Expression of HHLA2 in hepatocellular carcinoma tissues and its clinical significance

Objective: To investigate the expression of human endogenous retrovirus subfamily H long terminal repeat associating protein 2 (HHLA2) in hepatocellular carcinoma (HCC) tissues and its correlation with the clinicopathological characteristics and prognosis of patients with HCC. Methods: Based on TCGA database, the correlation between HHLA2 mRNA expression and B7 family genes in human HCC tissues was analyzed. HHLA2 expression in 90 pairs of HCC tissues and their adjacent tissues was detected by tissue microarry and immunohistochemical staining. Wilcoxon rank sum test was used to compare the difference of HHLA2 expression between HCC tissues and its adjacent tissues. The chi-square test was used to analyze the relationship between HHLA2 expression in human HCC tissues and clinicopathological features of the patients. Kaplan-Meier survival analysis was performed to analyze the correlation between HHLA2 expression and patients'overall survival (OS), and the Cox model was used to evaluate the prognostic value of different indices. Results: The expression level of HHLA2 mRNA in HCC tissues was correlated with B7 familyCD274, C10orf54, PDCD1LG2, ICOSLG and CD276. The expression level of HHLA2 in HCC tissues was significantly correlated with tumor size (χ2=4.531, P<0.05). The OS of HCC patients with high HHLA2 expression was significantly shorter than that of the patients with lower HHLA2 expression (HR=1.878, 95%CI: 1.066-3.309, P<0.05). The COX model showed that tumor size (HR=2.493, 95%CI: 1.310-4.742, P<0.01) could be used as an independent risk factor for the prognostic prediction of the patients. Conclusion: HHLA2 is significantly correlated with the prognosis of HCC patients, and can be used as a potential target for HCC immunotherapy.