NUDT1 and neoplasm: Mice transgenically deficient for mutT homolog-1 (Mth1) are unable to process oxygen free radicals, which cause DNA damage, and are susceptible to several spontaneous tumours, including gastric tumours, which develop over ∼18 months; 14% (13 of 93) of Mth1-null mice developed gastric tumours, compared with 4% (4 of 90) of littermate controls (Tsuzuki et al., 2001).