Role of beta-catenin in apoptosis resistance of hepatocellular carcinoma

描述（由申请人提供）：拟议研究的总体长期目标是设计一种新颖有效的治疗晚期肝细胞癌（HCC）的治疗方法。HCC是最常见的胃肠道（GI）恶性肿瘤之一，也是世界范围内死亡的主要原因，可用的治疗方案有限。因此，设计安全有效的治疗方法来治疗这种疾病至关重要。配体活化核受体PPAR？已知可以调节多种癌细胞的生长和分化，包括HCC。在我们早期的研究中尽管PPAR的激活？通过其配体Troglitazone （TZD）抑制HCC细胞增殖，但不能诱导任何细胞凋亡。具有诱导生长停滞和细胞凋亡的潜力的药物（或组合）被认为是治疗晚期癌症最有效的药物。为了确定TZD是否可以作为一种联合治疗方法，我们将TZD与促凋亡剂肿瘤坏死因子相关凋亡诱导配体（TRAIL）联合治疗HCC细胞。我们的研究表明，与单独用药相比，TRAIL-TZD联合用药可显著诱导HCC细胞凋亡，并与聚（adp -核糖）聚合酶（PARP）和Caspase 3切割的显著增加有关。我们设计了更深入的研究来确定这种凋亡的分子靶点，以提高我们对参与HCC细胞凋亡抵抗的效应物的理解。这些研究表明？肝癌细胞对trail - tzd诱导的凋亡的敏感性需要-catenin通路。自单用TZD治疗起拮抗？-catenin通路在多个水平通过新机制，和拮抗？-catenin促进HCC细胞凋亡，我们假设PPAR？（或TZD）通过拮抗？-catenin通路使HCC细胞对TRAIL敏感，否则它们对单独的TRAIL不敏感。目前的建议旨在利用体外（细胞）和体内（异种移植）模型验证我们的假设，同时阐明哪些机制？-catenin拮抗细胞凋亡和PPAR？对抗?连环蛋白。为了实现我们的目标，我们提出了以下具体目标：(1)确定？-catenin介导HCC细胞存活和耐药，(2)确定其作用机制？-catenin在肝癌细胞凋亡和存活过程中受到调节，并且(3)决定？-catenin对肝癌存活和体内耐药的影响。这些研究的成功完成有望为TRAIL-TZD联合治疗HCC细胞凋亡的疗效提供重要的临床前数据，并从根本上了解是否？-catenin是介导细胞凋亡抵抗的分子靶点。基于这些，作为我们长期目标的一部分，更具体的下一代抑制剂？-catenin（附带毒性较小）可设计用于联合治疗，有效治疗晚期HCC患者。

DESCRIPTION (provided by applicant): The overall long-term goal of the proposed research is to design a novel and efficient therapeutic approach for treating advanced hepatocellular carcinoma (HCC). HCC is one of the most common gastrointestinal (GI) malignancies and a major cause of death worldwide, with limited available therapeutic options. Designing safe and efficient therapeutic approaches for treating this disease is thus critically important. Ligand-activated nuclear receptor PPAR? is known to regulate growth and differentiation in a variety of cancer cells, including HCC. In our earlier studies although activation of PPAR? by its ligand Troglitazone (TZD) inhibited HCC cell proliferation, it was unable to induce any apoptosis. The drugs (or combinations) which have the potential of inducing both growth arrest and apoptosis are believed to be most effective in treating advanced forms of cancer. To determine whether TZD can be utilized as a combination therapy instead, we treated HCC cells with TZD in combination with the proapoptotic agent Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Our studies indicated that TRAIL-TZD combination can induce a significant degree of apoptosis in the HCC cells compared to either drug treatment alone and was associated with a dramatic increase in the cleavage of poly (ADP-ribose) polymerase (PARP) and Caspase 3. More in-depth studies were designed to identify the molecular target of this apoptosis, in an effort to improve our understanding of the effectors involved in apoptosis resistance of HCC. These studies revealed that a complete antagonism of ?-catenin pathway is needed to sensitize HCC cells towards TRAIL-TZD-induced apoptosis. Since treatment with TZD alone antagonized ?-catenin pathway at multiple levels via novel mechanisms, and antagonism of ?-catenin promoted HCC cell apoptosis, we hypothesize that PPAR? (or TZD) via antagonizing ?-catenin pathway sensitizes HCC cells towards TRAIL, which are otherwise insensitive to TRAIL alone. The current proposal aims to validate our hypothesis utilizing both in vitro (cellular) and in vivo (xenograft) models while elucidating the mechanisms by which ?-catenin antagonizes apoptosis and PPAR? antagonizes ?-catenin. The following specific aims are proposed to achieve our goals: (1) determine the role of ?-catenin in mediating HCC cell survival and resistance, (2) determine the mechanism by which ?-catenin is modulated during apoptosis and survival of HCC and (3) determine the role of ?-catenin on HCC survival and resistance in vivo. Successful completion of the studies is expected to provide important preclinical data on the efficacy of TRAIL-TZD combination on HCC cell apoptosis and a fundamental understanding whether ?-catenin serves as a molecular target to mediate apoptotic resistance. Based on these and as part of our long-term goal, more specific next generation inhibitors of ?-catenin (with less collateral toxicity) can be designed to be utilized i combination therapies for effectively treating patients with advanced forms of HCC.