STAT5 Has Tumor Suppressor-Like Activity in a Murine Model of Myc-Initiated Acute B-Lymphoblastic Leukemia/Lymphoma

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 919-919 ◽  
Author(s):  
Zhengqi Wang ◽  
Geqiang Li ◽  
Zizhen Kang ◽  
Silvia T Bunting ◽  
William Tse ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
B Lymphocyte ◽  
Fetal Liver ◽  
Lymphoblastic Leukemia ◽  
Conditional Knockout ◽  
Lymphocyte Development ◽  
Wild Type ◽  
B Lymphocyte Development ◽  
B Lymphoid

Abstract Abstract 919 Signal transducer and activator of transcription 5 (STAT5) is a critical regulator of normal and leukemic lympho-myeloid hematopoiesis through activation downstream of early-acting cytokines, their receptors, and janus kinases (JAKs). Despite upstream activating mutations driving JAK-STAT phosphorylation in precursor-B acute lymphoblastic leukemia (B-ALL), activated JAK-STAT is absent from the aggressive “double hit” lymphomas expressing myc and bcl-2. Using C57BL/6 background transgenic mouse models for myc and bcl-2, we set out to determine whether endogenous STAT5 functions in guarding against B-ALL induced by combined myc/bcl-2 or myc alone. We first determined whether constitutive expression of bcl-2 driven from the H2K promoter and Moloney murine leukemia virus enhancer in C57BL/6 background STAT5-deficient hematopoietic cells could bypass blocks in B-lymphocyte development. Transgenic H2K/bcl-2 expression in hypomorphic STAT5abDN/DN mice, which are leaky and still produce some mature B-lymphocytes, largely rescued peripheral B-lymphocyte survival to near normal levels but could only rescue about 10% of the multilineage hematopoietic stem cell (HSC) competitive repopulating defect. Complete deletion of the entire STAT5ab locus resulted in the expected severe block of B-cell development at the pre-pro-B-cell stage following transplantation of STAT5ab null/null fetal liver cells into irradiated wild type or common γC−/− recipients. Peripheral B-lymphocyte development could not be restored by transgenic bcl-2 alone in the absence of STAT5. However, transgenic myc driven from an immunoglobulin H chain enhancer (Emu/myc) combined with H2K/bcl-2 induced B-ALL peripheral counts as high as 1.1 × 105 B-cells/ul and reduced latency (a median survival of 44 days) compared to wild-type control (a median survival of 91 days) in either lethally-irradiated (P<0.001; N range from 8–14 mice/group) or sub-lethally-irradiated cohorts of fetal liver transplanted mice (P=0.007; N range 10–20 mice/group). B-ALL in mice with or without STAT5 was a mix of Pro-B and Pre-B ALL (IgM-CD43+B220+CD19+/−CD4+/−) and morphologically similar in the spleen and bone marrow. Multi-parameter flow cytometry analysis of bone marrow cells from STAT5ab null/null fetal liver transplanted mice (N=4) showed that deletion of STAT5 significantly reduced by 11.5-fold (P=0.004) the fraction of long-term repopulating HSC (CD150+CD48-) c-Kit+Lin-Sca-1+ (KLS). In an independent adult Mx1-Cre conditional knockout of STAT5 by pI:pC treatment, lymphomas induced by Myc alone were also accelerated (P=0.05; N range 14–15 mice/group) with STAT5 maintained deleted in sorted B-cells. These mice also had reduced CD150+CD48- KLS cells (5.6-fold; N=4; P=0.006). Interestingly, several phenotypes recently reported as associated with increased HSC cycling and lymphoid-biased differentiation were observed. The mean fluorescence intensity of slamf1 (CD150) was reduced 2.2-fold (P<0.001; N=4) in conditional knockout mice and the B-lymphoid biased CD48+CD150+ or CD48-CD150- KLS cells representing short-term HSC/multipotent progenitors were not significantly reduced. Microarray analyses of the KLS fraction provided evidence that STAT5 promotes HSC maintenance and myeloid potential (limiting lymphoid commitment, cycling) in the KLS compartment. The deletion of STAT5 reduced expression of HSC self-renewal and quiescence promoting genes and increased immunoglobulin and B-lymphoid transcripts. Combined with the pre-pro-B-cell block, loss of STAT5 promotes accumulation of B-lineage committed progenitors as potential ALL initiating cells. The effects of bcl-2 and myc hits on STAT5 null/null hematopoietic cells are currently being further characterized with respect to B-cell developmental blocks and molecular heterogeneity. B-ALL has a high relapse rate and is driven by clonally diverse tumor propagating populations. Our work may have important implications for ALL drug therapy. In conclusion, we demonstrate that STAT5, considered primarily as functioning like an oncogene in hematologic malignancies upon persistent activation, can play a tumor suppressor-like role in subsets of B-ALL. These data add to an emerging understanding that endogenous STAT5 can suppress some cancers and transcriptionally regulate several cell cycle inhibitors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Flow cytometric analysis of human bone marrow. II. Normal B lymphocyte development

Blood ◽  
1987 ◽  
Vol 70 (5) ◽  
pp. 1316-1324 ◽  
Author(s):  
MR Loken ◽  
VO Shah ◽  
KL Dattilio ◽  
CI Civin
Keyword(s):  
Bone Marrow ◽  
Cell Surface ◽  
B Lymphocyte ◽  
Human Bone ◽  
Lymphocyte Development ◽  
Hla Dq ◽  
B Lymphocyte Development ◽  
B Lineage ◽  
B Lymphoid ◽  
B Lineage Cells

Abstract A panel of B lymphoid-reactive monoclonal antibodies was used to analyze the phenotypic changes that accompany B lymphocyte development in normal human bone marrow. The B lymphoid cells were identified using light scattering and the expression of CD19 on a flow cytometer. Quantitative three-color immunofluorescence was then used to correlate other cell surface antigens on these cells identified as B lymphoid in normal marrow. CD10 and CD20 identified almost exclusive populations and provided a convenient means of discriminating between the less and more mature B lineage cells. The CD10+ cells could be further subdivided using CD34. The population of CD19+, CD10+, CD34+ cells comprised only 0.6% of marrow cells, but these contained the majority of terminal deoxynucleotidyl transferase (TdT+) cells. In the assessment of class II antigens, HLA-DR was expressed on all B lineage cells whereas HLA-DP preceded HLA-DQ in appearance during the developmental process. Among the later antigens expressed on B lineage cells, cell surface IgM, CD20, and HLA-DQ were expressed at essentially the same time. Cell surface CD10 was lost at the time when CD21 and CD22 were acquired on the cell surface. These data illustrate that multiparameter flow cytometry can be used to define a continuous progression of stages of B lymphocyte development based on cell surface antigen expression even though these cells represent a minor fraction of normal marrow cells.

Pre-BCR Signaling Activity Predicts Sensitivity To Syk Kinase Inhibition In B Cell Acute Lymphoblastic Leukemia (B-ALL)

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 614-614
Author(s):  
Stefan Koehrer ◽  
Richard E. Davis ◽  
Greg Coffey ◽  
Ekaterina Kim ◽  
Nathalie Y. Rosin ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
B Lymphocyte ◽  
Lymphoblastic Leukemia ◽  
Cell Receptor ◽  
Lymphocyte Development ◽  
Bcr Signaling ◽  
Associated Proteins ◽  
Cell Acute Lymphoblastic Leukemia ◽  
B Lymphocyte Development

Abstract B lymphocyte development proceeds in a stepwise fashion and is tightly linked to the generation of a functional B cell receptor (BCR). At the preB cell stage B lymphocyte progenitors express the precursor B cell receptor (pre-BCR), an immature form of the BCR consisting of two µ heavy chains (µHC) and two surrogate light chains (SLC). Pre-BCR expression marks the proB to preB transition and induces a burst in preB lymphocyte proliferation. In 20% of the cases B cell acute lymphoblastic leukemia (B-ALL) arises from lymphocytes arrested at the pre-BCR positive stage of lymphocyte development (preB-ALL). Due to the essential role of the pre-BCR for preB cell proliferation we hypothesized that pre-BCR signaling also is involved in the maintenance of preB-ALL. Consequently, pharmacological inhibition of Spleen tyrosine kinase (Syk), the main transducer of pre-BCR signaling, may serve as effective treatment for this subtype of B-ALL. We analyzed a panel of six ALL cell lines (SMS-SB, RCH-ACV, Nalm-6, Kasumi-2, 697, KOPN-8) arrested at the pre-BCR+ stage of B lymphocyte development (cytoIgµ+, sIgM-). Assessment of the baseline phosphorylation levels of the pre-BCR associated kinases Lyn, Syk and Btk by immunoblotting and subsequent densitometric analysis allowed us to assign B-ALL cells into groups with either high levels of Lyn, Syk and Btk phosphorylation or with low or absent phosphorylation of these kinases, respectively. Moreover cell lines with highly phosphorylated Lyn, Syk and Btk also exhibited lower surface pre-BCR expression than cell lines with low phosphorylation levels. As pre-BCR activation is followed by its rapid internalization the concomitant presence of low pre-BCR expression and high phosphorylation of pre-BCR associated proteins suggests increased pre-BCR pathway activity. When we investigated the impact of pharmacological inhibition of the pre-BCR associated kinase Syk through the highly specific inhibitor PRT060318, preB-ALL cell lines with highly phosphorylated pre-BCR associated molecules turned out to be more sensitive to Syk inhibition (IC50 < 1.6µM) than preB-ALL cell lines with less phosphorylation (IC50 > 3.9µM). In proliferation assays PRT060318 inhibited preB-ALL proliferation in a dose dependent manner, whereas PRT060318 did not induce apoptosis in concentrations as high as 5µM. This supports the notion that pre-BCR signaling activity may be more relevant for preB-ALL proliferation than for preB-ALL viability. In line with these results the pre-BCR- proB-ALL cell lines REH and RS4;11 were highly resistant to Syk inhibition in all functional assays (IC50 > 10µM), suggesting that pre-BCR expression is a prerequisite for sensitivity to Syk inhibition. To examine the molecular changes following pre-BCR inhibition, ALL cells were treated with increasing concentrations of PRT060318 (100nM-5µM) for two hours and then subjected to immunoblotting. Syk inhibition led to a dose dependent decrease in AKT phosphorylation in all preB-ALL cell lines and subsequently reduced phosphorylation of FOXO transcription factors. In the resistant proB-ALL cell line REH, AKT and FOXO phosphorylation were not affected. Gene expression analysis of the preB-ALL cell lines RCH-ACV and Nalm-6 further suggested that PRT060318 interferes with pre-BCR signaling. Treatment with 1µM PRT060318 for 72h reduced the expression of genes associated with pre-BCR signaling (e.g. BCL6, CD22, PTPN6) and Ingenuity Pathway Analysis identified pre-BCR signaling as the main target of PRT060318 in both cell lines (p<0.05). We are currently validating the GEP analysis by quantitative PCR and immunoblotting. In conclusion, we provide evidence for the efficacy of Syk inhibition in pre-BCR+ ALL. Moreover we were able to correlate the baseline phosphorylation status of pre-BCR associated proteins and pre-BCR expression levels with the sensitivity of preB-ALL to the Syk inhibitor PRT060318. These findings provide a first rationale for the clinical testing of Syk inhibitors in preB-ALL, and suggest that activation status of pre-BCR associated molecules can help in selecting preB-ALL cases that are particularly sensitive to Syk inhibition. Disclosures: Coffey: Portola Pharmaceuticals: Employment.

scholarly journals Flow cytometric analysis of human bone marrow. II. Normal B lymphocyte development

Blood ◽  
1987 ◽  
Vol 70 (5) ◽  
pp. 1316-1324 ◽  
Author(s):  
MR Loken ◽  
VO Shah ◽  
KL Dattilio ◽  
CI Civin
Keyword(s):  
Bone Marrow ◽  
Cell Surface ◽  
B Lymphocyte ◽  
Human Bone ◽  
Lymphocyte Development ◽  
Hla Dq ◽  
B Lymphocyte Development ◽  
B Lineage ◽  
B Lymphoid ◽  
B Lineage Cells

A panel of B lymphoid-reactive monoclonal antibodies was used to analyze the phenotypic changes that accompany B lymphocyte development in normal human bone marrow. The B lymphoid cells were identified using light scattering and the expression of CD19 on a flow cytometer. Quantitative three-color immunofluorescence was then used to correlate other cell surface antigens on these cells identified as B lymphoid in normal marrow. CD10 and CD20 identified almost exclusive populations and provided a convenient means of discriminating between the less and more mature B lineage cells. The CD10+ cells could be further subdivided using CD34. The population of CD19+, CD10+, CD34+ cells comprised only 0.6% of marrow cells, but these contained the majority of terminal deoxynucleotidyl transferase (TdT+) cells. In the assessment of class II antigens, HLA-DR was expressed on all B lineage cells whereas HLA-DP preceded HLA-DQ in appearance during the developmental process. Among the later antigens expressed on B lineage cells, cell surface IgM, CD20, and HLA-DQ were expressed at essentially the same time. Cell surface CD10 was lost at the time when CD21 and CD22 were acquired on the cell surface. These data illustrate that multiparameter flow cytometry can be used to define a continuous progression of stages of B lymphocyte development based on cell surface antigen expression even though these cells represent a minor fraction of normal marrow cells.

Developmentally regulated cell surface expression and function of c-kit receptor during lymphocyte ontogeny in the embryo and adult mice

Development ◽  
1992 ◽  
Vol 115 (4) ◽  
pp. 1133-1147 ◽  
Author(s):  
R. Palacios ◽  
S. Nishikawa
Keyword(s):  
Bone Marrow ◽  
Stromal Cells ◽  
B Lymphocyte ◽  
Fetal Liver ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Lymphocyte Development ◽  
Fetal Thymus ◽  
Kit Receptor ◽  
B Lymphocyte Development

We have used a c-kit-specific monoclonal antibody, immuno-fluorescence staining and flow fluorocytometry or microscopy analysis to assess the cell surface expression of the c-kit receptor on a panel of non-transformed clones representing different stages of T- and B-lymphocyte development, freshly isolated lymphoid cells from thymus, bone marrow and spleen of young adult C57BL/6 mice and cells from yolk sac, thymus and liver of developing C57BL/6 mouse embryos. Pro-T, Pro-B and Pre-B clones derived from thymus or liver of 14-day embryos are c-kit+. Starting at day 8 to 8.5 in yolk sac, day-10 in fetal liver, and day 11 to 12 in fetal thymus, there are many c-kit+ cells. The number of c-kit+ cells in liver and thymus increases up to day 15 and progressively decreases thereafter. Cell sorter purified c-kit+ day 14 fetal liver cells fully reconstitute the T and B cell compartments of immunodeficient Scid mice. Stromal cells or epithelial cells derived from fetal thymus or liver, which can support growth and differentiation of c-kit+ lymphocyte progenitor clones, synthesize mRNA for Steel Factor (SF), the ligand of c-kit. In the adult mouse, however, c-kit expression is restricted to very early stages of T- and B-lymphocyte development (multipotent progenitors, B-cell/myelocytic progenitors, Pro-T and Pro-B lymphocyte progenitors). Most cells at the Pre-T, Pre-B and later stages of development do not bear detectable c-kit. Using Cos-1 cells transfected with mouse SF-cDNA and an antagonistic c-kit receptor-specific antibody, we show that the c-kit/SF system contributes to the survival of lymphocyte progenitors and enhances the proliferative responses of these cells to other growth factors (i.e. IL2, IL3, IL4, IL7). However, the c-kit receptor/SF ligand pair is neither sufficient nor necessary for the differentiation of lymphocyte progenitors into mature T- or B-lymphocytes. Finally, in stromal cell lines from fetal liver and adult bone marrow and thymic epithelial cell lines the level of steady state SF-RNA transcripts is inversely correlated with that of IL-7-mRNA. Moreover, IL7 inhibits the synthesis of SF-mRNA in stromal cells and rIL6 abrogates this inhibitory effect of rIL7. Thus, the expression of SF in stromal cells is subjected to complex regulation by other cytokines produced by the same stromal cells or by neighboring cells in a given microenvironment.(ABSTRACT TRUNCATED AT 400 WORDS)

ERP, a new member of the ets transcription factor/oncoprotein family: cloning, characterization, and differential expression during B-lymphocyte development

1994 ◽  
Vol 14 (5) ◽  
pp. 3292-3309
Author(s):  
M Lopez ◽  
P Oettgen ◽  
Y Akbarali ◽  
U Dendorfer ◽  
T A Libermann
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Gene Family ◽  
B Cell ◽  
Binding Sites ◽  
B Lymphocyte ◽  
Striking Similarity ◽  
Lymphocyte Development ◽  
B Lymphocyte Development ◽  
Ets Transcription Factor

The ets gene family encodes a group of proteins which function as transcription factors under physiological conditions and, if aberrantly expressed, can cause cellular transformation. We have recently identified two regulatory elements in the murine immunoglobulin heavy-chain (IgH) enhancer, pi and microB, which exhibit striking similarity to binding sites for ets-related proteins. To identify ets-related transcriptional regulators expressed in pre-B lymphocytes that may interact with either the pi or the microB site, we have used a PCR approach with degenerate oligonucleotides encoding conserved sequences in all members of the ets family. We have cloned the gene for a new ets-related transcription factor, ERP (ets-related protein), from the murine pre-B cell line BASC 6C2 and from mouse lung tissue. The ERP protein contains a region of high homology with the ETS DNA-binding domain common to all members of the ets transcription factor/oncoprotein family. Three additional smaller regions show homology to the ELK-1 and SAP-1 genes, a subgroup of the ets gene family that interacts with the serum response factor. Full-length ERP expresses only negligible DNA-binding activity by itself. Removal of the carboxy terminus enables ERP to interact with a variety of ets-binding sites including the E74 site, the IgH enhancer pi site, and the lck promoter ets site, suggesting a carboxy-terminal negative regulatory domain. At least three ERP-related transcripts are expressed in a variety of tissues. However, within the B-cell lineage, ERP is highly expressed primarily at early stages of B-lymphocyte development, and expression declines drastically upon B-cell maturation, correlating with the enhancer activity of the IgH pi site. These data suggest that ERP might play a role in B-cell development and in IgH gene regulation.

scholarly journals Expression of the c-myc oncogene under control of an immunoglobulin enhancer in E mu-myc transgenic mice.

1987 ◽  
Vol 7 (4) ◽  
pp. 1436-1444 ◽  
Author(s):  
W S Alexander ◽  
J W Schrader ◽  
J M Adams
Keyword(s):  
Bone Marrow ◽  
Transgenic Mice ◽  
B Lymphocyte ◽  
Lymphoid Cells ◽  
Lymphoid Tissues ◽  
Myc Oncogene ◽  
Feedback Model ◽  
B Lymphocyte Development ◽  
B Lymphoid ◽  
Spleen And Lymph Nodes

Transgenic mice bearing a cellular myc oncogene coupled to the immunoglobulin heavy-chain enhancer (E mu) exhibit perturbed B-lymphocyte development and succumb to B lymphoid tumors. To investigate how the enhancer has affected myc expression, we analyzed the structure and abundance of myc transcripts in tissues of prelymphomatous mice and in the lymphomas. Expression of the E mu-myc transgene appeared to be confined largely to B lymphoid cells, being dominant in bone marrow, spleen, and lymph nodes, with no detectable expression in T cells or other hematopoietic lineages examined. The myc transcripts initiated very predominantly at the normal myc promoters, although use of the more upstream myc promoter was accentuated and an enhancer-associated promoter may be used infrequently. The level of E mu-myc transcripts in the preneoplastic lymphoid tissues and in the E mu-myc tumors was not markedly higher than myc RNA levels in proliferating normal lymphocytes. Thus, enforced expression of structurally normal myc transcripts at only a modestly elevated level has profound biological consequences. The absence of detectable endogenous c-myc RNA in any tumor, or in preneoplastic bone marrow, supports a negative feedback model for normal c-myc regulation.

Pax5 Haploinsufficiency Cooperates with BCR-ABL1 to Induce Acute Lymphoblastic Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 293-293 ◽  
Author(s):  
ChristoPher B Miller ◽  
Charles G Mullighan ◽  
Xiaoping Su ◽  
Jing Ma ◽  
Michael Wang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Acute Lymphoblastic Leukemia ◽  
B Cell ◽  
Point Mutation ◽  
Copy Number ◽  
Lymphoblastic Leukemia ◽  
Wild Type ◽  
Lymphoid Development ◽  
B Lymphoid

Abstract Genes regulating B lymphoid development are somatically mutated in over 40% of B-progenitor acute lymphoblastic leukemia (ALL) cases, with the most common targets being the transcription factors PAX5, IKZF1 (encoding Ikaros), and EBF1. Notably, BCR-ABL1 ALL is characterized by a high frequency of mutations of IKZF1 (85%), PAX5 (55%), and CDKN2A/B (encoding INK4/ARF, 55%), suggesting that these lesions cooperate with BCR-ABL1 in lymphoid leukemogenesis. To examine cooperativity between Pax5 haploinsufficiency and BCR-ABL1, we transplanted Pax5+/+ and Pax5+/− bone marrow cells transduced with MSCV-GFP-IRES-p185 BCR-ABL1 retrovirus into lethally irradiated wild-type C57BL6 recipient mice. Mice transplanted with BCR-ABL1 transduced Pax5+/− marrow developed B progenitor cell ALL with significantly higher penetrance and decreased latency when compared to animals transplanted with BCR-ABL1 transduced Pax5+/+ marrow (median survival 36 vs. 60 days, P=0.0003). The latency of tumor onset was further decreased in the presence of Arf haploinsufficiency (Pax5+/+Arf+/+ 60 days, Pax5+/−Arf+/+ 36 days, Pax5+/−Arf+/− 21 days, P&lt;0.0001). All leukemias were of B cell lineage and were transplantable to secondary recipients. In addition, Southern blot analysis revealed the Pax5+/−Arf+/+ leukemias to be monoclonal, where as the Pax5+/−Arf+/− leukemias were oligoclonal. Importantly, the Pax5+/− leukemias exhibited a more immature B cell immunophenotype than Pax5 wild type leukemias. Moreover, a proportion of the Pax5+/− leukemias (19%) exhibited a very immature early pro B cell immunophenotype (Cd19−, Bp1−), suggesting the possibility of acquired lesions in other key regulators of normal B cell differentiation. To explore this possibility and to identify the total complement of genetic lesions required to generate overt leukemia, we performed genome-wide copy number analysis on 30 murine leukemias (15 Pax5+/+, 15 Pax5+/−) using a custom CGH microarray (Agilent) that interrogated 477,000 autosomal loci, including 18,000 probes covering 20 genes encoding B lymphoid transcription factors and genes targeted by recurring copy number abnormalities (CNAs) in human BCR-ABL1 ALL (Bcl11a, Cdkn2a, Ebf1, Ikzf1, Ikzf2, Ikzf3, Il7r, Lef1, Mdm2, Mef2c, Myb, Pax5, Pten, Rb1, Sfpi1, Sox4, Stat5a, Tcf3, Tcf4, and Trp53). This analysis identified focal recurring CNAs in multiple genes including Cdkn2a/b, Ebf1, Ikzf1, Ikzf2, Ikzf3, and Pax5, each of which is a target of mutation in human B-ALL. Overall, there were on average 3.5 CNAs in Pax5+/+ leukemias versus 0.7 CNAs in Pax5+/− leukemias. Genomic resequencing was also performed on Pax5 and revealed three missense mutations in the DNA binding paired domain (R38H, P80R and G85R), one of which (P80R) is the most common PAX5 point mutation in human B-ALL. All three point mutations are predicted to impair DNA binding of Pax5. Interestingly, the majority of the pro-B cell leukemias that arose in the Pax5+/−Arf+/+ animals were found to harbor mutations (CNAs or point mutation) of the retained Pax5 allele, consistent with the immature immunophenotype. To further explore the relationship between our murine model and human BCR-ABL1 ALL, we performed gene expression profiling of Pax5+/+ and Pax5+/− leukemias and compared their signatures to those of human BCR-ABL1 ALL and stage-specific murine B lymphoid developmental signatures using gene set enrichment analysis (GSEA). This analysis identified significant similarity between murine and human BCR-ABL1 leukemias, thus providing further evidence that this model closely recapitulates human BCR-ABL1 ALL. Notably, Pax5+/− leukemias, or Pax5+/+ leukemias that acquired additional mutations of B-lymphoid regulators exhibited a less mature gene expression profile than leukemias lacking B-lymphoid regulatory mutations. These data indicate that loss of Pax5 contributes to leukemogenesis, that additional genomic alterations in genes regulating B lymphoid development and cell cycle regulators/tumor suppressors (Arf) are frequent events in BCR-ABL1 acute lymphoblastic leukemia, and that these lesions result in impaired B-lymphoid maturation in B-ALL. The genetic complexity of BCR-ABL1 ALL is likely to have important therapeutic implications for this poor prognosis subtype of leukemia.

Hematopoietic Stem Cell Engraftment in Bone Marrow Is Dependent upon Gsα.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 857-857
Author(s):  
Gregor B. Adams ◽  
Ian R. Alley ◽  
Karissa T. Chabner ◽  
Ung-il Chung ◽  
Emily S. Marsters ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Conditional Knockout ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Cell Engraftment

Abstract During development, hematopoietic stem cells (HSCs) translocate from the fetal liver to the bone marrow, which remains the site of hematopoiesis throughout adulthood. In the bone marrow the HSCs are located at the endosteal surface, where the osteoblasts are a key component of the stem cell niche. The exogenous signals that specifically direct HSCs to the bone marrow have been thought to include stimulation of the chemokine receptor CXCR4 by its cognate ligand stromal derived factor-1α (SDF-1α or CXCL12). However, experiments in which CXCR4−/− fetal liver hematopoietic cells were transplanted into wild-type hosts demonstrated efficient engraftment of the HSCs in the bone marrow. In addition, treatment of HSCs with inhibitors of Gαi-coupled signaling, which blocks transmigration towards SDF-1αin vitro, does not affect bone marrow homing and engraftment in vivo. Therefore, we examined whether Gsα-coupled mechanisms play a key role in the engraftment of the HSCs in the bone marrow environment. Utilizing an inducible-conditional knockout of Gsα, we found that deletion of the gene in hematopoietic bone marrow cells did not affect their ability to perform in the in vitro primitive CFU-C or LTC-IC assay systems. However, Gsα−/− cells were unable to establish effective hematopoiesis in the bone marrow microenvironment in vivo in a competitive repopulation assay (41.1% contribution from wild-type cells versus 1.4% from knockout cells). These effects were not due to an inability of the cells to function in the bone marrow in vivo as deletion of Gsα following establishment of hematopoiesis had no effects on the HSCs. Examining the ability of the HSCs to home to the bone marrow, though, demonstrated that deletion of Gsα resulted in a marked impairment of the ability of the stem cells to localize to the marrow space (approximately 9-fold reduction in the level of primitive cell homing). Furthermore, treatment of BM MNCs with an activator of Gsα augmented the cells homing and thus engraftment potential. These studies demonstrate that Gsα is critical to the localization of HSCs to the bone marrow. Which receptors utilize this pathway in this context remains unknown. However, Gsα represents a previously unrecognized signaling pathway for homing and engraftment of HSCs to bone marrow. Pharmacologic activation of Gsα in HSC ex vivo prior to transplantation offers a potential method for enhancing stem cell engraftment efficiency.

scholarly journals Frequency of IKZF1 Deletions in a Peruvian Population with B-Cell Acute Lymphoblastic Leukemia

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 11-11
Author(s):  
Daniel J Enriquez ◽  
Rachel J. Mitchell ◽  
Krisztina Zuborne Alapi ◽  
Elizabeth Cervantes ◽  
Karina Cancino ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
B Cell ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Dominant Negative ◽  
White Blood Count ◽  
Induction Treatment ◽  
Wild Type ◽  
Cell Acute Lymphoblastic Leukemia

Frequency of IKZF1 Deletions in a Peruvian Population with B-cell Acute Lymphoblastic Leukemia Background: B-cell Acute Lymphoblastic Leukemia (B-ALL) is an aggressive disease with worse outcomes in older patients, and latino ethnicity. Additionally, Latino populations are at higher risk of developing B-ALL.IKZF1is an essential lymphoid transcription factor with deletions (ΔIKZF1)implicated in treatment failure and relapses. We aimed to evaluate the frequency ofIKZF1deletions in a cohort of Peruvian patients with newly diagnosed B-ALL. Methods: We collected diagnostic bone marrow samples from 41 consecutive patients with B-ALL diagnosed between 2015-2019 at Instituto Nacional de Enfermedades Neoplasicas (INEN; Lima, Peru). Bone marrow samples were cryopreserved prior to induction treatment. DNA was extracted using High Pure PCR Template Preparation Kit (Roche) at INEN. Samples with adequate DNA were screened forΔIKZF1by multiplex endpoint PCR covering four main deletions - dominant negative Δ4-7 or the loss of function Δ2-7, Δ4-8, and Δ2-8 IKZF1 deletions at UCL Cancer Insitute (London, UK) using the primers described by Caye et. al. We analyzed outcomes byIKZF1status. Results: Forty-one cases were enrolled during the study period. Clinical characteristics are presented in Table 1. Median age was 20 years[1-63]. Fifteen∆IKZF1cases (37%) were detected (67%BCR-ABL1 negand 33%BCR-ABL1pos).Cases withΔIKZF1were older than those with wild-typeIKZF1(median age 31 vs 13 years, p=0.002). Median presenting white blood count (WBC) was 48 x109/L [R:2-218], with a higher WBC inΔIKZF1compared to wild-type (87 vs 24 x109/L, p=0.001). The most frequent deletion was ∆4-7 (sevenBCR-ABL1 negand threeBCR-ABL1 pos) additional deletions are described in table 2. All patients received intensive 'pediatric-based' treatment, 21 with BFM-2009 and 19 with the CALGB 10403 protocol. CR rates after induction were 67% and 92% for∆IKZF1and wild-type cases, respectively. Eleven (73%) of patients with∆IKZF1subjects (73%) were MRD positive by flow cytometry after induction compared to 11 (44%) among wild-type. At a median follow-up of 2 years EFS was 38% in the∆IKZF1group and 58% in the wild type group, correspond OS was 38% and 58%, respectively. Conclusion: A high frequency of IKZF1 deletions was found in a Peruvian population with B-ALL and was associated with older age and higher presenting white blood counts. Prospective studies with larger Latino population are warranted to confirm this finding. Disclosures No relevant conflicts of interest to declare.

scholarly journals Regulation of B Lymphocyte Development by Histone H2A Deubiquitinase BAP1

2021 ◽  
Vol 12 ◽  
Author(s):  
Yun Hsiao Lin ◽  
Yue Liang ◽  
HanChen Wang ◽  
Lin Tze Tung ◽  
Michael Förster ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Cycle Progression ◽  
B Lymphocyte ◽  
Cell Development ◽  
B Cell Development ◽  
Lymphocyte Development ◽  
A Cell ◽  
B Lymphocyte Development

BAP1 is a deubiquitinase (DUB) of the Ubiquitin C-terminal Hydrolase (UCH) family that regulates gene expression and other cellular processes, via deubiquitination of histone H2AK119ub and other substrates. BAP1 is an important tumor suppressor in human, expressed and functional across many cell-types and tissues, including those of the immune system. B lymphocytes are the mediators of humoral immune response, however the role of BAP1 in B cell development and physiology remains poorly understood. Here we characterize a mouse line with a selective deletion of BAP1 within the B cell lineage (Bap1fl/fl mb1-Cre) and establish a cell intrinsic role of BAP1 in the regulation of B cell development. We demonstrate a depletion of large pre-B cells, transitional B cells, and mature B cells in Bap1fl/fl mb1-Cre mice. We characterize broad transcriptional changes in BAP1-deficient pre-B cells, map BAP1 binding across the genome, and analyze the effects of BAP1-loss on histone H2AK119ub levels and distribution. Overall, our work establishes a cell intrinsic role of BAP1 in B lymphocyte development, and suggests its contribution to the regulation of the transcriptional programs of cell cycle progression, via the deubiquitination of histone H2AK119ub.

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