title: Suppression of HSP70 expression sensitizes NSCLC cell lines to TRAIL-induced apoptosis by upregulating DR4 and DR5 and downregulating c-FLIP-L expressions.
abstract: Many cancer cell types are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Here, we examined whether HSP70 suppression by small interfering RNA (siRNA) sensitized non-small cell lung cancer (NSCLC) cells to TRAIL-induced apoptosis and the underlying mechanisms. We demonstrated that HSP70 suppression by siRNA sensitized NSCLC cells to TRAIL-induced apoptosis by upregulating the expressions of death receptor 4 (DR4) and death receptor 5 (DR5) through activating NF-κB, JNK, and, subsequently, p53, consequently significantly amplifying TRAIL-mediated caspase-8 processing and activity, cytosolic translocation of cytochrome c, and cell death. Consistently, the pro-apoptotic proteins Bad and Bax were upregulated, while the anti-apoptotic protein Bcl-2 was downregulated. The luciferase activity of the DR4 promoter was blocked by a NF-κB pathway inhibitor BAY11-7082, suggesting that NF-κB activation plays an important role in the transcriptional upregulation of DR4. Additionally, HSP70 suppression inhibited the phosphorylation of ERK, AKT, and PKC, thereby downregulating c-FLIP-L. A549 xenografts in mice receiving HSP70 siRNA showed TRAIL-induced cell death and increased DR4/DR5 levels and reduced tumor growth. The combination of psiHSP70 gene therapy with TRAIL also significantly increased the survival benefits induced by TRAIL therapy alone. Interestingly, HSP27 siRNA and TRAIL together could not suppress tumor growth or prolong the survival of tumor-bearing mice significantly, although the combination could efficiently induce the apoptosis of A549 cells in vitro. Our findings suggest that HSP70 suppression or downregulation might be promising to overcome TRAIL resistance in cancer.
authors.affiliation: The State Key Laboratory of Pharmaceutical Biotechnology, College of Life Science and School of Stomatology, Affiliated Stomatological Hospital, Nanjing University, 22 Han Kou Road, Nanjing, 210093, Jiangsu, People's Republic of China.
authors.forename: Hongqin
authors.initials: H
authors.lastname: Zhuang
authors.forename: Weiwei
authors.initials: W
authors.lastname: Jiang
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Fan
authors.initials: F
authors.lastname: Qiu
authors.forename: Ziyi
authors.initials: Z
authors.lastname: Gan
authors.forename: Wei
authors.initials: W
authors.lastname: Cheng
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Shengwen
authors.initials: S
authors.lastname: Guan
authors.forename: Bo
authors.initials: B
authors.lastname: Tang
authors.forename: Qilai
authors.initials: Q
authors.lastname: Huang
authors.forename: Xinhua
authors.initials: X
authors.lastname: Wu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Huang
authors.forename: Wenhui
authors.initials: W
authors.lastname: Jiang
authors.forename: Qingang
authors.initials: Q
authors.lastname: Hu
authors.forename: Min
authors.initials: M
authors.lastname: Lu
authors.forename: Zi-Chun
authors.initials: ZC
authors.lastname: Hua
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology* / Q000627:therapeutic use; D047368:Tumor Burden / Q000187:drug effects; D015854:Up-Regulation
chemical_list: D000970:Antineoplastic Agents; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D018840:HSP70 Heat-Shock Proteins; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505653:TNFSF10 protein, human