Strategy For Prostate Cancer Therapy Research Articles

Development of PSMA-specific immunotherapy for prostate cancer with PIN4 gene-modified T cells

BackgroundChimeric antigen receptors (CARs) are fusion molecules that re-direct T-cell specificity against a selected cell surface target. Recent successes in the treatment of haematological malignancies using CD19-specific CAR T cells has moved this approach into the clinical mainstream. On target, off tumour toxicity, inadequate homing, and limited survival of CAR T cells are important challenges to the adaptation of this promising technology to treat solid tumours. We aimed to address these limitations while developing a clinically applicable T-cell immunotherapy for the commonest male malignancy, prostate cancer. Targeting has been directed against prostate-specific membrane antigen (PSMA), a cell-surface glycoprotein that is overexpressed by more than 80% of cases, with highest levels in castration-resistant disease MethodsA tripartite cassette of genes named PIN4 was developed to re-direct human T cells against prostate cancer. PIN4 mediates the stoichiometric co-expression of: P28ζ, a CAR specific for PSMA; the human sodium iodide symporter (hNIS), which allows real-time PET/SPECT imaging of T cells; and 4αβ, a chimeric cytokine receptor that permits ex-vivo expansion and enrichment of PIN4-positive T cells using interleukin (IL) 4. To promote the survival and trafficking of PIN4 T cells to the tumour, methods for targeting IL4 to tumour-associated stroma are being developed. To test these immunotherapeutic strategies in vivo, we developed a metastatic model of prostate cancer using PSMA–firefly luciferase-engineered PC3-LN3 (PLP) cells, inoculated subcutaneously in immune compromised SCID/beige mice. Tumour metastases in this model were imaged with bioluminescence imaging. SPECT was used for serial imaging of T cells, after administration of technetium-99m pertechnetate (99mTcO4). FindingsEx-vivo expansion accompanied by selective enrichment of PIN4+ T cells occurred consistently in response to IL4, whereas comparable enrichment was not seen in response to the non-selective signal provided by IL2. IL4-expanded PIN4+ T cells retained type 1 polarity and showed potent P28ζ-dependent anti-tumour activity against a panel of PSMA-positive prostate cancer cell lines. Function of hNIS in PIN4+ T cells was first confirmed in vitro by 99mTcO4 uptake studies. Then, we infused PIN4+ or control T cells in mice with metastatic PSMA+ PLP prostate cancer. We showed that PIN4+ T cells could be repeatedly imaged by SPECT, after the administration of 99mTcO4. Evidence of proliferation of PIN4+ T cells at sites of metastatic PLP deposits was observed. InterpretationWe have a highly effective strategy for prostate cancer therapy with PIN4, which overcomes the challenges of ex-vivo expansion and T-cell survival. The goal of this work is to further improve the therapeutic window for PIN4 therapy, with a clear view to clinical translation. FundingThe Prostate Cancer Charity, Academy of Medical Sciences, King's Health Partners Biomedical Research Centre.

Activation of silenced tumor suppressor genes in prostate cancer cells by a novel energy restriction‐mimetic agent

Targeting tumor metabolism by energy restriction-mimetic agents (ERMAs) has emerged as a strategy for cancer therapy/prevention. Evidence suggests a mechanistic link between ERMA-mediated antitumor effects and epigenetic gene regulation. Microarray analysis showed that a novel thiazolidinedione-derived ERMA, CG-12, and glucose deprivation could suppress DNA methyltransferase (DNMT)1 expression and reactivate DNA methylation-silenced tumor suppressor genes in LNCaP prostate cancer cells. Thus, we investigated the effects of a potent CG-12 derivative, CG-5, vis-à-vis 2-deoxyglucose, glucose deprivation and/or 5-aza-deoxycytidine, on DNMT isoform expression (Western blotting, RT-PCR), DNMT1 transcriptional activation (luciferase reporter assay), and expression of genes frequently hypermethylated in prostate cancer (quantitative real-time PCR). Promoter methylation was assessed by pyrosequencing analysis. SiRNA-mediated knockdown and ectopic expression of DNMT1 were used to validate DNMT1 as a target of CG-5. CG-5 and glucose deprivation upregulated the expression of DNA methylation-silenced tumor suppressor genes, including GADD45a, GADD45b, IGFBP3, LAMB3, BASP1, GPX3, and GSTP1, but also downregulated methylated tumor/invasion-promoting genes, including CD44, S100A4, and TACSTD2. In contrast, 5-aza-deoxycytidine induced global reactivation of these genes. CG-5 mediated these epigenetic effects by transcriptional repression of DNMT1, which was associated with reduced expression of Sp1 and E2F1. SiRNA-mediated knockdown and ectopic expression of DNMT1 corroborated DNMT1's role in the modulation of gene expression by CG-5. Pyrosequencing revealed differential effects of CG-5 versus 5-aza-deoxycytidine on promoter methylation in these genes. These findings reveal a previously uncharacterized epigenetic effect of ERMAs on DNA methylation-silenced tumor suppressor genes, which may foster novel strategies for prostate cancer therapy.

782 SANGUINARINE INHIBITS STAT3 ACTIVATION AND TUMOR GROWTH IN PROSTATE CANCER CELLS

You have accessJournal of UrologyProstate Cancer: Basic Research IV1 Apr 2012782 SANGUINARINE INHIBITS STAT3 ACTIVATION AND TUMOR GROWTH IN PROSTATE CANCER CELLS Meng Sun, Chengfei Liu, Wei Lou, Nagalakshmi Nadiminty, Joy Yang, Christopher Evans, and Allen Gao Meng SunMeng Sun Sacramento, CA More articles by this author , Chengfei LiuChengfei Liu Sacramento, CA More articles by this author , Wei LouWei Lou Sacramento, CA More articles by this author , Nagalakshmi NadimintyNagalakshmi Nadiminty Sacramento, CA More articles by this author , Joy YangJoy Yang Sacramento, CA More articles by this author , Christopher EvansChristopher Evans Sacramento, CA More articles by this author , and Allen GaoAllen Gao Sacramento, CA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.870AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Signal Transducer and Activator of Transcription 3 (STAT3) is an oncogenic transcription factor implicated in prostate carcinogenesis and progression. Stat3 activation is associated with prostate cancer development and progression. Constitutively activated Stat3 activates androgen receptor signaling and promotes castration-resistant prostate cancer growth. Targeting Stat3 activation is an effective strategy in prostate cancer therapy. METHODS DU145, C4-2B and LNCaP cells were treated with sanguinarine for 4 hours and then stimulated with Interleukin-6 (IL-6) or vehicle. The phosphorylation status of STAT3 and related proteins were measured with western blots. Activation of transcription by STAT3 via the STAT3 responsive element was measured with luciferase reporter assay. The effect of sanguinarine on DU145 and LN/S17 cells anchorage-independent growth were examined with soft agar assay. The effect of sanguinarine on cells migration and invasion of DU145 cells were measured with scratch assay and invasion assay respectively. RESULTS Exposure to micromolar concentrations of sanguinarine resulted in suppression of constitutive as well as IL6-induced phosphorylation of STAT3 at both Tyr705 and Ser727 in DU145 cells. The inhibition of STAT3 phosphorylation correlated with the inhibition of Janus-activated Kinase 2 (JAK2) and src phosphorylation. Sanguinarine inhibited the constitutive and IL6-induced STAT3 responsive element luciferase activities. Several STAT3 regulated genes such as c-myc and survivin were downregulated by sanguinarine. We found that sanguinarine inhibited the migration and invasion of DU145 cells that express constitutively activated STAT3. Furthermore, sanguinarine inhibited the anchorage-independent growth of DU145 and LN/S17 cells and suppressed the growth of DU145 xenografts in nude mice. CONCLUSIONS These data suggest that sanguinarine targets multiple upstream kinases that mediate STAT3 activity. Sanguinarine is a potent STAT3 inhibitor that could be developed as a therapeutic agent for prostate cancer. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e320 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Meng Sun Sacramento, CA More articles by this author Chengfei Liu Sacramento, CA More articles by this author Wei Lou Sacramento, CA More articles by this author Nagalakshmi Nadiminty Sacramento, CA More articles by this author Joy Yang Sacramento, CA More articles by this author Christopher Evans Sacramento, CA More articles by this author Allen Gao Sacramento, CA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Development, Characterization and In Vitro Evaluation of Single or Co-Loaded Imatinib Mesylate Liposomal Formulations

Mitoxantrone-based combinations are a standard palliative treatment in hormone-refractory prostate cancer (HRPC) but with no survival benefit. Imatinib has shown preclinical activity against HRPC although minimal clinical therapeutic efficacy. Our previous in vitro studies demonstrated that simultaneous combination of imatinib with mitoxantrone yielded additive growth inhibition effects against PC-3 cell line. The main aim of the work was to develop novel liposomal formulations comprising imatinib co-encapsulated with mitoxantrone, by different loading methods and experimental conditions, in order to achieve the highest drug loading and maximum physical stability. In the optimized formulations, imatinib and mitoxantrone were actively co-loaded by means of a (NH4)2SO4 transmembrane gradient. Encapsulation efficiency, mean size diameter and drug retention in storage and in biological conditions were characterized. Our study presented for the first time an active loading method for imatinib and suggests that the optimized liposomal formulation co-encapsulates both drugs with high encapsulation efficiency (> 95%), shows enhanced drug retention under tested conditions and delivers a drug:drug ratio capable of improving tumor cell growth inhibition with a mitoxantrone dose reduction of 2.6-fold as compared to single liposomal formulation. Therefore, our nanotechnology-based drug combined platform may constitute a promising strategy in prostate cancer therapy.

Future perspectives of prostate cancer therapy.

We summarize several recent laboratory advances to tackle the problem of tumor-stroma-immune cell microenvironment interaction with the hope of developing and advancing new concepts and therapeutic strategies for prostate cancer therapy by improving bone and soft tissue metastases in prostate cancer patients. Given the emerging enthusiasm for immunotherapy in prostate cancer due to (I) improved understanding of the role of immune cells in the tumor microenvironment, (II) approval by the FDA of an immunotherapeutic drug to treat prostate cancer, and (III) recognition of immunotherapy as a novel approach to treat solid tumors by the Nobel Prize Committee (for discovery of dendritic cells that are used in immunotherapy), the field of tumor immunology is poised for growth in the next decade with the hope of developing new immunomodulatory drugs which will compliment and perhaps eventually replace traditional chemotherapeutic drugs. In this article, we provide a timely review of recent advances in the field of immunotherapy for prostate cancer, lessons learned from successes and failures, the contributory factors in the tumor microenvironment that could be rendered hostile to cancer cells, an exciting area of future research.

Focusing on Testosterone

Since Huggins and Hodges first established testosterone as the principal androgenic hormone responsible for the growth of prostate cancer in 1941, lowering the circulating testosterone to surgical castration levels (<50 ng/dL) has been a fundamental strategy for prostate cancer therapy. Until the 1980s, surgical castration (bilateral orchiectomy) and medical castration using estrogen (diethylstilbestrol) were the primary methods of testosterone suppression. However, during the past 30 years, newer agents that lower serum testosterone even more effectively have been approved and the indications for use of these newer agents re-evaluated.

Abstract 2073: Curcumin analog 27 induced reactive oxygen species mediate loss of androgen receptor protein expression in human prostate cancer cells

Abstract The androgen receptor (AR) is an established therapeutic target for prostate cancer. Therefore, agents that down-regulate AR expression may be effective for prostate cancer therapy. We show that the experimental therapeutic agent, curcumin analog 27 (ca27), induces the down-regulation of the AR in LNCaP and LAPC4 prostate cancer cell lines. Treatment with ca27 selectively inhibits AR mRNA expression, whereas ca27 did not alter mRNA levels for other steroid hormone receptors, such as the glucocorticoid receptor. In addition, ca27 decreases AR protein expression and increases AR protein ubiquitination within 3 hours. However, this rapid decrease in AR protein expression by ca27 is not mediated by proteasomal degradation. Interestingly, we observed an induction of reactive oxygen species (ROS) within 1 to 2 hours of ca27 treatment, which precedes AR degradation, leading to the hypothesis that ca27 mediates AR degradation through a cellular oxidative stress mechanism of action. In support of this hypothesis, the degradation of the AR following ca27 treatment is abrogated in the presence of the antioxidant, N-acetyl cysteine. Treatment with ca27 did not reduce cell viability by 24 hours suggesting that the increase in ROS and the inhibition of AR protein expression are independent of cell death. To further evaluate the cellular response to oxidative stress by ca27, we investigated the induction of a critical transcription factor activated as a cellular redox sensor, Nrf2. Treatment with ca27 lead to the increased transcriptional activation of Nrf2 as measured by an Nrf2-luciferase reporter assay. The ca27-induced Nrf2 activation was further supported by increased mRNA expression of the Nrf2-regulated genes NAD(P)H quinone oxidoreductase 1 and aldoketoreductase 1C1. This study begins to identify the mechanism of action of ca27-mediated AR protein degradation with the overall goal of gaining insight into targeting ROS-mediated AR down-regulation as a strategy for prostate cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2073. doi:10.1158/1538-7445.AM2011-2073

Combined treatment targeting HIF‐1α and Stat3 is a potent strategy for prostate cancer therapy

The Stat3 pathway and the hypoxia-sensing pathway are both up-regulated in prostate cancer. Stat3 is a specific regulator of pro-carcinogenic inflammation and represents a promising therapeutic target. Hypoxia-inducible factor-1 (HIF-1)α, which mediates the cellular response to hypoxia, has been demonstrated to be over-expressed in many human cancers and is associated with poor prognosis and treatment failure in clinic. To develop a potent strategy to increase therapeutic efficacy and reduce drug resistance in prostate cancer therapy, we combined two anti-cancer agents: T40214 (a p-Stat3 inhibitor) and JG244 (a HIF-1α inhibitor) together to treat nude mice bearing human prostate tumor (DU145) and immunocompetent mice (C57BL/6) bearing murine prostate tumor (TRAMP-C2). We employed in vitro and in vivo assays, including Western blots, cell cycle analysis, immunohistochemistry, TUNEL and xenograft models to determine the drug efficacy and mechanism of combination treatment of T40214 and JG244. We found that compared to treatment by T40214 or JG244 alone, the combination treatment using T40214 and JG244 together significantly suppressed growth of human or murine prostate tumors. Also, compared with apoptotic cells induced by T40214 or JG244 alone, the combined treatment greatly increased apoptosis in DU145 (P < 0.006) and TRAMP-C2 tumors (P < 0.008). Our results suggested that combination treatment including a HIF-1α/2α inhibitor not only has therapeutic efficacy in targeting HIF-1α/2α, but also could reduce the hypoxia-induced drug resistance to other therapies (e.g., T40214) and enhance drug efficacy. This approach could make prostate cancer treatments more effective.

Energy Restriction-mimetic Agents Induce Apoptosis in Prostate Cancer Cells in Part through Epigenetic Activation of KLF6 Tumor Suppressor Gene Expression

Although energy restriction has been recognized as an important target for cancer prevention, the mechanism by which energy restriction-mimetic agents (ERMAs) mediate apoptosis remains unclear. By using a novel thiazolidinedione-derived ERMA, CG-12 (Wei, S., Kulp, S. K., and Chen, C. S. (2010) J. Biol. Chem. 285, 9780-9791), vis-à-vis 2-deoxyglucose and glucose deprivation, we obtain evidence that epigenetic activation of the tumor suppressor gene Kruppel-like factor 6 (KLF6) plays a role in ERMA-induced apoptosis in LNCaP prostate cancer cells. KLF6 regulates the expression of many proapoptotic genes, and shRNA-mediated KLF6 knockdown abrogated the ability of ERMAs to induce apoptosis. Chromatin immunoprecipitation analysis indicates that this KLF6 transcriptional activation was associated with increased histone H3 acetylation and histone H3 lysine 4 trimethylation occupancy at the promoter region. Several lines of evidence demonstrate that the enhancing effect of ERMAs on these active histone marks was mediated through transcriptional repression of histone deacetylases and H3 lysine 4 demethylases by down-regulating Sp1 expression. First, putative Sp1-binding elements are present in the promoters of the affected histone-modifying enzymes, and luciferase reporter assays indicate that site-directed mutagenesis of these Sp1 binding sites significantly diminished the promoter activities. Second, shRNA-mediated knockdown of Sp1 mimicked the repressive effect of energy restriction on these histone-modifying enzymes. Third, ectopic Sp1 expression protected cells from the repressive effect of CG-12 on these histone-modifying enzymes, thereby abolishing the activation of KLF6 expression. Together, these findings underscore the intricate relationship between energy restriction and epigenetic regulation of tumor suppressor gene expression, which has therapeutic relevance to foster novel strategies for prostate cancer therapy.

Synergistic tumor growth-inhibitory effect of the prostate-specific antigen-activated fusion peptide BSD352 for prostate cancer therapy

Prostate-specific antigen (PSA), a serine protease, is a promising target for the development of prodrugs in prostate cancer treatment. In this study, we designed a novel fusion peptide, BSD352, containing three functional domains: a protein transduction domain from HIV transactivating regulatory protein (TAT) followed by the BH3 domain of the p53 upregulated modulator of apoptosis (TAT-BH3), an anti-vascular endothelial growth factor peptide (SP5.2), and an anti-basic fibroblast growth factor peptide (DG2). These different domains in BSD352 were linked together by a linker sequence corresponding to a PSA hydrolytic substrate peptide. The BSD352 fusion peptide could be selectively cleaved by PSA in PSA-producing LNCaP prostate cancer cells. Furthermore, the BSD352 fusion peptide was efficiently transduced into tumor cells both in vitro and in vivo, and the BH3 domain was found to induce tumor cell apoptosis by elevating the expression of Bax, cytochrome C release, and caspase-9 cleavage. Moreover, the SP5.2 and DG2 domains in the BSD352 fusion peptide also exhibited in-vitro endothelial cell growth inhibition and in-vivo antiangiogenic activities. Direct injection of BSD352 into an established LNCaP xenograft tumor in mice inhibited tumor growth, whereas a synergistic effect was observed with the combined use of wild-type BH3, SP5.2, and DG2 functional domains. These results suggest that BSD352 could be beneficial for the treatment of accessible prostate tumors and may provide a complementary strategy for prostate cancer therapy.

XAF1 expression and regulatory effects of somatostatin on XAF1 in prostate cancer cells

BackgroundSomatostatin prevents cell proliferation by inducing apoptosis. Downregulation of the XAF1 transcript may occur during the development of prostate cancer. It is interesting to evaluate the potential regulatory effects of somatostatin on XAF1 expression during the development of prostate cancer cells.MethodsXAF1 mRNA and protein expression in human prostate epithelial cells RWPE-1, androgen dependent prostate cancer LNCaP, and androgen independent DU145 and PC3 cells were evaluated using RT-PCR and Western blot. The regulation of XAF1 mRNA and protein expression by somatostatin and its analogue Octreotide was evaluated.ResultsSubstantial levels of XAF1 mRNA and proteins were detected in RWPE-1 cells, whereas prostate cancer cells LNCaP, DU145 and PC3 exhibited lower XAF1 expression. Somatostatin and Octreotide up-regulated XAF1 mRNA and protein expression in all prostate cancer cell lines.ConclusionsXAF1 down-regulation may contribute to the prostate cancer development. The enhanced XAF1 expression by somatostatin indicates a promising strategy for prostate cancer therapy.

103 Combination treatment of targeting Stat3 and HIF-1alpha is a potent strategy for prostate cancer therapy

Sorafenib is the standard of care for the treatment of advanced hepatocellular carcinoma (HCC). However, primary and acquired resistance is observed in patients. We examined whether gefitinib, which inhibits both epidermal growth factor receptor (EGFR) and HER-3 phosphorylation, could improve HCC cell response to sorafenib.Sorafenib and gefitinib were tested in HCC tumor xenografts and in sorafenib-sensitive and sorafenib-resistant HCC cell lines. Biomarkers relevant to the HER system were analyzed by Western blotting and ELISA. RNA interference was used to downregulate the HER system. Amphiregulin concentrations were measured by ELISA in sera from patients under sorafenib treatment.Sorafenib combined with gefitinib significantly inhibited tumor growth in mice and reduced cell viability in vitro compared to single agents. In cell lines cultured in 10% serum or treated with EGF, sorafenib alone inhibited phospho-STAT3 while it maintained or even increased phospho-ERK and/or phospho-AKT. The paradoxical effects of sorafenib were prevented by gefitinib or by downregulation of EGFR and HER-3 expression. In cells with acquired resistance to sorafenib, aberrant activation of EGFR/HER-3 receptors as well as overexpression of several EGFR ligands were observed. These enhanced autocrine/paracrine loops led to the constitutive activation of ERK and AKT and conferred increased sensitivity to gefitinib. Increased serum concentrations of amphiregulin were observed in 10 out of 14 patients under sorafenib treatment compared to baselines.Signaling pathways controlled by EGFR and HER-3 restrict sorafenib effects both in naive and sorafenib-resistant HCC cells. Consequently, gefitinib cooperates with sorafenib to increase antiproliferative response and to prevent resistance.

Adipose tissue‐derived stem cells promote prostate tumor growth

Recent evidence indicates that cancer stem cells play an important role in tumor initiation and maintenance. Additionally, the effect of tissue-resident stem cells located in the surrounding healthy tissue on tumor progression has been demonstrated. While most knowledge has been derived from studies of breast cancer cells, little is known regarding the influence of tissue resident stem cells on the tumor biology of prostate cancer. Twenty male athymic Swiss nu/nu mice (age: 6-8 weeks) were randomized into two treatment groups: (1) subcutaneous injection of 10(6) MDA PCa 118b human prostate cancer cells into the upper back or (2) subcutaneous injection of 10(6) MDA PCa 118b cells mixed directly with 10(5) GFP-labeled human adipose tissue-derived stem cells (hASCs). Tumor growth and volumes over the ensuing 3 weeks were assessed using calipers and micro-computed tomography. Immunohistochemistry was performed to identify engrafted hASCs in tumor sections. At 3 weeks after injection, the mean tumor volume in the MDA PCa 118b/hASC co-injection group (1019.95 ± 73.49 mm(3)) was significantly higher than that in the MDA PCa 118b-only group (308.70 ± 21.06 mm(3)). Engrafted hASCs exhibited the nuclear marker of proliferation Ki67 and expressed markers for endothelial differentiation, indicating their engraftment in tumor vessels. Our study revealed for the first time that ASCs subcutaneously co-injected with prostate cancer cells engraft and promote tumor progression. Further evaluation of the cross-talk between tumor and local tissue-resident stem cells may lead to new strategies for prostate cancer therapy.

Abstract 1216: The mechanism related to anti-apoptotic property of SOX2 in prostate cancer

Abstract SOX2 is one of the key regulatory genes to maintain the pluripotency and unlimited cell growth properties in embryonic stem cells. Recently, more and more researches on cancer stem cell (CSC) support the hypothesis that CSC is the progenitor of cancer cells and contributes to the chemoresistant properties of cancer cells. Although previous study showed SOX2 contributed to the tumorigenic properties in breast and gastric tumor, its function in prostate cancer and apoptosis are still largely unknown. In this study, we used immunohistochemistry method to analyze the expression of SOX2 in prostate cancer tissues and found that the degree of SOX2 staining increased when the Gleason histological grade went higher. We further investigate SOX2's function in cell growth and apoptosis process by using human prostate cancer cells-DU145 with SOX2 overexpression or down-regulation by shRNA. We found that SOX2 increased cell growth and the percentage of cells in S phase in cell cycle assay, it also increased the apoptosis resistant properties of DU145 with reduced mRNA expression of Orai1, STIM1 and decreased store-operated Ca2+ entry (SOCE) activity and cytosolic Ca2+ concentration. This study first investigated SOX2's function in apoptosis process of prostate cancer and elucidated SOX2's regulatory effect on SOCE activity. Our study supports the concept that targeting SOX2 to increase the SOCE activity may be a potential strategy in prostate cancer therapy. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1216.

Expression of Pluripotent Stem Cell Reprogramming Factors by Prostate Tumor Initiating Cells

We identified a discrete population of stem cell-like tumor cells expressing 5 essential transcription factors required to reprogram pluripotency in prostate tumor cell lines and primary prostate cancer tissue. DU145 and PC3 human prostate cancer cell lines (ATCC), tumor tissue from patients with prostate cancer and normal prostate tissue were evaluated for the reprogramming factors OCT3/4 (Cell Signaling Technology), SOX2, Klf4 (Santa Cruz Biotechnology, Santa Cruz, California), Nanog (BioLegend) and c-Myc (Cell Signaling) by semiquantitative reverse transcriptase-polymerase chain reaction, histological and immunohistochemical analysis. Stem cell-like tumor cells were enriched by flow cytometric cell sorting using E-cadherin (R&D Systems) as a surface marker, and soft agar, spheroid and tumorigenicity assays to confirm cancer stem cell-like characteristics. mRNA expression of transcription factors OCT3/4 and SOX2 highly correlated in primary prostate tumor tissue samples. The number of OCT3/4 or SOX2 expressing cells was significantly increased in prostate cancer tissue compared to that in normal prostate or benign prostate hyperplasia tissue (p <0.05). When isolated from the DU145 and PC3 prostate cancer cell lines by flow cytometry, stem cell-like tumor cells expressing high OCT3/4 and SOX2 levels showed high tumorigenicity in immunodeficient mice. In vivo growth of the parental DU145 and PC3 prostate cancer cell lines was inhibited by short hairpin RNA knockdown of OCT3/4 or SOX2. Data suggest that prostate tumor cells expressing pluripotent stem cell transcription factors are highly tumorigenic. Identifying such cells and their importance in prostate cancer growth could provide opportunities for novel targeting strategies for prostate cancer therapy.

Technology Insight: vaccine therapy for prostate cancer

The lack of effective therapies for advanced prostate cancer mandates continued development of alternative treatment strategies. Insights into the regulation of immune responses and the malignant process have facilitated the emergence of new immune-based strategies, currently under investigation in clinical trials. Like other forms of targeted therapy, cancer vaccines hold the promise of achieving cancer control without inducing overt toxicity. Many prostate cancer vaccines at different phases of development have been tested in clinical trials. Vaccination strategies under consideration include: immunization with defined antigenic preparations such as synthetic peptides, proteins or plasmid DNA; antigen-loaded dendritic cells; manipulated tumor cells; or with viral vectors engineered to express immunogenic genes. Although the underlying mechanisms of immunization may vary, all strategies share the common goal of eliciting immune responses against prostate tumor-associated antigens or of enhancing an otherwise weak antitumor response in the cancer patient. Unlocking the therapeutic potential of cancer vaccines will require a thorough understanding of cellular and molecular mechanisms that modulate the immune response. In this review, we provide an overview of vaccine-based strategies for prostate cancer therapy, discuss their mechanisms of action, and provide relevant clinical trial data.

Protein kinase C and prostate carcinogenesis: targeting the cell cycle and apoptotic mechanisms.

A series of both genetic and epigenetic factors have been implicated in the genesis and progression of prostate cancer. Recent evidence revealed that protein kinase C (PKC) isozymes play a crucial role in the control of cell proliferation and apoptosis in prostate cancer models, as well as in the transition from an androgen-dependent to an androgen-independent status. Indeed, PKCalpha and PKCdelta promote apoptosis in androgen-dependent prostate cancer cells. Due to the relevance of PKC isozymes in the control of cell cycle, both in G1/S and G2/M, the elucidation of such complex intracellular networks using cellular and animal models has become of outmost importance. In this review, we present the current knowledge on the regulation of apoptosis and tumorigenicity by PKC isozymes and the functional roles of cell cycle regulators in prostate carcinogenesis. The development of animal models where overexpression of discrete PKCs or cell cycle regulators is targeted to the prostate will greatly contribute to the understanding of the molecular basis of the disease, and more importantly, it will have profound implications for the development of novel strategies for prostate cancer therapy.