RESUMO
BACKGROUND: Cyclooxygenase (COX)-2 is up-regulated in most colorectal cancers. Chronic use of non-steroidal anti-inflammatory drugs, which target cyclooxygenases, have been shown to reduce the risk of these cancers. However, the mechanisms underlying this protective effect remain unclear. AIMS: The aim of our study was to characterize the effects of two COX-2 selective inhibitors, NS-398 and nimesulide, on colorectal cancer cell proliferation, and to describe the molecular mechanisms involved. MATERIALS AND METHODS: HT-29 and SW-1116 cell lines were cultured with either NS-398 or nimesulide. Cell proliferation was assessed by staining DNA with crystal violet. Cell cycle repartition and apoptosis were analysed by flow cytometry. The expression of COX-1 and COX-2. and of two cyclin dependent kinase inhibitors, p21Cip1 and p27Kip1, was analysed by Western blotting and RT-PCR. RESULTS: Both drugs dose-dependently inhibited cell proliferation and induced G1 cell cycle blockade. HT-29 cells were more sensitive to both drugs than SW-1116 cells. p21Cip1 and p27Kip1 were induced on both cell lines. Concomitant induction of p21Cip1 mRNA indicates transcriptional modulation, whereas induction of p27Kip1 only at the protein level suggests post-translational modulation. CONCLUSION: NS-398 and nimesulide inhibit colorectal cell proliferation through induction of p21Cip1 and p27Kip1.
