Hypomethylation of long interspersed nuclear element-1 (LINE-1) leads to activation of proto-oncogenes in human colorectal cancer metastasis.
Hypomethylation of long interspersed nuclear element-1 (LINE-1) leads to activation of proto-oncogenes in human colorectal cancer metastasis.
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DOI：
10.1136/gutjnl-2012-304219
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发表时间：
2014-04
期刊：
影响因子：
24.5
通讯作者：
Goel A
中科院分区：
文献类型：
--
作者：
Hur K;Cejas P;Feliu J;Moreno-Rubio J;Burgos E;Boland CR;Goel A
LINE-1元件的低甲基化已成为人类癌症的显著特征。有限的证据表明，一些LINE-1元件编码一个额外的内部反义启动子，并且该区域的低甲基化增加可能导致进化上甲基化沉默的下游基因的意外激活。然而，这一基本的表观遗传机制在结直肠癌（CRC）中的意义以前尚未研究。我们分析了77例结直肠癌患者的组织标本，其中包括正常结肠粘膜、原发性结直肠癌组织（PC）和肝转移组织（LM）。LINE-1甲基化水平通过定量亚硫酸氢盐焦磷酸测序测定。免疫印迹法和免疫组化法检测MET、RAB 3 IP和CHRM 3蛋白表达。采用实时定量PCR检测MET原癌基因转录和5-羟甲基胞嘧啶（5-hmc）。LM中的总体LINE-1甲基化水平显著低于匹配的PC（PC= 66.2%vs LM=63.8%; p<0.001）。更重要的是，我们观察到与相应的匹配PC相比，位于多个原癌基因MET（p<0.001）、RAB 3 IP（p=0.05）和CHRM 3（p=0.01）的内含子区域内的特定LINE-1序列在LM组织中显著低甲基化。此外，MET基因内特定LINE-1元件甲基化的降低与CRC转移灶中MET表达的诱导呈负相关（R=-0.44; p<0.0001）。最后，5-hmc含量增加与LINE-1低甲基化相关。我们的研究结果提供了新的证据，即特定LINE-1元件的低甲基化允许甲基化沉默的MET、RAB 3 IP和CHRM 3原癌基因在CRC转移中的意外激活。此外，由于5-hmc含量与肿瘤组织中LINE-1低甲基化呈负相关，我们的研究结果为人类CRC中全球DNA低甲基化的基本过程提供了重要的机制见解。
Hypomethylation of LINE-1 elements has emerged as a distinguishing feature in human cancers. Limited evidence indicates that some LINE-1 elements encode an additional internal antisense promoter, and increased hypomethylation of this region may lead to inadvertent activation of evolutionarily methylation-silenced downstream genes. However, the significance of this fundamental epigenetic mechanism in colorectal cancer (CRC) has not been investigated previously. We analysed tissue specimens from 77 CRC patients with matched sets of normal colonic mucosa, primary CRC tissues (PC), and liver metastasis tissues (LM). LINE-1 methylation levels were determined by quantitative bisulfite pyrosequencing. MET, RAB3IP and CHRM3 protein expression was determined by western blotting and IHC. MET proto-oncogene transcription and 5-hydroxymethylcytosine (5-hmc) were evaluated by quantitative real-time-PCR. Global LINE-1 methylation levels in LM were significantly lower compared with the matched PC (PC=66.2% vs LM=63.8%; p<0.001). More importantly, we observed that specific LINE-1 sequences residing within the intronic regions of multiple proto-oncogenes, MET (p<0.001), RAB3IP (p=0.05) and CHRM3 (p=0.01), were significantly hypomethylated in LM tissues compared with corresponding matched PC. Furthermore, reduced methylation of specific LINE-1 elements within the MET gene inversely correlated with induction of MET expression in CRC metastases (R=−0.44; p<0.0001). Finally, increased 5-hmc content was associated with LINE-1 hypomethylation. Our results provide novel evidence that hypomethylation of specific LINE-1 elements permits inadvertent activation of methylation-silenced MET, RAB3IP and CHRM3 proto-oncogenes in CRC metastasis. Moreover, since 5-hmc content inversely correlated with LINE-1 hypomethylation in neoplastic tissues, our results provide important mechanistic insights into the fundamental processes underlying global DNA hypomethylation in human CRC.
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影响因子：
5.3
作者：
MANDAHL, N;HEIM, S;MITELMAN, F
通讯作者：
MITELMAN, F
影响因子：
24.5
作者：
Hur K;Toiyama Y;Takahashi M;Balaguer F;Nagasaka T;Koike J;Hemmi H;Koi M;Boland CR;Goel A
通讯作者：
Goel A
影响因子：
2.4
作者：
Fujita, S;Sugano, K
通讯作者：
Sugano, K
影响因子：
11.4
作者：
Hohjoh, H;Singer, MF
通讯作者：
Singer, MF
影响因子：
50.3
作者：
Holm, TM;Jackson-Grusby, L;Jaenisch, R
通讯作者：
Jaenisch, R