胸苷酸合成酶基因多态性及其蛋白表达与食管鳞状细胞癌淋巴结转移的关系

Polymorphisms of Thymidylate Synthase Gene and Correlation of Its Protein Expression to Lymph Node Metastasis of Esophageal Squamous Cell Carcinoma

背景与目的:胸苷酸合成酶(thymidylatesynthase,TS)是DNA合成的关键酶。TS基因5′非编码区(untranslatedregion,UTR)串联重复序列和G/C单核苷酸多态性(singlenucleotidepolymorphism,SNP)可能导致酶表达或活性的改变,从而改变个体对肿瘤的易感性及预后。本实验的目的是探讨TS5′-UTR多态性与食管鳞状细胞癌(esophagealsquamouscellcarcinoma,ESCC)淋巴结转移的关系,并探讨此多态性对TS蛋白表达的影响。方法:从232例ESCC患者和348例健康对照的外周血中提取白细胞DNA,分别用PCR和PCR-RFLP方法检测TS5′UTR28bp串联重复序列和G/CSNP的基因型。51例患者的术后切除组织采用免疫组织化学染色的方法(S-P法)检测肿瘤组织中的TS蛋白的表达情况。结果:5′UTR的3G/3G,3G/3C,3C/3C,2R/3G,2R/3C,2R/2R和其它基因型频率在健康对照组分别为17.5%,17.3%,29.3%,12.9%,17.8%,3.7%,1.5%和在病例组中分别为16.0%,16.0%,29.3%,13.8%,17.6%,4.3%,3.0%;3G,3C,2R和其它等位基因型频率在健康对照组中分别为32.8%,47.0%,19.5%,0.7%和在病例组中分别为31.2%,46.8%,20.5%,1.5%。与3G/3G基因型相比,2R/3G基因型显著增加淋巴结转移的危险性(年龄和性别校正OR=11.53,95%CI=2.67～49.74)。TS表达水平与患者的性别、年龄、淋巴结转移和临床病理分期无关,而与TS5'UTR基因型密切相关(P<0.05)。结论:TS5′UTR重复序列及SNP多态性与ESCC淋巴结转移有关,而TS蛋白表达水平与淋巴结转移无关。

BACKGROUND ＆ OBJECTIVE： Thymidylate synthase （TS） is a key enzyme in DNA synthesis. The 28-bp tandem repeat in the 5＇- untranslated region （UTR） of TS gene and the G/C single nucleotide polymorphism （SNP） of TS gene may modify the expression and activity of TS protein, therefore, may change the susceptibility and prognosis of tumors. This study was to explore the correlations of TS 5＇-UTR polymorphism to lymph node metastasis of esophageal squamous cell carcinoma （ESCC） and the expression of TS protein. METHODS. Peripheral leucocyte DNA was extracted from 232 ESCC patients and 348 age- and gender-matched healthy controls. TS 5＇-UTR tandem repeat and the G/C SNP genotype was detected by polymerase chain reaction （PCR） and PCR-restriction fragment length polymorphism （PCR-RFLP）, respectively. TS expression in 51 specimens of ESCC was detected by SP immunohistochemistry. RESULTS. The frequencies of 3G/3G, 3G/3C, 3C/3C, 2R/3G, 2R/3C, 2R/2R, and other genotypes were 17.5%, 17.3%, 29.3%, 12.9%, 17.8%, 3.7%, and 1.5% in the healthy controls, and 16.0%, 16.0%, 29.3%, 13.8%, 17.6%, 4.3%, and 3.0% in the ESCC patients; whereas the frequencies of 3G, 3C, 2R, and other alleles were 32.8%, 47.0%, 19.5%, and 0.7% in the healthy controls, and 31.2%, 46.8%, 20.5%, and 1.5% in the ESCC patients, respectively. Compared with 3G/3G genotype, 2R/3G genotype significantly increased the risk of lymph node metastasis of ESCC [age and gender adjusted odds ratio （OR）, 11.53; 95% confidence interval （CI）, 2.67-49.74]. TS protein expression was significantly related to TS 5＇-UTR genotype （P〈0.05）, but was not related to gender, age, lymph node metastasis and clinicopathologic stage. CONCLUSION. TS 5＇-UTR tandem repeat and G/C SNP genotype, but not TS expression, might be a candidate molecular marker to predict lymph node metastasis of ESCC.