Dendritic cells modified to express CD40 ligand elicit therapeutic immunity against preexisting murine tumors

Close the cancer-immunity cycle by integrating lipid nanoparticle-mRNA formulations and dendritic cell therapy

Effective cancer immunotherapy is usually blocked by immunosuppressive factors in the tumour microenvironment, resulting in tumour promotion, metastasis and recurrence. Here we combine lipid nanoparticle-mRNA formulations and dendritic cell therapy (named CATCH) to boost the cancer-immunity cycle via progressive steps to overcome the immunosuppressive tumour microenvironment. Multiple types of sugar-alcohol-derived lipid nanoparticles are conceived to modulate the cancer-immunity cycle. First, one type of lipid nanoparticle containing CD40 ligand mRNA induces robust immunogenic cell death in tumoural tissues, leading to the release of tumour-associated antigens and the expression of CD40 ligand. Next, dendritic cells engineered by another type of lipid nanoparticle encapsulating CD40 mRNA are adoptively transferred, which are then activated by the CD40 ligand molecules in tumoural tissues. This promotes the secretion of multiple cytokines and chemokines, and the upregulation of co-stimulatory molecules on dendritic cells, which are crucial for reprogramming the tumour microenvironment and priming the T-cell responses. After dendritic cells present tumour-associated antigens to T cells, all the above stepwise events contribute to boosting a potent tumour-specific T-cell immunity that eradicates established tumours, suppresses distal lesions and prevents tumour rechallenge.

Predicting combinations of immunomodulators to enhance dendritic cell-based vaccination based on a hybrid experimental and computational platform

Dendritic cell (DC)-based vaccines have been largely used in the adjuvant setting for the treatment of cancer, however, despite their proven safety, clinical outcomes still remain modest. In order to improve their efficacy, DC-based vaccines are often combined with one or multiple immunomodulatory agents. However, the selection of the most promising combinations is hampered by the plethora of agents available and the unknown interplay between these different agents. To address this point, we developed a hybrid experimental and computational platform to predict the effects and immunogenicity of dual combinations of stimuli once combined with DC vaccination, based on the experimental data of a variety of assays to monitor different aspects of the immune response after a single stimulus. To assess the stimuli behavior when used as single agents, we first developed an in vitro co-culture system of T cell priming using monocyte-derived DCs loaded with whole tumor lysate to prime autologous peripheral blood mononuclear cells in the presence of the chosen stimuli, as single adjuvants, and characterized the elicited response assessing 18 different phenotypic and functional traits important for an efficient anti-cancer response. We then developed and applied a prediction algorithm, generating a ranking for all possible dual combinations of the different single stimuli considered here. The ranking generated by the prediction tool was then validated with experimental data showing a strong correlation with the predicted scores, confirming that the top ranked conditions globally significantly outperformed the worst conditions. Thus, the method developed here constitutes an innovative tool for the selection of the best immunomodulatory agents to implement in future DC-based vaccines.

Electroporation as a method of choice to generate genetically modified dendritic cell cancer vaccines

In the last few decades, immunotherapy has emerged as an alternative therapeutic approach to treat cancer. Immunotherapy offers a plethora of different treatment possibilities. Among these, dendritic cell (DC)-based cancer vaccines constitute one of the most promising and valuable therapeutic options. DC-vaccines have been introduced into the clinics more than 15 years ago, and preclinical studies showed their general safety and low toxic effects on patients. However, their treatment efficacy is still rather limited, demanding for novel avenues to improve vaccine efficacy. One way to potentially achieve this is to focus on improving the DC-T cell interaction to further increase T cell priming and downstream activity. A successful DC-T cell interaction requires three different signals (Figure 1): (1) Major Histocompatibility Complex (MHC) and antigen complex interaction with T cell receptor (TCR) (2) interaction between co-stimulatory molecules and their cognate ligands at the cell surface and (3) secretion of cytokines to polarize the immune response toward a Type 1 helper (Th1) phenotype. In recent years, many studies attempted to improve the DC-T cell interaction and overall cancer vaccine therapeutic outcomes by increasing the expression of mediators of signal 1, 2 and/or 3, through genetic modifications of DCs. Transfection of genes of interest can be achieved through many different methods such as passive pulsing, lipofection, viral transfection, or electroporation (EP). However, EP is currently emerging as the method of choice thanks to its safety, versatility, and relatively easy clinical translation. In this review we will highlight the potential benefits of EP over other transfection methods as well as giving an overview of the available studies employing EP to gene-modify DCs in cancer vaccines. Crucial aspects such as safety, feasibility, and gene(s) of choice will be also discussed, together with future perspectives and opportunities for DC genetic engineering.

Ex vivo dendritic cell generation-A critical comparison of current approaches

Dendritic cells (DCs) are professional antigen-presenting cells, required for the initiation of naïve and memory T cell responses and regulation of adaptive immunity. The discovery of DCs in 1973, which culminated in the Nobel Prize in Physiology or Medicine in 2011 for Ralph Steinman and colleagues, initially focused on the identification of adherent mononuclear cell fractions with uniquely stellate dendritic morphology, followed by key discoveries of their critical immunologic role in initiating and maintaining antigen-specific immunity and tolerance. The medical promise of marshaling these key capabilities of DCs for therapeutic modulation of antigen-specific immune responses has guided decades of research in hopes to achieve genuine physiologic partnership with the immune system. The potential uses of DCs in immunotherapeutic applications include cancer, infectious diseases, and autoimmune disorders; thus, methods for rapid and reliable large-scale production of DCs have been of great academic and clinical interest. However, difficulties in obtaining DCs from lymphoid and peripheral tissues, low numbers and poor survival in culture, have led to advancements in ex vivo production of DCs, both for probing molecular details of DC function as well as for experimenting with their clinical utility. Here, we review the development of a diverse array of DC production methodologies, ranging from cytokine-based strategies to genetic engineering tools devised for enhancing DC-specific immunologic functions. Further, we explore the current state of DC therapies in clinic, as well as emerging insights into physiologic production of DCs inspired by existing therapies.

Improving Efficacy and Safety of Agonistic Anti-CD40 Antibody Through Extracellular Matrix Affinity

CD40 is an immune costimulatory receptor expressed by antigen-presenting cells. Agonistic anti-CD40 antibodies have demonstrated considerable antitumor effects yet can also elicit serious treatment-related adverse events, such as liver toxicity, including in man. We engineered a variant that binds extracellular matrix through a super-affinity peptide derived from placenta growth factor-2 (PlGF-2_123-144) to enhance anti-CD40's effects when administered locally. Peritumoral injection of PlGF-2_123-144-anti-CD40 antibody showed prolonged tissue retention at the injection site and substantially decreased systemic exposure, resulting in decreased liver toxicity. In four mouse tumor models, PlGF-2_123-144-anti-CD40 antibody demonstrated enhanced antitumor efficacy compared with its unmodified form and correlated with activated dendritic cells, B cells, and T cells in the tumor and in the tumor-draining lymph node. Moreover, in a genetically engineered Braf^V600E βCat^STA melanoma model that does not respond to checkpoint inhibitors, PlGF-2_123-144-anti-CD40 antibody treatment enhanced T-cell infiltration into the tumors and slowed tumor growth. Together, these results demonstrate the marked therapeutic advantages of engineering matrix-binding domains onto agonistic anti-CD40 antibody as a therapeutic given by tumori-regional injection for cancer immunotherapy.Implications: Extracellular matrix-binding peptide conjugation to agonistic anti-CD40 antibody enhances antitumor efficacy and reduces treatment-related adverse events. Mol Cancer Ther; 17(11); 2399-411. ©2018 AACR.

Strategies to Genetically Modulate Dendritic Cells to Potentiate Anti-Tumor Responses in Hematologic Malignancies

Dendritic cell (DC) vaccination has been investigated as a potential strategy to target hematologic malignancies, while generating sustained immunological responses to control potential future relapse. Nonetheless, few clinical trials have shown robust long-term efficacy. It has been suggested that a combination of surmountable shortcomings, such as selection of utilized DC subsets, DC loading and maturation strategies, as well as tumor-induced immunosuppression may be targeted to maximize anti-tumor responses of DC vaccines. Generation of DC from CD34+ hematopoietic stem and progenitor cells (HSPCs) may provide potential in patients undergoing allogeneic HSPC transplantations for hematologic malignancies. CD34+ HSPC from the graft can be genetically modified to optimize antigen presentation and to provide sufficient T cell stimulatory signals. We here describe beneficial (gene)-modifications that can be implemented in various processes in T cell activation by DC, among which major histocompatibility complex (MHC) class I and MHC class II presentation, DC maturation and migration, cross-presentation, co-stimulation, and immunosuppression to improve anti-tumor responses.

Cd40 Activation as Potential Tool in Malignant Neoplasms

Background

CD40, a cell surface molecule, is expressed on B-cell malignancies and many different solid tumors. It is capable of mediating diverse biological phenomena such as the induction of apoptosis in tumors and stimulation of the immune response. It has thus been studied as a possible target for antitumor therapy. The general aim of this review is to focus the attention of clinical oncologists on the involvement of CD40 in tumors and the rationale of CD40-activation-based therapies in new, biologically oriented antitumor protocols.

Methods

A Medline review of published papers about the role of CD40 activation in cancer therapy.

Results

Many authors have shown that CD40 activation promotes apoptotic death of tumor cells and that the presence of the molecule on the surface of carcinoma lines is an important factor in the generation of tumor-specific T-cell responses that contribute to tumor cell elimination. The CD40 ligand (CD40L) is the natural ligand for CD40; it is expressed primarily on the surface of activated T lymphocytes. Preclinical studies suggest that CD40-CD40L interaction could be useful for cytotoxicity against CD40-expressing tumors and for immune stimulation. Tumor inhibition was observed when tumor cells were treated with agonistic anti-CD40 monoclonal antibodies or with the soluble form of CD40L. The results of the first phase I clinical trial to treat cancer patients with subcutaneous injection of recombinant human CD40L have been recently reported. Immunohistochemical studies have revealed that detection of CD40 in primary cutaneous malignant melanoma and lung cancer may have a negative prognostic value. Interestingly, up-regulation of CD40 was observed in the tumor vessels of renal carcinomas and Kaposi's sarcoma, suggesting possible involvement of CD40 in tumor angiogenesis. Recently, it has also been shown that CD40 engagement on endothelial cells induces in vitro tubule formation and expression of matrix metalloproteinases, two processes involved in the neovascularization and progression of tumors.

Conclusions

CD40 activation represents an exciting target for hematological malignancies and solid tumors expressing the molecule, but its functional role in cancer development still remains unclear and controversial.

Spontaneous Activation of Antigen-presenting Cells by Genes Encoding Truncated Homo-Oligomerizing Derivatives of CD40

The interaction between the CD40 receptor on antigen-presenting cells (APCs) and its trimeric ligand on CD4 T cells is essential for the initiation and progression of the adaptive immune response. Here we undertook to endow CD40 with the capacity to trigger spontaneous APC activation through ligand-independent oligomerization. To this end we exploited the GCN4 yeast transcriptional activator, which contains a leucine zipper DNA-binding motif that induces homophilic interactions. We incorporated GCN4 variants forming homodimers, trimers, or tetramers at the intracellular domain of human and mouse CD40 and replaced the extracellular portion with peptide-β2m or other peptide tags. In parallel we examined similarly truncated CD40 monomers lacking a GCN4 motif. The oligomeric products appeared to arrange in high-molecular-weight aggregates and were considerably superior to the monomer in their ability to trigger nuclear factor kB signaling, substantiating the anticipated constitutively active (ca) phenotype. Cumulative results in human and mouse APC lines transfected with caCD40 mRNA revealed spontaneous upregulation of CD80, IL-1β, TNFα, IL-6, and IL-12, which could be further enhanced by caTLR4 mRNA. In mouse bone-marrow-derived dendritic cells caCD40 upregulated CD80, CD86, MHC-II, and IL-12 and in human monocyte-derived dendritic cells it elevated surface CD80, CD83 CD86, CCR7, and HLA-DR. Oligomeric products carrying the peptide-β2m extracellular portion could support MHC-I presentation of the linked peptide up to 4 days post-mRNA transfection. These findings demonstrate that the expression of a single caCD40 derivative in APCs can exert multiple immunostimulatory effects, offering a new powerful tool in the design of gene-based cancer vaccines.

Adenovirus co-expressing CD40 ligand and interleukin (IL)-2 contributes to maturation of dendritic cells and production of IL-12

The aim of the present study was to construct a chimeric adenovirus (Ad)5/F35 co-expressing human CD4O ligand (CD4OL) and interleukin (IL)-2 (Ad5/F35 CD40L-IL-2). The infection efficiency to human monocyte-derived dendritic cells (Mo-DCs), expression of genes, phenotype changes and IL-12 production of Mo-DC by Ad5/F35 CD40L-IL-2 were investigated. CD40L and IL-2 from total RNA extracted from human peripheral blood mononuclear cells (PBMCs) were cloned by reverse transcription-polymerase chain reaction and used to construct Ad5/F35 CD40L-IL-2. The infection efficiency, expression of CD40L, and phenotype changes of Mo-DC infected with Ad5/F35 CD40L-IL-2 were analyzed using flow cytometry. The quantities of IL-2 and IL-12 in the supernatants of Mo-DC following infection of Ad5/F35 CD40L-IL-2 were measured by enzyme-linked immunosorbent assay. The CD40L and IL-2 genes were successfully cloned and the Ad5/F35 CD40L-IL-2 was constructed. Ad5/F35 CD40L-IL-2 efficiently infected Mo-DCs with an infection efficiency of >75%, and the infected Mo-DCs expressed CD40L and secreted IL-2. The expression levels of cluster of differentiation (CD)80, CD86, CD40, and human leukocyte antigen-antigen D related on Mo-DC were moderate; however, CD83 was low prior to infection of Ad5/F35 CD40L-IL-2. Those molecules, particularly CD83, were markedly upregulated 24 h after the infection. Increasing quantities of IL-12 in the supernatants were detected subsequent to infection at different time points in a time-dependent manner. Thus, Ad5/F35 CD40L-IL-2 efficiently infected human Mo-DCs and its products, CD40L and IL-2, were subsequently expressed. In addition, infection with Ad5/F35 CD40L-IL-2 stimulated the maturation of Mo-DC and high levels of IL-12 production.

Intranodal vaccination with mRNA-optimized dendritic cells in metastatic melanoma patients

Autologous dendritic cell (DC) therapy is an experimental cellular immunotherapy that is safe and immunogenic in patients with advanced melanoma. In an attempt to further improve the therapeutic responses, we treated 15 patients with melanoma, with autologous monocyte-derived immature DC electroporated with mRNA encoding CD40 ligand (CD40L), CD70 and a constitutively active TLR4 (caTLR4) together with mRNA encoding a tumor-associated antigen (TAA; respectively gp100 or tyrosinase). In addition, DC were pulsed with keyhole limpet hemocyanin (KLH) that served as a control antigen. Production of this DC vaccine with high cellular viability, high expression of co-stimulatory molecules and MHC class I and II and production of IL-12p70, was feasible in all patients. A vaccination cycle consisting of three vaccinations with up to 15×106 DC per vaccination at a biweekly interval, was repeated after 6 and 12 months in the absence of disease progression. mRNA-optimized DC were injected intranodally, because of low CCR7 expression on the DC, and induced de novo immune responses against control antigen. T cell responses against tyrosinase were detected in the skin-test infiltrating lymphocytes (SKIL) of two patients. One mixed tumor response and two durable tumor stabilizations were observed among 8 patients with evaluable disease at baseline. In conclusion, autologous mRNA-optimized DC can be safely administered intranodally to patients with metastatic melanoma but showed limited immunological responses against tyrosinase and gp100.

Dendritic cell immunotherapy in uterine cancer

Uterine cancer is the most common pelvic gynecological malignancy. Uterine sarcomas and relapsed uterine carcinomas have limited treatment options. The search for new therapies is urgent. Dendritic cell (DC) immunotherapy holds much promise, though has been poorly explored in uterine cancer. This commentary gives an insight in existing DC immunotherapy studies in uterine cancer and summarizes the possibilities and the importance of the loading of tumor antigens onto DC and their subsequent maturation. However, the sole application of DC immunotherapy to target uterine cancer will be insufficient because of tumor-induced immunosuppression, which will hamper the establishment of an effective anti-tumor immune response. The authors give an overview on the limited existing immunosuppressive data and propose a novel approach on DC immunotherapy in uterine cancer.

Multifunctional CD40L: pro- and anti-neoplastic activity

The CD40 ligand is a type I transmembrane protein that belongs to a tumor necrosis factor (TNF) superfamily. It is present not only on the surface of activated CD4+ T cells, B cells, blood platelets, monocytes, and natural killer (NK) cells but also on cancer cells. The receptor for ligand is constitutively expressed on cells, TNF family protein: CD40. The role of the CD40/CD40L pathway in the induction of body immunity, in inflammation, or in hemostasis has been well documented, whereas its involvement in neoplastic disease is still under investigation. CD40L ligand may potentiate apoptosis of tumor cells by activation of nuclear factor-κB (NF-κB), AP-1, CD95, or caspase-depended pathways and stimulate host immunity to defend against cancer. Although CD40L has a major contribution to anti-cancer activity, many reports point at its ambivalent nature. CD40L enhance release of strongly pro-angiogenic factor, vascular endothelial growth factor (VEGF), and activator of coagulation, TF, the level of which is correlated with tumor metastasis. CD40L involvement in the inhibition of tumor progression has led to the emergence of not only therapy using recombinant forms of the ligand and vaccines in the treatment of cancer but also therapy consisting of inhibiting platelets-main source of CD40L. This article is a review of studies on the ambivalent role of CD40L in neoplastic diseases.

Optimized dendritic cell-based immunotherapy for melanoma: the TriMix-formula

Since decades, the main goal of tumor immunologists has been to increase the capacity of the immune system to mediate tumor regression. In this regard, one of the major focuses of cancer immunotherapy has been the design of vaccines promoting strong tumor-specific cytotoxic T lymphocyte responses in cancer patients. Here, dendritic cells (DCs) play a pivotal role as they are regarded as nature's adjuvant and as such have become the natural agents for antigen delivery in order to finally elicit strong T cell responses (Villadangos and Schnorrer in Nat Rev Immunol 7:543-555, 2007; Melief in Immunity 29:372-383, 2008; Palucka and Banchereau in Nat Rev Cancer 12:265-277, 2012; Vacchelli et al. in Oncoimmunology 2:e25771, 2013; Galluzzi et al. in Oncoimmunology 1:1111-1134, 2012). Therefore, many investigators are actively pursuing the use of DCs as an efficient way of inducing anticancer immune responses. Nowadays, DCs can be generated at a large scale in closed systems, yielding sufficient numbers of cells for clinical application. In addition, with the identification of tumor-associated antigens, which are either selectively or preferentially expressed by tumors, a whole range of strategies using DCs for immunotherapy have been designed and tested in clinical studies. Despite the evidence that DCs loaded with tumor-associated antigens can elicit immune responses in vivo, clinical responses remained disappointingly low. Therefore, optimization of the cellular product and route of administration was urgently needed. Here, we review the path we have followed in the development of TriMixDC-MEL, a potent DC-based cellular therapy, discussing its development as well as further modifications and applications.

Therapeutic cancer vaccines: past, present, and future

Therapeutic vaccines represent a viable option for active immunotherapy of cancers that aim to treat late stage disease by using a patient's own immune system. The promising results from clinical trials recently led to the approval of the first therapeutic cancer vaccine by the U.S. Food and Drug Administration. This major breakthrough not only provides a new treatment modality for cancer management but also paves the way for rationally designing and optimizing future vaccines with improved anticancer efficacy. Numerous vaccine strategies are currently being evaluated both preclinically and clinically. This review discusses therapeutic cancer vaccines from diverse platforms or targets as well as the preclinical and clinical studies employing these therapeutic vaccines. We also consider tumor-induced immune suppression that hinders the potency of therapeutic vaccines, and potential strategies to counteract these mechanisms for generating more robust and durable antitumor immune responses.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

mRNA: From a chemical blueprint for protein production to an off-the-shelf therapeutic

Two decades ago, mRNA became the focus of research in molecular medicine and was proposed as an active pharmaceutical ingredient for the therapy of cancer. In this regard, mRNA has been mainly used for ex vivo modification of antigen-presenting cells (APCs), such as dendritic cells (DCs). This vaccination strategy has proven to be safe, well tolerated and capable of inducing tumor antigen-specific immune responses. Recently, the direct application of mRNA for in situ modification of APCs, hence immunization was shown to be feasible and at least as effective as DC-based immunization in pre-clinical models. It is believed that application of mRNA as an off-the-shelf vaccine represents an important step in the development of future cancer immunotherapeutic strategies. Here, we will discuss the use of ex vivo mRNA-modified DCs and “naked mRNA” for cancer immunotherapy focusing on parameters such as the employed DC subtype, DC activation stimulus and route of immunization. In addition, we will provide an overview on the clinical trials published so far, trying to link their outcome to the aforementioned parameters.

Enhanced antitumoral efficacy and immune response following conditionally replicative adenovirus containing constitutive HSF1 delivery to rodent tumors

Background

Oncolytic adenoviruses are promising as anticancer agents but have limited clinical responses. Our previous study showed that heat shock transcription factor 1 (HSF1) overexpression could increase the anti-tumor efficacy of E1B55kD deleted oncolytic adenovirus through increasing the viral burst. Due to the important roles of heat shock proteins (HSPs) in eliciting innate and adaptive immunity, we reasoned that besides increasing the viral burst, HSF1 may also play a role in increasing tumor specific immune response.

Methods

In the present study, intra-dermal murine models of melanoma (B16) and colorectal carcinoma (CT26) were treated with E1B55kD deleted oncolytic adenovirus Adel55 or Adel55 incorporated with cHSF1, HSF1i, HSP70, or HSP90 by intra-tumoral injection. Tumors were surgically excised 72 h post injection and animals were analyzed for tumor resistance and survival rate.

Results

Approximately 95% of animals in the Adel55-cHSF1 treated group showed sustained resistance upon re-challenge with autologous tumor cells, but not in PBS, Adel55, or Adel55-HSF1i treated groups. Only 50–65% animals in the Adel55-HSP70 and Adel55-HSP90 treated group showed tumor resistance. Tumor resistance was associated with development of tumor type specific cellular immune responses. Adel55-cHSF1 treatment also showed higher efficacy in diminishing progression of the secondary tumor focus than Adel55-HSP70 or Adel55-HSP90 treatment.

Conclusions

Besides by increasing its burst in tumor cells, cHSF1 could also augment the potential of E1B55kD deleted oncolytic adenovirus by increasing the tumor-specific immune response, which is beneficial to prevent tumor recurrence. cHSF1 is a better gene for neoadjuvant immunotherapy than other heat shock protein genes.

CD40 stimulates a "feed-forward" NF-κB-driven molecular pathway that regulates IFN-β expression in carcinoma cells

IFN-β and the CD40L (CD154) share important roles in the antiviral and antitumor immune responses. In this study, we show that CD40 receptor occupancy results in IFN-β upregulation through an unconventional "feed-forward" mechanism, which is orchestrated by canonical NF-κB and involves the sequential de novo synthesis of IFN regulatory factor (IRF)1 and Viperin (RSAD2), an IRF1 target. RelA (p65) NF-κB, IRF1, and Viperin-dependent IRF7 binding to the IFN-β promoter largely controls its activity. However, full activation of IFN-β also requires the parallel engagement of noncanonical NF-κB2 signaling leading to p52 recruitment to the IFN-β promoter. These data define a novel link between CD40 signaling and IFN-β expression and provide a telling example of how signal propagation can be exploited to ensure efficient regulation of gene expression.

Combined Tbet and IL12 gene therapy elicits and recruits superior antitumor immunity in vivo

We have recently shown that intratumor (i.t.) injection of syngenic dendritic cells (DC) engineered to express the transcription factor Tbet (TBX21) promotes protective type-1 T cell-mediated immunity via a mechanism that is largely interleukin (IL)-12p70-independent. Since IL-12 is a classical promoter of type-1 immunity, the current study was undertaken to determine whether gene therapy using combined Tbet and IL-12 complementary DNA (cDNA) would yield improved antitumor efficacy based on the complementary/synergistic action of these biologic modifiers. Mice bearing established subcutaneous (s.c.) tumors injected with DC concomitantly expressing ectopic Tbet and IL12 (i.e., DC.Tbet/IL12) displayed superior (i) rates of tumor rejection and extended overall survival, (ii) cross-priming of Tc1 reactive against antigens expressed within the tumor microenvironment, and (iii) infiltration of CD8(+) T cells into treated tumors in association with elevated locoregional production of CXCR3 ligand chemokines. In established bilateral tumor models, i.t. delivery of DC.Tbet/IL12 into a single lesion led to slowed growth or regression at both tumor sites. Furthermore, DC.Tbet/IL12 pulsed with tumor antigen-derived peptides and injected as a therapy distal to the tumor site prevented tumor growth and activated robust antigen-specific Tc1 responses. These data support the translation use of combined Tbet and IL-12p70 gene therapy in the cancer setting.

Chapter six--Adenovirus-based immunotherapy of cancer: promises to keep

Progress in vector design and an increased knowledge of mechanisms underlying tumor-induced immune suppression have led to a new and promising generation of Adenovirus (Ad)-based immunotherapies, which are discussed in this review. As vaccine vehicles Ad vectors (AdVs) have been clinically evaluated and proven safe, but a major limitation of the commonly used Ad5 serotype is neutralization by preexistent or rapidly induced immune responses. Genetic modifications in the Ad capsid can reduce intrinsic immunogenicity and facilitate escape from antibody-mediated neutralization. Further modification of the Ad hexon and fiber allows for liver and scavenger detargeting and selective targeting of, for example, dendritic cells. These next-generation Ad vaccines with enhanced efficacy are now becoming available for testing as tumor vaccines. In addition, AdVs encoding immune-modulating products may be used to convert the tumor microenvironment from immune-suppressive and proinvasive to proinflammatory, thus facilitating cell-mediated effector functions that can keep tumor growth and invasion in check. Oncolytic AdVs, that selectively replicate in tumor cells and induce an immunogenic form of cell death, can also be armed with immune-activating transgenes to amplify primed antitumor immune responses. These novel immunotherapy strategies, employing highly efficacious AdVs in optimized configurations, show great promise and warrant clinical exploration.

Engineering dendritic cells to enhance cancer immunotherapy

Cancer immunotherapy aims to establish immune-mediated control of tumor growth by priming T-cell responses to target tumor-associated antigens. Three signals are required for T-cell activation: (i) presentation of cognate antigen in self MHC molecules; (ii) costimulation by membrane-bound receptor-ligand pairs; and (iii) soluble factors to direct polarization of the ensuing immune response. The ability of dendritic cells (DCs) to provide all three signals required for T-cell activation makes them an ideal cancer vaccine platform. Several strategies have been developed to enhance and control antigen presentation, costimulation, and cytokine production. In this review, we discuss progress toward developing DC-based cancer vaccines by genetic modification using RNA, DNA, and recombinant viruses. Furthermore, the ability of DC-based vaccines to activate natural killer (NK) and B-cells, and the impact of gene modification strategies on these populations is described. Clinical trials using gene-modified DCs have shown modest results, therefore, further considerations for DC manipulation to enhance their clinical efficacy are also discussed.

Carcinoma-derived interleukin-8 disorients dendritic cell migration without impairing T-cell stimulation

Background

Interleukin-8 (IL-8, CXCL8) is readily produced by human malignant cells. Dendritic cells (DC) both produce IL-8 and express the IL-8 functional receptors CXCR1 and CXCR2. Most human colon carcinomas produce IL-8. IL-8 importance in malignancies has been ascribed to angiogeneis promotion.

Principal Findings

IL-8 effects on human monocyte-derived DC biology were explored upon DC exposure to recombinant IL-8 and with the help of an IL-8 neutralizing mAb. In vivo experiments were performed in immunodeficient mice xenografted with IL-8-producing human colon carcinomas and comparatively with cell lines that do not produce IL-8. Allogenic T lymphocyte stimulation by DC was explored under the influence of IL-8. DC and neutrophil chemotaxis were measured by transwell-migration assays. Sera from tumor-xenografted mice contained increasing concentrations of IL-8 as the tumors progress. IL-8 production by carcinoma cells can be modulated by low doses of cyclophosphamide at the transcription level. If human DC are injected into HT29 or CaCo2 xenografted tumors, DC are retained intratumorally in an IL-8-dependent fashion. However, IL-8 did not modify the ability of DC to stimulate T cells. Interestingly, pre-exposure of DC to IL-8 desensitizes such cells for IL-8-mediated in vitro or in vivo chemoattraction. Thereby DC become disoriented to subsequently follow IL-8 chemotactic gradients towards malignant or inflamed tissue.

Conclusions

IL-8 as produced by carcinoma cells changes DC migration cues, without directly interfering with DC-mediated T-cell stimulation.

Incorporation of CD40 ligand into SHIV virus-like particles (VLP) enhances SHIV-VLP-induced dendritic cell activation and boosts immune responses against HIV

Engagement of CD40 with CD40L induces dendritic cell (DC) maturation and activation, thereby promoting immune responses. The objective of this study was to investigate whether immunization with chimeric CD40L/SHIV virus-like particles (CD40L/SHIV-VLP) could enhance immune responses to SIV Gag and HIV Env proteins by directly activating DCs. We found that CD83, CD40, and CD86 were significantly up-regulated and significantly increased cytokines production were observed after hCD40L/SHIV-VLP treatment in human CD14(+) monocyte-derived DCs as compared to SHIV-VLP treatment. Mice immunized with mCD40L/SHIV-VLP showed more than a two-fold increase in HIV Env-specific IgG antibody production, an increase in SIV Gag and HIV Env-specific IFN-gamma and IL-4 producing cells, and an increase in HIV Env-specific cytotoxic activity compared to that in SHIV-VLP immunized mice. Furthermore, multifunctional CD4(+) Th1 cells, which simultaneously produce IFN-gamma, IL-2 and TNF-alpha triple cytokines, and CD8(+) T-cells, which produce IFN-gamma were elevated in the mCD40L/SHIV-VLP immunized group. These data demonstrate that chimeric CD40L/SHIV-VLP potently induce DC activation and enhance the magnitude of both humoral and cellular immune responses to the SIV Gag and HIV Env proteins in the mouse model. Therefore, incorporation of CD40L into VLP may represent a novel strategy to develop effective HIV vaccines.

Immunogene therapy against colon cancer metastasis using an adenovirus vector expressing CD40 ligand

BACKGROUND

Colon cancer is one of the most common cancers worldwide, and liver metastasis is a poor prognostic factor for all types of digestive cancers, including colon cancer. We studied CD40 ligand (CD40L)-mediated immunogene therapy for metastatic liver cancer in rats.

METHODS

We studied whether in vitro infection of a rat colon cancer cell line (RCN9) with an adenoviral-vector that expresses the CD40L (AxCAmCD40L) induced CD40L expression. In vivo to confirm the antitumor effect induced by AxCAmCD40L, the tumor cells that had been transduced by AxCAmCD40L were implanted into the subcutaneous tissues of syngenic rats (prevention model) or AxCAmCD40L was injected into the tumor tissues of the rats (treatment model). Furthermore, immune cells including NK cells, cytotoxic T cells, and tumor-specific antibodies induced by AxCAmCD40L were examined.

RESULTS

Immunogene therapy using AxCAmCD40L suppressed the tumor growth strongly or reduced tumor size in the prevention model and treatment model. NK cells, cytotoxic T cells, and tumor-specific antibodies contributed to this antitumor effect in both groups.

CONCLUSION

These observations suggest that CD40L-mediated immunogene therapy for metastatic colon cancer in the liver and lungs is effective and is mediated by the activation of both the cellular and humoral immune systems.

Immunotherapy of cancer with dendritic cells loaded with tumor antigens and activated through mRNA electroporation

Since decades, the main goal of tumor immunologists has been to increase the capacity of the immune system to mediate tumor regression. Considerable progress has been made in enhancing the efficacy of therapeutic anticancer vaccines. First, dendritic cells (DCs) have been identified as the key players in orchestrating primary immune responses. A better understanding of their biology and the development of procedures to generate vast amounts of DCs in vitro have accelerated the development of potent immunotherapeutic strategies for cancer. Second, tumor-associated antigens have been identified which are either selectively or preferentially expressed by tumor cells and can be recognized by the immune system. Finally, several studies have been performed on the genetic modification of DCs with tumor antigens. In this regard, loading the DCs with mRNA, which enables them to produce/process and present the tumor antigens themselves, has emerged as a promising strategy. Here, we will first overview the different aspects that must be taken into account when generating an mRNA-based DC vaccine and the published clinical studies exploiting mRNA-loaded DCs. Second, we will give a detailed description of a novel procedure to generate a vaccine consisting of tumor antigen-expressing dendritic cells with an in vitro superior capacity to induce anti-tumor immune responses. Here, immature DCs are electroporated with mRNAs encoding a tumor antigen, CD40 ligand (CD40L), CD70, and constitutively active (caTLR4) to generate mature antigen-presenting DCs.

Dendritic and tumor cell fusions transduced with adenovirus encoding CD40L eradicate B-cell lymphoma and induce a Th17-type response

Fusion of dendritic cells and tumor cells (FCs) constitutes a promising tool for generating an antitumor response because of their capacity to present tumor antigens and provide appropriate costimulatory signals. CD40-CD40L interaction has an important role in the maturation and survival of dendritic cells and provides critical help for T-cell priming. In this study, we sought to improve the effectiveness of FC vaccines in a murine model of B-cell lymphoma by engineering FCs to express CD40L by means of an adenovirus encoding CD40L (Adv-CD40L). Before transduction with Adv-CD40L, no CD40L expression was detected in FCs, DCs or tumor cells. The surface expression of CD40L in FC transduced with Adv-CD40L (FC-CD40L) ranged between 50 and 60%. FC-CD40L showed an enhanced expression of CD80, CD86, CD54 and MHC class II molecules and elicited a strong in vitro immune response in a syngeneic mixed lymphocyte reaction. Furthermore, FC-CD40L showed enhanced migration to secondary lymphoid organs. Splenocytes from mice treated with FC-CD40L had a dramatic increase in the production of IL-17, IL-6 and IFN-gamma, compared with controls. Treatment with the FC-CD40L vaccine induced regression of established tumors and increased survival. Our data demonstrate that FC transduced with Adv-CD40L enhances the antitumor effect of FC vaccines in a murine lymphoma model and this is associated with an increased Th17-type immune response.

Increase of in vivo antitumoral activity by CD40L (CD154) gene transfer into pancreatic tumor cell-dendritic cell hybrids

OBJECTIVES

Fusion of dendritic cells (DC) with tumor cells is an approach in immunotherapy combining antigenicity and capacity of antigen presentation to activate T cells for the induction of tumor-specific cytotoxic immunity. Although there have been reports of clinical benefit, response rates have been limited and further improvements are warranted.

METHODS

We used murine DC and a novel protocol for an effective fusion of those cells with the murine pancreatic cell line Panc02.

RESULTS

We observed 2 events: only moderate in vitro and in vivo cytotoxicity of tumor cell/DC hybrids and a down-regulation of costimulatory molecules on fused cells. Therefore, we transfected tumor cell/DC hybrids with an adenovirus expressing CD154 to improve DC activation and generating antitumor immune response without the need of CD4 T cells. High CD154 expression could be obtained by transfection of DC and Panc02 cells prior fusion. Furthermore, vaccination with CD154-transfected tumor cell/DC hybrid led to a significantly increased induction of cytotoxic T cells in vitro and to an improved antitumoral effect in an orthotopic in vivo mouse model.

CONCLUSIONS

CD154-transfected tumor cell/DC hybrids are a promising approach to increase the efficiency of antitumoral response.

Improved therapeutic efficacy using vaccination with glioma lysate-pulsed dendritic cells combined with IP-10 in murine glioma

The purpose of the present study was to evaluate the therapeutic efficacy of glioma lysate-pulsed DCs in combination with plasmid DNA vector encoding the murine interferon-induced protein of 10kDa (IP-10 or CXCL10) gene. Mouse models of brain glioma (GL261) were treated with combining glioma lysate-pulsed DCs with direct intratumoral injection of a nonviral plasmid DNA vector encoding the murine IP-10 gene. The survival of mice bearing GL261 glioma was observed. Enzyme-linked immuno-spot assay was used to determine the frequency of brain-infiltrating lymphocytes (BILs) capable of responding to GL261. Cytolytic T lymphocyte (CTL) response was measured by cytotoxic assay, vessel density and tumor cell proliferation were observed by immunostaining, and tumor apoptosis was determined by TUNEL staining. The results revealed that the combination therapy groups showed more significantly enhanced anti-tumor activity, attraction of lymphocytes into tumor tissues, apoptosis of tumor cells, and reduced neovascularization, cell proliferation, and developed a strong CTL response in these mice. In summary, the therapy of glioma lysate-pulsed DCs combined with the IP-10 gene has significant synergistic effect against glioma.

The Janus faces of CD40 in cancer

CD40 is a TNF receptor family member that is widely recognized for its prominent role in immune regulation and homeostasis. Expression of CD40 is not restricted to normal lymphoid cells but is also evident in the majority of haemopoietic and epithelial malignancies where it has been implicated in oncogenic events. Accumulating evidence, however, suggests that the CD40 pathway can be exploited for cancer therapy by virtue of its ability to stimulate the host anti-tumor immune response, normalize the tumor microenvironment and directly suppress the growth of CD40-positive tumors. Here, we provide an overview of the multifaceted functions of the CD40 pathway in cancer and its emerging role in the treatment of malignancy.

Molecular mechanism and function of CD40/CD40L engagement in the immune system

SUMMARY

During the generation of a successful adaptive immune response, multiple molecular signals are required. A primary signal is the binding of cognate antigen to an antigen receptor expressed by T and B lymphocytes. Multiple secondary signals involve the engagement of costimulatory molecules expressed by T and B lymphocytes with their respective ligands. Because of its essential role in immunity, one of the best characterized of the costimulatory molecules is the receptor CD40. This receptor, a member of the tumor necrosis factor receptor family, is expressed by B cells, professional antigen-presenting cells, as well as non-immune cells and tumors. CD40 binds its ligand CD40L, which is transiently expressed on T cells and other non-immune cells under inflammatory conditions. A wide spectrum of molecular and cellular processes is regulated by CD40 engagement including the initiation and progression of cellular and humoral adaptive immunity. In this review, we describe the downstream signaling pathways initiated by CD40 and overview how CD40 engagement or antagonism modulates humoral and cellular immunity. Lastly, we discuss the role of CD40 as a target in harnessing anti-tumor immunity. This review underscores the essential role CD40 plays in adaptive immunity.

Indirect recruitment of a CD40 signaling pathway in dendritic cells by B7-DC cross-linking antibody modulates T cell functions

The human IgM B7-DC XAb protects mice from tumors in both therapeutic and prophylactic settings. Its mechanism of action is mediated by its binding to B7-DC/PD-L2 molecules on the surface of dendritic cells (DCs) to induce a multimolecular cap and subsequent activation of signaling cascades that determine a unique combination of DC phenotypes. One such phenotype, the B7-DC XAb-induced antigen accumulation in mTLR-matured DCs, has been linked to signaling through TREM-2, but the signals required for other DC phenotypes critical for the therapeutic effects in animal models remain unclear. Here, FRET and co-immunoprecipitation studies show that CD40 is recruited to the multi-molecular complex by B7-DC XAb. Signals emanating from CD40 are important, as CD40^−/− DCs treated with B7-DC XAb (DC^XAb) activated DAP12, but failed to activate NFκB, and were not protected from cell death upon cytokine withdrawal or treatment with Vitamin D₃. CD40^−/− DC^XAb also failed to secrete IL-6 and were unable to support the conversion of T regulatory cells into IL-17+ effector T cells in vitro. Importantly, the expression of CD40 was required for the overall ability of B7-DC XAb to induce anti-tumor CTL, to provide protection from a number of tumor types, and for DC^XAb to be effective anti-tumor vaccines in vivo. These results indicate that B7-DC XAb modulation of DC phenotypes is through its ability to indirectly recruit common signaling molecules and elements of their endogenous signaling pathways through targeted binding to a cell-specific surface determinant.

Immunotherapy for liver tumors: present status and future prospects

Increasing evidence suggests that immune responses are involved in the control of cancer and that the immune system can be manipulated in different ways to recognize and attack tumors. Progress in immune-based strategies has opened new therapeutic avenues using a number of techniques destined to eliminate malignant cells. In the present review, we overview current knowledge on the importance, successes and difficulties of immunotherapy in liver tumors, including preclinical data available in animal models and information from clinical trials carried out during the lasts years. This review shows that new options for the treatment of advanced liver tumors are urgently needed and that there is a ground for future advances in the field.

CD40ligand-expressing dendritic cells induce regression of hepatocellular carcinoma by activating innate and acquired immunity in vivo

Dendritic cells (DCs) are professional antigen-presenting cells able to prime T-cells against tumor-associated antigens (TAA), but their potential to induce hepatocellular carcinoma (HCC) regression is still limited. CD40/CD40L interaction is essential for DC activation and induction of antigen-specific T-cells. In this study, transduction of TAA-pulsed DC with a CD40L-encoding adenovirus (Ad-CD40L) was used to improve the immune response induced by DC toward HCC. Bone marrow-derived DC from C3H/HeNcrl mice were cultured with granulocyte-macrophage colony-stimulating factor and interleukin-4. On day 6, tumor-lysate pulsed DCs were infected with adenoviruses. HCCs were induced by inoculation of mice with Hepa129-cells subcutaneously. When tumor-volume was 100 to 400 mm(3), DCs were injected intratumorally, subcutaneously, or intravenously. Ad-CD40L transduction exerted CD40/CD40L interactions between DCs, increasing DC immunostimulation with up-regulation of CD80/CD86- and interleukin-12 (IL-12) expression. Intratumoral injection of CD40L-DC was superior to intravenous or subcutaneous treatments, yielding tumor elimination in almost 70% of mice. Moreover, all tumor-free animals were protected against hepatic tumor cell rechallenge. In a preventive setting, subcutaneous injection of CD40L-expressing DCs protected 50% of mice for more than 3 months toward tumor cell challenge. The induced immune response seemed to be dependent on cross-priming with Th1-lymphocytes in the lymph nodes, because transduced DCs were redetected in lymphoid tissues. In addition, immunohistochemistry of tumors indicated a significant tumor infiltration with CD4+, CD8+ T cells and natural killer (NK) cells. Tumor-infiltrating lymphocytes were tumor-specific, as shown in interferon-gamma (IFN-gamma) enzyme-linked immunosorbent spot and T-cell proliferation assays.

CONCLUSION

Transduction of DCs with Ad-CD40L increases significantly the stimulatory capacity of DCs. Intratumoral injection of DCs activates both acquired and innate immunity, inducing complete regression of established tumors and long-term immunity against tumor recurrence. This approach improves the antitumoral potential of DCs.

Enhancing the T-cell stimulatory capacity of human dendritic cells by co-electroporation with CD40L, CD70 and constitutively active TLR4 encoding mRNA

The effectiveness of the dendritic cell (DC) vaccination protocols that are currently in use could be improved by providing the DCs with a more potent maturation signal. We therefore investigated whether the T-cell stimulatory capacity of human monocyte-derived DCs could be increased by co-electroporation with different combinations of CD40L, CD70, and constitutively active toll-like receptor 4 (caTLR4) encoding mRNA. We show that immature DCs electroporated with CD40L and/or caTLR4 mRNA, but not those electroporated with CD70 mRNA, acquire a mature phenotype along with an enhanced secretion of several cytokines/chemokines. Moreover, these DCs are very potent in inducing naive CD4(+) T cells to differentiate into interferon-gamma (IFN-gamma)-secreting type 1 T helper (Th1) cells. Further, we assessed the capacity of the electroporated DCs to activate naive HLA-A2-restricted MelanA-specific CD8(+) T cells without the addition of any exogenous cytokines. When all three molecules were combined, a >500-fold increase in MelanA-specific CD8(+) T cells was observed when compared with immature DCs, and a >200-fold increase when compared with cytokine cocktail-matured DCs. In correlation, we found a marked increase in cytolytic and IFN-gamma/tumor necrosis factor-alpha (TNF-alpha) secreting CD8(+) T cells. Our data indicate that immature DCs genetically modified to express stimulating molecules can induce tumor antigen-specific T cells in vitro and could prove to be a significant improvement over DCs matured with the methods currently in use.

OX40 ligand expressed by DCs costimulates NKT and CD4+ Th cell antitumor immunity in mice

The exceptional immunostimulatory capacity of DCs makes them potential targets for investigation of cancer immunotherapeutics. We show here in mice that TNF-alpha-stimulated DC maturation was accompanied by increased expression of OX40 ligand (OX40L), the lack of which resulted in an inability of mature DCs to generate cellular antitumor immunity. Furthermore, intratumoral administration of DCs modified to express OX40L suppressed tumor growth through the generation of tumor-specific cytolytic T cell responses, which were mediated by CD4+ T cells and NKT cells. In the tumors treated with OX40L-expressing DCs, the NKT cell population significantly increased and exhibited a substantial level of IFN-gamma production essential for antitumor immunity. Additional studies evaluating NKT cell activation status, in terms of IFN-gamma production and CD69 expression, indicated that NKT cell activation by DCs presenting alpha-galactosylceramide in the context of CD1d was potentiated by OX40 expression on NKT cells. These results show a critical role for OX40L on DCs, via binding to OX40 on NKT cells and CD4+ T cells, in the induction of antitumor immunity in tumor-bearing mice.

Cooperating gene mutations in acute myeloid leukemia: a review of the literature

Acute myeloid leukemia (AML) is a heterogeneous group of neoplastic disorders with great variability in clinical course and response to therapy, as well as in the genetic and molecular basis of the pathology. Major advances in the understanding of leukemogenesis have been made by the characterization and the study of acquired cytogenetic abnormalities, particularly reciprocal translocations observed in AML. Besides these major cytogenetic abnormalities, gene mutations also constitute key events in AML pathogenesis. In this review, we describe the contribution of known gene mutations to the understanding of AML pathogenesis and their clinical significance. To gain more insight in this understanding, we clustered these alterations in three groups: (1) mutations affecting genes that contribute to cell proliferation (FLT3, c-KIT, RAS, protein tyrosine standard phosphatase nonreceptor 11); (2) mutations affecting genes involved in myeloid differentiation (AML1 and CEBPA) and (3) mutations affecting genes implicated in cell cycle regulation or apoptosis (P53, NPM1). This nonexhaustive review aims to show how gene mutations interact with each other, how they contribute to refine prognosis and how they can be useful for risk-adapted therapeutic management of AML patients.

Gene transfer of CD40-ligand to dendritic cells stimulates interferon-gamma production to induce growth arrest and apoptosis of tumor cells

In this study, we present evidence that gene transfer of the CD40-ligand (CD154) into human immature dendritic cells (DC) imparts direct antitumor effects on tumor cells. DC infected with adenovirus directed to express human CD154 on the cell surface (CD154-DC) elicited significantly higher levels of immune accessory molecules commonly found on mature DC. We found that co-cultivation with a human squamous cell carcinoma cell line (OSC-70) with CD154-DC significantly inhibited cell growth. We further demonstrate that OSC-70 cells stimulated with CD154-DC were more susceptible to apoptosis via TNF-related apoptosis inducing ligand (TRAIL). Importantly, tumor cells co-cultured with CD154-DC in transwell plates expressed upregulated cell surface TRAIL-R2. CD154-DC produced higher levels of interferon (IFN)-gamma, IL-12p70 and soluble CD154, but the ability of CD154-DC to inhibit tumor cell growth was significantly abrogated by a neutralizing antibody to IFN-gamma, indicating that this was mainly mediated by IFN-gamma. Furthermore, intratumoral injection of CD154-DC significantly suppressed OSC-70 tumor growth in a xenograft model. Overall, these results reveal that CD154-DC have potential as an anti-cancer therapy by producing IFN-gamma to arrest adjacent tumor cell growth and increase the susceptibility of apoptosis via TRAIL.

All-transRetinoic Acid Enhances Murine Dendritic Cell Migration to Draining Lymph Nodes via the Balance of Matrix Metalloproteinases and Their Inhibitors

Cancers escape immune surveillance through the manipulation of the host's immune system. Sequestration of dendritic cells (DCs) within tumor tissues and the subsequent inhibition of their migration is one of the several mechanisms by which tumors induce immunosuppression. In view of recent findings depicting the improvement of tumor immune responses in cancer patients following all-trans retinoic acid (ATRA) treatment, we sought to identify the effects of ATRA on DC mobility in the context of tumor immunotherapy. Our results demonstrate that ATRA, added to differentiating murine bone marrow progenitor cells, enhances the invasive capacity of the resulting DCs. Immature DCs injected intratumorally in mice show increased accumulation in draining lymph nodes, but not in nondraining lymph nodes and spleens, when differentiated in the presence of ATRA. The in vitro migration of mature DCs through the basement membrane matrix toward the lymphoid chemokines CCL19 and CCL21 is enhanced in these cells, albeit not in the presence of a matrix metalloproteinase (MMP) inhibitor. An increase in MMP production with a simultaneous decrease in the production of their inhibitors (tissue inhibitors of matrix metalloproteinase or TIMPs) is provoked by ATRA. This affects the MMP/TIMP balance in DCs, in particular that of MMP-9 and TIMP-1, favoring protease activity and thus allowing for enhanced DC mobilization. In conclusion, this study demonstrates that ATRA is capable of improving DC trafficking in a tumor milieu and, in view of the encouraging results obtained in the clinic, further supports the notion that ATRA might be a valuable chemical adjuvant to current immunotherapeutic strategies for cancer.

Dendritic cells for active immunotherapy: optimizing design and manufacture in order to develop commercially and clinically viable products

Dendritic cell (DC) active immunotherapy is potentially efficacious in a broad array of malignant disease settings. However, challenges remain in optimizing DC-based therapy for maximum clinical efficacy within manufacturing processes that permit quality control and scale-up of consistent products. In this review we discuss the critical issues that must be addressed in order to optimize DC-based product design and manufacture, and highlight the DC based platforms currently addressing these issues. Variables in DC-based product design include the type of antigenic payload used, DC maturation steps and activation processes, and functional assays. Issues to consider in development include: (a) minimizing the invasiveness of patient biological material collection; (b) minimizing handling and manipulations of tissue at the clinical site; (c) centralized product manufacturing and standardized processing and capacity for commercial-scale production; (d) rapid product release turnaround time; (e) the ability to manufacture sufficient product from limited starting material; and (f) standardized release criteria for DC phenotype and function. Improvements in the design and manufacture of DC products have resulted in a handful of promising leads currently in clinical development.

Immunostimulatory monoclonal antibodies for cancer therapy

Increasing immune responses with immunostimulatory monoclonal antibodies (mAbs) directed to immune-receptor molecules is a new and exciting strategy in cancer therapy. This expanding class of agents functions on crucial receptors, either antagonizing those that suppress immune responses or activating others that amplify immune responses. Complications such as autoimmunity and systemic inflammation are problematic side effects associated with these agents. However, promising synergy has been observed in preclinical models using combinations of immunostimulatory antibodies and other immunotherapy strategies or conventional cancer therapies. Importantly, mAbs of this type have now entered clinical trials with encouraging initial results.

Gene transfer of the CD40-ligand to human dendritic cells induces NK-mediated antitumor effects against human carcinoma cells

The CD40-ligand (CD40L) is a key molecule for the activation of dendritic cells (DCs), followed by the induction of DC maturation and cytokine production. Here we found that DC infected with adenovirus vector encoding human CD40L (CD40L-DC) displayed significantly higher levels of immune accessory molecules and IL-12 production than did uninfected cells, and that CD40L-DC produced much higher levels of IFN-gamma. To investigate whether CD40L-DC-derived these soluble factors could stimulate NK cells without physical cell-to-cell contact, we cocultured NK cells with CD40L-DC in transwell culture plates. NK cells showed up-regulated cytotoxic activity toward various squamous oral cell carcinoma (OSC-70, HSC-2, HSC-3), and we determined that both IL-12 and IFN-gamma contributed to the CD40L-DC-mediated NK cell activation. NK cells stimulated with CD40L-DC resulted in the induction of the cell surface expression of TRAIL, the production of IFN-gamma and intracellular accumulation of granzyme B. The cytotoxic activity of NK cells stimulated with CD40L-DC could be mostly inhibited by neutralizing antibody for TRAIL and completely abrogated by the combination of antibody and exocytosis inhibitor, indicating that this was mainly mediated by a TRAIL-TRAIL-receptor interaction and granule exocytosis. Moreover, CD40L-DC-activated NK cells could induce up-regulation of a death-receptor TRAIL-R2 (DR5) and down-regulation of a decoy receptor TRAIL-R3 (DcR1) on carcinoma cells. Overall, these results have revealed that CD40L-DC could activate an innate immune reaction by stimulating NK cells followed by carcinoma cells, supporting that administration of CD40L-DC may have potential as an anticancer therapy.

Dendritic cells modified to express fractalkine/CX3CL1 in the treatment of preexisting tumors

Fractalkine (CX3CL1) is a unique membrane-bound CX3C chemokine that serves as a potent chemoattractant for lymphocytes. The hypothesis of this study is that dendritic cells (DC) genetically modified ex vivo to overexpress fractalkine would enhance the T cell-mediated cellular immune response with a consequent induction of anti-tumor immunity to suppress tumor growth. To prove this hypothesis, established tumors of different mouse cancer cells (B16-F10 melanoma, H-2b, and Colon-26 colon adenocarcinoma, H-2d) were treated with intratumoral injection of bone marrow-derived DC that had been modified in vitro with an RGD fiber-mutant adenovirus vector expressing mouse fractalkine (Ad-FKN). In both tumor models tested, treatment of tumor-bearing mice with Ad-FKN-transduced DC gave rise to a significant suppression of tumor growth along with survival advantages in the treated mice. Immunohistochemical analysis of tumors treated with direct injection of Ad-FKN-transduced DC demonstrated that the treatment prompted CD8+ T cells and CD4+ T cells to accumulate in the tumor milieu, leading to activation of immune-relevant processes. Consistent with the finding, the intratumoral administration of Ad-FKN-transduced DC evoked tumor-specific cytotoxic T lymphocytes, which ensued from in vivo priming of Th1 immune responses in the treated host. In addition, the anti-tumor effect provided by intratumoral injection of Ad-FKN-transduced DC was completely abrogated in CD4+ T cell-deficient mice as well as in CD8+ T cell-deficient mice. These results support the concept that genetic modification of DC with a recombinant fractalkine adenovirus vector may be a useful strategy for cancer immunotherapy protocols.

Dendritic cells engineered to express CD40L continuously produce IL12 and resist negative signals from Tr1/Th3 dominated tumors

TNFalpha-matured dendritic cells (DCs) pulsed with tumor antigens are being evaluated as cancer vaccines. It has been shown that DCs produce IL12 during a limited time span and subsequently enter a stage of IL12 exhaustion. If DCs are generated ex vivo, the patient could receive IL12-exhausted DCs which may be detrimental for stimulating anti-tumor Th1 responses. Furthermore, many cancer patients exhibit a cytokine profile skewed toward IL10 and TGFbeta. This immunological profile, called the Tr1/Th3 response, is associated with the presence of regulatory T-cells. Tr1/Th3 responses potently inhibit DC maturation, thereby regulating Th1 responses. In the present study, we produced genetically engineered DCs that continuously express Th1-related cytokines such as IL12, and resist negative signals from Tr1/Th3-dominated bladder carcinoma cells. Human immature DCs were genetically engineered by adenoviral vectors to express CD40L, or were treated with TNFalpha as a positive control for maturation. The expression of different Th1/Th3 and inflammatory cytokines was monitored. IL12 and IFNgamma were expressed by CD40L-engineered DCs, while TNFalpha-matured DCs lacked IFNgamma and exhibited low IL12 expression. The addition of recombinant IL10 to genetically engineered DCs did not abolish their Th1 profile. Likewise, coculture with tumor cell lines expressing TGFbeta with or without recombinant IL10 did not revert to the engineered DCs. We further demonstrate that the resistance of CD40L-expressing DCs to TGFbeta and IL10 may be due to decreased levels of TGFbeta and IL10 receptors. Thus, CD40L-engineered DCs are robust Th1-promoting ones that are resistant to Tr1/Th3-signaling via IL10 and TGFbeta.

Antisense therapy for restenosis following percutaneous coronary intervention

Recent advances in vascular gene transfer have shown potential new treatment modalities for cardiovascular disease, particularly in the treatment of vascular restenosis. The antisense approach to inhibiting gene expression involves introducing oligonucleotides complementary to mRNA into cells in order to block any one of the following processes: uncoiling of DNA, transcription of DNA, export of RNA, DNA splicing, RNA stability, or RNA translation involved in the synthesis of proteins in cellular proliferation. The approach includes the use of antisense oligonucleotides, antisense mRNA, autocatalytic ribozymes, and the insertion of a section of DNA to form a triple helix. Proof of principle has been established that inhibition of several cellular proto-oncogenes, including DNA binding protein c-myb, non-muscle myosin heavy chain, PCNA proliferating-cell nuclear antigen, platelet-derived growth factor, basic fibroblast growth factor and c-myc, inhibits smooth muscle cell proliferation in vitro and in several animal models. The first clinical study demonstrated the safety and feasibility of local delivery of antisense in the treatment and prevention of restenosis; another randomised clinical trial (AVAIL) with local delivery of c-myc morpholino compound in patients with coronary artery disease demonstrated its long-term effect on reducing neointimal formation, as well as its safety. These preliminary findings from the small cohort of patients require confirmation in a larger trial utilising more sophisticated drug-eluting technologies.

Comparative analysis of antitumor activity of CD40L, RANKL, and 4-1BBL in vivo following intratumoral administration of viral vectors or transduced dendritic cells

The tumor necrosis factor (TNF) family comprises a group of ligands that regulate cell proliferation, differentiation, activation, maturation and apoptosis through interaction with the corresponding TNF receptor family members. In this study, we have evaluated whether adenovirus-mediated intratumoral gene transfer of CD40L, RANKL, or 4-1BBL elicits an immune response to established murine MC38 and TS/A tumors. Intratumoral administration of the recombinant adenoviral vectors expressing CD40L, RANKL or 4-1BBL 7 days post-tumor cell inoculation resulted in significant inhibition of MC38 tumor growth for all three ligands when compared with control groups treated with either saline or control adenovirus. However, intratumoral injection of Ad-4-1BBL or Ad-CD40L resulted in a significantly stronger inhibition of TS/A tumor progression than did Ad-RANKL treatment. We also demonstrated that intratumoral administration of dendritic cells (DC) transduced with adenoviral vectors encoding the TNF-related ligands resulted in a significant inhibition of MC38 tumor growth as compared with control groups treated with Ad-LacZ-transduced DC or saline-treated DC. In addition, DC overexpressing CD40L secreted considerably more IL-12 and expressed higher levels of the co-stimulatory molecules, CD80, CD86 and CD40, than did DC overexpressing LacZ, 4-1BBL or RANKL. We have also demonstrated that DC/CD40L, DC/4-1BBL, and DC/RANKL survived significantly longer than control DC or DC infected with the LacZ vector. Taken together, these results demonstrate that adenoviral gene transfer of CD40L, RANKL or 4-1BBL elicit a significant antitumor effect in two different tumor models, with CD40L gene transfer inducing the strongest antitumor effect.

Genetically modified dendritic cells for therapeutic immunity

Dendritic cells are professional antigen presenting cells, which show an extraordinary capacity to initiate primary immune responses by stimulating T cells. This established function of dendritic cells has attracted much attention in efforts to develop useful vaccines for the treatment of cancer and infectious diseases. Designing effective strategies to generate clinical dendritic cell-based vaccine protocols remains a challenging field of research. The successful realization of immunotherapy utilizing dendritic cells will depend on modifications of these protocols to optimize the natural stimulatory properties of dendritic cells, such as genetic modification of dendritic cells. This review focuses on dendritic cell gene modifications for enhancing the multiple effector functions of dendritic cells, including viral and non-viral gene transfer into dendritic cells, and a variety of transferred genes, such as those encoding antigens, co-stimulatory molecules, cytokines, and chemokines.

Involvement of fractalkine/CX3CL1 expression by dendritic cells in the enhancement of host immunity against Legionella pneumophila

Legionnaires' disease is clinically manifested as severe pneumonia caused by Legionella pneumophila. However, the dendritic cell (DC)-centered immunological framework of the host defense against L. pneumophila has not been fully delineated. For this study, we focused on a potent chemoattractant for lymphocytes, fractalkine/CX3CL1, and observed that the fractalkine expression of DCs was somewhat up-regulated when they encountered L. pneumophila. We therefore hypothesized that fractalkine expressed by Legionella-capturing DCs is involved in the induction of T-cell-mediated immune responses against Legionella, which would be enhanced by a genetic modulation of DCs to overexpress fractalkine. In vivo immunization-challenge experiments demonstrated that DCs modified with a recombinant adenovirus vector to overexpress fractalkine (AdFKN) and pulsed with heat-killed Legionella protected immunized mice from a lethal Legionella infection and that the generation of in vivo protective immunity depended on the host lymphocyte subsets, including CD4(+) T cells, CD8(+) T cells, and B cells. Consistent with this, immunization with AdFKN/Legionella/DC induced significantly higher levels of serum anti-Legionella antibodies of several isotypes than those induced by control immunizations. Further analysis of spleen cells from the immunized mice indicated that the AdFKN/Legionella/DC immunization elicited Th1-dominated immune responses to L. pneumophila. These observations suggest that fractalkine may play an important role in the DC-mediated host defense against intracellular pathogens such as L. pneumophila.

Anti-tumor immune responses following neoadjuvant immunotherapy with a recombinant adenovirus expressing HSP72 to rodent tumors

Gene modification of tumor cells is commonly utilized in various strategies of immunotherapy preventive both as treatment and a means to modify tumor growth. Gene transfer prior to surgery as neoadjuvant therapy has not been studied systematically. We addressed, whether direct intra-tumoral injection of a recombinant adenovirus expressing the immunomodulatory molecule, heat shock protein 72 (ADHSP72), administered prior to surgery could result in sustainable anti-tumor immune responses capable of affecting tumor progression and survival in a number of different murine and rat tumor models. Using intra-dermal murine models of melanoma (B16), colorectal carcinoma (CT26), prostate cancer (TrampC2) and a rat model of glioblastoma (9L), tumors were treated with vehicle or GFP expressing adenovirus (ADGFP) or ADHSP72. Tumors were surgically excised after 72 h. Approximately 25-50% of animals in the ADHSP72 treatment group but not in control groups showed sustained resistance to subsequent tumor challenge. Tumor resistance was associated with development of anti-tumor cellular immune responses. Efficacy of ADHSP72 as neoadjuvant therapy was dependent on the size of the initial tumor with greater likelihood of immune response generation and tumor resistance associated with smaller tumor size at initial treatment. ADHSP72 neoadjuvant therapy resulted in prolonged survival of animals upon re-challenge with autologous tumor cells compared to ADGFP or vehicle control groups. To study the effects on tumor progression of distant metastases, a single tumor focus of animals with multifocal intra-dermal tumors was treated. ADHSP72 diminished progression of the secondary tumor focus and prolonged survival, but only when the secondary tumor focus was <50 mm3 . Our results indicate that gene modification of tumors prior to surgical intervention may be beneficial to prevent recurrence in specific circumstances.

Adenovirus Transduction and Culture Conditions Affect the Immunogenicity of Murine Dendritic Cells

Adenovirus vectors encoding carcinoembryonic antigen (Ad-CEA) or costimulatory molecules CD80, intercellular adhesion molecule-1 (ICAM-1) and leucocyte function-associated antigen-3 (LFA-3) (Ad-STIM) were used to transduce murine bone marrow-derived dendritic cells (BMDC). BMDC were characterized for expression of activation markers and for their ability to elicit protective immunity against MC38-CEA tumours in wildtype and CEA-transgenic (CEA-tg) mice. To determine optimal culture conditions, studies were conducted using BMDC cultured in heterologous bovine serum or autologous mouse serum. Transduction of cells grown in presence of heterologous serum increased the expression of costimulatory molecules, major histocompatibility complex class II, of IL-6 and IL-12. Upon vaccination, tumour protection was not specific and was observed also with untransduced cells. Transduced BMDC cultured in the presence of autologous serum showed low expression of the activation markers, did not express IL-6 and had reduced ability to stimulate T-cell proliferation. Nonetheless, CEA-specific CD8+ T-cell response was enhanced upon coinfection of Ad-STIM and Ad-CEA in both mouse strains, although this immune response was not sufficient to protect CEA-tg mice from tumour challenge. These studies support the use of BMDC transduced with Ad vectors encoding tumour antigens for cancer immunotherapy and demonstrate that culture conditions greatly affect the immunological properties of these cells.