bcr rearrangement and C-abl gene expression in Ph1-positive hybrid acute leukemia with simultaneous proliferation of lymphoid and myeloid blasts

Abstract

bcr gene rearrangement and c-abl gene expression were analyzed in a patient with Philadelphia chromosome (Ph¹)-positive hybrid acute leukemia with simultaneous proliferation of lymphoid and myeloid blasts. These data were compared with those from a patient with chronic myelogenous leukemia (CML) in mixed crisis. The leukemic cells of both patients showed immuno-phenotypic profiles such as non-T, non-B common ALL with some MPO-positive leukemic cells and rearranged J_H genes. On analysis of molecular events associated with the Ph¹ chromosome, the leukemic cells of a patient with CML in mixed crisis showed bcr rearrangement and an 8.5-kb bcr-abl chimeric mRNA, but those of a patient with Ph¹-positive hybrid acute leukemia showed no 8.5-kb bcr-abl mRNA, as previously reported in a number of Ph¹-positive acute lymphoblastic leukemia (ALL) cases. These results revealed that the molecular event found in Ph¹-positive ALL is not only restricted to lymphoid lineage but may play an important role in the proliferation of the myeloid lineage.