Activation of Siglec-7 Results in Inhibition of in Vitro and in Vivo Growth of Human Mast Cell Leukemia Cells

Advanced systemic mastocytosis is a rare and still untreatable disease. Blocking antibodies against inhibitory receptors, also known as 'immune checkpoints', have revolutionized anti-cancer treatment. Inhibitory receptors are expressed not only on normal immune cells, including mast cells but also on neoplastic cells. Whether activation of inhibitory receptors through monoclonal antibodies can lead to tumor growth inhibition remains mostly unknown. Here we show that the inhibitory receptor Siglec-7 is expressed by primary neoplastic mast cells in patients with systemic mastocytosis and by mast cell leukemia cell lines. Activation of Siglec-7 by anti-Siglec-7 monoclonal antibody caused phosphorylation of Src homology region 2 domain-containing phosphatase-1 (SHP-1), reduced phosphorylation of KIT and induced growth inhibition in mast cell lines. In SCID-beige mice injected with either the human mast cell line HMC-1.1 and HMC-1.2 or with Siglec-7 transduced B cell lymphoma cells, anti-Siglec-7 monoclonal antibody reduced tumor growth by a mechanism involving Siglec-7 cytoplasmic domains in 'preventive' and 'treatment' settings. These data demonstrate that activation of Siglec-7 on mast cell lines can inhibit their growth in vitro and in vivo. This might pave the way to additional treatment strategies for mastocytosis

How the Immune System Responds to Allergy Immunotherapy

IgE-mediated diseases represent a highly diversified and multifactorial group of disorders that can deeply impact the patients’ quality of life. Currently, allergy immunotherapy (AIT) still remains the gold standard for the management of such pathologies. In this review, we comprehensively examine and discuss how AIT can affect both the innate and the adaptive immune responses at different cell levels and propose timing-scheduled alterations induced by AIT by hypothesizing five sequential phases: after the desensitization of effector non-lymphoid cells and a transient increase of IgE (phase 1), high doses of allergen given by AIT stimulate the shift from type 2/type 3 towards type 1 response (phase 2), which is progressively potentiated by the increase of IFN-γ that promotes the chronic activation of APCs, progressively leading to the hyperexpression of Notch1L (Delta4) and the secretion of IL-12 and IL-27, which are essential to activate IL-10 gene in Th1 and ILC1 cells. As consequence, an expansion of circulating memory Th1/Tr1 cells and ILC-reg characterizes the third phase addressed to antagonize/balance the excess of type 1 response (phase 3). The progressive increase of IL-10 triggers a number of regulatory circuits sustained by innate and adaptive immune cells and favoring T-cell tolerance (phase 4), which may also be maintained for a long period after AIT interruption (phase 5). Different administration approaches of AIT have shown a similar tailoring of the immune responses and can be monitored by timely, optimized biomarkers. The clinical failure of this treatment can occur, and many genetic/epigenetic polymorphisms/mutations involving several immunological mechanisms, such as the plasticity of immune responses and the induction/maintenance of regulatory circuits, have been described. The knowledge of how AIT can shape the immune system and its responses is a key tool to develop novel AIT strategies including the engineering of allergen or their epitopes. We now have the potential to understand the precise causes of AIT failure and to establish the best biomarkers of AIT efficacy in each phase of the treatment

Activation of CEACAM1 with an agonistic monoclonal antibody results in inhibition of melanoma cells

nhibitory receptors (IRs), such as the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), are cell surface molecules expressed on both normal epithelial, endothelial, and hematopoietic cells and on neoplastic cells. IRs are usually used by cancer cells to inhibit immune cell functions. Thus, CEACAM1 positive tumor cells can interact homophilically with CEACAM1 expressed on T and NK cells to inhibit their antibody-dependent cell-mediated cytotoxicity (ADCC). In this study, we investigated the effect of agonistic/activating anti-CEACAM1 monoclonal antibody (mAb) on melanoma cell lines in vitro and in vivo, following our hypothesis that activation of CEACAM1 on melanoma cells by distinct mAbs may induce inhibition of cancer cell proliferation and/or their death. To address this, we established an activating anti-CEACAM1 mAb (CCM5.01) and characterized its binding to the CEACAM1 receptor. Using this mAb, we assessed the expression of CEACAM1 on four different human melanoma cell lines by western blot and flow cytometry and determined its effect on cell viability in vitro by MTT assay. Furthermore, we evaluated the mAb mechanism of action and found that binding of CEACAM1 with CCM5.01 induced SHP1 phosphorylation and p53 activation resulting in melanoma cell apoptosis. For in vivo studies, a xenograft model of melanoma was performed by injection of Mel-14 cells subcutaneously (s.c.) in SCID/Beige mice followed by intraperitoneal (i.p.) injection of CCM5.01 or of IgG1 isotype control every other day. CCM5.01 treated mice showed a slight but not significant decrease in tumor weight in comparison to the control group. Based on the obtained data, we suggest that activating CEACAM1 on melanoma cells might be a promising novel approach to fight cancers expressing this IR

Activation of CEACAM1 with an agonistic monoclonal antibody results in inhibition of melanoma cells

nhibitory receptors (IRs), such as the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), are cell surface molecules expressed on both normal epithelial, endothelial, and hematopoietic cells and on neoplastic cells. IRs are usually used by cancer cells to inhibit immune cell functions. Thus, CEACAM1 positive tumor cells can interact homophilically with CEACAM1 expressed on T and NK cells to inhibit their antibody-dependent cell-mediated cytotoxicity (ADCC). In this study, we investigated the effect of agonistic/activating anti-CEACAM1 monoclonal antibody (mAb) on melanoma cell lines in vitro and in vivo, following our hypothesis that activation of CEACAM1 on melanoma cells by distinct mAbs may induce inhibition of cancer cell proliferation and/or their death. To address this, we established an activating anti-CEACAM1 mAb (CCM5.01) and characterized its binding to the CEACAM1 receptor. Using this mAb, we assessed the expression of CEACAM1 on four different human melanoma cell lines by western blot and flow cytometry and determined its effect on cell viability in vitro by MTT assay. Furthermore, we evaluated the mAb mechanism of action and found that binding of CEACAM1 with CCM5.01 induced SHP1 phosphorylation and p53 activation resulting in melanoma cell apoptosis. For in vivo studies, a xenograft model of melanoma was performed by injection of Mel-14 cells subcutaneously (s.c.) in SCID/Beige mice followed by intraperitoneal (i.p.) injection of CCM5.01 or of IgG1 isotype control every other day. CCM5.01 treated mice showed a slight but not significant decrease in tumor weight in comparison to the control group. Based on the obtained data, we suggest that activating CEACAM1 on melanoma cells might be a promising novel approach to fight cancers expressing this IR

The anti-inflammatory cytokine IL-37 improves the NK cell-mediated anti-tumor response

ABSTRACTIL-37 is a member of the IL-1 superfamily exerting anti-inflammatory functions in a number of diseases. Extracellular IL-37 triggers the inhibitory receptor IL-1R8 that is known to regulate different NK cell pathways and functional activities including their anti-tumor effect. However, the effect of IL-37 on human NK cell functions is still to be unveiled. This study aimed to investigate the functional effect of IL-37 in human NK cells activated with IL-15. We found that IL-37 enhanced both NK cell cytotoxic activity against different tumor cell lines and cytokines production. These effects were associated with increased phosphorylation of ERK and NF-Kb. The improved NK cell activity was also strictly related to a time-dependent GSK3β-mediated degradation of IL-1R8. The enhanced activation profile of IL-37 treated NK cells possibly due to IL-1R8 degradation was confirmed by the results with IL-1R8-silenced NK cells. Lastly, in line with these data, through the analysis of the TNM plot database of a large group of patients, IL-37 mRNA expression was found to be significantly lower in colon and skin cancers than in normal tissues. Colon adenocarcinoma and neuroblastoma patients with higher IL-37 mRNA levels had significantly higher overall survival, suggesting that the presence of IL-37 might be considered an independent positive prognostic factor for this tumor. Our results provide novel information on the mechanisms regulating IL-1R8 function in human NK cells, highlighting the IL-37-IL-1R8 axis as a potential new target to improve the anti-tumor immune response