Silencing of expression by promoter methylation activates the Wnt/β-catenin signaling pathway to promote tumor proliferation and metastasis in salivary adenoid cystic carcinoma.

BACKGROUND

Salivary adenoid cystic carcinoma (SACC) is a unique malignant tumor of the salivary gland with poor prognosis, which is not effective with chemotherapy and targeted drugs. Therefore, it is important to explore the molecular mechanism underlying SACC invasion and metastasis to develop novel therapeutic strategies and targets in clinical research.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot (WB) were performed to detect the expression of Adherens Junctions Associated Protein 1 (). Methylation-specific PCR was used to evaluate the methylation of the promoter. was overexpressed or knocked down by lentivirus-mediated transfection. Kaplan-Meier analysis was conducted to create a survival curve and the log-rank test was used to analyze the overall survival (OS). The prognostic correlation was assessed using univariate and multivariate Cox regression analyses. Co-immunoprecipitation (Co-IP) was utilized to pull down the possible binding protein of and laser scanning confocal microscopy was applied to detect the subcellular localization of , E-cadherin, and β-catenin. Cell viability, colony formation, wound healing, and Transwell invasion assays were performed to evaluate the function of AJAP1 . A subcutaneous xenograft assay in nude mice was performed to verify the function of .

RESULTS

was downregulated in SACC tumors and was closely related to SACC lymph node/distant metastasis, which was an independent risk factor for SACC prognosis. Methylation-specific PCR confirmed that high methylation of the promoter was the main cause of its silencing. Overexpression or knockdown of in SACC cells could significantly inhibit or promote the proliferation, invasion, and metastasis of SACC cells, respectively, in both the and experiments. Mechanically, we found that binds to E-cadherin and β-catenin to form a complex in cytomembrane, reducing the nuclear translocation of β-catenin and blocking the Wingless/Integrated/β-catenin (Wnt/β-catenin) signaling pathway to play a suppressive role in cancer.

CONCLUSIONS

In conclusion, these results suggest that the downregulation of protein expression may play a certain role in progression and metastasis of SACC. Our study indicates that may be a potential prognostic molecular marker and therapeutic target for SACC.