RESUMO
<p><b>OBJECTIVE</b>To investigate the effect of celecoxib in enhancing the chemosensitivity of oral cancer cells and the correlation of this effect with cell cycle arrest.</p><p><b>METHODS</b>KB/VCR cell line was treated with celecoxib (10, 20, 40, and 80 µmol/L) and/or VCR (0.375, 0.75, 1.5, and 3 µmol/L), and the growth inhibition rates of KB/VCR cells were assessed with MTT assay. Flow cytometry was employed to analyze the distribution of cell cycle. Western blotting was performed to detect the expression of P-glycoprotein (P-gp) and the cell cycle related proteins Cyclin D1 and p21(WAF1/CIP1).</p><p><b>RESULTS</b>Low concentrations of celecoxib (<20 µmol/L) produced no obvious effect on the proliferation of the cells. But at 10 µmol/L, celecoxib significantly enhanced the toxicity of VCR in a time-dependent manner, and the combined treatments for 24, 48, and 72 h caused growth inhibition rates of (37.53∓2.05)%, (46.67∓3.17)% and (54.02∓1.53)%, respectively, significantly higher than those following treatments with celecoxib or VCR alone (P<0.01). Compared with the cells treated with VCR alone , the cells with combined treatments showed a significantly increased cell percentage in G0/G1 phase [(56.08∓0.46)%] with decrease percentages in S phase [(22.83∓0.20)%] and G2/M phase [(21.09%∓0.66)%]. The combined treatment also significantly down-regulated cyclin D1, up-regulated p21(WAF1/CIP1), and reduced P-gp expressions in the cells.</p><p><b>CONCLUSIONS</b>Celecoxib enhances the chemosensitivity of KB/VCR cells by down-regulating P-gp expression, which is partially mediated by modification of cyclin D1 and p21(WAF1/CIP1) to result in cell cycle arrest.</p>