treated PrP/SCs revealed global gene expression signatures consistent with induction of differentiation. Interestingly, one of the most highly upregulated genes by vitamin D(3) was the proinflammatory cytokine interleukin-1α (IL-1α). Systems biology analyses supported a central role for IL-1α in the vitamin D(3) response in PrP/SCs. siRNA-mediated knockdown of IL-1α abrogated vitamin D(3)-induced growth suppression, establishing a requirement for IL-1α in the antiproliferative effects of vitamin D(3) in PrP/SCs. These studies establish a system to study the molecular profile of PrP/SC differentiation, proliferation, and senescence, and they point to an important new role for IL-1α in vitamin D(3) signaling in PrP/SCs.

The tissue-specific stem cell as a target for chemoprevention

While cancer treatment modalities are gradually improving due to increased knowledge about tumor heterogeneity and the cancer stem cell hypothesis, there remains a disconnect between tumor detection and mortality rates. The increasing knowledge of stem cell biology and its contribution to cancer progression illuminates the potential for chemopreventative regimens that effectively target the tissue-specific stem cell. Several signaling pathways have emerged that are critical for regulating stem cell self-renewal and multilineage differentiation over a range of tissue types, including Wnt, Hedgehog, and Notch signaling. Dysregulation of these genes can lead to cancer, which supports the cancer stem cell hypothesis. Several known chemopreventative agents have recently been shown to impact these and other pathways in the stem cell population, suggesting that their efficacies may be attributed in part to maintaining homeostasis of tissue-specific stem cells. Further understanding of the mechanisms of action of chemopreventative agents and of stem cell biology will generate better chemoprevention regimens that can be recommended especially to those in high-risk populations.

1,25-dihydroxyvitamin D(3) and PI3K/AKT inhibitors synergistically inhibit growth and induce senescence in prostate cancer cells

BACKGROUND

1-Alpha, 25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) inhibits proliferation of multiple cancer cell types including prostate cells and upregulates p21 and/or p27, while loss of Pten and PI3K/AKT activation stimulates survival and downregulates p21 and p27. We hypothesized that inhibition of the PI3K/AKT pathway synergizes with the antiproliferative signaling of 1,25(OH)(2)D(3).

METHODS

Viability, cell cycle and senescence of cells were evaluated upon combinational treatment with 1,25(OH)(2)D(3) and pharmacological PI3K/AKT inhibitors.

RESULTS

Pharmacological inhibitors of PI3K or Akt and 1,25(OH)(2)D(3) synergistically inhibited growth of DU145, LNCaP, primary human prostate cancer cell strains and Pten null mouse prostatic epithelial cells (MPEC). The inhibitors used included API-2 (Triciribine) and GSK690693 which are currently in clinical trials for treatment of cancer. A novel mechanism for antiproliferative effects of 1,25(OH)(2)D(3) in prostate cells, induction of senescence, was discovered. Combination of 1,25(OH)(2)D(3) and AKT inhibitor cooperated to induce G(1) arrest, senescence, and p21 levels in prostate cancer cells. As AKT is commonly activated by PTEN loss, we evaluated the role of Pten in responsiveness to 1,25(OH)(2)D(3) using shRNA knockdown and by in vitro knockout of Pten. MPEC that lost Pten expression remained sensitive to the antiproliferative action of 1,25(OH)(2)D(3), and showed higher degree of synergism between AKT inhibitor and 1,25(OH)(2)D(3) compared to Pten-expressing counterparts.

CONCLUSIONS

These findings provide the rationale for the development of therapies utilizing 1,25(OH)(2)D(3) or its analogs combined with inhibition of PI3K/AKT for the treatment of prostate cancer.

Regulation of Skp2 levels by the Pim-1 protein kinase

The Pim-1 protein kinase plays an important role in regulating both cell growth and survival and enhancing transformation by multiple oncogenes. The ability of Pim-1 to regulate cell growth is mediated, in part, by the capacity of this protein kinase to control the levels of the p27, a protein that is a critical regulator of cyclin-dependent kinases that mediate cell cycle progression. To understand how Pim-1 is capable of regulating p27 protein levels, we focused our attention on the SCF(Skp2) ubiquitin ligase complex that controls the rate of degradation of this protein. We found that expression of Pim-1 increases the level of Skp2 through direct binding and phosphorylation of multiple sites on this protein. Along with known Skp2 phosphorylation sites including Ser(64) and Ser(72), we have identified Thr(417) as a unique Pim-1 phosphorylation target. Phosphorylation of Thr(417) controls the stability of Skp2 and its ability to degrade p27. Additionally, we found that Pim-1 regulates the anaphase-promoting complex or cyclosome (APC/C complex) that mediates the ubiquitination of Skp2. Pim-1 phosphorylates Cdh1 and impairs binding of this protein to another APC/C complex member, CDC27. These modifications inhibit Skp2 from degradation. Marked increases in Skp2 caused by these mechanisms lower cellular p27 levels. Consistent with these observations, we show that Pim-1 is able to cooperate with Skp2 to signal S phase entry. Our data reveal a novel Pim-1 kinase-dependent signaling pathway that plays a crucial role in cell cycle regulation.

MicroRNA-101 negatively regulates Ezh2 and its expression is modulated by androgen receptor and HIF-1alpha/HIF-1beta

BACKGROUND

In prostate cancer (PCa), the common treatment involving androgen ablation alleviates the disease temporarily, but results in the recurrence of highly aggressive and androgen-independent metastatic cancer. Therefore, more effective therapeutic approaches are needed. It is known that aberrant epigenetics contributes to prostate malignancy. Unlike genetic changes, these epigenetic alterations are reversible, which makes them attractive targets in PCa therapy to impede cancer progression. As a histone methyltransferase, Ezh2 plays an essential role in epigenetic regulation. Since Ezh2 is overexpressed and acts as an oncogene in PCa, it has been proposed as a bona fide target of PCa therapy. MicroRNAs (miRNAs) regulate gene expression through modulating protein translation. Recently, the contribution of miRNAs in cancer development is increasingly appreciated. In this report, we present our study showing that microRNA-101 (miR-101) inhibits Ezh2 expression and differentially regulates prostate cancer cells. In addition, the expression of miR-101 alters upon androgen treatment and HIF-1alpha/HIF-1beta induction.

RESULT

In our reporter assays, both miR-101 and miR-26a inhibit the expression of a reporter construct containing the 3'-UTR of Ezh2. When ectopically expressed in PC-3, DU145 and LNCaP cells, miR-101 inhibits endogenous Ezh2 expression in all three cell lines, while miR-26a only decreases Ezh2 in DU145. Ectopic miR-101 reduces the invasion ability of PC-3 cells, while restored Ezh2 expression rescues the invasiveness of PC-3 cells. Similarly, miR-101 also inhibits cell invasion and migration of DU145 and LNCaP cells, respectively. Interestingly, ectopic miR-101 exhibits differential effects on the proliferation of PC-3, DU-145 and LNCaP cells and also causes morphological changes of LNCaP cells. In addition, the expression of miR-101 is regulated by androgen receptor and HIF-1alpha/HIF-1beta. While HIF-1alpha/HIF-1beta induced by deferoxamine mesylate (DFO) decreases miR-101 levels, the overall effects of R-1881 on miR-101 expression are stimulatory.

CONCLUSIONS

This study indicates that miR-101 targets Ezh2 and decreases the invasiveness of PCa cells, suggesting that miR-101 introduction is a potential therapeutic strategy to combat PCa. MiR-101 differentially regulates prostate cell proliferation. Meanwhile, the expression of miR-101 is also modulated at different physiological conditions, such as androgen stimulation and HIF-1alpha/HIF-1beta induction.

Yin Yang 1 regulates the transcriptional activity of androgen receptor

The multifunctional protein Yin Yang 1 (YY1) plays an important role in epigenetic regulation of gene expression. YY1 is highly expressed in various types of cancers, including prostate cancer. Currently, the mechanism underlying the functional role of YY1 in prostate tumorigenesis remains unclear. In this report, we investigated the functional interplay between YY1 and androgen receptor (AR), and the effect of YY1 on AR-mediated transcription. We found that YY1 physically interacts with AR both in a cell-free system and in cultured cells. YY1 is required for the optimal transcriptional activity of AR in promoting the transcription of the prostate specific antigen (PSA) promoter. However, ectopic YY1 expression in LNCaP cells did not further enhance the reporter driven by the PSA promoter, suggesting an optimal level of YY1 is already established in prostate tumor cells. Consistently, YY1 depletion in LNCaP cells reduced endogenous PSA levels, but overexpressed YY1 did not significantly increase PSA expression. We also observed that YY1-AR interaction is essential to YY1-mediated transcription activity of AR and YY1 is a necessary component in the complex binding to the androgen response element (ARE). Thus, our study demonstrates that YY1 interacts with AR and regulates its transcriptional activity.

Association of reported prostate cancer risk alleles with PSA levels among men without a diagnosis of prostate cancer

BACKGROUND

Prostate specific antigen (PSA) is widely used for prostate cancer screening but its levels are influenced by many non cancer-related factors. The goal of the study is to estimate the effect of genetic variants on PSA levels.

METHODS

We evaluated the association of SNPs that were reported to be associated with prostate cancer risk in recent genome-wide association studies with plasma PSA levels in a Swedish study population, including 1,722 control subjects without a diagnosis of prostate cancer.

RESULTS

Of the 16 SNPs analyzed in control subjects, significant associations with PSA levels (P < or = 0.05) were found for six SNPs. These six SNPs had a cumulative effect on PSA levels; the mean PSA levels in men were almost twofold increased across increasing quintile of number of PSA associated alleles, P-trend = 3.4 x 10(-14). In this Swedish study population risk allele frequencies were similar among T1c case patients (cancer detected by elevated PSA levels alone) as compared to T2 and above prostate cancer case patients.

CONCLUSIONS

Results from this study may have two important clinical implications. The cumulative effect of six SNPs on PSA levels suggests genetic-specific PSA cutoff values may be used to improve the discriminatory performance of this test for prostate cancer; and the dual associations of these SNPs with PSA levels and prostate cancer risk raise a concern that some of reported prostate cancer risk-associated SNPs may be confounded by the prevalent use of PSA screening.

Fine mapping association study and functional analysis implicate a SNP in MSMB at 10q11 as a causal variant for prostate cancer risk

A single nucleotide polymorphism (SNP) at 10q11 (rs10993994) in the 5' region of the MSMB gene was recently implicated in prostate cancer risk in two genome-wide association studies. To identify possible causal variants in the region, we genotyped 16 tagging SNPs and imputed 29 additional SNPs in approximately 65 kb genomic region at 10q11 in a Swedish population-based case-control study (CAncer of the Prostate in Sweden), including 2899 cases and 1722 controls. We found evidence for two independent loci, separated by a recombination hotspot, associated with prostate cancer risk. Among multiple significant SNPs at locus 1, the initial SNP rs10993994 was most significant. Importantly, using an MSMB promoter reporter assay, we showed that the risk allele of this SNP had only 13% of the promoter activity of the wild-type allele in a prostate cancer model, LNCaP cells. Curiously, the second, novel locus (locus 2) was within NCOA4 (also known as ARA70), which is known to enhance androgen receptor transcriptional activity in prostate cancer cells. However, its association was only weakly confirmed in one of the three additional study populations. The observations that rs10993994 is the strongest associated variant in the region and its risk allele has a major effect on the transcriptional activity of MSMB, a gene with previously described prostate cancer suppressor function, together suggest the T allele of rs10993994 as a potential causal variant at 10q11 that confers increased risk of prostate cancer.

Association of prostate-specific antigen promoter genotype with clinical and histopathologic features of prostate cancer

The serum test for the secreted protease prostate-specific antigen (PSA) is the most widely used screening tool for prostate cancer. The PSA gene contains multiple functional and nonfunctional single nucleotide polymorphisms (SNP) in its promoter. We showed previously that the rs925013 G/A SNP, but not the rs266882 G/A SNP, was significantly associated with serum PSA in healthy men. In this study, we evaluated the association of the PSA promoter genotype with clinical data in a cohort of 1,224 men with prostate cancer. Previous work with a subset of this cohort has shown that percent high-grade (Gleason grades 4 and 5) cancer was the strongest predictor of biochemical recurrence (PSA relapse). We found a statistically significant association (P < 0.05) of the rs925013 SNP with several clinical and histomorphologic variables. The G allele was associated with higher serum PSA at diagnosis, higher percent Gleason grade 3 cancer, and lower percent high-grade and Gleason grade 4 cancer. The rs266882 SNP was modestly associated with PSA at diagnosis in a dominant model but was not associated with cancer grade. Neither SNP was associated with biochemical recurrence. The statistically significant predictors of biochemical recurrence were tumor location in the peripheral zone [odds ratio (OR), 10.71; 95% confidence interval (95% CI), 3.15-36.49], presence of any Gleason grade 4/5 cancer (OR, 4.26; 95% CI, 1.30-14.00), presence of any intraductal cancer (OR, 1.03; 95% CI, 1.00-1.04), and serum PSA at diagnosis (OR, 2.04; 95% CI, 1.50-2.77).

Characterization of adult prostatic progenitor/stem cells exhibiting self-renewal and multilineage differentiation

Demonstration of the hallmarks of stem cells, self-renewal and multilineage differentiation, is a challenge that has not been met for numerous tissues postulated to possess adult stem cells, including prostate tissue. Using a defined medium, we reproducibly isolated and maintained adult mouse prostatic cells with characteristics of progenitor/stem cells. Clonal populations of cells demonstrated tissue-specific multilineage differentiation by their ability to generate organized prostatic ductal structures in vivo, with luminal and basal cell layers, when grafted under the renal capsules of mice in the presence of fetal rat urogenital mesenchyme. Complete differentiation was demonstrated by the expression and secretion of terminally differentiated prostatic secretory products into the lumens. Self-renewal was demonstrated by serial transplantation of clonal populations that generated fully differentiated ductal structures in vivo. In vitro, undifferentiated cells expressed markers associated with prostate stem cells, including Sca 1 and CD49f, as well as basal cell markers (p63 and cytokeratins 5 and 14) and, at a low level, luminal cell markers (androgen receptor and cytokeratins 8 and 18). When grafted and allowed to differentiate in the presence of fetal urogenital mesenchyme, the cells differentiated into luminal cells and basal cells with more restricted protein expression patterns. These studies are the first to report a reproducible system to assess adult prostatic progenitor/stem cells.

Glyoxylate reductase activity in blood mononuclear cells and the diagnosis of primary hyperoxaluria type 2

BACKGROUND

Primary hyperoxaluria type 2 (PH2) is a rare monogenic disorder characterized by an elevated urinary excretion of oxalate. Increased oxalate excretion in PH2 patients can cause nephrolithiasis and nephrocalcinosis, and can, in some cases, result in renal failure and systemic oxalate deposition. The disease is due to a deficiency of glyoxylate reductase/hydroxypyruvate reductase (GRHPR) activity. A definitive diagnosis of PH2 is currently made by the analysis of GR activity in a liver biopsy. GRHPR is expressed in virtually every tissue in the body, suggesting that utilization of more readily available cells could be used to determine GRHPR deficiency. In this study, we have evaluated the potential of determining GR and d-glycerate dehydrogenase (DGDH) activity in blood mononuclear cells (BMC) as a diagnostic indicator of PH2.

METHODS

Blood samples were obtained from 10 male and 10 female normal subjects, median age 31, range 21-63, at the Wake Forest University Medical Center and from primary hyperoxaluria patients at the Mayo Clinic. The BMC were isolated and GR and DGDH activities measured in cell lysates.

RESULTS

An assay of 20 normal individuals indicated that BMC contained a DGDH and GR activity of 0.97+/-0.20 (range 0.62-1.45), and 10.6+/-3.3 (range 8.3-16.6) nmol/min/mg protein, respectively. The intra-assay coefficient of variation for DGDH and GR activity was 8.2 and 11.5%, respectively. The BMC lysates from normal adult subjects and patients with PH1 showed similar GR and DGDH activities. This was confirmed by the presence of immunoreactive GRHPR protein by western blot analysis. In contrast, PH2 BMC lysates did not exhibit DGDH or GR activity, and showed no immunoreactive GRHPR by western blot analysis.

CONCLUSION

These results suggest that the assay of DGDH or GR activity in BMC could be used as a minimally invasive diagnostic test for PH2.

Glyoxylate reductase activity in blood mononuclear cells and the diagnosis of primary hyperoxaluria type 2

BACKGROUND

Primary hyperoxaluria type 2 (PH2) is a rare monogenic disorder characterized by an elevated urinary excretion of oxalate. Increased oxalate excretion in PH2 patients can cause nephrolithiasis and nephrocalcinosis, and can, in some cases, result in renal failure and systemic oxalate deposition. The disease is due to a deficiency of glyoxylate reductase/hydroxypyruvate reductase (GRHPR) activity. A definitive diagnosis of PH2 is currently made by the analysis of GR activity in a liver biopsy. GRHPR is expressed in virtually every tissue in the body, suggesting that utilization of more readily available cells could be used to determine GRHPR deficiency. In this study, we have evaluated the potential of determining GR and d-glycerate dehydrogenase (DGDH) activity in blood mononuclear cells (BMC) as a diagnostic indicator of PH2.

METHODS

Blood samples were obtained from 10 male and 10 female normal subjects, median age 31, range 21-63, at the Wake Forest University Medical Center and from primary hyperoxaluria patients at the Mayo Clinic. The BMC were isolated and GR and DGDH activities measured in cell lysates.

RESULTS

An assay of 20 normal individuals indicated that BMC contained a DGDH and GR activity of 0.97+/-0.20 (range 0.62-1.45), and 10.6+/-3.3 (range 8.3-16.6) nmol/min/mg protein, respectively. The intra-assay coefficient of variation for DGDH and GR activity was 8.2 and 11.5%, respectively. The BMC lysates from normal adult subjects and patients with PH1 showed similar GR and DGDH activities. This was confirmed by the presence of immunoreactive GRHPR protein by western blot analysis. In contrast, PH2 BMC lysates did not exhibit DGDH or GR activity, and showed no immunoreactive GRHPR by western blot analysis.

CONCLUSION

These results suggest that the assay of DGDH or GR activity in BMC could be used as a minimally invasive diagnostic test for PH2.

5-Oxo-ETE analogs and the proliferation of cancer cells

MDA-MB-231, MCF7, and SKOV3 cancer cells, but not HEK-293 cells, expressed mRNA for the leukocyte G protein-coupled 5-oxo-eicosatetraenoate (ETE) OXE receptor. 5-Oxo-ETE, 5-oxo-15-OH-ETE, and 5-HETE stimulated the cancer cell lines but not HEK-293 cells to mount pertussis toxin-sensitive proliferation responses. Their potencies in eliciting this response were similar to their known potencies in activating leukocytes and OXE receptor-transfected cells. However, high concentrations of 5-oxo-ETE and 5-oxo-15-OH-ETE, but not 5-HETE, arrested growth and caused apoptosis in all four cell lines; these responses were pertussis toxin-resistant. The same high concentrations of the oxo-ETEs but again not 5-HETE also activated peroxisome proliferator-activated receptor (PPAR)-gamma. Pharmacological studies indicated that this activation did not mediate their effects on proliferation. These results are the first to implicate the OXE receptor in malignant cell growth and to show that 5-oxo-ETEs activate cell death programs as well as PPARgamma independently of this receptor.

Growth sensitivity of a recombinant simian virus 5 P/V mutant to type I interferon differs between tumor cell lines and normal primary cells

A paramyxovirus SV5 mutant (rSV5-P/V-CPI-) that encodes 6 naturally-occurring P/V gene substitutions is a potent inducer of type I interferon (IFN) and is restricted for low moi growth, two phenotypes not seen with WT SV5. In this study, we have compared the IFN sensitivity of WT SV5 and the rSV5-P/V-CPI- mutant in tumor cell lines and in cultures of normal primary cells. We have tested the hypothesis that differences in IFN induction elicited by WT rSV5 and rSV5-P/V-CPI- are responsible for differences in low moi growth and spread. In contrast to WT SV5, low moi infection of A549 lung carcinoma cells with rSV5-P/V-CPI- resulted in a plateau of virus production by 24-48 h pi when secreted IFN levels were between approximately 100 and 1000 U/ml. Gene microarray and RT-PCR analyses identified IFN genes and IFN-stimulated genes whose expression were increased by infection of A549 cells with WT and P/V mutant viruses. Restricted low moi growth and spread of rSV5-P/V-CPI- in A549 cells was relieved in the presence of neutralizing antibodies to IFN-beta but not TNF-alpha. When A549 or MDA-MB-435 breast tumor cells were pretreated with IFN, both WT and P/V mutant viruses showed delayed spread and approximately 10-fold reduction in virus yield, but infections were not eliminated. Using normal primary human epithelial cells that have undergone limited passage in culture, WT rSV5 and rSV5-P/V-CPI- displayed high moi growth properties that were similar to that seen in A549 cells. However, IFN pretreatment of these primary cells as well as normal human lung cells eliminated low moi spread of both mutant and WT rSV5 infections. Together, these data demonstrate that SV5 growth in normal primary human cells is highly sensitive to IFN compared to growth in some tumor cell lines, regardless of whether the P/V gene is WT or mutant. These results suggest a model in which spread of WT SV5 in normal human cells is dependent on the ability of the virus to prevent IFN synthesis. The implications of these results for the use of recombinant paramyxoviruses as vectors are discussed.

Culture of mouse prostatic epithelial cells from genetically engineered mice

BACKGROUND

The lack of appropriate prostate cancer models is a major problem for prostate cancer research. Progress has been made towards the development of better in vivo rodent genetic models for prostatic disease. However, an in vitro model is often preferred for the elucidation of cellular mechanisms involved in the disease.

METHODS

We microdissected the four prostatic lobes from young male mice, harvested the epithelial components, and grew epithelial cells from these tissues. We maintained the growth of these cells in long-term and three-dimensional culture.

RESULTS

We have reproducibly harvested and cultured for extended passages mouse prostatic epithelial cells (MPECs) from a variety of mouse genetic strains. These cells express luminal and basal epithelial markers as well as the androgen receptor. Additionally, MPECs form classic branching structures in a three-dimensional collagen matrix.

CONCLUSIONS

We have developed a novel culture system to harvest and grow MPECs in long-term culture. These cells will serve as a useful in vitro complement to studies using mouse genetic models for prostatic disease.

Sensitivity of prostate tumors to wild type and M protein mutant vesicular stomatitis viruses

Because of its potent ability to induce apoptosis, vesicular stomatitis virus (VSV) is an attractive candidate as an oncolytic virus for tumor therapy. Previous studies have suggested that VSV selectively infects tumor cells due to defects in their antiviral responses making them more susceptible to VSV infection than normal cells. We tested this hypothesis in the prostate tumor system by comparing LNCaP and PC-3 prostate tumor cells to benign human prostatic epithelial cells from patient prostatectomy specimens. We compared the cell killing ability of a recombinant virus containing a wild-type (wt) M protein (rwt) and an isogenic M protein mutant virus (rM51R-M) that induces interferon (IFN) in infected cells and should display a greater selectivity for tumor cells. Our results showed that in single-cycle infection experiments, LNCaP cells were sensitive to killing by both wt and mutant viruses, while PC-3 cells were highly resistant to VSV-induced cell killing. LNCaP and benign prostate cells were similarly susceptible to both viruses, indicating that normal prostate cells are not inherently resistant to killing by VSV. In each of the cell lines, the rM51R-M virus induced similar levels of apoptosis to rwt virus, showing that the M protein does not play a significant role in apoptosis induction by VSV in these cells. In multiple-cycle infection experiments, LNCaP cells were more sensitive than benign prostatic epithelial cells to virus-induced cell killing by rM51R-M virus, but not rwt virus. Both viruses were equally effective at reducing LNCaP tumor volume in vivo following intratumoral and intravenous inoculation in nude mice, while PC-3 tumors were resistant to VSV treatment. None of the mice treated with rM51R-M virus died as a result of virus infection, while 50-71% of mice treated with rwt virus succumbed to virus infection. Similarly, when inoculated by the more sensitive intranasal route, the rM51R-M virus was less pathogenic than the rwt virus from which it was derived. These results indicate that M protein mutant viruses are superior candidates as oncolytic viruses for therapies of prostate tumors, but future strategies for use of VSV will require testing individual tumors for their susceptibility to virus infection.

Selective inactivation of a Fas-associated death domain protein (FADD)-dependent apoptosis and autophagy pathway in immortal epithelial cells

Although evasion of apoptosis is thought to be required for the development of cancer, it is unclear which cell death pathways are evaded. We previously identified a novel epithelial cell death pathway that works in normal cells but is inactivated in tumor cells, implying that it may be targeted during tumor development. The pathway can be activated by the Fas-associated death domain (FADD) of the adaptor protein but is distinct from the known mechanism of FADD-induced apoptosis through caspase-8. Here, we show that a physiological signal (tumor necrosis factor-related apoptosis-inducing ligand) can kill normal epithelial cells through the endogenous FADD protein by using the novel FADD death domain pathway, which activates both apoptosis and autophagy. We also show that selective resistance to this pathway occurs when primary epithelial cells are immortalized and that this occurs through a mechanism that is independent of known events (telomerase activity, and loss of function of p53, Rb, INK4a, and ARF) that are associated with immortalization. These data identify a novel cell death pathway that combines apoptosis and autophagy and that is selectively inactivated at the earliest stages of epithelial cancer development.

A system for studying epithelial-stromal interactions reveals distinct inductive abilities of stromal cells from benign prostatic hyperplasia and prostate cancer

The development of normal and abnormal glandular structures in the prostate is controlled at the endocrine and paracrine levels by reciprocal interactions between epithelium and stroma. To study these processes, it is useful to have an efficient method of tissue acquisition for reproducible isolation of cells from defined histologies. Here we assessed the utility of a standardized system for acquisition and growth of prostatic cells from different regions of the prostate with different pathologies, and we compared the abilities of stromal cells from normal peripheral zone, benign prostatic hyperplasia (BPH-S), and cancer to induce the growth of a human prostatic epithelial cell line (BPH-1) in vivo. Using the tissue recombination method, we showed that grafting stromal cells (from any histology) alone or BPH-1 epithelial cells alone produced no visible grafts. Recombining stromal cells from normal peripheral zone with BPH-1 cells also produced no visible grafts (n = 15). Recombining BPH-S with BPH-1 cells generated small, well-organized, and sharply demarcated grafts approximately 3-4 mm in diameter (n = 9), demonstrating a moderate inductive ability of BPH-S. Recombining stromal cells from cancer with BPH-1 cells generated highly disorganized grafts that completely surrounded the host kidney and invaded into adjacent renal tissue, demonstrating induction of an aggressive phenotype. We conclude that acquisition of tissue from toluidine blue dye-stained specimens is an efficient method to generate high-quality epithelial and/or stromal cultures. Stromal cells derived by this method from areas of BPH and cancer induce epithelial cell growth in vivo, which mimics the natural history of these diseases.

Glycolate and glyoxylate metabolism in HepG2 cells

Oxalate synthesis in human hepatocytes is not well defined despite the clinical significance of its overproduction in diseases such as the primary hyperoxalurias. To further define these steps, the metabolism to oxalate of the oxalate precursors glycolate and glyoxylate and the possible pathways involved were examined in HepG2 cells. These cells were found to contain oxalate, glyoxylate, and glycolate as intracellular metabolites and to excrete oxalate and glycolate into the medium. Glycolate was taken up more effectively by cells than glyoxylate, but glyoxylate was more efficiently converted to oxalate. Oxalate was formed from exogenous glycolate only when cells were exposed to high concentrations. Peroxisomes in HepG2 cells, in contrast to those in human hepatocytes, were not involved in glycolate metabolism. Incubations with purified lactate dehydrogenase suggested that this enzyme was responsible for the metabolism of glycolate to oxalate in HepG2 cells. The formation of14C-labeled glycine from14C-labeled glycolate was observed only when cell membranes were permeabilized with Triton X-100. These results imply that peroxisome permeability to glycolate is restricted in these cells. Mitochondria, which produce glyoxylate from hydroxyproline metabolism, contained both alanine:glyoxylate aminotransferase (AGT)2 and glyoxylate reductase activities, which can convert glyoxylate to glycine and glycolate, respectively. Expression of AGT2 mRNA in HepG2 cells was confirmed by RT-PCR. These results indicate that HepG2 cells will be useful in clarifying the nonperoxisomal metabolism associated with oxalate synthesis in human hepatocytes.