DNA Methylation Status of RETN and ADIPOQ Genes in Sporadic Colon Cancer

Background: Colon cancer develops through a complex process that involves epigenetic alterations. Compelling evidence has been achieved that adipocytokines link obesity with colon cancer progression Therefore, understanding the epigenetic modifications in adipokine genes might help in clarifying their role in colon cancer pathogenesis. The aim of the present project was to study the DNA methylation status of RETN and ADIPOQ genes in sporadic colon cancer patients. Methods: 70 cancerous colon tissue and adjacent paired non-cancerous tissue was used to determine the DNA methylation status using methylation-specific polymerase chain reaction (MS-PCR) assay. Quantitative real-time PCR (qRT-PCR) was used to determine the expression level of RETN and ADIPOQ genes. Results: In colon cancer tissues, the CpG sites in the three selected promoter regions of ADIPOQ and RETN were hypermethylated in all samples. DNA methylation level at the CpG sites in exon one of the RETN gene exhibited a lower level in the non-cancerous tissue compared to the cancerous tissue and paired blood samples. The RETN mRNA was upregulated. Conclusion: We postulate that DNA methylation status at the CpG sites in exon one of the RETN gene might help uncover cancer signatures in sporadic colon cancer and may be used as a biomarker. The upregulation of the RETN mRNA level might play a role in sporadic colon cancer tumorigenesis.

IBD-associated Colon Cancers Differ in DNA Methylation and Gene Expression Profiles Compared With Sporadic Colon Cancers

Background and Aims As ulcerative colitis [UC]-associated colorectal cancer [CRC] and sporadic CRC differ in presentation and molecular features, we sought to evaluate differences in the impact of DNA methylation on gene expression. Methods DNA methylation was assessed in 11 UC-CRCs and adjacent tissue and 11 sporadic CRCs and adjacent tissue, using Illumina arrays. RNA sequencing was performed on 10 UC-CRCs and adjacent tissue and eight sporadic CRCs and adjacent tissues. Differences in DNA methylation and transcript expression, as well as their correlation in the same tissues, were assessed. Immunohistochemistry was performed for three proteins, ANPEP, FAM92A1, and STK31, all of which exhibited an inverse correlation between DNA methylation and transcript expression in UC. Results Thirty three loci demonstrated differences in DNA methylation between UC-CRC and adjacent tissue. In contrast, there were 4204 differentially methylated loci between sporadic colon cancer and adjacent tissue. Eight hundred eighty six genes as well as 10 long non-coding RNAs [lncRNA] were differentially expressed between UC-CRC and adjacent tissues. Although there were no differentially methylated loci between UC and sporadic CRC, 997 genes and 38 lncRNAs were differentially expressed between UC-CRC and sporadic CRC. In UC, 18 genes demonstrated a negative correlation between DNA methylation and transcript expression. Evaluation of protein expression related to three genes, ANPEP, FAM92A1, and STK31, confirmed down-regulation of ANPEP and up-regulation of STK31 in UC-CRC. Conclusions Regulation of transcript expression by DNA methylation involves genes key to colon carcinogenesis and may account for differences in presentation and outcomes between inflammatory bowel disease and sporadic colon cancer.