Early growth response-1 is a regulator of DR5-induced apoptosis in colon cancer cells

• Published in: British journal of cancer 2010-02, Vol.102 (4), p.754-764
• Main Authors: Mahalingam, D, Natoni, A, Keane, M, Samali, A, Szegezdi, E
• Format: Article
• Language: English
• Subjects: 631/208/200; 631/80/82/23; 692/699/67/1504/1885/1393; Apoptosis; Apoptosis - genetics; Biochemistry; Biomedical and Life Sciences; Biomedicine; Cancer Research; Cancer therapies; Carcinoma - genetics; Carcinoma - pathology; CASP8 and FADD-Like Apoptosis Regulating Protein - genetics; CASP8 and FADD-Like Apoptosis Regulating Protein - physiology; Cell death; Colonic Neoplasms - genetics; Colonic Neoplasms - pathology; Colorectal cancer; Cytochrome; Drug Resistance; Early Growth Response Protein 1 - antagonists & inhibitors; Early Growth Response Protein 1 - genetics; Early Growth Response Protein 1 - physiology; Epidemiology; Gene Expression Regulation, Neoplastic - drug effects; Genes; Humans; Kinases; Ligands; Medical research; Mitochondria - drug effects; Mitochondria - metabolism; Molecular Diagnostics; Molecular Medicine; Mutant Proteins - genetics; Mutant Proteins - physiology; Oncology; Proteins; Receptors, TNF-Related Apoptosis-Inducing Ligand - genetics; Receptors, TNF-Related Apoptosis-Inducing Ligand - metabolism; Receptors, TNF-Related Apoptosis-Inducing Ligand - physiology; Receptors, Tumor Necrosis Factor - genetics; Receptors, Tumor Necrosis Factor - metabolism; Receptors, Tumor Necrosis Factor - physiology; Recombinant Proteins - pharmacology; RNA, Small Interfering - pharmacology; Signal transduction; Signal Transduction - drug effects; Signal Transduction - genetics; TNF-Related Apoptosis-Inducing Ligand - pharmacology; Transfection; Tumor Cells, Cultured; Tumor necrosis factor-TNF
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/sj.bjc.6605545

Background: Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces tumour cell apoptosis by binding to death receptor 4 (DR4) and DR5. DR4 and DR5 activation however can also induce inflammatory and pro-survival signalling. It is not known how these different cellular responses are regulated and what the individual role of DR4 vs DR5 is in these processes. Methods: DNA microarray study was carried out to identify genes differentially expressed after DR4 and DR5 activation. RT–PCR and western blotting was used to examine the expression of early growth response gene-1 (Egr-1) and the proteins of the TRAIL signalling pathway. The function of Egr-1 was studied by siRNA-mediated knockdown and overexpression of a dominant-negative version of Egr-1. Results: We show that the immediate early gene, Egr-1, regulates TRAIL sensitivity. Egr-1 is constitutively expressed in colon cancer cells and further induced upon activation of DR4 or DR5. Our results also show that DR4 mediates a type II, mitochondrion-dependent apoptotic pathway, whereas DR5 induces a mitochondrion-independent, type I apoptosis in HCT15 colon carcinoma cells. Egr-1 drives c-FLIP expression and the short splice variant of c-FLIP (c-FLIP S ) specifically inhibits DR5 activation. Conclusion: Selective knockdown of c-FLIP S sensitises cells to DR5-induced but not DR4-induced apoptosis and Egr-1 exerts an effect as an inhibitor of the DR5-induced apoptotic pathway, possibly by regulating the expression of c-FLIP S .