The E-cadherin gene is silenced by CpG methylation in human oral squamous cell carcinomas

Reduction of E-cadherin strongly relates to invasiveness and metastasis in vitro. To clarify CpG methylation around the promoter region of the E-cadhe rin gene in oral squamous cell carcinoma (SCC), we examined the DNA samples of various human SCC cell lines and primary oral SCC tissues by methylatio n-specific polymerase chain reaction (MSP). CpG methylation of the E-cadher in gene markedly correlated to the reduction of E-cadherin expression in hu man oral SCC cell lines. In primary oral SCC tissues, only 1 of 5 preserved E-cadherin-expressing tissues was methylated, whereas methylation was foun d in 17 (94.4%) of 18 E-cadherin-reduced tissues. Our results suggest that reduction of E-cadherin expression is associated with CpG methylation of th e E-cadherin gene promoter. We recently established two cell lines with hig h and low metastatic potential, UM I and UM2, from SCC primary tongue tissu e of a patient. E-cadherin expression of high-metastatic UM I was clearly l ower than that of low-metastatic UM2, and MSP results showed CpG methylatio n in the UM I but not the UM2 cell line. To investigate whether demethylati on of CpG methylation of the E-cadherin gene could restore expression and f unction of E-cadherin, we treated UM I with the demethylating agent S-azacy tidine (5-aza) and found that E-cadherin expression was indeed restored by demethylation. Moreover, in the demethylated UM 1, invasion of the collagen gel was clearly suppressed compared with the untreated UM 1. These results suggested that inactivation of E-cadherin expression resulted from CpG met hylation of the gene promoter; a correlation between CpG methylation of the E-cadherin gene promoter and invasive potential was also suggested. (C) 20 01 Wiley-Liss, Inc.