Interaction of EGFR 497Arg>Lys with EGF +61A>G polymorphism: modulation of risk in esophageal cancer

Lack of Association between Epidermal Growth Factor or Its Receptor and Reflux Esophagitis, Barrett’s Esophagus, and Esophageal Adenocarcinoma: A Case-Control Study

The epidermal growth factor (EGF) and its receptor (EGFR) gene-gene interactions were shown to increase the susceptibility to esophageal cancer. However, the role of the EGF/EGFR pathway in the development of gastroesophageal reflux disease (GERD) and its complications (reflux esophagitis (RE), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC)) remains unclear. This association study is aimed at investigating functional EGF and EGFR gene polymorphisms, their mRNA expression in esophageal tissues, and EGF plasma levels in relation to RE, BE, and EAC development in the Central European population. 301 patients with RE/BE/EAC (cases) as well as 98 patients with nonerosive reflux disease (NERD) and 8 healthy individuals (controls) were genotyped for +61 A>G EGF (rs4444903) and +142285 G>A EGFR (rs2227983) polymorphisms using the TaqMan quantitative polymerase chain reaction (qPCR). In random subgroups, the EGF and EGFR mRNA expressions were analyzed by reverse transcription qPCR in esophageal tissue with and without endoscopically visible pathological changes; and the EGF plasma levels were determined by enzyme-linked immunosorbent assay. None of the genotyped SNPs nor EGF-EGFR genotype interactions were associated with RE, BE, or EAC development (p > 0.05). Moreover, mRNA expression of neither EGF nor EGFR differed between samples of the esophageal tissue with and without endoscopically visible pathology (p > 0.05) nor between samples from patients with different diagnoses, i.e., RE, BE, or EAC (p > 0.05). Nevertheless, the lower EGF mRNA expression in carriers of combined genotypes AA +61 EGF (rs4444903) and GG +142285 EGFR (rs2227983; p < 0.05) suggests a possible direct/indirect effect of EGF-EGFR gene interactions on EGF gene expression. In conclusion, EGF and EGFR gene variants and their mRNA/protein expression were not associated with RE, BE or EAC development in the Central European population.

Genetic variants of EGF and VEGF predict prognosis of patients with advanced esophageal squamous cell carcinoma

PURPOSE

To investigate the association between genetic polymorphisms of growth factor-related genes and prognosis in patients with advanced esophageal squamous cell carcinoma (ESCC).

PATIENTS AND METHODS

A total of 334 ESCC patients with advanced tumor stages (stages IIB, III and IV) were enrolled in the study. The genotypes of 14 candidate single nucleotide polymorphisms (SNPs) involved in growth factor-related functions were analyzed using iPLEX Gold technology from the genomic DNA of peripheral leukocytes, and were correlated with the clinical outcome of patients. Serum levels of growth factors were examined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The genetic polymorphisms of EGF:rs4444903, EGF:rs2237051 and VEGF:rs2010963 showed significant associations with overall survival (OS) of advanced ESCC patients (A/A+ A/G vs. GG, [HR = 0.77, 95% CI = 0.60-0.99, P = 0.039 for rs4444903; A/G+ G/G vs. A/A, [HR = 0.74, 95% CI = 0.58-0.95, P = 0.019 for rs2237051; G/G+G/C vs. C/C, [HR] inves = 0.69, 95% CI = 0.50-0.95, P = 0.023 for rs2010963). EGFR:rs2227983 and 3 SNPs of PIK3CA also showed borderline significant correlation with OS of advanced ESCC patients (P = 0.058 for rs2227983; P = 0.069, 0.091 and 0.067 for rs6443624, rs7651265 and rs7621329 of PIK3CA respectively). According to cumulative effect analysis of multiple SNPs, patients carrying 4 unfavorable genotypes exhibited more than a 3-fold increased risk of mortality. Finally, both EGF and VEGF expression levels significantly associated with patient mortality.

CONCLUSION

The genetic variants and expression levels of EGF and VEGF can serve as prognostic predictors in patients with advanced ESCC, and thus provide more information for optimizing personalized therapies for patients with ESCC.

Epidermal growth factor receptor: an important target in esophageal cancer

INTRODUCTION

Even after complete tumor removal by surgery, the clinical outcomes remain poor in patients with advanced esophageal cancer, justifying the need for new treatment options. Epidermal growth factor receptor (EGFR) is a molecular target for antibody-based therapy in various cancer types, and it may play important roles in the development of esophageal cancer.

AREAS COVERED

This review evaluates the expression, function, and mechanism of EGFR in esophageal cancer and analyzes its value for the prognosis and therapy of esophageal cancer. Future developments toward the clinical applications of EGFR to cancer treatment are also envisaged.

EXPERT OPINION

EGFR may function as an ideal therapeutic target for esophageal cancer. Further investigation of epidermal growth-factor-receptor-mediated pathways will push insight into the novel strategies of target therapy for esophageal cancer. More clinical trials should be performed to promote the success of therapeutic-clinical use of EGFR and its targets in esophageal cancer.

Comprehensive study on associations between nine SNPs and glioma risk

AIM

Glioma cancer is the most common type of adult brain tumor. Recent genome-wide association studies (GWAS) have identified various new susceptibility regions and here we conducted an extensive analysis of associations between 12 single nucleotide polymorphisms (SNPs) and glioma risk.

METHODS

A total of 197 glioma cases and 197 health controls were selected, and 9 SNPs in 8 genes were analyzed using the Sequenom MassARRAY platform and Sequenom Assay Design 3.1 software.

RESULTS

We found the MAF among selected controls were consistent with the MAF from the NCBI SNP database. Among 9 SNPs in 8 genes, we identified four significant SNP genotypes associated with the risk of glioma, C/C genotype at rs730437 and T/T genotype at rs1468727 in ERGF were protective against glioma, whereas the T/T genotype at rs1799782 in XRCC1 and C/C genotype at rs861539 in XRCC3 conferred elevated risk.

CONCLUSION

Our comprehensive analysis of nine SNPs in eight genes suggests that the rs730437 and rs1468727 in ERGF, rs1799782 in XRCC1 gene, and rs861539 in XRCC3 gene are associated with glioma risk. These findings indicate that genetic variants of various genes play a complex role in the development of glioma.

EGF +61A>G polymorphism and gastrointestinal cancer risk: a HuGE review and meta-analysis

Emerging evidences from preclinical and clinical studies have shown that epidermal growth factor (EGF) has some effectiveness against endogenously arising carcinogenesis. Functional +61A>G polymorphism (rs4444903 A>G) in the promoter region of the EGF gene was observed to modulate EGF levels, thus affecting the susceptibility to gastrointestinal cancer; but individually published studies showed inconclusive results. The aim of this Human Genome Epidemiology (HuGE) review and meta-analysis was to derive a more precise estimation of the association between EGF +61A>G polymorphism and gastrointestinal cancer risk. A literature search of Pubmed, Embase, Web of Science and Chinese BioMedical databases from inception through July 2012 was conducted. Twelve studies were assessed with a total of 2868 gastrointestinal cancer cases and 4278 healthy controls. When all the eligible studies were pooled into the meta-analysis, the results showed that the G allele and GG genotype of EGF +61A>G polymorphism might increase the risk of gastrointestinal cancer. In the stratified analysis by cancer types, the G allele and GG genotype of EGF +61A>G polymorphism showed displayed significant correlations with increased risk of esophageal cancer. We also found significant correlations between the G carrier (GG+AG) and GG genotype of EGF +61A>G polymorphism and colorectal cancer risk. However, EGF +61A>G polymorphism did not appear to have an influence on gastric cancer susceptibility. Results from the current meta-analysis indicate that EGF +61A>G polymorphism might increase the risk of esophageal and colorectal cancers. Nevertheless, further studies are needed to determine whether genetic associations between EGF +61A>G polymorphism and susceptibility to gastric cancer are significant.

Role of epidermal growth factor receptor tyrosine kinase inhibitors in the treatment of esophageal carcinoma and the suggested mechanisms of action

Cumulative evidence indicates that epidermal growth factor receptor (EGFR) is one of the most commonly altered genes in human cancer, via overexpression, amplification and mutation. Targeted inhibition of EGFR activity suppresses signal transduction pathways which control tumor cell growth, proliferation and resistance to apoptosis. Small molecule tyrosine kinase inhibitors (TKIs) are among the most common EGFR-targeting agents and have been used clinically to treat various malignancies. This review discusses the mechanism of action and clinical data that are relevant to the use of EGFR-TKIs in the treatment of esophageal carcinoma. The clinical and basic scientific experience of these agents thus far have implications for the future of therapeutic targeting of EGFR.

Genetic variation in the EGFR gene and the risk of glioma in a Chinese Han population

Previous studies have shown that regulation of the epidermal growth factor gene (EGFR) pathway plays a role in glioma progression. Certain genotypes of the EGFR gene may be related to increased glioblastoma risk, indicating that germ line EGFR polymorphisms may have implications in carcinogenesis. To examine whether and how variants in the EGFR gene contribute to glioma susceptibility, we evaluated nine tagging single-nucleotide polymorphisms (tSNPs) of the EGFR gene in a case-control study from Xi'an city of China (301 cases, 302 controls). EGFR SNP associations analyses were performed using SPSS 16.0 statistical packages, PLINK software, Haploview software package (version 4.2) and SHEsis software platform. We identified two susceptibility tSNPs in the EGFR gene that were potentially associated with an increased risk of glioma (rs730437, p = 0.016; OR: 1.32; 95%CI: 1.05-1.66 and rs1468727, p = 0.008; OR: 1.31; 95%CI: 1.04-1.65). However, after a strict Bonferroni correction analysis was applied, the significance level of the association between EGFR tSNPs and risk of glioma was attenuated. We observed a protective effect of haplotype "AATT" of the EGFR gene, which was associated with a 29% reduction in the risk of developing glioma, while haplotype "CGTC" increased the risk of developing glioma by 36%. Our results, combined with previous studies, suggested an association between the EGFR gene and glioma development.

Functional single-nucleotide polymorphism of epidermal growth factor is associated with the development of Barrett's esophagus and esophageal adenocarcinoma

Reflux esophagitis (RO) and Barrett's esophagus (BO) can cause esophageal adenocarcinoma (OAC). The esophageal mucosa in the RO-BO-OAC cascade is chronically exposed to gastro-esophageal reflux. Epidermal growth factor (EGF) has an important role in the protection and repair of mucosal damage, and non-physiologic levels are associated with gastrointestinal tumors. The aim is to determine the functional effect of EGF gene polymorphisms on RO, BO and OAC development. A cohort of 871 unrelated Dutch Caucasians consisted of 198 healthy controls, 298 RO patients, 246 BO patients and 129 OAC patients. The frequency of the EGF-production-associated 5'UTR A+61G polymorphism was determined in these four groups. EGF immunohistochemistry was performed on BO biopsies. EGF expression was significantly lower in the G/G genotype compared with the A/G (P=0.008) and A/A (P=0.002) group. The G/G genotype was significantly more prevalent in RO (odds ratios (OR)=2.6; 95% confidence intervals (95% CI): 1.3-5.2), BO (OR=3.0; 95% CI: 1.5-6.2) and OAC (OR=4.1; 95% CI: 1.8-9.7) than in controls. The G allele is associated with reduced EGF expression and increased risk for RO, BO and OAC development. This indicates that reduced mucosal protection resulting from genetically decreased EGF expression enhances esophageal tumor development.

Association between EGF promoter polymorphisms and cancer risk: a meta-analysis

EGF promoter polymorphisms are observed to modulate EGF levels and thought to have effect on susceptibility to various carcinomas but the results are inconsistent. In this meta-analysis, we assessed published studies of the association between three EGF polymorphisms and cancer risk from 21 studies with 14,609 subjects for EGF G61A, from two studies with 2,535 subjects for G-1380A and A-1744G, respectively. For EGF G61A, the contrast of homozygote (OR=0.80, 95% CI=0.65-0.98), allele (OR=0.90, 95% CI=0.81-0.99) and dominant model (OR=0.86, 95% CI=0.74-0.99) produced significant association among 21 studies with relatively large heterogeneity (Pheterogeneity<0.001). Through the stratified analysis, heterogeneity decreased significantly. In the stratified analysis by racial descent, the significant risks were found among Asians for homozygote contrast (OR=0.83, 95% CI=0.69-0.99, Pheterogeneity=0.506) and Americans for the contrast of homozygote (OR=0.50, 95% CI=0.30-0.84, Pheterogeneity=0.051), allele (OR=0.70, 95% CI=0.51-0.96, Pheterogeneity=0.008) and dominant model (OR=0.57, 95% CI=0.42-0.77, Pheterogeneity=0.28). No significant associations were found in all Caucasians genetic models. In the subgroup analyses by cancer types, for gastric cancer and esophageal cancer significant associations were found in all genetic models without heterogeneity. Significant risk was also found in the contrast of homozygote (OR=0.41, 95% CI=0.20-0.81, Pheterogeneity=0.184) and recessive model (OR=0.53, 95% CI=0.33-0.85, Pheterogeneity=0.384) for hepatoma and recessive model (OR=0.72, 95% CI=0.53-0.99, Pheterogeneity=0.474) for glioma. For EGF G-1380A and A-1744G, no significant associations were found in all genetic models. This meta-analysis suggests that the EGF G61A polymorphism most likely contributes to decreased susceptibility to cancers among Asians and Americans, and A allele may be a protective factor for gastric cancer, esophageal cancer, hepatoma and glioma. Both EGF G-1380A and A-1744G is marginally associated with cancer susceptibility.

Epidermal growth factor A61G gene polymorphism, gastroesophageal reflux disease and esophageal adenocarcinoma risk

BACKGROUND

Single-nucleotide polymorphisms of key cancer genes, such as EGF A61G, are associated with an elevated risk of esophageal adenocarcinoma (EAC). As gastroesophageal reflux disease (GERD) is an established risk factor for EAC, we evaluated whether the association between epidermal growth factor (EGF) polymorphism and EAC development is altered by the presence of GERD.

METHODS

EGF genotyping of DNA samples was performed and GERD history was collected for 309 EAC patients and 275 matched healthy controls. Associations between genotypes and EAC risk were evaluated using adjusted logistic regression. Genotype-GERD relationships were explored using analyses stratified by GERD history and joint effects models that considered severity and duration of GERD symptoms.

RESULTS

EGF variants (A/G or G/G) were more common (P = 0.02) and GERD was more prevalent (P < 0.001) in cases than in controls. When compared with the EGF wild-type A/A genotype, the G/G variant was associated with a substantial increase in EAC risk among individuals with GERD [Odds ratio 9.7; 95% confidence interval (CI), 3.8-25.0; P < 0.001] and a slight decrease in risk for GERD-free individuals (odds ratio 0.4; 95% CI = 0.22-0.90; P = 0.02). In the joint effects models, the odds of EAC was also highest for G/G patients (when compared with A/A) who either experienced frequent GERD of more than once per week (odds ratio 21.8; 95% CI = 5.1-94.0; P < 0.001) or suffered GERD for longer than 15 years (odds ratio 22.4; 95% CI = 6.5-77.6; P < 0.001). There was a highly significant interaction between the G/G genotype and the presence of GERD (P < 0.001).

CONCLUSIONS

EGF A61G polymorphism may alter EAC susceptibility through an interaction with GERD.

Genetic variations in esophageal cancer risk and prognosis

Investigations into inherited genetic variations in the DNA code (known as polymorphisms) in the field of oncology have provided preliminary support for an association with cancer risks and outcomes. Early studies have highlighted several genes with this potential predictive and prognostic power. However, these studies have had methodological limitations and have produced inconsistent results, making impractical as yet the routine evaluation of such genetic polymorphisms in general clinical practice. Continued research in this area is essential if we are to be able to soon use genetic polymorphisms to better select patients for targeted anticancer interventions. This review discusses the role of genetic polymorphisms and their association with esophageal cancer risk and prognosis. The article also highlights future directions in this new, emerging field of molecular epidemiology.