Abstract Stat3(signal transducer and activator of transcription 3) gene was amplified from POTB7 plasmid which contained human stat3 gene cDNA fragment, then inserted into pEGFP-C1 vector to construct recombinant plasmid .The recombinant plasmid was transfected into bovine mammary epithelial(BME) cells mediated by LipofectaminTM 2000.The positive cell clones were obtained after selected by G418，The BME cells transfected with stat3cDNA were determined by RT- PCR, Flow cytometry was used to analyze the cell cycles 、multiplication capacity and DNA content. The results indicated that 24h after exposure to the recombinant plasmid the transfection rate of the BME cells was 16%,The strong expression of stat3 in transfected BME cells was confirmed at mRNA levels. After introduction of the recombinant plasmid into BME cells, the capability of proliferation was obviously enhanced and the DNA content was changed, the cell proliferation lifespan was elongated to 13 population doublings to control. Our research indicated that the cell proliferation life-span was elongated invitro with introduction of the recombinant plasmid into BME cells.
