Inhibitor of DNA-Binding Protein 4 Suppresses Cancer Metastasis through the Regulation of Epithelial Mesenchymal Transition in Lung Adenocarcinoma

Metastasis is a predominant cause of cancer death and the major challenge in treating lung adenocarcinoma (LADC). Therefore, exploring new metastasis-related genes and their action mechanisms may provide new insights for developing a new combative approach to treat lung cancer. Previously, our research team discovered that the expression of the inhibitor of DNA binding 4 (Id4) was inversely related to cell invasiveness in LADC cells by cDNA microarray screening. However, the functional role of Id4 and its mechanism of action in lung cancer metastasis remain unclear. In this study, we report that the expression of Id4 could attenuate cell migration and invasion in vitro and cancer metastasis in vivo. Detailed analyses indicated that Id4 could promote E-cadherin expression through the binding of Slug, cause the occurrence of mesenchymal-epithelial transition (MET), and inhibit cancer metastasis. Moreover, the examination of the gene expression database (GSE31210) also revealed that high-level expression of Id4/E-cadherin and low-level expression of Slug were associated with a better clinical outcome in LADC patients. In summary, Id4 may act as a metastatic suppressor, which could not only be used as an independent predictor but also serve as a potential therapeutic for LADC treatment.