目的：探讨细胞周期蛋白G2 (cyclin G2，CCNG2 ) 在甲状腺癌组织中表达的意义及其过量表达对甲状腺癌SW579细胞增殖、凋亡的影响。方法：收集唐山市工人医院头颈科2003-2008年手术切除的63例甲状腺癌标本及其癌旁组织，免疫组织化学方法、Western blotting检测其中CCNG2蛋白的表达情况，分析CCNG2蛋白表达与临床病理指标、患者生存期之间的关系。通过慢病毒转染方法建立过表达CCNG2的甲状腺癌SW579细胞，采用RT-PCR及Western blotting检测转染后SW579细胞内 CCNG2 基因的表达水平，MTT比色法及流式细胞术观察 CCNG2 过表达对SW579细胞增殖、凋亡的影响。结果：CCNG2蛋白在甲状腺癌组织中的表达阳性率（33.3% vs 96.8%， P <0.05）及相对表达量（0.343±0.033 vs 0.713±0.062， P <0.05）均显著低于癌旁组织；CCNG2蛋白表达在甲状腺癌患者不同性别、年龄、肿瘤大小组间无显著差异（均 P >005），而在不同的甲状腺癌细胞分化程度、淋巴结转移以及肿瘤临床分期组间有显著差异（均 P <0.05）；CCNG2表达阳性的甲状腺癌患者的5年总生存率明显高于其表达阴性者（ P <0.05）。成功构建CCNG2过表达的SW579细胞，CCNG2过表达能明显抑制SW579细胞增殖能力，促进肿瘤细胞凋亡\[（15.1±2.3）% vs （5.6±1.1） %， P <0.05\]。结论：CCNG2在甲状腺癌组织中低表达，CCNG2过表达能够抑制甲状腺癌SW579细胞的增殖并促进其凋亡。

Objective:To analyze the expression of cyclin G2 (CCNG2) in thyroid carcinoma tissue specimens and evaluate the effect of CCNG2 on the proliferation and apoptosis of thyroid carcinoma SW579 cells in vitro . Methods: Sixty-three patients diagnosed with thyroid carcinoma in the Department of Endocrinology of Tangshan Workers Hospital between 2003 and 2008 were recruited. Biopsy specimens were collected from primary tumors and the corresponding adjacent tissues. CCNG2 protein presence and content in these specimens were determined by immunohistochemistry and Western blotting. The relationships of CCNG2 expression with clinicopathologic variables and patient survival were assessed. To evaluate the effect of CCNG2 on thyroid carcinoma cell proliferation and apoptosis in vitro , SW579 cells were transfected with a lentiviral vector expressing CCNG2 and the transfectants were then subjected to reverse transcription-polymerase chain reaction (RT-PCR) determination of CCNG2 mRNA abundance, Western blotting analysis of CCNG2 protein content, MTT assay of cell viability and flow cytometric assessment of apoptosis, respectively. Results: CCNG2 protein was detected at significantly lower levels in thyroid cancer tissue than in the paraneoplastic tissues (0.343±0.033 vs 0.713±0.062, P <0.05). While the level of CCNG2 protein was not correlated with gender, age, and tumor size ( P >0.05), it was significantly correlated with lymph node metastasis, clinic stage, histological grade and 5-year overall survival ( P <0.05). Overexpression of CCNG2 significantly lowered SW579 cell viability and enhanced SW579 cell apoptosis (15.1±2.3)% as compared with the control (5.6±1.1 in vitro , P <0.05). Conclusion: CCNG2 protein content is significantly lower in thyroid carcinoma tissue than in peritumor tissue. Overexpression of CCNG2 in thyroid carcinoma cells in vitro results in a significant inhibition of proliferation and a significant enhancement of apoptosis. These observations suggest that CCNG2 may serve as a potential therapeutic target for thyroid carcinoma.