Devereux T R, White C M, Sills R C, Bucher J R, Maronpot R R, Anderson M W
Environmental Carcinogenesis Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
Carcinogenesis. 1994 May;15(5):1083-7. doi: 10.1093/carcin/15.5.1083.
Oxazepam has been the subject of recent toxicological and carcinogenesis studies because it is a commonly prescribed tranquilizer and has been shown to cause tumors in rodents. In this study, male and female B6C3F1 mice received 0, 125, 2500 or 5000 p.p.m. oxazepam in the diet for up to 2 years. Hepatocellular adenomas and carcinomas, as well as hepatoblastomas, which developed in these mice, were examined for the presence of activated ras proto-oncogenes. DNA was isolated from 20 or more tumors from each exposure group and analyzed by oligonucleotide hybridization, single-stranded conformation polymorphism analysis and direct sequencing of PCR-amplified H-ras gene fragments for codon 61 mutations. Thirteen of 37 (35%) hepatocellular adenomas and carcinomas from the 125 p.p.m. exposure group had mutations in codon 61, while mutations were detected in only 2 of 25 or 8% of the liver tumors from the 2500 p.p.m. exposure group and none of the 22 tumors from the 5000 p.p.m. group. This compares to 63% of 126 historical control liver tumors and 55% of 20 liver tumors from unexposed B6C3F1 mice in this study. In addition, 12 hepatoblastomas from the two high dose groups were examined for H-ras mutations at codon 61, but none were detected. No tumor DNAs from any of the exposure groups tested had mutations in codons 12, 13 or 117 of the H-ras gene or codons 12 or 13 of the K-ras gene, the other known hotspots for ras activation in mouse liver tumors. These results, together with those from the National Toxicology Program study showing no evidence of cytotoxicity or genotoxicity by oxazepam, suggest that oxazepam preferentially promotes cells that have activating lesions other than ras.
奥沙西泮一直是近期毒理学和致癌作用研究的对象，因为它是一种常用的镇静剂，并且已被证明会在啮齿动物中引发肿瘤。在本研究中，雄性和雌性B6C3F1小鼠在饮食中摄入0、125、2500或5000 ppm的奥沙西泮，持续长达2年。对这些小鼠中发生的肝细胞腺瘤、癌以及肝母细胞瘤进行检测，以确定是否存在激活的ras原癌基因。从每个暴露组的20个或更多肿瘤中分离DNA，并通过寡核苷酸杂交、单链构象多态性分析以及对PCR扩增的H-ras基因片段的密码子61突变进行直接测序来进行分析。在125 ppm暴露组的37个肝细胞腺瘤和癌中，有13个（35%）在密码子61处发生了突变，而在2500 ppm暴露组的25个肝肿瘤中只有2个（8%）检测到突变，5000 ppm组的22个肿瘤中未检测到突变。相比之下，本研究中126个历史对照肝肿瘤中有63%以及未暴露的B6C3F1小鼠的20个肝肿瘤中有55%检测到突变。此外，对两个高剂量组的12个肝母细胞瘤进行了密码子61处H-ras突变的检测，但未检测到任何突变。在任何测试的暴露组的肿瘤DNA中，H-ras基因的密码子12、13或117以及K-ras基因的密码子12或13（小鼠肝肿瘤中ras激活的其他已知热点）均未发生突变。这些结果，连同国家毒理学计划研究中表明奥沙西泮没有细胞毒性或遗传毒性证据的结果，表明奥沙西泮优先促进具有除ras之外的激活损伤的细胞。
