Yasuo Horikoshi

Internal tandem duplication of the FLT3 gene and clinical evaluation in childhood acute myeloid leukemia

We analyzed tandem duplication in the juxtamembrane (JM) domain of the FLT3 (FMS-like tyrosine kinase 3/FLK2, CD135) gene in 94 children with acute myeloid leukemia (AML) and evaluated its correlation with clinical features. Longer polymerase chain reaction (PCR) products were observed in five patients; 1/3 of M0, 1/9 of M1, 1/39 of M2, 1/9 of M3 and 1/12 of M5. The sequence analyses of abnormal PCR products showed that all the abnormal products were derived from tandem duplications involving the JM domain and that all the lengthened sequences were in-frame as we previously reported. Statistical analyses revealed a significantly lower incidence of the tandem duplication in childhood AML patients than in adult patients (P < 0.05), and significantly shorter disease-free survival in patients with mutant FLT3 than in patients with wild-type FLT3 (P < 0.05). our results suggest that the tandem duplication in the jm domain of the FLT3 gene is not a frequent phenomenon but might be a factor of poor prognosis in childhood patients with AML.

Chromosome abnormalities and MLL rearrangements in acute myeloid leukemia of infants.

Of 29 infants with acute myeloid leukemia (AML), 14 (48%) had various 11q23 translocations. MLL rearrangements were examined in 21 of the 29 patients, and 11 (52%) showed the rearrangements. 11q23 translocations and/or MLL rearrangements were found in 17 (58%) of the 29 patients. While all but one of the 17 patients with 11q23/MLLrearrangements had M4 or M5 type of the FAB classification, the 12 patients without such rearrangements had various FAB types, including M2, M4, M4EO, M6 and M7. Of the 12 patients with other chromosome abnormalities or normal karyotypes, two had inv(16) or t(16;16), one had t(1;22)(p13;q13), and two had a novel translocation, t(7;12)(q32;p13). The breakpoint on 12p of the t(7;12) was assigned to intron 1 or the region just upstream of exon 1 of the TEL/ETV6 gene by fluorescence in situ hybridization. The event-free survival at 5 years for the 17 patients with 11q23/MLL rearrangements was 42.2%, and that for the 12 patients without such rearrangements was 31.3% (P = 0.5544). 11q23/MLLrearrangements have been frequently reported and a poor prognosis in infant acute lymphoblastic leukemia implied. Our study showed that while 11q23/MLL rearrangements were also common in infant AML, AML infants with such rearrangements had a clinical outcome similar to that of AML infants without such rearrangements.

Risk factors for early death in neonates with Down syndrome and transient leukaemia.

Transient leukaemia (TL) in neonates with Down syndrome (DS) is characterized by the transient appearance of blast cells in the peripheral blood that resolves spontaneously. Some TL patients die at an early age due to organ failure. Seventy DS patients with TL were studied retrospectively to identify clinical and laboratory characteristics associated with early death (<6 months of age). Sixteen of 70 patients (22·9%) died early. The main causes of death were organ failure, particularly hepatic and cardiopulmonary failure. On univariate analysis, early gestational age (EGA), high white blood cell (WBC) count (≥100 × 109/l), percentage of peripheral blasts, elevated aspartate transaminase (AST), elevated direct bilirubin (DB), and low Apgar score were significantly associated with poor survival. On multivariate analysis, EGA, WBC count, and DB were independent predictors of poor outcome. A simple risk stratification system combining EGA and WBC count was devised to predict poor outcome. Term infants (EGA ≥ 37 weeks) whose WBC count was lower than 100 × 109/l had the best outcome [7·7% (3/39) died early], while preterm infants (EGA < 37 weeks) whose WBC count was higher than 100 × 109/l had the worst outcome [54·5% (6/11) died early]. This stratification system may be useful for identifying high‐risk patients who need early therapeutic interventions.

Minimal residual disease-based augmented therapy in childhood acute lymphoblastic leukemia: A report from the Japanese Childhood Cancer and Leukemia Study Group†

The majority of minimal residual disease (MRD)‐positive patients with acute lymphoblastic leukemia (ALL) have poor outcomes. The ALL2000 study was performed to evaluate the efficacy of augmented chemotherapy based on MRD‐restratification in childhood ALL.

Minimal residual disease with TEL-AML1 fusion transcript in childhood acute lymphoblastic leukaemia with t(12;21).

We analysed the TEL‐AML1 transcript using reverse transcription‐polymerase chain reaction (RT‐PCR) in order to detect minimal residual disease (MRD) in seven children with t(12;21)‐associated B‐lineage ALL. Leukaemic cells with the TEL‐AML1 transcript appear to be very sensitive to chemotherapy, and may be eradicated in most patients if adequate chemotherapy is given. However, a small number of patients with t(12;21) ALL may relapse under the currently used chemotherapy, and we believe that RT‐PCR for detecting MRD with the transcript is a suitable tool for monitoring the efficacy of chemotherapy or impending relapse in these patients. We analysed the TEL‐AML1 transcript using reverse transcription‐polymerase chain reaction (RT‐PCR) in order to detect minimal residual disease (MRD) in seven children with t(12;21)‐associated B‐lineage ALL. Two sets of primers, TEL exon 5 and AML1 exon 3 or 4, detected two types of transcript in four patients and two other types in two other patients. The two different translocation breakpoints in the AML1 gene with or without splicing out of AML1 exon 3 seemed to result in these four types of transcript in leukaemia samples.

Clonal and non-clonal karyotypically abnormal cells in haemophagocytic lymphohistiocytosis

We studied chromosomes in bone marrow (BM) or peripheral blood cells of nine patients with haemophagocytic lymphohistiocytosis (HLH); three of them had a family history of HLH and four others underwent concurrent Epstein‐Barr virus (EBV) infection. In addition to a large population of normal mitotic cells, karyotypically abnormal clonal cells were found in two patients, abnormal clonal cells and a nonclonal (single) abnormal cell in one, and nonclonal abnormal cells in three. All the six patients with chromosome abnormalities died of progressive disease; one of them also had EBV infection and EBV‐associated clonal proliferation. Two of three patients with EBV infection and only normal mitotic cells in BM completely recovered from the disease.

Frequent Increase of DNA Copy Number in the 2q24 Chromosomal Region and Its Association with a Poor Clinical Outcome in Hepatoblastoma: Cytogenetic and Comparative Genomic Hybridization Analysis

In a cytogenetic and comparative genomic hybridization (CGH) study of 38 hepatoblastomas, we found gain of Iq in 17 tumors (44.7%), that of 2/2q in 14 (36.8%), that of 20/20q in 9 (23.7%) and that of 8/8q in 8 (21.0%), loss of 4q in 4 (10.5%) and no DNA copy changes with normal karyotype or no mitotic cells in 11 (28.9%). Eleven tumors with 2/2q gain detected by CGH had a total chromosome 2 gain, a partial 2q gain, or a total chromosome 2 gain with an augmented partial 2q region; the common region for DNA copy gain was 2q24. Two‐color fluorescence in situ hybridization (FISH) analyses using probes covering the centromere of chromosome 2 or HOXD13 (2q31) confirmed the CGH findings, and showed that the common region for gain in 2q was centromeric to HOXD13. Event‐free survival (EFS)±standard error (SE) at 5 years was lowest in patients with 2q gain [37±15%], highest in those with no DNA copy changes [82±12%], and intermediate in those with DNA copy changes other than 2q gain [74±13%] (P=0.0549). Multivariate analysis showed that 2q gain was an independent factor predicting a poor outcome. These findings suggest the presence of a growth‐promoting gene or an oncogene in the 2q24 chromosome band, and a tumor suppressor gene in terminal 4q, which have important roles in the development and progression of hepatoblastoma.

Second allogeneic hematopoietic SCT for relapsed ALL in children

A second SCT is generally accepted as the only potentially curative approach for ALL patients that relapse after SCT, but the role of second SCT for pediatric ALL is not fully understood. We performed a retrospective analysis of 171 pediatric patients who received a second allo-SCT for relapsed ALL after allo-SCT. OS at 2 years was 29.4±3.7%, the cumulative incidence of relapse was 44.1±4.0% and non-relapse mortality was 18.8±3.5%. Relapse occurred faster after the second SCT than after the first SCT (117 days vs 164 days, P=0.04). Younger age (9 years or less), late relapse (180 days or more after first SCT), CR at the second SCT, and myeloablative conditioning were found to be related to longer survival. Neither acute GVHD nor the type of donor influenced the outcome of second SCT. Multivariate analysis showed that younger age and late relapse were associated with better outcomes. Our analysis suggests that second SCT for relapsed pediatric ALL is an appropriate treatment option for patients that have achieved CR, which is associated with late relapse after the first SCT.

Continuous and high-dose cytarabine combined chemotherapy in children with down syndrome and acute myeloid leukemia: Report from the Japanese children's cancer and leukemia study group (JCCLSG) AML 9805 down study.

The aim of the JCCLSG AML 9805 Down study was to evaluate the effect of continuous and high‐dose cytarabine combined chemotherapy on the survival outcome of acute myeloid leukemia (AML) with Down syndrome (DS).

Long-term results of the Japanese Childhood Cancer and Leukemia Study Group studies 811, 841, 874 and 911 on childhood acute lymphoblastic leukemia

We analyzed the long-term outcomes of 1021 patients with acute lymphoblastic leukemia (ALL), enrolled in four successive clinical trials (ALL811, ALL841, ALL874 and ALL911) between 1981 and 1993. All patients received risk-adopted therapy according to leukocyte count and age at the time of diagnosis. The median follow-up durations of the four studies were 17.8 years in ALL811, 15.5 years in ALL841, 11.9 years in ALL874 and 15.8 years in ALL911. Patients’ event-free survival (EFS) and overall survival (OS) rates at 12 years were 41.0 and 54.3% in ALL811, 50.2 and 60.2% in ALL841, 57.3 and 64.7% in ALL874, and 63.4 and 71.7% in ALL911, respectively. Thus, cure can become a reality for about 70% of children with ALL. There is, however, still a significant difference in survival outcomes according to risk group. Late effects were observed in 70 patients out of 834 (8.4%); hepatitis and short stature were most commonly reported. Reduction of late adverse effects for all patients and development of new treatment strategies for very-high-risk patients are major issues for upcoming trials to address.