Long noncoding RNAs (IncRNAs) are involved in tumorigenesis. Previously, IncRNA MNX1-AS1 was reported to increase the malignancy of ovarian cancer, cervical cancer and lung cancer. However, the potential function of MNX1-AS1 in hepatocellular carcinoma (HCC) remains unclear. In this study, we found that MNX1-AS1 was remarkably upregulated in HCC tissues and cell lines. Furthermore, MNX1-AS1 overexpression was related to advanced stage and metastasis, and predicted poor prognosis. Loss of-function assays showed that MNX1-AS1 knockdown suppressed the proliferation, migration and invasion of HCC cells in vitro. Further investigation indicated that MNX1-AS1 silencing delayed HCC growth in vivo. Mechanistically, we identified that MNX1-AS1 was a competing endogenous RNA (ceRNA) for miR-218-5p. We demonstrated that MNX1-AS1 promoted COMMD8 expression through sponging miR-218-5p, and then contributed to HCC progression. Restoration of COMMD8 significantly reversed the effects of MNX1-AS1 knockdown. Taken together, our findings demonstrated that MNX1-AS1 promoted the malignant properties of HCC through targeting miR-218-5p/COMMD8 pathway. (C) 2019 Elsevier Inc. All rights reserved.