Effect of 5-Aza-CdR on expression and methylation of E-cadherin gene in human colon carcinoma cells

Department of Gastroenterology, The 2nd Xiangya Hospital, Central Southern University, Changsha, Hunan 410011, People's Republic of China.
Chinese journal of cancer (Impact Factor: 2.16). 01/2010; 29(1):38-42. DOI: 10.5732/cjc.009.10293
Source: PubMed


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

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    ABSTRACT: Prostate cancer is the second most common malignancy in men worldwide. Abnormal epigenetic alterations such as DNA methylation and histone modification play an important role in tumor initiation, progression and regulation of cancer-related genes such as integrin α4 and E-cadherin. Expression of these genes was determined by semi-quantitative reverse transcriptase-PCR in prostate cancer cell lines, DU145 and PC3, before and after treatment with 5-aza-2-deoxycytidine and trichostatin A. Laser capture microdissection microscopy was used to obtain exclusively affected epithelial cells from prostate gland biopsies of 30 patients with prostate cancer and 40 with benign prostate hyperplasia. DNA bisulfite modifications followed by methylation-specific PCR were used to evaluate the promoter methylation status of E-cadherin and α4 integrin genes in extracted DNA from patients and aforementioned cell lines. The integrin α4 promoter in DU145 was fully methylated, whereas in PC3 cells, partial methylation was detected. E-cadherin was expressed in both cell lines; trichostatin A and 5-aza-2-deoxycytidine treatment had no effect on E-cadherin expression, however the combined treatment of both drugs or 5-aza-2-deoxycytidine alone increased integrin α4 expression. Integrin α4 and E-cadherin were hypermethylated in 66.6 % and 6.6 % of prostate cancer cases, respectively; no hypermethylation was observed in patients with benign prostate hyperplasia. These results together suggest that aberrant DNA methylation is one of the mechanisms involved in integrin α4 expression and may play an important role in human prostate carcinogenesis. In addition, the higher rate of integrin α4 gene methylation in prostate cancer patients elects it as a potential molecular tumor marker.
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