XRCC3 and cancer: Nelson et al (2002) also highlight that high UV exposure to the skin results in p53 mutant cells which do not apoptose. The variant XRCC3 exon 7 T allele with reduced repair capacity could result in an increased cancer risk in the skin (by the fixation of mutations in p53 mutant cells) and a protective effect in the gut (by more efficient apoptosis).