Implications of Procaspase-8 Mutations in Oral Squamous Cell Carcinoma

 描述(申请人提供)：在美国，每年大约有40,000例口腔鳞状细胞癌(OSCC)被诊断出来。手术、化疗和放射治疗是晚期口腔鳞状细胞癌的主要治疗手段，但通常会导致畸形和不良细胞毒性。导致死亡的复发疾病与化疗和/或辐射抵抗力的产生有关。由于对疾病进展机制的不完全了解，以及缺乏可用于预测化疗和放射反应的分子标记，防治口腔鳞状细胞癌的努力受到严重阻碍。我们的长期目标是确定基因突变在口腔鳞癌中所起的作用，将这一知识应用于患者的风险分层，并开发治疗策略。 以克服这些突变带来的负面后果。我们和其他人已经报道了口腔鳞癌的突变情况，发现原天冬氨酸蛋白酶-8基因是这种疾病中最常见的突变基因之一。癌症基因组图谱(TCGA)对302例口腔鳞癌肿瘤的分析证实，在8%的患者肿瘤中发现了前天冬氨酸氨基转移酶-8酶原编码区的突变。已知野生型caspase-8介导死亡受体介导的细胞凋亡。在四个口腔鳞状细胞癌相关的Proaspase-8突变体的功能研究中，我们确定这些突变体蛋白有效地抑制死亡受体介导的细胞凋亡，并且一个具有代表性的突变体干扰死亡诱导信号复合体(DISC)的形成。Proaspase-8突变体还增强了对顺铂和辐射的抗性。抑制DNA损伤反应蛋白ATR和ATM分别逆转了顺铂和辐射抗性，在具有突变的proaspase-8的细胞中。我们假设口腔鳞状细胞癌相关的proaspase-8突变促进了对死亡配体、化疗和放射的抵抗，同时定义了可能受益于ATR或ATM抑制剂治疗的患者的相当大的亚群。为了检验这一假设，我们提出了三个具体目标。目的1将利用创新的口腔鳞状细胞癌模型来研究广泛的口腔鳞状细胞癌相关原天冬氨酸蛋白酶8突变蛋白对死亡受体激活后的椎间盘形成、细胞凋亡和坏死性下垂的影响。目的2将在体外和体内确定突变蛋白是否对顺铂或辐射具有抵抗力，并将使用正在进行的包含顺铂/放射治疗的正在进行的第二阶段临床试验的样本来比较携带野生型和突变型proaspase-8的口腔鳞癌患者的临床结果。在目标3中，体外和体内研究将确定ATR/ATM抑制作为逆转化疗和辐射耐药的策略的潜力。我们的研究结果将确定频繁的proaspase-8突变对口腔鳞癌对死亡受体激动剂、化疗和放射的反应性的意义和后果，以及这些影响的机制。我们还期望，我们的发现将为生物标记物驱动的临床试验奠定基础，评估ATR或ATM抑制在Proaspase-8突变患者中的价值。

 DESCRIPTION (provided by applicant): Approximately 40,000 cases of oral squamous cell carcinoma (OSCC) are diagnosed each year in the United States. Surgery, chemotherapy, and radiation are the mainstays of treatment for advanced OSCC, but frequently result in disfigurement and adverse cytotoxicities. Recurrent disease, leading to death, is associated with development of chemotherapy and/or radiation resistance. Efforts to combat OSCC have been severely hindered by an incomplete understanding of the mechanisms of disease progression and a lack of molecular markers that can be used to predict responsiveness to chemotherapy and radiation. Our long-term goal is to determine the role that gene mutations play in OSCC, to apply this knowledge towards risk stratification in patients, and to develop therapeutic strategies to overcome the negative consequences of these mutations. We and others have reported the mutational landscape of OSCC, identifying the procaspase-8 gene as one of the most commonly mutated genes in this disease. Mutations in the coding region for procaspase-8 zymogen were identified in 8 percent of patient tumors, a finding confirmed by analysis of 302 OSCC tumors by The Cancer Genome Atlas (TCGA). Wild-type caspase-8 is known to mediate death receptor-mediated apoptosis. In functional studies of four OSCC-associated, procaspase-8 mutants, we determined that the mutant proteins potently inhibit death receptor-mediated apoptosis, and a representative mutant interfered with formation of the death inducing signaling complex (DISC). The procaspase-8 mutants also conferred enhanced resistance to cisplatin and radiation. Inhibition of the DNA damage response proteins ATR and ATM reversed cisplatin and radiation resistance, respectively, in cells with mutant procaspase-8. We hypothesize that OSCC- associated procaspase-8 mutations promote resistance to death ligands, chemotherapy, and radiation, while defining a substantial subpopulation of patients who may benefit from treatment with ATR or ATM inhibitors. To test this hypothesis, we propose three Specific Aims. Aim 1 will utilize innovative OSCC models to investigate the impact of a broad panel of OSCC-associated procaspase-8 mutant proteins on DISC formation, apoptosis, and necroptosis following death receptor activation. Aim 2 will determine whether the mutant proteins confer resistance to cisplatin or radiation in vitro and in vivo, and will compare clinical outcomes of OSCC patients harboring wild-type versus mutant procaspase-8 using specimens from an ongoing Phase II clinical trial incorporating concurrent cisplatin/radiation treatment. In Aim 3, i vitro and in vivo studies will determine the potential of ATR/ATM inhibition as a strategy for reversing chemotherapy and radiation resistance. Results from our studies will determine the significance and consequences of frequent procaspase-8 mutation on OSCC responsiveness to death receptor agonists, chemotherapy, and radiation, and the mechanisms responsible for these effects. We also expect that our findings will lay the foundation for biomarker-driven clinical trials evaluating the value of ATR or ATM inhibition in patients with procaspase-8 mutations.