Promotor hypermethylation of p14ARF is a key alteration for progression of oral squamous cell carcinoma.

We investigated the promotor hypermethylation status of multiple genes in 49 oral squamous cell carcinomas (OSCC), using the methylation-specific PCR (MSP) assay. The genes examined included p16INK4a, p14ARF, RB1, p21Waf1, p27Kip1, PTEN, p73, 0(6)-MGMT, and GST-P. Detailed clinicopathological data, such as patient age, sex, tobacco use, alcohol consumption, lesion site, degree of tumor differentiation, tumor size, presence of lymph node metastasis, and clinical stage, were collected for all 49 samples. Overall, gene methylation was detected in 46.9% (23/49) of samples and was closely correlated with tobacco use or/and alcohol consumption. Of the genes investigated, p16INK4a, p14ARF, 0(6)-MGMT, RB1, PTEN, and p27Kip1 were found to be methylated in 34.7%, 20.4%, 12.2%, 10.2%, 6.1%, and 4.1% of these 49 tumors, respectively, but methylation of p21Waf1, p73, and GST-P was not detected at all. Methylation frequencies were much higher for each gene when computed among informative cases only. Concurrent promotor hypermethylation of p16INK4a and p14ARF correlated significantly with tumor size, lymph node metastasis, and stage III/IV advanced OSCC; p14ARF hypermethylation, in particular, was significantly associated with both lymph node metastasis and late clinical stage. Our results suggest that DNA methylation of multiple genes, especially hypermethylation of the p14ARF promoter, is common in OSCC and is associated with the use of tobacco and/or alcohol consumption. For this type of cancer, the data further implicates gene methylation as playing an important role in tumor progression.