Background: Recent studies have shown that cyclooxygenase-2 (COX-2) inhibitors may participate in the proliferation of cancer cells. Because the cadherin-catenin complex is not only a key component of the adherens junction but also has been suggested to regulate cell proliferation, modulation of these molecules may be a mechanism by which COX-2 activity affects cell proliferation. In this study, we evaluated the effect of a COX-2 inhibitor on the proliferation and expression of E-cadherin-complexes in gastrointestinal cancer cell lines.
Methods: The gastrointestinal cancer cell lines Caco2, HT29, and MKN45 were grown for 24 h in the presence and absence of a selective COX-2 inhibitor, etodolac (10(-5), 10(-4), and 10(-3) M). Cell proliferation was assessed by (3)H-thymidine incorporation, and the expression of E-cadherin and catenins was assessed by Western blotting, Northern blotting, and immunofluorescence.
Results: Etodolac induced a significant reduction in cell proliferation in Caco2 and MKN45 cells. E-cadherin expression was upregulated after stimulation with etodolac in Caco2 cells, whereas the expression of alpha-, beta-, gamma- and p120-catenins was not modified. The expression of E-cadherin mRNA was also upregulated in Caco2 cells, and was upregulated also in MKN45 cells, which did not express normal E-cadherin protein by the use of a mouse monoclonal antibody against human E-cadherin, HECD-1 antibody. Immunofluorescence revealed that the increased E-cadherin was localized at the cytoplasmic membrane.
Conclusions: The inhibition of cell growth by etodolac in Caco-2 cells was associated with a dose-dependent upregulation and intense cytoplasmic localization of E-cadherin. No quantitative change in catenin expression was found in this phenomenon. These findings suggest that the COX-2 inhibitor affects the transcription of E-cadherin, or that there may be some homeostatic link between the cell cycle and E-cadherin transcription.