Immunotherapy of cancer with dendritic-cell-based vaccines

Advances in dendritic cell vaccination therapy of cancer

Traditionally, vaccines have helped eradication of several infectious diseases and also saved millions of lives in the human history. Those prophylactic vaccines have acted through inducing immune responses against a live attenuated, killed organism or antigenic subunits to protect the recipient against a real infection caused by the pathogenic microorganism. Nevertheless, development of anticancer vaccines as valuable targets in human health has faced challenges and requires further optimizations. Dendritic cells (DCs) are the most potent antigen presenting cells (APCs) that play essential roles in tumor immunotherapies through induction of CD8+ T cell immunity. Accordingly, various strategies have been tested to employ DCs as therapeutic vaccines for exploiting their activity against tumor cells. Application of whole tumor cells or purified/recombinant antigen peptides are the most common approaches for pulsing DCs, which then are injected back into the patients. Although some hopeful results are reported for a number of DC vaccines tested in animal and clinical trials of cancer patients, such approaches are still inefficient and require optimization. Failure of DC vaccination is postulated due to immunosuppressive tumor microenvironment (TME), overexpression of checkpoint proteins, suboptimal avidity of tumor-associated antigen (TAA)-specific T lymphocytes, and lack of appropriate adjuvants. In this review, we have an overview of the current experiments and trials evaluated the anticancer efficacy of DC vaccination as well as focusing on strategies to improve their potential including combination therapy with immune checkpoint inhibitors (ICIs).

Nanotechnology-based cell-mediated delivery systems for cancer therapy and diagnosis

The global prevalence of cancer is increasing, necessitating new additions to traditional treatments and diagnoses to address shortcomings such as ineffectiveness, complications, and high cost. In this context, nano and microparticulate carriers stand out due to their unique properties such as controlled release, higher bioavailability, and lower toxicity. Despite their popularity, they face several challenges including rapid liver uptake, low chemical stability in blood circulation, immunogenicity concerns, and acute adverse effects. Cell-mediated delivery systems are important topics to research because of their biocompatibility, biodegradability, prolonged delivery, high loading capacity, and targeted drug delivery capabilities. To date, a variety of cells including blood, immune, cancer, and stem cells, sperm, and bacteria have been combined with nanoparticles to develop efficient targeted cancer delivery or diagnosis systems. The review paper aimed to provide an overview of the potential applications of cell-based delivery systems in cancer therapy and diagnosis.

The mononuclear phagocyte system in hepatocellular carcinoma

The mononuclear phagocyte system (MPS) consists of monocytes, dendritic cells and macrophages, which play vital roles in innate immune defense against cancer. Hepatocellular carcinoma (HCC) is a complex disease that is affected or initiated by many factors, including chronic hepatitis B virus infection, hepatitis C virus infection, metabolic disorders or alcohol consumption. Liver function, tumor stage and the performance status of patients affect HCC clinical outcomes. Studies have shown that targeted treatment of tumor microenvironment disorders may improve the efficacy of HCC treatments. Cytokines derived from the innate immune response can regulate T-cell differentiation, thereby shaping adaptive immunity, which is associated with the prognosis of HCC. Therefore, it is important to elucidate the function of the MPS in the progression of HCC. In this review, we outline the impact of HCC on the MPS. We illustrate how HCC reshapes MPS cell phenotype remodeling and the production of associated cytokines and characterize the function and impairment of the MPS in HCC.

Magnetic Particle Imaging Is a Sensitive In Vivo Imaging Modality for the Detection of Dendritic Cell Migration

PURPOSE

The purpose of this study was to evaluate magnetic particle imaging (MPI) as a method for the in vivo tracking of dendritic cells (DC). DC are used in cancer immunotherapy and must migrate from the site of implantation to lymph nodes to be effective. The magnitude of the ensuing T cell response is proportional to the number of lymph node-migrated DC. With current protocols, less than 10% of DC are expected to reach target nodes. Therefore, imaging techniques for studying DC migration must be sensitive and quantitative. Here, we describe the first study using MPI to detect and track DC injected into the footpads of C57BL/6 mice migrating to the popliteal lymph nodes (pLNs).

PROCEDURES

DC were labelled with Synomag-D™ and injected into each hind footpad of C57BL/6 mice (n = 6). In vivo MPI was conducted immediately and repeated 48 h later. The MPI signal was measured from images and related to the signal from a known number of cells to calculate iron content. DC numbers were estimated by dividing iron content in the image by the iron per cell measured from a separate cell sample. The presence of SPIO-labeled DC in nodes was validated by ex vivo MPI, histology, and fluorescence microscopy.

RESULTS

Day 2 imaging showed a decrease in MPI signal in the footpads and an increase in signal at the pLNs, indicating DC migration. MPI signal was detected in the left pLN in four of the six mice and two of the six mice showed MPI signal in the right pLN. Ex vivo imaging detected signal in 11/12 nodes. We report a sensitivity of approximately 4000 cells (0.015 µg Fe) in vivo and 2000 cells (0.007 µg Fe) ex vivo.

CONCLUSIONS

Here, we describe the first study to use MPI to detect and track DC in a migration model with immunotherapeutic applications. We also bring attention to the issue of resolving unequal signals within close proximity, a challenge for any pre-clinical study using a highly concentrated tracer bolus that shadows nearby lower signals.

Dendritic Cell-Based Immunotherapy in Multiple Myeloma: Challenges, Opportunities, and Future Directions

Immunotherapeutic approaches, including adoptive cell therapy, revolutionized treatment in multiple myeloma (MM). As dendritic cells (DCs) are professional antigen-presenting cells and key initiators of tumor-specific immune responses, DC-based immunotherapy represents an attractive therapeutic approach in cancer. The past years, various DC-based approaches, using particularly ex-vivo-generated monocyte-derived DCs, have been tested in preclinical and clinical MM studies. However, long-term and durable responses in MM patients were limited, potentially attributed to the source of monocyte-derived DCs and the immunosuppressive bone marrow microenvironment. In this review, we briefly summarize the DC development in the bone marrow niche and the phenotypical and functional characteristics of the major DC subsets. We address the known DC deficiencies in MM and give an overview of the DC-based vaccination protocols that were tested in MM patients. Lastly, we also provide strategies to improve the efficacy of DC vaccines using new, improved DC-based approaches and combination therapies for MM patients.

Ribonucleic Acid Engineering of Dendritic Cells for Therapeutic Vaccination: Ready 'N Able to Improve Clinical Outcome?

Targeting and exploiting the immune system has become a valid alternative to conventional options for treating cancer and infectious disease. Dendritic cells (DCs) take a central place given their role as key orchestrators of immunity. Therapeutic vaccination with autologous DCs aims to stimulate the patient's own immune system to specifically target his/her disease and has proven to be an effective form of immunotherapy with very little toxicity. A great amount of research in this field has concentrated on engineering these DCs through ribonucleic acid (RNA) to improve vaccine efficacy and thereby the historically low response rates. We reviewed in depth the 52 clinical trials that have been published on RNA-engineered DC vaccination, spanning from 2001 to date and reporting on 696 different vaccinated patients. While ambiguity prevents reliable quantification of effects, these trials do provide evidence that RNA-modified DC vaccination can induce objective clinical responses and survival benefit in cancer patients through stimulation of anti-cancer immunity, without significant toxicity. Succinct background knowledge of RNA engineering strategies and concise conclusions from available clinical and recent preclinical evidence will help guide future research in the larger domain of DC immunotherapy.

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.

Exosomes derived from rAAV/AFP-transfected dendritic cells elicit specific T cell-mediated immune responses against hepatocellular carcinoma

Background

Dendritic cell (DC)-derived exosomes (Dexs) have been proved to induce and enhance antigen-specific T cell responses in vivo, and previous clinical trials have shown the feasibility and safety of Dexs in multiple human cancers. However, there is little knowledge on the efficacy of Dexs against hepatocellular carcinoma (HCC) until now.

Methods

In this study, human peripheral blood-derived DCs were loaded with recombinant adeno-associated viral vector (rAAV)-carrying alpha-fetoprotein (AFP) gene (rAAV/AFP), and high-purity Dexs were generated. Then naive T cells were stimulated with Dexs to investigate the specific T cell-mediated immune responses against HCC.

Results

Our findings showed that Dexs were effective to stimulate naive T cell proliferation and induce T cell activation to become antigen-specific cytotoxic T lymphocytes (CTLs), thereby exhibiting antitumor immune responses against HCC. In addition, Dex-sensitized DC precursors seemed more effective to trigger major histocompatibility complex class I (MHC I)-restricted CTL response and allow DCs to make full use of the minor antigen peptides, thereby maximally activating specific immune responses against HCC.

Conclusion

It is concluded that Dexs, which combine the advantages of DCs and cell-free vectors, are promising to completely, or at least in part, replace mature DCs (mDCs) to function as cancer vaccines or natural antitumor adjuvant.

A new cancer immunotherapy via simultaneous DC-mobilization and DC-targeted IDO gene silencing using an immune-stimulatory nanosystem

The activity of negative immune regulatory molecules, such as indoleamine 2,3-oxygenase (IDO), significantly attenuates DC (Dendritic cells)-mediated immunotherapy. We have previously reported that knockdown of IDO using siRNA can reinstall anti-tumor immunity. However, a DC-targeted siRNA delivery system for in vivo mobilized DCs remains to be developed, while gene silencing in mobilized DCs for cancer immunotherapy has never been explored. In our study, we developed a novel DC-targeted siRNA delivery system, man-GNR-siIDO, using as a nanocarrier of siRNA specific for IDO (siIDO) and mannose (man) as a guide molecule for targeting DCs. We explored the immunostimulatory man-GNR-siIDO nano-construct in DCs mobilized by Flt3-L, a receptor-type tyrosine kinase ligand, for lung cancer immunotherapy. In vivo DC-targeted gene silencing of IDO resulted in robust anti-tumor immunity as evidenced by promoting DC maturation, up-regulating tumor antigen-specific T-cell proliferation and enhancing tumor-specific cytotoxicity. A combinatorial treatment for Lewis Lung Carcinoma (LLC)-bearing mice, with man-GNR-siIDO and Flt3-L, significantly attenuated tumor growth and delayed tumor formation, suggesting the treatment feasibility of the man-GNR-siIDO system in Flt3-L mobilized DCs in the immunotherapy of lung cancer. Therefore, our study highlights a clinical potential for a first-in-class anti-cancer immunotherapy through simultaneous DC-mobilization and DC-targeted gene silencing of IDO with man-GNR-siIDO and Flt3-L treatments.

Extra-Large Pore Mesoporous Silica Nanoparticles Enabling Co-Delivery of High Amounts of Protein Antigen and Toll-like Receptor 9 Agonist for Enhanced Cancer Vaccine Efficacy

Cancer vaccine aims to invoke antitumor adaptive immune responses to detect and eliminate tumors. However, the current dendritic cells (DCs)-based cancer vaccines have several limitations that are mostly derived from the ex vivo culture of patient DCs. To circumvent the limitations, direct activation and maturation of host DCs using antigen-carrying materials, without the need for isolation of DCs from patients, are required. In this study, we demonstrate the synthesis of extra-large pore mesoporous silica nanoparticles (XL-MSNs) and their use as a prophylactic cancer vaccine through the delivery of cancer antigen and danger signal to host DCs in the draining lymph nodes. Extra-large pores of approximately 25 nm and additional surface modification of XL-MSNs resulted in significantly higher loading of antigen protein and toll-like receptor 9 (TLR9) agonist compared with conventional small-pore MSNs. In vitro study showed the enhanced activation and antigen presentation of DCs and increased secretion of proinflammatory cytokines. In vivo study demonstrated efficient targeting of XL-MSNs co-delivering antigen and TLR9 agonist to draining lymph nodes, induction of antigen-specific cytotoxic T lymphocytes (CTLs), and suppression of tumor growth after vaccination. Furthermore, significant prevention of tumor growth after tumor rechallenge of the vaccinated tumor-free mice resulted, which was supported by a high level of memory T cells. These findings suggest that mesoporous silica nanoparticles with extra-large pores can be used as an attractive platform for cancer vaccines.

Tailoring of physicochemical properties of nanocarriers for effective anti-cancer applications

Nanotechnology has emerged strongly as a viable option to overcome the challenge of early diagnosis and effective drug delivery, for cancer treatment. Emerging research articles have expounded the advantages of using a specific type of nanomaterial-based system called as "nanocarriers," for anti-cancer therapy. The nanocarrier system is used as a transport unit for targeted drug delivery of the therapeutic drug moiety. In order for the nanocarriers to be effective for anticancer therapy, their physicochemical parameter needs to be tuned so that bio-functionalisation can be achieved to (1) allow drugs being attached to the substrate and for their controlled release, (2) ensure the stability of the nanocarrier up to the point of delivery, and (3) clearance of the nanocarrier after the delivery. It is therefore envisaged that tailoring of the physicochemical properties of nanocarriers can greatly influence their reactivity and interaction in the biological milieu, and this is becoming an important parameter for increasing the efficacy of cancer therapy. This review emphasizes the importance of physicochemical properties of nanocarriers, and how they influence its usage as chemotherapeutic drug carriers. The goal of this review is to present a correlation between the physicochemical properties of the nanocarriers and its intended action, and how their design based on these properties can enhance their cancer combating abilities while minimizing damage to the healthy tissues. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2906-2928, 2017.

Drug delivery with living cells

The field of drug delivery has grown tremendously in the past few decades by developing a wide range of advanced drug delivery systems. An interesting category is cell-based drug delivery, which includes encapsulation of drugs inside cells or attached to the surface and subsequent transportation through the body. Another approach involves genetic engineering of cells to secrete therapeutic molecules in a controlled way. The next-generation systems integrate expertise from synthetic biology to generate therapeutic gene networks for highly advanced sensory and output devices. These developments are very exciting for the drug delivery field and could radically change the way we administer biological medicines to chronically ill patients. This review is covering the use of living cells, either as transport system or production-unit, to deliver therapeutic molecules and bioactive proteins inside the body. It describes a wide range of approaches in cell-based drug delivery and highlights exceptional examples.

Dendritic-Tumor Fusion Cell-Based Cancer Vaccines

Dendritic cells (DCs) are potent antigen-presenting cells (APCs) that play a critical role in the induction of antitumor immunity. Therefore, various strategies have been developed to deliver tumor-associated antigens (TAAs) to DCs as cancer vaccines. The fusion of DCs and whole tumor cells to generate DC-tumor fusion cells (DC-tumor FCs) is an alternative strategy to treat cancer patients. The cell fusion method allows DCs to be exposed to the broad array of TAAs originally expressed by whole tumor cells. DCs then process TAAs endogenously and present them through major histocompatibility complex (MHC) class I and II pathways in the context of costimulatory molecules, resulting in simultaneous activation of both CD4⁺ and CD8⁺ T cells. DC-tumor FCs require optimized enhanced immunogenicity of both DCs and whole tumor cells. In this context, an effective fusion strategy also needs to produce immunogenic DC-tumor FCs. We discuss the potential ability of DC-tumor FCs and the recent progress in improving clinical outcomes by DC-tumor FC-based cancer vaccines.

Brain Tumor Immunotherapy: What have We Learned so Far?

High grade glioma is a rare brain cancer, incurable in spite of modern neurosurgery, radiotherapy, and chemotherapy. Novel approaches are in research, and immunotherapy emerges as a promising strategy. Clinical experiences with active specific immunotherapy demonstrate feasibility, safety and most importantly, but incompletely understood, prolonged long-term survival in a fraction of the patients. In relapsed patients, we developed an immunotherapy schedule and we categorized patients into clinically defined risk profiles. We learned how to combine immunotherapy with standard multimodal treatment strategies for newly diagnosed glioblastoma multiforme patients. The developmental program allows further improvements related to newest scientific insights. Finally, we developed a mode of care within academic centers to organize cell-based therapies for experimental clinical trials in a large number of patients.

Quantifying the Efficiency of N-Phenyl-D-mannosamine to Metabolically Engineer Sialic Acid on Cancer Cell Surface

A convenient method was developed for the quantification of sialic acids expressed by cells and used to analyze the efficiency of N-phenylacetyl-D-mannosamine (ManNPhAc) to metabolically glycoengineer SKMEL-28 cancer cell. For this purpose, ManNPhAc-cultured cells were treated with 2M acetic acid to release sialic acids, and the products were treated with 1,2-diamino-4,5-methylenedioxybenzene to form the corresponding derivatives that had strong UV absorptions. The reaction mixture was then applied to HPLC-UV analysis to determine the amounts and the ratios of natural sialic acid and its unnatural analog. It was confirmed that after incubation with ManNPhAc SKMEL-28 cell was effectively glycoengineered to express a significant amount of unnatural sialic acid.

Optimizing dendritic cell-based immunotherapy for cancer

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells and are unique in their capability to initiate, maintain and regulate the intensity of primary immune responses, including specific antitumor responses. Development of practical procedures to prepare sufficient numbers of functional human DCs in culture from the peripheral blood precursors, paved the way for clinical trials to evaluate various DC-based strategies in patients with malignant diseases. However, no definite conclusions regarding the clinical and even immunological efficacy of DC vaccination can be stated, despite the fact that 12 years have passed since the first clinical trial utilizing DCs in cancer patients. Many unanswered questions hamper the development of DC-based vaccines, including the source of DC preparation and protocols for DC generation, activation and loading with tumor antigens, source of tumor antigens, route of vaccine administration and methods of immunomonitoring. Fortunately, in spite of the many obstacles, DC vaccines continue to hold promise for cancer therapy.

Strategies for the development of PSA-based vaccines for the treatment of advanced prostate cancer

Prostate cancer is the second leading cause of cancer death in males in the USA. Vaccine strategies represent a novel therapeutic approach. One potential target for a prostate cancer vaccine is prostate-specific antigen (PSA), due to its restricted expression in prostate cancer and normal prostatic epithelial cells. A number of PSAspecific epitopes have been identified that can activate cytotoxic T-lymphocytes (CTLs) and in turn lead to the killing of tumor targets by the peptide-specific CTLs. Strategies have now been employed in clinical trials using RNA-pulsed dendritic cell vaccines, recombinant protein vaccines, and recombinant viral vector delivery of vaccines. Newer approaches incorporating costimulatory molecules that enhance Tcell activation are also being investigated.

Immunogene therapy

Antigenic differences between normal and malignant cells of the cancer patient form the rationale for clinical immunotherapeutic strategies. Because the antigenic phenotype of neoplastic cells varies widely among different cells within the same malignant cell-population, immunization with a vaccine that stimulates immunity to the broad array of tumor antigens expressed by the cancer cells is likely to be more efficacious than immunization with a vaccine for a single antigen. A vaccine prepared by transfer of DNA from the tumor into a highly immunogenic cell line can encompass the array of tumor antigens that characterize the patient's neoplasm. Poorly immunogenic tumor antigens, characteristic of malignant cells, can become strongly antigenic if they are expressed by highly immunogenic cells. A DNA-based vaccine was prepared by transfer of genomic DNA from a breast cancer that arose spontaneously in a C3H/He mouse into a highly immunogenic mouse fibroblast cell line, where genes specifying tumor-antigens were expressed. The fibroblasts were modified in advance of DNA-transfer to secrete an immune augmenting cytokine and to express allogeneic MHC Class I-determinants. In an animal model of breast cancer metastatic to the brain, introduction of the vaccine directly into the tumor bed stimulated a systemic cellular antitumor immune response measured by two independent in vitro assays and prolonged the lives of the tumor-bearing mice. Furthermore, using antibodies against the various T-cell subsets, it was determined that the systemic cellular antitumor immunity was mediated by CD8+, CD4+ and NK/LAK cells. In addition an enrichment strategy has also been developed to increase the proportion of immunotherapeutic cells in the vaccine which has resulted in the development of enhanced antitumor immunity. Finally regulatory T cells (CD4+CD25+Fox p3+-positive) were found to be relatively deficient in the spleen cells from the tumor-bearing mice injected intracerebrally with the enriched vaccine. The application of DNA-based genomic vaccines for the treatment of a variety of brain tumors is being explored.

Measles virus glycoprotein-pseudotyped lentiviral vectors are highly superior to vesicular stomatitis virus G pseudotypes for genetic modification of monocyte-derived dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells capable of promoting or regulating innate and adaptive immune responses against non-self antigens. To better understand the DC biology or to use them for immune intervention, a tremendous effort has been made to improve gene transfer in these cells. Lentiviral vectors (LVs) have conferred a huge advantage in that they can transduce nondividing cells such as human monocyte-derived DCs (MDDCs) but required high amounts of viral particles and/or accessory proteins such as Vpx or Vpr to achieve sufficient transduction rates. As a consequence, these LVs have been shown to cause dramatic functional modifications, such as the activation or maturation of transduced MDDCs. Taking advantage of new pseudotyped LVs, i.e., with envelope glycoproteins from the measles virus (MV), we demonstrate that MDDCs are transduced very efficiently with these new LVs compared to the classically used vesicular stomatitis virus G-pseudotyped LVs and thus allowed to achieve high transduction rates at relatively low multiplicities of infection. Moreover, in this experimental setting, no activation or maturation markers were upregulated, while MV-LV-transduced cells remained able to mature after an appropriate Toll-like receptor stimulation. We then demonstrate that our MV-pseudotyped LVs use DC-SIGN, CD46, and CD150/SLAM as receptors to transduce MDDCs. Altogether, our results show that MV-pseudotyped LVs provide the most accurate and simple viral method for efficiently transferring genes into MDDCs without affecting their activation and/or maturation status.

Dendritic cells crosspresent antigens from live B16 cells more efficiently than from apoptotic cells and protect from melanoma in a therapeutic model

Dendritic cells (DC) are able to elicit anti-tumoral CD8⁺ T cell responses by cross-presenting exogenous antigens in association with major histocompatibility complex (MHC) class I molecules. Therefore they are crucial actors in cell-based cancer immunotherapy. Although apoptotic cells are usually considered to be the best source of antigens, live cells are also able to provide antigens for cross-presentation by DC. We have recently shown that prophylactic immunotherapy by DC after capture of antigens from live B16 melanoma cells induced strong CD8⁺ T-cell responses and protection against a lethal tumor challenge in vivo in C57Bl/6 mice. Here, we showed that DC cross-presenting antigens from live B16 cells can also inhibit melanoma lung dissemination in a therapeutic protocol in mice. DC were first incubated with live tumor cells for antigen uptake and processing, then purified and irradiated for safety prior to injection. This treatment induced stronger tumor-specific CD8⁺ T-cell responses than treatment by DC cross-presenting antigens from apoptotic cells. Apoptotic B16 cells induced more IL-10 secretion by DC than live B16 cells. They underwent strong native antigen degradation and led to the expression of fewer MHC class I/epitope complexes on the surface of DC than live cells. Therefore, the possibility to use live cells as sources of tumor antigens must be taken into account to improve the efficiency of cancer immunotherapy.

Cyclophosphamide potentiates the antitumor effect of immunization with injection of immature dendritic cells into irradiated tumor

Growth of a tumor on the left flank was suppressed by direct injection of immature DCs (iDCs) into the irradiated tumor on the right thigh (IR/DC). This antitumor immune effect of IR/DC was enhanced by pretreatment with CTX (CTX+IR/DC) and this effect was related with increased number of tumor-specific IFN-γ secreting T cells and decreased ratio of CD4(+)CD25(+)/CD4(+) T cells. The treatment with CTX+IR/DC increased or decreased the levels of IL-2 or IL-10, respectively. These results demonstrated that antitumor effect of IR/DC could be augmented by pretreatment with low-dose CTX, suggesting a new antitumor therapeutic modality of chemoradioimmunotherapy.

Increased tumor-specific CD8+ T cell induction by dendritic cells matured with a clinical grade TLR-agonist in combination with IFN-gamma

The limited response rate of cancer patients treated with dendritic cell (DC)-based vaccines indicates that vast improvements remain necessary. In many murine tumour models it has been demonstrated that the use of innate triggers (e.g. TLR triggers) in the maturation of DC results in higher efficacy. However, as few of these innate triggers are generated clinical grade, there remains a great necessity to fill the gap between fundamental mouse studies and a clinical trial in humans. In the present study we used a TLR2/4-agonist (FMKp which is available clinical grade) in combination with IFN-gamma (FIcocktail) in the maturation of elutriated monocyte-derived DC and compared it with the most used DC in current clinical trials (TNF-alpha/PGE-2, i.e. TP-cocktail). In addition to the assessment of CD4+ T cell polarizing capacity, we compared the quantity and intrinsic quality of induced CD8+ T cells of 2 different DC maturation protocols with all cells from the same donor. Besides differences in the cytokine profile, which could be coupled to increased Th1 and Th17 polarization, we demonstrate in this study that FMKp/IFN-gamma matured DC are twice as effective in inducing cytotoxic T cells against known tumor antigens. Both DCs induced phenotypically equivalent effector memory CD8+ T cells that did not show a significant difference in their intrinsic capacity to kill tumor cells. These findings point to the therapeutic applicability of FI-DC as superior inducers of functional antigen-specific T cells. Their increased chemokine secretion is suggestive of a mechanism by which these DC may compensate for the limited migration observed for all ex vivo cultured DC when applied in patients.

Cross-presentation by dendritic cells from live cells induces protective immune responses in vivo

Cross-presentation is an essential mechanism that allows dendritic cells (DCs) to efficiently present exogenous antigens to CD8(+) T cells. Among cellular antigen sources, apoptotic cells are commonly considered as the best for cross-presentation by DCs. However, the potential of live cells as a source of antigen has been overlooked. Here we explored whether DCs were able to capture and cross-present antigens from live cells. DCs internalized cytosolic and membrane material into vesicles from metabolically labeled live cells. Using time-lapse confocal microscopy in whole spleens, we showed that DCs internalized material from live cells in vivo. After ovalbumin uptake from live cells, DCs cross-primed ovalbumin-specific naive OT-I CD8(+) T cells in vitro. Injected into mice previously transferred with naive OT-I T cells, they also cross-primed in vivo, even in the absence of endogenous DCs able to present the epitope in the recipient mice. Interestingly, DCs induced stronger natural CD8(+) T-cell responses and protection against a lethal tumor challenge after capture of antigens from live melanoma cells than from apoptotic melanoma cells. The potential for cross-presentation from live cells uncovers a new type of cellular intercommunication and must be taken into account for induction of tolerance or immunity against self, tumors, grafts, or pathogens.

Phase I study of autologous dendritic cell tumor vaccine in patients with non-small cell lung cancer

BACKGROUND

A dendritic cell vaccine has been developed as a novel strategy for generating antitumor immunity in the treatment of cancer. The purpose of this study was to assess the maximal tolerated dose, safety, and immunologic response of a new dendritic cell vaccine (DC-Vac) into which tumor lysate was loaded by electroporation and pulse in patients with advanced non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Fifteen patients with inoperable stage III or IV NSCLC were assigned to cohorts that received 3, 6, or 12 × 10(6) DC-Vac intradermally 3 times at 2 week intervals. We also evaluated immunologic and tumor responses.

RESULTS

The maximum dose of DC-Vac (12 × 10(6)) was shown to be safe. In 5 of 9 patients, the vaccine resulted in increased interferon (IFN)-γ production by CD8+ cells after exposure to tumor lysate. Additionally, there were mixed responses which do fulfill progressive disease definition but demonstrate some clinical benefit in two patients.

CONCLUSION

The administration of tumor lysate-loaded autologous dendritic cells by electroporation and pulse was non-toxic and induced immunologic responses to tumor antigens. The two mixed tumor responses which were achieved may represent a potential benefit of this new DC-Vac.

Optimised electroporation mediated DNA vaccination for treatment of prostate cancer

BACKGROUND

Immunological therapies enhance the ability of the immune system to recognise and destroy cancer cells via selective killing mechanisms. DNA vaccines have potential to activate the immune system against specific antigens, with accompanying potent immunological adjuvant effects from unmethylated CpG motifs as on prokaryotic DNA. We investigated an electroporation driven plasmid DNA vaccination strategy in animal models for treatment of prostate cancer.

METHODS

Plasmid expressing human PSA gene (phPSA) was delivered in vivo by intra-muscular electroporation, to induce effective anti-tumour immune responses against prostate antigen expressing tumours. Groups of male C57 BL/6 mice received intra-muscular injections of phPSA plasmid. For phPSA delivery, quadriceps muscle was injected with 50 microg plasmid. After 80 seconds, square-wave pulses were administered in sequence using a custom designed pulse generator and a custom-designed applicator with 2 needles placed through the skin central to the muscle. To determine an optimum treatment regimen, three different vaccination schedules were investigated. In a separate experiment, the immune potential of the phPSA vaccine was further enhanced with co- administration of synthetic CpG rich oligonucleotides. One week after last vaccination, the mice were challenged subcutaneously with TRAMPC1/hPSA (prostate cancer cell line stably expressing human PSA) and tumour growth was monitored. Serum from animals was examined by ELISA for anti-hPSA antibodies and for IFN gamma. Histological assessment of the tumours was also carried out. In vivo and in vitro cytotoxicity assays were performed with splenocytes from treated mice.

RESULTS

The phPSA vaccine therapy significantly delayed the appearance of tumours and resulted in prolonged survival of the animals. Four-dose vaccination regimen provided optimal immunological effects. Co - administration of the synthetic CpG with phPSA increased anti-tumour responses, preventing tumour occurrence in 54% of treated animals. Vaccination with phPSA resulted in anti-hPSA Abs production and a significant production of IFN gamma was observed in immunised animals (p < 0.05). Immune responses were tumour specific and were transferable in adoptive T cell transfer experiments.

CONCLUSIONS

This phPSA plasmid electroporation vaccination strategy can effectively activate tumour specific immune responses. Optimisation of the approach indicated that a four-dose regimen provided highest tumour protection. In vivo electroporation mediated vaccination is a safe and effective modality for the treatment of prostate cancer and has a potential to be used as a neo-adjuvant or adjuvant therapy.

Personalized dendritic cell-based tumor immunotherapy

Advances in the understanding of the immunoregulatory functions of dendritic cells (DCs) in animal models and humans have led to their exploitation as anticancer vaccines. Although DC-based immunotherapy has proven clinically safe and efficient to induce tumor-specific immune responses, only a limited number of objective clinical responses have been reported in cancer patients. These relatively disappointing results have prompted the evaluation of multiple approaches to improve the efficacy of DC vaccines. The topic of this review focuses on personalized DC-based anticancer vaccines, which in theory have the potential to present to the host immune system the entire repertoire of antigens harbored by autologous tumor cells. We also discuss the implementation of these vaccines in cancer therapeutic strategies, their limitations and the future challenges for effective immunotherapy against cancer.

Killer dendritic cells and their potential for cancer immunotherapy

Known for years as the principal messengers of the immune system, dendritic cells (DC) represent a heterogeneous population of antigen presenting cells critically located at the nexus between innate and adaptive immunity. DC play a central role in the initiation of tumor-specific immune responses as they are endowed with the unique ability to take up, process and present tumor antigens to naïve CD4(+) or CD8(+) effector T lymphocytes. By virtue of the cytokines they produce, DC also regulate the type, strength and duration of T cell immune responses. In addition, they can participate in anti-tumoral NK and NKT cell activation and in the orchestration of humoral immunity. More recent studies have documented that besides their primary role in the induction and regulation of adaptive anti-tumoral immune responses, DC are also endowed with the capacity to directly kill cancer cells. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. First, the direct killing of malignant cells by DC may foster the release and thereby the immediate availability of specific tumor antigens for presentation to cytotoxic or helper T lymphocytes. Second, DC may participate in the effector phase of the immune response, potentially augmenting the diversity of the killing mechanisms leading to tumor elimination. This review focuses on this non-conventional cytotoxic function of DC as it relates to the promotion of cancer immunity and discusses the potential application of killer DC (KDC) in tumor immunotherapy.

Dendritic cell therapy of high-grade gliomas

The prognosis of patients with malignant glioma is poor in spite of multimodal treatment approaches consisting of neurosurgery, radiochemotherapy and maintenance chemotherapy. Among innovative treatment strategies like targeted therapy, antiangiogenesis and gene therapy approaches, immunotherapy emerges as a meaningful and feasible treatment approach for inducing long-term survival in at least a subpopulation of these patients. Setting up immunotherapy for an inherent immunosuppressive tumor located in an immune-privileged environment requires integration of a lot of scientific input and knowledge of both tumor immunology and neuro-oncology. The field of immunotherapy is moving into the direction of active specific immunotherapy using autologous dendritic cells (DCs) as vehicle for immunization. In the translational research program of the authors, the whole cascade from bench to bed to bench of active specific immunotherapy for malignant glioma is covered, including proof of principle experiments to demonstrate immunogenicity of patient-derived mature DCs loaded with autologous tumor lysate, preclinical in vivo experiments in a murine orthotopic glioma model, early phase I/II clinical trials for relapsing patients, a phase II trial for patients with newly diagnosed glioblastoma (GBM) for whom immunotherapy is integrated in the current multimodal treatment, and laboratory analyses of patient samples. The strategies and results of this program are discussed in the light of the internationally available scientific literature in this fast-moving field of basic science and translational clinical research.

Fluorine-containing nanoemulsions for MRI cell tracking

In this article we review the chemistry and nanoemulsion formulation of perfluorocarbons used for in vivo(19)F MRI cell tracking. In this application, cells of interest are labeled in culture using a perfluorocarbon nanoemulsion. Labeled cells are introduced into a subject and tracked using (19)F MRI or NMR spectroscopy. In the same imaging session, a high-resolution, conventional ((1)H) image can be used to place the (19)F-labeled cells into anatomical context. Perfluorocarbon-based (19)F cell tracking is a useful technology because of the high specificity for labeled cells, ability to quantify cell accumulations, and biocompatibility. This technology can be widely applied to studies of inflammation, cellular regenerative medicine, and immunotherapy.

[Experimental models in oncology: contribution of cell culture on understanding the biology of cancer]

In the beginning of the 20th century, tissue culture was started with the aim of studying the behaviour of animal cells in normal and stress conditions. The cell study at molecular level depends on their capacity of growing and how they can be manipulated in laboratory. In vitro cell culture allows us the possibility of studying biological key processes, such as growth, differentiation and cell death, and also to do genetic manipulations essential to the knowledge of structure and genes function. Human stem cells culture provides strategies to circumvent other models' deficiencies. It seems that cancer stem cells remain quiescent until activation by appropriated micro-environmental stimulation. Several studies reveal that different cancer types could be due to stem cell malignant transformations. Removal of these cells is essential to the development of more effective cancer therapies for advanced disease. On the other hand, dendritic cells modified in culture may be used as a therapeutic vaccine in order to induce tumour withdraw.

Immunotherapy for head and neck cancer

Overall survival for patients with squamous cell carcinoma of the head and neck (SCCHN) has not improved appreciably over the past few decades. Novel therapeutic approaches, such as immunotherapy, are under clinical investigation since the standard treatments are toxic and have not successfully controlled this disease with sufficiently high success rates. Cancer immunotherapy describes various techniques to expand and activate the immune system to control tumor growth in vivo, and clinical evaluation has so far demonstrated low toxicity. Immunotherapy appears to have the most applicability in settings of minimal residual disease and to reduce distant metastases after other therapeutic interventions, and its potential clinical value is now receiving intensive evaluation. Emerging forms of SCCHN immunotherapy involve both the use of monoclonal antibodies (mAb) that target growth factor receptors where immune activation appears to contribute to tumor cell lysis, as well as various forms of active vaccination strategies which activate and direct the patient's cellular immunity against the tumor. This article reviews immunotherapeutic strategies currently in clinical trials or under development for patients with SCCHN.

The balance between immunity and tolerance: the role of Langerhans cells

Langerhans cells are immature skin-homing dendritic cells that furnish the epidermis with an immune surveillance system, and translate information between the internal and external milieu. Dendritic cells, in particular Langerhans cells, are gaining prominence as one of the potential principal players orchestrating the decision between immunity and tolerance. Langerhans cells capture aberrant self-antigen and pathogen-derived antigen for display to the efferent immune response. Recent evidence suggests redundancy in the antigen-presenting function of Langerhans cells, with dermal dendritic subsets capable of fulfilling an analogous role. There is mounting evidence that Langerhans cells can cross-prime T cells to recognize antigens. Langerhans cells are proposed to stimulate T regulatory cells, and are implicated in the pathogenesis of cutaneous T cell lymphoma.The phenotype of Langerhans cells, which may be tolerogenic or immunogenic, appears to depend on their state of maturity, inciting immunogen and cytokine environment, offering the potential for manipulation in immunotherapy.

Gene immunotherapy for non-small cell lung cancer

Historically, limited results have been observed with immunity in non-small cell lung cancer (NSCLC). In the last 5 years, however, several immune-stimulating products have demonstrated enhancement of tumor antigen recognition through activation of dendritic cell-involved processes. Moreover, clinical benefit has been demonstrated in subsets of patients, justifying ongoing phase III investigation. Results of key gene immunotherapies being tested in NSCLC are reviewed. Preliminary results in advanced NSCLC suggest evidence of well-tolerated immune activation with suggested evidence of clinical benefit with respect to survival and response.

Dendritic cell activation by combined exposure to anti-CD40 plus interleukin (IL)-12 and IL-18 efficiently stimulates anti-tumor immunity

Despite as yet limited clinical effectiveness, dendritic cell (DC)-based immunotherapy remains a promising approach for the treatment of cancer, but requires further improvement in its immunostimulatory effectiveness. Potent anti-tumor immunity often depends on the induction of type 1 (T(H)1) immune responses. Therefore, we combined different DC maturation stimuli that are known to induce T(H)1 immunity [anti-CD40, interleukin (IL)-12, IL-18], with the aim to trigger a T(H)1 driven anti-tumor CTL response. When compared with untreated DC or DC treated with anti-CD40 alone, DC matured with anti-CD40 plus IL-12 and IL-18 expressed significantly more IFN-gamma and IL-12, induced enhanced CD8(+) T-cell proliferation, prolonged synaptic interaction with T cells and increased CD8(+) T-cell-mediated cytotoxicity. To analyse if these DC are able to induce efficient anti-tumor immunity, mice carrying a B16-OVA tumor were treated with tumor antigen (TA)-loaded DC that had been exposed to anti-CD40 or to anti-CD40 plus IL-12 and IL-18. Our data show that anti-CD40 plus IL-12 and IL-18 matured DC are superior to controls in retarding tumor growth. These data indicate that maturation of DC with anti-CD40 plus IL-12 and IL-18 potently stimulates the generation of an anti-tumor immune response and may lead to improved immunotherapeutic capacity of DC vaccination.

Synthetic and immunological studies of 5'-N-phenylacetyl sTn to develop carbohydrate-based cancer vaccines and to explore the impacts of linkage between carbohydrate antigens and carrier proteins

5'- N-Phenylacetyl sTn (sTnNPhAc), an unnatural derivative of sTn antigen expressed by many tumors, and its alpha-linked protein conjugates were prepared and investigated to explore glycoconjugate cancer vaccines. sTnNPhAcalpha-KLH elicited a robust T cell dependent immunity. The antiserum derived from sTnNPhAcalpha- or sTnNPhAcbeta-KLH-inoculated mice was similarly reactive to sTnNPhAcalpha and sTnNPhAcbeta but showed very little reactivity to sTn, NeuNPhAcalpha(2,3)GalNAc--a regioisomer of sTnNPhAc, isolated phenylacetyl group, and the linker employed to conjugate sTnNPhAc and carrier protein. It was concluded that the sTnNPhAc-elicited immunity was specific for the whole antigen rather than the phenylacetyl group or other partial structures of sTnNPhAc and that the reducing end configuration or linkage of sTnNPhAc did not affect its immunological identity. It was also concluded that a new linker designed to conjugate carbohydrates and proteins did not provoke any immune reaction and that the linker, as well as the associated new and convenient coupling strategy, can be safely used for the development of glycoconjugate vaccines.

Induction of HIV-specific T and B cell responses with a replicating and conditionally infectious lentiviral vaccine

The development of an HIV vaccine that induces broad and potent immunity is critically needed. Viruses, including lentiviruses, have been used as vectors for ex vivo transduction of antigens into dendritic cells (DC). We hypothesized that DC transduced with a vector that allows selective infection of DC could induce potent immunity by continually priming DC. A lentiviral vector encoding HIV gag-pol without env would form viral cores in transduced DC, but would release non-infectious particles by budding into endosomes and releasing apoptotic bodies or exosomes containing viral cores. DC function by endocytosing DC-derived apoptotic bodies, and they are specialized in their ability to move endocytic contents into the cytoplasm. We postulated that endocytosis of vector cores could lead to transduction of a second round of DC. In this report, we demonstrate accumulation of viral cores inside transduced DC and show second-round transduction of immature DC that endocytose transduced DC in vitro. The effectiveness of immunization of mice with transduced DC to induce specific lymphocyte activation was assessed. Mice developed antigen-specific T cell responses and specific antibodies after immunization. Transduction of DC with a replication-competent but conditionally infectious lentivirus could be a novel vaccine strategy for HIV.

An immunotherapy approach with dendritic cells genetically modified to express the tumor-associated antigen, HER2

Dendritic cells (DC), genetically modified to express ovalbumin by the retroviral vector GCDNsap, can elicit stronger anti-tumor immunity than those loaded with the peptides. To assess the clinical feasibility of the strategy, such DC were prepared by differentiation of hematopoietic progenitor cells transduced with the human epidermal growth factor receptor 2 (HER2). When inoculated in mice, the DC primed both HER2-specific cytotoxic T lymphocytes and type 1 T helper lymphocytes, resulting in production of HER2-specific antibody. Of importance is that the antibody mediated antibody-dependent cellular cytotoxicity and opsonization. The potent anti-tumor effects were also confirmed by results of experiments using HER2-transgenic mice. Inoculation of HER2-transduced DC resulted in longer disease-free survival of treated mice that showed significant reduction of primary and metastatic tumors. Interestingly, footpad inoculation resulted in stronger anti-tumor effects compared to subcutaneous administration and induced higher levels of the HER2-specific antibody, suggesting that an important role of humoral immunity in anti-tumor effects for malignancies with membrane-type tumor-associated antigens (TAA). Taken together, vaccination of the TAA-transduced DC may represent a promising form of therapy for breast cancers expressing HER2.

Glycan modification of the tumor antigen gp100 targets DC-SIGN to enhance dendritic cell induced antigen presentation to T cells

Dendritic cells (DC) have gained much interest in the field of anticancer vaccine development because of their central function in immune regulation. However, the clinical application of ex vivo cultured DC has significant disadvantages. A vaccine that targets dendritic cells in vivo and enhances antigen presentation would be of great benefit. Because of its DC-restricted expression pattern, and its function as an antigen uptake receptor, DC-SIGN is an interesting candidate target structure for human immature DC. Here, we studied whether modification of the melanoma differentiation antigen gp100 with DC-SIGN-interacting glycans enhances targeting to human DC. A high-mannose form of gp100, as protein or as tumor lysate, not only interacted specifically with DC through DC-SIGN but also resulted in an enhanced antigen presentation to gp100-specific CD4(+) T cells. Our results indicate that glycan modification of tumor antigens to target C-type lectin receptors, such as DC-SIGN, is a new way to develop in vivo targeting DC strategies that simultaneously enhance the induction of tumor-specific T cells.

Multicenter study on in vitro characterization of dendritic cells

BACKGROUND

There is growing interest in the use of in vitro-expanded dendritic cells (DC) in cancer immunotherapy as cellular-based vaccines. However, the methods used for in vitro preparation vary widely between institutions. Therefore, a strong need exists for standardization, characterization and quality control (QC) of such vaccines. A first prospective multicenter pilot study was performed to investigate basic QC parameters of frozen/thawed DC. The study design was focused on comparison of test results for cell counts, immunophenotyping and cell viability.

METHODS

CD14+ monocytes were isolated from three healthy volunteers. The cells were expanded in vitro, matured and cryopreserved using a standardized protocol in one laboratory. The aliquots of cryopreserved DC and a panel of reagents were shipped to eight laboratories worldwide. The objective was to compare the results of non-functional QC assays between sites by testing identical DC vaccines and using a pre-defined test protocol.

RESULTS

Measurements of nucleated cell (NC) content of thawed DC vaccines with different types of hematology analyzers (HA) gave similar results for the majority of sites. Immunophenotyping using identical clones of monoclonal antibodies for the detection of surface antigens (i.e. CD1a, CD14, CD16, CD83, CD86 and HLA-DR) provided mostly comparable results between laboratories with an acceptable level of variation. In contrast, highly different results between study sites were generated for measuring the viability of thawed DC by flow cytometry using 7-amino-actinomycin D (7-AAD) dye exclusion.

DISCUSSION

In characterizing frozen/thawed DC vaccines, NC counts generated by HA yielded similar results between different laboratories. Furthermore, immunophenotyping of DC vaccines can be standardized between centers, i.e. by using identical reagents. Because of highly variable results between laboratories, 7-AAD viability testing of thawed DC needs to be studied further to identify potential causes for the observed variability.

Efficient glycoengineering of GM3 on melanoma cell and monoclonal antibody-mediated selective killing of the glycoengineered cancer cell

To verify the principal of a new immunotherapeutic strategy for cancer, a monoclonal antibody 2H3 against N-phenylacetyl GM3, an unnatural form of the tumor-associated antigen GM3, was prepared and employed to demonstrate that murine melanoma cell B16F0 could be effectively glycoengineered by N-phenylacetyl-d-mannosamine to express N-phenylacetyl GM3 and that 2H3 was highly cytotoxic to the glycoengineered B16F0 cell in the presence of complements. It was further demonstrated that B16F0 cell could be glycoengineered 4-5 times more effectively than 3T3 A31 cell, a normal murine embryo fibroblast cell, and that the antibody and complement mediated cytotoxicity was at least 200 times more potent to the glycoengineered B16F0 cell than to the N-phenylacetyl-d-mannosamine-treated 3T3 A31 cell. These results show the promise for developing useful melanoma immunotherapies based on vaccination against N-phenylacetyl GM3 followed by treatment with N-phenylacetyl-d-mannosamine.