喉鳞状细胞癌组织中NDRG1、NDRG2基因启动子区CpG岛甲基化状态及其蛋白的表达

Promoter region CpG island methylation status and protein levels of NDRG1 and NDRG2 in laryngeal squamous cell carcinoma

目的:探讨喉鳞状细胞癌(laryngeal squamous cell carcinoma,LSCC)组织中N-myc下游调节基因1(N-myc downstream regulated gene 1,NDRG1)及NDRG2基因启动子甲基化状态和蛋白表达情况及其临床意义。方法:应用甲基化特异性PCR(methylation specific polymerase chain reaction,MSP)技术及免疫组织化学(immunohistochemestry,IHC)法检测45例LSCC组织、18例癌旁组织中NDRG1、NDRG2基因启动子区Cp G岛甲基化及蛋白表达情况,分析其与临床特征的关系。结果:LSCC组织中NDRG1及NDRG2基因启动子区的甲基化发生率显著高于癌旁正常组织[66.7%(30/45)vs 33.3%(6/18),53.3%(24/45)vs 22.2%(4/18),均P<0.05],其高甲基化与淋巴结转移及临床分期有关(P<0.05),与病理分级、临床分型、吸烟史、年龄和性别无关(P>0.05)。在LSCC组织中,NDRG1及NDRG2蛋白的阳性表达率显著低于癌旁组织[37.8%(17/45)vs 88.9%(16/18),33.3%(15/45)vs 83.3%(15/18),均P<0.01],其低蛋白表达与淋巴结转移及临床分期有关(P<0.05),与病理分级、临床分型、吸烟史、年龄和性别无关(P>0.05)。LSCC组织中NDRG1及NDRG2启动子区甲基化与其蛋白表达呈负相关(r1=-0.713,P<0.01;r2=-0.472,P<0.01)。结论:在LSCC组织中NDRG1及NDRG2基因均呈高甲基化及低蛋白表达状态,这可能与喉癌的发生和发展有关,NDRG1及NDRG2基因启动子区Cp G岛的异常甲基化可能是抑制它们蛋白表达的机制之一。

Objective： To investigate the promoter region CpG island methylation status and protein levels of NDRG1 and NDRG2 in laryngeal carcinoma. Methods： Larynx tumor tissue （ n = 45 ） and normal lung tissue （ n = 18 ） specimens were collected from 45 patients with laryngeal squamous cell carcinoma （ LSCC ） who underwent surgery in the Department of Head and Neck Surgery, the Fourth Hospital of Hebei Medical University between January, 2010 and December, 2011. The promoter CpG island methylation status and protein levels of NDRG1 and NDRG2 in the collected specimens were quantified by methylation specific polymerase chain reaction and immunohistochemistry, respectively. Results： The meth- ylation level of promoter CpG island was significantly higher in LSCC tissue and in normal larynx tissue for both NDRG1 （66.7% vs33.3%, P〈0.05） and NDRG2 （53.3% vs22.2%, P〈0. 05） genes. The proportion of NDRG1 and NDRG2 promoter methylation in LSCC tissue specimens was associated with lymph node metastasis and clinical stage （ P 〈 0.05 ）, but neither with pathological grade and clinical classification of the lesion nor with smoking history, age and sex （ P 〉 0. 05 ）. NDRG1 protein was detected in 37.8% （ 17/45 ） of LSCC specimens and in 88.9% （ 16/18 ） of normal tis- sue specimens （P 〈 0. 01 ） and NDRG2 protein in 33.3% （ 15/45 ） of LSCC specimens and in 83.3% （ 15/18 ） of nor- mal larynx tissue specimens （P 〈 0. 01 ）. Like promoter methylation status, NDRG1 and NDRG2 protein levels in LSCC tissue were associated with lymph node metastasis and clinical stage （ P 〈 0.05 ）, but not with pathological grading and clinical classification of the lesions, smoking history, age and sex （ P 〉 0.05 ）. CpG island methylation in the promoter re- gion was negatively correlated with protein expression for both NDRG1 （ r1 = - 0. 713, P 〈 0. 01 ） and NDRG2 （ r2 = - 0. 472, P 〈 0. 01 ） genes. Conclusion ： Both NDRGI and NDRG2 promoters are hypermethylated, resulting in de- creased NDRG! and NDRG2 protein expression, in LSCC tissue. This observation suggests that anti-methylation of CpG is- land in the promoter region of the NDRG1 and NDRG2 genes may offer a novel therapeutic strategy for LSCC.