Bullatacin--in vivo and in vitro experience in an ovarian cancer model.

The cytotoxicity and antitumor effects of the acetogenin Bullatacin were evaluated in vitro in multiple ovarian cancer cell lines and in vivo in a murine ovarian teratocarcinoma (MOT) model in C3HeB/FeJ mice. The in vitro cytotoxicity of Bullatacin against four human ovarian epithelial tumor cell lines (OC-194, OC-222, OVCAR-3, and A-2780) was assessed in 48- and 72-h tetrazolium-dye (MTT) cytotoxicity assays. The percentage of cytotoxicity was determined on the basis of the mean optical density of the respective untreated cells and the dose effective against 50% of the cells (ED50) was calculated for each cell line. In vivo experiments were performed on adult female C3HeB/FeJ mice, which were injected i.p. with 10(5) MOT cells and varying amounts of Bullatacin given either in a single dose or in 5 subsequent doses over 72 h. All mice were observed for survival relative to that of the control groups, which were injected either with 10(5) MOT cells with or without serial injections of vehicle or with vehicle only. All four epithelial ovarian cancer cell lines displayed sensitivity to Bullatacin. The relative cytotoxic effects were very heterogeneous, with the ED50 value ranging between 10(-7) micrograms/ml for OC-194 and 4 micrograms/ml for the cisplatin-resistant cell line OVCAR-3 in a 72-h MTT cytotoxicity assay. All mice that had been injected i.p. with 10(5) MOT cells and 1.4 mg/kg or more of Bullatacin died within the first 24 h after injection, whereas all mice that had received 600 micrograms/kg of Bullatacin or less survived equally as long as the controls that had been injected with MOT only (21.1 +/- 0.9 days). Mice that had received Bullatacin at a dose ranging from 600 micrograms/kg to 1.4 mg/kg either died during the 1st day postinjection or survived, but not longer than the MOT control group. Serial i.p. injections of Bullatacin again either led to death of the mice within 24-48 h of the last dose of Bullatacin or did not have any effect on the survival of the mice as compared with the respective control groups, which had been injected with the tumor and serial injections of vehicle (22.5 +/- 2.2 days). In summary, Bullatacin showed no effect on MOT-caused animal death in C3HeB/FeJ mice at nonlethal dose ranges, whether it was given as a single i.p. dose or serially over 72 h. In vitro, however, it proved to be a very potent cytotoxic agent in a variety of ovarian cancer cell lines.(ABSTRACT TRUNCATED AT 400 WORDS)