摘要Background Epithelial-mesenchymal transition is a cellular process characterized by the loss of cell adhesion,inhibition of E-cadherin expression,and increased cell mobility.Cells without Napsin A are susceptible to transition.Further studies are required to investigate whether this transition can be reversed by restoration of Napsin A.Methods A Napsin A expression vector PLJM1-Napsin A plasmid was constructed and then transfected into the epithelial cell line A549 by lentivirus transfection to obtain A549-PLJM1-Napsin A cell line.Cell proliferation was assayed by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide and cell cycle was measured by flow cytometry.The E-cadherin,type I collagen,and focal adhesion kinase mRNA level was detected by reverse transcription-polymerase chain reaction.The Napsin A,E-cadherin,type I collagen,and focal adhesion kinase protein level in A549 cells was detected by Westen blotting.Results Transforming growth factor-β1 induced epithelial-mesenchymal transition in A549 cells,as demonstrated by significant reduction of E-cadherin mRNA and protein levels (P ＜0.01) as well as up-regulation of type I collagen (P ＜0.01 ).Transfection of Napsin A in A549 cells can partially block the transforming growth factor-β1-regulated expression of E-cadherin and type I collagen (P ＜0.01).In addition,transforming growth factor-β1-induced cell proliferation was inhibited by Napsin A (P ＜0.01).Further study demonstrated that Napsin A caused Go/G1 arrest and inhibited the expression of focal adhesion kinase (P ＜0.01),a key protein in the integrin signaling pathway,in the in vitro epithelial-mesenchymal transition model.Conclusions Sustained Napsin A expression in A549 cells can inhibit the transforming growth factor-β1-induced epithelial-mesenchymal transition.This may be due to the Napsin A-mediated inhibition of focal adhesion kinase expression and integrin signaling pathway.