Role of Inflammation in tumor promotion and progression

描述(由申请人提供)：本次续展申请是基于当前项目期间取得的一项概念和技术突破--鉴定和分离作为小鼠肝细胞癌(HCC)先兆的前肿瘤细胞。肝癌是最具侵袭性和难治性的癌症之一，目前的5年生存率为8%，但在慢性肝炎(肝炎)和损害的背景下，肝癌的发展经历了20-40年的过程。肝细胞癌发生之前会出现病灶改变的肝细胞(FAH)，一直被怀疑(但从未被证实)代表癌前病变。我们成功地从两种不同的小鼠肝癌模型中分离出了肝细胞癌前体细胞(HPC)，并获得了证据表明HPC存在于用一种针对肝细胞的化学致癌物处理的小鼠的FAH内。奇怪的是，根据其基因表达谱，HPC似乎与卵圆细胞有关，卵圆细胞是一种双潜能的前体细胞，参与修复小鼠和人类的某些肝损伤。然而，目前尚不清楚HPC是来自卵圆形细胞还是来自分化后的肝细胞，后者是致癌物的靶标。了解控制HPC形成和发展为完全发展的肝癌的机制将有助于在这种恶性肿瘤变得对所有已知的治疗方法无效之前，及早制定预防和治疗策略以根除肝癌。除了细胞内的因素外，HPC向肝细胞癌的进展还受到微环境的控制。相应地，我们将研究在HPC中启动和维持激活的STAT3的机制，这是一个关键的致癌转录因子。这些研究将解释如何在HPC和肝细胞癌中保持STAT3的激活，而不是在邻近的正常肝脏中，即使正常组织暴露在激活STAT3的细胞因子中。我们将通过它们在分离的HPC中的基因操作来研究这些机制对HPC在肝细胞癌进展中的贡献。我们还将研究细胞表面蛋白和干细胞标记物CD44在HPC形成和HPC向肝细胞癌进展中的作用，因为我们的初步结果表明，HPC表达CD44，CD44在FAH的形成和肝细胞癌的发展中是必不可少的。我们将研究在HPC中CD44上调的机制，以及产生与c-Met相互作用并增强其信号活性的选择性剪接的CD44v6亚型。HPC表达的另一个标记是转录因子Sox9，它也在椭圆形细胞中表达。我们将研究Sox9在HPC中表达的机制，重点是Notch途径的作用，并将利用Sox9进行谱系追踪实验，以确定HPC的起源。

DESCRIPTION (provided by applicant): This renewal application is based on a conceptual and technological breakthrough made during the current project period - identification and isolation of pre-neoplastic cells that serve as precursors for hepatocellular carcinoma (HCC) in mice. HCC is one of the most aggressive and difficult to treat cancers, with a current 5 year survival rate of 8%, yet HCC develops over the course of 20-40 years in the context of chronic liver inflammation (hepatitis) and damage. HCC development is preceded by appearance of foci of altered hepatocytes (FAH), which have been suspected (but never proven) to represent pre-neoplastic lesions. We succeeded in isolating HCC progenitor cells (HPC) from two different mouse HCC models and obtained evidence suggesting that HPC reside within FAH in mice treated with a chemical carcinogen that targets hepatocytes. Curiously, HPC appear to be related, based on their gene expression profile, to oval cells, a bipotential progenitor cell involved in repair of certain liver injuries in mice and men. However, it is not clear whether HPC arise from oval cells or from differentiated hepatocytes which are the target for the carcinogen. Understanding the mechanisms that control formation of HPC and their progression to full blown HCC will enable the development of preventive and therapeutic strategies for HCC eradication at an early stage, before this malignancy becomes refractory to all known therapies. In addition to cell intrinsic factors, progression of HPC to HCC is subject to micro environmental control. Correspondingly, we will investigate the mechanisms responsible for initiation and maintenance of activated STAT3, a critical oncogenic transcription factor, in HPC. These studies will explain how STAT3 activation is maintained within HPC and HCCs, but not in the adjacent normal liver, even though the normal tissue is exposed to STAT3-activating cytokines. We will investigate the contribution of these mechanisms to HPC to HCC progression by their genetic manipulation within isolated HPC. We will also study the role of the cell surface protein and stem cell marker CD44 in HPC formation and HPC to HCC progression, as our preliminary results indicate that HPC express CD44 and that CD44 is essential for FAH formation and HCC development. We will study the mechanisms responsible for CD44 upregulation in HPC and for production of the alternatively spliced CD44v6 isoform that interacts with c-Met and potentiates its signaling activity. Another marker expressed by HPC is the transcription factor Sox9, which is also expressed in oval cells. We will investigate the mechanisms responsible for Sox9 expression in HPC, focusing on the role of the Notch pathway and will exploit Sox9 in lineage tracing experiments that will determine the origin of HPC.