Synergistic co-targeting of pro-apoptotic BAX and anti-apoptotic BCL-XL in cancer

摘要： 癌细胞的存活取决于它们阻断细胞死亡机制的能力。逃避凋亡癌 细胞通过调节BCL-2蛋白家族的控制和功能来阻断细胞凋亡的内在途径。 凋亡的内在或线粒体途径由BCL-2蛋白家族调节，包括：1） 促细胞凋亡多结构域蛋白BAX和巴克，2）抗细胞凋亡蛋白例如BCL-2、MCL-1、MCL-2、MCL-3、MCL-4、MCL-5、MCL-6、MCL-7、MCL-8、MCL-9、MCL-10、MCL-11、MCL-12、MCL-13、MCL-14、MCL-15、MCL-16、MCL-17、MCL-18、MCL-19 XL，和3）促细胞凋亡的仅BH 3蛋白。癌细胞通常通过上调BCL-1受体阻断凋亡。 2抗凋亡蛋白和/或下调或抑制BCL-2促凋亡蛋白。因此，BCL-2 家族成员在调节癌症中的细胞凋亡和对化疗的治疗反应中具有关键作用。 靶向内源性细胞凋亡途径的蛋白质已经成为开发具有高度吸引力的方法 新的抗癌疗法。人们的努力集中在开发抑制选择性肿瘤生长的小分子上。 BCL-2抗凋亡蛋白，诱导仅BH 3激活蛋白的释放，并促进BAX/BAK介导的细胞凋亡。 凋亡这一策略导致FDA最近批准了BCL-2抑制剂维奈托克和其他药物 分子在临床开发中的应用我们的实验室最近开发了一种促凋亡BAX的直接激活剂， BTSA 1诱导凋亡独立于BH 3-only蛋白。为了广泛地扩展促凋亡活性， 癌细胞，我们假设将BAX激活剂与选择性抗凋亡蛋白抑制剂组合联合收割机。Bax 对抗凋亡蛋白BCL-XL具有高亲和力，BCL-XL是一种在固体中过表达的常见致癌驱动因子 因此，我们合理地认为，BCL-XL抗凋亡蛋白的合成抑制将敏化 癌细胞与我们的直接BAX激活剂BTSA 1的共同治疗。为了抑制BCL-XL，我们将使用Navitoclax a 选择性BCL-2/BCL-XL抑制剂，目前正在进行临床试验。初步数据显示， BTSA 1/Navitoclax组合在实体瘤细胞系中具有显著的协同作用，如通过图1所示。 双重处理后细胞活力降低。拟议研究的目标是研究治疗性 在耐药肿瘤中合理靶向BAX和BCL-XL蛋白的潜力和机制。总的来说， 该提案将使用一种创新的方法来强调如何合理地共同靶向两种抗凋亡存活 机制可以广泛地克服对凋亡的抵抗。我们提出以下具体目标， 我们的目标是：1）评估共同靶向BAX和BCL-XL在人癌细胞系中的功效，2）确定BAX和BCL-XL在人癌细胞系中的作用。 BTSA 1和Navitoclax共同靶向BAX和BCL-XL的作用机制，以及3）评估和优化 共靶向BAX和BCL-XL的治疗潜力和安全性。在我导师的帮助和专业知识下 和合作者，我将能够实现这些目标，并提供第一个概念的证明，如何合理地 靶向两种抗凋亡存活机制可以导致肿瘤细胞死亡增加，这可能 转化为对癌症患者更有效的治疗方法。

Abstract: Cancer cells survival depends on their ability to block cell death mechanisms. To evade apoptosis cancer cells block the intrinsic pathway of apoptosis by modulating the control and function of the BCL-2 protein family. The intrinsic or mitochondrial pathway of apoptosis is regulated by the BCL-2 family of proteins that include: 1) the pro-apoptotic multi-domain proteins BAX and BAK, 2) the anti-apoptotic proteins e.g. BCL-2, MCL-1, BCL- XL, and 3) the pro-apoptotic BH3 only proteins. Cancer cells commonly block apoptosis by upregulating the BCL- 2 anti-apoptotic proteins and/or downregulating or inhibiting the BCL-2 pro-apoptotic proteins. Thus, the BCL-2 family members have a critical role in regulating apoptosis in cancer and treatment response to chemotherapy. Targeting proteins of the intrinsic apoptosis pathway has been a highly attractive approach for the development of novel-anticancer therapies. Efforts have focused on the development of small molecules that inhibit selective BCL-2 anti-apoptotic proteins, induce release of BH3-only activator proteins and promote BAX/BAK-mediated apoptosis. This strategy has led to the recent FDA approval of the BCL-2 inhibitor Venetoclax and other molecules in clinical development. Our laboratory recently developed a direct activator of pro-apoptotic BAX, BTSA1 that induces apoptosis independently of BH3-only proteins. To broadly extend pro-apoptotic activity in cancer cells, we hypothesized to combine the BAX activator with selective anti-apoptotic proteins inhibitors. BAX has high affinity for the anti-apoptotic protein BCL-XL, a common oncogenic driver overexpressed in solid tumors, therefore we rationalized that the synthetic inhibition of BCL-XL anti-apoptotic protein will sensitize cancer cells to a co-treatment with our direct BAX activator BTSA1. To inhibit BCL-XL we will use Navitoclax a selective BCL-2/BCL-XL inhibitor, which is currently in clinical trials. Preliminary data indicates that the BTSA1/Navitoclax combination has a significant synergistic effect in solid tumor cell lines, as shown by the decrease in cell viability upon dual treatment. The goal for the proposed studies is to investigate the therapeutic potential and mechanism of rationally targeting both BAX and BCL-XL proteins in resistant tumors. In summary, this proposal will use an innovative approach to highlight how rationally co-targeting two anti-apoptotic survival mechanisms could broadly overcome resistance to apoptosis. We propose the following specific aims to achieve our goal: 1) evaluate the efficacy of co-targeting BAX and BCL-XL in human cancer cell lines, 2) determine the mechanism of action of co-targeting BAX and BCL-XL with BTSA1 and Navitoclax, and 3) evaluate and optimize the therapeutic potential and safety of co-targeting BAX and BCL-XL. With the help and expertise of my mentor and collaborators, I will be able to accomplish these goals and provide the first proof of concept of how rationally targeting two anti-apoptotic survival mechanisms can lead to enhance cell death in tumors, something that could be translated to more effective therapies for cancer patients.