GSTM1 and cancer: Previous data have suggested that the null genotypes of both GSTM1 and GSTT1 are associated with a slightly increased risk of some forms of cancer, although this does not appear to concern all cancers (Bolufer et al. 2006; Bolt and Thier 2006; Carlsten et al. 2008; Hiyama et al. 2008; Parl 2005; Shi et al. 2008; Vineis et al. 2007; White et al. 2008).