title: Expression of anti-apoptotic factors modulates Apo2L/TRAIL resistance in colon carcinoma cells.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) selectively induces apoptosis in transformed cells. Normal cells and certain tumor cells can evade Apo2L/TRAIL induced cell death, but the determinants of Apo2L/TRAIL sensitivity are poorly understood. To better understand the factors that contribute to Apo2L/TRAIL resistance, we characterized two colon carcinoma lines with pronounced differences in Apo2L/TRAIL sensitivity. Colo205 cells are highly sensitive to Apo2L/TRAIL whereas Colo320 cells are unresponsive. Components of the DISC (death inducing signaling complex) could be immunoprecipitated from both cell lines in response to Apo2L/TRAIL. Sensitizing agents including a proteasome inhibitor conferred Apo2L/TRAIL sensitivity in Colo320 cells, indicating that the apoptotic machinery was intact and functional. We specifically suppressed the expression of Bcl-2, FLIP or XIAP in Colo320 cells. Downregulation of either FLIP or XIAP but not Bcl-2 restored sensitivity of Colo320 cells to Apo2L/TRAIL. Moreover, stable knockdown of XIAP expression in Colo320 subcutaneous tumors resulted in suppression of tumor growth and sensitivity to Apo2L/TRAIL in vivo. Our results indicate that only a specific subset of anti-apoptotic proteins can confer resistance to Apo2L/TRAIL in Colo320 cells. Elucidation of the factors that contribute to Apo2L/TRAIL resistance in tumor cells may provide insight into combination therapies with Apo2L/TRAIL in a clinical setting.
authors: Department of Oncology, Amgen Inc., 1201 Amgen Ct. West, Seattle, WA 98119, USA.
authors: Mara S
authors: MS
authors: Lippa
authors: Laura D
authors: LD
authors: Strockbine
authors: Tiep T
authors: TT
authors: Le
authors: Daniel G
authors: DG
authors: Branstetter
authors: Craig A
authors: CA
authors: Strathdee
authors: Pamela M
authors: PM
authors: Holland
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics; D002277:Carcinoma / Q000235:genetics* / Q000473:pathology; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D053218:Receptors, Death Domain / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human