Background and objectives: The limited value of qualitative reverse transcription polymerase chain-reaction (RT-PCR) for monitoring chronic myeloid leukemia (CML) patients has prompted the development of quantitative assays. We have developed a quantitative real-time PCR (QC-PCR) method in the LightCycler, based on the use of fluorescently labeled probes (HybProbes), to estimate BCR-ABL fusion gene transcripts in samples from CML patients.
Design and methods: Fifty-two samples (45 peripheral blood, five bone marrow, and two apheresis product samples) from nine patients with CML were analyzed. Seven patients were studied at diagnosis and during follow-up after hematopoietic stem cell transplantation (HSCT), whereas two were evaluated only after HSCT. The PCR reaction was carried out in capillary tubes in a final volume of 10 microL, using 2 microL cDNA, the Mensik et al. primers, and two HybProbes. The results for BCR-ABL were normalized with reference to ABL. The PCR program is completed in only 45 min.
Results: The sensitivity attained allowed the detection of rearrangements at dilutions of between 5-10(-4) and 10(-5) K562 cDNA. The within-assay coefficient of variation was 11% for BCR-ABL, and 9% for ABL. A greater than 2 log reduction in the BCR-ABL/ABL ratio was evident shortly after transplantation in all allografted patients.
Interpretation and conclusions: We may conclude that the TaqMan probe technology can be easily adapted to HybProbes with equivalent results. Besides, the results of BCR-ABL quantification in the follow-up of patients clearly confirm that real-time PCR with HybProbes is a reliable and sensitive method for monitoring minimal residual leukemia after HSCT in CML patients.