Sumoylation Inhibits the Growth Suppressive Properties of Ikaros.

The Ikaros transcription factor is a tumor suppressor that is also important for lymphocyte development. How post-translational modifications influence Ikaros function remains partially understood. We show that Ikaros undergoes sumoylation in developing T cells that correspond to mono-, bi- or poly-sumoylation by SUMO1 and/or SUMO2/3 on three lysine residues (K58, K240 and K425). Sumoylation occurs in the nucleus and requires DNA binding by Ikaros. Sumoylated Ikaros is less effective than unsumoylated forms at inhibiting the expansion of murine leukemic cells, and Ikaros sumoylation is abundant in human B-cell acute lymphoblastic leukemic cells, but not in healthy peripheral blood leukocytes. Our results suggest that sumoylation may be important in modulating the tumor suppressor function of Ikaros

Large deletions of the 5' region of IKZF1 lead to haploinsufficiency in B-cell precursor acute lymphoblastic leukaemia

No abstract availabl

Azacitidine Plus Venetoclax for the Treatment of Relapsed and Newly Diagnosed Acute Myeloid Leukemia Patients

International audienceVenetoclax (VEN) belongs the BH3-mimetic class that selectively targets BCL-2, activating apoptosis. The combination of VEN and azacitidine (AZA) has changed the paradigm of treatment of newly diagnosed (ND) acute myeloid leukemia (AML) patients ineligible for intensive chemotherapy. There is scarce evidence for the use of VEN–AZA for relapsed or refractory (R/R) AML. We compared the outcome of 39 R/R AML and 38 ND AML patients treated between 01/20 and 12/21. The median age was 69 (22–86) and 73 (61–81) in the R/R and ND groups, respectively. Adverse cytogenetics were found in 36% of patients in the R/R group and 59% of patients in the ND group. Overall response rate was 37% in R/R AML, including 13% CR, 8% CRi, 3% PR and 13% MLFS, and 58% in the ND AML, including 32% CR, 13% CRi and 13% MLFS. Adverse cytogenetics was associated with treatment failure in the R/R group (Relative Risk = 0.13, p = 0.005). Median overall survival (OS) was 5.9 months in the R/R group and 9.4 months in the ND group. Median OS was 2.2 months in the adverse cytogenetics group versus 8.7 months in the intermediate cytogenetics group in the R/R group (p = 0.02). Median leukemia-free survival was not different between the two groups (9.4 months and 10.3 months), indicating that VEN–AZA can be an efficient salvage treatment for selected R/R AML patients. In conclusion, VEN–AZA is a promising treatment for ND AML and for selected R/R AML patients

Impact of Ikaros mutations on sumoylation.

<p><b>(A)</b> Schematic representation of Ik1-ER deletion mutants. (<b>B</b>) Modification pattern of Ik1-ER deletion mutants. ILC87 cells expressing Ik1-ER or deletion mutants were treated and lysed as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157767#pone.0157767.g001" target="_blank">Fig 1D</a>. Nuclear extracts were immunoprecipitated with an anti-ER antibody, separated by SDS-PAGE (6%) and analyzed with anti-Ikaros antibodies against C-terminal or N-terminal epitopes. (<b>C</b>) Nuclear extracts from 50x10⁶ ILC87 cells expressing Ik1-ER or the indicated point mutants were immunoprecipitated with an anti-ER antibody, separated on a NuPAGE Novex 3–8% Tris-Acetate gel and analyzed with an anti-Ikaros antibody. The pattern of the various modified proteins is schematized on the right and the corresponding modifications indicated. In (B) and (C), arrowheads point to unmodified proteins.</p

Genetic characterization of B-cell prolymphocytic leukemia: a prognostic model involving and MYC and TP53

B-cell prolymphocytic leukemia (B-PLL) is a rare hematological disorder whose underlying oncogenic mechanisms are poorly understood. Our cytogenetic and molecular assessment of 34 patients with B-PLL revealed several disease-specific features and potential therapeutic targets. The karyotype was complex ({greater than or equal to}3 abnormalities) in 73% of the patients and highly complex (5 abnormalities) in 45%. The most frequent chromosomal aberrations were translocations involving [t()] (62%), deletion (del)17p (38%), trisomy (tri)18 (30%), del13q (29%), tri3 (24%), tri12 (24%), and del8p (23%). Twenty-six of the 34 patients (76%) exhibit aberration, resulting from mutually exclusive translocations or gains. Whole-exome sequencing revealed frequent mutations in , , , , , , , , and The majority of B-PLL used the or subgroups (89%), and displayed significantly mutated genes (79%). We identified three distinct cytogenetic risk groups: low-risk (no aberration), intermediate-risk ( aberration but no del17p), and high-risk ( aberration and del17p) (p=.0006). drug response profiling revealed that the combination of a B-cell receptor or BCL2 inhibitor with OTX015 (a bromodomain and extra-terminal motif (BET) inhibitor targeting ) was associated with significantly lower viability of B-PLL cells harboring a t(). We conclude that cytogenetic analysis is a useful diagnostic and prognostic tool in B-PLL. Targeting may be a useful treatment option in this disease

Sumoylation limits the growth-inhibitory effects of Ikaros.

<p><b>(A)</b> Western blot showing similar level of Ik1-ER and Ik-TM-ER proteins in nuclear extracts of ILC87-Ik1-ER and ILC87-Ik-TM-ER cells treated with EtOH or 4OHT. <b>(B)</b> Scatter plots showing the distributions of the fold changes (4OHT- vs EtOH-treated cells, expressed as log2 values) in the 2 independent analyses performed with ILC87-Ik1-ER cells (top panel), or between representative analyses performed with ILC87-Ik1-ER and ILC87-Ik-TM-ER cells (bottom panel). The red diagonal highlights the theoritical position for probe sets with similar fold-changes. <b>(C)</b> RT-qPCR analysis of repression of the <i>Mpzl2</i> and <i>Scn4b</i> genes in ILC87-Ik1-ER and ILC87-Ik-TM-ER cells treated with 4OHT for 24h, in 2 independent experiments (duplicate measurements in each case). <b>(D-F)</b> Competitive growth inhibition assay. <b>(D)</b> Experimental setup: ILC87 cells transduced with IK1-ER or Ik-TM-ER (GFP⁺) were mixed at a 1:1 ratio with ILC87 cells (or ILC87 cells mock-transduced with an empty Mig-NGFR retrovirus) and cultured for 6 days in the presence of EtOH or 4OHT. <b>(E)</b> Proportion of GFP⁺ cells in living cells of EtOH and 4OHT-treated ILC87-Ik1-ER and ILC87-Ik-TM-ER cells in a representative experiment. <b>(F)</b> Growth inhibition over time by Ik1-ER and Ik-TM-ER (ratio of GFP⁺ cells in 4OHT-treated over EtOH-treated samples; average of 4 experiments). Statistical significance was evaluated with a Student's t-test.</p

Clinical and biological features of B‐cell neoplasms with CDK6 translocations: an association with a subgroup of splenic marginal zone lymphomas displaying frequent CD5 expression, prolymphocytic cells, and TP53 abnormalities

International audienceA translocation involving the cyclin‐dependent kinase 6 (CDK6) gene [t(CDK6)] is a rare but recurrent abnormality in B‐cell neoplasms. To further characterise this aberration, we studied 57 cases; the largest series reported to date. Fluorescence in situ hybridisation analysis confirmed the involvement of CDK6 in all cases, including t(2;7)(p11;q21) immunoglobulin kappa locus (IGK)/CDK6 (n = 51), t(7;14)(q21;q32) CDK6/immunoglobulin heavy locus (IGH) (n = 2) and the previously undescribed t(7;14)(q21;q11) CDK6/T‐cell receptor alpha locus (TRA)/T‐cell receptor delta locus (TRD) (n = 4). In total, 10 patients were diagnosed with chronic lymphocytic leukaemia, monoclonal B‐cell lymphocytosis or small lymphocytic lymphoma, and 47 had small B‐cell lymphoma (SmBL) including 36 cases of marginal zone lymphoma (MZL; 34 splenic MZLs, one nodal MZL and one bronchus‐associated lymphoid tissue lymphoma). In all, 18 of the 26 cytologically reviewed cases of MZL (69%) had an atypical aspect with prolymphocytic cells. Among the 47 patients with MZL/SmBL, CD5 expression was found in 26 (55%) and the tumour protein p53 (TP53) deletion in 22 (47%). The TP53 gene was mutated in 10/30 (33%); the 7q deletion was detected in only one case, and no Notch receptor 2 (NOTCH2) mutations were found. Immunoglobulin heavy‐chain variable‐region (IGHV) locus sequencing revealed that none harboured an IGHV1‐02*04 gene. Overall survival was 82% at 10 years and not influenced by TP53 aberration. Our present findings suggest that most t(CDK6)+ neoplasms correspond to a particular subgroup of indolent marginal zone B‐cell lymphomas with distinctive features

Genetic characterization of B-cell prolymphocytic leukemia: a prognostic model involving MYC and TP53

International audienceB-cell prolymphocytic leukemia (B-PLL) is a rare hematological disorder whose underlying oncogenic mechanisms are poorly understood. Our cytogenetic and molecular assessment of 34 patients with B-PLL revealed several disease-specific features and potential therapeutic targets. The karyotype was complex ({greater than or equal to}3 abnormalities) in 73% of the patients and highly complex (&gt;5 abnormalities) in 45%. The most frequent chromosomal aberrations were translocations involving MYC [t(MYC)] (62%), deletion (del)17p (38%), trisomy (tri)18 (30%), del13q (29%), tri3 (24%), tri12 (24%), and del8p (23%). Twenty-six of the 34 patients (76%) exhibit MYC aberration, resulting from mutually exclusive translocations or gains. Whole-exome sequencing revealed frequent mutations in TP53, MYD88, BCOR, MYC, SF3B1, SETD2, CHD2, CXCR4, and BCLAF1 The majority of B-PLL used the IGHV3 or IGHV4 subgroups (89%), and displayed significantly mutated IGHV genes (79%). We identified three distinct cytogenetic risk groups: low-risk (no MYC aberration), intermediate-risk (MYC aberration but no del17p), and high-risk (MYC aberration and del17p) (p=.0006). In vitro drug response profiling revealed that the combination of a B-cell receptor or BCL2 inhibitor with OTX015 (a bromodomain and extra-terminal motif (BET) inhibitor targeting MYC) was associated with significantly lower viability of B-PLL cells harboring a t(MYC). We conclude that cytogenetic analysis is a useful diagnostic and prognostic tool in B-PLL. Targeting MYC may be a useful treatment option in this disease