Background and aim: DNA methylation plays an important role during colorectal cancer (CRC) carcinogenesis. DNA methyltransferase 1 (DNMT1) is responsible for maintaining DNA methylation. We addressed the significance of DNMT1 expression in CRC.
Materials and methods: We measured the expression of DNMT1 in CRC tissues and in their corresponding distal normal colorectal mucosa using reverse transcriptase-polymerase chain reaction and immunohistochemical analysis.
Results: The mean +/- SD of DNMT1 mRNA in CRC tissues was 1.04 +/- 0.36, which was significantly higher than that in their corresponding distal normal colorectal mucosa (0.58 +/- 0.44, P < 0.05). Fifty-eight out of 77 (75.3%) CRC tissues and only 30 out of 77 (39%) corresponding distant normal colorectal mucosa showed immunoreactivity (P < 0.001). We also found that the immunoreactivity of DNMT1 was higher in mucosa adjacent to cancer than in corresponding normal colorectal mucosa; high immunoreactivity was significantly correlated with poor differentiation in CRC tissues (P = 0.008). No significant associations were found between DNMT1 immunoreactivity and the following variables: age, sex, locations of cancer, Duke's phase, and the presence of lymph-node metastasis.
Conclusion: These findings suggested that DNMT1 was associated with the malignant phenotype, and dysregulation of DNMT1 expression was present in tumor cells of CRC.