Dendritic cells in cancer vaccines

Prognostic Model and Tumor Immune Microenvironment Analysis of Complement-Related Genes in Gastric Cancer

Introduction

The complement system is integral to the innate and adaptive immune response, helping antibodies eliminate pathogens. However, the potential role of complement and its modulators in the tumor microenvironment (TME) of gastric cancer (GC) remains unclear.

Methods

This study assessed the expression, frequency of somatic mutations, and copy number variations of complement family genes in GC derived from The Cancer Genome Atlas (TCGA). Lasso and Cox regression analyses were conducted to develop a prognostic model based on the complement genes family, with the training and validation sets taken from the TCGA-GC cohort (n=371) and the International Gene Expression Omnibus (GEO) cohort (n=433), correspondingly. The nomogram assessment model was used to predict patient outcomes. Additionally, the link between immune checkpoints, immune cells, and the prognostic model was investigated.

Results

In contrast to patients at low risk, those at high risk had a less favorable outcome. The prognostic model-derived risk score was shown to serve as a prognostic marker of GC independently, as per the multivariate Cox analysis. Nomogram assessment showed that the model had high reliability for predicting the survival of patients with GC in the 1, 3, 5 years. Additionally, the risk score was positively linked to the expression of immune checkpoints, notably CTLA4, LAG3, PDCD1, and CD274, according to an analysis of immune processes. The core gene C5aR1 in the prognostic model was found to be upregulated in GC tissues in contrast to adjoining normal tissues, and patients with elevated expressed levels of C5aR1 had lower 10-year overall survival (OS) rates.

Conclusion

Our work reveals that complement genes are associated with the diversity and complexity of TME. The complement prognosis model help improves our understanding of TME infiltration characteristics and makes immunotherapeutic strategies more effective.

Exploring Prognosis, Tumor Microenvironment and Tumor Immune Infiltration in Hepatocellular Carcinoma Based on ATF/CREB Transcription Factor Family Gene-Related Model

Introduction

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. It is the fourth leading cause of cancer-related death worldwide. Deregulation of the ATF/CREB family is associated with the progression of metabolic homeostasis and cancer. Because the liver plays a central role in metabolic homeostasis, it is critical to assess the predictive value of the ATF/CREB family in the diagnosis and prognosis of HCC.

Methods

Using data from The Cancer Genome Atlas (TCGA), this research evaluated the expression, copy number variations, and frequency of somatic mutations of 21 genes in the ATF/CREB family in HCC. A prognostic model based on the ATF/CREB gene family was developed via Lasso and Cox regression analyses, with the TCGA cohort serving as the training dataset and the International Cancer Genome Consortium (ICGC) cohort serving as the validation set. Kaplan-Meier and receiver operating characteristic analyses verified the accuracy of the prognostic model. Furthermore, the association among the prognostic model, immune checkpoints, and immune cells was examined.

Results

High-risk patients exhibited an unfavorable outcome as opposed to those in the low-risk category. Multivariate Cox analysis revealed that the risk score calculated based on the prognostic model was an independent prognostic factor for HCC. Analysis of immune mechanisms revealed that the risk score had a positive link to the expression of immune checkpoints, particularly CD274, PDCD1, LAG3, and CTLA4. Differences in immune cells and immune-associated roles were found between the high- and low-risk patients, as determined by single-sample gene set enrichment analysis. The core genes ATF1, CREB1, and CREB3 in the prognostic model were shown to be upregulated in HCC tissues as opposed to adjoining normal tissues, and the 10-year overall survival (OS) rate was worse among patients with elevated expression levels of ATF1, CREB1, and CREB3. Elevated expression levels of ATF1, CREB1, and CREB3 in HCC tissues were confirmed by qRT-PCR and immunohistochemistry studies.

Conclusion

According to the results of our training set and test set, the risk model based on the six ATF/CREB gene signatures predicting prognosis has certain predictive accuracy in predicting the survival of HCC patients. This study provides novel insights into the individualized treatment of patients with HCC.

Endometrial cancer prognosis prediction using correlation models based on CDK family genes

Cyclin-dependent kinases (CDKs) play an important role in cell division. Given that abnormal cell proliferation caused by dysregulation of cell division is one of the major causes of endometrial cancer (EC), it is important to elucidate the role of CDK family genes in the diagnosis and prognosis of EC. In this study, The Cancer Genome Atlas (TCGA) database was used to analyze the frequency of copy number variations and somatic mutations in 26 CDK family genes. Subsequently, the expression of these genes in EC was assessed, and their relationship with overall survival (OS) was examined via Kaplan–Meier analysis to assess their prognostic significance. A prognostic model based on seven CDK genes was constructed using Lasso and Cox regression, and the predictive performance of the model was analyzed using Kaplan–Meier analysis and column line plots. The correlation between CDK genes and immune cells was also examined. Patients with EC in the high-risk group had a poorer prognosis. The results of qRT-PCR and immunohistochemical analyses validated that CDK16 is highly expressed in EC tissues. Patients with EC with high CDK16 expression had worse 10-year OS than patients with low CDK16 expression. These findings suggest that the prognostic model constructed based on CDK genes can help to develop individualized and targeted treatment strategies for patients with EC.

Multi-Level Computational Modeling of Anti-Cancer Dendritic Cell Vaccination Utilized to Select Molecular Targets for Therapy Optimization

Dendritic cells (DCs) can be used for therapeutic vaccination against cancer. The success of this therapy depends on efficient tumor-antigen presentation to cytotoxic T lymphocytes (CTLs) and the induction of durable CTL responses by the DCs. Therefore, simulation of such a biological system by computational modeling is appealing because it can improve our understanding of the molecular mechanisms underlying CTL induction by DCs and help identify new strategies to improve therapeutic DC vaccination for cancer. Here, we developed a multi-level model accounting for the life cycle of DCs during anti-cancer immunotherapy. Specifically, the model is composed of three parts representing different stages of DC immunotherapy – the spreading and bio-distribution of intravenously injected DCs in human organs, the biochemical reactions regulating the DCs’ maturation and activation, and DC-mediated activation of CTLs. We calibrated the model using quantitative experimental data that account for the activation of key molecular circuits within DCs, the bio-distribution of DCs in the body, and the interaction between DCs and T cells. We showed how such a data-driven model can be exploited in combination with sensitivity analysis and model simulations to identify targets for enhancing anti-cancer DC vaccination. Since other previous works show how modeling improves therapy schedules and DC dosage, we here focused on the molecular optimization of the therapy. In line with this, we simulated the effect in DC vaccination of the concerted modulation of combined intracellular regulatory processes and proposed several possibilities that can enhance DC-mediated immunogenicity. Taken together, we present a comprehensive time-resolved multi-level model for studying DC vaccination in melanoma. Although the model is not intended for personalized patient therapy, it could be used as a tool for identifying molecular targets for optimizing DC-based therapy for cancer, which ultimately should be tested in in vitro and in vivo experiments.

The effect of a novel glycolysis-related gene signature on progression, prognosis and immune microenvironment of renal cell carcinoma

Background

Glycolysis is a central metabolic pathway for tumor cells. However, the potential roles of glycolysis-related genes in renal cell carcinoma (RCC) have not been investigated.

Methods

Seven glycolysis-related gene sets were selected from MSigDB and were analyzed through GSEA. Using TCGA database, the glycolysis-related gene signature was constructed. Prognostic analyses were based on the Kaplan–Meier method. The cBioPortal database was employed to perform the mutation analyses. The CIBERSORT algorithm and TIMER database were used to determine the immunological effect of glycolytic gene signature. The expressions in protein level of eight glycolytic risk genes were determined by HPA database. Finally, qPCR, MTT and Transwell invasion assays were conducted to validate the roles of core glycolytic risk genes (CD44, PLOD1 and PLOD2) in RCC.

Results

Four glycolysis-related gene sets were significantly enriched in RCC samples. The glycolytic risk signature was constructed (including CD44, PLOD2, KIF20A, IDUA, PLOD1, HMMR, DEPDC1 and ANKZF1) and identified as an independent RCC prognostic factor (HR = 1.204). Moreover, genetic alterations of glycolytic risk genes were uncommon in RCC (10.5%) and glycolytic risk signature can partially affect immune microenvironment of RCC. Six glycolytic risk genes (except for IDUA and HMMR) were over-expression in A498 and 786-O renal cancer cells through qPCR test. MTT and Transwell assays revealed that silencing of CD44, PLOD1 and PLOD2 suppressed the proliferation and invasion of renal cancer cells.

Conclusions

The glycolysis-related risk signature is closely associated with RCC prognosis, progression and immune microenvironment. CD44, PLOD1 and PLOD2 may serve as RCC oncogenes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07702-7.

Nanomedicine for improvement of dendritic cell-based cancer immunotherapy

Dendritic cell (DC)-based cancer immunotherapy has shown impressive outcomes, including the development of the first FDA-approved anti-cancer vaccine. However, the clinical application of DC-based cancer immunotherapy is associated with various challenges. Promising novel tools for the administration of cancer vaccines has emerged from recent developments in nanoscale biomaterials. One current strategy to enhance targeted drug delivery, while minimizing drug-related toxicities, is the use of nanoparticles (NPs). These can be utilized for antigen delivery into DCs, which have been shown to provide potent T cell-stimulating effects. Therefore, NP delivery represents one promising approach for creating an effective and stable immune response without toxic side effects. The current review surveys cancer immunotherapy with particular attention toward NP-based delivery methods that target DCs.

Lycium barbarum Polysaccharide Promotes Maturation of Dendritic Cell via Notch Signaling and Strengthens Dendritic Cell Mediated T Lymphocyte Cytotoxicity on Colon Cancer Cell CT26-WT

Lycium barbarum polysaccharide (LBP) is the major function component of Lycium barbarum L. and has been previously reported to induce the phenotypic and functional maturation of dendritic cells (DCs) as well as activating T lymphocytes. In the current study, the immunologic cytotoxicity promoting effect of LBP was assessed and the underlying mechanism was explored. The impact of LBP on the phenotype, maturation, and immunogenicity of DCs was assessed. The activity of Notch pathway which is involved in the regulation of LBP on DCs was detected. Afterwards, the influence of LBP on cytotoxicity of DC-mediated cytotoxicity T lymphocytes (CTLs) to CT26-WT colon cancer cells was further assessed. Administration of LBP induced the phenotypic and functional maturation of DCs. After being subjected to LBP, the expression of Notch and Jagged and Notch targets Hes1 and Hes5 was all upregulated. The cytotoxicity of DC-mediated CTLs was strengthened by administration of LBP. Additionally, cytotoxicity of DC-mediated CTLs on CT26-WT colon cancer cells also increased with effector-target ratio. In conclusion, LBP could induce the phenotypic and functional maturation of DCs via Notch signaling and promote the cytotoxicity of DC-mediated CTLs, which could be employed as a promising adjuvant for cancer immunotherapy.

Noncoding RNAs in Cancer Immunology

Cancer immunology is the study of interaction between cancer cells and immune system by the application of immunology principle and theory. With the recent approval of several new drugs targeting immune checkpoints in cancer, cancer immunology has become a very attractive field of research and is thought to be the new hope to conquer cancer. This chapter introduces the aberrant expression and function of noncoding RNAs, mainly microRNAs and long noncoding RNAs, in tumor-infiltrating immune cells, and their significance in tumor immunity. It also illustrates how noncoding RNAs are shuttled between tumor cells and immune cells in tumor microenvironments via exosomes or other microvesicles to modulate tumor immunity.

Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems

Vaccination is one of the most popular technologies in disease prevention and eradication. It is promising to improve immunization efficiency by using vectors and/or adjuvant delivery systems. Nanoparticle (NP)-based delivery systems have attracted increasing interest due to enhancement of antigen uptake via prevention of vaccine degradation in the biological environment and the intrinsic immune-stimulatory properties of the materials. Mitochondria play paramount roles in cell life and death and are promising targets for vaccine delivery systems to effectively induce immune responses. In this review, we focus on NPs-based delivery systems with surfaces that can be manipulated by using mitochondria targeting moieties for intervention in health and disease.

Antitumor effect of dendritic cell loaded ex vivo and in vivo with tumor-associated antigens in lung cancer model

Various ex vivo or in vivo loading protocols have been developed or evaluated for the delivery of tumor antigens to dendritic cells (DCs). We compared the antitumor effect of mature DCs electroporation-pulsed (EP/mDC) ex vivo with tumor cell lysate and immature DCs (iDCs) injected into the tumor apoptosed by ionizing radiation (IR/iDC) in lung cancer model. DCs were generated from bone marrow of C57BL/6 mice. Ionizing radiation (IR) was applied at a dose of 10 Gy to the tumor on the right thigh. iDCs were intratumorally injected into the irradiated tumor and EP/mDC was injected subcutaneously in the right flank. DC injection induced strong tumor-specific immunity against Lewis lung carcinoma, as compared with the tumor-bearing control and IR only treated mice. The growth of a distant tumor on the right and left flank was inhibited by IR/iDC and EP/mDC. Particularly, IR/iDC resulted in a more significant inhibition of tumor growth and prolonged survival time. It was related to increase of tumor-specific interferon-gamma, cytotoxicity, and decrease of regulatory T-cells. The results indicate that DCs electroporation-pulsed with tumor cell lysate induce a potent antitumor effect, but that iDCs intratumoral injected into the irradiated tumor induce a more potent antitumor effect.

Optimizing dendritic cell-based immunotherapy for cancer

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

Vaccination as a treatment for breast or ovarian cancer

The immune system recognizes breast and ovarian cancer cells but whether it is effective in controlling these cancers in patients has yet to be proven. The challenge with vaccination strategies is to break tolerance so that the patient's immune system will recognize cancer cells. The success of vaccines depends on the identification of appropriate tumor antigens, establishment of effective immunization strategies and their ability to circumvent inhibitory immune mechanisms.

Dendritic cell vaccination and immunostimulation in advanced melanoma

The most recent advances in immunology bear witness to the fact that tumors, in particular melanoma, escape recognition by the host's immune system and can locally inactivate its effectors, T-cells and antigen presenting cells. There is, however, preclinical evidence that the immune system, opportunely stimulated, is capable of recognizing and killing tumor cells. It has been verified that the activation of autologous dendritic cells, derived from peripheral blood and pulsed with tumor antigens, results in the specific stimulation of T-cells against the tumor. Preliminary data from dendritic cell vaccination trials, mainly of advanced melanoma, show unequivocal evidence of immunization and of the first clinical responses. Many questions remain to be answered before more effective and widespread use of this type of vaccination is possible, especially in the early stages of the disease.

Active immunotherapy using dendritic cells in the treatment of glioblastoma multiforme

OBJECTIVE

Glioblastoma multiforme, the most common malignant brain tumor still has a dismal prognosis with conventional treatment. Therefore, it is necessary to explore new and/or adjuvant treatment options to improve patient outcomes. Active immunotherapy is a new area of research that may be a successful treatment option. The focus is on vaccines that consist of antigen presenting cells (APCs) loaded with tumor antigen. We have conducted a systematic review of prospective studies, case reports and clinical trials. The goal of this study was to examine the efficacy and safety in terms of complications, median overall survival (OS), progression free survival (PFS) and quality of life.

METHODS

A PubMed search was performed to include all relevant studies that reported the characteristics, outcomes and complications of patients with GBM treated with active immunotherapy using dendritic cells. Reported parameters were immune response, radiological findings, median PFS and median OS. Complications were categorized based on association with the craniotomy or with the vaccine itself.

RESULTS

A total of 21 studies with 403 patients were included in our review. Vaccination with dendritic cells (DCs) loaded with autologous tumor cells resulted in increased median OS in patients with recurrent GBM (71.6-138.0 wks) as well as those newly diagnosed (65.0-230.4 wks) compared to average survival of 58.4 wks.

CONCLUSIONS

Active immunotherapy, specifically with autologous DCs loaded with autologous tumor cells, seems to have the potential of increasing median OS and prolonged tumor PFS with minimal complications. Larger clinical trials are needed to show the potential benefits of active immunotherapy.

Enhanced maturation and function of dendritic cells using hydrogel coated plate and antigen electroporation

Dendritic cells (DCs) are potent antigen-presenting cells that can be matured in vitro from immature dendritic cells (iDCs) in the presence of several biological agents such as cytokine cocktail, CD40L, TNF-a and antigen loading, which are necessary and achieved using various protocols, such as lipofection, passive pulse or electroporation. However, these DCs maturation protocols may cause with a significant loss of cells because of cellular attachment and spreading during culturing. Some biomaterials that influence adhesion and development of cells have been used in cell culture techniques, and it was thought that they might be applied on the culture of DCs. In this study, we used polyHEMA, which is a hydrogel coating biomaterial that prevents DCs from adherence, and investigated whether hydrogel coating affects the maturation of iDCs. The efficiency in the generation of mDCs was improved through hydrogel coating procedure and a dendritic cell maturation marker, CD83, was significantly increased in hydrogel-coated culture condition. The antigen-loaded mDCs from electroporation were further expressed the CD83. The mDCs generated in the hydrogel-coated culture condition showed more, longer and thicker dendrites, and produced more amounts of cytokines such as IL-12 and IFN-γ. Therefore, it was suggested that the hydrogel-coated culture condition could improve function of mDCs. Cheol-Hun Son and Jae-Ho Bae contributed equally to this work.

Maturation of monocyte derived dendritic cells with OK432 boosts IL-12p70 secretion and conveys strong T-cell responses

Background

Design of tumour specific immunotherapies using the patients' own dendritic cells (DC) is a fast advancing scientific field. The functional qualities of the DC generated in vitro are critical, and today's gold standard for maturation is a cytokine cocktail consisting of IL-1β, IL-6, TNF-α and PGE₂ generating cells lacking IL-12p70 production. OK432 is an immunotherapeutic agent derived from killed Streptococcus pyogenes that has been used clinically to treat malignant and benign neoplasms for decades.

Methods

In this study, we analysed the effects of OK432 on DC maturation, DC migration, cytokine and chemokine secretion as well as T-cell stimulatory capacity, and compared it to the cytokine cocktail alone and combinations of OK432 with the cytokine cocktail.

Results

OK432 induced a marked up-regulation of CD40 on the cell surface as well as a strong inflammatory response from the DC with significantly more secretion of 19 different cytokines and chemokines compared to the cytokine cocktail. Interestingly, secretion of IL-15 and IL-12p70 was detected at high concentrations after maturation of DC with OK432. However, the OK432 treated DC did not migrate as well as DC treated with cytokine cocktail in a transwell migration assay. During allogeneic T-cell stimulation OK432 treated DC induced proliferation of over 50 percent of CD4 and 30 percent of CD8 T-cells for more than two cell divisions, whereas cytokine cocktail treated DC induced proliferation of 12 and 11 percent of CD4 and CD8 T-cells, respectively.

Conclusions

The clinically approved compound OK432 has interesting properties that warrants its use in DC immunotherapy and should be considered as a potential immunomodulating agent in cancer immunotherapy.

Induction of cytotoxic T lymphocytes primed with tumor RNA-loaded dendritic cells in esophageal squamous cell carcinoma: preliminary step for DC vaccine design

Background

Dendritic Cells (DC) are potent antigen presenting cells with the ability to prime naïve T cells and convert them to cytotoxic T-lymphocytes (CTL). We evaluated the capability of autologous DCs transfected with total tumor and normal RNA to induce cytotoxic CTL as the preliminary step to design a DC-based vaccine in the esophageal squamous cell carcinoma (ESCC).

Methods

Monocytes-derived DCs were electroporated with either total tumor RNA or normal RNA. T cells were then primed with tumor RNA transfected DCs and lytic effects of the generated CTL were measured with Cytotoxicity assay and IFN-γ Release Elispot assay.

Results

Cytotoxicity was induced against DCs loaded with tumoral RNA (%24.8 ± 5.2 SEM) while in normal RNA-loaded DCs, it was minimal (%6.1 ± 2.4 SEM) and significantly lower (p < 0.05). INF-γ secretion was more than 2-folds higher in tumoral RNA-loaded DCs when compared with normal RNA-loaded DCs (p < 0.05).

Conclusion

Electroporating DCs with tumor RNA generated tumor antigen presenting cells which in turn enhanced cytotoxic effects of the T cells against ESCC. This may be a useful autologous ex vivo screening tool for confirming the lytic effects of primed T cells on tumors and evaluate probable further adverse effects on noncancerous tissues. These data provide crucial preliminary information to establish a total tumor RNA-pulsed DC vaccine therapy of ESCC.

Analysis of peripheral blood dendritic cell subtypes in thymomatous MG

The object of this work was to measure the levels of monocyte-derived dendritic cell precursors (pDC1) and plasmacytoid dendritic cell precursors (pDC2) in peripheral blood mononuclear cells (PBMC) of patients with thymomatous MG and to assess the ratio of pDC1/pDC2 in these patients. Three-colour monoclonal antibody labelling technology was used to detect the cell counts and ratio of pDC1 and pDC2 in PBMCs of 18 patients with myasthenia gravis (MG), nine thymomatous patients without MG, and 15 normal controls. The number of pDC and pDC subsets in peripheral blood of patients with thymomatous generalized MG was significantly lower than that in thymomatous controls before and after the treatment. After the treatment, patients with both generalized MG and ocular MG had significantly lower number of pDC compared with thymomatous controls. We found no significant differences in pDC1/pDC2 ratio among groups. Before the extended thymomatous treatment, the number of pDC in patients with generalized MG was significantly lower than that in patients with ocular MG (P < 0.05). The counts of peripheral blood pDC and pDC subsets of patients with thymomatous MG were significantly lower 1 week after extended thymectomy. The counts of pDC and pDC subsets decreased in generalized thymomatous MG, and the patients with generalized MG had lower pDC counts than the patients with ocular MG before the treatment. Treatment resulted in decreased counts of pDC and pDC subsets in thymomatous MG. We suggest that the level of peripheral blood pDC can be used as a marker to define the progress of the disease.

The role of vaccine therapy in the treatment of melanoma

BACKGROUND

Melanoma is a tumour that is usually resistant to systemic therapy. Since it has been considered to be a highly immunogenic tumour, it has become an excellent target for the active specific immunotherapy. Vaccine therapy represents a novel approach to the treatment of melanoma.

OBJECTIVE

To evaluate different vaccines tested in stage III and/or IV melanoma patients.

METHODS

Systematic review of the published evidence on vaccine therapy in melanoma.

RESULTS

Melanoma vaccines can be classified into six groups: whole-cell vaccines, dendritic cell vaccines, peptide vaccines, ganglioside vaccines, DNA vaccines and viral vectors. The main characteristics of these vaccines including their advantages and disadvantages and the results from conducted trials are presented. Clinical responses to melanoma vaccines are still poor and currently there is no melanoma vaccine with a proven efficacy.

CONCLUSION

Vaccine therapy still remains an experimental therapy in patients with metastatic melanoma. Further research is required although a future therapy for advanced melanoma is probably a multimodal approach including vaccines, adjuvants and negative co-stimulatory blockade.

RNA-loaded CD40-activated B cells stimulate antigen-specific T-cell responses in dogs with spontaneous lymphoma

Cell-based vaccination strategies to induce functional tumor-specific T cells in cancer patients have focused on using autologous dendritic cells. An alternative approach is to use RNA-loaded CD40 activated B cells (CD40-B) that are highly efficient antigen-presenting cells capable of priming naive T cells, boosting memory T-cell responses and breaking tolerance to tumor antigens. The use of tumor RNA as the antigenic payload allows for gene transfer without viruses or vectors and permits major histocompatibility complex (MHC)-independent, multiple-antigen targeting. Here, we use CD40L transfected K562 cells to generate functional CD40-B cells from the peripheral blood of humans and dogs. Testing of RNA-loaded CD40-B cells in dogs allows not only for its development in veterinary medicine but also for determination of its safety and efficacy in a large animal model of spontaneous cancer prior to initiation of human clinical trials. We found that CD40-B cells from healthy humans, healthy dogs and tumor-bearing dogs express increased levels of immune molecules such as MHC and CCR7. Moreover, RNA-loaded CD40-B cells induce functional, antigen-specific T cells from healthy dogs and dogs with lymphoma. These findings pave the way for immunotherapy trials using tumor RNA-loaded CD40-B cells to stimulate antitumor immunity in a large animal model of spontaneous neoplasia.

Paradoxical enhancement of CD8 T cell-dependent anti-tumor protection despite reduced CD8 T cell responses with addition of a TLR9 agonist to a tumor vaccine

Generation of antigen-specific CD8+ T cell responses is considered optimal for an effective immunotherapy against cancer. In this study, we provide a proof of principle that in vitro observed diminished CD8+ T cell response provided a strong in vivo tumor protection. Immunization with an adenovirus vaccine containing ovalbumin (OVA) gene (Ad5-OVA) strongly induces antigen-specific CD8+ T cell responses measured in vitro using various immunological assays. However, in an attempt to augment the antigenic CD8+ T cell response, coinjection of a TLR9 agonist CpG ODN with the viral vaccine unexpectedly reduced the CD8+ T cell responses measured in vitro but provided a remarkably enhanced tumor protection compared to the CD8+ T cell response generated by Ad5-OVA vaccine alone. Interestingly, despite reduced ex vivo/in vitro CD8+ T cell responses following Ad5-OVA+CpG immunization, immunodepletion studies revealed that the augmented anti-tumor immunity was primarily dependent on CD8+ T cells. The magnitude and effector function of anti-OVA CD8+ T cells remain low following primary and secondary antigenic challenge, presenting a dichotomy between in vitro CD8 T cell responses and in vivo anti-tumor immunity. To examine the impact of CpG ODN, we observed that presence of CpG suppresses the CD8+ T cell proliferation both in vitro and in vivo. These data demonstrate that coadministration of adenovirus vaccine with a TLR9 agonist can generate potentially effective tumor-reactive CD8+ T cells in vivo. In addition, the results indicate that widely used standard immune parameters may not predict the vaccine efficacy containing a TLR9 agonist as adjuvant.

Combined treatment with intratumoral injection of dendritic cells and topical application of imiquimod for murine melanoma

BACKGROUND

The maturation state of dendritic cells is one of the factors that affect their capacity to induce antigen-specific cytotoxic T lymphocytes. Topical cutaneous application of imiquimod can induce the maturation and migration of cutaneous dendritic cells.

OBJECTIVES

To evaluate the synergistic effect of topical application of imiquimod plus intratumoral injection of syngeneic bone marrow-derived dendritic cells in the treatment of melanoma.

METHODS

For the B16F10 melanoma model, naive C57BL/6 mice were inoculated intradermally with 2x10(3) B16F10 melanoma cells in the right upper flank. Four groups (untreated control, dendritic cells alone, imiquimod alone and imiquimod plus dendritic cells) were included in the animal study, with five mice in each group. Tumour size was measured every 2 weeks, and histochemical and immunohistochemical staining carried out. ELISpot and PKH assays were performed to assess immune activity.

RESULTS

Combined treatment of topical application of imiquimod and intratumoral injection of dendritic cells led to significant tumour regression, in contrast to partial eradication of the tumours with imiquimod or dendritic cells alone.

CONCLUSION

These findings suggest that combination therapy with topical application of imiquimod and intratumoral administration of dendritic cells is a potent strategy for the treatment of melanoma.

“Pathogen-Mimicking” Nanoparticles for Vaccine Delivery to Dendritic Cells

A clinically relevant delivery system that can efficiently target and deliver antigens and adjuvant to dendritic cells (DCs) is under active investigation. Immunization with antigens and immunomodulators encapsulated in poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles elicits potent cellular immune responses; but understanding how this mode of delivery affects DCs and priming of naive T cells needs further investigation. In the current study, we assessed the extent of maturation of DCs after treatment with monophosphoryl lipid A (MPLA) encapsulated in PLGA nanoparticles and the generation of primary T-cell immune responses elicited by DCs loaded with antigens using this approach. Results indicated that DCs up-regulated the expression of surface maturation markers and demonstrated an enhanced allostimulatory capacity after treatment with MPLA containing PLGA nanoparticles. Treatment of DCs with MPLA containing nanoparticles released high amounts of proinflammatory and TH1 (T helper 1) polarizing cytokines and chemokines greater than that achieved by MPLA in solution. The delivery of ovalbumin in PLGA nanoparticles to DCs induced potent in vitro and in vivo antigen-specific primary TH1 immune responses that were furthermore enhanced with codelivery of MPLA along with the antigen in the nanoparticle formulation. Delivery of MUC1 lipopeptide (BLP25, a cancer vaccine candidate) and MPLA in PLGA nanoparticles to human DCs induced proliferation of MUC1 reactive T cells in vitro demonstrating the break in tolerance to self-antigen MUC1. These results demonstrated that targeting antigens along with toll-like receptor ligands in PLGA nanoparticles to DCs is a promising approach for generating potent TH1 polarizing immune responses that can potentially override self-tolerance mechanisms and become beneficial in the immunotherapy of cancer and infectious diseases.

Impact of transfection with total RNA of K562 cells upon antigen presenting, maturation, and function of human dendritic cells from peripheral blood mononuclear cells

BACKGROUND

Vaccination of dendritic cells (DCs) with tumor antigens is a potential strategy to induce tumor-specific immunity in tumor-bearing patients. The purpose of this study was to investigate whether human monocyte-derived DCs were able to present P210(Bcr-Ab1) protein and induce antigen-specific cytotoxic T lymphocyte (CTL) responses in vitro after transfected with total RNA of K562 cells (K562-RNA).

STUDY DESIGN AND METHODS

DCs derived from human peripheral blood mononuclear cells were transfected with K562-RNA with electroporation or DOTAP lipofection. The successful transfection was determined by reverse transcription-polymerase chain reaction and Western blot. The phenotypes of the DCs were analyzed by flow cytometry (FCM), and cytotoxicity of CTL was assessed by propidium iodide staining followed by FCM analysis. The CD1a expression and purity of DCs were measured by FCM.

RESULTS

The Bcr-Abl fusion gene was detected in the DCs with 24 hours after the transfection. The transfected cell expressed increased levels of CD80, CD83, CD86, and HLA-DR. Moreover, the transfected DCs strongly stimulated the T lymphocytes to gain cytotoxic activity against K562 cells. Culture medium containing 1 percent human plasma was the most effective for DC growth.

CONCLUSION

Human DCs transfected with K562-RNA effectively induce specific immune responses. This method can be used to induce tumor-specific immune response and may have potential application in immunotherapy of tumors.

An improved protocol for generation of immuno-potent dendritic cells through direct electroporation of CD14+ monocytes

In this study we demonstrate a novel protocol showing that electroporation of CD14+ monocytes directly isolated from blood with green fluorescent protein (GFP) RNA results in a 3-fold higher yield of antigen presenting dendritic cells (DCs) when compared to conventional methods employing immature DCs for electroporation. We further show a stable electroporation efficacy resulting in 60% of GFP positive cells. Expression of co-stimulatory molecules and maturation markers such as CD80, CD86, CD83 as well of the chemokine receptor 7 (CCR7) was found in 90% of the mature DCs. Importantly, production of IL-12p70 was 10 times higher in cells electroporated at the monocyte stage compared to cells electroporated at the immature DC stage. Stimulation of autologous naïve lymphocytes by DCs electroporated at monocytes stage elicited proliferation of CD8+ T-cell with 7-fold increase in IFN-gamma release. Blocking of the MHC-Class I molecules significantly inhibited the IFN-gamma release, indicating that antigen presentation was MHC-Class I mediated. In summary, electroporation of CD14+ monocytes with RNA results in a high yield of antigen presenting DCs with high immuno-stimulatory capacity and antigen presentation on MHC-Class I molecules. This improved method may represent an attractive approach for RNA-based DC immunotherapy.

Effects of imatinib on normal hematopoiesis and immune activation

The selective tyrosine kinase inhibitor imatinib (Glivec; Novartis International, Basel, Switzerland, http://www.glivec.com/content/home.jsp) is increasingly used for the treatment of Philadelphia chromosome-positive leukemias and other malignancies. In principle, the drug is well tolerated and clinical side effects are mostly moderate. However, it was shown that imatinib can affect the function of normal, nonmalignant cells, resulting in myelosuppression in treated patients. Recently, it has been demonstrated that imatinib might affect mobilization, proliferation, and differentiation of hematopoietic progenitor cells while leaving hematopoietic stem cells unaffected. Furthermore, in several in vitro studies and animal models, it was demonstrated that imatinib can affect the function and differentiation of antigen-presenting cells and inhibit the effector functions of T lymphocytes. Moreover, the induction of specific cytotoxic T cells seems to be impaired in chronic myeloid leukemia (CML) patients treated with imatinib compared with patients receiving interferon-alpha. This is of importance because some of the therapeutic effects in the treatment of patients with CML are mediated by the induction of leukemia-specific T-cell responses. Further studies investigating the effects of imatinib on normal hematopoiesis are of interest as they might lead to a better understanding of the clinically observed side effects and also might help identify new therapeutic applications of the drug, possibly in Bcr-Abl-negative myeloproliferative disorders and potentially as an immunomodulatory agent.

IFN-γ Regulates Donor CD8 T Cell Expansion, Migration, and Leads to Apoptosis of Cells of a Solid Tumor

We previously reported that IFN-gamma secreted by donor cytotoxic T cell 1 (Tc1) cells was the most important factor in promoting EG7 (an OVA transfection the EL4 thymoma) rejection in mice. In this study, we show that the ability of the host to respond to Tc1-secreted IFN-gamma is critical for promoting acute tumor rejection, while host production of IFN-gamma is not important. CFSE-labeled wild-type and IFN-gamma-deficient Tc1 cells divide rapidly in secondary lymphoid organs, indicating no defect in rate of cell division. However, wild-type Tc1 cells accumulate to significantly greater numbers in the tumor than deficient Tc1 cells. Hosts injected with wild-type Tc1 effectors had more T cells within the tumor at day 4, had higher levels of MCP-1, IFN-gamma-inducible protein-10, MIP-1alpha, and MIP-1beta mRNA transcripts, had greater numbers of CD11b+ and Gr-1+ cells within the tumor, and had massive regions of tumor cell apoptosis as compared with IFN-gamma knockout Tc1 cell-treated hosts. NO has a cytostatic effect on EG7 growth in vitro, and NO is important for tumor eradication by day 22. These observations are compatible with a model in which the donor CD8 Tc1 effectors expand rapidly in the host, migrate to the tumor site, and induce the secretion of a number of chemokines that in turn recruit host cells that then attack the tumor.

Human platelets target dendritic cell differentiation and production of proinflammatory cytokines

BACKGROUND

Dendritic cells (DCs) are the most potent antigen-presenting cells that initiate and regulate immune responses. They are unique in their feature to produce bioactive interleukin (IL)-12, a major proinflammatory cytokine connecting innate and adaptive immunity. Platelets (PLTs) are highly reactive components of the circulatory system with fundamental importance in hemostasis and innate immunity. Recently, immunomodulatory capacities of single specific human PLT-derived products on DC effector functions were identified. To improve the understanding of PLT-DC interactions, this study investigates the influence of intact resting and activated PLTs on DC phenotype and key functions.

STUDY DESIGN AND METHODS

Magnetic beads sorted CD14+ cells were expanded in the presence and absence of resting or activated PLTs. DC differentiation, maturation, allostimulatority capacity, antigen uptake, and cytokine profile were estimated to control group.

RESULTS

Activated PLTs potently impaired DC differentiation according to CD1a expression (mean reduction, 62%; p < 0.05). Production of IL-12p70 and tumor necrosis factor-alpha was reduced in the presence of resting (mean reduction, 46 and 55%, respectively; p < 0.05) as well as activated PLTs (mean reduction, 63 and 49%, respectively; p < 0.05). In contrast to the suppression of proinflammatory cytokines, activated PLTs increased production of the immunoregulatory cytokine IL-10 by DCs (mean increase, 52%; p < 0.05). DC allostimulatority capacity, antigen uptake, and phenotypic maturation remained unaffected.

CONCLUSION

It is proposed that intact PLTs connect immunity and hemostasis by interfering with DC differentiation and cytokine production. This interference might be of importance in clinical settings, such as DC therapy and PLT transfusions.

Epithelial-specific transcription factor ESE-3 is involved in the development of monocyte-derived DCs

Dendritic cells (DCs) are recognized as the most potent antigen-presenting cells of the immune system with the unique ability to initiate and maintain primary immune responses. In order to better characterize the functional and phenotypic features of DCs, a subtractive cDNA library to identify differentially expressed genes in monocyte-derived DCs (MDCs) was constructed. Using this approach, we found that the epithelial transcription factor ESE-3, which was previously shown to be exclusively expressed in cells of epithelial origin, is differentially expressed in MDCs. This was further confirmed by reverse transcriptase–polymerase chain reaction (RT-PCR) and Western blot analyses. The expression of ESE-3 is up-regulated upon maturation of MDCs and inhibited by treating the cells with IL-10 or IFN-γ. Knockdown experiments using siRNA suggest that ESE-3 plays an important role during MDC development. Our results might help to improve the phenotypic characterization of DCs and lead to a better understanding of the cellular mechanisms involved in antigen presentation and T-cell stimulation.

Effect of Tyrosine Kinase Inhibition Using Imatinib on Normal Lymphohematopoietic Cells

Imatinib is a selective tyrosine kinase inhibitor used for the treatment of Philadelphia chromosome-positive leukemias and other malignancies. An important clinical observation is that imatinib can affect the function of normal nonmalignant cells resulting in myelosuppression in treated patients. This observation is supported by the recent findings suggesting that imatinib might affect mobilization, proliferation, and differentiation of hematopoietic progenitor cells while leaving hematopoietic stem cells unaffected. Furthermore, the induction of a specific T cell response seems to be impaired in chronic myeloid leukemia (CML) patients treated with imatinib in contrast to patients receiving interferon-alpha. Recent studies demonstrate that in vitro exposure of mobilized human CD34(+) progenitors to imatinib inhibits their differentiation into dendritic cells. This is of importance as some of the therapeutic effects in the treatment of patients with CML are mediated by the induction of leukemia-specific T cell responses. Studies investigating the effects of imatinib on normal hematopoiesis are of interest because they might help us better understand the side effects observed clinically and might lead to the identification of novel therapeutic applications of the drug (e.g., in Bcr-Abl(-) myeloproliferative disorders and potentially as an immunomodulatory agent).

Severe Impairment of Dendritic Cell Allostimulatory Activity by Sendai Virus Vectors Is Overcome by Matrix Protein Gene Deletion

Delivery of Ags to dendritic cells (DCs) plays a pivotal role in the induction of efficient immune responses ranging from immunity to tolerance. The observation that certain viral pathogens are able to infect DCs has led to a concept in which applications of recombinant viruses are used for Ag delivery with the potential benefit of inducing potent Ag-specific T cell responses directed against multiple epitopes. As a prerequisite for such an application, the infection of DCs by recombinant viruses should not interfere with their stimulatory capacity. In this context, we could show that an emerging negative-strand RNA viral vector system based on the Sendai virus (SeV) is able to efficiently infect monocyte-derived human DCs (moDCs). However, after infection with SeV wild type, both the response of DCs to bacterial LPS as a powerful mediator of DC maturation and the allostimulatory activity were severely impaired. Interestingly, using various recombinant SeV vectors that were devoid of single viral genes, we were able to identify the SeV matrix (M) protein as a key component in moDC functional impairment after viral infection. Consequently, use of M-deficient SeV vectors preserved the allostimulatory activity in infected moDCs despite an efficient expression of all other virally encoded genes, thereby identifying M-deficient vectors as a highly potent tool for the genetic manipulation of DCs.

Recent advances in immunotherapy of B-CLL using ex vivo modified dendritic cells

Chronic lymphocytic leukemia (CLL) results from the relentless accumulation of small mature, slowly dividing, monoclonal B-lymphocytes. The clinical course is heterogeneous, some patients with aggressive form of the disease progressing rapidly with early death while others exhibit a more stable, possibly, non-progressing indolent type of the disease lasting many years. Despite progress in modern treatment modalities, relapse invariably occurs and disease still remains incurable. The clinical management of CLL is therefore challenging and considerable effort has been directed towards novel therapeutic strategies aimed at reducing minimal residual disease which can increase remission duration. Recent insight into the role of dendritic cells (DCs) as pivotal antigen presenting cells that initiate immune responses may provide the basis for generating more specific and effective immune responses. Ex-vivo modified and monocyte-derived DCs represents a promising approach within the context of CLL. However, understanding the relationship between DCs and the cellular immune response is crucial in devising strategies for manipulating immune responses. After a brief survey of general properties of DCs, this review focuses on the different approaches exploiting monocyte-derived DCs in CLL, which may help to design novel strategies for phase-I clinical trials.

An experimental study of dendritic cells-mediated immunotherapy against intracranial gliomas in rats

OBJECT

To investigate the effect of dendritic cells(DC) pulsed with apoptotic tumor cells for treatment of intracranial gliomas in rats.

METHODS

C6 glioma cells were injected into brain of Wistar rats under stereotactic monitor to establish an animal model of glioma. The precursors of DCs were isolated from bone marrow of rats, stimulated in vitro with recombinent rat granulocyte-macrophage colony-stimulating factor (rrGM-CSF) and interleukin-4 (rrIL-4). These DCs were then pulsed ex vivo with apoptotic C6 glioma cells induced by heating and subsequently injected subcutaneously into rats harboring intracranial C6 glioma. Rats were treated with five weekly subcutaneous injections of either control media, unpulsed DCs, or DCs pulsed with apoptotic tumor cells. The animals were followed for survival, volume of tumor by MRI, CD8 + T cells, cytotoxicity assay in vitro and proliferational function of lymphocytes in peripheral blood were determined by flow cytometry(FCM). The concentration of cytokines interferon-gamma (IFN-gamma) and interleukin-10(IL-10) were monitored through enzyme-linked immunosorbent assay(ELISA) using ELISAkit.

RESULTS

Our results indicated that C6 glioma model rats treated with apoptotic tumor cells pulsed DCs prolonged survival, inhibited the tumor growth and increased the level of CD8 + T lymphocytes in peripheral blood comparing with control group. Cytotoxicity assay suggested that vaccination with these apoptotic cells pulsed DCs can induce cytotoxic T lymphocytes response against C6 tumor cells compared with control group. Furthermore, significantly enhanced IFN-gamma and reduced IL-10(even undetectable) were observed in peripheral blood of rats treated with pulsed-DCs. No evident autoimmune response were detected.

CONCLUSIONS

Our data demonstrated that systemic vaccination with DCs pulsed with apoptotic cells is a safe and effective immunotherapy for intracranial glioma.

Electroporation of immature and mature dendritic cells: implications for dendritic cell-based vaccines

Until now, studies utilizing mRNA electroporation as a tool for the delivery of tumor antigens to human monocyte-derived dendritic cells (DC) have focused on DC electroporated in an immature state. Immature DC are considered to be specialized in antigen capture and processing, whereas mature DC present antigen and have an increased T-cell stimulatory capacity. Therefore, the consensus has been to electroporate DC before maturation. We show that the transfection efficiency of DC electroporated either before or after maturation was similarly high. Both immature and mature electroporated DC, matured in the presence of an inflammatory cytokine cocktail, expressed mature DC surface markers and preserved their capacity to secrete cytokines and chemokines upon CD40 ligation. In addition, both immature and mature DC can be efficiently cryopreserved before or after electroporation without deleterious effects on viability, phenotype or T-cell stimulatory capacity including in vitro antigen-specific T-cell activation. However, DC electroporated after maturation are more efficient in in vitro migration assays and at least as effective in antigen presentation as DC electroporated before maturation. These results are important for vaccination strategies where an optimal antigen presentation by DC after migration to the lymphoid organs is crucial.

An insect antibacterial peptide-based drug delivery system

The ability of the short, proline-rich native antibacterial peptides to penetrate bacterial and host cells suggests the utility of these transport systems in delivering peptidic cargo into cells. We studied the uptake of pyrrhocoricin and its most potent dimeric analogue by bacteria as well as human dendritic cells and fibroblasts. Native pyrrhocoricin entered the susceptible organism Escherichia coli very efficiently and the nonsusceptible bacterium Staphylococcus aureus to a significant degree. The antibacterial peptide also penetrated human monocyte-derived dendritic cells. It failed, however, to enter fibroblasts, whereas the designer analogue Pip-pyrr-MeArg dimer penetrated all the cell types that were studied. When glucoincretin hormone Glp-1 fragment 7-36 was cosynthesized with the dimer, the antibacterial peptide derivative lost its ability to cross the bacterial membrane layer. In contrast, a chimera of the Pip-pyrr-MeArg dimer and two copies of a shorter (nine residues) class I major histocompatibility complex epitope successfully entered bacterial and mammalian cells. While the Pip-pyrr-MeArg dimer was not immunogenic when inoculated into mice, the chimera elicited a strong cytotoxic T-cell response, indicating the maintenance of the antigenic integrity of the cargo in the peptide conjugate. The chimera when tested for its immunological properties activated human dendritic cells significantly more strongly than any of the two independent fragments alone, yet lacked mammalian cell toxicity. These results confirm the utility of designed pyrrhocoricin analogues for delivery of peptidic cargo across cell membranes in general, and their potential as carriers for epitope-based vaccines in particular.

Rapid construction of a dendritic cell vaccine through physical perturbation and apoptotic malignant T cell loading

We have demonstrated that adherence and release of monocytes from a plastic surface drives their differentiation into immature dendritic cells (DC,) that can mature further during overnight incubation in the presence of apoptotic malignant T cells. Based on these results, we sought to develop a clinically, practical, rapid means for producing DC loaded with malignant cells. A leukapheresis harvest containing the clonal, leukemic expansion of malignant CD4+ T cells was obtained from the blood of patients with cutaneous T cell lymphoma (CTCL). CTCL cells were purified with a CD3-magnetic bead column where CD3 engagement rendered the malignant T cells apoptotic. The monocyte fraction was simultaneously activated by column passage, re-added to the apoptotic CTCL cells and co-cultured overnight. CTCL cell apoptosis, DC differentiation and apoptotic malignant T cell ingestion were measured by immunostaining. The results demonstrate that as monocytes passed through the column matrix, they became activated and differentiated into semi-mature DC expressing significantly increased levels of class II, CD83 and CD86 (markers associated with maturing DC) and reduced expression of the monocyte markers CD14 and CD36. Apoptotic malignant T cells were avidly engulfed by the phagocytic transitioning DC. The addition of supportive cytokines further enhanced the number of DC that contained apoptotic malignant T cells. Functional studies confirmed that column passaged DC increased class II expression as shown by significantly enhanced stimulation in mixed leukocyte culture compared to control monocytes. In addition, DC loaded with apoptotic CTCL cells stimulated an increase in the percentage and absolute number of CD8 T cells compared to co-cultivation with non-loaded DC. After CD8 T cells were stimulated by DC loaded with malignant cells, they mediated increased apoptosis of residual CTCL cells and TNF-alpha secretion indicating development of enhanced cytolytic function. We report a simple one-step procedure where maturing DC containing apoptotic malignant T cells can be prepared rapidly for potential use in vaccine immunotherapy. Ready access to both the DC and apoptotic cells provided by this system will allow extension to other malignancies through the addition of a variety of apoptotic tumor cells and maturation stimuli.

Allogeneic dendritic cell vaccination against metastatic renal cell carcinoma with or without cyclophosphamide

In this phase I/II study, we evaluated the feasibility, safety and efficacy of allogeneic dendritic cells (DCs) with or without cyclophosphamide in the treatment of patients with metastatic renal cell carcinoma (RCC). Immunomagnetic beads were used to isolate CD14(+) monocytes from healthy donor leukapheresis products, and CD83(+) antigen-pulsed monocyte-derived DCs (moDCs) loaded with tumor lysate and keyhole limpet hemocyanin (KLH) were generated. Twelve patients were treated with allogeneic moDCs alone, while ten patients also received cyclophosphamide on days 4 and 3 prior to vaccination. Of the 22 patients enrolled, 20 received full treatment consisting of at least three vaccinations at monthly intervals. Two mixed responses with substantial tumor regression were observed. In 3 patients, disease stabilization occurred, in 13 patients disease progressed and 4 patients were lost to follow-up. Overall, immune responses against KLH and tumor lysate were weak or absent; however, the strongest increases in antigen-independent and KLH-specific responses were observed in the 2 patients with mixed responses. In addition, 1 of them showed a substantial increase in oncofetal antigen (OFA)-specific IFN-gamma production. Importantly, the 2 mixed responders and 1 patient with stable disease belonged to the cyclophosphamide group. Median overall survival in the cyclophosphamide group was 23.2 and 20.3 months in the group that received allogeneic moDCs alone. Allogeneic immunotherapy with moDCs is feasible and well tolerated. However, the immunogenicity of allogeneic moDCs is clearly less pronounced than that of autologous moDC immunotherapy. Cyclophosphamide may have the capacity to augment DC-induced antitumor immunity.

Effects of imatinib on monocyte-derived dendritic cells are mediated by inhibition of nuclear factor-kappaB and Akt signaling pathways

Dendritic cells are the most powerful antigen-presenting cells playing a decisive role for the initiation and maintenance of primary immune responses. However, signaling pathways involved in the differentiation of these cells have not been fully determined. Imatinib is a novel tyrosine kinase inhibitor effective against Abl kinases, c-Kit, and platelet-derived growth factor receptor. Using this compound, we show that human monocyte-derived dendritic cells generated in the presence of therapeutic concentrations of imatinib show a reduced expression of CD1a, MHC class I and II, and costimulatory molecules as well as decreased secretion of chemokines and cytokines resulting in an impaired capacity of dendritic cells to elicit primary T-cell responses. Using Western blot analyses, we found that these effects are mediated by inhibition of phosphatidylinositol 3-kinase/Akt pathways and a pronounced down-regulation of nuclear localized protein levels of nuclear factor-kappaB family members. Importantly, using blocking antibodies and tyrosine kinase inhibitors, we show that the inhibitory effects of imatinib on dendritic cell differentiation are not mediated via platelet-derived growth factor receptor and c-Kit. Taken together, our study reveals that imatinib inhibits dendritic cell differentiation and function via Akt and nuclear factor-kappaB signal transduction. Importantly, we show that imatinib can inhibit the function of normal, nonmalignant cells that may result in immunosuppression of these patients.

Immunologic approaches to breast cancer treatment

The need for less toxic adjuvant therapies and a better understanding of the processes by which the immune system can eradicate micrometastatic disease has generated significant interest in breast cancer immunotherapy. There are many potential approaches to stimulating an immune response against a tumor, each with relative advantages and disadvantages in regards to cost, immunogenicity, and clinical applicability in treating breast cancer. This article will review the mechanisms by which the immune system can recognize and eradicate neoplastic cells and the various methods of stimulating an anti-tumor immune response. Obstacles to the clinical effectiveness of immunotherapies in breast cancer are also discussed.

Dendritic cells derived from metastatic cancer patients vaccinated with allogeneic dendritic cell-autologous tumor cell hybrids express more CD86 and induce higher levels of interferon-gamma in mixed lymphocyte reactions

Dendritic cells (DCs) are highly effective antigen-presenting cells that, when derived from cancer patients, seem to be functionally deficient. Herein, we show that vaccination with allogeneic DC-autologous tumor cell hybrids affects the phenotype and improves the function of monocyte-derived DCs (Mo-DCs) from cancer patients. Mononuclear cells were isolated from patients' peripheral blood by density gradient centrifugation, and adherent cells were cultured in medium containing GM-CSF plus IL-4 and, after 5 days, TNF-alpha. After 2 more days, Mo-DCs were harvested and their CD80, CD86, and CD83 expression was assessed by flow cytometry. They were also used as stimulators in mixed lymphocyte reactions (MLR), where IFN-gamma production was measured by ELISA. Mo-DCs from unvaccinated patients expressed significantly lower levels of CD86, and tended to express lower levels of CD83 than Mo-DCs from healthy donors. However, Mo-DCs generated after hybrid cell vaccination presented increased expression of the same markers and induced significantly higher levels of IFN-gamma in MLR. These results indicate that the use of allogeneic DC-based cancer vaccines induces recovery of DC function in metastatic cancer patients and, therefore, could precede the use of autologous DCs for vaccine preparation. Such an approach could be relevant and should be investigated in clinical trials.

Systematic Comparison of Dendritic Cell-based Immunotherapeutic Strategies for Malignant Gliomas: In Vitro Induction of Cytolytic and Natural Killer-like T Cells

OBJECTIVE

To compare the efficacy of various immunotherapeutic strategies of loading dendritic cells (DCs) with whole-glioma cell antigens and characterize the effector responses induced.

METHODS

DCs were either fused with major histocompatibility complex (MHC)-matched glioma cells (Fusion) or pulsed with apoptotic tumor cells (DC/Apo), total tumor ribonucleic acid (RNA) (DC/RNA), or tumor lysate (DC/Lys). These tumor-DC preparations were then assessed for their phenotype, cytokine profile, and capacity to stimulate autologous peripheral blood mononuclear cells (PBMCs) in vitro. Phenotype and tumor-specific cytolytic activities of various effector cell populations were characterized and compared.

RESULTS

The various tumor-DC preparations exhibited similar phenotype and cytokine profiles irrespective of the method of loading tumor-cell antigens. However, the fusion, DC/Apo, and DC/RNA induced superior tumor cytolytic activities in PBMCs compared with DC/Lys or DC and tumor controls. DC/Apo induced the greatest expansion of tumor-specific lymphocytes, as detected by trypan blue exclusion and thymidine incorporation assays. Flow cytometric analyses also revealed the highest relative percentages of T helper cells (CD3+CD4+), cytotoxic T lymphocytes (CTLs) (CD3+CD8+), and natural killer (NK)-like T cells (CD3+CD56+) in the DC/Apo group among all the groups studied, indicating that DC/Apo induced expansion of PBMCs bearing multiple T and NK cell markers. Interestingly, isolated NK-like T cells demonstrated significantly higher tumor cytotoxicity compared with CTLs isolated from the same groups and was also non-MHC-restricted.

CONCLUSION

Apoptotic tumor cells may be an optimal source of whole-tumor-cell antigen for immunotherapy of gliomas. The study also demonstrates for the first time that both CTLs and NK-like T cells are expanded and stimulated by mature, tumor-pulsed DCs.

Function and survival of dendritic cells depend on endothelin-1 and endothelin receptor autocrine loops

The biologic effects of endothelin-1 (ET-1) are not limited to its potent vasoconstricting activity. The endothelin receptors, ETA and ETB, have differential tissue and functional distributions. Here we showed that dendritic cells (DCs), the major antigen-presenting cells in the adaptive limb of the immune system, produce large amounts of ET-1 and significantly increase the expression of endothelin receptors upon maturation. Selective blockade of the ETA receptor significantly reduced expression of the mature DC marker CD83, decreased the production of the immunostimulatory cytokine interleukin-12, down-regulated DC ability to stimulate T cells, and promoted DC apoptosis. Selective ETB receptor blockade, on the other hand, resulted in increased expression of CD83 and improved DC survival. Therefore, ET-1/ETA/ETB autocrine/paracrine loops on DCs appear to be essential for the normal maturation and function of human DCs, presenting a unique target for immunomodulatory therapies.

Role of CD44 and hyaluronic acid (HA) in activation of alloreactive and antigen-specific T cells by bone marrow-derived dendritic cells

In the current study, the role played by hyaluronic acid (HA) and its receptor CD44 on the activation and functions of dendritic cells (DCs) was investigated. Activation of DCs with HA enhanced their ability to stimulate allogeneic and antigen (Ag)-specific T cells markedly. HA treatment upregulated the expression of costimulatory molecules such as CD40, CD80, and CD86 on DCs. Cell mixing experiments using DC or T cells from CD44 wild-type or CD44 knockout mice as well as blocking studies with anti-CD44 monoclonal antibodies revealed that CD44 expression on T cells but not DC played a critical role in Ag-specific T-cell responsiveness. Also, the HA-induced activation of DC was independent of CD44. When conjugate formation between Ag-pulsed DCs and Ag-specific T cells was studied, the deficiency of CD44 on T cells rather than on DCs was found to play a key role in T-cell-DC interaction. Together, these data demonstrated that HA can activate DC independently of CD44; however, CD44 expressed on Ag-specific T cells plays a critical role in its interaction with DC and resultant expansion of T cells.