Totsuka Y, Fukutome K, Takahashi M, Takahashi S, Tada A, Sugimura T, Wakabayashi K
Biochemistry Division, National Cancer Center Research Institute, Tokyo, Japan.
Carcinogenesis. 1996 May;17(5):1029-34. doi: 10.1093/carcin/17.5.1029.
One of the mutagenic and carcinogenic heterocyclic amines (HCAs), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), is present in cooked foods and we are chronically exposed to this compound in our daily life. To study the role of HCAs in human carcinogenesis, we analyzed MeIQx-DNA adducts in 38 DNA samples obtained from surgical and autopsy specimens by the 32P-postlabeling method under adduct-intensification conditions with the modification of additional digestion with nuclease P1 and phosphodiesterase I after 32P-labeling at 5'-hydroxyl termini. This modified 32P-postlabeling method can detect N2-(deoxyguanosin-8-yl)-2-amino-3,8-dimethylimidazo- [4,5-f]quinoxaline 5'-monophosphate (5'-pdG-C8-MeIQx) at levels down to 1/10(10) nucleotides. The DNA samples from colon and rectum surgical specimens and a kidney taken at autopsy were found to contain an adduct spot corresponding to that of standard 5'-pdG-C8-MeIQx on TLC at levels of 14,18 and 1.8 per 10(10) nucleotides, respectively. Each adduct spot was extracted from TLC and identified to be 5'-pdG-C8-MeIQx by HPLC. Thus, MeIQx-DNA adducts actually exist in human tissues and this adduct formation may be involved in human cancer development.
2-氨基-3,8-二甲基咪唑并[4,5-f]喹喔啉（MeIQx）是具有致突变性和致癌性的杂环胺（HCA）之一，存在于熟食中，我们在日常生活中会长期接触该化合物。为了研究HCA在人类致癌过程中的作用，我们采用32P后标记法，在加合物强化条件下，对从手术和尸检标本中获取的38份DNA样本中的MeIQx-DNA加合物进行了分析。该方法在5'-羟基末端进行32P标记后，额外用核酸酶P1和磷酸二酯酶I消化，以进行修饰。这种改进的32P后标记法能够检测低至1/10(10)核苷酸水平的N2-（脱氧鸟苷-8-基）-2-氨基-3,8-二甲基咪唑并[4,5-f]喹喔啉5'-单磷酸（5'-pdG-C8-MeIQx）。结肠和直肠手术标本以及尸检时获取的肾脏的DNA样本，在薄层色谱（TLC）上被发现含有与标准5'-pdG-C8-MeIQx相对应的加合物斑点，其水平分别为每10(10)核苷酸14、18和1.8个。每个加合物斑点从TLC上提取出来，并通过高效液相色谱（HPLC）鉴定为5'-pdG-C8-MeIQx。因此，MeIQx-DNA加合物确实存在于人体组织中，这种加合物的形成可能与人类癌症的发生有关。
