Targeting the Chk1-Suppressed Apoptotic Pathway in HNSCC

描述（由申请人提供）：在许多人类癌症中，p53信号的缺陷消除了放射治疗的凋亡反应。头颈部鳞状细胞癌（HNSCC）是世界上第五大常见的癌症，TP53突变导致放射耐药肿瘤的局部复发，这是该疾病的一种致命形式。因此，迫切需要绕过突变TP53的药物来恢复HNSCC的放射敏感性。这一建议的重点是一种新兴的凋亡途径，称为“Chk1抑制”（CS）凋亡，Chk1抑制剂激活该途径可恢复p53缺陷斑马鱼、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提供了一个有希望的治疗机会。我们的工作已经阐明了CS通路的核心主干，它包括一个新的ATM/ATR-caspase-2轴，绕过p53和伴随的线粒体和死亡受体信号级联。最近，我们发现了PIDDosome （PIDD-RAIDD-caspase-2复合物），而不是固有的凋亡细胞或外源性的DISC，作为caspase在CS通路中起作用的激活平台。这些结果加强了CS轴在脊椎动物细胞中定义第三种凋亡途径的观点，并发表在9月14日的《分子细胞》（Ando et al.）上。Mol Cell, 2012)。虽然我们假设CS途径在TP53突变型HNSCC中具有治疗效果，但这种疾病的极端异质性使得我们必须开发预测或评估肿瘤中PIDDosome活性的生物学工具。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通路治疗的预测性和药效学生物标志物，我们提出了三个具体目标。第一个和第二个目标是通过阐明我们最近发现的四个pidd相互作用分子的作用，分别鉴定新的PIDDosome调节剂和底物。第三个目标是将尖端的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通路治疗反应的遗传预测因子。候选预测基因型将使用Aim 1、Aim 2或我们之前的研究中发现的功能性CS通路标记进行功能表征，并在来自or的原发性HNSCC样本的离体培养中进行验证。总之，我们的目标是在piddosome介导的凋亡信号的新兴领域产生重大影响，从而将CS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.