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Objectives: Adult T‐cell leukemia/lymphoma (ATL) is an intractable T‐cell malignancy caused by long‐term infection with human T‐cell leukemia virus type‐1 (HTLV‐1). While ATL pathogenesis has been associated with HTLV‐1‐derived oncogenic proteins, including Tax and HBZ, the contribution of genomic aberrations remains poorly defined. Methods: To elucidate the genomic basis of ATL, whole exome sequencing was performed on cells from 47 patients with aggressive ATL. Results: We discovered the novel mutation RLTPR Q575E in four patients (8.5%) with a median variant allele frequency of 0.52 (range 0.11‐0.68). Despite being reported in cutaneous T‐cell lymphoma, three ATL patients carrying RLTPR Q575E lacked skin involvement. Patients carrying RLTPR Q575E also harbored CARD11 (75%), PLCG1 (25%), PRKCB (25%), or IKBKB (25%) mutations related to TCR/NF‐κB signaling. Jurkat cells transfected with RLTPR Q575E cDNA displayed increased NF‐κB activity and significantly increased IL‐2 mRNA levels under stimulation. RLTPR Q575E increased the interaction between RLTPR and CARD11, while RLTPR directly interacted with Tax. Conclusions: We identified, and functionally validated, a novel gain‐of‐function mutation in patients with aggressive ATL. During TCR activation by Tax or gain‐of‐function mutations, RLTPR Q575E selectively upregulates NF‐κB signaling and may exert oncogenic effects on ATL pathogenesis. [ABSTRACT FROM AUTHOR]

Adult T-cell leukemia/lymphoma (ATL) is caused by human T-lymphotrophic virus type 1 infection and is one of the most refractory malignant T-cell lymphomas. Improvement of ATL therapy options requires the establishment of appropriate ATL animal models. In this study, we successfully generated an ATL mouse model by xenotransplantation of primary peripheral blood mononuclear cells (PBMCs) isolated from ATL patients (ATL cells) into nonobese diabetic/severe combined immunodeficiency/ Jak3 -null mice (NOJ mice). To generate the model, the ATL S1T cell line was subcutaneously injected into mice. Primary ATL cells were then transplanted subcutaneously, intraperitoneally, or intravenously. ATL cells infiltrated multiple organs, and elevated human soluble interleukin 2 receptor (IL-2R) levels were detected in peripheral blood. Injection of one million primary ATL cells was needed for successful engraftment into host mice. Thawed cells, frozen long-term in liquid nitrogen, could also be transplanted; however, more cells were required to achieve similar results. The median mouse survival time was proportional to the number of cells injected. Successful secondary transplantation of ATL cells from one NOJ mouse into another was achieved and confirmed by T-cell receptor analysis. Finally, we examined the effects of the antioxide pyrrolidine dithiocarbamate (PDTC) as an antitumor agent in vivo. PDTC administration inhibited the increase of soluble IL-2R and improved mouse survival, suggesting that this compound has potential as an anti-ATL agent. We demonstrated that ATL cells could be stably xenotransplanted into NOJ mice using primary cells. This model will be useful in the establishment of novel therapies to treat ATL. [ABSTRACT FROM AUTHOR]