Molecular cytogenetic study of instability at 1q21∼q32 in adult acute lymphoblastic leukemia

Successful treatment of ICE-rituximab chemotherapy and subsequent bone marrow transplantation in a patient with early-relapse Burkitt leukemia and inverted duplication of 1q

Although childhood acute lymphoblastic leukemias are of good prognosis than leukemias of adulthood, some chromosomal abnormalities may have negative effects on their prognosis. Inverted duplication (1q) is a chromosomal abnormality with negative effect on outcome of Burkitt leukemia and lymphomas. We report a case of CD20 Burkitt leukemia with inverted duplication (1q) mutation, who had an early relapse during NHL-BFM 95 treatment. Two courses of ICE-rituximab treatment were administered after relapse and a successful HLA-full match bone marrow transplantation was carried out. He is in follow-up for 18 months without any problem after the bone marrow transplantation. We suggest the usage of ICE protocol combined with rituximab in childhood CD20 Burkitt leukemia with poor prognostic criteria such as inverted duplication (1q) mutation.

Jumping translocations

Jumping translocations (JT) are uncommon constitutional or acquired chromosome rearrangements involving one donor and several recipient chromosomes. They occur in various pathologic conditions and the mechanism of their formation remains elusive. A review of the literature showed that the major localizations of the breakpoints of JTs in human samples are nonrandomly located in pericentromeric and telomeric regions of chromosomes. Interestingly, comparison of the localization of the chromosomal breakpoints and of presence of interstitial DNA repeats showed differences between constitutional and acquired JTs suggesting differences in the mechanisms for the genesis of JTs and their consequences.

MYC-containing double minutes in hematologic malignancies: evidence in favor of the episome model and exclusion of MYC as the target gene

Double minutes (dmin)-circular, extra-chromosomal amplifications of specific acentric DNA fragments-are relatively frequent in malignant disorders, particularly in solid tumors. In acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), dmin are observed in approximately 1% of the cases. Most of them consist of an amplified segment from chromosome band 8q24, always including the MYC gene. Besides this information, little is known about their internal structure. We have characterized in detail the genomic organization of 32 AML and two MDS cases with MYC-containing dmin. The minimally amplified region was shown to be 4.26 Mb in size, harboring five known genes, with the proximal and the distal amplicon breakpoints clustering in two regions of approximately 500 and 600 kb, respectively. Interestingly, in 23 (68%) of the studied cases, the amplified region was deleted in one of the chromosome 8 homologs at 8q24, suggesting excision of a DNA segment from the original chromosomal location according to the 'episome model'. In one case, sequencing of both the dmin and del(8q) junctions was achieved and provided definitive evidence in favor of the episome model for the formation of dmin. Expression status of the TRIB1 and MYC genes, encompassed by the minimally amplified region, was assessed by northern blot analysis. The TRIB1 gene was found over-expressed in only a subset of the AML/MDS cases, whereas MYC, contrary to expectations, was always silent. The present study, therefore, strongly suggests that MYC is not the target gene of the 8q24 amplifications.