ObjectiveTo investigate the inhibitory effects of antisense oligodeoxynucleotide(ASODN) of signal transducer and activator of transcription 3 (STAT3) on development and growth of transplanted lung A549 cell adenocarcinoma in nude mice. MethodsThe inhibitory effects of STAT3 ASODN on A549 cell growth was evaluated by CCK8 assay. STAT3 ASODNtreated A549 cells were implanted subcutaneously into nude mice; the tumor growth was observed and the tumorforming rate was calculated. After subcutaneous implantation of the untreated A549 cells, the tumorbearing mice were randomized into 3 groups: control group, STAT3 ASODN group, and nonsense oligodeoxynucleotide (NSODN) group, with normal saline, STAT3 ASODN, and STAT3 NSODN injected intatumorally (15 mg/kg daily for 3 weeks). The tumor volumes were measured every other day and the tumor weights were determined. The protein expressions of STAT3 and pSTAT3 in xenografts were examined by Western blotting analysis. ResultsSTAT3 ASODN significantly inhibited the growth of A549 cells compared with STAT3 NSODN group (P<0.05). The tumor formation ability of A549 cells treated with STAT3 ASODN was significantly decreased (with the tumor inhibitory rate being 75.8%). Moreover, the growth of transplanted tumor was also significantly inhibited in STAT3 ASODN group as compared with those in NSODN group and control group (P<0.05) . The tumor weights were significantly reduced in STAT3 ASODN group than in STAT3 NSODN group and control group (with the tumor inhibitory rate being 51.1%). The expression of STAT3 protein and pSTAT3 was also downregulated in STAT3 ASODN group. ConclusionSTAT3 ASODN can suppress the tumorigenic ability of A549 cells and inhibit the growth of transplanted tumor in nude mice.