Development of DNA methylation biomarkers as an early detection tool for human lung adenocarcinoma

UnrestrictedLung cancer is the leading cause of cancer-related death in the United States. It is estimated that more than 160,000 lung cancer patients will die of the disease in 2008. Early detection is key to improving patient survival; however, current screening strategies have low specificity and/or sensitivity in detecting early lung cancer. Our focus was to study DNA methylation and its role in lung cancer development and progression with the hope of developing molecular markers for the early detection of lung adenocarcinoma (AD; the most common histology of lung cancer). Understanding the timing of DNA methylation changes during the multi-stage process of AD development could provide a panel of biomarkers potentially used to detect the disease at earlier stages. We have developed a panel of 15 loci that have significant differential methylation between AD and adjacent non-tumor lung tissues (AdjNTL) by MethyLight, a quantitative DNA methylation assay. When used in a panel, all 15 loci showed a sensitivity of 92.85% and specificity of 100%. These tumor-specific DNA methylation markers were used to study whether the same methylation signatures are present in Atypical Adenomatous Hyperplasia (AAH, putative precancerous lesion of lung AD). In our analysis of tissues from AD patients with AAH lesions, we observed variability in the pattern of methylation between the different loci. Some loci (e.g. CDKN2A) were aberrantly methylated even in non-cancerous tissues. Other loci started accumulating methylation marks in AAH (e.g. SFRP1) while other loci do not become hypermethylated until in its invasive state (RASSF1). The difference in timing of methylation between the different loci could be a reflection of the roles of the pathways involved in adeno-carcinogenesis. Additional cancer-specific DNA methylation markers had recently been indentified through high-throughput Illumina GoldenGate Methylation assay.; The onset of DNA methylation of the loci identified by Illumina GoldenGate assay in AD development remains to be elucidated. The knowledge of sequential methylation changes in AAH-AD continuum could yield powerful risk and/or early detection biomarkers for AD. In addition, our findings could provide insights into the natural history of this lethal disease