Androgen-independent Prostate Carcinoma Research Articles

Abstract 2858: Radiotherapy and NK cell-based immunotherapy: An evolutionary double-bind

Abstract Evolution-informed therapies exploit the ecological and evolutionary consequences of drug resistance to inhibit the expansion of treatment resistant populations and prolong time to progression. One strategy, termed an evolutionary double-bind, uses an initial therapy to elicit a specific adaptive mechanism that is then selectively targeted by a follow-on therapy. Here we examine combining radiation therapy followed by immunotherapy as a double bind strategy. Radiotherapy (RT) induces lethal double-strand DNA breaks in tumor cells and radiosensitivity is governed by the cells’ DNA repair capabilities. Radioresistant cancer cells upregulate DNA damage response pathways. However, successful adaptations to RT and other DNA damaging agents can increase natural killer (NK) cell ligand expression on tumor cells increasing their vulnerability to the immune system. We conducted a multidisciplinary investigation of this potential evolutionary double bind using an isogenic cell line model of radiation resistance derived from an androgen-independent human prostate carcinoma cell line (22Rv1). We demonstrate that RT-resistant cells maintain higher expression of NK cell ligands and have a 2-fold increase in sensitivity to NK cell mediated killing. Furthermore, we show that preferential targeting of the RT-resistant population by NK cells is preserved in competition assays with varying initial population frequencies. Scope of treatment responses are dependent on population frequencies in our in vitro analysis. Mathematical modeling quantified three key elements of a double-bind: cost of resistance, inter-specific competition between RT-sensitive and RT-resistant lines, and preferential targeting of RT-resistant lines by NK cells. We conclude that RT followed by immunotherapy produces an evolutionary double bind that can be exploited in heterogenous tumors to limit RT resistance. Furthermore, model simulations predict that extinction of both populations is achievable by sequential RT and NK cell therapy. Citation Format: Kimberly Luddy, Jeffery West, Mark Robertson-Tessi, Bina Desai, Taylor M. Bursell, Sarah Barrett, Joel Brown, Jacintha O'Sullivan, Robert Gatenby, Laure Marignol, Alexander R. Anderson, Cliona O'Farrelly. Radiotherapy and NK cell-based immunotherapy: An evolutionary double-bind [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 2858.

Arglabin, an EGFR receptor tyrosine kinase inhibitor, suppresses proliferation and induces apoptosis in prostate cancer cells

Evidence for clinical efficacy of a semisynthetic derivative of arglabin in anticancer treatment prompted us to examine molecular mechanisms and cellular targets of arglabin. Arglabin, a sesquiterpene lactone isolated from Artemisia glabella was cytotoxic to different human cancer cell lines including those derived from advanced triple-negative breast, lung, androgen-dependent and androgen-independent prostate carcinomas. Noteworthy, arglabin was less toxic to non-neoplastic prostate epithelial cells indicating selectivity for cancer cells. At the molecular level, prior to any biochemical signs of cellular toxicity, arglabin reduced levels of cell-surface sulphanyl groups and inhibited phosphorylation of the redox-sensitive receptor tyrosine kinase EGFR, the only active RTK in PC-3 prostate cancer cells among 49 TRKs analyzed by the assay. Henceforth, arglabin inhibited the EGFR downstream signaling pathways mTORC1 and mTORC2. Accordingly, arglabin induced autophagosome formation and autophagic flux, inhibited phosphorylation of ribosomal protein S6 kinase beta-1 (S6K1) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), and impeded cell cycle progression and proliferation of PC-3 cells. In agreement with inhibition of the mTORC2 pathway, arglabin induced sustained actin polymerization, inhibited cell migration, and triggered apoptosis in vitro in 2D cell culture and colony formation assay and in vivo in prostate cancer xenografts grown on chick chorioallantoic membranes. Under physiological conditions, arglabin rapidly formed adducts with reduced glutathione (GSH). Moreover, thiol-based antioxidants GSH and β-mercaptoethanol abolished arglabin-induced cancer cell toxicity, whereas the non-thiol antioxidant trolox was ineffective pointing to a crucial role of interaction with cell-surface sulphanyl groups for arglabin cytotoxic activity against cancer cells.

Synthesis, Radiolabeling, and Biological Evaluation of the trans-Stereoisomers of 1-Amino-3-(fluoro-18F)-4-fluorocyclopentane-1-carboxylic Acid as PET Imaging Agents.

The enantiomeric non-natural cyclic amino acids (3R,4R)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid and (3S,4S)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid ([ 18 F]5) have been prepared as a racemic mixture in 1.3% decay corrected radiochemical yield and in greater than 99% radiochemical purity. [ 18 F]5 is transported primarily via system L with some transport occurring via system ASC, as assessed in rat 9L gliosarcoma, human U87 ΔEGFR glioblastoma, and human DU145 androgen-independent prostate carcinoma tumor cells. In rats bearing intracranial 9L gliosarcoma, [ 18 F]5 gave tumor to contralateral brain tissue ratios of up to 2.8. Biodistribution studies in healthy rats demonstrated that bladder accumulation is delayed until 10 min postinjection.

Synthesis, Radiolabeling, and Biological Evaluation of the cis Stereoisomers of 1-Amino-3-Fluoro-4-(fluoro-18F)Cyclopentane-1-Carboxylic Acid as PET Imaging Agents.

The non-natural cyclic amino acids (1S,3R,4S)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid ([18F]9) and (1S,3S,4R)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid ([18F]28) have been prepared in 10 and 1.7% decay corrected radiochemical yield, respectively, and in greater than 99% radiochemical purity. Cell assays in rat 9L gliosarcoma, human U87 ΔEGFR glioblastoma, and human DU145 androgen-independent prostate carcinoma tumor cells indicated that both compounds are substrates for amino acid transport primarily by system L, with some transport taking place via system ASC. In rats with 9L gliosarcoma, [18F]9 and [18F]28 provided high tumor to normal brain tissue ratios, with maximal ratios of 3.5 and 4.1, respectively. Biodistribution studies in healthy rats confirmed that both compounds are BBB permeable and that bladder accumulation is low until at least 5 min post injection.

Anti-Cancer Activity of Novel Dihydrotestosterone-Derived Ring A-Condensed Pyrazoles on Androgen Non-Responsive Prostate Cancer Cell Lines.

Regioselective synthesis of novel ring A-fused arylpyrazoles of dihydrotestosterone (DHT) was carried out in two steps under facile reaction conditions. Aldol condensation of DHT with acetaldehyde afforded a 2-ethylidene derivative regio- and stereo-selectively, which was reacted with different arylhydrazines in the presence of iodine via microwave-assisted oxidative cyclization reactions. The 17-keto analogs of steroidal pyrazoles were also synthesized by simple oxidation in order to enlarge the compound library available for pharmacological studies and to obtain structure–activity relationship. The antiproliferative activities of the structurally related heteroaromatic compounds were tested in vitro on human cervical and breast adenocarcinoma cell lines (HeLa, MCF-7 and MDA-MB-231) and on two androgen-independent malignant prostate carcinoma cell lines (PC-3 and DU 145). Based on primary cytotoxicity screens and IC50 assessment, a structure-function relationship was identified, as derivatives carrying a hydroxyl group on C-17 exhibit stronger activity compared to the 17-one counterparts. Cancer cell selectivity of the derivatives was also determined using non-cancerous MRC-5 cells. Furthermore, the proapoptotic effects of some selected derivatives were verified on androgen therapy refractive p53-deficient PC-3 cells. The present study concludes that novel DHT-derived arylpyrazoles exert cancer cell specific antiproliferative activity and activate apoptosis in PC-3 cells.

Endoplasmic reticulum stress, autophagic and apoptotic cell death, and immune activation by a natural triterpenoid in human prostate cancer cells.

Though the current therapies are effective at clearing an early stage prostate cancer, they often fail to treat late-stage metastatic disease. We aimed to investigate the molecular mechanisms underlying the anticancer effects of a natural triterpenoid, ganoderic acid DM (GA-DM), on two human prostate cancer cell lines: the androgen-independent prostate carcinoma (PC-3), and androgen-sensitive prostate adenocarcinoma (LNCaP). Cell viability assay showed that GA-DM was relatively more toxic to LNCaP cells than to PC-3 cells (IC50 s ranged 45-55 µM for PC-3, and 20-25 µM for LNCaP), which may have occurred due to differential expression of p53. Hoechst DNA staining confirmed detectable nuclear fragmentation in both cell lines irrespective of the p53 status. GA-DM treatment decreased Bcl-2 proteins while it upregulated apoptotic Bax and autophagic Beclin-1, Atg5, and LC-3 molecules, and caused an induction of both early and late events of apoptotic cell death. Biochemical analyses of GA-DM-treated prostate cancer cells demonstrated that caspase-3 cleavage was notable in GA-DM-treated PC-3 cells. Interestingly, GA-DM treatment altered cell cycle progression in the S phase with a significant growth arrest in the G2 checkpoint and enhanced CD4 + T cell recognition of prostate tumor cells. Mechanistic study of GA-DM-treated prostate cancer cells further demonstrated that calpain activation and endoplasmic reticulum stress contributed to cell death. These findings suggest that GA-DM is a candidate for future drug design for prostate cancer as it activates multiple pathways of cell death and immune recognition.

Adipocyte secreted factors enhance aggressiveness of prostate carcinoma cells.

Obesity has been associated with increased incidence and risk of mortality of prostate cancer. One of the proposed mechanisms underlying this risk association is the change in adipokines expression that could promote the development and progression of the prostate tumor cells. The main goal of this study was to evaluate the effect of preadipocyte and adipocyte secretome in the proliferation, migration and invasion of androgen independent prostate carcinoma cells (RM1) and to assess cell proliferation in the presence of the adiposity signals leptin and insulin. RM1 cells were co-cultured in with preadipocytes, adipocytes or cultured in their respective conditioned medium. Cell proliferation was assessed by flow cytometry and XTT viability test. Cell migration was evaluated using a wound healing injury assay of RM1 cells cultured with conditioned media. Cellular invasion of RM1 cells co-cultured with adipocytes and preadipocytes was assessed using matrigel membranes. Preadipocyte conditioned medium was associated with a small increase in RM1 proliferation, while adipocytes conditioned media significantly increased RM1 cell proliferation (p<0.01). Adipocytes also significantly increased the RM1 cells proliferation in co-culture (p <0.01). Cell migration was higher in RM1 cells cultured with preadipocyte and adipocyte conditioned medium. RM1 cell invasion was significantly increased after co-culture with preadipocytes and adipocytes (p <0.05). Insulin also increased significantly the cell proliferation in contrast to leptin, which showed no effect. In conclusion, prostate carcinoma cells seem to be influenced by factors secreted by adipocytes that are able to increase their ability to proliferate, migrate and invade.

Immunological Approaches for Treatment of Advanced Stage Cancers Invariably Refractory to Drugs

Worldwide, deaths due to cancers are taking an increasing toll. Invariably over time cancer cells become refractory to available drugs. At this stage, the tumor is largely metastasized and not amenable to radical surgery or focal radiations. This review seeks to bring out the existence of heterogeneity of cell types in each cancer, and proposes adoption of a combined approach employing more than one therapeutic agent for a more lasting treatment. Also proposed is the use of monoclonal therapeutic antibodies and vaccines against ectopically expressed key molecules for killing of cancer cells and prevention of their multiplication. Focus is on androgenindependent carcinoma of prostate and a variety of cancers expressing ectopically human chorionic gonadotropin (hCG) and/or Carcino-embryonic antigen (CEA). The utility of using antibodies directed against cell membrane located epitopes for homing and delivery of a safe anti-cancerous compound Curcumin to cancer cells is also described.

Bortezomib.

The ubiquitin-mediated degradation of proteins in numerous cellular processes, such as turnover and quality control of proteins, cell cycle and apoptosis, transcription and cell signaling, immune response and antigen presentation, and inflammation and development makes the ubiquitin-proteosome systems a very interesting target for various therapeutic interventions. Proteosome inhibitors were first synthesized as tools to probe the function and specificity of this particle's proteolytic activities. Most synthetic inhibitors rely on a peptide base, which mimics a protein substrate, attached at a COOH terminal "warhead." Notable warheads include boronic acids, such as bortezomib and epoxy ketones, such as carfilzomib. A variety of natural products also inhibit the proteosome that are not peptide-based, most notably lactacystin, that is related to NPI-0052, or salinosporamide A, another inhibitor in clinical trials. The possibility that proteosome inhibitors could be drug candidates was considered after studies showed that they induced apoptosis in leukemic cell lines. The first proteasome inhibitor in clinical application, bortezomib showed activity in non-small-cell lung and androgen-independent prostate carcinoma, as well as MM and mantle cell and follicular non-Hodgkin's lymphoma. It is now licensed for the treatment of newly diagnosed as well as relapsed/progressive MM and has had a major impact on the improvement in the treatment of MM in the last few years.

Human Prostate DU145 Carcinoma Cells Implanted in Nude Mice Remove the Peritoneal Mesothelium to Invade and Grow as Carcinomas

Implanted human, androgen-independent prostatic carcinoma cells (DU145) into athymic (NCr nu/nu) mice produce diverse tumors on the peritoneal surfaces of many organs. Light and ultrastructural observations show that the mesothelial covering these surfaces are typically microvilli-coated, squamous cells or secretory cuboidal cells. The peritoneal regions colonized by tumors lack mesothelial cells and are covered by actively replicating carcinoma cells that grow as poorly differentiated cell clusters made of cell aggregates to somewhat compact spheroids covered with pleiomorphic microvilli and containing an undifferentiated vascular supply. These xenografts clusters invade the diaphragm and develop into tumors with both a basal solid aspect and an upper region of cribriform morphology. Furthermore, each tumor contains two cell types: (1) a poorly differentiated clear cell type, which grows into intraperitoneal tumors and (2) a large, basophilic cell type, which invades the peritoneal stroma of organs, including of the diaphragm.

Androgen-independent prostate cancer cells circumvent EGFR inhibition by overexpression of alternative HER receptors and ligands

The deregulation of the epidermal growth factor receptor (EGFR) pathway plays a major role in the pathogenesis of prostate cancer (PCa). However, therapies targeting EGFR have demonstrated limited effectiveness in PCa. A potential mechanism to overcome EGFR blockade in cancer cells is the autocrine activation of alternative receptors of the human EGFR (HER) family through the overexpression of the HER receptors and ligands. In the present study, we were interested in analyzing if this intrinsic resistance mechanism might contribute to the inefficacy of EGFR inhibitors in PCa. To this end, we selected two androgen-independent human prostate carcinoma cell lines (DU145 and PC3) and established DU145 erlotinib-resistant cells (DUErR). Cells were treated with three EGFR inhibitors (cetuximab, gefinitib and erlotinib) and the sensitivity to each treatment was assessed. The gene expression of the four EGFR/HER receptors and seven ligands of the HER family was analyzed by real-time PCR prior to and after each treatment. The receptors expression and activation were further characterized by flow cytometry and western blot analysis. EGFR inhibition rapidly induced enhanced gene expression of the EGF, betacellulin and neuregulin-1 ligands along with HER2, HER3 and HER4 receptors in the DU145 cells. In contrast, slight changes were observed in the PC3 cells, which are defective in the phosphatase and tensin homolog (PTEN) tumor suppressor gene. In the erlotinib-resistant DUErR cells, the expression of HER2 and HER3 was increased at mRNA and protein levels together with neuregulin-1, leading to enhanced HER3 phosphorylation and the activation of the downstream PI3K/Akt survival pathway. HER3 blockage by a monoclonal antibody restored the cytostatic activity of erlotinib in DUErR cells. Our results confirm that the overexpression and autocrine activation of HER3 play a key role in mediating the resistance to EGFR inhibitors in androgen-independent PCa cells.

Abstract 2697: Role of a novel flavonoid enriched in ocimum sanctum linn for prostate cancer chemoprevention and therapy

Abstract The present study was conducted to determine the efficacy of novel flavonoid vicenin-2 (VCN-2), an active constituent of the medicinal herb Ocimum Sanctum Linn or Tulsi, as a single agent and in combination with docetaxel (DTL) in carcinoma of prostate (CaP). VCN-2 effectively induced anti-proliferative, anti-angiogenic and pro-apoptotic effect in CaP cells (PC-3, DU-145 and LNCaP) irrespective of their androgen responsiveness or p53 status. VCN-2 inhibited EGFR/Akt/mTOR/ p70S6K pathway along with decreasing c-Myc, cyclin D1, cyclin B1, CDK4, PCNA and hTERT in vitro. VCN-2 reached a level of 2.6 + 0.3 μM in serum after oral administration in mice which reflected that VCN-2 is orally absorbed. The i.v. administration of docetaxel (DTL), current drug of choice in androgen-independent CaP, is associated with dose-limiting toxicities like febrile neutropenia which has lead to characterization of alternate routes of administration and potential combinatorial regimens. In this regard, VCN-2 in combination with DTL synergistically inhibited the growth of prostate tumors in vivo with a greater decrease in the levels of AR, pIGF1R, pAkt, PCNA, cyclin D1, Ki67, CD31, and increase in E-cadherin. VCN-2 has been investigated for radio-protection and anti-inflammatory properties. This is the first study on the anti-cancer effects of VCN-2. In conclusion, our investigations collectively provide strong evidence that VCN-2 is effective against CaP progression along with indicating that VCN-2 and DTL co-administration is more effective than either of the single agents in androgen-independent prostate cancer. (Supported in part by NIH grant CA 77495) 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 2697. doi:1538-7445.AM2012-2697

Cell-to-Cell Signaling Influences the Fate of Prostate Cancer Stem Cells and Their Potential to Generate More Aggressive Tumors

An increasing number of malignancies has been shown to be initiated and propelled by small subpopulations of cancer stem cells (CSC). However, whether tumor aggressiveness is driven by CSC and by what extent this property may be relevant within the tumor mass is still unsettled. To address this issue, we isolated a rare tumor cell population on the basis of its CD44+CD24− phenotype from the human androgen-independent prostate carcinoma cell line DU145 and established its CSC properties. The behavior of selected CSC was investigated with respect to the bulk DU145 cells. The injection of CSC in nude mice generated highly vascularized tumors infiltrating the adjacent tissues, showing high density of neuroendocrine cells and expressing low levels of E-cadherin and β-catenin as well as high levels of vimentin. On the contrary, when a comparable number of unsorted DU145 cells were injected the resulting tumors were less aggressive. To investigate the different features of tumors in vivo, the influence of differentiated tumor cells on CSC was examined in vitro by growing CSC in the absence or presence of conditioned medium from DU145 cells. CSC grown in permissive conditions differentiated into cell populations with features similar to those of cells held in aggressive tumors generated from CSC injection. Differently, conditioned medium induced CSC to differentiate into a cell phenotype comparable to cells of scarcely aggressive tumors originated from bulk DU145 cell injection. These findings show for the first time that CSC are able to generate differentiated cells expressing either highly or scarcely aggressive phenotype, thus influencing prostate cancer progression. The fate of CSC was determined by signals released from tumor environment. Moreover, using microarray analysis we selected some molecules which could be involved in this cell-to-cell signaling, hypothesizing their potential value for prognostic or therapeutic applications.

Immunohistochemical analysis of gastrin-releasing peptide receptor (GRPR) and possible regulation by estrogen receptor βcx in human prostate carcinoma

Gastrin-releasing peptide (GRP) belongs to the family of bombesin-like peptides. GRP was demonstrated to stimulate the proliferation and invasiveness of androgen-independent prostate carcinoma. GRP mediates its action through the membrane-bound receptor, GRP receptor (GRPR), which is characterized by a high-affinity binding for both GRP and bombesin. In human prostate cancer tissue, GRPR mRNA was reported to be detectable in more than 90% but its immunolocalizaition has not been reported. Therefore, in this study we immunolocalized GRPR in 51 human prostate cancer cases and correlated the findings with several clinicopathological parameters in order to better understand the function and regulation of GRPR in human prostate cancer. GRPR was immnolocalized in carcinoma cells and their values were significantly associated with Gleason score and immunoreactivity of estrogen receptor βcx (ERβcx) that is one of splicing variants of ligand dependent transcription factor, ERβ, and considered to be prognostic factor of prostate cancer patients. The amounts of GRPR and ERβcx mRNA in three prostate cancer cell lines PC-3, DU-145 and LNCaP evaluated by quantitative RT-PCR (qPCR) analysis were also significantly correlated. In addition, we established stable transformants of prostate carcinoma cell line PC-3 introduced with ERβcx, and confirmed that GRPR mRNA was induced in ERβcx over-expressing PC-3 cells by qPCR analysis. These results also suggest that ERβcx contributes to prostate cancer development possibly through mediating GRPR expression in carcinoma cells.

Anti-cancer effects of novel flavonoid vicenin-2 as a single agent and in synergistic combination with docetaxel in prostate cancer

The present study was conducted to determine the efficacy of novel flavonoid vicenin-2 (VCN-2), an active constituent of the medicinal herb Ocimum Sanctum Linn or Tulsi, as a single agent and in combination with docetaxel (DTL) in carcinoma of prostate (CaP). VCN-2 effectively induced anti-proliferative, anti-angiogenic and pro-apoptotic effect in CaP cells (PC-3, DU-145 and LNCaP) irrespective of their androgen responsiveness or p53 status. VCN-2 inhibited EGFR/Akt/mTOR/p70S6K pathway along with decreasing c-Myc, cyclin D1, cyclin B1, CDK4, PCNA and hTERT in vitro. VCN-2 reached a level of 2.6±0.3μmol/l in serum after oral administration in mice which reflected that VCN-2 is orally absorbed. The i.v. administration of docetaxel (DTL), current drug of choice in androgen-independent CaP, is associated with dose-limiting toxicities like febrile neutropenia which has lead to characterization of alternate routes of administration and potential combinatorial regimens. In this regard, VCN-2 in combination with DTL synergistically inhibited the growth of prostate tumors in vivo with a greater decrease in the levels of AR, pIGF1R, pAkt, PCNA, cyclin D1, Ki67, CD31, and increase in E-cadherin. VCN-2 has been investigated for radioprotection and anti-inflammatory properties. This is the first study on the anti-cancer effects of VCN-2. In conclusion, our investigations collectively provide strong evidence that VCN-2 is effective against CaP progression along with indicating that VCN-2 and DTL co-administration is more effective than either of the single agents in androgen-independent prostate cancer.

Alpha- versus Beta-Particle Radiopeptide Therapy in a Human Prostate Cancer Model (213Bi-DOTA-PESIN and 213Bi-AMBA versus177Lu-DOTA-PESIN)

Recurrent prostate cancer presents a challenge to conventional treatment, particularly so to address micrometastatic and small-volume disease. Use of α-radionuclide therapy is considered as a highly effective treatment in such applications due to the shorter range and exquisite cytotoxicity of α-particles as compared with β-particles. (213)Bi is considered an α-emitter with high clinical potential, due to its short half-life (45.6 minutes) being well matched for use in peptide-receptor radionuclide α-therapy; however, there is limited knowledge available within this context of use. In this study, two novel (213)Bi-labeled peptides, DOTA-PEG(4)-bombesin (DOTA-PESIN) and DO3A-CH(2)CO-8-aminooctanoyl-Q-W-A-V-G-H-L-M-NH(2) (AMBA), were compared with (177)Lu (β-emitter)-labeled DOTA-PESIN in a human androgen-independent prostate carcinoma xenograft model (PC-3 tumor). Animals were injected with (177)Lu-DOTA-PESIN, (213)Bi-DOTA-PESIN, or (213)Bi-AMBA to determine the maximum tolerated dose (MTD), biodistribution, and dosimetry of each agent; controls were left untreated or were given nonradioactive (175)Lu-DOTA-PESIN. The MTD of (213)Bi-DOTA-PESIN and (213)Bi-AMBA was 25 MBq (0.68 mCi) whereas (177)Lu-DOTA-PESIN showed an MTD of 112 MBq (3 mCi). At these dose levels, (213)Bi-DOTA-PESIN and (213)Bi-AMBA were significantly more effective than (177)Lu-DOTA-PESIN. At the same time, (177)Lu-DOTA-PESIN showed minimal, (213)Bi-DOTA-PESIN slight, and (213)Bi-AMBA marked kidney damage 20 to 30 weeks posttreatment. These preclinical data indicate that α-therapy with (213)Bi-DOTA-PESIN or (213)Bi-AMBA is more efficacious than β-therapy. Furthermore, (213)Bi-DOTA-PESIN has a better safety profile than (213)Bi-AMBA, and represents a possible new approach for use in peptide-receptor radionuclide α-therapy treating recurrent prostate cancer.

Growth inhibitory efficacy of lycopene and β‐carotene against androgen‐independent prostate tumor cells xenografted in nude mice

In this study, we evaluated the efficacy of lycopene against the growth of prostate cancer in vivo. Athymic nude mice were implanted subcutaneously with human androgen-independent prostate carcinoma PC-3 cells. They were supplemented with a low or a high dose of lycopene (4 and 16 mg/kg) and a single dose of β-carotene (16 mg/kg) twice a week for 7 wk. At the end of the experiment, both lycopene and β-carotene strongly inhibited the tumor growth, as evidenced by the decrease in tumor volume and tumor weight. High-dosage lycopene and β-carotene significantly decreased the expression of proliferating cell nuclear antigen in tumor tissues and increased the levels of insulin-like growth factor-binding protein-3 in plasma. In addition, high-dosage lycopene supplementation significantly decreased the vascular endothelial growth factor (VEGF) levels in plasma. In contrast, β-carotene supplementation significantly increased the VEGF levels, as compared with tumor control group. Lycopene and β-carotene supplementation suppressed the growth of prostate tumor cells, and the effects are likely associated with reduction of proliferation (attenuation of proliferating cell nuclear antigen expression) and with interference of the insulin-like growth factor 1 signaling (increased plasma insulin-like growth factor-binding protein-3 levels). Furthermore, the inhibition of VEGF by lycopene suggests that the antitumor mechanisms of lycopene also involve anti-angiogenesis.

Suppression of human prostate cancer PC-3 cell growth by N-acetylcysteine involves over-expression of Cyr61

N-acetylcysteine (NAC), sulfidryl-containing thiol antioxidant, has been heralded as chemopreventive agent, generally because of its ability to scavenge free radicals. It also suppresses the proliferation of many cancer cells; however, the antiproliferative mechanism(s) remain to be fully elucidated. In this study, we investigated a growth-suppressive mechanism of NAC action in androgen-independent prostate carcinoma PC-3 cells. NAC (⩾1 mM) inhibited the proliferation of PC-3 cells in a dose- and time-dependent manner. Moreover, NAC treatment suppressed the activation of NF-κB induced by IKK-β as detected by the NF-κB reporter gene assay. NAC exerted a biphasic effect on the intracellular ROS levels depending on incubation time; the antioxidant effect was seen within 2 h after NAC treatment, however, a pro-oxidant effect was evident after 48 h treatment. In addition to these effects, NAC treatment elicited a dose- and time-dependent increase in the Cyr61 expression that was accompanied by an increase in its mRNA and blocked by cycloheximide pretreatment. Importantly, NAC treatment caused an early but transient activation of Akt and Erk1/2. The NAC-induced increase in Cyr61 protein levels was suppressed by the PI3K inhibitor (Ly294002) and, to a lesser extent, MEK/Erk1/2 inhibitor (PD98059). Taken together, our data suggest that the antiproliferative effect of NAC is partially mediated by intracellular ROS production, the inhibition of NF-κB activity, and the activation of PI3K- and/or MEK/Erk-related intracellular signaling pathways, which lead to up-regulation of Cyr61 expression.

Evaluation of Cisplatin in Combination with β‐Elemene as a Regimen for Prostate Cancer Chemotherapy

Cisplatin is one of the most potent chemotherapeutic agents for the treatment of many types of solid tumours. Nevertheless, it is not the first-line drug for prostate cancer chemotherapy, because prostate tumour cells exhibit intrinsic and acquired resistance to cisplatin. We have previously demonstrated that β-elemene, a novel plant-derived anti-neoplastic with low toxicity, inhibits lung and ovarian carcinoma cell growth in vitro. In the present study, we explored the therapeutically chemosensitizing effect of β-elemene on cisplatin anti-tumour efficacy in androgen-independent prostate cancer cells as well as the underlying mechanism. β-Elemene significantly increased cisplatin cytotoxicity in the androgen-independent prostate carcinoma cell lines DU145 and PC-3. In addition, β-elemene markedly promoted cisplatin-induced apoptotic cell death in both cell lines, as determined by three different apoptosis assays. β-Elemene augmented the cisplatin-induced activation of caspase-3/7/10 and caspase-9, cleavage of caspase-3 and -9, suppression of Bcl-2 and Bcl-X(L) expression, and release of cytochrome c from mitochondria in these cells. Thus, β-elemene enhancement of cisplatin-induced apoptosis via mitochondrial activation of the caspase-mediated apoptotic pathway may account for the augmented anti-cancer potency of cisplatin in prostate cancer. Cisplatin combined with β-elemene as a chemosensitizer or adjuvant warrants further study and may be potentially useful as a first-line treatment of androgen-independent prostate carcinomas.

Effects of oridonin nanosuspension on cell proliferation and apoptosis of human prostatic carcinoma PC-3 cell line

This study aims to investigate the inhibitory effects of oridonin nanosuspension on human prostatic carcinoma PC-3 cell line in vitro. The PC-3 cells were incubated with increasing concentrations of oridonin solution and nanosuspensions for 12 hours, 24 hours, and 36 hours. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was performed to measure cellular viability and investigate the effect of oridonin on cell growth of PC-3. Annexin V-FITC/PI staining method was used to determine the effect of oridonin by fluorescence microscope and flow cytometry, respectively. Nanosuspension on early apoptosis of PC-3 cells was also evaluated. Oridonin significantly inhibited the growth of PC-3 cells after 12 hours, 24 hours, and 36 hours of treatment in a dose-dependent manner (P < 0.05). Compared with the same concentration of oridonin solution, oridonin nanosuspension enhanced the inhibition ratio of proliferation. The observation of propidium iodide fluorescence staining confirmed the MTT assay results. The cell proportion of PC-3 at the G2/M phase in the nanosuspension treatment group was upregulated compared with that of the control and oridonin solution groups. Both oridonin solution and nanosuspension promoted the early apoptosis of PC-3 cells. Furthermore, while improving the ratio of early apoptosis, oridonin nanosuspensions also enhanced growth suppression, and induced apoptosis of PC-3 cells. This shows great potential in the treatment of androgen-independent carcinoma of prostate by oridonin nanosuspensions.