Structure-based anti-cancer drug development

 描述(由申请人提供)：肺癌患者的生存结果仍然很差，部分原因是肺癌细胞中的遗传改变介导的生存信号通路和治疗耐药性。BAX是细胞凋亡的重要通道。我们先前发现BAX的丝氨酸(S)184磷酸化位点是功能上控制BAX促凋亡活性的关键开关。Akt和PKC是一种生理性的Bax激酶，可直接磷酸化BAX的S184位点，导致其促凋亡功能失活。已知K-RAS、EGFR和PTEN基因突变可激活PI3K/AKT生存通路，导致包括肺癌在内的多种肿瘤对放化疗的耐药性增加。非小细胞肺癌(NSCLC)患者肿瘤组织中磷酸化Bax(即pBax)水平升高。我们推测pBax可能在非小细胞肺癌中提供一个新的预测和预后的生物标志物。K-RAS G12D突变体的表达或经放射、顺铂或雷帕霉素处理后，AKT和/或PKC被激活，导致bax的磷酸化增加，这可能是放射、化疗或雷帕洛格耐药的原因之一。由于在辐射抵抗和拉帕洛格耐药的肺癌细胞以及K-RAS突变型肺癌中也观察到pBax(即非活性形式的Bax)的水平增加，因此开发新的激活Bax的小分子对于治疗K-RAS突变型肺癌或克服放射或拉帕洛格耐药至关重要。我们已经确定了三个小分子Bax激活剂(SMBA1-3)，它们选择性地结合Bax蛋白的S184口袋，但不结合其他Bcl2家族成员。先导化合物SMBA1不仅逆转辐射抗性，而且在体外也克服了Rapalog耐药性。SMBA1通过激活肿瘤组织中的Bax诱导细胞凋亡，从而有效地抑制肺癌移植瘤。在这项提案中，确定了两个特定的目标：(1)确定基因改变或mTOR抑制是否以及如何调节人肺癌细胞中Bax的磷酸化导致Bax失活和治疗耐药。研究将确定pBax是否是非小细胞肺癌患者的新的预后生物标志物或治疗靶点；(2)通过靶向Bax磷酸化位点周围的结构口袋开发新型小分子Bax激活剂(SMBA)用于肺癌治疗。研究将在患者来源的异种移植(PDX)、放射抵抗肺癌和基因工程K-RAS驱动的肺癌动物模型中测试SMBA或与mTOR抑制剂RAD001或Bcl2 BH4拮抗剂BDA-366联合使用的抗肿瘤效果。通过靶向Bax有望开发出一类新的抗癌药物和治疗肺癌的最佳策略。

 DESCRIPTION (provided by applicant): Survival outcomes remain poor for lung cancer patients, in part due to genetic alterations-mediated survival signaling pathways in lung cancer cells and treatment resistance. Bax functions as an essential gateway to apoptotic cell death. 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 physiologic Bax kinases that can directly phosphorylate Bax at S184 site leading to inactivation of its proapoptotic function. It is known that genetic mutations in K-Ras, EGFR and PTEN can activate PI3K/AKT survival pathway leading to increased resistance to radiotherapy or chemotherapy in various cancers, including lung cancer. Increased levels of phospho-Bax (i.e. pBax) were observed in tumor tissues in patients with non-small cell lung cancer (NSCLC). We hypothesize that pBax may provide a new predictive and prognostic biomarker in NSCLC. Expression of constitutively active K-Ras G12D mutant or treatment with radiation, cisplatin or rapamycin resulted in activation of AKT and/or PKC leading to increased phosphorylation of Bax, which may contribute to radio-, chemo- or rapalog resistance. Since increased levels of pBax (i.e. inactive form of Bax) were also observed in both radioresistant and rapalog resistant lung cancer cells as well as K-Ras mutant lung cancer, development of novel small molecules that activate Bax should be critical for treatment of K-Ras mutant lung cancer or overcoming radio- or rapalog resistance. We have identified three small molecule Bax activators (SMBA1-3) that selectively bind the S184 pocket of Bax protein but do not bind other Bcl2 family members. The lead compound SMBA1 not only reverses radioresistance but also overcomes rapalog resistance in vitro. SMBA1 potently represses lung cancer xenografts through induction of apoptosis by activating Bax in tumor tissues. In this proposal, two specific aims have been identified: (1) To determine whether and how genetic alterations or mTOR inhibition regulate Bax phosphorylation leading to Bax inactivation and treatment resistance in human lung cancer cells. Studies will determine whether pBax is a novel prognostic biomarker or therapeutic target in NSCLC patients; (2) Development of novel small molecule Bax activators (SMBA) by targeting the structural pocket around the Bax phosphorylation site for lung cancer therapy. Studies will test the antitumor efficacy of SMBA or in combination with mTOR inhibitor RAD001 or Bcl2 BH4 antagonist BDA-366 in patient-derived xenograft (PDX), radioresistant lung cancer and genetically engineered K-Ras-driven lung cancer animal models. It is expected that a new class of anti-cancer agents and optimal strategies for lung cancer treatment will be developed by targeting Bax.