Effect of 4-hydroperoxycyclophosphamide on leukemic and normal human myeloid progenitor cells

The sensitivity of myeloid progenitor cells from normal subjects (N-CFU-GM) and from leukemic patients in complete remission (LR-CFU-GM) to 4-hydroperoxycyclophosphamide (4-HC) were compared to the sensitivity of leukemic progenitor cells (L-CFU) to this drug. The results were expressed as the dose of 4-HC needed to kill 90% (TD 90) of the progenitor cells. The mean TD 90 were respectively for N-CFU-GM : 59 (+/- 11 S.E.M.) nM ml-1 and for L-CFU 79 (+/- 6 S.E.M.) nM ml-1. Thus, L-CFU were equally sensitive to 4-HC as N-CFU-GM. Moreover, the mean TD 90 for LR-CFU-GM was 87 (+/- 5 S.E.M.) nM ml-1. Thus, the sensitivity of N-CFU-GM and LR-CFU-GM did not differ significantly from that of L-CFU. These results are not encouraging for the use of 4-HC in vitro to eliminate the residual leukemic cells from autologous bone marrow of AML patients in complete remission. The sensitivity of L-CFU was modified neither by previous cytoreductive therapy (different from cyclophosphamide) nor by the time elapsed since diagnosis of AML.     

The kinetics of colony-stimulating activity elaboration from human bone marrow cells by immunoadjuvants: Interactions between light density adherent and nonadherent cells in vitro

To examine the myelopoietic activity of immunoadjuvants like Bacillus Calmette Guerin (BCG), methanol extraction residue of BCG (MER), Corynebacterium parvum and Pyran, we performed experiments to delineate their action on human marrow cells. Whole light-density (<1.077 g/ml) cells (LD) (2 × 10⁶/ml and 2 ml/dish), adherent (Ad) cells, and nonadherent (N-Ad) cells alone (derived from 4 × 10⁶ LD cells/dish) from human marrow were incubated with and without the above agents. The conditioned media (CM) were harvested at 24, 72, 96 and 168 h and colony-stimulating activity (CSA) assayed against light-density nonadherent human marrow cells (0.5 × 10⁵or 1.0 × 10⁵ per dish). Maximum CSA elaboration was shown to occur after 72 or 96 of incubation, and an invariable drop in the activity was noted after an incubation of 168 h. The optimal concentrations elaborating maximum CSA for BCG, MER and C. parvum were 1000, 100 and 10 μg/ml, respectively. The CM prepared with higher concentrations were less active. Pyran-produced CM were found to be inactive for CSA. The CSA elaborated from LD cells was always more than additive to that from Ad and N-Ad cells when incubated separately. However, when Ad and N-Ad cells were incubated together (ratio 1:3), the CSA in CM was as potent as from LD cells. Immunoadjuvants themselves had no colony-stimulating effect on N-Ad target cells in the presence of CSA source. On the other hand, they inhibited colony growth at higher concentrations. This inhibition seems to be due partly to the products of the cycloxigenase pathway of arachidonic acid metabolism.