Aflatoxin B1 hepatocarcinogenesis in the mGSTA3-/- mouse

描述（由申请人提供）：我们建议在谷胱甘肽S-转移酶A3敲除小鼠（mGSTA 3-/-或KO）中使用黄曲霉毒素肝癌发生的新实验模型，以探索卵圆细胞（OC）作为肝细胞癌（HCC）前体的作用，这在其他实验模型中是不可能的。HCC是全球癌症死亡率的主要原因，而膳食黄曲霉毒素B1（AFB 1）暴露是一个主要的风险因素。成年小鼠对AFB 1诱导的肝损伤具有抵抗力，因为高水平的组成型表达mGSTA 3可以解毒激活的AFB 1。人类没有这种有效的解毒途径，因此mGSTA 3-/-小鼠在AFB 1代谢和敏感性方面可能被认为是人源化的。雄性和雌性mGSTA 3 KO小鼠对低剂量的AFB 1都有反应，伴有肝损伤和大量OC增殖。在具体目标1中，我们将通过测量AFB 1代谢的步骤、AFB 1-DNA加合物的水平和肝组织中氧化损伤的程度来确定mGSTA 3缺失对AFB 1诱导的毒性的影响。这将为AFB 1致癌机制提供一个机制性的见解，并应解释我们观察到的雄性和雌性mGSTA 3-/-小鼠对急性AFB 1毒性敏感性的差异。在特定目标2中，将使用mGSTA 3-/-小鼠中的四种AFB 1暴露方案来确定一种或几种最适合研究AFB 1诱导的肝细胞癌损伤和发展的方案。该模型将被设计为靶向卵圆细胞，模拟启动+促进方案，并包括与慢性肝炎易感转基因小鼠的杂交育种。在具体目标3中，将专门讨论增殖后卵圆细胞的命运。在AFB 1诱导的肝损伤后，将在不同的AFB 1暴露方案下研究它们的起源、扩增和分化为成熟细胞或肝癌。mGSTA 3-/-小鼠的卵圆细胞反应更大，生长模式不同，与其他小鼠模型报告的人类健康更相关。这些研究将为黄曲霉毒素B1相关的致癌作用提供新的见解，确定导致肿瘤发展的事件序列，确定卵圆细胞作为癌症干细胞的作用，并提供可靶向预防AFB 1诱导的肝毒性和癌症的机制。

DESCRIPTION (provided by applicant): We propose to use a new experimental model of aflatoxin hepatocarcinogenesis in glutathione S- transferase A3 knockout mice (mGSTA3-/- or KO) to explore the role of oval cells (OCs) as precursors to hepatocellular carcinoma (HCC) not possible in other experimental models. HCC is a leading cause of cancer mortality worldwide, and dietary aflatoxin B1 (AFB1) exposure is a major risk factor. Adult mice are resistant to AFB1-induced liver injury because of high levels of constitutively expressed mGSTA3 that detoxifies activated AFB1. Humans do not have this efficient detoxification pathway, so that the mGSTA3-/- mice may be considered humanized in regard to AFB1 metabolism and sensitivity. Both male and female mGSTA3 KO mice respond to low doses of AFB1 with liver injury and massive OC proliferation. In Specific Aim 1, we will define the effects of loss of the mGSTA3 on AFB1-induced toxicity, by measuring the steps of AFB1 metabolism, the levels of AFB1-DNA adducts and extent of oxidative damage in liver tissues. This will provide a mechanistic insight into AFB1 carcinogenesis and should explain the differences in susceptibility to acute AFB1 toxicity between male and female mGSTA3-/- mice that we have observed. In Specific Aim 2, four regimens of AFB1 exposure in mGSTA3-/- mice will be used to determine one, or several, that would best serve to study the AFB1-induced injury and development of HCCs. The models will be designed to target oval cells, mimic initiation + promotion protocols and include cross-breeding with chronic hepatitis-prone transgenic mice. In Specific Aim 3, the fate of oval cells after proliferation will be specifically addressed. Following AFB1- induced liver injury, their origin, expansion and differentiation into either mature cells or to liver cancer, will be studied under different AFB1 exposure protocols. The oval cell response in mGSTA3-/- mice is much greater, different in growth pattern and more relevant to human health than other mouse models reported. These studies will provide new insights into aflatoxin B1-associated carcinogenesis, identify the sequence of events that leads to tumor development, determine the role of oval cells as cancer stem cells and provide mechanisms that can be targeted to prevent AFB1-induced liver toxicity and cancer in the future.