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

摘要唾液腺癌（SGC）是一种孤儿病，目前尚无靶向治疗药物获批。 SGCs分为组织型，最常见的是腺样囊性癌（ACC）和粘液表皮样癌 癌（MEC）。我们已经产生了一个最大的报告SGC PDX银行，包括主要组织型 如ACC和MEC的第一个报告的PDX模型。我们的SGC PDX银行包括来自同一个案例的几个案例， 患者，在随后的复发后收集，这使得可以探索获得致癌基因 基因事件与其他报道相似，我们的SGC模型通过全外显子组测序具有低突变负荷， 和RNA-seq分析鉴定了ACC中已知的（MYB-NFIB）、新的（NFIB-MTFR 2）甚至双基因融合 引起致癌融合蛋白产物的病例。SGC中的其他遗传事件聚集在PI 3 K中 和mTOR途径，它们影响蛋白质合成。MEC和ACC都过表达关键转录 例如Myc或SOX 2，其决定了SGC中的致瘤性和生长。总的来说，我们认为蛋白质 合成是SGC中未探索的目标。SVC 112是一种小分子，可抑制蛋白质合成， 通过抑制eEF 2的延伸步骤。在我们首次报道SVC 112的开创性研究中， SVC 112对癌细胞的作用大于对非癌细胞的作用; 耗尽SOX 2、Myc和Cyclin D1，并在体内抑制生长。在ACC和MEC细胞系中，我们发现， SVC 112抑制天然Myb和MYB融合蛋白的蛋白产物以及关键蛋白如Myc。SVC112 在体外试验中，在ACC和MEC中均抑制增殖和球体形成，并且具有显著的单药作用。 活性（包括实际肿瘤收缩），一个具有MYB融合，另一个显示非- 融合介导的Myb上调。我们建议研究癌基因融合在SGC中的作用， SVC 112在SGC中的作用，以及SVC 112在复杂的SGC模型中的功效。首先，我们将目录和 优先考虑来自大型患者和PDX队列的MYB融合。然后，为了了解关键的遗传事件，我们将插入 在非癌细胞系中进行融合，并在融合和非融合的SGC中部署CRISPR和慢病毒载体 我们还将测试SVC 112抑制，以增加一个额外的测试层， 蛋白质调节SVC 112的选择性作用是由于选择性消耗关键蛋白质的假设 将通过核糖体分析（以识别mRNA靶标）和蛋白质组学分析（以识别蛋白质 目标）。最后，我们将使用携带MYB的天然SGC PDX模型和携带MYB的天然SGC PDX模型来测试SVC 112的体内功效。 其他融合体和野生型tpy，以及使用CRISPR缺失的MYB融合体菌株的体内模型。总体上我们的 目的是通过其他分子机制检查对融合事件与蛋白质过表达的依赖性， SVC 112易感性。该项目将推动SVC 112的翻译，SVC 112是一种新的SGC药物， 科罗拉多，通过解剖其效果和治疗窗口的基础，并确定其在高级 SGC模型与计划，使识别哪些亚组的SGC患者可以获得更多的好处。

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.