Abstract

DFMO, an irreversible inhibitor of ornithine decarboxylase, blocks polyamine biosynthesis, is reported to have antitumor effects in vitro at the peak achievable plasma concentration (about 0.5 mM). We determined the effects of DFMO on the growth of gastric and colorectal carcinoma cell lines using the semiautomated tetrazollum MTT assay. At a concentration of 0.5 mM and a 4 day incubation periad, DFMO inhibited the growth of 4 gastric cell lines by a median value of 5% and the growth of 7 colorectal cell lines by a median value of 22%. These effects were reversible by the addition of 0.1 mM of putrescine. Conciusians: 1) at the peak achievable plasma concentration, DFMO has very modest inhibitory effects on the growth of gastrointestinal carcinoma cell lines: and 2) DFMO may have a greater growth inhibitory effect on colorectal than on gastric carcinoma cell lines.