OSU-03012, a non-Cox inhibiting celecoxib derivative, induces apoptosis of human esophageal carcinoma cells through a p53/Bax/cytochrome c/caspase-9-dependent pathway.

OSU-03012 is a celecoxib derivative devoid of cyclooxygenase-2 inhibitory activity. It was previously reported to inhibit the growth of some tumor cells through the AKT-signaling pathway. In the current study, we assessed the ability of OSU-03012 to induce apoptosis in human esophageal carcinoma cells and the mechanism by which this occurs. A cell proliferation assay indicated that OSU-03012 inhibited the growth of human esophageal carcinoma cell lines with an IC50 below 2 μmol/l and had the most effective cytotoxicity against Eca-109 cells. Terminal deoxynucleotidyl transferase-mediated nick-end labeling assay and flow cytometry analysis showed that OSU-03012 could induce the apoptosis in Eca-109 cells. After treatment of Eca-109 cells with 2 μmol/l OSU-03012 for 24 h, the apoptosis index increased from 14.07 to 53.72%. OSU-03012 treatment resulted in a 30-40% decrease in the mitochondrial membrane potential and caused cytochrome c release into the cytosol. Further studies with caspase-9-specific and caspase-8-specific inhibitors (z-LEHDfmk and z-IETDfmk, respectively) pointed toward the involvement of the caspase-9 pathway, but not the caspase-8 pathway, in the execution of OSU-03012-induced apoptosis. Immunoblot analysis demonstrated that OSU-03012-induced cellular apoptosis was associated with upregulation of Bax, cleaved caspase-3, and cleaved caspase-9. Ser-15 of p53 was phosphorylated after 24 h of treatment of the cancer cells with OSU-03012. This increase in p53 was associated with the decrease in Bcl-2 and increase in Bax. An inhibitor of p53, pifithrin-α, attenuated the anticancer effects of OSU-03012 and downregulated the expression of Bax and cleaved caspase-9. Altogether, our results show that OSU-03012 could induce apoptosis in human esophageal carcinoma cells through a p53/Bax/cytochrome c/caspase-9-dependent pathway.