Expression Of TGF-β1, Snail, E-cadherin And N-cadherin In Gastric Cancer And Their Significance

Objective To investigate the expression of TGF-β1, Snail, E-cadherin and N-cadherin in gastric cancer (GC) tissues and their relationship with clinical pathological features, and to explore the effects of human recombinant TGF-β1 on the human gastric cancer cell line BGC-823 by analyzed the expression changes of Snail, E-cadherin and N-cadherin protein. Through this research, we hope to explore their roles in progression of gastric carcinoma and to evaluate their clinicopathologic significances. Methods Part 1: The expression of TGF-β1, Snail, E-cadherin and N-cadherin proteins was detected in GC and adjacent tissues by immunohistochemical staining (IHC), and compared with the clinico-pathological data. Part 2: We treated human low- differentiated gastric adenocarcinoma cell line BGC-823 with or without TGF-β1, and the effects of TGF-β1 on expression of Snail, E-cadherin and N-cadherin were measured by immunocytochemical staining (ICC), immunofluorescence assay (IFA) and flow cytometry (FCM). MTT assay was used to evaluate the growth of BGC-823. The changes of migration and invasion ability of BGC-823 were detected by traditional wound healing assay and transwell cell culture chambers. It is worth point out that cells of human umbilical vein endothelial cell line (ECs) and BGC-823 cells were co- cultured in the transwell chambers system, and the effect of TGF-β1 on the migration of ECs induced by GCs was investigated. Results Part 1: Positive rates of expression for TGF-β1, Snail, E-cadherin and N-cadherin were 63.5%, 83.3%, 37.5% and 44.8% in GC, and 28.8%, 41.3%, 100%, 11.3% in adjacent tissues, respectively. The expression of all four proteins showed a significant difference between the GCs and adjacent tissues (P<0.05). The positive rate of TGF-β1, Snail and N-cadherin, or the negative rate of E-cadherin expression was significantly related to the differentiated degree, histological type, invasion and metastasis of GC. In addition, the expression of N-cadherin was positively related to that of TGF-β1, but negatively related to that of E-cadherin. There was negative correlation between expression of E-cadherin and TGF-β1 and Snail in GC (P<0.05). Part 2:⑴The expression of Snail, E-cadherin and N-cadherin were measured at different levels after culture in the presence of human recombinant TGF-β1. The opposite trend was showed between E-cadherin and N-cadherin. TGF-β1 inhibited the expression of E-cadherin, but enhanced that of N-cadherin.⑵After exposure to TGF-β1 (1, 5 and 10ng/ml) for 18h, the growth of GCs was promoted dose-dependently. Meanwhile the inhibitory effect of TGF-β1 (20 and 50ng/ml) was observed unexpectedly. Then the cell growth curve was measured at different time (18h, 42h, 66h). As a result, it didn't show time-dependent manner.⑶The changes of migration and invasion were detected in BGC-823 cells exposed to TGF-β1 (1, 10 and 20ng/ml), of which the rate was significantly high at dose of 10ng/ml. Besides, the chemotaxis of ECs to GCs induced by TGF-β1 (10ng/ml) was also much greater than that in control group (P<0.05). Conclusion The over-expression of TGF-β1 and Snail and decreased expression of E-cadherin and the abnormal expression of N-cadherin were involved in the process of invasion and metastasis of GC. Cadherin isoforms can change from E-cadherin to N-cadherin in cultured GCs, which is associated with epithelial-mesenchymal transition. TGF-β1 and Snail might play a fundamental role in the process.