ALBERT

Description: Background: The non-steroidal anti-inflammatory drug (NSAID) sulindac has shown efficacy in preventing colorectal cancer. This potent anti-tumorigenic effect is mediated through multiple cellular pathways but is also accompanied by gastrointestinal side effects, such as colon inflammation. We have recently shown that sulindac can cause up-regulation of pro-inflammatory factors in the mouse colon mucosa. The aim of this study was to determine the signaling pathways that mediate the transcriptional activation of pro-inflammatory cytokines in colon cancer epithelial cells treated with sulindac sulfide. Results: We found that sulindac sulfide increased NF-kappaB signaling in HCT15, HCT116, SW480 and SW620 cells, although the level of induction varied between cell lines. The drug caused a decrease in IkappaBalpha levels and an increase of p65(RelA) binding to the NF-kappaB DNA response element. It induced expression of IL-8, ICAM1 and A20, which was inhibited by the NF-kappaB inhibitor PDTC. Sulindac sulfide also induced activation of the AP-1 transcription factor, which co-operated with NF-kappaB in up-regulating IL-8. Up-regulation of NF-kappaB genes was most prominent in conditions where only a subset of cells was undergoing apoptosis. In TNFalpha stimulated conditions the drug treatment inhibited phosphorylation on IkappaBalpha (Ser 32) which is consistent with previous studies and indicates that sulindac sulfide can inhibit TNFalpha-induced NF-kappaB activation. Sulindac-induced upregulation of NF-kappaB target genes occurred early in the proximal colon of mice given a diet containing sulindac for one week. Conclusions: This study shows for the first time that sulindac sulfide can induce pro-inflammatory NF-kappaB and AP-1 signaling as well as apoptosis in the same experimental conditions. Therefore, these results provide insights into the effect of sulindac on pro-inflammatory signaling pathways, as well as contribute to a better understanding of the mechanism of sulindac-induced gastrointestinal side effects.