Expression Of CD137 Ligand Research Articles

Astrocytic expression of CD137 in the lumbar spinal cord following sciatic nerve crush model of neuropathic pain in mice

Abstract Previously we have shown that CD137–CD137 ligand (CD137L) mediates pro-nociceptive behaviors in the sciatic nerve crush (SNC) model of neuropathic pain. Global CD137L knockout (KO) mice and wildtype (WT) mice intrathecally treated with neutralizing antibody against either CD137L or CD137 displayed significantly reduced neuropathic pain-like behaviors and faster functional recovery compared to WT mice following SNC. To identify the cellular sources of CD137 and CD137L in the spinal cord, a series of immunohistochemistry analyses was performed. While we could not detect significant expression of CD137L (in part due to both technical and biological issues), we observed CD137 expression exclusively co-localized with astrocytic marker glial fibrillary acidic filament (GFAP). We then conducted a time course study of CD137 expression in the lumbar spinal cord dorsal horn region, the region relevant to nociceptive behaviors, in B6-CD137L KO and B6 WT mice. Significant increases in CD137 expression (represented by integrated density) were observed in WT mice from days 7 to 28 following either SNC or sham surgery. The expression of CD137 in KO mice was slightly (however not statistically significantly) higher than that in WT mice at baseline, and did not change overtime post-either surgery. When RNA expression of CD137 was evaluated, although SNC induced significant upregulation of GFAP RNA expression in WT mice, no changes in CD137 RNA expression were detected in any treatment groups or any genotype of mice. Altogether, we report a novel expression of CD137 on murine spinal cord astrocytes. The underlying mechanism through which astrocytic CD137 mediates SNC-induced nociceptive behavior requires further investigation. NIH/NINDS R01NS098426 (Cao) and Peter Caradonna from the COBRE Histology and Imaging Core funded by NIH/NIGMS P20GM103643 (Meng).

Use of CD137 ligand expression in the detection of small B-cell lymphomas involving the bone marrow

Staging for small B-cell lymphomas is important for prognostic and therapeutic decision making; however, the detection of lymphoid infiltrates in the bone marrow is often hampered by the lack of specific diagnostic markers. We recently described the hematopoietic tissue distribution patterns of CD137 and CD137 ligand (CD137L), which have shown promise as immunotherapeutic targets. CD137 expression was primarily confined to cells in the microenvironment, whereas CD137L was expressed in neoplastic cells in most B-cell lymphomas. Here we evaluate the use of CD137L in the detection of small B-cell lymphomas involving the bone marrow. To test the potential efficacy of CD137L in detecting bone marrow lymphoid infiltrates, 166 small B-cell lymphomas were evaluated by immunohistochemistry and double-immunofluorescence labeling on formalin-fixed, paraffin-embedded bone marrow core biopsies. CD137L was highly expressed in bone marrows involved by small B-cell lymphomas and included hairy cell leukemia, mantle cell lymphoma, follicular lymphoma, B-lymphoblastic leukemia, and chronic lymphocytic leukemia. In addition, a small subset of marginal zone lymphoma and most of lymphoplasmacytic lymphoma showed staining. Normal bone marrow cells including myeloid, erythroid and megakaryocytic precursors, and reactive lymphoid aggregates lacked staining. Our findings show that immunohistochemistry for CD137L is capable of reliably distinguishing small B-cell lymphomas from reactive lymphoid aggregates. These data also suggest that CD137L is useful in providing staging information for clinical diagnosis and is likely to furnish a potential target for minimal residual disease assessment as well as immunotherapy in patients with stage 4 disease.

CD137 ligand signalling induces differentiation of primary acute myeloid leukaemia cells

CD137 ligand (CD137L), a member of the tumour necrosis factor family, is expressed as a cell surface molecule. Engagement of CD137L on haematopoietic progenitor cells induces monocytic differentiation, and in peripheral monocytes CD137L signalling promotes differentiation to mature dendritic cells. We hypothesized that CD137L signalling would also induce differentiation in transformed myeloid cells. Here we show that recombinant CD137 protein, which crosslinks CD137L and initiates reverse CD137L signalling in myeloid cells, induces morphological changes (adherence, spreading), loss of progenitor markers (CD117), expression of maturation markers (CD11b, CD13) and secretion of cytokines that are indicative of myeloid differentiation. Under the influence of CD137L signalling, acute myeloid leukaemia (AML) cells acquired expression of co-stimulatory molecules (CD80, CD86, CD40), the dendritic cell marker CD83 and dendritic cell activities, enabling them to stimulate T cells. CD137L signalling induced differentiation in 71% (15 of 21) of AML samples, irrespective of French-American-British classification and CD137L expression level. However, the type of response varied with the AML subtype and patient sample. In summary, this study demonstrated that CD137L signalling induced differentiation in malignant cells of AML patients, and suggests that it may be worthwhile to investigate treatment with recombinant CD137 protein as a potential novel therapeutic approach for AML.

Cross-linking of CD137 ligand modulates immune responses of thioglycollate-elicited mouse peritoneal macrophages

The aim of this study was to investigate effects of CD137 ligand (CD137L)-mediated reverse signaling on cellular responses in thioglycollate-elicited mouse peritoneal macrophages. Five-week-old male C57B6 mice were injected intraperitoneally with thioglycollate for 3 days to isolate peritoneal macrophages. We counted total cell numbers with a Cell Lab Quanta SC. CD137L expression was examined with a flow cytometer. We also measured expression of inflammatory cytokines by flow cytometry and/or real time-PCR. Cross-linking of CD137L with recombinant CD137-Fc protein (rCD137-Fc) increased total numbers of thioglycollate-elicited mouse peritoneal macrophages (hIgG-Fc- vs. rCD137-Fc-treated group, p < 0.05). However, ligation reduced the increase in IL-1β and IL-6 levels. Real-time PCR analysis showed that treatment of cells with rCD137-Fc also reduced transcript levels of IL-1β, IL-6, iNOS and COX2 (hIgG-Fc- vs. rCD137-Fc-treated group, p < 0.05), as well as expression of CD137L. Reverse signals initiated by CD137L negatively modulate certain immune functions of thioglycollate-elicited peritoneal macrophages.

CD137 ligand, a member of the tumor necrosis factor family, regulates immune responses via reverse signal transduction

CD137 (4-1BB, TNFR superfamily 9) and its ligand are members of the TNFR and TNF families, respectively, and are involved in the regulation of a wide range of immune activities. CD137 ligand cross-links its receptor, CD137, which is expressed on activated T cells, and costimulates T cell activities. CD137 ligand can also be expressed as a transmembrane protein on the cell surface and transmit signals into the cells on which it is expressed (reverse signaling). CD137 ligand expression is found on most types of leukocytes and on some nonimmune cells. In monocytic cells (monocytes, macrophages, and DCs), CD137 ligand signaling induces activation, migration, survival, and differentiation. The activities of T cells, B cells, hematopoietic progenitor cells, and some malignant cells are also influenced by CD137 ligand, but the physiological significance is understood only partly. As CD137 and CD137 ligand are regarded as valuable targets for immunotherapy, it is pivotal to determine which biological effects are mediated by which of the 2 molecules.

The Role of CD137 and Its Ligand in Chronic Lymphocytic Leukemia (CLL)

Tumor immunosurveillance is dependent on the reciprocal interaction between tumor cells and anti-tumor immunity mediated e.g. by NK cells. This has led to the concept of tumor immunoediting, which incorporates the multitude of mechanisms underlying this dual tumor- and immune-sculpting interaction. Various members of the TNF/TNFR family modulate differentiation, proliferation, activation, and death of both tumor and immune effector cells. Very recently the TNFR family member CD137 has been shown to be induced on NK cells by Fc receptor triggering indicating that not only the Fab region but also the Fc part of a given antibody may be responsible for effects attributed to CD137 modulation (Lin et al., Blood 2008, 112: 699). Thus we here studied the role of human CD137 and its cognate counterpart, the CD137 ligand (CD137L) in the interaction of CLL with NK cells. High levels of CD137L expression were detected on B-CLL cells in all investigated patients (n=40). Incubation of CLL cells in the presence of an immobilized CD137-Ig fusionprotein significantly induced the release of the immunoregulatory cytokine TNF demonstrating that CLL-expressed CD137L was capable to transduce bidirectional signals. Furthermore, we found that NK cells of CLL patients displayed substantial CD137 expression. While being absent on resting NK cells, CD137 expression was upregulated on the CD56dimCD16+ but not the CD56brightCD16− NK cell subset of healthy donors upon activation e.g. with IL-2 or IL-15. In addition, CD137 was also induced on NK cells after incubation in supernatants of PBMC of CLL patients. Surprisingly, disruption of CD137-CD137L interaction in cocultures of allogenic NK cells with patient CLL cells by blocking CD137 antibody caused a significant increase in NK cell cytotoxicity. The observed inhibitory effect of CD137L on NK cell reactivity was confirmed in cytotoxicity assays using CD137L-transfectants with mock-transfectants as control. Furthermore, blocking CD137-CD137L interaction also substantially enhanced Rituximab-induced antibody dependent cellular cytotoxicity in an allogenic setting. Importantly, CD137 blockade also substantially enhanced CD107a expression as a surrogate marker for granule mobilization on autologous NK cells within PBMC of B-CLL patients, and this effect was observed both in the absence and more pronounced in the presence of Rituximab. Thus, expression of functional CD137L by CLL cells impairs anti-tumor immunity by diminishing both direct and antibody-dependent cellular cytotoxicity of allogenic and autologous NK cells. Modulation of the CD137-CD137L system might therefore be a suitable therapeutic approach in strategies like antibody therapy which rely on a sufficient NK cell anti-tumor response.

Induction of Proliferation and Monocytic Differentiation of Human CD34+ Cells by CD137 Ligand Signaling

CD137 is a member of the tumor necrosis factor receptor family and is involved in the regulation of activation, proliferation, differentiation, and cell death of leukocytes. Bidirectional signaling exists for the CD137 receptor/ligand system, as CD137 ligand, which is expressed as a transmembrane protein, can also transduce signals into the cells on which it is expressed. In this study, we have identified expression of CD137 in human bone marrow and expression of CD137 ligand on a subset of CD34+ cells. Cross-linking of CD137 ligand on CD34+ cells by CD137 ligand agonists induces activation, prolongation of survival, proliferation, and colony formation. CD137 ligand agonists induce differentiation of early hematopoietic progenitor cells to colony-forming units-granulocyte/macrophage and subsequently to monocytes and macrophages but not to dendritic cells. These data uncover a novel function of CD137 and CD137 ligand by showing their participation in the growth and differentiation of hematopoietic progenitor cells.