Monitoring of Residual Disease in Patients with Chronic Myelogenous Leukemia Using Specific Fluorescent Hybridization Probes for Real-Time Quantitative RT-PCR

In many ways, chronic myelogenous leukemia (CML) serves as a paradigm for the utility of molecular methods to diagnose malignancy or to monitor patient response to therapy [1]. CML constitutes a clinical model for molecular detection and therapy surveillance since this entity was the first leukemia known to be associated with a specific chromosomal rearrangement, the Philadelphia (Ph) translocation t(9;22)(q34;q11), and the presence of two chimeric genes, BCR-ABL on chromosome 22 and ABL-BCR on chromosome 9. BCR-ABL is transcribed to a specific BCR-ABL mRNA and encodes in most patients a 210-kDa chimeric protein with increased tyrosine kinase activity. The central role of BCR-ABL in several pathways which lead to uncontrolled proliferation has been shown in vitro and in vivo. Several approaches have been introduced that can specifically detect the Ph translocation or its products, such as fluorescent in situ hybridization, Southern blotting, western blotting, and reverse transcriptase polymerase chain reaction (RT-PCR) [2–4]. Of these, RT-PCR for BCR-ABL mRNA is by far the most sensitive and consequently has received the most attention in the context of minimal residual disease.