目的： 探讨生长阻滞和DNA损伤诱导45A（growth arrest and DNA-damage-inducible 45 alpha, GADD45A ）基因在贲门腺癌（gastric cardia adenocarcinoma，GCA）中的异常甲基化及表达，并探讨其临床意义。 方法: 选取河北医科大学第四医院2004-2007年期间GCA患者组织标本（138例）。分别应用亚硫酸氢盐测序法（bisulfite sequencing，BS-Seq）、亚硫酸氢盐转换-甲基化特异性聚合酶链式反应（bisulfite conversion-methylation specific polymerase chain reaction，BS-MSP）、RT-PCR和免疫组织化学法检测 GADD45A 基因在GCA组织及癌旁正常组织中的甲基化、 GADD45A mRNA及蛋白表达的情况。 结果: GADD45A 远端启动子区的4个CpG位点在GCA组织中的甲基化率\[44.93% (62/138）\]显著高于癌旁正常组织\[0.00% (0/138）\]（P<0.01），且在Ⅲ期和Ⅳ期GCA组织中的甲基化率显著高于Ⅰ期和Ⅱ期GCA组织（P<005），但 GADD45A 在GCA组织中的甲基化与患者的年龄、性别及病理分化程度无关（P>0.05）。 GADD45A 近端启动子（region 2）及第一外显子区（region 3）的CpG岛在GCA及癌旁组织中均未检测到甲基化。GCA组织中 GADD45A mRNA和蛋白阳性表达率显著低于癌旁正常组织\[(0.35±0.15) vs (0.78±0.26)，42.75% vs 71.01%，均P<0.05\]，且与其远端启动子区4个CpG位点的甲基化状态之间有明显的相关性（r=-0.52，P<0.01）。 结论: GADD45A 基因远端启动子区的4个CpG位点的高甲基化导致的基因沉默可能与GCA中 GADD45A 基因表达降低有关。

Objective:To investigate the expression and aberrant methylation of growth arrest and DNA-damage-inducible 45 alpha ( GADD45A ) gene in gastric cardia adenocarcinoma (GCA) and to explore its clinical significance. Methods: Tissue samples in GCA patients (138 cases) were selected from Fourth Hospital of Hebei University during 2004 to 2007. Bisulfite sequencing (BS-Seq), bisulfite conversion-methylation specific polymerase chain reaction (BS-MSP), reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry methods were used respectively to detect the methylation status, mRNA and protein expression of GADD45A gene in GCA tissues and the para-carcinoma normal tissues. Results: The methylation frequency of four CpG sites in distal promoter of GADD45A in GCA tissues (44.93%, \[62/138\]) was significantly higher than that in the para-carcinoma normal tissues (0.00%, 0/138) (P<0.01). The methylation frequency of 4 CpG sites in stage Ⅲ and Ⅳ GCA tissues was significantly higher than that in stage Ⅰ and Ⅱ GCA tissues (P<0.05). However, the methylation status GADD45A in GCA tissues was not correltaed with age, gender and pathological differentiation (P>0.05). For GADD45A region 2 and 3 located in proximal promoter and exon 1, no methylation was detected in GCA and the para-carcinoma normal tissues. The expression of GADD45A mRNA and positive expression rate of GADD45A protein in GCA tissues were significantly lower than those in the para-carcinoma normal tissues (\[0.35±0.15\] vs \[0.78±0.26\], 42.75% vs 71.01%, P<0.05) and was associated with methylation status of 4 CpG sites in distal promoter (r=-0.52, P<0.01). Conclusion:Hypermethylation of four CpG sites in distal promoter of GADD45A gene may be responsible for the decreased expression of GADD45A in GCA.

国家自然科学基金资助项目（No. 81101854）；河北省科技厅资助项目（No.072761223）