Inhibited LNCaP Cell Proliferation Research Articles

Assessment of Anti-Prostate Cancer Activity among Four Seaweeds, with Focus on Caulerpa lentillifera J.Agardh.

In response to a global shift towards health-conscious and environmentally sustainable food choices, seaweed has emerged as a focus for researchers due to its large-scale cultivation potential and the development of bioactive substances. This research explores the potential anticancer properties of seaweed extracts, focusing on analyzing the impact of four common edible seaweeds in Taiwan on prostate cancer (PCa) cells' activity. The study used bioassay-guided fractionation to extract Cl80 from various seaweeds with androgen receptor (AR)-inhibitory activity. Cl80 demonstrated effective suppression of 5α-dihydrotestosterone (DHT)-induced AR activity in 103E cells and attenuated the growth and prostate-specific antigen (PSA) protein expression in LNCaP and 22Rv1 cells. Additionally, Cl80 exhibited differential effects on various PCa cell lines. Concentrations above 5 μg/mL significantly inhibited LNCaP cell proliferation, while 22Rv1 cells were more resistant to Cl80. PC-3 cell proliferation was inhibited at 5 μg/mL but not completely at 50 μg/mL. A clonogenic assay showed that at a concentration of 0.5 μg/mL, the colony formation in LNCaP and PC-3 cells was significantly reduced, with a dose-dependent effect. Cl80 induced apoptosis in all PCa cell types, especially in LNCaP cells, with increased apoptotic cells observed at higher concentrations. Cl80 also decreased the mitochondrial membrane potential (ΔΨm) in a dose-dependent manner in all PCa cell lines. Furthermore, Cl80 suppressed the migration ability of PCa cells, with significant reductions observed in LNCaP, 22Rv1, and PC-3 cells at various concentrations. These compelling findings highlight the promising therapeutic potential of C. lentillifera J.Agardh and its isolated compound Cl80 in the treatment of PCa.

Enhanced Antitumor Efficacy of Radium-223 and Enzalutamide in the Intratibial LNCaP Prostate Cancer Model.

Radium-223 dichloride and enzalutamide are indicated for metastatic castration-resistant prostate cancer and their combination is currently being investigated in a large phase 3 clinical trial. Here, we evaluated the antitumor efficacy of radium-223, enzalutamide, and their combination in the intratibial LNCaP model mimicking prostate cancer metastasized to bone. In vitro experiments revealed that the combination of radium-223 and enzalutamide inhibited LNCaP cell proliferation and showed synergistic efficacy. The combination of radium-223 and enzalutamide also demonstrated enhanced in vivo antitumor efficacy, as determined by measuring serum PSA levels in the intratibial LNCaP model. A decreasing trend in the total area of tumor-induced abnormal bone was associated with the combination treatment. The serum levels of the bone formation marker PINP and the bone resorption marker CTX-I were lowest in the combination treatment group and markedly decreased compared with vehicle group. Concurrent administration of enzalutamide did not impair radium-223 uptake in tumor-bearing bone or the ability of radium-223 to inhibit tumor-induced abnormal bone formation. In conclusion, combination treatment with radium-223 and enzalutamide demonstrated enhanced antitumor efficacy without compromising the integrity of healthy bone. The results support the ongoing phase 3 trial of this combination.

Neoisoliquiritin exerts tumor suppressive effects on prostate cancer by repressing androgen receptor activity

BackgroundProstate cancer (PCa) is a major cause of morbidity and mortality in men in both developed and developing countries. Androgens and the androgen receptor (AR) play predominant roles in the progression of PCa. Neoisoliquiritin (NEO) belongs to the class of licorice (Glycyrrhiza) flavonoids, which have a variety of biological activities including anti-depressant, anti-tumor-promoting, and anti-inflammation properties. Licorice root has cancer chemopreventive effects and has been given to PCa patients as an ingredient of PC-SPES, a commercially available combination of eight herbs. Therefore, we determined if NEO can suppress the proliferation of PCa cells. PurposeWe investigated whether and how NEO exerts its anti-neoplastic activity against PCa. MethodsThe Cell Counting Kit 8 and flow cytometry were used to evaluate the effects of NEO on the proliferation and cell cycle progression of AR-dependent (LNCaP) and AR-independent (PC3) PCa cells. RNA sequencing was employed to examine the genome-wide changes in responsiveness to NEO in LNCaP cells. Quantitative PCR, Western blotting, docking, chromatin immunoprecipitation, and dual-luciferase reporter assays were conducted to determine the mechanism of action of NEO and its potential cross-talk with AR. A LNCaP xenograft nude mouse model was used to determine the inhibitory effects of NEO on AR-dependent PCa tumors in vivo. ResultsNEO inhibited LNCaP cell proliferation in vitro by inducing G0/G1 phase cell cycle arrest. Conversely, NEO treatment had no effect on PC3 cells. Transcriptomic analysis indicated that AR signaling might be the key target of NEO in preventing PCa. NEO regulated AR-mediated cell growth suppression and AR-sensitized cell cycle arrest in LNCaP cells. NEO also blocked several key steps in the AR signaling pathway, including proposed targeting to the ligand binding pocket of AR by computer modeling, modulating AR–androgen response element DNA-binding activity, inhibiting the expression and transcriptional activity of AR, and suppressing downstream AR signaling. ConclusionsNEO negatively regulates AR expression and activity, thus supporting the tumor suppressive role for NEO in AR-dependent PCa.

The Antiproliferative Effects of Flavonoid MAO Inhibitors on Prostate Cancer Cells.

Prostate cancer (PCa) patients commonly experience clinical depression. Recent reports indicated that monoamine oxidase-A (MAO-A) levels elevate in PCa, and antidepressant MAO-Is show anti-PCa properties. In this work, we aimed to find potential drugs for PCa patients suffering from depression by establishing novel anti-PCa reversible monoamine oxidase-A inhibitors (MAO-AIs/RIMA); with an endeavor to understand their mechanism of action. In this investigation, twenty synthesized flavonoid derivatives, defined as KKR compounds were screened for their inhibitory potentials against human MAO-A and MAO-B isozymes. Meanwhile, the cytotoxic and antiproliferative effects were determined in three human PCa cell lines. MAO-A-kinetics, molecular docking, SAR, cell morphology, and cell migration were investigated for the most potent compounds. The screened KKRs inhibited MAO-A more potently than MAO-B, and non-toxically inhibited LNCaP cell proliferation more than the DU145 and PC3 cell lines, respectively. The results showed that the three top MAO-AI KKRs compounds (KKR11, KKR20, and KKR7 (IC50s 0.02–16 μM) overlapped with the top six antiproliferative KKRs against LNCaP (IC50s ~9.4 μM). While KKR21 (MAO-AI) and KKR2A (MAO-I) were ineffective against the PCa cells. Furthermore, KKR21 and KKR11 inhibited MAO-A competitively (Kis ≤ 7.4 nM). Molecular docking of the two compounds predicted shared hydrophobic and distinctive hydrophilic interactions—between the KKR molecule and MAO-A amino acid residues—to be responsible for their reversibility. The combined results and SAR observations indicated that the presence of specific active groups—such as chlorine and hydroxyl groups—are essential in certain MAO-AIs with anti-PCa effects. Additionally, MAO-A inhibition was found to be associated more with anti-PCa property than MAO-B. Distinctively, KKR11 [(E)-3-(3,4-dichlorophenyl)-1-(2-hydroxy-4,6-dimethoxyphenyl)prop-2-en-1-one] exhibited anti-metastatic effects on the DU145 cell line. The chlorine substitution groups might play vital roles in the KKR11 multiple actions. The obtained results indicated that the flavonoid derivative KKR11 could present a novel candidate for PCa patients with depression, through safe non-selective potent inhibition of MAOs.

Abstract 271: Diterpenoid pseudolaric acid B induces M-phase arrest and apoptosis primarily through JNK stress signaling in LNCaP prostate cancer cells

Abstract Pseudolaric acid B (PAB) is a major diterpenoid component isolated from the root bark of the traditional Chinese medicinal plant Pseudolarix kaempferi Gordon (Pinaceae). PAB has shown potential as an anticancer agent via inducing cell cycle arrest, apoptosis and DNA damage in several cancer models. To explore potential use of PAB for prostate cancer chemoprevention, we used human LNCaP prostate cancer cells that harbor wild-type p53, functional androgen receptor (AR), and defective PTEN that are characteristic of early stage prostate adenocarcinomas to study cell fates and signaling mechanisms upon PAB exposure in cell culture. Our results show that PAB inhibited LNCaP cell proliferation in a dose- and time-dependent manner (IC50 ~5.4 µM at 24 h and ~ 0.2 µM at 72 h). PAB induced M phase cell cycle arrest as confirmed by increased phosphorylation of histone H3 (p-H3 Ser10). PAB also induced apoptosis evidenced by Annexin V staining and cleavage of the canonical caspase substrate PARP. PAB at lethal exposure concentration decreased AR protein and its best-known target prostate-specific antigen (PSA). Timewise, PAB treatment increased p-H3 (mitosis marker) and the expression of another mitosis/prosurvival protein survivin several hours ahead of PARP cleavage. PAB induced p-H2A.X, which would mark DNA double-strand breaks, and the best-known DNA damage response protein P53 and its target P21Cip1 preceding cPARP. PAB stimulated phosphorylative activation of c-Jun N-terminal kinase (JNK), and the JNK inhibitor SP600125 decreased PAB-induced p-H2A.X, P53/P21Cip1 and cleavage of PARP as well as M phase arrest. Furthermore, PAB significantly increased 2',7'-dichlorofluorescin diacetate (DCF)-reactive oxygen species (DCF-ROS) in LNCaP cells and addition of antioxidant N-acetyl-L-cysteine (NAC) attenuated P53/P21Cip1 cascade and cPARP/apoptosis, but did not affect M phase arrest. Knocking-down of P53 or P21Cip1 by siRNA attenuated cPARP and apoptosis without affecting p-H2A.X. Taken together, these results suggest a rapid induction of M phase arrest by PAB that was primarily mediated by JNK stress signaling, either parallel to or upstream of ROS-DNA damage-driven P53-P21Cip1 apoptosis cascade in LNCaP cells. Citation Format: Kartick C. Pramanik, Nehal Gupta, Min Ye, Junxuan Lu, Cheng Jiang. Diterpenoid pseudolaric acid B induces M-phase arrest and apoptosis primarily through JNK stress signaling in LNCaP prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 271.

MiR-17 Regulates Prostate Cancer Cell Proliferation and Apoptosis Through Inhibiting JAK-STAT3 Signaling Pathway.

STAT3 is an important protein in Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway that facilitates B-cell lymphoma 2 (Bcl-2) expression. MiR-17 was found to be significantly reduced in prostate cancer tissues and cells, suggesting that it might be a tumor suppressor in prostate cancer tumorigenesis. Bioinformatics analysis showed the complementary binding site between miR-17 and STAT3. This study aimed to investigate the role of miR-17 in regulating JAK-STAT signaling pathway, as well as prostate cancer cell proliferation and apoptosis. Dual luciferase assay was used to verify the targeted relationship between miR-155 and STAT3. LNCaP cells were cultured in vitro and divided into four groups, including mimic NC, miR-17 mimic, si-NC, and si-STAT3 groups. STAT3, p-STAT3, and Bcl-2 expressions were tested by western blot. Cell apoptosis was detected by flow cytometry. Cell proliferation was assessed by EdU staining. MiR-17 mimic transfection significantly reduced the relative luciferase activity in HEK293T cells. MiR-17 targeted regulated STAT3 expression. MiR-17 expression and cell apoptosis were obviously declined, while STAT3 level and cell proliferation markedly were elevated in LNCaP cells compared with RWPE-1 cells. MiR-17 mimic and/or si-STAT3 transfection significantly downregulated the expression of STAT3, p-STAT3, and Bcl-2, attenuated cell proliferation, and enhanced cell apoptosis in LNCaP cells. Upregulation of miR-17 inhibited LNCaP cell proliferation and induced cell apoptosis by downregulating the expression of STAT3, p-STAT3, and Bcl-2.

Polygodial analog induces apoptosis in LNCaP prostate cancer cells

Prostate cancer (PCa) is the second leading cause of death in American men. The chemotherapeutic treatment strategies are generally not effective and can lead to side effects. Hence, there is an urgent need to identify novel chemotherapeutic agents. The aim of this study was to synthesize and evaluate the therapeutic effects of a synthetic analog of polygodial (PG), a pungent constituent abundantly present in mountain pepper, water pepper and dorrigo pepper, on LNCaP PCa cell line and its anti-cancer mechanisms in a preclinical study. We evaluated the anti-cancer potential of the PG analog namely DRP-27 using various assays such as cell viability by MTT assay, anchorage independent growth by soft agar assay, reactive oxygen species generation by 2′,7′-dichlorofluorescein probe-based fluorescence assay, and apoptosis by Annexin-V and TUNEL assays respectively. Western blot analysis was performed to identify the molecular mechanism of DRP-27-induced cell death. Our results showed that DRP-27 significantly inhibited LNCaP cell proliferation in a dose-dependent manner at 48 h treatment in vitro. In addition, DRP-27 potently inhibited anchorage-independent growth of these cells. Flow cytometry, Annexin-V and TUNEL assays confirmed that DRP-27 induces apoptosis in LNCaP cells. DRP-27 also induced the activation of intracellular reactive oxygen species. Western blot analysis revealed that DRP-27 downregulated the expression of survivin, while activating Bax and DNA damage marker pH2AX in LNCaP cells. In conclusion, our study suggests that DRP-27 might be an effective anti-cancer agent for PCa.

Abstract 5707: STAT3 and STAT5a are potential therapeutic targets in castration-resistant prostate cancer

Abstract Background: Currently, there is no effective pharmacotherapy for metastatic castration-resistant prostate cancer (mCRPC). The mechanisms underlying mCRPC are not clearly understood, thus hindering rational-based drug design. Evidence suggests that signal transducer and activator of transcription 3 (STAT3) and 5a/b (STAT5a/b), key components of the JAK/STAT pathway, play a significant role in aggressive PC. However, expression of STAT3/5 in prostate tumor samples have not been studied. Here, we evaluated the possible role of STAT3/5a in aggressive PC. Materials and Methods: Expression of STAT3 and STAT5a in high grade PC (HGPC, n=15) and in benign prostatic hyperplasia (BPH, n=15) tissue sections were evaluated by immunohistochemistry (IHC) according to the protocol approved by Institutional Review Board. Age ranged from 59 to 95 years (median = 81) in the former and 57 years to 86 years (median = 68 years) in the latter category. In addition, the effects of STAT inhibitor, Pimozide, on androgen-sensitive LNCaP and its castration-resistant subline C4-2 PC cell growth were assessed in vitro. Results: A strong nuclear immunoreactivity for STAT3 and STAT5a in 93% (n=14) and 80% (n=12) of HGPC cases, respectively, were observed. Only one BPH case showed strong STAT3 expression. Focal and weak positivity for STAT3 and STAT5a were noted in 47% (n=7) and 67% (n=10) of BPH cases. None of the BPH cases showed strong STAT5a expression. HGPC cases showed significantly higher STAT3 positivity compared with BPH (p=0.01). No significant differences were observed for STAT5a expression between HGPC and BPH group (p=0.4). However, multifocal or diffuse and strong STAT3 (p<0.0001) and STAT5a (p<0.0001) expression was significantly higher in HGRPC than BPH. Pimozide exposure significantly inhibited LNCaP cell proliferation at 10 μM and C4-2 cell proliferation at 20 μM concentration. Conclusion: Our results demonstrate that increased expression of STAT3 and STAT5a may serve as a predictive biomarker for efficacy of the JAK/STAT targeted therapy. Since JAK/STAT and androgen receptor signaling are functionally synergistic in contributing PC progression, the inhibition of JAK/STAT-alone or in combination with AR may lead to a novel treatment modality for mCRPC. Citation Format: Sambit K. Mohanty, Kader Yagiz, Luthringer Luthringer, Mahul B. Amin, Serhan Alkan, Bekir Cinar. STAT3 and STAT5a are potential therapeutic targets in castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5707. doi:10.1158/1538-7445.AM2017-5707

Abstract 613: Synergistic antiproliferative activity of combined administration of atorvastatin and zoledronic acid in LNCaP and PC3 prostate cancer cells

Abstract Atorvastatin (ATO) and other statins demonstrate anti-inflammatory, anti-proliferative, and pro-apoptotic activities that suggest possible utility in cancer chemoprevention. Bisphosphonates such as zoledronic acid (ZOL) are used clinically to manage bone metastases from prostate and other cancers, and also demonstrate anti-apoptotic and growth inhibitory effects on cancer cells. Should these agents demonstrate significant chemopreventive activity in preclinical cancer models, their desirable clinical safety profiles would make them high priority candidates for clinical evaluation as chemopreventive agents. The present studies were performed to characterize the effects of ATO and ZOL on the in vitro proliferation kinetics of parental LNCaP and PC3 human prostate cancer cells, and in sub-clones of LNCaP and PC3 cells that differ phenotypically from the parental cell lines. When administered as single agents, ATO and ZOL both inhibited the proliferation of parental LNCaP cells and LNCaP cell sub-clones in a dose-dependent (1 - 20 µM) and time-dependent manner. Administration of ATO and ZOL in combination at concentrations at which each agent was minimally active as a single agent resulted in synergistic antiproliferative activity in both LNCaP cells and LNCaP sub-clones. For example, at 5 µM, ATO and ZOL each inhibited LNCaP cell proliferation by 5 to 10%; combined administration of ATO + ZOL at 5 µM inhibited LNCaP cell proliferation by nearly 50%. PC3 cells and sub-clones were also sensitive to statin administration: exposure of parental PC3 cells to ATO (5 µM) for 6 days induced significant cell death. ZOL inhibited proliferation in both PC3 cells and PC3 sub-clone cells in a dose and time-dependent manner; enhanced antiproliferative activity was seen in cells exposed to ATO + ZOL in combination. Because the autophagosomal marker, LC3-II, is reported to be induced by ATO in PC3 cells; LC3-II expression was evaluated in parental LNCaP cells and in PC3 cells by immunoblotting. ATO consistently induced LC3-II expression in PC3 cells, but had minimal effect on LC3-II expression in LNCaP cells. ZOL did not induce LC3-II expression in either cell line. Exposure to ATO + ZOL in combination induced LC3-II expression in PC3 cells only. These data demonstrate synergistic antiproliferative effects of ATO + ZOL in both LNCaP prostate cancer cells and PC3 prostate cancer cells, as well as in sub-clones derived from both prostate cancer cell lines. Enhanced chemotherapeutic and/or chemopreventive efficacy may be achieved in prostate cancer cells by administration of drug combinations that act through different molecular mechanisms. (N01-CN-43303 from the NCI, DHHS). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 613. doi:1538-7445.AM2012-613

Abstract 944: Down-regulation of CAMKK2 by androgen deprivation induces castration-resistant prostate cancer

Abstract One of the mechanisms through which prostate cancer (PCa) relapses after androgen deprivation therapy (ADT) is to become androgen-hypersensitive and adapt to the low concentration of androgen during ADT. cDNA microarray analysis between PCa tissues before ADT and normal prostate tissues revealed that the level of calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2) mRNA was overexpressed 6 times in PCa more than in normal prostate. Immunohistochemical analysis of CAMKK2 protein using prostate tissue microarray showed that CAMKK2 protein was expressed well in PCa compared with normal tissue. However, the expression of CAMKK2 for the high grade PCa diminished compared with the low grade PCa. Moreover, we confirmed that the narrowness of a positive regional area of the CAMKK2 expression before ADT was a poor prognostic factor. Expression of CAMKK2 mRNA was up-regulated in the presence of DHT in LNCaP cells. Stable overexpression of CAMKK2 in LNCaP cells (LNCaP/GFP-CAMKK2), however, attenuated androgen-sensitivity. Tumorigenesis of LNCaP/GFP-CAMKK2 cells by subcutaneous injection in male SCID mice was also inhibited compared with control cells irrespective of castration. In contrast, knockdown of CAMKK2 mRNA in LNCaP cells induced androgen-hypersensitivity and stimulated LNCaP cell proliferation without DHT. Overexpression and knockdown of CAMKK2 in the presence of DHT were correlated with activation and inactivation of AMP-activated protein kinase (AMPK) that is a key kinase important for regulating cell proliferation, respectively. AMPK activation inhibited LNCaP cell proliferation. Taken together, induction of androgen-hypersensitivity after ADT may be involved in down-regulation of CAMKK2. This result may provide new therapeutic approach to keep androgen-sensitivity of PCa after ADT. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 944. doi:1538-7445.AM2012-944

Overexpression of aldo-keto reductase 1C3 (AKR1C3) in LNCaP cells diverts androgen metabolism towards testosterone resulting in resistance to the 5α-reductase inhibitor finasteride

Type 5 17β-hydroxysteroid dehydrogenase (AKR1C3) is the major enzyme in the prostate that reduces 4-androstene-3,17-dione (Δ4-Adione) to the androgen receptor (AR) ligand testosterone. AKR1C3 is upregulated in prostate cancer (PCa) and castrate resistant prostate cancer (CRPC) that develops after androgen deprivation therapy. PCa and CRPC often depend on intratumoral androgen biosynthesis and upregulation of AKR1C3 could contribute to intracellular synthesis of AR ligands and stimulation of proliferation through AR signaling. To test this hypothesis, we developed an LNCaP prostate cancer cell line overexpressing AKR1C3 (LNCaP-AKR1C3) and compared its metabolic and proliferative responses to Δ4-Adione treatment with that of the parental, AKR1C3 negative LNCaP cells. In LNCaP and LNCaP-AKR1C3 cells, metabolism proceeded via 5α-reduction to form 5α-androstane-3,17-dione and then (epi)androsterone-3-glucuronide. LNCaP-AKR1C3 cells made significantly higher amounts of testosterone-17β-glucuronide. When 5α-reductase was inhibited by finasteride, the production of testosterone-17β-glucuronide was further elevated in LNCaP-AKR1C3 cells. When AKR1C3 activity was inhibited with indomethacin the production of testosterone-17β-glucuronide was significantly decreased. Δ4-Adione treatment stimulated cell proliferation in both cell lines. Finasteride inhibited LNCaP cell proliferation, consistent with 5α-androstane-3,17-dione acting as the major metabolite that stimulates growth by binding to the mutated AR. However, LNCaP-AKR1C3 cells were resistant to the growth inhibitory properties of finasteride, consistent with the diversion of Δ4-Adione metabolism from 5α-reduced androgens to increased formation of testosterone. Indomethacin did not result in differences in Δ4-Adione induced proliferation since this treatment led to the same metabolic profile in LNCaP and LNCaP-AKR1C3 cells. We conclude that AKR1C3 overexpression diverts androgen metabolism to testosterone that results in proliferation in androgen sensitive prostate cancer. This effect is seen despite high levels of uridine glucuronosyl transferases suggesting that AKR1C3 activity can surmount the effects of this elimination pathway. Treatment options in prostate cancer that target 5α-reductase where AKR1C3 co-exists may be less effective due to the diversion of Δ4-Adione to testosterone.

Oct1 regulates cell growth of LNCaP cells and is a prognostic factor for prostate cancer

The androgen receptor (AR) plays a critical role in the development and the progression of prostate cancer. Alterations in the expression of AR coregulators lead to AR hypersensitivity, which is one of the mechanisms underlying the progression of prostate cancer into a castrate-resistant state. Octamer transcription factor 1 (Oct1) is a ubiquitous member of the POU-homeodomain family that functions as a coregulator of AR. In our study, the contribution of Oct1 to prostate cancer development was examined. Immunocytochemistry analysis showed that Oct1 is expressed in the nuclei of LNCaP cells. siRNA-mediated silencing of Oct1 expression inhibited LNCaP cell proliferation. Immunohistochemical analysis of Oct1 expression in tumor specimens obtained from 102 patients with prostate cancer showed a positive correlation of Oct1 immunoreactivity with a high Gleason score and AR immunoreactivity (p = 0.0042 and p < 0.0001, respectively). Moreover, patients with high immunoreactivity of Oct1 showed a low cancer-specific survival rate, and those patients with high immunoreactivities of both Oct1 and AR exhibited poorer cancer-specific prognosis. Multivariate hazard analysis revealed a significant correlation between high Oct1 immunoreactivity and poor cancer-specific survival (p = 0.012). These results demonstrate that Oct1 can be a prognostic factor in prostate cancer as a coregulator of AR and may lead to the development of a new therapeutic intervention for prostate cancer.

Abstract 4500: What distinguishes a PKC activator like phorbol ester from a PKC functional antagonist like bryostatin 1? Bryologues permit mechanistic insight

Abstract Bryostatin 1, a promising anticancer agent in clinical trials, is a potent PKC activator in vitro that paradoxically often antagonizes the effects of the typical PKC activator phorbol 12-myristate 13-acetate (PMA) in cellular systems. Understanding the underlying mechanism(s) responsible for this functional PKC antagonism should afford a new generation of drugs for PKC, a validated therapeutic target. We use the synthetic bryostatin look-alike (bryologue) Merle 23 that differs structurally from bryostatin 1 to only a modest degree as a tool to dissect mechanisms responsible for the unique effects of bryostatin 1. We have previously reported that Merle 23 is PMA like, bryostatin-1 like, intermediate or unique in its behavior depending on the system and response examined. In LNCaP prostate cancer cells Merle 23 is bryostatin 1 like in failing to inhibit cell proliferation, to induce apoptosis, or to induce secretion of TNF-alpha, responses induced by PMA. Using siRNAs and PKC inhibitors we show that PKC delta, but not PKC alpha or epsilon, was responsible for induction of apoptosis. Nuclear localized PKC delta was previously shown to be responsible for the apoptotic response, and we found that Merle 23 resembled bryostatin 1 and was unlike PMA in that failed to induce translocation of PKC delta and phospho-PKD1 to the nucleus. In contrast, Merle 23 was PMA-like in inducing nuclear translocation of PKC alpha and PKC epsilon. Bryostatin 1 is unique in down-regulating PKC alpha very efficiently in LNCaP cells and Merle 23 is unique for quick and very efficient down-regulation of PKC delta. If proteosome inhibitors were used to prevent down-regulation of PKC delta, the bryostatin 1-like effects of Merle 23 on proliferation and TNF-alpha secretion were transformed to PMA-like effects: Merle 23 inhibited LNCaP cell proliferation and induced secretion of TNF-alpha when co-applied with lactacystin or MG-132. Similarly, for tyrosine phosphorylation of PKC delta at position 311 and for cFos activation, responses where Merle 23 had effects intermediate between bryostatin 1 and PMA, Merle 23 became more PMA-like when co-applied with proteosome inhibitors. Finally, consistent with stability of PKC signaling elements varying between ligands, we found that phosphorylation of ERK, Mek1 and Mek2, and AKT in response to bryostatin 1, PMA, and Merle 23 was similar at 30 min but returned to the basal level at 150 min for bryostatin 1, but not PMA or Merle 23, as determined using capillary iso-electrofocusing immune-assay. We conclude that differential regulation of PKC isoforms by bryostatin and the bryologues is an important contributor to their differential biological activity relative to PMA. 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 4500.

Inhibition of de novo purine synthesis in human prostate cells results in ATP depletion, AMPK activation and induces senescence

4-[2-(2-Amino-4-oxo-4,6,7,8-tetrahydro-3H-pyrimidino[5,4,6][1,4]thiazin-6-yl)-(S)-ethyl]-2,5-thienoylamino-l-glutamic acid (AG2034), is a classical antifolate shown to be an excellent inhibitor of glycinamide ribonucleotide formyltransferase (GARFT), ultimately inhibiting de novo purine synthesis. We examined some metabolic effects of this drug in prostate cancer cells, LNCaP, versus non-tumorigenic prostatic epithelial cells, RWPE-1. Cells were cultured in medium containing 10 nM 5-methyl-tetrahydrofolate supplemented with/without 1.7 microM hypoxanthine/1.5 microM thymidine. Cytotoxicity of AG2034 was determined by clonogenic assays. Total ATP was quantified by reverse-phase HPLC and [(14)C]-glycine incorporation and [(3)H]-hypoxanthine conversion into ATP by liquid scintillation counting. Protein expression levels were determined by Western blotting, cell cycle analysis by propidium iodide staining and cell-senescence by beta-galactosidase staining. AG2034 inhibited LNCaP cell proliferation causing death in the absence of hypoxanthine and cytostasis in its presence. However, RWPE-1 cells were resistant to AG2034 when hypoxanthine was present. AG2034 elevates AMP/ATP ratios but is unable to activate AMPK in RWPE-1 when hypoxanthine is present. Drug exposure increased expression levels of p53, p21, p27, and p16 in both cell lines and increased senescence-associated-beta-gal staining in LNCaP with/without hypoxanthine, but primarily in its absence in RWPE-1. LNCaP cells primarily depend upon de novo while RWPE-1 cells largely favor salvage synthesis for maintenance of their ATP pools. With AG2034 treatment, ATP synthesis via hypoxanthine salvage is insufficient to support growth of LNCaP but enough to restore ATP levels and support RWPE-1 growth. The anti-proliferative effect of AG2034 involves increasing phosphorylation of AMPK. These results indicate that AG2034 activates p53 and AMPK mediating the induction of signaling pathways leading to senescence.

Overexpression of CXCL10 in human prostate LNCaP cells activates its receptor (CXCR3) expression and inhibits cell proliferation

Chronic or recurrent inflammation plays a role in the development of many types of cancer including prostate cancer. CXCL10 (interferon-γ inducible protein-10, IP-10) is a small secretory protein of 8.7 kDa. Recently, it has been shown that normal prostate epithelial (PZ-HPV-7) cells produce lower amounts of angiogenic CXC chemokines (GRO-α, IL-8) and higher amounts of angiostatic chemokines (CXCL10, CXCL11) as compared to prostate cancer cells (CA-HPV-10 and PC-3). Accordingly, we studied the effects of overexpression of CXCL10 in human prostate cancer LNCaP cells. LNCaP cells were transiently transfected with CXCL10 cDNA in pIRES2-EGFP vector. CXCL10, CXCR3, PSA and G3PDH mRNA levels were determined by semi-quantitative conventional and quantitative real-time RT-PCR and fluorescence-activated cell sorting (FACS). The expression of CXCL10 was markedly enhanced in the transfected cells at mRNA and protein levels in the cells. Overexpression of CXCL10 inhibited cell proliferation of the transfected cells by 30%–40% in serum-limited medium (1% FCS in RPMI1640 medium) and decreased PSA production. CXCR3 expression was significantly induced by the overexpression of CXCL10 as determined by RT-PCR and FACS. These results indicated that CXCL10 inhibited LNCaP cell proliferation and decreased PSA production by up-regulation of CXCR3 receptor. CXCL10 may be potentially useful in the treatment of prostate cancer.

A low-calcemic vitamin D analog (Ro 25-4020) inhibits the growth of LNCaP human prostate cancer cells with increased potency by producing an active 24-oxo metabolite (Ro 29-9970).

In this study, we have characterized a novel less-calcemic vitamin D analog Ro 25-4020 (1alpha, 25 dihydroxy-16-ene-5,6-trans-vitamin D3) and investigated the mechanisms underlying its enhanced growth inhibitory properties. We found that Ro 25-4020 (IC50 = 0.3 nM) exhibited greater inhibitory activity than 1,25(OH)2D3 (IC50 = 1 nM) on LNCaP human prostate cancer cell growth. However, Ro 25-4020 was tenfold less active than 1,25(OH)2D3 in receptor-binding assays, ligand-induced heterodimerization and transactivation assays using VDR. HPLC and GC-MS analyses revealed that 1,25(OH)2D3 is converted to a 24-hydroxy metabolite, which has been shown to be less potent than 1,25(OH)2D3. In contrast, Ro 25-4020 was converted to a major 24-oxo metabolite that was more stable. Ligand-binding assays reveal that both Ro 25-4020 and its 24-oxo metabolite have similar affinity for VDR. Synthetic 24-oxo-Ro 25-4020, however, inhibited LNCaP cell proliferation as potently as 1,25(OH)2D3 and was more potent in transactivation of two out of three vitamin D target genes tested. These results suggest that conversion of Ro 25-4020 into an active and more stable 24-oxo metabolite with longer half-life contributes significantly to its potent antiproliferative actions on the LNCaP cells.

Effect of interleukins on UGT2B15 and UGT2B17 steroid uridine diphosphate-glucuronosyltransferase expression and activity in the LNCaP cell line.

Cytokines are known to modulate the level of both phase 1 and phase 2 drug-metabolizing enzymes in hepatocytes. Although the effects of cytokines on cytochrome P450 (CYP450) enzymes are well understood, there is limited knowledge on how cytokines may affect steroid UDP-glucuronosyltransferase (UGT) phase 2 enzyme activity and expression in different cell types, including hepatocytes and steroid target cells. LNCaP cells, which is a human prostate cancer cell line, is a good model to study the effect of cytokines in steroid target cells because it is known to express steroidogenic enzymes, including UGT2B15 and UGT2B17, which are widely expressed steroid UGT enzymes known to conjugate androgens. In this study, we examined the possible interaction among interleukin-1alpha (IL-1alpha), IL-4, IL-6, and steroid UGT enzymes (UGT2B15 and UGT2B17). Treatment of LNCaP cells with IL-1alpha led to a dose-dependent inhibition of dihydrotestosterone (DHT) glucuronidation. IL-1alpha decreased both UGT activity and LNCaP cell proliferation in the absence and presence of DHT (0.5 nM); a maximal inhibition of 70% was observed. IL-6 inhibited LNCaP cell proliferation as well as the DHT-induced proliferation of these cells. However, neither IL-4 nor IL-6 significantly affected the formation of DHT glucuronide. Ribonuclease protection and Western blot analyses demonstrated a specific reduction of UGT2B17 transcript and protein levels in IL-1alpha-treated LNCaP cells. The level of UGT2B15 was not affected by cytokine treatments, indicating a differential regulation between these two UGT enzymes. Transfection experiments performed with the UGT2B17 gene promoter region indicates that the regulation occurs at the transcription level via putative cis-acting elements. This study indicates that cell proliferation and UGT expression in steroid-responsive cancer cells are differentially regulated depending on the cytokines present in the cell microenvironment.