CLINICAL IMPACT OF BREAKPOINT POSITION WITHIN M-BCR IN CHRONIC MYELOID-LEUKEMIA

We have analyzed the M-bcr breakpoint position in 133 Philadelphia-pos itive chronic myeloid leukemia patients and correlated the findings wi th clinical, hematologic, and cytogenetic data. We also investigated t he splicing pattern of the BCR-ABL mRNA in 30 patients, using reverse transcriptase PCR. No statistically significant differences were found between breakpoint position within M-bcr and clinical parameters at d iagnosis, the karyotypic evolution pattern, or the leukemic phenotype during blast crisis. Furthermore, the breakpoint position within M-bcr did not correlate with the duration of chronic phase or survival time . When the splicing pattern of the BCR-ABL mRNA was compared with the results of the genomic breakpoint mapping, it was found that approxima tely 60% (8/14) of the patients with a 5' break expressed b2a2 fusion mRNA, whereas all patients (10/10) with a 3' break expressed b3a2 BCR- ABL mRNA.