Activation-Induced Cytidine Deaminase Accelerates Clonal Evolution of BCR-ABL1-Driven B Cell Lineage Acute Lymphoblastic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 181-181
Author(s):  
Tanja Gruber ◽  
Mi Sook Chang ◽  
Richard Sposto ◽  
Markus Müschen
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
B Cell ◽  
Genetic Instability ◽  
Tumor Suppressor Genes ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Lymphoblastic Leukemia ◽  
Clonal Evolution ◽  
Activation Induced Cytidine Deaminase

Abstract Abstract 181 Activation-Induced Cytidine Deaminase (AID) is required for somatic hypermutation and immunoglobulin (Ig) class switch recombination in germinal center (GC) B cells. Occasionally, AID can target non-Ig genes and thereby promote GC B cell lymphomagenesis. We recently demonstrated that the oncogenic BCR-ABL1 kinase induces aberrant expression of AID in pre-B acute lymphoblastic leukemia (ALL). Compared to other ALL subtypes, BCR-ABL1 ALL is considered high risk and is characterized by a high degree of genetic instability. Because aberrant mutational activity of AID is associated with malignant transformation in B cell lymphoma, we sought to determine whether aberrant AID expression contributes to clonal evolution and genetic instability in Ph+ ALL. To investigate the function of AID expression in Ph+ ALL, we established a genetic loss-of-function model for Ph+ ALL: Bone marrow cells from AID−/− mice and AID+/+ controls were transformed by retroviral transduction with BCR-ABL1 under B lymphoid culture conditions and subsequently injected into lethally irradiated congenic recipients. Mice transplanted with AID−/−BCR-ABL1 ALL had prolonged median survival as compared to mice transplanted with leukemia cells generated from AID+/+ bone marrow (AID−/− 34 days (n=18) vs AID+/+ 13 days (n=21); p<0.0001). In secondary and tertiary transplant experiments, however, the difference between AID−/− and AID+/+BCR-ABL1 ALL narrowed as determined by a decreasing hazard ratio (from 25.5 in the primary transplant to 5.1 in the secondary and 2.9 in the tertiary transplantation). These findings suggest that aberrant AID expression accelerates clonal evolution of Ph+ ALL, but AID-independent factors exist that are sufficient for transformation. In support of enzymatic activity of AID in BCR-ABL1-transformed ALL cells, we observed that aberrant somatic hypermutation of non-immunoglobulin genes in these leukemias was largely dependent on AID: mutations in the known hypermutation target genes Pax5 and Rhoh were increased in AID+/+ but not AID−/−BCR-ABL1 ALL cells. Mutations in the first intron of Rhoh as observed here are relevant because they interfere with Rhoh transcription. Indeed, we found that Rhoh mRNA levels are significantly higher in AID−/− compared to AID+/+BCR-ABL1 ALL cells. Rhoh is a hematopoietic specific GTPase that negatively regulates Rac-mediated signaling downstream of the oncogenic BCR-ABL1 kinase. AID-dependent mutation and transcriptional inactivation of Rhoh in BCR-ABL1 ALL therefore likely augments oncogenic BCR-ABL1 signaling. Consistent with a causative role of AID in genetic instability, AID−/− leukemia had a lower frequency of amplifications (17+2 vs 45+7; p=0.002) and deletions (11+2 vs 40+7; p=0.003) as compared to AID+/+ leukemias. AID−/− and AID+/+ ALL cells showed a markedly distinct gene expression pattern with 2,365 differentially expressed genes (p=0.003; FDR 0.05). A detailed analysis of these differences in gene expression revealed that AID−/−BCR-ABL1 ALL cells failed to downregulate a number of tumor suppressor genes including p53, Rhoh, Cdkn1a (p21), and Blnk (SLP65). AID-dependent downregulation of p53 in BCR-ABL1 ALL cells is of particular importance, because previous work demonstrated that transcriptional repression of p53 in normal GC B cells is required to make these cells permissive to high levels of AID expression. AID-induced DNA damage would otherwise activate p53 and rapidly induce apoptosis. Compared to AID-deficient BCR-ABL1 ALL, AID+/+BCR-ABL1 ALL cells are more resistant to Imatinib-treatment. However, acquisition of BCR-ABL1 kinase domain mutations does not appear to be the main cause of drug-resistance in this experiment, since only one relevant mutation was amplified from AID+/+ ALL cells (no mutations in AID−/− ALL cells). We conclude that AID accelerates clonal evolution in BCR-ABL1 ALL by enhancing genetic instability, aberrant somatic hypermutation, and by negative regulation of tumor suppressor genes. Disclosures: No relevant conflicts of interest to declare.

Activation Induced Cytidine Deaminase (AID) Is Required for Germinal-Center Derived Lymphomagenesis.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 223-223
Author(s):  
Laura Pasqualucci ◽  
Mara Compagno ◽  
Tongwei Mo ◽  
Paula Smith ◽  
Herbert C. Morse ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Somatic Hypermutation ◽  
Profile Analysis ◽  
Cytidine Deaminase ◽  
Receptor Gene ◽  
Activation Induced Cytidine Deaminase ◽  
Hodgkin's Lymphomas

Abstract Most B cell non-Hodgkin’s lymphomas (B-NHL) derive from germinal center (GC) B cells and their pathogenesis is associated with the accumulation of distinct genetic lesions, including chromosomal translocations and a more recently identified mechanism of genomic instability, termed aberrant somatic hypermutation. These alterations are thought to be due to mistakes occurring during two GC-associated immunoglobulin (Ig) genes remodeling processes: class switch recombination (CSR) and somatic hypermutation (SHM). However, this model has never been formally proven. To conclusively investigate the role of CSR and SHM in the pathogenesis of B-NHL, we examined whether lymphoma development in mice requires the function of activation induced cytidine deaminase (AID), a DNA editing enzyme expressed specifically in GC and activated B cells and essential for both processes. Three transgenic mouse models were generated by crossing lymphoma-prone mice (λMYC, λMYC/IμHABCL6 and IμHABCL6) with mice (AID−/−) that are unable to undergo both SHM and CSR. The λMYC mice develop a diffusely infiltrating monoclonal proliferation of pre-GC origin, with unmutated IgV genes and lack of BCL6 expression, and therefore presumably independent from AID-associated DNA remodeling events. Conversely, lymphomas in λMYC/IμHABCL6 and IμHABCL6 mice recapitulate GC/post GC-derived malignancies, in that the former display somatically mutated IgV genes and upregulation of post-GC markers (CD138) in most of the cases, while the latter develop a splenic lymphoproliferative syndrome that culminates, past 12 months of age, in clonal B cell lymphomas with DLBCL morphology and somatically mutated IgV genes (~70% of the animals) (Cattoretti et al., Cancer Cell 7:445–455, 2005). Mice were monitored for tumor incidence and survival, and a combination of histologic, immunophenotypic and gene expression profiling analysis was used for tumor characterization. As expected, no significant differences in event-free survival and lymphoma type were observed between AID-proficient and AID-deficient λMYC mice, in agreement with their pre-GC derivation. Conversely, a phenotypic shift of the tumor was observed in λMYC/IμHABCL6 mice when bred into an AID−/− background, with >80% of the cases (N=21/26) reverting to a pre-GC phenotype (loss of GC/post GC markers) undistinguishable from that of the λMYC and λMYC/AID−/− mice. Gene expression profile analysis on representative cases (N=10 λMYC/IμHABCL6 and 5 each for λMYC, λMYC/AIDKO, λMYC/IμHABCL6/AIDKO) confirmed significant phenotypic similarities between pre-GC derived λMYC lymphomas and the λMYC/IμHABCL6/AID −/− lymphomas, which co-segregated in a separate cluster from λMYC/IμHABCL6 tumors. Analogously, a significant reduction in DLBCL frequency was observed in the IμHABCL6/AIDKO cohort as compared to IμHABCL6 mice (N= 4/19, 21% vs 8/14, 57%; p=0.03). Taken together, these results indicate that GC-derived lymphomas cannot develop in the absence of AID, thereby providing direct support to the notion that AID-mediated mistakes in antigen receptor gene modification events (CSR and SHM) represent major contributors to B-NHL pathogenesis.

scholarly journals miR-181b negatively regulates activation-induced cytidine deaminase in B cells

2008 ◽  
Vol 205 (10) ◽  
pp. 2199-2206 ◽  
Author(s):  
Virginia G. de Yébenes ◽  
Laura Belver ◽  
David G. Pisano ◽  
Susana González ◽  
Aranzazu Villasante ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Molecular Mechanisms ◽  
Bystander Effect ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Fine Tuning ◽  
Functional Screening ◽  
Activation Induced Cytidine Deaminase ◽  
Activated B Cells

Activated B cells reshape their primary antibody repertoire after antigen encounter by two molecular mechanisms: somatic hypermutation (SHM) and class switch recombination (CSR). SHM and CSR are initiated by activation-induced cytidine deaminase (AID) through the deamination of cytosine residues on the immunoglobulin loci, which leads to the generation of DNA mutations or double-strand break intermediates. As a bystander effect, endogenous AID levels can also promote the generation of chromosome translocations, suggesting that the fine tuning of AID expression may be critical to restrict B cell lymphomagenesis. To determine whether microRNAs (miRNAs) play a role in the regulation of AID expression, we performed a functional screening of an miRNA library and identified miRNAs that regulate CSR. One such miRNA, miR-181b, impairs CSR when expressed in activated B cells, and results in the down-regulation of AID mRNA and protein levels. We found that the AID 3′ untranslated region contains multiple putative binding sequences for miR-181b and that these sequences can be directly targeted by miR-181b. Overall, our results provide evidence for a new regulatory mechanism that restricts AID activity and can therefore be relevant to prevent B cell malignant transformation.

Pediatric Acute Lymphoblastic Leukemia Outcome Predictor Genes OPAL1 and RANTES Modulate Transformation by the V-Abl Oncogene

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5318-5318
Author(s):  
Jason H. Rogers ◽  
Kristin S. Owens ◽  
Jake M. Vargas ◽  
Cheryl L. Willman ◽  
Robert Hromas ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
Lymph Nodes ◽  
B Cell ◽  
Drug Targets ◽  
Lymphoblastic Leukemia ◽  
Novel Drug ◽  
Novel Drug Targets

Abstract B-precursor acute lymphoblastic leukemia (ALL) is the most common cancer of childhood. While it represents a highly curable malignancy, a significant number of children still relapse or present with disease that is resistant to therapeutic intensification. With the increasing intensity of curative treatment, there is also an increased incidence of late effects that adversely affect the quality of life of survivors. Previously, a large scale microarray gene expression analysis was undertaken in order to identify genes predictive of outcome that could enhance risk classification, thereby identifying children who might be cured with less intensive therapy or those who fail current regimens and require novel therapies for cure. From analysis of 254 pediatric ALL samples registered to various COG clinical trials, gene expression classifiers were identified that are highly predictive of poor and favorable outcome in precursor B-cell ALL. The goal of this project is to study the biologic function and role in hematopoiesis and leukemogenesis of the genes predictive of outcome and to determine whether any of these genes may serve as novel drug targets. To this end, we have developed a system to examine the effect of these genes on the cancer-promoting activity of the v-Abl oncogene. We have established pre-B cell lines by infecting primary mouse bone marrow cells with a virus expressing v-Abl. These lines were then engineered to express two of the genes we identified that were associated with poor or good treatment outcomes, RANTES (CCL5) and OPAL1 respectively. Consistent with the association of RANTES expression with poor outcome, v-Abl/RANTES pre-B cells are more proliferative than v-Abl cells, and form larger colonies in methylcellulose cultures without added cytokines. OPAL1 had the opposite effect on pre-B cell growth. V-Abl pre-B cells expressing OPAL1 were less proliferative and generated fewer colonies in methylcellulose cultures. To determine whether RANTES made the v-Abl pre-B cells more leukemic, we transplanted v-Abl or v-Abl/RANTES pre-B cells into syngeneic mice. Mice were noticeably ill 30 days post-transplant. Mice injected with v-Abl/RANTES cells had enlarged lymph nodes and increased numbers of white cells in their peripheral blood. The percentage of pre-B cells in the bone marrow, lymph nodes and spleen was higher in v-Abl/RANTES transplanted mice compared to v-Abl transplanted mice. Currently our data demonstrates that the outcome genes are playing a mechanistic role in the susceptibility of leukemic cells to therapy, and are not merely epiphenomenon. This suggests that the products of these genes and their associated pathways may be novel drug targets. Such targeted therapy has the potential of being less toxic than current nonspecific treatment regimens.

AID constrains germinal center size by rendering B cells susceptible to apoptosis

Blood ◽  
2009 ◽  
Vol 114 (3) ◽  
pp. 547-554 ◽  
Author(s):  
Ahmad Zaheen ◽  
Bryant Boulianne ◽  
Jahan-Yar Parsa ◽  
Shaliny Ramachandran ◽  
Jennifer L. Gommerman ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Cytidine Deaminase ◽  
Enzyme Activation ◽  
Specific Enzyme ◽  
Tissue Microenvironment ◽  
Activation Induced Cytidine Deaminase ◽  
Immunoglobulin Locus

Abstract The germinal center (GC) is a transient lymphoid tissue microenvironment that fosters T cell–dependent humoral immunity. Within the GC, the B cell–specific enzyme, activation-induced cytidine deaminase (AID), mutates the immunoglobulin locus, thereby altering binding affinity for antigen. In the absence of AID, larger GC structures are observed in both humans and mice, but the reason for this phenomenon is unclear. Because significant apoptosis occurs within the GC niche to cull cells that have acquired nonproductive mutations, we have examined whether a defect in apoptosis could account for the larger GC structures in the absence of AID. In this report, we reveal significantly reduced death of B cells in AID−/− mice as well as in B cells derived from AID−/− bone marrow in mixed bone marrow chimeric mice. Furthermore, AID-expressing B cells show decreased proliferation and survival compared with AID−/− B cells, indicating an AID-mediated effect on cellular viability. The GC is an etiologic site for B-cell autoimmunity and lymphomagenesis, both of which have been linked to aberrant AID activity. We report a link between AID-induced DNA damage and B-cell apoptosis that has implications for the development of B-cell disorders.

scholarly journals Overexpression of Activation-Induced Cytidine Deaminase in MTX- and Age-Related Epstein-Barr Virus-Associated B-Cell Lymphoproliferative Disorders of the Head and Neck

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Kentaro Kikuchi ◽  
Toshiyuki Ishige ◽  
Fumio Ide ◽  
Yumi Ito ◽  
Ichiro Saito ◽  
...  
Keyword(s):  
B Cell ◽  
Epstein Barr Virus ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Lymphoproliferative Disorders ◽  
Barr Virus ◽  
Age Related ◽  
Activation Induced Cytidine Deaminase ◽  
Epstein Barr

Recent research has shown that activation-induced cytidine deaminase (AID) triggers somatic hypermutation and recombination, in turn contributing to lymphomagenesis. Such aberrant AID expression is seen in B-cell leukemia/lymphomas, including Burkitt lymphoma which is associated withc-myctranslocation. Moreover, Epstein-Barr virus (EBV) latent membrane protein-1 (LMP-1) increases genomic instability through early growth transcription response-1 (Egr-1) mediated upregulation of AID in B-cell lymphoma. However, few clinicopathological studies have focused on AID expression in lymphoproliferative disorders (LPDs). Therefore, we conducted an immunohistochemical study to investigate the relationship between AID and LMP-1 expression in LPDs (MTX-/Age-related EBV-associated), including diffuse large B-cell lymphomas (DLBCLs). More intense AID expression was detected in LPDs (89.5%) than in DLBCLs (20.0%), and the expression of LMP-1 and EBER was more intense in LPDs (68.4% and 94.7%) than in DLBCLs (10.0% and 20.0%). Furthermore, stronger Egr-1 expression was found in MTX/Age-EBV-LPDs (83.3%) than in DLBCLs (30.0%). AID expression was significantly constitutively overexpressed in LPDs as compared with DLBCLs. These results suggest that increased AID expression in LPDs may be one of the processes involved in lymphomagenesis, thereby further increasing the survival of genetically destabilized B-cells. AID expression may be a useful indicator for differentiation between LPDs and DLBCLs.

Evaluation of FOXP1 gene expression in pediatric B-cell precursor acute lymphoblastic leukemia patients at remission induction therapy

2020 ◽  
Author(s):  
Gholamhossein Tamaddon ◽  
Mehran Bahraini ◽  
Alieh Fazeli
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
B Cell ◽  
Cell Line ◽  
Lymphoblastic Leukemia ◽  
Remission Induction ◽  
Control Group ◽  
Cell Precursor ◽  
New Diagnosis

Background: Transcription factors (TFs) play a key role in the development, therapy, and relapse of B-cell malignancies, such as B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Given the essential function of Forkhead box protein P1 (FOXP1) transcription factor in the early development of B-cells, this study was designed to evaluate FOXP1 gene expression levels in pediatric BCP-ALL patients and NALM6 cell-line. Materials and Methods: This case-control study was done on the NALM6 cell-line and bone marrow specimens of 23 pediatric BCP-ALL patients (median age: 7.5 years; range: 2.0 – 15.0 years) at different clinical stages including new diagnosis, 15th day after the treatment, and relapse. Also, 10 healthy children were included as the control group. FOXP1 gene expression was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). The correlation analysis was performed between the FOXP1 gene expression and patients’ demographic and laboratory characteristics. Results: The results showed that FOXP1 gene expression was significantly downregulated in the NALM-6 cell-line (median=0.05, P<0.001) and patients at new diagnosis (median=0.06, p<0.0001), and relapse (median=0.001, p<0.0001) phases, compared to the control group (median=0.08). FOXP1 gene expression on the 15th day of the treatment was significantly higher than its level at the new diagnosis stage (p<0.001). Moreover, FOXP1 gene was significantly downregulated in the relapse phase compared to the new diagnosis. Patients whose number of bone marrow blasts on the 15th day of the treatment was below 5% had higher FOXP1 gene expression at the diagnosis phase (Spearman’s correlation, P<0.05, r=-0.485) and higher ratio of diagnosis/day 15 (p<0.001, Mann-Whitney U test). Conclusions: FOXP1 levels could be a potential biomarker of therapy response in remission induction therapy for pediatric BCP-ALL patients.

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