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 respectiv e fusion RNAs reflect disease progression as well as remission upon therape utic intervention in CML patients. However, there is no quick and reliable method that: would allow the quantitative routine monitoring of bcr/abl hyb rid transcripts. A fluorescent probe-based PCR assay (TaqMan) has been desc ribed to quantitfy the exact amount of target sequences. We have establishe d TaqMan real-time RT-PCRs for M-bcr/abl (b2a2, b2a3, b3a2, b3a3) and m-bcr /abl (e1a2) fusion transcripts as well as for p-actin. All PCRs quantified as little as 10 copies/100 ng total cDNA. In order to investigate whether t his procedure is appropriate for routine diagnostic monitoring, we performe d retrospective measurements on 9 documented CML disease courses. Our data show that ongoing or relapsing CML is paralleled by increasing peripheral l evels of bcr/abl fusion RNAs. Furthermore, sucessful anti-leukemic treatmen t is reflected by decreasing absolute bcr/abl transcript numbers. In contra st with conventional bcr/abl PCR techniques we could distinguish single pos itive values and gradually increasing copy numbers.