Patterns of DNA adduct formation in liver and mammary epithelial cells of rats treated with 7,12-dimethylbenz(a)anthracene, and selective effects of chemopreventive agents.
Patterns of DNA adduct formation in liver and mammary epithelial cells of rats treated with 7,12-dimethylbenz(a)anthracene, and selective effects of chemopreventive agents.
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发表时间：
1999-09
期刊：
影响因子：
11.2
通讯作者：
A. Izzotti;A. Camoirano;C. Cartiglia;C. Grubbs;R. Lubet;G. Kelloff;S. De Flora
中科院分区：
文献类型：
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作者：
A. Izzotti;A. Camoirano;C. Cartiglia;C. Grubbs;R. Lubet;G. Kelloff;S. De Flora
7，12-二甲基苯并（a）蒽（DMBA）是一种原型致癌物，其在单次喂养后在大鼠中诱导高产量的乳腺肿瘤。我们研究了DNA加合物的诱导和化学预防雌性Sprague道利大鼠接受DMBA管饲根据各种治疗方案。32 P-后标记的DNA加合物在肝脏和乳腺上皮细胞中的模式是相似的代谢活化的DMBA与小牛胸腺DNA的体外反应所产生的。有一个高的和统计学上显着的相关性DMBA给药大鼠（0，0.6，2.4，和12毫克/公斤体重）和两种类型的细胞中的DNA加合物的水平。DMBA剂量与总DNA加合物水平相关的回归线在1.5 mg/kg体重时显著发散和交叉，表明在较低剂量下，靶乳腺细胞中DNA加合物的形成更强烈，而在较高剂量下，肝细胞中DNA加合物水平更高，推测是由于该器官的代谢能力更大。当大鼠在DMBA给药后7天而不是2天被处死时，肝脏和乳腺细胞中的DNA加合物水平大约减半。可以根据毒代动力学因素、局部和远端代谢、通过切除修复去除DNA加合物和细胞增殖率来解释观察到的模式。在三种化学预防剂中，5，6-苯并异丁酮（1650 ppm）是最有效的，抑制肝和乳腺细胞中DNA加合物的形成，分别为96.5%和83.5%。喂食1，2-二硫杂环戊烯-3-酮（600 ppm）可抑制该生物标志物68.5%和50.2%，而丁基羟基茴香醚（BHA; 5000 ppm）在肝脏中显示出显著抑制作用（46.5%），但在乳腺细胞中无效（29.0%，不显著）。这些数据与一项平行研究的结果很好地相关，在该研究中，5，6-苯并异丁酮、1，2-二硫杂环戊烯-3-酮和BHA分别抑制血红蛋白加合物的形成80.0%、44.0%和0%，乳腺肿瘤的发生率分别为82.4%、47.1%和5.9%;多重性分别提高了92.6%、80.0%和7.4%。因此，生物学有效剂量的生物标志物高度预测DMBA大鼠乳腺模型中化学预防剂的疗效。BHA选择性抑制肝脏中的DNA加合物，但不抑制乳腺细胞中的DNA加合物，这与这种酚类抗氧化剂刺激肝脏中的II相活性，但不刺激乳腺中的II相活性的发现一致（L. L. Song等人，手稿正在编写中）。在任何情况下，广谱诱导剂5，6-BF似乎比两种单功能II期诱导剂更有效，大概是因为DMBA对活性代谢物的增强活化与其阻断、解毒和排泄相协调。
7,12-Dimethylbenz(a)anthracene (DMBA) is a prototype carcinogen that induces a high yield of mammary tumors in rats after a single feeding. We investigated the induction and chemoprevention of DNA adducts in female Sprague Dawley rats receiving DMBA by gavage according to a variety of treatment schedules. The patterns of 32P-postlabeled DNA adducts in liver and mammary epithelial cells were similar to those produced by the in vitro reaction of metabolically activated DMBA with calf thymus DNA. There was a high and statistically significant correlation between dose of DMBA administered to rats (0, 0.6, 2.4, and 12 mg/kg body weight) and levels of DNA adducts in both types of cells. The regression lines relating DMBA doses to total DNA adduct levels were significantly divergent and crossed at 1.5 mg/kg body weight, indicating that, at lower doses, the formation of DNA adducts is more intense in target mammary cells, whereas at higher doses, DNA adduct levels are more elevated in liver cells, presumably due to the greater metabolic capacity of this organ. When the rats were sacrificed 7 days rather than 2 days after DMBA administration, DNA adduct levels were approximately halved in both liver and mammary cells. The observed patterns can be interpreted based on toxicokinetic factors, local and distant metabolism, removal of DNA adducts by excision repair, and cell proliferation rate. Of three chemopreventive agents given with the diet to rats treated with 12 mg of DMBA, 5,6-benzoflavone (1650 ppm) was the most effective, inhibiting DNA adduct formation in liver and mammary cells by 96.5 and 83.5%, respectively. Feeding of 1,2-dithiole-3-thione (600 ppm) inhibited this biomarker by 68.5 and 50.2%, whereas butyl hydroxyanisole (BHA; 5000 ppm) showed a significant inhibition in the liver (46.5%) but was ineffective in mammary cells (29.0%, not significant). These data correlate nicely with the results of a parallel study in which 5,6-benzoflavone, 1,2-dithiole-3-thione, and BHA inhibited formation of hemoglobin adducts by 80.0, 44.0, and 0%, respectively; the incidence of mammary tumors by 82.4, 47.1, and 5.9%, respectively; and their multiplicity by 92.6, 80.0, and 7.4%, respectively. Therefore, biomarkers of biologically effective dose are highly predictive of the efficacy of chemopreventive agents in the DMBA rat mammary model. The selective inhibition by BHA of DNA adducts in the liver but not in mammary cells is consistent with the finding that this phenolic antioxidant stimulated phase II activities in the liver but not in the mammary gland (L. L. Song et al., manuscript in preparation). In any case, the broad-spectrum inducer 5,6-BF appears to be more effective than the two monofunctional phase II inducers, presumably because an enhanced activation of DMBA to reactive metabolites is coordinated with their blocking, detoxification, and excretion.