Background: Abnormal DNA methylation is a hallmark of human cancers and may be a promising biomarker for early diagnosis of human cancers. However, the majority of DNA methylation biomarkers that have been identified are based on the hypothesis that early differential methylation regions (DMRs) are maintained throughout carcinogenesis and could be detected at all stages of cancer.
Methods: In this study, we identified potential early biomarkers of colorectal cancer (CRC) development by genome-wide DNA methylation assay (Illumina infinium450, 450 K) of normal (N = 20) and pre-colorectal cancer samples including 18 low-grade adenoma (LGA) and 22 high-grade adenoma (HGA), integrated with GEO and ArrayExpress datasets (N = 833).
Results: We identified 209 and 8692 CpG sites that were significantly hyper-methylated in LGA and HGA, respectively. Pathway analysis identified nervous system-related methylation changes that are significantly associated with early adenoma development. Integration analysis revealed that DNA methylation in the promoter region of ADHFE1 has the most potential for being an early diagnostic biomarker for colorectal adenoma and cancer (sensitivity = 0.96, specificity = 0.95, area under the curve = 0.97).
Conclusions: Overall, we demonstrated that DNA methylation have been shown significant changes in the stage of LGA and HGA in the development of colon cancer. Genome-wide DNA methylation to LGA and HGA provided an important proxy to identify promising early diagnosis biomarkers for colorectal cancer.
Keywords: Biomarker; Colorectal cancer; DNA methylation; High-grade adenoma; Low-grade adenoma.