Cellular Immunotherapy with Dendritic Cells in Cancer: Current Status

One Single Site Clinical Study: To Evaluate the Safety and Efficacy of Immunotherapy With Autologous Dendritic Cells, Cytokine-Induced Killer Cells in Primary Hepatocellular Carcinoma Patients

Dendritic cells (DCs) and cytokine-induced killer (CIK) cells play an important role in the anti-tumor immune response. In this study, we evaluated the clinical effectiveness of DC/CIK-CD24 immunotherapies to primary hepatocellular carcinoma patients who received radical resection. 36 resected primary hepatocellular carcinoma (HCC) patients were enrolled from August 2014 to December 2015. All patients received two or four times of DC/CIK immunotherapy after radical resection. 1-4 years patients' survival rates were evaluated during the follow-up. The 4-year survival rate of patients who received two times of immunotherapy was 47.1%, and the rate of those who received four times of immunotherapies was 52.6%. Compared to baseline, after receiving the DC/CIK-CD24 autotransfusion, the serum Treg concentration of the patients decreased, while CD3+, CD4+, CD56+ increased slightly. The adverse effect of immunotherapy was I-II° transient fever and could be tolerable. DC/CIK-CD24 immunotherapy can delay the relapse time.

Autologous dendritic cells pulsed with lysate from an allogeneic hepatic cancer cell line as a treatment for patients with advanced hepatocellular carcinoma: A pilot study

OBJECTIVES

This is a randomized trial adopted to evaluate the safety and efficacy of immunization with specific anti-hepatocellular carcinoma dendritic cells (DCs) in Egyptian patients with advanced hepatocellular carcinoma (HCC) as a treatment or adjuvant therapy in comparison with the traditional therapy.

METHODS

This study was conducted on 20 HCC patients who were assigned to four groups according to BCLC staging; group I: HCC patients (stage B) received trans-arterial chemoembolization (TACE) and DCs as an adjuvant therapy; group II: HCC patients (stage B) received TACE only; group III: advanced HCC patients (stage D) received DCs vaccine; group IV: advanced HCC patients (stage D) received supportive treatment. DCs were generated from peripheral blood monocytes and pulsed with a lysate of an allogeneic hepatic cancer cell line (HepG2). Toxicity and immunological response were reported as primary outcomes whereas clinical biochemical and radiological responses were reported as secondary outcomes.

RESULTS

Our study detected that patients who received DCs vaccine (group III) showed mild decrease in Child-Pugh score as well as AFP and PIVKA II levels and developed 20% partial response [PR] 40% stable disease [SD] and 40% progressive disease [PD] compared to the patients of group IV on supportive treatment who developed 100% PD. Although group I patients developed PR (60%) SD (20%) and PD (20%) no significant difference was detected in the clinical biochemical or radiological response between group I and group II patients. DCs vaccine had minimal adverse effects with no autoimmunity and elicited a better immunological response such as increased CD8 cells percentage and number as well as decreased TGFβ levels in the vaccinated patients.

CONCLUSION

DCs vaccine is safe as it is not associated with significant toxicity. However due to the small number of included patients the efficacy and immune response of using DCs vaccine in the treatment of advanced HCC patients need to be justified by testing of a large cohort.

Biophysical effects in off-resonant gold nanoparticle mediated (GNOME) laser transfection of cell lines, primary- and stem cells using fs laser pulses

Gold nanoparticle mediated (GNOME) laser transfection is a powerful technique to deliver small biologically relevant molecules into cells. However, the transfection of larger and especially negatively charged DNA remains challenging. The efficiency for pDNA was 0.57% using parameter that does not influence the endo- and exogenous DNA. In order to gain a deeper understanding of the actual molecule uptake process, the uptake efficiency was determined using molecules of different sizes. It was evaluated that uncharged dextran molecules (2000 kDa) were delivered with an efficiency of 68%. The intracellular distribution of injected molecules was visualized and larger molecules were primary found in the cytoplasm. Patch clamp measurements suggested a permeabilization time up to 15 minutes. The uptake efficiency depended on the size and charge of the molecule to deliver as well as the cell size. A minor role for transfection plays the cell type since primary stem cells were successfully transfected. The perforation efficiency of semi-adherent and suspension cells is influenced by the cell and molecule size.

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.

A prospective study of the efficacy of a combination of autologous dendritic cells, cytokine-induced killer cells, and chemotherapy in advanced non-small cell lung cancer patients

Dendritic cells (DC) play a crucial role in the induction of an effective antitumor immune response. Cytokine-induced killer (CIK) cells, a subset of T lymphocytes, have the capacity to eliminate cancer cells. This study was to evaluate the correlation between the frequency of DC/CIK immunotherapies following regular chemotherapy, the time-to-progression (TTP), and overall survival (OS) of advanced non-small lung cancer patients. Sixty patients with IIIB-IV non-small-cell lung carcinoma (NSCLC) were enrolled from August 2007 to December 2009 and were randomized into two groups. All 60 patients received four courses of navelbine-platinum (NP) chemotherapy. In one group, 30 patients were treated with adoptive autologous DC/CIK cell transfusion twice every 30 days. In the other group, the patients received immunotherapies more than twice every 30 days. The adverse effects, TTP, and OS were evaluated between the two groups. Median survival time of all 60 patients was 13.80 months. The 1-, 2-, and 3-year overall survival rates were 60.0, 21.7, and 15.0 %, respectively. The 1-, 2-, and 3-year overall survival rates of patients receiving more than two immunotherapies were 63.3, 30.0, and 23.3 %, and the rates of those receiving two immunotherapies were 56.7, 13.3, and 6.7 %, respectively. The difference between the two groups was statistically significant (P = 0.037). Compared with patients in the fewer immunotherapies group, TTP in the group receiving more immunotherapies significantly prolonged, with the median improving from 6.2 months (95 % CI, 5.35-9.24) to 7.3 months (95 % CI, 5.45-6.95; P = 0.034). The adverse effects of chemoimmunotherapy were tolerable. Advanced NSCLC patients can benefit from the combination of DC/CIK immunotherapies following conventional chemotherapy. More than two immunotherapies improved TTP and OS of those patients in this study.

Enhanced function of cytotoxic T lymphocytes induced by dendritic cells modified with truncated PSMA and 4-1BBL

Interactions between costimulatory molecules and their receptors are vital for Ag-presenting dendritic cells (DCs) to initiate T cells activation, expansion and their antitumor immune responses. Augmentation of costimulatory signal due to the interaction of DCs and T cells may amplify, sustain and drive diversity of cytotoxic T lymphocytes (CTLs) and consequently enhance the antitumor response. 4-1BBL/4-1BB is such a pair of costimulatory ligand and receptor, playing an important role in the co-stimulation of CTLs. Previously, we demonstrated that DCs transduced with recombinant adenovirus encoding truncated PSMA (tPSMA) and m4-1BBL could induce prostate cancer regression in mouse models. In the present study, we further explored the adjuvant role of 4-1BBL in modulating CTLs activation induced by tPSMA gene-pulsed DCs. The apoptosis and cytotoxicity against tPSMA expressing RM-1 cells of CTLs were determined. Results showed that tPSMA gene-pulsed DCs effectively induced T lymphocyte activation and cytotoxicity, which was enhanced by upregulated expression of 4-1BBL, displaying better cell viability, lower CTLs apoptosis, higher expression anti-apoptotic protein of Bcl-xL and phosphorylation of P38, enhanced NF-κB activation, as well as more IFN-γ production. These results demonstrated that 4-1BBL may play a significant role in the co-stimulation pathway for Ag-presenting DCs-mediated CTLs activity, which might be a beneficial adjuvant factor for DCs-based cancer immunotherapy.

Interleukin-15 enhances T-cell responses by stimulation with dendritic cells

INTRODUCTION

Cytokines play important roles in regulating immune responses. Interleukin-2 (IL-2) has usually been used as an adjuvant to enhance antitumour immune responses. However, its crucial role in activation-induced cell death, inhibition of homeostatic proliferation of CD8+ memory T cells and its notable biological side effects impair its prospect of application. IL-15 has several similar functions to IL-2 and shows potential advantages over IL-2, and is being investigated to enhance antitumour dendritic cell (DC) vaccine strategies in our ongoing studies.

OBJECTIVE

In this preliminary study, we evaluated the ability of IL-15, compared with IL-2, to act as an adjuvant to enhance T-cell responses activated by DCs in vitro.

MATERIALS AND METHODS

Bone marrow-derived DCs (BMDCs) were pulsed with tumour antigens and used to stimulate lymphocyte responses in the presence of IL-15 or IL-2. The activated T lymphocytes were examined by flow cytometric analysis, and interferon-γ (IFN-γ) enzyme-linked immunospot and cytotoxicity assays.

RESULTS

IL-15 was observed to activate lymphocytes with comparable phenotype characteristics of activated/memory CD8+ lymphocytes, compared with IL-2. Both in primary and secondary stimulation with DCs, when using IL-15 as an adjuvant, activated lymphocytes showed higher proportions of IFN-γ-secreting subsets. In secondary stimulation with BMDCs in the presence of IL-15, the activated lymphocytes showed a stronger cytotoxicity to antigen-specific tumour target cells.

CONCLUSIONS

Our study suggested that IL-15 might be a prospective adjuvant for a DC vaccine strategy against cancers. The further observation that IL-15 acts as an adjuvant for an antitumour DC vaccine strategy is worth investigating.

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

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

Immunotherapy in renal cell carcinoma

Treatment of metastatic renal cell cancer is still challenging due to its resistance to conventional therapies, such as radiotherapy or chemotherapy. Immunotherapeutic approaches with IL-2 and/or IFN-alpha have become standard regimens in treating metastatic renal cell cancer. Furthermore, molecularly targeted therapies, such as VEGF-pathway inhibition or use of mammalian target of rapamycin inhibitors, have demonstrated promising results and might become even more important in the following years. Finally, vaccination therapies have gained increasing interest and have been tested in multiple clinical trials. There is a vast choice of different application and production types of these vaccines, ranging from dendritic cell-based principals to the application of naked RNA. The development of new immune-enhancing strategies led to the option of interesting, potent combination regimes. This review has a focus on vaccination therapies in renal cell cancer, especially dendritic cell-based principals, and aims to give an overview of this rapidly changing field of investigation.

A polysaccharide extracted from Grifola frondosa enhances the anti-tumor activity of bone marrow-derived dendritic cell-based immunotherapy against murine colon cancer

We previously isolated the novel heteropolysaccharide maitake Z-fraction (MZF) from the maitake mushroom (Grifola frondosa), and demonstrated that MZF significantly inhibited tumor growth by inducing cell-mediated immunity. In this study, we demonstrated that MZF upregulated the expression of CD80, CD86, CD83, and MHC II on bone marrow-derived dendritic cells (DCs) and significantly increased interleukin-12 (IL-12) and tumor necrosis factor-alpha production by DCs in a dose-dependent manner. MZF-treated DCs significantly stimulated both allogeneic and antigen-specific syngenic T cell responses and enhanced antigen-specific interferon-gamma (IFN-gamma) production by syngenic CD4(+) T cells; however, MZF-treated DCs did not affect IL-4 production. Furthermore, the enhancement of IFN-gamma production in CD4(+) T cells, which was induced by MZF-treated DCs, was completely inhibited by the addition of an anti-IL-12 antibody. These results indicate that MZF induced DC maturation and antigen-specific Th1 response by enhancing DC-produced IL-12. We also demonstrated that DCs pulsed with colon-26 tumor lysate in the presence of MZF induced both therapeutic and preventive effects on colon-26 tumor development in BALB/c mice. These results suggest that MZF could be a potential effective adjuvant to enhance immunotherapy using DC-based vaccination.

Anti-tumor immune response induced by dendritic cells transduced with truncated PSMA IRES 4-1BBL recombinant adenoviruses

Up-regulation of receptor-ligand pairs during interaction of a peptide-bound MHC complex on dendritic cells (DCs) with cognate TCR may amplify, sustain, and drive diversity in the ensuing T cell immune response. Members of the TNF ligand superfamily and the TNFR superfamily contribute to this costimulatory molecule signaling. In the present study, we used replication deficient adenoviruses to introduce a tumor-associated Ag (a truncated human prostate-specific membrane antigen (tPSMA)) and the T cell costimulatory molecule 4-1BBL into murine DCs, and observed the ability of these recombinant DCs to elicit tPSMA-directed T-cell responses in vitro and anti-tumor immunity to RM-1-tPSMA in a murine tumor model. Infection of DCs with Ad-tPSMA-IRES-m4-1BBL induced tPSMA-specific proliferative responses and up-regulated CD80 and CD86 s signaling molecules. The cytotoxic T lymphocytes activated by the Ad-tPSMA-IRES-m4-1BBL-transfected DCs showed significantly higher IFN-gamma production and cytotoxicity against the RM-1 cells transfected with tPSMA. Moreover, vaccination of mice with Ad-tPSMA-IRES-m4-1BBL-transfected DCs induced a potent protective and therapeutic anti-tumor immunity to RM-1-tPSMA in a tumor model. These results demonstrated that development of DCs engineered to express tPSMA and 4-1BBL by recombinant adenovirus-mediated gene transfer may offer a new strategy for prostate cancer immunotherapy.

Enhanced antigen presentation and CTL activity by transduction of mature rather than immature dendritic cells with octaarginine-modified liposomes

To improve uptake and cross-presentation of exogenous antigens (Ag) by dendritic cells (DCs), octaarginine-modified liposomes (R8-Lip) were used as a novel strategy for protein-Ag transduction. Immature DCs endocytose macromolecules efficiently. While mature DCs lose their ability to capture Ag, but have an increased capacity for T-cell activation. Thus Ag-transduction has been performed mostly in immature DCs. In the present study, R8-Lip were efficiently taken up by both immature and mature DCs. DCs transduced after maturation were highly efficient at cross-presentation of Ag and induced higher cytotoxic T-lymphocytes (CTL) activity than were DCs transduced before maturation. The mechanism of Ag presentation involved the escape of R8-Lip from endosomes to cytosol, which require the acidic environment. The Ag released was then processed by a proteasome-dependent pathway. This novel transduction approach is clinically applicable, easy to perform, and has more practical advantages than current protein transduction methods.

Adhesive substrate-modulation of adaptive immune responses

While it is well-known that adsorbed proteins on implanted biomaterials modulate inflammatory responses, modulation of dendritic cells (DCs) via adhesion-dependent signaling has only been begun to be characterized. In this work, we demonstrate that adhesive substrates elicit differential DC maturation and adaptive immune responses. We find that adhesive substrates support similar levels of DC adhesion and expression of stimulatory and co-stimulatory molecules. Conversely, DC morphology and differential production of pro- and anti-inflammatory cytokines (IL-12p40 and IL-10, respectively) is adhesive substrate-dependent. For example, DCs cultured on collagen and vitronectin substrates generate higher levels of IL-12p40, whereas DCs cultured on albumin and serum-coated tissue culture-treated substrates produce the higher levels of IL-10 compared to other substrates. Additionally, our results suggest substrate-dependent trends in DC-mediated allogeneic CD4(+) T-cell proliferation and T-helper cell type responses. Specifically, we show that substrate-dependent modulation of DC IL-12p40 cytokine production correlates with CD4(+) T-cell proliferation and T(h)1 type response in terms of IFN-gamma producing T-helper cells. Furthermore, our results suggest substrate-dependent trends in DC-mediated stimulation of IL-4 producing T-cells, but this T(h)2 type response is not dependent on DC production of IL-10 cytokine. This work has impact in the rational design of biomaterials for diverse applications such as tissue-engineered constructs, synthetic particle-based vaccines and the ex vivo culture of DCs for immunotherapies.

Immunotherapy with dendritic cells for cancer

Dendritic cells are professional antigen-presenting cells with a key role in both immunity induction and tolerance maintenance. Dendritic cells are highly specialized in antigen capture, processing and presentation, and express co-stimulation signals which activate T lymphocytes and NK cells. Dendritic cells generated in culture and loaded with an antigen efficiently induce antigen-specific immunity after injection. More recently, methods have been developed that target antigens to dendritic cells in vivo, bypassing the need for ex vivo cell manipulations. Numerous ongoing studies aim to evaluate the effectiveness of dendritic cell vaccines in preventing tumor relapses and extending patients' survival. Further implementation of this form of immunotherapy is expected following the identification of the mechanisms controlling dendritic cell immunogenicity, and from a better understanding of the cell dynamics whereby immune responses are orchestrated. Here, we discuss these new insights together with an overview of the dendritic cell-based clinical studies carried out to date.

The use of dendritic cells in cancer immunotherapy

Cancer immunotherapy aims at eliciting an immune response directed against tumor antigens to help fight off residual tumor cells and thereby improve survival and quality of life of cancer patients. Different immunotherapeutic approaches share the use of dendritic cells (DCs) to present tumor-associated antigens to T-lymphocytes. Ex vivo generated DCs can be loaded with antigens and re-infused to the patients, or they can be used for ex vivo expansion of antitumor lymphocytes. Alternatively, methods exist to target antigens to DCs in vivo without need for ex vivo cell manipulations. The clinical studies have shown that DC administration to patients is safe and induces antigen-specific immunity. However, it seldom elicits objective clinical responses in patients with advanced-stage malignancies. Novel insights into DC and lymphocyte regulation are expected to lead to more effective vaccines in the near future. Meanwhile, efforts are directed at identifying the most appropriate clinical targets for active specific immunotherapies. Data suggests that vaccinations may indeed be beneficial when given in the adjuvant setting rather than to treat metastatic cancers. These issues are discussed here together with an overview of the DC-based antitumor immunotherapy studies.

An ex vivo readout for evaluation of dendritic cell-induced autologous cytotoxic T lymphocyte responses against esophageal cancer

Esophageal cancer is a highly malignant disease that despite surgery and adjuvant therapies has an extremely poor outcome. Dendritic cell (DC) immunotherapy as a novel promising strategy could be an alternative for treating this malignancy. Effective DC-mediated immune responses can be achieved by raising cytotoxic T lymphocyte (CTL) response against multiple antigens through loading DCs with total tumor RNA. However, the efficacy of this strategy first needs to be evaluated in a pre-clinical setting. The aim of the study was to set up an ex vivo autologous human readout assay for assessing the effects of DC-mediated cytotoxic responses, using total tumor RNA as an antigen load. Biopsy specimens of seven esophageal cancer patients were used to establish primary cultures of normal and cancer cells and to obtain autologous RNA for loading DCs. Mature DCs loaded with either normal or tumor RNA were obtained and subsequently used to raise various lymphocytes populations. Apoptosis levels of the autologous cultures were measured before and after incubating the cultures with the different lymphocytes populations. The mean apoptosis levels in the tumor cell cultures, induced by lymphocytes instructed by DCs loaded with tumor RNA, significantly increased with 15.6% +/-2.9 SEM (range 3.4-24.5%, t-test, P < 0.05). Incubation of the normal cultures with the lymphocytes populations showed a mean non-significant increase in apoptosis of 0.4% +/-3.4 SEM (range -13.9 to 9.8%, t-test, P = 0.7). Here, we introduce a practical, patient-specific autologous readout assay for pre-clinical testing of DC-mediated cytotoxic responses. Additionally, we demonstrated that the use of autologous tumor RNA as a strategy for raising cytotoxic responses against multiple tumor antigens could be effective for treating esophageal cancer.

Isolation and characterization of dendritic cells from common marmosets for preclinical cell therapy studies

Dendritic cells (DCs) have important functions as modulators of immune responses, and their ability to activate T cells is of great value in cancer immunotherapy. The isolation of DCs from the peripheral blood of rhesus and African green monkeys has been reported, but the immune system in the common marmoset remains poorly characterized, although it offers many potential advantages for preclinical studies. In the present study, we devised methods, based on techniques developed for mouse and human DC preparation, for isolating DCs from three major tissue sources in the common marmoset: bone marrow (BM), spleen and peripheral blood. Each set of separated cells was analysed using the cell surface DC-associated markers CD11c, CD80, CD83, CD86 and human leucocyte antigen (HLA)-DR, all of which are antibodies against human antigens, and the cells were further characterized both functionally and morphologically as antigen-presenting cells. BM proved to be an excellent cell source for the isolation of DCs intended for preclinical studies on cell therapy, for which large quantities of cells are required. In the BM-derived CD11c(+) cell population, cells exhibiting the characteristic features of DCs were enriched, with the typical DC morphology and the abilities to undergo endocytosis, to secrete interleukin (IL)-12, and to stimulate Xenogenic T cells. Moreover, BM-derived DCs produced the neurotrophic factor NT-3, which is also found in murine splenic DCs. These results suggest that BM-derived DCs from the common marmoset may be useful for biological analysis and for preclinical studies on cell therapy for central nervous system diseases and cancer.

Dendritic cell vaccination

There has been a surge of interest in the use of dendritic cell (DC) vaccination as cellular immunotherapy for numerous cancers. Despite some encouraging results, this therapeutic modality is far from being considered as a therapy for cancer. This review will first discuss preclinical DC vaccination in murine models of cancer, with an emphasis on comparative studies investigating different methods of antigen priming. We will then comment on the various murine DC subsets and how these relate to human DC preparations used for clinical studies. Finally, the methodology used to generate human DCs and some recent clinical trials in several cancers are reviewed.

Immunotherapy against metastatic renal cell carcinoma with mature dendritic cells

OBJECTIVE

We performed a clinical trial of immunotherapy using autologous mature dendritic cells (DC) pulsed with autologous tumor lysate, for patients with metastatic renal cell carcinoma (RCC).

METHODS

Patients with refractory metastatic RCC were enrolled in the study. All of them received interferon (IFN)-alpha treatment after nephrectomy and were followed over 3 months prior to this study. Autologous monocyte-derived immature DC were pulsed with lysate from autologous primary tumor as the antigen and keyhole limpet hemocyanin (KLH) as immunomodulator, and cultured in the presence of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and prostaglandin (PG)E2 to generate mature DC. Mature DC were injected intradermally near bilateral inguinal lymph nodes of the patients. A delayed-type hypersensitivity (DTH) test and enzyme-linked immunospot (ELISPOT) assay were performed to evaluate the immunological response. After 4 months from first injection, the clinical effect was evaluated by diagnostic imaging.

RESULTS

The treatments were well tolerated without significant toxicity by the patients who were an average of 65.7 years old and had multiple metastases in the lung and other organs. One of the two patients developed a positive DTH reaction to tumor lysate and the other patient only to KLH. The patient with a positive DTH reaction to tumor lysate had stable disease in the clinical evaluation.

CONCLUSIONS

We confirmed the safety of DC therapy in this clinical trial. The DTH test revealed that the DC therapy induced immunological response to RCC. On the other hand, it was necessary to reconsider the patient selection criteria.

High transfection efficiency, gene expression, and viability of monocyte-derived human dendritic cells after nonviral gene transfer

Dendritic cells (DCs) are bone marrow-originated, professional antigen-capturing cells and APCs, which can function as vaccine carriers. Although efficient transfection of human DCs has been achieved with viral vectors, viral gene products may influence cellular functions. In contrast, nonviral methods have generally resulted in inefficient gene transfer, low levels of gene expression, and/or low cell viability. Monocyte-derived DCs are the most common source of DCs for in vitro studies and for in vivo applications. We hypothesized that reduction of the time to generate immature DCs (iDCs) might result in higher viability after transfection. Therefore, we established a protocol to generate human iDCs from CD14(+) monocytes within 3 days. These "fast" iDCs were phenotypically and functionally indistinguishable from conventional iDCs, showing high endocytic ability and low antigen-presenting capacity. Furthermore, the fast iDCs matured normally and had similar antigen-presenting capacity to conventional mature DCs. To optimize transfection of iDCs, we compared nonviral transfection of plasmid DNA and in vitro-transcribed (IVT) RNA with transfection reagents, electroporation, and nucleofection. Nucleofection of IVT RNA with the X1 program of an Amaxa Co. Nucleofector resulted in the most efficient transfection, with an average of 93% transfected iDCs, excellent long-term viability, and strong protein expression. Furthermore, the IVT RNA-transfected iDCs retained all phenotypic and functional characteristics of iDCs. This method is applicable to most purposes, including in vitro functional assays, in vivo DC immunotherapy, and DC-based vaccines.

Blood donor derived dendritic cells and cytotoxic T cells for specific fusion-gene adoptive immunotherapy

BACKGROUND AND OBJECTIVES

Therapeutic immunological reagents tailored to individual patients have been shown to be a viable treatment strategy for some forms of leukaemia. This work investigates the possibility of using blood donations as a source of leukaemia-specific immune therapeutics.

MATERIALS AND METHODS

The acute promyelocytic cell line NB4 carrying the PML-RAR alpha fusion was used as a target for cytotoxic T lymphocytes (CTL) stimulated to recognize the fusion. Stimulation of CTL was by production of dendritic cells pulsed with plasmid vectors containing polymerase chain reaction (PCR)-generated sequences of PML-RAR alpha derived from NB4 cells. PCR primer design included a Kozak consensus sequence to allow correct translation of the nucleic acid into protein. Identification of specific cytotoxicity was by both Granzyme B ELISPOT and by (51)Cr-release assays.

RESULTS

Specific CTL activity targeting NB4 cells can be generated from donor-derived peripheral blood mononuclear cells. However, individual donors appear to respond differently to the length of stimulatory sequence encoded in the vector. Use of an internal methionine in the PML gene, which also satisfies the Kozak rules, allows translation in vitro and, thus, might provide a suitable start site for stimulation using acute promyelocytic leukaemia-specific sequence.

CONCLUSION

The work presented here suggests that blood donor derived dendritic cells can be used to stimulate leukaemia-specific CTL from the same donation ex vivo. This would enable the generation of patient-specific therapeutics from major histocompatibility (MHC)-matched allogeneic donors. However, different MHC-matched donors might vary in their response depending on the length of the antigenic sequence.

Dendritic cell-based active specific immunotherapy for malignant glioma

Immunotherapy is an appealing therapeutic modality for malignant gliomas because of its potential to selectively target residual tumor cells that have invaded the normal brain. Most immunotherapeutic studies are designed to exploit the capacity of dendritic cells for inducing cell-mediated effects as well as immune memory responses for destroying residual tumor cells and preventing recurrence. Although initial clinical studies on dendritic cell-based immunotherapy resulted in very limited success, they have prompted many new studies on exploring strategies to induce a more robust antitumor immune response by using novel adjuvants for maturation and activation of dendritic cells. More studies have focused on the mechanisms of immune suppression by tumor cells and the role of regulatory T cells in tumor growth and progression. In this article, the authors review the evolution of dendritic cell-based immunotherapeutic strategies for adjuvant treatment of malignant gliomas. The authors also discuss how new knowledge on tumor-intrinsic mechanisms of tolerance induction and immunosuppression are likely to shape the future of immunotherapy for high-grade gliomas.

Improved generation of anti-tumor immunity by antigen dose limitation

Background

The malignant cells of cutaneous T cell lymphoma (CTCL) display immunogenic peptides derived from the clonal T cell receptor (TCR) providing an attractive model for refinement of anti-tumor immunization methodology. To produce a clinically meaningful anti-tumor response, induction of cytotoxic anti-CTCL cells must be maximized while suppressive T regulatory cells (Treg) should be minimized. We have demonstrated that engulfment of apoptotic CTCL cells by dendritic cells (DC) can lead to either CD8 anti-CTCL responses or immunosuppressive Treg induction. Treg generation is favored when the number of apoptotic cells available for ingestion is high.

Methods

In this study, we sought to determine whether the balance between immunity and immunosuppression could be shifted towards a CD8 anti-CTCL response by lowering the ratio of apoptotic CTCL cells available for DC ingestion. CTCL cell apoptosis was produced by engagement of the TCR by anti-CD3 antibody affixed to magnetic beads.

Results

The physical perturbation inherent in passage through a separation column induced monocytes to differentiate into DC, demonstrated by increased expression of class II and CD86 and decreased expression of the monocyte marker CD14. The immature DC internalized and processed apoptotic CTCL cells and could potentially present the tumor-derived peptides in the context of MHC class I and II. As the number of apoptotic cells increased, there was a dose-dependent increase in the expression of Treg markers CTLA-4, CD25, and FoxP3, with a ratio of apoptotic cell/DC loading of > 10:1 corresponding to the greatest Treg induction. These inducible phenotypic Treg also functionally inhibited CD8-mediated perforin expression in vitro. At lower levels of apoptotic cell/DC loading of < 5:1, there was an expansion of the CD8 T cell compartment with increased perforin expression and increased CTCL cell death, indicating anti-tumor activity.

Conclusion

These findings demonstrate that the ratio of apoptotic cells supplied to DC is an important determinant of whether CD8 anti-tumor immunity or immunosuppression is generated.

Defective killing of dendritic cells by autologous natural killer cells from acute myeloid leukemia patients

At the frontier between innate and adaptive immunity, dendritic cells (DCs) secrete numerous cytokines and express costimulatory molecules that initiate or enhance natural killer (NK) and T-lymphocyte responses. NK cells also regulate DC physiology by killing immature DCs (iDCs), thus limiting inflammation and inappropriate T-lymphocyte tolerization. In a previous study, we have reported that NK cells from acute myeloid leukemia patients (AML-NK cells) have deficient natural cytotoxicity receptor (NCR) expression. Herein, we analyzed the consequences of such a defect regarding the regulatory role of AML-NK cells in DC physiology. We show that NK cells display poor cytolytic capacities against DCs derived from healthy donor monocytes or derived from autologous leukemic blasts. These data point to a novel defect in the regulation of adaptive immune responses initiated by DCs in AML patients. This may lead to specific T-lymphocyte tolerization by spontaneous or ex vivo expanded iDCs expressing leukemia-derived antigens. (Blood. 2005;106: 2186-2188)

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.

Processing and presentation of HLA class I and II epitopes by dendritic cells after transfection with in vitro-transcribed MUC1 RNA

RNA transfection of dendritic cells (DCs) was shown to be highly efficient in eliciting CD8+ and CD4+ T-cell responses. However, antigen presentation pathways involved in generation of human leukocyte antigen (HLA) class I and class II peptides have remained elusive. To analyze this we incubated mucin 1 (MUC1) RNA-transfected DCs with compounds known to inhibit HLA class I presentation and used these cells in chromium 51 (51Cr)-release assays. As effectors, we used cytotoxic T lymphocyte (CTL) lines specific for the MUC1 peptides M1.1 and M1.2. We observed that the presentation of HLA-A*02 epitopes is inhibited by brefeldin A and lactacystin. To determine the requirement of a functional transporter associated with antigen processing (TAP), we cotransfected DCs with MUC1 and infected cell peptide 47 (ICP47) RNA. ICP47 could only inhibit the presentation of the M1.1 but not the M1.2 peptide, indicating that this epitope derived from the signal sequence is presented independently of TAP. Cocultivation of MUC1 RNA-transfected DCs with MUC1-specific CD4+ T lymphocytes revealed that the presentation of HLA class II peptides is sensitive to proteasomal inhibitors and brefeldin A. Furthermore, the presentation pathway requires lysosomal and endosomal processing and is mediated by autophagy. Our results demonstrate that the efficient presentation of cytosolic proteins on major histocompatibility complex (MHC) class II combines the proteolytic and lysosomal pathways.