Patients with Lynch syndrome (germline mutation in MMR gene) or patients with sporadic microsatellite unstable (MSI) cancers (hypermethylation of the MMR gene hMLH1) do not show a survival advantage with systemic 5-FU therapy [3], [4], [5], [6], whereas patients with MMR-proficient tumors improve their survival. Here, MRC1 is linked to Lynch syndrome.