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Hyper-expression and hypomethylation of TM4SF1 are associated with lymph node metastases in papillary thyroid carcinoma patients.

Lymph node metastases (LNM) are an indicator for recurrence in papillary thyroid carcinoma (PTC) patients. However, prophylactic neck dissection (ND) cannot improve survival or recurrence rate because of increased surgical complications and occult lymph node metastases. Biomarkers are needed for the prediction of high-risk of LNM to avoid unnecessary operation and reduce the missed malignant lymph nodules. GEO database was searched for the differentially expressed genes (DEGs) between PTC patients with LNM (N1) and those without LNM (N0), transcriptional and methylation data of DEGs in THCA were examined from databases. The expression and methylation of TM4SF1 in fresh and paraffin tissues of PTC patients were examined by qRT-PCR, IHC, and MSP. TM4SF1 was the only one significantly associated with LNM. UALCAN revealed that TM4SF1 was overexpressed and hypomethylated in LNM patients. MEXPRESS presented a negative correlation between gene expression and promoter methylation of TM4SF1. DEGs were enriched in multiple pathways and the Extracellular Matrix (ECM)-receptor interaction pathway showed the greatest correlation with LNM. IHC and qRT-PCR of tissues demonstrated that the expression of TM4SF1 in the N1 group was 4.5-fold higher than that in the N0 group (p < 0.05). MSP exhibited that the positive rate of aberrant promoter methylation of TM4SF1 was 8.38% in N1 and 66.7% in N0 group (p < 0.05). Hyper-expression and hypomethylation of TM4SF1 are associated with lymph node metastases in PTC patients.