
<ArticleTitle>The E-cadherin gene is silenced by CpG methylation in human oral squamous cell carcinomas.</ArticleTitle>
<AbstractText>Reduction of E-cadherin strongly relates to invasiveness and metastasis in vitro. To clarify CpG methylation around the promoter region of the <prot>E-cadherin</prot> gene in oral squamous cell carcinoma (SCC), we examined the DNA samples of various human SCC cell lines and primary oral SCC tissues by methylation-specific polymerase chain reaction (MSP). CpG methylation of the <prot>E-cadherin</prot> gene markedly correlated to the reduction of <prot>E-cadherin</prot> expression in human oral SCC cell lines. In primary oral SCC tissues, only 1 of 5 preserved <prot>E-cadherin</prot>-expressing tissues was methylated, whereas methylation was found in 17 (94.4%) of 18 <prot>E-cadherin</prot>-reduced tissues. Our results suggest that reduction of <prot>E-cadherin</prot> expression is associated with CpG methylation of the <prot>E-cadherin</prot> gene promoter. We recently established two cell lines with high and low metastatic potential, UM1 and UM2, from SCC primary tongue tissue of a patient. <prot>E-cadherin</prot> expression of high-metastatic UM1 was clearly lower than that of low-metastatic UM2, and MSP results showed CpG methylation in the UM1 but not the UM2 cell line. To investigate whether demethylation of CpG methylation of the <prot>E-cadherin</prot> gene could restore expression and function of <prot>E-cadherin</prot>, we treated UM1 with the demethylating agent 5-azacytidine (5-aza) and found that <prot>E-cadherin</prot> expression was indeed restored by demethylation. Moreover, in the demethylated UM1, invasion of the collagen gel was clearly suppressed compared with the untreated UM1. These results suggested that inactivation of <prot>E-cadherin</prot> expression resulted from CpG methylation of the gene promoter; a correlation between CpG methylation of the <prot>E-cadherin</prot> gene promoter and invasive potential was also suggested.</AbstractText>
