Application of a MYC degradation screen identifies sensitivity to CDK9 inhibitors in KRAS-mutant pancreatic cancer
Application of a MYC degradation screen identifies sensitivity to CDK9 inhibitors in KRAS-mutant pancreatic cancer
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DOI：
10.1126/scisignal.aav7259
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发表时间：
2019-07-16
影响因子：
7.3
通讯作者：
Der, Channing J.
中科院分区：
文献类型：
--
作者：
Blake, Devon R.;Vaseva, Angelina V.;Der, Channing J.
通过KRAS信号稳定MYC癌蛋白对胰腺导管腺癌（PDAC）的生长有重要促进作用。因此，了解MYC蛋白的稳定性是如何调节的可能会导致有效的治疗。在这里，我们使用了一种先前开发的基于流式细胞术的检测方法，该方法筛选了一个包含>800种蛋白激酶抑制剂的文库，并鉴定了在KRAS突变型PDAC细胞系中促进MYC稳定性或降解的化合物。我们验证了稳定或破坏MYC稳定性的化合物，然后集中在一种化合物UNC10112785上，该化合物在二维（2D）和3D细胞培养物中诱导MYC蛋白的大量损失。我们确定该化合物是一种有效的CDK9抑制剂，具有以前未表征的支架，通过转录和翻译后机制引起MYC损失，并抑制PDAC锚定依赖性和锚定非依赖性生长。我们发现，CDK9通过一种以前未知的KRAS非依赖性机制增强了MYC蛋白的稳定性，该机制涉及MYC在Ser62的直接磷酸化。因此，我们的研究不仅确定了KRAS突变型PDAC患者的潜在治疗靶点，而且还提出了一种筛选策略的应用，该策略可以更广泛地适用于确定蛋白质稳定性的调节剂。
Stabilization of the MYC oncoprotein by KRAS signaling critically promotes the growth of pancreatic ductal adenocarcinoma (PDAC). Thus, understanding how MYC protein stability is regulated may lead to effective therapies. Here, we used a previously developed, flow cytometry-based assay that screened a library of >800 protein kinase inhibitors and identified compounds that promoted either the stability or degradation of MYC in a KRAS-mutant PDAC cell line. We validated compounds that stabilized or destabilized MYC and then focused on one compound, UNC10112785, that induced the substantial loss of MYC protein in both two-dimensional (2D) and 3D cell cultures. We determined that this compound is a potent CDK9 inhibitor with a previously uncharacterized scaffold, caused MYC loss through both transcriptional and posttranslational mechanisms, and suppresses PDAC anchorage-dependent and anchorage-independent growth. We discovered that CDK9 enhanced MYC protein stability through a previously unknown, KRAS-independent mechanism involving direct phosphorylation of MYC at Ser62. Our study thus not only identifies a potential therapeutic target for patients with KRAS-mutant PDAC but also presents the application of a screening strategy that can be more broadly adapted to identify regulators of protein stability.