Abstract: Objective To investigate the relationship between the methylation level of PAQR3 and colorectal cancer, the methylation level and mRNA expression of PAQR3 gene in colorectal cancer were detected. Methods 54 colorectal cancers and 54 colorectal normal tissues were collected to detect the expression of mRNA level by reverse transcriptase PCR(RT-PCR), the methylation level of PAQR3 gene were detected by Methylation Specific PCR(MSP), which were used to analyze the relationship between methylation of PAQR3 and clinical data. Results Expression of PAQR3 mRNA in 54 normal tissues were significantly higher than that in 54 colorectal cancer tissues , the expression rates were 18.5%(10/54) and 57.4%(31/54), there was significant difference between cancer and normal tissues(P= 0.000).The PAQR3 gene promoter methylation rate of colorectal cancer and colorectal normal tissues were 33.3%(18/54)and 5.6 %(3/54), there was significant difference between cancer and normal tissues(P= 0.000).There was significant difference in age, differentiation, infiltration, clinical stage and the metastasis of lymph node in colorectal cancer, but not in sex and location. Conclusion PAQR3 expression can be reduced in colorectal cancer, PAQR3 gene promoter hypermethylation may play an important role in oncogenesis of colorectal cancer.

Key words: PAQR3, colorectal cancer, methylation, MSP