[Overexpression of Nei endonuclease VIII-like protein 3 in hepatocellular carcinoma indicates increased levels of immune infiltration and an unfavorable prognosis]

Objective: To evaluate the role and molecular mechanism of Nei endonuclease VIII-like protein 3 (NEIL3) in hepatocellular carcinoma (HCC) through The Cancer Genome Atlas database. Methods: RNA sequencing of HCC samples was the first step in determining the level of gene NEIL3 expression in normal tissues and tumors. Then, NEIL3 was used for the Gene Ontology, the Kyoto Encyclopedia of Genes and Genomes, gene enrichment analysis, immune cell infiltration analysis. The samples were divided into high and low expression groups according to the median expression level of NEIL3 in liver cancer tissues. Logistic regression analysis, Kaplan-Meier analysis, univariate and multivariate Cox regression analysis, and a nomogram prognostic model were used to explore the clinical and prognostic significance of NEIL3 in HCC. Results: Compared with normal samples, NEIL3 was highly expressed in most malignant tumors, including HCC (P < 0.05). High expression of NEIL3 was related to cell cycle, DNA replication, and cell receptor pathways. In addition, the high expression of NEIL3 was significantly positively correlated with T-helper 2 lymphocytes and infiltration levels (R = 0.670, P < 0.001). Compared with the NEIL3 low expression group, the NEIL3 high expression group had a higher level of Th2 cell infiltration in tumor tissues (P < 0.001). Logistic regression analysis showed that NEIL3 overexpression was associated with high T stage, high pathological stage, high tissue grade, AFP > 400 μg/L and vascular invasion of HCC. The Kaplan-Meier analysis results showed that overall survival [hazard ratio (HR) = 2.53, P < 0.001)], disease-specific survival (HR = 2.52, P < 0.001), and progression-free interval (HR = 1.82, P < 0.001) in patients with HCC with high NEIL3 expression were unfavorable. Cox regression analysis results showed that high NEIL3 expression was an independent risk factor for an unfavorable prognosis in HCC patients (P = 0.002). The nomogram and calibration chart further demonstrated that high NEIL3 expression was one of the risk factors for an unfavorable prognosis in HCC patients. Conclusion: Elevated expression of NEIL3 is associated with an unfavorable prognosis and an increased proportion of immune cells in HCC, and it is likely to be used as a potential biomarker for evaluating the prognosis and immune infiltration level.