Exploiting vulnerabilities in GIST using novel combination therapies

胃肠道间质瘤(GIST)的靶向治疗，如甲磺酸伊马替尼(IM)，舒尼替尼， 和瑞可非尼，一般能逃脱疾病控制和随着时间的推移而进展。目前的护理标准是 高级不可手术GIST涉及到针对激活形式的这些抑制剂的顺序应用 GIST中发现的试剂盒或PDGFRA受体。我们假设抑制额外的分子靶点 与IM相结合可能会提供更实质性的疾病控制。最近的研究表明，PI3- KK/AKT通路在IM耐药GIST细胞系和肿瘤存活中的作用因此，我们挑战IM-- 用IM和AKT抑制剂的新组合测试敏感的GIST异种移植 通过一线IM治疗增强了疾病的稳定性。在这些初步研究中，组合 与单一疗法相比，疗法的疗效显著提高，因为 以肿瘤反应和动物存活率来衡量。这些结果为额外的临床前研究提供了理由 挑战各种GIST异种移植的研究，模拟固有和获得性IM抵抗，如上所述 在这份提案中。为了探索肿瘤对这种新组合反应的分子方面，我们进行了 对这些异种移植物进行RNASEQ研究，以期确定GIST的其他治疗靶点。这 分析取得了丰硕的成果，确定了两个基因，脑表达，X-连锁1(BEX1)和神经元五角蛋白I (NPTX1)，其表达仅在联合治疗的肿瘤中显著上调。BEX1和 NPTX1已被认为是多种癌症的抑癌基因，并伴随着 不同细胞类型中的凋亡途径。具体地说，BEX1作为bcl2拮抗剂，通过以下方式诱导细胞凋亡 结合bcl2并抑制抗凋亡的bcl2/bax异二聚体的形成，而NPTX1 表达与促凋亡的BAD和Bax蛋白的线粒体移位增强有关 增强了神经细胞的死亡。我们假设这种结合导致了这两个因素的诱导 影响肿瘤细胞命运的基因，通过bcl-2将促/抗凋亡平衡转向细胞死亡， BAD/BAX途径，可能为GIST治疗提供额外途径。这项建议旨在 从功能上测试这一中心假设，并评估这两条路径中的目标成员 IM敏感和耐GIST异种移植模型。拟议的研究旨在为以下方面提供支持 这些新的治疗方式在临床环境中的潜在应用。

Gastrointestinal stromal tumor (GIST) treated with targeted therapies such as imatinib mesylate (IM), sunitinib, and regorafenib, generally escape disease control and progress over time. The current standard of care for advanced inoperable GIST involves the sequential application of these inhibitors that target the activated forms of the KIT or PDGFRA receptors found in GIST. We hypothesized that inhibiting additional molecular targets in combination with IM may provide more substantial disease control. Recent studies have implicated the PI3- kinase/AKT pathway in survival of IM-resistant GIST cell lines and tumors. We therefore challenged IM- sensitive GIST xenografts with a novel combination of IM and an AKT inhibitor to test if the combination enhanced disease stabilization afforded by front-line IM therapy. In these preliminary studies, the combination therapy provided significantly improved efficacy as compared to treatment with monotherapy alone, as measured by tumor response and animal survival. These results provide justification for additional pre-clinical studies challenging various GIST xenografts modeling both intrinsic and acquired IM resistance, as described in this proposal. To explore the molecular aspects of tumor response to this novel combination, we carried out RNAseq studies on these xenografts, in the hope of identifying additional therapeutic targets for GIST. This analysis was fruitful, identifying two genes, brain expressed, X-linked 1 (BEX1) and neuronal pentraxin I (NPTX1), whose expression was significantly up-regulated only in combination-treated tumors. BEX1 and NPTX1 have been implicated as tumor-suppressor genes in various cancers, and with the induction of apoptotic pathways in diverse cell types. Specifically, BEX1 acts as a BCL-2 antagonist, inducing apoptosis by binding BCL-2 and suppressing the formation of anti-apoptotic BCL-2/BAX heterodimers, while NPTX1 expression has been linked to enhanced mitochondrial translocation of pro-apoptotic BAD and BAX proteins and enhanced neuronal cell death. We hypothesize that this combination results in induction of these two genes that influence tumor cell fate by shifting the pro/anti-apoptotic balance towards cell death via the BCL-2, BAD/BAX pathways, and may provide additional avenues to approach GIST treatment. This proposal seeks to functionally test this central hypothesis, as well as to evaluate targeting members of these pathways in both IM- sensitive and –resistant GIST xenograft models. The proposed studies are designed to provide support for potential application of these novel therapeutic modalities in the clinical setting.