Human Endogenous Retrovirus-H Long Terminal Repeat-Associating Protein 2 Possesses Prognostic Significance and Promotes Progression of Papillary Thyroid Cancer

Purpose: Identification of novel biomarkers could benefit the clinical therapy and management of papillary thyroid carcinoma (PTC). Human endogenous retrovirus long terminal repeat-associating protein 2 (HHLA2) has been reported to play roles in the development of various cancers. The clinical significance and biological function of HHLA2 in PTC were investigated. Patients and Methods: The expression level of HHLA2 was evaluated in PTC tissues (from 107 PTC patients) and cell lines (TPC1, IHH-4, CGTH-W3, and MDA-T32 cells) by RT-qPCR. The clinical significance of HHLA2 was estimated with a series of statistical analyses. The biological function of HHLA2 was assessed with the CCK8 assay and transwell assay. Results: HHLA2 was upregulated in PTC compared with the normal samples and was associated with the positive lymph node metastasis and advanced TNM stage of PTC patients. HHLA2 was an independent prognostic factor associated with the poor survival of PTC patients. Additionally, HHLA2 functioned as a tumor promoter that enhanced the progression of PTC cells. Conclusion: HHLA2 could serve as a prognostic biomarker and tumor promoter in PTC, providing a novel therapeutic target of PTC.