LINE-1 hypomethylation during primary colon cancer progression

• Published in: PloS one Vol. 6; no. 4; p. e18884
• Main Authors: Sunami, Eiji, de Maat, Michiel, Vu, Anna, Turner, Roderick R, Hoon, Dave S B
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.04.2011; Public Library of Science (PLoS)
• Subjects: Accuracy; Adenoma; Analysis; Biology; Biomarkers; Bisulfite; Breast cancer; Cancer; Care and treatment; Colon; Colon cancer; Colonic Neoplasms - genetics; Colonic Neoplasms - pathology; Colorectal cancer; Colorectal carcinoma; Demethylation; Deoxyribonucleic acid; Development and progression; Disease Progression; DNA; DNA Methylation; Epithelial cells; Epithelium; Genes; Genomes; Histopathology; Humans; Long Interspersed Nucleotide Elements; Lymphatic system; Medical prognosis; Medicine; Mesenchyme; Metastasis; Methylation; Oncology; Paraffin; Pathology; Patients; Quantitative analysis; Sodium; Stability analysis; Stem cells; Sulfites; Tumors; United States > US; California
• DOI: 10.1371/journal.pone.0018884
• ISSN: 1932-6203

Methylation levels of genomic repeats such as long interspersed nucleotide elements (LINE-1) are representative of global methylation status and play an important role in maintenance of genomic stability. The objective of the study was to assess LINE-1 methylation status in colorectal cancer (CRC) in relation to adenomatous and malignant progression, tissue heterogeneity, and TNM-stage. DNA was collected by laser-capture microdissection (LCM) from normal, adenoma, and cancer tissue from 25 patients with TisN0M0 and from 92 primary CRC patients of various TNM-stages. The paraffin-embedded tissue sections were treated by in-situ DNA sodium bisulfite modification (SBM). LINE-1 hypomethylation index (LHI) was measured by absolute quantitative analysis of methylated alleles (AQAMA) realtime PCR; a greater index indicated enhanced hypomethylation. LHI in normal, cancer mesenchymal, adenoma, and CRC tissue was 0.38 (SD 0.07), 0.37 (SD 0.09), 0.49 (SD 0.10) and 0.53 (SD 0.08), respectively. LHI was significantly greater in adenoma tissue compared to its contiguous normal epithelium (P = 0.0003) and cancer mesenchymal tissue (P<0.0001). LHI did not differ significantly between adenoma and early cancer tissue of Tis stage (P = 0.20). LHI elevated with higher T-stage (P<0.04), was significantly greater in node-positive than node-negative CRC patients (P = 0.03), and was significantly greater in stage IV than all other disease stages (P<0.05). By using in-situ SBM and LCM cell selection we demonstrated early onset of LINE-1 demethylation during adenomatous change of colorectal epithelial cells and demonstrated that LINE-1 demethylation progression is linear in relation to TNM-stage progression.