DNA repair gene XRCC2 and XRCC3 polymorphisms and susceptibility to cancers of the upper aerodigestive tract.

Cigarette smoke can generate reactive oxygen species, which are capable of inducing double-strand breaks (DSBs) in DNA. Polymorphisms in XRCC2 and XRCC3 genes, involved in DSBs repair pathways, may alter an individual's susceptibility to smoking-related cancers. We investigated the effect of XRCC2 Arg(188)His and XRCC3 Thr(241)Met polymorphisms in cancer proneness in 121 oral/pharynx cancer cases, 129 larynx cancer cases and 172 noncancer controls, all Caucasian smokers. The XRCC2 His-allele was associated with a significantly increased risk of pharyngeal cancer (OR=2.9, 95% CI: 1.3-6.2). No significant associations were observed between the XRCC3 Thr(241)Met polymorphism and overall risk of developing UADT cancers. However, quite opposite to the expectations, a reduced risk of supraglottic cancer was found for carriers of the XRCC3 Met variant allele (OR=0.3, 95% CI: 0.2-0.7). These findings provide evidence for the view that polymorphisms in DNA repair genes may modify individual susceptibility to smoking-related cancers.