Open AccessLoss of 5‐hydroxymethylcytosine is accompanied with malignant cellular transformation
Author(s) -
Kudo Yotaro,
Tateishi Keisuke,
Yamamoto Keisuke,
Yamamoto Shinzo,
Asaoka Yoshinari,
Ijichi Hideaki,
Nagae Genta,
Yoshida Haruhiko,
Aburatani Hiroyuki,
Koike Kazuhiko
Publication year - 2012
Publication title -
cancer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.035
H-Index - 141
eISSN - 1349-7006
pISSN - 1347-9032
DOI - 10.1111/j.1349-7006.2012.02213.x
Subject(s) - dna demethylation , dna methylation , carcinogenesis , epigenetics , 5 hydroxymethylcytosine , dnmt1 , methyltransferase , biology , cancer research , methylation , demethylation , dna , malignant transformation , microbiology and biotechnology , cancer , gene , gene expression , genetics
Dysregulated DNA methylation followed by abnormal gene expression is an epigenetic hallmark in cancer. DNA methylation is catalyzed by DNA methyltransferases, and the aberrant expression or mutations of DNA methyltransferase genes are found in human neoplasm. The enzymes for demethylating 5‐methylcytosine were recently identified, and the biological significance of DNA demethylation is a current focus of scientific attention in various research fields. Ten–eleven translocation ( TET ) proteins have an enzymatic activity for the conversion from 5‐methylcytosine to 5‐hydroxymethylcytosine (5‐hm C ), which is an intermediate of DNA demethylation. The loss‐of‐function mutations of TET2 gene were reported in myeloid malignancies, suggesting that impaired TET ‐mediated DNA demethylation could play a crucial role in tumorigenesis. It is still unknown, however, whether DNA demethylation is involved in biological properties in solid cancers. Here, we show the loss of 5‐hm C in a broad spectrum of solid tumors: for example, a significant reduction of 5‐hm C was found in 72.7% of colorectal cancers ( CRCs ) and 75% of gastric cancers compared to background tissues. TET1 expression was decreased in half of CRC s, and a large part of them was followed by the loss of 5‐hm C . These findings suggest that the amount of 5‐hm C in tumors is often reduced via various mechanisms, including the downregulation of TET1 . Consistently, in the in vitro experiments, the downregulation of TET1 was clearly induced by oncogene‐dependent cellular transformation, and loss of 5‐hm C was seen in the transformed cells. These results suggest the critical roles of aberrant DNA demethylation for oncogenic processes in solid tissues. ( Cancer Sci 2012; 103: 670–676)