Biomedical subjects

Marc Gregoire

Publications and source records attributed to Marc Gregoire.

6 recordsLinked to original sources

PubMed2004

Opposite role of Bax and BCL-2 in the anti-tumoral responses of the immune system.

BACKGROUND: The relative role of anti apoptotic (i.e. Bcl-2) or pro-apoptotic (e.g. Bax) proteins in tumor progression is still not completely understood. METHODS: The rat glioma cell line A15A5 was stably transfected with human Bcl-2 and Bax transgenes and the viability of theses cell lines was analyzed in vitro and in vivo. RESULTS: In vitro, the transfected cell lines (huBax A15A5 and huBcl-2 A15A5) exhibited different sensitivities toward apoptotic stimuli. huBax A15A5 cells were more sensitive and huBcl-2 A15A5 cells more resistant to apoptosis than mock-transfected A15A5 cells (pCMV A15A5). However, in vivo, in syngenic rat BDIX, these cell lines behaved differently, as no tumor growth was observed with huBax A15A5 cells while huBcl-2 A15A5 cells formed large tumors. The immune system appeared to be involved in the rejection of huBax A15A5 cells since i) huBax A15A5 cells were tumorogenic in nude mice, ii) an accumulation of CD8+ T-lymphocytes was observed at the site of injection of huBax A15A5 cells and iii) BDIX rats, which had received huBax A15A5 cells developed an immune protection against pCMV A15A5 and huBcl-2 A15A5 cells. CONCLUSIONS: We show that the expression of Bax and Bcl-2 controls the sensitivity of the cancer cells toward the immune system. This sensitization is most likely to be due to an increase in immune induced cell death and/or the amplification of an anti tumour immune response

Animals↗

PubMed2003

Optimizing dendritic cell-based anticancer immunotherapy: maturation state does have clinical impact.

Tumour immunotherapy using dendritic cells (DCs) is a new therapeutic approach, which has been applied to a variety of different cancers over the last 5 years. Here we discuss the clinical results of these trials in relation to the different protocols used to generate DCs, and in particular the effect that DC maturation state has had on clinical responses. In ten different melanoma trials a total of 167 patients have been treated, resulting in 9 complete tumour regressions, 24 partial regressions, 26 patients with stable disease, and 108 with progressive disease. Favourable response, defined as any outcome other than progressive disease, was not associated with previous chemotherapy, but was significantly correlated ( p<0.001) with the addition of TNF-alpha for the maturation of DCs in vitro. Hence DC maturation state has had an impact on clinical responses to therapy. However, TNF-alpha is not the only molecule capable of inducing DC maturation, and strategies for improving clinical responses by optimizing DC maturation are discussed.

Antineoplastic Agents↗

PubMed2003

Transient exposure of dendritic cells to maturation stimuli is sufficient to induce complete phenotypic maturation while preserving their capacity to respond to subsequent restimulation.

Dendritic cells (DC) are activated by pathogens, cytokines and activated T cells. We investigated the impact of a transient initial DC stimulation on the kinetics of maturation using a combination of double-stranded RNA and TNFalpha and subsequent restimulation by T cell-derived stimuli. Transient stimulation of DC was sufficient to start an irreversible program of phenotypic maturation which proceeded in the absence of the initial stimulus. Transiently stimulated DC secreted lower amounts of IL-12 during the 48-h period of the first stimulation than cells activated for 48 h. Although both DC preparations expressed the same level of maturation-associated markers at 48 h, DC stimulated for shorter periods preserved higher sensitivity to boosting upon subsequent stimulation by T cell-derived signals. We showed that DC initially stimulated for shorter periods were more potent stimulators of T lymphocytes and they induced a more polarized Th1 response. These results indicate that short exposure of DC to maturation stimuli enables an efficient defensive immune response induction by differentially regulating phenotypic maturation and cytokine production of DC.

Antigen Presentation↗

PubMed2002

Apoptotic body-loaded dendritic cells efficiently cross-prime cytotoxic T lymphocytes specific for NA17-A antigen but not for Melan-A/MART-1 antigen.

DCs hold promise for cancer immunotherapy due to their functional ambivalence: iDCs internalize antigens, then mDCs trigger naive T-cell activation. However, no consensus has been reached concerning the optimal mode of antigen acquisition for efficient cross-priming of TAA-specific CTLs, and this remains a field of investigation. Here, we used highly purified apobodies derived from an HLA-A*0201-negative melanoma line as a source of tumor antigens for HLA-A*0201 DCs. We compared in vitro mDCs loaded with apobodies to DCs loaded with antigenic peptides, NA17-A(1-9) and Melan-A/MART-1(26-35) A27L analogue, for their capacity to stimulate melanoma antigen-specific T cells from autologous PBLs. Apobody phagocytosis did not induce spontaneous DC maturation, but phagocytic DCs were still responsive to maturation signals, resulting in a functional ability to activate antigen-specific lymphocytes. NA17-A-specific T lymphocytes were activated by both types of stimulation, whereas only peptide-pulsed DCs stimulated the growth of Melan-A/MART-1-specific lymphocytes. We also observed a lack of staining of melanoma-derived apobodies with a Melan-A-specific MAb, suggesting protein alteration during apoptosis induction. After HLA-A*0201/NA17-A multimer sorting, antigen-specific lymphocytes induced by mature DCs loaded with either peptide or apobodies displayed similar functional capacity against peptide-pulsed T2 cells and melanoma cells. Therefore, apobody-loaded DCs can achieve T-cell priming similar to that induced by peptide-pulsed DCs, provided that the apoptotic process allows the preservation of antigen expression.

Antigen Presentation↗

PubMed2002

Induction of leukemia-specific cytotoxic response by cross-presentation of late-apoptotic leukemic blasts by autologous dendritic cells of nonleukemic origin.

Acute myeloid leukemias (AMLs) are monoclonal proliferations of undifferentiated myeloid progenitors in blood and bone marrow. Long-term remissions are achieved in <50% of patients. There is hope that activation of specific antileukemic immune responses could efficiently eliminate minimal residual disease at the end of chemotherapy and decrease the frequency of relapses. It was demonstrated that AML leukemic blasts can acquire the morphology and phenotype of dendritic cells (DCs), i.e., differentiate into leukemic DCs. However, this method has limitations as a potential immunotherapy. The alternative approach for the induction of leukemia-specific cytotoxicity we explored in this study consisted of using DCs of nonleukemic origin, pulsed with autologous apoptotic leukemic blasts. We show that mature pulsed nonleukemic DCs were successfully generated from remission samples of all tested patients with minimal interindividual differences. Mature pulsed DCs were used as antigen-presenting cells for leukemia-specific CTL induction. Specific cytotoxic activity against autologous AML blasts was demonstrated. Tumor lysis was autologous blast specific, with no killing activity against allogeneic leukemic cells or autologous mature unpulsed DCs and was MHC class I and class II restricted. In one patient, autologous CTLs stimulated by leukemic DCs or pulsed nonleukemic DCs showed similar significant cytotoxic activity against autologous AML cells. These findings demonstrate the induction of leukemia-specific cytotoxic response by nonleukemic mature DCs cross-presenting apoptotic leukemic blasts and offer a complementary approach to the use of leukemic DCs. We believe that this strategy permits the generation of DC vaccines for the majority of patients with hematological malignancies.

Acute Disease↗

PubMed2001

Rats injected with syngenic rat apoptotic neutrophils develop antineutrophil cytoplasmic antibodies.

Antineutrophil cytoplasmic antibodies (ANCA) are present in sera from patients with various forms of vasculitis-associated glomerulonephritis. Because autoantibodies may be directed against antigens presented by apoptotic cells, generation of ANCA using apoptotic neutrophils (PMN) in syngenic Brown Norway (BN) rats was attempted. These rats are T-helper type 2-prone animals, already used successfully in other ANCA-positive animal models. BN rats received repeated injections of buffer or of nonapoptotic or apoptotic PMN aged in cultures, in the footpad and once intravenously. Four of five rats that received injections of PMN aged for 48 h developed ANCA, which cross-reacted with human leukocyte elastase in three cases. None of the rats that received injections of freshly isolated neutrophils developed ANCA. One rat that received buffer injection and that exhibited chronic skin infection developed delayed ANCA. None of the rats showed signs of disease: no weight loss and no proteinuria. Then a subnephritogenic dose of antibody directed against rat glomerular basement membrane was injected. Rats then were killed, and different organs were frozen and studied. No significant lesions were found in kidneys or lungs. It is concluded that injections of apoptotic but not freshly isolated PMN can generate ANCA in BN rats. Additional studies are needed to elucidate the immunization mechanism and the ability of these autoantibodies to initiate vasculitis in these experimental animals.

Animals↗