Transforming growth factor-β (TGF-β)-mediated epithelial mesenchymal transition (EMT) of human lung cancer cells may contribute to lung cancer metastasis. It has been reported that EGCG can inhibit tumorigenesis and cancer cell growth in lung cancer; however, the effect of EGCG on EMT in nonsmall cell lung cancer (NSCLC) cells has not been investigated. In this study, we found that NSCLC cells A549 and H1299 were converted to the fibroblastic phenotype in response to TGF-β. Epithelial marker E-cadherin was down-regulated, and mesenchymal marker vimentin was up-regulated simultaneously. Our results illustrated that TGF-β was able to induce EMT in NSCLC cells, and EGCG would reverse TGF-β-induced morphological changes, up-regulate the expression of E-cadherin, and down-regulate the expression of vimentin. Immunofluorescent staining also demonstrated that E-cadherin was up-regulated and that vimentin was down-regulated by EGCG pretreatment. Moreover, wound-healing and the in vitro invasion assay showed that EGCG could inhibit TGF-β-induced migration and invasion of NSCLC cells. By using the dual-luciferase reporter assay, we demonstrated that EGCG inhibited TGF-β-induced EMT at the transcriptional level. EGCG decreased the phosphorylation of Smad2 and Erk1/2, inhibited the nuclear translocation of Smad2, and repressed the expression of transcription factors ZEB1, Snail, Slug, and Twist, and up-regulated the expression of E-cadherin. In summary, our results suggest that EGCG can inhibit TGF-β-induced EMT via down-regulation of phosphorylated Smad2 and Erk1/2 in NSCLC cells.

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Non-homologous end-joining (NHEJ) system is a major route in repairing double strand breaks (DSBs), and is important in maintaining the genome stability. The gene XRCC4 is a central role of the NHEJ system, and it is critical in carcinogenesis. In order to reveal the association between XRCC4 and lung cancer, we recruited 164 lung cancer patients and 649 healthy controls from central Taiwan, investigated seven novel polymorphic variants of XRCC4, includes C-1622T (rs7727691), G-1394T (rs6869366), G-652T (rs2075685), C-571T (rs2075686), intron3 DIP (rs28360071), S247A (rs3734091) and intron7 DIP (rs28360317), and analyzed the association of specific genotype with lung cancer susceptibility. The results showed that the XRCC4 G-1394T is significant in Taiwanese lung cancer and the GT genotype of G-1394T is an obvious risk factor of lung cancer susceptibility (P=0.0049), and the G allele is a risky factor (P=0.0087). As for XRCC4 C-1622T (rs7727691), G-652T (rs2075685), C-571T (rs2075686), intron3 DIP (rs28360071), S247A (rs3734091) and intron7 DIP (rs28360317) polymorphism sites, there was no difference in the distribution between the lung cancer and control groups. The analyzing results of joint effect for smoking habit and XRCC4 G-1394T polymorphism was that people with GT genotype and smoking habit present the highest risk of lung cancer than other groups (OR=2.31, 95% CI=1.43-3.72). The G allele of the XRCC4 G-1394T may be responsible for lung carcinogenesis and maybe useful in early detection and prevention of lung cancer.