Racial and tissue-specific cancer risk associated with PARP1 (ADPRT) Val762Ala polymorphism: a meta-analysis

The Val762Ala polymorphism poly [ADP-ribose] polymerase 1 (PARP1) gene [ADPRT (adenosine diphosphate ribosyltransferase) gene] affects enzymatic activity, which modulates cancer susceptibility among human populations. Individual data on 13,745 cases and 16,947 controls from 28 published case-control studies were re-evaluated. Odds ratios (OR) were estimated for ethnic group, cancer type, smoking joint effects and studies confined to the Hardy-Weinberg equilibrium. We applied subgroup, sensitivity and outlier analyses as well as the Bonferroni correction for multiple testing. The results show strong evidence that the variant (C) allele confers significant increased risk in the Chinese (OR 1.20-1.44, P < 0.0001-0.002), exacerbated by smoking (OR 1.66-2.53, P < 0.0001) and joint interaction with XRCC1 Arg399Gln (OR 1.39, P < 0.0001) as well as adjustment for tumor type (gastric carcinoma ORs 1.39-2.01, P < 0.0001). These significant effects were unaltered following conservative correction for multiple tests. By contrast, this procedure erased the protective significance in Caucasians, but not in two American subgroups, (i) those in the brain tumor category (0.77-0.79, P < 0.0001) and (ii) smokers in the dominant model (OR 0.86, P < 0.0001). These differential findings between the two ethnicities maybe correlated with significantly (P < 0.0001) greater allele frequency of the variant allele (C) among the Chinese compared to Caucasians. Our racial and tissue-specific summary estimates imply consideration of the Val762Ala polymorphism as candidate gene marker for screening cancer patients' best suited for PARP inhibitor therapy.