Activation Induced Cytidine Deaminase-Associated DNA Repair Pathways Influence Germinal Center B Cell Lymphomagenesis

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1247-1247
Author(s):  
Xiwen Gu ◽  
Carmen J. Booth ◽  
Zongzhi Liu ◽  
Matthew P. Strout
Keyword(s):  
Dna Repair ◽  
B Cell ◽  
Germinal Center ◽  
Cell Lymphoma ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Chromosome Abnormalities ◽  
B Cell Lymphomas ◽  
Activation Induced Cytidine Deaminase ◽  
Repair Pathways

Abstract Somatic hypermutation and class switch recombination of immunoglobulin (Ig) genes occur in germinal center (GC) B cells and are initiated through deamination of cytidine to uracil by activation induced cytidine deaminase (AID). Resulting uracil-guanine (U-G) mismatches are processed by UNG-dependent base-excision repair (BER) and MSH2-dependent mismatch repair (MMR) pathways to yield mutations and DNA strand lesions. Although off-target AID activity also contributes to oncogenic point mutations and chromosome translocations associated with B cell lymphomas, the role of downstream AID-associated DNA repair pathways in lymphomagenesis is not defined. Through deregulated expression of BCL6, IµHABcl6 mice develop an AID-dependent GC-derived lymphoma that resembles human diffuse large B cell lymphoma (DLBCL). We have previously demonstrated that IµHABcl6 Ung-/-Msh2-/- mice have a similar incidence (35% vs 27%) but a 2.5-fold shorter median time to development of B220+ IgM+ PNAhi CD138- DLBCL compared with IµHABcl6 mice (6.5 months vs. 16.2 months; P = 0.0003). This suggests that AID-associated DNA repair pathways serve to protect the GC B cell and delay BCL6-driven lymphomagenesis. To investigate the individual contribution of BER and MMR in the pathogenesis of GC-derived lymphoma, we have now generated IµHABcl6 Ung-/- and IµHABcl6 Msh2-/- single-deficient mice. The majority of IµHABcl6 Ung-/- mice remained healthy beyond 20 months with only 3 of 22 (13.6%) mice becoming sick starting at ∼16 months. Sick mice were found to have splenic lymphomas comprised of mature B220+ IgM+ PNAlow CD138- B cells. Histological examination revealed expanded follicles with a population of small lymphocytes, consistent with a follicular B cell lymphoma which has been shown to arise in Ung-/- mice. In contrast, 18 of 22 (81.8%) IµHABcl6 Msh2-/- mice rapidly succumbed to malignancy starting at ∼3 months and had a median survival of 6 months. Of 15 tumors available for analysis, there was 1 histiocytic sarcoma, 1 squamous cell carcinoma, 4 T cell lymphomas, and 9 B220+ IgM- PNA- CD138- pre-B cell lymphomas (determined by histology, immunophenotyping and gene expression profiling). None of the IµHABcl6 Ung-/- or IµHABcl6 Msh2-/- mice developed DLBCL. Since lack of UNG is strongly protective when MSH2 is present, we conclude that in the setting of deregulated BCL6, UNG promotes the development of DLBCL. In contrast, MSH2 is protective against the development of tumors in general and does not facilitate DLBCL in the absence of UNG. Combined with the observation that IµHABcl6 Ung-/-Msh2-/- mice develop DLBCL with a significantly shorter latency than IµHABcl6 mice, this data indicates that a complex interplay between AID-associated BER and MMR produces a net protective effect against lymphomagenesis. In the absence of UNG and MSH2, AID-generated U-G mismatches are not processed into strand lesions and are simply replicated, yielding C/G to T/A transition mutations. Thus, to assess how combined lack of UNG and MSH2 might promote the accelerated development of BCL6-driven lymphoma, we carried out spectral karyotyping and sequence analysis of AID target genes (IgJH4, cMyc, Pim1, RhoH, Cd79a, CD79b, H2afx, Pax5, and Cd83) in lymphomas from the different genotypes. IµHABcl6 DLBCLs (3/3) harbored various complex chromosome abnormalities, consistent with previous findings. Numerous clonal and sub-clonal chromosome abnormalities including translocations, duplications, deletions, and aneuploidies were also detected in IµHABcl6 Ung-/-Msh2-/- (4/4) and IµHABcl6 Ung-/- (2/2) lymphomas. Pre-B cell tumors from IµHABcl6 Msh2-/- mice could not be stimulated to produce metaphase chromosomes. Clonal and non-clonal mutations of the IgJH4 intronic region were identified in lymphomas from IµHABcl6 (2/3), IµHABcl6 Ung-/-Msh2-/- (4/4), and IµHABcl6 Ung-/- (2/3) mice, consistent with ongoing AID activity. No mutations were detected in 3 pre-B cell lymphomas, consistent with their pre-GC origin. Six clonal mutations within AID hotspots (all C/G to T/A) were identified in Pim1, RhoH, and Pax5 in 2 of 4 IµHABcl6 Ung-/-Msh2-/- DLBCLs. None of the other genotypes carried any clonal mutations of non-Ig genes. Thus, chromosome abnormalities in GC B cell lymphomas can arise through mechanisms independent of BER and MMR but may be due to off-target effects of AID on other genes that regulate cell cycle, apoptosis, or genomic stability. Disclosures: No relevant conflicts of interest to declare.

The Role of DNA Repair in the Pathogenesis of Activation Induced Cytidine Deaminase Dependent B Cell Lymphoma

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 397-397
Author(s):  
Xiwen Gu ◽  
Carmen J. Booth ◽  
David G. Schatz ◽  
Matthew P. Strout
Keyword(s):  
Dna Repair ◽  
B Cells ◽  
B Cell ◽  
Median Survival ◽  
Cell Lymphoma ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Enzyme Activation ◽  
Activation Induced Cytidine Deaminase

Abstract Abstract 397 Upon antigenic stimulation of B cells, germinal centers (GCs) are formed where somatic hypermutation (SHM) and class switch recombination (CSR) of immunoglobulin (Ig) genes serve to diversify the immune response. SHM and CSR are initiated by the enzyme activation induced cytidine deaminase (AID) through the conversion of C/G base pairs to U-G mismatches. These mismatches are processed by UNG-dependent base excision repair (BER) and MSH2-dependent mismatch repair (MMR) pathways to yield mutations (for SHM) and DNA strand lesions (for CSR). Despite this essential role in immune diversification, the intrinsic activity of AID as a DNA mutator poses a threat to genomic integrity. Indeed, aberrant targeting of AID activity is associated with translocations and point mutations of proto-oncogenes associated with B cell malignancies. A specific dependence on AID in the pathogenesis of lymphomas of GC B cell origin is exemplified in Iμ-Bcl6 knock-in mice. These mice develop a diffuse large B cell lymphoma (DLBL) that resembles the human disease but are protected from development of this lymphoma when crossed onto an Aid-deficient background. To investigate the role of Aid-associated DNA repair in the pathogenesis of this disease, we crossed Iμ-Bcl6 mice onto a background deficient in BER (Ung−/−) and MMR (Msh2−/−). Young healthy Iμ-Bcl6 and Iμ-Bcl6 Ung−/−Msh2−/− mice displayed a normal number and distribution of B cells and normal architecture of lymphoid organs. Five of 28 Iμ-Bcl6 mice (17.9%) became sick starting at ∼12 months of age. Historically, median survival in these mice has not been reached and ∼80% survive to 15 months. In contrast, 21 of 28 Iμ-Bcl6 Ung−/−Msh2−/−mice (75%) developed disease with an onset of ∼3 months and had a median survival of 6.2 months (p<0.0001). All 5 of the Iμ-Bcl6 mice and the majority of Iμ-Bcl6 Ung−/−Msh2−/−mice developed B cell lymphoma with splenic involvement and variable nodal involvement. Five of the Iμ-Bcl6 Ung−/−Msh2−/−mice developed other cancers (3 T cell lymphomas, 1 pre-B cell lymphoma and 1 colon adenocarcinoma). Tumors from both genotypes expressed a mature B cell phenotype (B220+ IgM+ Igκ+ CD138-) and morphology revealed loss of normal lymphoid architecture with infiltration by lymphoid blasts. Additional staining demonstrated expression of at least one GC marker (Fas, GL7 and/or PNA). Similar to Iμ-Bcl6 mice, while many of the Iμ-Bcl6 Ung−/−Msh2−/−tumors had clonal mutated Ig heavy chain gene variable regions, two of the tumors were identified as oligoclonal, suggesting a preceding lymphoproliferative stage. In the absence of Ung and Msh2, Aid-generated U-G mismatches are not recognized and are simply replicated, causing only C/G to T/A transition mutations and no strand lesions. Thus, as expected, all Ig mutations in Iμ-Bcl6 Ung−/−Msh2−/−mice were C/G to T/A transitions. Lymphomas from Iμ-Bcl6 mice have been found to harbor numerous chromosome translocations and aneuploidies. Although additional analyses are underway, spectral karyotyping of 3 Iμ-Bcl6 Ung−/−Msh2−/−tumors revealed 2 with normal cytogenetics and 1 with a 40–41,XX,t(2;17),+15,+19. Surprisingly, sequence analysis of several known Aid target genes (cMyc, Pim1, RhoH, Pax5, Cd79a, Fas, H2ax and OcaB) in tumors from 3 Iμ-Bcl6 Ung−/−Msh2−/− mice did not identify any clonal mutations. However, non-clonal C/T to T/A transition mutations in cMyc were present at a frequency of 1.2 × 10−4, suggestive of ongoing Aid activity. The presence of Aid activity but absence of off-target Aid-mediated clonal SHM suggests that either other genes are targeted by Aid or that Aid has a secondary role in lymphomagenesis such as epigenetic reprogramming, as has been shown in iPS cells. Nonetheless, the incidence of Aid-dependent lymphomagenesis in the absence of Aid-associated DNA repair is significantly increased and the latency is greatly shortened. Altogether, this data suggests that Aid-associated BER and MMR pathways afford a protective effect against the development of Aid-dependent GC B cell lymphomas such as DLBL. To investigate the role of the individual Aid-associated DNA repair pathways, we have also generated Iμ-Bcl6 Ung−/− and Iμ-Bcl6 Msh2−/− single knockout mice. These studies are ongoing but preliminary results suggest that while the effect of Ung and Msh2 deficiency on lymphomagenesis may be synergistic, Msh2 might play a more critical role in preventing Aid-mediated genomic instability. Disclosures: No relevant conflicts of interest to declare.

Frequent expression of activation-induced cytidine deaminase in diffuse large B-cell lymphoma tissues from persons living with HIV

AIDS ◽  
2020 ◽  
Vol 34 (14) ◽  
pp. 2025-2035
Author(s):  
Volodymyr Shponka ◽  
Candace Y. Reveles ◽  
Sinthia Alam ◽  
Melba Jaramillo ◽  
Alanna Maguire ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lymphoma ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Large B Cell Lymphoma ◽  
Persons Living With Hiv ◽  
Activation Induced Cytidine Deaminase ◽  
Living With Hiv ◽  
Large B Cell

Profiles Of De Novo CD25-Positive Mature B-Cell Lymphomas

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4308-4308
Author(s):  
Shin-ichiro Fujiwara ◽  
Raine Tatara ◽  
Kiyoshi Okazuka ◽  
Iekuni Oh ◽  
Ken Ohmine ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
High Expression ◽  
B Cell Lymphomas ◽  
Cns Involvement ◽  
Cd25 Expression

Abstract Background Interleukin 2 (IL-2) is an important cytokine that controls the proliferation and differentiation of not only T- but also B-lymphocytes. Recently, we reported that CD25 (IL-2 receptor alpha chain, IL-2R) is expressed in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL), and high expression of CD25 in the two types of lymphoma is correlated with a poor prognosis following chemotherapy regimens containing rituximab (ASH annual meeting, 2011 118:2666, 2012 120:1543). We evaluated the clinical significance of CD25 expression in a larger series of different mature B-cell lymphomas (BCL). Patients and Methods Four hundred and thirty-seven newly diagnosed patients who were admitted to our hospital between 2002 and 2013 were retrospectively evaluated. Lymph node or related tissue biopsy samples of BCL were analyzed using flow cytometry, as follows: 182 patients, DLBCL; 92, FL; 48, chronic lymphocytic leukemia (CLL); 21, mantle cell lymphoma (MCL); 23, marginal zone lymphoma (MZL); 8, Burkitt lymphoma (BL); 18, B-cell lymphoma unclassifiable with features intermediate between BL and DLBCL (BL/DLBCL); 5, lymphoplasmacytic lymphoma (LPL); and 39, reactive lymphadenopathy with sufficient B-cells. CD25-positivity was defined as >20% of clonal B-cells in a gated region. Results CD25 expression in patients with MCL, CLL, MZL, and DLBCL was significantly higher than that in patients with reactive lymphadenopathy (P<0.001,<0.001, =0.019, and <0.001, respectively). BL and FL, which were derived from germinal center B-cells, did not express CD25. These results indicate that pre- or post- germinal center-derived B-cells, activated by IL-2/IL-2R signaling, may give rise to CD25+ BCL such as CD25+ MCL, CLL, MZL, and DLBCL. The highest median CD25 expression (41.5%) was observed in MCL. CD25 expression was higher in MCL than CD5+ BCL (CLL and CD5+ DLBCL) (median, 41.5 vs. 16.9%, respectively; P<0.001). With a cut-off value of 60% CD25-positivity, patients with CD25-high (>60%) MCL (n=9) were not treated with aggressive chemotherapy regimens such as Hyper-CVAD due to their age and characteristics, compared with those with CD25-low (<60%) MCL (n=12) (11.1 vs. 72.7%, respectively, P=0.021). In patients with CLL, the range of CD25 expression was wide (0.4-90.7%), and 29 patients (60%) showed CD25-positivity (CD25+ CLL). CD25+ CLL showed higher soluble IL-2R (sIL-2R) levels and an inferior overall survival (OS) than CD25- CLL (median sIL-2R, 2,195 vs. 706 U/ml P=0.047; 5-year OS, 62.7 vs. 100%; P=0.037). There was a significant correlation between levels of CD25 and sIL-2R (r=0.53, P=0.0053). It is clinically important to distinguish between DLBCL and BCL involving MYC oncogene rearrangement (BL and BL/DLBCL, MYC+ BCL). The former showed higher CD25 expression than the latter (median, 10.2 vs. 2.1%, respectively, P=0.04). The progression-free survival rate (PFS) after rituximab containing chemotherapy was inferior in patients with CD25+ DLBCL (n=72) than those with CD25- DLBCL (n=110) and MYC+ BCL (5-year PFS, 49 vs. 70.4, 66.3%, respectively). In patients with DLBCL, central nerve system (CNS) involvement was observed in 15 patients (7 at diagnosis and 8 at relapse). CD25+ DLBCL showed a higher frequency of CNS involvement than CD25– DLBCL (13.8 vs. 4.5%, respectively, P=0.049). Regarding MZL, CD25 was highly expressed in nodal MZL, but it showed a low expression in splenic MZL. Regarding the sites of extranodal MZL, CD25 expression was lower in the thyroid than at other sites (median, 5.1 vs. 21.2%, respectively, P=0.37). There were some differences between CD25+ (n=9) and CD25- (n=14) MZL concerning the presence of B symptoms (33.3 vs. 0%, respectively) and advanced stage (66.6 vs. 35.7%, respectively). Conclusion CD25 expression using flow cytometry can potentially provide diagnostic and prognostic implications on BCL patient. The high expression of CD25 in MCL and CLL suggests the possibility of targeted anti-CD25 immunotherapy. These findings may shed light on the role of CD25 expression in B-cell lymphomagenesis. Disclosures: No relevant conflicts of interest to declare.

Prognostic impact of activation-induced cytidine deaminase expression for patients with diffuse large B-cell lymphoma

2017 ◽  
Vol 59 (9) ◽  
pp. 2085-2095 ◽  
Author(s):  
Hiroshi Arima ◽  
Masakazu Fujimoto ◽  
Momoko Nishikori ◽  
Toshiyuki Kitano ◽  
Wataru Kishimoto ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lymphoma ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Prognostic Impact ◽  
Large B Cell Lymphoma ◽  
Activation Induced Cytidine Deaminase ◽  
Large B Cell

Identification of Surrogate Prognostic Markers and Genes Implicated in Immunoglobulin Gene (IgVH) Somatic Hypermutation in Small B-Cell Lymphomas.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1004-1004
Author(s):  
Lorraine Tracey ◽  
Mohit Aggarwal ◽  
Patrocinio Algara ◽  
Juan F. Garcia ◽  
Monica Garcia-Cosio ◽  
...  
Keyword(s):  
Dna Repair ◽  
B Cell ◽  
Cell Line ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Differentially Expressed ◽  
Splenic Marginal Zone Lymphoma ◽  
Immunoglobulin Gene ◽  
B Cell Lymphomas

Abstract Immunoglobulin (Ig) gene somatic hypermutation (SHM) is a prognostic factor in small B-cell lymphomas, as demonstrated by studies reporting that hypermutated chronic lymphocytic leukemia (CLL) and splenic marginal zone lymphoma (SMZL) cases show a better prognosis, while hypermutated mantle cell lymphoma (MCL) cases display specific clinicopathological features (leukemic course, increased survival). However both the mechanisms and markers of SHM are poorly characterized, with the partial exception of the role of the genes ZAP70 and AID. With the purpose of identifying SHM surrogate markers in small B-cell lymphomas, we analyzed IgVH mutational status and expression profiles of 93 small B-cell lymphoma patient samples including SMZL (24 cases), MCL (33 cases) and CLL (36 cases). Patients were classified into two groups: high SHM (&gt;5% mutations) and low SHM (&lt;5% mutations). T-test analysis with 100,000 permutations was performed and 39 genes were identified whose expression is significantly different (p&lt;0.005, FDR&lt;0.05) between cases with high and low SHM burdens. To dissect the molecular mechanisms of Ig somatic hypermutation and validate the observed findings, SHM was induced in a model system and compared to results in patient samples. The BL2 cell line was used, and SHM was induced by treating the cells with IL4 and CD40. After 24 hours, active SHM was confirmed by western blot using an anti-AID monoclonal antibody on treated and untreated cells. These same cells were analyzed using microarrays, to identify the genes that were induced or downregulated during the SHM activation. A total of 29 genes (18 upregulated and 11 downregulated) were identified which are significantly differentially expressed in the cell line model during induction of SHM (expression change &gt;0.4 Log2 scale) and are also differentially expressed between cases with high and low SHM (p&lt;0.001, FDR&lt;0.1). In both analyses, the upregulated genes are implicated in transcription, DNA repair and replication and chromosome maintenance, correlating well with previous hypotheses indicating that active transcription is necessary for SHM. Based on these observations, a group of 10 key genes, implicated in DNA repair, replication and transcription, were selected and protein expression was analyzed in a set of tissue microrrays containing 150 paraffin embedded small B-cell lymphoma cases, for which clinical data is available and SHM status is known. These proteins may provide a surrogate marker for prognosis and/or analysis of IgVH SHM in patient samples using paraffin-embedded tissue samples.

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