Increased NF-κB DNA binding but not transcriptional activity during apoptosis induced by the COX-2-selective inhibitor NS-398 in colorectal carcinoma cells

Abstract

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit colorectal neoplasia, an effect that is associated with their ability to induce apoptosis. Although NSAIDs have been reported to inhibit NF-kB, more recent studies show activation of NF-kB by NSAIDs. NF-kB commonly shows antiapoptotic activity and is implicated in the therapeutic resistance of cancer cells. The effects of highly COX-2-selective NSAIDs such as NS-398 on NF-kB in colorectal tumour cells have not been reported. Therefore, we addressed whether NF-kB has a role in NS-398-induced apoptosis of colorectal cancer cells. Treatment of HT-29 colorectal carcinoma cells with doses of NS-398 (50 -75 mM) known to induce apoptosis had no effect on NF-kB for up to 48 h. However after 72 and 96 h NF-kB DNAbinding activity was increased by NS-398, in parallel with apoptosis induction. NS-398-treated HT-29 cells showed increased p50 homodimer binding and an induction of p50/p65 heterodimers, as demonstrated by supershift assay. However, although NS-398 increased NF-kB DNA binding it did not increase NF-kB-dependent reporter activity and inhibition of NF-kB DNA binding did not enhance NS-398-induced apoptosis. This indicates that NF-kB activated by NS-398 is transcriptionally inactive and is an encouraging result for the use of COX-2-selective NSAIDs not only in chemoprevention but also as novel therapies for colon cancer.

Differential induction and activation of NF‐κB transcription complexes in radiation‐induced chromosomally unstable cell lines

“…The discrepancy between the induction of DNA binding and the lack of commensurate transcriptional activation has been described previously [Smartt et al, 2003]. Even after successful translocation of NF-kB complexes to the nucleus, other events such as p65 subunit phosphorylation are necessary to induce transcription [Zhong et al, 1998].…”

Insulin-like growth factor binding protein 3 (IGFBP-3) potentiates TRAIL-induced apoptosis of human colorectal carcinoma cells through inhibition of NF-κB

“…For example, inhibition of NF-kB has been shown to enhance TNFa-induced cytotoxicity in a number of different cell types including intestinal epithelial cells. [26][27][28] Interestingly, IGFBP-3 has also been shown to enhance TNFa-induced cytotoxicity in breast cancer cells. 29 Therefore to determine whether IGFBP-3 potentially enhances TRAILinduced apoptosis through inhibiting the opposing actions of the NF-kB pathway, we used a reporter assay to determine NF-kB activation in the presence of the IGFBP-3 synthetic protein.…”

Reduced tumour progression and angiogenesis in 1,2-dimethylhydrazine mice treated with NS-398 is associated with down-regulation of cyclooxygenase-2 and decreased beta-catenin nuclear localisation

“…The prevalence of proliferating cells in adenomas was signifi cantly reduced in mice treated with NS-398 (mean Ϯ SE, 25.51 Ϯ 1.74 vs 16.88 Ϯ 1.26 vs 11.63 Ϯ 1.01, untreated, high and low dose respectively, p Ͻ 0.001, Kruskal-Wallis test). COX-2 inhibitors have been shown to induce apoptosis both in vivo and in vitro Smartt 2003). In our study, NS 398 treatment resulted in a signifi cant increase in apoptosis in adenomas (mean Ϯ SE: 1.60 Ϯ 0.24 vs 5.16 Ϯ 0.49 vs 6.94 Ϯ 0.58 mean percentages in untreated, low dose, and high dose groups respectively, p Ͻ 0.001, Chi-square test).…”