Therapeutic Inducers of Natural Killer cell Killing (ThINKK): preclinical assessment of safety and efficacy in allogeneic hematopoietic stem cell transplant settings.

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) remains the standard of care for chemotherapy-refractory leukemia patients, but cure rates are still dismal. To prevent leukemia relapse following HSCT, we aim to improve the early graft-versus-leukemia effect mediated by natural killer (NK) cells. Our approach is based on the adoptive transfer of Therapeutic Inducers of Natural Killer cell Killing (ThINKK).

Monoallelic Deletion Reduces the Requirement for NOTCH1 Hyperactivation in T-Cell Acute Lymphoblastic Leukemia.

Early T-cell development is precisely controlled by E proteins, that indistinguishably include HEB/TCF12 and E2A/TCF3 transcription factors, together with NOTCH1 and pre-T cell receptor (TCR) signalling. Importantly, perturbations of early T-cell regulatory networks are implicated in leukemogenesis. NOTCH1 gain of function mutations invariably lead to T-cell acute lymphoblastic leukemia (T-ALL), whereas inhibition of E proteins accelerates leukemogenesis.

Patients' NK cell stimulation with activated plasmacytoid dendritic cells increases dinutuximab-induced neuroblastoma killing.

Targeted immunotherapy has improved the outcome of patients with high-risk neuroblastoma (NB). However, immune escape of tumor cells still occurs and about 40% of NB patients relapse and die from their disease. We previously showed that natural killer (NK) cell stimulation by Toll-like receptor (TLR)-activated plasmacytoid dendritic cells (pDC) increases the efficacy of dinutuximab-based immunotherapy against NB cell lines via the TRAIL death-receptor pathway.

Activation of innate immunity in primary human cells using a plant virus derived nanoparticle TLR7/8 agonist.

Rod-shaped virus-like nanoparticles (VLNP) made of papaya mosaic virus (PapMV) coat proteins (CP) self-assembled around a single stranded RNA (ssRNA) were showed to be a TLR7 agonist. Their utilization as an immune modulator in cancer immunotherapy was shown to be promising. To establish a clinical relevance in human for PapMV VLNP, we showed that stimulation of human peripheral blood mononuclear cells (PBMC) with VLNP induces the secretion of interferon alpha (IFNα) and other pro-inflammatory cytokines and chemokines.

Expression of Disialoganglioside (GD2) in Neuroblastic Tumors: A Prognostic Value for Patients Treated With Anti-GD2 Immunotherapy.

Neuroblastoma, a malignant neoplasm of the sympathetic nervous system, is one of the most aggressive pediatric cancers. Patients with stage IV high-risk neuroblastoma receive an intensive multimodal therapy ending with an immunotherapy based on a chimeric monoclonal antibody ch14.18.

In vitro differentiated plasmacytoid dendritic cells as a tool to induce anti-leukemia activity of natural killer cells.

Acute lymphoblastic leukemia (ALL) is believed to be resistant to NK cell-mediated killing. To overcome this resistance, we developed an innovative approach based on NK cell stimulation with Toll-like receptor (TLR)-activated plasmacytoid dendritic cells (pDC). The translation of this approach into the clinic requires the production of high numbers of human pDC.

Efficient Killing of High Risk Neuroblastoma Using Natural Killer Cells Activated by Plasmacytoid Dendritic Cells.

High-risk neuroblastoma (NB) remains a major therapeutic challenge despite the recent advent of disialoganglioside (GD2)-antibody treatment combined with interleukin (IL)-2 and granulocyte monocyte-colony stimulating factor (GM-CSF). Indeed, more than one third of the patients still die from this disease. Here, we developed a novel approach to improve the current anti-GD2 immunotherapy based on NK cell stimulation using toll-like receptor (TLR)-activated plasmacytoid dendritic cells (pDCs).

TRAIL-mediated killing of acute lymphoblastic leukemia by plasmacytoid dendritic cell-activated natural killer cells.

Acute lymphoblastic leukemia (ALL) still frequently recurs after hematopoietic stem cell transplantation (HSCT), underscoring the need to improve the graft-versus-leukemia (GvL) effect. Natural killer (NK) cells reconstitute in the first months following HSCT when leukemia burden is at its lowest, but ALL cells have been shown to be resistant to NK cell-mediated killing. We show here that this resistance is overcome by NK cell stimulation with TLR-9-activated plasmacytoid dendritic cells (pDCs).

SCL, LMO1 and Notch1 reprogram thymocytes into self-renewing cells.

The molecular determinants that render specific populations of normal cells susceptible to oncogenic reprogramming into self-renewing cancer stem cells are poorly understood. Here, we exploit T-cell acute lymphoblastic leukemia (T-ALL) as a model to define the critical initiating events in this disease. First, thymocytes that are reprogrammed by the SCL and LMO1 oncogenic transcription factors into self-renewing pre-leukemic stem cells (pre-LSCs) remain non-malignant, as evidenced by their capacities to generate functional T cells.

Reconstitution of maturating and regulatory lymphocyte subsets after cord blood and BMT in children.

Some clinical characteristics of cord blood transplantation (CBT) might be explained by specificities in the reconstitution of immune subsets differing by their maturation stage or their implication in GVHD, tolerance or immune responses against tumor or infectious agents. Here, we compare the immune reconstitution of several of these subsets after CBT and BMT. B-cell count recovery was faster after CBT.

Post-transcriptional down-regulation of Toll-like receptor signaling pathway in umbilical cord blood plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (PDCs) from human umbilical cord blood (UCB) produce lower amounts of IFN-α upon TLR stimulation compared with adult counterparts. This difference may play a role in the low graft-versus-host disease rate after UCB transplantation and in the impaired immune response of the neonate to pathogens. Comparing UCB PDC to their adults counterparts, we found that they exhibited a mature surface phenotype and a normal antigen uptake.

Modeling T-cell acute lymphoblastic leukemia induced by the SCL and LMO1 oncogenes.

Deciphering molecular events required for full transformation of normal cells into cancer cells remains a challenge. In T-cell acute lymphoblastic leukemia (T-ALL), the genes encoding the TAL1/SCL and LMO1/2 transcription factors are recurring targets of chromosomal translocations, whereas NOTCH1 is activated in >50% of samples. Here we show that the SCL and LMO1 oncogenes collaborate to expand primitive thymocyte progenitors and inhibit later stages of differentiation.

IL-7 enhances survival of human CD56bright NK cells.

Lymphoid differentiation and activation critically depend on cytokine stimulation and the interleukin-7 (IL-7) signaling in particular. Although it has been demonstrated that IL-7 may play a role in natural killer (NK) cell maturation, the effect of IL-7 stimulation on mature human NK cells has not been studied. We, therefore, investigated the expression and functional activity of IL-7Ralpha on mature NK populations from adult blood.

Scl regulates the quiescence and the long-term competence of hematopoietic stem cells.

The majority of long-term reconstituting hematopoietic stem cells (LT-HSCs) in the adult is in G(0), whereas a large proportion of progenitors are more cycling. We show here that the SCL/TAL1 transcription factor is highly expressed in LT-HSCs compared with short-term reconstituting HSCs and progenitors and that SCL negatively regulates the G(0)-G(1) transit of LT-HSCs. Furthermore, when SCL protein levels are decreased by gene targeting or by RNA interference, the reconstitution potential of HSCs is impaired in several transplantation assays.

ETO2 coordinates cellular proliferation and differentiation during erythropoiesis.

The passage from proliferation to terminal differentiation is critical for normal development and is often perturbed in malignancies. To define the molecular mechanisms that govern this process during erythropoiesis, we have used tagging/proteomics approaches and characterized protein complexes nucleated by TAL-1/SCL, a basic helix-loop-helix transcription factor that specifies the erythrocytic lineage. In addition to known TAL-1 partners, GATA-1, E2A, HEB, LMO2 and Ldb1, we identify the ETO2 repressor as a novel component recruited to TAL-1 complexes through interaction with E2A/HEB.

SCL assembles a multifactorial complex that determines glycophorin A expression.

SCL/TAL1 is a hematopoietic-specific transcription factor of the basic helix-loop-helix (bHLH) family that is essential for erythropoiesis. Here we identify the erythroid cell-specific glycophorin A gene (GPA) as a target of SCL in primary hematopoietic cells and show that SCL occupies the GPA locus in vivo. GPA promoter activation is dependent on the assembly of a multifactorial complex containing SCL as well as ubiquitous (E47, Sp1, and Ldb1) and tissue-specific (LMO2 and GATA-1) transcription factors.

Biallelic transcriptional activation of oncogenic transcription factors in T-cell acute lymphoblastic leukemia.

Aberrant expression of transcription factor oncogenes such as HOX11, HOX11L2, TAL1/SCL, LYL1, LMO1, and LMO2 can be detected in lymphoblasts from up to 80% of patients with acute T-cell lymphoblastic leukemia (T-ALL). Transcriptional activation of these oncogenes in leukemic cells typically results from chromosomal rearrangements that place them next to highly active cis-acting transcriptional regulatory elements. However, biallelic activation of TAL1 in some T-ALL cases has been previously proposed.

Growth factor independence-1B expression leads to defects in T cell activation, IL-7 receptor alpha expression, and T cell lineage commitment.

T cell differentiation in the thymus is dependent upon signaling through the TCR and is characterized by the resulting changes in expression patterns of CD4 and CD8 surface coreceptor molecules. Although recent studies have characterized the effects of proximal TCR signaling on T cell differentiation, the downstream integration of these signals remains largely unknown. The growth factor independence-1 (GFI1) and GFI1B transcriptional repressors may regulate cytokine signaling pathways to affect lymphocyte growth and survival.

Regulation of pT alpha gene expression by a dosage of E2A, HEB, and SCL.

The expression of the pT alpha gene is required for effective selection, proliferation, and survival of beta T-cell receptor (beta TCR)-expressing immature thymocytes. Here, we have identified two phylogenetically conserved E-boxes within the pT alpha enhancer sequence that are required for optimal enhancer activity and for its stage-specific activity in immature T cells. We have shown that the transcription factors E2A and HEB associate with high affinity to these E-boxes.

The SCL complex regulates c-kit expression in hematopoietic cells through functional interaction with Sp1.

The combinatorial interaction among transcription factors is believed to determine hematopoietic cell fate. Stem cell leukemia (SCL, also known as TAL1 [T-cell acute lymphoblastic leukemia 1]) is a tissue-specific basic helix-loop-helix (bHLH) factor that plays a central function in hematopoietic development; however, its target genes and molecular mode of action remain to be elucidated. Here we show that SCL and the c-Kit receptor are coexpressed in hematopoietic progenitors at the single-cell level and that SCL induces c-kit in chromatin, as ectopic SCL expression in transgenic mice sustains c-kit transcription in developing B lymphocytes, in which both genes are normally down-regulated.

Gradient of E2A activity in B-cell development.

The E2A locus is a frequent target of chromosomal translocations in B-cell acute lymphoblastic leukemia (B-ALL). E2A encodes two products, E12 and E47, that are part of the basic helix-loop-helix (bHLH) family of transcription factors and are central in B lineage differentiation. E2A haplo-insufficiency hinders progression through three major checkpoints in B-cell development: commitment into the B lineage, at the pro-B to pre-B transition, and in the induction of immunoglobulin M (IgM) expression required for a functional BCR.

SCL and LMO1 alter thymocyte differentiation: inhibition of E2A-HEB function and pre-T alpha chain expression.

Cooperation between the stem cell leukemia (SCL) transcription factor and its nuclear partners LMO1 or LMO2 induces aggressive T cell acute lymphoblastic leukemia when inappropriately expressed in T cells. This study examined the cellular and molecular targets of the SCL-LMO complex at the preleukemic stage. We show that SCL and its partners are coexpressed in the most primitive thymocytes.

IL-2-dependent expression of genes involved in cytoskeleton organization, oncogene regulation, and transcriptional control.

IL-2 induces growth, differentiation, and/or apoptosis of lymphoid cells. To study further the molecular basis of IL-2 function, we used a cDNA subtraction approach involving a cell line grown in IL-2 or IL-4. From the corresponding library, 66 nonredundant sequences were characterized; 16 of them encode identified proteins.