Abstract： Objective To detect the expression of translationally controlled tumor protein (TCTP) in squamous cell carcinoma (SCC) tissue and cell lines A431 and SCL-1,and to evaluate the effect of TCTP on apoptosis in and proliferation of SCC cells.Methods An immunohistochemical method was used to measure the expression of TCTP in tissue specimens from 65 patients with SCC.Western blot was performed to detect the expression of TCTP in A431 and SCL-1 cells.Three small interference RNAs (siRNAs) targeting the TPT1 gene were designed,synthesized,and transfected into A431 cells.Then,reverse transcription (RT)-PCR and Western blot were conducted to measure the expression of TPT1 mRNA and TCTP,respectively,methyl thiazolyl tetrazolium (MTT) assay and flow cytometry were carried out to detect cell proliferation and apoptosis,respectively.Results TCTP was overexpressed in SCC tissue specimens,and the expression level was positively correlated with the histologic grading of SCC (P ＜ 0.05).Western blot showed that TCTP was expressed in both A431 and SCL-1 cells,and the expression was relatively high in A431 cells.The transfection efficiency of siRNAs varied from 90％ to 95％.A decrease in the expression of TPT1 mRNA and TCTP was induced by the siRNAs in A375 cells (all P ＜ 0.05).Conclusion The downregulation of TCTP expression may increase the apoptosis in and suppress the proliferation of A431 cells.