DC-based Vaccines Research Articles

DC-Derived Exosomes for Cancer Immunotherapy

Simple SummaryDendritic cells (DCs)-based cancer vaccines have not succeeded in generating significant clinical responses despite their capacity to induce host anti-tumor CD8 T cell immunity, and one major hurdle is tumor-mediated immunosuppression. Exosomes are nano-sized inert membrane vesicles derived from the endocytic pathway that play a critical role in intercellular communication. DC-derived exosomes (DCexos) additionally carried MHC class I/II (MHCI/II) often complexed with antigens and co-stimulatory molecules, thus capable of priming antigen-specific CD4 and CD8 T cells. Indeed, vaccines with DCexos have been shown to exhibit better anti-tumor efficacy in eradicating tumors compared to DC vaccines in pre-clinical models. Coupled with their resistance to tumor immunosuppression, DCexo-based cancer vaccines have been heralded as the superior alternative cell-free therapeutic vaccines over DC vaccines, and have now been tested in multiple clinical trials. In this review, current studies of DCexo cancer vaccines as well as potential future directions will be discussed.As the initiators of adaptive immune responses, DCs play a central role in regulating the balance between CD8 T cell immunity versus tolerance to tumor antigens. Exploiting their function to potentiate host anti-tumor immunity, DC-based vaccines have been one of most promising and widely used cancer immunotherapies. However, DC-based cancer vaccines have not achieved the promised success in clinical trials, with one of the major obstacles being tumor-mediated immunosuppression. A recent discovery on the critical role of type 1 conventional DCs (cDC1s) play in cross-priming tumor-specific CD8 T cells and determining the anti-tumor efficacy of cancer immunotherapies, however, has highlighted the need to further develop and refine DC-based vaccines either as monotherapies or in combination with other therapies. DC-derived exosomes (DCexos) have been heralded as a promising alternative to DC-based vaccines, as DCexos are more resistance to tumor-mediated suppression and DCexo vaccines have exhibited better anti-tumor efficacy in pre-clinical animal models. However, DCexo vaccines have only achieved limited clinical efficacy and failed to induce tumor-specific T cell responses in clinical trials. The lack of clinical efficacy might be partly due to the fact that all current clinical trials used peptide-loaded DCexos from monocyte-derived DCs. In this review, we will focus on the perspective of expanding current DCexo research to move DCexo cancer vaccines forward clinically to realize their potential in cancer immunotherapy.

SO-26 In-silico Lynch syndrome-related neoantigens prediction for a dendritic cell-based cancer prevention vaccine

Lynch syndrome (LS), caused by germline mutations in DNA mismatch-repair genes (MLH1, MSH2, MSH6, PMS2) predisposes patients to colorectal and endometrial cancer (CRC, EC), among other tumors. Although CCR prevention methods are effective, no preventive strategies exist for the majority of LS-related tumors. Ex-vivo generated and tumor-antigen-loaded dendritic cell (DC) vaccines are one of the recently featured antitumoral immunotherapies. However, their full therapeutic potential would likely be as a preventive approach in high-risk cancer patients. LS is a paradigmatic model for its limited and predictive mutational spectrum in repetitive DNA sequences termed microsatellites (MS). This study aims to identify the main frame-shift derived neopeptides (FSDN) that are shared among cancers from LS patients with the purpose of developing a DC-based neoepitope vaccine. A systematic search of coding MS and FSDN in LS tumors published in literature and in public databases was performed (Seltar Database; The Cancer Genome Atlas, TCGA), with application of epitope prediction pipelines and priorization of FSDN with the greatest coverage on the most frequent HLA-I and HLA-II haplotypes (pVACbind; pVACtools v2.0.1). 531 frame-shift peptide sequences derived from -1 (m1) and -2 (m2) nucleotide deletions from 269 coding microsatellites (cMS) of at least 8 bases were retrieved from SelTarbase and TCGA. Data in FASTA format was computed through the pVACbind epitope prediction pipeline with a labile HLA-binding affinity threshold (IC50 = < 5000 nM) to consider immunoediting events. We prioritized 98 epitopes, 53 HLA-I and 45 HLA-II restricted, from an original predicted number of 42828 HLA-I and 8350 HLA-II-restricted (m1 and m2) epitopes with a median coverage of 9,4 HLA-I alleles and 8,7 HLA-II alleles per epitope. Our predicted neoepitope set has an optimal coverage among LS patients in terms of HLA alleles, associated cancers and prevalence. These results are key to first perform ex vivo functional analysis to determine neoepitopes immunogenicity to later design a preventive antitumoral vaccine for LS.

Complement Promotes Gvhd through Suppressing Autophagy in Recipient Dendritic Cells after Allogeneic Hematopoietic Cell Transplantation in Mice

Graft-versus-host disease (GVHD) limits the success of allogeneic hematopoietic stem cell transplantation (allo-HCT). Traditional therapies have targeted T cells, yet immunostimulatory dendritic cells (DCs) are critical in the pathogenesis of GVHD. Autophagy is a self-degradative process for cytosolic components and is required for maintaining homeostasis after allo-HCT. Complement receptors C3aR/C5aR can regulate immune responses by translating information gathered by complement fluid phase sensors into cellular responses. C3aR/C5aR have been reported to activate the autophagy inhibitor mTOR in cells. While depletion of autophagy in recipient DCs aggravates GVHD severity, and enhancing autophagy represents as a promising approach for treating immunological diseases, it is not known how escalation of autophagy regulates DC-functionality in GVHD pathogenesis. In the current study, we found that deficiency of C3aR/C5aR signaling significantly upregulated mTOR-independent autophagy in DCs (Figure 1B), which is associated with increased apoptosis, and reduced activation and antigen presenting capacity of C3aR/C5aR-/-DCs (Figure 1, A-C).To evaluate the role of C3aR/C5aR in modulating DC function in GVHD pathogenesis, we compared the severity of GVHD in WT versus C3aR/C5aR-/- recipients using murine models of allo-HCT. C3aR/C5aR-/- recipients developed less severe GVHD than their WT counterparts, reflected by a significantly higher rate of survival and lower clinical scores (Figure 1D). Donor T-cell survival and Th1-differentiation were significantly decreased, whereas Treg generation was increased in C3aR/C5aR-/- recipients. Glycolytic activity of donor T cells was significantly abrogated in the absence of recipient C3aR/C5ar (Figure 1E). Donor T-cells expressed lower levels of chemokine receptors, CXCR3 and CCR6, which were likely contributed to the decreased migration of the effector T cells into GVHD target organs of C3aR/C5aR-/- recipients. Using chimeric recipients in which either the hematopoietic or non-hematopoietic compartment is deficient for C3aR/C5aR, we found that C3aR/C5aR in the recipient hematopoietic cells was primarily responsible for donor T-cell response and pathogenicity in GVHD. Transfusion of C3aR/C5aR-/- DCs along with allo-HCT mitigated GVHD severity, indicating that C3aR/5aR signaling in DCs plays a predominant role in the pathogenesis of GVHD. Elevated autophagy was required for the suppressive effect of C3aR/C5aR-/- DCs on GVHD as autophagy inhibitor chloroquine (CQ) reverted the GVHD-suppressive effect of C3aR/C5aR-/-DCs (Figure 1F). For translational purpose, we evaluated the therapeutic potential of a combination of C3aR and C5aR antagonists, and found that pharmacological blockade of C3aR/C5aR could effectively reduce GVHD severity while sparing GVL effect through persevering CD8 cytolytic activity.The current study reveals for the first time that escalation of autophagy in DCs is an effective therapeutic approach for the control of GVHD, and establishes and interaction between complement and autophagy in allo-HCT. We also provide a novel strategy of enhancing autophagy as a DC-based vaccination strategy for the control of GVHD after transplantation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Crosstalk Between Dendritic Cells, Cytokine-Induced Killer Cells And Cancer Cells From The Perspective Of Combination Therapy

Dendritic cells (DCs) are considered the most potent professional antigen-presenting cells (APCs) that elicit adaptive antitumour immunity. DCs integrate multiple environmental signals by efficiently processing tumour-associated antigens (TAAs) and migrating to draining lymph nodes (dLNs), where they present foreign antigens to T cells for priming. DCs thus serve as a major link between innate and adaptive immunity. Although DCs (mostly monocyte-derived DCs [mo-DCs]) have already been used in cancer therapies, such approaches have shown limited efficacy. Mo-DCs have the unique ability to present antigens to T cells in peripheral tissues. CD3+CD56+ cytokine-induced killer (CIK) cells are characterized by both MHC-restricted and MHC-unrestricted antitumour cytotoxicity against a broad range of cancer cells. This review presents an overview of the mechanisms by which mo-DCs and CIK cells’ interact with each other and with tumours. The maturation of DCs was identified as a crucial step in the development of effective DC-based vaccines against cancer. A further improved adoptive immunotherapy strategy involves a combination of mature mo-DCs and CIK cells. Combination therapy presents many opportunities for cancer treatment, as reported by a number of clinical trials. However, there is a lack of fundamental studies on the interaction of in vitro-generated mo-DCs with CIK cells. We discuss several methods of boosting DC-based vaccines and review the current knowledge of contact-dependent and cytokine-induced interactions of mo-DCs with CIK cells. We highlight that the combination of mo-DCs with CIK cells activates MHC-restricted and MHC-unrestricted immune responses.

Innate immune cells in the tumor microenvironment.

The tumor immune microenvironment (TIME) is a complex ecosystem that contains adaptive and innate immune cells that have tumor-promoting and anti-tumor effects. There is still much to learn about the diversity, plasticity, and functions of innate immune cells in the TIME and their roles in determining the response to immunotherapies. Experts discuss recent advances in our understanding of their biology in cancer as well as outstanding questions and potential therapeutic avenues.

Phenotypic and genetic evaluation of human monocyte-derived dendritic cells generated from whole blood for immunotherapy

BackgroundDendritic cells (DCs) recognize different pathogens and cancer cells and activate the adaptive immune response. The generation of effective DC-based cancer vaccines depends on the appropriate differentiation of monocytes in vitro. This study aimed to standardize a protocol for the in vitro differentiation of human peripheral blood monocytes into immature DCs upon treatment with growth factors and generate monocyte-derived DCs (MoDCs). Peripheral blood mononuclear cells were separated from peripheral blood. After monocyte enrichment by plastic adhesion, monocytes were cultured for 6 days in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 to generate immature DCs. The cells were examined by microscopy. Using flow cytometry, DCs were evaluated for the expression of the CD83 and HLA-DR surface antigens, for the uptake of fluorescein isothiocyanate conjugated dextran, and also for the expression of CD80 and CD86 mRNA.ResultsCD80 and CD86 genes expression was upregulated at day six and exhibited a significant difference (P < 0.05). DCs showed positive expression of the CD83 and HLA-DR surface antigens by flow cytometry and FITC-conjugated dextran uptake.ConclusionThis study represents a preliminary trial to generate immature MoDCs in vitro from blood monocytes collected by the flask adherence method. It offers a panel of surface markers for DCs characterization and provides Immature DCs for experimental procedures after 6 incubation days.

Recent Progress in Dendritic Cell-Based Cancer Immunotherapy

Simple SummaryCancer immunotherapy has now attracted much attention because of the recent success of immune checkpoint inhibitors. However, they are only beneficial in a limited fraction of patients most probably due to lack of sufficient CD8+ cytotoxic T-lymphocytes against tumor antigens in the host. In this regard, dendritic cells are useful tools to induce host immune responses against exogenous antigens. In particular, recently characterized cross-presenting dendritic cells are capable of inducing CD8+ cytotoxic T-lymphocytes against exogenous antigens such as tumor antigens and uniquely express the chemokine receptor XCR1. Here we focus on the recent progress in DC-based cancer vaccines and especially the use of the XCR1 and its ligand XCL1 axis for the targeted delivery of cancer vaccines to cross-presenting dendritic cells. Cancer immunotherapy aims to treat cancer by enhancing cancer-specific host immune responses. Recently, cancer immunotherapy has been attracting much attention because of the successful clinical application of immune checkpoint inhibitors targeting the CTLA-4 and PD-1/PD-L1 pathways. However, although highly effective in some patients, immune checkpoint inhibitors are beneficial only in a limited fraction of patients, possibly because of the lack of enough cancer-specific immune cells, especially CD8+ cytotoxic T-lymphocytes (CTLs), in the host. On the other hand, studies on cancer vaccines, especially DC-based ones, have made significant progress in recent years. In particular, the identification and characterization of cross-presenting DCs have greatly advanced the strategy for the development of effective DC-based vaccines. In this review, we first summarize the surface markers and functional properties of the five major DC subsets. We then describe new approaches to induce antigen-specific CTLs by targeted delivery of antigens to cross-presenting DCs. In this context, the chemokine receptor XCR1 and its ligand XCL1, being selectively expressed by cross-presenting DCs and mainly produced by activated CD8+ T cells, respectively, provide highly promising molecular tools for this purpose. In the near future, CTL-inducing DC-based cancer vaccines may provide a new breakthrough in cancer immunotherapy alone or in combination with immune checkpoint inhibitors.

Efficacious Dendritic Cell Based Immunotherapy for Advanced Solid Tumors: Three Case Studies

Background and Aims: Dendritic cell (DC)-based immunotherapy is promising as a viable tool in cancer treatment. Dendritic cell (DC)-based vaccination can provoke antitumor T cell responses in vivo. These case studies examined feasibility and outcome of DC-based tumor vaccination for patients with advanced cancers. This approach has been used mostly in patients in the presence of defined tumor antigens. Experimental Design: Accessible tumor tissue was disrupted into single cell suspensions. Autologous DCs were prepared from adherent peripheral blood mononuclear cells and cultured in granulocyte macrophage colony-stimulating factor, interleukin and autologous plasma. Tumor cells and DCs were co-cultured in the presence of polyethylene glycol to generate the fusions. Fusion cells were quantified by determining the percentage of cells that co-express tumor and DC markers. Patients were vaccinated with three doses of DC (10 X 106 ) were administered after every 2 weeks’ intervals and assessed weekly for toxicity, and tumor response was assessed at 3 months after completion of vaccination. Results: Vaccination was well tolerated. No physical signs of autoimmunity were detected. There was no evidence of significant toxicity from vaccine or adjuvant. There was increased expression of T helper type 1 cytokines. Vaccination resulted in a significant reduction in the level of prostate-specific antigen (PSA) in the prostate cancer patient. Disease was stable upto 6 months in cases of breast and cervical cancer patients. Conclusion: DC-based vaccination can stimulate an antitumoral T cell response in patients with various cancers. This data indicates that vaccination with autologous tumor-pulsed DCs generated from peripheral blood is safe and can induce tumorspecific cellular cytotoxicity. Clinical responses are achievable, even in patients with advanced disease.

Vaccine Development Against SARS-CoV-2: From Virology to Vaccine Clinical Trials

An urgent vaccine development is required against the recent pandemic of a novel coronavirus. Currently, there is no approved vaccine against COVID-19. Vaccination is proved to be the most beneficial way to protect humans from infections. Several vaccine candidates have been conducted to different phases of clinical trials, and more vaccine candidates are on the way to enter the trials. Different vaccine types have developed, including inactivated virus vaccines, subunit-based vaccines, adenovirus- vector vaccines, DNA-based vaccines, DC-based vaccines, and mRNA-based vaccines. The mRNA- 1273 was the first vaccine candidate that started evaluating in the clinical trial. Also, AZD1222 is the first vaccine candidate that started phase II/III of clinical trials. Both of these vaccine candidates were considered as promising vaccine candidates against SARS-CoV-2. This review aims to overview and share various strategies to develop efficient therapeutic and preventive vaccines based on the origin, biology, structure, and immune-evasion of SARS-CoV-2.

Plasma-Activated Medium Potentiates the Immunogenicity of Tumor Cell Lysates for Dendritic Cell-Based Cancer Vaccines

Simple SummaryDendritic cells (DCs)-based anti-cancer vaccines displayed limited efficacy in clinical trials, mostly due to a lack of protocols for preparing immunogenic tumor antigens used in the vaccine. Here, a unique atmospheric pressure plasma jet was used to prepare a plasma-activated medium (PAM) which induced immunogenic cell death in tumor cells. This procedure increased the efficacy of tumor lysates in enhancing the immunogenicity of DCs according to their increased maturation, production of IL-12, and the capacity to induce cytotoxic CD8 T cells able to kill tumor cells. In contrast to the tumor lysates commonly used in DC vaccines, PAM-tumor lysates lacked the capacity to increase IL-10 production by DCs, and their potential to induce protumorogenic Th2 and regulatory T cells. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients.Autologous dendritic cells (DCs)-based vaccines are considered quite promising for cancer immunotherapy due to their exquisite potential to induce tumor antigen-specific cytotoxic T cells. However, a lack of efficient protocols for inducing immunogenic tumor antigens limits the efficacy of DC-based cancer vaccines. Here, we found that a plasma-activated medium (PAM) induces immunogenic cell death (ICD) in tumor cells but not in an immortalized L929 cell line or human peripheral blood mononuclear cells. PAM induced an accumulation of reactive oxygen species (ROS), autophagy, apoptosis, and necrosis in a concentration-dependent manner. The tumor lysates prepared after PAM treatment displayed increased immunogenicity in a model of human monocyte-derived DCs, compared to the lysates prepared by a standard freezing/thawing method. Mature DCs loaded with PAM lysates showed an increased maturation potential, as estimated by their increased expression of CD83, CD86, CD40, IL-12/IL-10 production, and attenuated PDL1 and ILT-4 expression, compared to the DCs treated with control tumor lysates. Moreover, in co-culture with allogeneic T cells, DCs loaded with PAM-lysates increased the proportion of cytotoxic IFN-γ+ granzyme A+ CD8+ T cells and IL-17A-producing T cells and preserved the Th1 response. In contrast, control tumor lysates-treated DCs increased the frequency of Th2 (CD4+IL-4+), CD4, and CD8 regulatory T cell subtypes, none of which was observed with DCs loaded with PAM-lysates. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients.

Human type 1 and type 2 conventional dendritic cells express indoleamine 2,3-dioxygenase 1 with functional effects on T cell priming.

Dendritic cells (DCs) are key regulators of the immune system that shape T cell responses. Regulation of T cell induction by DCs may occur via the intracellular enzyme indoleamine 2,3‐dioxygenase 1 (IDO), which catalyzes conversion of the essential amino acid tryptophan into kynurenine. Here, we examined the role of IDO in human peripheral blood plasmacytoid DCs (pDCs), and type 1 and type 2 conventional DCs (cDC1s and cDC2s). Our data demonstrate that under homeostatic conditions, IDO is selectively expressed by cDC1s. IFN‐γ or TLR ligation further increases IDO expression in cDC1s and induces modest expression of the enzyme in cDC2s, but not pDCs. IDO expressed by conventional DCs is functionally active as measured by kynurenine production. Furthermore, IDO activity in TLR‐stimulated cDC1s and cDC2s inhibits T cell proliferation in settings were DC‐T cell cell‐cell contact does not play a role. Selective inhibition of IDO1 with epacadostat, an inhibitor currently tested in clinical trials, rescued T cell proliferation without affecting DC maturation status or their ability to cross‐present soluble antigen. Our findings provide new insights into the functional specialization of human blood DC subsets and suggest a possible synergistic enhancement of therapeutic efficacy by combining DC‐based cancer vaccines with IDO inhibition.

Bombyx batryticatus Protein-Rich Extract Induces Maturation of Dendritic Cells and Th1 Polarization: A Potential Immunological Adjuvant for Cancer Vaccine.

Bombyx batryticatus, a protein-rich edible insect, is widely used as a traditional medicine in China. Several pharmacological studies have reported the anticancer activity of B. batryticatus extracts; however, the capacity of B. batryticatus extracts as immune potentiators for increasing the efficacy of cancer immunotherapy is still unverified. In the present study, we investigated the immunomodulatory role of B. batryticatus protein-rich extract (BBPE) in bone marrow-derived dendritic cells (BMDCs) and DC vaccine-immunized mice. BBPE-treated BMDCs displayed characteristics of mature immune status, including high expression of surface molecules (CD80, CD86, major histocompatibility complex (MHC)-I, and MHC-II), increased production of proinflammatory cytokines (tumor necrosis factor-α and interleukin-12p70), enhanced antigen-presenting ability, and reduced endocytosis. BBPE-treated BMDCs promoted naive CD4+ and CD8+ T-cell proliferation and activation. Furthermore, BBPE/ovalbumin (OVA)-pulsed DC-immunized mice showed a stronger OVA-specific multifunctional T-cell response in CD4+ and CD8+ T cells and a stronger Th1 antibody response than mice receiving differently treated DCs, which showed the enhanced protective effect against tumor growth in E.G7 tumor-bearing mice. Our data demonstrate that BBPE can be a novel immune potentiator for a DC-based vaccine in anticancer therapy.

Preventive cancer vaccination with P5 HER-2/neo-derived peptide-pulsed peripheral blood mononuclear cells in a mouse model of breast cancer.

This study compared the prophylactic effects from vaccines based on dendritic cells (DCs) and peripheral blood mononuclear cells (PBMCs) by pulsing the cells in-vitro with p5 peptide. The different test groups of mice were injected with free peptide or with peptide pulsed with DCs or PBMCs. Two weeks after the last booster dose, immunological tests were performed on splenocyte suspensions from three mice in each group and the remaining mice (5/each group) were evaluated for tumor growth and survival time. The levels of IFN-γ, granzyme B, and IL-10 were detected in T cells. Additionally, IFN-γ and perforin as well as mRNA levels of some genes associated with immune responses were assessed after challenging the splenocytes with TUBO cells. A significant increase was observed in frequency of CD4+ IFN-γ+, CD8+ IFN-γ+, and CD8+ granzyme B+ T cells, and the perforin of supernatants from mice in the DC and PBMC treatment groups. Significant expression levels of Fas ligand (FasL) and forkhead box P3 (Foxp3) were observed in the DC and PBMC groups. These responses led to smaller tumors and longer survival time in our mouse model of breast cancer. The efficacy of the PBMC-based vaccine in improving the protective immune response makes it a simpler and less expensive candidate vaccine compared with DC-based vaccines.

The subtle interplay between gamma delta T lymphocytes and dendritic cells: is there a role for a therapeutic cancer vaccine in the era of combinatorial strategies?

Human gamma delta (γδ) T cells represent heterogeneous subsets of unconventional lymphocytes with an HLA-unrestricted target cell recognition. γδ T cells display adaptive clonally restricted specificities coupled to a powerful cytotoxic function against transformed/injured cells. Dendritic cells (DCs) are documented to be the most potent professional antigen-presenting cells (APCs) able to induce adaptive immunity and support the innate immune response independently from T cells. Several data show that the cross-talk of γδ T lymphocytes with DCs can play a crucial role in the orchestration of immune response by bridging innate to adaptive immunity. In the last decade, DCs, as well as γδ T cells, have been of increasing clinical interest, especially as monotherapy for cancer immunotherapy, even though with unpredictable results mainly due to immune suppression and/or tumor-immune escape. For these reasons, new vaccine strategies have to be explored to reach cancer immunotherapy's full potential. The effect of DC-based vaccines on γδ T cell is less extensively investigated, and a combinatorial approach using DC-based vaccines with γδ T cells might promote a strong synergy for long-term tumor control and protection against escaping tumor clones. Here, we discuss the therapeutic potential of the interaction between DCs and γδ T cells to improve cancer vaccination. In particular, we describe the most relevant and updated evidence of such combinatorial approaches, including the use of Zoledronate, Interleukin-15, and protamine RNA, also looking towards future strategies such as CAR therapies.

Activity-regulated cytoskeleton-associated protein/activity-regulated gene 3.1 (Arc/Arg3.1) enhances dendritic cell vaccination in experimental melanoma

ABSTRACT Dendritic cell (DC) vaccination has proven to be an effective and safe adjuvant for cancer immunotherapies. As the presence of DCs within the tumor microenvironment promotes adaptive antitumor immunity, enhancement of DC migration toward the tumor microenvironment following DC vaccination might represent one possible approach to increase its therapeutic efficacy. While recent findings suggest the activity-regulated cytoskeleton-associated protein/activity-regulated gene 3.1 (Arc/Arg3.1) as critical regulator of DC migration in the context of autoimmune diseases, we aimed to investigate the impact of Arc/Arg3.1 expression for DC-based cancer vaccines. To this end, DC migration capacity as well as the induction of T cell-mediated antitumor immunity was assessed in an experimental B16 melanoma model with Arc/Arg3.1−/- and Arc/Arg3.1-expressing BMDCs applied as a subcutaneous vaccine. While antigen presentation on DCs was critical for unleashing effective T cell mediated antitumor immune responses, Arc/Arg3.1 expression enhanced DC migration toward the tumor and secondary lymphoid organs. Moreover, Arc/Arg3.1-expressing BMDCs shape the tumor immune microenvironment by facilitating tumor recruitment of antigen-specific effector T cells. Thus, Arc/Arg3.1 may represent a novel therapeutic target in DCs in order to increase the therapeutic efficacy of DC vaccination.

Multiple Myeloma and Dendritic Cell Vaccines

Despite advances in the treatment of multiple myeloma, most of patients after its completion retain minimal residual disease (MRD-positive status), which increases the risk of relapse. Antigen-specific immunotherapy of tumors contributes to improving the clinical outcomes in such patients by the killing of cancer drug resistant clone of tumor cells without any damage to normal tissues. Dendritic cells (DC) are antigen-presenting elements with the main function of antigen-capturing, processing, and presenting them to naive T-lymphocytes for the activation of immune response against the captured antigen. The unique ability of DC to activate T-helpers and cytotoxic T-lymphocytes as well as to target thereby the immune reactions was used in developing DC-based tumor immunotherapy. This approach suggests the implementation of the so-called ‘DC-vaccines’. The clinical trials performed by now also showed the results of using DC-vaccines in various tumors including hematological ones. On the whole, according to the studies DC-vaccines are characterized by satisfactory safety profile, moderate immunological activity, and moderate clinical efficacy. The present review provides the results of clinical trials dealing with the use of DC-based vaccines in multiple myeloma patients. Besides, the potentials of improving the clinical efficacy of this therapy are discussed.

Cell therapies in ovarian cancer.

Epithelial ovarian cancer (EOC) is the most important cause of gynecological cancer-related mortality. Despite improvements in medical therapies, particularly with the incorporation of drugs targeting homologous recombination deficiency, EOC survival rates remain low. Adoptive cell therapy (ACT) is a personalized form of immunotherapy in which autologous lymphocytes are expanded, manipulated ex vivo, and re-infused into patients to mediate cancer rejection. This highly promising novel approach with curative potential encompasses multiple strategies, including the adoptive transfer of tumor-infiltrating lymphocytes, natural killer cells, or engineered immune components such as chimeric antigen receptor (CAR) constructs and engineered T-cell receptors. Technical advances in genomics and immuno-engineering have made possible neoantigen-based ACT strategies, as well as CAR-T cells with increased cell persistence and intratumoral trafficking, which have the potential to broaden the opportunity for patients with EOC. Furthermore, dendritic cell-based immunotherapies have been tested in patients with EOC with modest but encouraging results, while the combination of DC-based vaccination as a priming modality for other cancer therapies has shown encouraging results. In this manuscript, we provide a clinically oriented historical overview of various forms of cell therapies for the treatment of EOC, with an emphasis on T-cell therapy.

Mixed cultures of allogeneic dendritic cells are phenotypically and functionally stable - a potential for primary cell-based "off the shelf" product generation.

Vaccination against tumors using antigen-pulsed dendritic cell (DC) vaccines has greatly evolved over the last decade, with hundreds of active human clinical trials well on the way. The use of an autologous source for DC-based vaccine therapeutics remains the obvious choice in the majority of clinical studies; however, novel evidence suggests that an allogeneic source of DCs can yield success if administered in the right context. One of the challenges facing successful DC vaccination protocols is the generation of large enough numbers of DCs intended for vaccination and standardization of these procedures. In addition, variations in the quality of DC vaccines due to donor-to-donor variation represent an important therapeutic factor. To this day it has not been shown whether DCs from different donors can readily co-exist within the same co-culture for the extended periods required for vaccine manufacture. We demonstrate that generation of allogeneic DC co-cultures, generated from multiple unrelated donors, allows the preservation of their phenotypical and functional properties in vitro for up to 72 hours. Therefore, in the case of an allogeneic vaccination approach, one could ensure large numbers of DCs generated from a primary cell source intended for multiple vaccinations. By generating large amounts of ex vivo manufactured DCs from multiple donors, this would represent the possibility to ensure sufficient amounts of equipotent “off the shelf” product that could e.g. be used for an entire cohort of patients within a study.

DC-Based Vaccines for Cancer Immunotherapy.

As the sentinels of the immune system, dendritic cells (DCs) play a critical role in initiating and regulating antigen-specific immune responses. Cross-priming, a process that DCs activate CD8 T cells by cross-presenting exogenous antigens onto their MHCI (Major Histocompatibility Complex class I), plays a critical role in mediating CD8 T cell immunity as well as tolerance. Current DC vaccines have remained largely unsuccessful despite their ability to potentiate both effector and memory CD8 T cell responses. There are two major hurdles for the success of DC-based vaccines: tumor-mediated immunosuppression and the functional limitation of the commonly used monocyte-derived dendritic cells (MoDCs). Due to their resistance to tumor-mediated suppression as inert vesicles, DC-derived exosomes (DCexos) have garnered much interest as cell-free therapeutic agents. However, current DCexo clinical trials have shown limited clinical benefits and failed to generate antigen-specific T cell responses. Another exciting development is the use of naturally circulating DCs instead of in vitro cultured DCs, as clinical trials with both human blood cDC2s (type 2 conventional DCs) and plasmacytoid DCs (pDCs) have shown promising results. pDC vaccines were particularly encouraging, especially in light of promising data from a recent clinical trial using a human pDC cell line, despite pDCs being considered tolerogenic and playing a suppressive role in tumors. However, how pDCs generate anti-tumor CD8 T cell immunity remains poorly understood, thus hindering their clinical advance. Using a pDC-targeted vaccine model, we have recently reported that while pDC-targeted vaccines led to strong cross-priming and durable CD8 T cell immunity, cross-presenting pDCs required cDCs to achieve cross-priming in vivo by transferring antigens to cDCs. Antigen transfer from pDCs to bystander cDCs was mediated by pDC-derived exosomes (pDCexos), which similarly required cDCs for cross-priming of antigen-specific CD8 T cells. pDCexos thus represent a new addition in our arsenal of DC-based cancer vaccines that would potentially combine the advantage of pDCs and DCexos.

Improvement of DC-based vaccines using adjuvant TLR4-binding 60S acidic ribosomal protein P2 and immune checkpoint inhibitors.

Cancer immunotherapy has fewer side effects and higher efficiency than conventional methods. Dendritic cell (DC)-based vaccine, a cancer immunotherapeutic, is prepared by processing mature DCs and pulsing with tumor antigen peptide ex vivo, to induce the activation of tumor-specific T lymphocytes followed by tumor clearance in vivo. Unfortunately, clinical trials of this method mostly failed due to low patient response, possibly due to the absence of novel adjuvants that induce DC maturation through Toll-like receptor (TLR) signals. Interestingly, immune checkpoint inhibitor (ICI) therapy has shown remarkable anti-tumor efficacy when combined with cancer vaccines. In this study, we identified 60S acidic ribosomal protein P2 (RPLP2) through pull-down assay using human cancer cells derived proteins that binds to Toll-like receptor 4 (TLR4). Recombinant RPLP2 induced maturation and activation of DCs in vitro. This DC-based vaccine, followed by pulsing with tumor-specific antigen, has shown to significantly increase tumor-specific CD8+IFN-γ+ T cells, and improved both tumor prevention and tumor treatment effects in vivo. The adjuvant effects of RPLP2 were shown to be dependent on TLR4 using TLR4 knockout mice. Moreover, ICIs that suppress the tumor evasion mechanism showed synergistic effects on tumor treatment when combined with these vaccines.