A naturally occurring frameshift mutation in MBD4 results in a truncated protein, lacking its intervening region and glycosylase domain, occurs in human colon and other carcinomas that exhibit microsatellite instability (MSI), generally associated with defects in mismatch repair (MMR) [Bader et al., 1999; Riccio et al., 1999; Bader et al., 2007]. This evidence concerns the gene MBD4 and carcinoma.