Pettenati, Mark J.

Abstract The dic(9;12)(p12;p11.2) has been described as a rare cytogenetic abnormality in pediatric precursor B-cell ALL. Initial studies suggested that the rearrangement is associated with a favorable outcome, and recent studies demonstrated the presence of a PAX5-ETV6 fusion gene was associated with this cytogenetic abnormality. Twenty cases with a cytogenetic dic(9;12) were identified in the Children’s Oncology Group (COG) cytogenetics databases. FISH analysis with the ETV6-RUNX1 (TEL-AML1) probes was done on 12 of these samples. Five cases were positive for fusion, indicating a cryptic t(12;21)(p13;q22), and also had loss of the ETV6 probe from the chromosome 12 not involved in the t(12;21). Seven cases were negative for fusion and had loss of an ETV6 signal, although one of the latter had a diminished ETV6 signal identified. To determine whether both PAX5-ETV6 and ETV6-RUNX1 rearrangements occurred in some patients, a diagnostic sample from each patient was analyzed by RT-PCR for the PAX5-ETV6 and ETV6-RUNX1 fusion genes. Primers from exon 3 of PAX5 and exon 3 of ETV6 were used for the PAX5-ETV6 analysis and from exon 5 of ETV6 and exon 4 of RUNX1 for the ETV6-RUNX1 analysis. Of the 20 cases, only 8 were RT-PCR positive for the PAX5-ETV6 fusion with the above primers; however, an additional 2 were RT-PCR positive with alternate primers, and all 10 of these were negative for the ETV6-RUNX1 fusion by RT-PCR. Of the remaining 10 patients, 9 were RT-PCR positive for the ETV6-RUNX1 fusion, including all of the ETV6-RUNX1 cases positive by FISH. The gene rearrangement associated with the dic(9;12) in these cases is not known. One patient was negative for both fusions by RT-PCR, negative by FISH for ETV6-RUNX1 rearrangement, yet had loss of an ETV6 signal. No cytogenetic differences could be seen between the 2 groups, either in the appearance of the dic(9;12) or in the other abnormalities identified. These results demonstrate the presence of two mutually exclusive dic(9;12) rearrangements in pediatric ALL; one associated with ETV6-RUNX1 rearrangement and one resulting in PAX5-ETV6 fusion. Both PAX5-ETV6 and ETV6-RUNX1 rearrangements are associated with a favorable prognosis. However, molecular analysis of the dic(9;12) patients must be performed to determine whether the dicentric chromosome results in PAX5-ETV6 fusion or whether the case has ETV6-RUNX1 fusion.

Abstract The inv(16)(p13q22)/t(16;16)(p13;q22) in acute myeloid leukemia results in multiple CBFB-MYH11 fusion transcripts, with type A being most frequent. The biologic and prognostic implications of different fusions are unclear. We analyzed CBFB-MYH11 fusion types in 208 inv(16)/t(16;16) patients with de novo disease, and compared clinical and cytogenetic features and the KIT mutation status between type A (n = 182; 87%) and non–type A (n = 26; 13%) patients. At diagnosis, non–type A patients had lower white blood counts (P = .007), and more often trisomies of chromosomes 8 (P = .01) and 21 (P < .001) and less often trisomy 22 (P = .02). No patient with non–type A fusion carried a KIT mutation, whereas 27% of type A patients did (P = .002). Among the latter, KIT mutations conferred adverse prognosis; clinical outcomes of non–type A and type A patients with wild-type KIT were similar. We also derived a fusion-type–associated global gene-expression profile. Gene Ontology analysis of the differentially expressed genes revealed—among others—an enrichment of up-regulated genes involved in activation of caspase activity, cell differentiation and cell cycle control in non–type A patients. We conclude that non–type A fusions associate with distinctclinical and genetic features, including lack of KIT mutations, and a unique gene-expression profile.

Purpose To evaluate the prognostic significance of the international European LeukemiaNet (ELN) guidelines for reporting genetic alterations in acute myeloid leukemia (AML). Patients and Methods We analyzed 1,550 adults with primary AML, treated on Cancer and Leukemia Group B first-line trials, who had pretreatment cytogenetics and, for cytogenetically normal patients, mutational status of NPM1, CEBPA, and FLT3 available. We compared complete remission (CR) rates, disease-free survival (DFS), and overall survival (OS) among patients classified into the four ELN genetic groups (favorable, intermediate-I, intermediate-II, adverse) separately for 818 younger (age < 60 years) and 732 older (age ≥ 60 years) patients. Results The percentages of younger versus older patients in the favorable (41% v 20%; P < .001), intermediate-II (19% v 30%; P < .001), and adverse (22% v 31%; P < .001) genetic groups differed. The favorable group had the best and the adverse group the worst CR rates, DFS, and OS in both age groups. Both intermediate groups had significantly worse outcomes than the favorable but better than the adverse group. Intermediate-I and intermediate-II groups in older patients had similar outcomes, whereas the intermediate-II group in younger patients had better OS but not better CR rates or DFS than the intermediate-I group. The prognostic significance of ELN classification was confirmed by multivariable analyses. For each ELN group, older patients had worse outcomes than younger patients. Conclusion The ELN classification clearly separates the genetic groups by outcome, supporting its use for risk stratification in clinical trials. Because they have different proportions of genetic alterations and outcomes, younger and older patients should be reported separately when using the ELN classification.