Researchers at the Mayo Clinic have developed a new screening procedure to detect whether colorectal cancer patients under 50 have Lynch Syndrome. Lynch Syndrome, formerly known as hereditary nonpolyposis colorectal cancer, causes anywhere from 3,200 to 11,200 new cases a year of colorectal cancer. It often causes earlier onset of colorectal polyps which are more likely to become cancerous than in people without Lynch Syndrome. Lynch Syndrome is a dominant genetic disorder that disrupts the genes any of the MLH1, MSH2, MSH6, and PMS2 genes. These genes are involved in repairing DNA that was copied wrong during replication. Since DNA repair is an important part of the cell cycle, with defects in any of these genes, mitosis will continue despite the mistakes in the newly synthesized DNA. This often leads to mutations in the daughter cell and over time, these mutations will lead to tumor growth.About 80 percent of people with Lynch Syndrome will develop colorectal cancer. However,many other cancer types are seen with patients with Lynch Syndrome, including endometrial, stomach, ovarian and skin cancers. Since the only known symptom of Lynch Syndrome is the increased risk of cancer, finding the colorectal patients who do have Lynch Syndrome and alerting them can help long-term. The Microsatellite Instability (MSI) test is used to determine whether a patient has a Lynch Syndrome. The MSI test looks at microsatellites, repeated portions of DNA. Since any single person’s microsatellites are a set length, if the lengths of their microsatellites is highly variable, this is indicative of large numbers of mutations occurring. The MSI test groups these people with high microsatellite instability together. Tests shows that about 90 percent of people afflicted with Lynch Syndrome have high microsatellite instability.
The MSI test is useful because it helps not only the patient but also their families. Through a simple test like MSI, the cost and anxiety associated with genetic testing can largely be avoided. Although about 10 percent of people with high microsatellite instability may not have Lynch Syndrome, a genetic test can prove that they have no need to worry. Patients who do have Lynch Syndrome, however, are suggested to tell their immediate family so that they can begin early screenings for cancers. By diagnosing more cases of Lynch Syndrome, more cancers can be caught early and prevented from becoming aggressive.
Sources
http://www.genetichealth.com/CRC_HNPCC_Microsatellite_Instability_Testing.shtml
http://en.wikipedia.org/wiki/Hereditary_nonpolyposis_colorectal_cancer
http://www.mayoclinic.com/health/lynch-syndrome/DS00669
