Mdig suppresses epithelial-mesenchymal transition and inhibits the invasion and metastasis of non­small cell lung cancer via regulating GSK-3ß/ß-catenin signaling.

Mineral dust-induced gene (mdig) can inhibit the invasion and metastasis of A549 cells. The main purpose of this study was to explore the molecular mechanism underlying the inhibitory effect of mdig on cell invasion and metastasis. Mdig-knockdown and mdig-overexpressing A549 cells and an mdig-overexpressing human umbilical vein endothelial cell (HUVEC) line were constructed using lentiviral vectors, and western blot analysis was performed to verify the silencing and overexpression of the mdig protein. A Transwell invasion assay was used to detect the invasive abilities of each experimental group, and Transwell migration and scratch assays were used to detect cell migration ability. Western blotting was subsequently conducted to detect the major biochemical indices of the GSK-3ß/ß-catenin pathway and the protein expression levels and modifications of epithelial­mesenchymal transition (EMT) transcription factors, as well as changes in the expression levels of EMT molecular markers and intercellular adhesion proteins. The results indicated that overexpression of mdig in A549 cells inhibited cell invasion and metastasis, while silencing of mdig increased the invasive and metastatic properties of cells. The molecular mechanism underlying the effects of mdig downregulation on A549 cell invasion and metastasis was found to involve the inhibition of GSK-3ß phosphorylation, which in turn promoted the phosphorylation and destabilization of ß-catenin. This was associated with downregulation of the downstream transcription factors slug, snail and ZEB1, thus leading to increased expression levels of epithelial cell markers and upregulation of the intercellular adhesion molecules E-cadherin, claudin­1, ZO­1, integrin ß1 and integrin ß4, which was accompanied by downregulation of the mesenchymal cell markers vimentin and N-cadherin. The HUVECs were used to validate the aforementioned molecular mechanisms and the same conclusions were obtained. The present results indicate that mdig can inhibit the phosphorylation of GSK-3ß and promote the phosphorylation and destabilization of ß-catenin, in order to suppress the expression of slug, snail, and ZEB1 and the occurrence of EMT, and thereby inhibit the invasion and metastasis of non-small cell lung cancer (NSCLC).