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Background and Objective: So far several reports have described changes in the expression of surface antigens in progenitor cells and blasts following cryopreservation. However, there are no data on the effects of cryopreservation on the expression of the three CD34 epitope classes, and on their relationship with the clonogenic capacity of PBPC collected by leukapheresis., Design and Methods: In order to analyze the effects of freezing/thawing procedures (Eth 80C storage for 3 months) and use of dimethylsulfoxide (DMSO) on the immunophenotype profile and colony production of peripheral blood progenitor cells (PBPC) in apheresis products derived from 20 patients with stage 0-III non-Hodgkin's lymphoma (nHL), a flow cytometry study was undertaken using different CD34 monoclonal antibodies (MoAbs) capable of recognizing the 3 epitope classes of CD34 molecule (class III: HPCA-2/FITC, HPCA-2/PE, 581/FITC, 581/PE; class II: Q-Bend 10/PE; class I: ICH3/PE, BI3C5-PE, Immu-133-PE). CD34 epitope expression was also analyzed in thawed CD34+ blasts obtained from 14 patients with acute myeloid leukemia (AML), who were analyzed using a larger number (#17) of CD34 epitope class I, II, and III reactive MoAbs., Results: Under our experimental conditions it was found that class III and class II CD34 epitopes (differentially resistant to enzymatic cleavage with neuraminidase, chymopapain and glycoprotease) are better preserved than class I epitope Eth sensitive to degradation Eth after cell exposure to cryoprotectant DMSO and the freezing- thawing procedures. Results further showed a concomitant decrease in class I CD34+ counts and in BFU-E colony production. A significant increase in CD34 antigen expression levels (i.e. antibody binding capacity, ABC) by cryopreserved cells stained with CD34 epitope class III, and class II reactive MoAbs was also documented, while no changes after cryopreservation were noted using class I-reactive MoAbs. The slight increase in the percentage of CD34+ cells detected after frozen storage was correlated to a concomitant decrease in the number of more mature myeloid cells (CD15+, CD13+, CD33+). Compared to pre-cryopreservation values, a slight reduction in class I CD34 epitope expression was also found in thawed CD34+ AML blasts., Interpretation and Conclusions: As far as the reduction of class I CD34 epitope is concerned, it may be hypothesized that the freezing procedure, use of DMSO, and/or lysis methodology may either damage a CD34 subset, or induce distinct alterations of the CD34 glycoprotein, possibly determining a reduction in their immunoreactivity with some CD34 MoAbs. In conclusion, this study has shown that exposure to the cryoprotectant DMSO and the freezing/thawing procedures modifies the distribution of CD34 epitopes as well as the clonogenic capacity of PBPCs from nHL patients, and CD34+ blasts from AML. These findings need to considered when selecting CD34 MoAbs for enumeration and positive selection of stem/progenitor cells for research and clinical purposes.

Background and Objective: The use of all-trans retinoic acid (ATRA) has changed the natural course of acute promyelocytic leukemia (APL), increasing the percentage of lasting complete remissions. However, management of the few relapses remains undefined. The purpose of the present study was to evaluate the different behavior of APL patients relapsed after induction chemotherapy which had or had not included ATRA., Design and Methods: We retrospectively studied 8 patients (3 male and 5 female) who had relapsed after a clinical and molecular complete remission (CR). Five patients relapsed after conventional chemotherapy including anthracyclines, without ATRA which was not available at the onset (group A), 3 relapsed after induction treatment according to AIDA protocol (Idarubicin + ATRA) (group B). Seven patients had both molecular and clinical relapses, 1 (group B) had only a molecular relapse. The median first CR duration was 33 months (range 8-63). To induce a second CR all patients were treated with ATRA 45 mg/m2/day given orally until CR, combined with mitoxantrone 6 mg/m2/day for 6 days and cytarabine 1 g/m2/day for 6 days., Results: Seven out of 8 patients (87.5%) achieved second CR, 1 (group A) did not respond and died within two months. Second CR duration was 21, 43+, 56+, 62+ months in group A and 5, 10, 12+ (with molecular relapse) months in group B. Therefore, only one patient relapsed in group A, while all the group B patients relapsed., Interpretation and Conclusions: ATRA combined with chemotherapy is an effective approach to treating APL relapse. It produces a high incidence of second CR with an acceptable toxicity. The duration of the second CR seems, however, to be longer in patients never treated with ATRA before than in patients who relapsed after the AIDA protocol. Therefore, it might be appropriate to adopt more aggressive protocols in this latter subset of patients.