title: In vitro schedule dependency in the treatment of topoisomerase I and II inhibitor.
abstract: Topoisomerase targeting chemotherapy is an excellent strategy for lung cancer treatment. We studied the cytotoxic effects of exposure to topoisomerase I inhibitor SN-38 and topoisomerase II inhibitor etoposide (VP-16) in lung cancer cell line Ma-1 using WST-1 assay and isobologram analysis. Cells were concurrently or sequentially exposed to drugs for 30 minutes, 2 hours and 24 hours. Simultaneous exposure for 30 minutes showed antagonistic. However, 2 hours or 24 hours exposure resulted in additive or supra-additive interaction, respectively. Sequential exposures to SN-38 followed by VP-16 resulted in synergistic interaction for all schedules. Whereas, VP-16 followed by SN-38 resulted in sub-additive interaction for 30 minutes and 2 hours exposures, however, 24 hours exposure resulted in additive interaction. These findings suggest that maximum cytotoxic effects can be obtained when SN-38 precedes VP-16, and that prolonged simultaneous administration may circumvent antagonistic interaction between them. These findings may be useful in clinical trials.
authors.affiliation: The First Department of Internal Medicine, Osaka City University Medical School, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D004334:Drug Administration Schedule; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D005047:Etoposide / Q000008:administration & dosage; D006801:Humans; D000077146:Irinotecan; D008175:Lung Neoplasms / Q000188:drug therapy*; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D000077146:Irinotecan; D002166:Camptothecin