Background: Epithelial-mesenchymal transition (EMT) is associated with invasion and metastasis of cancer cells. High-mobility group AT-hook 2 (HMGA2) has been found to play a critical role in EMT in a number of malignant tumors. However, whether HMGA2 regulates the EMT in human nasopharyngeal carcinoma (NPC) is unclear. Objective: The aim of this study was to investigate the effect and mechanism of HMGA2 in inducing invasion and migration in NPC. Methods: In NPC tissues samples, the association of HMGA2 mRNA expression with clinicopathological characteristics were estimated by real-time quantitative RT-PCR(qRT-PCR). In vitro, following the silencing of HMGA2 in CNE-1 and CNE-2 cell lines, the viability and metastatic ability were analyzed using Cell Counting Kit-8 (CCK8), colony formation assay, and transwell assay. EMT and transforming growth factor-beta (TGF beta)/Smad3 signaling pathway-related protein expression changes were evaluated using western blot. Results: HMGA2 was upregulated in NPC cell lines and clinical specimens (P < 0.01), and HMGA2 expression correlated significantly with metastasis (P = 0.02) and disease-free survival of NPC (hazard ratio: 3.52; 95% confidence interval: 1.34-7.79; P = 0.01). In addition, following in vitro knockdown of HMGA2, the aggressiveness of cells was markedly inhibited, Vimentin and Snail level was downregulated and E-cadherin expression was upregulated. Moreover, the expression of key proteins TGF beta RII and p-Smad3 of the TGF beta/Smad3 signaling pathway was inhibited by the downregulation of HMGA2. Conclusion: HMGA2 might maintain EMT-induced invasion and migration through the TGF beta/Smad3 signaling pathway in NPC cell lines. (C) 2015 Elsevier Inc. All rights reserved.