Zhou Yu-Jiao, Yang Min-Li, He Xin, Gu Hui-Ying, Ren Ji-Hua, Cheng Sheng-Tao, Fu Zhou, Zhang Zhen-Zhen, Chen Juan
Department of Infectious Disease, Children's Hospital of Chongqing Medical University, National Clinical Research Center for Child Health and Disorders, Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing Key Laboratory of Child Rare Diseases in Infection and Immunity, No.20 Jinyu Road, Yubei District, Chongqing, 401122, China.
The Key Laboratory of Molecular Biology of Infectious Diseases designated by the Chinese Ministry of Education, Chongqing Medical University, Chongqing, China.
J Exp Clin Cancer Res. 2024 Feb 8;43(1):45. doi: 10.1186/s13046-023-02929-1.
Metastasis is one of the leading cause contributes to treatment failure and poor prognosis of hepatocellular carcinoma (HCC) patients. The underlying mechanism of HCC metastasis remains to be determined. Although several RNA binding proteins (RBPs) have been found to participate in tumorigenesis and progression of liver cancer, the role of RBPs in HCC patients with extrahepatic metastases is poorly understood.
By performing RNA-seq of primary HCC tissues (including HCC with extrahepatic metastasis and those did not develop metastasis), we identified a set of HCC metastasis-associated RBPs candidates. Among which, ribosomal protein S7 (RPS7) was found to be remarkably increased in HCC tissues and be strongly related to HCC poor survival. Overexpression or CRISPR-Cas9-mediated knockout were applied to investigate the role of RPS7 on the metastasis-associated phenotypes of HCC cells. RNA sequencing, RIP, RNA-pull down, dual luciferase reporter assay, nascent RNA capture assay, and RNA decay and so on, were applied to reveal the underlying mechanism of RPS7 induced HCC metastasis.
Gain- and loss- of function analyses revealed that RPS7 promoted HCC cells adhesion, migration and invasion capabilities, as well as lung metastasis. Mechanistically, we uncovered that lysyl oxidase-like 2 (LOXL2) was a critical downstream target of RPS7. RPS7 could stabilize LOXL2 mRNA by binding to AUUUA motifs in the 3155-3375 region of the 3'UTR of LOXL2 mRNA, thus increased LOXL2 expression via elevating LOXL2 mRNA abundance. Further research revealed that LOXL2 could accelerate focal adhesion formation through maintaining the protein stability of ITGB1 and activating ITGB1-mediated FAK/SRC signaling pathway, and thereby contribute to the pro-metastasis effect of RPS7.
Taken together, our data reveal a novel function of RPS7 in HCC metastasis, also reveal the critical roles of the RPS7/LOXL2/ITGB1 axis in HCC metastasis and shed new light on the exploration of molecular drugs against HCC.
转移是导致肝细胞癌（HCC）患者治疗失败和预后不良的主要原因之一。HCC转移的潜在机制仍有待确定。尽管已发现几种RNA结合蛋白（RBPs）参与肝癌的发生和发展，但RBPs在伴有肝外转移的HCC患者中的作用仍知之甚少。
通过对原发性HCC组织（包括伴有肝外转移的HCC和未发生转移的HCC）进行RNA测序，我们鉴定出一组与HCC转移相关的RBPs候选物。其中，核糖体蛋白S7（RPS7）在HCC组织中显著增加，且与HCC患者的不良生存密切相关。应用过表达或CRISPR-Cas9介导的敲除来研究RPS7对HCC细胞转移相关表型的作用。采用RNA测序、RNA免疫沉淀、RNA下拉、双荧光素酶报告基因检测、新生RNA捕获检测以及RNA降解等方法，揭示RPS7诱导HCC转移的潜在机制。
功能获得和功能缺失分析表明，RPS7促进HCC细胞的黏附、迁移和侵袭能力以及肺转移。机制上，我们发现赖氨酰氧化酶样2（LOXL2）是RPS7的关键下游靶点。RPS7可通过与LOXL2 mRNA 3'UTR的3155 - 3375区域中的AUUUA基序结合来稳定LOXL2 mRNA，从而通过提高LOXL2 mRNA丰度增加LOXL2表达。进一步研究表明，LOXL2可通过维持整合素β1（ITGB1）的蛋白质稳定性并激活ITGB1介导的黏着斑激酶/原癌基因酪氨酸蛋白激酶Src（FAK/SRC）信号通路来加速黏着斑形成，从而促进RPS7的促转移作用。
综上所述，我们的数据揭示了RPS7在HCC转移中的新功能，也揭示了RPS7/LOXL2/ITGB1轴在HCC转移中的关键作用，并为抗HCC分子药物的探索提供了新的思路。
