Abstract: Background and purpose: Epithelial-to-mesenchymal transition (EMT) is the key biological process of tumor cell metastasis. Blocking EMT inhibits tumor metastasis, therefore it is of great significance to elucidate the molecular mechanism of EMT. Tumor suppressor protein H2AX regulates apoptosis-related gene expression of tumor cells, and then produces anti-tumor effect. This study aimed to reveal the relationship between H2AX and EMT, and to explore the possible mechanism of H2AX regulating EMT in lung cancer cells. Methods: About 5% fetal bovine serum was used to induce EMT in lung cancer A549 stable cells including H2AX gene silencing, H2AX overexpression and H2AX phosphorylation site mutation. Western blot and real- time fluorescent quantitative polymerase chain reaction (RTFQ-PCR) were used to detect the expressions of E-cadherin, vimentin, vascular endothelial growth factor receptor 2 (VEGFR2) and other EMT-related proteins. Transwell experiment was used to analyze the migration and invasion of A549 cells. Results: Knockdown of H2AX in lung cancer A549 cells resulted in the downregulation of E-cadherin and the upregulation of vimentin, and enhanced the migration and invasion ability of A549 cells. Overexpression of H2AX in lung cancer A549 cells upregulated E-cadherin, downregulated vimentin, and inhibited the migration and invasion of A549 cells. Mutation of H2AX phosphorylation site eliminated the regulation of E-cadherin and vimentin by H2AX, and the inhibition of EMT by H2AX. H2AX knockdown in A549 cells stimulated the expression of VEGFR2, while overexpression of H2AX inhibited VEGFR2 expression. Mutation of H2AX phosphorylation site eliminated the VEGFR2 expression inhibition caused by H2AX. Knockdown of VEGFR2 inhibited the EMT of A549. Knockdown of H2AX stimulated the expression of EMT-related factors Slug and β-catenin, whereas overexpression of H2AX inhibited the expression of Slug and β-catenin. Reducing H2AX phosphorylation eliminated the expression inhibition of Slug and β-catenin by H2AX. Conclusion: H2AX inhibits EMT of lung cancer A549 cells by downregulating the expressions of VEGFR2, Slug and β-catenin.

Key words:  H2AX, Epithelial-to-mesenchymal transition, Lung cancer cells, Invasion, Migration