scholarly journals Lmo2's Oncogenic Function in T-Cell Leukemia Requires Ldb1

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3663-3663
Author(s):  
Liqi Li ◽  
Justin H. Layer ◽  
Claude Warzecha ◽  
Rati Tripathi ◽  
Paul Love ◽  
...  
Keyword(s):  
T Cell ◽  
Transgenic Mice ◽  
Conflicts Of Interest ◽  
Protein Complexes ◽  
Lymphoblastic Leukemia ◽  
Conditional Knockout ◽  
Lim Domain ◽  
Double Positive ◽  
Hematopoietic Stem ◽  
T Cell Progenitors

Abstract LIM domain Only-2 (LMO2) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL). LMO2 encodes a small protein with 2 LIM domains that is part of a large multiprotein complex in hematopoietic stem and progenitor cells, where it is required for HSC specification and maintenance. Many of LMO2's protein partners in HSPCs are expressed in T-ALL implying that protein complexes similar to those nucleated by LMO2 in HSPCs also play a role in leukemia. In this study, we analyzed a critical component of the LMO2 associated complex, LIM domain binding1 (LDB1). LDB1 appears to be an obligate partner of LMO2 in HSPCs but it is not required for T-cell development from committed progenitors. LDB1 is concordantly expressed with LMO2 in human T-ALL although its expression is more widespread than LMO2. To further define Ldb1's role in leukemia, we induced its conditional knockout in CD2-Lmo2 transgenic mice. CD2-Lmo2 transgenic mice develop T-ALL with high penetrance and closely model the human disease. We discovered that Lmo2-induced T-ALL was markedly attenuated in penetrance and latency by Ldb1 deletion. Since Lmo2 induces a distinct differentiation arrest in T-cell progenitors prior to leukemic transformation, we analyzed the differentiation of T-cell progenitors in CD2-Lmo2 transgenic/floxed-Ldb1/Lck-Cre mice and in non-Lmo2 transgenics: floxed-Ldb1/Lck-Cre mice. Ldb1 deletion by Lck-Cre was efficient in double negative and double positive T-cell progenitors. In striking contrast, Ldb1 deletion could not be induced in CD2-Lmo2 transgenic T-cell progenitors. Consistent with this finding, T-ALLs that developed in CD2-Lmo2/floxed-Ldb1/Lck-Cre mice had incomplete deletion of Ldb1. These results imply that Ldb1 is a required factor for Lmo2 to induce T-ALL. Lastly, gene expression analysis of Lmo2-induced T-ALLs and ChIP-exonuclease analysis of Ldb1 occupancy in T-ALL suggested that the Lmo2/Ldb1 complex enforced a gene signature similar to that seen in HSPCs and in Early T-cell Precursor ALL. In conclusion, Ldb1 is a required partner for Lmo2 to induce T-ALL. Additionally, the HSPC function of Lmo2/Ldb1 complexes may be recapitulated in T-cell progenitors prior to T-ALL. Disclosures No relevant conflicts of interest to declare.

scholarly journals LIM Domain Protein 1 (Ldb1) Is Required for Lmo2 Oncogene-Induced Thymocyte Self-Renewal and T-Cell Leukemia in a Mouse Model of Human T-ALL

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2538-2538
Author(s):  
Liqi Li ◽  
Apratim Mitra ◽  
Bin Zhao ◽  
Seeyoung Choi ◽  
Jan Lee ◽  
...  
Keyword(s):  
T Cell ◽  
Mouse Model ◽  
Transgenic Mice ◽  
Progenitor Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Conditional Knockout ◽  
Lim Domain ◽  
Self Renewal ◽  
Hematopoietic Stem

LIM domain Only-2 (LMO2) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL) and is generally expressed in the clinically aggressive Early Thymocyte Precursor ALL. LMO2 encodes a small protein with 2 LIM domains that is part of a large multiprotein complex in hematopoietic stem and progenitor cells (HSPC), where it is required for HSC specification and maintenance. Many of LMO2's protein partners in HSPCs are expressed in T-ALL implying that protein complexes like those scaffolded by LMO2 in HSPCs also play a role in leukemia. LDB1 is concordantly expressed with LMO2 in human T-ALL although its expression is more widespread than LMO2. In this study, we analyzed a critical component of the Lmo2 associated complex, LIM domain binding 1 (Ldb1), in the CD2-Lmo2 transgenic mouse model of human T-ALL. To further define Ldb1's role in leukemia, we induced its conditional knockout in CD2-Lmo2 transgenic mice with the use of Lck-Cre, Rag1-Cre, and Il7r-Cre transgenic mice. CD2-Lmo2 transgenic mice develop T-ALL with high penetrance and closely model the human disease. We discovered that the penetrance and latency of Lmo2-induced T-ALL were markedly attenuated in the Lck-Cre model and T-ALL onset was completely abrogated in the Rag1-Cre and Il7r-Cre models. The latter two models induced more efficient deletions of Ldb1, earlier in the T-cell differentiation program compared to Lck-Cre. Interestingly, Lck-Cre deletion was efficient in thymocytes without the Lmo2 transgene. In striking contrast, Ldb1 deletion could not be induced in CD2-Lmo2 transgenic T-cell progenitors. Consistent with this finding, T-ALLs that developed in CD2-Lmo2/floxed-Ldb1/Lck-Cre mice had incomplete deletion of Ldb1. These results imply that Ldb1 is a required factor for Lmo2 to induce T-ALL. To further probe the pathogenesis of Lmo2-induced T-ALL, we analyzed preleukemic phenotypes in the Rag1-Cre (or Il7r-Cre) conditional knockout models. Our results showed that Ldb1 is required for the induction of thymocyte self-renewal and radioresistance. Ldb1 was also required for the acquisition of the pre-leukemic ETP gene expression signature observed in immature CD2-Lmo2 transgenic thymocytes. Detailed biochemical experiments show that LMO2 protein is directly stabilized by LDB1 in leukemia cells perhaps on chromatin. In conclusion, these results support a model where Lmo2-induced T-ALL is caused by a failure to downregulate Ldb1/Lmo2 nucleated transcription complexes that normally function to enforce self-renewal in bone marrow hematopoietic progenitor cells. Disclosures No relevant conflicts of interest to declare.

Hhex Is a Critical Gene In The Development Of Normal and Malignant Lymphoid Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3788-3788
Author(s):  
Charnise Goodings ◽  
Stephen B. Smith ◽  
Elizabeth Mathias ◽  
Elizabeth Smith ◽  
Rati Tripathi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Transgenic Mice ◽  
Conflicts Of Interest ◽  
Lymphoid Cells ◽  
Conditional Knockout ◽  
Hematopoietic Stem ◽  
Direct Transcriptional Target ◽  
Cell Counts ◽  
Transcriptional Target

Abstract Hematopoietically expressed homeobox (Hhex) is a T-cell oncogene. It is frequently deregulated in murine retroviral insertional mutagenesis screens and its enforced expression induces T-cell leukemia in bone marrow transduction and transplantation experiments. We discovered that HHEX is a direct transcriptional target of an LIM domain Only-2 (LMO2)-associated protein complex. HHEX clusters with LMO2-overexpressing T-ALLs and is especially overexpressed in Early T-cell Precursor (ETP) – ALL where it is a direct transcriptional target of LMO2. To further understand Hhex's function, we induced a conditional knockout in floxed Hhex mice with the Vav-iCre transgene. Mice were viable and showed normal blood cell counts with highly efficient deletion of Hhex in all hematopoietic tissues. Thymocytes from conditional knockouts showed a normal pattern of development. Most impressively, Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice (figure 1). Hhex conditional knockouts (Hhex cKOs) also had a significant decrease in mature B cells in the spleen and bone marrow. Interestingly, hematopoietic stem and progenitor cells plated on OP9-GFP or OP9-DL1 stromal cells showed proliferative defects and incomplete differentiation towards both B and T lineage. Also under stress conditions such as sublethal irradiation and competitive bone marrow transplants, Hhex conditional knockouts show a marked defect in both B and T lineages but an increase in early progenitor populations. Our experiments show that Hhex is a critical transcription factor in lymphoid development and in LMO2-induced T-ALL.Figure 1Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic miceFigure 1. Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice Disclosures: No relevant conflicts of interest to declare.

Thymic overexpression of Ttg-1 in transgenic mice results in T-cell acute lymphoblastic leukemia/lymphoma

1992 ◽  
Vol 12 (9) ◽  
pp. 4186-4196
Author(s):  
E A McGuire ◽  
C E Rintoul ◽  
G M Sclar ◽  
S J Korsmeyer
Keyword(s):  
Transcription Factors ◽  
T Cell ◽  
Transgenic Mice ◽  
Lymphoblastic Leukemia ◽  
Intermediate Stage ◽  
Proximal Promoter ◽  
Minority Population ◽  
Primary Role ◽  
Double Positive ◽  
Aberrant Expression

T-cell translocation gene 1 (Ttg-1), also called rhombotin, is deregulated upon translocation into the alpha/delta T-cell receptor loci in acute lymphoblastic leukemias bearing the t(11;14)(p15;q11). Ttg-1 encodes a nuclear protein, expressed predominantly in neuronal cells, which belongs to a novel family of transcription factors possessing LIM domains. We utilized the lck proximal promoter to overexpress this candidate oncogene in immature thymocytes of transgenic mice. lckPr Ttg-1 mice develop immature, aggressive T-cell leukemia/lymphomas. Tumor incidence is proportional to the level of Ttg-1 expression. Most tumors contain CD4+8+ cells as well as CD4-8+ cells, which have an immature rather than a mature peripheral phenotype. Ttg-1-induced tumorigenesis preferentially affects a minority population of thymocytes representing an immature CD4-8+ intermediate stage between double-negative CD4-8- cells and double-positive CD4+8+ cells. This model indicates that the aberrant expression of putative transcription factors plays a primary role in the genesis of T-cell acute lymphoblastic leukemias.

scholarly journals Thymic overexpression of Ttg-1 in transgenic mice results in T-cell acute lymphoblastic leukemia/lymphoma.

1992 ◽  
Vol 12 (9) ◽  
pp. 4186-4196 ◽  
Author(s):  
E A McGuire ◽  
C E Rintoul ◽  
G M Sclar ◽  
S J Korsmeyer
Keyword(s):  
Transcription Factors ◽  
T Cell ◽  
Transgenic Mice ◽  
Lymphoblastic Leukemia ◽  
Intermediate Stage ◽  
Proximal Promoter ◽  
Minority Population ◽  
Primary Role ◽  
Double Positive ◽  
Aberrant Expression

T-cell translocation gene 1 (Ttg-1), also called rhombotin, is deregulated upon translocation into the alpha/delta T-cell receptor loci in acute lymphoblastic leukemias bearing the t(11;14)(p15;q11). Ttg-1 encodes a nuclear protein, expressed predominantly in neuronal cells, which belongs to a novel family of transcription factors possessing LIM domains. We utilized the lck proximal promoter to overexpress this candidate oncogene in immature thymocytes of transgenic mice. lckPr Ttg-1 mice develop immature, aggressive T-cell leukemia/lymphomas. Tumor incidence is proportional to the level of Ttg-1 expression. Most tumors contain CD4+8+ cells as well as CD4-8+ cells, which have an immature rather than a mature peripheral phenotype. Ttg-1-induced tumorigenesis preferentially affects a minority population of thymocytes representing an immature CD4-8+ intermediate stage between double-negative CD4-8- cells and double-positive CD4+8+ cells. This model indicates that the aberrant expression of putative transcription factors plays a primary role in the genesis of T-cell acute lymphoblastic leukemias.

scholarly journals Treatment of Post- HSCT Immunodeficiency By Infusion of Ex Vivo- Generated T Cell Precursors from Adult and Cord Blood Hematopoietic Stem and Progenitor Cells

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1887-1887
Author(s):  
Laura Simons ◽  
Corinne De La Chappedelaine ◽  
Christian Reimann ◽  
Elodie Elkaim ◽  
Sandrine Susini ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
Cord Blood ◽  
Conflicts Of Interest ◽  
T Cell Differentiation ◽  
Cell Compartment ◽  
Differentiation Potential ◽  
Hematopoietic Stem ◽  
T Cell Progenitors

Abstract Non-HLA identical hematopoietic stem cell transplantation (HSCT) provides a corrective therapy for most life-threatening primary immunodeficiencies (PID) and some malignant hemopathies. Despite advances made, severe complications following the treatment such as the prolonged persistence of T cell immunodeficiency still limit the use of this partially incompatible HSCT. After HSCT, the reconstitution of a functional T cell compartment relies on the availability of T cell precursors to rapidly seed the thymus and differentiate into mature T cells. We have previously demonstrated that an in vitro culture system based on the use of a modified Delta-like-4 (DLL4) Notch ligand and T cell cytokines allows for the effective generation of human T cell precursors from cord blood within 7 days. Moreover, once injected into NOD/SCID/gcko mice, T cell precursors generated in this system were able to colonize the thymus and generate a diversified and functional T-cell compartment. Here, we aimed at testing the capacity of adult HSPCs in this reconstitution system. We found that, like their CB- derived counterparts, T cell precursors generated from adult HPSCs phenotypically resembled thymic CD34+CD7+ cells with high in vitro T-cell differentiation potential. Interestingly, the peak of T cell progenitors for adult HSPCs occurred around day 3, compared to day 7 in CB. At this timepoint, T cell precursors derived from adult HSPC already expressed all critical genes for T cell lineage development, as well as the major chemokine receptors implicated in thymus homing. The introduction of retronectin further improved differentiation and proliferation of T cell progenitors from both HPSC sources in our in vitro system. Comparative molecular analysis of adult- and CB- derived progenitors suggested, that differential requirements for Notch receptor/ligand interactions may explain the differences in kinetics observed during the culture of the two types of HSPC. It remains to be further evaluated, whether targeted modifications of the Notch signaling pathway can improve the outcome of this in vitro T cell differentiation system for adult HPSCs. Overall our results suggest that adult HSPCs, like their CB- derived counterparts, provide an effective source of in vitro cultured T cell progenitors harboring all the necessary requirements for the in vivo -reconstitution of a functional T cell compartment. This is particularly important in the context of future clinical applications in HSCT where adult HSPCs are more available and more frequently used than CB HSPCs. Based on our results, we propose that upon injection into a patient, DLL4- cultured T cell precursors from both HSPC sources could significantly accelerate the reconstitution of the adaptive immune system after a partially HLA-incompatible HSCT. Currently, we are translating these results into a phase I clinical trial including adult and pediatric patients transplanted for malignant hemopathies or PIDs requiring an allogeneic HSCT from a HLA-partially mismatched donors. Disclosures No relevant conflicts of interest to declare.

Transcriptional Regulation of Oncogenic MEF2C In T-Cell Acute Lymphoblastic Leukemia (T-ALL).

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3636-3636
Author(s):  
Stefan Nagel ◽  
Letizia Venturini ◽  
Corinna Meyer ◽  
Maren Kaufmann ◽  
Michaela Scherr ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Regulatory Elements ◽  
Hematopoietic Stem ◽  
Cell Acute Lymphoblastic Leukemia ◽  
Bhlh Proteins

Abstract Abstract 3636 Myocyte enhancer factor 2C (MEF2C) is a transcription factor of the MADS-box family which is physiologically expressed in hematopoietic stem cells and during development of B-cells. Recently, we identified ectopic expression of MEF2C in T-cell acute lymphoblastic leukemia (T-ALL) cell lines activated either via chromosomally mediated ectopic expression of homeodomain protein NKX2-5 or via deletion of non-coding exon and promoter regions at 5q14, suggesting loss of negative regulatory elements. Our aim was to identify additional transcriptional regulators of MEF2C in T-ALL. Therefore, we analyzed the sequence of the MEF2C 5′-region, thus identifying potential regulatory binding sites for GFI1B, basic helix-loop-helix (bHLH) proteins, STAT5 and HOXA9/HOXA10. Overexpression studies demonstrated MEF2C activation by GFI1B (strong), LYL1 and TAL1 leukemic bHLH proteins (weak), and inhibition by STAT5 (strong) and HOXA9/HOXA10 (weak). Chromatin-Immuno-Precipitation analysis demonstrated direct binding of GFI1B, LYL1 and STAT5 but not of HOXA10 to the MEF2C 5′-region in T-ALL cells. However, HOXA9/HOXA10 activated expression of NMYC which in turn mediated MEF2C repression, indicating an indirect mode of MEF2C regulation. Chromosomal deletion of the 5′-MEF2C STAT5 binding site in LOUCY cells by del(5)(q14), reduced expression levels of STAT5 protein in some MEF2C-positve T-ALL cell lines, and the presence of inhibitory IL7-JAK-STAT5-signaling highlighted the repressive impact of this factor in MEF2C regulation. Taken together, our results indicate that ectopic expression of MEF2C in T-ALL cells is mainly regulated via activating leukemic transcription factors GFI1B or NKX2-5 and by escaping inhibitory STAT5-signaling. Disclosures: No relevant conflicts of interest to declare.

Enforced E47 Expression Has Differential Effects on Lmo2-Induced T-Cell Leukemia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4637-4637
Author(s):  
Charnise Goodings ◽  
Utpal P. Dave
Keyword(s):  
T Cell ◽  
Knockout Mice ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Tamoxifen Treatment ◽  
Hematopoietic Stem ◽  
Differential Effects ◽  
Human T Cell ◽  
High Level

Abstract Abstract 4637 Lmo2 is one of the most commonly deregulated oncogenes in human T-cell acute lymphoblastic leukemia (T-ALL). In mouse models, Lmo2 overexpression causes a differentiation block before the onset of T-ALL at a developmental stage that is similar to the block seen in E47 knockout mice. Furthermore, Lmo2 and E47 are part of an oligomeric protein complex in hematopoietic stem and progenitor cells. Since E47 knockout mice also develop T-ALL, it has been hypothesized that Lmo2 may induce T-ALL by redirecting E47 activity away from its normal target genes. We noted downregulation of many E2A targets in Lmo2-induced T-ALL. To directly test whether E47 is required in Lmo2-induced T-ALLs, we transduced four stable T-ALL lines established from Lmo2 transgenic mice with retrovirus expressing E47 fused with estrogen receptor. All 4 lines tolerated stable high- level protein expression of E47-ER with no change in from their baseline growth rates. The E47-ER fusion protein allowed forced dimerization upon treatment with 4-hydroxytamoxifen. Tamoxifen treatment increased expression CD4 and other described E2A targets in all 4 T-ALL lines; but two lines underwent G0/G1 cell cycle arrest. Our data suggest that E47 deficiency is not a universal feature of Lmo2- induced T-ALL and E47 forced expression has differential effects on T-ALL. Disclosures: No relevant conflicts of interest to declare.

The Notch Signaling Pathway as a Suppressor of Myeloid Transformation

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. SCI-13-SCI-13
Author(s):  
Iannis Aifantis
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Notch Signaling ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Notch Pathway ◽  
Stem Cell Differentiation ◽  
Lineage Tracing ◽  
Specific Gene ◽  
Hematopoietic Stem

Abstract Abstract SCI-13 Notch signaling is a central regulator of differentiation in a variety of organisms and tissue types. Its activity is controlled by the multi-subunit γ-secretase complex (γSE) complex. Although Notch signaling can play both oncogenic and tumor suppressor roles in solid tumors, in the hematopoietic system, it is exclusively oncogenic, notably in T cell acute lymphoblastic leukemia (T-ALL), a disease characterized by Notch1 activating mutations. We identified somatic inactivating Notch pathway mutations in a fraction of chronic myelomonocytic leukemia (CMML) patients. Inactivation of Notch signaling in mouse hematopoietic stem cells (HSC) results in an aberrant accumulation of granulocyte/monocyte progenitors (GMP), extramedullary hematopoieisis and the induction of CMML-like disease. Transcriptome analysis reveals that Notch signaling regulates an extensive myelomonocytic-specific gene signature, through the direct suppression of gene transcription by the Notch target Hes1. These studies identify a novel role for Notch signaling during early hematopoietic stem cell differentiation and suggest that the Notch pathway can play both tumor-promoting and suppressive roles within the same tissue. These observations also suggest that Notch activity is not simply a promoter of the T cell lineage in the thymus but that Notch signaling thresholds could regulate commitment and/or survival of distinct hematopoietic lineages in the bone marrow. To address these issues in vivo, we have generated Notch receptor lineage tracing and activity reporter genetic tools. Analysis of these animal models identified unique novel functions for the Notch pathway during early bone marrow hematopoiesis. Disclosures: No relevant conflicts of interest to declare.

Fetal Vs. Adult Hematopoietic Progenitors Respond Differently to NOTCH1: Implications for Pediatric Vs. Adult T-ALL.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2381-2381
Author(s):  
Vincenzo Giambra ◽  
Sonya H Lam ◽  
Amy Ng ◽  
Claudia Benz ◽  
Olena O Shevchuk ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Lymphoblastic Leukemia ◽  
Mouse Bone Marrow ◽  
Hematopoietic Stem ◽  
Adult Bone Marrow ◽  
Old Adult ◽  
Adult Bone

Abstract Abstract 2381 T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of T-cell progenitors which affects both children and adults. Whereas pediatric T-ALL is curable in 80–90% of cases, only 40% of adults with T-ALL survive beyond 5 years. Fetal liver and adult bone marrow-derived hematopoietic stem/progenitor cells (HSPCs) are known to differ in terms of their gene expression programs and functional properties. Despite this work, the extent to which differential programming of fetal and adult HSPCs may impact the biology of their respective leukemias in children and adults remains unexplored. NOTCH1 is a prominent oncogene in T-ALL and activated by mutation in over 50% of cases. The retroviral NOTCH1 mouse bone marrow transplant model of T-ALL is well established; however, most investigators use 8–12 week-old adult mice as bone marrow donors for these experiments and thus these studies could be interpreted as having modeled adult disease. In order to explore the possibility that fetal program HSPCs would more accurately model pediatric disease, we transduced lineage-negative fetal liver HSPCs with activated NOTCH1 (ΔE) retrovirus, transplanted them into syngeneic (C57BL/6) recipients, and compared the behavior of the resulting leukemias to those generated from lineage-negative 8-week-old adult bone marrow HSPCs. Primary transplant recipient mice developed nearly identical T-ALL disease in terms of penetrance, latency, disease distribution/burden, and immunophenotype. Serial transplantation of these leukemias into secondary recipients, however, revealed stark differences in that whereas “adult” leukemias were readily transplantable, “fetal” leukemias were largely non-transplantable. In order to quantitate leukemia-initiating cell (LIC) frequencies in these two situations, we performed secondary transplants into highly permissive, immunodeficient (NOD/Scid/Il2rg−/−) recipients at limiting dilution and observed fetal leukemias to exhibit 500-fold lower LIC activity than adult leukemias (1 in ∼4500 cells vs. 1 in ∼9 cells, respectively). To identify potential mechanisms that might underlie this difference in LIC activity, we compared the behaviors of fetal liver vs. adult bone marrow-derived HSPCs shortly after transduction with NOTCH1(ΔE) virus. Interestingly, NOTCH1 induced fetal HSPCs to cycle rapidly whereas adult HSPCs were largely quiescent. We also noted that non-transduced cells in fetal HSPC cultures were also cycling rapidly, and through a series of fetal/adult mixing and conditioned media experiments, we determined that NOTCH1 induces an autocrine IGF1 signaling circuit in fetal, but not adult HSPCs. This observation was also confirmed to hold true for CD34+ human cord blood vs. adult bone marrow HSPCs. Expression profiling/qRT-PCR and chromatin immunoprecipitation (ChIP) studies further revealed NOTCH1 to induce IGF1 transcription and altered chromatin structure (increased H3K4me3 and decreased H3K27me3 marks) specifically in fetal, but not adult HSPCs. These findings suggest that developmental stage-specific programming in fetal vs. adult progenitors underlies their differential responses to oncogenic NOTCH1 signaling, and also the biological aggressiveness of resulting leukemias. Therapeutic targeting of adult-specific pathways may thus achieve improved clinical responses in adults with T-ALL and perhaps also the minority of pediatric patients with more aggressive, possibly “adult-like” disease. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Differentiation of a CD4+/CD8αβ+ Double Positive T Cell Population From The CD8 Pool Is Sufficient To Mediate Graft-vs-Host Disease but not Graft-vs-Leukemia Effects

2022 ◽  
Author(s):  
Nicholas J Hess ◽  
David P Turicek ◽  
Kalyan Nadiminti ◽  
Amy Hudson ◽  
Peiman Hematti ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Lymphoblastic Leukemia ◽  
T Cell Subsets ◽  
Double Positive ◽  
Hematopoietic Stem ◽  
Host Disease ◽  
Graft Vs Host Disease ◽  
Xenogeneic Transplantation

Acute graft-vs-host disease (aGVHD) and tumor relapse remain the primary complications following allogeneic hematopoietic stem cell transplantation (allo-HSCT) for malignant blood disorders. While post-transplant cyclophosphamide has reduced the overall prevalence and severity of aGVHD, relapse rates remain a concern. Thus, there remains a need to identify the specific human T cell subsets mediating GVHD pathology versus graft-versus-leukemia (GVL) effects. In xenogeneic transplantation studies using primary human cells from a variety of donors and tissue sources, we observed the development of a mature CD4+/CD8αβ+ double positive T cell (DPT) population in mice succumbing to lethal aGVHD but not in mice that failed to develop aGVHD. The presence of DPT, irrespective of graft source, was predictive of lethal GVHD as early as one week after xenogeneic transplantation. DPT co-express the master transcription factors of the CD8 and CD4 lineages, RUNX3 and THPOK respectively, and produce both cytotoxic and modulatory cytokines. To identify the origin of DPT, we transplanted isolated human CD4 or CD8 T cells, which in turn revealed that DPT only arise from the CD8 pool. Interestingly, re-transplantation of sorted CD8 T cells from GVHD mice did not reveal a second wave of DPT differentiation. Re-transplantation of flow-sorted DPT, CD8 or CD4 T cells from GVHD mice revealed that DPT are sufficient to mediate GVHD pathology but not GVL effects versus B-cell acute lymphoblastic leukemia. Lastly, we confirmed the presence and correlation of DPT with aGVHD pathology in a small cohort of allo-HSCT patients that developed grade 2-4 aGVHD in our clinic. Further understanding of DPT differentiation and pathology may lead to targeted prophylaxis and/or treatment regimens for aGVHD and potentially other human chronic inflammatory diseases.

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