Hepatocellular carcinoma (HCC) is the most prevalent type of liver cancer. In this study, we aimed to explore the role and mechanism of lncRNA ST8SIA6-AS1 in HCC. We found that ST8SIA6-AS1 was upregulated in HCC tissues and associated with poorer overall survival of HCC patients from TCGA. Moreover, ST8SIA6-AS1 was highly expressed in HCC in-house tissues and cells, and ST8SIA6-AS1 upregulation was related to aggressive tumor phenotypes and the poor overall survival of HCC patients. Downregulation of ST8SIA6-AS1 suppressed HCC cell proliferation, migration and invasion in vitro and restrained HCC tumorigenesis in vivo. In terms of mechanism, ST8SIA6-AS1 regulated melanomaassociated antigen (MAGE)-A3 (MAGEA3) and DDB1-and Cul4-associated factor 4-like 2 (DCAF4L2) expression, and rescue experiments verified that ST8SIA6-AS1 played a protumorigenic role in HCC via the regulation of MAGEA3 and DCAF4L2. ST8SIA6-AS1 partly directly bound to miR-129-5p and functioned as a competing endogenous RNA (ceRNA), subsequently facilitating the expression of the miR-129-5p target gene DCAF4L2 to play its role in HCC. In summary, our results identified ST8SIA6-AS1 as an oncogenic lncRNA predicting poor clinical outcomes of patients with HCC. These findings suggest that ST8SIA6-AS1 is a potential therapeutic target for HCC. (C) 2020 Elsevier Inc. All rights reserved.