Abstract：
Dysregulation of the transforming growth factor-β (TGF-β) signaling pathway regulates cancer stem cells (CSCs) and drug sensitivity, whereas it remains largely unknown how feedback regulatory mechanisms are hijacked to fuel drug-resistant CSCs. Through a genome-wide CRISPR activation screen utilizing stem-like drug-resistant properties as a readout, the TGF-β receptor-associated binding protein 1 (TGFBRAP1) is identified as a TGF-β-inducible positive feedback regulator that governs sensitivity to tyrosine kinase inhibitors (TKIs) and promotes liver cancer stemness. By interacting with and stabilizing the TGF-β receptor type 1 (TGFBR1), TGFBRAP1 plays an important role in potentiating TGF-β signaling. Mechanistically, TGFBRAP1 competes with E3 ubiquitin ligases Smurf1/2 for binding to TGFΒR1, leading to impaired receptor poly-ubiquitination and proteasomal degradation. Moreover, hyperactive TGF-β signaling in turn up-regulates TGFBRAP1 expression in drug-resistant CSC-like cells, thereby constituting a previously uncharacterized feedback mechanism to amplify TGF-β signaling. As such, TGFBRAP1 expression is correlated with TGFΒR1 levels and TGF-β signaling activity in hepatocellular carcinoma (HCC) tissues, as well as overall survival and disease recurrence in multiple HCC cohorts. Therapeutically, blocking TGFBRAP1-mediated stabilization of TGFBR1 by selective inhibitors alleviates Regorafenib resistance via reducing CSCs. Collectively, targeting feedback machinery of TGF-β signaling pathway may be an actionable approach to mitigate drug resistance and liver cancer stemness.
摘要：
转化生长因子-β(TGF-β)信号通路失调调节肿瘤干细胞(CSCs)和药物敏感性,而反馈调节机制是如何被劫持到燃料耐药CSC上的,目前还不清楚.通过利用干细胞样耐药特性作为读数的全基因组CRISPR激活筛选，TGF-β受体相关结合蛋白1(TGFBRAP1)被鉴定为TGF-β诱导的正反馈调节因子,其控制对酪氨酸激酶抑制剂(TKIs)的敏感性并促进肝癌干性.通过与TGF-β受体1型（TGFBR1）相互作用并稳定，TGFBRAP1在增强TGF-β信号传导中起重要作用。机械上,TGFβ1与E3泛素连接酶Smurf1/2竞争结合TGFβR1，导致受损的受体聚泛素化和蛋白酶体降解。此外，过度活跃的TGF-β信号传导上调耐药CSC样细胞中TGF-β1的表达，从而构成先前未表征的反馈机制以放大TGF-β信号传导。因此，TGFβ1表达与肝细胞癌(HCC)组织中TGFβR1水平和TGF-β信号活性相关,以及多个HCC队列中的总体生存率和疾病复发。治疗学上,通过选择性抑制剂阻断TGFBR1介导的TGFBR1稳定通过减少CSC减轻Regorafenib耐药性。总的来说，TGF-β信号通路的靶向反馈机制可能是减轻耐药和肝癌干性的可行方法。
