title: Contribution of apoptosis in the cytotoxicity of the oxaliplatin-irinotecan combination in the HT29 human colon adenocarcinoma cell line.
abstract: Interactions between the topoisomerase I inhibitor irinotecan (CPT-11) and the platinum derivative oxaliplatin (L-OHP) were investigated in HT29 colon cancer cell line. Synergism was observed when cells were simultaneously exposed to drugs or when cells were first exposed to CPT-11. Flow cytometric studies showed a G(2)/M accumulation when cells were exposed to the simultaneous and CPT-11-->L-OHP combinations whereas a persistent S phase delay was observed when cells were first exposed to L-OHP. We characterised the cytotoxic effect by assessing the induction of apoptosis. Irinotecan induced substantial DEVDase activity and poly(ADP-ribose) polymerase cleavage while this activity was moderate and delayed after exposure to L-OHP. Combination experiments showed a sequence-dependent onset of apoptosis, the CPT-11-->L-OHP schedule being the earliest and the most effective; on the other hand the apoptotic signaling generated by CPT-11 was partly inhibited in the simultaneous combination and in the L-OHP-->CPT-11 sequence. Cell death studies using a dual staining technique showed a shift from apoptosis to necrosis when combining these drugs at high concentrations. Synergistic interactions observed using CPT-11 before L-OHP may be linked to an early apoptotic signaling while the L-OHP-induced S phase block could account for the observed additive effect in the reverse sequence. An additional phenomenon might work towards synergism for the simultaneous combination.
authors.affiliation: Groupe de Pharmacologie Clinique et Expérimentale, Institut Claudius Regaud, Toulouse, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Arnould
authors.forename: Sylvie
authors.initials: S
authors.lastname: Guichard
authors.forename: Isabelle
authors.initials: I
authors.lastname: Hennebelle
authors.forename: Georges
authors.initials: G
authors.lastname: Cassar
authors.forename: Roland
authors.initials: R
authors.lastname: Bugat
authors.forename: Pierre
authors.initials: P
authors.lastname: Canal
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000473:pathology; D004347:Drug Interactions; D005434:Flow Cytometry; D019073:HT29 Cells; D006801:Humans; D000077146:Irinotecan; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D010447:Peptide Hydrolases / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; D000077146:Irinotecan; D011065:Poly(ADP-ribose) Polymerases; D010447:Peptide Hydrolases; C108711:DEVDase; D002166:Camptothecin