Allogeneic gastric cancer cell-dendritic cell hybrids induce tumor antigen (carcinoembryonic antigen) specific CD8(+) T cells

Could gastrointestinal tumor-initiating cells originate from cell-cell fusion in vivo?

Tumor-initiating cells (TICs) or cancer stem cells are believed to be responsible for gastrointestinal tumor initiation, progression, metastasis, and drug resistance. It is hypothesized that gastrointestinal TICs (giTICs) might originate from cell-cell fusion. Here, we systemically evaluate the evidence that supports or opposes the hypothesis of giTIC generation from cell-cell fusion both in vitro and in vivo. We review giTICs that are capable of initiating tumors in vivo with 5000 or fewer in vivo fused cells. Under this restriction, there is currently little evidence demonstrating that giTICs originate from cell-cell fusion in vivo. However, there are many reports showing that tumor generation in vitro occurs with more than 5000 fused cells. In addition, the mechanisms of giTIC generation via cell-cell fusion are poorly understood, and thus, we propose its potential mechanisms of action. We suggest that future research should focus on giTIC origination from cell-cell fusion in vivo, isolation or enrichment of giTICs that have tumor-initiating capabilities with 5000 or less in vivo fused cells, and further clarification of the underlying mechanisms. Our review of the current advances in our understanding of giTIC origination from cell-cell fusion may have significant implications for the understanding of carcinogenesis and future cancer therapeutic strategies targeting giTICs.

Induction of antigen-specific cytotoxic T lymphocytes by fusion cells generated from allogeneic plasmacytoid dendritic and tumor cells

Previous work has demonstrated that fusion cells generated from autologous monocyte-derived dendritic cells (MoDCs) and whole tumor cells induce efficient antigen-specific cytotoxic T lymphocytes. A major limitation to the use of this strategy is the availability of adequate amounts of autologous tumor cells. Moreover, MoDCs from cancer patients are often defective in their antigen-processing and presentation machinery. In this study, two types of allogeneic cells, a leukemia plasmacytoid dendritic cell (pDC) line (PMDC05) and pancreatic cancer cell lines (PANC-1 or MIA PaCa-2), were fused instead of autologous MoDCs and tumor cells. We created four types of pDC/tumor fusion cells by alternating fusion partners and treating with lipopolysaccharide (LPS): i) PMDC05 fused with PANC-1 (pDC/PANC-1), ii) PMDC05 fused with MIA PaCa-2 (pDC/MIA PaCa-2), iii) LPS-stimulated pDC/PANC-1 (LPS-pDC/PANC-1) and iv) LPS-stimulated pDC/MIA PaCa-2 (LPS-pDC/MIA PaCa-2) and examined their antitumor immune responses. The LPS-pDC/tumor cell fusions were the most active, as demonstrated by their: i) upregulated expression of HLA-DR and CD86 on a per-fusion-cell basis, ii) increased production of IL-12p70, iii) generation of a higher percentage of IFN-γ-producing CD4⁺ and CD8⁺ T cells and iv) augmented induction of MUC1-specific CD8⁺ T cells that lyse target tumor cells. This study provides the first evidence for an in vitro induction of antigen-specific cytotoxic T lymphocytes by LPS-stimulated fusion cells generated from leukemia plasmacytoid DCs and tumor cells and suggests that this strategy has potential applicability to the field of adoptive immunotherapy.

Superior anti-tumor protection and therapeutic efficacy of vaccination with dendritic cell/tumor cell fusion hybrids for murine Lewis lung carcinoma

BACKGROUND

The development of protocols for the ex vivo generation of dendritic cells (DCs) has led to intensive research into their potential use in immunotherapy in the treatment of cancer. In this study, we examined the efficacy of dendritic cell-tumor cell fusion hybrid vaccines in eliciting an immune response against Lewis lung carcinoma (LLC) cells, as compared to other types of tumor vaccines. In addition, we also tested whether the efficacy of the vaccines was affected by the route of administration. Four different tumor vaccines were compared: (1) HC (hybrid cell), consisting of DC/LLC hybrids; (2) DC+LLC (DCs pulsed with apoptotic LLCs); (3) DC without antigen loading/pulsing; (4) LLC (apoptotic/irradiated tumor cells). We also compared four different routes of administration for each vaccine: (1) Preimmunization; (2) Vaccination therapy; (3) Adoptive immunotherapy; (4) Vaccination therapy combined with adoptive immunotherapy. Anti-tumor immunity was assessed in vivo and the CTL (cytotoxic T lymphocyte) response as well as the expression of key cytokines, IFN-γ and IL-10 were further evaluated using in vitro assays.

RESULTS

Our data demonstrate that vaccination with HC hybrids provides more effective anti-tumor protective immunity and significantly greater therapeutic immunity than vaccination with DC+LLC, DC or LLC. Most remarkably, vaccination therapy with HC hybrids was more successful than combination (vaccination + adoptive) therapy for the induction of anti-tumor responses. Splenocytes harvested from mice immunized with HC hybrids demonstrated the greatest cytotoxic T lymphocyte (CTL) activity and their production of IFN-γ was high, while their production of IL-10 was very low.

CONCLUSIONS

Our results suggest that vaccination therapy with DC-tumor cell fusion hybrids provides more effective protection against lung cancer.

Allogeneic tumor vaccine produced by electrofusion between osteosarcoma cell line and dendritic cells in the induction of antitumor immunity

OBJECTIVE

Fusion of dendritic cells, DCs, with tumor cells is an effective approach for delivering tumor antigens to DCs, and DC-tumor fusion cells are potent stimulators of T cells. However, the integration of allogeneic DC-osteosarcoma fusion cells has not been fully examined. This study was designed to investigate the antitumor effects of tumor vaccine produced by electrofusion between rat osteosarcoma cells and allogeneic DCs.

METHODS

In the present study, we electrofused Wistar rat bone marrow-derived DCs to SD rat osteosarcoma cells (UMR106) and purified them by monoclonal antibody OX62 and magnetic beads. Coculture of SD or Wistar bone marrow derived T lymphocytes with DC-tumor fusion cells resulted in activation of T cells, and the proportion of CD8(+), CD4(+) cells was determined using flow cytometry. Then cytotoxic T lymphocytes, CTLs, assay was assessed according to results of MTT assay.

RESULTS

After T cells were cultured with allogeneic DC-osteosarcoma fusion cells, DOF, and effective activation of T cells was observed. The proportion of CD8(+) cells in the SD T cell group increases from 34.16% before induction to 74.85%, while that of CD4(+) cells is from 63.35% to 71.75% in Wistar T cell group. The immunization using allogeneic DC-osteosarcoma vaccine induced UMR106-specific CTL responses which were statistically significant (P < 0.05) and the cytotoxic activity was inhibited by the treatment with anti-CD8 and anti-MHC-class I monoclonal antibodies but not with anti-CD4 and anti-MHC-class II antibodies.

CONCLUSION

The present study provided valid evidence of integration of rat allogeneic DCs electrofused with tumor cells and analyzed their properties in T cell activation. The fusion cells may thus represent a promising strategy for DC-based immunotherapy of patients with osteosarcoma.

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.

Alpha-Type 1 Polarized Dendritic Cells Loaded with Apoptotic Allogeneic Breast Cancer Cells Can Induce Potent Cytotoxic T Lymphocytes against Breast Cancer

Purpose

Various tumor antigens can be loaded onto dendritic cells (DCs) to induce a potent cytotoxic T lymphocyte (CTL) response in DC-based immunotherapy against breast cancer. However, in the clinical setting, obtaining a sufficient number of autologous tumor cells as a source of tumor antigens is a laborious process. We therefore investigated the feasibility of immunotherapy using breast-cancer-specific CTLs generated in vitro by use of alpha-type 1 polarized DCs (α DC1s) loaded with ultraviolet B-irradiated cells of the breast cancer cell line MCF-7.

Materials and Methods

αDC1s were induced by loading allogeneic tumor antigen generated from the MCF-7 UVB-irradiated breast cancer cell line. Antigen-pulsed αDC1s were evaluated by morphological and functional assays, and the breast-cancer-specific CTL response was analyzed by cytotoxic assay.

Results

The αDC1s significantly increased the expression of several molecules related to DC maturation without differences according to whether the αDC1s were loaded with tumor antigens. The αDC1s showed a high production of interleukin-12 both during maturation and after subsequent stimulation with CD40L, which was not significantly affected by loading with tumor antigens. Breast-cancer-specific CTLs against autologous breast cancer cells were successfully induced by αDC1s loaded with apoptotic MCF-7 cells.

Conclusion

Autologous DCs loaded with an allogeneic breast cancer cell line can generate potent breast-cancer-specific CTL responses. This may be a practical method for cellular immunotherapy in patients with breast cancer.

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.

Induction of antitumor immunity by semi-allogeneic and fully allogeneic electrofusion products of tumor cells and dendritic cells

Immunization with the electrofusion product of tumor cells and dendritic cells (DCs) is a promising approach to cancer immunotherapy. Production of electrofusion vaccines currently requires the acquisition of tumor material and must be tailored to each individual. Alternative vaccine configurations were explored in this study. Results indicated that fusion vaccines with fully syngeneic, semi-allogeneic or fully allogeneic components, were all effective in inducing specific, long-lasting antitumor immunity. This previously undescribed activity of a fully allogeneic fusion product introduces the possibility of using defined allogeneic tumor and DC lines to simplify vaccine manufacturing.

Alpha-type 1-polarized dendritic cells loaded with apoptotic allogeneic myeloma cell line induce strong CTL responses against autologous myeloma cells

To induce a potent cytotoxic T lymphocyte (CTL) response, various tumor antigens should be loaded onto dendritic cells (DCs). In multiple myeloma (MM), it is difficult to obtain a sufficient number of autologous tumor cells as a source of tumor antigens in the clinical setting. We investigated the feasibility of immunotherapy in patients with MM, using myeloma-specific CTLs generated in vitro by alpha-type 1-polarized DCs (alphaDC1s) loaded with the ultraviolet B-irradiated allogeneic myeloma cell line, ARH77. alphaDC1s significantly increased the expression of several costimulatory molecules without differences in loading with tumor antigens. alphaDC1s showed a high production of interleukin-12 during maturation and after subsequent stimulation with CD40L but were not significantly affected by loading tumor antigens. Myeloma-specific CTLs against autologous myeloma cells from MM patients were induced by alphaDC1s pulsed with apoptotic ARH77 cells. Our data indicate that autologous DCs loaded with an allogeneic myeloma cell line can generate potent myeloma-specific CTL responses against autologous myeloma cells and might provide a practical method for cellular immunotherapy in patients with MM.

Characterization of gastric adenocarcinoma cell lines established from CEA424/SV40 T antigen-transgenic mice with or without a human CEA transgene

Background

Gastric carcinoma is one of the most frequent cancers worldwide. Patients with gastric cancer at an advanced disease stage have a poor prognosis, due to the limited efficacy of available therapies. Therefore, the development of new therapies, like immunotherapy for the treatment of gastric cancer is of utmost importance. Since the usability of existing preclinical models for the evaluation of immunotherapies for gastric adenocarcinomas is limited, the goal of the present study was to establish murine in vivo models which allow the stepwise improvement of immunotherapies for gastric cancer.

Methods

Since no murine gastric adenocarcinoma cell lines are available we established four cell lines (424GC, mGC3, mGC5, mGC8) from spontaneously developing tumors of CEA424/SV40 T antigen (CEA424/Tag) mice and three cell lines derived from double-transgenic offsprings of CEA424/Tag mice mated with human carcinoembryonic antigen (CEA)-transgenic (CEA424/Tag-CEA) mice (mGC2^CEA, mGC4^CEA, mGC11^CEA). CEA424/Tag is a transgenic C57BL/6 mouse strain harboring the Tag under the control of a -424/-8 bp CEA gene promoter which leads to the development of invasive adenocarcinoma in the glandular stomach. Tumor cell lines established from CEA424/Tag-CEA mice express the well defined tumor antigen CEA under the control of its natural regulatory elements.

Results

The epithelial origin of the tumor cells was proven by morphological criteria including the presence of mucin within the cells and the expression of the cell adhesion molecules EpCAM and CEACAM1. All cell lines consistently express the transgenes CEA and/or Tag and MHC class I molecules leading to their susceptibility to lysis by Tag-specific CTL in vitro. Despite the presentation of CTL-epitopes derived from the transgene products the tumor cell lines were tumorigenic when grafted into C57BL/6, CEA424/Tag or CEA424/Tag-CEA-transgenic hosts and no significant differences in tumor take and tumor growth were observed in the different hosts. Although no spontaneous tumor rejection was observed, vaccination of C57BL/6 mice with lysates from gastric carcinoma cell lines protected C57BL/6 mice from tumor challenge, demonstrating the tumorigenicity of the tumor cell lines in nontransgenic mice of the H-2^b haplotype.

Conclusion

These tumor cell lines grafted in different syngeneic hosts should prove to be very useful to optimize immunotherapy regimens to be finally tested in transgenic animals developing primary gastric carcinomas.