DNA methylation-mediated suppression of TUSC1 expression regulates the malignant progression of esophagogastric junction cancer.

Background: Esophagogastric junction cancer (EJC) refers to malignant tumors that develop at the junction between the stomach and the esophagus. TUSC1 is a recently identified tumor suppressor gene known for its involvement in various types of cancer. The objective of this investigation was to elucidate the regulatory influence of DNA methylation on TUSC1 expression and its role in the progression of EJC.

Methods: Bioinformatics software was utilized to analyze the expression of TUSC1, enriched pathways, and highly methylated sites in the promoter region. TUSC1 expression in EJC was assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot (WB), and immunohistochemistry. Methylation-specific PCR was employed to detect the methylation level of TUSC1. To analyze the effects of TUSC1 and 5-AZA-2 on tumor cell proliferation, migration, invasion, cell cycle, and apoptosis, several assays including CCK-8, colony formation, transwell, and flow cytometry were conducted. The expression of MDM2 was assessed using qRT-PCR and WB. WB detected the expression of p53, and p-p53, markers for EJC cell proliferation, epithelial-mesenchymal transition, and apoptosis. The role of TUSC1 in tumor occurrence in vivo was examined using a xenograft mouse model.

Results: TUSC1 expression was significantly downregulated in EJC. Overexpression of TUSC1 and treatment with 5-AZA-2 inhibited the malignant progression of EJC cells. In EJC, low methylation levels promoted the expression of TUSC1. Upregulation of TUSC1 suppressed the expression of MDM2 and activated the p53 signaling pathway. Inactivation of this pathway attenuated the inhibitory effect of TUSC1 overexpression on EJC cell proliferation, migration, invasion, and other behaviors. Animal experiments demonstrated that TUSC1 overexpression inhibited EJC tumor growth and metastasis in vivo.

Conclusion: TUSC1 was commonly downregulated in EJC and regulated by methylation. It repressed the malignant progression of EJC tumors by mediating the p53 pathway, suggesting its potential as a diagnostic and therapeutic target for EJC.