Chromosomal rearrangements of the human MLL (mixed lineage leukemia) gene are associated with high-risk infant, pediatric, adult and therapy-induced acute leukemias. We used long-distance inverse-polymerase chain reaction to characterize the chromosomal rearrangement of individual acute leukemia patients. We present data of the molecular characterization of 1590 MLL-rearranged biopsy samples obtained from acute leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and novel TPGs identified. All patients were classified according to their gender (852 females and 745 males), age at diagnosis (558 infant, 416 pediatric and 616 adult leukemia patients) and other clinical criteria. Combined data of our study and recently published data revealed a total of 121 different MLL rearrangements, of which 79 TPGs are now characterized at the molecular level. However, only seven rearrangements seem to be predominantly associated with illegitimate recombinations of the MLL gene (∼90%): AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, ELL, partial tandem duplications (MLL PTDs) and MLLT4/AF6, respectively. The MLL breakpoint distributions for all clinical relevant subtypes (gender, disease type, age at diagnosis, reciprocal, complex and therapy-induced translocations) are presented. Finally, we present the extending network of reciprocal MLL fusions deriving from complex rearrangements.

Translocations involving chromosome 11q23 frequently occur in pediatric acute myeloid leukemia (AML) and are associated with poor prognosis. In most cases, the MLL gene is involved, and more than 50 translocation partners have been described. Clinical outcome data of the 11q23-rearranged subgroups are scarce because most 11q23 series are too small for meaningful analysis of subgroups, although some studies suggest that patients with t(9;11)(p22;q23) have a more favorable prognosis. We retrospectively collected outcome data of 756 children with 11q23-or MLL-rearranged AML from 11 collaborative groups to identify differences in outcome based on translocation partners. All karyotypes were centrally reviewed before assigning patients to subgroups. The event-free survival of 11q23/ MLL-rearranged pediatric AML at 5 years from diagnosis was 44% (؎ 5%), with large differences across subgroups (11% ؎ 5% to 92% ؎ 5%). Multivariate analysis identified the following subgroups as independent prognostic predictors: t(1;11)(q21;q23) (hazard ratio [HR] ‫؍‬ 0.1, P ‫؍‬ .004); t(6; 11)(q27;q23) (HR ‫؍‬ 2.2, P < .001); t(10; 11)(p12;q23) (HR ‫؍‬ 1.5, P ‫؍‬ .005); and t(10;11)(p11.2;q23) (HR ‫؍‬ 2.5, P ‫؍‬ .005). We could not confirm the favorable prognosis of the t(9;11)(p22;q23) subgroup. We identified large differences in outcome within 11q23/MLL-rearranged pediatric AML and novel subgroups based on translocation partners that independently predict clinical outcome. Screening for these translocation partners is needed for accurate treatment stratification at diagnosis. (Blood. 2009;114:2489-2496)

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/ AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

Key Points• Dexamethasone vs prednisone in induction of pediatric ALL led to significant relapse reduction and increased treatment-related mortality.• No overall survival benefit was achieved with dexamethasone except in the subset of patients with T-cell ALL and good early treatment response.Induction therapy for childhood acute lymphoblastic leukemia (ALL) traditionally includes prednisone; yet, dexamethasone may have higher antileukemic potency, leading to fewer relapses and improved survival. After a 7-day prednisone prephase, 3720 patients enrolled on trial Associazione Italiana di Ematologia e Oncologia Pediatrica and BerlinFrankfurt-Münster (AIEOP-BFM) ALL 2000 were randomly selected to receive either dexamethasone (10 mg/m 2 per day) or prednisone (60 mg/m 2 per day) for 3 weeks plus tapering in induction. The 5-year cumulative incidence of relapse (6 standard error) was 10.8 6 0.7% in the dexamethasone and 15.6 6 0.8% in the prednisone group (P < .0001), showing the largest effect on extramedullary relapses. The benefit of dexamethasone was partially counterbalanced by a significantly higher induction-related death rate (2.5% vs 0.9%, P 5 .00013), resulting in 5-year event-free survival rates of 83.9 6 0.9% for dexamethasone and 80.8 6 0.9% for prednisone (P 5 .024). No difference was seen in 5-year overall survival (OS) in the total cohort (dexamethasone, 90.3 6 0.7%; prednisone, 90.5 6 0.7%). Retrospective analyses of predefined subgroups revealed a significant survival benefit from dexamethasone only for patients with T-cell ALL and good response to the prednisone prephase (prednisone good-response [PGR]) (dexamethasone, 91.4 6 2.4%; prednisone, 82.6 6 3.2%; P 5 .036). In patients with precursor B-cell ALL and PGR, survival after relapse was found to be significantly worse if patients were previously assigned to the dexamethasone arm. We conclude that, for patients with PGR in the large subgroup of precursor B-cell ALL, dexamethasone especially reduced the incidence of better salvageable relapses, resulting in inferior survival after relapse. This explains the lack of benefit from dexamethasone in overall survival that we observed in the total cohort except in the subset of T-cell ALL patients with PGR. This trial was registered at www.clinicaltrials.gov

Key Points• Risk-adapted therapy and broad use of HSCT resulted in a significant improvement in outcome.• AUTO-or ALLO-HSCT in high-risk patients resulted in a cumulative incidence of leukemia relapse superimposable to that of SR.We evaluated the outcome of 482 children with acute myeloid leukemia (AML) enrolled in the Associazione Italiana di Ematologia e Oncologia Pediatrica AML 2002/01 trial. Treatment was stratified according to risk group; hematopoietic stem cell transplantation (HSCT) was used in high-risk (HR) children. Patients with core binding factor leukemia achieving complete remission (CR) after the first induction course were considered standard risk (SR; 99 patients), whereas the others (n 5 383) were assigned to the HR group. Allogeneic (ALLO) or autologous (AUTO) HSCT was employed, respectively, in 141 and 102 HR patients after consolidation therapy. CR, early death, and induction failure rates were 87%, 3%, and 10%, respectively. Relapse occurred in 24% of patients achieving CR. The 8-year overall survival (OS), event-free survival (EFS), and disease-free survival (DFS) were 68%, 55%, and 63%, respectively. OS, EFS, and DFS for SR and HR patients were 83%, 63%, and 66% and 64%, 53%, and 62%. DFS was 63% and 73% for HR patients given AUTO-HSCT and ALLO-HSCT, respectively. In multivariate analysis, risk group, white blood cell >100 3 10 9 /L at diagnosis, and monosomal karyotype predicted poorer EFS. Risk-oriented treatment and broad use of HSCT result in a long-term EFS comparing favorably with previously published studies on childhood AML. (Blood. 2013; 122(2):170-178)

Chromosomal rearrangements of the human MLL gene are a hallmark for aggressive (high-risk) pediatric, adult and therapyassociated acute leukemias. These patients need to be identified in order to subject these patients to appropriate therapy regimen. A recently developed long-distance inverse PCR method was applied to genomic DNA isolated from individual acute leukemia patients in order to identify chromosomal rearrangements of the human MLL gene. We present data of the molecular characterization of 414 samples obtained from 272 pediatric and 142 adult leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) was determined and several new TPGs were identified. The combined data of our study and published data revealed a total of 87 different MLL rearrangements of which 51 TPGs are now characterized at the molecular level. Interestingly, the four most frequently found TPGs (AF4, AF9, ENL and AF10) encode nuclear proteins that are part of a protein network involved in histone H3K79 methylation. Thus, translocations of the MLL gene, by itself coding for a histone H3K4 methyltransferase, are presumably not randomly chosen, rather functionally selected.

Relapsed pediatric acute lymphoblastic leukemia (ALL) has high rates of treatment failure. Epigenetic regulators have been proposed as modulators of chemoresistance, here we sequence genes encoding epigenetic regulators in matched diagnosis-remission-relapse ALL samples. We find significant enrichment of mutations in epigenetic regulators at relapse with recurrent somatic mutations in SETD2, CREBBP, MSH6, KDM6A and MLL2, mutations in signaling factors are not enriched. Somatic alterations in SETD2, including frameshift and nonsense mutations, are present at 12% in a large de novo ALL patient cohort. We conclude that the enrichment of mutations in epigenetic regulators at relapse is consistent with a role in mediating therapy resistance.

We examined the efficacy of unrelated cord blood (CB) transplantation in children with thalassemia (n = 35) and sickle cell disease (n = 16), using data reported to 3 registries. Donor-recipient pairs were matched at HLA-A and -B (antigen level) and DRB1 (allele level) in 7 or HLA mismatched at 1 (n = 18), 2 (n = 25), or 3 loci (n = 1). Transplant conditioning was myeloablative (n = 39) or reduced intensity (n = 12). Neutrophil recovery with donor chimerism was documented in 24 patients; 11 patients developed grade II-IV acute graft-versus-host disease (aGVHD) and 10 patients, chronic GVHD (cGVHD). Overall survival (OS) and disease-free survival (DFS) were 62% and 21% for thalassemia and 94% and 50% for sickle cell disease (SCD), respectively. In multivariate analysis, engraftment rate (hazard ratio [HR] 2.2, P =.05) and DFS (HR 0.4, P =.01) were higher with cell dose >5 × 107/kg. The 2-year probability of DFS was 45% in patients who received grafts with cell dose >5 × 107/kg and 13% with lower cell dose. Primary graft failure was the predominant cause of treatment failure occurring in 20 patients with thalassemia and 7 patients with SCD. Primary graft failure was fatal in 5 patients with thalassemia. These results suggest that only CB units containing an expected infused cell dose >5 × 107/kg should be considered for transplantation for hemoglobinopathy.