Study the relationship between the gene regulation and microsatellite instability of the cyclooxygen-ase-2,hMLH1 in colon carcinoma

Abstract

Objective To investigate the cyclooxygenase-2 (COX-2),human mut-lhomologue 1 (hMLH1) of genes promoter methylation and microsatellite instability (MSI) frequency in 42 cases of human colon carcinoma and normal tissues, and to evaluate the relationship between them and occurrence of colon carcinoma. Methods Methylation specific polymerease chain reaction ( MSP) and polymerase chain reaction (PCR) methods were employed in this study in order to investigate the promoter methylation of these genes and 5 loci MSI frequency in human colon carcinoma and normal tissues. Results Of 42 colon carcinoma cases,the total frenquency of MSI was 43.86 % ( 18/42). The MSI frenquency no significant discrepancy was found among the 5 loci (P > 0.05). The number of MSI, MSS was 18 and 24, respectively. Cases with methylation of COX-2 and hMLH1 gene promoter CpG islands in colon carcinoma were 13 and 15 ,and they were not detected in normal tissues. 8 cases with methylation of COX-2 gene promoter CpG islands only occurred in MSI-H colon carcinoma, and 6 cases both with methylation of COX-2 and hMLH1 gene promoter CpG islands was observed in MSI-H. Conclusion The methylation rate of hMLH1 gene promoter CpG islands in MSI colon carcinoma was higher than that in MSS colon carcinoma. It suggested that detecting the methylation of hMLH1 gene promoter CpG islands might be a useful method for determining the colon carcinoma type. Key words: Colon carcinoma; Cyclooxygenase-2; hMLH1; Methylation specific polymerease chain reaction