The correlation between CpG methylation and protein expression of P16 in oral squamous cell carcinomas.

We examined the P16 expression by immunohistochemical stain and detected the methylation by methylation specific polymerase chain reaction (MSP) in 48 primary oral squamous cell carcinoma (SCC) tissues. The results showed that 20/48 (41.7%) of cancerous tissues had CpG methylation around the promoter region, but 8/48 (17%) of the nearby non-cancerous tissues also had CpG methylation, around the promoter region. The results from immunohistochemical studies showed that reduced and heterogeneous expression of P16 were found in the tissues, which had CpG methylation around the promoter region. In conclusion, the methylation of P16 in oral SCC occurs in pre-cancerous and cancerous stage, which results in decreasing or abolishing the P16 expression, which is heterogeneous in the cancer cells.