The cytotoxicity of mafosfamide on G-CSF mobilized hematopoietic progenitors is reduced by SH groups of albumin--implications for further purging strategies.
The efficacy of mafosfamide purging depends on factors like incubation time, drug and erythrocyte concentration. To determine the influence of protein-bound SH groups in the incubation medium, the cytotoxicity of mafosfamide on G-CSF mobilized CD34+/- cells was evaluated by short-term culture assays and drug concentration measurements. 100 micromol/ml mafosfamide was incubated for 30 min in five buffers (PBS, PBS with 1%, 5% and 10% BSA and plasma). The mean calculated areas under the concentration-time curves (AUC) were 2489 +/- 198, 1561 +/- 286, 976 +/- 201, 585 +/- 62 and 605 +/- 196 micromol/l/min. The mean reductions of CFU-GM growth were 79.4%, 73.0%, 62.5%, 30.3%, 6.2% respectively. Similar results were obtained for BFU-E. Regression analysis showed a good correlation between cytotoxicity and AUCs (CFU-GM: r = 0.8195; BFU-E: r = 0.8207). This effect is well explained by the different concentrations of SH moieties in the incubation medium resulting in a higher drug binding capacity. The profound difference between AUCs and CFU-GMs in plasma and 10% BSA cannot be explained by the quantity of SH-groups. It is probably due to an additional enzymatic drug degeneration by the 3'-5'exonuclease subsite of plasma DNA polymerase. In conclusion, the concentration of albumin-associated SH groups strongly influences the cytotoxicity of mafosfamide. It has to be considered as a new and important aspect in ex vivo bone marrow purging.
Schlenke
P
P
Institute of Immunology and Transfusion Medicine, University of Luebeck School of Medicine, Germany.
Kisro
J
J
Deeken
M
M
Zajac
S
S
Klich
S
S
Wagner
T
T
D000418:Albumins / Q000378:metabolism; D018952:Antigens, CD34 / Q000097:blood; D019540:Area Under Curve; D016465:Bone Marrow Purging / Q000379:methods*; D002478:Cells, Cultured / Q000378:metabolism; D003114:Colony-Forming Units Assay; D003520:Cyclophosphamide / Q000031:analogs & derivatives* / Q000633:toxicity; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D008875:Middle Aged; D013997:Time Factors
D000418:Albumins; D018952:Antigens, CD34; C048341:mafosfamide; D003520:Cyclophosphamide