Molecular characteristics of chronic myelogenous leukemia in blast crisis

We have studied the expression of c- abl and c- myc in leukemic cells of patients in all clinical phases of chronic myelogenous leukemia. We demonstrate that an aberrant 8-Kb c- abl related transcript is present in the RNA of the leukemic cell from all patients with Ph+ CML and that the loss of both normal chromosome #9 is associated with the loss of the normal c- abl related transcripts. This represents direct evidence that the normal c- abl related transcripts derive from the normal c- abl gene locus on the normal chromosome #9, while the aberrant c- abl related transcript in Ph+ CML derives from the hybrid bcr-abl gene, formed as a result of the t(9;22). We further demonstrate that trisomy 8 in some instances is associated with enhanced expression of the c- myc oncogene.