Loránd L. Kis

Disruption of the estrogen receptor β gene in mice causes myeloproliferative disease resembling chronic myeloid leukemia with lymphoid blast crisis

Proliferation of pluripotent, bone marrow stem cells, which develop to lymphoid and myeloid progenitors, is negatively regulated by estrogen. Although in estrogen deficiency and in estrogen receptor knockout mice there is significant alteration in bone marrow hematopoiesis, the effects of aging on estrogen receptor deficiencies in mice have not been investigated yet. In this study we show that by 1.5 years of age, estrogen receptor β knockout (ERβ–/–) mice develop pronounced splenomegaly that is much more severe in females than in males. Further characterization of these mice revealed myelogenous hyperplasia in bone marrow, an increase in the number of granulocytes and B lymphocytes in blood, lymphadenopathy, and infiltration of leukocytes in the liver and lung. Analysis by flow cytometry of the bone marrow cells revealed that the percentage and total number of Gr-1hi/Mac-1hi-positive granulocytes were increased by 15–30% and 100%, respectively. The numbers of B cells in the bone marrow and spleen were significantly higher in ERβ–/– mice than in WT littermates. Some of the ERβ–/– mice also had a severe lymphoproliferative phenotype. Thus the absence of ERβ results in a myeloproliferative disease resembling human chronic myeloid leukemia with lymphoid blast crisis. Our results indicate a previously unknown role for ERβ in regulating the differentiation of pluripotent hematopoietic progenitor cells and suggest that the ERβ–/– mouse is a potential model for myeloid and lymphoid leukemia. Furthermore, we suggest that ERβ agonists might have clinical value in the treatment of leukemia.

Epstein–Barr virus infection in humans: from harmless to life endangering virus–lymphocyte interactions

After the primary infection, that may or may not cause infectious mononucleosis, the ubiquitous Epstein–Barr virus (EBV) is carried for lifetime. The great majority of adult humans are virus carriers. EBV was discovered in a B-cell lymphoma (Burkitt lymphoma). EBV infection in humans is the example for the power of immune surveillance against virus transformed, potentially malignant cells. Although the virus can transform B lymphocytes in vitro into proliferating lines, it induces malignancy directly only in immunosuppressed hosts. EBV-induced growth transformation occurs only in B lymphocytes. It is the result of a complex interaction between virally encoded and cellular proteins. Different forms of the virus–cell and the cell–host interactions have evolved during a long period of coexistence between the virus and all Old World (but not New World) primates. The asymptomatic carrier state is based on a viral-strategy that downregulates the expression of the transforming proteins in the virus-carrying cell. In addition to the silent viral-gene carriers and the expressors of the nine virus-encoded genes that drive the growth program, virus carrying cells exist that show other patterns of gene expression, depending on the differentiated state of the host cell. Certain combinations contribute to malignant transformation, but only in conjunction with additional cellular changes. These are induced by direct or cytokine-mediated interactions with normal cells of the immune system.

Differential expression of oestrogen receptors in human secondary lymphoid tissues.

Many autoimmune diseases including rheumatoid arthritis (RA), Sjögrens syndrome (SS) and systemic lupus erythematosus (SLE) occur much more frequently in women than in men. There is much evidence that oestrogen is the major cause of this gender difference. Interestingly, oestrogen relieves the symptoms of RA and SS but it exacerbates SLE. This contradictory effect of oestrogen on autoimmune diseases is not well understood. Most of the effects of oestrogen are mediated by two receptors: oestrogen receptor α and β (ERα and ERβ). To determine whether these contradictory effects of oestrogen relate to the involvement of distinct effects of the two ERs, we investigated expression of ERα and ERβ in human secondary lymphoid tissues. We observed that, in tonsils, ERβ is expressed in lymphocytes of germinal centres (GC) and the follicular mantle zone as well as in granulocytes, while ERα is expressed only in activated germinal centres but not in the follicular zone. ERβ is the predominant ER in human leucocytes from peripheral blood, spleen and in leucocytes infiltrating cancers in both males and females. In addition, in different human lymphoma cell lines including Hodgkin lymphoma, Burkitt lymphoma, and multiple myeloma, ERβ is abundant while ERα is not detectable. Our results indicate that ERβ is the predominant type of ER in mature lymphocytes. We suggest that ERα and ERβ have distinct roles in secondary lymphoid tissues and that further studies with ERβ‐specific agonists will help to elucidate the role of ERβ in these tissues. Copyright

IL-21 imposes a type II EBV gene expression on type III and type I B cells by the repression of C- and activation of LMP-1-promoter.

Epstein–Barr virus (EBV) is associated with a variety of human tumors. Although the EBV-infected normal B cells in vitro and the EBV-carrying B cell lymphomas in immunodeficient patients express the full set of latent proteins (type III latency), the majority of EBV-associated malignancies express the restricted type I (EBNA-1 only) or type II (EBNA-1 and LMPs) viral program. The mechanisms responsible for these different latent viral gene expression patterns are only partially known. IL-21 is a potent B cell activator and plasma cell differentiation-inducer cytokine produced by CD4+ T cells. We studied its effect on EBV-carrying B cells. In type I Burkitt lymphoma (BL) cell lines and in the conditional lymphoblastoid cell line (LCL) ER/EB2-5, IL-21 potently activated STAT3 and induced the expression of LMP-1, but not EBNA-2. The IL-21-treated type I Jijoye M13 BL line ceased to proliferate, and this was paralleled by the induction of IRF4 and the down-regulation of BCL6 expression. In the type III LCLs and BL lines, IL-21 repressed the C-promoter-derived and LMP-2A mRNAs, whereas it up-regulated the expression of LMP-1 mRNAs. The IL-21-treated type III cells underwent plasma cell differentiation with the induction of Blimp-1, and high levels of Ig and Oct-2. IL-21 might be involved in the EBNA-2-independent expression of LMP-1 in EBV-carrying type II cells. In light of the fact that IL-21 is already in clinical trials for the treatment of multiple malignancies, the in vivo modulation of EBV gene expression by IL-21 might have therapeutic benefits for the EBV-carrying malignancies.

STAT6 signaling pathway activated by the cytokines IL-4 and IL-13 induces expression of the Epstein-Barr virus–encoded protein LMP-1 in absence of EBNA-2: implications for the type II EBV latent gene expression in Hodgkin lymphoma

In line with the B-lymphotropic nature of Epstein-Barr virus (EBV), the virus is present in several types of B-cell lymphomas. EBV expresses a different set of latent genes in the associated tumors, such as EBV nuclear antigen 1 (EBNA-1) and latent membrane proteins (LMPs; type II latency) in classical Hodgkin lymphomas (HLs). We previously reported that exposure of in vitro EBV-converted, HL-derived cell line KMH2-EBV to CD40-ligand and interleukin-4 (IL-4) induced the expression of LMP-1. Here, we show that exposure to IL-4 or IL-13 alone induced LMP-1 in the absence of EBNA-2. Induction of LMP-1 by IL-4 and IL-13 was mediated by the signal transducer signal transducer and activator of transcription 6 (STAT6) and a newly defined high-affinity STAT6-binding site in the LMP-1 promoter. IL-4 induced LMP-1 also in Burkitt lymphoma-derived lines and in tonsillar B cells infected with the EBNA-2-deficient EBV strain P3HR-1. Furthermore, coculture of EBV-carrying Burkitt lymphoma cells with activated CD4(+) T cells resulted in the induction of LMP-1 in the absence of EBNA-2. Because Hodgkin/Reed-Sternberg cells are known to secrete IL-13, to have constitutively activated STAT6, and to be closely surrounded by CD4(+) T cells, these mechanisms may be involved in the expression of LMP-1 in EBV-positive chronic HLs.

Concomitant increase of LMP1 and CD25 (IL‐2‐receptor α) expression induced by IL‐10 in the EBV‐positive NK lines SNK6 and KAI3

Extranodal, nasal NK/T‐cell lymphomas are regularly Epstein‐Barr virus (EBV)‐positive, with a type II latency pattern, expressing thus EBNA‐1 and LMP1. The contribution of EBV to the tumor development is not known. Similarly to normal natural killer (NK) cells, cell lines derived from malignancies with a NK phenotype require IL‐2 for in vitro proliferation. In our effort to explore the contribution of EBV, particularly the role of the LMP1 protein, to the pathogenesis of the NK lymphoma we found that its expression, studied in the NK‐lines SNK6 and KAI3, depended on the supply of IL‐2 or other cytokines. In the absence of IL‐2 other cytokines, such as IL‐10 and IFN‐γ, could maintain LMP1, but the cells did not proliferate. When grown in IL‐2, the SNK6 cells produced IL‐10 and IFN‐γ, and these cytokines mediated the expression of LMP1. IL‐10 treatment enhanced, while IFN‐γ receptor blocking antibody reduced, the expression of CD25 and CD54 in the EBV‐positive, but not in the EBV‐negative lines. IL‐10 treated cells required lower amount of IL‐2 for proliferation compared to the untreated cells. This effect was seen only with the EBV‐positive NK lines in which LMP1 and CD25 were concomitantly upregulated. By this mechanism EBV could have an important role in the development of NK lymphoma since the inflammatory component in the tumor tissue can provide these cytokines.

In vitro EBV-infected subline of KMH2, derived from Hodgkin lymphoma, expresses only EBNA-1, while CD40 ligand and IL-4 induce LMP-1 but not EBNA-2.

In about 50% of classical Hodgkin lymphomas, the Hodgkin/Reed Sternberg (H/RS) cells carry Epstein‐Barr virus (EBV). The viral gene expression in these cells is restricted to EBNA‐1, EBERs, LMP‐1 and LMP‐2 (type II latency). The origin of H/RS cells was defined as crippled germinal center B cells that escaped apoptosis. In spite of numerous attempts, only few typical Hodgkin lymphoma (HL) lines have been established. This suggests that the cells require survival factors that they receive in the in vivo microenvironment. If EBV is expected to drive the cells for growth in culture, the absence of EBNA‐2 may explain the incapacity of H/RS cells for in vitro proliferation. In EBV carrying B lymphocytes, functional EBNA‐2 and LMP‐1 proteins are required for in vitro growth. For analysis of the interaction between EBV and the H/RS cells, we infected the CD21‐positive HL line KMH2 with the B958 and Akata viral strains. Only EBNA‐1 expression was detected in a few cells in spite of the fact that all cells could be infected. Using a neomycin‐resistance‐tagged recombinant EBV strain (Akata‐Neo) we established an EBV‐positive subline that was carried on selective medium. In contrast to the type II EBV expression pattern of H/RS cells in vivo, the KMH2 EBV cells did not express LMP‐1. The EBV expression pattern could be modified in this type I subline. LMP‐1 could be induced by the histone deacetylase inhibitors TSA and n‐butyrate, by 5‐AzaC, a demethylating agent, and by phorbol ester. None of these treatments induced EBNA‐2. Importantly, exposure to CD40 ligand and IL‐4 induced LMP‐1 without EBNA‐2 expression and lytic replication. The KMH2 EBV cells expressed LMP‐2A, but not LMP‐2B mRNAs. This result is highly relevant for the type II expression pattern of H/RS cells in vivo, since these stimuli can be provided by the surrounding activated T lymphocytes.

The proapoptotic function of SAP provides a clue to the clinical picture of X-linked lymphoproliferative disease.

Deletion or mutation of the SAP gene is associated with the X-linked lymphoproliferative disease (XLP) that is characterized by extreme sensitivity to Epstein-Barr virus (EBV). Primary infection of the affected individuals leads to serious, sometimes fatal infectious mononucleosis (IM) and proneness to lymphoma. Our present results revealed a proapoptotic function of SAP by which it contributes to the maintenance of T-cell homeostasis and to the elimination of potentially dangerous DNA-damaged cells. Therefore, the loss of this function could be responsible for the uncontrolled T-cell proliferation in fatal IM and for the generation of lymphomas. We show now the role of SAP in apoptosis in T and B lymphocyte-derived lines. Among the clones of T-ALL line, the ones with higher SAP levels succumbed more promptly to activation induced cell death (AICD). Importantly, introduction of SAP expression into lymphoblastoid cell lines (LCL) established from XLP patients led to elevated apoptotic response to DNA damage. Similar results were obtained in the osteosarcoma line, Saos-2. We have shown that the anti-apoptotic protein VCP (valosin-containing protein) binds to SAP, suggesting that it could be instrumental in the enhanced apoptotic response modulated by SAP.

SH2D1A expression in Burkitt lymphoma cells is restricted to EBV positive group I lines and is downregulated in parallel with immunoblastic transformation

The SH2 domain containing SH2D1A protein has been characterized in relation to the X‐linked lymphoproliferative disease (XLP), a primary immunodeficiency that leads to serious clinical conditions after Epstein‐Barr virus (EBV) infection. The SH2D1A gene is mutated in the majority of XLP patients. We previously detected SH2D1A in activated T and NK cells, but not in B lymphocytes. We have found SH2D1A protein in Burkitt lymphoma (BL) lines, but only in those that carried EBV and had a Group I (germinal center) phenotype. All the EBV‐carrying Group III (immunoblastic) and the EBV‐negative BL lines tested were SH2D1A‐negative. Motivated by these differences, we studied the impact of EBV and the cellular phenotype on SH2D1A expression. We approached the former question with BL sublines after both the loss of the virus and subsequent reinfection. We also tested original EBV‐negative BL lines carrying transfected EBV genes, such as EBNA1, EBNA2, EBNA6, EBER1, 2 and LMP1, respectively. In our experiments, no direct relationship could be seen between EBV and SH2D1A expression. We modified the phenotype of the Group I BL cells by LMP1 transfection or CD40 ligation. The phenotypic changes, indicated by expression of immunoblastic markers, e.g., SLAM, were accompanied by downregulation of SH2D1A. It seems, therefore, that the presence of EBV and the phenotype of the cell together regulate SH2D1A expression in the BL cells. It is possible that SH2D1A is expressed in a narrow window of B cell development represented by germinal center cells.

Digital image analysis outperforms manual biomarker assessment in breast cancer

In the spectrum of breast cancers, categorization according to the four gene expression-based subtypes ‘Luminal A,’ ‘Luminal B,’ ‘HER2-enriched,’ and ‘Basal-like’ is the method of choice for prognostic and predictive value. As gene expression assays are not yet universally available, routine immunohistochemical stains act as surrogate markers for these subtypes. Thus, congruence of surrogate markers and gene expression tests is of utmost importance. In this study, 3 cohorts of primary breast cancer specimens (total n=436) with up to 28 years of survival data were scored for Ki67, ER, PR, and HER2 status manually and by digital image analysis (DIA). The results were then compared for sensitivity and specificity for the Luminal B subtype, concordance to PAM50 assays in subtype classification and prognostic power. The DIA system used was the Visiopharm Integrator System. DIA outperformed manual scoring in terms of sensitivity and specificity for the Luminal B subtype, widely considered the most challenging distinction in surrogate subclassification, and produced slightly better concordance and Cohen’s κ agreement with PAM50 gene expression assays. Manual biomarker scores and DIA essentially matched each other for Cox regression hazard ratios for all-cause mortality. When the Nottingham combined histologic grade (Elston–Ellis) was used as a prognostic surrogate, stronger Spearman’s rank-order correlations were produced by DIA. Prognostic value of Ki67 scores in terms of likelihood ratio χ2 (LR χ2) was higher for DIA that also added significantly more prognostic information to the manual scores (LR−Δχ2). In conclusion, the system for DIA evaluated here was in most aspects a superior alternative to manual biomarker scoring. It also has the potential to reduce time consumption for pathologists, as many of the steps in the workflow are either automatic or feasible to manage without pathological expertise.