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。逃避细胞凋亡性癌症 细胞通过调节bcl2蛋白家族的控制和功能来阻断细胞凋亡的内在途径。 细胞凋亡的内在途径或线粒体途径受bcl2家族蛋白的调控，这些蛋白包括：1) 促凋亡多结构域蛋白Bax和BAK，2)抗凋亡蛋白如bcl2、mcl1、bcl1、bcl2、bcl1、bcl1、bcl2、bcl1、bcl2、b XL，以及3)只有BH3促凋亡蛋白。癌细胞通常通过上调bcl-1来阻断细胞的凋亡。 2抗凋亡蛋白和/或下调或抑制bcl2促凋亡蛋白。因此，bcl-2 家庭成员在调节癌症的细胞凋亡和化疗的治疗反应方面起着关键作用。 靶向内源性细胞凋亡途径的蛋白已成为目前研究的热点。 新的抗癌疗法。努力的重点是开发抑制选择性的小分子 BCL-2抗细胞凋亡蛋白，诱导BH3-Only激活蛋白释放，促进Bax/BAK介导 细胞凋亡。这一策略导致了FDA最近批准了bcl2抑制剂Venetclax和其他 临床发展中的分子。我们的实验室最近开发了一种促凋亡Bax的直接激活剂， BTSA1，可独立于BH3-Only蛋白诱导细胞凋亡。为了广泛地扩大促细胞凋亡的活性 癌细胞，我们假设将Bax激活剂与选择性抗凋亡蛋白抑制剂结合起来。BAX 与抗凋亡蛋白BCL-XL有很高的亲和力，BCL-XL是一种在固体中过度表达的常见致癌驱动因子 肿瘤，因此我们合理地认为，bclxl抗凋亡蛋白的合成抑制将使 与我们的直接BAX激活剂BTSA1共同治疗癌细胞。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， BTSA1/Navitoclax联合应用在实体瘤细胞系中具有显著的协同作用， 双重处理后细胞存活率下降。拟议研究的目标是调查治疗方法 在耐药肿瘤中合理靶向bax和bcl-xl蛋白的可能性和机制。总而言之， 这项提案将使用一种创新的方法来强调如何理性地共同瞄准两种抗细胞凋亡的生存 这些机制可以在很大程度上克服对凋亡的抵抗。我们提出以下具体目标，以实现 我们的目标：1)评估共靶向bax和bcl-xl在人类癌细胞系中的疗效；2)确定 BTSA1和Navitoclax共靶向bax和bcl-xl的作用机制及3)评价和优化 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是如何理性的 靶向两种抗凋亡的生存机制可以增强肿瘤细胞的死亡，这可能 将转化为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.