Differential effects of MDM2 SNP309 polymorphism on breast cancer risk along with race: a meta-analysis.

MDM2 SNP309 is a single nucleotide T > G polymorphism present in intron 1 of the MDM2 gene. A variety of case-control studies have been published evaluating the association between MDM2 SNP309 and breast cancer risk. However, the published studies, as well as the subsequent meta-analyses, have yielded contradictory results. This meta-analysis aims to examine whether MDM SNP309 polymorphism may exert a differential effect on breast cancer risk along with race. Eligible articles were identified by a search of MEDLINE, Cochrane and EMBASE bibliographical databases for the period July 1993 to June 2009; 16 case-control studies were eligible (12,986 breast cancer cases, 12,993 controls). Subanalyses in case-control studies conducted on Chinese (3 studies, 892 cases, 1,435 controls) and non-Chinese populations (13 studies, 12,094 cases, 11,558 controls) were performed. All pooled odds ratios (ORs) were derived from fixed-effects models given that the between-study heterogeneity was not statistically significant. Subanalysis on Chinese subjects demonstrated that GT and GG genotype were associated with increased breast cancer risk (pooled OR = 1.272, 95% CI 1.025-1.578 and pooled OR = 1.323, 95% CI 1.034-1.694, respectively); as a result the overall effect of the G allele was statistically significant (pooled OR = 1.287, 95% CI 1.048-1.579). On the contrary, no significant associations between MDM2 SNP309 status and breast cancer risk were demonstrated in non-Chinese populations. In conclusion, the association between MDM2 SNP309 and breast cancer is modified by race. MDM2 SNP309 represents a risk factor for breast cancer in Chinese women but not in non-Chinese women. This phenomenon is analogous to that described in the context of lung cancer.