Objective       To deternine the role and mechanism of Wnt5a regulating the proliferation and epithelial mesenchymal transition (EMT) in lung cancer A549 spheres.        Methods       A549 spheres were cultured in serum-free medium for 2 weeks. CD133

+

CD44

+

rate of those cells was detected by FACS. Four experimental groups including a control group

a Wnt5a group

a p38 group and a Wnt5a+ p38 group were designed. The protein expr

ession of Wnt5a

p-p38

β-catenin

vimentin and E-cadherin among the 4 groups was detected by Western blotting. The cell inhibitory rate and tumorigenicity were detected after Wnt5a shRNA lentivirus transfection of A549 spheres.        Results       CD133

+

CD44

+

rate was 60.5% in A549 spheres and 1.65% in A549 cells. Wnt5a protein expression was significantly lower in the Wnt5a and Wnt5a+ p38 groups than in the control group (P0.05). Compared to the control group

the protein expression of p-p38

β-catenin and vimentin was obviously lower but that of E-cadherin was higher in the Wnt5a

p38 and Wnt5a+ p38 groups (P0.05). The cell inhibitory rate was significantly higher and tumor size in node mice was remarkably smaller at 12

24 and 48 h after Wnt5a shRNA lentivirus transfection (P0.05).        Conclusion       Wnt5a expression down-regulation inhibits the proliferation and EMT of A549 spheres

and Wnt5a might be a novel target for treatment of non-small-cell lung cancer.