REGULATION OF BENIGN AND MALIGNANT HEPATOCYTE GROWTH

描述(申请人提供)：肝细胞癌(HCC)每年导致超过35,000美国人死亡，也是全球癌症死亡的主要原因之一。手术切除是肝癌患者可用的最佳治疗方法，但对于确诊的患者中只有20%-40%是可行的选择。未能开发出肝癌的替代治疗方法是因为我们在细胞和分子水平上缺乏对疾病病因的了解。我们实验室以前的报告已经发现，丝裂原活化蛋白激酶(MAPK)级联的成分是处理不同来源信号的焦点，包括与鸟嘌呤核苷酸调节蛋白(C-蛋白)偶联和酪氨酸激酶连接的受体相关的信号。具体地说，我们已经证明了抑制性G蛋白(GiProteins)在所分析的80%以上的人肝细胞癌中的表达和功能发生了变化。此外，在人和动物的肝细胞癌模型中，GI蛋白的激活通过丝裂原激活的蛋白激酶(MAPK)级联导致有丝分裂的增强，这一效应在未转化的肝细胞中没有观察到。我们实验室的其他数据显示，肝脏胰岛素样生长因子-I(IGF一L)在肝细胞癌和肿瘤负荷动物的非致瘤性、组织学正常的肝组织中的表达发生了变化。胰岛素样生长因子-L刺激肝癌细胞后，通过丝裂原活化蛋白激酶途径促进细胞有丝分裂，这种作用被Gi蛋白信号通路抑制所消除。基于这些观察，本研究的中心假设是，丝裂原活化蛋白激酶级联反应代表了不同来源的跨膜信号之间的焦点联系，其调控直接在多个水平上影响肝肿瘤的增殖，并与肝细胞癌细胞有丝分裂增加的特性存在内在联系。NIH-R01一等奖的目的是“确定MAPK成分在膜、细胞质和核水平上调节细胞有丝分裂的机制。”具体地说，我们将(I)过度表达G-蛋白/胰岛素样生长因子-L-丝裂原活化蛋白激酶信号通路的结构性活性或显性负性成分，并结合刺激或抑制这些信号通路的特定药物。这些数据将确定C蛋白亚基和TK连接受体及其相关的第二信使在调节肝细胞癌细胞质(MAPK)信号通路中的作用。(2)探讨G-蛋白/胰岛素样生长因子-L-丝裂原活化蛋白K信号通路在正常肝细胞和癌变肝细胞中对核转录因子及细胞增殖和存活的调控作用。因此，在细胞质和核水平上阐明控制细胞增殖的机制是发展不可切除的肝癌新治疗方法的潜在突破。

DESCRIPTION (provided by applicant): Hepatocellular cancer (HCC) leads to the death of more than 35,000 Americans annually in addition to being one of the leading causes of cancer death worldwide. Surgical resection is the best treatment available to patients with HCC but is a viable option for only 20-40% of those diagnosed. The failure to develop alternative treatments for HCC is due to our lack of understanding of the disease etiology at the cellular and molecular level. Previous reports from our laboratory have identified components of a mitogen activated protein kinase (MAPK) cascades as a focal point in processing signals of diverse origin including those associated with guanine nucleotide regulatory protein (C-protein) coupled and tyrosine kinase-linked receptors. Specifically, we have demonstrated altered expression and function of inhibitory G-proteins (Giproteins) in more than 80% of human HCC analyzed. Furthermore, activation of Gi-proteins in human and animal models of HCC leads to enhanced mitogenesis via a mitogen activated protein kinase (MAPK) cascade, an effect not observed in non-transformed hepatocytes. Other data from our laboratory demonstrate changes in hepatic insulin-like growth factor-I (IGF-l) expression in HCC and non-tumorigenic, histologically normal hepatic tissue in tumor burdened animals. Stimulation of HCC cells with IGF-l leads to increased cell mitogenesis via a MAPK pathway, an effect abrogated by inhibition of Gi-protein signaling.Based on these observations the central hypothesis of this proposal is that a MAPK cascade represents a focal link between transmembrane signals of diverse origin, regulation of which directly affects hepatic tumor proliferation at multiple levels and is intrinsically linked to the increased cell mitogenesis characteristic of HCC. It is the aim of this NIH-R01 First Award to "determine the mechanisms by which MAPK components regulate cell mitogenesis at the membrane, cytoplasmic and nuclear levels." Specifically we will (i) over-express constitutively active or dominant negative components of G-protein/IGF-l-MAPK signaling pathways in conjunction with specific pharmacological agents that stimulate or inhibit these pathways. These data will determine the role of C-protein subunits and TK-linked receptors and their associated second messengers in regulating cytoplasmic (MAPK) signaling pathways in HCC. (ii) determine the role of G-protein/IGF-l-MAPK pathways in regulating nuclear transcription factors and cell proliferation and survival in normal and transformed (HCC) hepatocytes.Because the mortality associated with HCC is so high, deciphering the mechanisms by which cell growth and tumor progression occurs is clearly of major clinical importance and significance. Accordingly, elucidation of the mechanisms controlling cell proliferation at the cytoplasmic and nuclear level represents a potential breakthrough in the development of new treatments for non-resectable HCC.