Background and Aim:
Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related mortal ity, globally. It is also the third common cause of malignancy in Iran. Despite recent advances in screening strategies, the means of CRC early detection remains limited. Thus, identification of novel biomarkers for the early detection of CRC are still on demand. Since genetic and epigenetic changes in colon epithelial cells play an important role in CRC, the aim of this study is to find epigenetic biomarkers or risk factors for the early detection of this cancer.Methods: SureSelectXT Methyl-Seq was performed on ۶ normal and ۶ colorectal tumor tissues. MethyLight assay was further performed on ۶۷ tumor tissues (۳۹ formalin-fixed paraffin-embedded (FFPE) and ۲۸ fresh tissues) and ۷۳ tumor-adjacent tissues (۴۷ FFPE and ۲۶ fresh tissues). All fresh tissues were obtained from Reza Radiotherapy and Oncology Center, Mashhad by colonoscopy and FFPE tissues were obtained from Razavi hospital, Mashhad. In order to perform MethyLight assay, bisulfate treatment was done on DNA extracted from FFPE and fresh tissues. The multiplex PCR reactions were performed on bisulfite converted DNA and the results were normalized to the β-actin from the same sample. ARMS-PCR was conducted on DNA extracted from CRC and control groups on a specific polymorphism identified through the MethyLight assay.Results: Methyl-Seq data showed that a nucleotide on chromosome ۲۱ (chr۲۱: ۴۶۶۷۰۷۱۵) was significantly methylated in normal samples whereas it was unmethylated in tumor tissues (P-value < ۰.۰۵). In addition, MethyLight assay showed a degree of methylation in all ۷۳ control tissues whereas no methylation was seen in all ۶۷ tumor tissues. In addition, association study of rs۹۶۳۷۲۳۱polymorphism as a potential risk factor with CRC is currently underway (۷۰۰ samples as of August ۲۰۲۰) and its results will be presented later.Conclusion: Our data suggest that the methylation status and probably the polymorphism on chr۲۱:۴۶۶۷۰۷۱۵ could be used as a biomarker or risk factor for the detection of CRC.