Inhibition of DNMT3B Suppresses the Proliferation and Migration of Oral Squamous Cell Carcinoma Cells through the Regulation of GPX3 Expression

Abstract

Background: DNA (cytosine-5-)-methyltransferase 3 beta (DNMT3B) can promote the development of oral squamous cell carcinoma (OSCC), while glutathione peroxidase 3 (GPX3) can inhibit it. In this study, we aimed to investigate the underlying mechanism by which DNMT3B and GPX3 influence OSCC. Methods: Bioinformatics was used to analyze the expression patterns of DNMT3B and GPX3 in head and neck squamous cell carcinoma (HNSC), as well as the methylation sites in the promoter region of GPX3. Additionally, various cellular assays were conducted to assess the proliferation, migration, invasion, and apoptosis of OSCC cells including colony formation, Transwell®, and flow cytometry analyses. The levels of DNMT3B, GPX3, and factors related to the Jun N-terminal kinase (JNK)/c-JUN axis were quantified using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. The methylation of the GPX3 promoter and the interaction between DNMT3B and the GPX3 promoter were evaluated through quantitative methylation-specific PCR and chromatin immunoprecipitation-PCR assays. Results: The analysis revealed elevated expression of DNMT3B and reduced expression of GPX3 in HNSC. Additionally, methylation sites were identified in the promoter region of the GPX3 gene. Further investigation demonstrated that silencing DNMT3B suppressed the proliferation, migration, and invasion of OSCC cells while promoting apoptosis. This was accompanied by an increase in GPX3 level and dephosphorylation of the JNK and c-JUN signaling pathways. DNMT3B was found to directly bind to the promoter of the GPX3 gene. Overexpression of GPX3 inhibited the proliferation, migration, and invasion of OSCC cells and promoted apoptosis. It also suppressed the JNK/c-JUN pathway. Conversely, silencing GPX3 had the opposite effects and counteracted the effects of DNMT3B silencing. Conclusions: After inhibiting DNMT3B, the expression of GPX3 is upregulated, which may suppress the progression of OSCC.