Hypermethylation of APC2 Is a Predictive Epigenetic Biomarker for Chinese Colorectal Cancer

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_CPG_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.