BACKGROUND AND OBJECTIVEColon cancer is one of the most common malignant tumors, and its pathogenesis is not fully understood. Transcriptional silencing by DNA methylation is believed to be an important mechanism of carcinogenesis. E-cadherin can suppress tumor cell invasion and metastasis, and is considered as an invasion/metastasis suppressor gene. Inactivation of E-cadherin gene often occurs in colon carcinoma. This study was to investigate the correlation between E-cadherin gene expression and the methylation status of E-cadherin 5' CpG islands in human colon carcinoma cell line HT-29, and to explore the mechanism of carcinogenesis of colon cancer.

METHODSImmunocytochemical dicho-step method and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect the expression of E-cadherin protein and mRNA in HT-29 cells after 5-Aza-CdR treatment; methylation specific PCR was used to analyze the methylation status at promoter of E-cadherin gene.

RESULTSThe expression of E-cadherin gene could be restored by 5-Aza-CdR treatment, immunocytochemical staining showed the positive expression ratio of E-cadherin increased from (21+/-7)% (1 micromol/L) to (39+/-13)% (5 micromol/L); E-cadherin genes were methylated and not expressed in HT-29 cells in the colon carcinoma.

CONCLUSIONSE-cadherin methylation plays an important role in the carcinogenesis of colon carcinoma cells and can re-express after the treatment with 5-Aza-CdR.