Confirmation of a novel recurrent association: BCR-ABL t(9;22) and t(19;21)

Chronic myeloid leukemia with insertion-derived BCR-ABL1 fusion: redefining complex chromosomal abnormalities by correlation of FISH and karyotype predicts prognosis

Chromosomal insertion-derived BCR-ABL1 fusion is rare and mostly cryptic in chronic myeloid leukemia (CML). Most of these cases present a normal karyotype, and their risk and/or prognostic category are uncertain. We searched our database and identified 41 CML patients (20 M/21 F, median age: 47 years, range 12-78 years) with insertion-derived BCR-ABL1 confirmed by various FISH techniques: 31 in chronic phase, 1 in accelerated phase, and 9 in blast phase at time of diagnosis. Conventional cytogenetics analysis showed a normal karyotype (n = 19); abnormal karyotype with morphologically normal chromosomes 9 and 22 (n = 5); apparent ins(9;22) (n = 2) and abnormal karyotype with apparent abnormal chromosomes 9, der(9) and/or 22, der(22) (n = 15). The locations of insertion-derived BCR-ABL1 were identified on chromosome 22 (68.3%), 9 (29.3%), and 19 (2.4%). Complex chromosomal abnormalities were often overlooked by conventional cytogenetics but identified by FISH tests in many cases. After a median follow-up of 58 months (range 1-242 months), 11 patients died, and 3 lost contact, while the others achieved different cytogenetic/molecular responses. The locations of BCR-ABL1 (der(22) vs. non-der(22)) and the karyotype results (complex karyotype vs. noncomplex karyotype) by conventional cytogenetics were not associated with overall survival in this cohort. However, redefining the complexity of chromosomal abnormality by correlating karyotype and FISH findings, CML cases with simple chromosomal abnormalities had a more favorable overall survival than that with complex chromosomal abnormalities. We conclude that insertion-derived BCR-ABL1 fusions often involve complex chromosomal abnormalities which are overlooked by conventional cytogenetics, but can be identified by one or more FISH tests. We also suggest that the traditional cytogenetic response criteria may not apply in these patients, and the complexity of chromosomal abnormalities redefined by correlating karyotype and FISH findings can plays a role in stratifying patients into more suitable risk groups for predicting prognosis. (Word count: 292).

A possible 5'-NRIP1/UHRF1-3' fusion gene detected by array CGH analysis in a Ph+ ALL patient

A translocation between chromosomes 19 and 21 [dic/t(19;21)(p13;v)] is very rare. To date, only three cases of this particular chromosomal abnormality have been reported. The translocations in these three cases were secondary changes in acute lymphoblastic leukemia (ALL) patients with the t(9;22) translocation. The gene(s) at the breakpoints of either chromosome 19p13 or 21q have not yet been identified. Here, we present a case study of a 21-year-old female with a diagnosis of precursor B cell ALL, with the t(9;22) translocation and secondary changes including a der(19)t(19;21) and an extra Philadelphia (Ph+) chromosome [der(22)t(9;22)]. Array comparative genomic hybridization (aCGH) analysis identified UHRF1 and NRIP1 as genes that were interrupted at the breakpoints of 19p13.3 and 21q21.1, and joined together as a possible fusion gene, 5'-NRIP1/UHRF1-3', on the derivative chromosome 19. To our knowledge, this is the first description of possible genes involved in the unbalanced translocation between chromosomes 19 and 21 in a patient with an ALL-positive for a t(9;22) translocation.