MICA polymorphisms and cancer risk: a meta-analysis

The major histocompatibility complex class I chain-related gene A transmembrane (MICA-TM) polymorphism has been implicated in susceptibility to cancer. However, the results are inconsistent. The aim of this meta-analysis is to evaluate the association between the MICA-TM polymorphisms and cancer risk. All eligible case-control studies published up to August 20, 2014 were identified by searching PubMed, Web of Science, CNKI and Wanfang databases. The cancer risk associated with the MICA polymorphism was estimated for each study by odds ratios (OR) together with its 95% confidence interval (CI), respectively. 21 studies from 19 publications with 3620 cases and 4903 controls were included. Overall, no significant associations between the MICA-TM polymorphism and cancer risk were found (A4 allele: OR = 0.97, 95% CI: 0.88-1.07; A5 allele: OR = 0.91, 95% CI: 0.81-1.04; A5.1 allele: OR = 1.03, 95% CI: 0.89-1.18; A6 allele: OR = 1.05, 95% CI: 0.95-1.15; A9 allele: OR = 0.96, 95% CI: 0.80-1.14; A10 allele: OR = 0.88, 95% CI: 0.43-1.79; del: OR = 2.50, 95% CI: 0.73-8.58; A7 allele: OR = 0.93, 95% CI: 0.43-2.00). When stratified by ethnicity, similar results were observed among Asians; however, there were significant association in Caucasian population for A5 (OR = 0.77, 95% CI: 0.68-0.87) and A9 allele (OR = 0.75, 95% CI: 0.66-0.85). This meta-analysis suggests that the MICA-TM A5 and A9 alleles may be an important protective factor for cancer in Caucasian populations.