title: Knockdown of c-FLIP(L) enhanced AD5-10 anti-death receptor 5 monoclonal antibody-induced apoptosis in human lung cancer cells.
abstract: It is reported that the agonistic antibodies against death receptors 4 and 5 (DR4, DR5) are cytotoxic to various cancer cells. In the present study, the sensitivity of five human lung cancer cell lines to previously reported AD5-10 agonistic antibody against DR5 were investigated. Of these cell lines, A549 and small cell lung cancer showed a moderate sensitivity to AD5-10 and three other cell lines were resistant. Cell line H460 is resistant to AD5-10 despite a high level of cell-surface DR5 expression. We demonstrated that the resistance of H460 cells to AD5-10 was not related to the expression level of DR5, but the expression and cleavage of c-FLIP(L) in the cells. Inhibition of endogenous c-FLIP(L) expression by siRNA significantly enhanced AD5-10-induced cell death in these lung cancer cells. We further showed that this sensitizing effect was associated with decreased expression of Bcl-2 family proteins Bid and Bcl-X(L), change of mitochondrial membrane potential, release of cytochrome c from mitochondria, and caspase activation. Therefore, these data provide evidence that c-FLIP(L) is involved in the resistance of lung cancer cells to AD5-10-induced apoptosis. Moreover, immunohistochemistry on paraffin-embedded tissue revealed that c-FLIP(L) was expressed in 87.9% (29 of 33) of lung carcinoma tissues from the patients, but little in tissues from normal controls. This suggests that inhibition of c-FLIP(L) expression might be a potential strategy for lung cancer therapy, especially for those lung cancers resistant to the agonistic antibody against death receptors.
authors.affiliation: National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Juntang
authors.initials: J
authors.lastname: Guo
authors.forename: Yaxi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Naikang
authors.initials: N
authors.lastname: Zhou
authors.forename: Shilian
authors.initials: S
authors.lastname: Liu
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Liu
authors.forename: Dexian
authors.initials: D
authors.lastname: Zheng
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D009367:Neoplasm Staging; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000276:immunology*; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand