As expected based on the genomic instability phenotypes of cancer cells, Msh2+/+ MEFs immortalized with CIN (tetraploidy) but without MSI, whereas Msh2−/− MEFs immortalized with stable diploidy and MSI (Fig. 1b–d; Supplementary Fig. 1a–e; see red arrows showing the signal change corresponding to MSI induction). Here, MSH2 is linked to cancer.