Project description:IKAROS is an important tumor suppressor in human pre-B ALL and is mutated or deleted in a high percentage of human BCR-ABL1+ (Ph+) pre-B ALL. We here report the genome-wide binding of IKAROS in two independent patient-derived BCR-ABL1+ (Ph+) pre-B ALL xenograft cells that express wild type full-length IKAROS.
Project description:To examine Ikaros tumor suppressor mechanisms, we have utilized inducible RNAi to dynamically restore endogenous Ikaros expression in BCR-ABL1+ B-ALL driven by its knockdown (Ikaros knockdown), and compared these tumors to tumors driven by BCR-ABL1 alone (control). Restoration of Ikaros causes rapid regression of tumor cells in vivo, significantly prolonging tumor transplant recipient survival. Using both transgenic and retroviral approaches, we conducted expression analysis of B-ALL by RNA-Seq and have identified a series of Ikaros-regulated genes within established tumor cell in vivo. Comparison of Ikaros-activated and Ikaros-repressed genes with human B-ALL expression data shows a set of conserved Ikaros target genes, some of which are associated with patient outcome (namely, CTNND1, IFITM3 and EMP1).
Project description:BCR-ABL1 lymphoblastic leukaemia is characterized by the deletion of Ikaros. The Philadelphia chromosome, encoding BCR-ABL1, is the defining lesion of chronic myelogenous leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL) cases. To define oncogenic lesions that cooperate with BCR-ABL1 to induce ALL, we performed genome-wide analysis of leukemic samples from 23 CML cases and 304 ALL cases, including 43 BCR-ABL1 B-ALL cases. IKZF1 (encoding the transcription factor Ikaros) was deleted in 83.7% of BCR-ABL1 B-ALL cases, but not in chronic phase CML. Deletion of IKZF1 was also identified as an acquired lesion in lymphoid blast crisis of CML. The IKZF1 deletions resulted in haploinsufficiency, expression of a dominant negative Ikaros isoform or the complete loss of Ikaros expression. Sequencing of IKZF1 deletion breakpoints suggested that aberrant V(D)J recombination is responsible for the deletions. These findings suggest that genetic lesions resulting in the loss of Ikaros function are a key event in the development of BCR-ABL1 ALL. *** Due to privacy concerns, the primary SNP array data is no longer available with unrestricted access. Individuals wishing to obtain this data for research purposes may request access using the Web links below. *** This SuperSeries is composed of the SubSeries listed below.
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:Deletions within the human IKZF1 gene, which encodes Ikaros, a zinc finger transcription factor critical for lymphopoiesis, appear to be the most prominent recurring lesion in human BCR-ABL1+ (Ph+) B-ALL. Furthermore, IKZF1 mutations correlate with poor prognosis of progenitor B-ALL, further strengthening the notion that IKZF1 is a critical tumor suppressor gene in human B-lineage malignancies. To better understand the relationship between Ikzf1 mutations, BCR-ABL, and B-lineage leukemia, we examined the effect of two newly generated Ikzf1 germline mutation on BCR-ABL-induced proliferation and leukemogenesis in vitro and in vivo. We recently showed that deletion of either the exon encoding the first or the fourth DNA-binding zinc finger of Ikaros (IkZnF1-/- and IkZnF4-/-) led to distinct defects in lymphoid development and tumor suppression with de-regulation of distinct subsets of genes, providing a powerful tool for elucidation of Ikaros target genes and mechanism of function. Importantly, IkZnF4-/- had lost Ikaros tumor suppression function, while not abolishing B-cell development. Retroviral expression of BCR-ABL1 p185 in bone marrow cells from the two Ikzf1 mutant strains demonstrated that loss of ZnF4 resulted in expansion of progenitor B cells, with enhanced proliferation in vitro and a less mature cell surface B-cell phenotype in comparison to transduced wild-type bone marrow. Furthermore, in an in vivo model of BCR-ABL+ B-ALL, leukemias generated in the IkZnF4-/- background were more aggressive than those observed in a wild-type background, with cell phenotype corresponding to the in vitro cell cultures. Genome wide high throughput expression analysis (RNA-Seq) revealed a distinct subset of deregulated genes in the IkZnF4-/- BCR-ABL+ in vitro cell cultures, and molecular analysis demonstrated that this in vitro system is amendable for functional studies. These results establish a mouse model for studying the role of Ikzf1 mutations in B-ALL, and for understanding how BCR-ABL collaborates with Ikzf1 mutations to generate aggressive B-ALL.
Project description:Traditional response criteria in MDS and AML are based on bone marrow morphology and may not accurately reflect tumor burden in patients treated with hypomethylating agents. We used massively parallel sequencing of serial bone marrow samples to monitor MDS and AML tumor burden during treatment with epigenetic therapy (decitabine and panobinostat). Serial bone marrow samples (and skin as a source of normal DNA) from 25 MDS and AML patients were sequenced . We observed that responders, including those in complete remission (CR), can have persistent measurable tumor burden for at least one year without disease progression. Using an ultra-sensitive barcode sequencing approach, we detected extremely rare mutations months to years prior to disease relapse. While patients can live with persistent clonal hematopoiesis in a CR or stable disease, ultimately we find evidence that expansion of a rare subclone can drive relapse or progression. Digital sequencing provides an alternative measure of tumor burden and disease response which may augment traditional clinical response criteria in patients treated with hypomethylating agents and its use should be explored in future clinical trials. BCR-ABL1 lymphoblastic leukaemia is characterized by the deletion of Ikaros. The Philadelphia chromosome, encoding BCR-ABL1, is the defining lesion of chronic myelogenous leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL) cases. To define oncogenic lesions that cooperate with BCR-ABL1 to induce ALL, we performed genome-wide analysis of leukemic samples from 23 CML cases and 304 ALL cases, including 43 BCR-ABL1 B-ALL cases. IKZF1 (encoding the transcription factor Ikaros) was deleted in 83.7% of BCR-ABL1 B-ALL cases, but not in chronic phase CML. Deletion of IKZF1 was also identified as an acquired lesion in lymphoid blast crisis of CML. The IKZF1 deletions resulted in haploinsufficiency, expression of a dominant negative Ikaros isoform or the complete loss of Ikaros expression. Sequencing of IKZF1 deletion breakpoints suggested that aberrant V(D)J recombination is responsible for the deletions. These findings suggest that genetic lesions resulting in the loss of Ikaros function are a key event in the development of BCR-ABL1 ALL.
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.