Carcinogenesis Advance Access originally published online on November 28, 2006
Carcinogenesis 2007 28(5):968-976; doi:10.1093/carcin/bgl220
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Aspirin activates the NF-
B signalling pathway and induces apoptosis in intestinal neoplasia in two in vivo models of human colorectal cancer
Division of Oncology, School of Clinical and Molecular Medicine, University of Edinburgh, Colon Cancer Genetics Group, MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK
1 Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3US, UK
2 Beatson Institute for Cancer Research, Garscube Estate, Glasgow, UK G61 1BD
3 Pharmacology and Drug Development Group, Cancer Research UK Centre, University of Edinburgh, Edinburgh EH4 2XR, UK
* To whom correspondence should be addressed. Tel: +44 131 467 8440; Fax: +44 131 343 2620; Email: lesley.stark{at}hgu.mrc.ac.uk
Substantial evidence indicates that aspirin has antitumour activity against large bowel cancer and modulation of the NF-kappaB (NF-
B) signalling pathway has been identified as a key mechanism in this effect. However, studies examining how aspirin affects the NF-B pathway to promote apoptosis have been restricted to in vitro analysis in tissue culture systems and have produced contrasting results. Here, we employed two animal models of human colorectal cancer to determine aspirin effects on the NF-B pathway in colorectal neoplasia in vivo, and the relationship of such effects to the induction of apoptosis. We demonstrate that aspirin induces phosphorylation and degradation of cytoplasmic IB
in xenografted HT-29 tumours and in adenomas from APCMin+/– mice. Furthermore, we show that this response occurs in a time-dependent manner and is paralleled by nuclear translocation of p65 and caspase activation. Using high performance liquid chromatography analysis, we demonstrate that >0.5 mM salicylate levels are achievable in xenografted tumours after low-dose aspirin (40 mg/kg) treatment and that these levels, which are pharmacologically relevant to humans, are sufficient to stimulate an NF-B and apoptotic response. We demonstrate that activation of the NF-B pathway is associated with increased apoptosis in neoplastic epithelial cells, but found that aspirin has a minimal effect on nuclear p65 and apoptosis in normal intestinal mucosa from APCMin+/– mice. These in vivo findings further establish that aspirin induces activation of the NF-B pathway in neoplastic epithelial cells and provide further support that this effect is important for the antitumour activity of the agent. These data have considerable relevance to cancer prevention and therapy.
Abbreviations: NF-B, NF-kappaB; NSAIDs, non-steroidal anti-inflammatory drugs; IB, I-kappaB; WT, wild-type; SR, super-repressor
Received January 16, 2006; revised October 6, 2006; accepted November 3, 2006.