Bristol Myers Squibb, Summit, New Jersey.
Genentech, San Francisco, California.
Clin Cancer Res. 2022 Aug 2;28(15):3367-3377. doi: 10.1158/1078-0432.CCR-21-3347.
Cereblon (CRBN), a substrate receptor of the E3 ubiquitin ligase complex CRL4CRBN, is the target of the small molecules lenalidomide and avadomide. Upon binding of the drugs, Aiolos and Ikaros are recruited to the E3 ligase, ubiquitylated, and subsequently degraded. In diffuse large B-cell lymphoma (DLBCL) cells, Aiolos and Ikaros are direct transcriptional repressors of interferon-stimulated genes (ISG) and degradation of these substrates results in increased ISG protein levels resulting in decreased proliferation and apoptosis. Herein, we aimed to uncover the mechanism(s) Aiolos and Ikaros use to repress ISG transcription and provide a mechanistic rationale for a combination strategy to enhance cell autonomous activities of CRBN modulators (CELMoD).
We conducted paired RNA sequencing with histone modification and Aiolos/Ikaros chromatin immunoprecipitation sequencing to identify genes regulated by these transcription factors and to elucidate correlations to drug sensitivity. We confirmed Aiolos/Ikaros mediated transcriptional complex formation in DLBCL patient samples including those treated with avadomide.
In DLBCL, the repression of ISG transcription is accomplished in part through recruitment of large transcriptional complexes such as the nucleosome remodeling and deacetylase, which modify the chromatin landscape of these promoters. A rational combination approach of avadomide with a specific histone deacetylase inhibitor leads to a significant increase in ISG transcription compared with either single agent, and synergistic antiproliferative activity in DLBCL cell lines.
Our results provide a novel role for lineage factors Aiolos and Ikaros in DLBCL as well as further insight into the mechanism(s) of Aiolos and Ikaros-mediated transcriptional repression and unique therapeutic combination strategies.
CRBN（E3 泛素连接酶复合物 CRL4CRBN 的底物受体）是小分子来那度胺和阿伐度胺的靶标。药物结合后，Aiolos 和 Ikaros 被招募到 E3 连接酶，泛素化，随后降解。在弥漫性大 B 细胞淋巴瘤（DLBCL）细胞中，Aiolos 和 Ikaros 是干扰素刺激基因（ISG）的直接转录抑制剂，这些底物的降解导致 ISG 蛋白水平升高，导致增殖减少和凋亡。在此，我们旨在揭示 Aiolos 和 Ikaros 抑制 ISG 转录的机制，并为增强 CRBN 调节剂（CELMoD）细胞自主活性的组合策略提供机制依据。
我们进行了配对的 RNA 测序，结合组蛋白修饰和 Aiolos/Ikaros 染色质免疫沉淀测序，以鉴定受这些转录因子调节的基因，并阐明与药物敏感性的相关性。我们在包括用阿伐度胺治疗的 DLBCL 患者样本中证实了 Aiolos/Ikaros 介导的转录复合物形成。
在 DLBCL 中，ISG 转录的抑制部分是通过募集大型转录复合物完成的，如核小体重塑和去乙酰化酶，它们修饰这些启动子的染色质景观。与单一药物相比，阿伐度胺与特定组蛋白去乙酰化酶抑制剂的合理联合方法导致 ISG 转录显著增加，并且在 DLBCL 细胞系中具有协同的抗增殖活性。
我们的结果为 Aiolos 和 Ikaros 在 DLBCL 中的作用提供了新的认识，以及对 Aiolos 和 Ikaros 介导的转录抑制的机制的进一步了解，以及独特的治疗联合策略。
