CDX2 expression in the hematopoietic lineage promotes leukemogenesis via TGFβ inhibition

The intestine-specific caudal-related homeobox gene-2 (CDX2) homeobox gene, while being a tumor suppressor in the gut, is ectopically expressed in a large proportion of acute leukemia and is associated with poor prognosis. Here, we report that turning on human CDX2 expression in the hematopoietic lineage of mice induces acute monoblastic leukemia, characterized by the decrease in erythroid and lymphoid cells at the benefit of immature monocytic and granulocytic cells. One of the highly stimulated genes in leukemic bone marrow cells was BMP and activin membrane-bound inhibitor (Bambi), an inhibitor of transforming growth factor-β (TGF-β) signaling. The CDX2 protein was shown to bind to and activate the transcription of the human BAMBI promoter. Moreover, in a leukemic cell line established from CDX2-expressing mice, reducing the levels of CDX2 or Bambi stimulated the TGF-β-dependent expression of Cd11b, a marker of monocyte maturation. Taken together, this work demonstrates the strong oncogenic potential of the homeobox gene CDX2 in the hematopoietic lineage, in contrast with its physiological tumor suppressor activity exerted in the gut. It also reveals, through BAMBI and TGF-β signaling, the involvement of CDX2 in the perturbation of the interactions between leukemia cells and their microenvironment

BCR-associated factors driving chronic lymphocytic leukemia cells proliferation ex vivo

International audienceA chronic antigenic stimulation is believed to sustain the leukemogenic development of chronic lymphocytic leukemia (CLL) and most of lymphoproliferative malignancies developed from mature B cells. Reproducing a proliferative stimulation ex vivo is critical to decipher the mechanisms of leukemogenesis in these malignancies. However, functional studies of CLL cells remains limited since current ex vivo B cell receptor (BCR) stimulation protocols are not sufficient to induce the proliferation of these cells, pointing out the need of mandatory BCR co-factors in this process. Here, we investigated benefits of several BCR co-stimulatory molecules (IL-2, IL-4, IL-15, IL-21 and CD40 ligand) in multiple culture conditions. Our results demonstrated that BCR engagement (anti-IgM ligation) concomitant to CD40 ligand, IL-4 and IL-21 stimulation allowed CLL cells proliferation ex vivo. In addition, we established a proliferative advantage for ZAP70 positive CLL cells, associated to an increased phosphorylation of ZAP70/SYK and STAT6. Moreover, the use of a tri-dimensional matrix of methylcellulose and the addition of TLR9 agonists further increased this proliferative response. This ex vivo model of BCR stimulation with T-derived cytokines is a relevant and efficient model for functional studies of CLL as well as lymphoproliferative malignancies. Like in most mature lymphoproliferative malignancies, an antigenic stimulation is believed to drive the leukemo-genic process in chronic lymphocytic leukemia (CLL) 1-3. A restricted use of IGHV genes and the existence of ste-reotypic B cell receptor (BCR) on CLL cells 4-6 provides evidence in favor of antigenic stimulation where different microbial antigens, as well as auto-antigens, have been suspected as actors of this chronic stimulation 7. In addition , a chronic BCR self-activation has been shown in subtypes of CLL cells 8. Moreover, several signaling aberrations have been described downstream of the BCR, notably in aggressive CLL with unmutated IGHV (UM-CLL), in which the expression of ZAP70 reinforces BCR responsiveness 9-12. BCR activation, which is essential for the physiological development of lymphocytes 13 would also be indispensable for the survival and proliferation of CLL cells in vivo 2. Accordingly, withdrawal of this stimulation is believed to be responsible for the rapid spontaneous apoptosis of CLL cells ex vivo 14. The cellular consequences of this BCR activation has been extensively studied an

Modulation of expression of genes induced by ex vivo antigen receptor stimulation in primary lymphocytes of chronic lymphocytic leukemia

Dans les leucémies et lymphomes développées à partir de lymphocytes B matures, la prolifération tumorale est induite par une stimulation antigénique chronique. La réponse transcriptionnelle en aval du récepteur à l’antigène pourrait permettre de développer de nouvelles thérapies dans ces hémopathies encore incurables. Une étude préliminaire a permis de caractériser des gènes clés de cette réponse transcriptionnelle après activation du récepteur à l’antigène. L’objectif de ma thèse a consisté à moduler l’expression de certains de ces gènes clés dans ces lymphocytes de leucémie lymphoïde chronique difficilement transfectables. Après validation du profil d’expression dynamique de gènes après activation du récepteur à l’antigène ex vivo, j’ai analysé l’efficacité de délivrance de petites molécules à l’aide de différentes méthodes de transfection. L’utilisation d’une méthode lipidique a permis de diminuer l’expression du gène CALR de 31% (min 18% - max 68%) dans ces lymphocytes tumoraux. Des analyses supplémentaires seront nécessaires pour évaluer l’effet de cette modulation d’expression sur la réponse proliférative de ces lymphocytes tumorauxIn leukemias and lymphomas developed from mature B-lymphocytes, tumor proliferation is induced by chronic antigenic stimulation. The downstream transcriptional response of the antigen receptor could allow the development of new therapies in these still incurable hematological diseases. A preliminary study has characterized key genes of this transcriptional response after activation of the antigen receptor. The objective of my thesis was to modulate the expression of some of these key genes in these difficult-to-transfect chronic lymphocytic leukemia lymphocytes. After validation of the dynamic gene expression profile after activation of the antigen receptor ex vivo, I analyzed the delivery efficiency of small molecules using different transfection methods. The use of a lipidic method allowed to decrease the expression of the CALR gene by 31% (min 18% - max 68%) in these tumor lymphocytes. Further analyses will be required to evaluate the effect of this expression modulation on the proliferative response of these tumor lymphocytes

CDX2

The intestine-specific caudal-related homeobox gene-2 (CDX2) homeobox gene, while being a tumor suppressor in the gut, is ectopically expressed in a large proportion of acute leukemia and is associated with poor prognosis. Here, we report that turning on human CDX2 expression in the hematopoietic lineage of mice induces acute monoblastic leukemia, characterized by the decrease in erythroid and lymphoid cells at the benefit of immature monocytic and granulocytic cells. One of the highly stimulated genes in leukemic bone marrow cells was BMP and activin membrane-bound inhibitor (Bambi), an inhibitor of transforming growth factor-β (TGF-β) signaling. The CDX2 protein was shown to bind to and activate the transcription of the human BAMBI promoter. Moreover, in a leukemic cell line established from CDX2-expressing mice, reducing the levels of CDX2 or Bambi stimulated the TGF-β-dependent expression of Cd11b, a marker of monocyte maturation. Taken together, this work demonstrates the strong oncogenic potential of the homeobox gene CDX2 in the hematopoietic lineage, in contrast with its physiological tumor suppressor activity exerted in the gut. It also reveals, through BAMBI and TGF-β signaling, the involvement of CDX2 in the perturbation of the interactions between leukemia cells and their microenvironment

CDX2 expression in the hematopoietic lineage promotes leukemogenesis via TGFβ inhibition

The intestine-specific caudal-related homeobox gene-2 (CDX2) homeobox gene, while being a tumor suppressor in the gut, is ectopically expressed in a large proportion of acute leukemia and is associated with poor prognosis. Here, we report that turning on human CDX2 expression in the hematopoietic lineage of mice induces acute monoblastic leukemia, characterized by the decrease in erythroid and lymphoid cells at the benefit of immature monocytic and granulocytic cells. One of the highly stimulated genes in leukemic bone marrow cells was BMP and activin membrane-bound inhibitor (Bambi), an inhibitor of transforming growth factor-β (TGF-β) signaling. The CDX2 protein was shown to bind to and activate the transcription of the human BAMBI promoter. Moreover, in a leukemic cell line established from CDX2-expressing mice, reducing the levels of CDX2 or Bambi stimulated the TGF-β-dependent expression of Cd11b, a marker of monocyte maturation. Taken together, this work demonstrates the strong oncogenic potential of the homeobox gene CDX2 in the hematopoietic lineage, in contrast with its physiological tumor suppressor activity exerted in the gut. It also reveals, through BAMBI and TGF-β signaling, the involvement of CDX2 in the perturbation of the interactions between leukemia cells and their microenvironment