Murine and human leukemias.

Essentially all the drugs which are active against human leukemias and lymphomas are active against one type or another of the rodent leukemias and lymphomas. Leukemia L1210 has been generally the most successful screening tool for clinically active compounds. Leukemia P388, however, seems to be better in detecting active antibiotics and natural products and P1534 is particularly sensitive to the Vinca alkaloids, while L5178Y, EARAD, and 6C3HED are useful in detecting the activities of various asparaginase containing fractions. Cell cultures of these leukemias can demonstrate mechanism of drug action and quantitate resistance. Spontaneous AKR leukemia is a model of the advanced human disease. In these leukemias vincristine and prednisone produce a 4 log cell kill. Cytoxan and arabinosyl cytosine (Ara-C) are also effective. On the other hand drugs such as mercaptopurine (6MP) and methotrexate which are highly active in the maintenance phase of acute lymphocytic leukemia (ALL) and in L1210 have little or no activity against the AKR spontaneous system. Mouse leukemias can also detect schedule dependence, synergistic combinations, cross resistance, oral activity, and the ability of drugs to pass the blood brain barrier. A case in point is the Ara-C analog 2,2'-anhydro-arabinofuranosyl-5-fluorocytosine (AAFC) which is not schedule dependent, is active orally, is potentiated by thioguanine, and is effective against intracerebrally inoculated mouse leukemia. AAFC and its analogs might thus be a considerable improvement over Ara-C which is at the present time the most important component of the combination treatment of acute myelogenous leukemia (AML).