Singh Shilpa, Gleason Catherine E, Fang Min, Laimon Yasmin N, Khivansara Vishal, Xie Shanhai, Durmaz Yavuz T, Sarkar Aniruddha, Ngo Kenneth, Savla Varunika, Li Yixiang, Abu-Remaileh Muhannad, Li Xinyue, Locquet Marie-Anais, Tuladhar Bishma, Odeh Ranya, Hamkins-Indik Frances, He Daphne, Membreno Miles W, Nosrati Meisam, Gushwa Nathan N, Leung Siegfried S F, Fraga-Walton Breena, Hernandez Luis, Baldomero Miguel P, Lent Bryan M, Spellmeyer David, Luna Joshua F, Hoang Dalena, Gritsenko Yuliana, Chand Manesh, DeMart Megan K, Metobo Sammy, Bhatt Chinmay, Shapiro Justin A, Yang Kai, Dupper Nathan J, Bockus Andrew T, Fang Jinshu, Bambal Ramesh, Cremin Peadar, Doench John G, Aggen James B, Liu Li-Fen, Levin Bernard, Wang Evelyn W, Vendrell Iolanda, Fischer Roman, Kessler Benedikt, Gokhale Prafulla C, Signoretti Sabina, Spektor Alexander, Kreatsoulas Constantine, Evangelista Marie, Singh Rajinder, Earp David J, Nijhawan Deepak, Garcia Pablo D, Oser Matthew G
Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
Circle Pharma, San Francisco, CA, USA.
Nature. 2025 Aug 20. doi: 10.1038/s41586-025-09433-w.
Small-cell lung cancers (SCLCs) contain near-universal loss-of-function mutations in RB1 and TP53, compromising the G1-S checkpoint and leading to dysregulated E2F activity. Other cancers similarly disrupt the G1-S checkpoint through loss of CDKN2A or amplification of cyclin D or cyclin E, also resulting in excessive E2F activity. Although E2F activation is essential for cell cycle progression, hyperactivation promotes apoptosis, presenting a therapeutic vulnerability. Cyclin proteins use a conserved hydrophobic patch to bind to substrates bearing short linear RxL motifs. Cyclin A represses E2F through an RxL-dependent interaction, which, when disrupted, hyperactivates E2F. However, this substrate interface has remained difficult to target. Here we developed cell-permeable, orally bioavailable macrocyclic peptides that inhibit RxL-mediated interactions of cyclins with their substrates. Dual inhibitors of cyclin A and cyclin B RxL motifs (cyclin A/Bi) selectively kill SCLC cells and other cancer cells with high E2F activity. Genetic screens revealed that cyclin A/Bi induces apoptosis through cyclin B- and CDK2-dependent spindle assembly checkpoint activation. Mechanistically, cyclin A/Bi hyperactivates E2F and cyclin B by blocking cyclin A-E2F and cyclin B-MYT1 RxL interactions. Notably, cyclin A/Bi promoted the formation of neomorphic cyclin B-CDK2 complexes, which drive spindle assembly checkpoint activation and mitotic cell death. Finally, orally administered cyclin A/Bi showed robust anti-tumour activity in chemotherapy-resistant SCLC patient-derived xenografts. These findings reveal gain-of-function mechanisms through which cyclin A/Bi triggers apoptosis and support their development for E2F-driven cancers.
小细胞肺癌（SCLCs）在RB1和TP53中几乎普遍存在功能丧失突变，损害了G1-S检查点并导致E2F活性失调。其他癌症同样通过CDKN2A缺失或细胞周期蛋白D或细胞周期蛋白E扩增破坏G1-S检查点，也导致E2F活性过高。虽然E2F激活对于细胞周期进展至关重要，但过度激活会促进细胞凋亡，这是一种治疗上的脆弱点。细胞周期蛋白通过保守的疏水补丁与带有短线性RxL基序的底物结合。细胞周期蛋白A通过依赖RxL的相互作用抑制E2F，这种相互作用一旦被破坏，就会使E2F过度激活。然而，这个底物界面一直难以靶向。在这里，我们开发了可穿透细胞、口服生物可利用的大环肽，它们抑制细胞周期蛋白与其底物之间的RxL介导的相互作用。细胞周期蛋白A和细胞周期蛋白B RxL基序的双重抑制剂（细胞周期蛋白A/Bi）选择性地杀死具有高E2F活性的SCLC细胞和其他癌细胞。基因筛选表明，细胞周期蛋白A/Bi通过细胞周期蛋白B和CDK2依赖的纺锤体组装检查点激活诱导细胞凋亡。从机制上讲，细胞周期蛋白A/Bi通过阻断细胞周期蛋白A-E2F和细胞周期蛋白B-MYT1 RxL相互作用使E2F和细胞周期蛋白B过度激活。值得注意的是，细胞周期蛋白A/Bi促进了新形态的细胞周期蛋白B-CDK2复合物的形成，该复合物驱动纺锤体组装检查点激活和有丝分裂细胞死亡。最后，口服细胞周期蛋白A/Bi在化疗耐药的SCLC患者来源的异种移植模型中显示出强大的抗肿瘤活性。这些发现揭示了细胞周期蛋白A/Bi触发细胞凋亡的功能获得机制，并支持其用于E2F驱动的癌症的开发。
