DNA氧化损伤在肺癌发生中的作用

A Study on the Role of Oxidative DNA Damage in Development of Human Lung Cancer

目的:为探明DNA氧化损伤在人群肺癌发生中的作用及其分子机制而进行本研究。方法:使用针对DNA经受氧化损伤标志物8-羟基-脱氧鸟苷(8-OH-dG)的鼠抗人单克隆抗体,通过免疫学方法检测150例肺癌、120例癌旁肺组织、40例肺良性病变和40例正常肺组织中DNA氧化损伤标志的含量;同时检测相应肺组织中P53、C-MYC、K-RAS、BCL-2、hTERT等癌变相关基因的表达,分析DNA氧化损伤与上述癌变相关基因表达的关系;并在B(a)P-7,8二醇-9,10环氧化物(BPDE)和NiS诱导的体外人气管上皮细胞癌变模型上检测癌变过程中DNA氧化损伤的变化。结果:肺癌组织、癌旁肺组织、肺良性病变和正常肺组织氧化损伤标志物8-OH-dG的阳性率分别为92.7％(139/150)、17.5％(21/120)、10.0％(4/40)和5.0％(2/40),肺癌的氧化损伤高于其他肺组织(P<0.01)。按性别、年龄、细胞类型和吸烟史分层,未见其与DNA氧化损伤之间的关联。分析DNA氧化损伤与癌变相关基因的关系,发现肺癌组织K-RAS、BCL-2基因的过度表达与DNA氧化损伤的含量高有关,而P53、C-MYC和hTERT基因表达与DNA氧化损伤无关联。在体外用BPDE和NiS作用于人气管上皮细胞系诱导其转化和癌变过程中,DNA氧化损伤标志8-OH-dG出现于细胞转化之前,其量与细胞癌变进程相一致。

Objective: To investigate the role of oxidative DNA damage in development of human lung cancer and its molecular mechanism of carcinogenesis. Methods A specific monoclonal antibody to the biomarker of oxidative DNA damage,8-hydroxydeoxyguanine (8 - OH - dG) , and biotin-streptavidin immuno-staining were used to detect oxidative DNA damage in 150 cases of human lung cancer tissues, 120 adjacent lung tissues without cancer cells,40 benign lung lesions and 40 normal lung tissues. Protein expressions of P53 , C-MYC, K-RAS, BCL - 2 and hTERT (human telomerase reverse transcriptase)in lung tissues were assessed by immuno-histochemistry. The relationship between the oxidative DNA damage and these genes was analyzed. We also detected the oxidative DNA damage during the process of carcinogenesis in human bronchial epithelial cells induced by Benzo (a) pyrene diol-epoxide (BPDE) and sulfide nickel (NiS) in vitro. Result The positive rate of oxidative DNA damage in lung cancer specimens,adjacent lung tissues,benign lung lesions and normal lung tissues was 92. 7 % (139 of 150) , 17. 5% (21 of 120) , 10. 0% (4 of 40) and 5. 0% (2 of 40) respectively. The level of oxidative DNA damage in lung cancer tissues was significantly higher than that of adjacent lung tissues, benign lung lesions and normal lungs(P < 0.01). With the lung cancer patients stratified by sex, age, cell types and smoking history, these characteristics were not correlated with the level of oxidative DNA damage. In the investigation of the relationship between the oxidative DNA damage and five cancer related genes, higher oxidative DNA damage levels were observed in lung cancer patients with over-expression of K-RAS and BCL-2,whereas the expressions of P53,C-MYC and hTERT were not correlated with the level of oxidative DNA damage. During the process of malignant transformation and carcinogenesis of human bronchial epithelial cells induced by BPDE and NiS in vitro, oxidative DNA damage emerged before cell transformation, and quantity of that was consistent with the progress of cell cancerization. Conclusion Oxidative DNA damage may play an important role in the initiation of human lung cancer. And K-RAS and BCL - 2 genes may correlate with oxidative DNA damage in the process of lung carcinogenesis.