Expression And Clinical Significance Of B7 Family Member HHLA2 In Hepatocellular Carcinoma

Objective:To investigate the expression level of HHLA2 in hepatocellular carcinoma patients and its relationship with clinicopathological factors,and further explore its expression level in hepatoma cell lines and normal liver cell lines.Methods: 55 cases of hepatocellular carcinoma(hepatocellular carcinoma group,C)and corresponding paracancerous tissues(paracance group,P)were surgically removed from January 2016 to June 2018 in the Department of Hepatology,Affiliated Tumor Hospital of Guangxi Medical University.Hepatocellular carcinoma was diagnosed by pathology,and the patient did not receive any anti-tumor treatment before surgery.The paraventricular tissue(normal control group)of 11 patients with benign liver tumors confirmed by histopathology was collected.Western blot and real-time quantitative PCR(RT-qPCR)were used to detect the expression of HHLA2 protein and mRNA in55 cases of hepatocellular carcinoma and adjacent normal tissues and 11 normal liver tissues.To analyze the relationship between clinicopathological factors such as age,gender,ethnicity(Han and Zhuang),serum AFP level,Barcelona(BCLC)stage,differentiation degree,tumor size,peripheral invasion behaviorand lymph node metastasis,and HHLA2 protein expression in patients with hepatocellular carcinoma;Western blot and RT-qPCR were used to detect the expression of HHLA2 protein and mRNA in hepatocellular carcinoma cell lines HepG2,SMMC-7721,Huh-7 and normal liver cell line HL-7702.Results: The expression of HHLA2 protein in hepatocellular carcinoma group was significantly higher than that in the paracancerous group and the normal control group,which were 0.877±0.271,0.580±0.383 and 0.375±0.319,respectively,and the difference was statistically significant(P<0.05).There was no significant difference in the expression of HHLA2 protein between the paracancerous group and the normal control group(P>0.05).The expression of HHLA2 mRNA in hepatocellular carcinoma group was higher than that in hepatocellular carcinoma and normal liver control group,the difference was statistically significant(1.628±0.413 vs.1.080±0.323 vs.1.038±0.286,P<0.05).There was no significant difference between the paracancerous group and the normal control group(P>0.05).The hepatocellular carcinoma group with no tumor invasion was significantly lower than the hepatocellular carcinoma group with peripheral tumor invasion(0.837±0.274 vs.1.090±0.166,P<0.05).The clinicopathological analysis showed that the difference in the relative expression of HHLA2 protein in BCLC-A,B,and C hepatocellular carcinoma groups was statistically significant(0.726±0.206 vs.1.006±0.233 vs.1.137±0.126,P<0.05).Futher comparison showed that the relative expression of HHLA2 protein in BCLC-A was significantly lower than that in stage B and stage C(P<0.05).However,there was no significant difference between stage B and stage C(P>0.05).The level of HHLA2 protein in the moderately and highly differentiated group was significantly lower than that in the poorly differentiated group(0.811±0.272 vs.1.008±0.237,P<0.05).In addition,HHLA2 proteinexpression levels were not significantly associated with age,gender,ethnicity,serum AFP levels,chronic hepatitis B,cirrhosis,tumor diameter,and portal vein tumor thrombus(P>0.05).HHLA2 protein is highly expressed in HepG2 cell line and low in HL-7702,SMMC-7721 and Huh-7 cell lines;Compared with the normal liver cell line HL-7702,the expression level of HHLA2 mRNA increased in hepatoma cell lines HepG2 and Huh-7,the difference was statistically significant(1.194±0.699 vs.3.170±1.276 vs.45.100±19.450,P<0.05).However,there was no significant difference in HHLA2 mRNA expression between cell line HL-7702 and hepatoma cell line SMMC-7721(1.194 ± 0.699 vs.0.651 ± 0.353,P>0.05).Conclusions: The expression level of HHLA2 protein in hepatocellular carcinoma tissues is increased,suggesting that HHLA2 may be involved in the development of hepatocellular carcinoma;HHLA2 was positively correlated with clinical stage,differentiation and peripheral invasion of hepatocellular carcinoma,suggesting that HHLA2 may be involved in hepatocellular carcinoma invasion and metastasis.HHLA2 protein expression level was increased in HepG2 cell line,but low expression in Huh7 cell line;HHLA2mRNA expression level was both increased in HepG2 and Huh7 cell lines,suggesting that HHLA2 may participate in hepatocellular carcinoma formation through different regulatory mechanisms.