Targeting the Chk1-Suppressed Apoptotic Pathway in HNSCC

描述（由申请人提供）：p53 信号传导的缺陷消除了许多人类癌症对放射治疗的细胞凋亡反应。在头颈鳞状细胞癌 (HNSCC) 中，TP53 突变导致放射抗性肿瘤的局部复发，这是一种致命的疾病形式。因此，迫切需要能够绕过突变型 TP53 来恢复 HNSCC 放射敏感性的药物。该提案重点关注一种新兴的细胞凋亡途径，称为“Chk1 抑制”(CS) 细胞凋亡，Chk1 抑制剂激活该途径可恢复 p53 缺陷的斑马鱼、小鼠和人类癌细胞的放射敏感性（Sidi 等人，Cell 2008）。我们认为 Chk1 抑制剂和相关的 CS 通路为 TP53 突变型 HNSCC 提供了一个有前景的治疗机会。我们的工作阐明了 CS 途径的核心主干，该途径包含一个新型 ATM/ATR-caspase-2 轴，该轴绕过 p53 以及伴随的线粒体和死亡受体信号级联。最近，我们确定了 PIDDosome（PIDD-RAIDD-caspase-2 复合物），而不是内在凋亡体或外在 DISC，作为 CS 途径中起作用的 caspase 激活平台。这些结果强化了 CS 轴定义了脊椎动物细胞中第三种凋亡途径的观点，并发表在 9 月 14 日出版的《分子细胞》杂志上（Ando 等人，Mol Cell 2012）。虽然我们假设 CS 途径对 TP53 突变型 HNSCC 具有治疗效果，但这种疾病的极端异质性使得我们有必要开发预测或评估肿瘤中 PIDDosome 活性的生物工具。然而，我们对 PIDDosome 生物学的分子理解非常有限。为了加深我们对 PIDDosome 信号传导的理解并确定 CS 途径治疗的预测和药效生物标志物，我们提出了三个具体目标。第一个和第二个目标旨在通过阐明我们最近确定的四种 PIDD 相互作用分子的作用，分别确定新型 PIDDosome 调节剂和底物。第三个目标将尖端癌症基因组学与斑马鱼体内功能遗传学相结合，以确定 HNSCC 对 CS 途径治疗反应的遗传预测因子。候选预测基因型将使用目标 1、目标 2 或我们之前的研究中鉴定的功能性 CS 通路标记进行功能表征，并在来自手术室的原代 HNSCC 样本的离体培养物中进行验证。总之，我们的目标是在 PIDDosome 介导的细胞凋亡信号传导的新兴领域产生重大影响，从而将 CS 细胞凋亡转化为有效的 HNSCC 治疗。

DESCRIPTION (provided by applicant): Defects in p53 signaling eliminate apoptotic responses to radiation therapy in many human cancers. In head and neck squamous cell carcinoma (HNSCC), the fifth most common cancer worldwide, TP53 mutations cause locoregional recurrence of radioresistant tumors, an invariably fatal form of the disease. Thus there is an urgent need for agents that will bypass mutant TP53 to restore radiosensitivity in HNSCC. This proposal focuses on an emerging apoptotic pathway, designated 'Chk1-suppressed' (CS) apoptosis, whose activation by Chk1 inhibitors restores radiosensitivity in p53-deficient zebrafish, mouse, and human cancer cells (Sidi et al., Cell 2008). We propose that Chk1 inhibitors and associated CS pathway define a promising therapeutic opportunity for TP53 mutant HNSCC. Our work has elucidated the core backbone of the CS pathway, which comprises a novel ATM/ATR-caspase-2 axis that bypasses p53 and attendant mitochondrial and death-receptor signaling cascades. Recently, we identified the PIDDosome (PIDD-RAIDD-caspase-2 complex), but not the intrinsic apoptosome or extrinsic DISC, as the caspase-activation platform at work in the CS pathway. These results strengthen the notion that the CS axis defines a third apoptotic pathway in vertebrate cells and were published in the September 14th issue of Molecular Cell (Ando et al. Mol Cell 2012). While we hypothesize that the CS pathway will be therapeutically effective in TP53 mutant HNSCC, the extreme heterogeneity of this disease makes it essential that we develop biologic tools that predict or assess PIDDosome activity in tumors. However, our molecular understanding of PIDDosome biology is very limited. To both deepen our understanding of PIDDosome signaling and identify predictive and pharmacodynamic biomarkers of CS pathway therapy, we propose three specific aims. The first and second aims are designed to identify novel PIDDosome regulators and substrates, respectively, by elucidating the roles of four PIDD-interacting molecules we recently identified. The third aim integrates cutting-edge cancer genomics with in vivo functional genetics in zebrafish to identify genetic predictors of HNSCC response to CS pathway therapy. Candidate predictive genotypes will be functionally characterized using the functional CS pathway markers identified in Aim 1, Aim 2, or our previous studies, and validated in ex vivo cultures of primary HNSCC samples from the OR. In summary, we aim to make a significant impact in the newly emerging area of PIDDosome-mediated apoptotic signaling, thereby translating CS apoptosis into an effective HNSCC therapy.