Open Access

ARTICLE

Disruption of T cell regulatory pathways is necessary for immunotherapeutic cure of T cell acute lymphoblastic leukemia in mice

S. Fiorentino^1,4, M. Chopin¹, H. Dastot¹, N. Boissel², M. Reboul¹, L. Legrès¹, A. Janin¹, P. Aplan³, F. Sigaux¹, Armelle Regnault¹

1 Unité U728 INSERM-Laboratoire de Pathologie Université Paris VII, Hôpital Saint-Louis – Institut Universitaire d’Hématologie, 1 avenue Claude-Vellefaux, 75475 Paris Cedex 10, France
2 Unité INSERM U396, Institut Universitaire d’Hématologie, Hôpital Saint-Louis, Paris, France
3 NIH/NCI/Genetics Branch, Navy 8, Room 5101, 8901 Wisconsin Ave. Bethesda, MD 20889-5105, USA
4 Present address: Universidad Javeriana. Departamento de Microbiologia, Bogota, Colombia

* Corresponding Author: A. Regnault,

European Cytokine Network 2005, 16(4), 300-308.

Abstract

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. In recent years, the outcome has been globally improved by current therapies, but it remains poor in patients with high, persistent residual disease following the first course of chemotherapy, prompting evaluation of the possible beneficial effects of immunotherapy protocols. In this study, we hypothesized that the disruption of two immunoregulatory pathways controlling the auto-reactive T cell response might synergize with dendritic cell-based immunotherapy of the disease, which is considered to be poorly immunogenic. In this study, we used TAL1xLMO1 leukemia cells adoptively transferred in mice, to generate murine leukemia with poorly immunogenic cells as a model for human T-ALL. Subsequently, these animals were treated with several different immunotherapeutic protocols. We compared the efficiency of a classical, dendritic cell-based immunotherapy (injection of dendritic cells loaded with tumor-derived antigenic products), to a combined treatment associating injection of antigen-loaded dendritic cells and disruption of the two immunoregulatory pathways: CD25+ suppressive T cells and cytotoxic T lymphocyteassociated antigens (CTLA-4). We show that this combined treatment resulted in cure, concomitantly with in vivo generation of immune memory, and TNF-alpha secretion. This study demonstrates that the disruption of these two immunoregulatory pathways synergized with immunostimulation by dendritic cells loaded with tumor-derived antigens, and paves the way for the testing of this combination in clinical trials.

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