SYNERGISTIC EFFECT OF 4-HYDROPEROXYCYCLOPHOSPHAMIDE AND ETOPOSIDE ON A HUMAN PROMYELOCYTIC LEUKEMIA-CELL LINE (HL-60) DEMONSTRATED BY COMPUTER-ANALYSIS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 45  (6) , 2434-2439
Abstract
Autologous stem cell transplantation using cryopreserved bone marow offers the opportunity to rescue patients from hematopoietic toxicity caused by intesive chemotherapy. This approach is potentially useful for high-risk leukemias as well as for other cancers. The development of suitable methods for purging malignant cells from the bone marrow will offer a better chance of success for autologous stem cell transplantation. Efforts a purging myeloid cells were described. HL-60, a promyelocytic leukemia cell line, was used as a model. 4-Hydroperoxycyclophosphamide (4-HC) and VP 16-213 (VP-16) (either alone or in combination) were used to treat HL-60 cells and normal bone marrow. The cytotoxic effect of 4-HC (29.2 .mu.g/ml; 100 .mu.M) upon the HL-60 cell line was 99.8 .+-. 0.12% (SE) and the colony-forming units-granulocyte, macrophage (CFU-cs) of normal bone marrow was inhibited by 82.5%. VP-16, at a concentration of 25 .mu.g/ml (42.5 .mu.m), can kill 99% of HL-60 cells and inhibit 72.7% of the CFU-cs. A drug mixture containing 4-HC (29.2 .mu.g/ml) and VP-16 (10 .mu.g/ml) (combination ratio, 1:0.342) reduces HL-760 cells to an undetectable number and the CFU-cs were inhibited by 87.2%. The laboratory data were further analyzed for the synergistic effect of these 2 drugs by quantitative determination of the median effect plot and the multiple drug equation recently described by Chou and Talalay. Interactions of 2 drugs at different effect levels and at different combination ratios were then determined by computer simulation. At high effect levels, 4-HC and VP-16 in combination gave a synergistic cytocidal effect onHL-60 leukemia cells and gave an antagonistic inhibitory effect on normal bone marrow CFU-cs. This combination greatly increase the safety margin. Computer simulation of a dose effect relationship has also shown that the 4-HC:VP-16 combination ratio of 1:0.342 yields a better selection effect than a ratio of 1:0.856. This quantitative analysis suggests that the combination of these 2 drugs at the selected dose level offer a good method for purging nonlymphoblastic leukemia cells.