[Expression of methylthioadenosine phosphorylase (MTAP) gene and demethylation of its promoter in human colorectal cancer].

BACKGROUND AND OBJECTIVE

Abnormal expression of 5'-methylthioadenosine phosphorylase (MTAP) is found in various tumor tissues. This study was to explore the correlation of MTAP expression to demethylation of MTAP promoter in colorectal cancer tissues.

METHODS

The contents of MTAP mRNA in 50 colorectal cancer tissue samples and the adjacent normal tissues were detected by real-time PCR; expression of MTAP protein was detected by immunohistochemistry; methylation of MTAP promoter in colorectal cancer tissues and its adjacent normal tissues were detected by methylation-specified PCR (MSP).

RESULTS

Compared with the adjacent normal tissues, the expression of MTAP mRNA was dramatically increased in colorectal cancer tissues (P<0.01). The positive rate of MTAP protein in colorectal cancer was significantly higher than that in colorectal adenoma and in adjacent normal tissues (98.0% vs. 85.0% and 12.5%, P<0.05), and the difference of the latter two groups was also significantly different (P<0.01). The methylation frequency of MTAP promoter was significantly lower in colorectal cancer group (32.0%) than in normal tissue (93.8%) and colorectal adenoma (75.0%) groups (P<0.01).

CONCLUSIONS

Expression of MTAP is significantly higher in human colorectal cancer than in normal colorectal tissues. Demethylation of MTAP promoter may play an important role in up-regulating MTAP expression.