Proliferation Of Prostate Cancer Cell Lines Research Articles

USP54 is a potential therapeutic target in castration-resistant prostate cancer

BackgroundUSP54, a ubiquitin-specific protease in the deubiquitinase (DUB) family, facilitates the malignant progression of several types of cancer. However, the role of USP54 in prostate cancer (PCa), especially castration-resistant prostate cancer (CRPC), remains unknown.MethodsWe established the CRPC LNCaP-AI cell line from the hormone-sensitive prostate cancer (HSPC) LNCaP cell line. RNA-Seq was utilized to explore DUB expression levels in LNCaP and LNCaP-AI. USP54 was knocked down, and its effects on cell growth were evaluated in vitro and in vivo. Bioinformatics analyses were conducted to explore signaling pathways affected by USP54 in PCa. Quantitative polymerase chain reaction was used to confirm key signaling pathways involved.ResultsUSP54 was the most strongly upregulated DUB in LNCaP-AI cells compared with LNCaP cells. USP54 levels were higher in PCa than in normal tissues. USP54 silencing suppressed the proliferation of PCa cell lines, both in vitro and in vivo. USP54 expression was positively correlated with the androgen receptor (AR) signaling level in PCa samples, and USP54 knockdown inhibited AR signaling in PCa cells.ConclusionsUSP54 was upregulated during HSPC progression to CRPC. USP54 depletion suppressed CRPC cell proliferation both in vitro and in vivo. USP54 may facilitate PCa progression by regulating AR signaling.

Microrna 138 Upregulation is Associated with Decreasing Levels of CCND1 Gene Expression and Promoting Cell Death in Human Prostate Cancer Cell Lines

Background: This research intended to discover the significance of miR-138 (microRNA 138) on the expression profile, proliferation, and the associated regulatory mechanisms in prostate cancer (PCa). Methods: Thirty-five specimens of prostate were studied to evaluate the expression level of miR138 by RT-qPCR (Quantitative reverse transcription polymerase chain reaction). Bioinformatics analysis was performed to search for the target genes of miR-138; and ABL1 (ABL proto-oncogene 1, non-receptor tyrosine kinase), CCND1 (cyclin D1), CCND3 (cyclin D3), VIM (vimentin), TWIST1 (twist family bHLH transcription factor 1), HIF1A (hypoxia-inducible factor 1 subunit alpha), and TERT (telomerase reverse transcriptase) genes were selected. Then, the biological role of miR-138 and CCND1 in the progression of PCa was investigated using RT-qPCR and luciferase reporter gene assay. Finally, overexpression of miR-138 on the proliferation in PCa cell lines was analyzed using the MTT (3-(4, 5-dimethylthiazol-2-Yl)-2, 5-diphenyltetrazolium bromide, Sigma, Germany) assay. Results: RT-qPCR showed that the expression of miR-138 downregulated in PCa tissues and cell lines. Bioinformatics analysis and RT-qPCR assay demonstrated that CCND1 expression level was negatively correlated with miR-138 in PCa tissues and the PC3 cell line. Moreover, CCND1 was predicted to be the target gene of miR138 in the PC3 cell line based on the results of luciferase reporter gene assay. Substantially, over-expression of miR138-5p mimic could inhibit the expression level of CCND1 gene in PC3 cell lines. Lastly, over-expression of miR-138 inhibited the proliferative capacities in PC3 and DU-145 cells. Conclusion: Our research introduces miR-138 as a negative regulator of CCND1 in the progression of PCa with an inhibitory impact on the proliferation rate of PCa cell lines. This regulatory mechanism could be utilized for the design and target selection of remedial miRNA-based approaches.

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.

Identification of molecular subtypes and a prognostic signature based on chromatin regulators related genes in prostate cancer.

The clinical and molecular phenotypes of prostate cancer (PCa) exhibit substantial heterogeneity, ranging from indolent to metastatic disease. In this study, we aimed to identify PCa subtypes and construct a gene signature that can predict the recurrence-free survival (RFS) of PCa patients based on chromatin regulators genes (CRGs). Strikingly, we identified two heterogeneous subtypes with distinct clinical and molecular characteristics. Furthermore, by performing differential analysis between the two CRGs subtypes, we successfully constructed a gene signature to predict PCa prognosis. The signature, comprising four genes (MXD3, SSTR1, AMH and PPFIA2), was utilized to classify PCa patients into two risk groups; the high-risk group was characterized by poor prognosis and more aggressive clinical features. Moreover, we investigated the immune profile, mutation landscape and molecular pathways in each of the groups. Additionally, drug-susceptibility testing was performed to explore sensitive drugs for high-risk patients. Furthermore, we found that MXD3 downregulation suppressed the proliferation of PCa cell lines in vitro. Overall, our results highlight the signature based on CRGs as a powerful tool for predicting RFS of PCa patients, as well as an indicator for personalized treatment of those patients.

MP33-09 GUT MICROBIOTA-DERIVED SHORT-CHAIN FATTY ACIDS PROMOTE PROSTATE CANCER GROWTH VIA IGF-1 SIGNALING IN OBESE MICE

MP33-09 GUT MICROBIOTA-DERIVED SHORT-CHAIN FATTY ACIDS PROMOTE PROSTATE CANCER GROWTH VIA IGF-1 SIGNALING IN OBESE MICE

Discovery of novel antagonists targeting the DNA binding domain of androgen receptor by integrated docking-based virtual screening and bioassays.

Androgen receptor (AR), a ligand-activated transcription factor, is a master regulator in the development and progress of prostate cancer (PCa). A major challenge for the clinically used AR antagonists is the rapid emergence of resistance induced by the mutations at AR ligand binding domain (LBD), and therefore the discovery of novel anti-AR therapeutics that can combat mutation-induced resistance is quite demanding. Therein, blocking the interaction between AR and DNA represents an innovative strategy. However, the hits confirmed targeting on it so far are all structurally based on a sole chemical scaffold. In this study, an integrated docking-based virtual screening (VS) strategy based on the crystal structure of the DNA binding domain (DBD) of AR was conducted to search for novel AR antagonists with new scaffolds and 2-(2-butyl-1,3-dioxoisoindoline-5-carboxamido)-4,5-dimethoxybenzoicacid (Cpd39) was identified as a potential hit, which was competent to block the binding of AR DBD to DNA and showed decent potency against AR transcriptional activity. Furthermore, Cpd39 was safe and capable of effectively inhibiting the proliferation of PCa cell lines (i.e., LNCaP, PC3, DU145, and 22RV1) and reducing the expression of the genes regulated by not only the full-length AR but also the splice variant AR-V7. The novel AR DBD-ARE blocker Cpd39 could serve as a starting point for the development of new therapeutics for castration-resistant PCa.

MicroRNA miR-145-5p inhibits Phospholipase D 5 (PLD5) to downregulate cell proliferation and metastasis to mitigate prostate cancer

ABSTRACT Prostate cancer (PCa), a frequently detected malignant tumor, is the fifth leading global cancer mortality cause in men. Although research has improved the PCa survival rate, significantly reduced survival occurs among patients at the metastatic stage. MiRNAs, which are short non-coding proteins, are crucial for several biological roles, essential for PCa proliferation, differentiation, multiplication, and migration. The investigation aimed to explore miR-145-5p and PLD5 association and clarify their function in regulating proliferation in PCa cell lines. The study used PC-3, LNCaP, DU-145 PCa, and RWPE-1 non-cancerous cell line, PCa, and BPH tissue specimens, and nude mice to validate results. MiR-145-5p and PLD5 manifestation were assessed through RT-qPCR. PLD5 and miR-145 binding was determined through dual-luciferase reporter gene assays. Validation of cell proliferation, migration, and invasion was assessed through MTT, scratch wound, and transwell assays, respectively. The results indicated a downregulation of miR-145-5p level in PCa cell lines and tissues in comparison to the non-cancerous controls. PLD5 overexpression exerted a cancerous effect while mimicking of miR-145-5p reversed the PLD5-oncogenic effects and significantly inhibited PCa cells proliferation, migration, invasion, and metastasis. In conclusion, the study revealed that miR-145-5p upregulated apoptosis and repressed migration, invasion, and metastasis of PCa via direct PLD5 modulation.

Blockade of γ-Glutamylcyclotransferase Enhances Docetaxel Growth Inhibition of Prostate Cancer Cells.

γ-Glutamylcyclotransferase (GGCT) is highly expressed in many forms of cancer, and is a promising therapeutic target. The present study investigated whether inhibition of GGCT enhanced the antiproliferative effects of the drug docetaxel in prostate cancer cells. Immunohistochemistry and western blot analysis were conducted to measure GGCT expression in prostate cancer tissue samples and cell lines. GGCT was inhibited using RNAi and a novel enzymatic inhibitor, pro-GA, and cell proliferation was evaluated with single and combination treatments of GGCT inhibitors and docetaxel. GGCT was highly expressed in cultured prostate cancer cells and patient samples. GGCT inhibition alone inhibited prostate cancer cell line proliferation and induced cellular senescence. GGCT inhibition in combination with apoptosis-inducing docetaxel had more potent antiproliferative effects than either drug used alone. GGCT inhibition may potentiate anticancer drug efficacy.

New basic insights on the potential of a chitosan-based medical device for improving functional recovery after radical prostatectomy.

To evaluate: (i) the neuro-regenerative potential of chitosan membrane (CS-Me) on acutely axotomised autonomic neurones in vitro; (ii) to exclude the possibility that a pro-regenerative biomaterial could interfere with the proliferation activity of prostate cancer cell lines; (iii) to provide an in vivo proof of the biocompatibility and regeneration promoting effect of CS-Me in a standardised rat model of peripheral nerve injury and repair; (iv) finally, to evaluate the tissue reaction induced by the degrading material; as previous studies have shown promising effects of CS-Me for protection of the neurovascular bundles for potency recovery in patients that undergo nerve-sparing radical prostatectomy (RP). Addressing aim (i), the neuro-regenerative potential, organotypic cultures derived from primary sympathetic ganglia were cultured on CS-Me over 3days and neurite extension and axonal sprouting were evaluated. Addressing aim (ii), effects of CS on cancer cells, different human prostate cancer cell lines (PC3, DU-145, LN-Cap) were seeded on CS-coated plates or cultured in the presence of CS-Me dissolution products. Addressing aims (iii) and (iv), functional recovery of peripheral nerve fibres and tissue reaction with the biomaterial, CS-Me and CS nerve guides were used to repair a median nerve injury in the rat. Functional recovery was evaluated during the post-recovery time by the behavioural grasping test. CS-Me significantly stimulated axon elongation from autonomic ganglia in comparison to control conditions in organotypic three-dimensional cultures. CS coating, as well as the dissolution products of CS-Me, led to a significantly lower proliferation rate of prostate cancer cell lines in vitro. Tissue reaction towards CS-Me and standard CS nerve guides was similar in the rat median nerve model, as was the outcome of nerve fibre regeneration and functional recovery. The results of this study provide the first experimental evidence in support of the clinical safety of CS-Me and of their postulated effectiveness for improving functional recovery after RP. The presented results are coherent in demonstrating that acutely axotomised autonomic neurones show increased neurite outgrowth on CS-Me substrate, whilst the same substrate reduces prostate cancer cell line proliferation in vitro. Furthermore, CS-Me do not demonstrate any disadvantage for peripheral nerve repair in a standard animal model.

Low expression of microRNA-30c promotes prostate cancer cells invasion involved in downregulation of KRAS protein.

Aberrant microRNA expression is associated with tumor development. The present study aimed to elucidate the role of miR-30c in the development of prostate cancer. Quantitative polymerase chain reaction was performed to compare miR-30c expression in LNCaP, DU145, PC-3 and RWPE-1 cell lines. Lentivirus expressing miR-30c was used to create stable overexpression cell lines to investigate the effects of miR-30c overexpression on cell proliferation, migration and invasion, which were determined in the prostate cancer cell line PC-3 by MTT, colony formation, wound healing and Transwell assays. Effects of miR-30c on KRAS were examined by western blot analysis. miR-30c expression was significantly lower (P<0.05) in the PC-3 cell line compared with LNCaP, DU145 and RWPE-1 cell lines. miR-30c overexpression in PC-3 inhibited tumor cell proliferation, migration and invasion in vitro. Furthermore, KRAS protein expression was downregulated in miR-30c overexpression cell lines compared with the negative control (NC) group (P<0.05). The present results demonstrated that overexpression of miR-30c inhibits prostate cancer cell line proliferation, migration and invasion, which was possibly caused by downregulation of KRAS protein by miR-30c. The data implicate miR-30c in the prognosis and treatment of prostate cancer.

Abstract 5069: p66Shc regulates the migration of castration-resistant prostate cancer

Abstract Purpose and Background: Prostate cancer (PCa) remains the most commonly diagnosed solid tumor and is the second leading cause of cancer-related death in United States men. While androgen deprivation therapy is the current standard-of-care treatment for metastatic PCa, most patients eventually relapse and develop castration-resistant (CR) tumors for which there is currently no effective treatment. p66Shc, a 66 kDa Src and collagen homologue oxidase, is elevated in clinical PCa as well as multiple PCa cell lines which correspond with advanced CR PCa. Additionally, p66Shc has been demonstrated to promote proliferation in PCa cell lines via generation of reactive oxygen species (ROS). This study is the first to demonstrate p66Shc also regulates PCa cell migration. Understanding of the mechanism through which p66Shc promotes migration may lead to the development of therapeutic strategies to treat metastatic CR PCa. Experimental Methods: Human prostate adenocarcinoma cell lines LNCaP C-33 and C-81, androgen-sensitive (AS) and androgen independent (AI) MDA PCa2b, PC-3, and DU145 were used to determine the role of p66Shc in PCa migration. Stable p66Shc cDNA transfected subclones S-31, S-32, and S-36 were established from LNCaP C-33 cells. p66Shc's impact on migration was determined using transwell migration assays. Immunoblotting was performed to profile potential proteins involved in the mechanism through which p66Shc influences migration. Small-molecule inhibitors were used to confirm these proteins’ involvement in migration. Results: Levels of p66Shc protein positively correlate with metastatic potential across multiple PCa cell lines as well as LNCaP and MDA call progressive models. p66Shc is an authentic oxidase and promotes ROS production. In this study, we further demonstrate peroxide treatment is able to induce C-33 cell migration in a dose-dependent manner, while antioxidants inhibit migration. Similarly, p66Shc subclones possess increased migratory ability which is abolished upon antioxidant treatment and demonstrates the involvement of ROS in p66Shc-mediated migration. Molecular profiling reveals the correlation of p66Shc protein level with the activation of ErbB-2, PYK2, AKT, ERK, p38, RAC1, STAT3, and STAT5 as well as suppression of cPAcP. Conclusions: Altogether, our results indicate p66Shc is involved in PCa cell migration, in part, by inducing ROS generation. Understanding the role p66Shc in advanced PCa progression will help to determine its potential as a therapeutic target, and elucidating its mechanism of intracellular signaling will enable us to design new treatments for metastatic CR PCa. Citation Format: Matthew A. Ingersoll, Sakthivel Muniyan, Fen-Fen Lin, Ta-Chun Yuan, Yu-Wei Chou, Surinder K. Batra, Ming-Fong Lin. p66Shc regulates the migration of castration-resistant prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5069.

Growth Modulation of Diabetic Factors and Antidiabetic Drugs on Prostate Cancer Cell Lines.

Risk factors for prostate cancer (PCa) include age, hormones, race, family history and diet. Recently, epidemiologic evidence has indicated that history of diabetes mellitus (DM) is inversely associated with risk of PCa. However, epidemiological investigations have yielded inconsistent results. Hence, the exact mechanism of DM-induced reduction in the incidence of PCa has yet to be fully elucidated. The aim of this study was to investigate the effects of DM factors, including glucose, insulin and insulin-like growth factor-1 (IGF-1), on the proliferation of PCa cell lines in vitro. Cell proliferation and expression of hormone receptors was examined in MTT assay and Western blot analysis, respectively. The results showed that DM factors did not affect the viability of androgen receptor (AR)-expressing PCa cell lines. However, cell proliferation increased after treatment with DM factors in androgen-independent PCa cell lines. On PCa tissue arrays, intensities of total AR and nuclear IGF-1R were higher in malignant tissues than in normal prostate glands. In terms of hormonal receptors, androgen-dependent LNCaP cells treated with insulin and IGF-1 in a low-serum medium showed decreased expression of insulin receptor beta (IRβ) and elevated expression of IGF-1 receptor beta (IGF-1Rβ). Moreover, expression of AR was upregulated after insulin and IGF-1 treatment in LNCaP cells, but not in the other PCa cell lines. Most of the studied antidiabetic drugs promoted the viability of PCa cells. However, metformin decreased the viability of AR-expressing PCa cells. These results suggest that diabetic factors modify the expression of AR, IR and IGF-1R to increase cancer cell proliferation. Moreover, the growth suppressing effects of metformin on PCa may be via the regulation of the AR signaling pathway.

MicroRNA‑126 inhibits proliferation and metastasis by targeting pik3r2 in prostate cancer.

The dysregulation of miR-126 has been reported to correlate with the progression of several cancer types. The present study demonstrated that miR-126 was significantly downregulated in prostate cancer (PCa) tissues compared with normal prostate tissues. In vitro and in vivo studies indicated that forced overexpression of miR-126 significantly suppressed the proliferation of PCa cell lines. Additionally, a Transwell assay showed that enhanced expression of miR-126 inhibited metastasis in PCa in vitro. Furthermore, pik3r2 was confirmed to be a direct target of miR-126 in PCa. It was also shown that pik3r2 was upregulated in PCa tissues and this inversely correlated with miR-126 in PCa tissues. In conclusion, these results revealed that aberrant expression of miR-126 promoted the progression of PCa and may serve as a novel therapeutic biomarker for PCa.

Secretogranin II is overexpressed in advanced prostate cancer and promotes the neuroendocrine differentiation of prostate cancer cells

AimIn prostate cancer (PCa), neuroendocrine differentiation (NED) is commonly observed in relapsing, hormone therapy-resistant tumours after androgen deprivation. However, the molecular mechanisms involved in the NED of PCa cells remain poorly understood. In this study, we investigated the expression of the neuroendocrine secretory protein secretogranin II (SgII) in PCa, and its potential involvement in the progression of this cancer as a granulogenic factor promoting NED. MethodsWe have examined SgII immunoreactivity in 25 benign prostate hyperplasia and 32 PCa biopsies. In vitro experiments were performed to investigate the involvement of SgII in the neuroendocrine differentiation and the proliferation of PCa cell lines. ResultsWe showed that immunoreactive SgII intensity correlates with tumour grade in PCa patients. Using the androgen-dependent lymph node cancer prostate cells (LNCaP) cells, we found that NED triggered by androgen deprivation is associated with the induction of SgII expression. In addition, forced expression of SgII in LNCaP cells implemented a regulated secretory pathway by triggering the formation of secretory granule-like structures competent for hormone storage and regulated release. Finally, we found that SgII promotes prostate cancer (CaP) cell proliferation. ConclusionThe present data show that SgII is highly expressed in advanced PCa and may contribute to the neuroendocrine differentiation by promoting the formation of secretory granules and the proliferation of PCa cells.

Abstract 3311: The cholesterol/ 27-hydroxycholesterol axis is a novel therapeutic target in castrate resistant prostate cancer

Abstract The most recent estimates indicate that men have a seventeen percent chance of developing invasive prostate cancer (PCa) over their lifetime. This makes PCa the most commonly diagnosed malignancy among men in industrialized countries, accounting for the second leading cause of cancer-related deaths. Although PCa almost always develops resistance to androgen-deprivation therapy, both androgen receptor (AR) itself and the processes downstream of the receptor remain active and are necessary for cancer progression and thus continue to be viable targets for therapeutic intervention. In this regard, it is of significance that several independent studies demonstrate a link between elevated intra-prostatic levels of cholesterol and the presence of malignancy. This puts into context our current finding that 27-hydroxycholesterol (27HC), a primary metabolite of cholesterol, regulates pathways and processes that oppose AR action. For example, AR activation results in a net uptake of cholesterol by PCa cells and enhances denovo lipogenesis, while 27HC down-regulates genes involved in cholesterol uptake and activates those involved in its efflux. More importantly, we show that treatment of PCa cell lines with 27HC inhibits their proliferation, an activity that is reversed upon supplementing the cells with an exogenous source of cholesterol or upon over-expression of low density lipoprotein receptor (LDLR), a membrane protein that mediates the uptake of cholesterol. In prostatic tissues, 27HC is synthesized directly from cholesterol by the cytochrome P450 enzyme, CYP27A1. To further highlight the above axis as a novel therapeutic target, using data mining approaches from clinical databases, we show that (1) transcript levels of CYP27A1 are dramatically down-regulated during PCa progression and (2) patients whose tumors express high levels of CYP27A1transcript exhibit longer disease free survival. Most notably, we were able to show that over-expression of CYP27A1 inhibits the proliferation of PCa cell lines in vitro and delays the growth of xenografts in castrated immune-deficient mice. In summary, our data thus far strongly implicates that CYP27A1 is a potential tumor suppressor in PCa and highlights the cholesterol/27HC axis as a target for the development of novel therapeutics for castrate resistant disease. Citation Format: Mahmoud A. Alfaqih, Erik R. Nelson, Rachid Safi, Jeff Jasper, Ching-yi Chang, Stephen J. Freedland, Donald P. McDonnell. The cholesterol/ 27-hydroxycholesterol axis is a novel therapeutic target in castrate resistant prostate cancer. [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 3311. doi:10.1158/1538-7445.AM2014-3311

Erythropoietin supports the survival of prostate cancer, but not growth and bone metastasis

Erythropoietin (Epo) is used in clinical settings to enhance hematopoietic function and to improve the quality of life for patients undergoing chemotherapy by reducing fatigue and the need for transfusions. However, several meta-analyses have revealed that Epo treatments are associated with an increased risk of mortality in cancer patients. In this study, we examined the role of Epo in prostate cancer (PCa) progression, using in vitro cell culture systems and in vivo bone metastatic assays. We found that Epo did not stimulate the proliferation of PCa cell lines, but did protect PCa cells from apoptosis. In animal models of PCa metastasis, no evidence was found to support the hypothesis that Epo enhances metastasis. Together, these findings suggest that Epo may be useful for treating severe anemia in PCa patients without increasing metastatic risk.

Cardiac Glycosides Decrease Prostate Specific Antigen Expression by Down-Regulation of Prostate Derived Ets Factor

While cardiac glycosides are the mainstay of congestive heart failure treatment, early studies showed that pharmacological doses of cardiac glycosides inhibited prostate cancer cell line proliferation. We evaluated the mechanisms of cardiac glycosides, including digoxin, digitoxin and ouabain (Sigma®), on prostate specific antigen gene expression in vitro. We cultured LNCaP cells (ATCC®) and used them to determine the effect of cardiac glycosides on prostate derived Ets factor and prostate specific antigen expression. We determined prostate derived Ets factor and prostate specific antigen expression by reverse transcription-polymerase chain reaction, immunoblot, transient gene expression assay or enzyme-linked immunosorbent assay. Noncytotoxic doses (100 nM) of cardiac glycosides for 24 hours inhibited prostate specific antigen secretion by LNCaP cells. Reverse transcriptase-polymerase chain reaction and immunoblot revealed that cardiac glycosides significantly down-regulated prostate specific antigen and prostate derived Ets factor expression. Transient gene expression assays showed that prostate derived Ets factor over expression enhanced prostate specific antigen promoter activity. However, prostate specific antigen and prostate derived Ets factor gene promoter activity was attenuated when LNCaP cells were treated with 100 nM cardiac glycosides. When LNCaP cells were treated with 25 nM digitoxin or digoxin for 60 hours, prostate specific antigen secretion decreased by 30%. Results suggest that cardiac glycoside inhibition of prostate specific antigen gene expression may be caused by the down-regulation of prostate derived Ets factor gene expression. When cells were chronically treated with digoxin or digitoxin at concentrations close to or at therapeutic plasma levels, prostate specific antigen secretion decreased. This phenomenon merits further study to determine whether it occurs in men on cardiac glycoside therapy.

Abstract 5662: RBAC, a modified form of Arabinoxylan from rice bran, impairs prostate cancer cell line proliferation, adhesion, and invasion in vitro

Abstract Introduction and objective: Prostate cancer (CaP) remains a major concern of public health in the United States. Standard treatment already in clinical use has a high curability rate in patients diagnosed with localized and androgen-dependent CaP; however, the progression to hormone refractory CaP is associated with disease relapse and poor prognosis. Hence, it is important to discover a novel strategy to prevent progression of disease whilst minimizing toxicity. One such promising approach is the dietary administration of certain natural compounds such as RBAC, a rice bran carbohydrate extract hydrolyzed by Shiitake mushroom enzymes. Several experimental studies have shown that RBAC in vitro increases both susceptibility and sensitivity of many human malignant cells to undergo apoptosis and to respond to chemotherapeutic drugs. Furthermore, RBAC immunomodulates natural killer (NK) cells in vitro and in vivo and enhances plasma cytokine production and anti-tumor activity in an in vivo mouse model. The aim of this study was to investigate the direct anti-tumor activity of RBAC on CaP cell lines and its impact on cell proliferation, adhesion, and invasion. Methods: A panel of stromal and epithelial cell lines was used [Mesenchymal Stromal Cells (MSC) and CaP epithelial cell lines (PC3 and LNCaP)]. Cell lines were cultured in appropriate media supplemented with 10% FBS in a 5% CO2 incubator. Cells were treated for 24, 48, and 72h with different doses of RBAC (0-1000 µg/ml). The cell proliferation, adhesion, and invasion assays were determined by Trypan blue and AlamarBlue® proliferation assays, Cytotracker™ adhesion assay, and CytoSelect™ invasion assay, respectively. Results: RBAC significantly decreased the epithelial cell proliferation of MSC, and CaP human malignant cell lines (PC3 and LNCaP) (p&amp;lt;0.05). The inhibition occurred in a dose-dependent manner and was more pronounced at high doses of RBAC (1000 µg/ml). Also, that same dose of RBAC impaired the MSC-PC3 cell adhesion and PC3 cell invasion in vitro. Conclusions: These data suggest that RBAC exhibits an anti-proliferative and pro-apoptotic effects on CaP cell lines in vitro and might have therapeutic potential in advanced human CaP. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5662.

Regulation of Phosphatase Homologue of Tensin Protein Expression by Bone Morphogenetic Proteins in Prostate Epithelial Cells

AbstractPhosphatase homologue of tensin (PTEN) is the key endogenous inhibitor of phosphoinositide signaling and is the most commonly mutated gene in human prostate cancer. The bone morphogenetic proteins (BMPs) are secreted developmental signaling molecules known to promote differentiation in the prostate. BMP ligands have been shown to inhibit prostate cancer cell line proliferation and tumor growth and expression of BMPs, BMP ligands, receptors and signaling effectors are diminished in prostate cancer. A previous report in the colon led us to investigate the potential mechanistic relationship between PTEN and BMP signaling in prostate epithelial cells. We show here that BPM signaling positively regulates PTEN in normal and malignant prostate cells by increasing mRNA expression and stabilizing PTEN protein. Further, we show that BMP attenuates prostate cell growth at least in part through its effects on PTEN. BMP treatment did not further inhibit the growth of conditional PTEN over-expressing cells, and stable shRNA-PTEN transfectants were refractory to BMP-mediated growth inhibition. Loss-of-function of PTEN in prostate cancer cells may render them insensitive to the normal differentiating and growth-inhibitory effects of BMPs. These data are the first to identify a mechanistic linkage between BMP signaling and PTEN in normal prostate epithelial cells and to suggest coordinate dysregulation in prostate cancer.

Elevated Blood Active Ghrelin and Unaltered Total Ghrelin and Obestatin Concentrations in Prostate Carcinoma

Purpose: Ghrelin and its functional receptor are highly expressed in prostate cancer (PC) and ghrelin may activate proliferation of PC cell lines. This study was therefore designed to characterize the association between serum acylated and total ghrelin, and obestatin levels in patients with benign prostate hyperplasia (BPH) and PC. Methods: Blood serum concentrations of active and total ghrelin and obestatin were estimated by EIA methods. Results: Serum level of active ghrelin in PC was significantly higher compared to control and BPH groups. On the other hand, concentrations of total ghrelin and of obestatin did not differ between studied groups of patients. In the control group the ratio of active to total ghrelin concentrations amounted to 0.16, and it was similar in BPH (0.14), while it was notably elevated in PC (0.42). Also the ratio of active ghrelin to obestatin concentrations was higher in the group with PC than in the control and BPH groups. In all studied groups, the ratio of total circulating ghrelin to obestatin was similar. Conclusions: Obtained results suggest the link between elevated blood active ghrelin and PC, and we cannot exclude that elevated circulating active ghrelin may affect growth of malignant prostatic tissues.