Methylation characteristics and clinical significance of glutathione peroxidase 3 in malignant pleomorphic adenoma

[Objective:] To observe the methylation and protein levels of glutathione peroxidase 3 (GPX3) in malignant pleomorphic adenoma (MPA) tissue and its clinical significance. [Methods:] A total of 55 cases of salivary gland pleomorphic adenoma (SPA), 24 cases of MPA, and 55 cases of normal glandular tissue from patients who underwent surgical treatment at the Second Affiliated Hospital of Xinjiang Medical University from January 2021 to January 2023 were selected. Immunohistochemical method was used to detect the expression of GPX3 protein in tissues. Methylation specific polymerase chain reaction (MSP) method was used to detect the degree of GPX3 methylation in tissues. The relationship between clinical pathological features and methylation was analyzed. Human malignant pleomorphic adenoma cell line SM-AP1 was selected and transfected with GPX3 overexpression vector and empty vector, and they were divided into Vector group and OE-GPX3 group. Real-time quantitative polymerase chain reaction(RT-qPCR) and western blotting were used to detect GPX3 mRNA and protein expression. CCK8 was used to detect cell proliferation ability. Transwell chamber was used to detect cell invasion ability. [Results:] The positive rate of GPX3 protein in normal glandular tissues (90.9%, 50/55) was higher than that in SPA (56.4%, 31/55) and MPA (29.2%, 7/24) (P<0.001). The proportion of GPX3 protein methylation in normal glandular tissues (7.3%, 4/55) was lower than that in SPA tissues (34.5%, 19/55) and MPA tissues (66.7%, 16/24) (P<0.001). The methylation level of GPX3 was related to TNM stage, differentiation degree, and proportion of malignant components in MPA patients (P<0.05). The positive rate of GPX3 protein was related to TNM stage and the proportion of malignant components (P<0.05). Compared with the Vector group, the OE-GPX3 group showed a statistically significant increase in the mRNA and protein expression levels of GXP3, optical density values at 48 and 72 hours, and the number of invasive cells were decreased, and the difference was statistically significant (P<0.01). [Conclusion:] The GPX3 gene in MPA has a high degree of methylation initiation, which is negatively related to TNM stage, differentiation, and proportion of malignant components. It has the potential to become a warning molecular indicator for diagnosing malignant pleomorphic adenoma and a gene regulatory target in clinical treatment.