Tumor Biol. DOI 10.1007/s13277-013-1529-x
RESEARCH ARTICLE
Associations between methylenetetrahydrofolate reductase polymorphisms and hepatocellular carcinoma risk in Chinese population Xiaosheng Qi & Xing Sun & Junming Xu & Zhaowen Wang & Jinyan Zhang & Zhihai Peng
Received: 29 July 2013 / Accepted: 21 August 2013 # International Society of Oncology and BioMarkers (ISOBM) 2014
Abstract Genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are considered to have some influence on both folate metabolism and cancer risk. Previous studies on the associations of MTHFR genetic polymorphisms with hepatocellular carcinoma (HCC) risk in Chinese population reported inconsistent results. We performed this metaanalysis to comprehensively assess the associations. Finally, 12 individual case–control studies were included into the metaanalysis. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism and five studies (4,502 subjects) on the MTHFR A1298C polymorphism. Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population (T versus C, odds ratio (OR)=1.09, 95 % confidence interval (95 % CI) 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/ CT versus CC, OR=1.12, 95 % CI 1.00–1.26). MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR=0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90). The sensitivity analysis confirmed the reliability and stability of the meta-analysis. Thus, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. Keywords MTHFR . Hepatocellular carcinoma . Association
worldwide [1]. However, HCC is the fourth most prevalent cancer and the second most frequent cause of cancer-related death in China [2, 3]. Previously, epidemiological studies have suggested that low folate and viral hepatitis are associated with an increased risk of cancer, including HCC [1, 3, 4]. Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in the folate metabolism, and MTHFR can catalyze 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate which is the predominant circulating form of folate [5, 6]. In addition, MTHFR also plays an important role in the folate metabolism by directing folate metabolites through the DNA methylation pathway [5, 7]. There are two common functional polymorphisms identified in the MTHFR gene, including MTHFR C677T polymorphism and A1298C polymorphism [5, 7]. Previous studies have suggested that MTHFR C677T polymorphism and A1298C polymorphism are both associated with changes of plasma folate levels and the MTHFR activity [5, 7, 8]. Genetic polymorphisms of MTHFR gene are considered to have an important influence on the host's susceptibility to common cancers, including HCC [9, 10]. However, previous studies on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population reported inconsistent results [11–16]. We performed this meta-analysis to comprehensively assess the associations.
Methods Introduction Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the third most frequent cause of cancer-related death X. Qi : X. Sun : J. Xu : Z. Wang : J. Zhang : Z. Peng (*) Department of General Surgery, The First People’s Hospital of Shanghai, Shanghai 200080, China e-mail: [email protected]
Literature search A computerized literature search was carried out in PubMed, Chinese National Knowledge Infrastructure, and Wanfang databases to collect eligible publication on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population. The PubMed search was run using the following
Tumor Biol.
keywords: (“hepatocellular carcinoma” or “HCC”) and (“mthfr” or “methylenetetrahydrofolate reductase”). Inclusion criteria The following inclusion criteria were used to include eligible studies: (1) case–control with the distributions of MTHFR genetic polymorphisms in both cases and controls, (2) all participants were Chinese, and (3) the distribution of the genotypes in control groups was in the Hardy–Weinberg equilibrium (HWE). When there were multiple publications from the same population, only the latest or the largest study was included. Abstracts, case reports, editorials, and reviews were all excluded. Data extraction Data were independently extracted by two reviewers using a standardized data extraction form, and discrepancies were resolved by discussion. The following information was collected from each study: the first author, year of publication, study design, sample size, geographical location, definition and numbers of cases and controls, and the distributions of MTHFR genetic polymorphisms in both cases and controls. Statistical analysis We calculated the odds ratio (OR) and 95 % confidence interval (95 % CI) to assess the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population. Chi-square test was used for the test of HWE of genotypes in control group of each included study. Statistical heterogeneity among studies was assessed with both the Q and I 2 statistics [17, 18]. Dependent on the results of heterogeneity test among individual studies, the fixed effect model (Mantel–Haenszel) or random effect model (DerSimonian and Laird) was selected Table 1 Summary of the metaanalysis of the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population
Genetic models
MTHFR C677T T versus C TT versus CC TT versus CC/CT
I 2 inconsistency
TT/CT versus CC MTHFR A1298C C versus A CC versus AA CC versus AA/AC CC/AC versus AA
Participants
to calculate the pooled OR [19, 20]. The significance of the pooled OR was determined by the Z test. Publication bias was investigated with the funnel plot, in which the standard error of log OR of each study was plotted against its OR. Funnel plot's asymmetry was further assessed by the method of Egger's linear regression test [21]. Analyses were performed using the software Stata version 11.0 (StataCorp LP, College Station, TX, USA). All the P values were two-sided, and a P value less than 0.05 was considered statistically significant.
Results Study selection and characteristics We preliminarily identified 31 articles through the literature search. However, after screening of the titles and abstracts of all 31 articles, 24 were excluded, and 7 publications were finally included into the meta-analysis [11–16, 22]. Among those seven studies, five were on the associations of both MTHFR C677T polymorphism and A1298C with HCC risk [11–16, 22]. Thus, 12 individual case–control studies were included into the meta-analysis [11–16, 22]. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism [11–16, 22] and five studies (4,502 subjects) on the MTHFR A1298C polymorphism [12–14, 16, 22]. The distribution of the genotypes of both MTHFR C677T polymorphism and A1298C in control groups was all in the HWE [11–16, 22]. There were four studies published in English [12, 13, 15, 16], and three studies were published in Chinese [11, 14, 22]. MTHFR C677T and HCC risk Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population
OR (95 % CI)
Significance
Test for heterogeneity
Z
P value
I 2 (%)
P value
6,834 6,834 6,834
1.09 (1.01–1.17) 1.17 (1.00–1.38) 1.10 (0.96–1.26)
2.11 1.94 1.38
0.03 0.05 0.17
0.0 0.0 0.0
0.71 0.82 0.92
6,834
1.12 (1.00–1.26)
1.99
0.04
23.9
0.25
4,502 4,502 4,502 4,502
0.96 (0.86–1.07) 0.65 (0.46–0.91) 0.64 (0.46–0.90) 1.01 (0.89–1.15)
0.78 2.50 2.59 0.12
0.43 0.01 0.01 0.90
0.0 43.9 49.7 0.0
0.86 0.13 0.09 0.99
Tumor Biol.
Publication bias
(T versus C, odds ratio (OR)=1.09, 95 % CI 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/CT versus CC, OR=1.12, 95 % CI 1.00–1.26) (Table 1, Fig. 1). The sensitivity analysis confirmed the reliability and stability of the meta-analysis.
Publication bias was investigated with the funnel plot and Egger's linear regression test. In the meta-analysis of the association between MTHFR C677T polymorphism and HCC risk, there was no obvious asymmetry in the funnel plot, and the P values for Egger's test were more than 0.05 (Fig. 3). Thus, there was low risk of publication bias in the meta-analysis.
MTHFR A1298C and HCC risk MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR= 0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90) (Table 1, Fig. 2). The sensitivity analysis confirmed the reliability and stability of the meta-analysis.
Fig. 1 Meta-analysis of the association between MTHFR C677T polymorphism and HCC risk in Chinese population. a T versus C. b TT/CT versus CC
Discussion MTHFR is a key regulatory enzyme in the folate metabolism, and MTHFR can catalyze 5,10-methylenetetrahydrofolate to
a %
Study ID
OR (95% CI)
Weight
Zhu ZZ 2006
1.02 (0.86, 1.21)
20.04
Mu LN 2007
1.22 (0.95, 1.56)
8.96
Yuan JM 2007
0.95 (0.70, 1.28)
6.77
Liu J 2010
1.05 (0.83, 1.33)
10.62
Yang H 2007
0.98 (0.69, 1.38)
5.15
Cui LH 2012
1.20 (1.00, 1.45)
15.89
An Y 2008
1.09 (0.95, 1.24)
32.57
Overall (I-squared = 0.0%, p = 0.713)
1.09 (1.01, 1.17)
100.00
.642
1
1.56
b %
Study ID
OR (95% CI)
Weight
Zhu ZZ 2006
0.91 (0.71, 1.18)
21.78
Mu LN 2007
1.52 (1.04, 2.23)
7.87
Yuan JM 2007
0.94 (0.65, 1.35)
10.63
Liu J 2010
1.07 (0.72, 1.60)
8.40
Yang H 2007
0.99 (0.66, 1.47)
8.77
Cui LH 2012
1.36 (0.95, 1.94)
9.75
An Y 2008
1.21 (0.99, 1.47)
32.80
Overall (I-squared = 23.9%, p = 0.247)
1.12 (1.00, 1.26)
100.00
.449
1
2.23
Tumor Biol. Fig. 2 Meta-analysis of the association between MTHFR A1298C polymorphism and HCC risk in Chinese population. a CC versus AA. b CC versus AA/AC
a Study
%
ID
OR (95% CI)
Weight
Mu LN 2007
1.16 (0.33, 4.05)
5.29
Yuan JM 2007
0.48 (0.22, 1.05)
22.22
Yang H 2007
1.14 (0.60, 2.19)
20.26
Cui LH 2012
0.26 (0.09, 0.76)
21.89
An Y 2008
0.62 (0.33, 1.18)
30.34
Overall (I-squared = 43.9%, p = 0.129)
0.65 (0.46, 0.91)
100.00
.0916
1
10.9
b %
Study
ID
OR (95% CI)
Weight
Mu LN 2007
1.16 (0.34, 4.02)
5.12
Yuan JM 2007
0.46 (0.21, 0.99)
22.74
Yang H 2007
1.17 (0.62, 2.19)
20.70
Cui LH 2012
0.26 (0.09, 0.74)
21.56
An Y 2008
0.61 (0.32, 1.15)
29.89
Overall (I-squared = 49.7%, p = 0.093)
0.64 (0.46, 0.90)
100.00
.0897
5-methyltetrahydrofolate which is the predominant circulating form of folate [5, 6]. In addition, MTHFR also plays an important role in the folate metabolism by directing folate metabolites through the DNA methylation pathway [5, 7]. There are two common functional polymorphisms identified in the MTHFR gene, including MTHFR C677T polymorphism and A1298C polymorphism [5, 7]. Previous studies have suggested that MTHFR C677T polymorphism and A1298C polymorphism are both associated with changes of plasma folate levels and the MTHFR activity [5, 7, 8]. Thus, genetic polymorphisms of MTHFR gene are considered to have some influence on both folate metabolism and cancer risk [23, 24]. Currently, MTHFR C677T polymorphism has been suggested to be associated with risks of many cancers, such as
1
11.1
colorectal cancer, breast cancer, and cervical cancer [23–25]. However, previous studies failed to identify the associations of MTHFR A1298C polymorphism with the several cancers above [23–25]. There are also a number of studies on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population, but they reported inconsistent results [11–16, 22]. We performed this meta-analysis to comprehensively assess the associations. Finally, 12 individual case–control studies were included into the meta-analysis. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism and five studies (4,502 subjects) on the MTHFR A1298C polymorphism [11–16, 22]. Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population (T versus C, OR=
Tumor Biol.
a
Begg's funnel plot with pseudo 95% confidence limits 1.4
1.2
OR
Fig. 3 Funnel plots in the metaanalysis of the associations between MTHFR polymorphisms and HCC risk. a T versus C for MTHFR C677T polymorphism (P Egger's test =0.62). b C versus A for MTHFR A1298C polymorphism (P Egger's test =0.83)
1
.8
.6 0
.1 s.e. of: OR
.2
b Begg's funnel plot with pseudo 95% confidence limits 1.4
OR
1.2
1
.8
.6 0
1.09, 95 % CI 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/CT versus CC, OR=1.12, 95 % CI 1.00–1.26) (Table 1). Interestingly, MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR=0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90) (Table 1). Thus, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. Nevertheless, there are several limitations to this metaanalysis. Firstly, observational studies are susceptible to various biases because of their retrospective nature. Therefore, recall bias could invalidate the results from this meta-analysis. Secondly, the choice of control participants in those case– control studies may distort the results because hospital-based
.1 s.e. of: OR
.2
controls may not be as representative as population-based controls. More studies with population-based controls are needed. Thirdly, there are possible interactions between MTHFR C677T polymorphism and A1298C polymorphism in their effects on HCC risk. However, we did not perform analysis on the possible interactions owing to the lack of usable data from the included studies. Future studies are needed to further study on the possible interactions between MTHFR C677T polymorphism and A1298C polymorphism in their effects on HCC risk. In conclusion, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. MTHFR C677T polymorphism is significantly associated with susceptibility to HCC in Chinese population, while MTHFR
Tumor Biol.
A1298C polymorphism is conversely associated with HCC risk.
Conflicts of interest None.
References 1. Forner A, Llovet JM, Bruix J. Hepatocellular carcinoma. Lancet. 2012;379:1245–55. 2. Bridges JF, Joy SM, Gallego G, Kudo M, Ye SL, Han KH, et al. Needs for hepatocellular carcinoma control policy in the Asia-Pacific region. Asian Pac J Cancer Prev. 2011;12:2585–91. 3. El-Serag HB. Epidemiology of viral hepatitis and hepatocellular carcinoma. Gastroenterology. 2012;142:1264–1273e1. 4. Yu MC, Yuan JM, Lu SC. Alcohol, cofactors and the genetics of hepatocellular carcinoma. J Gastroenterol Hepatol. 2008;23 Suppl 1: S92–97. 5. Fodinger M, Horl WH, Sunder-Plassmann G. Molecular biology of 5,10-methylenetetrahydrofolate reductase. J Nephrol. 2000;13:20–33. 6. Dong LM, Potter JD, White E, Ulrich CM, Cardon LR, Peters U. Genetic susceptibility to cancer: the role of polymorphisms in candidate genes. JAMA. 2008;299:2423–36. 7. Schneider JA, Rees DC, Liu YT, Clegg JB. Worldwide distribution of a common methylenetetrahydrofolate reductase mutation. Am J Hum Genet. 1998;62:1258–60. 8. Goyette P, Sumner JS, Milos R, Duncan AM, Rosenblatt DS, Matthews RG, et al. Human methylenetetrahydrofolate reductase: isolation of cDNA, mapping and mutation identification. Nat Genet. 1994;7:195–200. 9. Kim YI. Role of the MTHFR polymorphisms in cancer risk modification and treatment. Future Oncol. 2009;5:523–42. 10. Izmirli M. A literature review of MTHFR (C677T and A1298C polymorphisms) and cancer risk. Mol Biol Rep. 2013;40:625–37. 11. Zhu ZZ, Cong WM, Liu SF, Xian ZH. Wu WQ: [A study on the association of MTHFR c677T polymorphism with genetic susceptibility to hepatocellular carcinoma]. Zhonghua Gan Zang Bing Za Zhi. 2006;14:196–8.
12. Mu LN, Cao W, Zhang ZF, Cai L, Jiang QW, You NC, et al. Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and the risk of primary hepatocellular carcinoma (HCC) in a Chinese population. Cancer Causes Control. 2007;18:665–75. 13. Yuan JM, Lu SC, Van Den Berg D, Govindarajan S, Zhang ZQ, Mato JM, et al. Genetic polymorphisms in the methylenetetrahydrofolate reductase and thymidylate synthase genes and risk of hepatocellular carcinoma. Hepatology. 2007;46:749–58. 14. An Y, Jin L, Chen J. Folate metabolic network gene polymorphism and primary liver cancer genetic susceptibility. Wanfang Doctoral Dissertation. 2008;2008:2008. 15. Liu J, Gao Y, Du Z, Yang B, Jing X, Wang Y. Relationship between the MTHFR C677T polymorphism and the outcome of hepatitis B virus infection. World Chinese Journal of Digestology. 2010;18: 1555–62. 16. Cui LH, Song Y, Si H, Shen F, Shin MH, Kim HN, et al. Folate metabolism-related gene polymorphisms and susceptibility to primary liver cancer in North China. Med Oncol. 2012;29:1837–42. 17. Cochran WG. The combination of estimates from different experiments. Biometrics. 1954;10:101–29. 18. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ. 2003;327:557–60. 19. Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst. 1959;22:719–48. 20. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986;7:177–88. 21. Egger M, Davey Smith G, Schneider M, Minder C. Bias in metaanalysis detected by a simple, graphical test. BMJ. 1997;315:629–34. 22. Yang H, He F, Zhou G. Genetic association studies on candidate genes for chronic hepatitis B, liver and nasopharyngeal cancers. Wanfang Doctoral Dissertation. 2007;2007:2007. 23. Yu L, Chen J. Association of MTHFR Ala222Val (rs1801133) polymorphism and breast cancer susceptibility: an update meta-analysis based on 51 research studies. Diagn Pathol. 2012;7:171. 24. Zhong S, Yang JH, Liu K, Jiao BH, Chang ZJ. Quantitative assessment of the association between MTHFR C677T polymorphism and colorectal cancer risk in East Asians. Tumour Biol. 2012;33:2041– 51. 25. Mei Q, Zhou D, Gao J, Shen S, Wu J, Guo L, et al. The association between MTHFR 677C>T polymorphism and cervical cancer: evidence from a meta-analysis. BMC Cancer. 2012;12:467.
RESEARCH ARTICLE
Associations between methylenetetrahydrofolate reductase polymorphisms and hepatocellular carcinoma risk in Chinese population Xiaosheng Qi & Xing Sun & Junming Xu & Zhaowen Wang & Jinyan Zhang & Zhihai Peng
Received: 29 July 2013 / Accepted: 21 August 2013 # International Society of Oncology and BioMarkers (ISOBM) 2014
Abstract Genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are considered to have some influence on both folate metabolism and cancer risk. Previous studies on the associations of MTHFR genetic polymorphisms with hepatocellular carcinoma (HCC) risk in Chinese population reported inconsistent results. We performed this metaanalysis to comprehensively assess the associations. Finally, 12 individual case–control studies were included into the metaanalysis. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism and five studies (4,502 subjects) on the MTHFR A1298C polymorphism. Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population (T versus C, odds ratio (OR)=1.09, 95 % confidence interval (95 % CI) 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/ CT versus CC, OR=1.12, 95 % CI 1.00–1.26). MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR=0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90). The sensitivity analysis confirmed the reliability and stability of the meta-analysis. Thus, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. Keywords MTHFR . Hepatocellular carcinoma . Association
worldwide [1]. However, HCC is the fourth most prevalent cancer and the second most frequent cause of cancer-related death in China [2, 3]. Previously, epidemiological studies have suggested that low folate and viral hepatitis are associated with an increased risk of cancer, including HCC [1, 3, 4]. Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in the folate metabolism, and MTHFR can catalyze 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate which is the predominant circulating form of folate [5, 6]. In addition, MTHFR also plays an important role in the folate metabolism by directing folate metabolites through the DNA methylation pathway [5, 7]. There are two common functional polymorphisms identified in the MTHFR gene, including MTHFR C677T polymorphism and A1298C polymorphism [5, 7]. Previous studies have suggested that MTHFR C677T polymorphism and A1298C polymorphism are both associated with changes of plasma folate levels and the MTHFR activity [5, 7, 8]. Genetic polymorphisms of MTHFR gene are considered to have an important influence on the host's susceptibility to common cancers, including HCC [9, 10]. However, previous studies on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population reported inconsistent results [11–16]. We performed this meta-analysis to comprehensively assess the associations.
Methods Introduction Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the third most frequent cause of cancer-related death X. Qi : X. Sun : J. Xu : Z. Wang : J. Zhang : Z. Peng (*) Department of General Surgery, The First People’s Hospital of Shanghai, Shanghai 200080, China e-mail: [email protected]
Literature search A computerized literature search was carried out in PubMed, Chinese National Knowledge Infrastructure, and Wanfang databases to collect eligible publication on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population. The PubMed search was run using the following
Tumor Biol.
keywords: (“hepatocellular carcinoma” or “HCC”) and (“mthfr” or “methylenetetrahydrofolate reductase”). Inclusion criteria The following inclusion criteria were used to include eligible studies: (1) case–control with the distributions of MTHFR genetic polymorphisms in both cases and controls, (2) all participants were Chinese, and (3) the distribution of the genotypes in control groups was in the Hardy–Weinberg equilibrium (HWE). When there were multiple publications from the same population, only the latest or the largest study was included. Abstracts, case reports, editorials, and reviews were all excluded. Data extraction Data were independently extracted by two reviewers using a standardized data extraction form, and discrepancies were resolved by discussion. The following information was collected from each study: the first author, year of publication, study design, sample size, geographical location, definition and numbers of cases and controls, and the distributions of MTHFR genetic polymorphisms in both cases and controls. Statistical analysis We calculated the odds ratio (OR) and 95 % confidence interval (95 % CI) to assess the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population. Chi-square test was used for the test of HWE of genotypes in control group of each included study. Statistical heterogeneity among studies was assessed with both the Q and I 2 statistics [17, 18]. Dependent on the results of heterogeneity test among individual studies, the fixed effect model (Mantel–Haenszel) or random effect model (DerSimonian and Laird) was selected Table 1 Summary of the metaanalysis of the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population
Genetic models
MTHFR C677T T versus C TT versus CC TT versus CC/CT
I 2 inconsistency
TT/CT versus CC MTHFR A1298C C versus A CC versus AA CC versus AA/AC CC/AC versus AA
Participants
to calculate the pooled OR [19, 20]. The significance of the pooled OR was determined by the Z test. Publication bias was investigated with the funnel plot, in which the standard error of log OR of each study was plotted against its OR. Funnel plot's asymmetry was further assessed by the method of Egger's linear regression test [21]. Analyses were performed using the software Stata version 11.0 (StataCorp LP, College Station, TX, USA). All the P values were two-sided, and a P value less than 0.05 was considered statistically significant.
Results Study selection and characteristics We preliminarily identified 31 articles through the literature search. However, after screening of the titles and abstracts of all 31 articles, 24 were excluded, and 7 publications were finally included into the meta-analysis [11–16, 22]. Among those seven studies, five were on the associations of both MTHFR C677T polymorphism and A1298C with HCC risk [11–16, 22]. Thus, 12 individual case–control studies were included into the meta-analysis [11–16, 22]. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism [11–16, 22] and five studies (4,502 subjects) on the MTHFR A1298C polymorphism [12–14, 16, 22]. The distribution of the genotypes of both MTHFR C677T polymorphism and A1298C in control groups was all in the HWE [11–16, 22]. There were four studies published in English [12, 13, 15, 16], and three studies were published in Chinese [11, 14, 22]. MTHFR C677T and HCC risk Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population
OR (95 % CI)
Significance
Test for heterogeneity
Z
P value
I 2 (%)
P value
6,834 6,834 6,834
1.09 (1.01–1.17) 1.17 (1.00–1.38) 1.10 (0.96–1.26)
2.11 1.94 1.38
0.03 0.05 0.17
0.0 0.0 0.0
0.71 0.82 0.92
6,834
1.12 (1.00–1.26)
1.99
0.04
23.9
0.25
4,502 4,502 4,502 4,502
0.96 (0.86–1.07) 0.65 (0.46–0.91) 0.64 (0.46–0.90) 1.01 (0.89–1.15)
0.78 2.50 2.59 0.12
0.43 0.01 0.01 0.90
0.0 43.9 49.7 0.0
0.86 0.13 0.09 0.99
Tumor Biol.
Publication bias
(T versus C, odds ratio (OR)=1.09, 95 % CI 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/CT versus CC, OR=1.12, 95 % CI 1.00–1.26) (Table 1, Fig. 1). The sensitivity analysis confirmed the reliability and stability of the meta-analysis.
Publication bias was investigated with the funnel plot and Egger's linear regression test. In the meta-analysis of the association between MTHFR C677T polymorphism and HCC risk, there was no obvious asymmetry in the funnel plot, and the P values for Egger's test were more than 0.05 (Fig. 3). Thus, there was low risk of publication bias in the meta-analysis.
MTHFR A1298C and HCC risk MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR= 0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90) (Table 1, Fig. 2). The sensitivity analysis confirmed the reliability and stability of the meta-analysis.
Fig. 1 Meta-analysis of the association between MTHFR C677T polymorphism and HCC risk in Chinese population. a T versus C. b TT/CT versus CC
Discussion MTHFR is a key regulatory enzyme in the folate metabolism, and MTHFR can catalyze 5,10-methylenetetrahydrofolate to
a %
Study ID
OR (95% CI)
Weight
Zhu ZZ 2006
1.02 (0.86, 1.21)
20.04
Mu LN 2007
1.22 (0.95, 1.56)
8.96
Yuan JM 2007
0.95 (0.70, 1.28)
6.77
Liu J 2010
1.05 (0.83, 1.33)
10.62
Yang H 2007
0.98 (0.69, 1.38)
5.15
Cui LH 2012
1.20 (1.00, 1.45)
15.89
An Y 2008
1.09 (0.95, 1.24)
32.57
Overall (I-squared = 0.0%, p = 0.713)
1.09 (1.01, 1.17)
100.00
.642
1
1.56
b %
Study ID
OR (95% CI)
Weight
Zhu ZZ 2006
0.91 (0.71, 1.18)
21.78
Mu LN 2007
1.52 (1.04, 2.23)
7.87
Yuan JM 2007
0.94 (0.65, 1.35)
10.63
Liu J 2010
1.07 (0.72, 1.60)
8.40
Yang H 2007
0.99 (0.66, 1.47)
8.77
Cui LH 2012
1.36 (0.95, 1.94)
9.75
An Y 2008
1.21 (0.99, 1.47)
32.80
Overall (I-squared = 23.9%, p = 0.247)
1.12 (1.00, 1.26)
100.00
.449
1
2.23
Tumor Biol. Fig. 2 Meta-analysis of the association between MTHFR A1298C polymorphism and HCC risk in Chinese population. a CC versus AA. b CC versus AA/AC
a Study
%
ID
OR (95% CI)
Weight
Mu LN 2007
1.16 (0.33, 4.05)
5.29
Yuan JM 2007
0.48 (0.22, 1.05)
22.22
Yang H 2007
1.14 (0.60, 2.19)
20.26
Cui LH 2012
0.26 (0.09, 0.76)
21.89
An Y 2008
0.62 (0.33, 1.18)
30.34
Overall (I-squared = 43.9%, p = 0.129)
0.65 (0.46, 0.91)
100.00
.0916
1
10.9
b %
Study
ID
OR (95% CI)
Weight
Mu LN 2007
1.16 (0.34, 4.02)
5.12
Yuan JM 2007
0.46 (0.21, 0.99)
22.74
Yang H 2007
1.17 (0.62, 2.19)
20.70
Cui LH 2012
0.26 (0.09, 0.74)
21.56
An Y 2008
0.61 (0.32, 1.15)
29.89
Overall (I-squared = 49.7%, p = 0.093)
0.64 (0.46, 0.90)
100.00
.0897
5-methyltetrahydrofolate which is the predominant circulating form of folate [5, 6]. In addition, MTHFR also plays an important role in the folate metabolism by directing folate metabolites through the DNA methylation pathway [5, 7]. There are two common functional polymorphisms identified in the MTHFR gene, including MTHFR C677T polymorphism and A1298C polymorphism [5, 7]. Previous studies have suggested that MTHFR C677T polymorphism and A1298C polymorphism are both associated with changes of plasma folate levels and the MTHFR activity [5, 7, 8]. Thus, genetic polymorphisms of MTHFR gene are considered to have some influence on both folate metabolism and cancer risk [23, 24]. Currently, MTHFR C677T polymorphism has been suggested to be associated with risks of many cancers, such as
1
11.1
colorectal cancer, breast cancer, and cervical cancer [23–25]. However, previous studies failed to identify the associations of MTHFR A1298C polymorphism with the several cancers above [23–25]. There are also a number of studies on the associations of MTHFR genetic polymorphisms with HCC risk in Chinese population, but they reported inconsistent results [11–16, 22]. We performed this meta-analysis to comprehensively assess the associations. Finally, 12 individual case–control studies were included into the meta-analysis. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism and five studies (4,502 subjects) on the MTHFR A1298C polymorphism [11–16, 22]. Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population (T versus C, OR=
Tumor Biol.
a
Begg's funnel plot with pseudo 95% confidence limits 1.4
1.2
OR
Fig. 3 Funnel plots in the metaanalysis of the associations between MTHFR polymorphisms and HCC risk. a T versus C for MTHFR C677T polymorphism (P Egger's test =0.62). b C versus A for MTHFR A1298C polymorphism (P Egger's test =0.83)
1
.8
.6 0
.1 s.e. of: OR
.2
b Begg's funnel plot with pseudo 95% confidence limits 1.4
OR
1.2
1
.8
.6 0
1.09, 95 % CI 1.01–1.17; TT versus CC, OR=1.17, 95 % CI 1.00–1.38; TT/CT versus CC, OR=1.12, 95 % CI 1.00–1.26) (Table 1). Interestingly, MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR=0.65, 95 % CI 0.46–0.91; CC versus AA/AC, OR=0.64, 95 % CI 0.46–0.90) (Table 1). Thus, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. Nevertheless, there are several limitations to this metaanalysis. Firstly, observational studies are susceptible to various biases because of their retrospective nature. Therefore, recall bias could invalidate the results from this meta-analysis. Secondly, the choice of control participants in those case– control studies may distort the results because hospital-based
.1 s.e. of: OR
.2
controls may not be as representative as population-based controls. More studies with population-based controls are needed. Thirdly, there are possible interactions between MTHFR C677T polymorphism and A1298C polymorphism in their effects on HCC risk. However, we did not perform analysis on the possible interactions owing to the lack of usable data from the included studies. Future studies are needed to further study on the possible interactions between MTHFR C677T polymorphism and A1298C polymorphism in their effects on HCC risk. In conclusion, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population. MTHFR C677T polymorphism is significantly associated with susceptibility to HCC in Chinese population, while MTHFR
Tumor Biol.
A1298C polymorphism is conversely associated with HCC risk.
Conflicts of interest None.
References 1. Forner A, Llovet JM, Bruix J. Hepatocellular carcinoma. Lancet. 2012;379:1245–55. 2. Bridges JF, Joy SM, Gallego G, Kudo M, Ye SL, Han KH, et al. Needs for hepatocellular carcinoma control policy in the Asia-Pacific region. Asian Pac J Cancer Prev. 2011;12:2585–91. 3. El-Serag HB. Epidemiology of viral hepatitis and hepatocellular carcinoma. Gastroenterology. 2012;142:1264–1273e1. 4. Yu MC, Yuan JM, Lu SC. Alcohol, cofactors and the genetics of hepatocellular carcinoma. J Gastroenterol Hepatol. 2008;23 Suppl 1: S92–97. 5. Fodinger M, Horl WH, Sunder-Plassmann G. Molecular biology of 5,10-methylenetetrahydrofolate reductase. J Nephrol. 2000;13:20–33. 6. Dong LM, Potter JD, White E, Ulrich CM, Cardon LR, Peters U. Genetic susceptibility to cancer: the role of polymorphisms in candidate genes. JAMA. 2008;299:2423–36. 7. Schneider JA, Rees DC, Liu YT, Clegg JB. Worldwide distribution of a common methylenetetrahydrofolate reductase mutation. Am J Hum Genet. 1998;62:1258–60. 8. Goyette P, Sumner JS, Milos R, Duncan AM, Rosenblatt DS, Matthews RG, et al. Human methylenetetrahydrofolate reductase: isolation of cDNA, mapping and mutation identification. Nat Genet. 1994;7:195–200. 9. Kim YI. Role of the MTHFR polymorphisms in cancer risk modification and treatment. Future Oncol. 2009;5:523–42. 10. Izmirli M. A literature review of MTHFR (C677T and A1298C polymorphisms) and cancer risk. Mol Biol Rep. 2013;40:625–37. 11. Zhu ZZ, Cong WM, Liu SF, Xian ZH. Wu WQ: [A study on the association of MTHFR c677T polymorphism with genetic susceptibility to hepatocellular carcinoma]. Zhonghua Gan Zang Bing Za Zhi. 2006;14:196–8.
12. Mu LN, Cao W, Zhang ZF, Cai L, Jiang QW, You NC, et al. Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and the risk of primary hepatocellular carcinoma (HCC) in a Chinese population. Cancer Causes Control. 2007;18:665–75. 13. Yuan JM, Lu SC, Van Den Berg D, Govindarajan S, Zhang ZQ, Mato JM, et al. Genetic polymorphisms in the methylenetetrahydrofolate reductase and thymidylate synthase genes and risk of hepatocellular carcinoma. Hepatology. 2007;46:749–58. 14. An Y, Jin L, Chen J. Folate metabolic network gene polymorphism and primary liver cancer genetic susceptibility. Wanfang Doctoral Dissertation. 2008;2008:2008. 15. Liu J, Gao Y, Du Z, Yang B, Jing X, Wang Y. Relationship between the MTHFR C677T polymorphism and the outcome of hepatitis B virus infection. World Chinese Journal of Digestology. 2010;18: 1555–62. 16. Cui LH, Song Y, Si H, Shen F, Shin MH, Kim HN, et al. Folate metabolism-related gene polymorphisms and susceptibility to primary liver cancer in North China. Med Oncol. 2012;29:1837–42. 17. Cochran WG. The combination of estimates from different experiments. Biometrics. 1954;10:101–29. 18. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ. 2003;327:557–60. 19. Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst. 1959;22:719–48. 20. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986;7:177–88. 21. Egger M, Davey Smith G, Schneider M, Minder C. Bias in metaanalysis detected by a simple, graphical test. BMJ. 1997;315:629–34. 22. Yang H, He F, Zhou G. Genetic association studies on candidate genes for chronic hepatitis B, liver and nasopharyngeal cancers. Wanfang Doctoral Dissertation. 2007;2007:2007. 23. Yu L, Chen J. Association of MTHFR Ala222Val (rs1801133) polymorphism and breast cancer susceptibility: an update meta-analysis based on 51 research studies. Diagn Pathol. 2012;7:171. 24. Zhong S, Yang JH, Liu K, Jiao BH, Chang ZJ. Quantitative assessment of the association between MTHFR C677T polymorphism and colorectal cancer risk in East Asians. Tumour Biol. 2012;33:2041– 51. 25. Mei Q, Zhou D, Gao J, Shen S, Wu J, Guo L, et al. The association between MTHFR 677C>T polymorphism and cervical cancer: evidence from a meta-analysis. BMC Cancer. 2012;12:467.
