FABP4 Released from Steatotic Hepatocytes in Alcoholic Liver Disease Enhances Hepatic Tumor Progression

摘要 在美国，酒精使用障碍(AUD)是严重的临床和经济医疗负担 以及全球范围内。在AUDS影响的病理范围内，肝脏在酒精中的中心作用 新陈代谢使其特别容易受到损害。酒精性肝病(ALD)是由慢性、 大量饮酒，以一系列恶化的肝脏病理(脂肪堆积)为特征 (肝骨病)、酒精性肝炎、纤维化--肝硬变)。在ALD中，肝细胞色素P450 2E1被诱导为 代谢乙醇导致肝内乙醛升高和氧化应激，这些因素会增加 遗传损伤和发展为肝细胞癌的风险。 细胞内脂质的运动和储存是维持肝脏和 全身动态平衡。在健康人中，脂肪酸结合蛋白(FABP)在组织中表达- 在脂类隔离和运动过程中作为关键伴侣的特定方式和功能。在健康的肝脏中， FABP1是在肝细胞中主要表达的FABP。最近的研究报告FABP4(通常是一种异构体 在脂肪细胞和巨噬细胞中表达)由脂肪细胞合成并释放，作为旁分泌- 特定疾病状态下的内分泌信号分子，包括发生在脂肪附近的癌症 组织。我们小组的研究报告FABP4的mRNA和蛋白表达显著上调 酒精喂养的啮齿类动物肝细胞的分离及表达细胞色素P4502的肝癌细胞对酒精代谢的影响 细胞。在ALD模型系统中FABP4表达增加的这些发现也在组织和 ALD/ALD-肝细胞癌患者血清。在功能上，我们报告了外源rhFABP4刺激ERK-MAPK和 JNK信号通路在体外诱导肝细胞癌的增殖和迁移。总而言之，这些数据使我们 假设ALD诱导的脂肪变性肝细胞的酒精代谢导致FABP4的诱导 合成和释放，进而刺激肝癌细胞的生长和迁移。 提出了两个具体的目标；目标1将确定肝脏酒精的作用机制[S] 代谢诱导FABP4表达，明确FABP4调控的信号机制[S] 肝癌细胞功能。为了实现这一点，我们将结合从我们的初步数据获得的知识，使用 用创新的蛋白质组学方法(细胞信号磷酸抗体阵列)建立体外模型 准确确定FABP4监管的信令网络。目标2将演示以下内容的重要性 FABP4信号在酒精依赖的肝细胞癌体内扩张和进展中的作用。这些研究将利用一本小说 肝细胞特异性FABP4-/-小鼠(HS-FABP4-/-)和原位肿瘤进展模型。同时， 我们将扩大对ALD和ALD-HCC患者组织和血清中FABP4的正在进行的分析 目的：研究在酒精性肝病和肝细胞癌进展过程中FABP4表达改变的临床相关性。

SUMMARY Alcohol use disorders (AUDs) are significant clinical and financial healthcare burdens in the United States and globally. Within the spectrum of pathologies affected by AUDs, the central role of the liver in alcohol metabolism makes it particularly susceptible to damage. Alcoholic liver disease (ALD) arises from sustained, heavy alcohol ingestion and is characterized by a series of worsening liver pathologies (fat accumulation (hepatosteatosis), alcoholic hepatitis, fibrosis-cirrhosis). In ALD, hepatic cytochrome P450 2E1 is induced to metabolize ethanol leading to elevated intrahepatic acetaldehyde and oxidative stress, factors that increase the risk of genetic damage and development of hepatocellular carcinoma (HCC). Intracellular lipid movement and storage are closely regulated processes required to maintain liver and systemic homeostasis. In healthy individuals fatty acid binding proteins (FABPs) are expressed in a tissue- specific manner and function as critical chaperones during lipid sequestration and movement. In the healthy liver, FABP1 is the predominant FABP expressed in hepatocytes. Recent studies report FABP4 (an isoform usually expressed in adipocytes and macrophages) is synthesized and released by adipocytes to act as a paracrine- endocrine signaling molecule in specific disease states, including cancers arising in close proximity to adipose tissue. Studies by our group report FABP4 mRNA and protein expression is dramatically upregulated in hepatocytes isolated from alcohol-fed rodents, and following alcohol metabolism by CYP2E1-expressing HCC cells. These findings of increased FABP4 expression in ALD model systems are also evidenced in tissue and serum from ALD/ALD-HCC patients. Functionally, we report exogenous rhFABP4 stimulates ERK-MAPK and JNK signaling leading to HCC proliferation and migration in vitro. Collectively, these data have led us to hypothesize that “alcohol metabolism in ALD-induced steatotic hepatocytes leads to the induction of FABP4 synthesis and release which in turn stimulates HCC cell growth and migration”. Two Specific Aims are proposed; Aim 1 will determine the mechanism[s] by which hepatic alcohol metabolism induces FABP4 expression, and define the signaling mechanism[s] by which FABP4 regulates hepatoma cellfunction. To achieve this, we will combine knowledge derived from our Preliminary Data using established in vitro models with innovative proteomic approaches (Cell Signaling Phospho-Antibody Array) to accurately determine the signaling networks regulated by FABP4. Aim 2 will demonstrate the significance of FABP4 signaling in alcohol-dependent HCC expansion and progression in vivo. These studies will utilize a novel hepatocyte-specific FABP4-/- mouse (HS-FABP4-/-) and an orthotopic model of tumor progression. In parallel, we will expand our ongoing analyses of tissue and serum from ALD and ALD-HCC patients for FABP4 expression to determine the clinical relevance of altered FABP4 expression during ALD and HCC progression.