Epstein-Barr Virus (EBV) activates NKL homeobox gene HLX in DLBCL

NKL homeobox genes encode developmental transcription factors regulating basic processes in cell differentiation. According to their physiological expression pattern in early hematopoiesis and B-cell development, particular members of this homeobox gene subclass constitute an NKL-code. These B-cell specific genes generate a regulatory network and their deregulation is implicated in B-cell lymphomagenesis. Epstein-Barr virus (EBV) infects B-cells and influences the activity of signalling pathways including JAK/STAT and several genes encoding developmental regulators. Therefore, EBV-infection impacts the pathogenesis and the outcome of B-cell malignancies including Hodgkin lymphoma and diffuse large B-cell lymphoma (DLBCL). Here, we isolated EBV-positive and EBV-negative subclones from the DLBCL derived cell line DOHH-2. These subclones served as model to investigate the role of EBV in deregulation of the B-cell specific NKL-code members HHEX, HLX, MSX1 and NKX6-3. We showed that the EBV-encoded factors LMP1 and LMP2A activated the expression of HLX via STAT3. HLX in turn repressed NKX6-3, SPIB and IL4R which normally mediate plasma cell differentiation. In addition, HLX repressed pro-apoptotic factor BCL2L11/BIM supporting cell survival. Thus, EBV aberrantly activated HLX thereby disturbing both B-cell differentiation and apoptosis in DLBCL. The results of our study contribute to better understand the pathogenic role of EBV in B-cell malignancies. Molecular characterization of EBV-positive and EBV-negative subclones of DLBCL cell line DOHH-2