Malignant melanoma is one of the most fatal and aggressive skin cancers, originating from pigment containing melanocytes. Despite progress in clinical research, treatment options for malignant melanoma have been limited. The nuclear factor of activated T-cell 5 (NFAT5), originally identified as tonicity regulated transcription factor Ton/EBP, is now known as a carcinogenic gene in several types of cancer pathology. In this study, we knocked down NFAT5 to investigate its role in melanoma cancer. shRNAmediated knockdown of NFAT5 led to a significant decrease in cell proliferation in vitro. Additionally, depletion of NFAT5 inhibited the cell migratory ability of B15BL6 melanoma cells and led to more accumulation at the G2/M phase of the cell cycle. Furthermore, NFAT5 was essential for the development of melanoma cancer pathophysiology in an in vivo mouse model. NFAT5 knockdown-induced tumor growth was slow and tumor volume was significantly reduced compared to mock controls. Moreover, NFAT5 knockdown was associated with a low number of metastatic nodules on the lung and liver. To our knowledge, our data demonstrate for the first time a role of NFAT5 in the development of melanoma. We provide evidence for NFAT5 as a marker of cell migration and metastasis, indicating that NFAT5 represents a novel therapeutic target in melanoma. (C) 2018 Elsevier Inc. All rights reserved.