Sensitivity of myeloid progenitor cells in healthy subjects and patients with chronic myeloid leukemia to chemotherapeutic agents.

The different sensitivity of myeloid progenitor cells (CFUc) to chemotherapeutic agents was measured with an in vitro clonogenic assay. Normal marrow and peripheral blood CFUc and blood CFUc obtained from patients with chronic myelogenous leukemia (CML) were tested for their sensitivity to medications used currently in the management of CML. The drugs tested were adriamycin, L-asparaginase, busulfan, beta-cytosine arabinoside (Ara-C), daunorubicin, hydroxyurea, melphalan, and thioguanine. CML CFUc were significantly more sensitive to Ara-C [drug dose required for 90% inhibition of CFUc growth (LD90) = 0.015 +/- 0.003 microgram/ml] than were normal CFUc (LD90 = 0.038 +/- 0.009 microgram/ml). A shift to enhanced sensitivity to L-asparaginase was detected in patients studied sequentially who entered blast transformation during this study. In vitro and in vivo pharmacokinetic data are compared.

Sensitivity of normal human bone marrow myeloid progenitor cells to anthracycline, cisplatin, anthracene and flavone acetic acid derivatives, and its relevance for the prediction of human plasma concentrations of anticancer drugs.

Many in vitro investigations with anticancer agents are performed at concentrations equal to the peak concentrations or fractions of the peak concentrations achieved in human plasma after administration of these agents. In an effort to develop an in vitro test capable of predicting these peak plasma concentrations prior to the completion of pharmacokinetic studies, the effect of several classes of anticancer agents against normal human bone marrow myeloid progenitor cells (CFU-GM) was studied. The investigated agents included anthracycline antibiotics, cisplatin and its analogs, anthracene derivatives and two flavone acetic acid derivatives. The CFU-GM were exposed to these agents for 30-60 min. An exponential relationship between drug concentration and CFU-GM growth was observed for all compounds with the exception of the flavone acetic acid derivatives which were inactive. For the latter two compounds, an inhibition of CFU-GM growth was observed after continuous exposure. When compared to the plasma concentrations after parenteral administration of these agents, there was a very good agreement between 1/10 of the peak plasma concentration and the concentration inducing a 90% inhibition of the CFU-GM growth for the anthracycline antibiotics and anthracene derivatives. In contrast, for cisplatin and its analogs, there was a better agreement between 1/10 of the peak plasma concentration and the concentration inducing a 10% inhibition of CFU-GM growth. The combination of concentrations inducing inhibitions of 10 and 90% of the CFU-GM growth provides a range of concentrations that predict reasonably well the peak plasma concentrations of several anticancer agents and that could be used as guides for other in vitro investigations.

Effect of daunorubicin, carminomycin, idarubicin and 4-demethoxydaunorubicinol against human normal myeloid stem cells and human malignant cells in vitro.

The cytotoxic effect of daunorubicin, carminomycin, idarubicin and the major metabolite of idarubicin in man, 4-demethoxydaunorubicinol, was investigated in a human normal progenitor myeloid stem cell assay and in a human tumor stem cell assay. Against normal myeloid progenitor cells, idarubicin and carminomycin were equally potent; both agents were significantly (P less than or equal to 0.01) more potent than daunorubicin. Idarubicin was approx. 2.5 times more potent than 4-demethoxydaunorubicinol. Against malignant tumor cells, 50% cell kill after exposure to idarubicin was observed in four out 24 samples; this inhibition occurred at a drug concentration of 0.1 micrograms/ml. Two of the samples sensitive to idarubicin were also sensitive to 4-demethoxydaunorubicinol at a concentration of 0.1 micrograms/ml. Overall, idarubicin was active against two out of six ovarian carcinomas and against one out of three breast carcinomas. Our data confirm that 4-demethoxydaunorubicinol may play a role in the biological activity of idarubicin.

Quantitation of differential sensitivity of normal marrow myeloid progenitor cells to anthracene derivatives.

The effect of 3 anthracene derivatives, mitoxantrone, ametantrone, bisantrene, on 4 normal human bone marrows, was studied using the myeloid stem cell assay developed by Pike and Robinson, in order to define to what extent this test could be used to predict the relative clinical hematologic toxicity of new anticancer agents. For the 3 drugs, an exponential relationship between colony survival and drug concentration was found, but was much steeper for mitoxantrone (slope = -195.2 +/- 8.8/micrograms/ml) than for ametantrone (slope = 5.1 +/- 1.0/micrograms/ml, p less than or equal to 0.001) and bisantrene (slope = 7.1 +/- 0.3/micrograms/ml, p less than or equal to 0.001). The difference of slope between ametantrone and bisantrene was of borderline significance (p less than or equal to 0.05). The ratios of concentrations inducing a 50% growth inhibition for mitoxantrone versus bisantrene and for ametantrone versus bisantrene were close to the corresponding ratios of concentrations inducing a 90% growth inhibition. The relative in vitro toxicities reproduce very well the relative myelosuppression observed in clinical trials with mitoxantrone versus bisantrene but the results were less satisfactory for the comparison of these 2 agents with ametantrone. In addition, our data suggest that, for these 3 compounds, intrinsic myeloid progenitor sensitivity is a major determinant of leukopenia.

Increased levels of myeloid progenitor cells in the blood of patients with metastatic invasion of the marrow.

Granulocyte-macrophage clusters and colony-forming cells (CFU-C) in the peripheral blood have been studied in 26 cancer patients with neoplastic bone marrow involvement. The concentration of CFU-C in the blood of normal individuals and of cancer patients with no bone marrow invasion, ranged from 0 to 99 ml. In contrast, out of 27 cancer patients with marrow invasion, 9 (35%) showed a significant increase of blood CFU-C (100 to 21000/ml) and of those 5 (19%) showed an increase of blood colonies (41 to 9000/ml). There was a strong correlation between increased CFU-C or colony concentration and the presence of myeloid or/and erythroid immature cells in the peripheral blood. On the other hand, there was no apparent correlation between an increased CFU-C level and anaemia or abnormal blood leucocyte count or marrow fibrosis. These observations suggest that bone marrow involvement by neoplastic cells may cause spatial redistribution of the granulocyte macrophage progenitor cells.