Microsatellite instability – MSI
Microsatellite instability (MSI) is the mutational signature found in colorectal cancers that evolve as a result of inactivation of the DNA mismatch repair system. Defects in the genes involved in mismatch repair lead to an accumulation of somatic mutations in a cell, which may result in the cell becoming malignant. Germline mutations in mismatch repair genes are associated with developing Hereditary Non-Polyposis Colon Cancer. Approximately 90% of colon cancers from families meeting Amsterdam Criteria have MSI.
MSI test is a fragment analysis based test, to detect fluctuations in the length of six microsatellite markers: BAT25, BAT26, BAT40, D5S346, D2S123 and D17S250.
MSI testing can be performed to determine if a tumor exhibits microsatellite instability by comparing the microsatellites in the tumor specimen to a normal tissue of the individual. If the tumor specimen exhibits alterations within the microsatellite regions, it is indicative of a probable defect in the mismatch repair genes. MSI testing for demonstrating instability in the tumor specimen is helpful in identifying patients with hereditary non-polyposis colorectal cancer (HNPCC) and sporadic cancers with defective DNA mismatch repair. MSI status determination in sporadic cancers is useful in establishing prognosis and may be predictive of tumor response to certain chemotherapeutic agents.
The test is available with diagnostic package service (includes DNA extraction, genotyping, interpretation, hard copy of the results report).
Requirements for DNA samples for testing the microsatellite instability:
>> The sample materials are tumor- and normal tissue from colon.
>> The best material of tumor tissue is pre-treatment biopsy.
>> The best material of normal tissue is surgical resection or 2-4 ml of blood (with anticoagulant EDTA).
>> Storage and transport temperature for paraffin-embedded, formalin-fixed tissue blocks is 20-25°C.
View ordering information
Microsatellite instability – read more
|
