However, no significant association was found in Asians. It might not be uncommon for the same polymorphism playing different roles in cancer susceptibility among different ethnic populations,

selleckchem because cancer is a complicated multi-genetic disease, and different genetic backgrounds may contribute to the discrepancy. Nevertheless, owing to the limited number of relevant studies among Asian populations included in this meta-analysis, the observed negative association between MDM2 SNP309 polymorphism and endometrial cancer risk in Asians is likely to be caused by chance because study with small sample sizes may have insufficient statistical power to detect a slight effect or may have generated a fluctuated risk estimate. Currently there were only two studies [13, 15] on MDM2 SNP309 polymorphism and endometrial

cancer risk in Asian populations, and the genotype distributions in the control population of one study [13] was deviate from HWE. Therefore, the negative results of the Asian population should be interpreted with caution. To clarify an association between genetic polymorphisms and cancer risk, the quality of the study design is of great importance. In addition to controls that should be in HWE, strict definitions of the study population, appropriate materials used to CP673451 in vivo assess GSK2126458 genotype as well as sufficient statistical power are required. Of the eigh eligible studies, three were considered as low quality studies [11, 13, 18] and 5 were considered as high quality studies [12, 14, 15, 19]. When stratified according to the quality of the articles, we found that the MDM2 SNP309 polymorphism was associated with elevated Temsirolimus endometrial cancer risk in both high and low quality studies in additive model (CC vs. CG) and recessive model (GG vs. TG + TT). Interestingly, similarly elevated risks were found in high quality studies,

but not in low quality studies in the dominant model (GG + TG vs. TT). Several possibilities exist which may explain this finding, such as selection bias and recall bias. Genotyping methods without quality control in low quality studies should be considered when deciphering these inconsistent results, which reinforces that the importance of precise methodologically design is of great value in case–control studies. It seemed that selection bias could have played a role because the genotype distribution of the MDM2 SNP309 polymorphism among control subjects disobeyed the law of HWE in one of the included studies [13]. It is widely believed that deviation from HWE may be as a result of genetic reasons including non-random mating, or the alleles reflect recent mutations that have not reached equilibrium, as well as methodological reasons including biased selection of subjects from the population or genotyping errors [34, 35].