H19 and cancer: IGF2/H19 imprinted domain and early lead exposure. The paternally expressed insulin-like growth factor-2 (IGF2) is a commonly studied imprinted gene, and is frequently shown to be altered epigenetically by in utero environmental perturbations, and in cancer (Cruz-Correa et al. 2004, 2009; Cui et al. 2003; Heijmans et al. 2008; Hoyo et al. 2011, 2012; Murphy et al. 2012a).