Additional c-abl/bcr rearrangements in a CML patient exhibiting two ph1 chromosomes during blast crisis

Recent data suggest that two human genes, c-abl on chromosome 9 and bcr on chromosome 22, are involved in the generation of Ph1-positive CML. To examine a possible role of these sequences in transition from chronic towards blastic phase, rearrangements within bcr were analysed in 4 patients with Ph1-positive CML during chronic and acute phase. In 3 patients bcr rearrangements were identical in both phases, while in a fourth patient with duplicated Ph1 an amplified additional bcr fragment was detected in acute phase. Northern blot analysis of blast cells of the latter patient showed a novel 10.3 kb RNA species that replaced the altered 8 kb RNA transcript usually found in Ph1-positive CML.