LINE-1 hypomethylation in familial and sporadic cancer.
Increased and decreased methylation at specific sequences (hypermethylation and hypomethylation, respectively) is characteristic of tumor DNA compared to normal DNA and promotes carcinogenesis in multiple ways including genomic instability. Long interspersed element (LINE), an abundant class of retrotransposons, provides a surrogate marker for global hypomethylation. We developed methylation-specific multiplex ligation-dependent probe amplification assays to study LINE-1 methylation in cases of colorectal, gastric, and endometrial cancer (N = 276), stratified by patient category [sporadic; Lynch syndrome (LS); familial colorectal cancer type X (FCCX)] and microsatellite instability status. Within each patient group, LINE-1 showed lower methylation in tumor DNA relative to paired normal DNA and hypomethylation was statistically significant in most cases. Interestingly, normal colorectal mucosa samples from different patient groups displayed differences in LINE-1 methylation that mirrored differences between the respective tumor tissues, with a decreasing trend for LINE-1 methylation from patients with sporadic colorectal cancer to LS to FCCX. Despite the fact that the degree of LINE-1 methylation is generally tissue specific, normal colorectal mucosa, gastric mucosa, and endometrium from LS patients showed similar levels of LINE-1 methylation. Our results suggest that the degree of LINE-1 methylation may constitute a "field defect" that may predispose normal tissues for cancer development.
Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, PO Box 63 00014, Finland.
Walter
W
Pavicic
Emmi I
EI
Joensuu
Taina
T
Nieminen
Päivi
P
Peltomäki
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018899:CpG Islands; D019175:DNA Methylation; D005190:Family; D023061:Gene Order; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008875:Middle Aged; D009369:Neoplasms / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics
D025521:Tumor Suppressor Proteins