Potential of Personalized Dendritic Cell-Based Immunohybridoma Vaccines to Treat Prostate Cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second most common cause of death due to cancer. About 30% of patients with PCa who have been castrated develop a castration-resistant form of the disease (CRPC), which is incurable. In the last decade, new treatments that control the disease have emerged, slowing progression and spread and prolonging survival while maintaining the quality of life. These include immunotherapies; however, we do not yet know the optimal combination and sequence of these therapies with the standard ones. All therapies are not always suitable for every patient due to co-morbidities or adverse effects of therapies or both, so there is an urgent need for further work on new therapeutic options. Advances in cancer immunotherapy with an immune checkpoint inhibition mechanism (e.g., ipilimumab, an anti-CTLA-4 inhibitor) have not shown a survival benefit in patients with CRPC. Other immunological approaches have also not given clear results, which has indirectly prevented breakthrough for this type of therapeutic strategy into clinical use. Currently, the only approved form of immunotherapy for patients with CRPC is a cell-based medicine, but it is only available to patients in some parts of the world. Based on what was gained from recently completed clinical research on immunotherapy with dendritic cell-based immunohybridomas, the aHyC dendritic cell vaccine for patients with CRPC, we highlight the current status and possible alternatives that should be considered in the future.

Bacterial outer membrane vesicles as a candidate tumor vaccine platform

Cancer represents a serious concern for human life and health. Due to drug resistance and the easy metastasis of tumors, there is urgent need to develop new cancer treatment methods beyond the traditional radiotherapy, chemotherapy, and surgery. Bacterial outer membrane vesicles (OMVs) are a type of double-membrane vesicle secreted by Gram-negative bacteria in the process of growth and life, and play extremely important roles in the survival and invasion of those bacteria. In particular, OMVs contain a large number of immunogenic components associated with their parent bacterium, which can be used as vaccines, adjuvants, and vectors to treat diseases, especially in presenting tumor antigens or targeted therapy with small-molecule drugs. Some OMV-based vaccines are already on the market and have demonstrated good therapeutic effect on the corresponding diseases. OMV-based vaccines for cancer are also being studied, and some are already in clinical trials. This paper reviews bacterial outer membrane vesicles, their interaction with host cells, and their applications in tumor vaccines.

Changing Landscape of Cancer Vaccines-Novel Proteomics Platform for New Antigen Compositions

The creation of cancer vaccines is a constant priority for research and biotechnology. Therefore, the emergence of any new technology in this field is a significant event, especially because previous technologies have not yielded results. Recently, the development of a cancer vaccine has been complemented by a new proteomics technology platform that allows the creation of antigen compositions known as antigenic essences. Antigenic essence comprises a target fraction of cellular antigens, the composition of which is precisely controlled by peptide mass spectrometry and compared to the proteomic footprint of the target cells to ensure similarity. This proteomics platform offers potential for a massive upgrade of conventional cellular cancer vaccines. Antigenic essences have the same mechanism of action, but without the disadvantages, and with notable advantages such as precise targeting of the immune response, safety, controlled composition, improved immunogenicity, addressed MHC restriction, and extended range of vaccination doses. The present paper calls attention to this novel platform, stimulates discussion of the role of antigenic essence in vaccine development, and consolidates academic science with biotech capabilities. A brief description of the platform, list of cellular cancer vaccines suitable for the upgrade, main recommendations, limitations, and legal and ethical aspects of vaccine upgrade are reported here.

Rapidly Growing Mycobacterium Species: The Long and Winding Road from Tuberculosis Vaccines to Potent Stress-Resilience Agents

Inflammatory diseases and stressor-related psychiatric disorders, for which inflammation is a risk factor, are increasing in modern Western societies. Recent studies suggest that immunoregulatory approaches are a promising tool in reducing the risk of suffering from such disorders. Specifically, the environmental saprophyte Mycobacterium vaccae National Collection of Type Cultures (NCTC) 11659 has recently gained attention for the prevention and treatment of stress-related psychiatric disorders. However, effective use requires a sophisticated understanding of the effects of M. vaccae NCTC 11659 and related rapidly growing mycobacteria (RGMs) on microbiome–gut–immune–brain interactions. This historical narrative review is intended as a first step in exploring these mechanisms and provides an overview of preclinical and clinical studies on M. vaccae NCTC 11659 and related RGMs. The overall objective of this review article is to increase the comprehension of, and interest in, the mechanisms through which M. vaccae NCTC 11659 and related RGMs promote stress resilience, with the intention of fostering novel clinical strategies for the prevention and treatment of stressor-related disorders.

Mycobacteria-Based Vaccines as Immunotherapy for Non-urological Cancers

The arsenal against different types of cancers has increased impressively in the last decade. The detailed knowledge of the tumor microenvironment enables it to be manipulated in order to help the immune system fight against tumor cells by using specific checkpoint inhibitors, cell-based treatments, targeted antibodies, and immune stimulants. In fact, it is widely known that the first immunotherapeutic tools as immune stimulants for cancer treatment were bacteria and still are; specifically, the use of Mycobacterium bovis bacillus Calmette-Guérin (BCG) continues to be the treatment of choice for preventing cancer recurrence and progression in non-invasive bladder cancer. BCG and also other mycobacteria or their components are currently under study for the immunotherapeutic treatment of different malignancies. This review focuses on the preclinical and clinical assays using mycobacteria to treat non-urological cancers, providing a wide knowledge of the beneficial applications of these microorganisms to manipulate the tumor microenvironment aiming at tumor clearance.

Defining Genome-Wide Expression and Phenotypic Contextual Cues in Macrophages Generated by Granulocyte/Macrophage Colony-Stimulating Factor, Macrophage Colony-Stimulating Factor, and Heat-Killed Mycobacteria

Heat-killed (HK) Mycobacterium obuense (NCTC13365) is currently being evaluated in the clinic as an immunotherapeutic agent for cancer treatment. Yet, the molecular underpinnings underlying immunomodulatory properties of HK M. obuense are still largely undefined. To fill this void, we sought to perform immunophenotyping, chemokine/cytokine release analysis and genome-wide characterization of monocyte-derived macrophages (MDM) in which monocytes were originally isolated from healthy donors and differentiated by HK M. obuense (Mob-MDM) relative to macrophage colony-stimulating factor (M-MDM) and granulocyte/macrophage colony-stimulating factor (GM-MDM). Immunophenotyping and cytokine release analysis revealed downregulated surface expression of CD36, decreased spontaneous release of CCL2 and increased spontaneous secretion of CCL5, CXCL8/IL-8, IL-6, and TNF-α in Mob-MDM relative to M-MDM and GM-MDM. Analysis of cytostatic activity showed that Mob-MDM exhibited similar growth inhibitory effects on immortalized and malignant epithelial cells compared with GM-MDM but at an elevated rate relative to M-MDM. To understand global cues in Mob-MDM, we performed comparative RNA-sequencing (RNA-Seq) analysis of Mob-MDM relative to GM-MDM and M-MDM (n = 4 donors). Clustering analysis underscored expression profiles (n = 256) that were significantly modulated in Mob-MDM versus both M-MDM and GM-MDM including, among others, chemokines/cytokines and their receptors, enzymes and transcriptions factors. Topological functional analysis of these profiles identified pathways and gene sets linked to Mob-MDM phenotype including nitric oxide production, acute phase response signaling and microbe recognition pathways as well as signaling cues mediated by the proinflammatory cytokine, interferon-gamma, and the intracellular pattern recognition receptor, nucleotide-binding oligomerization domain-containing protein 2. Taken together, our study highlights molecular immune phenotypes and global signaling cues in Mob-MDM that may underlie immunomodulatory properties of HK M. obuense. Such properties could be of valuable use in immunotherapy approaches such as adoptive cell therapy against cancer.

Analysis of the immunomodulatory properties of two heat-killed mycobacterial preparations in a human whole blood model

The significant role played by mycobacteria in modulating immune responses through enhancing the crosstalk between innate and adaptive immunity has been highlighted in several studies. Owing to their unique antigenic profile, heat killed (HK) preparations of rapid-growing mycobacteria, currently undergoing clinical development, have been assessed as adjuvant therapy in various diseases. The purpose of this study is to investigate the regulation of leukocyte surface receptors, in whole blood from healthy donors, following in vitro stimulation with HK Mycobacterium vaccae (M. vaccae) or M. obuense. We have demonstrated the ability of both mycobacterial preparations to target monocytes and neutrophils and to regulate the surface expression of selected adhesion receptors, antigen-presenting and costimulatory receptors, pattern recognition receptors, complement and Fc receptors, as well as cytokine/chemokine receptors. Toll-like receptors (TLRs) 1 and 2 were also shown to be involved in mediating the M. obuense-induced upregulation of selected surface receptors on monocytes. Whole blood stimulation with M. vaccae or M. obuense resulted in a significant increase in the secretion of a specific set of cytokines and chemokines. Both mycobacterial preparations induced strong antigen-specific proliferative responses in peripheral blood mononuclear cells. Collectively, our data shows that M. vaccae and M. obuense have the potential to act as potent immunomodulators. Future research based on these findings may reveal novel immune pathways induced by these preparations with potential implication for their use in diverse immunotherapeutic approaches.

An ultra scale-down analysis of the recovery by dead-end centrifugation of human cells for therapy

An ultra scale-down method is described to determine the response of cells to recovery by dead-end (batch) centrifugation under commercially defined manufacturing conditions. The key variables studied are the cell suspension hold time prior to centrifugation, the relative centrifugal force (RCF), time of centrifugation, cell pellet resuspension velocities, and number of resuspension passes. The cell critical quality attributes studied are the cell membrane integrity and the presence of selected surface markers. Greater hold times and higher RCF values for longer spin times all led to the increased loss of cell membrane integrity. However, this loss was found to occur during intense cell resuspension rather than the preceding centrifugation stage. Controlled resuspension at low stress conditions below a possible critical stress point led to essentially complete cell recovery even at conditions of extreme centrifugation (e.g., RCF of 10000 g for 30 mins) and long (∼2 h) holding times before centrifugation. The susceptibility to cell loss during resuspension under conditions of high stress depended on cell type and the age of cells before centrifugation and the level of matrix crosslinking within the cell pellet as determined by the presence of detachment enzymes or possibly the nature of the resuspension medium. Changes in cell surface markers were significant in some cases but to a lower extent than loss of cell membrane integrity. Biotechnol. Bioeng. 2015;112: 997–1011. © 2014 Wiley Periodicals, Inc.

Affinity proteomics led identification of vimentin as a potential biomarker in colon cancers: insights from serological screening and computational modelling

Proteomic analysis using multiplex affinity reagents is perhaps the most reliable strategy to capture differentially expressed proteins that are slightly or immensely modified. In addition to expressional variation, it is comprehensively evident that the immunogenicity of a protein can be a deciding factor for instigating an inflammation afflicted-carcinogenesis. Considering both these factors, a simple and systematic strategy was designed to capture the immunogenic cancer biomarkers from sera of colorectal cancer patients. The affinity reagent, in the form of an antibody repertoire against the secretome of the HT29 cell line was used to grade the sera samples on the basis of the degree of immuno-reactivity and to capture differentially expressed antigens from the patient sera. Following affinity based 2DE-MALDI-TOF; the proteins were identified as (1) soluble vimentin; and (2) TGF-beta-inhibited membrane-associated protein (PP16B), in colon cancer sera and (3) keratin, type II cytoskeletal protein in rectal cancer sera. Pathway reconstruction and protein-protein networking of identified proteins predicted only Vimentin to be physically and genetically engaged in close proximity with the most established colorectal cancer associated tumorigenic pathways. Furthermore, our findings suggest that a possible surface stoichiometric shift in the structure of protein could be due to mutations in the coding sequence of Vimentin that may elicit its enhanced secretion possibly due to protein-hyperphosphorylation. Of the three proteins identified, only Vimentin showed higher expression in sera of colon cancer patients alone. Thus, it could be argued that vimentin might help in predicting individuals at higher risk of developing colon cancers. Our data are therefore suggestive of using vimentin as an antigen for tumor vaccination in an autologous set-up for colon cancers.

Allogeneic tumor cell vaccines: the promise and limitations in clinical trials

The high mortality rate associated with cancer and its resistance to conventional treatments such as radiation and chemotherapy has led to the investigation of a variety of anti-cancer immunotherapies. The development of novel immunotherapies has been bolstered by the discovery of tumor-associated antigens (TAAs), through gene sequencing and proteomics. One such immunotherapy employs established allogeneic human cancer cell lines to induce antitumor immunity in patients through TAA presentation. Allogeneic cancer immunotherapies are desirable in a clinical setting due to their ease of production and availability. This review aims to summarize clinical trials of allogeneic tumor immunotherapies in various cancer types. To date, clinical trials have shown limited success due potentially to extensive degrees of inter- and intra-tumoral heterogeneity found among cancer patients. However, these clinical results provide guidance for the rational design and creation of more effective allogeneic tumor immunotherapies for use as monotherapies or in combination with other therapies.

Immunotherapy for castration-resistant prostate cancer

The improved survival with sipuleucel-T, an autologous antigen-presenting cell-based agent, for the treatment of patients with metastatic asymptomatic and minimally symptomatic castration-resistant prostate cancer supports immunotherapy as a valid approach. Also, multiple novel immunotherapeutic approaches are undergoing vigorous investigation. T-lymphocyte checkpoint blockade and poxvirus-based prime-boost approaches are in phase III evaluation. Other immunotherapeutic platforms undergoing early investigation include radioimmunoconjugates and adenovirus-based, DNA-based, and Listeria-based approaches. The development of predictive markers for immune response that translate into improved long-term outcomes is important. This article reviews the emerging data and the unique strengths and weaknesses of these approaches.

Immunotherapeutic strategies for cancer treatment: a novel protein transfer approach for cancer vaccine development

Cancer cells have developed numerous ways to escape immune surveillance and gain unlimited proliferative capacity. Currently, several chemotherapeutic agents and radiotherapy, either alone or in combination, are being used to treat malignancies. However, both of these therapies are associated with several limitations and detrimental side effects. Therefore, recent scientific investigations suggest that immunotherapy is among the most promising new approaches in modern cancer therapy. The focus of cancer immunotherapy is to boost both acquired and innate immunity against malignancies by specifically targeting tumor cells, and leaving healthy cells and tissues unharmed. Cellular, cytokine, gene, and monoclonal antibody therapies have progressively become promising immunotherapeutic approaches that are being tested for several cancers in preclinical models as well as in the clinic. In this review, we discuss recent advances in these immunotherapeutic approaches, focusing on new strategies that allow the expression of specific immunostimulatory molecules on the surface of tumor cells to induce robust antitumor immunity.

Endpoints, patient selection, and biomarkers in the design of clinical trials for cancer vaccines

Therapeutic cancer vaccines are an emerging and potentially effective treatment modality. Cancer vaccines are usually very well tolerated, with minimal toxicity compared with chemotherapy. Unlike conventional cytotoxic therapies, immunotherapy does not result in immediate tumor shrinkage but may alter growth rate and thus prolong survival. Multiple randomized controlled trials of various immunotherapeutic agents have shown a delayed separation in Kaplan-Meier survival curves, with no evidence of clinical benefit within the first 6-12 months of vaccine treatment. Overall survival benefit is seen in patients with lower disease burden who are not expected to die within those initial 6-12 months. The concept of improved overall survival without marked initial tumor reduction represents a significant shift from the current paradigms established by standard cytotoxic therapies. Future clinical studies of therapeutic vaccines should enroll patients with either lower tumor burden, more indolent disease or both, and must seek to identify early markers of clinical benefit that may correlate with survival. Until then, improved overall survival is the only clear, discriminatory endpoint for therapeutic vaccines as monotherapies.

Mycobacteria activate γδ T-cell anti-tumour responses via cytokines from type 1 myeloid dendritic cells: a mechanism of action for cancer immunotherapy

Attenuated and heat-killed mycobacteria display demonstrable activity against cancer in the clinic; however, the induced immune response is poorly characterised and potential biomarkers of response ill-defined. We investigated whether three mycobacterial preparations currently used in the clinic (BCG and heat-killed Mycobacterium vaccae and Mycobacterium obuense) can stimulate anti-tumour effector responses in human γδ T-cells. γδ T-cell responses were characterised by measuring cytokine production, expression of granzyme B and cytotoxicity against tumour target cells. Results show that γδ T-cells are activated by these mycobacterial preparations, as indicated by upregulation of activation marker expression and proliferation. Activated γδ T-cells display enhanced effector responses, as shown by upregulated granzyme B expression, production of the T_H1 cytokines IFN-γ and TNF-α, and enhanced degranulation in response to susceptible and zoledronic acid-treated resistant tumour cells. Moreover, γδ T-cell activation is induced by IL-12, IL-1β and TNF-α from circulating type 1 myeloid dendritic cells (DCs), but not from type 2 myeloid DCs or plasmacytoid DCs. Taken together, we show that BCG, M. vaccae and M. obuense induce γδ T-cell anti-tumour effector responses indirectly via a specific subset of circulating DCs and suggest a mechanism for the potential immunotherapeutic effects of BCG, M. vaccae and M. obuense in cancer.

Current vaccination strategies for prostate cancer

CONTEXT

The first therapeutic cancer vaccine demonstrating effectiveness in a phase 3 study was approved by the US Food and Drug Administration on 29 April 2010. The pivotal trial demonstrated overall survival (OS) benefit in patients treated with antigen-loaded leukapheresis cells compared with a control infusion. Results of other prostate cancer (PCa) vaccination strategies are awaited, as this approach may herald a new era in the care for patients with advanced PCa.

OBJECTIVE

Consider effectiveness and safety of vaccination strategies in the treatment of PCa.

EVIDENCE ACQUISITION

We searched three bibliographic databases (January 1995 through October 2010) for randomised phase 2 and 3 studies of vaccination strategies for PCa based on predetermined relevant Medical Subject Heading terms and free text terms.

EVIDENCE SYNTHESIS

Data from 3 randomised phase 3 and 10 randomised phase 2 vaccination trials are discussed with respect to clinical outcome in terms of progression-free survival and OS, toxicity, prostate-specific antigen (PSA) response, and immunologic response. Three phase 3 trials (D9901, D9902A, and D9902B) that enrolled a total of 737 patients, all controlled and double-blinded, tested the efficacy of sipuleucel-T. The largest of these three trials, called Immunotherapy for Prostate Adenocarcinoma Treatment (IMPACT), has demonstrated safety and effectiveness of sipuleucel-T (now marketed as Provenge) as measured by prolonged survival of 512 asymptomatic patients with metastatic castration-resistant PCa (mCRPC). The study showed a 4.1-mo median survival benefit in the sipuleucel-T vaccine-treated group compared with the control group (25.8 vs 21.7 mo; hazard ratio [HR]: 0.78; 95% confidence interval [CI], 0.62-0.98; p=0.032) and extended 3-yr survival (31.7% vs 23.0%). In contrast, two phase 3 vaccination trials with a whole-tumour-cell mixture of two PCa cell lines (GVAX) and testing GVAX either alone or in combination with chemotherapy versus chemotherapy alone (VITAL1 and 2) were terminated prematurely based on futility and increased deaths. Other phase 2 vaccination trials testing different types of vaccines in castration-resistant PCa patients have been reported with variable outcomes. Notably, a controlled, double-blind, randomised phase 2 vaccine trial of PROSTVAC-VF, a recombinant viral vector containing complementary DNA encoding PSA, in 125 patients with chemotherapy-naïve, minimally symptomatic mCRPC also demonstrated safety but no significant effect on the time to disease progression. In comparison with controls (n=40), PROSTVAC-VF-treated patients (n=82) experienced longer median survival of 8.5 mo (25.1 vs 16.6 mo; HR: 0.56; 95% CI, 0.37-0.85; p=0.0061) and extended 3-yr survival (30% vs 17%). In general, PCa vaccines are perceived to have less toxicity compared with current cytotoxic or targeted therapies. Evaluation of clinical efficacy of different vaccination strategies (eg, protein-, peptide- and DNA-based vaccines) in the context of properly designed and controlled phase 3 studies is warranted.

CONCLUSIONS

Cancer vaccines represent a new paradigm in the treatment of PCa. The IMPACT trial showed improved survival but no difference in time to disease progression in mCRPC patients with minimal tumour burden. Observations in phase 2 and 3 trials pave the way for other vaccination approaches for this disease, raise questions regarding the most appropriate clinical trial designs, and underscore the importance of identifying biomarkers for antitumour effect to better implement such therapies.

Therapeutic vaccines in metastatic castration-resistant prostate cancer: principles in clinical trial design

Although docetaxel was approved for the treatment of metastatic castration-resistant prostate cancer in 2004, additional therapies are still required. Prostate cancer is often slow-growing and expresses many tumor-associated antigens, making it a feasible target for immunotherapy. Several therapeutic cancer vaccines have been developed for prostate cancer, including antigen-presenting-cell-based, vector-based, and whole tumor cell vaccines. Initial trials demonstrated that vaccine approaches have limited toxicity. Clinical trials of targeted biologic therapies have demonstrated that patient selection is vital, and there is preliminary evidence that clinical parameters can be used to encompass metastatic prostate cancer patients who will more probably respond to vaccine treatment. In addition to appropriate patient selection, a successful clinical trial must have an appropriate primary endpoint as well. Three randomized, 'placebo'-controlled studies in metastatic castration-resistant prostate cancer have suggested a clinically significant survival advantage in spite of a lack of improvement in time to progression, implying that overall survival is the ideal endpoint for such trials. Careful examination of data from completed immunotherapy clinical trials in prostate cancer has identified appropriate patient populations and endpoints. Those principles need to be applied to future trial design to properly evaluate prostate cancer vaccines.

Overview of Tumor Cell–Based Vaccines

Whole-cell tumor vaccines have been investigated for more than 20 years for their efficacy in both preclinical models and in clinical trials in humans. There are clear advantages of whole-cell/polyepitope vaccination over those types of immunotherapy that target specific epitopes. Multiple and unknown antigens may be targeted to both the innate and adaptive immune system, and this may be further augmented by genetic modification of the vaccine cells to provide cytokines and costimulation. In this review, we give an overview of the field including the preclinical and clinical advances using unmodified and modified tumor-cell vaccines.

Cancer vaccines: will we ever learn?

Scientists and clinicians engaged in developing therapeutic cancer vaccines cannot be anything other than troubled by the sheer number of Phase III clinical trial failures in the field. Are we inveterate optimists or do we have reason for continuing to plough our lonely furrow? In this perspective article, we answer why Phase III failures have been to the fore and highlight why the field should be optimistic given the knowledge gained from these pioneering studies and our improved understanding of how the immune system interacts with cancer.

Grundlagen der systemischen Therapie

Die Einführung sog. »zielgerichteter Medikamente« hat einen Paradigmenwechsel in der Systemtherapic maligner Erkrankungen ausgelöst. Voraussetzung hierfür waren die in den letzten 25 Jahren gesammelten Erkenntnisse der molekularbiologischen, molekulargenetischen und immunologischen Grundlagenforschung, die ein besseres Verständnis der pathogenetischen Prozesse im Rahmen der malignen Transformation und Tumorprogression sowie die Identifikation strategischer Zielstrukturen (»Targets«) ermöglichen. Auf diese Weise wurde ein neuer Ansatz der Entwicklung antineoplastischer Therapeutika angestoßen, der auf die Wirkung an spezifischen Molekülaktivitäten und nicht primär auf zelluläre Endpunkte (Wachstumshemmung, Zelltod) ausgerichtet ist.

A novel murine model of allogeneic vaccination against renal cancer

OBJECTIVES

To develop a murine model for whole-cell allogeneic vaccination in renal cancer, as such vaccines aim to direct immune responses against patient tumour cells, due to shared antigens between the vaccine and tumour cells.

MATERIALS AND METHODS

A novel murine renal cell line, allogeneic to BALB/c, was developed from a C57BL/6 mouse by primary cell culture (RVIK). It was immortalized by HPV16 E6/E7 and transfected with ras in an attempt to improve its immunogenicity. The cell line was characterized and tested as a vaccine in a BALB/c tumour-protection model after subsequent tumour challenge with autologous RenCa tumour cells.

RESULTS

RVIK alone, with no ras induced cross-reactive immunity, providing a valid non-tumorigenic allogeneic whole-cell vaccine model for renal cancer. Ras transfection per se did not improve RVIK immunity.

CONCLUSIONS

RVIK is a novel immunogenic murine renal epithelial cell line, which confers protection when used as an allogeneic vaccine. It provides proof of principle for the effectiveness of allogeneic whole-cell vaccines and may therefore form the basis of a useful model of allogeneic vaccination to further optimize vaccination schedules, formulation and adjuvants for a clinical setting.

A novel murine model of allogeneic vaccination against prostate cancer

Prostate cancer continues to be a major cause of death in men. Surgical and medical treatments of the disease have improved, but metastasic disease remains a significant clinical problem. Novel therapies such as whole cell vaccination offer the potential of treating disease by stimulating the immune system. To study the efficacy of a whole cell vaccine in prostate cancer two strains of mice were used: C57BL/6 (H-2Kb) and C3H/HeJ (H-2K(k)) in combination with four different cell lines. Thus, a model was constructed of allogeneic and syngeneic vaccine, as well as a challenge tumour for each strain. Two novel cell lines were developed during this study. Firstly, the non tumourigeneic PMC-1 was derived from a normal mouse prostate and immortalized with HPV16. Secondly, the tumourigeneic PMC-1 C6ras1p1 was transformed with human ras gene which formed tumours in both SCID and C3H/HeJ mice. Protection, and the nature of the immune response to syngeneic and allogeneic vaccine, in males and females was examined in both strains. Vaccination with both syngeneic and allogeneic irradiated whole cell vaccines induced protection from syngeneic challenge in females. However, no protection was observed when allogeneic vaccine was given to male mice. This correlated with the immune response. Two types of cellular immune responses were generated in females. A NK-mediated response was observed in C57BL/6 mice, whilst C3H/HeJ mice developed a CTL response. Little or no cellular immune response was observed in males. The cytokine profile in C3H/HeJ females was a mixture of Th1 and Th2 whilst a mainly Th1 profile was observed in C57BL/6 mice. Male mice showed a diminished cytokine secretion compared to females which was further depressed after challenge. The difference in immunity was largely as expected, since tolerance to prostate antigens should not normally develop in female mice. However, this makes this model particularly relevant clinically since it directly mimics the human situation and thus may accelerate the development of whole cell vaccines for clinical use.

Prevention of human PC-346C prostate cancer growth in mice by a xenogeneic tissue vaccine

Vaccination, as an approach to prostate cancer, has largely focused on immunotherapy utilizing specific molecules or allogeneic cells. Such methods are limited by the focused antigenic menu presented to the immune system and by immunotolerance to antigens recognized as "self". To examine if a xenogeneic tissue vaccine could stimulate protective immunity in a human prostate cancer cell line, a vaccine was produced by glutaraldehyde fixation of harvested PAIII prostate cancer cells tumors (GFT cell vaccine) from Lobund-Wistar rats. Immunocompetent Ncr-Foxn1 mice were vaccinated with the GFT cell vaccine four times, 7 days apart. The control animals were either not vaccinated or vaccinated with media or glutaraldehyde-fixed PC346C human prostate cancer cells and adjuvant. About 8 days after the final boost, serum and spleens were harvested. The splenocytes were co-incubated with PC346C cells and then transplanted orthotopically into sygneneic immunodeficient nude mice. About 10 weeks later, the prostates were weighed and sampled for histolologic examination. The spleens were harvested from additional mice, and the splenocytes were cultured, either with or without pulsing by GFT cells, and the supernatants harvested 72 h later for cytokine analysis. Results showed that vaccination with GFT cells resulted in increased serum antibody to a PAIII cell lysate; reduced weight of the prostate/seminal vesicle complex and reduced incidence of prostate cancer in nude mice; increased splenocyte supernatant levels of TNF-alpha, IL-2, IFN-gamma and IL-12, cytokines associated with Th1 immunity; and increased splenocyte supernatant levels of IL-4 and IL-10, cytokines associated with Th2 immunity. In summary, the results suggest that use of a xenogeneic tissue vaccine can stimulate protective immunity against human prostate cancer cells.

Immunology and immunotherapy approaches for prostate cancer

Several mechanisms that impair the immune response to promote tumour progression are reported. These mechanisms aim to reduce the ability of antigen-presenting cells to present antigen and activate naïve T cells to support an active immune response or to create a suppressive environment that induce non-functional tumour-associated antigen-specific T cells. Prostate cancer (PC) alone accounts for 33% of incident cancer cases and about 9% of all cancer-related deaths among men in the USA during 2006. Whereas androgen deprivation has remained the first line of therapy for advanced PC, other therapies are still required due to progression to an androgen-resistant state and eventually loss of control in patients receiving hormonal therapy. Immunotherapy seems to be a promising approach to enhance tumour-specific T-cell responses in different cancers including prostate. More importantly, clinical trials in advanced PC patients have shown that immunotherapy may generate significant clinical responses. Immunology and immunotherapy aspects of PC with focus on prostate-specific antigen will be presented.

Allogeneic retrovirally transduced, IL-2- and IFN-γ-secreting cancer cell vaccine in patients with hormone refractory prostate cancer—a phase I clinical trial

BACKGROUND

The purpose of this vaccine study was to determine the safety and feasibility of vaccination with an allogeneic prostate carcinoma cell line, LNCaP, expressing recombinant interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) and to evaluate the efficacy of inducing tumor-specific immune responses in HLA-A2-matched patients with hormone refractory prostate cancer (HRPC).

METHODS

In a dose-escalating phase I study, HLA-A2-matched HRPC patients received four vaccinations of irradiated allogeneic LNCaP cells retrovirally transduced to secrete IL-2 and IFN-gamma at study day 1, 15, 29 and 92 and subsequently every 91 days unless tumor progression was evident.

RESULTS

Three patients receiving the first dose level (7.5 million cells) showed no evidence of dose-limiting toxicity or vaccine-related adverse events including autoimmunity. One of three patients receiving the second dose level (15 million cells) developed a transient self-limiting grade 3 local injection site reaction (ulceration) after the eighth vaccination. Vaccine-induced immune responses against a broad array of prostate tumor associated antigens were detected in all six patients. Two of the three patients receiving the higher dose showed a decline in serum prostate-specific antigen (PSA) values of more than 50%, with one patient remaining on protocol for 3 years.

CONCLUSIONS

Immunisation with the allogeneic LNCaP/IL-2/IFN-gamma vaccine is safe and feasible without any dose-limiting toxicity or autoimmunity. A 50% PSA decline was achieved in two of the six patients. This encouraging data provides the scientific rationale for further investigation of the vaccine in a phase II trial.

Advances in Prostate Cancer Immunotherapies

Prostate cancer is a major cause of mortality in men in the Western world. Although treatment of early stage prostate cancer with radiation therapy or prostatectomy is efficient in most cases, some patients develop a fatal hormone-refractory disease. Treatments in this case are limited to aggressive chemotherapies, which can reduce serum prostate-specific antigen (PSA) levels in some patients. Taxane- and platinum-compound-based chemotherapies produce a survival benefit of only a few months. Therefore, it is crucial to develop novel, well tolerated treatment strategies. Over the past years, immunotherapy of hormone-refractory prostate cancer has been studied in numerous clinical trials. The fact that the prostate is a non-essential organ makes prostate cancer an excellent target for immunotherapy. Administration of antibodies targeting the human epidermal growth factor receptor-2 or the prostate-specific membrane antigen led to stabilisation of PSA levels in several patients. Vaccination of prostate cancer patients with irradiated allogeneic prostate cell lines has demonstrated that whole cell-based vaccines can significantly attenuate increases in PSA. Two different recombinant viral expression vectors have been applied in prostate cancer treatment: poxvirus and adenovirus vectors. Both vaccines have the advantages of using a natural method to induce immune responses and achieving high levels of transgene expression. Vaccinia viruses in combination with recombinant fowlpox or canarypox virus have been used to express recombinant PSA. Several studies demonstrated that this approach is safe and can lead to stabilisation of PSA values. A very promising approach in prostate cancer immunotherapy is vaccination of patients with dendritic cells. Thereby, peptides, recombinant proteins, tumour lysates or messenger RNA have been used to deliver antigens to autologous dendritic cells. Loading of dendritic cells with up to five different peptides derived from multiple proteins expressed in prostate cancer demonstrated that cytotoxic T-cell responses could be elicited in prostate cancer patients. Sipuleucel-T (APC8015), an immunotherapy product consisting of antigen-presenting cells, loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase linked to granulocyte-macrophage colony-stimulating factor, demonstrated in a phase III, placebo-controlled trial an improvement in median time to disease progression. The improvement in overall survival was 4.5 months for sipuleucel-T-treated patients compared with the placebo group. Although there is a minor increase in overall survival of metastatic prostate cancer patients with some approaches, more effective therapeutic strategies need to be developed.

Immunotherapy for Prostate Cancer: What's the Future?

Prostate cancer is the most common noncutaneous cancer and second leading cause of cancer death among US men. A greater understanding of basic immunologic principles has led to a variety of new techniques,which has led to advancements in prostate cancer vaccines. This article discusses the rationale for the development of antibody-based therapy and vaccines therapy, including whole tumor cells, dendritic cells, and pox viral vectors. A summary of selected clinical studies incorporating these strategies and new approaches incorporating a combination of immunotherapy with traditional treatments for prostate cancer is presented.

Cancer vaccines as a therapeutic modality: The long trek

The development of cancer vaccines has been one of the several false dawns in which initial promising Phase I and Phase II clinical data have not been followed up with conclusive Phase III trials. In this review, we describe some of the successes and failures, and review the most likely reasons for Phase III failure, such as protocol changes, which are common between Phase II and III, and poorly defined patient groups. Nevertheless, significant survival results have been reported with autologous vaccines for colorectal, renal and, more recently, prostate cancer. In addition, it is becoming evident that immunotherapy is potentially synergistic with other treatment modalities, such as chemotherapy, which can reduce T-regulatory activity that inhibits the immune response to cancer vaccines. This potential for synergy should allow cancer vaccines to become part of the standard treatment regimen for many common tumours.

Phase I clinical trial of a TGF-beta antisense-modified tumor cell vaccine in patients with advanced glioma

We performed a phase I clinical trial in grade IV astrocytoma to assess the safety of a whole-cell vaccine comprising autologous tumor cells genetically modified by a transforming growth factor-beta2 (TGF-beta2) antisense vector. Blocking secretion of the immunosuppressive molecule TGF-beta in this manner should inhibit one of the major mechanisms by which tumor cells evade immune surveillance and should lead to clinically effective antitumor immunity. Six patients with progressive WHO grade IV astrocytoma were enrolled in the trial. Patients received 2-7 subcutaneous injections of 5 x 10(6)-2 x 10(7) autologous tumor cells per injection. TGF-beta2 secretion by the tumor cells used to vaccinate patients was inhibited by 53-98%. Treatment was well tolerated with only low-grade, transient treatment-related toxicities reported. Two patients had partial regressions and two had stable disease following therapy. The overall median survival was 68 weeks. Median survival of the responding patients was 78 weeks, compared to a historic value of 47 weeks for glioma patients treated conventionally. There were indications of humoral and cellular immunity induced by the vaccine. These findings support further clinical evaluation of vaccines comprised of TGF-beta antisense-modified tumor cells.

Management of prostate cancer. Part 3: metastatic disease

Despite the increased detection of prostate cancer at an early stage, men are still dying of this disease. Management of advanced disease focuses on controlling the disease process, palliation of symptoms and improving quality of life. In this review, the basis for androgen deprivation in hormone-dependent disease is discussed and the role of maximum and intermittent androgen deprivation, as well as management options for hormone-refractory disease is addressed. Local radiotherapy continues to be of importance in pain control and the maintenance of quality of life. Radiopharmaceuticals and bisphosphonates also have a role to play, the latter particularly in the reduction of skeletal-related events. Chemotherapy in hormone-refractory disease is now well established following pivotal trials demonstrating a survival benefit with docetaxel. The emergence of novel agents targeting growth factors, angiogenesis and immunotherapy present exciting possibilities for future treatment.

Therapeutic Vaccines for Prostate Cancer

Prostate cancer is the most common, noncutaneous cancer for men in the U.S., leading to more than 30,000 deaths a year. Vaccines for prostate cancer, which for several years have been shown to generate immunologic responses, are beginning to show significant clinical promise. At present, numerous therapeutic options are being investigated, including autologous and allogeneic whole-tumor cell vaccines, dendritic cell vaccines, and poxvirus-based vaccines. Advances in basic immunology have translated into new, more complex therapeutic strategies. The findings from current trials and the demonstrated potential to combine vaccines with conventional therapies herald a promising future for the treatment of prostate cancer. This review highlights recent advances and clinical trials in immunotherapy for prostate cancer, along with current thoughts on immunologic and clinical monitoring of these trials.

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.

Constitutively Active STAT5b Induces Cytokine-Independent Growth of the Acute Myeloid Leukemia–Derived MUTZ-3 Cell Line and Accelerates Its Differentiation Into Mature Dendritic Cells

The CD34(+) human acute myeloid leukemia-derived cell line MUTZ-3 is dependent on hematopoietic growth factors for its proliferation and is able to differentiate into dendritic cells (DCs) in response to the combination of granulocyte-macrophage colony-stimulating factor, interleukin-4, and tumor necrosis factor-alpha. This cell line carries human leukocyte antigen (HLA)-A2.1, HLA-A3, and HLA-B44, which cover most of the caucasian population, and it could therefore be used as an off-the-shelf allogeneic DC-based vaccine. Signal transduction and activation of transcription (STAT) 5b is involved in cytokine signal transduction, particularly of cytokines involved in DC precursor growth and differentiation. The constitutively active form of STAT5b induced cytokine-independent growth of MUTZ-3 cells. Furthermore, STAT5b-transduced cells differentiated into mature DCs in 3 to 4 days after stimulation with DC differentiation-inducing cytokines, reducing the culture period to obtain mature DCs with 5 days compared with unmodified MUTZ-3-derived mature DC cultures. Both DC types expressed DC maturation markers and were equally effective in inducing primary T-cell responses. DCs derived from the STAT5b-transduced cells had a more stable mature phenotype after cytokine deprivation, which was reflected in a better performance in functional assays. In conclusion, these results show that STAT5b-transduced MUTZ-3 can be propagated in cytokine-free medium and rapidly differentiated into functional mature DCs that sustain a mature phenotype over a period of 3 to 5 days in the absence of differentiation-inducing cytokines. The simplified propagation and rapid differentiation into mature DCs may facilitate clinical application of this cell line as an allogeneic DC-based vaccine.

The biological effects of syngeneic and allogeneic cytokine-expressing prophylactic whole cell vaccines and the influence of irradiation in a murine melanoma model

Allogeneic whole tumour cell vaccines are inherently practical compared with autologous vaccines. Cell lines are derived from allogeneic tumour, grown in bulk and then administered as a vaccine to the patient, following irradiation, which not only prevents any replication but also enhances antigen presentation. Protection is believed to occur through the presentation of antigens shared between the syngeneic and allogeneic tumours. Although cytokine-transfected tumour whole cell vaccines have been used clinically, little data is available comparing the effects of immunomodulatory cytokine-transfection directly on the same cells when used as both an allogeneic and autologous vaccine. To address this, weakly immunogenic B16-F10 (H-2b) murine melanoma was transfected to secrete either GM-CSF, IL-4 or IL-7. Prophylactic vaccination of both syngeneic C57/BL6 (H-2b) (B6) and allogeneic C3H/Hej (H-2k) (C3H) mice showed the effects of transfected cytokine varied between models. Both GM-CSF and IL-7 significantly (P<0.05) increased the levels of protection within syngeneic B6 mice, but had a diminished effect (P>0.05) within C3H allogeneic mice. Allogeneic B16-F10 cells and syngeneic K1735 cells generated CTL against K1735 suggesting cross-reactive immunity. Using cells labeled with fluorescent dye we demonstrate that irradiated vaccines, of either syngeneic or allogeneic origin, appear to generate potent immune responses and fragments of either vaccine remain at the injection site for up to 9 days. This study shows that protection can be enhanced in vivo by using transfected cytokine, but suggests that irradiated whole cell vaccines, of either tissue-type, are rapidly processed. This leads to the conclusion that the cytokine effects are transient and thus transfection with cytokine may be of limited long-term use in situ.

Immunotherapy with allotumour mRNA-transfected dendritic cells in androgen-resistant prostate cancer patients

Here, we present results from a clinical trial employing a new vaccination method using dendritic cells (DCs) transfected with mRNA from allogeneic prostate cancer cell lines (DU145, LNCaP and PC-3). In all, 20 patients were enrolled and 19 have completed vaccination. Each patient received at least four weekly injections with 2 × 10⁷ transfected DCs either intranodally or intradermally. Safety and feasibility of vaccination were determined. Immune responses were measured as delayed-type hypersensitivity and by in vitro immunoassays including ELISPOT and T-cell proliferation in pre- and postvaccination peripheral blood samples. Serum prostate-specific antigen (PSA) levels and bone scans were monitored. No toxicity or serious adverse events related to vaccinations were observed. A total of 12 patients developed a specific immune response to tumour mRNA-transfected DCs. In total, 13 patients showed a decrease in log slope PSA. This effect was strengthened by booster vaccinations. Clinical outcome was significantly related to immune responses (n=19, P=0.002, r=0.68). Vaccination with mRNA-transfected DCs is safe and results in cellular immune responses specific for antigens encoded by mRNA derived from the prostate cancer cell lines. The observation that in some patients vaccination affected the PSA level suggests that this approach may become useful as a treatment modality for prostate cancer patients.

Delayed disease progression after allogeneic cell vaccination in hormone-resistant prostate cancer and correlation with immunologic variables

PURPOSE

There are a significant number of patients with asymptomatic hormone-resistant prostate cancer who have increasing prostate-specific antigen (PSA) levels but little or no evaluable disease. The immunogenicity and minimal toxicity associated with cell-based vaccine therapy makes this approach attractive for these patients.

EXPERIMENTAL DESIGN

We have evaluated a vaccine comprising monthly intradermal injection of three irradiated allogeneic prostate cell lines (8 x 10(6) cells each) over 1 year. The first two doses were supplemented with bacille Calmette-Guérin as vaccine adjuvant. Twenty-eight hormone-resistant prostate cancer patients were enrolled. Patients were assessed clinically and PSA levels were measured monthly. Radiologic scans (X-ray, computed tomography, and bone scan) were taken at baseline and at intervals throughout the treatment period. Comprehensive monthly immunologic monitoring was undertaken including proliferation studies, activation markers, cytokine protein expression, and gene copy number. This longitudinal data was analyzed through predictive modeling using artificial neural network feed-forward/back-propagation algorithms with multilayer perceptron architecture.

RESULTS

Eleven of the 26 patients showed statistically significant, prolonged decreases in their PSA velocity (PSAV). None experienced any significant toxicity. Median time to disease progression was 58 weeks, compared with recent studies of other agents and historical control values of around 28 weeks. PSAV-responding patients showed a titratable T(H)1 cytokine release profile in response to restimulation with a vaccine lysate, while nonresponders showed a mixed T(H)1 and T(H)2 response. Furthermore, immunologic profile correlated with PSAV response by artificial neural network analysis. We found predictive power not only in expression of cytokines after maximal stimulation with phorbol 12-myristate 13-acetate, but also the method of analysis (qPCR measurement of IFN-gamma > qPCR measurement tumor necrosis factor-alpha > protein expression of IFN-gamma > protein expression of interleukin 2).

CONCLUSIONS

Whole cell allogeneic vaccination in hormone-resistant prostate cancer is nontoxic and improves the natural history of the disease. Longitudinal changes in immunologic function in vaccinated patients may be better interpreted through predictive modeling using tools such as the artificial neural network rather than periodic "snapshot" readouts.

Immunotherapy of murine prostate cancer using whole tumor cells killed ex vivo by herpes simplex viral thymidine kinase/ganciclovir suicide gene therapy

Whole cell cancer vaccines are currently under clinical evaluation. Their immunogenicity may depend on the mode of death of the vaccine cells prior to uptake by professional antigen-presenting cells and crosspriming of T cells. Destruction of tumor in vivo by genetic prodrug activation therapy leads to a marked local and systemic immune response, local T-cell infiltration and the establishment of T-cell memory. We postulated that this immunostimulation may be due to induction of danger signals and the inherent immunogenicity of products of HSVtk/ganciclovir kill. Using established models of murine prostate cancer, we have evaluated the efficacy of anti-tumor vaccines comprising irradiated allogeneic or autologous whole cells expressing HSVtK, which are first killed in vitro by prodrug activation using ganciclovir. HSVtk/ganciclovir-induced cell kill was through the induction of apoptosis. The vaccine was found to be effective in both models and superior to traditional irradiated whole tumor cells even after single doses. Protection against tumor challenge was associated with marked proliferative and Th1 cytokine responses. This approach would be applicable clinically in terms of ease of vaccine production, safety, storage and avoidance of potential toxicities of in vivo gene transfer.

Future therapies in hormone-refractory prostate cancer

Hormone-refractory prostate cancer (HRPC) remains true to its name: it is largely refractory to attempts to delay its progression. Although the number of men presenting with metastatic prostate cancer has decreased significantly over the last several years, the death rate for those men is essentially unchanged. To alter the currently inevitable progression of HRPC to death, new targets and new therapies are needed. This article reviews investigational therapies directed against standard targets (eg, the hypothalamic-pituitary-gonadal axis) as well as novel targets (eg, the endothelin axis).

Immunotherapy for superficial bladder cancer

The treatment of superficial bladder cancer requires adjuvant therapies besides transurethral resection because of a high recurrence rate after this standard treatment alone. Current adjuvant therapies involve intravesical chemotherapy for patients at low and intermediate risk for recurrence and progression, and intravesical bacillus Calmette-Guérin for patients at intermediate and high risk. However, these adjuvant therapies fail in a significant number of patients, dictating the need for new and improved adjuvant treatment modalities for superficial bladder cancer. Immunotherapy aiming at the modulation of the immune system of the patient is a promising alternative adjuvant. This review discusses the current status of the clinical development of various immunotherapy approaches for superficial bladder cancer, including passive immunotherapy, immune stimulants, immunogene therapy and cancer vaccination.

Intratumoral vaccination and diversified subcutaneous/ intratumoral vaccination with recombinant poxviruses encoding a tumor antigen and multiple costimulatory molecules

PURPOSE

Intratumoral (i.t.) vaccination represents a potential modality for the therapy of tumors. Previous i.t. vaccination studies have focused on the efficacy of i.t. vaccination alone. There are no reports that clearly compared i.t. vaccination with systemic vaccination achieved by s.c., intradermal, or i.m. injection, or combining both modalities of systemic and i.t. vaccination. Here, we compared the antitumor effects induced by a systemic vaccination regimen (s.c.) and i.t. vaccination, and a sequential s.c/i.t. vaccination regimen. In this study, we used a recombinant vaccinia virus containing the transgenes for carcinoembryonic antigen (CEA) and a triad of T-cell costimulatory molecules (B7-1, ICAM-1, and LFA-3; designated rV-CEA/TRICOM) for s.c. priming and a replication defective avipox (fowlpox) virus containing the same four transgenes (designated rF-CEA/TRICOM) for i.t. vaccination or s.c. booster vaccinations.

EXPERIMENTAL DESIGN

Vaccination was started on day 8 after s.c. implantation with CEA-positive tumors. We compared the antitumor activity induced by these vaccines when administered via the i.t. route versus the s.c. route. Subsequent therapy studies examined the sequential combination of these routes, s.c. priming with rV-CEA/TRICOM followed by i.t. boosting with rF-CEA/TRICOM. Initial studies were conducted in conventional mice to define optimal vaccine regimens and then in CEA-transgenic mice that expressed CEA as a "self" antigen in a manner similar to that of an advanced colorectal cancer patient.

RESULTS

The results demonstrate that the antitumor activity induced by i.t. vaccination is superior to that induced by s.c. vaccination. For more advanced tumors, a s.c. priming vaccination, followed by i.t. boosting vaccinations was superior to either s.c. or i.t. vaccination alone. Both of these phenomena were observed in tumor models where the tumor-associated antigen is a foreign antigen and in a CEA-transgenic tumor model where the tumor-associated antigen is a self-antigen. The cytokine, granulocyte macrophage colony-stimulating factor admixed in vaccines, was shown to be essential in inducing the antitumor activity.

CONCLUSIONS

These studies demonstrate that the diversified vaccine regimens that consisted of s.c. prime and i.t. boosts with CEA/TRICOM vectors could induce antitumor therapy superior to that seen by either route alone.

Dendritic cell immunotherapy for urological cancers using cryopreserved allogeneic tumour lysate-pulsed cells: a phase I/II study

OBJECTIVE

To assess the feasibility, toxicity and immunogenicity of dendritic cell (DC)-based immunotherapy in patients with advanced urological cancers.

PATIENTS AND METHODS

Patients with hormone-refractory prostate cancer (11) and metastatic renal cell carcinoma (five) received 1-3 x 10(6) intradermal allogeneic tumour lystate-pulsed DCs fortnightly for six vaccinations then monthly until disease progression. Intradermal keyhole limpet haemocyanin was injected near the DCs as the adjuvant. DC vaccine was prepared from buffy coats, then lysate-pulsed, cryopreserved in aliquots, and tested for phenotypic expression and activity in an allogeneic mixed lymphocyte reaction before clinical use.

RESULTS

There was no evidence of significant toxicity from vaccine or adjuvant. Delayed-type hypersensitivity skin testing and biopsy revealed a cellular infiltrate to intradermal re-challenge to tumour lysate and adjuvant in almost all patients. In addition, there was increased expression of T helper type 1 cytokines, interferon-gamma-expressing T cell by ELISPOT analysis, but also interleukin-10 in a few patients. Vaccination resulted in a reduction in the level of prostate-specific antigen (PSA) in one patient, a reduction in PSA velocity in a further man and an increased PSA doubling time in six. Two of five patients with renal cell carcinoma had stabilization of disease.

CONCLUSION

The cryopreservation and repeated administration of DC vaccine was feasible and not toxic. There was evidence of induction of both humoral and cellular immunity to vaccine and adjuvant in most patients. The use of sequential aliquots of identical cryopreserved vaccine will ensure quality control and greatly facilitate future clinical studies in terms of consistency of vaccine administered and the provision of primed DCs for in vitro assessment of response.

Disabled infectious single cycle herpes simplex virus (DISC-HSV) is a candidate vector system for gene delivery/expression of GM-CSF in human prostate cancer therapy

BACKGROUND

DISC-HSV is a replication incompetent herpes simplex virus that is a highly efficient vector for the transduction of genes in vivo and in vitro. We examine the ability of DISC-HSV to infect human prostate cancer cell-lines and xenograft tumor models, and induce expression of reporter and therapeutic cytokine genes.

METHODS

Infection was confirmed by cellular staining for the beta-galactosidase reporter gene product, and by EM. Human GM-CSF production following DISC-hGMCSF infection was measured using ELISA. The metabolic activity of infected cells was determined by NADP/NADPH assay. Cell death was estimated by cell-cycle analysis using flow cytometry with propidium iodide staining.

RESULTS

Infection of DU145, PC3 and LNCaP cells with DISC-HSV was dose dependent. Cells infected with DISC-hGM-CSF released significant levels of hGM-CSF for 3 days. NADP/NADPH assay suggested that infected cells continued to be metabolically active for 3 days post-infection, which was consistent with flow cytometry findings that cell death did not occur within 7 days of infection. Tumor xenografts injected with DISC-HSV expressed beta-galactosidase, and intracellular viral particles were demonstrated using EM.

CONCLUSIONS

We have previously reported the rejection of established tumors following intra-tumoral injection of DISC-GMCSF. This study demonstrates the ability of DISC-HSV to infect prostate cancer and express GMCSF at significant levels. We suggest that prostate cancer is a potential target for therapy using DISC-HSV containing GM-CSF.

Renal-cell carcinoma: tumour markers, T-cell epitopes, and potential for new therapies

Advanced renal-cell carcinoma is a very difficult tumour to treat, and response rates to biological therapies are less than 20%. The identification of various molecular and cellular markers has led to the development of novel therapies. Despite evaluation of their association with histological subtype, immune infiltration, molecular markers of cell proliferation, p53 mutation, and growth-factor-receptor expression, none of these markers has proved better predictive factors than tumour stage and histological grade. The identification of tumour-associated antigens and the specificity of cellular immune responses have led to the development of targeted immunotherapy with monoclonal antibodies, radioimmunotherapy, and T-cell therapies. In this review, we evaluate a range of markers associated with renal-cell carcinoma and new treatment approaches based on tumour-associated antigens and, in particular, T-cell epitopes.