Ornithine decarboxylase (ODC),the first enzyme of polyamine biosynthesis,was found toincrease in cancer cells,especially lung cancer cells.Some chemotherapeutic agents aimed at decreasingODC gene expression showed inhibitory effects on cancer cells,ha this study,we examined the effects ofadenoviral transduced antisense ODC on lung cancer cells.An adenovirus carrying antisense ODC(rAd-ODC/Ex3as) was used to infect lung cancer cell line A-549.The 3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay was used to analyze the effect on cell growth.Expression of ODC and concentrationof polyamines in cells were determined by Western blot analysis and high performance liquid chromatography.Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling was used to analyze cellapoptosis.The expression of ODC in A-549 cells was reduced to 54%,and that of three polyamines wasalso decreased through the rAd-ODC/Ex3as treatment.Consequently,cell growth was substantially inhibitedand terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling showed that rAd-ODC/Ex3ascould lead to cell apoptosis,with apoptosis index of 46%.This study suggests that rAd-ODC/Ex3as has anantitumor effect on the human lung cancer cells. Ornithine decarboxylase (ODC), the first enzyme of polyamine biosynthesis, was found to increase in cancer cells, especially lung cancer cells. Some chemotherapeutic agents aimed at decreasing ODC gene expression showed inhibitory effects on cancer cells, ha this study, we examined the effects of adenoviral transduced antisense ODC on lung cancer cells. An adenovirus carrying antisense ODC (rAd-ODC / Ex3as) was used to infect lung cancer cell line A-549. The 3- (4,5-methylthiazol- diphenyl-tetrazolium bromide assay was used to analyze the effect on cell growth. Expression of ODC and concentration of polyamines in cells were determined by Western blot analysis and high performance liquid chromatography. Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling was used to analyze cellapoptosis.The expression of ODC in A-549 cells was reduced to 54%, and that of three polyamines was decreased as the rAd-ODC / Ex3as treatment. mediated, cell growth was substantially inhi bitedand terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling showed that rAd-ODC / Ex3ascould lead to cell apoptosis, with apoptosis index of 46%. This research suggests that rAd-ODC / Ex3as has anantitumor effect on the human lung cancer cells .