title: A rapid mechanism-based screen to detect potential anti-cancer agents.
abstract: Several mutant Chinese hamster ovary (CHO) cell lines have been adapted to the microtiter tetrazolium assay in order to obtain useful mechanistic information relevant to the cytotoxic activity of marine natural products. The sensitivity of a DNA double-strand break repair deficient CHO line, xrs-6, was compared with that of a DNA repair competent CHO line, BR1, to several known drugs. The deficiency of the xrs-6 cells makes them overly sensitive to compounds [e.g. topoisomerase II (topo II) inhibitors] that produce DNA double-strand breaks. Described here is the validation of this unique cellular screen to detect such compounds. Those drugs thought to produce their effects by the inhibition of topo II, produced the largest differential cytotoxicity against the mutant CHO pair. Other agents that are known to either produce single-strand breaks, cross-links or to inhibit the synthesis of DNA did not possess appreciably enhanced cytotoxicity to the xrs-6 line. The usefulness of the screen was shown by its ability to detect topo II inhibitory activity in several new marine natural products. This activity was confirmed by an in vitro enzyme inhibition assay. In contrast, the screen predicted a lack of topo II inhibitory activity in some other structurally related marine natural products and this lack of activity was confirmed by an in vitro enzyme inhibition assay.
authors.affiliation: Division of Pharmacology and Toxicology, School of Pharmacy, Northeast Louisiana University, Monroe 71209.
authors.forename: D S
authors.initials: DS
authors.lastname: Swaffar
authors.forename: C M
authors.initials: CM
authors.lastname: Ireland
authors.forename: L R
authors.initials: LR
authors.lastname: Barrows
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016466:CHO Cells; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents; D006224:Cricetinae; D004260:DNA Repair; D004354:Drug Screening Assays, Antitumor; D008387:Marine Toxins / Q000494:pharmacology; D013778:Tetrazolium Salts; D013844:Thiazoles; D059005:Topoisomerase II Inhibitors
chemical_list: D000970:Antineoplastic Agents; D004396:Coloring Agents; D008387:Marine Toxins; D013778:Tetrazolium Salts; D013844:Thiazoles; D059005:Topoisomerase II Inhibitors; C022616:thiazolyl blue