Progressive loss of CD3 expression after HTLV-I infection results from chromatin remodeling affecting all the CD3 genes and persists despite early viral genes silencing

BACKGROUND: HTLV-I infected CD4+ T-cells lines usually progress towards a CD3- or CD3low phenotype. In this paper, we studied expression, kinetics, chromatin remodeling of the CD3 gene at different time-points post HTLV-I infection. RESULTS: The onset of this phenomenon coincided with a decrease of CD3gamma followed by the subsequent progressive reduction in CD3delta, then CD3epsilon and CD3zeta mRNA. Transient transfection experiments showed that the CD3gamma promoter was still active in CD3- HTLV-I infected cells demonstrating that adequate amounts of the required transcription factors were available. We next looked at whether epigenetic mechanisms could be responsible for this progressive decrease in CD3 expression using DNase I hypersensitivity (DHS) experiments examining the CD3gamma and CD3delta promoters and the CD3delta enhancer. In uninfected and cells immediately post-infection all three DHS sites were open, then the CD3gamma promoter became non accessible, and this was followed by a sequential closure of all the DHS sites corresponding to all three transcriptional control regions. Furthermore, a continuous decrease of in vivo bound transcription initiation factors to the CD3gamma promoter was observed after silencing of the viral genome. Coincidently, cells with a lower expression of CD3 grew more rapidly. CONCLUSION: We conclude that HTLV-I infection initiates a process leading to a complete loss of CD3 membrane expression by an epigenetic mechanism which continues along time, despite an early silencing of the viral genome. Whether CD3 progressive loss is an epiphenomenon or a causal event in the process of eventual malignant transformation remains to be investigated.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Differentiation associated regulation of microRNA expression in vivo in human CD8+ T cell subsets

BACKGROUND: The differentiation of CD8+ T lymphocytes following priming of naïve cells is central in the establishment of the adaptive immune response. Yet, the molecular events underlying this process are not fully understood. MicroRNAs have been recently shown to play a key role in the regulation of haematopoiesis in mouse, but their implication in peripheral lymphocyte differentiation in humans remains largely unknown. METHODS: In order to explore the potential implication of microRNAs in CD8+ T cell differentiation in humans, microRNA expression profiles were analysed using microarrays and quantitative PCR in several human CD8+ T cell subsets defining the major steps of the T cell differentiation pathway. RESULTS: We found expression of a limited set of microRNAs, including the miR-17~92 cluster. Moreover, we reveal the existence of differentiation-associated regulation of specific microRNAs. When compared to naive cells, miR-21 and miR-155 were indeed found upregulated upon differentiation to effector cells, while expression of the miR-17~92 cluster tended to concomitantly decrease. CONCLUSIONS: This study establishes for the first time in a large panel of individuals the existence of differentiation associated regulation of microRNA expression in human CD8+ T lymphocytes in vivo, which is likely to impact on specific cellular functions

A microRNA profile of human CD8(+) regulatory T cells and characterization of the effects of microRNAs on Treg cell-associated genes.

Recently, regulatory T (Treg) cells have gained interest in the fields of immunopathology, transplantation and oncoimmunology. Here, we investigated the microRNA expression profile of human natural CD8(+)CD25(+) Treg cells and the impact of microRNAs on molecules associated with immune regulation. We purified human natural CD8(+) Treg cells and assessed the expression of FOXP3 and CTLA-4 by flow cytometry. We have also tested the ex vivo suppressive capacity of these cells in mixed leukocyte reactions. Using TaqMan low-density arrays and microRNA qPCR for validation, we could identify a microRNA 'signature' for CD8(+)CD25(+)FOXP3(+)CTLA-4(+) natural Treg cells. We used the 'TargetScan' and 'miRBase' bioinformatics programs to identify potential target sites for these microRNAs in the 3'-UTR of important Treg cell-associated genes. The human CD8(+)CD25(+) natural Treg cell microRNA signature includes 10 differentially expressed microRNAs. We demonstrated an impact of this signature on Treg cell biology by showing specific regulation of FOXP3, CTLA-4 and GARP gene expression by microRNA using site-directed mutagenesis and a dual-luciferase reporter assay. Furthermore, we used microRNA transduction experiments to demonstrate that these microRNAs impacted their target genes in human primary Treg cells ex vivo. We are examining the biological relevance of this 'signature' by studying its impact on other important Treg cell-associated genes. These efforts could result in a better understanding of the regulation of Treg cell function and might reveal new targets for immunotherapy in immune disorders and cancer

La greffe de moelle osseuse: evolution du concept durant les vingt-cinq derniéres années.

Journal Articleinfo:eu-repo/semantics/publishe

Chronic myeloid leukaemia : from molecular genetics to therapeutic approaches

The BCR-ABL fusion gene is both a marker of the disease and one of the causal events in the disease itself. This work will deal with both properties of the gene in chronic phase CML. The mechanisms underlying the acute transformation (acquisitions of new oncogenic changes) could be the matter of another thesis, but will not be discussed in the present work, since I did not work on this subject. In the second and third chapters, I will present data about the use of molecular genetics as a tool for diagnosis, prognosis and follow-up if CML patients. Part of chapter II will also be devoted to some aspects of the mechanisms underlying the generation of the hybrid messenger RNA. The fourth chapter will present preliminary data from ongoing work: the use of antisense molecules to inhibit the expression of the fused ongoing BCR-ABL transcript. This latte part is based upon the evidence that P210 is a causal event in the course of the disorder; if one could inhibit the expression of the abnormal protein, one might have new therapeutic tools, specific for the malignant cellsThèse d'agrégation de l'enseignement supérieur (faculté de médecine) -- UCL, 199

The impact of molecular biology techniques on the management of newly diagnosed chronic myeloid leukemia patients in chronic phase. A review

Since the introduction of tyrosine kinase inhibitors (TKI) in chronic myeloid leukemia (CML), the management of this disease has completely changed. The aim has been first to bring to the patient a maximal response and to identify at different time-points what could be considered an optimal response (which is to render the progression free survival as important as possible). To achieve this, new molecular tools were needed, the most important being the real time quantitative PCR (RT-qPCR), to measure the number of remaining transcripts after several period of treatment. The second important tool was the sequencing of the BCR-ABL kinase domain to identify potential mutations giving rise to resistance to imatinib first and next to second generation TKIs. This technique, much more sensitive than cytogenetics, has allowed the definition of important levels of transcripts (the major molecular response i.e. a three log reduction and the complete molecular response i.e. a 4.5 log reduction) the first ensuring a long term PFS on treatment, the second allowing the birth of studies looking at whether it would be possible to discontinue the treatment in this group of patients. © 2013 Elsevier Ltd.SCOPUS: re.jinfo:eu-repo/semantics/publishe

La leucémie myéloïde chronique en 2003.

The recent introduction of imatinib mesylate has deeply changed the treatment of chronic myeloid leukemia. This first physiopathology-based therapy, which targets the molecular anomaly that gives rise to the disease (the abnormal tyrosine kinase activity generated by the fusion protein P210 Bcr-Abl) has demonstrated an impressive activity. However, its long-term efficacy remains unknown. On the other hand, other treatment modalities, such as stem cell transplantation or experimental ones (immunotherapy) are also profoundly evolving. In this review, the authors have tried to synthesize the current knowledge of this disease and suggest a therapeutic strategy based on the currently available data.English AbstractJournal ArticleReviewSCOPUS: re.jinfo:eu-repo/semantics/publishe

Allogeneic hematopoietic stem cell transplantation for malignant disease: how to prevent graft-versus-host disease without jeopardizing the graft-versus-tumor effect ?

The graft-versus leukemia (GVL) effect, closely related to allogeneic stem cell tranplantation, plays a crucial role in curing the disease but is often associated with a deleterious reaction, called graft-versus-host disease (GVHD). So far, most strategies aiming at reducing GVHD also diminish the GVL effect. We try here to give an overview of strategies that could reduce GVHD without affecting GVL, or augment GVL without increasing GVHD or achieve both at the same time. © 2006 Elsevier Ltd. All rights reserved.SCOPUS: re.jinfo:eu-repo/semantics/publishe