Project description:Recently, a subset of MYC-translocation negative aggressive B-cell lymphomas resembling Burkitt lymphoma (BL) characterized by proximal gains and distal losses in the long arm of chromosome 11 has been described. In the 2016 revision of the WHO classification these MYC-translocation negative lymphomas have been introduced as new provisional entity designated “Burkitt-like lymphoma with 11q aberration” (MNBLL 11q). Here, we show a comprehensive flow-cytometry analysis of 10 MNBLL 11q cases, well characterized genetically and pathologically. Twenty-three cases of MYC-positive BL, including three cases carrying both MYC rearrangements and 11q aberration, served as controls. All MNBLL 11q were CD20+/CD10+/BCL6+/BCL2- /MUM1- /MYC+/EBV negative , presented a high proliferation rate and showed a three-year overall survival (80%) similar to BL patients, with no recurrence after the end of treatment. MNBLL 11q immunophenotype was similar to that of MYC-positive BL without and with 11q, except for less frequent CD38higher expression (10% MNBLL 11q vs 91% MYC-positive BL, p<0.001), less frequent diminished CD45 expression (90% vs 23%, p=0.001), and CD16/CD56 co-expression (60% vs 0%, p<0.001). Our findings suggest subtle but important differences in MNBLL 11q immunophenotypes and MYC-positive BLs, which could not only aid in the differential diagnosis but also in the understanding of the pathogenesis of MNBLL 11q.
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) 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