Objective:To investigate the effect and mechanism of esophageal squamous cell carcinoma exosomal miR-181b-5p to the polarization of M2 macrophages.Methods:Extracted and identified exosomes from esophageal squamous cell carcinoma,and detected the expression of miR-181b-5p in esophageal squamous cell carcinoma cells and their exosomes by qRT-PCR.M0 type macro-phages were divided into PBS group,HEEC exo group,Eca-109 exo group,miR-NC exo group,miR-181b-5p exo group,miR-NC group,miR-181b-5p mimic group,si-NC group,si-PTEN group,miR-181b-5p exo+PTEN group.qRT-PCR was used to detect the expressions of CD163,CD206,iNOS and TNF-α in each group.The targeting relationship between miR-181b-5p and PTEN were veri-fied by double luciferase reporter gene experiment.Results:miR-181b-5p was significantly overexpressed in esophageal squamous cell carcinoma cells TE-13,TE-12,TE-10,Eca-109,KYSE30 and their exosomes(P<0.001).Compared with miR-NC group,the expression of CD163 and CD206 in cells were significantly upregulated in the miR-181b-5p mimic group,as well as the expressions of iNOS and TNF-α were significantly downregulated(P<0.001).The results of double luciferase reporter genes showed that PTEN was the target gene of miR-181b-5p.Compared with si-NC group,the expressions of CD163 and CD206 in cells were significantly upregu-lated in the si-PTEN group,as well as the expressions of iNOS and TNF-α were significantly downregulated(P<0.001).Compared with PBS group,the expressions of CD163 and CD206 in cells were significantly upregulated in the Eca-109 exo group,as well as the expressions of iNOS and TNF-α were significantly downregulated(P<0.001).Compared with miR-NC exo group,the expressions of CD163 and CD206 in cells were significantly upregulated in the miR-181b-5p exo group,as well as the expressions of iNOS and TNF-α were significantly downregulated(P<0.001).Compared with miR-181b-5p exo group,the expressions of CD163 and CD206 in cells were significantly downregulated in the miR-181b-5p exo+PTEN group,as well as the expressions of iNOS and TNF-α were significantly upregulated(P<0.001).Conclusion:Exosomal miR-181b-5p inhibits PTEN expressions to promote M2 macrophage polarization.