Chu Chun-Ho, Chang Shih-Ching, Wang Hsiu-Hua, Yang Shung-Haur, Lai Kuo-Chu, Lee Te-Chang
Institute of Pharmacology, National Yang-Ming University, Taipei 11221, Taiwan.
Department of Surgery, Koo Foundation, Sun Yat-Sen Cancer Center, Taipei 11259, Taiwan.
Cancers (Basel). 2018 Oct 22;10(10):393. doi: 10.3390/cancers10100393.
Aberrant DNA methylation is a potential mechanism underlying the development of colorectal cancer (CRC). Thus, identification of prognostic DNA methylation markers and understanding the related molecular functions may offer a new perspective on CRC pathogenesis. To that end, we explored DNA methylation profile changes in CRC subtypes based on the microsatellite instability (MSI) status through genome-wide DNA methylation profiling analysis. Of 34 altered genes, three hypermethylated (epidermal growth factor, ; carbohydrate sulfotransferase 10, ; ependymin related 1, ) and two hypomethylated (bone marrow stromal antigen 2, ; Rac family small GTPase 3, ) candidates were further validated in CRC patients. Based on quantitative methylation-specific polymerase chain reaction (Q-MSP), , and showed higher hypermethylated levels in CRC tissues than those in adjacent normal tissues, whereas showed hypomethylation in CRC tissues relative to adjacent normal tissues. Additionally, among 75 CRC patients, hypermethylation of and was significantly correlated with the MSI status and a better prognosis. Moreover, hypermethylation was significantly correlated with node negativity and a lower tumor stage as well as with mutations in B-Raf proto-oncogene serine/threonine kinase ) and human transforming growth factor beta receptor 2 (). Conversely, a negative correlation between the mRNA expression and methylation levels of in CRC tissues and cell lines was observed, revealing that DNA methylation has a crucial function in modulating expression in CRC cells. knockdown by a transient small interfering RNA significantly suppressed invasion by CRC cells, suggesting that decreased EPDR1 levels may attenuate CRC cell invasion. These results suggest that DNA methylation-mediated epigenetic silencing may play an important role in preventing CRC progression.
异常的DNA甲基化是结直肠癌（CRC）发生发展的潜在机制。因此，鉴定预后性DNA甲基化标志物并了解相关分子功能可能为CRC发病机制提供新的视角。为此，我们通过全基因组DNA甲基化谱分析，探索了基于微卫星不稳定性（MSI）状态的CRC亚型中的DNA甲基化谱变化。在34个改变的基因中，三个高甲基化基因（表皮生长因子、碳水化合物硫酸转移酶10、室管膜素相关1）和两个低甲基化基因（骨髓基质抗原2、Rac家族小GTP酶3）候选基因在CRC患者中进一步得到验证。基于定量甲基化特异性聚合酶链反应（Q-MSP），表皮生长因子、碳水化合物硫酸转移酶10和室管膜素相关1在CRC组织中的高甲基化水平高于相邻正常组织，而骨髓基质抗原2在CRC组织中相对于相邻正常组织表现为低甲基化。此外，在75例CRC患者中，表皮生长因子和室管膜素相关1的高甲基化与MSI状态及较好的预后显著相关。此外，表皮生长因子高甲基化与淋巴结阴性、较低的肿瘤分期以及B-Raf原癌基因丝氨酸/苏氨酸激酶和人转化生长因子β受体2的突变显著相关。相反，在CRC组织和细胞系中观察到表皮生长因子mRNA表达与甲基化水平之间呈负相关，表明DNA甲基化在调节CRC细胞中表皮生长因子的表达中起关键作用。通过瞬时小干扰RNA敲低表皮生长因子显著抑制了CRC细胞侵袭，表明表皮生长因子表达水平降低可能减弱CRC细胞侵袭。这些结果表明，DNA甲基化介导的表皮生长因子表观遗传沉默可能在预防CRC进展中起重要作用。
