The role of modifier genes in Lynch Syndrome

There are a number of inherited predispositions to colorectal cancer (CRC) which can be broadly categorized into two groups; those with associated polyposis, such as familial adenomatous polyposis and the hamartomatous polyposis syndromes; and those that are linked to the non-polyposis syndromes, such as hereditary non polyposis colorectal cancer (HNPCC). The genetic basis of both the polyposis and non-polyposis syndromes are reflected in the CRC population who have no apparent family history of disease. Approximately 80% of all cases of CRC are associated with chromosomal instability [1] and are likely to have mutations in the Adenomatous Polyposis Coli (APC) gene whereas the remaining 20% with microsatellite instability appears to be due primarily to epigenetic inactivation of the DNA mismatch repair (MMR) gene MLH1 [2].