In Vitro Recapitulating of TP53 Mutagenesis in Hepatocellular Carcinoma Associated With Dietary Aflatoxin B1 Exposure
In Vitro Recapitulating of TP53 Mutagenesis in Hepatocellular Carcinoma Associated With Dietary Aflatoxin B1 Exposure
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DOI：
10.1053/j.gastro.2009.06.002
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发表时间：
2009-09-01
期刊：
影响因子：
29.4
通讯作者：
Pfeifer, Gerd P.
中科院分区：
文献类型：
--
作者：
Besaratinia, Ahmad;Kim, Sang-In;Pfeifer, Gerd P.
背景与目的：除其他已知因素外，饮食暴露于黄曲霉毒素B-1（AF B（1））会增加人类肝细胞癌（HCC）的风险。来自AFB（1）暴露个体的HCC通常具有独特的TP 53突变，例如密码子249的第二个鸟嘌呤的G到T颠换（AGG到AGT），以及以G：C到T：A突变为主的特征性突变谱。方法：为了概括AFB（1）相关HCC中TP 53突变的特征，我们研究了体外暴露于AFB（1）的转基因小鼠成纤维细胞中AFB（1）诱导的DNA内收与胞壁形成的关系。研究结果：免疫斑点印迹法测定AFB（1）暴露细胞的整个基因组中的DNA加合物，发现持久的咪唑开环AFB（1）-DNA加合物的形成具有剂量依赖性。AFB（1）暴露中cII转基因的DNA足迹分析。细胞验证了DNA加合物的剂量依赖性和序列特异性形成。AFB（1）诱导的DNA加合物沿着cII转基因的优先形成几乎只局限于包含CpG二核苷酸的含鸟嘌呤序列。对暴露于AFB（1）的细胞中cII转基因的突变分析显示，cII突变频率的诱导呈剂量依赖性（P < .001），并显示出独特的诱导突变谱，其特征是在CpG序列背景下主要诱导G：C至T：A的颠换。值得注意的是，cII转基因的密码子42和45与人TP 53的密码子249具有相同的序列背景，构成了暴露于AFB（1）的细胞中2个频繁突变的位点，其第三个碱基位置含有G至T颠换特征突变。结论：在这个模型系统中，AFB（1）诱导的DNA加合和突变重现了AFB（1）相关的人类HCC中TP 53的独特突变特征。
BACKGROUND & AIMS: Dietary exposure to aflatoxin B-1 (AFB(1)), in addition to other known factors' increases risk for human hepatocellular carcinoma (HCC). HCCs from AFB(1)-exposed individuals frequently have distinct TP53 Mutations, Such as G to T transversions in the second guanine of codon 249 (AGG to AGT), and a characteristic mutational spectrum predominated by G:C to T:A mutations. METHODS: To recapitulate the distinctive features of TP53 mutations in AFB(1)-associated HCC, we investigated AFB(1)-induced DNA adduction in relation to muragenesis in transgenic mouse fibroblasts exposed to AFB(1) in vitro. RESULTS: Immunodotblot determination of DNA adducts in the overall genome of AFB(1)-exposed cells revealed the dose-dependant formation of persistent imidazole ring-opened AFB(1)-DNA adducts. DNA footprinting analysis of the cII transgene in AFB(1)-exposed. cells verified the dose-dependent and sequence-specific formation of DNA adducts. The preferential formation of AFB(1)-induced DNA adducts along the cII transgene was almost exclusively localized to guanine-containing sequences encompassing CpG dinucleotides. Mutation analysis of the cII transgene in AFB(1)-exposed cells revealed a dose-dependent induction of cII mutant Frequency (P < .001) and a unique induced mutational spectrum characterized by predominant induction of G:C to T:A transversions that Occurred within CpG sequence contexts. Notably, codons 42 and 45 of the cII transgene, which have identical sequence contexts to that of codon 249 of human TP53, constituted 2 frequently mutated sites in AFB(1)-exposed cells that contained the G to T transversion signature mutation at their third base positions. CONCLUSIONS: In this model system, AFB(1)-induced DNA adduction and mutagenesis recapitulate the unique mutational features of TP53 in AFB(1)-associated human HCC.