title: The LEF1/CYLD axis and cIAPs regulate RIP1 deubiquitination and trigger apoptosis in selenite-treated colorectal cancer cells.
abstract: Inhibitor-of-apoptosis protein (IAP) inhibitors have been reported to synergistically reduce cell viability in combination with a variety of chemotherapeutic drugs via targeted cellular IAP (cIAP) depletion. Here, we found that cIAP silencing sensitised colorectal cancer (CRC) cells to selenite-induced apoptosis. Upon selenite treatment, the K63-linked ubiquitin chains on receptor-interacting protein 1 (RIP1) were removed, leading to the formation of the death-inducing complex and subsequent caspase-8 activation. Although the ubiquitinases cIAP1 and cIAP2 were significantly downregulated after a 24-h selenite treatment, cylindromatosis (CYLD) deubiquitinase protein levels were marginally upregulated. Chromatin immunoprecipitation assays revealed that lymphoid enhancer factor-1 (LEF1) dissociated from the CYLD promoter upon selenite treatment, thus abolishing suppression of CYLD gene expression. We corroborated these findings in a CRC xenograft animal model using immunohistochemistry. Collectively, our findings demonstrate that selenite caused CYLD upregulation via LEF1 and cIAP downregulation, both of which contribute to the degradation of ubiquitin chains on RIP1 and subsequent caspase-8 activation and apoptosis. Importantly, our results identify a LEF1-binding site in the CYLD promoter as a potential target for combinational therapy as an alternative to cIAPs.
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: P
authors.initials: P
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: K J
authors.initials: KJ
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: J J
authors.initials: JJ
authors.lastname: An
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Y L
authors.initials: YL
authors.lastname: Ci
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: K Y
authors.initials: KY
authors.lastname: Hui
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: C M
authors.initials: CM
authors.lastname: Xu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D001665:Binding Sites; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000074749:Deubiquitinating Enzyme CYLD; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D016601:RNA-Binding Proteins / Q000378:metabolism*; D020887:Selenious Acid / Q000494:pharmacology*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D047368:Tumor Burden / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D054875:Ubiquitination; D023041:Xenograft Model Antitumor Assays
chemical_list: C119724:AGFG1 protein, human; D000970:Antineoplastic Agents; D051034:Inhibitor of Apoptosis Proteins; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; D028861:Nuclear Pore Complex Proteins; D016601:RNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C494833:BIRC2 protein, human; C494832:BIRC3 protein, human; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D044767:Ubiquitin-Protein Ligases; C409984:CYLD protein, human; D000074749:Deubiquitinating Enzyme CYLD; C505530:CASP8 protein, human; D053181:Caspase 8; D020887:Selenious Acid