Mobilization of bcr-ablneg progenitors (Cfc, ltc-ic) Into the blood of newly diagnosed cml patients after high dose hydroxyurea plus g-csf treatment at any time of hematopoietic regeneration

A new, low toxic out-patient based mobilization regimen for mobilizing Philadelphia chromosome negative (Ph−) progenitors in Ph+ CML using high-dose hydroxyurea (HU, 3.5g/m2 for 7 days) followed by G-CSF has been described recently. In order to obtain reliable information on clonal contamination and the genotype of primitive progenitors (LTC-IC) responsible for hematopoietic reconstitution we analyzed each apheresis product individually for its content of bcr/abl positive (bcr/abl+) and/or bcr/abl− CFC and LTC-IC, respectively by RT-PCR of individual colonies. In total, 30 PBPC aphereses were tested from 11 CML pts. Aphereses were started when the pts had ≥ 10 CD34+ cells/μL blood. The mean number of aphereses performed per patient was 2.6 (range 2-4) and sufficient numbers of CD34+ cells/kg could be easily obtained in all patients [Mean: 9.1 ± 2.0 (SEM) × 106/kg BW]. In 9/11 pts we were able to mobilize primarily bcr/abl− LTC-IC (87.4 ± 2.9%) and 84.7 ± 2.8% bcr/abl− CFC. Interestingly, although 1 patient had no detectable bcr/abl− CFC within 3 aphereses, we found 100% bcr/abl− LTC-IC in 2 and 86% bcr/abl− LTC-IC in 1 apheresis. One patient had no detectable bcr/abl− progenitors in 2 seperate aphereses. In general, in 10/11 patients could primarily bcr/abl− LTC-IC be mobilized with this procedure. In contrast to others, the mean percentage of bcr/abl− progenitors remained high throughout the complete collection phase (2.6 days, mean WBC counts before 3rd leukapheresis: 39.3 G/L) suggesting an easier handling of the aphereses for these patients in terms of timing.