title: Cellular pharmacology of the combination of the DNA topoisomerase I inhibitor SN-38 and the diaminocyclohexane platinum derivative oxaliplatin.
abstract: CPT-11, a DNA topoisomerase I inhibitor, and oxaliplatin, a diaminocyclohexane platinum derivative, are cytotoxic agents that have demonstrated clinical antitumor activity in colorectal cancer. Given the therapeutic potential of their combination, we studied the cellular pharmacology of SN-38, the active metabolite of CPT-11, and oxaliplatin in the human colon cancer HT29 cell line. Growth inhibition was studied after a 1- or 24-h exposure to SN-38 or oxaliplatin, given alone or in combination. The cytotoxicity analysis by the isobolograms method elicited synergy. SN-38 delayed the reversion of oxaliplatin-induced DNA interstrand cross-links (ISCs), measured in cells by alkaline elution. The amount of detectable ISCs 15 h after a 1-h exposure to 10 microm oxaliplatin was 27% of the ISC peak levels and increased to 68% in the presence of 0.1 microM SN-38. The presence of oxaliplatin DNA adducts led to a 3.3-fold increase in the SN-38-induced DNA elongation inhibition, as measured by pulse-labeling alkaline elution. Inhibition of DNA and RNA synthesis was longer after exposure to the combination of oxaliplatin and SN-38 than after exposure to each agent alone. Consistently, flow cytometry analyses revealed that preexposure to oxaliplatin enhanced SN-38-induced S-phase arrest. Filter binding assays indicated that the cells arrested in S-phase at 48 h were undergoing apoptosis. Hence, supra-additive cytotoxicity appears related to major modifications in the cellular response to DNA damage rather than to changes in DNA damage formation. The combination of CPT-11 and oxaliplatin induced a 2-fold higher tumor growth reduction in vivo than did oxaliplatin alone at feasible nonlethal doses. This study provides a rationale for the optimal use of CPT-11 and oxaliplatin in combination.
authors.affiliation: Fédération des Services des Maladies Sanguines, Immunitaires, et Tumorales, Hôpital Paul Brousse, Villejuif, France.
authors.forename: N
authors.initials: N
authors.lastname: Zeghari-Squalli
authors.forename: E
authors.initials: E
authors.lastname: Raymond
authors.forename: E
authors.initials: E
authors.lastname: Cvitkovic
authors.forename: F
authors.initials: F
authors.lastname: Goldwasser
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000473:pathology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018736:DNA Adducts; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000077146:Irinotecan; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009944:Organoplatinum Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D000077150:Oxaliplatin; D012334:RNA, Neoplasm / Q000096:biosynthesis; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D018736:DNA Adducts; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D009944:Organoplatinum Compounds; D012334:RNA, Neoplasm; D059004:Topoisomerase I Inhibitors; D000077150:Oxaliplatin; D000077146:Irinotecan; D002166:Camptothecin