title: Synergism between cisplatin and topoisomerase I inhibitors, NB-506 and SN-38, in human small cell lung cancer cells.
abstract: Topoisomerase I-targeting anticancer agents such as 7-ethyl-10-[4-(1-piperidyl)-1-piperidyl]carbonyloxy-camptothecin (CPT-11) and 6-N-formylamino-12,13-dihydro-1,11-dihydroxy-13-(beta-D- glucopyranosyl)-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7(6H)-di one (NB-506) have been developed and show strong antitumor activity against various cancers. We examined the interaction of these drugs and cisplatin (CDDP), and biochemical mechanisms of synergism between them. Interaction of drugs in human small cell lung cancer cells, SBC-3, was analyzed using the isobologram method. Combinations of CDDP with NB-506, CPT-11, and an active metabolite of CPT-11, 7-ethyl-10-hydroxy-CPT (SN-38), showed synergistic effects. Formation of DNA interstrand cross-links (ICLs) on the cells was analyzed using an alkaline elution assay and increased ICLs were observed by simultaneous exposure to CDDP (1.5 microM) and NB-506 (10 nM) compared with that in response to CDDP alone. DNA repair after ICL formation induced by 3-h exposure to CDDP (1.5 microM) was reduced by NB-506 (10 nM) exposure. On the other hand, a higher concentration of CDDP (150 microM) enhanced the topoisomerase I inhibitory activity of NB-506 and SN-38 determined by relaxation of supercoiled Escherichia coli DNA. These biological interactions might result in synergistic interactions between CDDP and NB-506 or SN-38. Topoisomerase I inhibitors and CDDP may be a key regimen for cancer chemotherapy and merit further examination.
authors.affiliation: Medical Oncology, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Fukuda
authors.forename: K
authors.initials: K
authors.lastname: Nishio
authors.forename: F
authors.initials: F
authors.lastname: Kanzawa
authors.forename: H
authors.initials: H
authors.lastname: Ogasawara
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.forename: H
authors.initials: H
authors.lastname: Arioka
authors.forename: K
authors.initials: K
authors.lastname: Bojanowski
authors.forename: M
authors.initials: M
authors.lastname: Oka
authors.forename: N
authors.initials: N
authors.lastname: Saijo
mesh_terms: D000970:Antineoplastic Agents / Q000633:toxicity*; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000633:toxicity; D002227:Carbazoles / Q000633:toxicity*; D018288:Carcinoma, Small Cell; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000633:toxicity*; D004260:DNA Repair / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005960:Glucosides / Q000633:toxicity*; D006801:Humans; D000077146:Irinotecan; D008175:Lung Neoplasms; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D002227:Carbazoles; D004791:Enzyme Inhibitors; D005960:Glucosides; C092476:NB 506; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D002945:Cisplatin; D002166:Camptothecin