Methylation status of the PTEN gene in adenoid cystic carcinoma cells.

The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is deficient in various types of human tumors due to mutations or epigenetic alterations. PTEN promoter hypermethylation is a major epigenetic silencing mechanism leading to self-repression in these tumors. The present study aimed to investigate whether PTEN promoter methylation is involved in the regulation of the PTEN gene in adenoid cystic carcinoma (ACC) cells. The expression of PTEN in ACC-2 cells was found to be significantly lower than that in normal salivary gland epithelial cells using RT-PCR analysis. The existence of CpG island methylation in the PETN promoter region in ACC-2 cells was demonstrated by methylation-specific PCR (MSP) analysis and direct sequencing of MSP product. RT-PCR, Western blot analysis and luciferase assay showed that mRNA and protein expression and the promoter activity of PTEN in ACC-2 cells treated with the DNA methylation inhibitor 5-aza-2-deoxycytidine were significantly up-regulated in a time-dependent manner. These results indicate that the hypermethylation of the PTEN promoter region leads to lower expression of PTEN gene in ACC cells, which aids in the development of PTEN as a molecular marker for the early diagnosis of this carcinoma.