Effect of nonsteroidal anti-inflammatory drugs on β-catenin protein levels and catenin-related transcription in human colorectal cancer cells

Elevated β-catenin levels in human colorectal cancer (CRC) cells lead to increased trans-activation of ‘protumorigenic’ β-catenin/T-cell factor (TCF) target genes such as cyclin D1. Therefore, possible targets for the anti-CRC activity of nonsteroidal anti-inflammatory drugs (NSAIDs) are β-catenin and catenin-related transcription (CRT). We tested the antiproliferative activity and the effects on levels of β-catenin and cyclin D1 protein, as well as CRT (measured using a synthetic β-catenin/TCF-reporter gene [TOPflash]), of a panel of NSAIDs (indomethacin, diclofenac, sulindac sulphide and sulphone, rofecoxib; range 10–600 μM) on SW480 human CRC cells in vitro. Following NSAID treatment, there was no consistent relationship between reduced cell proliferation, induction of apoptosis and changes in β-catenin protein levels or CRT. All the NSAIDs, except rofecoxib, decreased nuclear β-catenin content and cyclin D1 protein levels in parallel with their antiproliferative activity. However, cyclin D1 downregulation occurred prior to a decrease in total β-catenin protein levels and there was no correlation with changes in CRT, suggesting the existence of CRT-independent effects of NSAIDs on cyclin D1 expression. In summary, NSAIDs have differential effects on β-catenin protein and CRT, which are unlikely to fully explain their effects on cyclin D1 and their antiproliferative activity on human CRC cells in vitro.