Overexpression of DNMT1 Accelerates Migration and Invasion of Lung Squamous Cell Carcinoma Cells by Decreasing TCF21 Expression via the Akt/p65 Signaling Pathway

Background: Hypermethylation and downregulation of transcription factor 21 (TCF21) are frequently observed in non-small cell lung cancer (NSCLC). DNA methyltransferase 1 (DNMT1) is highly expressed in lung squamous cell carcinoma (LUSC). Accordingly, this study examines the biological roles of TCF21 and DNMT1 in LUSC cells. Methods: Analyses concerning TCF21 expression in LUSC and the correlation between DNMT1 and TCF21 were performed using bioinformatics. After transfection of DNMT1/TCF21 overexpression plasmids, or small interfering RNAs targeting TCF21 and DNMT1 (siTCF21 and siDNMT1) into LUSC cells, the regulatory effects of TCF21 and DNMT1 on the malignant behavior of LUSC cells were verified by cell counting kit-8 assay, flow cytometry, and transwell assay. Quantitative real-time reverse transcription polymerase chain reaction or western blot was used for quantification. Results: TCF21 expression was downregulated in LUSC tissues and cells (p < 0.05), and expressions of DNMT1 and TCF21 were negatively correlated (r = -0.09, p = 0.047). TCF21 silencing enhanced viability, migration, and invasion, reduced apoptosis, upregulated expressions of paired box 8 (PAX8), baculoviral IAP repeat containing 3 (BIRC3), B-cell lymphoma-2 (Bcl-2), Xlinked inhibitor of apoptosis (XIAP), matrix metallopeptidase 9 (MMP9), N-cadherin, Vimentin, phosphorylated-protein kinase B (p-Akt) and phosphorylated-p65 (p-p65), downregulated expressions of BCL2 associated X protein (Bax) and E-cadherin, and elevated p-Akt/Akt and p-p65/p65 ratios in LUSC cells (p < 0.05). DNMT1 overexpression exerted the same effects in LUSC cells as TCF21 silencing, while DNMT1 silencing did the opposite effect. DNMT1 overexpression decreased, while DNMT1 silencing increased TCF21 expression. Additionally, DNMT1 overexpression reversed the effects of TCF21 overexpression in LUSC cells (p < 0.05). Conclusion: DNMT1 overexpression promotes LUSC cell migration and invasion by downregulating TCF21 through activation of the Akt/p65 pathway.