Hormone-refractory Prostate Cancer Cells Research Articles

Narirutin. A flavonoid found in citrus fruits modulates cell cycle phases and inhibits the proliferation of hormone-refractory prostate cancer cells by targeting hyaluronidase.

Narirutin is a dietary flavanone found in lemons, oranges, passion fruit, bergamot and grapefruit. It possesses anti-allergic, cardioprotective, neuroprotective, hepatoprotective potential, and its enriched fraction suppresses the growth of prostate cancer cells; however, there is currently no information on the chemopreventive potential of narirutin alone against hormone-refractory prostate cancer cells (PC-3) and its mode of action. Thus, the chemopreventive possibility of narirutin was investigated in PC-3cells by utilising cytotoxicity assays. Further, a mechanism was deduced targeting hyaluronidase, an early-stage diagnosis marker, by cell-free, cell-based and in silico studies. The results indicate that narirutin reduced the viability of PC-3cells with the inhibitory concentration range of 66.87-59.80μM. It induced G0/G1 phase arrest with a fold change of 1.12. Besides, it increased the generation of reactive oxygen species (ROS) with a fold change of 1.34at 100μM. Narirutin inhibited hyaluronidase's activity in cell-free (11.17μM) and cell-based assays (67.23μM) and showed a strong binding interaction with hyaluronidase. Finally, the MD simulation analysis supported the idea that narirutin binding enhanced compactness and stability and created a stable complex with hyaluronidase. In addition, ADMET prediction indicates that it is a non-toxic, non-CYPs inhibitor and thus didn't alter the metabolism. The results reveal that narirutin may be a potential chemopreventive agent for hormone-resistant prostate cancer cells in addition to offering data for supporting diet-based nutraceutical agents to prevent prostate cancer.

Cannabidiol alters mitochondrial bioenergetics via VDAC1 and triggers cell death in hormone-refractory prostate cancer

In spite of the huge advancements in both diagnosis and interventions, hormone refractory prostate cancer (HRPC) remains a major hurdle in prostate cancer (PCa). Metabolic reprogramming plays a key role in PCa oncogenesis and resistance. However, the dynamics between metabolism and oncogenesis are not fully understood. Here, we demonstrate that two multi-target natural products, cannabidiol (CBD) and cannabigerol (CBG), suppress HRPC development in the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model by reprogramming metabolic and oncogenic signaling. Mechanistically, CBD increases glycolytic capacity and inhibits oxidative phosphorylation in enzalutamide-resistant HRPC cells. This action of CBD originates from its effect on metabolic plasticity via modulation of VDAC1 and hexokinase II (HKII) coupling on the outer mitochondrial membrane, which leads to strong shifts of mitochondrial functions and oncogenic signaling pathways. The effect of CBG on enzalutamide-resistant HRPC cells was less pronounced than CBD and only partially attributable to its action on mitochondria. However, when optimally combined, these two cannabinoids exhibited strong anti-tumor effects in TRAMP mice, even when these had become refractory to enzalutamide, thus pointing to their therapeutical potential against PCa.

Induction of apoptosis in human hormone‐refractory prostate cancer cell lines by using resveratrol in combination with AT‐101

The aim of this study was to determine the appropriate doses of AT-101 and resveratrol combination in the in vitro hormone-refractory prostate cancer (PC) cell lines, in order to evaluate the cytotoxic and genotoxic effects of this combination on the proliferation of cancer cells, namely PC-3, DU-145 and LNCAP. Cytotoxicity in PC cell lines was analysed by using the XTT Cell Proliferation Assay. DNA damage was performed with the cell death assay. Apoptotic protein levels were performed by Roche Human Apoptosis Array. IC50 values were determined by XTT analysis. The strongest combined doses (100µM resveratrol+5µM AT-101) were found to have the strongest synergistic apoptotic and cytotoxic effects on DU-145 cells at 72hr. While the combined use of resveratrol and AT-101 increased the expression of markers in apoptotic cell pathways on cells, a decrease in the expression of anti-apoptotic markers was detected (p˂0.05). Combined applications of these compounds showed an important synergism in the hormone-refractory PC cell lines, and it was determined that after the post-translational modification, they were significantly effective on the apoptotic pathway. These results have revealed that the combination of resveratrol and AT-101 holds great expectation as a new chemotherapeutic application in the treatment of human prostate cancer.

Cytotoxic and anti-angiogenic effects of zoledronic acid in DU-145 and PC-3 prostate cancer cell lines.

This study aims to investigate the apoptotic and anti-angiogenic effect of Zoledronic acid on hormone-refractory prostate cancer cell lines. XTT cell proliferation assay used to assess cytotoxicity. Caspase 3/7 activity and DNA fragmentation were measured to verify apoptosis. Angiogenic cytokine profiles investigated using the human angiogenesis antibody array I. Administration of Zoledronic acid on PC-3 and DU-145 prostate cancer cell lines resulted in increased cytotoxicity and apoptosis with a time- and dose-related manner. Also, the administration of Zoledronic acid significantly reduced several angiogenic cytokine productions in PC-3 and DU-145 cell lines. Zoledronic acid successfully induced apoptosis and reduced various angiogenic cytokine production in hormone-refractory prostate cancer cell lines. Novel treatment protocols may be developed in the future with chemotherapeutic combinations for the treatment of prostate cancer.

Activated Wnt/β-Catenin signaling contributes to E3 ubiquitin ligase EDD-conferred docetaxel resistance in prostate cancer

Docetaxel is commonly used to treat hormone-refractory prostate cancer (HRPC), but its clinical efficacy is limited by drug resistance, with the molecular mechanisms remaining elusive. The E3 ubiquitin ligase EDD modifies substrate proteins through ubiquitination and is involved in the regulation of cell proliferation and tumorigenesis. However, its role in docetaxel resistance of prostate cancer is unknown. Here, we show that EDD is upregulated in docetaxel-resistant HRPC cells, as well as in human HRPC treated with docetaxel chemotherapy. Functionally, EDD knockdown resensitizes HRPC cells to docetaxel in vitro and in vivo, and in reverse, EDD overexpression promotes docetaxel resistance. We further show that the Wnt/β-Catenin signaling is activated in docetaxel-resistant HRPC cells, which can be promoted by EDD. Finally, inhibiting Wnt signaling through β-Catenin knockdown remarkably attenuates EDD-mediated docetaxel resistance, suggesting that the activated Wnt/β-Catenin signaling is a key contributor to EDD-conferred docetaxel resistance in HRPC cells. Altogether, our study uncovers a positive role of EDD in docetaxel resistance in prostate cancer, and further links it with the regulation of Wnt/β-Catenin signaling.

Cytotoxicity of AMANTADIG – a semisynthetic digitoxigenin derivative – alone and in combination with docetaxel in human hormone-refractory prostate cancer cells and its effect on Na+/K+-ATPase inhibition

Cardiac glycosides (CGs) are natural compounds used to treat congestive heart failure. They have garnered attention as a potential cancer treatment option, especially because they bind to Na+/K+-ATPase as a target and activate intracellular signaling pathways leading to a variety of cellular responses. In this study we evaluated AMANTADIG, a semisynthetic cardenolide derivative, for its cytotoxic activity in two human androgen-insensitive prostate carcinoma cell lines, and the potential synergistic effects with docetaxel. AMANTADIG induced cytotoxic effects in both cell lines, and a combination with docetaxel showed a moderate and strong synergism in DU145 and PC-3 cells, respectively, at concentrations considerably lower than their IC50 values. Cell cycle analyses showed that AMANTADIG and its synergistic combination induced G2/M arrest of DU145 and PC-3 cells by modulating Cyclin B1, CDK1, p21 and, mainly, survivin expression, a promising target in cancer therapy. Furthermore, AMANTADIG presented reduced toxicity toward non-cancerous cell type (PBMC), and computational docking studies disclosed high-affinity binding to the Na+/K+-ATPase α subunit, a result that was experimentally confirmed by Na+/K+-ATPase inhibition assays. Hence, AMANTADIG inhibited Na+/K+-ATPase activity in PC-3 cells, as well as in purified pig kidney at nanomolar range. Altogether, these data highlight the potent effects of AMANTADIG in combination with docetaxel and offer important insights for the development of more effective and selective therapies against prostate cancer.

Polyprenylated polycyclic acylphloroglucinol: Angiogenesis inhibitor from Garcinia multiflora

A new polyprenylated polycyclic acylphloroglucinol, garcimultiflorone K (1), has been isolated from the stems of Garcinia multiflora, together with two known compounds, garcimultiflorone A (2) and garcimultiflorone B (3). The structure of new compound 1 was determined through spectroscopic methods including 1D and 2D NMR and MS analyses. The anti-angiogenic and anti-cancer effects of compounds 1–3 were evaluated in human endothelial progenitor cells (EPCs) and cancer cells. Of these, garcimultiflorone K (1) displayed the most potent anti-angiogenic property by suppressing cell growth and tube formation of EPCs. Compound 1 also exhibited growth-inhibitory activities against human hepatocellular carcinoma cell line SK-Hep-1 and hormone refractory prostate cancer cell line PC-3 with GI50 values of 4.3 ± 1.6 and 6.6 ± 0.4 μM, respectively.

Antagonistic activities of miR-148a and DNMT1: Ectopic expression of miR-148a impairs DNMT1 mRNA and dwindle cell proliferation and survival

Functional analyses of noncoding RNAs have associated many micro RNAs (miRNA, miR) with various physiological processes, including proliferation, differentiation, development, cell metabolism, and apoptosis. Aberrant expression of miRNA and imbalance in their functions may lead to cellular aberration and different disease development, including cancer. In silico analysis of miRNA target prediction suggested that miR-148a possess a binding site in the 3′ UTR of DNMT1 mRNA which can cause silencing of DNMT1 gene. Accordingly, we performed in vitro cell culture experiments to confirm the effect miR-148a on DNMT1 gene expression in prostate cancer cell lines. We demonstrated that there is a physical association between DNMT1 mRNA and miR-148a. We found that (i) ectopic expression of miR-148a induces programmed cell death and represses cell proliferation by targeting DNMT1; (ii) miR-148a gene is regulated by DNA methylation and DNMT1 in prostate cancer. We conclude that miR-148a is silenced by DNA methylation and ectopic expression of miR-148a suppresses DNMT1 expression and induced apoptotic genes expression in hormone-refractory prostate cancer cells.

Maspin Enhances the Anticancer Activity of Curcumin in Hormone-refractory Prostate Cancer Cells.

Androgen deprivation therapy remains the principal treatment for patients with advanced prostate cancer, though, most patients will eventually develop hormone-refractory prostate cancer (HRPC). Androgen ablation mediated maspin-induction has been identified in cancer patients. However, the role of maspin on the anticancer activity of curcumin derived from turmeric (Curcuma longa) in HRPC cells has not been elucidated. The anticancer action of curcumin in hormone-independent prostate cancer cells (DU145, and PC-3) was determined by measures of cell survival rate. The cause of maspin silencing on the anti-tumor abilities of curcumin in PC-3 cells was evaluated by measures of cell survival rate, cell-cycle distribution, and apoptosis signaling analysis. Our present study showed that PC-3 cells (with higher maspin expression) were more sensitive than DU145 cells to curcumin treatment (with lower maspin expression). RNA interference-mediated maspin silencing reduced curcumin sensitivity of PC-3 cells, as evidenced by reduced apoptotic cell death. After exposure to curcumin, maspin-knockdown cells showed lower expression levels of pro-apoptotic proteins, Bad and Bax, as compared with control cells. Maspin can enhance the sensitivity of HRPC cells to curcumin treatment.

Midostaurin inhibits hormone-refractory prostate cancer PC-3 cells by modulating nPKCs and AP-1 transcription factors and their target genes involved in cell cycle

The development of prostate cancer from a clinically localized, hormone-naive state to a hormonerefractory phenotype involves a complex interplay of protein kinase C (PKC) and activator protein-1 (AP-1). Therefore, the present study aimed to uncover the roles of PKC and AP-1 through midostaurin-mediated regulation—a multi-target protein kinase inhibitor. Androgen Receptor-negative, hormone-refractory prostate cancer cells (PC-3) were used as an in-vitro model system. The effect of midostaurin on cell viability was assessed by an MTT assay. Expression studies on PKC-α, PKC-d, different AP-1 transcription factors, and AP-1 regulating genes were analyzed by semiquantitative RT-PCR, and protein levels of Bcl-2 were evaluated by western blotting. Midostaurin decreased the viability of hormone-refractory PC-3 cells. Furthermore, midostaurin significantly induced the transcripts of apoptotic-mediated PKC-d, tumor suppressor p53, cell cycle inhibitor p21cip1/waf1, death receptor TNF-α, pro-apoptotic Bax, and Caspase-8, and eventually inhibited the expression of pro-survival PKC-e, pro-oncogene c-Jun, c-Fos, Fra-1, positive growth regulator cyclin D1, and anti-apoptotic Bcl-2. In addition, midostaurin also decreased the protein expression of anti-apoptotic Bcl-2. The present study provided evidence that midostaurin suppresses tumor growth and induces apoptosis in hormone-refractory PC-3 cells via modulation of PKC-d and PKC-e expression, and regulation of PMA-altered c-Jun, c-Fos, and Fra-1 AP-1 transcription factors and their target genes involved in cell cycle regulation (cyclin D1, p53, p21, Bcl-2, and TNF-α). Thus, pharmacological targeting of PKC and AP-1 factors may have therapeutic potential against hormone-refractory prostate cancer.

Abstract IA22: Emerging signaling pathways in prostate cancer therapy

Abstract One major prerequisite to develop targeted therapies is the identification of relevant cellular targets and the identification of the relevant patient population in which to test these therapies. Although androgen ablation therapy, surgery and radiation therapy are effective for the treatment of local prostate cancer (PCa), there is no effective treatment available for patients with metastatic disease. The receptor tyrosine kinase Axl has been implicated in the pathology of many cancers. Increased Axl expression correlates with metastasis, aggressive behavior, and poor survival and have been linked with resistance to chemotherapeutic regimens in tumors. Interestingly, in these reports inhibition of Axl leads to restoration of sensitivity to drug therapy, indicating that Axl may represent a promising therapeutic target whose inhibition could prevent or overcome acquired resistance to some drugs. We have shown that Axl is overexpressed in PCa and is an essential regulator of PCa proliferation and tumor growth. Axl expression is elevated in hormone-refractory PCa cell lines and Axl knockdown reduces migration and invasion and tumor formation in vivo. The Axl ligand, GAS6, acts as a growth and/or survival factor and its binding to Axl activates PI3K and its downstream targets S6K and Akt. Activation of these pathways has been reported to induce nuclear translocation of the transcription factor nuclear factor kappa B (NF-κB), IL-6 production and STAT3 activation. The molecule named R428 (now renamed BGB324) inhibits in a dose-dependent manner Gas6 stimulated Axl autophosphorylation and activity with high specificity, selectivity, and affinity and blocks Axl-dependent signaling events, such as Akt phosphorylation, cell invasion, and pro-inflammatory cytokine production. R428/BGB324 effectively prevents or reverses acquired resistance to several cancer therapies in preclinical models. Most importantly, as a result of these and other encouraging preclinical findings of therapeutic value this first-in-class, highly selective Axl inhibitor has entered the clinical trial phase. Docetaxel, the main chemotherapeutic drug used in aggressive prostate cancer treatment, has shown limited efficacy against metastatic PCa, primarily due to invariable development of drug resistance, necessitating a thorough investigation of the mechanisms underlying this drug resistance and the development of novel, more efficacious therapies to prevent or overcome resistance. Preliminary data from our laboratory provide strong evidence for the notion that Axl plays a pivotal role in resistance to docetaxel and possibly cabazitaxel treatment. Importantly, Axl inhibitor R428 enhances docetaxel efficacy. Citation Format: Luiz F. Zerbini. Emerging signaling pathways in prostate cancer therapy [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr IA22.

Taxane-Grafted Metal-Oxide Nanoparticles as a New Theranostic Tool against Cancer: The Promising Example of Docetaxel-Functionalized Titanate Nanotubes on Prostate Tumors.

The combination of anticancer drugs and metal oxide nanoparticles is of great interest in cancer nanomedicine. Here, the development of a new nanohybrid, titanate nanotube-docetaxel (TiONts-DTX) is reported, the two parts of which are conjugated by covalent linkages. Unlike most nanoparticles currently being developed for biomedical purposes, TiONts present a needle-shaped morphology. The surface of TiONts is linked with 3-aminopropyl triethoxysilane and with a hetero-bifunctional polymer (polyethylene glycol) to create well-dispersed and biocompatible nanovectors. The prefunctionalized surface of this scaffold has valuable attachments to graft therapeutic agents (DTX in our case) as well as chelating agents (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) to monitor the nanohybrids. To evaluate drug efficacy, in vitro tests have demonstrated that the association between TiONts and DTX shows cytotoxic activity against a hormone-refractory prostate cancer cell line (22Rv1) whereas TiONts without DTX do not. Finally, the first in vivo tests with intratumoral injections show that more than 70% of TiONts nanovectors are retained within the tumor for at least 7 d. Moreover, tumor growth in mice receiving TiONts-DTX is significantly slower than that in mice receiving free DTX. This nanohybrid can thus become a promising new tool in biomedicine to fight against prostate cancer.

MAOA-a novel decision maker of apoptosis and autophagy in hormone refractory neuroendocrine prostate cancer cells

Autophagy and apoptosis are two well-controlled mechanisms regulating cell fate. An understanding of decision-making between these two pathways is in its infancy. Monoamine oxidase A (MAOA) is a mitochondrial enzyme that is well-known in psychiatric research. Emerging reports showed that overexpression MAOA is associated with prostate cancer (PCa). Here, we show that MAOA is involved in mediating neuroendocrine differentiation of PCa cells, a feature associated with hormone-refractory PCa (HRPC), a lethal type of disease. Following recent reports showing that NED of PCa requires down-regulation of repressor element-1 silencing transcription factor (REST) and activation of autophagy; we observe that MAOA is a novel direct target gene of REST. Reactive oxygen species (ROS) produced by overexpressed MAOA plays an essential role in inhibiting apoptosis and activating autophagy in NED PCa cells. MAOA inhibitors significantly reduced NED and autophagy activation of PCa cells. Our results here show MAOA as a new decision-maker for activating autophagy and MAOA inhibitors may be useful as a potential therapy for neuroendocrine tumors.

Menthols as Chiral Auxiliaries for Asymmetric Cycloadditive Oligomerization: Syntheses and Studies of β-Proline Hexamers

To produce a novel class of structurally ordered poly-β-prolines, an emergent method for synthesizing chiral β-peptide molecular frameworks was developed based on 1,3-dipolar cycloaddition chemistry of azomethine ylides. Functionalized short β-peptides with up to six monomeric residues were efficiently synthesized in homochiral forms using a cycloadditive oligomerization approach. X-ray, NMR, and CD structural analyses of the novel β-peptides revealed secondary structure features that were generated primarily by Z/E-β-peptide bond isomerism. Anticancer in cellulo activity of the new β-peptides toward hormone-refractory prostate cancer cells was observed and was dependent on the absolute configuration of the stereogenic centers and the chain length of the β-proline oligomers.

Octreotide in combination with AT-101 induces cytotoxicity and apoptosis through up-regulation of somatostatin receptors 2 and 5 in DU-145 prostate cancer cells.

Prostate cancer (PCa) is the most common type of cancer among males. Although survival rate of early-stage PCa is high, treatment options are very limited for recurrent disease. In this study, the possible synergistic cytotoxic and apoptotic effect of octreotide in combination with AT-101 was investigated in DU-145 hormone and drug refractory prostate cancer cell line. To enlighten the action mechanisms of the combination treatment, expression levels of somatostatin receptors 2 and 5 (SSTR2 and SSTR5) were also investigated. Cell viability was measured by XTT assay. Apoptosis was assessed through DNA fragmentation analysis and caspase 3/7 assay. mRNA and protein levels of SSTR2 and SSTR5 were evaluated by qRT-PCR and western blot analysis, respectively. Octreotide in combination with AT-101 inhibited cell viability and induced apoptosis synergistically in DU-145 cells as compared to any agent alone. Combination treatment increased both SSTR2 and SSTR5 mRNA and protein levels in DU-145 cells. The data suggest that this combination therapy may be a good candidate for patients with advanced metastatic PCa do not respond to androgen deprivation.

Zerumbone, a ginger sesquiterpene, induces apoptosis and autophagy in human hormone-refractory prostate cancers through tubulin binding and crosstalk between endoplasmic reticulum stress and mitochondrial insult.

Zerumbone, a natural monocyclic sesquiterpene, is the main component of the tropical plant Zingiber zerumbet Smith. Zerumbone induced antiproliferative and apoptotic effects against PC-3 and DU-145, two human hormone-refractory prostate cancer (HRPC) cell lines. Zerumbone inhibited microtubule assembly and induced an increase of MPM-2 expression (specific recognition of mitotic proteins). It also caused an increase of phosphorylation of Bcl-2 and Bcl-xL, two key events in tubulin-binding effect, indicating tubulin-binding capability and mitotic arrest to zerumbone action. Furthermore, zerumbone induced several cellular effects distinct from tubulin-binding properties. First, zerumbone significantly increased, while paclitaxel (as a tubulin-binding control) decreased, Mcl-1 protein expression. Second, paclitaxel but not zerumbone induced Cdk1 activity. Third, zerumbone other than paclitaxel induced Cdc25C downregulation. The data suggest that, in addition to targeting tubulin/microtubule, zerumbone may act on other targets for signaling transduction. Zerumbone induced mitochondrial damage and endoplasmic reticulum (ER) stress as evidenced by the loss of mitochondrial membrane potential and upregulation of GRP-78 and CHOP/GADD153 expression. Zerumbone induced an increase of intracellular Ca(2+) levels, a crosstalk marker between ER stress and mitochondrial insult, associated with the formation of active calpain I fragment. It induced apoptosis through a caspase-dependent way and caused autophagy as evidenced by dramatic LC3-II formation. In summary, the data suggest that zerumbone is a multiple targeting compound that inhibits tubulin assembly and induces a crosstalk between ER stress and mitochondrial insult, leading to apoptosis and autophagy in HRPCs.

Abstract 3086: From profiling to function: A role for microRNA miR-888 in promoting prostate cancer progression

Abstract Prostate cancer remains the second leading cause of cancer-related deaths among men in the United States despite the widespread use of prostate specific antigen (PSA) as a diagnostic marker for prostate cancer and as a predictor of treatment outcome. MicroRNAs (MiRNAs) belong to a growing class of small non-coding RNAs that are often abnormally expressed in fluid and tissue specimens from prostate cancer patients compared to non-cancer individuals. These miRNAs are hypothesized to play a direct role in promoting disease progression and metastasis in the prostate and are intensely studied for both their diagnostic and therapeutic potential for human cancer. Our laboratory profiled candidate prostate-cancer associated miRNAs in an innovative prostatic fluid biomarker source called expressed prostatic secretions in urine (EPS urine) to determine their utility as discriminating biomarkers for advanced forms of prostate cancer. 10 out of 50 miRNA tested showed statistically significant differences in expression between cancer and non-cancer patient groups within the supernatant but not pellet fractions of whole EPS urine. We are investigating if differential miRNA expression in EPS supernatant is due to exosomal populations and how miRNA-loaded exosomes modulate prostate tumorigenesis in mice. Our profiling studies identified miR-888 as a novel factor that correlates with advanced prostate cancer in human prostate cancer cell lines, EPS urine, and primary tumors. Functional assays revealed that miR-888 promotes proliferation, migration, and colony formation of hormone-refractory and androgen-sensitive human prostate cancer cells. Our working model is that miR-888 overexpression in the diseased prostate suppresses SMAD4, RBL1, and TIMP2 targets leading to tumor progression and metastasis. Human miR-888 belongs to a genomic cluster of seven miRNAs on human chromosome Xq27.3. We are currently testing how this miR-888 cluster interacts within a growing network of coding and non-coding genes to regulate prostate tumor progression. This research will provide a better understanding how prostate tumor cells progress to a more metastatic, aggressive state and facilitate the development of more effective diagnostic and therapeutic strategies for this prevalent and deadly disease. Citation Format: Holly Lewis, Tsuyoshi Hasegawa, Garrison Glavich, Raymond Lance, O. John Semmes, Hind Beydoun, Richard Drake, Aurora Esquela-Kerscher. From profiling to function: A role for microRNA miR-888 in promoting prostate cancer progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3086. doi:10.1158/1538-7445.AM2015-3086

Ligustrazine Suppresses the Growth of HRPC Cells through the Inhibition of Cap- Dependent Translation Via Both the mTOR and the MEK/ERK Pathways.

Ligustrazine (TMP) has recently been used for the treatment of various cancers. However, its exact mechanisms of action, particularly the functions and the mechanisms of Ligustrazine in human hormone-refractory prostate cancer (HRPC), have not yet been extensively studied. Recently, our findings suggest that Ligustrazine dose- and time-dependently inhibits the growth of HRPC cells by reducing their proliferation and promoting apoptosis. Interestingly, the treatment of hormone-refractory prostate cancer (PC-3) cells with Ligustrazine results in a significant inhibition of the activation of mTOR and related downstream targets, which are critical for cell growth. Furthermore, pull-down assays with 7-methyl- GTP Sepharose 4B beads indicate that Ligustrazine reduces the available eIF4E for translation initiation. Accordingly, the results from the translation assay using a luciferase reporter system further demonstrate that Ligustrazine indeed inhibits cap-dependent translation. In addition, the transient overexpression of eIF4E or MNK1 prevents the Ligustrazine-induced inhibition of proliferation and confers significant protection against Ligustrazine-induced apoptosis. Therefore, the present study provides evidences that Ligustrazine may be a candidate for therapeutic reagent for the treatment of HRPC and certifies that Ligustrazine modulates the availability of eIF4E mainly through the mTOR and MEK/ERK signaling pathways to inhibit cap-dependent translation. Taken together, our results indicate that the inhibition of cap-dependent translation is likely an essential mechanism in Ligustrazine-induced apoptosis.

TGF-β1 mediates the radiation response of prostate cancer

Radiotherapy is the main treatment modality for prostate cancer. This study investigated the role of TGF-β1 in biological sequelae and tumor regrowth following irradiation, which are critical for the clinical radiation response of prostate cancer. Human and murine prostate cancer cell lines, and corresponding hormone-refractory (HR) cells, were used to examine the radiation response by clonogenic assays in vitro and tumor growth delay in vivo. Biological changes after irradiation, including cell death and tumor regrowth, were examined by experimental manipulation of TGF-β1 signaling. The correlations among tumor radiation responses, TGF-β1 levels, and regulatory T cells (Tregs) recruitment were also evaluated using animal experiments. HR prostate cancer cells appeared more radioresistant and had higher expression of TGF-β1 compared to hormone-sensitive (HS) cells. TGF-β1 expression was positively linked to irradiation and radioresistance, as demonstrated by in vitro and in vivo experiments. Inhibition of TGF-β1 increased tumor inhibition and DNA damage after irradiation. When mice were irradiated with a sub-lethal dose, the regrowth of irradiated tumors was significantly correlated with TGF-β1 levels and Tregs accumulation in vivo. Furthermore, blocking TGF-β1 clearly attenuated Tregs accumulation and tumor regrowth following treatment. These data demonstrate that TGF-β1 is important in determining the radiation response of prostate cancer, including tumor cell killing and the tumor microenvironment. Therefore, concurrent treatment with a TGF-β1 inhibitor is a potential therapeutic strategy for increasing the radiation response of prostate cancer, particularly for more aggressive or HR cancer cells. • HR prostate cancer cells appeared more radioresistant and had higher expression of TGF-β1. • TGF-β1 was positively linked to the radiation resistance of prostate cancer. • Tumor regrowth following irradiation was significantly correlated with TGF-β1 and Tregs levels. • Blocking TGF-β1 significantly attenuated RT-induced DNA repair and Tregs. • TGF-β1 inhibitor increases the radiation response of HR cancer cells.

MP55-07 FLAVONOIDS ENHANCE TRAIL SENSITIVITY IN PROSTATE CANCER CELLS BY TARGETING ADENINE NUCLEOTIDE TRANSLOCASE-2

You have accessJournal of UrologyProstate Cancer: Basic Research III1 Apr 2015MP55-07 FLAVONOIDS ENHANCE TRAIL SENSITIVITY IN PROSTATE CANCER CELLS BY TARGETING ADENINE NUCLEOTIDE TRANSLOCASE-2 Masakatsu Oishi, Takashi Ueda, Terukazu Nakamura, Yoshio Naya, Fumiya Hongo, Kazumi Kamoi, Koji Okihara, and Tsuneharu Miki Masakatsu OishiMasakatsu Oishi More articles by this author , Takashi UedaTakashi Ueda More articles by this author , Terukazu NakamuraTerukazu Nakamura More articles by this author , Yoshio NayaYoshio Naya More articles by this author , Fumiya HongoFumiya Hongo More articles by this author , Kazumi KamoiKazumi Kamoi More articles by this author , Koji OkiharaKoji Okihara More articles by this author , and Tsuneharu MikiTsuneharu Miki More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.2050AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent. Recombinant human TRAIL has been under clinical trials, whereas various kinds of malignant tumors have resistance to TRAIL. It has been shown that several anticancer agents and flavonoids (apigenin, quercetin etc.) overcome resistance to TRAIL by upregulating death receptor 5 (DR5) in malignant tumor cells. However, the mechanisms by which these compounds induce DR5 expression remain unknown. On the other hand, although docetaxel plus prednisone is effective in hormone-refractory prostate cancer, the outcome of this treatment is still insufficient. Therefore, new strategies are needed to treat this cancer. Thus we investigated the mechanism in a hormone-refractory prostate cancer cell line DU145. METHODS To elucidate the mechanisms by which flavonoids induce DR5 expression in DU145 cells, we explored the proteins binding to flavonoids using FG beads with epoxy linkers. We fixed genistein, which enhances TRAIL sensitivity without upregulating DR5, apigenin, and quercetin onto these beads (Figure 1A). The binding proteins of apigenin, quercetin, and genistein were purified from the DU145 whole cell extracts and were identified by MALDI-TOF MS analysis. Then, function of binding proteins was analized. RESULTS Comparing the binding proteins, we discovered that ANT2 was a target of apigenin and quercetin, but not genistein in DU145 cells (Figure 1B). Similarly to treatment of apigenin and quercetin, knockdown of ANT2 enhanced TRAIL-induced apoptosis by upregulating DR5 expression. Moreover, silencing of ANT2 attenuated the enhancement of TRAIL-induced apoptosis by apigenin or quercetin. CONCLUSIONS These results suggest that flavonoids upregulate DR5 and enhance TRAIL-induced apoptosis in hormone-refractory prostate cancer cells by binding and inhibiting ANT2 (Figure 1C). We propose that ANT2 inhibitors may contribute to TRAIL therapy in hormone-refractory prostate cancer. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e675 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Masakatsu Oishi More articles by this author Takashi Ueda More articles by this author Terukazu Nakamura More articles by this author Yoshio Naya More articles by this author Fumiya Hongo More articles by this author Kazumi Kamoi More articles by this author Koji Okihara More articles by this author Tsuneharu Miki More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...