Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin have been shown to suppress transcription factor NF-kappaB, which controls the expression of genes such as cyclooxygenase (COX)-2 and cyclin D1, leading to inhibition of proliferation of tumor cells. There is no systematic study as to how these drugs differ in their ability to suppress NF-kappaB activation and NF-kappaB-regulated gene expression or cell proliferation. In the present study, we investigated the effect of almost a dozen different commonly used NSAIDs on tumor necrosis factor (TNF)-induced NF-kappaB activation and NF-kappaB-regulated gene products, and on cell proliferation. Dexamethasone, an anti-inflammatory steroid, was included for comparison with NSAIDs. As indicated by DNA binding, none of the drugs alone activated NF-kappaB. All compounds inhibited TNF-induced NF-kappaB activation, but with highly variable efficacy. The 50% inhibitory concentration required was 5.67, 3.49, 3.03, 1.25, 0.94, 0.60, 0.38, 0.084, 0.043, 0.027, 0.024, and 0.010 mM for aspirin, ibuprofen, sulindac, phenylbutazone, naproxen, indomethacin, diclofenac, resveratrol, curcumin, dexamethasone, celecoxib, and tamoxifen, respectively. All drugs inhibited IkappaBalpha kinase and suppressed IkappaBalpha degradation and NF-kappaB-regulated reporter gene expression. They also suppressed NF-kappaB-regulated COX-2 and cyclin D1 protein expression in a dose-dependent manner. All compounds inhibited the proliferation of tumor cells, with 50% inhibitory concentrations of 6.09, 1.12, 0.65, 0.49, 1.01, 0.19, 0.36, 0.012, 0.016, 0.047, 0.013, and 0.008 mM for aspirin, ibuprofen, sulindac, phenylbutazone, naproxen, indomethacin, diclofenac, resveratrol, curcumin, dexamethasone, celecoxib, and tamoxifen, respectively. Overall these results indicate that aspirin and ibuprofen are least potent, while resveratrol, curcumin, celecoxib, and tamoxifen are the most potent anti-inflammatory and antiproliferative agents of those we studied.