摘要Objective::To define the properties of lung cancer cells that resisted conventionally fractionated radiation exposure.Methods::Acquired radioresistant lung cancer cell line A549 was constructed by X-ray irradiation with a clinical conventional fraction dose of 2 Gy daily during 30 fractions. Cell morphology, molecular markers, migration capacity and invasion potential were evaluated by the microscope, Western blot, immunofluorescence, wound healing test and transwell chamber assay, respectively.Results::Radioresistant A549 cells shifted from an epithelial to a mesenchymal morphology, termed as epithelial-mesenchymal transition (EMT), and was accompanied by decreased expressions of epithelial markers ( F = 4.568, P < 0.05) and increased expression of mesenchymal markers ( F = 4.270, P < 0.05), greater migratory and invasive capabilities ( t = 6.386, 5.644, P < 0.05). The expression of TGF-β, and phosphorylated levels of Akt and Smad3 were also enhanced ( F = 6.496, 4.685, 3.370, P < 0.05). Furthermore, the EMT phenotype induced by radiation could be reversed through inhibition of TGF-β, Akt or Smad3, indicating a functional relationship between them. Conclusions::EMT mediates acquired radioresistance of lung cancer cells induced by IR with clinical parameters, and the crosstalk mode of TGF-β/Akt/Smad signaling plays a critical regulatory role in this process.