Taijiro Mori

Risk-directed treatment of infant acute lymphoblastic leukaemia based on early assessment of MLL gene status: results of the Japan Infant Leukaemia Study (MLL96).

Summary.  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.

11;19 Translocation in a congenital leukemia with two cell populations of lymphoblasts and monoblasts

This report describes a case of a female infant of congenital leukemia with a chromosomal translocation t(11;19) (q23;p13) which presented initially with lymphoid features and at relapse with monocytic ones. The clinical course and the results of sequential cytochemical, cytogenetic and immunological studies are considered to be consistent with the interpretation of leukemogenesis of the myelo-monocytoid progenitor cell which still retains the capability of exhibiting lymphoid features to a limited extent. Although leukemia with t(11;19) has been classified as ANLL, most commonly M5 of FAB classification, the patient with this chromosomal abnormality may have a mixed leukemia in which cells with lymphoid features and those with monocytic ones exist.

A novel 203 kD aberrant BCR-ABL product in a girl with Philadelphia chromosome positive acute lymphoblastic leultaemia

Summary We report a girl with Ph1‐positive ALL with the aberrant BCR‐ABL product. In this case. bcr exon 3 jointed not to ordinal abl exon 2 but to exon 3 resulting in the production of a 20 3 kD BCR‐ABL fusion protein with marked tyrosine kinase activity. To our knowledge, this is the first report of an aberrant BCR‐ABL product in childhood. This case was characterized with younger age and low leucocyte count at the onset, but relapsed early like the typical Phl‐positive ALL, suggesting the diversity in the clinicopathogenesis of Ph1‐positive ALL.

A Pediatric Case of Secondary Leukemia Associated with t(16;21)(q24;q22) Exhibiting the Chimeric AML1-MTG16 Gene

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.

Acute myeloid leukemia possessing jumping translocation is related to highly elevated levels of EAT/mcl-1, a Bcl-2 related gene with anti-apoptotic functions

Jumping translocations (JTs) are unbalanced chromosomal translocations in which an identical chromosomal region is translocated to the telomeric region of different chromosomes. JTs are rare in hematological malignancies where they are second translocations and may be an indicator of poor prognosis. We report a case of acute myeloid leukemia with t(16;21) and a JT in which the long arm of chromosome 1 distal to q21 is translocated to the terminal region of chromosome 10. The leukemic cells exhibit high expression of EAT/mcl1, an anti-apoptotic Bcl-2 related gene. Since EAT/mcl1 is mapped to 1q21 near the breakpoint in the JTs, high level expression of EAT/mcl1 may be associated with the poor prognosis of leukemia with JTs.

Acute myeloid leukemia with hypergranular cytoplasm accompanied by t(X;11)(q24;q23) and rearrangement of the MLL gene

This report describes a unique case of acute myeloid leukemia with hypergranular cytoplasm and t(X;11)(q24;q23). The breakpoint on 11q23 was identified within the MLL gene. The hypergranular cytoplasm of leukemic cells and the associated coagulopathy resembled a characteristic of acute promyelocytic leukemia, despite the absence of RARalpha gene rearrangement in this case. The Xq24 site possibly played a role in this atypical blast phenotype.

Ph1-positive CML-derived myeloid-monocytoid precursor cell line producing substance(s) that stimulates normal CFU-C

A new Ph1-chromosome positive cell line, KOPM-28. was established from a patient with chronic myelogenous leukemia (CML) in blast crisis. KOPM-28 cells were phenotypically immature: without azurophilic granules; negative for myeloperoxidase and positive for specific and nonspecific esterases. The nonspecific esterase reaction was intensified by TPA, and retinoic acid reinforced the specific esterase reaction without inducing morphological changes. KOPM-28 cells were not phagocytic. The cells expressed complement receptors, myeloid-monocytoid antigens, an Ia-like antigen and T4 antigen. CALLA, T-lymphocyte specific antigens, B-lymphocyte related antigen and platelet-megakaryocyte-megakaryoblast specific antigen were not detected. KOPM-28 cells formed colonies in semi-solid medium; this ability was augmented by GM-CSA. The addition of culture medium conditioned by KOPM-28 cells to normal bone marrow cells resulted in the increase of the CFU-C colonies. These findings indicate that KOPM-28 cells have features of myeloid and monocytoid precursor cells and that they are producing substance(s) which stimulates normal CFU-C.

Analysis of cytoplasmic and surface antigens in childhood T‐cell acute lymphoblastic leukaemias: clinical relevance of cytoplasmic TCRβ chain expression

SUMMARY. Expression of surface and cytoplasmic antigens on the blasts from 42 cases of childhood T‐cell acute lymphoblastic leukaemia (T‐ALL) were analysed. All with childhood T‐ALL, except for one case expressing cytoplasmic TCR δ chain, were classified on the basis of differential expression of cytoplasmic CD3 (cCD3), TCRβ chain (cTCR β) and surface CD3 (sCD3) into the following three groups: group I (cCD3+, cTCRβ‐, sCD3‐), eight cases (19.5%); group II (cCD3+, cTCRβ+, sCD3‐), 23 cases (56.1%); group III (cCD3+, cTCRβ+, sCD3+), 10 cases (24.4%). Each group defines the stepwise maturational stage of the CD3/TCR complex along the intrathymic T‐cell differentiation. Group I had the lowest initial WBC count among the three groups (P < 0.05) and showed significantly (P < 0.05) a higher event‐free survival (0.75) than those of group II (0.33). There was no significant difference in both the initial WBC count and the event‐free survival between groups II and III. Thus, the absence of cTCRβ in sCD3‐negative T‐ALL appears to be a good prognostic factor, suggesting that this classification provides a useful tool to predict the prognosis of childhood T‐ALL. This is the first report, to our knowledge, studying the relationship between the expression of cytoplasmic CD3/TCR antigens and the clinical features in T‐ALL.

Establishment of a novel childhood acute myeloid leukaemia cell line, KOPM-88, containing partial tandem duplication of the MLL gene and an in vivo model for childhood acute myeloid leukaemia using NOD/SCID mice

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.

Expression of MDR-1/P-Glycoprotein in Childhood Acute Megakaryoblastic Leukemia Cells

Multidrug resistance is a major clinical problem in chemotherapy of malignant disease. Acute megakaryoblastic leukemia (AMKL) is a rare form of childhood leukemia, and is often more resistant to many anticancer chemotherapeutic drugs compared to other types of childhood leukemia. There have been reports of the increased expression in hematologic malignancy of multidrug resistant (mdr-1) gene, which encodes for a transmembrane glycoprotein P-glycoprotein that acts as an efflux pump for structurally unrelated chemotherapeutic drugs. We investigated the malignant cells of 15 newly diagnosed childhood AMKL patients by immunocytochemical analysis and found P-glycoprotein expression in all samples from these patients. RNA prepared from five patients at the time of presentation confirmed the expression of mdr-1 specific message in all cases by Northern blot analysis. These results imply that malignant cells from all childhood AMKL might express the mdr-1/P-glycoprotein.