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治疗晚期肝细胞癌的新的、有效的治疗方法。肝细胞癌是最常见的胃肠道(GI)恶性肿瘤之一，也是世界范围内死亡的主要原因，可供选择的治疗方法有限。因此，设计安全有效的治疗方法来治疗这种疾病是至关重要的。已知配体激活的核受体PPARγ调节包括肝癌在内的多种癌细胞的生长和分化。在我们早期的研究中，尽管PPARγ被其配体曲格列酮激活抑制了肝癌细胞的增殖，但它不能诱导任何细胞凋亡。具有诱导生长抑制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，我们用TZD联合促凋亡剂肿瘤坏死因子相关的凋亡诱导配体(TRAIL)处理肝癌细胞。这些研究表明，为了使肝癌细胞对TRAIL-TZD诱导的细胞凋亡敏感，需要完全拮抗TRAIL-Catenin通路。目前的建议旨在利用体外(细胞)和体内(异种移植)模型来验证我们的假设，同时阐明？连环蛋白拮抗细胞凋亡和PPARγ拮抗？连环蛋白的机制。这项研究的成功完成有望为TRAIL-TZD联合应用对肝癌细胞凋亡的有效性提供重要的临床前数据，并从根本上理解？连环蛋白是否作为介导凋亡抵抗的分子靶点。在此基础上，作为我们长期目标的一部分，可以设计出更具特异性的下一代连环蛋白抑制剂(副作用较小)，用于有效治疗晚期肝细胞癌患者。

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 PPARγ is known to regulate growth and differentiation in a variety of cancer cells, including HCC. In our earlier studies although activation of PPARγ 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 ß-catenin pathway is needed to sensitize HCC cells towards TRAIL-TZD-induced apoptosis. Since treatment with TZD alone antagonized ß-catenin pathway at multiple levels via novel mechanisms, and antagonism of ß-catenin promoted HCC cell apoptosis, we hypothesize that PPARγ (or TZD) via antagonizing ß-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 ß-catenin antagonizes apoptosis and PPARγ antagonizes ß-catenin. The following specific aims are proposed to achieve our goals: (1) determine the role of ß-catenin in mediating HCC cell survival and resistance, (2) determine the mechanism by which ß-catenin is modulated during apoptosis and survival of HCC and (3) determine the role of ß-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 ß-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 ß-catenin (with less collateral toxicity) can be designed to be utilized i combination therapies for effectively treating patients with advanced forms of HCC.