Possible correlation of b3-a2-type bcr-abl messenger RNA defined by semiquantitative RT-PCR to platelet and megakaryocyte counts in Philadelphia-positive chronic myelogenous leukemia.

Thirty-five patients with Philadelphia chromosome (Ph1)-positive chronic myelogenous leukemia (CML) were classified on the basis of the fusion pattern of bcr-abl mRNA determined by the reverse-transcriptase-polymerase chain reaction (RT-PCR) method. Semiquantitative assay of the bcr exon 2/abl exon 2 fused mRNA (b2-a2) and bcr exon 3/abl exon 2 fused mRNA (b3-a2) resulted in 21 patients showing b3-a2 type mRNA, seven showing b2-a2 type and seven showing coexpression. Quantification of the autoradiographic signals of amplified products was estimated using an MCID image analysis system. The relative intensity was defined as the ratio of bcr-abl signal to that of beta-actin. The relationship between the semiquantified bcr-abl mRNA and the platelet/megakaryocyte counts was analyzed. A possible correlation was found between the semiquantified b3-a2 type mRNA and the platelet (p < .05, N = 28) and megakaryocyte (p < .05, N = 13) counts of these patients. This finding suggests the possibility that b3-a2 mRNA may affect the thrombopoietic activity in Ph1-positive CML in a dose-response manner.