Lipid peroxidation product induced DNA damage in the p53 gene and liver cancer

脂质过氧化产物诱导 p53 基因 DNA 损伤和肝癌

• 批准号: 7195526
• 负责人: Eric Moon-shong M. TANG
• 金额: $ 40万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-28 至 2011-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7195526
• 关键词: DNA damage; DNA repair; adduct; aldehydes; carcinogenesis; choline deficiency; gene expression; gene mutation; genetic mapping; hepatocellular carcinoma; human tissue; isomer; laboratory rat; lipid metabolism; liver cells; neoplasm /cancer epidemiology; nucleic acid sequence; p53 gene /protein; peroxidation; tissue /cell culture

DESCRIPTION (provided by applicant): Hepatocellular carcinoma (HCC) is a major malignancy worldwide. Epidemiological studies have suggested that hepatitis B virus infection and dietary aflatoxin B1 (AFB1) are the two major etiological agents for human HCC. However, the underlying mechanisms of how these two agents induce hepatocarcinogenesis remain unclear. In rats HCC can be induced by a choline-deficient diet (CDD). The pathogenesis of CDD-induced HCC in rats mimics the pathogenesis of human HCC: hepatitis at an early stage, followed by steatosis, cirrhosis and finally HCC. Rats on CDD therefore provide an excellent model for studying HCC. It has been found that the lipid peroxidation (LPO) level and LPO product-induced DNA damage are significantly increased in liver cells of rats on CDD; LPO has thus been suspected of playing an important role in hepatocarcinogenesis. LPO is a cellular process that commonly takes place under normal physiological conditions, and this process becomes significant when cells are under oxidative stress. LPO generates a variety of aldehydes, such as acrolein (Acr), crotonaldehyde, malondialdehyde (MDA), and trans-4-hydroxy- 2-nonenal (4-HNE), that are able to interact with DNA; these adducts induce mainly G to T transversion. Aldehydes are also able to interact with proteins with a thiol group. We have recently found that 4-HNE and MDA are able to significantly inhibit cellular nucleotide excision repair (NER). Based on these results we hypothesize that these aldehydes may play important roles in carcinogenesis through two effects: induction of mutations by their interactions with DNA and inhibition of DNA repair by their interactions with repair proteins. By mapping the 4-HNE-DNA adduct distribution at the sequence level in human p53 gene fragments and genomic DNA we have found that 4-HNE preferentially binds to -GAGGC/A- sequences, including codon 249 of the p53 gene, the sole mutational hotspot in liver cancer. Our results raise the strong possibility that 4-HNE may play a particularly important role in hepatocarcinogenesis in both rats and humans. We propose to test these hypotheses using both the rat and cultured human hepatocyte model. We will determine how 4-HNE-DNA adducts in the p53 gene are processed, and the role of the p53 gene in aldehyde-mediated inhibition of DNA repair in human cells. We will also determine the effect of CDD on the repair capacity in rat liver cells, the formation of 4-HNE- and other aldehyde-induced DNA adducts formed in the p53 gene and the p53 mutational spectrum in CDD-induced HCC in rats. In addition, we will determine the effect of stereostructure of 4-HNE-dG at GAGGC sites on repair and mutagenicity. Results from these studies should greatly enhance our understanding of the role of LPO in hepatocarcinogenesis.

描述（由申请人提供）：肝细胞癌（HCC）是世界范围内的主要恶性肿瘤。流行病学研究表明，B型肝炎病毒感染和膳食黄曲霉毒素B1（AFB 1）是人类肝癌的两个主要病因。然而，这两种药物如何诱导肝癌发生的潜在机制仍不清楚。在大鼠中，肝细胞癌可以通过胆碱缺乏饮食（CDD）诱导。大鼠中CD诱导的HCC的发病机制模拟人类HCC的发病机制：早期肝炎，随后脂肪变性，肝硬化，最后是HCC。因此，CDD大鼠为研究HCC提供了一个很好的模型。研究发现，CDD大鼠肝细胞脂质过氧化（LPO）水平及LPO产物诱导的DNA损伤显著增加，推测LPO在CDD大鼠肝癌发生中起重要作用。LPO是通常在正常生理条件下发生的细胞过程，并且当细胞处于氧化应激下时，该过程变得显著。LPO产生多种醛类，如丙烯醛（Acr）、巴豆醛、丙二醛（MDA）和反式-4-羟基-2-壬烯醛（4-HNE），它们能够与DNA相互作用;这些加合物主要诱导G到T的颠换。醛也能够与具有巯基的蛋白质相互作用。我们最近发现4-HNE和MDA能够显著抑制细胞核苷酸切除修复（NER）。基于这些结果，我们推测，这些醛类可能通过两种效应在致癌作用中发挥重要作用：通过与DNA的相互作用诱导突变和通过与修复蛋白的相互作用抑制DNA修复。通过在人p53基因片段和基因组DNA中绘制4-HNE-DNA加合物在序列水平上的分布，我们发现4-HNE优先结合-GAGGC/A-序列，包括p53基因的密码子249，肝癌中唯一的突变热点。我们的研究结果提出了强烈的可能性，4-HNE可能在大鼠和人类的肝癌发生中发挥特别重要的作用。我们建议使用大鼠和培养的人肝细胞模型来测试这些假设。我们将确定p53基因中的4-HNE-DNA加合物是如何加工的，以及p53基因在人类细胞中DNA修复的酶介导的抑制中的作用。我们还将确定CDD对大鼠肝细胞修复能力的影响，在p53基因中形成的4-HNE-和其他环糊精诱导的DNA加合物的形成，以及CDD诱导的大鼠HCC中的p53突变谱。此外，我们将确定GAGGC位点4-HNE-dG的立体结构对修复和致突变性的影响。这些研究的结果将大大提高我们对LPO在肝癌发生中作用的认识。