摘要：To assess the influence of different schedules of drug exposure in human tumor clonogenic assay on in vitro cytotoxicity of antitumor drugs, the in vitro sensitivities of a human carcinoma cell line, PC-9, to various antitumor drugs were measured by using two different procedures : exposure was either by pulse for 1 h prior to plating or continuous throughout the period of growth in agar. Marked differences between the two procedures in testing actinomycin D, etoposide, 5-fluorouracil, vinblastine and vindesine but not in adriamycin, daunomycin, melphalan, nimustine and ranomustine were observed. The former and the latter were classified as schedule dependent drugs and a schedule independent drugs, respectively. In this study, the schedule dependency of in vitro drug response appears to be related mainly to time-dependency and partially to other factors, such as stability during culture in medium.
