Current approaches in dendritic cell generation and future implications for cancer immunotherapy

Current and Future Trends of Colorectal Cancer Treatment: Exploring Advances in Immunotherapy

Cancer of the colon and rectum (CRC) has been identified among the three most prevalent types of cancer and cancer-related deaths for both sexes. Even though significant progress in surgical and chemotherapeutic techniques has markedly improved disease-free and overall survival rates in contrast to those three decades ago, recent years have seen a stagnation in these improvements. This underscores the need for new therapies aiming to augment patient outcomes. A number of emerging strategies, such as immune checkpoint inhibitors (ICIs) and adoptive cell therapy (ACT), have exhibited promising outcomes not only in preclinical but also in clinical settings. Additionally, a thorough appreciation of the underlying biology has expanded the scope of research into potential therapeutic interventions. For instance, the pivotal role of altered telomere length in early CRC carcinogenesis, leading to chromosomal instability and telomere dysfunction, presents a promising avenue for future treatments. Thus, this review explores the advancements in CRC immunotherapy and telomere-targeted therapies, examining potential synergies and how these novel treatment modalities intersect to potentially enhance each other's efficacy, paving the way for promising future therapeutic advancements.

Stimuli-Responsive Hydrogel Microcapsules Harnessing the COVID-19 Immune Response for Cancer Therapeutics

The combination of gene therapy and immunotherapy concepts, along recent advances in DNA nanotechnology, have the potential to provide important tools for cancer therapies. We present the development of stimuli-responsive microcapsules, loaded with a viral immunogenetic agent, harnessing the immune response against the Coronavirus Disease 2019, COVID-19, to selectively attack liver cancer cells (hepatoma) or recognize breast cancer or hepatoma, by expression of green fluorescence protein, GFP. The pH-responsive microcapsules, modified with DNA-tetrahedra nanostructures, increased hepatoma permeation by 50 %. Incorporation of a GFP-encoding lentivirus vector inside the tumor-targeting pH-stimulated miRNA-triggered and Alpha-fetoprotein-dictated microcapsules enables the demonstration of neoplasm selectivity, with approximately 5,000-, 8,000- and 50,000-fold more expression in the cancerous cells, respectively. The incorporation of the SARS-CoV-2 spike protein in the gene vector promotes specific recognition of the immune-evading hepatoma by the COVID-19-analogous immune response, which leads to cytotoxic and inflammatory activity, mediated by serum components taken from vaccinated or recovered COVID-19 patients, resulting in effective elimination of the hepatoma (>85 % yield).

Tumor Vaccines: Unleashing the Power of the Immune System to Fight Cancer

This comprehensive review delves into the rapidly evolving arena of cancer vaccines. Initially, we examine the intricate constitution of the tumor microenvironment (TME), a dynamic factor that significantly influences tumor heterogeneity. Current research trends focusing on harnessing the TME for effective tumor vaccine treatments are also discussed. We then provide a detailed overview of the current state of research concerning tumor immunity and the mechanisms of tumor vaccines, describing the complex immunological processes involved. Furthermore, we conduct an exhaustive analysis of the contemporary research landscape of tumor vaccines, with a particular focus on peptide vaccines, DNA/RNA-based vaccines, viral-vector-based vaccines, dendritic-cell-based vaccines, and whole-cell-based vaccines. We analyze and summarize these categories of tumor vaccines, highlighting their individual advantages, limitations, and the factors influencing their effectiveness. In our survey of each category, we summarize commonly used tumor vaccines, aiming to provide readers with a more comprehensive understanding of the current state of tumor vaccine research. We then delve into an innovative strategy combining cancer vaccines with other therapies. By studying the effects of combining tumor vaccines with immune checkpoint inhibitors, radiotherapy, chemotherapy, targeted therapy, and oncolytic virotherapy, we establish that this approach can enhance overall treatment efficacy and offset the limitations of single-treatment approaches, offering patients more effective treatment options. Following this, we undertake a meticulous analysis of the entire process of personalized cancer vaccines, elucidating the intricate process from design, through research and production, to clinical application, thus helping readers gain a thorough understanding of its complexities. In conclusion, our exploration of tumor vaccines in this review aims to highlight their promising potential in cancer treatment. As research in this field continues to evolve, it undeniably holds immense promise for improving cancer patient outcomes.

Colorectal Cancer Immunotherapy: State of the Art and Future Directions

Cancer immunotherapy has become an indispensable mode of treatment for a multitude of solid tumor cancers. Colorectal cancer (CRC) has been one of the many cancer types to benefit from immunotherapy, especially in advanced disease where standard treatment fails to prevent recurrence or results in poor survival. The efficacy of immunotherapy in CRC has not been without challenge, as early clinical trials observed dismal responses in unselected CRC patients treated with checkpoint inhibitors. Many studies and clinical trials have since refined immunotherapies available for CRC, solidifying immunotherapy as a powerful asset for CRC treatment. This review article examines CRC immunotherapies, from their foundation, through emerging avenues for improvement, to future directions.

Adjuvant dendritic cell-based immunotherapy after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in patients with malignant peritoneal mesothelioma: a phase II clinical trial

BACKGROUND

Malignant peritoneal mesothelioma (MPM) is an aggressive malignancy with a poor prognosis. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) improves survival outcomes, but recurrence rates remain high. Dendritic cell-based immunotherapy (DCBI) showed promising results in patients with pleural mesothelioma. The primary aim of this trial was to determine feasibility of adjuvant DCBI after CRS-HIPEC.

METHODS

This open-label, single-center, phase II clinical trial, performed in the Erasmus MC Cancer Institute Rotterdam, the Netherlands, included patients with epithelioid MPM. 4-6 weeks before CRS-HIPEC leukapheresis was performed. 8-10 weeks after surgery, DCBI was administered three times biweekly. Feasibility was defined as administration of at least three adjuvant vaccinations in 75% of patients. Comprehensive immune cell profiling was performed on peripheral blood samples prior to and during treatment.

RESULTS

All patients who received CRS-HIPEC (n=16) were successfully treated with adjuvant DCBI. No severe toxicity related to DCBI was observed. Median progression-free survival (PFS) was 12 months (IQR 5-23) and median overall survival was not reached. DCBI was associated with increased proliferation of circulating natural killer cells and CD4+ T-helper (Th) cells. Co-stimulatory molecules, including ICOS, HLA-DR, and CD28 were upregulated predominantly on memory or proliferating Th-cells and minimally on CD8+ cytotoxic T-lymphocytes (CTLs) after treatment. However, an increase in CD8+ terminally differentiated effector memory (Temra) cells positively correlated with PFS, whereas co-expression of ICOS and Ki67 on CTLs trended towards a positive correlation.

CONCLUSIONS

Adjuvant DCBI after CRS-HIPEC in patients with MPM was feasible and safe, and showed promising survival outcomes. DCBI had an immune modulatory effect on lymphoid cells and induced memory T-cell activation. Moreover, an increase of CD8+ Temra cells was more pronounced in patients with longer PFS. These data provide rationale for future combination treatment strategies.

TRIAL REGISTRATION NUMBER

NTR7060; Dutch Trial Register (NTR).

COVID-19 immunotherapy: Treatment based on the immune cell-mediated approaches

Multiple efforts are currently underway to control and treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19) worldwide. Despite all efforts, the virus that emerged in Wuhan city has rapidly spread globally and led to a public health emergency of international concern (PHEIC) due to the lack of approved antiviral therapy. Nevertheless, SARS-CoV-2 has had a significant influence on the evolution of cellular therapeutic approaches. Adoptive immune cell therapy is innovative and offers either promising prophylactic or therapy for patients with moderate-to-severe COVID-19. This approach is aimed at developing safety and providing secure and effective therapy in combination with standard therapy for all COVID-19 infected individuals. Based on the effective results of previous studies on both inflammatory and autoimmune diseases, various immune cell therapies against COVID-19 have been reviewed and discussed. It must be considered that the application of cell therapy for treatment and to eliminate infected respiratory cells could result in excessive inflammation, so this treatment must be used in combination with other treatments, despite its many beneficial efforts.

Modulation of the immune response by heterogeneous monocytes and dendritic cells in lung cancer

Different subpopulations of monocytes and dendritic cells (DCs) may have a key impact on the modulation of the immune response in malignancy. In this review, we summarize the monocyte and DCs heterogeneity and their function in the context of modulating the immune response in cancer. Subgroups of monocytes may play opposing roles in cancer, depending on the tumour growth and progression as well as the type of cancer. Monocytes can have pro-tumour and anti-tumour functions and can also differentiate into monocyte-derived DCs (moDCs). MoDCs have a similar antigen presentation ability as classical DCs, including cross-priming, a process by which DCs activate CD8 T-cells by cross-presenting exogenous antigens. DCs play a critical role in generating anti-tumour CD8 T-cell immunity. DCs have plastic characteristics and show distinct phenotypes depending on their mature state and depending on the influence of the tumour microenvironment. MoDCs and other DC subsets have been attracting increased interest owing to their possible beneficial effects in cancer immunotherapy. This review also highlights key strategies deploying specific DC subpopulations in combination with other therapies to enhance the anti-tumour response and summarizes the latest ongoing and completed clinical trials using DCs in lung cancer.

Dendritic cell therapy with CD137L-DC-EBV-VAX in locally recurrent or metastatic nasopharyngeal carcinoma is safe and confers clinical benefit

INTRODUCTION

Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC), and provides a target for a dendritic cell (DC) vaccine. CD137 ligand (CD137L) expressed on antigen presenting cells, costimulates CD137-expressing T cells, and reverse CD137L signaling differentiates monocytes to CD137L-DC, a type of DC, which is more potent than classical DC in stimulating T cells.

METHODS

In this phase I study, patients with locally recurrent or metastatic NPC were administered CD137L-DC pulsed with EBV antigens (CD137L-DC-EBV-VAX).

RESULTS

Of the 12 patients treated, 9 received full 7 vaccine doses with a mean administered cell count of 23.9 × 10⁶ per dose. Treatment was well tolerated with only 4 cases of grade 1 related adverse events. A partial response was obtained in 1 patient, and 4 patients are still benefitting from a progression free survival (PFS) of currently 2-3 years. The mean pre-treatment neutrophil: lymphocyte ratio was 3.4 and a value of less than 3 was associated with prolonged median PFS. Progressors were characterized by a high frequency of naïve T cells but a low frequency of CD8⁺ effector T cells while patients with a clinical benefit (CB) had a high frequency of memory T cells. Patients with CB had lower plasma EBV DNA levels, and a reduction after vaccination.

CONCLUSION

CD137L-DC-EBV-VAX was well tolerated. The use of CD137L-DC-EBV-VAX is demonstrated to be safe. Consistent results were obtained from all 12 patients, indicating that CD137L-DC-EBV-VAX induces an anti-EBV and anti-NPC immune response, and warranting further studies in patients post effective chemotherapy.

PRECIS

The first clinical testing of CD137L-DC, a new type of monocyte-derived DC, finds that CD137L-DC are safe, and that they can induce an immune response against Epstein-Barr virus-associated nasopharyngeal carcinoma that leads to tumor regression or prevents tumor progression.

Prospects of immune checkpoint blockade and vaccine-based immunotherapy for glioblastoma

Glioblastoma multiforme (GBM) is the most prevalent primary brain tumor endowed with a dismal prognosis. Nowadays, immunotherapy in a particular immune checkpoint blockade and therapeutic vaccines are being extensively pursued. Yet, several characteristics of GBM may impact such immunotherapeutic approaches. This includes tumor heterogeneity, the relatively low mutational load of primary GBM, insufficient delivery of antibodies to tumor parenchyma and the unique immunosuppressive microenvironment of GBM. Moreover, standard treatment of GBM, comprising temozolomide chemotherapy, radiotherapy and in most instances the application of glucocorticoids for management of brain edema, results in a further increased immunosuppression. This review will provide a brief introduction to the principles of vaccine-based immunotherapy and give an overview of the current clinical studies, which employed immune checkpoint inhibitors, oncolytic viruses-based vaccination, cell-based and peptide-based vaccines. Recent experiences as well as the latest developments are reviewed. Overcoming obstacles, which limit the induction and long-term immune response against GBM when using vaccination approaches, are necessary for the implementation of effective immunotherapy of GBM.

Targeting the MHC Class II antigen presentation pathway in cancer immunotherapy

The success of immunotherapy relies on the participation of all arms of the immune system and the role of CD4+ T lymphocytes in preventing tumor growth is now well established. Understanding how tumors evade immune responses holds the key to the development of cancer immunotherapies. In this review, we discuss how MHC Class II expression varies in cancer cells and how this influences antitumor immune responses. We also discuss the means that are currently available for harnessing the MHC Class II antigen presentation pathway for the development of efficient vaccines to activate the immune system against cancer.

Activation of antigen-exposed iMC-DCs at the "right place" and "right time" promotes potent anti-tumor immunity

To better control the “licensing” of pro-Th1 dendritic cells (DCs), Spencer and colleagues have developed a synthetic ligand-inducible chimeric receptor, iMyD88/CD40 (iMC), incorporating synergistic Toll-like receptor (TLR) and costimulatory signaling elements, permitting DC regulation in vivo within the context of an immunological synapse. This novel technology results in potent anti-cancer activity.

Therapeutic cancer vaccines for pediatric malignancies: advances, challenges, and emerging technologies

Though outcomes for pediatric cancer patients have significantly improved over the past several decades, too many children still experience poor outcomes and survivors suffer lifelong, debilitating late effects after conventional chemotherapy, radiation, and surgical treatment. Consequently, there has been a renewed focus on developing novel targeted therapies to improve survival outcomes. Cancer vaccines are a promising type of immunotherapy that leverage the immune system to mediate targeted, tumor-specific killing through recognition of tumor antigens, thereby minimizing off-target toxicity. As such, cancer vaccines are orthogonal to conventional cancer treatments and can therefore be used alone or in combination with other therapeutic modalities to maximize efficacy. To date, cancer vaccination has remained largely understudied in the pediatric population. In this review, we discuss the different types of tumor antigens and vaccine technologies (dendritic cells, peptides, nucleic acids, and viral vectors) evaluated in clinical trials, with a focus on those used in children. We conclude with perspectives on how advances in combination therapies, tumor antigen (eg, neoantigen) selection, and vaccine platform optimization can be translated into clinical practice to improve outcomes for children with cancer.

DCs-based therapies: potential strategies in severe SARS-CoV-2 infection

Pneumonia caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is spreading globally. There have been strenuous efforts to reveal the mechanisms that the host defends itself against invasion by this virus. The immune system could play a crucial role in virus infection. Dendritic cell as sentinel of the immune system plays an irreplaceable role. Dendritic cells-based therapeutic approach may be a potential strategy for SARS-CoV-2 infection. In this review, the characteristics of coronavirus are described briefly. We focus on the essential functions of dendritic cell in severe SARS-CoV-2 infection. Basis of treatment based dendritic cells to combat coronavirus infections is summarized. Finally, we propose that the combination of DCs based vaccine and other therapy is worth further study.

Engineering anti-cancer nanovaccine based on antigen cross-presentation

Dendritic cells (DCs) present exogenous antigens on major histocompatibility complex (MHC) class I molecules, thereby activating CD8⁺ T cells, contributing to tumor elimination through a mechanism known as antigen cross-presentation. A variety of factors such as maturation state of DCs, co-stimulatory signals, T-cell microenvironment, antigen internalization routes and adjuvants regulate the process of DC-mediated antigen cross-presentation. Recently, the development of successful cancer immunotherapies may be attributed to the ability of DCs to cross-present tumor antigens. In this review article, we focus on the underlying mechanism of antigen cross-presentation and ways to improve antigen cross-presentation in different DC subsets. We have critically summarized the recent developments in the generation of novel nanovaccines for robust CD8⁺ T-cell response in cancer. In this context, we have reviewed nanocarriers that have been used for cancer immunotherapeutics based on antigen cross-presentation mechanism. Additionally, we have also expressed our views on the future applications of this mechanism in curing cancer.

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.

Dendritic cells loaded with CD44+ CT-26 colon cell lysate evoke potent antitumor immune responses

Increasing evidence supports the concept that cancer stem cells (CSCs) are responsible for cancer progression and metastasis, therapy resistance and relapse. In addition to conventional therapies for colon cancer, the development of immunotherapies targeting cancer stem cells appears to be a promising strategy to suppress tumor recurrence and metastasis. In the present study, dendritic cells (DCs) were pulsed with whole-tumor cell lysates or total RNA of CD44⁺ colon cancer stem cells (CCSCs) isolated from mouse colon adenocarcinoma CT-26 cell cultures and investigated for their antitumor immunity against CCSCs in vivo and in vitro. In a model of colon adenocarcinoma using BALB/c mice, a sequential reduction in tumor volume and weight was associated with an extended survival in tumor-bearing mice vaccinated with DCs pulsed with RNA or CCSC lysate. In addition, a lactate dehydrogenase assay indicated that cytotoxic T-cells derived from the treated mice exhibited strong cytotoxic activity. Additionally, an enzyme-linked immunosorbent assay revealed that the cytotoxic T-cells of the treated mice released higher levels of interferon-γ against CCSCs compared with those of the control group. In all experiments, the antitumor efficacy of the lysate-pulsed DC-treated and RNA-pulsed DC-treated groups were significantly higher compared with that of the DC-treated and control groups. The results of the present study indicated the potential use of DCs pulsed with cancer stem cell lysates as a potent therapeutic antigen to target CSCs in colon cancer. Additionally, the results provided a rationale for using lysate-pulsed DCs in vivo to eliminate residual tumor deposits in post-operative patients.

Dendritic Cell-Based and Other Vaccination Strategies for Pediatric Cancer

Dendritic cell-based and other vaccination strategies that use the patient’s own immune system for the treatment of cancer are gaining momentum. Most studies of therapeutic cancer vaccination have been performed in adults. However, since cancer is one of the leading causes of death among children past infancy in the Western world, the hope is that this form of active specific immunotherapy can play an important role in the pediatric population as well. Since children have more vigorous and adaptable immune systems than adults, therapeutic cancer vaccines are expected to have a better chance of creating protective immunity and preventing cancer recurrence in pediatric patients. Moreover, in contrast to conventional cancer treatments such as chemotherapy, therapeutic cancer vaccines are designed to specifically target tumor cells and not healthy cells or tissues. This reduces the likelihood of side effects, which is an important asset in this vulnerable patient population. In this review, we present an overview of the different therapeutic cancer vaccines that have been studied in the pediatric population, with a main focus on dendritic cell-based strategies. In addition, new approaches that are currently being investigated in clinical trials are discussed to provide guidance for further improvement and optimization of pediatric cancer vaccines.

The clinical application of cancer immunotherapy based on naturally circulating dendritic cells

Dendritic cells (DCs) can initiate and direct adaptive immune responses. This ability is exploitable in DC vaccination strategies, in which DCs are educated ex vivo to present tumor antigens and are administered into the patient with the aim to induce a tumor-specific immune response. DC vaccination remains a promising approach with the potential to further improve cancer immunotherapy with little or no evidence of treatment-limiting toxicity. However, evidence for objective clinical antitumor activity of DC vaccination is currently limited, hampering the clinical implementation. One possible explanation for this is that the most commonly used monocyte-derived DCs may not be the best source for DC-based immunotherapy. The novel approach to use naturally circulating DCs may be an attractive alternative. In contrast to monocyte-derived DCs, naturally circulating DCs are relatively scarce but do not require extensive culture periods. Thereby, their functional capabilities are preserved, the reproducibility of clinical applications is increased, and the cells are not dysfunctional before injection. In human blood, at least three DC subsets can be distinguished, plasmacytoid DCs, CD141⁺ and CD1c⁺ myeloid/conventional DCs, each with distinct functional characteristics. In completed clinical trials, either CD1c⁺ myeloid DCs or plasmacytoid DCs were administered and showed encouraging immunological and clinical outcomes. Currently, also the combination of CD1c⁺ myeloid and plasmacytoid DCs as well as the intratumoral use of CD1c⁺ myeloid DCs is under investigation in the clinic. Isolation and culture strategies for CD141⁺ myeloid DCs are being developed. Here, we summarize and discuss recent clinical developments and future prospects of natural DC-based immunotherapy.

The clinical application of cancer immunotherapy based on naturally circulating dendritic cells

Dendritic cells (DCs) can initiate and direct adaptive immune responses. This ability is exploitable in DC vaccination strategies, in which DCs are educated ex vivo to present tumor antigens and are administered into the patient with the aim to induce a tumor-specific immune response. DC vaccination remains a promising approach with the potential to further improve cancer immunotherapy with little or no evidence of treatment-limiting toxicity. However, evidence for objective clinical antitumor activity of DC vaccination is currently limited, hampering the clinical implementation. One possible explanation for this is that the most commonly used monocyte-derived DCs may not be the best source for DC-based immunotherapy. The novel approach to use naturally circulating DCs may be an attractive alternative. In contrast to monocyte-derived DCs, naturally circulating DCs are relatively scarce but do not require extensive culture periods. Thereby, their functional capabilities are preserved, the reproducibility of clinical applications is increased, and the cells are not dysfunctional before injection. In human blood, at least three DC subsets can be distinguished, plasmacytoid DCs, CD141+ and CD1c+ myeloid/conventional DCs, each with distinct functional characteristics. In completed clinical trials, either CD1c+ myeloid DCs or plasmacytoid DCs were administered and showed encouraging immunological and clinical outcomes. Currently, also the combination of CD1c+ myeloid and plasmacytoid DCs as well as the intratumoral use of CD1c+ myeloid DCs is under investigation in the clinic. Isolation and culture strategies for CD141+ myeloid DCs are being developed. Here, we summarize and discuss recent clinical developments and future prospects of natural DC-based immunotherapy.

The Journey of in vivo Virus Engineered Dendritic Cells From Bench to Bedside: A Bumpy Road

Dendritic cells (DCs) are recognized as highly potent antigen-presenting cells that are able to stimulate cytotoxic T lymphocyte (CTL) responses with antitumor activity. Consequently, DCs have been explored as cellular vaccines in cancer immunotherapy. To that end, DCs are modified with tumor antigens to enable presentation of antigen-derived peptides to CTLs. In this review we discuss the use of viral vectors for in situ modification of DCs, focusing on their clinical applications as anticancer vaccines. Among the viral vectors discussed are those derived from viruses belonging to the families of the Poxviridae, Adenoviridae, Retroviridae, Togaviridae, Paramyxoviridae, and Rhabdoviridae. We will further shed light on how the combination of viral vector-based vaccination with T-cell supporting strategies will bring this strategy to the next level.

Mesenchymal Stromal Stem Cell-Derived Microvesicles Enhance Tumor Lysate Pulsed Dendritic Cell Stimulated Autologous T lymphocyte Cytotoxicity

Background

Immunotherapy is one promising therapeutic strategy against glioma, an aggressive form of brain cancer. Previous studies have demonstrated that multiple tumor antigens exist and can be used to induce tumor specific T cell responses. Furthermore, recently it was shown that TLR4-primed mesenchymal stem cells (MSCs), also known as MSC1, mostly elaborate pro-inflammatory mediators. Compared to MSCs, MSC-derived microvesicles (MVs) have advantageous properties that present them as stable, long lasting effectors with no risk of immune rejection. Therefore, peripheral blood monocyte derived dendritic cells (MoDCs) have been used to load tumor antigens and stimulate T cell mediated responses in the presence of MSC1-derived MVs in vitro.

Methods

The B92 tumor cell line was heated to 43^°C for 90 min prior to preparation of tumor cell lysates. MVs were purified by differential ultracentrifugation after isolation, stimulation of proliferation and treatment of MSCs. Autologous T cells isolated from non-adherent cells were harvested during the procedure to generate MoDCs and then incubated with heat stressed tumor cell lysate pulsed DCs in the presence of MSC1-derived MVs. T cells were then co-cultured with tumor cells in 96-well plates at a final volume of 200 μl CM at an effector: target ratio of 100:1 to determine their specific cytotoxic activity.

Results

Flow cytometric analysis, T cell mediated cytotoxicity showed that heat stressed tumor antigen pulsed MoDCs and MSC1-derived MVs primed T cells elicited non-significantly enhanced cytotoxic activity toward B92 tumor cells (P≥0.05).

Conclusion

These findings may offer new insights into tumor antigen presenting technology involving dendritic cells and MSC1-derived MVs. Further exploration of the potential of such nanoscale particles in immunotherapy and in novel cancer vaccine settings appears warranted.

MAGE3 and Survivin activated dendritic cell immunotherapy for the treatment of non-small cell lung cancer

Dendritic cell (DC) immunotherapy is an optimal cancer treatment, resulting in its emergence as a therapeutic choice; however, there are limited studies investigating dual antigen-pulsed DC immunotherapy in non-small cell lung cancer (NSCLC). In order to determine the effect of a recombinant melanoma-associated antigen (rMAGE-3) and recombinant Survivin (rSurvivin) peptide-pulsed DC immunotherapy in patients with NSCLC, the present clinical study was performed. DC immunotherapy was generated from the monocytes of patients with NSCLC and primed with rMAGE-3 and rSurvivin peptides. The present open-label, non-randomised study enrolled 16 patients with histologically confirmed stage I-IIIB NSCLC between December 2013 and October 2014. A prime immunotherapy (9.1×10⁷ cells/dose) and a single boost (8.2×10⁷ cells/dose) were administered 1 month apart intradermally and the patients were evaluated for immunological and clinical response. DC immunotherapy was well tolerated, with no serious adverse events. There was a single incidence of grade 1 fever, chills and fatigue. Out of the 16 patients enrolled, 11 patients showed stable disease and 5 showed disease progression. There was a significant increase in IFN-γ expression on day 60 vs. day 0 (P=0.048). An increasing trend in the mean cluster of differentiation (CD)4:CD8 values of day 30 and day 90 was observed, but this was not significant. The present study established that DCs primed with rMAGE-3 and rSurvivin may be used in NSCLC treatment. However, a larger study is required to address prominent issues, including secretion of immunosuppressive cytokines and mechanisms of tumour escape from immune surveillance. Several factors associated with the manufacturing and quality of immunotherapy also require standardisation.

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

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

Signal transducer and activator of transcription 3 in myeloid-derived suppressor cells: an opportunity for cancer therapy

Cancer progression is in part determined by interactions between cancer cells and stromal cells in the tumor microenvironment (TME). The identification of cytotoxic tumor-infiltrating lymphocytes has instigated research into immune stimulating cancer therapies. Although a promising direction, immunosuppressive mechanisms exerted at the TME hamper its success. Myeloid-derived suppressor cells (MDSCs) have come to the forefront as stromal cells that orchestrate the immunosuppressive TME. Consequently, this heterogeneous cell population has been the object of investigation. Studies revealed that the transcription factor signal transducer and activator of transcription 3 (STAT3) largely dictates the recruitment, activation and function of MDSCs in the TME. Therefore, this review will focus on the role of this key transcription factor during the MDSC's life cycle and on the therapeutic opportunities it offers.

Generation of mouse and human dendritic cells in vitro

Dendritic cells (DC) that can orchestrate immune responses and maintain host homeostasis, are indispensable components of the immune system. Although distributed widely in many lymphoid and non-lymphoid tissues, their rarity in number has become a limiting factor for DC related research and therapies. Therefore, methods for efficiently generating large numbers of DC resembling their in vivo counterparts are urgently needed for DC related research and therapies. Herein we summarize the current methods for generating mouse and human DC in vitro and hope that these will facilitate both studies of DC biology and their clinical applications.

Primary Human Blood Dendritic Cells for Cancer Immunotherapy-Tailoring the Immune Response by Dendritic Cell Maturation

Dendritic cell (DC)-based cancer vaccines hold the great promise of tipping the balance from tolerance of the tumor to rejection. In the last two decades, we have gained tremendous knowledge about DC-based cancer vaccines. The maturation of DCs has proven indispensable to induce immunogenic T cell responses. We review the insights gained from the development of maturation cocktails in monocyte derived DC-based trials. More recently, we have also gained insights into the functional specialization of primary human blood DC subsets. In peripheral human blood, we can distinguish at least three primary DC subsets, namely CD1c⁺ and CD141⁺ myeloid DCs and plasmacytoid DCs. We reflect the current knowledge on maturation and T helper polarization by these blood DC subsets in the context of DC-based cancer vaccines. The maturation stimulus in combination with the DC subset will determine the type of T cell response that is induced. First trials with these natural DCs underline their excellent in vivo functioning and mark them as promising tools for future vaccination strategies.

Umbilical cord blood-derived CD11c(+) dendritic cells could serve as an alternative allogeneic source of dendritic cells for cancer immunotherapy

Introduction

Allogenic dendritic cells (DCs) generated from healthy donors, who are complete or partially HLA-matched, have been used for clinical trials. One of the sources for allogenic DCs is umbilical cord blood (UCB) cells. However, as far as cord blood cells are concerned, looking at their naïve nature, there is a concern as to whether the DCs generated from them will have enough potential to elicit a proper T cell response. For this, we compared CD11c⁺ UCB-DCs/ Cytotoxic T lymphocytes (CTLs) with the conventional source, i.e. peripheral blood (PBL) monocyte DCs/CTLs, using various parameters.

Methods

CD11c⁺ DCs generated from the two sources were compared morphologically, phenotypically and functionally. Functional assays included antigen uptake, chemotactic migration and MLR (mixed lymphocyte reaction). The CTLs generated were examined for the activation markers, granzyme A & granzyme B, and IFN-γ secretion. MUC1 (STAPPVHNV) peptide-specific CTLs were quantified by Streptamer staining. In vitro CTL activity was assessed by their efficiency in killing MCF-7 cells. For in vivo CTL assay, a xenograft of MCF-7-luc-F5 cells in female NOD/SCID mice was employed. Regression of tumors in mice was monitored using an in vivo imaging system before and after ten days of CTL infusion. Statistical analysis of all the experiments between the two groups was evaluated by one-way ANOVA.

Results

The CD11c⁺ DCs from the two sources were morphologically and phenotypically similar. Their capacity to uptake antigen, migration towards CCL-19 and MLR activity were equivalent. UCB-CTLs had significantly higher levels of activation markers, number of MUC1 specific CTLs, IFN-γ secretion and IL-12p70/IL-10 ratio than that of PBL-CTLs. Hematoxylin and Eosin-stained tumor sections showed T cell infiltration, which was further confirmed by immunofluorescence staining. In vivo CTL activity was found to be similar with the two sources.

Conclusions

Our data demonstrate that CD11c⁺ UCB-DCs/CTLs are as potent as standard CD11c⁺ PBL-DC/CTLs and could therefore be used as an allogenic source for therapeutic purposes. The findings of this study could help in taking us one step closer towards the personalized therapy using DC based cancer vaccines.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0160-8) contains supplementary material, which is available to authorized users.

A single bout of dynamic exercise by healthy adults enhances the generation of monocyte-derived-dendritic cells

The ex vivo generation of monocyte-derived-dendritic cells (mo-DCs) has facilitated the use of DCs in immunotherapy research. However, low blood monocyte numbers frequently limit the manufacture of sufficient numbers of mo-DCs for subsequent experimental and clinical procedures. Because exercise mobilizes monocytes to the blood, we tested if acute dynamic exercise by healthy adults would augment the generation of mo-DCs without compromising their differentiation or function. We compared mo-DC generation from before- and after-exercise blood over 8-days of culture. Function was assessed by FITC-dextran uptake and the stimulation of autologous cytomegalovirus (pp65)-specific-T-cells. Supporting the hypothesis, we found a near fourfold increase in number of mo-DCs generated after-exercise. Furthermore, relative FITC-dextran uptake, differentiation rate, and stimulation of pp65-specific-T-cells did not differ between before- and after-exercise mo-DCs. We conclude that exercise enhances the ex vivo generation of mo-DCs without compromising their function, and so may overcome some limitations associated with manufacturing these cells for immunotherapy.

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.

Immunogenicity of targeted lentivectors

To increase the safety and possibly efficacy of HIV-1 derived lentivectors (LVs) as an anti-cancer vaccine, we recently developed the Nanobody (Nb) display technology to target LVs to antigen presenting cells (APCs). In this study, we extend these data with exclusive targeting of LVs to conventional dendritic cells (DCs), which are believed to be the main cross-presenting APCs for the induction of a TH1-conducted antitumor immune response. The immunogenicity of these DC-subtype targeted LVs was compared to that of broad tropism, general APC-targeted and non-infectious LVs. Intranodal immunization with ovalbumin encoding LVs induced proliferation of antigen specific CD4+ T cells, irrespective of the LVs' targeting ability. However, the cytokine secretion profile of the restimulated CD4+ T cells demonstrated that general APC targeting induced a similar TH1-profile as the broad tropism LVs while transduction of conventional DCs alone induced a similar and less potent TH1 profile as the non-infectious LVs. This observation contradicts the hypothesis that conventional DCs are the most important APCs and suggests that the activation of other APCs is also meaningful. Despite these differences, all targeted LVs were able to stimulate cytotoxic T lymphocytes, be it to a lesser extent than broad tropism LVs. Furthermore this induction was shown to be dependent on type I interferon for the targeted and non-infectious LVs, but not for broad tropism LVs. Finally we demonstrated that the APC-targeted LVs were as potent in therapy as broad tropism LVs and as such deliver on their promise as safer and efficacious LV-based vaccines.

The natural killer cell response and tumor debulking are associated with prolonged survival in recurrent glioblastoma patients receiving dendritic cells loaded with autologous tumor lysates

Recurrent glioblastomas (GBs) are highly aggressive tumors associated with a 6–8 mo survival rate. In this study, we evaluated the possible benefits of an immunotherapeutic strategy based on mature dendritic cells (DCs) loaded with autologous tumor-cell lysates in 15 patients affected by recurrent GB. The median progression-free survival (PFS) of this patient cohort was 4.4 mo, and the median overall survival (OS) was 8.0 mo. Patients with small tumors at the time of the first vaccination (< 20 cm³; n = 8) had significantly longer PFS and OS than the other patients (6.0 vs. 3.0 mo, p = 0.01; and 16.5 vs. 7.0 mo, p = 0.003, respectively). CD8⁺ T cells, CD56⁺ natural killer (NK) cells and other immune parameters, such as the levels of transforming growth factor β, vascular endothelial growth factor, interleukin-12 and interferon γ (IFNγ), were measured in the peripheral blood and serum of patients before and after immunization, which enabled us to obtain a vaccination/baseline ratio (V/B ratio). An increased V/B ratio for NK cells, but not CD8⁺ T cells, was significantly associated with prolonged PFS and OS. Patients exhibiting NK-cell responses were characterized by high levels of circulating IFNγ and E4BP4, an NK-cell transcription factor. Furthermore, the NK cell V/B ratio was inversely correlated with the TGFβ2 and VEGF V/B ratios. These results suggest that tumor-loaded DCs may increase the survival rate of patients with recurrent GB after effective tumor debulking, and emphasize the role of the NK-cell response in this therapeutic setting.

The ReNAissanCe of mRNA-based cancer therapy

About 25 years ago, mRNA became a tool of interest in anticancer vaccination approaches. However, due to its rapid degradation in situ, direct application of mRNA was confronted with considerable skepticism during its early use. Consequently, mRNA was for a long time mainly used for the ex vivo transfection of dendritic cells, professional antigen-presenting cells known to stimulate immunity. The interest in direct application of mRNA experienced a revival, as researchers became aware of the many advantages mRNA offers. Today, mRNA is considered to be an ideal vehicle for the induction of strong immune responses against cancer. The growing numbers of preclinical trials and as a consequence the increasing clinical application of mRNA as an off-the-shelf anticancer vaccine signifies a renaissance for transcript-based antitumor therapy. In this review, we highlight this renaissance using a timeline providing all milestones in the application of mRNA for anticancer vaccination.

mRNA-based dendritic cell vaccines

Cancer immunotherapy has been proposed as a powerful treatment modality. Active immunotherapy aspires to stimulate the patient's immune system, particularly T cells. These cells can recognize and kill cancer cells and can form an immunological memory. Dendritic cells (DCs) are the professional antigen-presenting cells of our immune system. They take up and process antigens to present them to T cells. Consequently, DCs have been investigated as a means to stimulate cancer-specific T-cell responses. An efficient strategy to program DCs is the use of mRNA, a well-defined and safe molecule that can be easily generated at high purity. Importantly, vaccines consisting of mRNA-modified DCs showed promising results in clinical trials. Therefore, we will introduce cancer immunotherapy and DCs and give a detailed overview on the application of mRNA to generate cancer-fighting DC vaccines.

Tracking and quantification of dendritic cell migration and antigen trafficking between the skin and lymph nodes

Skin-derived dendritic cells (DCs) play a crucial role in the maintenance of immune homeostasis due to their role in antigen trafficking from the skin to the draining lymph nodes (dLNs). To quantify the spatiotemporal regulation of skin-derived DCs in vivo, we generated knock-in mice expressing the photoconvertible fluorescent protein KikGR. By exposing the skin or dLN of these mice to violet light, we were able to label and track the migration and turnover of endogenous skin-derived DCs. Langerhans cells and CD103⁺DCs, including Langerin⁺CD103⁺dermal DCs (DDCs), remained in the dLN for 4–4.5 days after migration from the skin, while CD103⁻DDCs persisted for only two days. Application of a skin irritant (chemical stress) induced a transient >10-fold increase in CD103⁻DDC migration from the skin to the dLN. Tape stripping (mechanical injury) induced a long-lasting four-fold increase in CD103⁻DDC migration to the dLN and accelerated the trafficking of exogenous protein antigens by these cells. Both stresses increased the turnover of CD103⁻DDCs within the dLN, causing these cells to die within one day of arrival. Therefore, CD103⁻DDCs act as sentinels against skin invasion that respond with increased cellular migration and antigen trafficking from the skin to the dLNs.

Preparation of triple-negative breast cancer vaccine through electrofusion with day-3 dendritic cells

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) in human immune system. DC-based tumor vaccine has met with some success in specific malignancies, inclusive of breast cancer. In this study, we electrofused MDA-MB-231 breast cancer cell line with day-3 DCs derived from peripheral blood monocytes, and explored the biological characteristics of fusion vaccine and its anti-tumor effects in vitro. Day-3 mature DCs were generated from day-2 immature DCs by adding cocktails composed of TNF-α, IL-1β, IL-6 and PEG₂. Day-3 mature DCs were identified and electofused with breast cancer cells to generate fusion vaccine. Phenotype of fusion cells were identified by fluorescence microscope and flow cytometer. The fusion vaccine was evaluated for T cell proliferation, secretion of IL-12 and IFN-γ, and induction of tumor-specific CTL response. Despite differences in morphology, day-3 and day-7 DC expressed similar surface markers. The secretion of IL-12 and IFN-γ in fusion vaccine group was much higher than that in the control group. Compared with control group, DC-tumor fusion vaccine could better stimulate the proliferation of allogeneic T lymphocytes and kill more breast cancer cells (MDA-MB-231) in vitro. Day-3 DCs had the same function as the day-7 DCs, but with a shorter culture period. Our findings suggested that day-3 DCs fused with whole apoptotic breast cancer cells could elicit effective specific antitumor T cell responses in vitro and may be developed into a prospective candidate for adoptivet immunotherapy.

CCL21 Cancer Immunotherapy

Cancer, a major health problem, affects 12 million people worldwide every year. With surgery and chemo-radiation the long term survival rate for the majority of cancer patients is dismal. Thus novel treatments are urgently needed. Immunotherapy, the harnessing of the immune system to destroy cancer cells is an attractive option with potential for long term anti-tumor benefit. Cytokines are biological response modifiers that stimulate anti-tumor immune responses. In this review, we discuss the anti-tumor efficacy of the chemotactic cytokine CCL21 and its pre-clinical and clinical application in cancer.

Crosstalk between dendritic cell subsets and implications for dendritic cell-based anticancer immunotherapy

Dendritic cells (DCs) are a family of professional antigen-presenting cells that have an indispensable role in the initiation of innate and adaptive immune responses against pathogens and tumor cells. The DC family is very heterogeneous. Two main types of naturally occurring DCs circulate in peripheral blood, each with its unique phenotypic and functional characteristics: myeloid DCs and plasmacytoid. There is an ample number of studies that have focused on the bi-directional crosstalk between DCs and natural killer cells or T cells. However, the crosstalk among the different DC subsets, in the context of infectious diseases and cancer, has until now not received much attention. Here, we review all available literature that has dealt with the crosstalk between plasmacytoid and myeloid DCs and the potential mode of action. Emphasis will be given to the therapeutic potential of the combination of DC subsets for DC-based immunotherapy.

Therapeutic cancer vaccines: past, present, and future

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

Dendritic cells derived from pluripotent stem cells: Potential of large scale production

Human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, are promising sources for hematopoietic cells due to their unlimited growth capacity and the pluripotency. Dendritic cells (DCs), the unique immune cells in the hematopoietic system, can be loaded with tumor specific antigen and used as vaccine for cancer immunotherapy. While autologous DCs from peripheral blood are limited in cell number, hPSC-derived DCs provide a novel alternative cell source which has the potential for large scale production. This review summarizes recent advances in differentiating hPSCs to DCs through the intermediate stage of hematopoietic stem cells. Step-wise growth factor induction has been used to derive DCs from hPSCs either in suspension culture of embryoid bodies (EBs) or in co-culture with stromal cells. To fulfill the clinical potential of the DCs derived from hPSCs, the bioprocess needs to be scaled up to produce a large number of cells economically under tight quality control. This requires the development of novel bioreactor systems combining guided EB-based differentiation with engineered culture environment. Hence, recent progress in using bioreactors for hPSC lineage-specific differentiation is reviewed. In particular, the potential scale up strategies for the multistage DC differentiation and the effect of shear stress on hPSC differentiation in bioreactors are discussed in detail.

[Progress in immunotherapy for non-small cell lung cancer]

In recent years, the five-year survival rate of patients with advanced stage non-small cell lung cancer (NSCLC) remains low despite recent advances in surgery, irradiation, chemotherapy, and targeted therapy. Immunotherapy which utilizes the immune system to control and eradicate cancer is a viable treatment approach for malignancy. Immunotherapy in patients with lung cancer has made breakthrough progress recently. Novel immunotherapeutic agents, such as antigen-specific tumour vaccines, checkpoint inhibitors, etc, have all been evaluated in lung cancer, and some have shown prolonged survival time in phase II trials and III trails. The immune-related response criteria for the evaluation of antitumor responses with immunotherapeutic agents have been made. Now, immunotherapy will likely be a fundamentally new concept for the treatment of NSCLC.

Interference with PD-L1/PD-1 co-stimulation during antigen presentation enhances the multifunctionality of antigen-specific T cells

The release of cytokines by T cells strongly defines their functional activity in vivo. The ability to produce multiple cytokines has been associated with beneficial immune responses in cancer and infectious diseases, while their progressive loss is associated with T-cell exhaustion, senescence and anergy. Consequently, strategies that enhance the multifunctional status of T cells are a key for immunotherapy. Dendritic cells (DCs) are professional antigen presenting cells that regulate T-cell functions by providing positive and negative co-stimulatory signals. A key negative regulator of T-cell activity is provided by binding of programmed death-1 (PD-1) receptor on activated T cells, to its ligand PD-L1, expressed on DCs. We investigated the impact of interfering with PD-L1/PD-1 co-stimulation on the multifunctionality of T cells, by expression of the soluble extracellular part of PD-1 (sPD-1) or PD-L1 (sPD-L1) in human monocyte-derived DCs during antigen presentation. Expression, secretion and binding of these soluble molecules after mRNA electroporation were demonstrated. Modification of DCs with sPD-1 or sPD-L1 mRNA resulted in increased levels of the co-stimulatory molecule CD80 and a distinct cytokine profile, characterized by the secretion of IL-10 and TNF-α, respectively. Co-expression in DCs of sPD-1 and sPD-L1 with influenza virus nuclear protein 1 (Flu NP1) stimulated Flu NP1 memory T cells, with a significantly higher number of multifunctional T cells and increased cytokine secretion, while it did not induce regulatory T cells. These data provide a rationale for the inclusion of interfering sPD-1 or sPD-L1 in DC-based immunotherapeutic strategies.

Dendritic cell vaccines in gastric cancer immunotherapy

Gastric cancer is one of the most common malignant tumors of the digestive tract. Current treatments for gastric cancer are mainly surgery, radiotherapy, and chemotherapy, and the effects of these treatments are not satisfactory. Dendritic cells are the most important antigen presenting cells, play an important role in the immune surveillance and immune escape of gastric cancer, and are closely related to the occurrence, development and outcome of gastric cancer. Dendritic cell vaccines in immunotherapy of tumors have become a hot research spot.

Complex evaluation of human monocyte-derived dendritic cells for cancer immunotherapy

Dendritic cell (DC) immunotherapy is capable of generating tumour-specific immune responses. Different maturation strategies were previously tested to obtain DC capable of anti-cancer responses in vitro, usually with limited clinical benefit. Mutual comparison of currently used maturation strategies and subsequent complex evaluation of DC functions and their stimulatory capacity on T cells was performed in this study to optimize the DC vaccination strategy for further clinical application. DC were generated from monocytes using granulocyte–macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, pulsed with whole tumour cell lysate and then matured with one of five selected maturation strategies or cultured without additional maturation stimulus. DC were characterized with regard to their surface marker expression, cytokine profiles, migratory capacity, allogeneic and autologous T cell stimulatory capacity as well as their specific cytotoxicity against tumour antigens. We were able to demonstrate extensive variability among different maturation strategies currently used in DC immunotherapeutic protocols that may at least partially explain limited clinical benefit of some clinical trials with such DC. We identified DC matured with interferon-γ and lipopolysaccharide as the most attractive candidate for future clinical trials in cancer immunotherapy.

CD137L-stimulated dendritic cells are more potent than conventional dendritic cells at eliciting cytotoxic T-cell responses

Dendritic cells (DCs) are highly potent initiators of adaptive immune responses and, as such, represent promising tools for immunotherapeutic applications. Despite their potential, the current efficacy of DC-based immunotherapies is poor. CD137 ligand (CD137L) signaling has been used to derive a novel type of DCs from human peripheral blood monocytes, termed CD137L-DCs. Here, we report that CD137L-DCs induce more potent cytotoxic T-cell responses than classical DCs (cDCs). Furthermore, in exploring several DC maturation factors for their ability to enhance the potency of CD137L-DCs, we found the combination of interferon γ (IFNγ) and the mixed Toll-like receptor (TLR)7/8 agonist R848, to display the highest efficacy in potentiating the T-cell co-stimulatory activity of CD137L-DCs. Of particular importance, CD137L-DCs were found to be more efficient than cDCs in activating autologous T cells targeting the cytomegalovirus (CMV)-derived protein pp65. Specifically, CD137L-DC-stimulated T cells were found to secrete higher levels of IFNγ and killed 2-3 times more HLA-matched, pp65-pulsed target cells than T cells activated by cDCs. Finally, in addition to stimulating CD8⁺ T cells, CD137L-DCs efficiently activated CD4⁺ T cells. Taken together, these findings demonstrate the superior potency of CD137L-stimulated DCs in activating CMV-specific, autologous T cells, and encourage the further development of CD137L-DCs for antitumor immunotherapy.

A personalized view on cancer immunotherapy

Recent progress in cancer immunotherapy has resulted in complete responses in patients refractory to current standard cancer therapies. However, due to tumor heterogeneity and inter-individual variations in anti-tumor immunity, only subsets of patients experience clinical benefit. This review highlights the implementation of a personalized approach to enhance treatment efficacy and reduce side effects, including the identification of tumor-specific antigens for cancer vaccination and adoptive T cell therapies. Furthermore, together with the current advances and promising clinical outcomes of combination cancer (immuno-)therapies, the screening for predictive biomarkers in a patient-specific manner is emphasized.

Tumour regression induced by co-administration of MIP-3α and CpG in an experimental model of colon carcinoma

CCL20/macrophage inflammatory protein-3α (MIP-3α) represents one of the potent chemoattractive proteins for dendritic cells (DCs). Herein, we investigated whether in vivo genetic modification of tumour cells aimed at intratumoural production of MIP-3α might lead to accumulation of DCs in tumour tissue. Mice injected with CT26, received recombinant adenovirus (Ad) vectors (AdMIP-3α) expressing MIP-3α protein. This was complemented by injections of CpG. Interestingly, MIP-3α gene therapy combined with CpG injections resulted in specific cytotoxicity. This was associated with significant suppression of tumour growth rate. These findings demonstrate the potential of strategies that utilize in vivo overexpression of chemokines.

Interleukin-15 dendritic cells as vaccine candidates for cancer immunotherapy

Owing to their professional antigen-presenting capacity and unique potential to induce tumor antigen-specific T cell immunity, dendritic cells (DCs) have attracted much interest over the past decades for therapeutic vaccination against cancer. Clinical trials have shown that the use of tumor antigen-loaded DCs in cancer patients is safe and that it has the potential to induce anti-tumor immunity which, in some cases, culminates in striking clinical responses. Unfortunately, in a considerable number of patients, DC vaccination is unable to mount effective anti-tumor immune responses and, if it does so, the resultant immunity is often insufficient to translate into tangible clinical benefit. This underscores the necessity to re-design and optimize the current procedures for DC vaccine manufacturing. A new generation of DC vaccines with improved potency has now become available for clinical use as a result of extensive pre-clinical research. One of the promising next-generation DC vaccine candidates are interleukin (IL)-15-differentiated DCs. In this commentary, we will compile the research data that have been obtained by our group and other groups with these so-called IL-15 DCs and summarize the evidence supporting the implementation of IL-15 DCs in DC-based cancer vaccination regimens.