Project 3: Targeting Bax signaling to overcome treatment resistance in NSCLC

总结 Bax作为凋亡性细胞死亡的重要途径发挥作用。靶向Bax提供了一个共同的途径， 治疗KRAS或p53突变的NSCLC患者，并克服对放疗的耐药性， 化疗我们以前发现Bax的丝氨酸（S）184磷酸化位点是一个关键的开关， 来控制Bax的促凋亡活性。AKT和PKC β已被鉴定为生理性Bax 可以在S184位点直接磷酸化Bax，导致其促凋亡功能失活的激酶。 已知KRAS和p53突变可以激活PI 3 K/AKT存活途径，导致增加的细胞凋亡。 在包括肺癌在内的各种癌症中对放射治疗或化学治疗的抗性。增加水平的 在非小细胞肺癌（NSCLC）患者的肿瘤组织中观察到磷酸化Bax（pBax）。我们 推测pBax可作为NSCLC中新预测和预后生物标志物。表达 KRAS G12 D突变体或p53 R273 H突变体或用放射、顺铂或RAD 001处理导致 AKT和/或PKC β的激活导致Bax磷酸化增加，这可能有助于放射性， 化疗或化疗耐受性。开发激活Bax的小分子可能提供一种新的 用于治疗突变型KRAS或突变型p53肺癌或用于克服放射性、化学或免疫治疗的方法 顽强的抵抗我们已经鉴定了一种新的Bax激活剂CYD-2-11，它选择性地结合S184口袋 Bax蛋白，但不结合其他Bcl 2家族成员。CYD-2-11不仅逆转辐射抗性， 也克服了油菜的体外抗性。CYD-2-11通过激活肺癌细胞， Bax和诱导肿瘤组织凋亡。为了表征和开发这种新型Bax激活剂， 针对耐药肺癌的治疗，我们提出了两个具体目标：（1）确定KRAS是否以及如何 p53突变调节人肺癌细胞中Bax活性和治疗抗性。研究将 确定pBax是否是NSCLC患者的新的预后生物标志物或治疗靶点;（2） 通过靶向Bax周围的结构口袋，开发新型小分子Bax激活剂（CYD-2-11） 磷酸化位点用于肺癌治疗。研究将测试CYD-2-11单独或联合 在患者来源的异种移植物（PDX）中与电离辐射、化学疗法和/或mTOR抑制剂组合， 抗辐射和基因工程突变KRAS驱动的肺癌动物模型。通过瞄准巴克斯 我们期望开发出一类新的抗癌剂和用于肺癌治疗的组合策略。

Summary Bax functions as an essential gateway to apoptotic cell death. Targeting Bax provides a common pathway to treat NSCLC patients with KRAS or p53 mutations and to overcome resistance to radiotherapy and chemotherapy. We previously discovered that the serine (S)184 phosphorylation site of Bax is a critical switch to functionally control Bax’s proapoptotic activity. AKT and PKC have been identified as physiological Bax kinases that can directly phosphorylate Bax at the S184 site, leading to inactivation of its proapoptotic function. It is known that KRAS and p53 mutations can activate the PI3K/AKT survival pathway leading to increased resistance to radiotherapy or chemotherapy in various cancers, including lung cancer. Increased levels of phospho-Bax (pBax) were observed in tumor tissues in patients with non-small cell lung cancer (NSCLC). We hypothesize that pBax may serve as a new predictive and prognostic biomarker in NSCLC. Expression of KRAS G12D mutant or p53 R273H mutant or treatment with radiation, cisplatin or RAD001 resulted in activation of AKT and/or PKC leading to increased phosphorylation of Bax, which may contribute to radio-, chemo- or rapalog resistance. Development of small molecules that activate Bax may provide a novel approach for the treatment of mutant KRAS or mutant p53 lung cancer or for overcoming radio-, chemo- or rapalog resistance. We have identified a novel Bax activator, CYD-2-11, that selectively binds the S184 pocket of Bax protein but does not bind other Bcl2 family members. CYD-2-11 not only reverses radioresistance but also overcomes rapalog resistance in vitro. CYD-2-11 potently represses lung cancer xenografts by activating Bax and inducing apoptosis in tumor tissues. To characterize and develop this novel Bax activator for the treatment of resistant lung cancer, we propose two specific aims: (1) To determine whether and how KRAS and p53 mutations regulate Bax activity and treatment resistance in human lung cancer cells. Studies will determine whether pBax is a novel prognostic biomarker or therapeutic target in patients with NSCLC; (2) To develop novel small molecule Bax activator (CYD-2-11) by targeting the structural pocket around the Bax phosphorylation site for lung cancer therapy. Studies will test the antitumor efficacy of CYD-2-11 alone or in combination with ionizing radiation, chemotherapy, and/or mTOR inhibitor in patient-derived xenograft (PDX), radioresistant, and genetically engineered mutant KRAS-driven lung cancer animal models. By targeting Bax, we expect to develop a new class of anti-cancer agents and combination strategies for lung cancer treatment.