title: Induction of spermidine/spermine N1-acetyltransferase (SSAT) by aspirin in Caco-2 colon cancer cells.
abstract: Epidemiological, experimental and clinical results suggest that aspirin and other NSAIDs (non-steroidal anti-inflammatory drugs) inhibit the development of colon cancer. It has been shown that the NSAID sulindac induces apoptosis and suppresses carcinogenesis, in part, by a mechanism leading to the transcriptional activation of the gene encoding SSAT (spermidine/spermine N1-acetyltransferase), a rate-limiting enzyme in polyamine catabolism. In the present study, we show that a variety of NSAIDs, including aspirin, sulindac, ibuprofen and indomethacin, can induce SSAT gene expression in Caco-2 cells. Aspirin, at physiological concentrations, can induce SSAT mRNA via transcriptional initiation mechanisms. This induction leads to increased SSAT protein levels and enzyme activity. Promoter deletion analysis of the 5' SSAT promoter-flanking region led to the identification of two NF-kappaB (nuclear factor kappaB) response elements. Electrophoretic mobility-shift assays showed binding of NF-kappaB complexes at these sequences after aspirin treatment. Aspirin treatment led to the activation of NF-kappaB signalling and increased binding at these NF-kappaB sites in the SSAT promoter, hence providing a potential mechanism for the induction of SSAT by aspirin in these cells. Aspirin-induced SSAT ultimately leads to a decrease in cellular polyamine content, which has been associated with decreased carcinogenesis. These results suggest that activation of SSAT by aspirin and different NSAIDs may be a common property of NSAIDs that plays an important role in their chemopreventive actions in colorectal cancer.
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA. nbabbar1@jhmi.edu
authors.forename: Naveen
authors.initials: N
authors.lastname: Babbar
authors.forename: Eugene W
authors.initials: EW
authors.lastname: Gerner
authors.forename: Robert A
authors.initials: RA
authors.lastname: Casero
mesh_terms: D000123:Acetyltransferases / Q000096:biosynthesis* / Q000235:genetics*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology* / Q000627:therapeutic use; D018938:Caco-2 Cells; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology / Q000517:prevention & control; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020218:Response Elements / Q000235:genetics; D000099228:Diamine N-Acetyltransferase
chemical_list: D000123:Acetyltransferases; D000894:Anti-Inflammatory Agents, Non-Steroidal; D001241:Aspirin; D016328:NF-kappa B; D047492:Peroxisome Proliferator-Activated Receptors; D000099228:Diamine N-Acetyltransferase