Microstatellite Instability and DNA Mismatch Repair Protein Deficiency in Chinese Patients with Sporadic Colorectal Cancer
Dan Huang, Xiaochen Chen, Baohua Yu, Weiqi Sheng, Xiang Du. Fudan University Cancer Center, Shanghai, China
Background: Sporadic colorectal carcinoma (SCRC) is one of the most common malignancies in the world, and its incidence is highly increased with the changes of lifestyle in Chinese. Researches suggest some SCRCs are developing through the replication error pathways, which could be detected by microsatellite instability (MSI) or DNA mismatch repair (MMR) proteins. This study was to evaluate the prevalence of MSI and loss of MMR protein expression in Chinese.
Design: An auto-immunohistochemical staining including 4 antibodies(MLH1, MSH2, PMS2 and MSH6) were used in the paraffin embedded tissue samples from 452 SCRCs. A total of 144 SCRCs including all MMR protein abnormalities performed MSI testing using PCR amplification for five microsatellite locus (BAT25, BAT26, D2S123, D5S346 and D17S250).
Results: MMR protein deficiency was seen in 43 of 452 (9.51%) SCRCs. The loss of expression of MLH1, MSH2, PMS2 and MSH6 was identified in 29/452(6.42%), 5/452(1.11%), 29/452(6.42%) and 11/452(2.43%), respectively. The most common concurrent loss was MLH1 and (observed in 25/452), followed by MSH2 and MSH6 (4/452).
The abnormality of four MMR proteins was detected in one case. For 144 SCRCs in MSI testing, forty-one were classified as MSI-High (MSI-H) and 3 as MSI-Low (MSI-L). MSI-H were seen in 24/29(82.76%), 5/5(100%), 25/29(86.20%) and 10/11(90.90%) SCRCs with loss expressions of MLH1, MSH2, PMS2 and MSH6, respectively.
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