Role of NF-kB in Fas-mediated Apoptosis and Tumor Suppression

描述(申请人提供)：Fas是死亡受体超家族的成员。Fas最主要也是最广为人知的功能是细胞凋亡。人类Fas或FASL基因编码序列的种系和体细胞突变或缺失导致自身免疫性淋巴增殖性综合征。自身免疫性淋巴增殖性综合征患者患血液性和非血液性癌症的风险均增加。此外，在人类中，Fas和FASL基因启动子的多态与Fas表达水平降低和发生血液性和非血液性癌症的风险增加相关。Fas受体的刺激也激活了“非凋亡性”信号，尤其是核因子-κB的激活。然而，Fas介导的NF-κB激活的功能在很大程度上仍不清楚。我们的初步研究表明，在人结肠癌细胞和小鼠胚胎成纤维细胞中，规范的NF-κB是Fas的转录激活因子和Fas介导的细胞凋亡的促进者，而交替的NF-κB是Fas的转录抑制因子和Fas介导的凋亡的抑制因子。此外，我们的初步研究表明，阻断典型的NF-κB激活会导致体内结肠癌细胞转移潜能的显著增加。基于这些观察结果，我们假设亚基组成是控制NF-κB蛋白复合体在Fas介导的细胞凋亡中的对比功能的分子开关，药物干预Fas耐药是提高CTL免疫治疗结肠癌转移疗效的有效途径。我们的长期目标是开发一种基于Fas的疗法来抑制人类结直肠癌的转移。我们建议在这个项目中实现三个特定的目标：1)验证关于NF-κB蛋白复合体的亚基组成决定了NF-κB在结肠癌细胞凋亡和存活中的功能的假设；2)验证了NF-κB调节Fas介导的凋亡通路以介导体内结肠癌发生的假设；以及3)验证了细胞凋亡增敏化疗增加了免疫治疗对结肠癌转移的疗效的假设。这一研究项目有可能开发一种辅助疗法来克服Fas耐药，以提高免疫疗法的疗效，有效地抑制自发性结肠癌转移。

DESCRIPTION (provided by applicant): Fas is a member of the death receptor superfamily. The major and best known function of Fas is apoptosis. Germline and somatic mutations or deletions of FAS or FASL gene coding sequences in humans lead to autoimmune lymphoproliferative syndrome. Patients with autoimmune lymphoproliferative syndrome exhibit increased risk of both hematopoietic and non-hematopoietic cancers. Furthermore, FAS and FASL gene promoter polymorphisms are associated with decreased Fas expression level and increased risk of both hematopoietic and non-hematopoietic cancer developments in humans. Stimulation of Fas receptor also activates "non-apoptotic" signaling, notably NF-κB activation. However, the function of Fas-mediated NF-κB activation remains largely unknown. Our preliminary studies demonstrated that canonical NF-κB is a transcription activator of Fas and a promoter of Fas-mediated apoptosis, whereas the alternate NF-κB is a transcription repressor of Fas and suppressor of Fas-mediated apoptosis in both human colon carcinoma cells and in mouse embryonic fibroblasts. Furthermore, our preliminary studies demonstrated that blocking the canonical NF-κB activation results in a significantly increase of colon carcinoma cell metastatic potential in vivo. Based on these observations, we hypothesize that subunit composition is the molecular switch that controls the contrasting functions of the NF-κB protein complexes in Fas-mediated apoptosis and pharmacological intervention of Fas resistance is an effective approach to increase CTL immunotherapy efficacy against colon cancer metastasis. Our long-term goal is to develop a Fas-based therapy to suppress human colorectal cancer metastasis. We propose to carry out three specific aims in this project: 1) test the hypothesis that subunit composition of the NF-κB protein complex determines NF-κB functions in colon carcinoma cell apoptosis and survival; 2) test the hypothesis that NF-κB regulates Fas-mediated apoptosis pathways to mediate colon carcinoma development in vivo; and 3) test the hypothesis that apoptosis sensitization chemotherapy increases the efficacy of immunotherapy against colon carcinoma metastasis. This research project has the potential to develop an adjunct therapy to overcome Fas resistance to increase the efficacy of immunotherapy for effective suppression of spontaneous colon cancer metastasis.