Aims

The mTOR/S6K1 signaling axis, known for cell growth regulation, is hyper-activated in multiple cancers. In this study, we have examined the mechanisms for ribosomal protein p70-S6 kinase 1 (S6K1) associated transformed human hepatocyte (THH) growth regulation.

Main methods

THH were treated with p70-S6K1 inhibitor and analyzed for cell viability, cell cycle distribution, specific marker protein expression by western blot, and tumor inhibition in a xenograft mouse model. We validated our results by knockdown of p70-S6K1 using specific siRNA.

Key findings

p70-S6K1 inhibitor treatment caused impairment of in vitro hepatocyte growth, and arrested cell cycle progression at the G1 phase. Further, p70-S6K1 inhibitor treatment exhibited a decrease in FAK and Erk activation, followed by altered integrin-β1 expression, caspase 8, and PARP cleavage appeared to be anoikis like growth inhibition. p70-S6K1 inhibitor also depolymerized actin microfilaments and diminished active Rac1/Cdc42 complex formation for loss of cellular attachment. Similar results were obtained with other transformed human hepatocyte cell lines. p70-S6K1 inhibition also resulted in a reduced phospho-EGFR, Slug and Twist; implicating an inhibition of epithelial-mesenchymal transition (EMT) state. A xenograft tumor model, generated from implanted THH in nude mice, following intraperitoneal injection of S6K1 inhibitor prevented further tumor growth.

Significance

Our results suggested that p70-S6K1 inhibition alters orchestration of cell cycle progression, induces cell detachment, and sensitizes hepatocyte growth impairment. Targeting p70 isoform of S6K1 by inhibitor may prove to be a promising approach together with other therapies for hepatocellular carcinoma (HCC) treatment.

中文翻译：

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抑制S6K1的p70亚型可诱导失神经，从而防止转化的人类肝细胞生长

目的

mTOR / S6K1信号轴以细胞生长调节而闻名，在多种癌症中被过度激活。在这项研究中，我们检查了核糖体蛋白p70-S6激酶1（S6K1）相关的转化人类肝细胞（THH）生长调节的机制。

主要方法

THH用p70-S6K1抑制剂处理，并在异种移植小鼠模型中分析了细胞活力，细胞周期分布，通过蛋白质印迹的特异性标记蛋白表达以及肿瘤抑制。我们通过使用特异性siRNA敲低p70-S6K1验证了我们的结果。

主要发现

p70-S6K1抑制剂治疗引起体外损伤肝细胞生长，并阻止了G1期的细胞周期进程。此外，p70-S6K1抑制剂治疗表现出FAK和Erk活化降低，随后整合素β1表达，胱天蛋白酶8改变，PARP裂解似乎是生长抑制之类的失常。p70-S6K1抑制剂还解聚了肌动蛋白微丝并减少了活性Rac1 / Cdc42复合物的形成，从而失去了细胞附着。用其他转化的人肝细胞系也获得了相似的结果。p70-S6K1抑制也导致磷酸化EGFR，Slug和Twist减少；暗示抑制上皮-间质转化（EMT）状态。腹膜内注射S6K1抑制剂后，从裸鼠体内植入THH生成的异种移植肿瘤模型阻止了肿瘤的进一步生长。

意义

我们的结果表明，p70-S6K1抑制作用改变了细胞周期进程的编排，诱导了细胞的脱离，并使肝细胞生长受损变得敏锐。抑制剂靶向S6K1的p70亚型可能与其他肝细胞癌（HCC）治疗方法一起被证明是一种有前途的方法。