Molecular mechanism of cyclooxygenase-2 inhibitor in inhibition of proliferation of colon cancer cells by modulating Stat5 signal transduction pathway

Abstract

To investigate the role of NS398, a selective cyclooxygenase (COX)-2 inhibitor, in proliferation and apoptosis of colorectal cancer, and to reveal the mechanism of inhibiting colon cancer by NS-398 Independent of COX-2. Human colon cancer cells of the line SW480 were cultured and then divided into 2 groups: experimental group and control group. NS398 of the concentrations of 12.5, 25, 50, 75, 100, and 125 micromol/L was added into the culture fluid of the experimental group. MTT assay was used to observe the proliferation of the cells, flow cytometry was used to test the cell cycle, RT-PCR analysis was performed to examine COX-2 mRNA expression, and Western blotting analysis was performed to detect the expression of Stat5, peroxisome proliferators-activated receptors (PPARs), cyclin D1 and Bcl-x(L). Expression of COX-2 mRNA was not detected in the SW480 colon cancer cells. 72 hours after the addition of NS398 75 micromol/L the proliferative level of the SW480 cells was decreased; the rate of the cells at the G(1) stage increased from 31.2% to 40.6%, and the rate of cells at the S stage decreased from 52.8% to 41.2%. The expression of Stat5, PPARdelta, cyclin D1 and Bcl-x(L) decreased along with the elongation of time of NS398 action. COX-2 inhibitor, such as NS-398 inhibits the colon cancer cell proliferation and induces apoptosis of colon cancer cells with the possible mechanism of inhibiting the proliferation and inducing the apoptosis of colon cancer cells through a pathway independent of COX-2.