OBJECTIVE Over-expression of transforming growth factorβ1(TGF-β1)has been observed in many advanced cancers. The present study was aimed at developing potential antisense oligonucleotides(ASONs)to repress TGF-β1 expression in rhabdomyosarcoma(RMS)RD cells,and to examine their effect on tumorigenicity of RD cells in vivo. METHODS ASONs targeting the region surrounding the start codon of TGF-β1 were synthesized and transferred into cells in the form of complexes with Lipofectamine 2000.The TGF-β1 protein was determined by immunofluorescence and ELISA. The cell viability and cell cycle were examined by MTT and flow cytometry.The RD cells,with or without TGF-β1ASON,in 50μ1 of serum-free EMDM medium were injected subcutaneously into the right flank of nude mice.The tumors were then measured and weighed. RESULTS The ASON sequence targeting the first start site at bases 841-855 of the human TGF-β1 gene had the greatest effect on attenuating the expression of TGF-β1(P<0.05).The ASONs induced a decrease in OD values after 6 d(P<0.05).Analvsis of the cell cycle revealed that the ASON induced a significant decrease in cells in the S phase and an increase in cells in the G1 phase(P<0.05).In the nude mice model,the mean tumor volume,after 2 weeks of treatment with Lipofectamine or ASON, decreased to 88.5% or 55% respectively,compared to the control tumor size,resulting in a significant difference(P<0.01). CONCLUSION The sequence of the ASON,which targeted the start condon at the bases 841-855 of the human TGF-β1 gene,was demonstrated to be a useful agent for studying the regulation of TGF-β1 over-expression in RD cells,and has important therapeutic potential for suppressing the tumorigenicity of human RMS in vivo. OBJECTIVE Over-expression of transforming growth factor β1 (TGF-β1) has been observed in many advanced cancers. The present study was aimed at developing potential antisense oligonucleotides (ASONs) to repress TGF-β1 expression in rhabdomyosarcoma (RMS) RD cells, and to METHODS Their effects on tumorigenicity of RD cells in vivo. METHODS ASONs targeting the region surrounding the start codon of TGF-β1 were synthesized and transferred into cells in the form of complexes with Lipofectamine 2000. The TGF-β1 protein was determined by immunofluorescence and ELISA . The cell viability and cell cycle were examined by MTT and flow cytometry. The RD cells, with or without TGF-β1ASON, in 50 μl of serum-free EMDM medium were injected subcutaneously into the right flank of nude mice. The tumors were then measured RESULTS The ASON sequence targeting the first start site at bases 841-855 of the human TGF-β1 gene had the greatest effect on attenuating the expression of TGF-β1 (P <0.05). The ASONs induced a decrease in OD values ​​after 6 d (P <0.05) .nalvsis of the cell cycle revealed that the ASON induced a significant decrease in cells in the S phase and an increase in cells in the G1 phase (P <0.05) .In the nude mice model, the mean tumor volume, after 2 weeks of treatment with Lipofectamine or ASON, decreased to 88.5% or 55% respectively, compared to the control tumor size, resulting in a significant difference (P <0.01). CONCLUSION The sequence of the ASON, which targeted the start of condon at the bases 841-855 of the human TGF-β1 gene, was demonstrated to be a useful agent for studying the regulation of TGF-β1 over-expression in RD cells, and has important therapeutic potential for suppressing the tumorigenicity of human RMS in vivo.