Cross-regulation of apoptosis and autophagy as a molecular basis for reversal of

描述(由申请人提供)：在肿瘤形成过程中演变的细胞凋亡能力的抽象缺陷促进肿瘤生长，提供生存优势，并混淆治疗。这些缺陷一直是TRAIL疗法发展的主要障碍。用重组TRAIL或激动型DR4或DR5特异性抗体靶向TRAIL-R被认为是一种有前途的癌症治疗方法，特别是由于肿瘤细胞对TRAIL的选择性凋亡易感性高于正常细胞。然而，认识到许多肿瘤对TRAIL治疗没有反应，这激发了人们对识别凋亡剂的兴趣，当与TRAIL联合使用时，可以使肿瘤细胞对TRAIL介导的凋亡敏感。我们的初步研究表明，在凋亡信号通路的不同点上，各种凋亡缺陷阻断了TRAIL介导的细胞死亡，将信号级联从默认凋亡转变为细胞保护性自噬。我们还获得了大量证据表明，抑制这种TRAIL介导的自噬反应会启动有效的凋亡级联反应。我们建议研究一种新的概念，即对TRAIL介导的凋亡的抵抗的不同机制涉及诱导保护性自噬，因此可以通过靶向抑制自噬过程的特定成分来逆转。我们假设，抑制自噬可以用于TRAIL治疗，因为它逆转了凋亡缺陷肿瘤细胞中TRAIL抵抗的某些机制。我们进一步假设，自噬形成过程的基本成分，特别是Beclin-1/Atg6、UVRAG、Vps34和ATG7，通过它们介导自噬和抑制凋亡的双重功能，参与了自噬和凋亡之间的持续串扰。因此，这些蛋白的敲除不仅会阻止自噬，还会以一种依赖于靶向ATG蛋白的抗凋亡功能的方式启动凋亡事件。虽然拟议的研究集中在TRAIL治疗的耐药机制上，但它们与根除耐多药癌细胞的更广泛目标高度相关，因为它们针对的是许多细胞毒性方案中的一个主要绊脚石，即在肿瘤形成过程中演变的凋亡能力缺陷。本研究旨在阐明自噬与细胞凋亡相互抑制的分子机制。更好地理解自噬和凋亡之间交叉调节的分子基础将有助于确定自噬的调节是否可以用于癌症治疗。公共卫生相关性：我们的初步结果表明，肿瘤细胞内的许多细胞机制通常干扰抗癌药物TRAIL的疗效，涉及激活细胞保护反应。我们还获得了证据表明，抑制这种细胞保护反应会导致有效的细胞死亡。目前应用的目标是阐明逆转肿瘤细胞对TRAIL治疗耐药性的分子机制。

DESCRIPTION (provided by applicant): Abstract Defects in apoptotic capability that evolve during tumorigenesis promote tumor growth, provide survival advantage, and confound treatment. Such defects have been a major hurdle in the development of TRAIL therapy. Targeting TRAIL-Rs with either recombinant TRAIL or agonistic DR4 or DR5-specific antibodies has been considered a promising treatment for cancer, particularly due to the preferential apoptotic susceptibility of tumor cells to TRAIL over normal cells. However, the realization that many tumors are unresponsive to TRAIL treatment has stimulated interest in identifying apoptotic agents that when used in combination with TRAIL can sensitize tumor cells to TRAIL-mediated apoptosis. Our preliminary studies suggest that various apoptosis defects that block TRAIL-mediated cell death at different points along the apoptotic signaling pathway shift the signaling cascade from default apoptosis toward cytoprotective autophagy. We also obtained substantial evidence that inhibition of such a TRAIL-mediated autophagic response initiates an effective apoptotic cascade. We propose to investigate a novel concept that divergent mechanisms of resistance to TRAIL- mediated apoptosis involve the induction of protective autophagy, and thus can be reversed by targeting for inhibition specific components of the autophagic process. We hypothesize that inhibition of autophagy can be utilized for TRAIL therapy since it reverses certain mechanisms of TRAIL resistance in apoptosis- defective tumor cells. We further hypothesize that essential components of the autophagosome formation process, particularly Beclin-1/Atg6, UVRAG, Vps34 and Atg7, are involved in a constant crosstalk between autophagy and apoptosis through their dual function of mediating autophagy and inhibiting apoptosis. Thus, the knockdown of such proteins would not only block autophagy, but would also initiate apoptotic events in a manner that depends on the antiapoptotic function of the targeted Atg protein. Although the proposed studies focus on mechanisms of resistance to TRAIL therapy, they are highly relevant to a broader goal of eradicating multidrug-resistant cancer cells, as they target a major stumbling block in numerous cytotoxic regimens, i.e., defects in apoptotic capability that evolve during tumorigenesis. The proposed studies are designed to elucidate molecular mechanisms involved in the mutual inhibition between autophagy and apoptosis. A better understanding of the molecular basis for the cross regulation between autophagy and apoptosis will help determine if modulation of autophagy can be utilized for cancer therapy. PUBLIC HEALTH RELEVANCE: Our preliminary results suggest that numerous cellular mechanisms within tumor cells that commonly interfere with the efficacy of the anticancer drug, TRAIL, involve the activation of a cytoprotective response. We also obtained evidence that inhibition of such a cellular protective response yields a productive cell death. The goal of the current application is to elucidate the molecular mechanisms that underlie the reversal of tumor cell resistance to TRAIL therapy.