Structure-based anti-cancer drug development

描述(申请人提供)：肺癌是癌症相关死亡的主要原因，大多数肺癌患者由于化疗耐药而预后不良。开发更有效的新药，通过包括细胞凋亡在内的基本分子机制来克服化疗耐药，对于改善肺癌患者的预后至关重要。BCL2是一种主要的抗凋亡分子，在小细胞肺癌(SCLC)和非小细胞肺癌(NSCLC)细胞中广泛表达。Bcl2的过度表达是导致肺癌耐药的主要因素之一，提示Bcl2应该成为肺癌治疗的一个有吸引力的靶点。Bcl2的BH4结构域包含一个两亲性的A1-螺旋，已被证明是Bcl2的S抗细胞凋亡功能所必需的结构域。因此，我们选择BH4结构域作为对接位置，使用计算机化的对接程序和国家癌症研究所(NCI)的数据库筛选可能使Bcl2失活的小分子。两百种被确定具有最高亲和力的化合物是从NCI获得的，并测试了它们对细胞死亡的影响。200种化合物中的4种已被发现能有效地诱导各种人类肺癌细胞的凋亡。我们将这些化合物命名为小分子BCl2抑制剂(SMBI-1~4)。有趣的是，与肺癌细胞相比，SMBI-1~4对正常小气道上皮细胞的凋亡作用显著降低，表明这些化合物对肿瘤细胞具有选择性。在NSCLC动物模型中，铅SMBI有效地抑制了肿瘤的生长，并增加了肿瘤组织中的细胞凋亡。这些初步发现表明，S作为一类新型抗肺癌药物可能具有很大的开发潜力。MTOR通路的调节正被临床开发为肺癌治疗的高级策略。然而，Bcl2的表达与肺癌细胞对mTOR抑制剂(S)的耐药性有关。因此，提高肺癌细胞对mTOR抑制剂的敏感性的有效方法是将mTOR抑制剂与bcl2抑制剂(即SMBI)联合使用。我们的初步数据显示，SMBI和雷帕霉素联合治疗肺癌细胞不仅协同诱导细胞凋亡，而且增强了对生长的抑制，表明mTOR和Bcl2联合抑制可能相加地抑制肺癌的生长，导致体内持续的消退。为了严格检验这些假说，我们确定了两个具体目标：(1)确定S(SMBI)诱导人肺癌细胞凋亡的机制(S)；(2)确定SMBI(S)是否抑制小细胞肺癌和非小细胞肺癌移植瘤的生长。研究将评估SMBI和mTOR抑制剂联合靶向bcl2和mTOR是否能在体内协同提高抗肺癌效果。从结果来看，通过共同靶向bcl2和mTOR，有望开发出一类新的抗癌药物和一种更有效的癌症治疗方法。

DESCRIPTION (provided by applicant): Lung cancer is the leading cause of cancer-related mortality and most patients with lung cancer have poor prognosis due to chemoresistance. Development of more effective, new drugs that act through basic molecular mechanisms, including apoptosis, to overcome chemoresistance is critical to improve the prognosis of patients with lung cancer. Bcl2, a major antiapoptotic molecule, is extensively expressed in both small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cells. One major factor implicated in the resistance to chemotherapy is the overexpression of Bcl2, suggesting that Bcl2 should be an attractive therapeutic target in human lung cancer. The BH4 domain of Bcl2, which encompasses an amphipathic a1-helix, has been demonstrated to be a required domain for Bcl2's antiapoptotic function. Therefore, we chose the BH4 domain as a docking site for screening of small molecules that may inactivate Bcl2 using the computerized DOCK program and a database from the National Cancer Institute (NCI). Two hundred of the compounds determined to have the highest affinity were obtained from the NCI and tested for their effects on cell death. Four of the two hundred compounds have been found to potently induce apoptosis of various human lung cancer cells. We named these compounds as small molecule Bcl2 inhibitors (i.e. SMBI-1~4). Intriguingly, SMBI-1~4 represent significantly less apoptotic effect on normal small airway epithelial cells as compared to lung cancer cells, indicating a selectivity of these compounds for tumor cells. The lead SMBI potently represses tumor growth in association with increased apoptosis in tumor tissues in NSCLC animal models. These preliminary findings suggest that SMBI(s) may have great potential to be developed as a new class of anti-lung cancer drugs. Modulation of the mTOR pathway is being clinically developed as an advanced strategy for lung cancer treatment. However, expression of Bcl2 is associated with resistance of lung cancer cells to mTOR inhibitor(s). Thus, an effective way to enhance the sensitivity of lung cancer cells to mTOR inhibition is to combine a mTOR inhibitor with a Bcl2 inhibitor (i.e. SMBI). Our preliminary data reveal that treatment of lung cancer cells with a combination of SMBI and rapamycin not only synergistically induces apoptosis but also augments growth inhibition, suggesting that the combined mTOR and Bcl2 inhibition may additively suppress lung tumor growth, leading to sustained regression in vivo. To critically test these hypotheses, we have identified two specific aims: (1) To determine the mechanism(s) by which SMBI(s) induces apoptosis in human lung cancer cells; (2) To determine whether SMBI(s) represses tumor growth in both SCLC and NSCLC xenografts. Studies will evaluate whether co-targeting Bcl2 and mTOR by a combination of SMBI and a mTOR inhibitor synergistically improves the anti-lung cancer efficacy in vivo. From the results, it is expected that a new class of anti-cancer drugs and a more effective approach for cancer treatment will be developed by co-targeting Bcl2 and mTOR.