Project description:Activation-Induced Cytidine Deaminase (AID) is required for somatic hypermutation and immunoglobulin (Ig) class switch recombination in germinal center B lymphocytes. Occasionally, AID targets non-Ig genes, thereby contributing to B cell lymphomagenesis. We recently reported aberrant expression of AID in BCR-ABL1-driven acute lymphoblastic leukemia (ALL). To elucidate the biological significance of aberrant AID expression, we studied loss of AID function in a murine model of BCR-ABL1 ALL. Mice transplanted with BCR-ABL1-transduced AID-/- bone marrow had prolonged survival as compared to mice transplanted with leukemia cells generated from AID+/+ bone marrow. Consistent with a causative role of AID in genetic instability, AID-/- leukemia had a decreased frequency of amplifications, deletions and a lower frequency of mutations in non-Ig genes including Pax5 and Rhoh as compared to AID+/+ leukemias. AID-/- and AID+/+ ALL cells showed a markedly distinct gene expression pattern as determined by principle component analysis, with 2,365 genes differentially expressed. In contrast to AID+/+ leukemia, AID-/- ALL cells failed to downregulate a number of tumor suppressor genes such as Rhoh, Cdkn1a (p21), and Blnk (SLP65). We conclude that AID accelerates clonal evolution in BCR-ABL1 ALL by enhancing genetic instability, aberrant somatic hypermutation, and by transcriptional inactivation of tumor suppressor genes. Experiment Overall Design: We used microarrays to detect differences in gene expression profiles between AID expressing leukemia and AID deficient leukemia
Project description:Activation-Induced Cytidine Deaminase (AID) is required for somatic hypermutation and immunoglobulin (Ig) class switch recombination in germinal center B lymphocytes. Occasionally, AID targets non-Ig genes, thereby contributing to B cell lymphomagenesis. We recently reported aberrant expression of AID in BCR-ABL1-driven acute lymphoblastic leukemia (ALL). To elucidate the biological significance of aberrant AID expression, we studied loss of AID function in a murine model of BCR-ABL1 ALL. Mice transplanted with BCR-ABL1-transduced AID-/- bone marrow had prolonged survival as compared to mice transplanted with leukemia cells generated from AID+/+ bone marrow. Consistent with a causative role of AID in genetic instability, AID-/- leukemia had a decreased frequency of amplifications, deletions and a lower frequency of mutations in non-Ig genes including Pax5 and Rhoh as compared to AID+/+ leukemias. AID-/- and AID+/+ ALL cells showed a markedly distinct gene expression pattern as determined by principle component analysis, with 2,365 genes differentially expressed. In contrast to AID+/+ leukemia, AID-/- ALL cells failed to downregulate a number of tumor suppressor genes such as Rhoh, Cdkn1a (p21), and Blnk (SLP65). We conclude that AID accelerates clonal evolution in BCR-ABL1 ALL by enhancing genetic instability, aberrant somatic hypermutation, and by transcriptional inactivation of tumor suppressor genes.
Project description:This comparative genomic hybridization (CGH) study investigated the effect of BCL6 on clonal evolution in BCR-ABL1-driven acute lymphoblastic leukemia (ALL). The frequencies of copy number alterations in BCR-ABL1-transformed BCL6+/+ and BCL6-/- leukemias were determined.
Project description:This comparative genomic hybridization (CGH) study investigated the effect of BCL6 on clonal evolution in BCR-ABL1-driven acute lymphoblastic leukemia (ALL). The frequencies of copy number alterations in BCR-ABL1-transformed BCL6+/+ and BCL6-/- leukemias were determined. Three BCR-ABL1-transformed BCL6+/+ and BCL6-/- ALL samples derived from mice were maintained for 4 month in cell culture and were subjected to CGH analysis. As control samples, normal untransformed splenoytes were used.
Project description:Activation-induced cytidine deaminase (AID) specific amplifications and deletions in BCR-ABL1 positive Leukemia mouse cells. Bone marrow from Balb/CJ WT and Balb/CJ AID KO mice was transduced with BCR-ABL1. The AID specific amplifications and deletions where analyzed with an Agilent 244A mouse whole Genome CGH Array.
Project description:The Philadelphia chromosome (Ph) encoding the oncogenic BCR-ABL1 kinase defines a subset of ALL with a particularly unfavorable prognosis. Acute lymphoblastic leukemia (ALL) cells are derived from B cell precursors in most cases and typically carry rearranged immunglobulin heavy chain (IGH) variable (V) region genes devoid of somatic mutations. Somatic hypermutation is restricted to mature germinal center B cells and depends on activation-induced cytidine deaminase (AID). Studying AID expression in 108 cases of ALL, we detected AID mRNA in 24 of 28 Ph-positive ALLs as compared to 6 of 80 Ph-negative ALLs. Forced expression of BCR-ABL1 in Ph-negative ALL cells and inhibition of the BCR-ABL1-kinase showed that aberrant expression of AID depends on BCR-ABL1 kinase activity. Consistent with aberrant AID expression in Ph-positive ALL, IGH V region genes and BCL6 were mutated in many Ph-positive but unmutated in most Ph-negative cases. In addition, AID introduced DNA-single-strand breaks within the tumor suppressor gene CDKN2B in Ph-positive ALL cells, which was sensitive to BCR-ABL1 kinase inhibition and silencing of AID expression by RNA interference. These findings identify AID as a BCR-ABL1-induced mutator in Ph-positive ALL cells, which may be relevant with respect to the particularly unfavorable prognosis of this leukemia subset. Experiment Overall Design: To study the gene expression profile of two Ph-positive ALL cell lines (BV173 and SUP-B15) in the presence or absence of 10 μmol/l STI571 for 16 hours
Project description:The Philadelphia chromosome (Ph) encoding the oncogenic BCR-ABL1 kinase defines a subset of ALL with a particularly unfavorable prognosis. Acute lymphoblastic leukemia (ALL) cells are derived from B cell precursors in most cases and typically carry rearranged immunglobulin heavy chain (IGH) variable (V) region genes devoid of somatic mutations. Somatic hypermutation is restricted to mature germinal center B cells and depends on activation-induced cytidine deaminase (AID). Studying AID expression in 108 cases of ALL, we detected AID mRNA in 24 of 28 Ph-positive ALLs as compared to 6 of 80 Ph-negative ALLs. Forced expression of BCR-ABL1 in Ph-negative ALL cells and inhibition of the BCR-ABL1-kinase showed that aberrant expression of AID depends on BCR-ABL1 kinase activity. Consistent with aberrant AID expression in Ph-positive ALL, IGH V region genes and BCL6 were mutated in many Ph-positive but unmutated in most Ph-negative cases. In addition, AID introduced DNA-single-strand breaks within the tumor suppressor gene CDKN2B in Ph-positive ALL cells, which was sensitive to BCR-ABL1 kinase inhibition and silencing of AID expression by RNA interference. These findings identify AID as a BCR-ABL1-induced mutator in Ph-positive ALL cells, which may be relevant with respect to the particularly unfavorable prognosis of this leukemia subset. Keywords: gene expression array-based (RNA / in situ oligonucleotide)
Project description:The Philadelphia chromosome (Ph) encodes the oncogenic BCR-ABL1 tyrosine kinase, which defines a subset of acute lymphoblastic leukemia (ALL) with a particularly unfavorable prognosis. Tyrosine kinase inhibitors (TKI) are widely used to treat patients with leukemia driven by BCR-ABL1 and other oncogenic tyrosine kinases. In response to TKI-treatment, BCR-ABL1 ALL cells upregulate BCL6 protein levels by ~90-fold, i.e. to similar levels as in diffuse large B cell lymphoma (DLBCL) with BCL6 translocations. In this study, we analyzed the gene expression changes after treatment with Imatinib or Imatinib + RI-BPI.
Project description:The Philadelphia chromosome (Ph) encodes the oncogenic BCR-ABL1 tyrosine kinase, which defines a subset of acute lymphoblastic leukemia (ALL) with a particularly unfavorable prognosis. Tyrosine kinase inhibitors (TKI) are widely used to treat patients with leukemia driven by BCR-ABL1 and other oncogenic tyrosine kinases. In response to TKI-treatment, BCR-ABL1 ALL cells upregulate BCL6 protein levels by ~90-fold, i.e. to similar levels as in diffuse large B cell lymphoma (DLBCL) with BCL6 translocations. In this study, we used genome tiling arrays to identify BCL6 target genes with specific recruitment of BCL6.