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Etude des mécanismes de résistance à l’apoptose induits par le virus d’Epstein-Barr et mise en place de nouvelles stratégies thérapeutiques pour le traitement des lymphomes B

Anaïs Pujals 1
1 IMC (UMR 8126) - Interactions moléculaires et cancer
UMR8126 - Signalisation, noyaux et innovations en cancérologie
Abstract : -Résumé en anglais : Our team is working on the mechanisms of apoptosis induced by nutlin-3, a small molecule which binds to MDM2 and activates p53, in different lymphomas associated with Epstein-Barr virus such as Burkitt lymphoma (BL) or Post-transplant lymphoproliferative disorder (PTLD). Our results show that nutlin-3 strongly induce apoptosis in EBV (-) cells whereas EBV (+) latency III cells are much more resistant. The aim of my PhD project was to study the mechanisms involved in the resistance of EBV (+) latency III cells to apoptosis and to develop new therapeutic strategies to bypass these mechanisms. A transcriptomic analysis was realized after treatment with nutlin-3 of two cell lines which only differs by their EBV status. Based on the results obtained, a study was performed which allow us to show that: 1) autophagy is induced after nutlin-3 treatment in EBV (+) latency III cells; 2) these cells strongly expressed beclin-1 and present a constitutively high level of autophagy; 3) autophagy is involved in the resistance of apoptosis observed in these cells. Furthermore, our results demonstrate that Bcl-2 also contributes to the resistance of EBV (+) latency III cells and that treatment with ABT-737, a Bcl-2 inhibitor, restores their susceptibility to nutlin-3 treatment. We thus assessed the efficiency of this compound in vivo, in monotherapy or associated with conventional treatments (Cyclophosphamide for BL and Rituximab for PTLD). Results obtained during these pre-clinical studies show that: 1) ABT-737 reduces tumor growth and increase the overall survival of mice xenografted with a lymphoblastoïd cell line (LCL, used as a model for PTLD studies) but has no effects on mice xenografed with BL cell lines; 2) the association ABT-737/Cyclophosphamide reduces tumor growth during treatment but doesn’t improve the overall survival of mice xenografed with BL cell lines; 3) the association ABT-737/Rituximab is very efficient and induces 70% of complete remission in mice xenografted with LCL.
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Submitted on : Wednesday, December 19, 2012 - 3:36:34 PM
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Anaïs Pujals. Etude des mécanismes de résistance à l’apoptose induits par le virus d’Epstein-Barr et mise en place de nouvelles stratégies thérapeutiques pour le traitement des lymphomes B. Biologie cellulaire. Université Paris Sud - Paris XI, 2012. Français. ⟨NNT : 2012PA11T054⟩. ⟨tel-00767146⟩

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