title: Caspase-9b Interacts Directly with cIAP1 to Drive Agonist-Independent Activation of NF-κB and Lung Tumorigenesis.
abstract: Alternate RNA processing of caspase-9 generates the splice variants caspase 9a (C9a) and caspase 9b (C9b). C9b lacks a domain present in C9a, revealing a tumorigenic function that drives the phenotype of non-small cell lung cancer (NSCLC) cells. In this study, we elucidated the mechanistic underpinnings of the malignant character of this splice isoform. In NSCLC cells, C9b expression correlated with activation of the canonical arm of the NF-κB pathway, a major pathway linked to the NSCLC tumorigenesis. Mechanistic investigations revealed that C9b activates this pathway via direct interaction with cellular inhibitor of apoptosis 1 (cIAP1) and subsequent induction of the E3 ligase activity of this IAP family member. The C9b:cIAP1 interaction occurred via the BIR3 domain of cIAP1 and the IAP-binding motif of C9b, but did not require proteolytic cleavage of C9b. This protein:protein interaction was essential for C9b to promote viability and malignant growth of NSCLC cells in vitro and in vivo, broadly translating to diverse NSCLC oncogenotypes. Overall, our findings identified a novel point for therapeutic invention in NSCLC that may be tractable to small-molecule inhibitors, as a new point to broadly address this widespread deadly disease. Cancer Res; 76(10); 2977-89. ©2016 AACR.
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Vietnam Education Foundation, Arlington, Virginia.
authors.forename: Ngoc T
authors.initials: NT
authors.lastname: Vu
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia. The VCU Institute of Molecular Medicine, The VCU Massey Cancer Center, and The VCU Johnson Center, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Park
authors.affiliation: Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Shultz
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Gamze B
authors.initials: GB
authors.lastname: Bulut
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Ladd
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia. The VCU Institute of Molecular Medicine, The VCU Massey Cancer Center, and The VCU Johnson Center, Virginia Commonwealth University, Richmond, Virginia. charles.chalfant@vcuhealth.org.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Chalfant
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D063646:Carcinogenesis; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D016513:Mice, SCID; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D059748:Proteolysis; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D054875:Ubiquitination; D023041:Xenograft Model Antitumor Assays
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D053453:Caspase 9