Doxorubicin and the alkylating anthracycline 3'-deamino-3'-(3-cyano-4-morpholinyl) doxorubicin: comparative in vitro potency against leukemia and bone marrow cells

In Vitro Toxicity Testing: Purpose, Validation and Strategy

The fullest potential for in vitro evaluation of toxicity will be realised in the context of the process of assessing the risk of human toxicity. This article is an attempt to clarify what contributions can be made by in vitro tests and what types of in vitro test can best be used. In vitro tests are clarified according to the type of biological endpoint evaluated, first into tests for general (‘basal’) cytotoxicity and, secondly, into tests for differentiated cell function. The role of each type of test is analysed and it is suggested that tests for general cytotoxicity, as opposed to differentiated function, are difficult to interpret in terms of in vivo toxicity. A general approach to evaluating in vitro tests is described, and a strategy for using these tests is proposed.

A cellular model for drug interactions on hematopoiesis: the use of human umbilical cord blood progenitors as a model for the study of drug-related myelosuppression of normal hematopoiesis

A cellular model of hematopoiesis which would be more convenient than bone marrow (BM) progenitors and directly relevant to human pathology is needed in order to investigate xenobiotic toxicity. Human umbilical cord blood (HCB), previously shown to be able to repopulate BM, provides a powerful in vitro model of normal human hematopoiesis. In order to validate the use of normal HCB progenitors as targets for dose-related myelosuppression, we used clonogenic assays and expansion in a liquid culture of progenitor-enriched cell suspensions from HCB. A series of 8 reference molecules, doxorubicin, cytosine-arabinoside, 5-fluorouracil, 3'-azido-3'-deoxythymidine, acetylsalicylic acid, sodium valproate and two cephalosporin antibiotics, were tested. In vitro 50% inhibition concentrations (IC50) were compared to those observed or reported with BM progenitors, and to the values of plasma concentrations from treated patients. HCB progenitors as in vitro targets for cytotoxic molecules were easy to access and handle, and their use was sensitive, specific and reproducible. They gave results similar to BM progenitors and allowed a qualitative approach to cellular metabolism and toxicity using morphological, flow cytometric and chromatographic methods.

Effects of the methoxymorpholino derivative of doxorubicin and its bioactivated form versus doxorubicin on human leukemia and lymphoma cell lines and normal bone marrow

The methoxymorpholino derivative of doxorubicin (MMDX; FCE 23672) has recently entered clinical trials because of its broad spectrum of preclinical antitumor activity and non-cross-resistance in multidrug-resistant (MDR) tumor models. MMDX is activated in the liver to a > 10 times more potent metabolite that cross-links DNA. To assess the potential of this drug in hematologic malignancies, we studied the myelotoxicity in vitro and antitumor effect of MMDX as well as its bioactivated form (MMDX+) in a panel of 14 different human leukemia and lymphoma cell lines. The tumor specificity of MMDX in CEM and K562 cells was similar to that of doxorubicin (DOX), and that of MMDX+ was slightly superior. All of the 14 cell lines were found to be more sensitive to MMDX and MMDX+ than were granulocyte-macrophage progenitors. On a molar basis, MMDX was approximately 3-100 times more active than DOX, and MMDX+ was 10-1,000 times more potent than DOX. The cytotoxic effect of MMDX and MMDX+ in two P-glycoprotein-positive MDR sublines was greatly improved in comparison with that of DOX. Whereas the response to DOX in the different leukemia and lymphoma cell lines was highly heterogeneous, the response to MMDX and MMDX+ was rather homogeneous. The novel anthracycline MMDX and its bioactivated form MMDX+ are highly active against this panel of human leukemia and lymphoma cell lines and demonstrate potentially greater selectivity for tumor cells in vitro as compared with normal bone marrow precursors.

New drugs in acute myelogenous leukemia: a review

Numerous clinical trials in adult patients with newly diagnosed acute myelogenous leukemia indicate that the survival rate is approximately 20%. A limited number of favorable prognostic features have been identified; patients who present with specific cytogenetic abnormalities such as t(15;17), t(8;21) and inv (16) tend to have survival rates approaching 40%. However, such patients constitute only a small proportion of the total denominator and it has therefore been a major focus of scientific endeavor to develop new drugs for the treatment of this disease. A wide variety of agents have undergone preliminary testing in this regard and include both natural substances such as homoherringtonine, a drug that has demonstrated modest complete remission rates in this disease and all-trans retinoic acid, a compound that has revolutionized the treatment of acute promyelocytic leukemia. This review will put in perspective some of the newer drugs for the treatment of acute myelogenous leukemia and allow for some conclusions to be drawn as to their impact in the treatment of this disease.

Comparison of the cytotoxicity of amsacrine and its analogue CI-921 against cultured human and mouse bone marrow tumour cells

Human and mouse bone marrow cells were cultured for 1 h in the presence of either the antileukaemia drug amsacrine or its 4-methyl,5-[N-methyl]carboxamide disubstituted analogue CI-921, before being plated in methylcellulose medium to determine the survival of granulocyte-macrophage colony forming units (CFU-GM). The drug concentration required for 50% reduction in survival was approx. 0.4 microM for both drugs and was similar for both human and mouse cells. A comparison of the two drugs was then made, at an added drug concentration of 0.5 microM, using cultured mouse L1210 and P388 leukaemia, Lewis lung carcinoma cell lines LLAK and LLTC, human Jurkat leukaemia, human histiocytic lymphoma U937 and human colon carcinoma SW620. The sensitivity of the mouse lines for amsacrine was in the order L1210 greater than P388 greater than LLAK greater than LLTC, similar to the in vivo sensitivity. The selectivity of CI-921 for L1210 versus bone marrow, and for LLAK versus L1210 or P388, was greater than that of amsacrine, again in keeping with its in vivo properties. The sensitivity of the human Jurkat and U937 lines for amsacrine was intermediate between that of L1210 and P388, while SW620 was resistant. The selectivity of CI-921 for Jurkat and U937 versus bone marrow was greater than that of amsacrine, suggesting that CI-921 could have additional advantages over amsacrine in the treatment of some tumours.