Cyclophosphamide activity against B16 melanoma in a rapid in vitro test system

An in vitro test system is described for evaluation of the response of tumor cells to chemotherapeutic agents. The test is simple and rapid and does not require the use of sterile technique. The response of B16 melanoma in vivo in C57BL/6 mice to single graded doses of cyclophosphamide is compared to the response of B16 tumor cells in vitro to cyclophosphamide that has been activated in vivo and recovered in plasma. The assay involves preincubating the tumor cells with the activated drug and subsequently measuring the ability of the cells to incorporate [3H]dThd ([3H] thymidine) into acid-insoluble material. In vivo activated drug is maximally effective in 20 min and the entire test can be completed within 8 hr. This test may be useful as a rapid preliminary screening method to predict the effect of chemotherapy on cancer.