| Background and Aims Gastric cancer is one of the most frequently diagnosed malignancies in the world, accounting for 12% of total cancer deaths. Despite its decreasing incidence and mortality during the last several years, this malignancy still remains a major public problem in eastern Asia, mainly due to early metastasis. Thus, identification of early genetic changes in gastric tumorigenesis is a challenging task. Reacently, epithelial-mesenchymal transitions (EMT) and mesenchymal to epithelial transition (MET), the fundamental processes regulating morphogenesis in multicellular organisms, is thought to play a key role during early steps of invasion and metasasis of epithelial malignancies. EMT involves an orchestrated series of events in which epithelial cells lose polarity and cell-cell contacts and undergo dramatic remodeling of the cytoskeleton which enables carcinoma cells to migrate through an extracellular environment and settle in distinct areas to form metastasis. Among lots of down-stream genes, loss of E-cadherin provides the strongest evidence in the development of EMT as well as the increasing of a mesenchymal marker Fibronectin (FN). E-cadherin is a homophilic type of adhesion molecule and is regarded as an invasion suppressor in gastric cancer and other types of cancer. Transcription factors including Snail, Slug and Twist are newly investigated as an EMT-inducer though repression of E-cadherin. As a EMT-inducer, Twist, a highly conserved basic helix-loop-helix transcription factor originally identifiedas a D. melanogaster EMT activator (Castanon and Baylies,2002), is thought to play a key role in regulating developmental EMT and tumor metastasis. Overexpression of Twist was observed in a variety of solid cancers including lobular carcinoma of breast, endometrial cancer, ovarian carcinoma, prostate cancer, nasopharyngeal and diffuse-type gastric carcinomas. In addition, Twist was proposed as an oncogen contributes to inhibit Myc-induced apoptosis in mouse embryo fibroblasts and neuroblastoma cells. Studies in prostate cancer have demostrated that Twist might regulate apoptosis through both p53-dependent and p53-independent pathways. Moreover, increased expression of Twist is correlated with shorter survival of patients and can serve as an independent marker to predict poor outcome in melanoma, endometrial cancer and ovarian carcinoma patients. However, little information is available concerning the role of Twist in gastric cancer. Recently, a study by Rosivatz et al. showing that Twist is high expressed in human diffuse-type gastric cancer correlated with the up-regulation of N-cadherin and down-regulation of E-cadherin. Studies in breat cancers have demostrated that Twist also have the binding affinity to the E boxes within the E-cadherin promoter and lead to the transcriptional repression of E-cadherin. Despite these increasing studies, the roles and mechanisms of Twist in human gastric cancer progression has not yet been fully characterized and has not been reported to date. Taken this, the present study is designed to investigate the effect of Twist on cells migration and invasion in gastric cancer.Method Liposome-mediated transfection was used to introduce a Twist antisence expression vector into gastric cancer MKN45 cell lines with high levels of Twist endogenously. Transfectants were tested in invasion and migration assay by a Transwell chamber and the expression of epithelial-mesenchymal transition associated genes by western blot analysis and polymerase chain reaction.Results The resulted showed that overexpression of Twist in gastric cancer cells can promote cancer cell migration and invasion in vitro. Mechanisms studies revealed that suppression of Twist enhanced the recruitment of E-cadherin and had a concomitant effect of down-regulated expression of Fibronectin and MMP9, which, in turn, lead to morphologic changes associated with mesenchymal to epithelial transition in MKN45 gastric cells.Conclusion Taken together, our results indicate the importance of Twist as an invasion-promoting gene in gastric cancer cells through EMT introduction.
|
PDF Full Text Request