Selected allogeneic dendritic cells markedly enhance human tumour antigen-specific T cell response in vitro.

BACKGROUND: Alloreaction is known to accumulate several theoretical advantages that can improve dendritic cell (DC)-based anti-infective or antitumour strategies. Allogeneic DC have already been tested in experimental and clinical studies, but their efficacy compared with their autologous counterparts was rarely investigated and conclusions diverge. OBJECTIVE: This study compared antigen-specific T cell responses following priming with autologous versus allogeneic DC and examined the possibility of screening these responses in order to select allogeneic DC that lead to a great amplification. RESULTS: Allogeneic DC obtained from donors matched with the single HLA-A2 allele were efficient in generating in vitro peptide-specific T cell responses. When randomly chosen, allogeneic DC generated a broad range of antigen-specific T cell responses in comparison with autologous DC. When screened and selected, allogeneic DC markedly enhanced peptide-specific T cell priming and allowed a more efficient boosting of resulting T cells. These selected allogeneic DC provided a favourable cytokinic and cellular environment that can help concurrent antigen-specific responses. CONCLUSION: Ex vivo selected allogeneic DC provide adjuvant effects that lead to amplification of concomitant antigen-specific T cell responses.

[State of the art about new therapeutic vaccines in prostate cancer: dendritic cells, engineered tumor cells and recombinant virus]. / Actualité des nouvelles thérapies vaccinales en évaluation dans le cancer de la prostate: cellules dendritiques, cellules tumorales transfectées et virus recombinants.

Therapeutic vaccines for prostate cancer were initially reported as limited with low immunological responses and uncertain clinical benefit. Recently, new methods become available, such preparations of well-characterized autologous dendritic cells, and use of gene therapy tools to increase whole-tumor cells or host tissue immunogenicity. These are able to enhance and diversify therapeutic options. Indeed, several vaccinal approaches are being investigated, including optimized mature dendritic cells, allogeneic genetically modified tumor cells, or viral vectors. Due to the description of immunological and clinical responses, large phase III randomized trials are now conducted. After summarizing the mechanistic basis for these approaches, this review describes the experience with the most recent and promising clinical studies and introduces short-term perspectives that could lead to improvement in healthcare offer for prostate cancer patients.

In vitro antitumor lymphocyte generation using dendritic cells and innate immunity mechanisms as tumor cell treatments.

Dendritic cells play a central role in the initiation and regulation of acquired and innate immunity, playing an important role in immunosurveillance and antitumor reaction. This reaction is mediated by effector cells and soluble factors. We chose to investigate four dendritic cell loading methods by mimicking innate immunity mechanisms and using whole tumor cell treatments in order to stimulate lymphocytes: sodium hypochlorite, TNFalpha and IFNgamma and IgG opsonization. These methods were compared in an HLA.A2 model of healthy donors and with the M74 melanoma cell line. Treated tumor cell-loaded DC were able to increase proliferation of lymphocytes. Moreover, a CTL population was stimulated, as shown by their specific cytotoxicity against tumor cells (with w6/32 antibody assays), against MelanA/MART-1 loaded T2 cells and using MelanA/MART-1 tetramer. IgG opsonization seemed to be less efficient than other tumor cell treatments. These loaded DC, or the obtained effector cells, could be interesting for therapeutic applications in antitumor cell therapy.

Ex vivo expansion of antitumor cytotoxic lymphocytes with tumor-associated antigen-loaded dendritic cells.

Cell therapy with lymphocytes is an attractive approach for cancer immunotherapy. Methods to generate ex vivo effector cells directed against whole autologous tumor antigens are under investigation. Our procedure involved stimulation of autologous lymphocytes with antigen-pulsed dendritic cells (DC). Experimental conditions were established with DC, matured with TNFa, LPS and CD40L, from healthy donors and the M74 melanoma cell line. DC were pulsed with either irradiated, apoptotic or necrotic tumor cells or fused with tumor cells. Increase of lymphocyte cytotoxicity and IFNy production were repeatedly observed with tumor cell-loaded DC. Stimulation of tumor-associated antigen-specific lymphocytes was clearly shown. MelanA-MART1 (dominant melanoma-associated antigen) tetramer staining revealed a high frequency of specific T cells. Lymphocytes were able to efficiently lyse MelanA-MART1-pulsed T2 target and MelanA-expressing target cells (M74) after CD56+ cells depletion. We confirmed with other tumor cell lines that this DC-mediated procedure induced activation of cytolytic lymphocytes.

Dendritic cells are defective in breast cancer patients: a potential role for polyamine in this immunodeficiency.

INTRODUCTION: Dendritic cells (DCs) are antigen-presenting cells that are currently employed in cancer clinical trials. However, it is not clear whether their ability to induce tumour-specific immune responses when they are isolated from cancer patients is reduced relative to their ability in vivo. We determined the phenotype and functional activity of DCs from cancer patients and investigated the effect of putrescine, a polyamine molecule that is released in large amounts by cancer cells and has been implicated in metastatic invasion, on DCs. METHODS: The IL-4/GM-CSF (granulocyte-macrophage colony-stimulating factor) procedure for culturing blood monocyte-derived DCs was applied to cells from healthy donors and patients (17 with breast, 7 with colorectal and 10 with renal cell carcinoma). The same peroxide-treated tumour cells (M74 cell line) were used for DC pulsing. We investigated the effects of stimulation of autologous lymphocytes by DCs pulsed with treated tumour cells (DC-Tu), and cytolytic activity of T cells was determined in the same target cells. RESULTS: Certain differences were observed between donors and breast cancer patients. The yield of DCs was dramatically weaker, and expression of MHC class II was lower and the percentage of HLA-DR-Lin- cells higher in patients. Whatever combination of maturating agents was used, expression of markers of mature DCs was significantly lower in patients. Also, DCs from patients exhibited reduced ability to stimulate cytotoxic T lymphocytes. After DC-Tu stimulation, specific cytolytic activity was enhanced by up to 40% when DCs were from donors but only up to 10% when they were from patients. IFN-gamma production was repeatedly found to be enhanced in donors but not in patients. By adding putrescine to DCs from donors, it was possible to enhance the HLA-DR-Lin- cell percentage and to reduce the final cytolytic activity of lymphocytes after DC-Tu stimulation, mimicking defective DC function. These putrescine-induced deficiencies were reversed by treating DCs with all-trans retinoic acid. CONCLUSION: These data are consistent with blockade of antigen-presenting cells at an early stage of differentiation in patients with breast cancer. Putrescine released in the microenvironmement of DCs could be involved in this blockade. Use of all-trans retinoic acid treatment to reverse this blockade and favour ex vivo expansion of antigen-specific T lymphocytes is of real interest.

Cytotoxic effector cells with antitumor activity can be amplified ex vivo from biopsies or blood of patients with renal cell carcinoma for cell therapy use.

Adoptive immunotherapy with antitumor effector cells is an attractive therapeutic approach in metastatic renal cell carcinoma (RCC). The aim of the work was to enhance in vitro activation of lymphocytes with optimal cytotoxic activity against tumor cells. We evaluated a procedure based on the use of dendritic cells (DCs) loaded with irradiated tumor cells (DC-Tu) to stimulate lymphocytes. Experimental conditions were established with cells from healthy donors and melanoma cell lines. Procedures were then applied to cells from RCC patients. A total of 30 tumor biopsies, 14 proximal lymph nodes, and 17 peripheral blood samples from 30 patients were used. When lymphocytes were stimulated in vitro with DC-Tu, they responded to tumor cells with an increased cytolytic activity for all the assays with donor cells (n=18). For RCC patients, DC-Tu stimulation improved the final cytotoxic activity in only half of the assays (16/31). When significantly enhanced (>10%, n=8), responder cells resulted in a final 43% cytotoxicity against autologous RCC cells. Mechanism of lysis was at least in part class I mediated. Effector cells have no lytic activity against normal renal cells. Percentage of cells with regulatory T-cell phenotype was not found to be enhanced in the DC-Tu stimulated lymphocytes. Individual differences were observed in the characteristics of DCs generated from RCC patients in contrast to that observed in donors and could explain why lymphocyte stimulation was not improved by DC-Tu in half of the RCC assays. T-cell spreading was suitable for a therapeutic use (>10(9) cells) irrespective of the procedure (with or without DC-Tu stimulation) or the tissular origin of lymphocytes from patients. Data show that precursors of selective antitumor effector cells are present in patients with RCC and can be amplified in vitro either with or without DC-Tu stimulation. One of these populations could be chosen for an adoptive transfer immunotherapy.

Adoptive immunotherapy monitored by micro-MRI in experimental colorectal liver metastasis.

In this study we used the colon carcinoma DHDK12 cell line and generated single metastasis after subcapsular injection in BDIX rats as an experimental tumor model. The aim of the work was to set up in vitro experimental conditions to prepare immune effector cells and in vivo conditions for monitoring the effects of such cells injected as adoptive immunotherapy. Dendritic cells can process tumor cell antigens, induce a T-cell response and be used ex vivo to prepare activated lymphocytes. Lymphocytes were harvested from mesenteric lymph nodes and cocultured with bone marrow-derived autologous dendritic cells previously loaded with irradiated tumor cells. In vitro, the coculture: 1) induced the proliferation of lymphocytes, 2) expanded a preferential subpopulation of T CD8 lymphocytes, and 3) was in favor of lymphocyte cytotoxic activity against the DHDK12 tumor cell line. Activated lymphocytes were injected in the tumor-bearing rat portal vein. Parameters could be set to monitor tumor volume by micro MRI. This monitoring before and after treatment and immunohistochemical examinations revealed that: 1) micro MRI is an appropriate tool to survey metastasis growth in rat, 2) injected lymphocytes increase lesional infiltration with T CD8 cells even 15 days after treatment, 3) a dose of 50 millions lymphocytes is not sufficient to act on the course of the tumor.