Murata Asuka, Baba Yoshifumi, Ishimoto Takatsugu, Miyake Keisuke, Kosumi Keisuke, Harada Kazuto, Kurashige Junji, Iwagami Shiro, Sakamoto Yasuo, Miyamoto Yuji, Yoshida Naoya, Yamamoto Manabu, Oda Shinya, Watanabe Masayuki, Nakao Mitsuyoshi, Baba Hideo
Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, Japan.
Department of Surgery, National Hospital Organization Kyushu Cancer Center, Japan.
Oncotarget. 2015 Sep 15;6(27):23372-82. doi: 10.18632/oncotarget.4281.
Mammalian DNA is epigenetically marked by 5'-cytosine methylation (5-methylcytosine [5-mC]). The Ten-eleven translocation (TET) enzymes (TET1, TET2, and TET3) are implicated in DNA demethylation, through dioxygenase activity that converts 5-mC to 5-hydroxymethylcytosine (5-hmC). Although decreased TET is reportedly associated with decreased 5-hmC levels in various cancers, functions of 5-hmC and TET expression in esophageal squamous cell carcinoma (ESCC) are unclear. We used ELISA and immunohistochemistry tests to analyze 5-hmC status in ESCC tissues, RT-qPCR to analyze TET family mRNA expression in normal and tumor tissues, and pyrosequencing to quantify LINE-1 (i.e., global DNA methylation) levels. ELISA and immunohistochemical testing showed 5-hmC levels were significantly lower in ESCC than in paired normal tissues (P < 0.0001). TET2 expression was significantly lower in ESCCs than paired normal tissues (P < 0.0001), and significantly associated with 5-hmC levels in ESCCs (P = 0.003, r = 0.33). 5-hmC levels were also significantly associated with LINE-1 methylation level (P = 0.0002, r = 0.39). Patients with low 5-hmC levels had shorter overall survival than those with higher levels, although not significantly so (P = 0.084). In conclusion, 5-hmC expression was decreased in ESCC tissues, and was associated with TET2 expression level. TET2 reduction and subsequent 5-hmC loss might affect ESCC development.
哺乳动物DNA通过5'-胞嘧啶甲基化（5-甲基胞嘧啶[5-mC]）进行表观遗传标记。10-11易位（TET）酶（TET1、TET2和TET3）参与DNA去甲基化，其双加氧酶活性可将5-mC转化为5-羟甲基胞嘧啶（5-hmC）。尽管据报道在各种癌症中TET减少与5-hmC水平降低有关，但5-hmC和TET表达在食管鳞状细胞癌（ESCC）中的功能尚不清楚。我们使用ELISA和免疫组织化学检测分析ESCC组织中的5-hmC状态，使用RT-qPCR分析正常组织和肿瘤组织中TET家族mRNA表达，并使用焦磷酸测序定量LINE-1（即整体DNA甲基化）水平。ELISA和免疫组织化学检测显示，ESCC中的5-hmC水平显著低于配对的正常组织（P < 0.0001）。ESCC中的TET2表达显著低于配对的正常组织（P < 0.0001），并且与ESCC中的5-hmC水平显著相关（P = 0.003，r = 0.33）。5-hmC水平也与LINE-1甲基化水平显著相关（P = 0.0002，r = 0.39）。5-hmC水平低的患者总生存期比水平高的患者短，尽管差异不显著（P = 0.084）。总之，ESCC组织中5-hmC表达降低，并且与TET2表达水平相关。TET2减少及随后的5-hmC缺失可能影响ESCC的发展。
