The duration of signaling through CD40 directs biological ability of dendritic cells to induce antitumor immunity

Profiling dendritic cell subsets in head and neck squamous cell tonsillar cancer and benign tonsils

Dendritic cells (DCs) have a key role in orchestrating immune responses and are considered important targets for immunotherapy against cancer. In order to develop effective cancer vaccines, detailed knowledge of the micromilieu in cancer lesions is warranted. In this study, flow cytometry and human transcriptome arrays were used to characterize subsets of DCs in head and neck squamous cell tonsillar cancer and compare them to their counterparts in benign tonsils to evaluate subset-selective biomarkers associated with tonsillar cancer. We describe, for the first time, four subsets of DCs in tonsillar cancer: CD123⁺ plasmacytoid DCs (pDC), CD1c⁺, CD141⁺, and CD1c^-CD141^- myeloid DCs (mDC). An increased frequency of DCs and an elevated mDC/pDC ratio were shown in malignant compared to benign tonsillar tissue. The microarray data demonstrates characteristics specific for tonsil cancer DC subsets, including expression of immunosuppressive molecules and lower expression levels of genes involved in development of effector immune responses in DCs in malignant tonsillar tissue, compared to their counterparts in benign tonsillar tissue. Finally, we present target candidates selectively expressed by different DC subsets in malignant tonsils and confirm expression of CD206/MRC1 and CD207/Langerin on CD1c⁺ DCs at protein level. This study descibes DC characteristics in the context of head and neck cancer and add valuable steps towards future DC-based therapies against tonsillar cancer.

Intralesional rose bengal in melanoma elicits tumor immunity via activation of dendritic cells by the release of high mobility group box 1

Intralesional (IL) therapy is under investigation to treat dermal and subcutaneous metastatic cancer. Rose bengal (RB) is a staining agent that was originally used by ophthalmologists and in liver function studies. IL injection of RB has been shown to induce regression of injected and uninjected tumors in murine models and clinical trials. In this study, we have shown a mechanism of tumor-specific immune response induced by IL RB. In melanoma-bearing mice, IL RB induced regression of injected tumor and inhibited the growth of bystander lesions mediated by CD8⁺ T cells. IL RB resulted in necrosis of tumor cells and the release of High Mobility Group Box 1 (HMGB1), with increased dendritic cell (DC) infiltration into draining lymph nodes and the activation of tumor-specific T cells. Treatment of DC with tumor supernatants increased the ability of DCs to stimulate T cell proliferation, and blockade of HMGB1 in the supernatants suppressed DC activity. Additionally, increased HMGB1 levels were measured in the sera of melanoma patients treated with IL RB. These results support the role of IL RB to activate dendritic cells at the site of tumor necrosis for the induction of a systemic anti-tumor immune response.

Transfer of in vitro-expanded naïve T cells after lymphodepletion enhances antitumor immunity through the induction of polyclonal antitumor effector T cells

The adoptive transfer of effector T cells combined with lymphodepletion has demonstrated promising antitumor effects in mice and humans, although the availability of tumor-specific T cells is limited. We and others have also demonstrated that the transfer of polyclonal naïve T cells induces tumor-specific effector T cells and enhances antitumor immunity after lymphodepletion. Because tumors have been demonstrated to induce immunosuppressive networks and regulate the function of T cells, obtaining a sufficient number of fully functional naïve T cells that are able to differentiate into tumor-specific effector T cells remains difficult. To establish culture methods to obtain a large number of polyclonal T cells that are capable of differentiating into tumor-specific effector T cells, naïve T cells were activated with anti-CD3 mAbs in vitro. These cells were stimulated with IL-2 and IL-7 for the CD8 subset or with IL-7 and IL-23 for the CD4 subset. Transfer of these hyperexpanded T cells after lymphodepletion showed significant antitumor efficacy, and tumor-specific effector T cells were primed from these expanded T cells in tumor-bearing hosts. Moreover, these ex vivo-expanded T cells maintained T cell receptor diversity and showed long-term persistence of memory against specific tumors. Further analyses revealed that combination therapy consisting of vaccination with dendritic cells that were co-cultured with irradiated whole tumor cells and the transfer of ex vivo-expanded T cells significantly enhanced antitumor immunity. These results indicate that the transfer of ex vivo-expanded polyclonal T cells can be combined with other immunotherapies and augment antitumor effects.

Extensive crosslinking of CD22 by epratuzumab triggers BCR signaling and caspase-dependent apoptosis in human lymphoma cells

Epratuzumab has demonstrated therapeutic activity in patients with non-Hodgkin lymphoma, acute lymphoblastic leukemia, systemic lupus erythematosus, and Sjögren's syndrome, but its mechanism of affecting normal and malignant B cells remains incompletely understood. We reported previously that epratuzumab displayed in vitro cytotoxicity to CD22-expressing Burkitt lymphoma cell lines (Daudi and Ramos) only when immobilized on plates or combined with a crosslinking antibody plus a suboptimal amount of anti-IgM (1 μg/mL). Herein, we show that, in the absence of additional anti-IgM ligation, extensive crosslinking of CD22 by plate-immobilized epratuzumab induced intracellular changes in Daudi cells similar to ligating B-cell antigen receptor with a sufficiently high amount of anti-IgM (10 μg/mL). Specifically, either treatment led to phosphorylation of CD22, CD79a and CD79b, along with their translocation to lipid rafts, both of which were essential for effecting caspase-dependent apoptosis. Moreover, such immobilization induced stabilization of F-actin, phosphorylation of Lyn, ERKs and JNKs, generation of reactive oxygen species (ROS), decrease in mitochondria membrane potential (Δψ_m), upregulation of pro-apoptotic Bax, and downregulation of anti-apoptotic Bcl-xl and Mcl-1. The physiological relevance of immobilized epratuzumab was implicated by noting that several of its in vitro effects, including apoptosis, drop in Δψ_m, and generation of ROS, could be observed with soluble epratuzumab in Daudi cells co-cultivated with human umbilical vein endothelial cells. These results suggest that the in vivo mechanism of non-ligand-blocking epratuzumab may, in part, involve the unmasking of CD22 to facilitate the trans-interaction of B cells with vascular endothelium.

Direct Interaction of CD40 on Tumor Cells with CD40L on T Cells Increases the Proliferation of Tumor Cells by Enhancing TGF-β Production and Th17 Differentiation

It has recently been reported that the CD40-CD40 ligand (CD40L) interaction is important in Th17 development. In addition, transforming growth factor-beta (TGF-β) promotes tumorigenesis as an immunosuppressive cytokine and is crucial in the development of Th17 cells. This study investigated the role of CD40 in breast cancer cells and its role in immunosuppressive function and tumor progression. CD40 was highly expressed in the breast cancer cell line MDA-MB231, and its stimulation with CD40 antibodies caused the up-regulation of TGF-β. Direct CD40-CD40L interaction between MDA-MB231 cells and activated T cells also increased TGF-β production and induced the production of IL-17, which accelerated the proliferation of MDA-MB231 cells through the activation of STAT3. Taken together, the direct CD40-CD40L interaction of breast tumor cells and activated T cells increases TGF-β production and the differentiation of Th17 cells, which promotes the proliferation of breast cancer cells.

Cytotoxic T lymphocytes elicited by dendritic cell-targeted delivery of human papillomavirus type-16 E6/E7 fusion gene exert lethal effects on CaSki cells

Human papillomavirus (HPV) is the primary etiologic agent of cervical cancer. Consideration of safety and non human leukocyte antigen restriction, protein vaccine has become the most likely form of HPV therapeutic vaccine, although none have so far been reported as effective. Since tumor cells consistently express the two proteins E6 and E7, most therapeutic vaccines target one or both of them. In this study, we fabricated DC vaccines by transducing replication-defective recombinant adenoviruses expressing E6/E7 fusion gene of HPV-16, to investigate the lethal effects of specific cytotoxic T lymphocytes (CTL) against CaSki cells in vitro. Mouse immature dendritic cells (DC) were generated from bone marrow, and transfected with pAd-E6/E7 to prepare a DC vaccine and to induce specific CTL. The surface expression of CD40, CD68, MHC II and CD11c was assessed by flow cytometry (FCM), and the lethal effects of CTL against CaSki cells were determined by DAPI, FCM and CCK-8 methods. Immature mouse DC was successfully transfected by pAd-E6/E7 in vitro, and the transfecting efficiency was 40%-50%. A DC vaccine was successfully prepared and was used to induce specific CTL. Experimental results showed that the percentage of apoptosis and killing rate of CaSki cells were significantly increased by coculturing with the specific CTL (p <0.05). These results illustrated that a DC vaccine modified by HPV-16 E6/E7 gene can induce apoptosis of CaSki cells by inducing CTL, which may be used as a new strategy for biological treatment of cervical cancer.

A novel potential therapy for vascular diseases: blood-derived stem/progenitor cells specifically activated by dendritic cells

BACKGROUND

Vascular diseases are a major cause of morbidity and mortality, particularly in diabetic patients. Stem/progenitor cell treatments with bone marrow-derived cells show safety and promising outcomes, albeit not without some preprocedural adverse events related to cell collection and mobilization. We describe a novel technology for generating a therapeutic population (BGC101) of enriched endothelial progenitor cells (EPCs) from non-mobilized blood, using dendritic cells to specifically direct stem/progenitor cell activity in vitro.

METHODS AND RESULTS

Selected immature plasmacytoid and myeloid dendritic cells from 24 healthy and two diabetic donors were activated with anti-inflammatory and pro-angiogenic molecules to induce specific activation signals. Co-culturing of activated dendritic cells with stem/progenitor cells for 12-66 h generated 83.7 ± 7.4 × 10(6) BGC101 cells with 97% viability from 250 mL of blood. BGC101, comprising 52.4 ± 2.5% EPCs (expressing Ulex-lectin, AcLDL uptake, Tie2, vascular endothelial growth factor receptor 1 and 2, and CD31), 16.1 ± 1.9% stem/progenitor cells (expressing CD34 and CD184) and residual B and T helper cells, demonstrated angiogenic and stemness potential and secretion of interleukin-8, interleukin-10, vascular endothelial growth factor and osteopontin. When administered to immunodeficient mice with limb ischemia (n = 40), BGC101 yielded a high safety profile and significantly increased blood perfusion, capillary density and leg function after 21 days. Cell tracking and biodistribution showed that engraftment was restricted to the ischemic leg.

CONCLUSIONS

These observations provide preliminary evidence that alternatively activated dendritic cells can promote the generation of EPC-enriched stem/progenitor cells within a 1-day culture. The resulting product BGC101 has the potential for treatment of various vascular conditions such as coronary heart disease, stroke and peripheral ischemia.

DEAD/H (Asp-Glu-Ala-Asp/His) box polypeptide 3, X-linked is an immunogenic target of cancer stem cells

Accumulating evidence suggests that most solid malignancies consist of heterogeneous tumor cells and that a relatively small subpopulation, which shares biological features with stem cells, survives through potentially lethal stresses such as chemotherapy and radiation treatment. Since the survival of this subpopulation of cancer stem cells (CSC) plays a critical role in recurrence, it must be eradicated in order to cure cancer. We previously reported that vaccination with CD133(+) murine melanoma cells exhibiting biological CSC features induced CSC-specific effector T cells. These were capable of eradicating CD133(+) tumor cells in vivo, thereby curing the parental tumor. In the current study, we indicated that DEAD/H (Asp-Glu-Ala-Asp/His) box polypeptide 3, X-linked (DDX3X) is an immunogenic protein preferentially expressed in CD133(+) tumor cells. Vaccination with DDX3X primed specific T cells, resulting in protective and therapeutic antitumor immunity. The DDX3X-primed CD4(+) T cells produced CD133(+) tumor-specific IFNγ and IL-17 and mediated potent antitumor therapeutic efficacy. DDX3X is expressed in various human cancer cells, including lung, colon, and breast cancer cells. These results suggest that anti-DDX3X immunotherapy is a promising treatment option in efforts to eradicate CSC in the clinical setting.

Vaccination with CD133(+) melanoma induces specific Th17 and Th1 cell-mediated antitumor reactivity against parental tumor

Accumulating evidence suggests that cancer cells possess a small subpopulation that survives during potentially lethal stresses, including chemotherapy, radiation treatment, and molecular-targeting therapy. CD133 is a putative marker that distinguishes a minor subpopulation from normal differentiated tumor cells in many cancers. Although it is necessary to eradicate all cancer cells to obtain a cure, effective treatment to eliminate the CD133(+) treatment-tolerant cells has not been elucidated. In this study, we demonstrated that a CD133(+) subpopulation in murine melanoma is immunogenic and that effector T cells specific for the CD133(+) melanoma cells mediated potent antitumor reactivity, curing the mice of the parental melanoma. CD133(+) melanoma antigens preferentially induced type 17 T helper (Th17) cells and Th1 cells but not Th2 cells. CD133(+) melanoma cell-specific CD4(+) T-cell treatment eradicated not only CD133(+) tumor cells but also CD133(-) tumor cells while inducing long-lasting accumulation of lymphocytes and dendritic cells with upregulated MHC class II in tumor tissues. Further, the treatment prevented regulatory T-cell induction. These results indicate that T-cell immunotherapy is a promising treatment option to eradicate CD133(+) drug-tolerant cells to obtain a cure for cancer.

Adipose inflammation initiates recruitment of leukocytes to mouse femoral artery: role of adipo-vascular axis in chronic inflammation

Background

Although inflammation within adipose tissues is known to play a role in metabolic syndrome, the causative connection between inflamed adipose tissue and atherosclerosis is not fully understood. In the present study, we examined the direct effects of adipose tissue on macro-vascular inflammation using intravital microscopic analysis of the femoral artery after adipose tissue transplantation.

Methods and Results

We obtained subcutaneous (SQ) and visceral (VIS) adipose tissues from C57BL/6 mice fed normal chow (NC) or a high fat diet (HF), then transplanted the tissues into the perivascular area of the femoral artery of recipient C57/BL6 mice. Quantitative intravital microscopic analysis revealed an increase in adherent leukocytes after adipose tissue transplantation, with VIS found to induce significantly more leukocyte accumulation as compared to SQ. Moreover, adipose tissues from HF fed mice showed significantly more adhesion to the femoral artery. Simultaneous flow cytometry demonstrated upregulation of CD11b on peripheral granulocyte and monocytes after adipose tissue transplantation. We also observed dominant expressions of the inflammatory cytokine IL-6, and chemokines MCP-1 and MIP-1β in the stromal vascular fraction (SVF) of these adipose tissues as well as sera of recipient mice after transplantation. Finally, massive accumulations of pro-inflammatory and dendritic cells were detected in mice with VIS transplantation as compared to SQ, as well as in HF mice as compared to those fed NC.

Conclusion

Our in vivo findings indicate that adipose tissue stimulates leukocyte accumulation in the femoral artery. The underlying mechanisms involve upregulation of CD11b in leukocytes, induction of cytokines and chemokines, and accumulation of pro-inflammatory cells in the SVF.

Targeting the tumor microenvironment with anti-neu/anti-CD40 conjugated nanoparticles for the induction of antitumor immune responses

Clinical and preclinical data indicate that immunotherapeutic interventions could induce immune responses capable of controlling or retard the tumor growth. However, immunotherapies need to be further optimized. We hypothesized that a more effective strategy for tumor eradication is to directly target the tumor microenvironment in order to generate a proinflammatory response and induce a localized antitumor immune response capable of eliminating the tumor cells. Nanoparticles have been proven to be an effective delivery system. In these studies we evaluated conjugated anti-RNEU and anti-CD40 antibodies onto PLA-(poly dl-lactic acid)-biodegradable nanoparticles (PLA-NP) for the induction of antitumor immune responses. The anti-neu/anti-CD40-NP were functional in vitro recognizing RNEU(+) tumors and activating dendritic cells. The delivery of anti-neu/anti-CD40-NP but not anti-neu-NP or anti-CD40-NP induced an antitumor response resulting in complete tumor elimination and generation of protective memory responses. The anti-neu/anti-CD40-NP specifically activated an antitumor response against RNEU(+) tumors but not against RNEU(-) tumors. The antitumor immune responses correlate with the induction of a Th1-proinflammatory response, reduction in the number of Tregs within the tumor and activation of a specific cytotoxic response. These results indicate that anti-neu/anti-CD40-NP with immunomodulatory properties are safe and can be used effectively as cancer vaccines strategy for the specific induction of antitumor immune responses.

Tumor-shed PGE(2) impairs IL2Rgammac-signaling to inhibit CD4 T cell survival: regulation by theaflavins

Background

Many tumors are associated with decreased cellular immunity and elevated levels of prostaglandin E2 (PGE2), a known inhibitor of CD4+ T cell activation and inducer of type-2 cytokine bias. However, the role of this immunomodulator in the survival of T helper cells remained unclear. Since CD4+ T cells play critical roles in cell-mediated immunity, detail knowledge of the effect tumor-derived PGE2 might have on CD4+ T cell survival and the underlying mechanism may, therefore, help to overcome the overall immune deviation in cancer.

Methodology/Principal Findings

By culturing purified human peripheral CD4+ T cells or Jurkat cells with spent media of theaflavin- or celecoxib-pre-treated MCF-7 cells, we show that tumor-shed PGE2 severely impairs interleukin 2 receptor γc (IL2Rγc)-mediated survival signaling in CD4+ T cells. Indeed, tumor-shed PGE2 down-regulates IL2Rγc expression, reduces phosphorylation as well as activation of Janus kinase 3 (Jak-3)/signal transducer and activator of transcription 5 (Stat-5) and decreases Bcl-2/Bax ratio thereby leading to activation of intrinsic apoptotic pathway. Constitutively active Stat-5A (Stat-5A1*6) over-expression efficiently elevates Bcl-2 levels in CD4+ T cells and protects them from tumor-induced death while dominant-negative Stat-5A over-expression fails to do so, indicating the importance of Stat-5A-signaling in CD4+ T cell survival. Further support towards the involvement of PGE2 comes from the results that (a) purified synthetic PGE2 induces CD4+ T cell apoptosis, and (b) when knocked out by small interfering RNA, cyclooxygenase-2 (Cox-2)-defective tumor cells fail to initiate death. Interestingly, the entire phenomena could be reverted back by theaflavins that restore cytokine-dependent IL2Rγc/Jak-3/Stat-5A signaling in CD4+ T cells thereby protecting them from tumor-shed PGE2-induced apoptosis.

Conclusions/Significance

These data strongly suggest that tumor-shed PGE2 is an important factor leading to CD4+ T cell apoptosis during cancer and raise the possibility that theaflavins may have the potential as an effective immunorestorer in cancer-bearer.

Abrogation of local cancer recurrence after radiofrequency ablation by dendritic cell-based hyperthermic tumor vaccine

Local recurrence is a therapeutic challenge for radiofrequency ablation (RFA) in treatment of small solid focal malignancies. Here we show that RFA induced heat shock proteins (HSPs) expression and high mobility group box-1 (HMGB1) translocation in xenografted melanoma, which might create a proinflammatory microenvironment that favors tumor antigen presentation and activation of the effector T cells. On this basis, we investigate whether a prime-boost strategy combining a prime with heat-shocked tumor cell lysate-pulsed dendritic cell (HT-DC) followed by an in situ boost with radiofrequency thermal ablation can prevent local tumor recurrence. The combination treatment with HT-DC and RFA showed potent antitumor effects, with >or=90% of tumor recurrence abrogated following RFA treatment. By contrast, prevaccination with unheated tumor lysate-pulsed DC had little effect on tumor relapse. Analysis of the underlying mechanism revealed that splenocytes from mice treated with HT-DC plus RFA contained significantly more tumor-specific, IFN-gamma-secreting T cells compared with control groups. Moreover, adoptive transfer of splenocytes from successfully treated tumor-free mice protected naive animals from tumor recurrence following RFA, and this was mediated mainly by CD8(+) T cells. Therefore, the optimal priming for the DC vaccination before RFA is important for boosting antigen-specific T cell responses and prevention of cancer recurrence.

Short-term activation induces multifunctional dendritic cells that generate potent antitumor T-cell responses in vivo

Dendritic cell (DC) vaccines have emerged as a promising strategy to induce antitumoral cytotoxic T cells for the immunotherapy of cancer. The maturation state of DC is of critical importance for the success of vaccination, but the most effective mode of maturation is still a matter of debate. Whereas immature DC carry the risk of inducing tolerance, extensive stimulation of DC may lead to DC unresponsiveness and exhaustion. In this study, we investigated how short-term versus long-term DC activation with a Toll-like receptor 9 agonist influences DC phenotype and function. Murine DC were generated in the presence of the hematopoietic factor Flt3L (FL-DC) to obtain both myeloid and plasmacytoid DC subsets. Short activation of FL-DC for as little as 4 h induced fully functional DC that rapidly secreted IL-12p70 and IFN-alpha, expressed high levels of costimulatory and MHC molecules and efficiently presented antigen to CD4 and CD8 T cells. Furthermore, short-term activated FL-DC overcame immune suppression by regulatory T cells and acquired high migratory potential toward the chemokine CCL21 necessary for DC recruitment to lymph nodes. In addition, vaccination with short-term activated DC induced a strong cytotoxic T-cell response in vivo and led to the eradication of tumors. Thus, short-term activation of DC generates fully functional DC for tumor immunotherapy. These results may guide the design of new protocols for DC generation in order to develop more efficient DC-based tumor vaccines.

Phenotype of dendritic cells generated in the presence of non-small cell lung cancer antigens - preliminary report

Therapeutic outcomes of definitively treated non-small-cell lung cancer (NSCLC) are unacceptably poor. It has been proposed that the manipulation of dendritic cells (DCs) as a "natural" vaccine adjuvant may prove to be a particularly effective way to stimulate antitumor immunity. Presently, there is no standardized methodology for preparing vaccines and many questions concerning the optimal source and type of antigens as well as maturation state and activity of DCs are still unsolved. The study population comprised of ten patients with histologically confirmed NSCLC (mean age: 67.63 +/- 6.15 years). Resected small tumor pieces were placed in tissue culture dishes containing different growth factors in order to obtain pure cancer cells. Seven days after the operation, the PBMC were collected and monocytes were purified by the adherence to culture dishes. Monocytes were cultured in RPMI 1640 medium supplemented with 10% of autologous plasma in the presence of rhIL-4 and rhGM-CSF to generate immature autologous (DCs). TNF-alpha with or without tumor cells' lysate were added to maturation of DCs. After 7 days of culture, DCs were harvested and the expression of CD1a, CD83, CD80, CD86 and HLA-DR antigens were analyzed by flow cytometry. We discovered higher (p=0.07) percentage of semimature DCs in tumor cell lysate culture in comparison with TNF-alpha culture (21.22 +/- 16.82% versus 11.27 +/- 11.64%). The expression of co-stimulatory and maturation markers (CD86, CD83 and HLA-DR) was higher on DCs from the culture with tumor cell lysate compared with TNF-alpha culture as a control. Specimen of NSCLC's culture prepared in this way could generate differences in DCs phenotype, which may have an influence on the therapeutic and protective antitumor immunity of the vaccine. Our research seems to be the next step in the development of DC-based vaccine. We are going to continue the investigation to start the preparation of a pattern of immunological vaccine against lung cancer.

Generation and characterization of an immunogenic dendritic cell population

Dendritic cells (DCs) capture, internalize and process antigens leading to the induction of antigen-specific immune responses. The aim of this study was to develop, implement and characterize an efficient approach for DC-based immunization. Dendritic cells were expanded in vivo by hydrodynamic delivery of a human flt3 ligand expression plasmid. Splenic DCs were isolated and purified with magnetic beads linked to hepatitis C virus (HCV) nonstructural protein-5 (NS5), anti-CD40 and/or LPS. The DCs that contained beads were purified by passage over a magnetic column and subsequently phenotyped. Enrichment resulted in a population consisting of 80% CD11c(+) cells. Uptake of uncoated microparticles promoted DC maturation and the expression of CD80, CD86, and MHC-II molecules; beads coated with LPS and anti-CD40 further increased the expression of these co-stimulatory molecules, as well as the secretion of IL-12. Mice immunized subcutaneously with DCs containing beads coated with HCV NS5 protein, anti-CD40 and LPS exhibited significant antigen-specific, increases in IFN-gamma-producing CD4(+) T cells and CTL activity. This approach combines three critical elements necessary for efficient DC-based immunization that include DC enrichment, maturation and antigen targeting.

Generation of anti-tumour effector T cells from naïve T cells by stimulation with dendritic/tumour fusion cells

Tumour-draining lymph node T cells are an excellent source of effector T cells that can be used in adoptive tumour immunotherapy because they have already been sensitized to tumour-associated antigens in vivo. However, such tumour-specific immune cells are not readily obtained from the host due to poor immunogenicity of tumours and reduced host immune responses. One obstacle in implementation of adoptive immunotherapy has been insufficient sensitization and expansion of tumour-specific effector cells. In this study, we aim to improve adoptive immunotherapy by generating anti-tumour effector T cells from naïve T lymphocytes. We attempted to achieve this by harnessing the advantages of dendritic cell (DC)-based anti-cancer vaccine strategies. Electrofusion was routinely employed to produce fusion cells with 30-40% efficiency by using the poorly immunogenic murine B16/F10 cell line, D5 cells, and DC generated from bone marrow cells. CD62L-positive T cells from spleens of naïve mice and the fusion cells were cocultured with a low concentration of IL-2. After 9 days of culture, the antigen-specific T cells were identified with an upregulation of CD25 and CD69 expression and a downregulation of CD62L expression. These cells secreted IFN-gamma upon stimulation with irradiated tumour cells. Moreover, when transferred into mice with 3-day established pulmonary metastases, these cells with coadministration of IL-2 exhibited anti-tumour efficacy. In contrast, naïve T cells cocultured with a mixture of unfused DC and irradiated tumour cells did not exhibit anti-tumour efficacy. Our strategy provides the basis for a new approach in adoptive T cell immunotherapy for cancer.

CMRF-56 Immunoselected Blood Dendritic Cell Preparations Activated With GM-CSF Induce Potent Antimyeloma Cytotoxic T-cell Responses

The efficient antigen-presenting function of dendritic cells (DC) makes them an attractive cellular adjuvant for clinical immunotherapeutic protocols aimed at eradicating minimal residual disease after conventional treatment of multiple myeloma (MM) and other malignancies. We used single-step positive immunoselection with biotinylated CMRF-56 monoclonal antibody to generate a CD11c blood DC (BDC) enriched antigen-presenting cell population, which, after exposure to activation stimuli for as little as 2 hours, displayed a mature costimulatory BDC phenotype and secreted inflammatory cytokines. Of the activation stimuli tested, granulocyte macrophage colony-stimulating factor (GM-CSF) provided optimal activation of the CMRF-56 immunoselected preparations and primed efficient cytotoxic T cell (CTL) responses using MART-1 peptide as a model tumor-associated antigen. In addition, GM-CSF activated CMRF-56 immunoselected cells cross-presented MM cell lysate and improved the MM-specific polyclonal CTL response (no activation 18.8%+/-4.3% vs. GM-CSF activation 40.9%+/-7.3%, P=0.051). CMRF-56 immunoselected BDC migrated in vitro both spontaneously and specifically toward the secondary lymphoid chemokine CCL21. Their migration was also significantly improved by GM-CSF and prostaglandin E2 activation and a greater percentage of activated BDC migrated specifically compared with monocyte-derived DC. These results indicate that the CMRF-56 immunoselected BDC preparations can cross-present antigen for effective anti-MM CTL responses and that limited exposure to maturation stimuli can produce phenotypically and functionally mature migrating DC. CMRF-56 immunoselected cells are suitable for use as part of an immunotherapeutic anti-MM vaccine.

In vitro treatment of monocytes with 8-methoxypsolaren and ultraviolet A light induces dendritic cells with a tolerogenic phenotype

Extracorporeal photopheresis (ECP) has been considered an efficient dendritic cell (DC) therapy, used for treating both T cell malignancy, as well as T cell-mediated diseases. During the ECP procedure leucocytes are exposed to photoactivable agent 8-methoxypsolaren (8-MOP) and ultraviolet (UV) A radiation (PUVA) prior to reinfusion. Despite its clinical efficacy the mechanism of action remains elusive. As it has been reported that ECP might promote the differentiation of monocytes into immature DCs, we investigated the effects of UVA light (2 J/cm(2)) and 8-MOP (100 ng/ml) on in vitro monocyte-to-DC differentiation from normal donors. DCs were generated from human purified CD14(+) cells. Because monocytes are killed by PUVA and taking into account that only 5-10% of circulating mononuclear cells are exposed to PUVA during the ECP procedure, we developed an assay in which 10% of PUVA-treated monocytes were co-cultured with untreated monocytes. We first demonstrate that the presence of 10% apoptotic cells and monocyte activation were not enough to induce monocyte differentiation into DCs. Adding cytokines to our culture system, we obtained immature DCs characterized by significantly higher phagocytic activity and human leucocyte antigen D-related (HLA-DR) expression. These DCs preserved the capacity to be activated by lipopolysaccharide, but showed a reduced capacity to induce allogeneic T cell proliferation when first co-cultured with 10% of PUVA-treated cells. Our experimental design provides a novel insight into the real action of 8-MOP and UVA light on dendritic cell biology, suggesting an additional mechanism by which 8-MOP and UVA light exposure may influence immune responses.

Combinational adenovirus-mediated gene therapy and dendritic cell vaccine in combating well-established tumors

Recent developments in tumor immunology and biotechnology have made cancer gene therapy and immunotherapy feasible. The current efforts for cancer gene therapy mainly focus on using immunogenes, chemogenes and tumor suppressor genes. Central to all these therapies is the development of efficient vectors for gene therapy. By far, adenovirus (AdV)-mediated gene therapy is one of the most promising approaches, as has confirmed by studies relating to animal tumor models and clinical trials. Dendritic cells (DCs) are highly efficient, specialized antigen-presenting cells, and DC-based tumor vaccines are regarded as having much potential in cancer immunotherapy. Vaccination with DCs pulsed with tumor peptides, lysates, or RNA, or loaded with apoptotic/necrotic tumor cells, or engineered to express certain cytokines or chemokines could induce significant antitumor cytotoxic T lymphocyte (CTL) responses and antitumor immunity. Although both AdV-mediated gene therapy and DC vaccine can both stimulate antitumor immune responses, their therapeutic efficiency has been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or to growth inhibition of small tumors. However, this approach has been unsuccessful in combating well-established tumors in animal models. Therefore, a major strategic goal of current cancer immunotherapy has become the development of novel therapeutic strategies that can combat well-established tumors, thus resembling real clinical practice since a good proportion of cancer patients generally present with significant disease. In this paper, we review the recent progress in AdV-mediated cancer gene therapy and DC-based cancer vaccines, and discuss combined immunotherapy including gene therapy and DC vaccines. We underscore the fact that combined therapy may have some advantages in combating well-established tumors vis-a-vis either modality administered as a monotherapy.

Conversion of Tolerogenic CD4¯8¯ Dendritic Cells to Immunogenic Ones Inducing Efficient Antitumor Immunity

Culturing conditions may affect dendritic cell (DC) maturation status and functional effects. We have previously demonstrated that different DC subsets play distinct roles in immune responses. The splenic CD4-8- DC subset that secretes transforming growth factor (TGF)-beta stimulates CD4+ regulatory T type 1 (Tr1) cell responses, and this leads to antitumor immune tolerance. In this study, we investigated the potential effect of culturing conditions, namely: (1) duration of culturing and (2) the dose of antigen ovalbumin (OVA) for DC pulsing, respectively, in the conversion of tolerogenic CD4-8- DC into immunogenic DCs. Our data showed that isolated CD4-8- DCs cultured for an additional 18 hours in medium containing 15-20 ng/mL granulocyte macrophage colony-stimulating factor (GM-CSF) became more mature compared to the freshly isolated CD4-8- DCs. When pulsed with OVA at the relatively high concentration of 1 mg/mL, but not at 0.1 mg/mL, the CD4-8- DCs could be converted into immunogenic CD4-8- DCs, which stimulated CD4+ T-cell differentiation into type 1 helper T (Th1) cells. Vaccination of mice with converted CD4-8- DCs induced strong OVA-specific cytotoxic T-lymphocyte (CTL) responses and protective immunity against OVA-expressing BL6-10OVA B16 melanoma. Taken together, our findings indicate that the conversion of DCs from a tolerogenic to an immunogenic state can be achieved by the elongation of DC culturing time in combination with a high-dose antigen for DC pulsing. Therefore, our results may have a significant impact in designing DC-based antitumor vaccines.

Dendritic cell immunizations alone or combined with low doses of interleukin-2 induce specific immune responses in melanoma patients

Dendritic cell (DC)-based therapy has proved to be effective in patients with a variety of malignancies. However, an optimal immunization protocol using DCs and the best means for delivering antigens has not yet been described. In this study, 20 patients with malignant melanoma in stages III or IV were vaccinated with autologous DCs pulsed with a melanoma cell lysate, alone (n = 13) or in combination with low doses of subcutaneous (s.c.) interleukin (IL)-2 injections (n = 7), to assess toxicity, immunological and clinical responses. Monocyte-derived DCs were morphological, phenotypic and functionally characterized in vitro. Peripheral blood mononuclear cells (PBMC), harvested from patients either prior to and after the treatment, were analysed using enzyme-linked immunosorbent spot (ELISPOT). After vaccination, 50% of the patients tested (seven of 13) from the first group and (three of seven) from the second, showed an increase in interferon (IFN)-gamma production in response to allogeneic melanoma cell lines but not to controls. Four of five tested human leucocyte antigen (HLA)-A2(+) patients with anti-melanoma activity also showed specific T cell responses against peptides derived from melanoma-associated antigens. Delayed type IV hypersensitivity reaction (DTH) against melanoma cell lysate was observed in six of 13 patients from the group treated with DC vaccines only and four of seven from the group treated with the combination of DCs and IL-2. Significant correlations were found between DTH-positive responses against tumour lysate and both disease stability and post-vaccination survival on the stage IV patients. There were no toxicities associated with the vaccines or evidence of autoimmunity including vitiligo. Furthermore, no significant enhancement was observed as a result of combining DC vaccination with IL-2. Our data suggest that autologous DCs pulsed with tumour lysate may provide a standardized and widely applicable source of melanoma specific antigens for clinical use. It is safe and causes no significant side effects and has been demonstrated to be partially efficient at triggering effective anti-melanoma immunity.

In Vivo Depletion of CD4+CD25+ Regulatory T Cells Enhances the Antigen-Specific Primary and Memory CTL Response Elicited by Mature mRNA-Electroporated Dendritic Cells

We previously described mRNA electroporation as an efficient gene delivery method to introduce tumor-antigens (Ag) into murine immature dendritic cells (DC). Here, we further optimize the protocol and evaluate the capacity of mRNA-electroporated DC as a vaccine for immunotherapy. First, the early DC maturation kinetics and the effect of different lipopolysaccharide incubation periods on the phenotypic maturation profile of DC are determined. Next, we show that either immature or mature DC are equally well electroporated and express and present the transgene at a comparable level after electroporation. We point out that the mRNA electroporation results in a negative effect on the interleukin (IL)-12p70, IL-6, and tumor necrosis factor-alpha secretion after maturation. Nevertheless, mRNA-electroporated DC induce an effective cytotoxic T lymphocyte (CTL) response in vivo. Mature electroporated DC are significantly more potent in eliciting an Ag-specific CD8+ CTL response compared to their immature electroporated counterparts. In addition, a significant improvement in CTL response is obtained both in the primary and in the memory effector phases when CD4+CD25+ regulatory T cells (Treg) are depleted in vivo prior to immunization. These findings are further substantiated in tumor protection experiments and hold convincing evidence for the merit of Treg cell depletion prior to immunization with mRNA-electroporated DC.

Generation and Maturation of Dendritic Cells for Clinical Application Under Serum-Free Conditions

Monocyte-derived dendritic cells (MoDCs) in clinical use for cancer immunotherapy are ideally generated in serum-free medium (SFM) with inclusion of a suitable maturation factor toward the end of the incubation period. Three good manfacturing practice (GMP) grade SFMs (AIM-V, X-VIVO 15, and X-VIVO 20) were compared with RPMI-1640, supplemented with 10% fetal bovine serum or 10% human serum. DCs generated for 7 days in SFM were less mature and secreted less interleukin (IL) 12p70 and IL-10 than DCs generated in 10% serum. DC yield was comparable in SFMs, and a greater proportion of cells was viable after maturation. Toll-like receptor (TLR) ligands were compared for their ability to induce cytokine secretion under serum-free conditions in the presence of interferon (IFN) gamma. With the exception of Poly I:C, TLR ligands stimulated high levels of IL-10 secretion. High levels of IL-12p70 were induced by two TLR4-mediated stimuli, lipopolysaccharide and Ribomunyl, a clinical-grade bacterial extract. When T-cell responses were compared in allogeneic mixed leukocyte reaction, DCs stimulated with Ribomunyl induced higher levels of IFNgamma than DCs stimulated with the cytokine cocktail: tumor necrosis factor-alpha, IL-1beta, IL-6, and prostaglandin E2. In the presence of IL-10 neutralizing antibodies, DC IL-12p70 production and T-cell IFNgamma were increased in vitro. Similarly, DCs stimulated with Ribomunyl, IFNgamma, and anti-IL-10 induced high levels of tetanus toxoid-specific T-cell proliferation and IFNgamma secretion. Thus, MoDCs generated in SFM efficiently stimulate T-cell IFNgamma production after maturation in the presence of a clinical-grade TLR4 agonist and IL-10 neutralization.

Both Regulatory T Cells and Antitumor Effector T Cells Are Primed in the Same Draining Lymph Nodes during Tumor Progression

The peripheral tolerance mechanism prevents effective antitumor immunity, even though tumor cells possess recognizable tumor-associated Ags. Recently, it has been elucidated that regulatory T cells (Treg) play a critical role in maintaining not only self-tolerance, but also tolerance of tumor cells. However, because the Treg that maintain self-tolerance arise naturally in the thymus and are thought to be anergic in peripheral, it is still unclear where and when Treg for tumor cells are generated. In this study we analyze tumor-draining lymph nodes (LNs) and demonstrate that both antitumor effector T cells and Treg capable of abrogating the antitumor reactivity of the effector T cells are primed in the same LNs during tumor progression. The regulatory activity generated in tumor-draining LNs exclusively belonged to the CD4(+) T cell subpopulation that expresses both CD25 and a high level of CD62L. Forkhead/winged helix transcription factor gene expression was detected only in the CD62L(high)CD4(+)CD25(+) T cells. CD62L(high)CD4(+)CD25(+) Treg and CD62L(low)CD4(+)CD25(+) T cells, which possess effector T cell functions, had comparable expression of LFA-1, VLA-4, CTLA-4, lymphocyte activation gene-3, and glucocorticoid-induced TNFR. Thus, only CD62L expression could distinguish regulatory CD4(+)CD25(+) cells from effector CD4(+)CD25(+) cells in draining LNs as a surface marker. The Treg generated in tumor-draining LNs possess the same functional properties as the Treg that arise naturally in the thymus but recognize tumor-associated Ag. CD62L(high)CD4(+)CD25(+) Treg contained a subpopulation that expressed CD86. Blocking experiments revealed that ligation of CTLA-4 on effector T cells by CD86 on Treg plays a pivotal role in regulating CD4(+) effector T cells.

Dexamethasone Induces IL-10-Producing Monocyte-Derived Dendritic Cells with Durable Immaturity

It is highly desirable that immature dendritic cells (DC) used for tolerance induction maintain steady immature state with predominant interleukin (IL)-10 production. In this study, we attempted to develop DC with durable immaturity and other tolerogenic features by using dexamethasone (Dex). We found DC derived from human monocytes in the presence of 10(-7) m Dex were negative for CD1a. Compared with control transduced DC (Ctrl-DC), Dex-DC expressed lower CD40, CD80 and CD86 but equivalent human leucocyte antigen-DR. Both immature Dex- and Ctrl-DC did not express CD83. Nevertheless, upon stimulation of lipopolysaccharide (LPS) or CD40 ligand, the expression of CD40, CD80, CD83 and CD86 was upregulated on Ctrl-DC but not on Dex-DC. The immaturity of Dex-DC was durable following Dex removal. Interestingly, Dex-DC maintained production of large amount of IL-10 and little IL-12 five days after Dex removed. Further study indicated that high-level IL-10 production by Dex-DC was associated with high-level phosphorylation of extracellular signal-regulated kinase (ERK) as blockade of this enzyme markedly attenuated IL-10 production. Furthermore, Dex-DC sustained the capability of high phosphorylation of ERK and IL-10 production 5 days after Dex removal. In addition, Dex-DC had significantly lower activity in stimulating T-cell proliferation. Neutralization of IL-10, to some extent, promoted DC maturation activated by LPS, as well as T-cell stimulatory activity of Dex-DC. The above findings suggest that IL-10-producing Dex-DC with durable immaturity are potentially useful for induction of immune tolerance.

Intratumoral administration of immature dendritic cells following the adenovirus vector encoding CD40 ligand elicits significant regression of established myeloma

Our previous study showed that J558 myeloma cells engineered CD40L lost their tumorigenicity in syngeneic mice, and the inoculation of J558/CD40L tumor cells further led to the protective immunity against wild tumors. In the present study, we investigated whether the vaccine can exert more efficient antitumor immunity by combination with adenovirus mediated CD40L gene therapy and immature dendritic cells (iDCs). The results demonstrated that intratumoral administration of iDCs 2 days after AdVCD40L injection, not only significantly suppressed the tumor growth, but also eradiated the established tumors in 40% of the mice. The potent antitumor effect produced by the combination therapy correlated with high expression of MHC, costimulatory and Fas molecules on J558 cells, which was derived from CD40L transgene expression. In addition, transgene CD40L expression could dramatically induce J558 cell apoptosis. Effectively capturing apoptotic bodies by iDCs in vivo could induce DC maturation, prime tumor-specific CTLs and tend to Th1-type immune response. Finally, in vivo depletion experimentation suggested both CD4+ and CD8+ T cells were involved in mediating the antitumor immune responses of combined treatment of AdVCD40L and iDCs, with CD8+ T cells being the major effector. These findings could be beneficial for designing strategies of DCs vaccine and CD40L for anticancer immunotherapy.

The role of CD40-CD154 interactions in autoimmunity and the benefit of disrupting this pathway

Many tissue injuries and immune mediated pathologies such as graft allo-rejections were found to involve CD40-CD40 ligand (CD40L, CD154) signaling pathway. The disruption of this pathway in many animal models led to the improvement of graft survival in these models. CD40-CD154 interactions were also shown to play a significant role in the maintenance of autoimmunity, and the production of auto-antibodies in systemic lupus erythematosus (SLE). High-level expression of CD154 has been detected on T cells from patients with active SLE, rheumatoid arthritis (RA) and other autoimmune diseases, indicating that such cells could account for the high-level expression of immune accessory molecules on B cells of patients with active disease. An increased serum level of soluble CD154 was also reported in SLE, RA, and Sjogren's disease in correlation with the relevant auto-antibodies and with the clinical disease activity. Anti-CD154 antibody therapy prevents auto-antibody production and renal immune complex deposition in lupus nephritis, indicating that disruption of this pathway could be a beneficial treatment in SLE. However, the etiology of the higher than expected number of thromboembolic events in anti-CD154 treated SLE patients should be investigated and preventive measures should be considered.

Immunopathogenesis and therapy of cutaneous T cell lymphoma

Cutaneous T cell lymphomas (CTCLs) are a heterogenous group of lymphoproliferative disorders caused by clonally derived, skin-invasive T cells. Mycosis fungoides (MF) and Sezary syndrome (SS) are the most common types of CTCLs and are characterized by malignant CD4(+)/CLA(+)/CCR4(+) T cells that also lack the usual T cell surface markers CD7 and/or CD26. As MF/SS advances, the clonal dominance of the malignant cells results in the expression of predominantly Th2 cytokines, progressive immune dysregulation in patients, and further tumor cell growth. This review summarizes recent insights into the pathogenesis and immunobiology of MF/SS and how these have shaped current therapeutic approaches, in particular the growing emphasis on enhancement of host antitumor immune responses as the key to successful therapy.