Abstract: Objective To study the effect of down-regulated AEG-1 expression on proliferation of non-small cell lung cancer A549 cells and their sensitivity to cisplatin. Methods Expression of A549 cells,down-regulated by siRNA,was detected by RT-PCR and immunocytochemistry,respectively.Effect of down-regulated AEG-1 expression in A549 cells was assayed by MTT assay and clonogenic assay,respectively.Sensitivity of A549 cells to cisplatin was measured by MTT assay after exposed to cisplatin at different concentrations for 48h. Results The proliferation of A549 cells was inhibited 48 and 72h after the down-regulation of AEG-1 expression with an inhibition rate of 54.6% and 59.7%,respectively.The cell clone ability decreased.The number of clones was 60.2% lower in AEG-1 expression group than in negative control group.Moreover,down-regulation of AEG-1 expression enhanced the sensitivity of A549 cells to cisplatin.The IC50was 4.8μmol/L and 20.4μmol/L respectively in experimental group and control group. Conclusion Down-regulated AEG-1 expression can significantly inhibit the proliferation of A549 cells and enhance their sensitivity to cisplatin.