Human Prostate Cancer Tissue Microarrays Research Articles

The estrogen signaling pathway reprograms prostate cancer cell metabolism and supports proliferation and disease progression.

Just like the androgen receptor (AR), the estrogen receptor α (ERα) is expressed in the prostate and is thought to influence prostate cancer (PCa) biology. Yet the incomplete understanding of ERα functions in PCa hinders our ability to fully comprehend its clinical relevance and restricts the repurposing of estrogen-targeted therapies for the treatment of this disease. Using 2 human PCa tissue microarray cohorts, we first demonstrate that nuclear ERα expression was heterogeneous among patients, being detected in only half of the tumors. Positive nuclear ERα levels were correlated with disease recurrence, progression to metastatic PCa, and patient survival. Using in vitro and in vivo models of the normal prostate and PCa, bulk and single-cell RNA-Seq analyses revealed that estrogens partially mimicked the androgen transcriptional response and activated specific biological pathways linked to proliferation and metabolism. Bioenergetic flux assays and metabolomics confirmed the regulation of cancer metabolism by estrogens, supporting proliferation. Using cancer cell lines and patient-derived organoids, selective estrogen receptor modulators, a pure anti-estrogen, and genetic approaches impaired cancer cell proliferation and growth in an ERα-dependent manner. Overall, our study revealed that, when expressed, ERα functionally reprogrammed PCa metabolism, was associated with disease progression, and could be targeted for therapeutic purposes.

Abstract 3046: The estrogen signaling pathway reprograms prostate cancer cell metabolism and supports proliferation and disease progression

Abstract Just as the androgen receptor (AR), the estrogen receptor α (ERα) is expressed in the prostate and is thought to influence prostate cancer (PCa) biology. Yet, the incomplete understanding of ERα cellular functions in PCa hinders our ability to fully comprehend its clinical relevance and restricts the repurposing of estrogen-targeted therapies for treatment of this disease. Using two human PCa tissue microarray cohorts, we first demonstrated that nuclear ERα expression was heterogeneous between patients, being only detected in half of tumors. Positive nuclear ERα levels were correlated with disease recurrence, progression to metastatic PCa, and patient survival. Using in vitro and in vivo models of the normal prostate and PCa, bulk and single cell RNA-seq analyses revealed that estrogens partially mimic the androgen transcriptional response and induce specific biological pathways linked to cellular proliferation and metabolism. Bioenergetic flux assays and metabolomics confirmed regulation of cancer metabolism by estrogens, supporting proliferation. Using cancer cell lines and patient-derived organoids, selective estrogen receptor modulators, a pure anti-estrogen, and genetic approaches impaired cancer cell proliferation and growth in an ERα-dependent manner. Overall, our study revealed that, when expressed, ERα functionally reprograms PCa metabolism, is associated with disease progression, and could be targeted for therapeutic purposes. Citation Format: Camille Lafront, Lucas Germain, Gabriel H. Campolina-Silva, Cindy Weidmann, Line Berthiaume, Hélène Hovington, Hervé Brisson, Cynthia Jobin, Lilianne Frégeau-Proulx, Raul Cotau, Kevin Gonthier, Aurélie Lacouture, Patrick Caron, Claire Ménard, Chantal Atallah, Julie Riopel, Éva Latulippe, Alain Bergeron, Paul Toren, Chantal Guillemette, Martin Pelletier, Yves Fradet, Clémence Belleannée, Frédéric Pouliot, Louis Lacombe, Éric Lévesque, Étienne Audet-Walsh. The estrogen signaling pathway reprograms prostate cancer cell metabolism and supports proliferation and disease progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3046.

Abstract A060: Genetic alterations induce distinct histone post-translational modifications during the transition to castration-resistant prostate cancer

Abstract Background: Epigenetic alterations can impact gene expression and have been implicated in tumorigenesis. One major process is the post-translational modification (PTM) of histone proteins governed by histone-modifying enzyme (HME) activity. There is growing evidence that the dysregulation of HMEs plays an essential role in cancer initiation and progression. In this study, we hypothesized that alterations in histone PTMs and their associated enzymes drive the development of castration-resistant prostate cancer (CRPC) from hormone-sensitive prostate cancer (HSPC). To address this, we performed an unbiased screen of histone PTMs in a series of prostate cancer (PC) PDXs before and after the transition to CRPC. Methods: Histone PTM levels were analyzed in 10 paired HSPC and CRPC PDXs using mass spectrometry. Histone PTM patterns were subcategorized based on common genetic alterations found in PC. RNA-sequencing data for the PDXs and publicly available human PC datasets were used to further characterize HMEs. Co-expression of CHD1, NSD2, and other HMEs was examined in human PC tissue microarrays (TMAs). CHD1 KO clones were generated using CRISPR and levels of histone PTMs and HMEs were assessed and quantified. Gene set enrichment analysis (GSEA) was performed to determine the pathways altered with CHD1 in CRPC PDXs. Results: A comparison of all PDX tumors revealed increased H3K14 and H4 acetylation in CRPC tumors relative to paired HSPC derivatives. We also observed distinct histone PTM patterns associated with common genetic alterations. When compared to tumors with CHD1 WT, tumors with CHD1 loss develop reduced histone PTM H3.3K36me2. CHD1 is a chromatin remodeler commonly deleted in ~ 15% of primary PCs. Screening the differential expression and activity of HMEs in these PDXs reveals that HME NSD2 correlates with CHD1. The human CRPC SU2C/PCF dataset shows a strong positive correlation between CHD1 and NSD2 mRNA (r=0.44). Human CRPC TMAs show decreased protein expression of NSD2 and its histone mark H3K36me2 is associated with reduced CHD1 levels. CHD1 KO in DU145 results in a loss of H3.3K36me2 and a 0.5-fold decrease in NSD2 expression. GSEA revealed that a reduction in the DNA repair pathway is associated with CHD1 loss. The CRPC PDXs (n=24) and human dataset SU2C/PCF 2019 showed a strong positive correlation between CHD1, NSD2, and DNA damage repair genes. Conclusions: We have identified for the first time that genetic alterations alter histone marks during the transition to castration-resistant cancer. Reduced histone H3.3K36 methylation is associated with the genetic loss of CHD1 during the transition to CRPC. The expression of NSD2 is altered in the CRPC state in a CHD1 status-dependent manner. The CHD1-NSD2 phenotype may be the target of novel therapeutic drug combinations – the subject of ongoing research. Citation Format: Tanaya A. Purohit, Joseph Gawdzik, Bing Yang, Eric A. Armstrong, Peter W. Lewis, John M. Denu, David F. Jarrard. Genetic alterations induce distinct histone post-translational modifications during the transition to castration-resistant prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A060.

PLK4 is upregulated in prostate cancer and its inhibition reduces centrosome amplification and causes senescence.

BackgroundIdentification of novel molecular target(s) is important for designing newer mechanistically driven approaches for the treatment of prostate cancer (PCa), which is one of the main causes of morbidity and mortality in men. In this study, we determined the role of polo‐like kinase 4 (PLK4), which regulates centriole duplication and centrosome amplification (CA), in PCa.Materials and MethodsEmploying human PCa tissue microarrays, we assessed the prevalence of CA, correlated with Gleason score, and estimated major causes of CA in PCa (cell doubling vs. centriole overduplication) by staining for mother/mature centrioles. We also assessed PLK4 expression and correlated it with CA in human PCa tissues and cell lines. Further, we determined the effects of PLK4 inhibition in human PCa cells.ResultsCompared to benign prostate, human PCa demonstrated significantly higher CA, which was also positively correlated with the Gleason score. Further, most cases of CA were found to arise by centriole overduplication rather than cell doubling events (e.g., cytokinesis failure) in PCa. In addition, PLK4 was overexpressed in human PCa cell lines and tumors. Moreover, PLK4 inhibitors CFI‐400945 and centrinone‐B inhibited cell growth, viability, and colony formation of both androgen‐responsive and androgen‐independent PCa cell lines. PLK4 inhibition also induced cell cycle arrest and senescence in human PCa cells.ConclusionsCA is prevalent in PCa and arises predominantly by centriole overduplication as opposed to cell doubling events. Loss of centrioles is cellular stress that can promote senescence and suggests that PLK4 inhibition may be a viable therapeutic strategy in PCa.

Sodium bicarbonate transporter NBCe1 regulates proliferation and viability of human prostate cancer cells LNCaP and PC3.

Studies on cultured cancer cells or cell lines have revealed multiple acid extrusion mechanisms and their involvement in cancer cell growth and progression. In the present study, the role of the sodium bicarbonate transporters (NBCs) in prostate cancer cell proliferation and viability was examined. qPCR revealed heterogeneous expression of five NBC isoforms in human prostate cancer cell lines LNCaP, PC3, 22RV1, C4-2, DU145, and the prostate cell line RWPE-1. In fluorescence pH measurement of LNCaP cells, which predominantly express NBCe1, Na+ and HCO3–-mediated acid extrusion was identified by bath ion replacement and sensitivity to the NBC inhibitor S0859. NBCe1 knockdown using siRNA oligonucleotides decreased the number of viable cells, and pharmacological inhibition with S0859 (50 µM) resulted in a similar decrease. NBCe1 knockdown and inhibition also increased cell death, but this effect was small and slow. In PC3 cells, which express all NBC isoforms, NBCe1 knockdown decreased viable cell number and increased cell death. The effects of NBCe1 knockdown were comparable to those by S0859, indicating that NBCe1 among NBCs primarily contributes to PC3 cell proliferation and viability. S0859 inhibition also decreased the formation of cell spheres in 3D cultures. Immunohistochemistry of human prostate cancer tissue microarrays revealed NBCe1 localization to the glandular epithelial cells in prostate tissue and robust expression in acinar and duct adenocarcinoma. In conclusion, our study demonstrates that NBCe1 regulates acid extrusion in prostate cancer cells and inhibiting or abolishing this transporter decreases cancer cell proliferation.

C1Q‐TNF‐related peptide 8 (CTRP8) in human prostate cancer

Introduction C1Q Tumor Necrosis Factor related Peptide 8 (CTRP8) is the one of the least characterized members of the C1Q/TNF family of proteins which is engaged in diverse functions ranging from metabolism to immunity and is one of only two CTRP family members absent in the mouse genome. CTRP8 was identified in our lab as a novel ligand of the RXFP1 receptor and was found to promote invasiveness and chemoresistance to temozolomide in glioblastoma (GB)(Glogowska et al., 2013; Thanasupawat et al., 2018). We have generated high-affinity rabbit antisera to human CTRP8 to identify a selective mast cell subpopulation in human prostate cancer tissues (Hempel Sullivan et al., 2020). Mast cells are innate immune cells which are primarily known for their role in the mediation of allergic responses. They have been detected within prostate cancer tissues and serve as potential prognostic marker in prostate cancer (Johansson et al., 2010; Hempel Sullivan et al., 2020). Methods Affinity-purified rabbit polyclonal antisera directed against an epitope unique to human CTRP8 were characterized by Western blot, immunofluorescence, and immunohistochemistry in prostate cancer tissue sections and human prostate cancer tissue microarrays (TMAs). Results Of several Flag-tagged human and mouse CTRP family members transiently expressed in HEK293T cells, the CTRP8 antisera exclusively detected human CTRP8 as assessed by Western blot, demonstrating the specificity of the antisera. We studied the expression of CTRP8 in human prostate tissues. CTRP8 was expressed in a subpopulation of human mast cells distributed in prostate cancer tissues, as demonstrated by co-localization of CTRP8 immunoreactivity and toluidine blue positive mast cells in prostate cancer tissues. This was further validated by dual immunofluorescence of CTRP8 with Tryptase, a marker for mature mast cells. Initial analysis of prostate cancer tissue microarrays (TMAs) (n= 360) revealed a comparative increase in the proportion of Tryptase+/ CTRP8+ cells versus total number of mast cells (Tryptase+/ CTRP8+ and Tryptase+/ CTRP8- cells) in the extra-tumoral compartment as compared to intra-tumoral regions for Gleason grades 6 and 7 prostate cancer samples. Weak staining of CTRP8 was detected in prostate epithelial cells. The RXFP1+ human prostate cancer cell line PC3 responded to CTRP8 treatment with increased protein kinase C delta signaling and enhanced motility as determined by real-time migration assays. Conclusions Here we have identified the expression of adipokine family member CTRP8 in prostate epithelial cells and in a subpopulation of mature mast cells in patient prostate cancer tissues, thus, identifying CTRP8 as a novel player in prostate cancer and associated mast cell compartment. References Glogowska, A., et al. J. Pathol., 231, 466–479, 2013 Thanasupawat, T., et al. Mol. Oncol. 12, 1464–1479, 2018 Johansson, A., Am. J. Pathol, 177, 1031–1041, 2010 Hempel Sullivan H, et al. J. Pathol., 2020 Hempel Sullivan H, et al. Cancer Epidemiol Biomarkers Prev., 2020

Down-regulation of ACACA suppresses the malignant progression of Prostate Cancer through inhibiting mitochondrial potential.

Background and aim: Silencing the expression of ACACA inhibits cell proliferation and induces apoptosis in prostate cancer LNCaP cells. However, the role of ACACA in other prostate cancer cells is not fully understood. Also, the effect of knocking down ACACA gene on mitochondria remains unclear. This study aimed to discover the specific role of ACACA gene in prostate cancer (PCa) DU145 and PC3 cells as well as its effects on mitochondrial potential.Methods: The expression of ACACA gene was detected in human prostate cancer tissue microarrays and assessed in different clinical stages. Then, prostate cancer cell lines with low expression of ACACA were constructed to evaluate the changes in their cell cycle, proliferation, and metabolites. The effect of ACACA on tumor formation in vivo was analyzed. Also, mito-ATP production, mitochondrial staining, and mtDNA, nicotinamide adenine dinucleotide (NAD+/NADH), and reactive oxygen species (ROS) levels were detected.Results: ACACA was expressed more strongly in prostate cancer tissues. The expression level of ACACA was higher in patients with advanced PCa than in patients with lower grades. The proliferation ability reduced in ACACA-knockdown cells. In in vivo tests, the tumor volume and weight were lower in the experimental group than in the control group. Mito-ATP production decreased significantly after ACACA suppression, mtDNA levels and MitoTracker staining decreased in the experimental group. The ratio of NAD+/NADH and ROS levels were upregulated in the experimental group.Conclusion: Targeting ACACA gene and mitochondria might serve as a novel therapy for prostate cancer treatment.

Abstract 2612: Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer

Abstract Background: Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer (PC) that emerges after androgen deprivation therapy in advanced PC patients, with incidence significantly increased in recent years due to the widespread use of highly potent antiandrogens such as enzalutamide (ENZ). This study investigated the role of neuropilin-2 (NRP2) in the development and progression of ENZ-induced NEPC. Methods: Human PC tissue microarrays with different characteristics, including hormone naïve, castration resistant (CR) and neuroendocrine (NE), were analyzed for NRP2 expression by immunohistochemistry. Human PC cells were manipulated for stable knockdown or overexpression of NRP2, and then subjected to cell proliferation, cell colony formation and tumorsphere formation assays, and Western blot/RT-qPCR examination of NE marker expression. Results: NRP2 expression was elevated in CRPC and NEPC patient samples compared to hormone-naïve counterparts, which was supported by association of higher NRP2 expression with hormone-refractory and NE status of PC from additional clinical data sets. Increased NRP2 expression was found in LNCaP cells treated with ENZ (10 µM, up to 7 days) as well as in the ENZ-resistant C4-2BENZR cells (with acquired resistance to ENZ at 20 µM). Both cell lines exhibited treatment-induced NEPC features, including NE differentiation cell morphology, AR suppression and NE marker induction. Silencing of NRP2 in C4-2BENZR and 22Rv1 (with inherent ENZ resistance and NE traits) cells decreased cell proliferation by 50% and 75% respectively, which was corroborated in colony formation and tumorsphere assays. Silencing of NRP2 also increased apoptosis in both cell lines. NRP2 silencing further led to reduced expression of NE markers, including CHGA, SYP, CD56 and SOX2. Conversely, enforced expression of NRP2 in LNCaP and 22Rv1 cells accelerated cell proliferation by up to 4-fold, which was paralleled by increased cell colony and tumorsphere formation, reduced cell apoptosis, upregulation of NE marker expression (CHGA, SYP, NSE, CD56 and SOX2), and downregulation of AR and AR target genes (PSA, TMPRSS2, FKBP5 and KLK2). Mechanistically, NRP2 induced phosphorylation of STAT3 in C4-2BENZR and 22Rv1 cells as revealed by phospho-kinase antibody arrays, which will be further investigated for downstream effectors mediating NRP2's function in NEPC. Conclusion: NRP2 contributes to PC disease progression towards a NE phenotype following ENZ treatment and subsequent emergence of ENZ resistance, which provides new insights into understanding the mechanism underlying development of antiandrogen-induced NEPC and developing a new target for treating this lethal disease. Citation Format: Jing Wang, Jingjing Li, Boyang Wu, Lijuan Yin. Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2612.

Transient Sox9 Expression Facilitates Resistance to Androgen-Targeted Therapy in Prostate Cancer.

Patients with metastatic prostate cancer are increasingly presenting with treatment-resistant, androgen receptor-negative/low (AR-/Low) tumors, with or without neuroendocrine characteristics, in processes attributed to tumor cell plasticity. This plasticity has been modeled by Rb1/p53 knockdown/knockout and is accompanied by overexpression of the pluripotency factor, Sox2. Here, we explore the role of the developmental transcription factor Sox9 in the process of prostate cancer therapy response and tumor progression. Unique prostate cancer cell models that capture AR-/Low stem cell-like intermediates were analyzed for features of plasticity and the functional role of Sox9. Human prostate cancer xenografts and tissue microarrays were evaluated for temporal alterations in Sox9 expression. The role of NF-κB pathway activity in Sox9 overexpression was explored. Prostate cancer stem cell-like intermediates have reduced Rb1 and p53 protein expression and overexpress Sox2 as well as Sox9. Sox9 was required for spheroid growth, and overexpression increased invasiveness and neural features of prostate cancer cells. Sox9 was transiently upregulated in castration-induced progression of prostate cancer xenografts and was specifically overexpressed in neoadjuvant hormone therapy (NHT)-treated patient tumors. High Sox9 expression in NHT-treated patients predicts biochemical recurrence. Finally, we link Sox9 induction to NF-κB dimer activation in prostate cancer cells. Developmentally reprogrammed prostate cancer cell models recapitulate features of clinically advanced prostate tumors, including downregulated Rb1/p53 and overexpression of Sox2 with Sox9. Sox9 is a marker of a transitional state that identifies prostate cancer cells under the stress of therapeutic assault and facilitates progression to therapy resistance. Its expression may index the relative activity of the NF-κB pathway.

Interleukin-35 is associated with the tumorigenesis and progression of prostate cancer.

Interleukin (IL)-35 is a novel member of the IL-12 cytokine family, which exhibits a unique immune regulatory function. Previously, it was demonstrated that IL-35 expression is significantly increased in a wide range of tumor tissues, promoting angiogenesis and inhibiting the anti-tumor immune response. In the present study, the IL-35 protein expression levels were measured in the plasma and tumor tissue of patients with prostate cancer (PCA), and its role was determined in the occurrence and progression of PCA. Plasma IL-35 expression levels were measured using ELISA, and the associations of plasma IL-35 and clinicopathological parameters were analyzed. Receiver operating characteristic curves were plotted to analyze the role of IL-35 as a clinical biomarker for the diagnosis of PCA. Survival curve analysis demonstrated a significant decrease in the survival time in months in patients with PCA and increased expression levels of IL-35 compared with the participants with relatively lower IL-35 protein expression levels. IL-35 expression was detected using immunohistochemical staining of a human PCA tissue microarray. Plasma IL-35 expression levels in the patients with PCA were significantly increased compared with the patients with benign prostatic hyperplasia and the healthy controls. An increase in the plasma concentration of IL-35 was associated with progression of PCA stage and an increase in the Gleason score. Significant differences in AUCs for IL-35 and prostate-specific antigen were observed with regard to the presence of lymph node and distant metastases in patients with PCA. The expression levels of Epstein-barr virus-induced gene 3 (EBI3) and IL-12A (p35; the subunits which together form IL-35) were significantly increased in the tumor tissue compared with the adjacent normal tissue. An association was identified between the Gleason score and the expression of EBI3 and p35. Therefore, increased expression of IL-35 in the plasma and tumor tissues may contribute to the progression and metastasis of PCA, and IL-35 may serve as a novel prognostic biomarker or therapeutic target for the treatment of PCA.

Abstract B012: Histone demethylase JMJD1A promotes the generation of androgen receptor variant 7 (AR-V7) in prostate cancer cells

Abstract Generation of androgen receptor (AR) splicing variant, AR-V7, has been shown to contribute to the resistance of prostate cancer to androgen deprivation therapy and development of castration-resistant prostate cancer (CRPC). We and others have reported that histone demethylase JMJD1A promotes the transcriptional activity of AR by functioning as an AR coactivator. Here, we identified a new role for JMJD1A in the generation of AR-V7 in prostate cancer cells through interaction with HNRFPF. Knockdown of JMJD1A or HNRNPF reduced the mRNA and protein level of AR-V7 but had little effect on the full-length AR (AR-FL). Mechanistically, we found that JMJD1A and HNRNPF cooperatively bound to a polyG motif adjacent to the 5′ splicing site of Exon3b of AR gene, where they promoted the assembly of splicesome. Re-expression of AR-V7 in the JMJD1A-knockdown cells partly rescued the growth defect of prostate cancer cells in vitro and in the mouse xenograft model. The staining of AR-V7 paralleled that of JMJD1A or HNRNFP in a human prostate cancer tissue microarray. Together, our data reveal that JMJD1A enhances the castration-resistant growth of prostate cancer cells through coactivation of AR-FL and generation of AR-V7. Citation Format: Lingling Fan, Fengbo Zhang, Ladan Fazli, Martin Gleave, Xuesen Dong, Jianfei Qi. Histone demethylase JMJD1A promotes the generation of androgen receptor variant 7 (AR-V7) in prostate cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B012.

Abstract 4436: Eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) is upregulated modulates prostate cancer growth and proliferation

Abstract Introduction: cap-dependent translation is necessary due to high protein requirement in cancer cells. An interaction between EIF4E and EIF4G is crucial for the formation of the EIF4F complex and initiation of cap-dependent translation. In the current study, we analyzed Human prostate cancer tissue microarray (TMA) and mRNA expression data in clinical datasets, and prostate tumor tissue from TRAMP (Transgenic Adenocarcinoma of the Mouse Prostate) model. We also assessed the functional role of EIF4G1 in commonly used PCa cell lines. Methods: Human prostate cancer tissue microarray was used to analyze the EIF4G1 level in patient samples. mRNA expression data for EIF4G1 was analyzed from TCGA and Trento/Cornell/Broad clinical data sets. PCa cells viz. LNCaP, C4-2b, 22Rv1, DU145, PC3 and normal human prostate cell line RWPE-1 were used. For an in-vivo model of PCa, we used TRAMP and wild-type mouse. Loss of function studies was performed by using siRNA/shRNA. Real-time PCR and Western Blot analysis were used to quantitate the relative mRNA and protein levels respectively. Analysis of polysome was performed by sucrose density gradient fractionation. Polysome-to-Monosome (P/M) ratios were determined for global translation activity. Cell cycle, cell proliferation, cell migration and Clonogenic activity were measured by standard methods. Results: Results from TMA analysis showed that protein levels of EIF4G1 are high in PCa as compared to normal prostate tissue, and there is a graded increase in EIF4G1 as the disease progresses. Results of our analysis of EIF4G1 expression in TCGA database revealed that increased expression of EIF4G1 positively correlated with higher tumor grade and stages (Gleason Score). Available data from Trento/Cornell/Broad clinical dataset revealed that 43% of castration-resistant prostate cancer (CRPC) patients have EIF4G1 mRNA up-regulation. PCa cells express a significantly higher level of EIF4G1 as compared to normal prostate cells. Similarly, prostate tumor tissue from TRAMP tissue showed higher EIF4G1 expression as compared to normal wild-type prostate tissue. Silencing of EIF4G1 causes G0/G1 cell cycle delay and decreases Cyclin D1 and p-Rb levels. There is a shift in polysome (P) to monosome (M) ratio with the siEIF4G1 knockdown in LNCaP and C4-2b. Loss of function studied by knockdown of EIF4G1 showed impaired Clonogenic activity as well as cell proliferation. Real-time PCR data suggests that EIF4G1 knockdown in LNCaP & C4-2b decreases the level of EMT markers such as N-Cadherin, Vimentin & Zeb1 and limits the cell migration in C4-2b cells. Conclusions: Taken all together, our data indicate that EIF4G1 may function as an oncoprotein and is a novel target for intervention in PCa and CRPC. Citation Format: Praveen K. Jaiswal, Sweaty Koul, Prakash Srinivasan Timiri Shanmugam, Hari K. Koul. Eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) is upregulated modulates prostate cancer growth and proliferation [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 4436.

Human ex vivo prostate tissue model system identifies ING3 as an oncoprotein

Background:Although the founding members of the INhibitor of Growth (ING) family of histone mark readers, ING1 and ING2, were defined as tumour suppressors in animal models, the role of other ING proteins in cellular proliferation and cancer progression is unclear.Methods:We transduced ex vivo benign prostate hyperplasia tissues with inducible lentiviral particles to express ING proteins. Proliferation was assessed by H3S10phos immunohistochemistry (IHC). The expression of ING3 was assessed by IHC on a human prostate cancer tissue microarray (TMA). Gene expression was measured by DNA microarray and validated by real-time qPCR.Results:We found that ING3 stimulates cellular proliferation in ex vivo tissues, suggesting that ING3 could be oncogenic. Indeed, ING3 overexpression transformed normal human dermal fibroblasts. We observed elevated levels of ING3 in prostate cancer samples, which correlated with poorer patient survival. Consistent with an oncogenic role, gene-silencing experiments revealed that ING3 is required for the proliferation of breast, ovarian, and prostate cancer cells. Finally, ING3 controls the expression of an intricate network of cell cycle genes by associating with chromatin modifiers and the H3K4me3 mark at transcriptional start sites.Conclusions:Our investigations create a shift in the prevailing view that ING proteins are tumour suppressors and redefine ING3 as an oncoprotein.

Targeting aggressive prostate cancer-associated CD44v6 using phage display selected peptides.

There is a crucial need to identify new biomarkers associated with aggressive prostate cancer (PCa) including those associated with cancer stem cells (CSCs). CD44v6, generated by alternative splicing of CD44, has been proposed as a CSC biomarker due to its correlation with aggressive PCa disease. We hypothesized that phage display selected peptides that target CD44v6 may serve as theranostic agents for aggressive PCa. Here, a 15 amino acid peptide (“PFT”) was identified by affinity selection against a peptide derived from the v6 region of CD44v6. Synthesized PFT exhibited specific binding to CD44v6 with an equilibrium dissociation constant (Kd) of 743.4 nM. PFT also bound CD44v6 highly expressed on human PCa cell lines. Further, an aggressive form of PCa cells (v6A3) was isolated and tagged by a novel CSC reporter vector. The v6A3 cells had a CSC-like phenotype including enriched CD44v6 expression, enhanced clonogenicity, resistance to chemotherapeutics, and generation of heterogeneous offspring. PFT exhibited preferential binding to v6A3 cells compared to parental cells. Immunohistofluorescence studies with human PCa tissue microarrays (TMA) indicated that PFT was highly accurate in detecting CD44v6-positive aggressive PCa cells, and staining positivity was significantly higher in late stage, metastatic and higher-grade samples. Taken together, this study provides for the first time phage display selected peptides that target CD44v6 overexpressed on PCa cells. Peptide PFT may be explored as an aid in the diagnosis and therapy of advanced PCa disease.

Targeting IκB Kinase β/NF-κB Signaling in Human Prostate Cancer by a Novel IκB Kinase β Inhibitor CmpdA.

NF-κB plays an important role in many types of cancer, including prostate cancer, but the role of the upstream kinase of NF-κB, IKKβ, in prostate cancer has neither been fully documented nor are there any effective IKKβ inhibitors used in clinical settings. Here, we have shown that IKKβ activity is mediated by multiple kinases including IKKα in human prostate cancer cell lines that express activated IKKβ. IHC analysis (IHC) of human prostate cancer tissue microarrays (TMA) demonstrates that phosphorylation of IKKα/β within its activation loop gradually increases in low to higher stage tumors as compared with normal tissue. The expression of cell proliferation and survival markers (Ki-67, Survivin) and epithelial-to-mesenchymal transition (EMT) markers (Slug, Snail), as well as cancer stem cell (CSC)-related transcription factors (Nanog, Sox2, Oct-4), also increase in parallel among the respective TMA samples analyzed. IKKβ, but not NF-κB, is found to regulate Nanog, which, in turn, modulates the levels of Oct4, Sox2, Snail, and Slug, indicating an essential role of IKKβ in regulating CSCs and EMT. The novel IKKβ inhibitor CmpdA inhibits constitutively activated IKKβ/NF-κB signaling, leading to induction of apoptosis and inhibition of proliferation, migration, and stemness in these cells. CmpdA also significantly inhibits tumor growth in xenografts without causing apparent in vivo toxicity. Furthermore, CmpdA and docetaxel act synergistically to inhibit proliferation of prostate cancer cells. These results indicate that IKKβ plays a pivotal role in prostate cancer, and targeting IKKβ, including in combination with docetaxel, may be a potentially useful strategy for treating advanced prostate cancer. Mol Cancer Ther; 15(7); 1504-14. ©2016 AACR.

Abstract 1233: Impairment of TFF3 induces cellular apoptosis in prostate cancer cell lines and overexpression of TFF3 may be a prognostic biomarker in human prostate cancers

Abstract Background: Human trefoil factor 3(TFF3)/ Intestinal trefoil factor(ITF) is originally known well as an essential regulator for epithelial restitution in gastrointestinal tract and also suggested as a potential cancer marker in serum. Furthermore, the aberrant overexpression of TFF3 has been reported in various human cancers, majorly colorectal cancers, suggesting that TFF3 may play a critical role in tumor growth. However, its molecular signaling pathway remains unclear. Objective: To clarify whether TFF3 is related to survival/anti-apoptotic cell signaling pathways, and to determine that tff3 could be a molecular marker in prostate cancers. Design, Setting, and Participants: TFF3 gene was silenced by using siRNA in prostate cancer two kinds of cell lines, LNCap and PC3, following investigation of genes related to apoptosis and cell migration. The expression of TFF3 was analyzed by immunohistochemistry in 109 prostate cancer and 106 normal prostate tissues. Results and Limitations: TFF3 silenced prostate cancer cell lines exhibited increased annexin V binding and the activation of caspase-9 and caspase-3 which are crucial for programmed cell death, consistent with an increased rate of apoptosis, reduced rate of proliferation and migration. In human prostate cancer tissue microarray, TFF3 was positive in 54.7% (49.1%, 2+; 5.6%, 1+) of cancer cases (59/108) and 2.8% (1.9%, 2+; 0.9%, 1+) of morphologically normal tissue cases (3/106), P<0.0001. Conclusions: The results suggest that TFF3 expression seems play a role in promoting cell survival and be a potential useful marker in prostate cancers. In these contexts, TFF3 in human prostate cancers deserves further investigation to exploit as a cancer marker and anticancer drug. Citation Format: So-Youn Kim, Ji-Ying Liu, Yeun-Jun Chung. Impairment of TFF3 induces cellular apoptosis in prostate cancer cell lines and overexpression of TFF3 may be a prognostic biomarker in human prostate cancers. [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 1233. doi:10.1158/1538-7445.AM2015-1233

ROS signaling by NADPH oxidase 5 modulates the proliferation and survival of prostate carcinoma cells.

Prostate cancer (PCa) is the most commonly diagnosed cancer and second leading cause of male cancer death in Western nations. Thus, new treatment modalities are urgently needed. Elevated production of reactive oxygen species (ROS) by NADPH oxidase (Nox) enzymes is implicated in tumorigenesis of the prostate and other tissues. However, the identity of the Nox enzyme(s) involved in prostate carcinogenesis remains largely unknown. Analysis of radical prostatectomy tissue samples and benign and malignant prostate epithelial cell lines identified Nox5 as an abundantly expressed Nox isoform. Consistently, immunohistochemical staining of a human PCa tissue microarray revealed distinct Nox5 expression in epithelial cells of benign and malignant prostatic glands. shRNA‐mediated knockdown of Nox5 impaired proliferation of Nox5‐expressing (PC‐3, LNCaP) but not Nox5‐negative (DU145) PCa cell lines. Similar effects were observed upon ROS ablation via the antioxidant N‐acetylcysteine confirming ROS as the mediators. In addition, Nox5 silencing increased apoptosis of PC‐3 cells. Concomitantly, protein kinase C zeta (PKCζ) protein levels and c‐Jun N‐terminal kinase (JNK) phosphorylation were reduced. Moreover, the effect of Nox5 knockdown on PC‐3 cell proliferation could be mimicked by pharmacological inhibition of JNK. Collectively, these data indicate that Nox5 is expressed at functionally relevant levels in the human prostate and clinical PCa. Moreover, findings herein suggest that Nox5‐derived ROS and subsequent depletion of PKCζ and JNK inactivation play a critical role in modulating intracellular signaling cascades involved in the proliferation and survival of PCa cells. © 2014 The Authors. Molecular Carcinogenesis published by Wiley Periodicals, Inc.

TR4 nuclear receptor functions as a tumor suppressor for prostate tumorigenesis via modulation of DNA damage/repair system

Testicular nuclear receptor 4 (TR4), a member of the nuclear receptor superfamily, plays important roles in metabolism, fertility and aging. The linkage of TR4 functions in cancer progression, however, remains unclear. Using three different mouse models, we found TR4 could prevent or delay prostate cancer (PCa)/prostatic intraepithelial neoplasia development. Knocking down TR4 in human RWPE1 and mouse mPrE normal prostate cells promoted tumorigenesis under carcinogen challenge, suggesting TR4 may play a suppressor role in PCa initiation. Mechanism dissection in both in vitro cell lines and in vivo mice studies found that knocking down TR4 led to increased DNA damage with altered DNA repair system that involved the modulation of ATM expression at the transcriptional level, and addition of ATM partially interrupted the TR4 small interfering RNA-induced tumorigenesis in cell transformation assays. Immunohistochemical staining in human PCa tissue microarrays revealed ATM expression is highly correlated with TR4 expression. Together, these results suggest TR4 may function as a tumor suppressor to prevent or delay prostate tumorigenesis via regulating ATM expression at the transcriptional level.

Targeting Amino Acid Transport in Metastatic Castration-Resistant Prostate Cancer: Effects on Cell Cycle, Cell Growth, and Tumor Development

L-type amino acid transporters (LATs) uptake neutral amino acids including L-leucine into cells, stimulating mammalian target of rapamycin complex 1 signaling and protein synthesis. LAT1 and LAT3 are overexpressed at different stages of prostate cancer, and they are responsible for increasing nutrients and stimulating cell growth. We examined LAT3 protein expression in human prostate cancer tissue microarrays. LAT function was inhibited using a leucine analog (BCH) in androgen-dependent and -independent environments, with gene expression analyzed by microarray. A PC-3 xenograft mouse model was used to study the effects of inhibiting LAT1 and LAT3 expression. Results were analyzed with the Mann-Whitney U or Fisher exact tests. All statistical tests were two-sided. LAT3 protein was expressed at all stages of prostate cancer, with a statistically significant decrease in expression after 4-7 months of neoadjuvant hormone therapy (4-7 month mean = 1.571; 95% confidence interval = 1.155 to 1.987 vs 0 month = 2.098; 95% confidence interval = 1.962 to 2.235; P = .0187). Inhibition of LAT function led to activating transcription factor 4-mediated upregulation of amino acid transporters including ASCT1, ASCT2, and 4F2hc, all of which were also regulated via the androgen receptor. LAT inhibition suppressed M-phase cell cycle genes regulated by E2F family transcription factors including critical castration-resistant prostate cancer regulatory genes UBE2C, CDC20, and CDK1. In silico analysis of BCH-downregulated genes showed that 90.9% are statistically significantly upregulated in metastatic castration-resistant prostate cancer. Finally, LAT1 or LAT3 knockdown in xenografts inhibited tumor growth, cell cycle progression, and spontaneous metastasis in vivo. Inhibition of LAT transporters may provide a novel therapeutic target in metastatic castration-resistant prostate cancer, via suppression of mammalian target of rapamycin complex 1 activity and M-phase cell cycle genes.

Targeting the androgen receptor with siRNA promotes prostate cancer metastasis through enhanced macrophage recruitment via CCL2/CCR2‐induced STAT3 activation

Increased CCL2 expression in prostate cancer (PCa) cells enhanced metastasis via macrophage recruitment. However, its linkage to androgen receptor (AR)-mediated PCa progression remains unclear. Here, we identified a previously unrecognized regulation: targeting AR with siRNA in PCa cells increased macrophage recruitment via CCL2 up-regulation, which might then result in enhancing PCa invasiveness. Molecular mechanism dissection revealed that targeting PCa AR with siRNA promoted PCa cell migration/invasion via CCL2-dependent STAT3 activation and epithelial–mesenchymal transition (EMT) pathways. Importantly, pharmacologic interruption of the CCL2/CCR2-STAT3 axis suppressed EMT and PCa cell migration, providing a new mechanism linking CCL2 and EMT. Simultaneously targeting PCa AR with siRNA and the CCL2/CCR2-STAT3 axis resulted in better suppression of PCa growth and metastasis in a xenograft PCa mouse model. Human PCa tissue microarray analysis suggests that increased CCL2 expression may be potentially associated with poor prognosis of PCa patients. Together, these results may provide a novel therapeutic approach to better battle PCa progression and metastasis at the castration resistant stage via the combination of targeting AR with siRNA and anti-CCL2/CCR2-STAT3 signalling.