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Tumor chemoresistance is often a major cause for the failure of chemotherapy. The resistance of hepatocellular carcinoma (HCC) cells to sorafenib significantly limits its therapeutic effect in HCC patients. For the first time, we found that FXYD domain-containing ion transport regulator 5 (FXYD5) is highly expressed in sorafenib-resistant HCC cells. In addition, the protein expression level of FXYD5 was markedly higher in HCC tissues than in paracancerous tissues. Remarkably, downregulation of FXYD5 expression in Huh7/sora cells reversed their resistance to sorafenib. Moreover, overexpression of FXYD5 reduced the sensitivity of HCC cells to sorafenib, while the downregulation of its expression in HCC cells had the opposite effect. We also found abnormal activation of the Akt/mTOR signaling pathway in Huh7/sora cells. Furthermore, MK2206, an Akt inhibitor, was found to significantly increase the sensitivity of HCC cells to sorafenib. More importantly, the expression level of p-Akt was positively correlated with the expression of FXYD5 in HCC tissues. Therefore, mechanistically, FXYD5 enhances the resistance of HCC cells to sorafenib by activating the Akt/mTOR signaling pathway. In conclusion, this study showed that the activation of the FXYD5/Akt/mTOR signaling axis plays key role in the resistance of HCC cells to sorafenib, and FXYD5 may represent a new potential target for HCC therapy. [ABSTRACT FROM AUTHOR]