Effects of EGCG on regulating NF-?B/p65 induced by TNF-? and on inducing apoptosis / 中国癌症杂志

ABSTRACT

Background and purpose:Anticancer mechanism of epigallocatechin-3-gallate(EGCG)remains unclear.This study was to investigate the effects of EGCG on induction of apoptosis by TNF-? through translocation of NF-?B/p65 into SGC-7901 cellular nucleus.Methods:Hoechst staining method was used to display the apoptosis form of SGC-7901 induced by EGCG.The disposition of NF-?B/p65 was detected by Western blot.The effect of EGCG on induction of apoptosis was analyzed by flow cytometry(FCM)and DNA agarose gel electrophoresis.Results:Hoechst staining method showed that EGCG could significantly induce apoptosis of SGC-7901.After being exposed to EGCG,the cell nucleus changed to shiver and pallor.After being treated by 10 ng/ml TNF-? at various times(30,60,90 and 120 min),an inductor of regulating NF-?B/p65,the expression of NF-?B/p65 in the cell nucleus increased obviously.It displayed a platform after being treated for 60 minutes.Incubation with 60 ?g/ml EGCG at various times(0,12,24,36,48 h)before TNF-?(10 ng/ml,60 min)treatment,the expression of NF-?B/p65 in the cell nucleus decreased in a time-depended manner that reached plateau after treated for 24 h.Being treated with EGCG for 24 h at various concentrations(40,60,80,100 ?g/ml)before the TNF-?(10 ng/ml,60 min),the expression of NF-?B/p65 in the cell nucleus decreased in a dose-depended manner.Analysis by flow cytometry showed that the percentages of apoptosis was 3.7% in cells exposed to 10 ng/ml TNF-?,60 min,apoptotic percentage was 16.6% after cells exposed to 60 ?g/ml EGCG(24 h)before TNF-?(10 ng/ml,60 min).It could reach to 21.4% after cells were exposed to PDTC(100 ?mol/L,30 min,before TNF-?),a suppressor of NF-?B.In DNA agarose gel electrophoresis,"Ladder"bands occurred after the treatment with EGCG(60 ?g/ml,24 h)before TNF-?(10 ng/ml,60 min).The "Ladder"bands also occurred after incubation with PDTC(100 ?mol/L,30 min)before TNF-?(10 ng/ml,60 min).Conclusions:EGCG could inhibit the translocation of NF-?B/p65's into the cell nucleus induced by TNF-?,and could significantly induce apoptosis through this pathway.