Background:Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer-related death around the world. Epithelial–mesenchymal transition (EMT) has been documented to increase motility and invasiveness of cancer cells, which promotes cancer metastasis.

Purpose:This study aims to investigate the inhibitory effects and mechanisms of the dinorditerpenoids and norditerpenoids isolated from the seeds of Podocarpus nagi against transforming growth factor (TGF)-β1-induced EMT.

Methods:A series of dinorditerpenoids and norditerpenoids were isolated from the seeds of P. nagi. Western blotand quantitative real-time PCR assays were performed to determine the expression levels of relative proteins and mRNA, along with immunofluorescence, Smad-binding element (SBE)-luciferase and chromatin im-munoprecipitation (ChIP) assays for the mechanism study. Transwell assays were conducted to determine theeffect of the compounds on cell migration and invasion.

Results:Nagilactone E (NLE) showed the superior inhibitory effect against TGF-β1-induced EMT. NLE treatment dramatically inhibited TGF-β1-induced expression of EMT markers in A549 cells. Mechanism study indicated that NLE markedly suppressed TGF-β1-induced Smad2 and Smad3 activation and nuclear translocation. SBE-luciferase and ChIP assays showed that NLE inhibited the combining of Smad3 to SBE in the promoters of the cell signaling factors. NLE co-treatment attenuated TGF-β1-induced up-regulation of the protein and mRNA levels ofTGF-βreceptor TβRI. Furthermore, NLE inhibited TGF-β1-stimulated cell migration and invasion, as well as upregulation of the key signaling proteins related with migration and invasion.

Conclusion:NLE inhibited TGF-β/Smad signaling pathway, thereafter suppressed TGF-β1-induced EMT, mi-gration and invasion in NSCLC A549 cells.