Microbiologic assays of cancer chemotherapeutic agents

Among various assay methods available for the study of drug distribution kinetics in cancer chemotherapy, a method that determines the drug in its active form is the most desirable. The microbiologic assay method, with its rapid, simple, and inexpensive procedures, fulfills such a requirement. Besides the two commonly used chemotherapeutic agents, methotrexate and cytosine arabinoside, microbiologic assays are available for other chemotherapeutic agents, such as 6-mercaptopurine, 5-fluorouracil, actinomycin D, adriamycin, and daunorubicin. Assays have been developed for citrovorum factor and 5-methyltetrahydrofolate in the presence of high levels of methotrexate. With the introduction of combination chemotherapy, microbiologic assay methods using resistant mutants, sensitive to a single drug but resistant (either due to mutation or due to culture conditions) to all other drugs involved in the combination, could well be the most efficient for the study of distribution kinetics. Several such assay methods employed in our laboratory are discussed.