Clinical Significance Of BTG2 Expression And DNA Methylation In Primary Hepatocellular Carcinoma

ObjectiveOur aim is to explore the expression of BTG2 and its Clinical significance in the patients with primary hepatocellular carcinoma,and to investigate the relationship between BTG2 expression and its DNA methylation,and the clinical significance of its DNA methylation in hepatocellular carcinoma.Methods1.125 patients with hepatocellular carcinoma pathologically confirmed were recruited in this study.The protein expression of BTG2 was evaluated by immunohistochemistry assay,and then we analyzed the correlation of BTG2 expression level and clinical pathological factors and overall survival in patients with HCC.2.We collected and analyzed information from TCGA data base,and then chose two CG sites(cg00567854 and cg01798157)to perform the pyrosequencing assay.3.From previous 125 patients,we selected 51 patients which have 66 tissues.Then the DNA methylation of BTG2 was detected by pyrosequencing assay.The correlation of BTG2 expression level and its DNA methylation,and the clinical significance of its DNA methylation in hepatocellular carcinoma were analyzed.Results1.In the 125 cases,there were 106,13 and 6 cases respectively with negative,low and high expression of BTG2 in tumor tissues,and the amounts were 41,14 and 22 respectively for the corresponding para-carcinoma tissues.The expression was significantly different between the two groups(Chi square= 28.102,P<0.001).2.BTG2 expression was significantly associated with occurrence of tumor thrombus(Chi square= 8.305,P=0.013).3.Kaplan-Meier analysis indicated that the medium overall survival of the low BTG2 expression group was 36 months(95% CI: 8.436~63.564),while the high expression and negative groups did not reach medium overall survival(Log-Rank Chi square=4.512,P=0.105).Subgroup analysis showed us that OS of the high BTG2 expression group was significantly longer than the low expression group(Chi square= 4.512,P=0.039).And there was no significant difference between the negative and high groups(Chi square=2.729,P=0.099),or between the negative and low groups(Chi square= 1.400,P=0.237).4.There was no significant difference of the DNA methylation level of the cg00567854(Kruskal-Wallis,P=0.739)located in TSS(transcriptional start site)of BTG2 gene between carcinoma tissues and para-carcinoma tissues,either was the cg01798157(Kruskal-Wallis,P=0.947)located in 3’-UTR of BTG2 gene.And there was no difference of the DNA methylation level of the two sites among different BTG2 expression groups(Kruskal-Wallis,cg00567854,P=0.714;cg01798157,P=0.448).5.Univariate and multivariate Cox analysis showed that DNA methylation of cg01798157 was an independent prognostic factor for OS of the HCC patients(P<0.001,HR=0.935).Divide all the 51 patients into two groups by 64% of the DNA methylation level of cg01798157,and the Kaplan-Meier analysis showed that OS of the high methylation group(>64%)was longer than the low methylation group(Log-Rank Chi square =8.316,P=0.004).Conclusion1.Our results showed that BTG2 expression level of carcinoma tissues was significantly lower than that of para-carcinoma tissues in HCC patients.2.There was significant correlation of BTG2 expression and occurrence of tumor thrombus.3.Our results also indicated that HCC patients with high BTG2 expression had better prognosis,so the BTG2 expression could be a promising prognostic factor.4.DNA methylation of the cg01798157 located in the 3’-UTR of BTG2 gene was an independent prognostic factor for OS of the HCC patients.