Microsatellite Instability in Intestinal Metaplasia and Gastric Cancer

Abstract：Objectiye: To investigate the changeable patterns of microsatellite instability (MSI)in intestinal metaplasia(IM)and gastric cancer(CC)and the role of MSI in gastric carcinogenesis. Methods: Silver staining single strand conformation polymorphism-polymeriase chain reaction(PCR-SSCP)was used to screen MSI markers at 5 loci in formalin-fixed, paraffin-embedded tissues of GC ( n ＝ 30), IM ( n 40) and corresponding normal gastric tissues. Results: The abnormal shifting of the single-strand DNA was identified in 7(23.3%)out of GC and in 8(20%)out of IM samples. Three( 10% )tumors and one(2.5% ) IM displayed high-frequency MSI( two or more loci altered) .Low-frequency MSI(one loci altered)was detected in 4 (13.3 % )of the tumors and in 7 (17.5%)IM samples. GC with MSI was associated with distal locaton of the tumors but age, sex, differentiation, lymph nodes metastasis and TNM stage( P = 0.044). MSI was more likely detected in moderate-grade IM than in mild-grade IM tssues(34.8% versus 0; P ＝ 0.013); and MSI had a tendency to be easily detected in female with IM. Conclusion: The progressive accumulation of MSI in areas of IM may contribute to GC development, representing an important molecular event in the multistep gastric carcinogenesis.