Abstract: Objective To explore the antagonizing effect of celecoxib against the cytotoxicity of carboplatin in human
esophageal cancer cells. Methods The cell viability of cisplatin-resistant cell line EC109/CDDP and its parental cell line EC109
exposed to carboplatin alone or carboplatin plus celecoxib was determined by MTT assay. The expression of CTR1, caspase-3
activation and PARP cleavage in the exposed cells were examined by Western blotting. Caspase-3 activity and cell apoptosis
after the exposure were detected with Caspase-3/7 assay and flow cytometry, respectively. The effect of celecoxib on
carboplatin accumulation in the cells was measured using inductively coupled plasma mass spectrometry (ICP-MS). Results
Celecoxib treatment significantly increased the IC50 of carboplatin, suppressed carboplatin-induced caspase-3 and PARP
cleavage and caspase-3 activity in EC109 and EC109/CDDP cells. Celecoxib also inhibited carboplatin-induced apoptosis and
suppressed intracellular carboplatin accumulation in both cell lines. A combined exposure to celecoxib and carboplatin did not
cause significant changes in the protein expression of CTR1. Conclusion Celecoxib antagonizes the cytotoxic effect of
carboplatin and inhibits carboplatin-induced apoptosis in human esophageal cancer cells by reducing intracellular carboplatin
accumulation.