BACKGROUND Lung cancer is the leading cancer of malignant tumor in China.It is the direction that poeple make efforts to seek gene therapy of lung cancer. The aim of this study is to explore the effects of transfected growth arrest-specific homeobox gene (Gax gene) on the proliferation and expressions of c-fos and c-jun mRNA in A549 cells. METHODS A549 cells were transfected with Gax gene by adenovirus. Expressions of Gax mRNA and protein were detected by RT-PCR and immunocytochemistry. The expressions of c-fos and c-jun mRNA were evaluated by RT-PCR. The proliferation inhibition effect of Gax transfection on A549 cells was evaluated by MTT assay. RESULTS Only in the A549 cells transfected with Gax gene the Gax expression was confirmed by RT-PCR and immunocytochemistry. Compared with that in the control group, c-fos and c-jun mRNA level decreased significantly in Gax-transfected A549 cells (t=7.755, P < 0.01; t= 5.938 , P < 0.01). MTT assay showed that the proliferation inhibition rates of A549 cells transfected by Ad-Gax for 24h, 48h and 72h were (47.35±5.36)%, (54.96±1.78)%, and (65.39±5.11)% respectively. And these proliferation inhibition rates were significantly higher than those in the control group (Chi-Square=7.152, 9.431 and 12.847, P < 0.01). CONCLUSIONS Gax gene can inhibit the proliferation of A549 cells. Its molecular mechanism may be through down-regulating the expressions of c-fos and c-jun.