Association between IL-17A G197A polymorphism and gastric cancer risk: an updated meta-analysis based on 6,624 cases and 7,631 controls

Immunological Aspects of the Tumor Microenvironment and Epithelial-Mesenchymal Transition in Gastric Carcinogenesis

Infection with Helicobacter pylori, a Gram-negative, microaerophilic pathogen often results in gastric cancer in a subset of affected individuals. This explains why H. pylori is the only bacterium classified as a class I carcinogen by the World Health Organization. Several studies have pinpointed mechanisms by which H. pylori alters signaling pathways in the host cell to cause diseases. In this article, the authors have reviewed 234 studies conducted over a span of 18 years (2002-2020). The studies investigated the various mechanisms associated with gastric cancer induction. For the past 1.5 years, researchers have discovered new mechanisms contributing to gastric cancer linked to H. pylori etiology. Alongside alteration of the host signaling pathways using oncogenic CagA pathways, H. pylori induce DNA damage in the host and alter the methylation of DNA as a means of perturbing downstream signaling. Also, with H. pylori, several pathways in the host cell are activated, resulting in epithelial-to-mesenchymal transition (EMT), together with the induction of cell proliferation and survival. Studies have shown that H. pylori enhances gastric carcinogenesis via a multifactorial approach. What is intriguing is that most of the targeted mechanisms and pathways appear common with various forms of cancer.

Genetic polymorphisms and gastric cancer risk: a comprehensive review synopsis from meta-analysis and genome-wide association studies

Objective

In the past few decades, more than 500 reports have been published on the relationship between single nucleotide polymorphisms (SNPs) on candidate genes and gastric cancer (GC) risk. Previous findings have been disputed and are controversial. Therefore, we performed this article to summarize and assess the credibility and strength of genetic polymorphisms on the risk of GC.

Methods

We used Web of Science, PubMed, and Medline to identify meta-analyses published before July 30th, 2018 that assessed associations between variants on candidate genes and the risk of GC. Cumulative epidemiological evidence of statistical associations was assessed combining Venice criteria and a false-positive report probability (FPRP) test.

Results

Sixty-one variants demonstrated a significant association with GC risk, whereas 29 demonstrated no association. Nine variants on nine genes were rated as presenting strong cumulative epidemiological evidence for a nominally significant association with GC risk, including APE1 (rs1760944), DNMT1 (rs16999593), ERCC5 (rs751402), GSTT1 (null/presence), MDM2 (rs2278744), PPARG (rs1801282), TLR4 (rs4986790), IL-17F (rs763780), and CASP8 (rs3834129). Eleven SNPs were rated as moderate, and 33 SNPs were rated as weak. We also used the FPRP test to identify 13 noteworthy SNPs in five genome-wide association studies.

Conclusions

Sixty-one variants are significantly associated with GC risk, and 29 variants are not associated with GC risk; however, five variants on five genes presented strong evidence for an association upgraded from moderate. Further study of these variants may be needed in the future. Our study also provides referenced information for the genetic predisposition to GC.

Genetic polymorphisms of IL-17A rs2275913, rs3748067 and IL-17F rs763780 in gastric cancer risk: evidence from 8124 cases and 9873 controls

Interleukin-17 (IL-17) is a critical cytokine involved in inflammation-associated cancers. Single nucleotide polymorphisms (SNPs) might promote carcinogenesis. In this current meta-analysis, we investigated the association of IL-17A and IL-17F gene polymorphisms with gastric cancer (GC) risk. Eligible genetic association studies were retrieved from PubMed, Web of Science and Scopus database sources. Two reviewers independently assessed methodological quality and extracted data from eligible articles. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Quantitative data synthesis was conducted using comprehensive meta-analysis v2. Subgroup analysis and heterogeneity analysis were performed. Begg's funnel plot and Egger's regression tests were used to judge publication bias. In silico data analysis was executed to analyze the functional and structural impact of the SNPs. A total of 21 case-control studies for rs2275913 c.-197G > A (7660 patients and 9409 controls), 9 studies for rs3748067 c.*1249C > T (3378 patients and 4120 controls), and 14 studies for rs763780 c.482A > G (4481 patients and 5354 controls) were included. The pooled estimate revealed an association between IL-17A rs2275913 polymorphism and the risk of GC under all genetic models (A vs. G, OR 1.187, 95% CI 1.086-1.297, P < 0.001; GA vs. GG, OR 1.108, 95% CI 1.008-1.218, P = 0.033; AA vs. GG, OR 1.484, 95% CI 1.236-1.781, P < 0.001), while no evidence of association was found with IL-17A rs3748067 or IL-17F rs763780 polymorphisms. Our results showed that IL-17A promoter rs2275913 variant might represent a potential risk factor for gastric cancer susceptibility.