Department of Integrated Traditional and Western Medicine, Chengdu Shangjinnanfu Hospital/West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China.
Department of Integrated Traditional and Western Medicine, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China.
Int J Biol Sci. 2020 Feb 4;16(6):1059-1070. doi: 10.7150/ijbs.40235. eCollection 2020.
Cullin 4A and 4B (CUL4A and 4B) function as oncogenes in colorectal cancer (CRC) cells. Both of them conservatively associate with DNA damage-binding protein 1 (DDB1) and DDB1-CUL4-associated factor 4 (DCAF4) to form Cullin-RING E3 ligases known as CRL4, which specifically ubiquitinate and degrade tumor suppressor ST7 (suppression of tumorigenicity 7). Knockdown either or significantly inhibits tumor cell growth and . Thus, targeting these CRL4 components and their interactions may be an effective strategy for the therapy of CRC. In this study, we developed an AlphaScreen assay to identify small molecules targeting the CUL4A-DDB1 interaction. We obtained a compound NSC1892, which strongly disrupted the CUL4A-DDB1 interaction (IC = 1.8 μM). Oncogenic phenotype analyses indicated that NSC1892 showed significant cytotoxicity to decrease cell proliferation, colony formation and invasion in CRC cells. Biochemical analyses demonstrated that NSC1892 treatment did not change CUL4A and CUL4B protein levels, but caused the degradation of DDB1, thereby leading to the impaired assembly of CRL4 E3 ligases and resulting in the accumulation of ST7. The administration of NSC1892 in mice also significantly inhibited tumor growth through degrading DDB1 and accumulating ST7. Interestingly, NSC1892 also showed promising cytotoxicity to decrease the growth of other or overexpressing tumor cells such as SKOV3 ovarian cells and Saos2 osteosarcoma cells. Our results provide a new avenue for the development of a therapeutic compound targeting tumors through disrupting the CUL4-DDB1 interaction.
Cullin 4A 和 4B（CUL4A 和 4B）在结直肠癌细胞中作为癌基因发挥作用。它们都保守地与 DNA 损伤结合蛋白 1（DDB1）和 DDB1-CUL4 相关因子 4（DCAF4）结合，形成称为 CRL4 的 Cullin-RING E3 连接酶，该酶特异性泛素化和降解肿瘤抑制因子 ST7（抑制肿瘤发生 7）。敲低 或 均可显著抑制肿瘤细胞生长 和 。因此，靶向这些 CRL4 成分及其相互作用可能是 CRC 治疗的有效策略。在这项研究中，我们开发了一种 AlphaScreen 测定法来鉴定靶向 CUL4A-DDB1 相互作用的小分子。我们获得了一种化合物 NSC1892，它强烈破坏了 CUL4A-DDB1 相互作用（IC = 1.8 μM）。致癌表型分析表明，NSC1892 对 CRC 细胞表现出显著的细胞毒性，可降低细胞增殖、集落形成和侵袭能力。生化分析表明，NSC1892 处理不会改变 CUL4A 和 CUL4B 蛋白水平，但会导致 DDB1 的降解，从而导致 CRL4 E3 连接酶的组装受损，并导致 ST7 的积累。在小鼠中给予 NSC1892 也通过降解 DDB1 和积累 ST7 显著抑制肿瘤生长。有趣的是，NSC1892 对其他过表达或过度表达肿瘤细胞（如 SKOV3 卵巢细胞和 Saos2 骨肉瘤细胞）的生长也表现出有希望的细胞毒性。我们的研究结果为通过破坏 CUL4-DDB1 相互作用开发靶向肿瘤的治疗性化合物提供了新途径。
