Carcinogenesis Advance Access originally published online on December 4, 2008
Carcinogenesis 2009 30(2):222-229; doi:10.1093/carcin/bgn271
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c-Jun N-terminal kinase (JNK1) upregulates XIAP-associated factor 1 (XAF1) through interferon regulatory factor 1 (IRF-1) in gastrointestinal cancer
1 Department of Digestive Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
2 Department of Medicine, University of Hong Kong, Queen Mary Hospital, Hong Kong, China
3 Center for Emerging Infectious Diseases, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
* To whom correspondence should be addressed. Tel: +852 28555995; Fax: +852 29049443; Email: bcywong{at}hku.hk
Correspondence may also be addressed to Jide Wang. Tel: +86 20 61641538; Fax: +86 20 87280770; Email: jidewang{at}gmail.com
Background and Aims: X-linked inhibitor of apoptosis protein-associated factor 1 (XAF1) is a tumor suppressor that can sensitize cancer cell to apoptosis. Intrinsic expression of XAF1 in cancer cell is low. Our purpose is to determine the effect of c-Jun N-terminal kinase 1 (JNK1) on XAF1 expression and the putative mechanism. Methods: XAF1 expression in gastrointestinal (GI) cancer cell line AGS and SW1116 was detected by reverse transcription–polymerase chain reaction (PCR), real-time PCR and immunoblotting. The role of JNK1 was assessed by ectopic overexpression with wild-type (JNK1-WT) and dominant-negative (JNK1-DN) JNK1 constructs. The effects of JNK1 activator, interferon (IFN)-
, tumor necrosis factor (TNF)- and phorbol-12-myristate-13-acetate (PMA), or JNK1 inhibitor, SP600125, were evaluated. An XAF1 promoter reporter pLUC107 with WT or mutated interferon regulatory factor 1-binding element (IRF-E) was used to assess JNK1-induced transcription by dual luciferase assay. Result: Ectopic overexpression of JNK1-WT or treatment with IFN-, TNF- and PMA induced whereas SP600125 suppressed intrinsic and induced XAF1 expression. Induction of XAF1 required de novo protein synthesis. Moreover, JNK1 stimulated whereas SP600125 suppressed XAF1 promoter activity. JNK1 stimulated interferon regulatory factor 1 (IRF-1) expression, whereas both IRF-1 small-interfering RNA and site mutation of IRF-E within XAF1 promoter abrogated the effect of JNK1. Conclusion: JNK1 stimulated and mediated the effects of IFN and TNF- on XAF1 expression through transcriptional regulation by induction of IRF-1. The linkage of JNK1, IRF-1 and XAF1 in the same signal pathway may unravel a novel mechanism in regulation of apoptosis and differentiation of GI cancers.
Abbreviations: AP-1, activator protein-1; cDNA, complementary DNA; ERK, extracellular signal-regulated kinase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GI, gastrointestinal; IFN, interferon; IRF-1, interferon regulatory factor 1; IRF-E, interferon regulatory factor 1-binding element; JNK, c-Jun N-terminal kinase; PCR, polymerase chain reaction; PMA, phorbol-12-myristate-13-acetate; RLU, relative luciferase units; siRNA, small-interfering RNA; TNF, tumor necrosis factor; XAF1, X-linked inhibitor of apoptosis protein-associated factor 1; XIAP, X-linked inhibitor of apoptosis protein
Received July 1, 2008; revised November 14, 2008; accepted November 29, 2008.