KRAS and cancer: RAS and RAF oncogenes are amongst the best-characterised driver oncogenes and are mutated in a significant proportion of human cancers, notably pancreatic (∼90%) and lung adenocarcinoma (∼30%) in the case of KRAS (Malumbres & Barbacid, 2003), and melanomas (∼50%) and thyroid cancers (∼30%) in the case of BRAF (Davies et al, 2002).