Human dialyzable leukocyte extracts (DLEs) are heterogeneous mixtures of low-molecular-weight peptides that modulate immune responses in various diseases. Due their complexity, standardized methods to identify their physicochemical properties and determine that production batches are biologically active must be established. We aimed to develop and validate a size exclusion ultra performance chromatographic (SE-UPLC) method to characterize Transferon™, a DLE that is produced under good manufacturing practices (GMPs). We analyzed an internal human DLE standard and 10 representative batches of Transferon™, all of which had a chromatographic profile characterized by 8 main peaks and a molecular weight range between 17.0 and 0.2kDa. There was high homogeneity between batches with regard to retention times and area percentages, varying by less than 0.2% and 30%, respectively, and the control chart was within 3 standard deviations. To analyze the biological activity of the batches, we studied the ability of Transferon™ to stimulate IFN-γ production in vitro. Transferon™ consistently induced IFN-γ production in Jurkat cells, demonstrating that this method can be included as a quality control step in releasing Transferon™ batches. Because all analyzed batches complied with the quality attributes that were evaluated, we conclude that the DLE Transferon™ is produced with high homogeneity.
Edited by Peter CresswellAcute myeloid leukemia (AML) is characterized by the proliferation of immature myeloid lineage blasts. Due to its heterogeneity and to the high rate of acquired drug resistance and relapse, new treatment strategies are needed. Here, we demonstrate that IFN␥ promotes AML blasts to act as effector cells within the context of antibody therapy. Treatment with IFN␥ drove AML blasts toward a more differentiated state, wherein they showed increased expression of the M1-related markers HLA-DR and CD86, as well as of Fc␥RI, which mediates effector responses to therapeutic antibodies. Importantly, IFN␥ was able to up-regulate CD38, the target of the therapeutic antibody daratumumab. Because the antigen (CD38) and effector receptor (Fc␥RI) were both simultaneously up-regulated on the AML blasts, we tested whether IFN␥ treatment of the AML cell lines THP-1 and MV4-11 could stimulate them to target one another after the addition of daratumumab. Results showed that IFN␥ significantly increased daratumumab-mediated cytotoxicity, as measured both by 51 Cr release and lactate dehydrogenase release assays. We also found that the combination of IFN␥ and activation of Fc␥R led to the release of granzyme B by AML cells. Finally, using a murine NSG model of subcutaneous AML, we found that treatment with IFN␥ plus daratumumab significantly attenuated tumor growth. Taken together, these studies show a novel mechanism of daratumumab-mediated killing and a possible new therapeutic strategy for AML.
Acute myeloid leukemia (AML) remains a significant health problem, with poor outcomes despite chemotherapy and bone marrow transplants. Although one form of AML, acute promyelocytic leukemia (APL), is successfully treated with all-trans retinoic acid (ATRA), this drug is seemingly ineffective against all other forms of AML. Here, we show that ATRA up-regulates CD38 expression on AML blasts to sufficient levels that promote antibody-mediated fratricide following the addition of anti-CD38 daratumumab (DARA). The combination of ATRA plus DARA induced Fc-dependent conjugate formation and cytotoxicity among AML blasts in vitro. Combination treatment also led to reduction in tumor volume and resulted in increased overall survival in murine engraftment models of AML. These results suggest that, although ATRA does not induce differentiation of non-APL, it may be effective as a therapy in conjunction with DARA.
TLRs, a family of membrane-bound pattern recognition receptors found on innate immune cells, have been well studied in the context of cancer therapy. Activation of these receptors has been shown to induce inflammatory anticancer events, including differentiation and apoptosis, across a wide variety of malignancies. In contrast, intracellular pattern recognition receptors such as NOD-like receptors have been minimally studied. NOD2 is a member of the NOD-like receptor family that initiates inflammatory signaling in response to the bacterial motif muramyl dipeptide. In this study, we examined the influence of NOD2 in human acute myeloid leukemia (AML) cells, demonstrating that IFN-g treatment upregulated the expression of NOD2 signaling pathway members SLC15A3 and SLC15A4, downstream signaling kinase RIPK2, and the NOD2 receptor itself. This priming allowed for effective induction of caspase-1-dependent cell death upon treatment with muramyl tripeptide phosphatidylethanolamine (MTP-PE), a synthetic ligand for NOD2. Furthermore, the combination of MTP-PE and IFN-g on AML blasts generated an inflammatory cytokine profile and activated NK cells. In a murine model of AML, dual treatment with MTP-PE and IFN-g led to a significant increase in mature CD27 2 CD11b + NK cells as well as a significant reduction in disease burden and extended survival. These results suggest that NOD2 activation, primed by IFN-g, may provide a novel therapeutic option for AML.
Monocytes and macrophages express FcgR that engage IgG immune complexes such as Ab-opsonized pathogens or cancer cells to destroy them by various mechanisms, including phagocytosis. FcgR-mediated phagocytosis is regulated by the concerted actions of activating FcgR and inhibitory receptors, such as FcgRIIb and SIRPa. In this study, we report that another ITIM-containing receptor, PECAM1/CD31, regulates FcgR function and is itself regulated by FcgR activation. First, quantitative RT-PCR and flow cytometry analyses revealed that human monocyte FcgR activation leads to a significant downregulation of CD31 expression, both at the message level and at surface expression, mainly mediated through FcgRIIa. Interestingly, the kinetics of downregulation between the two varied, with surface expression reducing earlier than the message. Experiments to analyze the mechanism behind this discrepancy revealed that the loss of surface expression was because of internalization, which depended predominantly on the PI3 kinase pathway and was independent of FcgR internalization. Finally, functional analyses showed that the downregulation of CD31 expression in monocytes by small interfering RNA enhanced FcgR-mediated phagocytic ability but have little effect on cytokine production. Together, these results suggest that CD31 acts as a checkpoint receptor that could be targeted to enhance FcgR functions in Ab-mediated therapies.
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