The
peroxisome proliferator-activated receptor gamma (
PPARgamma) has been suggested to act as a tumor suppressor gene. Two common variations of
PPARgamma, P12A (Pro12Ala, rs1801282) and C161T (His447His, rs3856806), are thought to have an effect on susceptibility to various
carcinomas but the results are inconsistent. In this meta-analysis, we assessed published studies of the association between two common
PPARgamma polymorphisms and
cancer risk from 26 studies with 27,677 subjects for
PPARgamma P12A, from 4 studies with 4,461 subjects for C161T. No significant associations were found in carriers of the rare Ala allele of the P12A polymorphism versus the common
Pro/Pro genotype among the studies. In the subgroup analyses by
cancer types, carriers of the Ala variant of P12A polymorphism were associated with protection from
colorectal cancer (OR=0.84, 95% CI=0.72-0.98, Pheterogeneity = 0.014), but the inverse association was found in
gastric cancer (OR=2.31, 95% CI=1.59-3.36, Pheterogeneity = 0.941). In the stratified analysis by ethnicity, no significant risks were found among Asians, Americans and Caucasians. For
PPARgamma C161T, no significant associations were found in any of the studies (OR=1.08, 95% CI=0.95-1.23, Pheterogeneity = 0.430) or subgroups. This meta-analysis suggests that the Ala allele of the
PPARgamma P12A polymorphism might be a protective factor for
colorectal cancer, but a risk factor for
gastric cancer. The
PPARgamma C161T is marginally associated with
cancer susceptibility.