Applicability of an absolute quantitative procedure to monitor intra-individual bcr/abl transcript kinetics in clinical samples from chronic myelogenous leukemia patients.

Chimeric bcr/abl fusion proteins are thought to be the molecular 'pathogen' of chronic myelogenous leukaemia (CML). Expression levels of the respective fusion RNAs reflect disease progression as well as remission upon therapeutic intervention in CML patients. However, there is no quick and reliable method that would allow the quantitative routine monitoring of bcr/abl hybrid transcripts. A fluorescent probe-based PCR assay (TaqMan) has been described to quantitfy the exact amount of target sequences. We have established TaqMan real-time RT-PCRs for M-bcr/abl (b2a2, b2a3, b3a2, b3a3) and m-bcr/abl (e1a2) fusion transcripts as well as for beta-actin. All PCRs quantified as little as 10 copies/100 ng total cDNA. In order to investigate whether this procedure is appropriate for routine diagnostic monitoring, we performed retrospective measurements on 9 documented CML disease courses. Our data show that ongoing or relapsing CML is paralleled by increasing peripheral levels of bcr/abl fusion RNAs. Furthermore, sucessful anti-leukemic treatment is reflected by decreasing absolute bcr/abl transcript numbers. In contrast with conventional bcr/abl PCR techniques we could distinguish single positive values and gradually increasing copy numbers.