Epstein–Barr virus (EBV) has been detected in several T- and NK-cell neoplasms such as extranodal NK/T-cell lymphoma nasal type, aggressive NK-cell leukemia, EBV-positive peripheral T-cell lymphoma, systemic EBV-positive T-cell lymphoma of childhood, and chronic active EBV infection (CAEBV). However, how this virus contributes to lymphomagenesis in T or NK cells remains largely unknown. Here, we examined NF-κB activation in EBV-positive T or NK cell lines, SNT8, SNT15, SNT16, SNK6, and primary EBV-positive and clonally proliferating T/NK cells obtained from the peripheral blood of patients with CAEBV. Western blotting, electrophoretic mobility shift assays, and immunofluorescent staining revealed persistent NF-κB activation in EBV-infected cell lines and primary cells from patients. Furthermore, we investigated the role of EBV in infected T cells. We performed an in vitro infection assay using MOLT4 cells infected with EBV. The infection directly induced NF-κB activation, promoted survival, and inhibited etoposide-induced apoptosis in MOLT4 cells. The luciferase assay suggested that LMP1 mediated NF-κB activation in MOLT4 cells. IMD-0354, a specific inhibitor of NF-κB that suppresses NF-κB activation in cell lines, inhibited cell survival and induced apoptosis. These results indicate that EBV induces NF-κB-mediated survival signals in T and NK cells, and therefore, may contribute to the lymphomagenesis of these cells.

Objective Primary vitreoretinal lymphoma (PVRL) is a rare type of lymphoma wherein the lesions are limited to the eyes. PVRL is difficult to diagnose because of the challenges related to obtaining sufficient samples for biopsy. Moreover, PVRL has poor outcomes and often leads to the development of central nervous system (CNS) lesions during its course. Two studies recently reported that approximately 70%‐80% of patients with vitreoretinal lymphoma have MYD88L265P, which is frequently mutated in primary CNS lymphoma (PCNSL). PCNSL is closely associated with PVRL. The mutation of CD79BY196 has been also frequently detected in PCNSL. Thus, we examined the mutation in PVRL to clarify its diagnostic and prognostic potential. Method By using direct sequencing and allele‐specific polymerase chain reaction, we examined the mutation of CD79BY196 and MYD88L265P in the DNA extracted from the vitreous fluid of 17 patients with PVRL upon diagnosis. We also retrospectively analyzed their prognostic potential for PVRL. Results Among the included patients, six patients (35%) were found with CD79BY196 mutations. Twelve (71%) patients were positive for MYD88L265P, and six samples from patients with benign uveitis were negative for both mutations. Interestingly, six patients with CD79BY196 mutations developed CNS diseases significantly earlier (16.5 months) than 11 patients with CD79BWT (67 months; P = 0.0135). Conclusion Detecting CD79BY196 in vitreous DNA may contribute to the confirmation of the diagnosis and may have a prognostic potential for patients with PVRL.

We performed a retrospective analysis of patients with adult-onset chronic active Epstein-Barr virus infection (CAEBV). First, we analyzed five patients (aged 28-72) diagnosed at our hospitals with EBV-infected clonally proliferating T cells. Four patients were administered cyclophosphamide/doxorubicin/vincristine/prednisone (CHOP) chemotherapy, but no remarkable decrease of viral load was observed in three of the patients. The other patient died 19 days after initiation of CHOP treatment due to disease progression. Addition of high-dose cytarabine to the regimens of two of the patients was discontinued shortly after administration, due to the development of grade 4 pericardial effusion. Together, these regimens may be insufficient for treating adult-onset CAEBV. We next reviewed 23 adult-onset CAEBV patients, adding 18 previously reported patients to the five patients described in the present study. T cells were frequently infected (87%), whereas NK- and T-cell types are known to be almost equally prevalent in childhood-onset cases. The time duration from the onset of disease to initiation of treatment averaged 20 months. Reports showed that 12 patients died; seven patients died at an average of 8 months after initiation of treatment. Patients' disease courses seemed to be rapidly progressive and more aggressive than those of childhood-onset cases. More cases must be studied to clarify clinical features and establish an optimal treatment strategy.

Chronic active Epstein-Barr virus infection (CAEBV) is a lymphoproliferative disorder characterized by the clonal proliferation of EBV-infected T or NK cells and is related to severe systemic inflammation. This study aims to investigate STAT3 to elucidate the mechanism underlying the CAEBV development. We determined that STAT3 was constitutively activated in EBV-positive T- or NK-cell lines. We also determined that STAT3 was activated in the peripheral blood mononuclear cells (PBMCs) containing EBV-infected clonally proliferating T or NK cells in six of seven patients with CAEBV. We conducted direct sequencing of the STAT3 Src homology 2 (SH2) domain, which has previously been reported to be mutated in T- or NK-cell neoplasms. No mutation was detected in the STAT3 SH2 domain in patients with CAEBV. Next, we investigated the effects of ruxolitinib, an inhibitor of both JAK1 and JAK2, which phosphorylates and activates STAT3. Ruxolitinib suppressed the phosphorylation of STAT3 in EBV-positive T- or NK-cell lines. Ruxolitinib also decreased the viable cell number of EBV-positive T- or NK-cell lines and PBMCs from patients with CAEBV. Furthermore, ruxolitinib suppressed the production of inflammatory cytokines in the cell lines and CAEBV patient-derived cells. In conclusion, constitutively activated STAT3, which promotes survival and cytokine production, could be a therapeutic target for CAEBV.