title: p21(WAF1/CIP1) inhibits initiator caspase cleavage by TRAIL death receptor DR4.
abstract: Death receptors of the Tumor Necrosis Factor (TNF) family form membrane-bound self-activating signaling complexes that initiate apoptosis through cleavage of proximal caspases including CASP8 and 10. Here we show that overexpression of the cytoplasmic domain (CD) of the DR4 TRAIL receptor (TNFRSF10A, TRAIL R1) in human breast, lung, and colon cancer cell lines, using an adenovirus vector (Ad-DR4-CD), leads to p53-independent apoptotic cell death involving cleavage of CASP8 and 10 proximally and CASP3, 6, and 7 distally. DR4-CD overexpression also leads to cleavage of poly(ADP-ribose) polymerase (PARP) and the DNA fragmentation factor (DFF45; ICAD). Importantly, normal lung fibroblasts are resistant to DR4-CD overexpression and show no evidence of PARP-, CASP8- or CASP3-cleavage despite similar levels of adenovirus-delivered DR4-CD protein as the cancer cells. These results suggest that DR4 may signal death through known caspases and that further studies are required to evaluate Ad-DR4-CD as a novel anti-cancer agent. Finally, we show that overexpression of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (CDKN1A), or its N-terminal 91 amino acids containing cell cycle-inhibitory activity, inhibits DR4-CD-dependent proximal caspase cleavage. The blockage of initiator caspase activation provides a novel insight into how p21 may suppress apoptosis and enhance cell survival.
authors.affiliation: Laboratory of Molecular Oncology and Cell Cycle Regulation, Departments of Medicine, Genetics, Cancer Center, Howard Hughes Medical Institute, Institute for Human Gene Therapy, 437 CRB, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
authors.forename: S Q
authors.initials: SQ
authors.lastname: Xu
authors.forename: W S
authors.initials: WS
authors.lastname: El-Deiry
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000494:pharmacology*; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D015870:Gene Expression; D005822:Genetic Vectors; D006801:Humans; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D011506:Proteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C105190:TNFRSF10A protein, human; D016159:Tumor Suppressor Protein p53; C109664:caspase-activated DNase inhibitor; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases