Quantitative Evaluation of BCR-ABL Amount of Transcript Post Mobilization with G-CSF of Peripheral Blood Stem Cells from Chronic Myeloid Leukemia Patients in Cytogenetic Response

We studied nine patients affected by chronic myeloid leukemia (CML Ph+ and bcr-abl positive) and treated with alpha-interferon (α-INF) in order to: first, to evaluate the feasibility of a mobilization of peripheral blood stem cells induced by granulocyte-colony-stimulating factor (G-CSF) and the contamination by Ph+ cells and second, to quantify the amount of bcr-abl leukemia associated transcript by a quantitative assay during mobilization procedures, and post mobilization follow-up. Eight achieved a complete karyotypic remission before mobilization obtained with discontinuation of a-INF for few days and G-CSF at a dosage of 15μg/kg/day for 5-7 consecutive days. By quantitative-competitive polymerase chain reaction (QC-PCR) assay, all the leukaphereses and bone marrow samples during post mobilization follow up were studied to determine the amount of bcr-abl transcript. Karyotypic and molecular analysis on evaluable leukapheresis showed that all the harvests were Ph negative and bcr-abl positive: in seven cases the levels of bcr-abl transcript were higher or equal to the pre-apheresis status. In three out of four patients, who underwent more than one leukapheresis procedure, we noticed a decreasing amount of bcr-abl contamination from the first to the last apheresis. Our results suggest that in patients who achieved a complete or major cytogenetic conversion with α-INF, it is possible to obtain a sufficient amount of PBSC for autografting by leukapheresis following priming G-CSF therapy and that the amount of neoplastic transcript does not seem to increase.