Polymerase Chain Reaction Studies on Chronic Myelogenous Leukemias and Detection of Residual Ph1 Clone after Bone Marrow Transplantation

Abstract

Thirty—four cases of chronic myelogenous leukemia (CML) were studied for the expression of breakpoint cluster region (bcr)/abl fused transcripts using the polymerase chain reaction (PCR). In all samples the bcr-abl chimeric mRNA was detected. Seven cases showed bcr exon 2/abl exon 2 (b2-a) chimeric mRNA, 15 cases showed bcr exon 3/abl exon 2 (b3-a) chimeric mRNA, and 12 cases showed both of these mRNAs. None of the 34 samples with expression of b3-a and/or b2-a showed either the expression of BCR-abl chimeric transcripts or bl-a chimeric mRNA, which is due to the alternative splicing of chimeric mRNA, as is the case for b2-a/b3-a mRNA. Taking advantage of the high sensitivity of this method, 24 CML patients, after bone marrow transplantation (BMT), were analyzed for the presence of Phi clones. Thirteen out of 24 patients showed residual Phi clones detected by PCR assay. The incidence of positive Phi clones detected by PCR is also discussed in relation to conditioning regimens for BMT.