Relationship between the rs2596542 polymorphism in the MICA gene promoter and HBV/HCV infection-induced hepatocellular carcinoma: a meta-analysis

Background & aims Various studies have investigated the relationship between the polymorphism, rs2596542, in the promoter of the major histocompatibility complex class I-related gene A (MICA) gene with susceptibility to hepatitis B virus (HBV)/ hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC); however, the results are inconclusive. This meta-analysis was conducted to investigate the relationship between rs2596542 and HCV/HBV-induced HCC. Methods Three electronic scientific publication databases (MEDLINE, Web of Science, and Embase) were screened using specific search terms and relevant literature identified using literature traceability methods. Selected publications were evaluated according to the inclusion and exclusion criteria, and 11 articles were included in the study. Effect size information (odds ratio [OR] and corresponding 95% confidence interval [CI]) were obtained following quality assessment and data extraction from the included publications, and a meta-analysis conducted. Results A total of 11 publications were included in the study, including 4582 patients with HCC and 21,095 non-HCC patients. TT genotype at rs2596542 was a risk factor for the development of HCC in patients with HCV/HBV infection (OR = 1.248, 95% CI: 1.040–1.499, P = 0.017), particularly those with HCV infection (OR = 1.326, 95% CI: 1.101–1.599, P = 0.003) and Asians (OR = 1.273, 95% CI: 1.002–1.618, P = 0.048), or when the control group was patients with chronic hepatitis C (CHC) (OR = 1.506, 95% CI: 1.172–1.936, P = 0.001). Conclusion The findings of this meta-analysis suggest that the rs2596542 variant in the MICA promoter region may affect MICA and soluble MICA (sMICA) protein expression, thereby influencing physiological vulnerability to HCC cells and the development of HCC. These data provide a theoretical basis for the diagnosis and treatment of patients with HCC and viral hepatitis infection. Electronic supplementary material The online version of this article (10.1186/s12881-019-0871-2) contains supplementary material, which is available to authorized users.


Background
Liver cancer is a common malignancy, and its mortality rate ranks third among malignant tumors; hence, this disease represents a serious threat to health and life [1]. Cirrhosis, caused by persistent hepatitis C virus (HCV) infection, is a key factor in the development of hepatocellular carcinoma (HCC) [2][3][4], while chronic hepatitis B virus (HBV) carriers are 100 times more likely to develop HCC than non-carriers [5][6][7]. HCV infection is a common cause of HCC in western countries and Japan, while HBV frequently causes HCC in other parts of Asia and developing countries [8].
Major histocompatibility complex class I-related gene A (MICA) is a tumor-associated gene containing numerous polymorphisms, which maps to the short arm of human chromosome 6 [9]. MICA is highly expressed in tumor cell lines and epithelial-derived primary tumors, such as lung, breast, liver, and prostate cancers [10]. MICA protein is a ligand of the NK cell surface activating receptor, NKG2D, which can effectively mediate NK cell killing of tumor cells by binding activation proteins [11]; however, many MICA-positive tumors release soluble MICA (sMICA) into the serum, which inhibits NK cell function [12]. MICA polymorphisms are associated with the development of numerous diseases, including cancer and autoimmune diseases [13,14].
The rs2596542 single nucleotide polymorphism (SNP) in the MICA promoter region may be associated with HCC induced by HCV [15], while the results of studies investigating the association of rs2569542 with susceptibility to HBV/HCV-induced HCC are variable [16][17][18], limiting their credibility. The aim of this study was to perform a meta-analysis of published reports concerning rs2596542 and HCC susceptibility, to provide more reliable evidence for basic research and clinical treatment.

Search strategy
A comprehensive search of three databases (MEDLINE, Web of Science, and Embase) was performed and relevant publications were retrieved by literature traceability, from inception to April 2019. The search phrase used was: ("liver cell carcinoma" or "carcinoma, hepatocellular" or "Hepatocellular carcinoma" or HCC or hepatoma) AND (MICA or "MHC class I polypeptide-related sequence A" or "Human Major Histocompatibility Complex class I polypeptide-related sequence A") AND ("polymorphism" or "SNP" or "variation" or "variants" or "locus" or "mutation").

Literature selection
All retrieved publications were screened by stepwise assessment of the title, abstract, and full text, according to the preset inclusion and exclusion criteria described below. Two independent investigators (Luo and Wang) conducted this work simultaneously, and any disagreement was resolved by discussion with a third investigator.
Inclusion criteria: (1) Studies including rs2596542 genotype and allele frequency data from patients with virus-induced live cirrhosis (LC), chronic hepatitis C (CHC)/chronic hepatitis B (CHB), and HCC; (2) Casecontrol studies; (3) Sufficient data to calculate an odds ratio (OR) and corresponding 95% confidence interval (CI); (4) In repeatedly published studies, the report with higher quality data and more comprehensive outcomes data, was selected; (5) English language.

Quality assessment of the studies and data extraction
Quality assessment of the studies and data extraction were performed independently by two investigators (Shen and Deng), based on a set of predetermined criteria (Table 1) extracted and modified from previous studies [19][20][21][22][23]. Any disagreement was resolved by discussion with a third investigator. Quality scores ranged from 0 to 10, with higher scores representing better quality. The following information was extracted: first author, year of publication, country, the characteristics of participants in each study, sample size, number of cases, number of controls, sample source, detection method, and Hardy-Weinberg equilibrium (HWE) in controls.

Statistical analysis
The chi-square test was used to assess HWE in control populations, with P > 0.05 considered to indicate consistency with HWE. Meta-analysis was performed using SAS 9.2 (SAS Institute Inc., Cary, NC, USA) and STATA 12.0 (STATA Corp, College Station, TX, USA) software. Pooled OR and 95% CI values were calculated to evaluate the association of MICA rs2596542 with susceptibility to HBV/ HCV-induced HCC, based on five genetic models: 1) allelic, C vs. T; 2) heterozygous, CT vs. CC; 3) homozygote, TT vs. CC; 4) dominant, TT/CT vs. CC; and 5) recessive, TT vs. CC/CT. When heterogeneity existed among different studies (P value of Q test < 0.10 and/or I 2 > 50%), pooled OR values were calculated using a random effect model, while a fixed effect model was used when heterogeneity analysis indicated P > 0.10 and/or I 2 < 50%. Publication bias was checked using Egger's test, and Begg's linear regression with funnel plots, and was considered present when P < 0.05, or the funnel plot was asymmetrical [24].

General characteristics of the included studies
The 11 articles included in the study involved 25,677 blood samples from 4582 patients with HCC and 21,095 non-HCC patients. The subjects included Chinese, Japanese, Egyptian, Swiss, Vietnamese, and Italian individuals infected with HCV or HBV. Quality scores were > 6, indicating that this meta-analysis included high quality studies. SNP data from the control groups of the 11 studies were consistent with HWE. The general characteristics of the included studies are presented in Table 2.

Meta-analysis
Our analyses demonstrated heterogeneity among the results generated using the five genetic models [I 2 > 50%, P (heterogeneity) < 0.10] (Table 3). Therefore, the results were pooled under a random effects model, and the results of the analysis showed that, under the recessive model, rs2569542 TT was a risk factor for the development of HBV/HCV-induced HCC. Individuals carrying   Fig. 2).

Publication bias
Publication bias was analyzed under the different genetic models, using Begg's test to plot funnel diagrams. Ten studies among the 11 included articles are presented in the plots, and their data points were scattered and distributed, with the pooled OR value at the center; that is, they basically formed a symmetrical, inverted funnel-shape (Fig. 3). Analysis using Egger's test demonstrated that all P values were > 0.05, suggesting no publication bias (Table 3).

Discussion
This study systematically evaluated the relationship between rs2596542, in the MICA gene promoter, and HCC susceptibility. The results suggest that HBV/HCV-infected individuals carrying the TT genotype at this locus are more likely to develop HCC than those carrying other genotypes, particularly if they are HCV-infected or of Asian ethnicity. This may be due to the persistent HBV/HCV infection associated with the TT genotype [27,31]. Further, infection with HBV/HCV can cause up-regulation of matrix metalloproteins, high levels of which lead to increased production of sMICA and decreased membrane-bound MICA tumor antigen protein [32,33]. These changes ultimately inhibit the anti-tumor effects of immune cells and facilitate the immune escape of HCC cells [10,12]. Compared with two previously published articles [24,34], this study explores the relationship between rs2596542 and susceptibility to HBV/HCV-induced HCC. Only studies In this study, a qualitative Begg's test plot and quantitative Egger's test analysis showed no significant publication bias, indicating that the combined results are reliable; however, the study had some limitations. First, the publications included in this study were limited to texts published in English, hence publication and cultural bias may still have affected the results of the meta-analysis. Second, the majority of genotype data in this study were derived from Chinese and Japanese individuals; this lack of genotype data from other ethnic groups reduces the wider applicability of our findings.

Conclusion
In summary, rs2596542 is a molecular marker for HCC, and HCV/HBV-infected individuals carrying the TT genotype of this SNP have higher genetic susceptibility to HCC than HCV/HBV-infected individuals carrying the CT/CC genotypes. In particular, among HCV-infected populations and Asians, individuals carrying the TT genotype are more likely to develop HCC than those carrying CC/CT genotypes. This study provides a theoretical basis for the personalized treatment of virus-infected individuals with HCC.