Quantitative assessment of the effect of epidermal growth factor 61A/G polymorphism on the risk of hepatocellular carcinoma
- Authors:
- Published online on: September 18, 2015 https://doi.org/10.3892/ol.2015.3723
- Pages: 3199-3205
Abstract
Introduction
Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and develops predominately in individuals with liver cirrhosis (1). Cirrhosis is the strongest known risk factor for HCC, particularly cirrhosis resulting from infection with hepatitis C virus (HCV) or hepatitis B virus (HBV) (2,3). Additionally, heavy alcohol consumption, diabetes, obesity and tobacco use have been considered to contribute to the local burden of HCC (4,5). However, only a small number of people exposed to these risk factors develop HCC, suggesting that other environmental and genetic factors may play a role in HCC development. For this reason, the pathogenesis of HCC has not been fully elucidated.
Additionally, numerous clinicians rely on serological α-fetoprotein testing and abdominal ultrasound imaging for HCC screening (6). However, these screening tools demonstrate low sensitivity and specificity (7–9) and the diagnoses of HCC are made late in the course of the disease. Therefore, early identification of molecular markers associated with an increased risk of HCC has been proposed as an alternative strategy for the diagnosis of HCC.
Epidermal growth factor (EGF) was first isolated in 1962 (10) and plays a critical role in liver tissue regeneration (11). In previous years, numerous studies have revealed that the EGF signaling pathway with the EGF 61A/G polymorphism (rs4444903), a commonly functional single-nucleotide polymorphism (SNP) in the 5′-untranslated region of the EGF gene, is associated with the risk of tumorigenesis in multiple human cancers (12–14). Studies have also reported that the EGF 61A/G polymorphism plays an important role in the occurrence of liver cancer. At present, there are three published meta-analyses that have investigated the association between the EGF 61A/G polymorphism and risk of cancer, including HCC (15–17). However, none of these studies searched a sufficient number of published studies and are not limited to HCC. Therefore, the studies are not conclusive in resolving the role of the EGF 61A/G polymorphism in HCC. Thus, the present meta-analysis was performed to address the association between the frequency of the EGF 61A/G polymorphism and the risk of HCC, and to complete an in-depth subgroup analysis of the study population characteristics.
Materials and methods
Inclusion criteria
The present meta-analysis was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (18). Studies that met all of the following criteria were included: (1) Use of a cohort or case-control design; (2) sufficient data for examining an odds ratio (OR), with its 95% confidence interval (CI); (3) assessment of the EGF 61A/G polymorphism and HCC risk; and (4) the diagnosis of HCC was confirmed histologically, pathologically or cytologically. The titles and abstracts of all relevant studies were evaluated, and case reports, editorials and reviews were excluded.
Search strategy
All cohort studies and case-control studies of the EGF 61A/G polymorphism and risk of HCC published prior to May 1, 2014 were identified through systematic searches in the PubMed (National Institutes of Health, Bethesda, MA, USA) and EMBASE (Elsevier, Amsterdam, Netherlands) databases, using the following search strategy: (‘epidermal growth factor’ or ‘EGF’) AND ‘polymorphism’ AND (‘hepatocellular carcinoma’ or ‘liver cancer’ or ‘HCC’). In addition, the reference lists of relevant publications were manually searched by two independent investigators.
Data extraction
For each study, the first author, year of publication, ethnicity of the population, type of control, number of patients and control individuals, genotyping method and Hardy Weinberg equilibrium (HWE) was extracted for the control group. The results were compared and discrepancies were resolved by consensus between two independent investigators.
Statistical analysis
The odds ratios (ORs) and relative 95% confidence intervals (CIs) were used to assess the strength of associations between the EGF 61A/G polymorphism and the risk of HCC by comparing five genetic models, which consisted of the G vs. A, AG vs. AA, GG vs. AA, GG vs. AG + AA, and AG + GG vs. AA models. Subgroup analysis was also performed based on the ethnicity and type of controls. Heterogeneity among the studies used was tested using the I2 test (19). I2<40% indicated an acceptable heterogeneity among the included studies in the present meta-analysis and the fix-effect model was used, otherwise the random-effect model was used.
The sensitivity analysis was conducted by omitting any single included study each turn. Publication bias was assessed by visual inspection of the funnel plots of the primary outcome and the Egger's test (20). The funnel plot was considered to be asymmetrical if the intercept of the Egger's regression line significantly deviated from zero, with a P-value of <0.05. HWE in the control group was assessed using Fisher's exact test, with P<0.05 considered to indicate a statistically significant difference. All statistical tests for the present meta-analysis were conducted using Comprehensive Meta-Analysis software, Version 2.2 (Biostat, Inc., Englewood, NJ, USA).
Results
Study selection and patient characteristics
The combined search yielded 132 studies, 123 of which were excluded as they clearly did not satisfy the inclusion criteria or were overlapping references (two or more publications from the same institute or duplicate publication using different languages). The publications by Zhong et al (15), Tanabe et al (21) and Yuan et al (22) all involved two independent case-control studies and were overall considered to be six single studies. Finally, a total of 12 studies (15,21–28) that examined the association between the EGF 61A/G polymorphism and the risk of HCC were included in the current meta-analysis (Fig. 1).
A database was created according to the information extracted from each study. The detailed characteristics of the included studies are summarized in Table I. Overall, 2,095 patients with HCC and 3,766 control individuals were retrieved. Seven of the studies enrolled Chinese individuals (15,22–26), three studies involved a mixed population, including Caucasian, Hispanic and Asian populations and individuals of African descent (21,22,27), one study enrolled only Caucasians (21) and one enrolled only Egyptian individuals (28). The genotype distributions in the controls for all studies were consistent with the HWE expectations.
Overall analysis
The evaluation of association between the EGF 61A/G polymorphism and the risk of HCC is reported in Table II. Calculation of overall ORs in the total population demonstrated that the EGF 61A/G polymorphism was associated with increased risk of HCC in the total population in the G vs. A (OR, 1.25; 95% CI, 1.11–1.40), GG vs. AA (OR, 1.53; 95% CI, 1.26–1.85), GG vs. AG + AA (OR, 1.34; 95% CI, 1.13–1.58) and GG + AG vs. AA (OR, 1.27; 95% CI, 1.08–1.49) models.
Subgroup analysis
The results were similar between the ethnicities, with the overall results in the Chinese population being similar to those of the other ethnicities. No significant association was observed between the EGF 61A/G polymorphism and HCC risk in the mixed population. When stratifying by source of controls, the EGF 61A/G polymorphism was associated with an increased risk of HCC in the control individuals with a liver disease. However, the meta-analysis revealed that there was no association between the EGF 61A/G polymorphism and the risk of HCC in healthy and mixed controls (Table II; Fig. 2).
Sensitivity analysis
For the sensitivity analysis, each study involved in the meta-analysis was omitted each time to reflect the influence of the individual dataset to the pooled ORs. The corresponding pooled ORs were not qualitatively altered, indicating that the present results were statistically robust (Fig. 3).
Publication bias
Funnel plot and Egger's test were performed to assess the publication bias of literature. The shape of the funnel plot (Fig. 4) appeared to be asymmetrical for the EGF 61A/G polymorphism in the genotype comparison of G vs. A, indicating the presence of publication bias. Therefore, Egger's test was performed to statistically assess the symmetry of the funnel plot. The result suggested that publication bias probably existed in the present study for the G vs. A (P=0.013), GG vs. AA (P=0.004), AG vs. AA (P=0.011), GG + AG vs. AA (P<0.001) and GG vs. AG + AA (P=0.051) genotypes.
Discussion
EGF has been hypothesized to promote hepatocyte transformation, and dysregulation of the EGF signaling pathway has been speculated to be important in early hepatocarcinogenesis (29,30). To the best of our knowledge, numerous previously published genetic studies have demonstrated a positive association between the EGF 61A/G polymorphism and risk of HCC, while other studies have found no notable evidence that this polymorphism increases the susceptibility to HCC. This encouraged the completion of the present meta-analysis. Meta-analysis is a method for combining relevant global studies to increase the statistical power and resolve the discrepancy issue of genetic association studies (31–34). In the present meta-analysis, a total of 12 case-control studies involving 2,095 patients and 3,766 control individuals were analyzed to provide a comprehensive assessment of the association between the EGF 61A/G polymorphism and HCC risk. The present results for the total population demonstrated that the EGF 61A/G polymorphism increased the risk of HCC. In addition, evaluation of heterogeneity was always conducted in statistical analysis. Thus, the subgroup meta-analyses were performed according to the ethnicity and source of the control individuals.
Subsequent to stratification by ethnicity, the present meta-analysis indicated that the A allele may reduce susceptibility to HCC in the Chinese population, but not in a mixed population. This finding in the mixed population is not in accordance with the results previously published by Zhong et al (15). In this previous meta-analysis, a significant association was indicated between the EGF 61A/G polymorphism and risk of HCC based on eight case-control studies. The considerably larger sample size of the present study may account for this difference. The frequency of the AA genotype varies extensively between different ethnicities, with a prevalence of 10% in those of Asian descent, ~30% in Caucasians, and 33% in those of African descent, suggesting a possible ethnicity-based difference. This may be the reason why no association with the EGF 61A/G polymorphism was detected among the mixed population. Although environmental factors may be the predominate factors in the development of HCC, the distribution of EGF genotypes in various ethnicities may also explain the increased prevalence of HCC in China (35).
In the stratified analysis by control source, the G allele was found to be significantly associated with an increased risk of HCC in the control individuals with liver diseases, consisting of HBV and HCV infection and cirrhosis. However, there was no significant association between the EGF 61A/G polymorphism and the risk of HCC among the healthy control individuals. The present findings suggest that the EGF 61A/G polymorphism may be a potential marker in the context of liver disease, consisting of HBV infection, HCV infection and cirrhosis, rather than a susceptibility gene polymorphism. The consideration of the history of relevant diseases was also a strength of the present meta-analysis compared with the previous meta-analyses performed on this topic.
There are also limitations to the present study. First, one of the major concerns is bias, due to selective publication. Evident publication bias was detected in the G vs. A, GG vs. AA, AG vs. AA, and GG + AG vs. AA genotype comparisons. Secondly, the Caucasian and Egyptian populations were assessed in only one study each, and therefore the results must be interpreted with caution. Thirdly, the majority of studies were performed using the Chinese population and additional studies are required using alternative ethnic groups. Finally, although the heterogeneity in the present study was not large, it was present in the genetic models. The subgroup analysis indicated that the heterogeneity may result from the mixed subgroup. Although heterogeneity is extremely common in meta-analyses of genetic association, this requires consideration.
In summary, the present meta-analysis suggests that the EGF 61A/G polymorphism is associated with an increased risk of HCC. Based on the evidence obtained in the present meta-analysis, the EGF 61A/G polymorphism was found to be a potential marker for HCC in the context of liver disease, such as HBV and HCV infection and liver cirrhosis. Considering the limited objectives of the present meta-analysis, additional studies should be conducted with larger sample sizes and more healthy control designs or prospective cohort designs.
Acknowledgements
The present study was supported by the Intramural Evidence-based Medicine Nursery Fund of Taihe Hospital (grant no., EBM2013035), funded by the Commonwealth Organization.
References
Jemal A, Bray F, Center MM, Ferlay J, Ward E and Forman D: Global cancer statistics. CA Cancer J Clin. 61:69–90. 2011. View Article : Google Scholar : PubMed/NCBI | |
Di Costanzo GG: Prospective analysis of risk factors for hepatocellular carcinoma on patients with cirrhosis. Hepatology. 38:10612003. View Article : Google Scholar : PubMed/NCBI | |
Thomas MB and Zhu AX: Hepatocellular carcinoma: the need for progress. J Clin Oncol. 23:2892–2899. 2005. View Article : Google Scholar : PubMed/NCBI | |
Caldwell SH, Crespo DM, Kang HS and Al-Osaimi AM: Obesity and hepatocellular carcinoma. Gastroenterology. 127(Suppl 1): S97–S103. 2004. View Article : Google Scholar : PubMed/NCBI | |
Yuan JM, Govindarajan S, Arakawa K and Yu MC: Synergism of alcohol, diabetes, and viral hepatitis on the risk of hepatocellular carcinoma in blacks and whites in the U.S. Cancer. 101:1009–1017. 2004. View Article : Google Scholar : PubMed/NCBI | |
El-Serag HB, Marrero JA, Rudolph L and Reddy KR: Diagnosis and treatment of hepatocellular carcinoma. Gastroenterology. 134:1752–1763. 2008. View Article : Google Scholar : PubMed/NCBI | |
Trevisani F, D'Intino PE, Morselli-Labate AM, et al: Serum alpha-fetoprotein for diagnosis of hepatocellular carcinoma in patients with chronic liver disease: Influence of HBsAg and anti-HCV status. J Hepatol. 34:570–575. 2001. View Article : Google Scholar : PubMed/NCBI | |
Bolondi L, Sofia S, Siringo S, et al: Surveillance programme of cirrhotic patients for early diagnosis and treatment of hepatocellular carcinoma: A cost effectiveness analysis. Gut. 48:251–259. 2001. View Article : Google Scholar : PubMed/NCBI | |
Kim CK, Lim JH and Lee WJ: Detection of hepatocellular carcinomas and dysplastic nodules in cirrhotic liver: accuracy of ultrasonography in transplant patients. J Ultrasound Med. 20:99–104. 2001.PubMed/NCBI | |
Cohen S: Isolation of a mouse submaxillary gland protein accelerating incisor eruption and eyelid opening in the new-born animal. J Biol Chem. 237:1555–1562. 1962.PubMed/NCBI | |
Michalopoulos GK and DeFrances MC: Liver regeneration. Science. 276:60–66. 1997. View Article : Google Scholar : PubMed/NCBI | |
Zhang YM, Cao C and Liang K: Genetic polymorphism of epidermal growth factor 61A>G and cancer risk: a meta-analysis. Cancer Epidemiol. 34:150–156. 2010. View Article : Google Scholar : PubMed/NCBI | |
Lanuti M, Liu G, Goodwin JM, et al: A functional epidermal growth factor (EGF) polymorphism, EGF serum levels and esophageal adenocarcinoma risk and outcome. Clin Cancer Res. 14:3216–3222. 2008. View Article : Google Scholar : PubMed/NCBI | |
Spindler KL, Nielsen JN, Ornskov D, Brandslund I and Jakobsen A: Epidermal growth factor (EGF) A61G polymorphism and EGF gene expression in normal colon tissue from patients with colorectal cancer. Acta Oncol. 46:1113–1117. 2007. View Article : Google Scholar : PubMed/NCBI | |
Zhong JH, You XM, Gong WF, et al: Epidermal growth factor gene polymorphism and risk of hepatocellular carcinoma: a meta-analysis. PLoS One. 7:e321592012. View Article : Google Scholar : PubMed/NCBI | |
Yang Z, Wu Q, Shi Y, Nie Y, Wu K and Fan D: Epidermal growth factor 61A>G polymorphism is associated with risk of hepatocellular carcinoma: A meta-analysis. Genet Test Mol Biomarkers. 16:1086–1091. 2012. View Article : Google Scholar : PubMed/NCBI | |
Li TF, Ren KW and Liu PF: Meta-analysis of epidermal growth factor polymorphisms and cancer risk: Involving 9,779 cases and 15,932 controls. DNA Cell Biol. 31:568–574. 2012. View Article : Google Scholar : PubMed/NCBI | |
Moher D, Liberati A, Tetzlaff J and Altman DG: PRISMA Group: Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement. Ann Intern Med. 151:264–269. 2009. View Article : Google Scholar : PubMed/NCBI | |
Coory MD: Comment on: Heterogeneity in meta-analysis should be expected and appropriately quantified. Int J Epidemiol. 39:932–933. 2010. View Article : Google Scholar : PubMed/NCBI | |
Egger M, Smith Davey G, Schneider M and Minder C: Bias in meta-analysis detected by a simple, graphical test. BMJ. 315:629–634. 1997. View Article : Google Scholar : PubMed/NCBI | |
Tanabe KK, Lemoine A, Finkelstein DM, et al: Epidermal growth factor gene functional polymorphism and the risk of hepatocellular carcinoma in patients with cirrhosis. JAMA. 299:53–60. 2008. View Article : Google Scholar : PubMed/NCBI | |
Yuan JM, Fan Y, Ognjanovic S, et al: Genetic polymorphisms of epidermal growth factor in relation to risk of hepatocellular carcinoma: two case-control studies. BMC Gastroenterol. 13:322013. View Article : Google Scholar : PubMed/NCBI | |
Wu J, Zhang W, Xu A, et al: Association of epidermal growth factor and epidermal growth factor receptor polymorphisms with the risk of hepatitis B virus-related hepatocellular carcinoma in the population of North China. Genet Test Mol Biomarkers. 17:595–600. 2013. View Article : Google Scholar : PubMed/NCBI | |
Qi P, Wang H, Chen YM, Sun XJ, Liu Y and Gao CF: No association of EGF 5′UTR variant A61G and hepatocellular carcinoma in Chinese patients with chronic hepatitis B virus infection. Pathology. 41:555–560. 2009. View Article : Google Scholar : PubMed/NCBI | |
Li Y, Xie Q, Lu F, et al: Association between epidermal growth factor 61A/G polymorphism and hepatocellular carcinoma susceptibility in Chinese patients. Liver Int. 30:112–118. 2010. View Article : Google Scholar : PubMed/NCBI | |
Chen K, Wei Y, Yang H and Li B: Epidermal growth factor +61 G/A polymorphism and the risk of hepatocellular carcinoma in a Chinese population. Genet Test Mol Biomarkers. 15:251–255. 2011. View Article : Google Scholar : PubMed/NCBI | |
Dayyeh Abu BK, Yang M, Fuchs BC, et al: A functional polymorphism in the epidermal growth factor gene is associated with risk for hepatocellular carcinoma. Gastroenterology. 141:141–149. 2011. View Article : Google Scholar : PubMed/NCBI | |
Abbas E, Shaker O, El Aziz Abd G, Ramadan H and Esmat G: Epidermal growth factor gene polymorphism 61A/G in patients with chronic liver disease for early detection of hepatocellular carcinoma: A pilot study. Eur J Gastroenterol Hepatol. 24:458–463. 2012.PubMed/NCBI | |
Borlak J, Meier T, Halter R, Spanel R and Spanel-Borowski K: Epidermal growth factor-induced hepatocellular carcinoma: Gene expression profiles in precursor lesions, early stage and solitary tumours. Oncogene. 24:1809–1819. 2005. View Article : Google Scholar : PubMed/NCBI | |
Kömüves LG, Feren A, Jones AL and Fodor E: Expression of epidermal growth factor and its receptor in cirrhotic liver disease. J Histochem Cytochem. 48:821–830. 2000. View Article : Google Scholar : PubMed/NCBI | |
Munafò MR and Flint J: Meta-analysis of genetic association studies. Trends Genet. 20:439–444. 2004. View Article : Google Scholar : PubMed/NCBI | |
Mao M, Zeng XT, Ma T, He W, Zhang C and Zhou J: Interleukin-1α-899 (+4845) C→T polymorphism increases the risk of chronic periodontitis: Evidence from a meta-analysis of 23 case-control studies. Gene. 532:114–119. 2013. View Article : Google Scholar : PubMed/NCBI | |
Leng WD, He MN, Chen QL, Gong H, Zhang L and Zeng XT: Vascular endothelial growth factor (VEGF) gene polymorphisms and risk of head and neck cancer: a meta-analysis involving 2,444 individuals. Mol Biol Rep. 40:5987–5992. 2013. View Article : Google Scholar : PubMed/NCBI | |
Zeng X, Zhang Y, Kwong JS, et al: The methodological quality assessment tools for preclinical and clinical studies, systematic review and meta-analysis, and clinical practice guideline: A systematic review. J Evid Based Med. 8:2–10. 2015. View Article : Google Scholar : PubMed/NCBI | |
Parkin DM: Global cancer statistics in the year 2000. Lancet Oncol. 2:533–543. 2001. View Article : Google Scholar : PubMed/NCBI |