In vitro activity of alkylating agents on human tumors as measured by a short-term antimetabolic assay.

Abstract

The activity of some alkylating agents widely used in clinical practice was studied by an in vitro antimetabolic assay, which evaluates the interference of drugs on the incorporation of 3H-thymidine and 3H-uridine in short-term cultures of human tumors. The effect of CCNU, chlorambucil, cisplatin, melphalan, prednimustine, procarbazine and the pro-active derivatives of cyclophosphamide and ifosfamide, 4-hydroperoxycyclophosphamide and 4-hydroperoxyifosfamide, was tested on non-Hodgkin lymphomas, germ cell testicular tumors, breast and ovarian cancers. Similar effects were generally produced by the drugs on both DNA and RNA precursor incorporation, and the in vitro response rates were similar to those clinically obtained for the same tumor types by using the same drugs in monochemotherapy. The effects of different alkylating agents on the individual tumors were not significantly associated, except for the analogues 4-hydroperoxycyclophosphamide and 4-hydroperoxyifosfamide, for which a significant agreement rate was observed. No evidence of acquired resistance to 4-hydroperoxycyclophosphamide and cisplatin after clinical treatment with the same drug was found in samples from ovarian cancer and non-Hodgkin lymphoma, but there was a definite trend in germ cell testicular tumors to lower sensitivity to cisplatin in previously treated patients.