Liu Yidong, Liu Haiou, Yang Liu, Wu Qian, Liu Weisi, Fu Qiang, Zhang Weijuan, Zhang Haijian, Xu Jiejie, Gu Jianxin
Departments of Biochemistry and Molecular Biology.
Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai 200032, China.
J Biol Chem. 2017 Feb 24;292(8):3186-3200. doi: 10.1074/jbc.M116.751685. Epub 2017 Jan 6.
Deregulated expression of -acetylgalactosaminyltransferases (GALNTs), which is responsible for the initial step of mucin-type -glycosylation, could produce abnormal truncated -glycans and thereby exert pivotal functions during malignant transformation. GALNT4 is one of the few isoforms preferring to catalyze partial GalNAc-glycosylated substrates and modify the sites not utilized by other known GALNTs. This study aims to evaluate the impact of GALNT4 expression on malignant transformation of hepatocellular carcinoma (HCC). Immunohistochemistry and hybridization analysis were performed to assess GALNT4 and miR-9 level in clinical specimens, respectively. GALNT4 expression is markedly repressed in primary HCC tissues, and reduced expression of GALNT4 is significantly associated with adverse survival of patients with HCC. Functional investigations demonstrate that repressed GALNT4 could promote migration, invasion, anoikis resistance, and stemness of HCC cells as well as tumor growth The wild-type GALNT4 could modify -linked glycosylation on EGFR and thus modulate the activity of EGFR. A luciferase activity assay further identified microRNA-9 (miR-9) as the crucial specific arbitrator for GALNT4 expression in HCC cells. Furthermore, restoring GALNT4 expression attenuates miR-9-mediated oncogenic functions. Kaplan-Meier survival analysis indicates that the miR-9/GALNT4 expression signature yields promising prognostic significance to refine the risk stratification of patients with HCC. In conclusion, this study establishes the miR-9/GALNT4 axis as a potential adverse prognostic factor and therapeutic target for HCC patients.
α-乙酰半乳糖胺基转移酶（GALNTs）的表达失调负责粘蛋白型O-糖基化的起始步骤，可能产生异常截短的O-聚糖，从而在恶性转化过程中发挥关键作用。GALNT4是少数倾向于催化部分GalNAc糖基化底物并修饰其他已知GALNTs未利用位点的亚型之一。本研究旨在评估GALNT4表达对肝细胞癌（HCC）恶性转化的影响。分别进行免疫组织化学和杂交分析以评估临床标本中GALNT4和miR-9水平。GALNT4表达在原发性HCC组织中明显受到抑制，GALNT4表达降低与HCC患者的不良生存显著相关。功能研究表明，抑制GALNT4可促进HCC细胞的迁移、侵袭、失巢凋亡抗性和干性以及肿瘤生长。野生型GALNT4可修饰EGFR上的O-连接糖基化，从而调节EGFR的活性。荧光素酶活性测定进一步确定微小RNA-9（miR-9）是HCC细胞中GALNT4表达的关键特异性调节因子。此外，恢复GALNT4表达可减弱miR-9介导的致癌功能。Kaplan-Meier生存分析表明，miR-9/GALNT4表达特征对完善HCC患者的风险分层具有有前景的预后意义。总之，本研究确立了miR-9/GALNT4轴作为HCC患者潜在的不良预后因素和治疗靶点。
