Aberrant methylation of multiple genes and clinicopathological features in oral squamous cell carcinoma.

The purpose of this study was to examine the methylation profile of various oral squamous cell carcinomas and to correlate the methylation of particular chromosomal loci with the clinicopathological features of the tumors. A semiquantitative analysis of the methylation status of 12 loci in 96 primary tumors and 13 cell lines was carried out. Methylation frequency was calculated as the percentage of methylated alleles detected by bisulfate-PCR. Of the 12 loci examined, 9 (p16INK4A, p15INK4B, p14ARF, DCC, DAP kinase, MINT1, MINT2, MINT27, and MINT31) exhibited aberrant methylation at various frequencies, whereas 3 (hMLH1, HRK, and CACNA1G) showed no methylation. Dense methylation of the 5' CpG island of DAP kinase and MINT1 was well correlated with loss of gene expression. In addition, methylation of DCC was correlated with bone invasion by gingival tumors (P = 0.036), with aggressive invasiveness of tumors of the tongue (P = 0.046), and with reduced survival (P = 0.050). Methylation of MINT1 and MINT31 also correlated with poor prognoses (P = 0.058 and 0.041), whereas methylation of p14ARF correlated with a good prognosis (P = 0.021). Cox regression analysis showed methylation of MINT31 to be an independent predictor of outcome (hazard ratio, 3.79; 95% confidence interval, 1.58-9.10) and to be associated with the T4 disease group (hazard ratio, 5.71; 95% confidence interval, 1.25-26.07). Analysis of DNA methylation is a useful approach to evaluation of the biological characteristics of oral cancers and may be a useful diagnostic indicator of patient prognosis.