title: RIP-1/c-FLIPL Induce Hepatic Cancer Cell Apoptosis Through Regulating Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL).
abstract: BACKGROUND Almost all hepatic cancer cells have resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. c-FLIPL and RIP-1 are apoptotic negative regulatory factors. This study investigated the role of c-FLIPL and RIP-1 in hepatic cancer cell resistance to TRAIL-induced apoptosis. MATERIAL AND METHODS HepG2 cells were treated by TRAIL, RIP-1 siRNA, and/or BY11-7082. Cell viability was detected by MTT assay. Cell apoptosis was tested by flow cytometry. DISC component proteins, RIP-1, and p-p65 were measured by Western blot. Caspase-8 and caspase-3 were determined by spectrophotometry. RESULTS Single TRAIL treatment showed no significant impact on cell proliferation and apoptosis. HepG2 cells expressed high levels of RIP1 and c-FLIPL, while a high concentration of TRAIL upregulated RIP-1 and c-FLIPL expression but not DR4 and DR5. Single TRAIL treatment did not obviously activate caspase-8 and caspase-3. RIP-1 or c-FLIPL siRNA markedly induced cell apoptosis and enhanced caspase-8 and caspase-3 activities. Combined transfection obviously increased apoptotic cells. TRAIL markedly upregulated RIP-1 expression and enhanced p-p65 protein. Downregulating RIP-1 and/or BAY11-7082 significantly reduced NF-kB transcriptional activity, blocked cells in G0/G1 phase, weakened proliferation, elevated caspase-8 and caspase-3 activities, and promoted cell apoptosis. CONCLUSIONS TRAIL can enhance RIP1 and c-FLIPL expression in HepG2 cells. High expression of RIP1 and c-FLIPL is an important reason for TRAIL resistance. Downregulation of RIP1 and c-FLIPL can relieve caspase-8 suppression, activate caspase-3, and promote cell apoptosis. TRAIL mediates apoptosis resistance through upregulating RIP-1 expression, enhancing NF-kB transcriptional activity, and weakening caspase activity.
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Jichun
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Xiao
authors.initials: X
authors.lastname: Yu
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Changfa
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Can
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of General Surgery, The 3rd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Wanpin
authors.initials: W
authors.lastname: Nie
authors.affiliation: Department of General Surgery, The 2nd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Xundi
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of General Surgery, The 2nd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Xiongying
authors.initials: X
authors.lastname: Miao
authors.affiliation: Department of General Surgery, The 2nd Xiangya Hospital, Central South University, Changsha, Hunan, China (mainland).
authors.forename: Xiaoxin
authors.initials: X
authors.lastname: Jin
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005434:Flow Cytometry; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology*; D016328:NF-kappa B / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053418:Death Domain Receptor Signaling Adaptor Proteins; D016328:NF-kappa B; D053221:TNF-Related Apoptosis-Inducing Ligand; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D020169:Caspases