Abstract: Objective To investig ate the effect of trichostatin A(TSA)on cell proliferation and cell cycle progression of nasopharyngeal carcinoma line CNE3,and to explore its potential mechanism sinvo lved.Methods CNE3 cells in logarithmic growth phase were incubated with TSA at different concen trations for 24 or 48 hours,respectively.The proliferation of CNE3 cells was measured with methyl thiazolyl tetrazolium(MTT)assay.The effect of TSA on cell cycle and apoptosis was detected by flowcy tometry(FCM).The expression of cyclin dependent kinase interacting prote in 1(CIP1,p21)was determined with RT-PCR.Results A fter 100-500nmol/L TSA admin istration,CNE3 proliferation inhibition ratioin creased significantly from 17.74% to 44.33% in concentration dependent manner(P<0.05).CNE3 cells showed DNA synthesis phase,second gap/mitosis phase/(S,G₂/Mphase)blockage 24.48 hours after the treamtent of TSA,and the apoptosis ratio increased.The apoptosis rate at different concentrations of TSA(400 and 500nM)were 14.67±0.21,18.73±1.80 in 24hr,and 16.3±0.96,39.17±1.27 in 48hr(P<0.05).The expression level of p21 was increased in dose dependent manner after TSA trea mtent.Conclusion TSA inhibits the proliferation of CNE3 cells and blocks the CNE3 cell cycle progression in S and G₂/Mphase.Itsmechanism may be related with the abnormal expression of p21.