The interaction of the MHC class I-related chain molecules A and B (MICA and MICB) and UL-16 binding protein (ULBP) family members expressed on tumor cells with the corresponding NKG2D receptor triggers cytotoxic effector functions in NK cells and γδ T cells. However, as a mechanism of tumor immune escape, NKG2D ligands (NKG2DLs) can be released from the cell surface. In this study, we investigated the NKG2DL system in different human glioblastoma (GBM) cell lines, the most lethal brain tumor in adults. Flow cytometric analysis and ELISA revealed that despite the expression of various NKG2DLs only ULBP2 is released as a soluble protein via the proteolytic activity of "a disintegrin and metalloproteases" (ADAM) 10 and 17. Moreover, we report that temozolomide (TMZ), a chemotherapeutic agent in clinical use for the treatment of GBM, increases the cell surface expression of NKG2DLs and sensitizes GBM cells to γδ T cell-mediated lysis. Both NKG2D and the T-cell receptor (TCR) are involved. The cytotoxic activity of γδ T cells toward GBM cells is strongly enhanced in a TCR-dependent manner by stimulation with pyrophosphate antigens. These data clearly demonstrate the complexity of mechanisms regulating NKG2DL expression in GBM cells and further show that treatment with TMZ can increase the immunogenicity of GBM. Thus, TMZ might enhance the potential of the adoptive transfer of ex vivo expanded γδ T cells for the treatment of malignant glioblastoma.
Abstract Tumor necrosis factor (TNF) is a key inflammatory cytokine that warns recipient cells of a nearby infection or tissue damage. Acute exposure to TNF activates characteristic oscillatory dynamics of the transcription factor NFκB and induces a characteristic gene expression program; these are distinct from the responses of cells directly exposed to pathogen‐associated molecular patterns (PAMPs). Here, we report that tonic TNF exposure is critical for safeguarding TNF's specific functions. In the absence of tonic TNF conditioning, acute exposure to TNF causes (i) NFκB signaling dynamics that are less oscillatory and more like PAMP‐responsive NFκB dynamics, (ii) immune gene expression that is more similar to the Pam3CSK4 response program, and (iii) broader epigenomic reprogramming that is characteristic of PAMP‐responsive changes. We show that the absence of tonic TNF signaling effects subtle changes to TNF receptor availability and dynamics such that enhanced pathway activity results in non‐oscillatory NFκB. Our results reveal tonic TNF as a key tissue determinant of the specific cellular responses to acute paracrine TNF exposure, and their distinction from responses to direct exposure to PAMPs.
Inflammatory pathologies often involve dysregulated macrophage functions. In health, macrophages are immune sentinels that initiate inflammatory responses via the transcription factor NFkB. The temporal pattern of NFkB activity determines which genes are expressed, but how such temporal signaling code works in primary immune cells remains unexplored. For this study, we developed tools to enable high-throughput analysis of live, primary macrophages responding to host- and pathogen-derived stimuli. An information-theoretic workflow identified six dynamical features that constitute codewords that convey stimulus information to the nucleus. In particular, oscillatory trajectories are a hallmark of the responses to host cytokine TNF. Remarkably, examining macrophages derived from a systemic autoimmune disease model suggests that confusion of two NFkB signaling codewords, and thus miscoding of TNF as a pathogen-derived stimulus, may underlie sporadic inflammatory pathology. Overall, this study identifies six codewords of the temporal NFkB signaling code for classifying immune threats and demonstrates their biological significance.
Abstract Acute and chronic inflammatory pathologies involve misregulation of macrophage functions. Physiologically, macrophages are immune sentinels that initiate inflammatory responses via the transcription factor NFκB. The temporal pattern of NFκB activity determines which genes are expressed, suggesting that a temporal signaling code specifies a stimulus-appropriate immune response. To identify the signaling codewords, we developed tools to enable high-throughput analysis of live, primary macrophages responding to host- and pathogen-derived stimuli. An information-theoretic workflow identified six dynamical features that constitute codewords that convey stimulus information to the nucleus. In particular, “oscillatory” trajectories are a hallmark of the responses to host cytokine TNF. Remarkably, examining macrophages derived from a systemic autoimmune disease model suggests that confusion of two NFκB signaling codewords, and thus miscoding of TNF as a pathogen-derived stimulus, may underlie sporadic inflammatory pathology. Overall, this study identifies six codewords of the temporal NFκB signaling code for classifying immune threats and demonstrates their biological significance.
Dataset (.mat structure) containing single cell p38 and NFkB activity dynamics in macrophages (iMPDMs) upon innate immune stimulation (LPS, TNF, P3C4, CpG) (1 h baseline + app 8 h stimulation). Two biological replicates per stimulation condition are included. 6 doses per stimulus are included. Signaling dynamics are quantified using live cell microscopy followed by automated image analysis by MACKtrack. Datasets include dynamic features ('metrics'), MACKtrack quantification outputs ('measure'), info on experimental (esp. dose), tracking, and quantification parameters, and filtering outcomes ('info').
Despite aggressive treatment regimens based on surgery and radiochemotherapy, the prognosis of patients with grade IV glioblastoma multiforme (GBM) remains extremely poor, calling for alternative options such as immunotherapy. Immunological mechanisms including the Natural Killer Group 2 member D (NKG2D) receptor-ligand system play an important role in tumor immune surveillance and targeting the NKG2D system might be beneficial. However, before considering any kind of immunotherapy, a precise characterization of the immune system is important, particularly in GBM patients where conventional therapies with impact on the immune system are frequently co-administered. Here we performed an in-depth immunophenotyping of GBM patients and age-matched healthy controls and analyzed NKG2D ligand expression on primary GBM cells ex vivo. We report that GBM patients have a compromised innate immune system irrespective of steroid (dexamethasone) medication. However, dexamethasone drastically reduced the number of immune cells in the blood of GBM patients. Moreover, higher counts of immune cells influenced by dexamethasone like CD45+ lymphocytes and non-Vδ2 γδ T cells were associated with better overall survival. Higher levels of NKG2D ligands on primary GBM tumor cells were observed in patients who received radiochemotherapy, pointing towards increased immunogenic potential of GBM cells following standard radiochemotherapy. This study sheds light on how steroids and radiochemotherapy affect immune cell parameters of GBM patients, a pre-requisite for the development of new therapeutic strategies targeting the immune system in these patients.
Incoming viruses challenge the cell with diverse foreign molecules, which need to be sensed quickly to initiate immune responses and to remove the viral components. In this study, we investigate the cellular requirements for sensing and degradation of incoming viral DNA and capsids during herpes simplex virus type 1 (HSV-1) infections. Using click chemistry labeling of the viral genome, we found that HSV-1 DNA was released from a subset of capsids into the cytosol early in infection. By next-generation sequencing of cyclic GMP-AMP (cGAMP) synthase (cGAS)-bound DNA from HSV-1-infected cells, we show that HSV-1 DNA was bound by the cytosolic DNA sensor cGAS. Activation of cGAS enzymatic activity by viral DNA did not require proteasomal activity, indicating that viral DNA release into the cytosol is not proteasome-dependent. However, induction of interferon (IFN)-β expression was blocked by inhibition of the proteasome, suggesting a contribution of the proteasome to IFN-β induction through the cGAS-stimulator of interferon genes pathway. Viral DNA was cleared from the cytosol within few hours, in a manner dependent on TREX1 and a cGAS-dependent process. Capsid material in the cytoplasm was also degraded rapidly. This was partially blocked by treatment with a proteasome inhibitor. This treatment led to accumulation of DNA-containing viral capsids near the nucleus and reduced nuclear entry of viral DNA. Thus, cells infected with HSV-1 use a panel of mechanisms to eliminate viral DNA and capsids. This represents a barrier for establishment of infection and potentially enables the host to gear the IFN-β response to a level required for antiviral defense without causing immunopathology.
