Activating Bax as a therapeutic strategy for lung cancer

描述(申请人提供)：大多数人类癌细胞对凋亡具有抵抗力。在细胞凋亡的主要调节因子中，有一种是Bcl2蛋白家族。一种新兴的癌症治疗策略是通过抑制抗凋亡的Bcl2蛋白的活性或促进促凋亡的Bcl2蛋白的功能来直接激活凋亡途径。然而，这些策略中的许多都是针对不同的Bcl2蛋白之间的相互作用，特别是促凋亡和抗凋亡的Bcl2蛋白之间的相互作用。由于Bcl2蛋白之间的功能冗余，这些方法可能只对有限的肿瘤类型有效或显示非特异性杀伤活性。作为一种重要的促凋亡蛋白，Bax S参与了肿瘤的发生发展过程，而Bax的激活与肺癌细胞的凋亡密切相关。鉴于BAX本身足以在几乎所有的凋亡范例中启动凋亡， 小分子化合物直接激活Bax可诱导表达Bax的肿瘤细胞死亡。我们在大型化学文库的电子筛选中的初步研究确定了一个预测与Bax疏水沟槽结合的小分子。该化合物能够激活Bax，导致Bax依赖的肿瘤细胞凋亡，抑制小鼠肿瘤生长。具体目的如下：1)研究Bax激活剂抑制小鼠肿瘤生长的机制。我们将测试Bax激活剂对小鼠移植人肿瘤和自发性小鼠肺肿瘤生长的抑制能力。此外，我们还将研究该活性化合物是否与其他治疗药物协同作用，以抑制肿瘤的生长。2)提高Bax激活剂激活Bax、诱导细胞凋亡和抑制肿瘤生长的能力。基于配基的分析将用于识别具有更大生物活性的潜在化合物，并将对这些化合物进行实验研究。3)探讨了Bax激活剂在生物膜上活化Bax的机理。我们将使用一种新的膜片钳技术，结合生化和细胞生物学的方法来研究Bax激活剂如何在体外诱导天然生物膜上的Bax渗透通道。我们还将研究Bax渗透孔的形成是如何受到抗凋亡蛋白Bclxl的调节的。由于Bax表达异常与肺癌的发生发展有关，通过直接激活Bax诱导肿瘤细胞凋亡有望成为治疗肺癌的一种新的治疗策略。

DESCRIPTION (provided by applicant): Most human cancer cells are resistant to apoptosis. Among the major regulators of apoptosis are the Bcl-2 family of proteins. An emerging cancer therapeutic strategy is directly activating the apoptotic pathways by inhibiting the activity of ani-apoptotic Bcl-2 proteins or promoting the function of pro-apoptotic Bcl-2 proteins. However, many of these strategies target the interaction among various Bcl-2 proteins, particularly the interaction between pro- apoptotic and anti-apoptotic Bcl-2 proteins. Due to functional redundancy among Bcl-2 proteins, these approaches are likely effective only on limited tumor types or display non-specific killing activities. As an important pro-apoptotic Bcl-2 protein, Bax s involved in the development of tumors, and Bax activation has been linked to apoptosis in lung tumors. Given that Bax alone is sufficient to initiate apoptosis in almost all apoptotic paradigms, direct activation of Bax by small molecule compounds could induce death of Bax-expressing tumor cells. Our preliminary studies using in silico screening of large chemical libraries identifid a small molecule predicted to bind to the Bax hydrophobic groove. This compound is able to activate Bax, leading to Bax-dependent tumor cell apoptosis and inhibition of mouse tumor growth. The following specific aims are proposed: 1) Examine the mechanisms by which the Bax activator inhibits tumor growth in mice. We will test the ability of the Bax activator to inhibt the growth of transplanted human tumors in mice as well as spontaneous mouse lung tumors. Furthermore, we will investigate whether the active compound acts synergistically with other therapeutic drugs to inhibit the growth of tumors. 2) Improve the ability of Bax activators to activate Bax, induce apoptosis and inhibit tumor growth. Ligand-based analyses will be used to identify potential compounds with greater biological activities and the compounds will be experimentally examined. 3) Investigate the mechanism of Bax activation on biological membranes by the Bax activators. We will use a novel patch-clamp technique combined with biochemical and cell biology approaches to investigate how the Bax activators induce Bax permeation channels on native biological membranes in vitro. We will also study how Bax permeation pore formation is regulated by the anti-apoptotic Bcl-2 protein Bcl-XL. As dysregulation of Bax expression has been implicated in lung tumor development, inducing apoptosis in tumor cells by directly activating Bax holds promise as a novel therapeutic strategy to treat lung cancer patients.