The Linker Protein GAS7 Negatively Regulates Pre-B Cell Differentiation and Amplifies Proliferation and Survival Signals in Acute Lymphoblastic Leukemia

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3777-3777 ◽  
Author(s):  
Jae-Woong Lee ◽  
Maike Buchner ◽  
Huimin Geng ◽  
Srividya Swaminathan ◽  
Eugene Park ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
Tyrosine Kinase ◽  
B Cell ◽  
Lymphoblastic Leukemia ◽  
Growth Arrest ◽  
Strong Increase ◽  
Fusion Partner ◽  
B Cell Differentiation

Abstract Background: Growth arrest-specific gene 7 (Gas7) functions as an adaptor for SH2- and SH3-containing proteins, in particular in cells that undergo growth arrest. Gas7 is abundantly expressed in the brain and is involved in neuronal differentiation. Interestingly, MLL-GAS7 fusion molecules resulting from the t(11;17)(q23;p13) chromosomal translocation have been reported in treatment-related acute myeloid leukemia (AML; Megonigal et al., 2000) and in a pediatric acute lymphoblastic leukemia (ALL). While the function of MLL has been extensively studied, the role of its fusion partner GAS7 in normal hematopoiesis and leukemia has not been elucidated. Results: Studying gene expression changes during normal B cell development, we identified Gas7 as the gene with the strongest relative increase at the pre-B cell receptor checkpoint. At the transition from IL7-dependent Fraction C’ to IL7-independent small resting pre-B cells (Fraction D), GAS7 mRNA levels were upregulated by >13-fold in both human and mouse B cell progenitors. Withdrawal of IL7 cytokine signaling and Cre-mediated conditional deletion of Stat5ab recapitulated the strong increase of GAS7 expression under cell culture conditions. These finding suggest that GAS7 is part of an adaptive response of differentiating pre-B cells to attenuation of cytokine/Stat5 signaling. Consistent with this scenario, we found that Gas7-/-pre-B cells undergo accelerated differentiation, including spontaneous Ig κ light chain gene recombination and loss of Stat5-signaling. Conversely, overexpression of GAS7, reduced responsiveness of pre-B cells to normal differentiation stimuli. These findings suggest that the linker molecule GAS7 is a negative regulator of pre-B cell differentiation. Likewise, we found that tyrosine kinase inhibitor treatment of human Ph+ ALL cells resulted in a strong increased of GAS7 expression, in parallel with loss of Stat5 function. To elucidate the function of Gas7 in B cell lineage leukemia, we transformed bone marrow pre-B cells from Gas7-/- mice with BCR-ABL1. Gas7 deficient Ph+ ALL cells showed decreased proliferation with reduced S phase and increased apoptosis. In agreement with effects of Stat5 on the sensitivity of Ph+ ALL cells against tyrosine kinase inhibitors (TKIs), Gas7 deficient Ph+ ALL cells showed massively increased susceptibility to Imatinib-induced apoptosis. In addition, absence of Gas7 caused loss of self-renewal capacity and failure to form colonies in methylcellulose assay. Co-immunoprecipitation experiments with flag tagged GAS7 in patient-derived Ph+ALL cells revealed that GAS7 physically interacts with STAT5 and retains STAT5-Y694 in an active conformation.Thereby, GAS7 can propagate even weak Stat5 activity and maintain residual cytokine or BCR-ABL1 oncogenic signaling in normal and malignant pre-B cells. Conclusions: Here show that GAS7 functions as an important positive regulator of Stat5 downstream of cytokine receptors in normal pre-B cells and downstream of BCR-ABL1 and other oncogenes in leukemia. Owing to the GAS7-dependent reinforcement of Stat5-dependent survival and proliferation signaling, normal and leukemic pre-B cells can survive periods of reduced cytokine/oncogene signaling. These findings suggest that the interaction interface between GAS7 and Stat5 represents a potential target for small molecule scaffolds and peptides. Disclosures No relevant conflicts of interest to declare.

scholarly journals Deletion of genes encoding PU.1 and Spi-B in B cells impairs differentiation and induces pre-B cell acute lymphoblastic leukemia

Blood ◽  
2011 ◽  
Vol 118 (10) ◽  
pp. 2801-2808 ◽  
Author(s):  
Kristen M. Sokalski ◽  
Stephen K. H. Li ◽  
Ian Welch ◽  
Heather-Anne T. Cadieux-Pitre ◽  
Marek R. Gruca ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
Lymphoblastic Leukemia ◽  
Cell Lineage ◽  
B Cell Differentiation ◽  
Cell Acute Lymphoblastic Leukemia ◽  
Ets Transcription Factor

Abstract The E26 transformation-specific (Ets) transcription factor PU.1 is required to generate lymphoid progenitor cells from hematopoietic stem cells, but it is not required to generate B cells from committed B-cell lineage progenitors. We hypothesized that PU.1 function in B-cell differentiation is complemented by the related Ets transcription factor Spi-B. To test this hypothesis, mice were generated lacking both PU.1 and Spi-B in the B-cell lineage. Unlike mice lacking PU.1 or Spi-B, mice deficient in both PU.1 and Spi-B in the B-cell lineage had reduced frequencies of B cells as well as impaired B-cell differentiation. Strikingly, all PU.1 and Spi-B–deficient mice developed pre-B cell acute lymphoblastic leukemia before 30 weeks of age. Pre-B cells accumulated in the thymus resulting in massive thymic enlargement and dyspnea. These findings demonstrate that PU.1 and Spi-B are essential transcriptional regulators of B-cell differentiation as well as novel tumor suppressors in the B-cell lineage.

The Balance between Myc and Bcl6 Determines Self-Renewal or Differentiation of Pre-B Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 797-797 ◽  
Author(s):  
Cihangir Duy ◽  
Ignacio Moreno de Alboran ◽  
Hassan Jumaa ◽  
Markus Muschen
Keyword(s):  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
De Novo ◽  
Lymphoblastic Leukemia ◽  
B Cell Development ◽  
B Cell Differentiation ◽  
Self Renewal ◽  
Immature B Cells

Abstract Myc and Bcl6 represent classical proto-oncogenes in B-cell malignancies, mainly through translocation into the immunoglobulin (Ig) heavy chain locus in Burkitt’s (MYC) and diffuse large B cell lymphoma (BCL6). While BCL6 was previously established as a factor regulating differentiation of germinal center B cells, the function of MYC and BCL6 in early B-cell development was not previously studied. Investigating requirements for the differentiation of pre-B cells into immature B-cells, we found that both withdrawal of IL7 from murine pre-B-cell cultures and inhibition of BCR-ABL1 in BCR-ABL1-transformed pre-B-cells terminates self-renewal and initiates differentiation into Ig light chain-expressing immature B-cells. Interestingly, IL7 and BCR-ABL1 are exchangeable at this checkpoint: Both IL7 and BCR-ABL1 promote self-renewal and prevent differentiation of pre-B-cells. While inhibition of BCR-ABL1 usually induces apoptosis and partial differentiation, both effects were entirely suppressed by IL7. These findings indicate that IL7 may confer resistance to BCR-ABL1 inhibitors in patients with BCR-ABL1-transformed acute lymphoblastic leukemia. Likewise, inhibition of either IL7 or BCR-ABL1 signaling resulted in complete silencing of Myc expression and strong de novo expression of Bcl6. Because expression of Myc and Bcl6 are mutually exclusive at the pre-B to immature B-cell checkpoint, we tested whether the two proto-oncogenes have distinct functions at this transition. Interestingly, forced expression of Myc rendered BCR-ABL1-transformed pre-B-cells resistant to induction of differentiation upon inhibition of BCR-ABL1. Besides downregulation of Myc, also de novo expression of Bcl6 is critical for the pre-B to immature B-cell differentiation: shmiR-mediated silencing of Bcl6 suppressed B-cell differentiation even if Myc was downregulated. However, forced expression of Bcl6 alone only modestly induced differentiation of pre-B cells if Myc was not downregulated. To test the interplay between Myc and Bcl6 at the pre-B to immature B cell transition more systematically, we analyzed bone marrow pre-B cells from Mycfl/fl mice. Mycfl/fl pre-B cells that also carry MxCre deleted the Myc locus on both alleles upon stimulation with IFNß. As controls, Mycfl/fl pre-B cells without MxCre were used. Pre-B cells were also transduced with a retroviral vector encoding Bcl6/GFP or GFP alone. Upon Myc deletion, more than 80 precent of the Bcl6/GFP transduced pre-B cells underwent differention as compared to 25 percent GFP-transduced pre-B cells. In the absence of Myc deletion, about 15 percent of Bcl6/GFP-transduced pre-B cells initiated differentiation as compared to 5 percent of GFP-transduced pre-B cells. These findings establish that Myc and Bcl6 have critical and antagonistic functions in early B cell development and that both downregulation of Myc together with upregulation Bcl6 are required to initiate differentiation of pre-B cells. The MYC/BCL6 balance may also be a target of leukemic transformation of human pre-B cells: The ratio of MYC/BCL6 mRNA levels in normal human pro- and pre-B cells at 0.52 is dramatically increased in various subtypes of acute lymphoblastic leukemia (6.4 for BCR-ABL1-, 2.6 for E2A-PBX1-, 14.4 for MLL-AF4- and 3.3 for TEL-AML1-transformed acute lymphoblastic leukemia).

scholarly journals Expression of A-myb, but not c-myb and B-myb, is restricted to Burkitt's lymphoma, sIg+ B-acute lymphoblastic leukemia, and a subset of chronic lymphocytic leukemias

Blood ◽  
1996 ◽  
Vol 87 (5) ◽  
pp. 1900-1911 ◽  
Author(s):  
J Golay ◽  
M Luppi ◽  
S Songia ◽  
C Palvarini ◽  
L Lombardi ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Lymphoblastic Leukemia ◽  
Burkitt’S Lymphoma ◽  
Burkitt's Lymphoma ◽  
B Cell Differentiation

Abstract The A-myb gene encodes a transcription factor that is related both functionally and structurally to the v-myb oncogene. Following our observations that A-myb is expressed in a restricted subset of normal mature human B lymphocytes, with the phenotype CD38+, CD39-, slgM-, we have now investigated the pattern of A-myb expression in neoplastic B cells representating the whole spectrum of B-cell differentiation and compared it to that of c-myb and B-myb. In a panel of 32 B-cell lines, A-myb was very strongly expressed in most Burkitt's lymphoma (BL) cell lines, but weak or negative in 2 pre-B acute lymphoblastic leukemia (ALL), 4 non-Hodgkin's lymphoma (NHL), 6 Epstein-Barr virus- immortalized lymphoblastoid cell lines, and 6 myeloma lines. Protein expression paralleled that of the RNA. We have also investigated A-myb expression in 49 fresh cases of B leukemias. Among 24 ALL, 6 were of the null and 11 of the common type and all these were negative for A- myb expression; on the other hand, all 7 B-ALL cases (slg+), as well as one fresh BL case with bone marrow infiltration, expressed A-myb. A-myb was undetectable in 4 prolymphocytic leukemias (PLL) but was strongly expressed in 5/20 (25%) of chronic lymphocytic leukemia (CLL) samples. In the latter A-myb did not correlate with phenotype or clinical stage. Finally, we have studied the progression of one case of CLL into Richter's syndrome and have found that the Richter's cells expressed about 25-fold less A-myb RNA than the CLL cells from the same patient. The pattern of c-myb and B-myb was clearly distinct from that of A-myb. C-myb and B-myb were expressed in all neoplastic groups, except in CLL cells. Thus, A-myb expression, unlike that of c-myb and B-myb, is restricted to a subset of B-cell neoplasias (in particular BL and slg+B- ALL) representative of a specific stage of B-cell differentiation. This expression may in part reflect expression of A-myb by the normal germinal center B cells that are the normal counterpart of these transformed B cells. The data presented strongly support a role for this transcription factor in B-cell differentiation and perhaps in B- cell transformation in some neoplasias.

scholarly journals Expression of A-myb, but not c-myb and B-myb, is restricted to Burkitt's lymphoma, sIg+ B-acute lymphoblastic leukemia, and a subset of chronic lymphocytic leukemias

Blood ◽  
1996 ◽  
Vol 87 (5) ◽  
pp. 1900-1911 ◽  
Author(s):  
J Golay ◽  
M Luppi ◽  
S Songia ◽  
C Palvarini ◽  
L Lombardi ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Lymphoblastic Leukemia ◽  
Burkitt’S Lymphoma ◽  
Burkitt's Lymphoma ◽  
B Cell Differentiation

The A-myb gene encodes a transcription factor that is related both functionally and structurally to the v-myb oncogene. Following our observations that A-myb is expressed in a restricted subset of normal mature human B lymphocytes, with the phenotype CD38+, CD39-, slgM-, we have now investigated the pattern of A-myb expression in neoplastic B cells representating the whole spectrum of B-cell differentiation and compared it to that of c-myb and B-myb. In a panel of 32 B-cell lines, A-myb was very strongly expressed in most Burkitt's lymphoma (BL) cell lines, but weak or negative in 2 pre-B acute lymphoblastic leukemia (ALL), 4 non-Hodgkin's lymphoma (NHL), 6 Epstein-Barr virus- immortalized lymphoblastoid cell lines, and 6 myeloma lines. Protein expression paralleled that of the RNA. We have also investigated A-myb expression in 49 fresh cases of B leukemias. Among 24 ALL, 6 were of the null and 11 of the common type and all these were negative for A- myb expression; on the other hand, all 7 B-ALL cases (slg+), as well as one fresh BL case with bone marrow infiltration, expressed A-myb. A-myb was undetectable in 4 prolymphocytic leukemias (PLL) but was strongly expressed in 5/20 (25%) of chronic lymphocytic leukemia (CLL) samples. In the latter A-myb did not correlate with phenotype or clinical stage. Finally, we have studied the progression of one case of CLL into Richter's syndrome and have found that the Richter's cells expressed about 25-fold less A-myb RNA than the CLL cells from the same patient. The pattern of c-myb and B-myb was clearly distinct from that of A-myb. C-myb and B-myb were expressed in all neoplastic groups, except in CLL cells. Thus, A-myb expression, unlike that of c-myb and B-myb, is restricted to a subset of B-cell neoplasias (in particular BL and slg+B- ALL) representative of a specific stage of B-cell differentiation. This expression may in part reflect expression of A-myb by the normal germinal center B cells that are the normal counterpart of these transformed B cells. The data presented strongly support a role for this transcription factor in B-cell differentiation and perhaps in B- cell transformation in some neoplasias.

A Critical Role of Blockade of Cell Differentiation in BCR-ABL-Induced B-Cell Acute Lymphoblastic Leukemia (B-ALL): Basis for Superb Therapeutic Effect on B-ALL in Mice by Promotion of Pro-B Leukemic Cell Differentiation and Treatment with Imatinib.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 844-844
Author(s):  
Yiguo Hu ◽  
Linghong Kong ◽  
Kevin Staples ◽  
Kevin Mills ◽  
John G. Monroe ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cell ◽  
Myeloid Leukemia ◽  
Lymphoblastic Leukemia ◽  
Leukemic Cell ◽  
Leukemic Cells ◽  
B Cell Differentiation ◽  
Cell Acute Lymphoblastic Leukemia

Abstract The BCR-ABL oncogene induces human Philadelphia-positive (Ph+) B-cell acute lymphoblastic leukemia (B-ALL) and chronic myeloid leukemia (CML) that advances to acute phase of CML called blast crisis. In this acute phase, CML patients can develop either B-ALL or acute myeloid leukemia. In B-ALL, differentiation of leukemic cells are blocked at pro-/pre-B stage, and the underlying mechanism is unknown. We hypothesize that this blockade of B-cell differentiation may be important for the development of B-ALL induced by BCR-ABL, and if so, promotion of B-leukemic cell differentiation would create a novel therapeutic strategy for B-ALL. To test this hypothesis, we first compared the percentages of IgM+ B-leukemic cells in BALB/c and C57BL/6 (B6) mice with BCR-ABL-induced B-ALL, because we have previously found that B-ALL develops more quickly in BALB/c mice than in B6 mice (Li et al, J. Exp. Med.189:1399–1412, 1999). We expressed BCR-ABL in bone marrow (BM) using retroviral transduction and transplantation in these two different strains of inbred mice to induce B-ALL. There were significantly more peripheral blood B220+ B cells in BALB/c B-ALL mice than those in B6 mice, correlating to faster B-ALL in BALB/c mice than in B6 mice. Among these B220+ cells, IgM+ cells were much less in BALB/c mice than in B6 mice. We also compared rearrangement of the B cell antigen receptor (BCR) heavy chains (m chains) between BALB/c and B6 backgrounds using BCR-ABL-expressing pro-B cell lines isolated from the B-ALL mice. Normal m chains rearrangement was found in B6 leukemic cells, but not in BALB/c leukemic cells. These results indicate that more differentiated B-leukemic cells are associated with less aggressive disease. To further demonstrate the role of blockade of B-cell differentiation in B-ALL development, we induced B-leukemic cell differentiation by co-expression of BCR-ABL and intact immunoregulatory tyrosine activation motifs (ITAM) contained in immunoglobulin (Ig)_/Igß complexes in BM cells of B-ALL mice, comparing to expression of BCR-ABL alone. We treated these mice with imatinib (orally, 100 mg/kg, twice a day). The treated mice with B-ALL induced by co-expression of BCR-ABL and ITAM lived three-week longer than those with B-ALL induced by BCR-ABL only, with some mice in long-term remission. Prolonged survival was associated with 50% increased B220+/IgM+ B-leukemic cells in peripheral blood of the mice. Taken together, our results demonstrate that blockade of B-cell differentiation is critical for the development of B-ALL induced by BCR-ABL, and provide a rationale for combination therapy of B-ALL with imatinib and induction of leukemic cell differentiation.

scholarly journals Downregulation of Mir-142 Promotes Leukemia Growth in Philadelphia Chromosome-Positive (Ph+) Acute Lymphoblastic Leukemia (ALL): A Possible Novel Therapeutic Target?

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1338-1338
Author(s):  
Huafeng Wang ◽  
Bin Zhang ◽  
Wei-Le Wang ◽  
Dandan Zhao ◽  
Ling Li ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Tyrosine Kinase ◽  
B Cell ◽  
Median Survival ◽  
Lymphoblastic Leukemia ◽  
Rapid Expansion ◽  
B Cell Differentiation ◽  
Hematopoietic Stem ◽  
Knock Out ◽  
Healthy Donors

Abstract The Philadelphia (Ph) chromosome or t(9;22) results in the generation of a fusion gene, namely BCR/ABL1, which encodes a chimeric protein with aberrant tyrosine kinase activity that drives leukemia cell growth and survival. This molecular/cytogenetic aberration occurs in ~20%-30% of ALL cases and confers poor prognosis. Ph+ ALL patients (pts) are often referred for allogeneic hematopoietic stem cell transplantation (alloHCT), although more recently BCR-ABL-specific tyrosine-kinase inhibitors (TKIs) and immunotherapeutic approaches seemingly induced long-term remission in some patients. Nevertheless, it is still a challenge to determine which Ph+ ALL of the pts could be treated more conservatively without alloHCT. Thus identification of new prognostic biomarkers and/or therapeutic targets may be helpful. Regulation of short non-coding microRNAs(miRNAs) associated with initiation and progression of acute leukemia has been reported. miR-142(both miR-142-3p and miR-142-5p) is expressed at a relatively high level in hematopoietic tissue, and plays a role in myeloid lineage differentiation. In fact, low miR-142-3p expression was associated with myeloid differentiation failure, and miR-142 mutations was reported to promote acute myeloid leukemia (AML). More recently, Kramer et al demonstrated a role of miR-142 in lymphopoiesis by showing that miR-142 deficiency impaired B cell production in a miR-142 knock-out(ko) mouse model (Blood. 2015). Here, we first investigated if miR-142 levels were altered in ALL pts. Analysis of a publically available miRNA expression dataset(GSE23024) showed lower level of miR-142-3p, but not miR-142-5p in Ph+ ALL pts(n=10) vs. healthy donors(n=7;p=0.0093); while no significant differences were observed in Ph- pre-B ALL pts(n=61) vs. healthy donors (n=7). In ALL Tg(P190-BCR/ABL) transgenic mice(Ph+ ALL; Nature. 1990), we found bone marrow (BM) miR-142-3p level to be ~2.3-fold lower than those in the wild-type (wt) controls(p=0.036). Compared to wt mice, Ph+ ALL mice showed significantly lower miR-142-3p level in all the immunophenotypically identified BM lymphoid subpopulations, including progenitor B (pro-B, B220+CD19+CD43+IgM-,~19.1-fold lower,p<0.0001), precursor B (pre-B, B220+CD19+CD43-IgM-,~9.7-fold lower, p<0.0001), and other immature B (B220lowCD19+CD43-IgM+, ~2.4-fold lower, p<0.001) cells, except for mature B (B220highCD19+CD43-IgM+) cells. Ph+ ALL mice exhibited a miR-142-3p gradient expression pattern following the lymphoid differentiation hierarchy, with the lowest levels found in the pro-B and pre-B populations. These results prompted us to hypothesize that, loss of miR-142 may contribute to primitive B cell expansion possibly due to B cell differentiation blockage in Ph+ ALL mice. To prove this, we crossed miR-142 double knock-out (d-ko)mice with Ph+ ALL mice to generate miR-142(ko)Tg(P190-BCR/ABL) mice. Homozygous miR-142(d-ko)Tg(P190-BCR/ABL) mice were not viable due to an overly aggressive leukemia phenotype. Heterozygous miR-142(wt/ko)Tg(P190-BCR/ABL) mice had evidence of more rapid expansion of pro-B cells in blood(PB; 47.9% vs. 9.8%, p<0.0001), BM (48.2% vs. 13.2%, p<0.01)and spleen(32.3%vs. 4.4%, p<0.01) at 6 weeks old and a significantly reduced survival(median survival 44 vs.80 days, p<0.0001), compared to miR-142(wt/wt)Tg(P190-BCR/ABL) controls. BM cells (CD45.2) from miR-142(wt/ko)Tg(P190-BCR/ABL) mice (n=4) or miR-142(wt/wt)Tg(P190-BCR/ABL) mice (n=5) were then transplanted into congenic CD45.1 recipient mice (n=18 and n=15 respectively).Recipients of BM cells from miR-142(wt/ko)Tg(P190-BCR/ABL) donors showed increased engraftment (94% vs. 77% in PB at 4 weeks, p<0.0001) and significantly reduced survival(median survival 25 vs. 49 days, p<0.0001), as compared with recipients of BM cells from miR-142(wt/wt)P190-BCR-ABL mice. Finally, upon ex vitro exposure to the TKI nilotinib (5uM for 48 hours), miR-142(wt/ko)Tg(P190-BCR/ABL) BM cells showed reduced apoptosis (7.0% vs.37.5% vs p<0.05) and increased cell viability (66% vs.16.2%, p<0.05) compared with miR-142 (wt/wt)Tg(P190-BCR/ABL) BM cells. In vivo treatment studies with TKI treatment are ongoing and data will be presented at the meeting. In conclusion, miR-142 downregulation promotes rapid Ph+ ALL growth likely by contributing to a blockage of B cell differentiation, and may mediate resistance to TKIs. Disclosures Stein: Celgene: Speakers Bureau; Amgen Inc.: Speakers Bureau. Jin:The National Natural Science Foundation of China: Research Funding; College of Medicine, Zhejiang University: Employment.

scholarly journals Germline PAX5 mutation predisposes to familial B acute lymphoblastic leukemia

Blood ◽  
2020 ◽  
Author(s):  
Nicolas Duployez ◽  
Laura Audrey Jamrog ◽  
Vincent Fregona ◽  
Camille Hamelle ◽  
Laurène Fenwarth ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
Genetic Basis ◽  
Target Genes ◽  
Lymphoblastic Leukemia ◽  
Convincing Evidence ◽  
B Cell Differentiation ◽  
Transcriptional Deregulation ◽  
Genome Analyses

In recent years, through whole genome analyses, convincing evidence for the contribution of genetic predisposition to childhood B-cell precursor - acute lymphoblastic leukemia (BCP-ALL) due to altered PAX5 has been provided. A recurrent mutation p.Gly183Ser affecting the octapeptide domain has been described in three unrelated families and a p.Arg38His mutation affecting the DNA-binding paired domain reported in another one. We strengthen here the assumption of the inherited character of familial BCP-ALL by identifying the PAX5 p.Arg38His mutation in a family in which the three children developed BCP-ALL. One relapsed two years after his initial diagnosis and was allografted with his brother's cells before the latter developed BCP-ALL. The patient allografted relapsed later from donor-related cells. By syngeneic transplantations in mice, we showed that p.Arg38His expression does not abrogate the engraftment capacity of transduced Pax5-/- pro-B cells unlike wild type PAX5-rescued Pax5-/- pro-B cells and can predispose to BCP-ALL. Through functional and molecular analyses, we demonstrated that p.Arg38His acts as a hypomorphic variant altering the pattern of expression of PAX5 target genes. Our data highlight the importance of transcriptional deregulation, particularly of genes involved in B cell differentiation in familial BCP-ALL. We demonstrated that inherited genetic basis of susceptibility to BCP-ALL has been underestimated and should be considered before any familial allograft.

IKZF1 (IKAROS) Deletions Are Independent On BCR-ABL1 Rearrangement and Are Associated with a Peculiar Gene Expression Signature and Poor Prognosis in Adult B-Progenitor Acute Lymphoblastic Leukemia (ALL) Patients.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 912-912
Author(s):  
Ilaria Iacobucci ◽  
Monica Messina ◽  
Nunzio Iraci ◽  
Annalisa Lonetti ◽  
Sabina Chiaretti ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Damage ◽  
Transcription Factor ◽  
Cell Differentiation ◽  
Acute Lymphoblastic Leukemia ◽  
B Cell ◽  
Lymphoblastic Leukemia ◽  
B Cell Differentiation ◽  
Poor Outcome ◽  
Stat Pathway

Abstract Abstract 912 Background: Recent genome-wide analyses in B-precursor acute lymphoblastic leukemia (ALL) demonstrated that deletions of IKZF1, which encodes the transcription factor Ikaros, play an important role in the pathogenesis of BCR-ABL1-positive and BCR-ABL1-like acute leukemias. IKZF1 deletions have been associated with poor outcome in children with ALL but a full understanding of their biological implications and clinical significance has not yet been defined in adult patients. Purpose and Methods: In order to address this issue and to evaluate whether the cases harbouring IKZF1 alterations display a peculiar gene expression profile, a cohort of 144 adult de novo ALL patients (106 BCR-ABL1-postive and 38 B-progenitor ALL negative for known molecular rearrangements) were analyzed with the use of single-nucleotide–polymorphism (SNP) microarrays (Affymetrix 250K NspI and SNP 6.0), FISH for IKZF1 deletions and gene expression profiling (HGU133 Plus 2.0 gene chips, Affymetrix). Patients had a median age of 49 years (range 18-78) and were enrolled into institutional (n = 17) or GIMEMA AL Working Party (n = 121) clinical trials. Results: Deletions of IKZF1 were identified in 75% adult BCR-ABL1-positive and in 58% BCR-ABL1-negative ALL cases, suggesting that IKZF1 deletion is more frequent in the BCR-ABL1-positive ALL subtype (p= 0.04). FISH analysis using a pool of fosmid probes for IKZF1 and genomic quantitative PCR confirmed SNP results. Among 144 patients, the entire IKZF1 locus was deleted in 18 (13%) whereas in 84 (58%) patients only a subgroup of exons or the genomic region immediately upstream of IKZF1 was deleted. In particular, in 46 patients (32%) there was a deletion of the coding exons 4 through 7, which resulted in the expression of a dominant-negative isoform, Ik6, lacking the DNA binding domain. In 24 cases (17%) we identified the loss of exons 2 through 7, producing an Ikaros isoform lacking the translation start site. Using gene-set enrichment analysis to compare the gene-expression data from patients with IKZF1 deletion versus wild-type patients, we identified a peculiar signature irrespective of BCR-ABL1 rearrangement but dependent on IKZF1 genomic status. Indeed, it was characterized by the presence of two subgroups of genes, the expression of which was deregulated in a reciprocal fashion. One subgroup was enriched with up-regulated genes involved in cell-cycle progression (STK17B, SERPINB9, CDKN1A), activation of signalling via JAK-STAT pathway (CISH, SOCS1, SOCS3, STAT3) and DNA damage (GADD45A, GADD45B, NFKBIA, the protoncogene REL). The second subgroup contained down-regulated genes, which are normally expressed during lymphocyte differentiation (e.g. VPREB1, VPREB3, IGLL3, BLK) or are involved in DNA damage repair (MSH2, MSH6) supporting the hypothesis that B-ALL cells with IKZF1 deletions are prone to a block of B-cell differentiation and accumulation of DNA damage events. To investigate whether Ikaros transcription factor is directly involved in the regulation of putative target genes identified in gene expression analysis, cross-linking chromatin immunoprecipitation (ChIP) assay was performed in cell lines and primary ALL cells. We found that the promoters of IGGL1, CD79A, BLK, EBF1, BLC2, MSH2, BUB3, ETV6, YES1, CDKN1A (p21) and CDKN2C (p18) genes, were bound in vivo only by Ikaros full-length protein, but not by Ik6 mutant. These data strongly support a model in which Ikaros deleted isoforms loose the ability to regulate a large set of genes, many of which may play crucial roles in B-ALL development. We next investigated whether the IKZF1 deletions associated with a poor outcome in ALL patients. Univariate analysis showed that the IKZF1 deletion negatively influenced the cumulative incidence of relapse (p=0.02) and disease-free survival (p=0.04, Wilcoxon test) as confirmed by multivariate analysis. Conclusion: In conclusion, our findings shed light on a new subgroup of adult ALL including BCR-ABL1 positive and BCR-ABL1 negative patients and characterized by a unique signature dependent on Ikaros genomic status. Loss of normal Ikaros activity results in the activation of JAK-STAT pathway, DNA repair gene down-regulation and a block of B-cell differentiation. Supported by: European LeukemiaNet, AIL, AIRC, FIRB 2006, Strategico di Ateneo, GIMEMA Onlus. Disclosures: No relevant conflicts of interest to declare.

Ikaros Mutation Confers Integrin-Dependent Survival Of Pre-B Cells and Progression To Acute Lymphoblastic Leukemia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1259-1259
Author(s):  
Nilamani Jena ◽  
Ila Joshi ◽  
Toshimi Yoshida ◽  
Xiaoqing Qi ◽  
Jiangwen Zhang ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
Dna Binding ◽  
B Cell ◽  
Focal Adhesion ◽  
Lymphoblastic Leukemia ◽  
Cell Receptor ◽  
Mapk Signaling ◽  
Dominant Negative ◽  
B Cell Differentiation

Abstract Deletion of the IKAROS DNA-binding domain generates dominant-negative isoforms that interfere with the transcriptional activity of the IKAROS family and correlate with poor prognosis in human precursor B cell acute lymphoblastic leukemias (B-ALL). In this study, we defined the role of the Ikaros family during pre-B cell differentiation, the stage from which human B-ALLs arise, by conditionally inactivating IKAROS DNA binding in the immediate precursors of pre-B cells in mice. We demonstrate a novel niche-dependent phase in early pre-B cell differentiation that supports self-renewal and proliferative expansion. Expression of dominant-negative IKAROS arrests cells in this state by augmenting integrin and MAPK signaling and attenuating pre-B cell receptor signaling and differentiation. Up-regulated genes in Ikaros mutant pre-B cells were highly enriched in pathways involved in focal adhesion and remodeling of the actin cytoskeleton. The mutant pre-B cells had increased β1 integrin-mediated adhesion and elevated levels of activated focal adhesion kinase (FAK), whereas treatment with a small molecule FAK inhibitor greatly reduced pre-B cell stromal adhesion and selectively induced apoptosis in Ikaros mutant but not WT pre-B cells. Transplantation of polyclonal Ikaros mutant pre-B cells into recipient mice resulted in long-latency oligoclonal pre-B-ALL, demonstrating that loss of IKAROS contributes to multistep B-leukemogenesis. The highly proliferative and aberrantly self-renewing phenotype of Ikaros-deficient pre-B cells illuminates mechanisms underlying human IKAROS mutant B-ALL and suggests new therapeutic strategies for treatment of this aggressive leukemia. Disclosures: Van Etten: Bristol Myers Squibb: Consultancy; Deciphera Pharmaceuticals: Consultancy; TEVA Pharmaceuticals: Consultancy, Research Funding.

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