(‐)‐Epigallocatechin‐3‐gallate induced apoptosis by dissociation of c‐FLIP/Ku70 complex in gastric cancer cells

Anti‐cancer properties of (‐)‐epigallocatechin‐3‐gallate (EGCG) are mediated via apoptosis induction, as well as inhibition of cell proliferation and histone deacetylase. Accumulation of stabilized cellular FLICE‐inhibitory protein (c‐FLIP)/Ku70 complex in the cytoplasm inhibits apoptosis through interruption of extrinsic apoptosis pathway. In this study, we evaluated the anti‐cancer role of EGCG in gastric cancer (GC) cells through dissociation of c‐FLIP/Ku70 complex. MKN‐45 cells were treated with EGCG or its antagonist MG149 for 24 h. Apoptosis was evaluated by flow cytometry and quantitative RT‐PCR. Protein expression of c‐FLIP and Ku70 was analysed using western blot and immunofluorescence. Dissociation of c‐FLIP/Ku70 complex as well as Ku70 translocation were studied by sub‐cellular fractionation and co‐immunoprecipitation. EGCG induced apoptosis in MKN‐45 cells with substantial up‐regulation of P53 and P21, down‐regulation of c‐Myc and Cyclin D1 as well as cell cycle arrest in S and G2/M check points. Moreover, EGCG treatment suppressed the expression of c‐FLIP and Ku70, decreased their interaction while increasing the Ku70 nuclear content. By dissociating the c‐FLIP/Ku70 complex, EGCG could be an alternative component to the conventional HDAC inhibitors in order to induce apoptosis in GC cells. Thus, its combination with other cancer therapy protocols could result in a better therapeutic outcome.