Microsatellite alteration and its characteristics in colorectal carcinoma

Objective: To determine the role of microsatellite alterations in carcinogenesis of colorectal carcinoma (CRC). Methods: Alterations of 10 microsatellite loci from 5 different chromosomes were detected in 92 colorectal cancers and their paired normal mucosa by PCR, denatured polyacrylamide gel electrophoresis and silver staining. Associations of microsatellite alterations with clinopathologic parameters were statistically clarifield. Results: Alterations of microsatellite were classified into microsatellite instability type I, type II and loss of heterozygosity (LOH). The carcinoma with ≧30% loci microsatellite alterations was defined as replication error(RER) positive tumors. Of 92 cases, 14 were RER+. Microsatellite alterations of P53₍₁₎ and D18S363 loci (64.29%) was most commonly identified in the RER+ tumors. RER+ were more commonly seen in poorly differentiated carcinomas and tended to occur in mucoid carcinomas. The type of microsatellite alterations varied in different histological types of CRC. Conclusions: Microsatellite alteration is a common molecular event in CRC. Different microsatellite loci showed various biologic significance. P53₍₁₎ and D18S363 should be essentially detected loci that can show the RER status of tumors. Project supported by the National Natural Science Foundation of China(No. 39770297) and Key Project of Zhejiang Committee of Science and Technology(No. 961103076)