Abstract：
Ras-related C3 botulinum toxin substrate 1 (Rac1) has emerged as a key regulator in the treatment of cancer metastasis because of its involvement in the formation of cell plate pseudopods and effects on cell migration. In this study, we found that incarvine C, a natural product isolated from Incarvillea sinensis, and its seven analogues exhibited antitumour activity by inhibiting cell cytoskeleton formation, with moderate cytotoxicity. Accordingly, these compounds inhibited the cytoskeleton-mediated migration and invasion of MDA-MB-231 cells, with inhibition rates ranging from 37.30 % to 69.72 % and 51.27 % to 70.90 % in vitro, respectively. Moreover, they induced G2/M phase cell cycle arrest in MDA-MB-231 cells. A pull-down assay revealed that the interaction between Rac1 and its downstream effector protein PAK1 was inhibited by these compounds and that the compound Ano-6 exhibited substantial activity, with an inhibition rate of more than 90 %. Molecular docking showed that incarvine C and its analogues could bind to the nucleotide-binding pocket of Rac1, maintaining high levels of inactivated Rac1. As Ano-6 exhibited significant activity in vitro, its anti-cancer activity was tested in vivo. Four weeks of oral treatment with Ano-6 was well-tolerated in mice, and it induced a potential anti-tumour response in xenografts of MDA-MB-231 cells. Further studies demonstrated that Ano-6 was enriched in tumour tissues after 2 h of administration and induced an increase in the number of dead tumour cells. In summary, these findings not only reveal the mechanism of incarvine C but also provide a new molecular template for Rac1 inhibitors and identify a promising candidate for breast cancer treatment.
摘要：
Ras相关的C3肉毒杆菌毒素底物1（Rac1）已成为治疗癌症转移的关键调节因子，因为它参与了细胞板假足的形成和对细胞迁移的影响。在这项研究中,我们发现了化身C,一种从中华衣原体中分离出的天然产物，它的七个类似物通过抑制细胞骨架的形成而表现出抗肿瘤活性，具有中等的细胞毒性。因此，这些化合物抑制细胞骨架介导的MDA-MB-231细胞的迁移和侵袭，体外抑制率从37.30%到69.72%和51.27%到70.90%，分别。此外，它们在MDA-MB-231细胞中诱导G2/M期细胞周期停滞。下拉测定显示Rac1与其下游效应蛋白PAK1之间的相互作用被这些化合物抑制，并且化合物Ano-6表现出实质性的活性，抑制率超过90%。分子对接表明，incarvineC及其类似物可以与Rac1的核苷酸结合袋结合，保持高水平的灭活Rac1。由于Ano-6在体外表现出显著的活性，在体内测试了其抗癌活性。用Ano-6口服治疗四周的小鼠耐受性良好，它在MDA-MB-231细胞的异种移植物中诱导了潜在的抗肿瘤反应。进一步的研究表明，给药后2小时，Ano-6在肿瘤组织中富集，并诱导死亡肿瘤细胞数量增加。总之,这些发现不仅揭示了incarvineC的机制，而且为Rac1抑制剂提供了新的分子模板，并确定了乳腺癌治疗的有希望的候选药物。
