Are aberrant BCR-ABL transcripts more common than previously thought?

We report the use of multiplex polymerase chain reaction (PCR), using 4% po lyacrylamide gel electrophoresis (PAGE) for the detection of BCR-ABL transc ripts in Philadelphia-positive disease. Three out of 50 cases [two out of 3 7 chronic myeloid leukaemia (CML), one out of 13 acute lymphoblastic leukae mia (ALL)] possessed rare breakpoints: an e19a2 and c13a3 in CML and an c1a 3 in the ALL. We suggest: that multiplex FCR using 4% PAGE and optimized fo r smaller transcript detection may lead to a higher detection rate of rare BCR-ABL breakpoints. Multiplex PCR, however, failed to distinguish e13a2 fr om e1a3 transcripts. Finally the presence of e13a3 in CML supports the view that abl exon 2 sequences are unnecessary for the pathogenesis of 'classic ' CML.