Abstract： Objective To investigate the effects of lung adenocarcinoma A549 cells derived exosome on proliferation,migration and apoptosis of tumor cells and its mechanism.Methods Exosomes were extracted by uhracentrifugationfrom the culture supernatant ofadenocarcinoma A549 cells.The morphology of exosomes was observed by transmission electron microscopy.Different doses of exosomes were co-cultured with adenocarcinoma A549 cells.The proliferation of A549 cells was detected by MTT assay after co-cuhivation.Flow cytometry was performed to detect the cellapoptosis.Transwell and scratch assay were performed to detect cell invasion and migration.Western blotting was performed to detect cell proliferation,apoptosis and expression of migration-related proteins.Results The shape and size of lung adenocarcinoma A549 cells derived exosome were uniform,with diameter of 30 nm to 10 nm.MTT assay showed that growth rate of lung adenocarcinoma A549 cells was increased with the prolongation of exosomes action time in a dose-effect manner.Flow cytometry showed that apoptotic rates of lung adenocarcinoma A549 cells in middle dose group (40 μg/ml) and high dose group (80μg/ml) were significantly lower than those in control group (all P＜0.05).Transwell and scratch test showed thatthecell invasive rate and migration rate of lung adenocarcinoma A549 cells in middle dose group and high dose group were significantly higher than those in control group (all P＜0.05).Western blot showed that theexpression levels of N-cadherin,Bcl-2,p-Src and p-Akt proteins in middle dose group and high dose group were significantly higher than those in control group (all P＜0.05),while theexpression levels of Caspase-3,E-cadherin,Bax,c-Cbl and Cbl-b proteinsin these two groups were significantly lower than those in control group (all P＜0.05).Conclusion The lung adenocarcinoma A549 cells derived exosome may promote proliferation and migration,and inhibit apoptosisof tumor cells,which may be associated with regulatedexpression of the proteinsrelated to proliferation,migration and apoptosis.