The exocyst, an evolutionarily conserved octomeric protein complex, has been demonstrated as an essential component for vesicle tethering during cell exocytosis, and participates in various physiological processes in the cell. Although subunits of the exocyst complex have been reported to be involved in the regulation of TGF-beta induced cancer cell migration and epithelial-mesenchymal transition (EMT), the potential function of Sec3 in these regulated processes remains unclear. Here, we show that Sec3 knockdown abolishes TGF-beta stimulated A549 lung cancer cell migration in vitro and causes defects in the regulated EMT process. In addition, we find that depletion of Sec3 significantly inhibits TGF-beta stimulated Akt phosphorylation in A549 cells, whereas the increase of Smad2 phosphorylation is unaffected. Furthermore, replenishment of an RNAi-resistant form of Sec3 is shown to restore the defects of TGF-beta induced cell migration, EMT and Akt signaling activation. In summary, our study provides evidence that Sec3 is involved in TGF-beta induced cell migration and EMT processes, presumably through the regulation of PI3K/Akt signaling activation in A549 cancer cells. (C) 2019 Elsevier Inc. All rights reserved.