Association between IL-27 Gene Polymorphisms and Cancer Susceptibility in Asian Population: A Meta-Analysis

Background: Interleukin 27 (IL-27) has potent antitumor activity. Several epidemiological studies have designated that genetic variants of the IL-27 gene may contribute to various cancer susceptibility, but the data were inconclusive. Objective: The current meta-analysis aimed to address the association between IL-27 rs153109, rs17855750, and rs181206 polymorphisms and the risk of cancer. Data Sources: Our team has selected eligible studies up to May 1, 2020, from several electronic databases, including Web of Science, PubMed, Scopus, and Google Scholar databases. Results: Our meta-analysis revealed that the carriers rs153109 A>G polymorphism in the IL-27 gene have higher risks of diseases in the heterozygous (OR=1.26, 95%CI=1.06-1.49, P=0.007, AG vs AA), homozygous (OR=1.18, 95%CI=1.01-1.37, p=0.33, GG vs AA), dominant (OR=1.25, 95%CI=1.07-1.47, P=0.006, AG+GG vs AA), and allele (OR=1.15, 95%CI=1.04-1.27, P=0.008, G vs A) genetic models. Stratified analysis by cancer type indicated that this variant was significantly associated with gastrointestinal cancer, colorectal cancer and breast cancer. The findings did not support an association between rs17855750 T>G, rs181206 T>C polymorphisms of IL-27 and cancer risk. Conclusion: the current study findings suggest that IL-27 rs153109 polymorphism significantly increased the risk of cancer susceptibility. Well-designed replication in a larger independent genetic association study with larger sample sizes in diverse ethnicities is required to verify the findings.


Identification of Eligible Studies
Two authors independently carried out a systematic literature search in PubMed, Web of Knowledge, and Scopus for all related reports using the key words "IL-27 or IL27 or interleukin 27" and "polymorphism or SNP or variation" and "cancer or tumor or carcinoma or malignancy or neoplasm". The last search was updated on March 04, 2019.

Inclusion and Exclusion Criteria
Studies were implemented in the current meta-analysis if they met all of the criteria: (1) Assessment of the relationship between IL-27 gene polymorphisms and cancer susceptibility; (2) Case-control studies; (3) Adequate data to estimate pooled ORs with a 95% CIs. The exclusion criteria were: (1) not a case-control study, reviews, case reports, meta-analysis, and comments; (2) duplicate publication; (3) studies with insufficient data.

Data extraction
The data extraction from the eligible studies was achieved independently by two researchers according to the inclusion and exclusion criteria mentioned above. In each study, the following items were collected from each study: first author's name, publication year, country, ethnicity, cancer type, source of controls, total number of cases and controls, genotype distributions of cases and controls, and Hardy-Weinberg equilibrium (HWE), respectively.

Statistical analysis
All statistical analyses were achieved using Stata, version 14.1 (Stata Corporation, College Station, TX, USA).
The HWE was evaluated for each study by the chi-square test in the control group. Pooled ORs and corresponding 95%CIs were calculated to estimate the strength of association between IL-27 gene polymorphism and cancer risk. The significance of the pooled OR was determined by Z test, in which p-value less than 0.05 was considered statistically significant.
The Q statistic test was used to check the heterogeneity among studies included in the meta-analysis. A p>0.10 indicated a lack of heterogeneity among studies, consequently the fixed effect model was used to calculate pooled OR. Otherwise, a random effects model was utilized.
Publication bias was evaluated by Begg's funnel plot qualitatively, and Begg's and Egger's tests quantitatively. P-value less than 0.05 considered significant publication bias.
Sensitivity analysis was done by removing each study in turn to measure the results stability.

Study Characteristics
In the current study, according to the inclusion and exclusion criteria, ultimately 20 case-control studies included in the meta-analysis. For rs153109, 21 studies containing 6,331 cases and 7,287 controls for were included in the quantitative analysis. Regarding rs17855750 variant, 4,023 cases and 4,671 controls from 14 studies and for rs181206 polymorphism, 2,078 cases and 2,242 controls from were 7 studies were included in the meta-analysis. The characteristics of the included studies are summarized in Table 1, Table 2 and Table 3.

Association between IL-27 polymorphisms and cancer risk
The frequency distribution of genotype and allele of the IL-27 polymorphisms in cases and controls are indicated in Table 1, Table 2 and Table 3. Table 4 shows the main findings of our meta-analysis. Regarding rs153109 A>G variant, 21 independent studies were pooled and a random effect was applied due to the presence of significant heterogeneity. The finding revealed that rs153109 variant significantly increased the risk of cancer in heterozygous (OR=1.26, 95%CI=1.06-1.49, P=0.007, AG vs AA), homozygous (OR=1.18, 95%CI=1.01-1.37, p=0.33, GG vs AA), dominant (OR=1.25, 95%CI=1.07-1.47, P=0.006, AG+GG vs AA), and allele (OR=1.15, 95%CI=1.04-1.27, P=0.008, G vs A) genetic models ( Figure 1 and Table 4).
The findings showed that rs17855750 T>G, and rs181206 T>C variants were not associated with cancer risk (Table 4).

Heterogeneity and publication bias
Heterogeneity among studies involved in the meta-analysis is presented in Table 4. The findings indicated that heterogeneity exist among studies and random-effects was used to estimate the pooled OR and 95% CI ( Figure 2 and Table 4).
Begg's funnel plot, Begg's test, and Egger's test ( Figure 3, and Table 4) indicated no evidence of significant publication bias.

Sensitivity analysis
After doing the sensitivity analyses, the pooled ORs showed no statistically significant changes in heterozygous, dominant, recessive, and allele representing that our findings are stable and reliable in overall analysis ( Figure 4).

Discussion
Several studies examined the association between IL-27 Gene Polymorphisms and Cancer Risk   (Wei et al., 2009;Zhao et al., 2009;Guo et al., 2012;Huang et al., 2012;Pan et al., 2012;Tao et al., 2012;Peng et al., 2013;Munretnam et al., 2014;Tang et al., 2014;Zhang et al., 2014a;Zhang et al., 2014b;Lyu et al., 2015;Pu et al., 2015;Zhang et al., 2015;Zhou et al., 2015;Ge and Xiao, 2016;Wang et al., 2016;Yu et al., 2016;Nie et al., 2017;Ghavami et al., 2018). The findings were controversial, though it is difficult to clarify the inconsistent findings. In this study, we conducted a comprehensive meta-analysis of all eligible studies to derive a more precise estimation of the relationship between IL-27 polymorphism and cancer risk. After pooling all the available data, the finding suggested that IL-27 rs153109 (-964 A>G) significantly increased the risk of overall cancer. Stratified analysis by cancer type designated that rs153109 polymorphism      DOI:10.31557/APJCP.2020.21.9.2507 Table 5. Stratified Analysis of IL-17 Polymorphisms and Cancer Susceptibility was positively associated with GI cancer, CRC and BC susceptibility. The findings did not support an association between rs17855750 (2905 T>G) and rs181206 (4730 T>C) polymorphisms and cancer susceptibility. The molecular mechanisms by which variant increased the risk of cancer have not been clarified. It seems reasonable to speculate that rs153109 polymorphism effects on IL-27 expression. There is increasing evidence that the expression level of IL-27p28 gene is decreased in various cancers including epithelial ovarian cancer (Zhang et al., 2014b), bladder cancer , esophageal cancer (Tao et al., 2012), osteosarcoma (Tang et al., 2014), as well as papillary thyroid cancer . It has been shown that IL-27 differentially regulates the expression of several microRNAs (miR) such as hsa- miR-7702, hsa-miR-7704, hsa-miR-7704 hsa-miR-6852, and hsa-miR-6852 (Swaminathan et al., 2013;Poudyal et al., 2018).
Some limitations should be addressed in our metaanalysis. First, heterogeneity among studies was observed which may be result of difference of ethnicity, source of control, and cancer type. Second, this study focused on the impact of limited variants of IL-27 and cancer susceptibility. Gene-gene as well as gene-environment interactions could influence cancer risk. Third, all studies were from Asian populations; consequently, conclusions drawn may not apply to the all population. Finally, the sample sizes of the studies are relatively small particularly in subgroup analysis. So, the results should be interpreted with caution.
In conclusion, the findings of this meta-analysis provide evidence for an association between IL-27 rs153109 polymorphism and cancer risk. Well-designed studies with larger sample sizes in various cancer and different ethnicities are still needed in the future.  logistics for the literature search. The work was not supported by any operating grant and fund and was not a part of any graduate and under graduate thesis.
We would like to dedicate this article to Professor Mohamad Hashemi who passed away recently after the submission of this work. He was a pioneer in genetic studies.