中文摘要：

目的探讨羟基脲对不同p53状态肝癌细胞的GADD45β诱导差异及可能调控机制。方法转染p53全序列建立Hep3B＋p53；体外合成GADD4513近端启动子序列群（-618～-314），构建荧光素表达质粒，转染肝癌细胞株HepG2、Hep3B和Hep3B＋p53；以实时荧光定量聚合酶链反应（PCR）比较羟基脲对GADD4513表达诱导及其近端启动子活性影响差异；比较对DNA合成和细胞克隆形成能力抑制差异；通过Caspase-3的表达变化测定凋亡的发生和发展。结果羟基脲对Hep3B中GADD45诱导并不明显，转染p53全基因序列后，Hep3B＋p53对羟基脲的敏感性明显增加，并呈现出剂量-效应的正相关。荧光素分析提示羟基脲作用Hep3B＋p53后的启动子核转录因子（NF）-κB（-618／＋6）和E2F-1（-470／＋6）活性较Hep3B明显增强约1．1倍和0．8倍。羟基脲能够更加明显地抑制Hep3B＋p53的DNA合成能力和细胞克隆形成能力，10mmol／L羟基脲对Hep3B＋p53DNA合成抑制率达到37．15％，对细胞克隆形成能力的抑制率达85．29％，与Hep3B比较差异有统计学意义（P〈0．05）。羟基脲作用后Hep3B＋p53的Caspase-3能够迅速地启动凋亡的发生和发展。结论p53对核糖核苷酸还原酶抑制性化疗药物对肝癌细胞的GADD45诱导起重要作用，增强转录调节因子的表达水平是其可能的作用机制。

英文摘要：

Objective To identify the role of p53 in the induction of growth arrest DNA damageinducible gene 45 （βGADD45β） in hepatocellular carcinoma （HCC） cells by hydroxyurea. Methods Hep3B ＋p53 clone was established by the transfection of the full-length p53 sequence to Hep3B. Following hydroxyurea administration, quantitative real-time polymerase chain reaction （PCR） was employed to validate the expression changes of GADD4513. pGL3 basic luciferase plasmids including promoter fragments were synthesized in vitro and transfected into cells. The effects on promoter activity, cell growth and the cleavage of Caspase-3 were further focused on. Results Hep3B ＋p3 could express p53 protein stably. The transfection of p53 could enhance the induction of GADD4513 in Hep3B by hydroxyurea. The promoter activity of fragments constructing nuclear factor-κB （NF-κB） and E2F-1 binding sites could be induced about 1.1 and 0. 8 folds by transfeetion of p53. The colony formation and DNA syntheses were inhibited apparently in Hep3B ＋p53 with p53 by hydroxyurea （37. 15% and 85.29% by 10mmol/L Hydroxyurea, respectively）. Moreover, the p53 transfection could trigger the cleavage of Caspase-3 more rapidly. Conclusion p53 may play a role in the induction of GADD4513 in Hep3B by ribonucleotide reductase inhibitor.