Targeting oncogenic Myb fusions in salivary gland cancer with the elongation inhibitor SVC112

总结。涎腺癌(SGC)是一种孤儿疾病，目前还没有针对它的靶向治疗方法。 SGCs分为组织类型，最常见的是腺样囊性癌(ACC)和粘液表皮样癌 癌症(MEC)。我们已经建立了最大的SGC PDX库之一，包括主要组织类型 像ACC和第一个报道的MEC的PDX模型。我们的SGC PDX银行包括几个相同的案例 患者，在随后的复发后收集，这使得探索获得致癌 基因事件。与其他报道类似，我们的SGC模型通过整个外显子组测序具有较低的突变负担， RNA-seq分析证实了已知的(MYB-NFIB)、新的(NFIB-MTFR2)，甚至在ACC中存在双基因融合 3例出现致癌融合蛋白产物。SGC中的其他遗传事件聚集在PI3K中 以及影响蛋白质合成的mTOR途径。MEC和ACC都过表达密钥转录 决定SGC的肿瘤发生和生长的因素，如Myc或SOX2。总体而言，我们认为蛋白质 在SGC中，合成是一个尚未探索的目标。SVC112是一种抑制蛋白质合成的小分子 通过抑制eEF2的伸长步骤。在我们首次报道SVC112的开创性研究中，蛋白质合成 和生长抑制相关；SVC112对癌症的影响比非癌细胞更大；SVC112 耗尽SOX2、Myc和Cyclin D1，体内生长受阻。在ACC和MEC细胞系中，我们发现 SVC112抑制天然Myb和MYB融合蛋白产物以及Myc等关键蛋白。SVC112 在体外抑制ACC和MEC的增殖和球体形成，并具有显著的单药效应 2例ACC PDX中的活动性(包括实际肿瘤缩小)，1例合并MYB融合，另1例显示非融合 融合基因介导的Myb上调。我们建议研究致癌融合在SGC中的作用，其机制 研究SVC112在SGC中的作用，以及在复杂SGC模型中的作用。首先，我们将编目和 优先考虑来自大型患者和PDX队列的MYB融合。然后，为了理解关键的遗传事件，我们将插入 在非癌细胞系中融合，并在融合和非融合SGC中部署CRISPR和慢病毒载体 我们还将测试SVC112的抑制作用，以增加额外一层测试的影响 蛋白质调节。SVC112的S选择性作用是由于关键蛋白选择性耗竭的假说 将通过核糖体分析(以确定mRNA靶标)和蛋白质组学分析(以确定蛋白质)进行测试 目标)。最后，我们将使用携带MYB和SGC PDX的本地模型来测试SVC112的体内效果 其他融合和野生型，以及与CRISPR缺失的MYB融合菌株的体内模型。整体来说，我们 目的是通过其他分子机制检查对融合事件的依赖与蛋白质过度表达 SVC112易感性。该项目将推动SGC新药SVC112的翻译 科罗拉多州，通过解剖其疗效和治疗窗口的基础，并确定其晚期疗效 SGC模型具有一个计划，该计划能够识别SGC患者的哪一个子集可能获得更多好处。

SUMMARY. Salivary gland cancer (SGC) is an orphan disease for which no targeted therapies are approved. SGCs are divided into histotypes, the most common being adenoid cystic carcinoma (ACC) and mucoepidermoid carcinoma (MEC). We have generated one of the largest reported SGC PDX banks including major histotypes like ACC and the first reported PDX models of MEC. Our SGC PDX bank includes several cases from the same patient, collected after subsequent relapses, which has allowed an exploration of the acquisition of oncogenic gene events. Similar to other reports, our SGC models had low mutation burden by whole exome sequencing, and RNA-seq analysis identified known (MYB-NFIB), novel (NFIB-MTFR2), and even dual gene fusions in ACC cases that gave rise to oncogenic fusion protein products. Other genetic events in SGC clustered in the PI3K and mTOR pathways, which impinge upon protein synthesis. Both MEC and ACC overexpress key transcription factors such as Myc or SOX2 that dictated tumorigenicity and growth in SGC. Overall, we propose that protein synthesis is an unexplored target in SGC. SVC112 is a small molecule that inhibits protein synthesis at the elongation step by inhibiting eEF2. In our seminal studies where SVC112 was first reported, protein synthesis and growth inhibition were associated; SVC112 had greater effect on cancer over non-cancer cells; SVC112 depleted SOX2, Myc, and Cyclin D1, and arrested growth in vivo. In both ACC and MEC cell lines we found that SVC112 inhibits both native Myb and the protein products of MYB fusions and key proteins like Myc. SVC112 inhibited proliferation and sphere formation in both ACC and MEC in vitro assays, and had notable single agent activity (including actual tumor shrinkage) in 2 ACC PDX, one with a MYB fusion and another one showing non- fusion mediated Myb upregulation. We propose to study the role of oncogenic fusions in SGC, the mechanism of action of SVC112 in SGC, and the efficacy of SVC112 in complex SGC models. First, we will catalogue and prioritize MYB fusions from large patient and PDX cohorts. Then, to understand key genetic events we will insert fusions in non-cancer cell lines, and deploy CRISPR and lentiviral vectors in fusion-and non-fusion-bearing SGC cell lines, respectively; we will also test SVC112 inhibition to add an additional layer of testing of the impact of protein modulation. The hypothesis that SVC112’s selective effect is due to selective depletion of key proteins will be tested by ribosome profiling (to identify mRNA targets) and proteomics analysis (to identify proteins targets). Lastly, we will test the in vivo efficacy of SVC112 using both native SGC PDX models bearing MYB and other fusions and wild-tpy, as well as in vivo models with the CRISPR-depleted MYB fusions strains. Overall our goal is to examine dependence on fusion events vs protein overexpression by other molecular mechanisms for SVC112 susceptibility. This project will propel the translation of SVC112, a new drug for SGC discovered in Colorado, by dissecting the basis for its effect and therapeutic window, and identifying its efficacy in advanced SGC models with a plan that enables identification of which subset of SGC patients may derive more benefit.