Abstract: Objective To explore the effect of tumor cell exosome profilin-1 (PFN1) on the proliferation and migration of gastric cancer cells and related mechanisms.Methods Real-time fluorescence quantitative PCR and Western blot were used to detect the mRNA and protein expression of PFN1 in normal gastric and gastric cancer cells. Then, CCK8 assay, cell cloning assay, scratch assay and Transwell assay were used to evaluate the effect of PFN1 on the viability, proliferation, migration and invasion of gastric cancer cells. The effect of PFN1 on the apoptosis of gastric cancer cells was detected by flow cytometry.Results The expression of PFN1 abnormally increased in gastric cancer tissues and cells (P<0.001). Over-expression of PFN1 resulted in increases in the viability, proliferation, migration and invasion of gastric cancer cells, while reducing the apoptotic rate in gastric cancer cells. Further studies indicated that PFN1 in the exosomes of tumor cells promoted the M2 polarization of macrophages, and exosomes secreted by gastric cancer cells overexpressing PFN1 stimulated the proliferation, migration and invasion of gastric cancer cells.Conclusions Over-expression of PFN1 can promote the proliferation, migration and invasion of gastric cancer cells and reduce the rate of apoptosis. PFN1 in the exosomes of gastric cancer cells can further promote the pathogenesis of gastric cancer by stimulating M2 polarization in macrophages.