Preventive antitumor activity against hepatocellular carcinoma (HCC) induced by immunization with fusions of dendritic cells and HCC cells in mice

Controllable and Stable Fusion Strategy on Microfluidics

This paper presents a microfluidic device with 200 cell "cage" structures. Based on this microfluidics device, a new simple and stable electrofusion method was developed. Under hydrodynamic force, the cells moved to the desired "cage" cell capture structure and efficiently formed cell pairs (∼80.0 ± 4.6%). Intimate intercellular connectivity was induced by the precise modulation of hypotonic solution substitution and the microstructure, which ensured no cell movement or displacement during the cell electroporation/electrofusion process. It also guaranteed repeated electroporation occurring in the same contact region and provided a stable cell membrane recombination and a cell fusion microenvironment. When the pulse signal was applied, a high fusion efficiency of ∼88.3 ± 0.6% was demonstrated on the microfluidic device.

A Novel Heat Shock Protein 70-Based Vaccine Prepared from DC Tumor Fusion Cells: An Update

We have developed an enhanced molecular chaperone-based vaccine through rapid isolation of Hsp70 peptide complexes after the fusion of tumor and dendritic cells (Hsp70.PC-F). In this approach, the tumor antigens are introduced into the antigen-processing machinery of dendritic cells through the cell fusion process, and thus we can obtain antigenic tumor peptides or their intermediates that have been processed by dendritic cells. Our results show that Hsp70.PC-F has increased immunogenicity compared to preparations from tumor cells alone and therefore constitutes an improved formulation of the chaperone protein-based tumor vaccine.

A Novel Heat Shock Protein 70-based Vaccine Prepared from DC-Tumor Fusion Cells

We have developed an enhanced molecular chaperone-based vaccine through rapid isolation of Hsp70 peptide complexes after the fusion of tumor and dendritic cells (Hsp70.PC-F). In this approach, the tumor antigens are introduced into the antigen processing machinery of dendritic cells through the cell fusion process and thus we can obtain antigenic tumor peptides or their intermediates that have been processed by dendritic cells. Our results show that Hsp70.PC-F has increased immunogenicity compared to preparations from tumor cells alone and therefore constitutes an improved formulation of chaperone protein-based tumor vaccine.

Cancer vaccines and immunotherapeutic approaches in hepatobiliary and pancreatic cancers

Hepatobiliary and pancreatic cancers along with other gastrointestinal malignancies remain the leading cause of cancer-related deaths worldwide. Strategies developed in the recent years on immunotherapy and cancer vaccines in the setting of primary liver cancer as well as in pancreatic cancer are the scope of this review. Significance of orthotopic and autochthonous animal models which mimic and/or closely reflect human malignancies allowing for a prompt and trustworthy analysis of new therapeutics is underlined. Combinational approaches that on one hand, specifically target a defined cancer-driving pathway, and on the other hand, restore the functions of immune cells, which effector functions are often suppressed by a tumor milieu, are shown to have the strongest perspectives and future directions. Among combinational immunotherapeutic approaches a personalized- and individual cancer case-based therapy is of special importance.

Experimental evaluation of combined immunotherapy for tumors

The minimal vaccination dose of tumor cells was determined on experimental models. The effectiveness of antitumor immunotherapy with activated natural killer cells or dendritic cell vaccine (monotherapy or combined treatment) was evaluated in vivo. The inhibition of tumor growth was more pronounced after combination therapy with activated natural killer cells and dendritic cell-based vaccine. Our results indicate that the effectiveness of antitumor immunotherapy increases in simultaneous modulation of both immune components (innate and adaptive immunity).

Improving immunotherapy of hepatocellular carcinoma (HCC) using dendritic cells (DC) engineered to express IL-12 in vivo

BACKGROUND

Interleukin 12 (IL-12), one of the most potent Th1-cytokines, has been used to improve dendritic cells (DC)-based immunotherapy of cancer. However, it failed to achieve clinical response in patients with hepatocellular carcinoma (HCC). In this study, improved conditions of immunotherapy with DC engineered to express IL-12 were studied in murine subcutaneous HCC.

METHODS

Tumour-lysate pulsed DC were transduced with IL-12-encoding adenoviruses or cultivated with recombinant (r)IL-12. DC were injected intratumourally, subcutaneously or intravenously at different stages of tumour-development.

RESULTS

Dendritic cell overexpressing IL-12 by adenoviruses showed enhanced expression of costimulatory molecules and stronger priming of HCC-specific effector cells than DC cultured with rIL-12. Intratumoural but not systemic injections of IL-12-DC induced the strongest antitumoural effects reaching complete regressions in 75% of early-staged tumours and in 33% of advanced tumours. Importantly, antitumoural effects could be further enhanced through combination with sorafenib. Analysing the tumour-environment, IL-12-DC increased the levels of Th1-cytokines/chemokines and of CD4(+) -, CD8(+) -T- and NK-cells. Induced immunity was tumour-specific and sustained since all tumour-free animals were protected towards hepatic tumour-cell rechallenge. However, IL-12-DC also enhanced immunosuppressive cytokines, regulatory T cells and even myeloid-derived suppressor cells within the tumours.

CONCLUSIONS

Induced IL-12-overexpression by adenoviral vectors can effectively immunostimulate DC. Intratumoural but not systemic injection of activated IL-12-DC was crucial for effective tumour regression. The mechanism of this approach seems to be the induction of a sufficient Th1 tumour-environment allowing the recruitment of effector cells rather than the inhibition of tumour immunosuppression. Thus, improved immunotherapy with IL-12-DC represents a promising approach towards HCC.

Dendritic/tumor fusion cells as cancer vaccines

A promising cancer vaccine involves the fusion of dendritic cells (DCs) with tumor cells such that a broad array of tumor antigens are presented in the context of DC-mediated costimulation and stimulatory cytokines. In diverse animal models, vaccination with DC/tumor fusions results in protection from an otherwise lethal challenge of tumor cells and eradication of established disease. In phase I clinical studies, vaccination with DC/tumor fusions was well tolerated, and induced immunologic responses in the majority of patients and clinical responses in a subset. Vaccine efficacy may be blunted by the immunosuppressive milieu characteristic of patients with malignancy, including the increased presence of regulatory T cells, and inhibitory pathways such as the PD-1/PDL-1 pathway. A current focus of research interest lies in enhancing response to cancer vaccines, by combining vaccination with tumor cytoreduction, regulatory T-cell depletion, and blockade of critical inhibitory pathways.

Immunologic monitoring of cellular responses by dendritic/tumor cell fusion vaccines

Although dendritic cell (DC)- based cancer vaccines induce effective antitumor activities in murine models, only limited therapeutic results have been obtained in clinical trials. As cancer vaccines induce antitumor activities by eliciting or modifying immune responses in patients with cancer, the Response Evaluation Criteria in Solid Tumors (RECIST) and WHO criteria, designed to detect early effects of cytotoxic chemotherapy in solid tumors, may not provide a complete assessment of cancer vaccines. The problem may, in part, be resolved by carrying out immunologic cellular monitoring, which is one prerequisite for rational development of cancer vaccines. In this review, we will discuss immunologic monitoring of cellular responses for the evaluation of cancer vaccines including fusions of DC and whole tumor cell.

Cancer immunotherapy by fusions of dendritic cells and tumor cells

Dendritic cells (DCs) are potent professional antigen-presenting cells and play a critical role in the induction of primary immune responses. DC-based vaccination represents a potentially powerful strategy for cancer immunotherapy. Thus, the use of cancer vaccines to eliminate residual tumor cells is a promising area of investigation. The immunotherapy of tumor antigen-loaded DCs has now been demonstrated in cancer patients and some clinical responses without any significant toxicity. Fusions of DCs and tumor cells represent an alternative but promising approach to overcome the inability of tumor antigens to induce a sustainable T-cell response. This review deals with recent progress in the immunotherapy of cancer with fusions of DCs and tumor cells.

Preparation of a heat-shock protein 70-based vaccine from DC-tumor fusion cells

We have developed an enhanced molecular chaperone-based vaccine through rapid isolation of heat-shock protein 70 peptide complexes (Hsp70.PC) after the fusion of tumor and dendritic cells (DCs) (Hsp70.PC-F). In this approach, the tumor antigens are introduced into the antigen-processing machinery of dendritic cells through the cell fusion process and, thus, we can obtain antigenic tumor peptides or their intermediates that have been processed by dendritic cells. Our results show that Hsp70.PC-F has increased immunogenicity compared to preparations from tumor cells alone and, therefore, constitutes an improved formulation of chaperone protein-based tumor vaccine.

Regulation of tumor immunity by tumor/dendritic cell fusions

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment.

The complete preventive effect of homologous tumor vaccines--based on a 5-year experimental study in mice

By using a frozen-thaw method, we developed homologous and heterologous cell-based tumor vaccines, which were derived from mouse H22 hepatoma, S180 sarcoma and human A549 lung carcinoma, SK-OV-3 ovarian, and SMMC-7721 hepatoma cell lines. The prophylactic and therapeutic effects of those vaccines were evaluated in mice challenged with live H22 or S180 cells. The result demonstrated that homologous vaccines and heterologous vaccines had no therapeutic effect on tumor growth. However, homologous vaccines showed a complete prevention against live H22 and S180 cell challenge and they could stimulate cross-immune response of anti-tumor in mice. Furthermore, these tumor-free mice immunized with homologous vaccines showed full protection against the repeat challenge every 3 months for 5 years. The study also revealed that tumor-free female, not male, mice transferred anti-tumor ability to some of their offsprings. Heterologous vaccines exhibited no protective effect on tumor development. Immunological analysis discovered that activities of CTLs and NK were enhanced and the levels of IL-2, IL-12 and IFN-γ were significantly increased. Our results demonstrated that homologous tumor vaccines could elicit complete cross-protection against the lethal challenge of tumor cells through enhancing cell-mediated immune response, which lasted for 5 years in mice. These observations may provide a new vaccine strategy for tumor prevention.

Antigen-specific polyclonal cytotoxic T lymphocytes induced by fusions of dendritic cells and tumor cells

The aim of cancer vaccines is induction of tumor-specific cytotoxic T lymphocytes (CTLs) that can reduce the tumor mass. Dendritic cells (DCs) are potent antigen-presenting cells and play a central role in the initiation and regulation of primary immune responses. Thus, DCs-based vaccination represents a potentially powerful strategy for induction of antigen-specific CTLs. Fusions of DCs and whole tumor cells represent an alternative approach to deliver, process, and subsequently present a broad spectrum of antigens, including those known and unidentified, in the context of costimulatory molecules. Once DCs/tumor fusions have been infused back into patient, they migrate to secondary lymphoid organs, where the generation of antigen-specific polyclonal CTL responses occurs. We will discuss perspectives for future development of DCs/tumor fusions for CTL induction.

Generation of highly pure fusions of colorectal carcinoma and antigen-presenting cells

PURPOSE

The induction of potent T cell responses against tumors is the goal of tumor immunotherapy. One approach is the fusion of antigen-presenting cells (APCs) with tumor cells. Hybrid cells combine the antigenicity of tumors with the immunostimulatory capacity of APCs. However, contaminating unfused cells present in the fusion reaction may prevent the induction of antitumoral immune responses. Here, we present a simple and effective protocol to substantially elevate the purity of hybrid cells.

METHODS

Colorectal tumor cell lines and CD40-activated B cells as APCs were fused using polyethylene glycol. Important parameters including cell numbers, concentrations, and handling and detection procedures were optimized. Combination of these optimized fusion conditions with both magnetic cell sorting and selective adherence delivered very pure preparations of APC/tumor cell hybrids. The T cell stimulatory capacity of these hybrids was tested using ELISpot.

RESULTS

The optimization of the fusion resulted in maximal fusion efficiencies of 31.6% (n = 10, range 13.5-46.6%). Prelabeling of APCs with magnetic beads allowed for easy elimination of up to 94.3% of unfused tumor cells from the cell mixture by magnetic separation. Hybrid cell capacity to firmly adhere to plastic was then used to remove unfused B cells from the remaining cell mixture by simple washing. The obtained 85.0% pure hybrids cells readily induced antitumoral T cell responses.

CONCLUSIONS

Our protocol delivers pure hybrid cell preparations with strong immunostimulatory potential. In subsequent experiments, the ability of hybrid cells to stimulate specific antitumoral T cell responses must be tested in vivo.

Cancer vaccine by fusions of dendritic and cancer cells

Dendritic cells (DCs) are potent antigen-presenting cells and play a central role in the initiation and regulation of primary immune responses. Therefore, their use for the active immunotherapy against cancers has been studied with considerable interest. The fusion of DCs with whole tumor cells represents in many ways an ideal approach to deliver, process, and subsequently present a broad array of tumor-associated antigens, including those yet to be unidentified, in the context of DCs-derived costimulatory molecules. DCs/tumor fusion vaccine stimulates potent antitumor immunity in the animal tumor models. In the human studies, T cells stimulated by DC/tumor fusion cells are effective in lysis of tumor cells that are used as the fusion partner. In the clinical trials, clinical and immunological responses were observed in patients with advanced stage of malignant tumors after being vaccinated with DC/tumor fusion cells, although the antitumor effect is not as vigorous as in the animal tumor models. This review summarizes recent advances in concepts and techniques that are providing new impulses to DCs/tumor fusions-based cancer vaccination.

Dendritic and tumor cell fusions transduced with adenovirus encoding CD40L eradicate B-cell lymphoma and induce a Th17-type response

Fusion of dendritic cells and tumor cells (FCs) constitutes a promising tool for generating an antitumor response because of their capacity to present tumor antigens and provide appropriate costimulatory signals. CD40-CD40L interaction has an important role in the maturation and survival of dendritic cells and provides critical help for T-cell priming. In this study, we sought to improve the effectiveness of FC vaccines in a murine model of B-cell lymphoma by engineering FCs to express CD40L by means of an adenovirus encoding CD40L (Adv-CD40L). Before transduction with Adv-CD40L, no CD40L expression was detected in FCs, DCs or tumor cells. The surface expression of CD40L in FC transduced with Adv-CD40L (FC-CD40L) ranged between 50 and 60%. FC-CD40L showed an enhanced expression of CD80, CD86, CD54 and MHC class II molecules and elicited a strong in vitro immune response in a syngeneic mixed lymphocyte reaction. Furthermore, FC-CD40L showed enhanced migration to secondary lymphoid organs. Splenocytes from mice treated with FC-CD40L had a dramatic increase in the production of IL-17, IL-6 and IFN-gamma, compared with controls. Treatment with the FC-CD40L vaccine induced regression of established tumors and increased survival. Our data demonstrate that FC transduced with Adv-CD40L enhances the antitumor effect of FC vaccines in a murine lymphoma model and this is associated with an increased Th17-type immune response.

Cell fusion: from hybridoma to dendritic cell-based vaccine

The deployment of dendritic cell (DC) and tumor cell fusions is increasing in tumor immunotherapy. In animal and human studies, fusion cell vaccines have been shown to possess the elements essential for processing and presenting tumor antigens to host immune cells, for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens. Moreover, fusion cell vaccines provide protection against challenge with tumor cells and mediate regression of established tumors. Despite these unique features of fusion cell vaccines and the observation of tumor eradication in animal studies, limited success has occurred in clinical trials. This article reviews the methods used for optimizing the preparation and selection of DC-tumor fusion cells and analyzes factors influencing the success or failure of fusion cell-mediated immunotherapy. In addition, we discuss the challenges facing effective fusion cell vaccine production, including factors in preparation, selection and quality control of fusion cell vaccines, as well as approaches for enhancing anti-tumor immunity.

CD40ligand-expressing dendritic cells induce regression of hepatocellular carcinoma by activating innate and acquired immunity in vivo

Dendritic cells (DCs) are professional antigen-presenting cells able to prime T-cells against tumor-associated antigens (TAA), but their potential to induce hepatocellular carcinoma (HCC) regression is still limited. CD40/CD40L interaction is essential for DC activation and induction of antigen-specific T-cells. In this study, transduction of TAA-pulsed DC with a CD40L-encoding adenovirus (Ad-CD40L) was used to improve the immune response induced by DC toward HCC. Bone marrow-derived DC from C3H/HeNcrl mice were cultured with granulocyte-macrophage colony-stimulating factor and interleukin-4. On day 6, tumor-lysate pulsed DCs were infected with adenoviruses. HCCs were induced by inoculation of mice with Hepa129-cells subcutaneously. When tumor-volume was 100 to 400 mm(3), DCs were injected intratumorally, subcutaneously, or intravenously. Ad-CD40L transduction exerted CD40/CD40L interactions between DCs, increasing DC immunostimulation with up-regulation of CD80/CD86- and interleukin-12 (IL-12) expression. Intratumoral injection of CD40L-DC was superior to intravenous or subcutaneous treatments, yielding tumor elimination in almost 70% of mice. Moreover, all tumor-free animals were protected against hepatic tumor cell rechallenge. In a preventive setting, subcutaneous injection of CD40L-expressing DCs protected 50% of mice for more than 3 months toward tumor cell challenge. The induced immune response seemed to be dependent on cross-priming with Th1-lymphocytes in the lymph nodes, because transduced DCs were redetected in lymphoid tissues. In addition, immunohistochemistry of tumors indicated a significant tumor infiltration with CD4+, CD8+ T cells and natural killer (NK) cells. Tumor-infiltrating lymphocytes were tumor-specific, as shown in interferon-gamma (IFN-gamma) enzyme-linked immunosorbent spot and T-cell proliferation assays.

CONCLUSION

Transduction of DCs with Ad-CD40L increases significantly the stimulatory capacity of DCs. Intratumoral injection of DCs activates both acquired and innate immunity, inducing complete regression of established tumors and long-term immunity against tumor recurrence. This approach improves the antitumoral potential of DCs.

Mechanism of antitumor effect on mouse hepatocellular carcinoma by intratumoral injection of OK-432, a streptococcal preparation

Intratumoral (i.t.) injection of OK-432, a streptococcal preparation, into implanted tumors of mouse hepatocellular carcinoma (MIH-2) showed antitumor effect including tumor eradication. Intraperitoneal administration of same dose OK-432 did not exhibit tumor suppressive effect. In vitro cytotoxic test suggested that direct cytotoxic effect of OK-432 was not associated with antitumor activity by i.t.-OK-432 treatment. It was also found that Toll-like receptor 4 signaling was not involved in i.t.-OK-432 treatment. Three mice out of five, which had shown tumor eradication by i.t.-OK-432 treatment did not reject re-challenge of MIH-2 cells. Splenocytes from i.t.-OK-432 treated mice did not produce IFN-gamma by stimulation with MIH-2 cells in vitro, but produced abundant IFN-gamma by stimulation with OK-432. Immunofluorescence microscopy demonstrated that CD4+T cells, but not CD8+T cells, infiltrated to i.t.-OK-432 treated tumor tissue produced IFN-gamma. Tumor-infiltrating CD4+T cells from i.t.-OK-432 treated tumor tissue produced IFN-gamma by in vitro stimulation with OK-432 higher than those from untreated tumor tissue. IFN-gamma directly induced apoptosis of MIH-2 cells in vitro. Collectively, i.t.-OK-432 treatment induced priming of CD4+T cells to antigenecity of OK-432, and repetitive i.t.-OK-432 treatment induced IFN-gamma production from OK-432-sensitized CD4+T cells in tumor site, leading to apoptosis of MIH-2 cells susceptible to IFN-gamma.

Cancer immunotherapy using dendritic/tumour-fusion vaccine induces elevation of serum anti-nuclear antibody with better clinical responses

Dendritic cell (DC) vaccines might induce both anti-tumour immunity and autoimmunity. In this report, we demonstrate elevated levels of anti-nuclear antibody (ANA) in the sera of patients with cancer who had received immunotherapy with a dendritic/tumour-fusion vaccine. Twenty-two patients were treated with DC vaccine of fusion cells composed of autologous DCs and tumour cells (DC/tumour-fusion vaccine), which was generated by treating each cell type with polyethylene glycol. Nine of the 22 patients were treated with both the DC/tumour-fusion vaccine and systemic administration of recombinant human interleukin (rhIL)-12. Serum levels of ANA were examined with an enzyme-linked immunosorbent assay kit. One patient with gastric carcinoma (patient 1, DC/tumour-fusion vaccine alone), one patient with breast cancer (patient 2, DC/tumour-fusion vaccine alone) and one patient with ovarian cancer (patient 3, DC/tumour-fusion vaccine + rhIL-12) showed significant elevations of serum ANA levels during treatment. In patient 1 malignant ascitic effusion resolved and serum levels of tumour markers decreased. Patients 2 and 3 remained in good physical condition during treatment for 24 and 9 months, respectively. Immunoblot analysis indicated antibody responses to autologous tumour cells after vaccination in patient 2. None of the treated patients showed clinical symptoms suggesting autoimmune disease. Patients with elevated serum levels of ANA had significantly longer treatment periods than those without it. Elevated serum levels of ANA after DC/tumour-fusion cell vaccine might be associated with anti-tumour immune response induced by the vaccination.

Phenotype-specific cells with proliferative potential are produced by polyethylene glycol-induced fusion of mouse embryonic stem cells with fetal cardiomyocytes

Because cardiomyocytes lose the ability to divide upon differentiation, myocardial failure is assumed to be generally irreversible. For terminal cardiac insufficiency, the potential for regenerative treatment by stem cells, especially embryonic stem (ES) cells, offers hope for the future. Recent studies showed that stem cells fuse spontaneously with cells remaining in damaged tissues, and restore tissue function. To imitate spontaneous fusion in vivo, we used polyethylene glycol (PEG) in vitro to fuse mouse ES cells and fetal cardiomyocytes and analyzed the cytochemical properties of the fused cells. Confocal laser scanning microscopy coupled with lipophilic dye labeling of the living cell membranes showed that there were fused cells of ES cells and cardiomyocytes after PEG treatment. By flow cytometry, the fusion efficiency between ES cells and cardiomyocytes was estimated to be about 45% of the total resulting cells. When green fluorescent protein (GFP)-expressing ES cells were fused with cardiomyocytes, the fused cells had immunoreactivity for GFP in their cytoplasm and cardiac troponin I in their myofibrils. Some of these cells also expressed proliferating cell nuclear antigen up to 11 days after fusion, the last time point examined. This study shows that PEG-induced fusions of mouse ES cells and cardiomyocytes have the cardiomyocyte phenotype and proliferation potential.

Superior protective and therapeutic effects of IL-12 and IL-18 gene-transduced dendritic neuroblastoma fusion cells on liver metastasis of murine neuroblastoma

Fusion vaccine of dendritic cells (DCs) and tumor cells has the advantage of inducing an immune response against multiple tumor Ags, including unknown tumor Ags. Using the liver metastasis model of C1300 neuroblastoma cells, we assessed the protective and therapeutic effects of fusion cells transduced with the IL-12 gene and/or the IL-18 gene. Improving the fusion method by combining polyethylene glycol and electroporation increased loading efficiency. In the A/J mice vaccinated with fusion cells modified with the LacZ gene (fusion/LacZ), IFN-gamma production and CTL activity increased significantly compared with that of DCs/LacZ, C1300/LacZ, or a mixture of the two (mixture/LacZ). With the transduction of IL-12 and IL-18 genes into the fusion cells (fusion/IL-12/IL-18), the level of IFN-gamma increased more than five times that of other fusion groups. In addition, NK cell activity and CTL activity increased significantly compared with that of mixture/LacZ, fusion/LacZ, DC/LacZ, or C1300/LacZ. In the protective and therapeutic studies of fusion cell vaccine, mice vaccinated with fusion/LacZ, fusion/IL-12, fusion/IL-18, or fusion/IL-12/IL-18 showed a significant decrease in liver metastasis and a significant increase in survival compared with mice given a mixture/LacZ, DCs/LacZ, or C1300/LacZ. In particular, the mice receiving fusion/IL-12/IL-18 vaccine showed a complete protective effect and the highest therapeutic effects. The present study investigates the improved loading efficiency of fusion cells and suggests that the introduction of IL-12 and IL-18 genes can induce extremely strong protective and therapeutic effects on liver metastasis of neuroblastoma.

Dendritic cell fusion vaccines for cancer immunotherapy

The use of tumour vaccines is being explored as a means of generating effective antitumour immune responses in patients with cancer. Dendritic cells (DCs) are the most potent antigen-presenting cells that are essential for initiating primary immune responses. As such, DCs are being studied as a platform for the design of cancer vaccines. DCs loaded with tumour antigens or whole tumour cell derivatives stimulate tumour-specific immunity. A promising vaccine strategy involves the fusion of DCs with whole tumour cells. DC/tumour fusions express a broad array of tumour antigens, including those yet to be identified, in the context of DC-mediated costimulation. Animal models have demonstrated that vaccination with fusion cells is protective against tumour challenge and results in the regression of established metastatic disease. In vitro human studies have demonstrated that DC/tumour fusions potently stimulate antitumour immunity and lysis of autologous tumour cells. Vaccination of cancer patients with DC/tumour fusions is being studied in Phase I/II clinical trials. Preliminary results demonstrate that generation of a vaccine is feasible and that vaccination is associated with minimal toxicity. Immunological and clinical responses have been found in a subset of patients.

Patient-derived dendritic cells transduced with an a-fetoprotein-encoding adenovirus and co-cultured with autologous cytokine-induced lymphocytes induce a specific and strong immune response against hepatocellular carcinoma cells

BACKGROUND/AIMS

Breaking immunologic tolerance towards the hepatocellular carcinoma (HCC)-associated alpha-fetoprotein (AFP) antigen is possible. The use of this potential for the treatment of immunocompromised HCC patients is limited. In this study, we analyzed whether dendritic cells (DCs) from HCC patients transduced with a human AFP (hAFP)-expressing adenovirus and co-cultured with cytokine-induced killer (CIK) cells can induce a strong specific immune response against HCC-cells.

METHODS

An hAFP-encoding adenovirus (Ad-hAFP) was generated. DCs from healthy donors or patients were transduced at a very high efficacy. Afterwards, DCs were co-cultured with autologous CIK-cells, and their ability to lyse HCC-cells was analyzed.

RESULTS

AFP-transduced DCs stimulated CIK cells strongly to lyse about 70% of AFP-expressing HCC cells. Cytotoxicity was significantly higher when lymphocytes were co-cultured with Ad-hAFP-transduced DCs than with Ad-mock-transduced DCs, indicating an AFP-specific immune response. More interestingly, CIK cells from patients with AFP-positive HCC could be stimulated to lyse AFP-expressing HCC cells as effectively as CIK cells from healthy individuals and stronger than CIK cells from patients without AFP-expressing HCC.

CONCLUSIONS

The data demonstrate that patient-derived DCs that were transduced with an AFP-expressing adenovirus and co-cultured with autologous CIK cells induce an AFP-specific, strong immune response against HCC cells. Therefore, this approach may have a potential for an adoptive and/or DC-based immunotherapy for HCC patients.

Autoimmune hepatic inflammation by vaccination of mice with dendritic cells loaded with well-differentiated hepatocellular carcinoma cells and administration of interleukin-12

Vaccination of mice with dendritic cells loaded with Hepa1-6, well-differentiated hepatocellular carcinoma cell line (DC/Hepa1-6), induced cytotoxic T lymphocytes against Hepa1-6. Liver-specific inflammation was generated by vaccination of mice with DC/Hepa1-6 and subsequent administration of interleukin (IL)-12. Vaccination with DCs loaded with MC38 or B16 and administration of IL-12 did not generate significant liver-specific inflammation. Splenic T cells from DC/Hepa1-6-vaccinated mice showed proliferative response by stimulation with S-100 protein of the liver and showed cytotoxic activity to hepatocytes. Hepatic mononuclear cells from DC/Hepa1-6 + IL-12-treated mice also showed cytotoxic activity to hepatocytes. Adoptive transfer of splenocytes from DC/Hepa1-6-vaccinated mice produced hepatic inflammation in recipient mice that had been pretreated with IL-12. IL-12 upregulated the expression of adhesion molecules and chemokines in the liver. In conclusion, CTLs responsive to hepatocytes induced by DC/Hepa1-6 and enhanced expression of adhesion molecules and chemokines in the liver by IL-12 would produce autoimmune hepatic inflammation.

Antitumour activity mediated by CD4+ cytotoxic T lymphocytes against MHC class II-negative mouse hepatocellular carcinoma induced by dendritic cell vaccine and interleukin-12

When BALA/c mice with BNL hepatocellular carcinoma (HCC) were treated with dendritic cells fused with BNL cells (DC/BNL) and recombinant murine interleukin (IL)-12, tumour development was significantly suppressed, whereas treatment with either DC/BNL or IL-12 alone did not show a tumour-suppressive effect. Antitumour activity induced by DC/BNL + IL-12 was abrogated by depletion of CD4+ T cells, but not by depletion of CD8+ T cells or natural killer cells. Splenic CD4+ T cells and CD8+ T cells from DC/BNL-treated mice showed cytotoxic activity against BNL cells after 3 days of incubation with DC/BNL, although BNL cells do not express major histocompatibility complex (MHC) class II molecules even after treatment with interferon (INF)-gamma. Furthermore, CD4+ T cells killed syngeneic-irrelevant CT26 cells and even allogeneic Hepa1-6 cells. This cytotoxicity was blocked by concanamycin A, but not by an anti-Fas ligand (FasL) monoclonal antibody, indicating that cytotoxic activity was mediated by perforin. Immunofluorescence microscopy demonstrated that abundant CD4+ T cells and MHC class II-positive macrophages, but not CD8(+) T cells, had infiltrated tumour tissue in mice treated with DC/BNL + IL-12. Flow cytometric analysis of tumour-infiltrating cells in mice treated with DC/BNL + IL-12 showed increases in CD4+ T cells and MHC class II+ CD11b+ cells but not in CD8+ T cells or MHC class I+ CD11b+ cells. Our results suggest that, in BNL-bearing mice treated with DC/BNL + IL-12, tumour macrophages activated by INF-gamma produced by IL-12-stimulated T cells might present BNL tumour antigens and activate DC/BNL-primed CD4+ cytotoxic T lymphocytes (CTLs) in a MHC class II-dependent manner, leading to perforin-mediated bystander killing of neighbouring MHC class II-negative tumour cells.

Intratumoral injection of immature dendritic cells enhances antitumor effect of hyperthermia using magnetic nanoparticles

Dendritic cells (DCs) are potent antigen-presenting cells that play a pivotal role in regulating immune responses in cancer and have recently been shown to be activated by heat shock proteins (HSPs). We previously reported that HSP70 expression after hyperthermia induces antitumor immunity. Our hyperthermia system using magnetite cationic liposomes (MCLs) induced necrotic cell death that was correlated with HSP70 release. In the present study, we investigated the therapeutic effects of DC therapy combined with MCL-induced hyperthermia on mouse melanoma. In an in vitro study, when immature DCs were pulsed with mouse B16 melanoma cells heated at 43 degrees C, major histocompatibility complex (MHC) class I/II, costimulatory molecules CD80/CD86 and CCR7 in the DCs were upregulated, thus resulting in DC maturation. C57BL/6 mice bearing a melanoma nodule were subjected to combination therapy using hyperthermia and DC immunotherapy in vivo by means of tumor-specific hyperthermia using MCLs and directly injected immature DCs. Mice were divided into 4 groups: group I (control), group II (hyperthermia), group III (DC therapy) and group IV (hyperthermia + DC therapy). Complete regression of tumors was observed in 60% of mice in group IV, while no tumor regression was seen among mice in the other groups. Increased cytotoxic T lymphocyte (CTL) and natural killer (NK) activity was observed on in vitro cytotoxicity assay using splenocytes in the cured mice treated with combination therapy, and the cured mice rejected a second challenge of B16 melanoma cells. This study has important implications for the application of MCL-induced hyperthermia plus DC therapy in patients with advanced malignancies as a novel cancer therapy.

Cancer immunotherapy by fusions of dendritic and tumour cells and rh-IL-12

BACKGROUND

Vaccination with fusion cells (FCs) comprising dendritic cells and tumour cells as well as administration of interleukin-12 (IL-12) showed a significant therapeutic effect against established tumours in mouse experimental models. We conducted immunotherapy against various malignant tumours using the FCs and rhIL-12, and investigated the safety and efficacy of the therapy.

MATERIALS AND METHODS

Patients' DCs were mixed with autologous irradiated tumour cells and treated with 50% polyethylene glycol to generate FCs. The FCs were inoculated intradermally, and then 30 ng kg(-1) of rhIL-12 was injected at the same sites 2 and 6 days later. This process was carried out as one cycle, and three of these cycles were repeated at 1-week intervals to comprise one course. After completing the course, its safety and therapeutic effects were estimated.

RESULTS

The most frequently observed adverse event was fever, observed in 26% of patients in the first cycle. Decrease in white blood cell and an increase in serum ALT were observed in 28% and 25%, respectively. Three out of 12 patients with a malignant brain tumour (25%) achieved a partial response (PR), but other patients with a malignant tumour showed no regression of their tumours. Thirteen out of 16 patients with a brain tumour (81%) showed cutaneous delayed hypersensitivity responses. However, only one of 16 patients (6%) with a malignant tumour other than a brain tumour developed such responses.

CONCLUSIONS

Immunotherapy using a FC vaccine and rhIL-12 induced no serious adverse reactions, and provided good therapeutic responses in some of the patients with a brain tumour.

Tumor vaccine against recurrence of hepatocellular carcinoma

AIM: To investigate the effects of autologous tumor vaccine on recurrence of hepatocellular carcinoma (HCC).

METHODS: Sixty patients with HCC who had undergone curative resection, were randomly divided into HCC vaccine group and control group. Three vaccinations at 2-wk intervals were performed after curative hepatic resection. Delayed-type- hypersensitivity (DTH) test was performed before and after vaccination. Primary endpoints were the time of recurrence.

RESULTS: Four patients in control group and 6 patients in HCC vaccine group were withdrawn from the study. The vaccine containing human autologous HCC fragments showed no essential adverse effect in a phase II clinical trial and 17 of 24 patients developed a DTH response against the fragments. Three of 17 DTH-positive response patients and 5 of 7 DTH- negative response patients had recurrences after curative resection. After the operation, 1-, 2- and 3-year recurrence rates of HCC vaccine group were 16.7%, 29.2% and 33.3%, respectively. But, 1-, 2- and 3-year recurrence rates of the control group were 30.8%, 53.8% and 61.5%, respectively. The time before the first recurrence in the vaccinated patients was significantly longer than that in the control patients (P<0.05).

CONCLUSION: Autologous tumor vaccine is of promise in decreasing recurrence of human HCC.

A novel, rapid strategy to form dendritomas from human dendritic cells and hepatocellular carcinoma cell line HCCLM3 cells using mature dendritic cells derived from human peripheral blood CD14+ monocytes within 48 hours of in vitro culture

AIM: Dendritomas formed by fusing cancer cells to dendritic cells have already been applied to clinical treatment trial of several types of cancers. Dendritic cells for the fusion in most trials and experiments were from blood monocytes in standard 7-d protocol culture, which requires 5-7 d of culture with granulocyte-macrophage–colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), followed by 2-3 d of activation with a combination of proinflammatory mediators such as tumor necrosis factor α (TNFα ), interleukin-1β (IL-1β ), interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂). One study showed that mature monocyte-derived dendritic cells could be obtained within 48 h of in vitro culture with the same protocol as standard 7-d culture and referred to as FastDCs. Here we aimed to fuse human hepatocellular carcinoma cell line HCCLM3 cells with mature monocyte-derived dendritic cells within 48 h of in vitro culture (FastDC).

METHODS: HCCLM3 cells were cultured in RPMI 1640 with 150 mL/L fetal calf serum (FCS). CD14+ monocytes from healthy human peripheral blood were purified with MACS CD14 isolation kit and cultured in six-well plates in fresh complete DC medium containing RPMI-1640, 20 mL/L heat inactivated human AB serum, 2 mmol/L L-glutamine, 100 µg/mL gentamicin, 1000 U/mL GM-CSF and 500 U/mL IL-4 for 24 h, then proinflammatory mediators such as TNFα (1000 U/mL), IL-1β (10 ng/mL), IL-6 (10 ng/mL) and PGE₂ (1 μg/mL) were supplemented for another 24 h, and thus mature FastDCs were generated. HCCLM3 cells and FastDCs were labeled with red fluorescent dye PKH26-GL and green fluorescent dye PKH67-GL respectively. After the red fluorescent-stained HCCLM3 cells were irradiated with 50 Gy, FastDCs and irradiated HCCLM3 cells were fused in 500 mL/L polyethylene glycol(PEG) + 100 mL/L dimethyl sulfoxide (DMSO) to generate novel dendritomas. The FastDCs and novel dendritomas were immunostained with anti-CD80, anti-CD86, anti-CD83, anti-HLA-DR mAbs and analyzed by fluorescence-activated cell sorting (FACS). Novel dendritomas were nucleus-stained with Hoechst 33258 and analyzed by confocal laser scanning microscopy.

RESULTS: Mature FastDCs with highly expressed surface markers CD80, CD86, CD83 and HLA-DR were generated within 48 h in vitro. Novel dendritomas with dual red-green fluorescence were constructed fast and successfully, and FACS analysis showed that the fusion efficiency was 24.27% and the novel dendritomas expressed the same activation markers as FastDCs. Confocal laser scanning microscopy analysis showed representative images of dendritomas.

CONCLUSION: Dendritomas can be formed fast with mature FastDCs from healthy human peripheral blood monocytes (PBMC) by incubation with GM-CSF and IL-4 for 24 h and by activation with proinflammatory mediators for an additional period of 24 h. Owing to shorter time required for in vitro DCs development, the generation of these novel dendritomas reduced labor and cost. This rapid method for formation of dendritomas may represent a new strategy for immunotherapy of hepatocellular carcinoma.

Dendritic cells fused with human cancer cells: morphology, antigen expression, and T cell stimulation

Fusion of human dendritic cells (DC) with tumor cells is an effective approach for delivering tumor antigens to DC, and DC/tumor fusion cells are potent stimulators of autologous T cells. However, the integration and morphology of DC/tumor fusion cells has not been examined. In the present study, we fused patient-derived DC to autologous breast or ovarian carcinoma cells. The fusion cells possessed the properties of both parent cells. After fusion, the cytoplasm of the two cells was integrated, whereas their nuclei remained separate entities. Colocalization of MUC1 peptide and HLA-DR molecules was observed on fusion cells under the immunoelectron microscope. Coculture of patient-derived peripheral blood mononuclear cells (PBMC) with DC/tumor fusion cells resulted in activation of CD4 and CD8 T cells as assessed by IFN-gamma secretion, HLA-A*0201-MUC1 tetramer, and standard cytotoxic T lymphocyte (CTL) assays. The present study provides first evidence of integration of human DC and tumor cells and links their properties to T cell activation.

Induction of anti-leukemic cytotoxic T lymphocytes by fusion of patient-derived dendritic cells with autologous myeloblasts

Presentation of AML antigens by dendritic cells (DC) could potentially induce a T cell-mediated anti-leukemic immune response. In the present study, we generated DC from adherent (AD-DC) and non-adherent (NAD-DC) myeloblasts obtained from bone marrows of AML patients. Both cell populations displayed morphological, phenotypic and functional properties of DC. The functions of NAD-DC were compared to AD-DC that had been fused with autologous AML blasts (FC/AML). The FC/AML induced greater T cell proliferation and CTL activity against autologous AML blasts (9/10 cases) as compared to NAD-DC. FC/AML may thus represent a promising strategy for DC-based immunotherapy of patients with AML.

Immunotherapeutic strategies for hepatocellular carcinoma

There is a continuing need for innovative, alternative therapies for hepatocellular carcinoma (HCC). Immunotherapy for cancer is attractive because of the exquisite specificity of the immune response. Activation of an HCC-specific response can be accomplished by strategies targeting tumor-associated self-antigens (for example, alpha-fetoprotein [AFP]). Gene array studies have added to the list of HCC-specific gene products that can be targeted. Alternatively, the immune response can be targeted against viral antigens in those patients infected with hepatitis B or C virus. Uncharacterized and mutated antigens can also be targeted with whole tumor cell or tumor lysate-based immunization strategies or with vectors coding for genes that make the tumor immunogenic, allowing the immune system to naturally evolve specificity against immunogenic target antigens. Strategies being investigated in animal models include increasing tumor immunogenicity by targeting cytokines or costimulatory molecules to tumor; immunization with tumor cells fused with antigen-presenting cells; adoptive transfer of viral antigen-specific T cells; and targeting AFP-expressing HCC cells by DNA, adenovirus, peptide, and dendritic cell (DC) strategies. Strategies that have been tested in human clinical trials include adoptive transfer of lymphocytes and autologous tumor-pulsed DC as well as 2 AFP-based strategies: AFP-derived peptides in Montanide and AFP peptides pulsed onto autologous DC. These trials, testing novel immune-based interventions in HCC subjects, have resulted in immunologic responses and have impacted recurrence and survival in HCC subjects.

Phase II randomized trial of autologous formalin-fixed tumor vaccine for postsurgical recurrence of hepatocellular carcinoma

PURPOSE

We conducted a Phase II clinical trial with randomized patients to determine whether autologous formalin-fixed tumor vaccine (AFTV) protects against postsurgical recurrence of hepatocellular carcinoma (HCC).

EXPERIMENTAL DESIGN

Forty-one patients with HCC who had undergone curative resection were randomly allocated to the vaccine treatment (n = 19) or no adjuvant control group (n = 22). Three intradermal vaccinations were administered at 2-week intervals beginning 4-6 weeks after hepatic resection. A delayed-type hypersensitivity test was performed before and after vaccination. Primary and secondary end points are recurrence-free survival and overall survival, respectively. Observation continued until the majority of surviving patients had lived >12 months after the curative resection.

RESULTS

In a median follow-up of 15 months, the risk of recurrence in vaccinated patients was reduced by 81% (95% confidence interval, 33-95%; P = 0.003). Vaccination significantly prolonged the time to first recurrence (P = 0.003) and improved recurrence-free survival (P = 0.003) and overall survival rates (P = 0.01). AFTV played a significant role in preventing recurrence in patients with small tumors. Adverse effects were limited to grade 1 or 2 skin toxicities such as erythema, dry desquamation, and pruritus.

CONCLUSIONS

AFTV therapy is a safe, feasible, and effective treatment for preventing postoperational recurrence of HCC. Patients with low tumor burdens benefit from the treatment. This treatment should be advanced to a large-scale randomized trial.

Lymphotactin enhances the in-vitro immune efficacy of dendritoma formed by dendritic cells and mouse hepatocellular carcinoma cells

OBJECTIVE

To investigate the in-vitro antitumor immune responses of dendritoma formed by mouse hepatocellular carcinoma (HCC) cells and lymphotactin (Lptn) gene modified dendritic cells (DCs).

METHOD

DCs prepared from mouse bone marrow were genetically modified by lymphotactin adenovirus, and fused with H22 cells by polyethylene glycol (PEG). RT-PCR and ELISA were employed to identify lymphotactin expression at mRNA and protein level. Cell phenotypes and fusion efficiency was detected by FACS. The stimulatory effect of DC on T cells was detected by mixed lymphocyte reaction. The cytotoxicity activity against H22 cells was assayed by LDH method.

RESULTS

Lymphotactin could be efficiently expressed by DCLptn/H22 hybridoma. DCLptn/H22 cells could induce potent T cell proliferation effect and generate strong cytotoxic T lymphocyte (CTL) reaction against allogenic H22 cells.

CONCLUSION

Lymphotactin genetic modification could enhance the in vitro immune activity of the dendritoma.

Dendritic cell vaccine therapy by immunization with fusion cells of interleukin-2 gene-transduced, spleen-derived dendritic cells and tumour cells

We examined the preventive and therapeutic effects of fusion cells prepared from spleen-derived dendritic cells (DCs) transduced with the interleukin-2 (IL-2) gene and QRsP fibrosarcoma cells in a mouse lung metastasis model. The IL-2 or LacZ gene was introduced into spleen-derived DCs using an adenoviral vector. Irradiated QRsP tumour cells were fused with IL-2 gene-transduced DCs (fusion/IL-2) or LacZ gene-transduced DCs (fusion/LacZ) by polyethylene glycol. These fusion cells expressed major histocompatibility complexes (MHC) class I and II, CD86, CD11c and CD8alpha. Splenocytes from mice vaccinated with fusion cells showed increased production of interferon-gamma (IFN-gamma) and cytotoxic T-lymphocyte (CTL) activity as compared with those vaccinated with DCs or tumour cells alone, and CTL levels were higher in fusion/IL-2-vaccinated mice than in fusion/LacZ-vaccinated mice. In our experiments on the protective and therapeutic effects on lung metastasis, mice vaccinated with fusion/IL-2 fusion/LacZ or fusion showed a significant reduction in pulmonary metastasis compared with those given DCs, tumour or phosphate-buffered saline. The introduction of the IL-2 gene into fusion cells produced more potent preventive and therapeutic effects. These results suggest that immunization with fusion cells prepared from spleen-derived DCs and tumour cells is capable of inducing preventive and therapeutic anti-tumour immunity against lung metastasis, and modification by the IL-2 gene may increase anti-tumour efficacy.

Prevention of gastrointestinal tumors based on adenomatous polyposis coli gene mutation by dendritic cell vaccine

Here we describe the effect of immunization with dendritic cells loaded with syngeneic tumor cells (DC/Ts) by polyethylene glycol treatment, on tumor development in adenomatous polyposis coli (APC) gene mutant mouse models, APC1309 and APC(Min-/+), in which adenomatous polyps of the gastrointestinal tracts develop with a high incidence. Treatment with DC/Ts prevented the development of gastrointestinal tumors, and coadministration of DC/Ts and IL-12 caused a further reduction in tumor incidence. Splenocytes from APC1309 mice treated with DC/Ts and IL-12 showed no cytotoxic activity toward the tumor cells, but serum antibody specific to them was detected. IgG from the treated mice exhibited cytotoxic activity against the tumor cells in vitro. Predominance of Th2 cell response over Th1 response was also suggested by ELISPOT assays in the treated mice. Depletion in vivo of CD4(+) T cells, not CD8(+) T cells, by the intraperitoneal administration of corresponding mAb's decreased the antitumor effect of DC/T inoculation. Immunofluorescence microscopic studies showed that Ig was attached to tumor cells in mice treated with DC/Ts and IL-12. These findings indicate that DC/T vaccination prevents tumor development through APC gene mutation and that its preventive effects are mediated by humoral antitumor immunity.

In vitro antitumor immune response induced by fusion of dendritic cells and colon cancer cells

AIM

The prevention of recurrence of colon cancer (CC) after operation is very important for improvement of the prognosis of CC patients, especially those with micro-metastasis. The generation of fused cells between dendritic cells (DCs) and tumor cells maybe an effective approach for tumor antigen presentation in immunotherapy. In this study, we fused human colon caner SW480 cells and human peripheral blood - derived DCs to induce an antitumor activity against human CC.

METHODS

CC SW480 cells and human peripheral blood - derived DCs were fused with 500 mL/L polyethylene glycol (PEG).

RESULTS

The specific T cell responses activated by fusion cells (FCs), were observed. About 100 mL/L to 160 mL/L of the PEG-treated non-adherent cells with fluorescences were considered to be dendritomas that highly expressed the key molecules for antigen presentation in our five cases. In vitro studies showed that fusions effectively activated CD8(+) T lymphocytes to secrete interferon-gamma. The early apoptotic ratio of the colon cancer SW480 cells was higher than that of controls, which was affected by cytotoxic T lymphocytes (CTLs) stimulated by dendritomas.

CONCLUSION

The data indicate that fusion of tumor cells with DCs is an attractive strategy to induce tumor rejection.

Eliciting specific antitumor immunity against hepatocellular carcinoma in vitro by fusions of HCC patient-derived dendritic cells with HCC cells

AIM: To investigate the ability of fusions of HCC patient-derived dendritic cells (DC) with HCC cells to induce autologous T lymphocytes to elicit specific immunity against HCC in vitro.

METHODS: Dendritic cells isolated from HCC patient peripheral blood were cultured and proliferated in vitro for one wk by using recombinant human granulocyte/macrophage-colony stimulating factor (rhGM-CSF) and interleukin-4 (rhIL-4). Expression of DC surface markers was assessed by flow cytometry. Fusions of DC with HepG2 cells (HepG2/DC) were achieved by polythyleneglycol (PEG). The ability of HepG2/DC to stimulate proliferation and differentiation of autologous T lymphocytes was assessed by MTT method, and the specific killing efficacy of HepG2/DC-induced cytotoxic T lymphocytes (CTL) to HepG2 was evaluated.

RESULTS: Following one wk culture, DC presented a high-level expression of CD1a, HLA-DR, CD54, CD80 and CD86. Fusions had remarkably greater ability to stimulate proliferation of autologous T lymphocytes in comparison with HepG2, HepG2+DC, DC and PBS, with an A value of 0.816±0.019 vs 0.541±0.020, 0.632±0.018, 0.564±0.018, 0.345±0.013, respectively (P<0.05). The HepG2/DC-activated CTLs showed a potent specific killing efficacy to HepG2.

CONCLUSION: Fusions of HCC patient-derived DC with HCC cells can effectively stimulate autologous T lymphocytes to elicit specific antitumor immunity against HCC, and may represent as a promising approach of immunotherapy for HCC.

Vaccination with hybrids of tumor and dendritic cells induces tumor-specific T-cell and clinical responses in melanoma stage III and IV patients

Hybrid cell vaccination was developed as therapeutic approach that aims at stimulating tumor-specific cytotoxic T-cell responses in cancer patients using hybrids of autologous tumor and allogeneic dendritic cells. We tested this concept and the efficacy of the vaccines in inducing clinical and immunologic responses in a clinical trial with melanoma stage III and IV patients. Of the 17 patients evaluated, 1 experienced a complete response, 1 a partial response and 6 stable disease with remarkably long survival times. In 11 of 14 patients analyzed, high-frequency T-cell responses to various tumor-associated T-cell epitope were induced and detectable in the peripheral blood. These immune responses were detected in clinical response patients as well as nonresponders. Failures of clinical responses in all the cases investigated correlated with loss of antigen expression and presentation. Hybrid cell vaccination thus proves effective in inducing tumor-specific T-cell responses in cancer patients.

Inhibition of spontaneous development of liver tumors by inoculation with dendritic cells loaded with hepatocellular carcinoma cells in C3H/HeNCRJ mice

We attempted to prevent spontaneous development of liver tumors by s.c. inoculation with DCs loaded with syngeneic HCC cells in C3H/HeNCrj mice. A new cell line, MIH-2, was established from an HCC that had developed spontaneously in a C3H/HeNCrj mouse. Bone marrow-derived DCs were loaded with irradiated MIH-2 cells by treatment with PEG. Fluorescence microscopy and flow-cytometric analysis showed that about 45% of PEG-treated DCs and MIH-2 cells (DC/MIH-2) were DCs loaded with MIH-2 cells. Thirteen-month-old mice received inoculations of DC/MIH-2 (9 x 10(5)/mouse) 4 times at 6-day intervals and were killed at 16 months of age to assess liver tumors. The incidence of liver tumors in these mice was significantly lower than that in mice not receiving inoculations (p < 0.05) but similar to that in 13-month-old mice (the age at which inoculation started), indicating that inoculation inhibited the development of new tumors. Splenocytes from inoculated mice, but not those from uninoculated mice, showed cytotoxic activity against MIH-2 cells. Cytotoxic activity was not elicited by CD4(+) T cells, CD8(+) T cells, or DX5(+) cells isolated from splenocytes but was elicited by adherent cells, identified as CD11b(+) macrophages. CD4(+) T cells, but not CD8(+) T cells, from inoculated mice produced IFN-gamma by incubation with DC/MIH-2. Cytotoxicity by splenocytes was attenuated by anti-IFN-gamma antibody. Immunization with DCs loaded with syngeneic HCC cells induces CD4(+) T cells that produce IFN-gamma by response to antigen of HCC, which would lead to macrophage activation to kill liver tumor cells at an early stage.

Immature dendritic cell/tumor cell fusions induce potent antitumour immunity

BACKGROUND

Maturation of dendritic cells (DCs) is important to induce antigen-specific antitumour immunity in cancer immunotherapy with antigen-loaded DCs. However, DCs from tumour-bearing hosts are immature and functionally defective for antigen presentation. We examined whether DCs from tumour-bearing mice could be an effective part of a DC/tumour cell fusion vaccine.

MATERIALS AND METHODS

Dendritic cells from healthy (DC-Hs) or MC38 tumour-bearing mice (DC-TBs) were examined for endocytotic capacity of FITC-labelled dextran, antigen-presenting capacity in allogeneic mixed leucocyte reaction (allo-MLR) and expression of I-Ab, CD80, and CD86. Fusion cells (FCs) of DC-Hs or DC-TBs and MC38 cells (FC-Hs or FC-TBs) were generated by treatment with polyethylene glycol (PEG). Mice vaccinated with FC-Hs or FC-TBs were studied for cytolytic activity of splenocytes and suppressive activity against established MC38 pulmonary metastases.

RESULTS

Dendritic cell-TBs showed higher endocytotic capacity and lower antigen-presenting capacity than did DC-Hs, results indicating that DC-TBs are more immature and functionally defective for antigen presentation than are DC-Hs. Expression of surface molecules, however, was almost same between DC-Hs and DC-TBs. Splenocytes from mice immunized with FC-Hs or FC-TBs induced the same high cytolytic activity against MC38 cells. Vaccination of mice with FC-Hs or FC-TBs resulted in the same significant suppressive effect against established pulmonary metastases of MC38.

CONCLUSION

Dendritic cells from tumour-bearing mice, despite being functionally defective, are effective vehicles for immunotherapy using DC/tumour cell fusion vaccines.

Tumor-derived TGF-beta reduces the efficacy of dendritic cell/tumor fusion vaccine

Dendritic cell (DC)-based antitumor vaccine is a novel cancer immunotherapy that is promising for reducing cancer-related mortality. However, results from early clinical trials were suboptimal. A possible explanation is that many tumors secrete immunosuppressive factors such as TGF-beta, which may hamper host immune response to DC vaccine. In this study, we demonstrated that TGF-beta produced by tumors significantly reduced the potency of DC/tumor fusion vaccines. TGF-beta-secreting (CT26-TGF-beta) stable mouse colon cancer cell lines were generated using a retroviral vector expressing TGF-beta. A non-TGF-beta-secreting (CT26-neo) cell line was generated using an empty retroviral vector. The efficacies of DC/tumor fusion vaccines were assessed in vitro and in vivo. DC/CT26-TGF-beta fusion cells failed to induce a strong T cell proliferative response in vitro, mainly due to the effect of TGF-beta on T cell responsiveness rather than DC stimulatory capability. Animals vaccinated with DC/CT26-TGF-beta fusion vaccine had lower tumor-specific CTL activity and had significantly lower survival after tumor challenge as compared with animals immunized with DC/CT26-neo hybrids (45 vs 77%, p < 0.05). Ex vivo exposure of DCs to TGF-beta did not appear to lessen the efficacy of DC vaccine. These data suggest that tumor-derived TGF-beta reduces the efficacy of DC/tumor fusion vaccine via an in vivo mechanism. Neutralization of TGF-beta produced by the fusion cells may enhance the effectiveness of DC-based immunotherapy.

Antitumor immunopreventive and immunotherapeutic effect in mice induced by hybrid vaccine of dendritic cells and hepatocarcinoma in vivo

AIM: To develop atumor vaccine by fusion of H22 hepatocarcinoma cells and DC, and to study its protective and therapeutical effect against H22 cell.

METHODS: H22-DC vaccine was produced by PEG fusion of H22 and DC induced by cytokine released from splenic mononuclear cells, sorted by CD11c magnetic microbead marker. It was injected through the tail vein of the mice and the H₂₂-DC oncogenesis was detected in the liver, spleen and lung. In order to study the therapeutical and protective effect of H₂₂-DC against tumor H₂₂, two groups were divided: immune group and therapeutic group. Immune group was further divided into P, D, HD and H subgroups, immunized by PBS, DC, H₂₂-DC and inactivated H₂₂, respectively, and attacked by H₂₂ cell. The tumor size, tumor weight, mice survival time and tumor latent period were recorded and statistically analyzed; Therapeutical group was divided into three subgroups of P, D and HD, and attacked by H₂₂, then treated with PBS, DC, and H₂₂-DC, respectively. Pathology and flow cytometry were also applied to study the mechanism how the H₂₂-DC vaccine attacked on the H₂₂ cell.

RESULTS: 1. No oncogenesis was found in spleen, lung and liver after H22-DC injection. 2. Hybrid vaccine immunized mice had strongest CTL activity. 3. In the immune group, latent period was longer in HD subgroup than that in P, H and D subgroup; and tumor size and weight were smaller in HD subgroup than that in P, H and D subgroup. 4. In therapeutic group, tumor size was smaller in HD subgroup than that in P, D subgroup.

CONCLUSION: 1. H22-DC tumor vaccine is safe without oncogenesis in vivo. 2. Hybrid vaccine can stimulate potent specific CTL activity against H22. 3. H22-DC vaccine has distinctive prophylatic effect on tumor H22 and can inhibit the tumor growth.