METABOLIC PROCESSING AND DNA ADDUCTION OF HETEROCYCLIC AMINES IN MAMMARY GLAND

新陈代谢在肺癌的致癌性中起重要作用 食源性杂环胺(HCAs)。代谢激活发生 通过细胞色素P450介导的两步过程 N-羟基化和第二阶段的酯化，如 N-乙酰转移酶(NAT)。在人类中，两种N-乙酰转移酶 指定的Nat1和Nat2催化不同的N-和O-乙酰化 芳胺，包括N-羟基-HCAs的O-乙酰化反应。在这 项目中，我们检测了HCAs在人类和 大鼠乳腺受NAT影响。大鼠和人的乳腺 几种HCAs的N-羟胺代谢物O-乙酰化，包括 N-羟基-IQ和N-羟基-PhIP。10例女性乳腺胞浆标本 和人乳腺上皮细胞原代培养的裂解物 NAT介导的代谢活化N-羟基苯丙氨酸 乙酰辅酶A促进的O-乙酰基转移酶结合 N-羟基胺对小牛胸腺DNA的体外作用。N-乙酰化 对氨基水杨酸，一种特定于Nat1的活性，但不是 磺胺二甲嘧啶的N-乙酰化，一种特定于Nat2的活性，是 在乳腺胞浆和人乳腺上皮细胞中检测到 细胞裂解物。人乳腺的免疫组织化学分析 切片显示上皮组织中Nat1蛋白染色阳性。 排列在乳腺导管内的细胞。逆转录-聚合酶链式反应 分析表明，NAT1和NAT2的mRNA转录本都是 存在于人乳腺中；然而，没有NAT2的催化活性 可检测到的。我们的数据首次证明人类的乳房 腺体对HCA的代谢活化具有催化活性 食物诱变剂，而这一活动很可能是由 Nat1在乳腺导管上皮细胞中表达。 鉴于这项研究表明Nat1具有催化活性和 在人类乳腺中表达，还需要更多的研究来 确定Nat1基因是否为人类乳腺的危险因素 癌症。为了更好地评估饮食中的六氯联苯对人体的作用 乳腺癌风险、Nat1基因与人类乳腺癌 经常吃熟肉的女性的发病率是 这是正当的。

Metabolism plays an important role in the carcinogenicity of the food-derived heterocyclic amines (HCAs). Metabolic activation occurs by a two-step process involving cytochrome P450-mediated N-hydroxylation and phase II esterification by enyzmes such as N-acetyltransferase (NAT). In humans, two N-acetyltransferases designated NAT1 and NAT2 catalyze N- and O-acetylation of various arylamines, including the O-acetylation of the N-hydroxy-HCAs. In this project, we examined the metabolic activation of HCAs in the human and rat mammary gland by NAT. The mammary gland from rat and human O-acetylated the N-hydroxylamine metabolites of several HCAs including N-hydroxy-IQ and N-hydroxy-PhIP. Mammary gland cytosol from 10 women and lysates from a primary culture of human mammary epithelial cells metabolically activated N-hydroxy-PhIP by NAT-mediated O-acetyltransferase, as measured by the acetyl CoA-enhanced binding of the N-hydroxylatmine to calf thymus DNA in vitro. N-Acetylation of p-aminosalicylic acid, an activity specific to NAT1, but not N-acetylation of sulfamethazine, an activity specific to NAT2, was detected in the mammary gland cytosols and human mammary epithelial cell lysates. Immunohistochemical analysis of human mammary gland sections showed positive staining for NAT1 protein in the epithelial cells lining the mammmary gland ducts. Reverse transcription-PCR analysis showed that mRNA transcripts from both NAT1 and NAT2 were present in human mammary gland; however, no NAT2 catalytic activity was detectable. Our data demonstrate for the first time that human mammary gland is catalytically active toward the metabolic activation of HCA food mutagens, and that this activity is most likely contributed by NAT1 expressed in the ductular epithelial cells of the mammary gland. In light of this study showing that NAT1 is catalytically active and expressed in the human mammary gland, additional studies are needed to determine if the NAT1 genotype is a risk factor for human mammary gland cancer. In order to better assess the role of dietary HCAs in human breast cancer risk, the NAT1 genotype and human mammary gland cancer incidence among women who regularly eat well-done cooked meats is warranted.