Distinctive pattern of LINE-1 methylation level in normal tissues and the association with carcinogenesis.
Genome-wide losses of DNA methylation have been regarded as a common epigenetic event in malignancies and may play crucial roles in carcinogenesis. Limited information is available on the global methylation status in normal tissues and other cancer types beyond colonic carcinoma. Here we applied the combined bisulfite restriction analysis PCR to evaluate the methylation status of LINE-1 repetitive sequences in genomic DNA derived from microdissected samples from several human normal and neoplastic tissues. We found that methylation of LINE-1 in leukocytes was independent of age and gender. In contrast, normal tissues from different organs showed tissue-specific levels of methylated LINE-1. Globally, most carcinomas including breast, colon, lung, head and neck, bladder, esophagus, liver, prostate, and stomach, revealed a greater percentage of hypomethylation than their normal tissue counterparts. Furthermore, DNA derived from sera of patients with carcinoma displayed more LINE-1 hypomethylation than those of noncarcinoma individuals. Finally, in a colonic carcinogenesis model, we detected significantly greater hypomethylation in carcinoma than those of dysplastic polyp and histological normal colonic epithelium. Thus, the methylation status is a unique feature of a specific tissue type and the global hypomethylation is a common epigenetic process in cancer, which may progressively evolve during multistage carcinogenesis.
Genetics Unit, Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand.
Krisanee
K
Chalitchagorn
Shanop
S
Shuangshoti
Nusara
N
Hourpai
Narisorn
N
Kongruttanachok
Pisit
P
Tangkijvanich
Duangporn
D
Thong-ngam
Narin
N
Voravud
Virote
V
Sriuranpong
Apiwat
A
Mutirangura
D001483:Base Sequence; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D004247:DNA; D019175:DNA Methylation; D005260:Female; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008297:Male; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000145:classification / Q000235:genetics
D004247:DNA