title: Precision of pyrosequencing assay to measure LINE-1 methylation in colon cancer, normal colonic mucosa, and peripheral blood cells.
abstract: Genome-wide DNA hypomethylation plays an important role in epigenomic and genomic instability and colorectal carcinogenesis. DNA methylation in the long interspersed nucleotide element-1, L1 (LINE-1) repetitive element is a good indicator of global DNA methylation level. In addition, LINE-1 hypomethylation in blood cells has been associated with colorectal adenoma risk, and LINE-1 hypomethylation in colorectal cancer is related with prognosis and linearly predicts shorter patient survival. However, no study has comprehensively evaluated the precision of sodium bisulfite conversion and PCR-pyrosequencing to measure LINE-1 methylation. Using 10 paraffin-embedded colon cancers, 5 matched normal colon mucosa, and 5 unrelated peripheral blood buffy coat leukocyte specimens, we enriched tumor DNA by macrodissection and laser capture microdissection. LINE-1 methylation was calculated as an average of 100 * C/(C + T) at 4 CpG sites after bisulfite-PCR-pyrosequencing. The LINE-1 methylation value in colon cancers varied, ranging approximately from 30 to 80. To measure assay precision, we performed bisulfite conversion on seven different DNA specimen aliquots and repeated PCR-pyrosequencing seven times. Run-to-run (between-run) SD ranged from 1.3 to 4.4 (median, 3.0) in macrodissected colon cancers; 1.1 to 10.5 (median, 3.8) in laser capture microdissection specimens; 1.3 to 2.5 (median, 1.9) in normal colon; and 1.5 to 3.4 (median, 1.9) in leukocyte DNA. In conclusion, bisulfite conversion and PCR-pyrosequencing assay can measure LINE-1 methylation in macrodissected colon cancer, normal colon, and blood DNA, and may be useful in clinical and research settings.
authors.affiliation: Molecular Oncologic Pathology, Dana-Farber Cancer Institute, Brigham and Women's Hospital, Harvard Medical School, 44 Binney St., Room JF-215C, Boston, MA 02115, USA.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Irahara
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Nosho
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Baba
authors.forename: Kaori
authors.initials: K
authors.lastname: Shima
authors.forename: Neal I
authors.initials: NI
authors.lastname: Lindeman
authors.forename: Aditi
authors.initials: A
authors.lastname: Hazra
authors.forename: Eva S
authors.initials: ES
authors.lastname: Schernhammer
authors.forename: David J
authors.initials: DJ
authors.lastname: Hunter
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
authors.forename: Shuji
authors.initials: S
authors.lastname: Ogino
mesh_terms: D001773:Blood Cells / Q000502:physiology*; D003106:Colon / Q000033:anatomy & histology* / Q000473:pathology / Q000502:physiology*; D003110:Colonic Neoplasms / Q000235:genetics*; D019175:DNA Methylation; D042822:Genomic Instability; D006801:Humans; D007413:Intestinal Mucosa / Q000502:physiology*; D020084:Long Interspersed Nucleotide Elements; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*; D013447:Sulfites / Q000737:chemistry
chemical_list: D013447:Sulfites; C009279:sodium bisulfite