肝细胞癌（HCC）是一种频发且具有侵袭性的癌症。虽然E3连接酶在HCC的发展中发挥重要作用，但有一些E3连接酶仍未知。通过在HCC裸鼠模型中进行体内CRISPR敲除（KO）筛选与相关E3连接酶基因目标，我们发现LTN1是HCC中的一种新的肿瘤抑制因子。通过与2D-LC-MS/MS相结合的Co-IP和随后的HCC细胞的免疫共沉淀及Western blotting技术，我们确定了LTN1的相互作用蛋白组。与相匹配的正常组织相比，LTN1在人HCC组织（ANT）中的表达下降（157/209）。临床上，HCC患者中表达低水平LTN1的预后较差。LTN1的过表达在体外和体内均减少了细胞生长，而LTN1的沉默则增加了细胞生长。从机制上看，高表达的LTN1通过泛素化及不稳定性化IGF2BP1蛋白来抑制HCC细胞的生长，从而抑制c-Myc和IGF-1R信号通路。在HCC组织中，LTN1蛋白表达与IGF2BP1蛋白表达呈负相关（R2=0.2799，P=0.0165）。LTN1可能是决定预后的关键肿瘤抑制因子，也是一种潜在的治疗靶点，因为它通过泛素化IGF2BP1来抑制HCC细胞的增殖。版权所有 © 2023 作者。由沃尔特斯·克鲁尔健康公司代表美国肝病研究协会发表。

Hepatocellular carcinoma (HCC) is a frequent and aggressive kind of cancer. Although E3 ligases play important roles in HCC development, several E3 ligases remain unknown.Through in vivo CRISPR knockout (KO) screens targeting related E3 ligase genes in HCC nude mice models, we discovered LTN1 as a novel tumor suppressor in HCC. Co-IP paired with 2D-LC-MS/MS and subsequent western blotting in HCC cells were used to identify the interactome of LTN1. Compared to matched normal tissues, the expression of LTN1 was decreased in human HCC tissues (ANT) (157/209). Clinically, patients with HCC who expressed low levels of LTN1 had a poor prognosis. Forced expression of LTN1 decreased cell growth in vitro and in vivo, whereas knockdown of LTN1 increased cell growth. Mechanistically, elevated LTN1 expression inhibited HCC cell growth by ubiquitinating and destabilizing the IGF2BP1 protein, which inhibited the c-Myc and IGF-1R signaling pathways. There was a negative correlation between the LTN1 protein expression and the IGF2BP1 protein expression in HCC tissues (R2=0.2799, P=0.0165).LTN1 may be a crucial tumor suppressor for determining the prognosis and a possible therapeutic target since it inhibits the proliferation of HCC cells by ubiquitinating IGF2BP1.Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Association for the Study of Liver Diseases.