In this study, we investigated the activity of the JAK3/STAT5 pathway in EBV-associated B, T and NK cell lines as well as in lymphocytes from patients with EBV-associated T cell lymphoma, and evaluated the antitumor effects of tofacitinib on those cell lines in culture and in a murine xenograft model. Here, JAK3 is linked to T-cell non-Hodgkin lymphoma.