Prognostic significance of BCR-ABL rearrangement in chronic myeloid leukemia

ABSTRACT

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the presence of a reciprocal translocation between chromosomes 9 and 22 in at least 95 per cent of cases. At the molecular level, this translocation results in the activation of the ABL oncogene of chromosome 9, which becomes contiguous with the 5'end of the BCR gene on chromosome 22. The breakpoint usually occurs between exons 2 and 3 (b2-a2 rearrangement), or 3 and 4 (b3-a2 rearrangement) of the major breakpoint cluster region (M-BCR) of the BCR gene. The aim of the present study was to characterize the type of BCR-ABL transcript in 32 patients with CML using the reverse transcriptase-polymerase chaim reaction (RT-PCR) and to determine if this type of rearrangement is related to the survival of the patients. Our results confirmed that RT-PCR is more sensitive than cytogenetic analysis for identifying the Philadelphia (Ph1) chromosome (96.9 per cent vs 79.3 per cent). The frequencies of b2-a2 and b3-a2 rearrangements were 28.1 per cent and 65.7 per cent, respectively. The survival of patients presenting the b2-a2 or the b3-a2 rearrangement was not significantly different (P = 0.27750). The data suggest that the type of transcript has no prognostic value for CML patients.