Sills R C, Hong H L, Greenwell A, Herbert R A, Boorman G A, Devereux T R
Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Carcinogenesis. 1995 Jul;16(7):1623-8. doi: 10.1093/carcin/16.7.1623.
The National Toxicology Program recently completed long-term ozone inhalation studies in B6C3F1 mice and F344/N rats. Mice and rats were exposed to 0, 0.5 or 1.0 p.p.m. ozone by inhalation for 24 or 30 months. There was an increased incidence of lung neoplasms in B6C3F1 mice. However, there was no evidence of carcinogenicity in F344/N rats. The objectives of this study were to (i) evaluate benign and malignant lung neoplasms from B6C3F1 mice for mutations in the K-ras gene at codons 12, 13 and 61, (ii) determine if the frequency and spectra of K-ras mutations were unique for ozone-induced lung neoplasms, (iii) determine if specific K-ras mutations were associated with the size and morphological patterns of lung neoplasms or ozone exposure concentrations and (iv) screen lung neoplasms by immunohistochemical methods for the p53 protein. K-ras mutations were detected by single-strand conformation analysis and identified by direct sequencing of polymerase chain reaction-amplified DNA isolated from formalin-fixed, paraffin-embedded neoplasms. K-ras mutations were detected in 73% of ozone-induced neoplasms, as compared with 33% of lung neoplasms from controls. The predominant mutations consisted of A-->T transversions at codon 61 (8/19) and G-->T transversions at codon 12 (7/19). Specific K-ras mutations in lung neoplasms were not associated with various morphological patterns. Our data suggests that ozone may cause direct and/or indirect DNA damage in the K-ras proto-oncogene of B6C3F1 mice.
国家毒理学计划最近完成了对B6C3F1小鼠和F344/N大鼠的长期臭氧吸入研究。小鼠和大鼠通过吸入0、0.5或1.0 ppm的臭氧，持续24或30个月。B6C3F1小鼠肺部肿瘤的发生率有所增加。然而，在F344/N大鼠中没有致癌性的证据。本研究的目的是：（i）评估B6C3F1小鼠的良性和恶性肺部肿瘤中K-ras基因第12、13和61密码子的突变情况；（ii）确定K-ras突变的频率和谱是否为臭氧诱导的肺部肿瘤所特有；（iii）确定特定的K-ras突变是否与肺部肿瘤的大小和形态模式或臭氧暴露浓度相关；（iv）通过免疫组织化学方法筛查肺部肿瘤中的p53蛋白。通过单链构象分析检测K-ras突变，并通过对从福尔马林固定、石蜡包埋的肿瘤中分离的聚合酶链反应扩增DNA进行直接测序来鉴定。在73%的臭氧诱导肿瘤中检测到K-ras突变，而对照组肺部肿瘤的这一比例为33%。主要突变包括第61密码子的A→T颠换（8/19）和第12密码子的G→T颠换（7/19）。肺部肿瘤中的特定K-ras突变与各种形态模式无关。我们的数据表明，臭氧可能会对B6C3F1小鼠的K-ras原癌基因造成直接和/或间接的DNA损伤。
