Jurkat cells were used as a negative control

Jurkat cells were used as a negative control. by IL-2 in EBV-T/NK-LPDs cells, induced endogenousCD137gene expression in T and NK-cell lines. In order to examinein vivoCD137 expression, we used EBV-T/NK-LPDs xenograft models generated by intravenous injection of patients’ cells. We identified EBV-positive and CD8-positive T cells, as well as CD137 ligand-positive cells, in their tissue lesions. In addition, we detected CD137 expression on the EBV infected cells from the lesions of the models by immune-fluorescent staining. Finally, CD137 stimulation suppressed etoposide-induced cell death not only in the EBV-positive T- or NK-cell lines, but also in the patients’ cells. These results indicate that upregulation of CD137 expression through LMP1 by EBV promotes cell survival in T or NK cells leading to development of EBV-positive T/NK-cell neoplasms. == Introduction == Epstein-Barr virus (EBV) infection can 4-hydroxyephedrine hydrochloride be found in lymphoid malignancies not only of B-cell lineage, but also of T- or NK-cell lineages. These EBV-positive T or NK-cell neoplasms, such as extranodal NK/T-cell lymphoma nasal type (ENKL), aggressive NK-cell leukemia (ANKL), and EBV-positive T- or NK- cell lymphoproliferative diseases (EBV-T/NK-LPDs), are relatively rare but lethal disorders classified as peripheral T/NK-cell lymphomas according to the WHO classification of tumors of hematopoietic and lymphoid malignancies. ENKL is a rapidly progressive lymphoma characterized by extranodal lesions with vascular damage and severe necrosis accompanied by infiltration of neoplastic NK or cytotoxic T cells[1]. ANKL is a markedly aggressive leukemia with neoplastic proliferation of NK cells[2]. EBV-T/NK-LPDs is a fatal disorder presenting sustained infectious mononucleosis-like symptoms, hypersensitivity to mosquito bites, or hydroa vacciniforme-like eruption accompanied by clonal proliferation of EBV-infected cells[3],[4]. Because most reported cases were children or young adults, 4-hydroxyephedrine hydrochloride and were mainly of the T-cell-infected type, the disorders were designated EBV-positive T-cell lymphoproliferative diseases of childhood in the WHO classification, although adult and NK-cell types have been reported[4][6]. The common clinical properties of EBV-T/NK-neoplasms are the presence of severe inflammation, resistance to chemotherapy, and a marked geographic bias for East Asia and Latin America, suggesting a genetic context for disease development[4]. Since these EBV-T/NK-neoplasms overlap[4], common mechanisms are thought to exist in the background and contribute to disease development. It is well known that EBV infects B cells and makes the infected cells immortal resulting in B-cell lymphomas. Similarly it is suspected that EBV may also cause T- or NK-cell neoplasms. However, why and how EBV latently infects T or NK cells, whether or not EBV directly causes these malignancies, and the mechanism of action responsible for the disease development remain to be clarified. Although new chemotherapy and stem cell transplantation have achieved good results for EBV-T/NK neoplasms recently[7][9], prognosis of the diseases is still poor. The mechanisms for development of the disease need to be determined to establish an optimal treatment. To clarify the molecular mechanism underlying the development of EBV-T/NK-neoplasms, we focused on the costimulatory receptor Rabbit Polyclonal to Cytochrome P450 17A1 CD137. CD137, also known as 4-1BB, is a member of the tumor necrosis factor (TNF) receptor superfamily, and expressed on the surface of activated T and NK cells[10]. In association with TCR stimulation, it plays a pivotal role in proliferation, survival, and differentiation of these cells as a costimulatory molecule[11]. Recently, it was reported that CD137 is expressed on tumor cells from adult T-cell leukemia/lymphoma (ATLL) and from T-cell lymphomas[12],[13]. Here we found CD137 expression on EBV-positive cells in EBV-T/NK-neoplasms and investigated its role for the lymphomagenesis using established cell lines as well as cells from EBV-T/NK-LPDs patients. == Results == == CD137 expression in EBV-T/NK-cell lines == Six EBV-positive T- and NK-cell lines, SNT8, SNT15, SNT16, SNK1, SNK6, and SNK10 had been established from primary lesions of ENKL patients (SNT8 and 4-hydroxyephedrine hydrochloride SNK6) and PB of EBV-T/NK-LPDs patients (SNT15, SNT16, SNK1, and SNK10)[14]. We investigatedCD137mRNA expression in the cell lines by RT-PCR.CD137mRNA was expressed in all of them, whereas EBV-negative T-cell lines (Jurkat, MOLT4, and HPB-ALL) and NK-cell line (KHYG1) were negative for the expression (Figure 1A). The mRNA was detected but weak in an EBV-negative NK-cell line, MTA, and in EBV-negative B-cell lines, BJAB, Ramos, and MD901. We also investigated 3 EBV-positive B cell lines, Raji, a lymphoblastoid cell line (LCL), and HS-sultun. The expression was detected in Raji. The expression was weak in LCL, and negative in HS-Sultan. We next investigated CD137 protein expression on the cell surface.Figure 1Bshows that CD137 protein was expressed on the cell surface of all EBV-positive T- or NK-cells. In contrast, 4-hydroxyephedrine hydrochloride EBV-negative T-, NK-, and B-cell lines were negative for CD137 expression. On the basis of these results, we concluded that CD137 expression was induced at the mRNA and protein levels in EBV-T/NK cell.