Cultured Prostate Cancer Cells Research Articles

A Marine Collagen-Based 3D Scaffold for In Vitro Modeling of Human Prostate Cancer Niche and Anti-Cancer Therapeutic Discovery.

Recently, the need to develop a robust three-dimensional (3D) cell culture system that serves as a valuable in vitro tumor model has been emphasized. This system should closely mimic the tumor growth behaviors observed in vivo and replicate the key elements and characteristics of human tumors for the effective discovery and development of anti-tumor therapeutics. Therefore, in this study, we developed an effective 3D in vitro model of human prostate cancer (PC) using a marine collagen-based biomimetic 3D scaffold. The model displayed distinctive molecular profiles and cellular properties compared with those of the 2D PC cell culture. This was evidenced by (1) increased cell proliferation, migration, invasion, colony formation, and chemoresistance; (2) upregulated expression of crucial multidrug-resistance- and cancer-stemness-related genes; (3) heightened expression of key molecules associated with malignant progressions, such as epithelial-mesenchymal transition transcription factors, Notch, matrix metalloproteinases, and pluripotency biomarkers; (4) robust enrichment of prostate cancer stem cells (CSCs); and (5) enhanced expression of integrins. These results suggest that our 3D in vitro PC model has the potential to serve as a research platform for studying PC and prostate CSC biology, as well as for screening novel therapies targeting PC and prostate CSCs.

Androgen deprivation induces neuroendocrine phenotypes in prostate cancer cells through CREB1/EZH2-mediated downregulation of REST.

Although effective initially, prolonged androgen deprivation therapy (ADT) promotes neuroendocrine differentiation (NED) and prostate cancer (PCa) progression. It is incompletely understood how ADT transcriptionally induces NE genes in PCa cells. CREB1 and REST are known to positively and negatively regulate neuronal gene expression in the brain, respectively. No direct link between these two master neuronal regulators has been elucidated in the NED of PCa. We show that REST mRNA is downregulated in NEPC cell and mouse models, as well as in patient samples. Phenotypically, REST overexpression increases ADT sensitivity, represses NE genes, inhibits colony formation in culture, and xenograft tumor growth of PCa cells. As expected, ADT downregulates REST in PCa cells in culture and in mouse xenografts. Interestingly, CREB1 signaling represses REST expression. In studying the largely unclear mechanism underlying transcriptional repression of REST by ADT, we found that REST is a direct target of EZH2 epigenetic repression. Finally, genetic rescue experiments demonstrated that ADT induces NED through EZH2's repression of REST, which is enhanced by ADT-activated CREB1 signaling. In summary, our study has revealed a key pathway underlying NE gene upregulation by ADT, as well as established novel relationships between CREB1 and REST, and between EZH2 and REST, which may also have implications in other cancer types and in neurobiology.

An Extracellular Matrix Overlay Model for Bioluminescence Microscopy to Measure Single-Cell Heterogeneous Responses to Antiandrogens in Prostate Cancer Cells.

Prostate cancer (PCa) displays diverse intra-tumoral traits, impacting its progression and treatment outcomes. This study aimed to refine PCa cell culture conditions for dynamic monitoring of androgen receptor (AR) activity at the single-cell level. We introduced an extracellular matrix-Matrigel (ECM-M) culture model, enhancing cellular tracking during bioluminescence single-cell imaging while improving cell viability. ECM-M notably tripled the traceability of poorly adherent PCa cells, facilitating robust single-cell tracking, without impeding substrate permeability or AR response. This model effectively monitored AR modulation by antiandrogens across various PCa cell lines. Single-cell imaging unveiled heterogeneous antiandrogen responses within populations, correlating non-responsive cell proportions with drug IC50 values. Integrating ECM-M culture with the PSEBC-TSTA biosensor enabled precise characterization of ARi responsiveness within diverse cell populations. Our ECM-M model stands as a promising tool to assess heterogeneous single-cell treatment responses in cancer, offering insights to link drug responses to intracellular signaling dynamics. This approach enhances our comprehension of the nuanced and dynamic nature of PCa treatment responses.

Abstract 388: Identifying synthetic lethalities in GCN2 KO tumors using an in vivo targeted CRISPRi screen

Abstract The integrated stress response (ISR) is an intracellular signaling pathway that fosters cell adaptation to diverse stresses. The ISR is mediated by a family of four eIF2 kinases that each sense distinct cellular stresses. Activation of the eIF2 kinases results in reprogrammed gene expression through translational and transcriptional mechanisms that help prevent stress damage. Previously, we reported that prostate cancer (PCa) cells rely on GCN2 eIF2 kinase for maintenance of amino acid (AA) homeostasis to sustain growth (Cordova et al., 2022 eLife 11:e81083). GCN2 inhibition through pharmacological or genetic means results in decreased expression of AA transporters, depletion of intracellular AAs, and reduced growth of PCa cells in culture and mouse xenograft models. Although loss of GCN2 results in a significant reduction in PCa cell growth, minimal cell death is observed. We hypothesize that loss of GCN2 in PCa cells results in vulnerabilities that can be exploited and targeted to induce cell death. To optimize GCN2-targeted therapies for PCa, we utilized a targeted CRISPR-interference (CRISPRi) screen in castration-resistant 22Rv1 cells with functional wild type (WT) GCN2 or those with it deleted (GCN2 KO). The CRISPRi screen was performed in cells grown in culture or grown as tumor xenografts in mice and featured a guide library targeting genes that encode druggable targets, including kinases, phosphatases, and metabolic enzymes. While reduced expression of 152 genes was synthetically lethal with loss of GCN2 in the in vitro screen, more genes (202) were synthetically lethal with loss of GCN2 in vivo. Of note, reduced expression of many metabolic enzymes was synthetically lethal with GCN2 ablation only in the in vivo screen, potentially due to the abundance of nutrients in standard culture media. A group of six metabolism-related genes, identified as hits in the in vivo screen and targets of FDA-approved drugs, were selected for follow-up studies. One of these metabolic enzymes was GART, a trifunctional enzyme that carries out 3 of the 10 enzymatic steps in de novo purine biosynthesis. Based on our findings showing that GCN2 maintains AA levels to support nucleotide pools in PCa cells, we initially focused on this critical enzyme. Inhibition of GART using antifolates, including the FDA-approved Pemetrexed, resulted in minimal cell death of parental and GCN2 KO PCa cells cultured in standard culture media. However, when cultured in reduced nutrient media that better mimicked reduced nutrient availability in vivo, GART inhibition resulted in selective death of GCN2 KO cells. Our CRISPRi screening strategy uncovers new vulnerabilities in GCN2-inhibited PCa cells and reveals a general strategy to identify actionable targets with the potential to combine with GCN2 inhibitors for the treatment of PCa. Citation Format: Noah R. Sommers, Ricardo A. Cordova, Angela J. Klunk, Ronald C. Wek, Kirk A. Staschke. Identifying synthetic lethalities in GCN2 KO tumors using an in vivo targeted CRISPRi screen [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 388.

Ligand-gated ion channels as potential biomarkers for ADT-mediated cognitive decline in prostate cancer patients.

Men with prostate cancer are at increased risk of developing cognitive decline by the use of second-generation androgen signaling inhibitors. To date, reliable and sensitive biomarkers that could distinguish men at high risk of cognitive dysfunction under androgen deprivation therapy (ADT) have not been characterized. We used high-throughput transcriptional profiling utilizing human prostate cancer cell culture models mimicking ADT, biomarker selection using minimal common oncology data elements-cytoscape, and bioinformatic analyses employing Advaita® iPathwayGuide and DisGeNET for identification of disease-related gene associations. Validation analysis of genes was performed on brain neuronal and glial cells by quantitative real-time polymerase chain reaction assay. Our systematic analysis of androgen deprivation-associated genes involved multiple biological processes, including neuroactive ligand-receptor interaction, axon guidance, cytokine-cytokine receptor interaction, and metabolic and cancer signaling pathways. Genes associated with neuroreceptor ligand interaction, including gamma-aminobutyric acid (GABA) A and B receptors and nuclear core proteins, were identified as top upstream regulators. Functional enrichment and protein-protein interaction network analysis highlighted the role of ligand-gated ion channels (LGICs) and their receptors in cognitive dysfunction. Gene-disease association assigned forgetfulness, intellectual disability, visuospatial deficit, bipolar disorder, and other neurocognitive impairment with upregulation of type-1 angiotensin II receptor, brain-derived neurotrophic factor, GABA type B receptor subunit 2 (GABBR2), GABRA3, GABRA5, GABRB1, glycine receptor beta, glutamate ionotropic receptor N-methyl-D-aspartate receptor (NMDA) type subunit 1, glutamate ionotropic receptor NMDA type subunit 2D, 5-hydroxytryptamine receptor 1D, interferon beta 1, and nuclear receptor subfamily 3 group C member 1 as top differentially expressed genes. Validation studies of brain glial cells, neurons, and patients on ADT demonstrated the association of these genes with cognitive decline. Our findings highlight LGICs as potential biomarkers for ADT-mediated cognitive decline. Further validation of these biomarkers may lead to future practical clinical use.

Alpha-santalol, a derivative of sandalwood oil prevents development of prostate cancer in TRAMP mice

BackgroundAlpha-santalol, a major component of sandalwood oil inhibits growth of cultured prostate cancer cells in vitro by causing apoptosis. However, its in vivo efficacy against prostate cancer development is not established. Hypothesis/purposeProstate cancer is one of the most commonly diagnosed cancers in men. The present study was undertaken to determine the in vivo efficacy of alpha-santalol using TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice as a model. MethodsTRAMP mice were used for the in vivo studies. Immunohistochemical analysis was used to assess prostate/tumor sections and Ki-67 staining. Western blot analysis was used to determine expression of various proteins. TUNEL assay was used to detect apoptotic bodies. ResultsAdministration of alpha-santalol (100 mg/kg body weight) decreased the incidence of prostate tumors, average wet weights of urogenital organs and prostate weight compared to control mice. In addition, the area occupied by normal prostate was significantly higher, along with poorly differentiated carcinoma that was significantly lower in the dorsolateral prostate sections of alpha-santalol-treated mice compared with the controls. Furthermore, the dorsolateral sections of prostate from alpha-santalol-treated mice exhibited decreased cell proliferation (Ki-67 staining) in association with induction of apoptosis (TUNEL-positive cells). In agreement with immunohistochemical analysis, Western blotting analysis of prostate/tumor samples from alpha-santalol-treated group revealed a decrease in survivin, XIAP, PCNA, cyclin D and CDC2 levels compared to control samples. ConclusionThe present study shows for the first time, that alpha-santalol administration inhibits the development of prostate cancer in TRAMP mice by decreasing cell proliferation and inducing apoptosis, and warrants future studies for its clinical development.

Targeted inhibition of mTOR by BML-275 induces mitochondrial-mediated apoptosis and autophagy in prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed cancer among men and the second leading cause of death in Western countries. Clinically, screening drugs and develop developing new therapeutics to treat PCa is of great significance. In this study, BML-275 was demonstrated to exert potent antitumor effects in PCa by antagonizing mTOR activity. In cultured PCa cells, BML-275 treatment reduced the expression levels of c-Myc and survivin, promoted the activation of p53, and thereby induced p21/cyclin D1/CDK4/6-dependent cell cycle G1/S arrest. As a result, BML-275 inhibited cellular proliferation and induced mitochondrial-mediated apoptosis. In addition, BML-275 treatment triggered autophagy. Interestingly, EACC-mediated suppression of autophagy did not affect BML-275-induced proliferation and apoptosis. Nude mouse tumorigenic experiments also confirmed that BML-275 inhibited PCa growth, induced PCa cell apoptosis and autophagy. Mechanistically, the activities of PI3K/AKT and AMPK pathways were downregulated by BML-275 treatment in vitro and in vivo. Importantly, mTOR, a common downstream negative protein of PI3K/AKT and AMPK signaling, was induced to inactivate, which may be associated with the induction of apoptosis and autophagy. The pharmacological activation of mTOR by MHY1485 abolished the induction of apoptosis and autophagy of BML-275. Molecular docking results showed that BML-275 can bind to the FKRP12-rapamycin binding site on mTOR protein, and thereby may have the same inhibitory activity on mTOR as rapamycin. Thus, these findings indicated that BML-275 induces mitochondrial-mediated apoptosis and autophagy in PCa by targeting mTOR inhibition. BML-275 may be a potential candidate for the treatment of PCa.

Complementary analysis of proteome-wide proteomics reveals changes in RNA binding protein-profiles during prostate cancer progression.

Accumulating evidence indicates importance of RNA regulation in cancer. This includes events such as splicing, translation, and regulation of noncoding RNAs, functions which are governed by RNA binding proteins (RBPs). To find which RBPs could be relevant for prostate cancer, we performed systematic screening of RBP expression in clinical prostate cancer. We interrogated four proteome-wide proteomics datasets including tumor samples of primary, castration resistant, and metastatic prostate cancer. We found that, while the majority of RBPs are expressed but not significantly altered during prostate cancer development and progression, expression of several RBPs increases in advanced disease. Interestingly, most of the differentially expressed RBPs are not targets of differential posttranscriptional phosphorylation during disease progression. The RBPs undergoing expression changes have functions in, especially, poly(A)-RNA binding, nucleocytoplasmic transport, and cellular stress responses, suggesting that these may play a role in formation of castration resistance. Pathway analyzes indicate that increased ribosome production and chromatin-related functions of RBPs are also linked to castration resistant and metastatic prostate cancers. We selected a group of differentially expressed RBPs and studied their role in cultured prostate cancer cells. With siRNA screens, several of these were indicated in survival (DDX6, EIF4A3, PABPN1), growth (e.g., EIF5A, HNRNPH2, LRRC47, and NVL), and migration (e.g., NOL3 and SLTM) of prostate cancer cells. Our analyzes further show that RRP9, a U3 small nucleolar protein essential for ribosome formation, undergoes changes at protein level during metastasis in prostate cancer. In this work, we recognized significant molecular alterations in RBP profiles during development and evolution of prostate cancer. Our study further indicates several functionally significant RBPs warranting further investigation for their functions and possible targetability in prostate cancer.

Abstract B072: Induction of PARP7 creates a vulnerability for growth inhibition by RBN2397 in prostate cancer cells

Abstract The ADP-ribosyltransferase PARP7 modulates protein function by conjugating ADP-ribose to the side chains of acceptor amino acids. PARP7 has been shown to affect gene expression in prostate cancer cells and certain other cell types by mechanisms that include transcription factor ADP-ribosylation. Here, we use a recently developed catalytic inhibitor to PARP7, RBN2397 (NCT04053673), to study the effects of PARP7 inhibition in androgen receptor-positive (AR+) and androgen receptor-negative (AR-) prostate cancer cells. Ribon Therapeutics developed RBN2397 as a first-in-class mono-ADP-ribosyltransferase inhibitor, and showed that it blocks PARP7 negative regulation of TBK1 [1]. We find that RBN2397 has nanomolar potency for inhibiting androgen-induced ADP-ribosylation of the androgen receptor. RBN2397 inhibits the growth of prostate cancer cells in culture when cells are treated with ligands that activate the androgen receptor (PC3-AR, VCaP, CWR22Rv1), or the aryl hydrocarbon receptor (PC3, DU145, NCI-H660), and induce PARP7 expression. We show that the growth inhibitory effects of RBN2397 are distinct from its enhancement of interferon signaling recently shown to promote tumor immunogenicity in lung cancer models [1]. Chemical inhibitors to PARP1 exert effects on cells by blocking enzyme function, but also via cytotoxic effects attributed to stabilizing PARP1-chromatin interactions in a process termed trapping [2]. Drug-induced trapping of PARP1 can be detected biochemically by immunoblotting the detergent-resistant chromatin fraction. We found that RBN2397 treatment of AR+ and AR- prostate cancer cells induces biochemical trapping of PARP7 within the nucleus, which was also detected by confocal microscopy. Potential therapeutic benefits of RBN2397 are likely to depend on the level of PARP7 expression, given its induction is necessary for growth inhibitory effects of RBN2397 in cell culture. As a first step towards evaluating whether PARP7 levels in human prostate cancer may be actionable with RBN2397, we used computational methods to analyze PARP7 gene expression data from primary prostate tumors and metastatic AR+ and AR- prostate tumors. To assess PARP7 mRNA levels, we used data from the online resource recount3, which uniformly reprocesses publicly available RNA-seq datasets using a Monorail analysis pipeline. Using the level of PARP7 expression in VCaP cells that confers sensitivity to RBN2397 as a threshold, 50% of primary tumors, 41% of metastatic AR- and 11% of AR+ tumors are predicted to have PARP7 expression levels that are sufficient for a response to RBN2397. Because RBN2397 can inhibit the growth of castration-resistant and neuroendocrine prostate cancer cells, PARP7 may be an actionable target in advanced prostate cancer. 1. Gozgit, J.M., et al., PARP7 negatively regulates the Type I interferon response in cancer cells and its inhibition triggers antitumor immunity. Cancer Cell, 2021. 39(9): p. 1214-1226 e10 2. Murai, J., et al., Trapping of PARP1 and PARP2 by Clinical PARP Inhibitors. Cancer Res, 2012. 72(21): p. 5588-99. Citation Format: Chunsong Yang, Krzysztof Wierbilowicz, Natalia M. Dworak, Song Yi Bae, Sachi B. Tengse, Nicki Abianeh, Justin M. Drake, Tarek Abbas, Aakrosh Ratan, David Wotton, Bryce M. Paschal. Induction of PARP7 creates a vulnerability for growth inhibition by RBN2397 in prostate cancer cells [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 B072.

Development and initial clinical testing of a multiplex assay evaluating histone modifier p300 acetylation in prostate cancer circulating tumor cells.

e17020 Background: Histone modifying enzymes (HMEs) hold promise as targets for drug discovery in cancer. Histone acetyltransferases and histone deacetylases dictate the presence of acetyl marks, which regulate chromatin and transcriptional activation. We previously developed a novel ‘histone array on a chip’ to measure HME dysregulation associated with the development of castration resistant prostate cancer (CRPC) (ACS Chem Biol 2017). This approach identified decreased SIRT2 expression and increased p300 activity leads to a concerted mechanism of hyperacetylation at specific histone lysine sites (H3K9, H3K14, and H3K18) in CRPC xenografts. These alterations were subsequently validated in castration-resistant tissues (BMC Cancer 2017). The goal of the current study was to determine if circulating tumor cells (CTCs) could be used as a therapeutic biomarker to identify patients with altered p300 acetylation activity. Methods: Blood was collected from 11 CRPC and 3 hormone-sensitive patients with advanced PC under an IRB-approved protocol. PBMCs were isolated with Ficoll-paque PLUS, and lymphocytes were depleted using anti-CD45 magnetic beads. CTCs were then captured with EpCAM labeled coated magnetic beads. Bound cells were isolated with Exclusion-based Sample Preparation (ESP) technology. Bound cells were moved through staining and washing wells prior to imaging at 20x on a fluorescent microscope. Images were analyzed with NIS Elements software. Results: We initially optimized the staining of acetyl-p300, total p300, H3K18ac, and SIRT2 in single cell prostate cancer cell cultures. Exposure to A-485, a selective p300/CBP catalytic inhibitor, reduced levels of p300 and H3K18 acetylation confirming assay specificity. CTCs from patient samples were then captured by EpCAM antibody binding and target staining revealed clear expression of acetyl-p300, acetyl-H3K18, SIRT2, and CK (cytokeratin). No expression of CD45+ cells (lymphocyte exclusion) is noted. Acetyl-p300 displayed a strong positive correlation with its target acetylated H3k18 (Pearson’s r = 0.61), and SIRT2 expression showed robust negative correlation with H3k18 (r = -0.60). A distinct group of 6/11 (55%) of CRPC patients demonstrated altered expression. In one subject with an untreated CSPC sample and subsequent CRPC sample ( > 12mo) a loss of SIRT2 expression, increased p300 activity, and histone H3 hyperacetylation are associated with the transition from hormone-sensitive to CRPC. Conclusions: Acetyl-p300, H3K18ac, and SIRT2 increase in a subset of CTC from patients with CRPC. These biomarkers are associated with increased CBP/p300 activity. This biomarker suite could potentially be used for noninvasive monitoring of outcomes and predicting tumor responses to CBP/p300 acetylation inhibitors in clinical development.

Chemical composition and antiproliferative activity on prostate and cervical cancer cell lines of Lantana camara Linn. essential oil

Lantana camara (LC) is an aromatic plant used in traditional medicine in Burkina Faso in association with other plants for the management of many microbial and inflammatory pathologies. The objective of this study was to determine the chemical composition, the antioxidant and antitumor activities on prostate and cervical cancer cells in culture of the essential oil (EO) of this plant. The chemical composition of Lantana camara EO was determined by Gas Chromatography with Flame-Ionization Detection (GC-FID) and Gas Chromatography–Mass spectrometry (GC-MS) analysis and the antiproliferative activity was evaluated through the 3[4.5-dimethylthiazol-2-yl]-diphenyltetrazolium bromide (MTT) test assay. A total of 48 compounds have been identified in the essential oil of Lantana camara of which cabinene, beta-caryophyllene, eucalyptol and alpha-humulene are found to be the majority. However, 4 compounds, unknown in the literature, present in this essential oil have not been identified. Lantana camara essential oil inhibits both the proliferation of HeLa cells from cervical cancer and LNCaP (Lymph Node Carcinoma of the Prostate) cells from prostate cancer. Beyond constituting the scientific basis for the use of Lantana camara in traditional medicine through its antiproliferative effect. These results require further study by determining the nature of its unidentified compounds and its mechanism of molecular action on these two cancer cell lines in vitro.

Abstract 4816: Targeting GCN2 regulation of amino acid homeostasis sensitizes prostate cancer cells to senolytic therapies

Abstract The integrated stress response (ISR) features a family of eIF2 kinases that sense cellular stress, triggering translational and transcriptional modes of gene expression that enhance cell adaptation to the underlying stress. Previously we reported (Cordova et al., 2022 eLife) that prostate cancer (PCa) cells rely on one of these eIF2 kinases, GCN2, for maintenance of amino acid homeostasis and sustained proliferation. GCN2 functions to enhance expression of amino acid transporters and subsequent import of essential amino acids (EAAs) that are necessary to sustain PCa growth. Genetic loss or pharmacological inhibition of GCN2 results in decreased expression of amino acid transporters, severe depletion of intracellular EAAs, and decreased proliferation of PCa cells in culture and mouse xenograft models. Although loss of GCN2 in PCa cells reduces proliferation, depletion of this eIF2 kinase is suggested to lead to cell stasis and modest cell death. We hypothesize that the static phenotype by GCN2 inhibition in PCa cells renders these cells vulnerable to senolytic treatment and is a potential therapeutic target in combination therapies. To address this idea, we utilized models of androgen-sensitive and castration-resistant PCa and non-tumorigenic prostate epithelial cells. GCN2 inhibition induced a static phenotype in PCa cell lines, but not non-tumorigenic prostate epithelial cells, and this was accompanied by increased expression of the senescent markers p53, p21, p27, and MCL-1. Furthermore, induction of senescent markers following GCN2 inhibition in PCa cells was reversed by supplementation with EAAs, suggesting that limitation of EAAs is critical to the induction of cell stasis. Of importance, treatment of PCa cells with Navitoclax, a senolytic agent that targets Bcl-2 family of anti-apoptotic proteins, in combination with GCN2 inhibition resulted in enhanced cell death and apoptosis compared to each single treatment alone. Our results suggest that GCN2 inhibition in PCa cells leads to depletion of EAAs and induction of a static phenotype, rendering these cells vulnerable to targeting the Bcl-2 family of proteins to expedite cell death. As such, therapies integrating GCN2 inhibition and senolytic agents are proposed to be effective strategies for treatment of PCa. Citation Format: Noah R. Sommers, Ricardo A. Cordova, Angela J. Klunk, Roberto Pili, Ronald C. Wek, Kirk A. Staschke. Targeting GCN2 regulation of amino acid homeostasis sensitizes prostate cancer cells to senolytic therapies. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4816.

Abstract 4818: GCN2 eIF2 kinase and p53 coordinate amino acid homeostasis and metabolism in prostate cancer

Abstract Activation of the integrated stress response (ISR) contributes to the progression of many cancers, including prostate cancer (PCa). The ISR features a family of protein kinases that phosphorylate the eukaryotic translation initiation factor 2 (eIF2) during different stress conditions, resulting in repression of global protein synthesis. In parallel, eIF2 phosphorylation also enhances the translation of select gene transcripts, such as ATF4, which directs the transcription of ISR-target genes that are critical for cancer stress adaptation. We recently reported (Cordova et al., 2022 eLife) that the eIF2 kinase GCN2 is a driver of the ISR in PCa and is critical for the maintenance of essential amino acid (EAA) homeostasis. GCN2 is activated in PCa due to EAA limitations, resulting in increased expression of key amino acid transporters which provide for nutrient import to facilitate protein synthesis and metabolism that drive PCa proliferation. Genetic loss or pharmacological inhibition of GCN2 results in lowered expression of amino acid transporters, leading to severe depletion of intracellular essential amino acids and reduced proliferation in PCa cell lines and xenograft models. These results support the therapeutic potential of targeting GCN2 in PCa.We recently determined that loss of GCN2 in PCa triggers a G1 nutrient-sensitive cell cycle checkpoint that is dependent on p53 and its target gene CDKN1A, encoding p21 inhibitor of cell cycle. Induced G1 arrest and p53/p21 signaling by GCN2 inhibition is reversed by supplementation with EAAs, suggesting amino acid limitation is critical for activation of p53. Metabolic stresses, such as amino acid starvation, have been suggested to activate p53 in different cancers and p53 regulates metabolic pathways that are critical for cancer cells adaptation to stresses. We also showed that depletion of specific amino acids activates GCN2 and p53 in cultured PCa cells. Using transcriptomic and metabolomic analyses, we determined that loss of GCN2 or p53 in PCa cells impacted multiple metabolic pathways, specifically those involved in amino acid and nucleotide metabolism, supporting the importance of GCN2 and p53 in metabolic homeostasis. In addition, deletion of p53 in PCa cells exacerbates the activation of GCN2 and the ISR, suggesting that loss of p53 results in amino acid imbalances that further activate GCN2. Importantly, inhibition of GCN2 in combination with loss of p53 resulted in increased cell death and apoptosis in PCa. Our study suggests that GCN2 and p53 can be activated in parallel in PCa and these stress response pathways are crucial for PCa cells to maintain homeostasis and adapt to metabolic stress. We propose that GCN2 and p53 function to coordinate PCa growth and progression by regulating metabolism and cell cycle control. Targeting these stress pathways in combination may provide enhanced efficacy for the treatment of PCa. Citation Format: Ricardo A. Cordova, Noah R. Sommers, Angela J. Klunk, Haroon M. Mohiuddin, Roberto Pili, Ronald C. Wek, Kirk A. Staschke. GCN2 eIF2 kinase and p53 coordinate amino acid homeostasis and metabolism in prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4818.

Receptor for Hyaluronic Acid-mediated Motility (RHAMM) Is Associated With Prostate Cancer Migration and Poor Prognosis.

Hyaluronic acid (HA) is a large glycosaminoglycan composed of an extracellular matrix. The HA-rich microenvironment and receptors of HA have been suggested to play roles in cancer progression. The biological and clinical significance of receptor for HA-mediated motility (RHAMM), known as CD168 in prostate cancer (PC) remains unknown. This study aimed to investigate the expression of RHAMM, as well as its functional and clinical relevance in PC. HA concentration and RHAMM mRNA expression were examined in 3 PC cell lines (LNCaP, PC3 and DU145). We investigated the effect of HA and RHAMM on the migratory ability of PC cells using a transwell migration assay. Immunohistochemistry was also used to evaluate the RHAMM expression pattern in pre-treatment tissue samples from 99 patients with metastatic hormone-sensitive PC (HSPC) who received androgen deprivation therapy (ADT). HA was secreted in all cultured PC cell lines. Among the total HA, low-molecular-weight HA (LMW-HA) (<100 kDa) was detected all examined cell lines. The number of migration cells was significantly increased by adding LMW-HA. RHAMM mRNA expression was increased in DU145 cells. Knockdown of RHAMM using small-interfering RNA resulted in decreased cell migration. Immunohistochemical analysis revealed strong RHAMM expression in 31 (31.3%) patients with metastatic HSPC. A strong RHAMM expression was significantly associated with short ADT duration and poor survival in univariate and multivariate analyses. The size of HA is important in terms of PC progression. LMW-HA and RHAMM enhanced PC cell migration. RHAMM could be used as a novel prognostic marker in patients with metastatic HSPC.

Co-Targeting ErbB Receptors and the PI3K/AKT Axis in Androgen-Independent Taxane-Sensitive and Taxane-Resistant Human Prostate Cancer Cells.

Simple SummaryAdvanced prostate cancer that has progressed after standard therapies such as hormone therapy and taxane-based chemotherapies is an invariably lethal disease state with limited treatment options. There remains an important need to continue to identify new treatment approaches for such patients. We used two cell culture models of prostate cancer that are resistant to hormonal therapy and chemotherapy, and which also manifest some characteristics that are often associated with advanced prostate cancer, such as neuroendocrine differentiation, to evaluate the potential anti-cancer effects of targeting the key molecules, ErbB receptors and AKT. Using several complementary approaches, we found that the concurrent targeting of ErbB receptors and AKT with specific inhibitors was more effective than targeting each of them individually, independent of the underlying molecular characteristics or relative degrees of resistance to the taxanes that defined the prostate cancer models that were studied. Enhanced anti-tumor responses occurred both in vitro and in vivo with dual targeting, with the consistent inhibition particularly of AKT occurring in both settings. These studies provide a framework to evaluate the role of signal pathway modulation as a potential therapeutic strategy in treatment-refractory prostate cancer.Using two representative models of androgen-independent prostate cancer (PCa), PC3 and DU145, and their respective paclitaxel- and docetaxel-resistant derivatives, we explored the anti-tumor activity of targeting the ErbB receptors and AKT using small-molecule kinase inhibitors. These cells manifest varying degrees of neuroendocrine differentiation characteristics and differ in their expression of functional PTEN. Although the specific downstream signaling events post the ErbB receptor and AKT co-targeting varied between the PC3- and DU145-lineage cells, synergistic anti-proliferative and enhanced pro-apoptotic responses occurred across the wild-type and the taxane-resistant cells, independent of their basal AKT activation state, their degree of paclitaxel- or docetaxel-resistance, or whether this resistance was mediated by the ATP Binding Cassette transport proteins. Dual targeting also led to enhanced anti-tumor responses in vivo, although there was pharmacodynamic discordance between the PCa cells in culture versus the tumor xenografts in terms of the relative activation and inhibition states of AKT and ERK under basal conditions and upon AKT and/or ErbB targeting. The consistent inhibition, particularly of AKT, occurred both in vitro and in vivo, independent of the underlying PTEN status. Thus, co-targeting AKT with ErbB, and possibly other partners, may be a useful strategy to explore further for potential therapeutic effect in advanced PCa.

YAP1-TEAD1 mediates the perineural invasion of prostate cancer cells induced by cancer-associated fibroblasts

Perineural invasion (PNI) driven by the tumor microenvironment (TME) has emerged as a key pattern of metastasis of prostate cancer (PCa), while its underlying mechanism is still elusive. Here, we identified increased CAFs and YAP1 expression levels in patients with metastatic PCa. In the cultured PCa cell line LNCaP, co-culture with cancer-associated fibroblasts (CAFs) could upregulate YAP1 protein expression. Either ectopic overexpression of YAP1 or co-culture with CAFs could promote the infiltration of LNCaPs towards dorsal root ganglia (DRG). This effect could be blocked using an YAP1 inhibitor. In vivo, overexpression of YAP1 could increase PNI in a mouse model of sciatic nerve tumor invasion. Mechanistically, TEAD1 binds to the NGF promotor and YAP1/TEAD1 activates its transcription and consequently increases NGF secretion. In turn, PCa cells treated with CM from CAFs or stable YAP1 overexpression can stimulate DRG to secrete CCL2. The epithelial-to-mesenchymal transition (EMT) of PCa cells is thus activated via CCL2/CCR2. Overall, our data demonstrate that CAFs can activate YAP1/TEAD1 signaling and increase the secretion of NGF, therefore promoting PCa PNI. In addition, EMT induced by PNI suggests a feedback loop is present between neurons and PCa cells.

Spindle pole body component 25 and platelet-derived growth factor mediate crosstalk between tumor-associated macrophages and prostate cancer cells.

Tumor-associated macrophages (TAMs) are involved in the growth of prostate cancer (PrC), while the molecular mechanisms underlying the interactive crosstalk between TAM and PrC cells remain largely unknown. Platelet-derived growth factor (PDGF) is known to promote mesenchymal stromal cell chemotaxis to the tumor microenvironment. Recently, activation of spindle pole body component 25 (SPC25) has been shown to promote PrC cell proliferation and is associated with PrC stemness. Here, the relationship between SPC25 and PDGF in the crosstalk between TAM and PrC was investigated. Significant increases in both PDGF and SPC25 levels were detected in PrC specimens compared to paired adjacent normal prostate tissues. A significant correlation was detected between PDGF and SPC25 levels in PrC specimens and cell lines. SPC25 increased PDGF production and tumor cell growth in cultured PrC cells and in xenotransplantation. Mechanistically, SPC25 appeared to activate PDGF in PrC likely through Early Growth Response 1 (Egr1), while the secreted PDGF signaled to TAM through PDGFR on macrophages and polarized macrophages, which, in turn, induced the growth of PrC cells likely through their production and secretion of transforming growth factor β1 (TGFβ1). Thus, our data suggest that SPC25 triggers the crosstalk between TAM and PrC cells via SPC25/PDGF/PDGFR/TGFβ1 receptor signaling to enhance PrC growth.

USE OF KNOTTIN AS A PSMA-TROPIC PEPTIDE CARRIER

Prostate cancer is the most common type of cancer in males. Approximately 1.3 million cases of prostate cancer and over 400,000 deaths from the disease are diagnosed annually. The number of deaths is expected to double by 2040. Common methods of prostate cancer treatment have many disadvantages; one of them is the relapse risk. The shortcomings of traditional therapy have led to peptide-receptor radionuclide therapy.&#x0D; The aim of the study is to examine binding efficiency of Lu177 labeled knottins containing PSMA-tropic peptide in different domains in vitro and their biodistribution in vivo.&#x0D; Materials and Methods. We used prostate cancer cell (LNCaP, PC3) and ovarian fibroblast cell (CHO-K1) cultures. The peptides were synthesized using a peptide synthesizer (ResPepSL, Intavis).&#x0D; We studied peptide stability, their toxicity, binding to cell cultures, and biodistribution on the example of breast adenocarcinoma-bearing BALB/c mice. Chromatographic methods and radiometric techniques &#x0D; were used.&#x0D; Results. The synthesized peptides with GTIQPYPFSWGY sequence inserted into U5-cytotoxin-Sth1a node are more stable in blood plasma and saline than 177Lu-PSMA-617a, but have a similar degree of binding. Biodistribution studies in BALB/c mice show a higher binding index of the synthesized peptide if compared to 177Lu-PSMA-617.&#x0D; Conclusion. Modified peptides with a PSMA-tropic peptide inserted into the structure of U5-Sth1a toxin demonstrate high stability both in saline and in blood plasma, as well as good binding to cell cultures and tumors.

Abstract 1471: Over-expression of WW domain containing transcription regulator 1 (TAZ/WWTR1) in prostate cancer and its modulation by prostate-derived ETS factor (PDEF)

Abstract Objective: WW domain containing transcription regulator 1 (TAZ/WWTR1), one of the two downstream effectors of the Hippo pathway, is known to regulate cancer cell proliferation, migration and apoptosis by acting as a transcriptional co-activator. Recently, we described altered expression of yes-associated protein (YAP1) (a paralog of TAZ) in prostate cancer. However, the expression and function of TAZ and its regulation in prostate cancer is not well characterized. In the present study, we profiled expression patterns of TAZ in clinical data sets of PCa and evaluated the effects of PDEF on TAZ phosphorylation in prostate cancer (PCa) cells in culture. Material &amp; Method: We analyzed the publicly available PCa datasets through Ualcan and c-Bioportal webservers. We transfected prostate cancer PC3 cells with PDEF or respective vector control. Protein levels of TAZ were analyzed by western blotting. Global changes in gene expression were analyzed using Affymetrix arrays followed by Gene Set Enrichment analysis. Results: Our analysis of publicly available PCa patient data in TCGA dataset, revealed a significant increase in TAZ mRNA levels in prostate cancer tissues as compared to normal prostate tissues (p=4.95E-08). Furthermore, we also found a significant gradual increase in TAZ mRNA expression during disease progression and metastasis. Our analysis of data sets in c-Bio portal revealed that patients with neuroendocrine PCa harbor much higher levels of TAZ mRNA as compared to CRPC phenotype. We also observed a negative correlation between PDEF and TAZ expression in CRPC/NEPC data set. We observed that the PC3 cells transfected with PDEF (PDEF-PC3) showed an increased phospho-TAZ as compared to the respective PC3 vector control (VC-PC3) suggesting that PDEF plays a critical role in modulating TAZ activity an important effector in Hippo signaling. Conclusions: These results provide first direct demonstration of elevated expression of TAZ in PCa, suggesting potential role of TAZ in prostate cancer. We also show for the first time increased TAZ phosphorylation in PCa cells by PDEF. Taken together with our recent work, our data suggest that PDEF modulates Hippo signaling by targeting both YAP1 and TAZ in PCa. Citation Format: Praveen K. Jaiswal, Suman Mohajan, Sweaty Koul, Hari K. Koul. Over-expression of WW domain containing transcription regulator 1 (TAZ/WWTR1) in prostate cancer and its modulation by prostate-derived ETS factor (PDEF) [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 1471.

Effect of berberine on cancer cell motility in glioma, lung cancer, and prostate cancer cell cultures.

e15079 Background: Initially, berberine was used as an antimicrobial agent in traditional medicine, but its anticancer properties were later discovered. In addition to its cytotoxic effect, berberine also has the ability to inhibit cell motility, which has been demonstrated in some permanent cancer cell lines. The objective of this study was to assess berberine anti-migratory activity in permanent cell cultures compared to primary cell cultures which are generally thought to better reflect tumor characteristics. Methods: H1299 lung cancer, PC3 prostate cancer, and T98G glioma cells, as well as primary cell cultures of the corresponding cancer obtained in our laboratory, were planted in an amount of 15*104 cells per well of a 24-well plate (Biofil, China) in DMEM medium (Gibco, USA) supplemented with 10% FBS (HyClone, USA). After cell adhesion berberine was added in concentration 5 µM, and a wound healing assay was performed according to the standard procedure. Cell plates were continuously incubated and photographed in Lionheart FX imager (BioTek, USA) at 37°C and 5.0% CO2. The extent of cell migration was measured as the percentage reduction in wound area after 48 hours of incubation relative to baseline. Data are presented as Mean ± 95% confidence interval (n = 12). Results: The use of berberine at a concentration of 5 µM led to a significant decrease in cell motility in permanent cultures of lung cancer, glioma and prostate cancer. Namely, the reduction in the wound area after 48 hours of incubation with bereberine was 74.52±12.3% (compared with 94.56±6.2% in the control) in H1299 cell culture, 38.22±10.6% (compared with 83.89±15.5% in the control) in T98G cell culture, and 48.6±7.5% (compared with 69.56±8.1% in the control) in PC3 cell culture. The resulting difference between the control and experimental groups in permanent cell cultures was statistically significant at a significance level of 5% (df = 22). At the same time, the values of wound area reduction for primary cultures of the same cancers did not differ significantly in the control and under the influence of 5 μM berberine at the accepted level of significance. Namely, the reduction in the wound area after 48 hours of incubation with bereberine was 84.79±11.2% (compared with 81.47±15.3% in the control) in lung cancer primary cell culture, 94.64±5.1% (compared with 91.73±6.8% in the control) in glioma primary culture, and 62.63±5.8% (compared with 61.1±8.9% in the control) in prostate cancer primary cell culture. Conclusions: Permanent cell lines are more sensitive to berberine anti-migratory activity than primary cancer cell lines of the same localization.