Modeling the Multi-Step Pathogenesis of Acute Myeloid Leukemia of Down Syndrome

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3579-3579
Author(s):  
Eric R. Lechman ◽  
Karin G. Hermans ◽  
Stephanie M. Dobson ◽  
Olga I. Gan ◽  
James A. Kennedy ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Down Syndrome ◽  
B Cell ◽  
Peripheral Blood ◽  
Trisomy 21 ◽  
Cell Development ◽  
B Cell Development ◽  
Bone Marrow Cellularity ◽  
Increased Risk ◽  
Marrow Cellularity

Abstract The multistep pathogenesis of Down Syndrome (DS)-associated pre-leukemia and subsequent progression to acute leukemia is one of the better characterized of all human blood malignancies. Children with DS have a 150 fold increased risk of developing acute megakaryoblastic leukemia (AMKL) and greater than 30 fold increased risk of developing B cell acute lymphoblastic leukemia (B-ALL). DS-AMKL is often preceded in late fetal development or soon after birth by a pre-leukemic syndrome termed transient myeloproliferative disorder (TMD), which is characterized by high numbers of abnormal megakaryocytes and megakaryoblasts in the circulation, spleen and liver. Previous work has demonstrated that constitutional trisomy 21 results in expansion of megakaryocyte-erythroid progenitors (MEP) in fetal liver (FL) with a concomitant reduction in fetal pre-pro-B cells. The expanded MEP population subsequently acquires an N-terminal truncating mutation in the transcription factor GATA1 (termed GATA1s), leading to selective expansion of a pre-leukemic erythromegakaryocytic blast population. While the majority of DS-TMD cases spontaneously resolve within 3 months, up to 15% of DS-TMD neonates can develop lethal progressive liver fibrosis. Progression to AMKL following spontaneous resolution of TMD is associated with acquisition of at least one additional germline mutation. While murine models implicate a role for trisomy 21 and GATA1s in the leukemogenic process, they do not faithfully recapitulate the pathology of the human disease. Previous attempts to model DS-associated TMD through xenotransplantation of DS-FL and DS-TMD cells have proven technically challenging. Therefore, there remains a need for a human model to investigate the genetic steps required for initiation of DS-TMD and progression to DS-AMKL. We previously identified a leukemia stem cell (LSC)-associated miRNA signature by sorting 13 adult AML patient samples into 4 sub-populations based on CD34/CD38 expression, followed by supervised analysis guided by the in vivo leukemia initiating capacity of each sub-population in an optimized xenotransplant model. Interestingly, the top three LSC-associated miRNA candidates are all located on chromosome 21. To determine the role of these miRNA in human leukemogenesis, we engineered a tri-cistronic lentivector for enforced expression. Compared to control vector-transduced cells, tri-cistronic vector-transduced Lin‒CD34+CD38‒ cord blood (CB) cells generated a myeloproliferative syndrome in xenotransplanted mice, with splenomegaly, enhanced CD45+ human bone marrow cellularity and blocked B cell development at the pro B cell stage. Human grafts were enriched for CD45+CD33+CD117+CD123+CD41lo/CD42lo cells in bone marrow, peripheral blood, spleen and liver. In the CD45‒ compartment, a distinct lineage switch was observed, with CD41+ megakaryocytic output supplanting normal CD235+ erythroid output. High numbers of CD41+CD42b+CD61+CD34lo human platelets were detected in peripheral blood and spleen. Blood films revealed large dysplastic platelets and megakaryoblast-like cells. Histology showed hCD45+ packed bone marrow cavities, with loss of normal architecture. Bone marrow, spleen and liver all showed extensive reticulin deposition. In the lineage negative (Lin-) fraction of BM, we observed an expansion in the proportion of human MEP and multi-lymphoid progenitors (MLP). To further model leukemic progression, we expressed GATA1s in combination with our tri-cistronic miRNA vector. Mice transplanted with double transduced cells showed intermediate levels of splenomegaly and bone marrow cellularity compared to mice transplanted with cells transduced with tri-cistronic vector alone. The addition of GATA1s induced a complete loss of B cell development while restoring erythroid development. In human Lin‒ cells isolated from the BM, addition of mutant GATA1s further augmented the proportion and total numbers of MEP while restoring the MLP compartment to normal levels. These data demonstrate that we have generated a human xenograft model of DS-TMD through enforced expression in normal CB cells of a tri-cistron comprising 3 LSC-associated miRNA in combination with mutant GATA1s. With this model in place, we plan to further interrogate the genetic lesions involved in progression from DS-TMD to DS-AMKL. Disclosures No relevant conflicts of interest to declare.

scholarly journals Regulated Expression of Human Histocompatibility Leukocyte Antigen (HLA)-DO During Antigen-dependent and Antigen-independent Phases of B Cell Development

2002 ◽  
Vol 195 (8) ◽  
pp. 1053-1062 ◽  
Author(s):  
Xinjian Chen ◽  
Oskar Laur ◽  
Taku Kambayashi ◽  
Shiyong Li ◽  
Robert A. Bray ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
B Cell ◽  
Peripheral Blood ◽  
Class Ii ◽  
Cell Development ◽  
B Cell Development ◽  
Negative Regulator ◽  
Leukocyte Antigen ◽  
Peptide Loading

Human histocompatibility leukocyte antigen (HLA)-DO, a lysosomal resident major histocompatibility complex class II molecule expressed in B cells, has previously been shown to be a negative regulator of HLA-DM peptide loading function. We analyze the expression of DO in human peripheral blood, lymph node, tonsil, and bone marrow to determine if DO expression is modulated in the physiological setting. B cells, but not monocytes or monocyte-derived dendritic cells, are observed to express this protein. Preclearing experiments demonstrate that ∼50% of HLA-DM is bound to DO in peripheral blood B cells. HLA-DM and HLA-DR expression is demonstrated early in B cell development, beginning at the pro-B stage in adult human bone marrow. In contrast, DO expression is initiated only after B cell development is complete. In all situations, there is a striking correlation between intracellular DO expression and cell surface class II–associated invariant chain peptide expression, which suggests that DO substantially inhibits DM function in primary human B cells. We report that the expression of DO is markedly downmodulated in human germinal center B cells. Modulation of DO expression may provide a mechanism to regulate peptide loading activity and antigen presentation by B cells during the development of humoral immune responses.

Deletions in B-Cell Development Genes in Down Syndrome ALL: IKAROS Causes Poor Outcome

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3963-3963
Author(s):  
Trudy Buitenkamp ◽  
Marry M. van den Heuvel ◽  
Astrid A Danen-van Oorschot ◽  
Valerie de Haas ◽  
Rob Pieters ◽  
...  
Keyword(s):  
Down Syndrome ◽  
Transcription Factors ◽  
High Risk ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development ◽  
Janus Kinase ◽  
Genetic Event ◽  
Cox Regression Analysis ◽  
Increased Risk

Abstract Abstract 3963 Poster Board III-899 Children with Down Syndrome (DS) have an increased risk of developing acute lymphoblastic leukemia (ALL). DS ALL patients differ in presenting characteristics from ALL patients without DS (non-DS ALL). Recent evidence suggests that a unique genetic event may characterize DS ALL, i.e. an activating mutation localized at R683 in the Janus Kinase 2 (JAK2) gene, which occurs in 18% of DS ALL cases, and differs from the JAK2 mutations that are typically found in Myeloproliferatieve diseases (Bercovich et al, The Lancet 2008). However, Mullighan et al. recently reported also JAK R683 mutations in non-DS high risk ALL (PNAS, 2009). Furthermore, we and others described deletions in B-cell development genes in high-risk ALL (Den Boer et al, Lancet Oncology 2009, and Mullighan, NEJM 2009). One of these genes, IKZF1, which encodes the lymphoid transcription factor IKAROS, was found to be an indicator of poor prognosis in this high-risk group. In the present study, we studied deletions in B-cell development genes in DS ALL, utilizing array-Comparative Genomic Hybridisation (array-CGH, 105K Agilent). Moreover, genomic DNA was PCR-amplified with specific primers to detect the isoform 6 of IKAROS, which consists of a deletion of exon 3-6 resulting in expression of a dominant-negative form of IKAROS, with intact homodimerization but reduced DNA-binding capacity. We used direct sequencing for mutation screening of the pseudo-kinase and kinase domains of JAK2. Of 34 DS ALL patients treated according to the DCOG treatment protocols samples were available. All 34 patients had B-cell precursor ALL. Median follow up time was 5.7 years (range 1.2 – 15.4 years).In total, 19/34 (56%) DS ALL patients had one or more deletions in B-cell development genes (Table 1). Affected genes included the transcription factors IKZF1 (41%, n=14), PAX5 (12%, n=4) and VPREB1 (18%, n=6). These aberrations were not mutually exclusive. No deletions were found in EBF1 and TCF3 (E2A). Deletions in the PAX5 gene were part of larger deletions (≥0.5 million bases), whereas the other genes were mainly affected by focal deletions (<0.5 million bases). In 10/14 cases with IKZF1 abnormalities, the Isoform 6 was detected, whereas in 4 patients the entire IKZF1 gene was deleted due to a larger deletion on chromosome 7p. There were 2 cases with hyperdiploidy and 2 with a TEL/AML rearrangement; 3 of them had a deletion in one of the named transcription factors. One DS patient with a Philadelphia chromosome had a focal deletion in IKZF1 resulting in isoform 6, as well as a deletion in PAX5 and VPREB1. JAK2 mutations were detected in 5/34 patients (15%). Only one of the JAK2 R683 mutated DS ALL patients had a deletion of IKZF. Patients with an IKZF1 deletion had a significantly worse outcome when compared to patients without IKZF1 deletion (pEFS 57% vs. 95%; p=0.005), pDFS (62% vs. 95%; p=0.01) and pOS (71% vs. 95%; p=0.04). For PAX5 deleted cases, the pOS was 50% vs. 90% in non-PAX5 deleted cases (p=0.03), but the differences for pEFS (50% vs. 83%; p=0.14) and pDFS (50.0% vs. 86%; p=0.06) were not significant. None of the JAK2 mutated patients had an event. Multivariate Cox regression analysis including age, WBC, JAK2, TEL/AML, IKZF1, PAX5 and VPREB1 showed that deletion of IKZF1 was the only independent prognostic factor for event free survival (RR 23.5; p=0.03). In fact, 6 of the 7 patients (86%) with an event had a deletion of IKZF1, of whom 2 had a deletion of the entire IKZF1 gene, and 4 patients had a focal deletion resulting in isoform 6. In conclusion, we found deletions in B-cell development genes in a comparable frequency as in high-risk types of ALL without DS. Especially a high incidence of IKAROS deletions was found, which identified an independent poor prognostic group within the DS ALL patients. The high frequency of IKZF1 deletions may in part be responsible for the worse prognosis of DS ALL compared to non-DS ALL as reported by some groups. Chromosomal location Number* Cytogenetics - Hyperdiploidy - 2/29 (6.9%) - BCR/ABL t(9;22) 1/26 (3.8%) - TEL/AML t(12;21) 2/34 (5.9%) JAK2 R683 mutation 9p24 5/34 (14.7%) B-cell development genes - IKZF1 7p12 14/34 (41.2%) - VPREB1 22q11.22 6/34 (17.6%) - PAX5 9p13.2 4/34 (11.7%) - EBF1 5q33.3 0 - TCF3 19p13.3 0 * Cytogenetic information was not always available for all patients Disclosures: No relevant conflicts of interest to declare.

scholarly journals In Vivo Tungsten Exposure Alters B-Cell Development and Increases DNA Damage in Murine Bone Marrow

2012 ◽  
Vol 131 (2) ◽  
pp. 434-446 ◽  
Author(s):  
Alexander D. R. Kelly ◽  
Maryse Lemaire ◽  
Yoon Kow Young ◽  
Jules H. Eustache ◽  
Cynthia Guilbert ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Dna Damage ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development ◽  
Murine Bone Marrow

scholarly journals Rictor Is Required for Early B Cell Development in Bone Marrow

PLoS ONE ◽  
2014 ◽  
Vol 9 (8) ◽  
pp. e103970 ◽  
Author(s):  
Yingchi Zhang ◽  
Tianyuan Hu ◽  
Chunlan Hua ◽  
Jie Gu ◽  
Liyan Zhang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development

scholarly journals Osteoclast activity modulates B-cell development in the bone marrow

Cell Research ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1102-1115 ◽  
Author(s):  
Anna Mansour ◽  
Adrienne Anginot ◽  
Stéphane J C Mancini ◽  
Claudine Schiff ◽  
Georges F Carle ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development ◽  
Osteoclast Activity

scholarly journals Mutations of the Igβ gene cause agammaglobulinemia in man

2007 ◽  
Vol 204 (9) ◽  
pp. 2047-2051 ◽  
Author(s):  
Simona Ferrari ◽  
Vassilios Lougaris ◽  
Stefano Caraffi ◽  
Roberta Zuntini ◽  
Jianying Yang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
Transmembrane Protein ◽  
Serum Levels ◽  
Cell Development ◽  
B Cell Development ◽  
Surrogate Light Chain ◽  
Human B Cell ◽  
Homozygous Nonsense Mutation

Agammaglobulinemia is a rare primary immunodeficiency characterized by an early block of B cell development in the bone marrow, resulting in the absence of peripheral B cells and low/absent immunoglobulin serum levels. So far, mutations in Btk, μ heavy chain, surrogate light chain, Igα, and B cell linker have been found in 85–90% of patients with agammaglobulinemia. We report on the first patient with agammaglobulinemia caused by a homozygous nonsense mutation in Igβ, which is a transmembrane protein that associates with Igα as part of the preBCR complex. Transfection experiments using Drosophila melanogaster S2 Schneider cells showed that the mutant Igβ is no longer able to associate with Igα, and that assembly of the BCR complex on the cell surface is abrogated. The essential role of Igβ for human B cell development was further demonstrated by immunofluorescence analysis of the patient's bone marrow, which showed a complete block of B cell development at the pro-B to preB transition. These results indicate that mutations in Igβ can cause agammaglobulinemia in man.

Rictor is required for early B cell development in bone marrow

2014 ◽  
Vol 42 (8) ◽  
pp. S39
Author(s):  
Chunlan Hua ◽  
Tianyuan Hu ◽  
Yingchi Zhang ◽  
Tao Cheng ◽  
Weiping Yuan
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development

Trisomy 21 Driven Pro-Inflammatory Signalling in Fetal Bone Marrow May Play a Role in Perturbed B-Lymphopoiesis and Acute Lymphoblastic Leukemia of Down Syndrome

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1206-1206 ◽  
Author(s):  
Sorcha Isabella O'Byrne ◽  
Natalina Elliott ◽  
Gemma Buck ◽  
Siobhan Rice ◽  
David O'Connor ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Down Syndrome ◽  
Trisomy 21 ◽  
Lymphoblastic Leukemia ◽  
B Lymphopoiesis ◽  
Increased Risk ◽  
Cd34 Cells ◽  
Inflammatory Signalling

Introduction: Children with Down syndrome (DS) have a markedly increased risk of acute lymphoblastic leukemia (ALL), suggesting that trisomy 21 (T21) has specific effects on hematopoietic stem and progenitor cell (HSPC) biology in early life. Data from human fetal liver (FL) indicates that T21 alters fetal hematopoiesis, causing multiple defects in lympho-myelopoiesis. The impact of T21 on fetal B lymphopoiesis and how this may underpin the increase in ALL is not well known. We have recently found that fetal bone marrow (FBM) rather than FL is the main site of B lymphopoiesis; with a marked enrichment of fetal-specific progenitors (early lymphoid progenitors, ELP and PreProB progenitors) that lie upstream of adult type ProB progenitors (O'Byrne et al, Blood, in press). Previous preliminary data suggested that B progenitors were also reduced in T21 FBM (Roy et al, Blood. 124, 4331). Aim: To dissect putative molecular mechanisms responsible for the defects in T21 FBM B-lymphopoiesis and its association with childhood DS ALL. Methods: Second trimester human FBM and paediatric ALL samples were obtained from the Human Developmental Biology Resource and UK Childhood Leukaemia Cell Bank respectively. Multiparameter flow cytometry/sorting, transcriptome analysis by RNA-sequencing and microarray, and stromal co-culture assays were used to characterize HSPC and mesenchymal stromal cells (MSC) from normal (NM) disomic (n=21-35) and T21 (n=7-12) human FBM; RNASeq was performed on cytogenetically matched non-DS (n=13) and DS ALL (n=7). Results: In contrast to NM FBM, fetal specific progenitors were virtually absent (CD34+CD10-CD19-CD127+ ELP 2.8±0.4% vs. 0.8±0.4% of CD34+ cells) or very severely reduced (CD34+CD10-CD19+ PreProB 12.8±1 vs 2.6±0.7%) in T21 FBM. This was despite a >4-fold increase in the frequency of immunophenotypic HSC (4.2±1.2% vs 0.9±0.2% of CD34+ cells) and similar frequencies of MPP and LMPP in T21 FBM. As in adult BM, the vast majority of B progenitors in T21 FBM were CD34+CD10+CD19+ ProB progenitors with a frequency (28.8±8.3%) similar to NM FBM (30.3±2.3% of CD34+ cells). Thus, T21 causes a severe block in B-progenitor commitment at the LMPP stage, in tandem with a compensatory expansion of ProB progenitors. Consistent with this, T21 FBM HSC, MPP and LMPP had reduced B cell potential in vitro compared to NM FBM in MS5 co-cultures. RNAseq of NM (n=3) and T21 (n=3) FBM HSPC demonstrated global transcriptomic disruption by T21, with increased gene expression in HSC, MPP, LMPP and ProB progenitors. Cell cycle genes were enriched in T21 ProB progenitors. Despite these functional and global gene expression differences, expression of key B-lineage commitment genes was maintained suggesting the defect in B-lymphopoiesis may be secondary to lineage skewing of multipotent progenitors towards a non-B lymphoid fate and/or mediated by extrinsic factors. GSEA pointed to a role for multiple inflammatory pathways in T21 hematopoiesis with dysregulation of IFNα, IL6 and TGFβ signalling pathways in T21 HSC/LMPP. To investigate the role of the T21 microenvironment, we co-cultured NM HSC, MPP and LMPP with T21 or NM primary FBM MSC. T21 FBM MSC (n=3) had reduced capacity to support B cell differentiation in vitro consistent with perturbation of MSC function by T21. Similar to T21 FBM HSPC, transcriptomic analysis of T21 FBM MSC by microarray showed enrichment for IFNα signalling compared to NM; and T21 HSPC and MSC both showed increased gene expression for IFNα receptors IFNAR1 and IFNAR2, which are encoded on chromosome 21. Since IFNα was undetectable by ELISA of conditioned media from NM and T21 MSC, differences in secreted IFNα from MSC are unlikely to fully explain the increased IFN signalling in T21 HSPC and MSC. This suggests that T21 may drive autocrine rather than paracrine IFN signalling in FBM cells. Finally, RNASeq showed perturbed inflammatory signalling in DS ALL compared to non-DS ALL, suggesting a role for T21-driven inflammatory pathways in the biology of DS ALL. Conclusions: These data show that T21 severely impairs B lymphopoiesis in FBM and is associated with expression of proinflammatory gene expression programs in T21 FBM HSPC and MSC and DS ALL. The compensatory expansion of T21 FBM ProB progenitors, through self-renewal or via an alternative differentiation pathway; with concomitant T21-driven proinflammatory signalling may underpin the increased risk of B progenitor ALL in childhood. Disclosures No relevant conflicts of interest to declare.

IL-7 Effects on Thymocyte Progenitors.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3318-3318
Author(s):  
Nahed El Kassar ◽  
Baishakhi Choudhury ◽  
Francis Flomerfelt ◽  
Philip J. Lucas ◽  
Veena Kapoor ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
B Cell ◽  
Notch Signaling ◽  
Stromal Cells ◽  
T Cell Development ◽  
Fold Increase ◽  
Cell Development ◽  
B Cell Development ◽  
Over Expression

Abstract IL-7 is a non-redundant cytokine in T cell development. We studied the role of IL-7 in early T-cell development using a model of transgenic (Tg) mice with the murine IL-7 gene under control of the lck proximal promoter. At high IL-7 over-expression (x39 fold increase at day 1 in total thymic tissue), we observed a disruption of TCRαβ development along with increased B cell development in the thymus (7- to 13-fold increase) (El Kassar, Blood, 2004). In order to further explore abnormal T and B cell thymic development in these mice, we first confirmed that they both arise in parallel and were non-cell autonomous, by in vivo injection of neutralizing anti-IL-7 MAb and mixed bone marrow chimera experiments. Using a six color flow cytometry analysis, we found a dramatic decrease of the early thymocyte progenitors (ETPs, lin−CD44+CD25−c-kithiIL-7R−/lo) in the adult Tg mice (x4.7 fold decrease). Lin−CD44+CD25−c-kit+ thymocytes were sorted and cultured on OP9 and OP9 delta-like1 (OP9-DL1) stromal cells (kindly provided by Pr Zuniga Pflucker). At day 14, we observed an important decrease of T cell development (54% vs. 1% of DP cells) and an increase of NK cells (x5 fold increase) in the Tg-derived DN1 cell culture. DN2 (Lin−CD44+CD25−c-kit+) Tg thymocytes showed the same, but less dramatic abnormalities. While DN1 progenitors developed effectively into B220+CD19+ cells on OP9 stromal cells, no B cell development was observed on OP-DL stromal cells from DN1-Tg derived progenitors or by addition of increasingly high doses of IL-7 (x10, x40, x160) to normal B6-derived DN1 progenitors. Instead, a block of T-cell development was observed with increased IL-7. We hypothesized a down regulation of Notch signaling by IL-7 over-expression and analyzed by FACS Notch expression in the DN thymocytes. By staining the intra-cellular part of Notch cleaved after Notch 1/Notch ligand activation, Tg-derived DN2 cells showed decreased Notch signaling. More importantly, HES expression was decreased in the DN2, DN3 and DN4 fractions by semi-quantitative PCR. Sorted Pro/Pre B cells from Tg thymi showed TCR Dβ1-Jβ1 rearrangement indicating their T specific origin, in opposition to Pro/Pre B cells sorted from the bone marrow of the same mice. We suggest that more than one immature progenitor seeds the thymus from the bone marrow. While ETPs had T and NK proliferative capacity, another thymic progenitor with B potential may be responsible for thymic B cell development in normal and IL-7 Tg mice. Finally, IL-7 over-expression may induce a decreased Notch signaling in thymic progenitors, inducing a switch of T vs. B lineage development.

Morphologic and Phenotypic Features of Concurrent Clonal T-Cell Large Granular Lymphocytic Expansion and Myelodysplastic Syndrome

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2803-2803
Author(s):  
Xiaohui Zhang ◽  
Lynn Moscinski ◽  
John M. Bennett ◽  
Reza Setoodeh ◽  
Deniz Peker ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
T Cell ◽  
Peripheral Blood ◽  
Low Grade ◽  
Gene Rearrangements ◽  
High Grade ◽  
Bone Marrow Cellularity ◽  
Hla Dr ◽  
Marrow Cellularity

Abstract Abstract 2803 Myelodysplastic syndrome (MDS) and T-cell large granular (T-LGL) leukemia are both bone marrow failure disorders. It has been reported in a small number of cases that clonal T-LGL proliferation or leukemia can coincidentally occur with MDS. Also, clonal CD8+/CD57+ effector T cells expansion was detected in as many as 50% of MDS bone marrows [Epling-Burnette, 2007]. How clonal LGL cells that reside in the bone marrow interfere with hematopoiesis remains unclear, particularly in the setting of MDS. We analyzed the clinicopathological features of concomitant MDS and T-LGL, and evaluated bone marrow status for lineage or pan-hypoplasia in these patients. Design: Clinical and pathologic data from patients with a diagnosis of MDS and flow cytometry performed on the peripheral blood between 1/2005 and 12/2009 were reviewed. The concurrent bone marrow biopsies from each patient at the time of flow cytometric analysis were reviewed by two hematopathologists. Bone marrow cellularity, lineage hypoplasia (M:E >5: 1 or <1:2) were documented. Peripheral lymphocyte count and CD3+/CD57+ and CD8+/CD57+ populations by flow cytometry were calculated and T cell gene receptor (TCR) rearrangements were correlated. Results: We performed LGL flow cytometry panel on 76 MDS patients (high grade MDS, n=23; low grade, n=54), as well as TCR gene rearrangements, and identified clonal T-LGL cells in peripheral blood of 37 patients (48.7%), including 15 high grade MDS (40.5%, RAEB-I and RAEB-II), and 22 low grade MDS (59.4%), including RCMD(13), RA(1), RS(1), RCMD-RA(1), RCMD-RS (2), 5q- MDS(1), and MDS unclassifiable(3). The immunophenotype of the T-LGL cells was typically CD3+/CD57+/CD7 dim+/CD5 dim+/CD8+ with variable CD11b,CD11c, CD16, CD56 and HLA-DR. A frequent variant in these MDS patients was CD11b-,CD11c -, CD16+/−, CD56+/−, HLA-DR- and CD62L+.The TCRβ or/and TCRγ gene rearrangements were positive in 35 of the 38 cases (92.1%). The peripheral blood lymphocyte counts were 300–3820 cells/μL (1199±799 cells/μL); the CD3+/CD8+/CD57+ T-LGL cell counts were 30–624 cells/μL (229±154 cells/μL). In comparison, the remaining 39 patients with non-clonal T-LGL included 11 high grade MDS cases, and 28 low grade MDS cases. The peripheral blood lymphocyte counts were 308–2210 cells/μL (1030±461 cells/μL). CD3+/CD57+ cells were 1–425 cells/μL (105±98 cells/μL). There was no identifiable phenotypic features suggestive of clonal T-LGL cells such as dim CD5 and/or dim CD7 with aforementioned aberrant expressions on T-cells, although 7 of the 39 cases had TCRβ or/and TCRγ gene rearrangements. Thirty healthy donors were included for controls with absolute lymphocyte counts of 2136±661 cells/μL and baseline CD3+/CD57+ cells of 162±109 cells/μL. All showed no clonal LGL phenotype and negative TCR gene rearrangements. Since the presence of T-LGL cells may impair bone marrow hematopoiesis, we examined if there are bone marrow status differences between these two groups. All the bone marrows were obtained at diagnosis or not on chemotherapy. The bone marrow cellularity of the MDS patients with clonal T-LGL ranged from <3% to almost 100%, averaging 56%, with 8 cases with dramatic hypocellularity (<3%-20%), while the bone marrow cellularity of the MDS patients without clonal T-LGL ranged from 20% to 90%, averaging 62%, with only 2 cases with mild hypocellularity (20% in 73- and 65-year-old). In addition, among MDS patients with clonal T-LGL cells, 14 of 37 (37.8%; 5 high grade, and 9 low grade) bone marrows had certain lineage hypoplasia, including 3 cases of trilineal hypoplasia, 9 cases of erythroid hypoplasia, and 2 cases of myeloid hypoplasia. In contrast, among 39 MDS patients without T-LGL, there were only 1 bone marrow with trilineal hypoplasia and 3 others with erythroid hypoplasia (10.2%). The difference between the two groups was statistically significant (p=0.004, chi square test). In conclusion, our studies indicate that clonal T-LGL cells expansion is a fairly common finding in high grade as well as low grade MDS. The clonal T-LGL cells have more than one variant immunophenotypes and are typically positive for TCR gene rearrangements. Additionally, we observed that the clonal LGL cells present in MDS bone marrows could be associated with lineage hypoplasia, which, in this respect, might impact clinical treatment. Disclosures: No relevant conflicts of interest to declare.

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