Differential molecular response of the transcripts B2A2 and B3A2 to imatinib mesylate in chronic myeloid leukemia.
PROBLEM It has been suggested that type of chimeric mRNA is associated with differences in the clinical and hematologic characteristics of chronic myeloid leukemia (CML). However, prognostic value of type of chimeric mRNA bcr-xabl (b3a2 or b2a2) is still controversial. METHODS We analyzed 97 cases of Philadelphia-positive CML to determine mRNA type by reverse-polymerase chain reaction (RT-PCR) and its relationship with clinical features. RESULTS We detected b3a2 bcr-abl transcripts in 27 (28%) cases, b2a2 in 57 (59%) cases, and 13 (13%) with both mRNA transcripts b3a2/b2a2. These frequencies were the total reverse of other reports. Age, sex, hemoglobin, and white-cell counts showed no significant difference for those with either b3a2 or b2a2 bcr-abl transcripts. However, platelet counts of b3a2 patients were significantly higher than those of b2a2 patients (743.3 vs 477.3 x 109/L; p = 0.01). In addition, in the subgroup of patients whose white-cell count at diagnosis was < 100 x 10(9)/L, those with b3a2 transcript had a significantly higher platelet count (679.1 vs. 352.2 x 10(9)/L; p = 0.001). CONCLUSIONS We observed reversed frequency of bcr-abl transcripts in this population, but agreement with other Latin-American reports. In addition, our data suggested that there is different CML biological behavior in our population and that there is a subpopulation of CML patients in whom b3a2 is associated witH higher thrombopoietic activity.