Mutations of the BCL6 proto-oncogene disrupt its negative autoregulation in diffuse large B-cell lymphoma

Blood ◽  
2003 ◽  
Vol 101 (8) ◽  
pp. 2914-2923 ◽  
Author(s):  
Laura Pasqualucci ◽  
Anna Migliazza ◽  
Katia Basso ◽  
Jane Houldsworth ◽  
R. S. K. Chaganti ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Chromosomal Translocations ◽  
Regulatory Sequences ◽  
Large B Cell Lymphoma ◽  
Noncoding Exon ◽  
Functional Consequences ◽  
Large B Cell

Abstract The BCL6 proto-oncogene encodes a transcriptional repressor whose expression is deregulated by chromosomal translocations in approximately 40% of diffuse large B-cell lymphomas (DLBCLs). The BCL6 regulatory sequences are also targeted by somatic hypermutation in germinal center (GC) B cells and in a fraction of all GC-derived lymphomas. However, the functional consequences of these mutations are unknown. Here we report that a subset of mutations specifically associated with DLBCL causes deregulated BCL6 transcription. These mutations affect 2 adjacent BCL6 binding sites located within the first noncoding exon of the gene, and they prevent BCL6 from binding its own promoter, thereby disrupting its negative autoregulatory circuit. These alterations were found in approximately 16% of DLBCLs devoid of chromosomal translocations involving the BCL6 locus, but they were not found in normal GC B cells. This study establishes a novel mechanism for BCL6 deregulation and reveals a broader involvement of this gene in DLBCL pathogenesis.

Aberrant Somatic Hypermutation Targets an Extensive Set of Genes in Diffuse Large B-Cell Lymphoma.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1528-1528 ◽  
Author(s):  
Laura Pasqualucci ◽  
Roberta Guglielmino ◽  
Sami N. Malek ◽  
Urban Novak ◽  
Mara Compagno ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Chromosomal Translocations ◽  
Total N ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract Genomic instability is a driving force in tumor development that can be achieved by a variety of mechanisms, such as defective chromosome segregation or inactivation of the DNA mismatch repair pathway. Although B-cell lymphomas are associated with chromosomal translocations deregulating oncogene expression, a mechanism for genome-wide instability during lymphomagenesis has long not been described. We have reported that the somatic hypermutation process (SHM), which normally targets the immunoglobulin variable region (IgV) and BCL6 genes in germinal center (GC) B-cells, functions aberrantly in >50% of diffuse large B-cell lymphoma (DLBCL), the most common type of B-cell non-Hodgkin lymphoma (Pasqualucci et al., Nature412:341, 2001). As a consequence, multiple somatic mutations are introduced into the 5′ region of genes that do not represent physiologic SHM targets, including known proto-oncogenes such as PIM1, PAX5, RhoH/TTF and cMYC. To further define the extent of this phenomenon, termed aberrant somatic hypermutation (ASHM), and to identify additional hypermutated loci of possible pathogenetic significance in DLBCL, we screened 113 genes for the presence of mutations affecting their 5′ sequences (≥1.3 Kb from the transcription start site, the target region for SHM) in 10 DLBCL cell lines. Fifteen genes (13.3%) were found to harbor a significant number of mutations (p<0.05), with 70% of the cell lines being mutated in 7 or more genes; among these, six B-cell specific loci -BCL7A, CIITA, IRF4, LRMP, NCOA3 and SIAT1- carried 9–53 mutational events distributed in 20 to 70% of the cases, corresponding to an overall mutation frequency of 0.032–0.15% (frequency in the mutated cases: 0.07–0.25%). The same genes were found hypermutated in a panel of 20 primary DLBCL biopsies, which displayed an overall mutation load of 7 to 45 distinct events/gene (total N=125). Mutations were of somatic origin, independent of chromosomal translocations to the Ig loci and were restricted to the first 1.5–2 Kb from the promoter. In addition, analogous to previously identified SHM and ASHM targets, the mutations exhibited characteristic features, including a bias for transitions over transversions, preferential hotspot (RGYW/WRCY motifs) targeting, and higher frequencies at G:C pairs. However, in contrast to physiologic SHM targets such as IgV and BCL6, none of the 4 newly identified hypermutated genes that have been analyzed so far (BCL7A, CIITA, SIAT1, LRMP) displayed significant levels of mutations in purified normal GC B-cells as well as in other B-cell malignancies. This finding indicates that these genes represent aberrant hypermutation targets resulting from a tumor-associated malfunction, possibly a loss of target specificity of the physiologic SHM process. Considering previous results and the present survey, 17 (13%) out of 130 genes investigated have been found involved in ASHM, suggesting that this aberrant activity may involve an extensive set of target genes in DLBCL. Since the mutations affect both regulatory and coding sequences of the targeted genes, aberrant SHM may represent a major contributor to the pathogenesis of this disease and may explain in part its phenotypic and clinical heterogeneity.

Inactivating SOCS1 mutations are caused by aberrant somatic hypermutation and restricted to a subset of B-cell lymphoma entities

Blood ◽  
2009 ◽  
Vol 114 (20) ◽  
pp. 4503-4506 ◽  
Author(s):  
Anja Mottok ◽  
Christoph Renné ◽  
Marc Seifert ◽  
Elsie Oppermann ◽  
Wolf Bechstein ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Rare Mutations ◽  
Large B Cell Lymphoma ◽  
Mantle Cell ◽  
Follicular Lymphomas ◽  
Large B Cell

Abstract STATs are constitutively activated in several malignancies. In primary mediastinal large B-cell lymphoma and Hodgkin lymphoma (HL), inactivating mutations in SOCS1, an inhibitor of JAK/STAT signaling, contribute to deregulated STAT activity. Based on indications that the SOCS1 mutations are caused by the B cell–specific somatic hypermutation (SHM) process, we analyzed B-cell non-HL and normal B cells for mutations in SOCS1. One-fourth of diffuse large B-cell lymphoma and follicular lymphomas carried SOCS1 mutations, which were preferentially targeted to SHM hotspot motifs and frequently obviously inactivating. Rare mutations were observed in Burkitt lymphoma, plasmacytoma, and mantle cell lymphoma but not in tumors of a non–B-cell origin. Mutations in single-sorted germinal center B cells were infrequent relative to other genes mutated as byproducts of normal SHM, indicating that SOCS1 inactivation in primary mediastinal large B-cell lymphoma, HL, diffuse large B-cell lymphoma, and follicular lymphoma is frequently the result of aberrant SHM.

scholarly journals Long-Term Survival and Gradual Recovery of B Cells in Patients (Pts) with Refractory Large B Cell Lymphoma (LBCL) Treated with Axicabtagene Ciloleucel (Axi-Cel)

2021 ◽  
Vol 27 (3) ◽  
pp. S404-S405
Author(s):  
Caron A. Jacobson ◽  
Frederick L. Locke ◽  
Armin Ghobadi ◽  
David B. Miklos ◽  
Lazaros J. Lekakis ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Term Survival ◽  
Long Term Survival ◽  
Large B Cell Lymphoma ◽  
Large B Cell

scholarly journals Primary Type3 (Non-ABC, Non-GCB) Subtype of Extranodal Diffuse Large B-Cell Lymphoma of the Thyroid Bearing No MYD88 Mutation by Padlock Probe Hybridization

2017 ◽  
Vol 10 (2) ◽  
pp. 508-514 ◽  
Author(s):  
Yukiko Nishi ◽  
Riko Kitazawa ◽  
Ryuma Haraguchi ◽  
Ayaka Ouchi ◽  
Yasuo Ueda ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Malignant Lymphoma ◽  
Cell Lymphoma ◽  
Clinical Phenotype ◽  
B Cell Lymphoma ◽  
Large B Cell Lymphoma ◽  
Japanese Female ◽  
Old Japanese ◽  
Large B Cell

Primary extranodal malignant lymphoma of the thyroid is a rare entity composed of mostly neoplastic transformation of germinal center-like B cells (GCB) or memory B cells. Other B-cell-type malignancies arising primarily in the thyroid have rarely been described. Immunohistochemical examination of autopsied primary malignant lymphoma of the thyroid in an 83-year-old Japanese female revealed the presence of a non-GCB subtype of diffuse large B-cell lymphoma (DLBCL) without the typical codon 206 or 265 missense mutation of MYD88. The lack of the highly oncogenic MYD88 gene mutation, frequently observed in DLBCL of the activated B-cell (ABC) subtype, and the detection of an extremely aggressive yet local clinical phenotype demonstrated that the present case was an exceptional entity of the type3 (non-GCB and non-ABC) subtype.

scholarly journals Prognostic analysis of aberrant somatic hypermutation of RhoH gene in diffuse large B cell lymphoma

Leukemia ◽  
2007 ◽  
Vol 21 (8) ◽  
pp. 1846-1847 ◽  
Author(s):  
J Hiraga ◽  
A Katsumi ◽  
T Iwasaki ◽  
A Abe ◽  
H Kiyoi ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Prognostic Analysis ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Effect of siRNA interference of ubiquitin-specific protease 9X on apoptosis and growth of diffuse large B cell lymphoma cell line

2020 ◽  
Vol 10 (3) ◽  
pp. 446-453
Author(s):  
Wei Peng ◽  
Meizuo Zhong ◽  
Youhong Tang
Keyword(s):  
B Cells ◽  
Protein Expression ◽  
B Cell ◽  
Cell Apoptosis ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Large B Cell Lymphoma ◽  
Specific Protease ◽  
Sirna Interference ◽  
Large B Cell

Ubiquitin-specific protease 9X (USP9X) is crucial in the diagnosis and treatment of many tumor types, but its role in Diffuse Large B Cell Lymphoma (DLBCL) has not been determined. The current study aimed to examine the effects of RNA interference on USP9X expression, and subsequently on the bioactivity of DLBCL Farage and Pfeiffer cells. There were two groups in the study: USP9X-siRNA and NC. USP9X siRNA was transiently transferred into DLBCL cells by Cationic liposome. The total RNA was extracted using Fe2O3 and was retrieved into the DNA using the MagBeads Total RNA Extraction Kit. The protein expression of USP9X in Farage, Pfeiffer, and normal human B cell line at the cellular level was observed by Western blot. The Farage and Pfeiffer cells were infected with USP9X-siRNA. Cell apoptosis and cell growth viability were analyzed by flow cytometry and CCK8, Mcl-1 protein, a potential target of USP9X, and apoptosis factor proteins (such as Bak, Cytochrome C, Caspase 3, Caspase 8, PARP) were detected by Western blot after siRNA interference. The results showed that the protein expression of USP9X in malignant B cells was four times higher than that of the normal B cells. Inhibition of USP9X reduced the Mcl-1 activity, and increased the caspase-3, Bak and Cytochrome C activity. In the malignant B cells, Mcl-1 and Bak were binding in vivo; Bak was a new partner of Mcl-1. Inhibition of USP9X reduced cell proliferation and increased apoptosis. The expression of USP9X is upregulated in Diffuse large B cell lymphoma cells, Farage, and Pfeiffer. Inhibition expression of USP9X may induce cell apoptosis, inhibit cell growth, and downregulate Mcl-1 protein expression in Diffuse large B cell lymphoma cells, Farage, and Pfeiffer. USP9X has the ability in regulating cell apoptosis.

Aberrant Somatic Hypermutation in Primary Mediastinal Large B-Cell Lymphoma.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2268-2268 ◽  
Author(s):  
Davide Rossi ◽  
Michaela Cerri ◽  
Daniela Capello ◽  
Clara Deambrogi ◽  
Eva Berra ◽  
...  
Keyword(s):  
B Cell ◽  
Base Pair ◽  
Mutation Frequency ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Single Base ◽  
Large B Cell Lymphoma ◽  
Single Base Pair ◽  
Large B Cell

Abstract Primary mediastinal large B-cell lymphoma (PMLBCL) is recognised as a subtype of diffuse large B-cell lymphoma (DLBCL) arising in the mediastinum. With respect to DLBCL, PMLBCL displays specific clinical, molecular and morphological features suggesting that PMLBCL may represent a distinct clinico-pathologic entity. Aberrant somatic hypermutation (SHM) of PIM-1, PAX-5, RhoH/TTF and c-MYC has been advocated as a molecular feature distinctive of DLBCL. To investigate wether the same mechanism is associated with PMLBCL, we performed mutational analysis of PIM-1, PAX-5, RhoH/TTF and c-MYC in a panel of 19 PMLBCL. For comparison, 19 DLBCL were also analysed. For each gene, a region previously shown to contain >90% of mutations was analysed by PCR amplification and DNA direct sequencing. Overall, the prevalence of mutated cases was similar among DLBCL and PMLBCL. Mutations targeting at least one of the 4 genes were found in 14/19 (73.6%) PMLBCL and 13/19 (68.4%) DLBCL, while mutations in more than one gene were found in 7/19 (36.8%) PMLBCL and 9/19 (47.3%) DLBCL. Among the four genes, the prevalence of mutation and the mutation frequency was superimposable between PMLBCL and DLBCL. In fact, PAX-5 was mutated in 9/19 (47.3%) PMLBCL with a mean mutation frequency of 0.20 x 10−2/bp and in 7/19 (36.8%) DLBCL with a mean mutation frequency of 0.18 x 10−2/bp; RhoH/TTF was mutated in 6/19 (31.5%) PMLBCL with a mean mutation frequency of 0.08 x 10−2/bp and in 8/19 (42.1%) DLBCL with a mean mutation frequency of 0.27 x 10−2/bp; PIM-1 was mutated in 3/19 (15.7%) PMLBCL with a mean mutation frequency of 0.09 x 10−2/bp and in 7/19 (36.8%) DLBCL with a mean mutation frequency of 0.11 x 10−2/bp; c-MYC was mutated in 6/19 (31.5%) PMLBCL with a mean mutation frequency of 0.23 x 10−2/bp and in 5/19 (26.3%) DLBCL with a mean mutation frequency of 0.11 x 10−2. The mutation pattern was also similar between PMLBCL and DLBCL and was consistent with the SHM process. A total of 74 mutational events were detected in PMLBCL. The majority of mutations were represented by single base-pair substitution (n=66), whereas only 8 deletions of a short DNA stretch were observed. Of the 66 single base-pair substitutions, 41 were transitions and 25 were transversions, with a transition/transversion ratio of 1.64 and a G+C/A+T ratio of 3.6. Eleven out of 66 (16.6%) single base-pair substitutions felt within RGYW/WRCY motifs. Among DLBCL a total of 87 mutational events were detected. Mutations were preferentially represented by single base-pair substitutions (n=81), whereas only 4 deletions and 2 insertions of a short DNA stretch were observed. Of the 81 single base-pair substitutions, 42 were transitions and 39 were transversions, with a transition/transversion ratio of 1.07 and a G+C/A+T ratio of 1.89. Twenty six out of 81 (32.1%) single base-pair substitutions felt within RGYW/WRCY motifs. The implication of our results are twofold. First, aberrant SHM is involved in the pathogenesis of PMLBCL. Second, our results indicate that aberrant SHM targets both PMLBCL and DLBCL with similar prevalence, distribution and mutation pattern. Since aberrant SHM has been advocated as a molecular marker of DLBCL, our results corroborate the notion that PMLBCL represent a subtype of DLBCL rather than a distinct clinico-pathologic entity.

Preferential Acquision of N-Glycosylation Sites in the VDJ Region in Germinal Center B-Cell-Like Difusse Large B-Cell Lymphoma

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1589-1589 ◽  
Author(s):  
Miguel Alcoceba ◽  
Elena Sebastián ◽  
Ana Balanzategui ◽  
Luis Marín ◽  
Santiago Montes-Moreno ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Marginal Zone ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Marginal Zone Lymphoma ◽  
Large B Cell Lymphoma ◽  
Glycosylation Sites ◽  
Large B Cell

Abstract Abstract 1589 Introduction: Acquired potentially N-glycosylation sites are produced by somatic hypermutation (SHM) in the immunoglobulin (Ig) variable region. This phenomenon is produced in ∼9% of normal B-cells and seems to be related to certain B-cell lymphoproliferative disorders (B-LPDs) such as follicular lymphoma (FL, 79%), endemic Burkitt lymphoma (BL, 82%) and diffuse large B-cell lymphoma (DLBCL, 41%). These data suggest that new potential N-glycosylation sites could be related to germinal center B (GCB)-LPDs. By contrast, in other B-LPDs, such as chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), MALT lymphoma, Waldenström macroglobulinemia (WM) or multiple myeloma (MM), these modifications have not been analyzed in deep. Aims: To evaluate the acquisition of potential N-glycosylation sites in B-LPDs, including immunohystochemical DLBCL subtypes (GCB and non-GCB) and specific non-GCB-LPDs, such as hairy cell leukemia (HCL), splenic marginal-zone lymphoma (SMZL), CLL, MCL, ocular extranodal marginal zone lymphoma (OAEMZL), MM and WM. Patients: A total of 953 sequences (203 from our group and 750 previously published sequences) of B-LPDs were included. Diagnosis distribution was as follows: DLBCL (n=235), MCL (n=235), CLL (n=166), MM (n=96), OAEMZL (n=82), SMZL (n=68), WM (n=38) and HCL (n=33). Methods: Acquired N-glycosylation sites were counted according to the sequence Asn-X-Ser/Thr, where X could be any amino acid except Pro. Natural motifs in germline sequences of IGHV1–08, IGHV4–34 e IGHV-5a were not considered. Fisher test was used to perform comparisons between groups. To distinguish DLBCL biological subtypes (GCB and non-GCB DLBCL), Hans' algorithm was used. Results: A total of 83 out of the 235 DLBCL cases acquired at least a new N-glycosylation site, a higher value than in normal B-cells (35% vs. 9%, p<0.0001). Higher incidence of these motifs in the group of GCB as compared to non-GCB DLBCL were observed (52% vs. 20%, p<0.0001). Those cases diagnosed of HCL, CLL, MCL, MM, WM, OAEMZL and SMZL presented a reduced number of new N-glycosylation sites, showing similar values than normal B-cells (range 3–18%, p=ns). Conclusions: We described for the first time the pattern of N-glycosylation in HCL, SMZL, OAEMZL and in the immunohystochemical DLBCL subtypes, where the GCB-DLBCL showed a higher number of new N-glycosylation sites with respect to non-GCB DLBCL and other non-GCB-LPDs. The presence of novel N-glycosylation sites in FL, BL and in GCB-DLBCL strongly suggests that these motifs are characteristic of the germinal center B-LPDs. Disclosures: No relevant conflicts of interest to declare.

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