Objective:To investigate the effect of Trichostatin A on the growth of human anaplastic thyroid carcinoma cell line in vitro. Methods:Human anaplastic thyroid carcinoma DRO cell line was treated with Trichostatin A of different concentrations and time. The antiproliferative effect was measured by methyl thiazolyl tetrazolium(MTT). Flow cytometry was used to examine apoptosis and cell cycle when TSA was 1.0 -滋mol/L in concentration and the exposure to DRO was 24 h,48 h and 72 h,respectively. The leves of hTERT-mRNA,p21-mRNA in cells were detected by RT-PCR,with TSA for 48 h. Results:After being treated with 0.1 -滋mol/L,0.2 -滋mol/L,0.5 -滋mol/L,1.0 -滋mol/L,and 1.5 -滋mol/L TSA,the prolifergation of DRO cells was significantly inhibited. IPCM showed that there were obvious morphologic changes after TSA treatment. Changes in the cells cycle occurred 48 h after treatment. hTERT expression was down-regulated after treatment with TSA. Conclusion:TSA significantly inhibited growth of the DRO cells and mechanism may be related to a down-regulation in hTERT expression.