Discovery of small-molecule degraders that activate ubiquitin ligase–mediated ubiquitination and degradation of targeted oncoproteins in cancer cells has been an elusive therapeutic strategy. Here, we report a cancer cell–based drug screen of the NCI drug-like compounds library that enabled identification of small-molecule degraders of the small ubiquitin-related modifier 1 (SUMO1). Structure-activity relationship studies of analogs of the hit compound CPD1 led to identification of a lead compound HB007 with improved properties and anticancer potency in vitro and in vivo. A genome-scale CRISPR-Cas9 knockout screen identified the substrate receptor F-box protein 42 (FBXO42) of cullin 1 (CUL1) E3 ubiquitin ligase as required for HB007 activity. Using HB007 pull-down proteomics assays, we pinpointed HB007’s binding protein as the cytoplasmic activation/proliferation-associated protein 1 (CAPRIN1). Biolayer interferometry and compound competitive immunoblot assays confirmed the selectivity of HB007’s binding to CAPRIN1. When bound to CAPRIN1, HB007 induced the interaction of CAPRIN1 with FBXO42. FBXO42 then recruited SUMO1 to the CAPRIN1-CUL1-FBXO42 ubiquitin ligase complex, where SUMO1 was ubiquitinated in several of human cancer cells. HB007 selectively degraded SUMO1 in patient tumor–derived xenografts implanted into mice. Systemic administration of HB007 inhibited the progression of patient-derived brain, breast, colon, and lung cancers in mice and increased survival of the animals. This cancer cell–based screening approach enabled discovery of a small-molecule degrader of SUMO1 and may be useful for identifying other small-molecule degraders of oncoproteins.

中文翻译：

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小分子降解剂对 SUMO1 的泛素化和降解可延长患者来源肿瘤小鼠的生存期

发现激活泛素连接酶介导的泛素化和癌细胞中靶向癌蛋白降解的小分子降解剂一直是一种难以捉摸的治疗策略。在这里，我们报告了 NCI 类药物化合物库的基于癌细胞的药物筛选，该筛选能够识别小泛素相关修饰剂 1 (SUMO1) 的小分子降解剂。对命中化合物 CPD1 类似物的结构-活性关系研究导致鉴定出一种先导化合物 HB007，其在体外和体内具有改善的特性和抗癌效力。基因组规模的 CRISPR-Cas9 敲除筛选鉴定了 HB007 活性所需的 cullin 1 (CUL1) E3 泛素连接酶的底物受体 F-box 蛋白 42 (FBXO42)。使用 HB007 下拉蛋白质组学分析，我们将 HB007 的结合蛋白确定为细胞质激活/增殖相关蛋白 1 (CAPRIN1)。生物层干涉法和复合竞争性免疫印迹分析证实了 HB007 与 CAPRIN1 结合的选择性。当与 CAPRIN1 结合时，HB007 诱导 CAPRIN1 与 FBXO42 的相互作用。然后 FBXO42 将 SUMO1 招募到 CAPRIN1-CUL1-FBXO42 泛素连接酶复合体中，其中 SUMO1 在几个人类癌细胞中被泛素化。HB007 在植入小鼠的患者肿瘤衍生异种移植物中选择性降解 SUMO1。HB007 的全身给药抑制了小鼠中源自患者的脑癌、乳腺癌、结肠癌和肺癌的进展，并提高了动物的存活率。