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Background/Aim: Transcriptional factor prospero homeobox-1 (PROX-1) is crucial for the embryonic development of various organs and cell fate specification. It exhibits either an oncogenic or tumor suppressive activity depending on cancer types. However, the relationship between PROX-1 and hepatocellular carcinoma (HCC) remains obscure. This study was conducted to investigate the effect of PROX-1 on the invasive and oncogenic phenotypes of human HCC cells. Materials and Methods: The effect of PROX-1 on tumor cell behavior was investigated by using a pcDNA-myc vector and a small interfering RNA in HepG2 and Huh7 human HCC cell lines. Flow cytometry, migration, invasion, proliferation, and tube formation assays were performed. PROX-1 expression in human HCC cells was explored by western blotting. Results: PROX-1 overexpression enhanced tumor cell proliferation and inhibited apoptosis and cell cycle arrest by modulating the activities of caspase-3, PARP, and cyclin-dependent kinase inhibitors, including p21, p27, and p57 in HCC cells. After PROX-1 overexpression, the number of migrating and invading HCC cells significantly increased, and the expression levels of N-cadherin and Snail increased in HCC cells. PROX-1 overexpression enhanced angiogenesis through increased VEGF-A and VEGF-C expression and decreased angiostatin expression. PROX-1 overexpression also increased the phosphorylation of glycogen synthase kinase-3ß (GSK-3ß) and forkhead box O1 (FOXO1) in HCC cells. After PROX-1 knockdown, their phosphorylation was reversed. Conclusion: PROX-1 overexpression is associated with the invasive and oncogenic phenotypes of human HCC cells via GSK-3ß and FOXO1 phosphorylation. [ABSTRACT FROM AUTHOR]