All-trans retinoic acid might also induce apoptosis in freshly isolated chronic myeloid leukemia cells.

strong correlation was found between the two variables (r = 0.86; p<0.0001), as suggested by linear regression analysis. The best results were obtained when the number of CD34 cells in PB was greater than 50 μL, while the worst results were related to a level of less than 10 μL (Figure 1). Only in 5 cases, because of the particular clinical history of the patients, did we perform leukapheresis when circulating CD34 cells were < 10 μL. None of these reached 0.5310/kg CD34 cells (mean value collected was 0.23, range 0.05-0.4310/kg). With more than 10/mL CD34 cells in PB we collected no less than 0.5310/kg, with rare exceptions. When CD34 cells exceeded 20/mL we usually reached more than 1310/kg. No statistical difference was found in patients with CD34 cell values ranging from 21 to 50 μL. Finally, in our hands, more than 50 μL circulating CD34 cells ensured a collection greater than 2310/kg in most patients. Though the quality of a leukapheresis does not depend only upon the absolute number of CD34 progenitors present, our data confirm that daily estimation of the circulating CD34 cell number by flow cytometry may guide our clinical decisions and may offer a useful tool for predicting the number of procedures to perform.