ABSTRACT
MLL gene rearrangement is common in both adult and childhood acute myeloid leukaemia (AML), and its role in oncogenesis has been investigated. While over 50 translocated-partner genes have been identified so far, few studies have detailed the molecular mechanism of partial tandem duplication (PTD) of the MLL gene. The prognostic impact and contribution to leukaemogenesis of MLL-PTD, especially in childhood cases, remain unknown. We have established a novel cell line containing MLL-PTD derived from an 11-year-old patient with AML and designated as KOPM-88. KOPM-88 cells exhibited certain characteristics associated with the myeloid lineage including abundant primary granules in the cytoplasm and the expression of myeloperoxidase. The cell growth of KOPM-88 was cytokine independent but was accelerated by granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor. MLL-PTD of exon 2 to exon 6 and exon 2 to exon 8 was revealed using Southern blotting, fluorescence in situ hybridisation, and reverse transcription polymerase chain reaction/DNA sequencing. Furthermore, non-obese diabetic/severe combined immunodeficient mice inoculated with KOPM-88 cells exhibited leukaemic infiltrations in the bone marrow and hemiparalysis because of compression myelopathy. This is the first report of an in vivo animal model exhibiting the systemic involvement of childhood AML containing MLL-PTD. KOPM-88 cells and our murine model may be useful for investigating the pathogenesis of childhood AML associated with MLL gene rearrangement.
Subject(s)
Gene Duplication , Leukemia, Myeloid, Acute/genetics , Myeloid-Lymphoid Leukemia Protein/genetics , Tandem Repeat Sequences/genetics , Animals , Antigens, Surface/immunology , Cell Division/immunology , Cell Line, Tumor , Cell Transplantation/methods , Child , Cytokines/immunology , Disease Models, Animal , Fatal Outcome , Flow Cytometry/methods , Gene Rearrangement/genetics , Histone-Lysine N-Methyltransferase , Humans , In Situ Hybridization, Fluorescence/methods , Leukemia, Myeloid, Acute/immunology , Leukemia, Myeloid, Acute/pathology , Male , Mice , Mice, Inbred NOD , Mice, SCID , Polymerase Chain Reaction/methodsABSTRACT
We studied the effectiveness of risk-directed therapy for infants younger than 13 months of age with acute lymphoblastic leukaemia (ALL). Fifty-five infants were assigned to different treatment programs (from December 1995 to December 1998) on the basis of their MLL gene status at diagnosis. Forty-two cases (76.3%) had a rearranged MLL gene (MLL+) and were treated with remission induction therapy followed by sequential intensive chemotherapy, including multiple genotoxic agents (MLL9601 protocol). Haematopoietic stem cell transplantation (HSCT) was attempted if suitable donors were available. Thirteen infants (23.7%) were classified as MLL- and treated for 2.5 years with intensive chemotherapy for high-risk B-ALL (MLL9602 protocol). Complete remission was induced in 38 of the 42 infants (90.5%) with MLL+ ALL and in all 13 patients (100%) with MLL- disease. In the MLL+ subgroup, the estimated event-free survival (EFS) rate at 3 years post diagnosis was 34.0% +/- 7.5%, compared with 92.3% +/- 7.4% in the MLL- subgroup (overall comparison, P = 0.001 by log-rank analysis). Both age less than 6 months (hazard ratio = 6.87, 95% CI = 0.91-52.3; P = 0.013) and central nervous system (CNS) involvement at diagnosis (hazard ratio = 2.92 95% CI = 1.29-6.63; P = 0.015) were significant independent predictors of an inferior outcome. These findings indicate a strategic advantage in classifying infant ALL as either MLL+ or MLL- early in the clinical course and selecting therapy accordingly. Standard chemotherapy for high-risk B-lineage ALL appeared adequate for MLL- cases. Novel therapeutic initiatives are warranted for infants with MLL+ disease, particularly those with initial CNS leukaemic involvement or age less than 6 months, or both.
Subject(s)
DNA-Binding Proteins/genetics , Gene Rearrangement , Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics , Precursor Cell Lymphoblastic Leukemia-Lymphoma/therapy , Proto-Oncogenes , Transcription Factors , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Cytogenetic Analysis , Disease-Free Survival , Follow-Up Studies , Histone-Lysine N-Methyltransferase , Humans , Immunosuppressive Agents/therapeutic use , In Situ Hybridization, Fluorescence , Infant , Infant, Newborn , Japan , Myeloid-Lymphoid Leukemia Protein , Patient Selection , Remission Induction , Risk Assessment , Stem Cell TransplantationABSTRACT
A chimeric gene, AML1-MTG16, showing high homology to AML1-MTG8, was recently identified in adult leukemic patients with the abnormal karyotype t(16;21)(q24;q22). We recently saw a child patient of 11 years of age who developed acute myelogenous leukemia with the karyotype t(16;21)(q24;q22), 11 months after autologous peripheral blood stem-cell transplantation (PBSCT) for acute promyelocytic leukemia with karyotype t(15;17)(q22;q11). The reciprocal translocation was localized by fluorescence in situ hybridization (FISH) analysis, reverse transcription polymerase chain reaction (RT-PCR), and Southern blot analysis of bone marrow blood cells and peripheral blood cells. FISH analysis identified a reciprocal translocation between chromosomes 16 and 21. RT-PCR analysis identified expression of the chimeric gene AML1-MTG16. Southern blot analysis revealed a breakpoint occurring at a 1.4 kb Eco RI fragment between exons 3 and 4 of MTG16. The breakpoint is within the same region as that of secondary leukemias, which has been reported previously. This case suggests the possibility that the region of the breakpoint of MTG16 is a characteristic of secondary leukemia.
