Association between +61G polymorphism of the EGF gene and glioma risk in different ethnicities: a meta-analysis

Epidermal growth factor (EGF) plays a key role in survival of neural and glial precursor cells. The +61A/G polymorphism of the EGF gene is located in the 5'-untranslated region of EGF mRNA and may affect DNA folding or gene transcription, leading to the increase in EGF protein expression. The association between the +61G allele and glioma risk has been widely reported; however, in general the data from published studies with individually low statistical power were controversial and underpowered. We conducted a search in the PubMed database without a language limitation, covering all papers published by the end of October 2010. Overall, 6 case-control studies with 1453 glioma cases and 1947 controls were retrieved based on the search criteria for glioma susceptibility related to the +61A/G polymorphism. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association. We found that EGF +61G allele is associated with the low glioma risk in Chinese population [G-allele vs. A-allele, OR = 0.93, 95%CI (0.89-0.97), P(heterogeneity) = 0.318, I² = 0.0], but with the high glioma risk in European population [G-allele vs. A-allele, OR = 1.14, 95%CI (1.04-1.24), P(heterogeneity) = 0.310, I² = 14.6]. In the stratified analysis by source of control, significant association was observed between hospital-based control and glioma risk [homozygote comparison, OR = 1.14, 95%CI (1.02-1.27), P(heterogeneity) = 0.179, I² = 71.8]. In conclusion, EGF +61G allele represents a risk factor for glioma in European population and conversely a protective factor in Chinese population.