Methylation array analysis of preoperative and postoperative saliva DNA in oral cancer patients.

PURPOSE: To perform methylation array analysis of 807 cancer-associated genes using tissue and saliva of oral squamous cell carcinoma (OSCC) patients with the objective of identifying highly methylated gene loci that hold diagnostic and predictive value as a biomarker. EXPERIMENTAL DESIGN: We did the methylation array on DNA extracted from preoperative saliva, postoperative saliva, and tissue of 13 patients with OSCC, and saliva of 10 normal subjects. We identified sites that were highly methylated in the tissue and preoperative saliva samples but not methylated in the postoperative saliva samples or in normal subjects. RESULTS: High quality DNA was obtained and the methylation array was successfully run on all samples. We identified significant differences in methylation patterns between the preoperative and postoperative saliva from cancer patients. We established a gene classifier consisting of 41 gene loci from 34 genes that showed methylation in preoperative saliva and tissue but were not methylated in postoperative saliva or normal subjects. Gene panels of 4 to 10 genes were constructed from genes in the classifier. The panels had a sensitivity of 62% to 77% and a specificity of 83% to 100% for OSCC. CONCLUSIONS: We report methylation array analysis of 807 cancer-associated genes in the saliva of oral cancer patients before and after oral cancer resection. Our methylation biomarker approach shows the proof of principle that methylation array analysis of saliva can produce a set of cancer-related genes that are specific and can be used as a composite biomarker for the early detection of oral cancer.