Abstract:

To study the changes of p16 gene protein expression and promoter methylation in carcinoma ex pleomorphic adenoma (CXPA) of the parotid gland, and to evaluate their significance for carcinogenesis of CXPA.  Methodsp16 gene protein expression and promoter methylation were determined in 40 samples of CXPAs of the parotid glands and 10 normal samples of the parotid gland(NM) using immunohistochemistry (IHC) and methylation specific PCR (MSP).  ResultsIn normal parotid glands, the p16 protein was positively expressed. In the CXPAs group, 21 cases (52.5%) showed a decreased (in different degrees) or absence of p16 protein expression. There was significant statistical difference (P＜0.05) between the two groups. Hypermethylation of the p16 gene promoter was found in 16 cases (16/40, 40%) of CXPAs, but was not found in normal salivary glands (P＜0.05). ConclusionThe decreased or absence of p16 protein expression and promoter hypermethylation play an important role in the carcinogenesis of CXPA. And hypermethylation may be the important inactivation mechanism of the p16 gene in CXPA.

Key words: Carcinoma ex pleomorphic adenoma; Gene; Immunohistochemistry; DNA methylation