title: Enhanced tumor killing by Apo2L/TRAIL and CPT-11 co-treatment is associated with p21 cleavage and differential regulation of Apo2L/TRAIL ligand and its receptors.
abstract: Apo2L/TRAIL exhibits enhanced apoptotic activity in tumor xenograft models when used in combination with the topoisomerase 1 inhibitor CPT-11. To investigate the cellular mechanisms involved in this increased tumor-killing activity, a series of in vitro experiments were conducted using the human colon carcinoma cell line (HCT116). Apo2L/TRAIL induced a transient upregulation of DR5 mRNA, while CPT-11 increased both death and decoy receptor expression. Upregulation of decoy receptors by CPT-11 was partially inhibited by co-administration of Apo2L/TRAIL. CPT-11 treatment resulted in accumulation of cells at G(2)M-phase and correlated with a substantial increase in the protein levels of the cyclin-dependent kinase inhibitor p21. However, cells co-treated with CPT-11 and Apo2L/TRAIL, or pretreated with CPT-11 for up to 24 h followed by 2 h Apo2L/TRAIL, resulted in a caspase-dependent degradation of p21, reversal of G(2)-M phase arrest with a concomitant increase in apoptosis. The sequential treatment produced the greatest induction of DR5 and DR4, caspase-3-like cleavage/activation and p21 degradation, as well as increased apoptosis. These data indicate that the up-regulation of Apo2L/TRAIL ligand and its death receptors as well as cleavage of p21 protein in the Apo2L/TRAIL plus CPT-11 treatment contributes to the positive cooperation between these agents in enhancing tumor cell apoptosis.
authors.affiliation: Department of Clinical and Experimental Pharmacology; Genentech, Inc., 1 DNA Way, South San Francisco, California, CA 94080, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Xiang
authors.forename: Judith A
authors.initials: JA
authors.lastname: Fox
authors.forename: Klara
authors.initials: K
authors.lastname: Totpal
authors.forename: Mina
authors.initials: M
authors.lastname: Aikawa
authors.forename: Kelly
authors.initials: K
authors.lastname: Dupree
authors.forename: Dominick
authors.initials: D
authors.lastname: Sinicropi
authors.forename: John
authors.initials: J
authors.lastname: Lowe
authors.forename: Enrique
authors.initials: E
authors.lastname: Escandón
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002166:Camptothecin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002277:Carcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D002478:Cells, Cultured; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004357:Drug Synergism; D006801:Humans; D000077146:Irinotecan; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D012334:RNA, Neoplasm / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008562:Membrane Glycoproteins; D012334:RNA, Neoplasm; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D000077146:Irinotecan; D020169:Caspases; D002166:Camptothecin