Deletions adjacent to BCR and ABL1 breakpoints occur in a substantial minority of chronic myeloid leukemia patients with masked Philadelphia rearrangements.

Deletions at the t(9;22) breakpoint regions, found in 15% of chronic myeloid leukemia patients (CML) with an overt Philadelphia (Ph) translocation, are associated with an adverse disease prognosis in patients receiving interferon-alpha therapy. The incidence of deletions has been shown to vary for different cytogenetic subgroups of CML, with a significantly higher incidence of deletion in patients with a variant Ph translocation. To date, however, the frequency of such deletions in the subgroup of CML patients in whom the BCR/ABL1 fusion arises via submicroscopic chromosomal insertion (masked Ph) has not been investigated. We report the evaluation of 14 patients with masked Ph-positive CML for the presence of deletions extending 3' from BCR and 5' from ABL1 using two triple-color BCR/ABL probes. Deletions were identified in 3 patients (21%), encompassing sequences 5' to ABL1 in two of these and sequences 3' to BCR in the remaining patient, thus demonstrating that the phenomenon is a significant feature of the masked Ph CML subgroup. Furthermore, our findings are consistent with the notion that loss of genomic material is a potential side effect of any DNA breakage event at the 9q34.1 and 22q11.2 chromosomal regions, regardless of the subsequent mechanism of chromosomal rearrangement.

Specific patterns of chromosomal gains and losses associate with t(3;14), t(8;14), and t(14;18) in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease. Certain chromosomal translocations are associated with clinical outcome, but it is likely that there are both tumor suppressor genes and oncogenes that cooperate with the primary translocations. We have used the Mitelman database to compare chromosomal losses and gains of DLBCL possessing t(14;18), t(8;14), or t(3;14) with DLBCL lacking any of these translocations. The data we obtained are low resolution, but results for t(3;14) validate the methodology. In accord with the literature, loss of 6q was associated with t(3;14). Chromosomes 11, 13, and X were gained significantly in t(3;14), whereas 8p23 was lost. Cases with t(14;18) were associated with gains of chromosomes 7 and 12; cases with t(8;14) were associated with gains of chromosomes 1 and 4.

Chronic myeloid leukemia in chronic phase responding to imatinib: the occurrence of additional cytogenetic abnormalities predicts disease progression.

BACKGROUND AND OBJECTIVES: The acquisition of additional cytogenetic changes (clonal evolution, CE) during treatment of chronic myeloid leukemia (CML) with imatinib mesylate is currently regarded as an index of increasing resistance to imatinib. Therefore, to investigate whether CE as an isolated event increases the risk of disease progression during imatinib treatment, we compared the outcome of patients with CML in chronic phase (CML-CP) who developed CE whilst in complete hematologic remission with the outcome of comparable patients in complete hematologic remission who showed no evidence of CE. DESIGN AND METHODS: We serially studied cytogenetic findings in 102 patients receiving the Abl-tyrosine kinase inhibitor, imatinib mesylate, as sole agent to treat CML-CP who had no evidence of CE before initiation of imatinib treatment. RESULTS: CE was identified during treatment with imatinib in 15 patients, 10 of whom were in complete hematologic remission. In most cases these changes occurred exclusively in the Ph+ population but in three patients additional changes occurred in a co-existing Ph-negative population. Patients with de novo CE in the absence of any other sign of disease progression had a significantly higher incidence of progression by 18 months than did non-CE patients (progression-free survival 34.3% (CI 10.5-69.8%) vs. 94.1% (CI 80.6-98.4%), p<0.0001). INTERPRETATION AND CONCLUSIONS: Based on this relatively small series of patients, we conclude that acquisition of clonal evolution increases the risk of subsequent disease progression also in CML patients in complete hematologic remission on imatinib.