The correlation between CpG methylation on promoter and protein expression of E-cadherin in oral squamous cell carcinoma

Background: Reduction of E-cadherin in most common epithelial tumors relates to metastasis, which results from the silence of E-cadherin by CpG methylation. Materials and Methods: We examined the E-cadherin expression by immunohistochemical staining and detected methylation by methylation-specific polymerase chain reaction (MSP) in 48 primary oral SCC tissues. Results: The results showed that 41 out of 48 (85.4%) cancerous tissues and 16 out of 48 (33.3%) nearby non-cancerous tissues had CpG methylation on the promoter region of E-cadherin. In these non-cancerous tissues, 2 out of 16 (12.5%) had no methylation change in their paired cancerous part. Immunohistochemical study showed that a decreased expression pattern was found in the tisssue which had CpG methylation on the promoter region, but an over expression island or aberrant expression was also frequently found in these cases. Conclusion: The methylation of E-cadherin in oral SCC may occur in the precancerous stage and the process is dynamic, which has no relationship with the aberrant expression of E-cadherin protein.