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Objective: To investigate methylation of the adenomatosis polyposis coli homologue (APC2) promoter and its correlation with prognostic implications in Chinese colorectal cancer (CRC)., Methods: The mRNA expression of APC2 in colorectal tissues was evaluated using the database of The Cancer Genome Atlas (TCGA). Methylation analysis of APC2 in tumor ( n = 66) and corresponding adjacent formalin-fixed and paraffin-embedded (FFPE) tissues ( n = 44) was performed by Sequenom EpiTYPER® and verified by cloning-based bisulfite sequencing analysis. Demethylation and retrieval of APC2 expression in cell lines HT29, HCT116, and SW480 were treated with 5-aza-2'-deoxycytidine (5-AZC)., Results: Analysis of TCGA showed that APC2 mRNA was significantly downregulated in primary tumors when compared to normal tissues ( p < 0.05). APC2 methylation was upregulated (43.93% vs 7.31%, p < 0.05) in tumors compared to adjacent FFPE tissues. In vitro experiments demonstrated that 5-AZC downregulated the methylation of APC2 and retrieved its expression of mRNA and protein levels ( p < 0.05). Multivariate Cox regression indicated that APC2&#95;CPG&#95;14 was an independent risk factor for overall survival (HR = 6.38, 95% CI: 1.59-25.64, p < 0.05)., Conclusion: This study indicates that APC2 is hypermethylated and may be a tumorigenesis biomarker for Chinese CRC patients.

Simple Summary: Previous studies have established an electrochemical detection method for the rapid detection of cfDNA (circulating free DNA) methylation and found that this technology might be a potential method for cancer diagnosis. However, the underlying mechanism and its role in the diagnosis and prognosis of malignant tumors are not well-characterized. In present study, we utilized the electrochemical detection method to detect the DNA methylation status by using electron microscopies and infrared spectroscopy and found that DNA with different methylated levels adsorbed to the gold surface differently, which was likely mediated by hydrophobic bonds. In addition, after detection of the cfDNA methylation status from 505 normal individuals, 725 cancer patients before treatment, and 549 patients after treatment, we found that the cfDNA adsorption rate could be used as an indicator for the diagnosis and prognosis prediction of pan-cancer. Our research provides a novel method for the liquid biopsy of cancer for diagnosis and prognosis predictions. Prior research has established an electrochemical method based on the differential adsorption capacity of gold surfaces with different methylated DNA degrees and found that this method might be valuable for cancer diagnosis by detecting circulating free DNA methylation. However, further investigation on the underlying mechanism and validation of its diagnostic and prognostic values in a large cohort of malignant tumors was limited. We found that DNA with different methylation levels formed particles of diverse sizes on the gold surface. Hydrophobic bonds played a significant role in the binding process of methylated DNA to the gold surface. The detection condition of an adsorption time of 10 min and temperature of 20 °C was optimal. In a large cohort of plasma samples from the patients with different malignant tumors, as well as normal individuals, we found that the electrochemical detection method based on the differential adsorption capacity of methylated DNA degree on a gold surface could be used as a noninvasive tool for malignant tumor diagnosis and prognostic evaluation. The diagnostic efficiency of this method in malignant tumors was even slightly better than that of the current tumor biomarkers widely used in routine clinical practice (circulating free DNA (cfDNA) vs. carcinoembryonic antigen (CEA), 0.8131 vs. 0.7191 and cfDNA vs. CA19-9, 0.7687 vs. 0.6693). [ABSTRACT FROM AUTHOR]