The hypoxic response in cells and tissues is mediated by the family of hypoxia-inducible factor (HIF) transcription factors; these play an integral role in the metabolic changes that drive cellular ...adaptation to low oxygen availability. HIF expression and stabilization in immune cells can be triggered by hypoxia, but also by other factors associated with pathological stress: e.g., inflammation, infectious microorganisms, and cancer. HIF induces a number of aspects of host immune function, from boosting phagocyte microbicidal capacity to driving T cell differentiation and cytotoxic activity. Cellular metabolism is emerging as a key regulator of immunity, and it constitutes another layer of fine-tuned immune control by HIF that can dictate myeloid cell and lymphocyte development, fate, and function. Here we discuss how oxygen sensing in the immune microenvironment shapes immunological response and examine how HIF and the hypoxia pathway control innate and adaptive immunity.
Hypoxia-inducible factor (HIF) transcription factors can be triggered by hypoxia and by other factors associated with pathological stress. Johnson and colleagues review the role of HIF and other key players in the hypoxic response in the control of innate and adaptive immunity.
Chimeric antigen receptor (CAR) T cell therapies have demonstrated remarkable efficacy for the treatment of hematological malignancies. However, in patients with solid tumors, objective responses to ...CAR-T cell therapy remain sporadic and transient. A major obstacle for CAR-T cells is the intrinsic ability of tumors to evade immune responses. Advanced solid tumors are largely composed of desmoplastic stroma and immunosuppressive modulators, and characterized by aberrant cell proliferation and vascularization, resulting in hypoxia and altered nutrient availability. To mount a curative response after infusion, CAR-T cells must infiltrate the tumor, recognize their cognate antigen and perform their effector function in this hostile tumor microenvironment, to then differentiate and persist as memory T cells that confer long-term protection. Fortunately, recent advances in synthetic biology provide a wide set of tools to genetically modify CAR-T cells to overcome some of these obstacles. In this review, we provide a comprehensive overview of the key tumor intrinsic mechanisms that prevent an effective CAR-T cell antitumor response and we discuss the most promising strategies to prevent tumor escape to CAR-T cell therapy.
Sialic acid-binding Ig-like lectin 15 (Siglec-15) is an immune modulator and emerging cancer immunotherapy target. However, limited understanding of its structure and mechanism of action restrains ...the development of drug candidates that unleash its full therapeutic potential. In this study, we elucidate the crystal structure of Siglec-15 and its binding epitope via co-crystallization with an anti-Siglec-15 blocking antibody. Using saturation transfer-difference nuclear magnetic resonance (STD-NMR) spectroscopy and molecular dynamics simulations, we reveal Siglec-15 binding mode to α(2,3)- and α(2,6)-linked sialic acids and the cancer-associated sialyl-Tn (STn) glycoform. We demonstrate that binding of Siglec-15 to T cells, which lack STn expression, depends on the presence of α(2,3)- and α(2,6)-linked sialoglycans. Furthermore, we identify the leukocyte integrin CD11b as a Siglec-15 binding partner on human T cells. Collectively, our findings provide an integrated understanding of the structural features of Siglec-15 and emphasize glycosylation as a crucial factor in controlling T cell responses.
2-Hydroxyglutarate (2HG) is a byproduct of the tricarboxylic acid (TCA) cycle and is readily detected in the tissues of healthy individuals. 2HG is found in two enantiomeric forms: S-2HG and R-2HG. ...Here, we investigate the differential roles of these two enantiomers in cluster of differentiation (CD)8+ T cell biology, where we find they have highly divergent effects on proliferation, differentiation, and T cell function. We show here an analysis of structural determinants that likely underlie these differential effects on specific α-ketoglutarate (αKG)-dependent enzymes. Treatment of CD8+ T cells with exogenous S-2HG, but not R-2HG, increased CD8+ T cell fitness in vivo and enhanced anti-tumor activity. These data show that S-2HG and R-2HG should be considered as two distinct and important actors in the regulation of T cell function.
Display omitted
•Octyl-ester S-2HG and R-2HG differentially modulate CD8+ T cell differentiation•S-2HG and R-2HG have different inhibitory potencies against aKG-dependent enzymes•CD8+ T cells pre-treated with octyl-ester S-2HG have enhanced anti-tumor activity
Foskolou et al. show that the enantiomeric forms S-2HG and R-2HG have distinct functions in CD8+ T proliferation, differentiation, and function. Treatment of CD8+ T cells with exogenous cell-permeable S-2HG, but not R-2HG, increased CD8+ T cell fitness in vivo and enhanced anti-tumor activity.
The syndecan (Sdc) family is comprised of four members of cell surface molecules (Sdc-1 to 4) with different biological functions. Syndecan-3 (Sdc-3) is known to be mainly expressed in the brain and ...nervous tissue and plays a key role in development, cell adhesion, and migration. Recent studies point to important roles for Sdc-3 in inflammatory disease, but the patterns of expression and significance of Sdc-3 in cancer remains unexplored. Here we show that Sdc-3 expression is upregulated on several cancer types, especially in solid tumors that are known to be hypoxic. The Cancer Genome Atlas program (TCGA) data demonstrated that Sdc-3 expression in the tumor microenvironment positively correlates with a hypoxia gene signature. To confirm a potential cause-effect, we performed experiments with tumor cell lines showing increased expression upon
exposure to 1% oxygen or dimethyloxalylglycine, an inhibitor of prolyl hydroxylases, indicating that Sdc-3 expression is promoted by hypoxia inducible factors (HIFs). HIF-1α was responsible for this upregulation as confirmed by CRISPR-engineered tumor cells. Using single-cell RNA sequencing data of melanoma patients, we show that Sdc-3 is expressed on tumor associated macrophages, cancer cells, and endothelial cells. Syndecan-3 expression positively correlated with a macrophage gene signature across several TCGA cancer types.
experiments demonstrated that hypoxia (1% oxygen) or treatment with IFN-γ stimulate Sdc-3 expression on RAW-264.7 derived macrophages, linking Sdc-3 expression to a proinflammatory response. Syndecan-3 expression correlates with a better patient overall survival in hypoxic melanoma tumors.
Immunological therapy of progressive tumors requires not only activation and expansion of tumor specific cytotoxic T lymphocytes (CTLs), but also an efficient effector phase including migration of ...CTLs in the tumor tissue followed by conjugation and killing of target cells. We report the application of an agent-based model to recapitulate both the effect of a specific immunotherapy strategy against B16-melanoma in mice and the tumor progression in a generic tissue section. A comparison of the in silico results with the in vivo experiments shows excellent agreement. We therefore use the model to predict a critical role for CD137 expression on tumor vessel endothelium for successful therapy and other mechanistic aspects. Experimental results are fully compatible with the model predictions. The biologically oriented in silico model derived in this work will be used to predict treatment failure or success in other pre-clinical conditions eventually leading new promising in vivo experiments.
Two years after its emergence, the coronavirus disease-2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) remains difficult to control despite the ...availability of several vaccines. The extensively glycosylated SARS-CoV-2 spike (S) protein, which mediates host cell entry by binding to the angiotensin converting enzyme 2 (ACE2) through its receptor binding domain (RBD), is the major target of neutralizing antibodies. Like to many other viral fusion proteins, the SARS-CoV-2 spike protein utilizes a glycan shield to thwart the host immune response. To grasp the influence of chemical signatures on carbohydrate mobility and reconcile the cryo-EM density of specific glycans we combined our cryo-EM map of the S ectodomain to 4.1 Å resolution, reconstructed from a limited number of particles, and all-atom molecular dynamics simulations. Chemical modifications modeled on representative glycans (defucosylation, sialylation and addition of terminal LacNAc units) show no significant influence on either protein shielding or glycan flexibility. By estimating at selected sites the local correlation between the full density map and atomic model-based maps derived from molecular dynamics simulations, we provide insight into the geometries of the α-Man-(1→3)-α-Man-(1→6)--β-Man-(1→4)-β-GlcNAc(1→4)-β-GlcNAc core common to all
-glycosylation sites.
In vitro assays that evaluate CD8
+
T cell-mediated cytotoxicity are important to aid in the development of novel therapeutic approaches to enhance anti-tumor immune responses. Here, we describe a ...novel cytotoxicity co-culture assay that circumvents the problem of highly variable allogeneic responses and obviates the constraints of HLA-restriction between effector and target cells. We show that this assay can be easily applied to a panel of tumor cell lines to provide additional insights into intrinsic drivers of sensitivity/resistance to T cell-mediated killing, and to evaluate the impact of targeted therapies on both tumor and T cell compartments.
A main clinical parameter of COVID-19 pathophysiology is hypoxia. Here we show that hypoxia decreases the attachment of the receptor-binding domain (RBD) and the S1 subunit (S1) of the spike protein ...of SARS-CoV-2 to epithelial cells. In Vero E6 cells, hypoxia reduces the protein levels of ACE2 and neuropilin-1 (NRP1), which might in part explain the observed reduction of the infection rate. In addition, hypoxia inhibits the binding of the spike to NCI-H460 human lung epithelial cells by decreasing the cell surface levels of heparan sulfate (HS), a known attachment receptor of SARS-CoV-2. This interaction is also reduced by lactoferrin, a glycoprotein that blocks HS moieties on the cell surface. The expression of syndecan-1, an HS-containing proteoglycan expressed in lung, is inhibited by hypoxia on a HIF-1α-dependent manner. Hypoxia or deletion of syndecan-1 results in reduced binding of the RBD to host cells. Our study indicates that hypoxia acts to prevent SARS-CoV-2 infection, suggesting that the hypoxia signalling pathway might offer therapeutic opportunities for the treatment of COVID-19.
Covalent and reversible post-translational modifications of proteins are a common theme in signaling. Ubiquitin conjugation was originally described to target proteins to proteasomal degradation by ...ubiquitin polymerization involving lysine (K) 48 residues. Differently linked polymers of polyubiquitin have been found that modify proteins without targeting to proteasomal degradation. Instead this pathway creates docking sites for signaling scaffolds that are key to control the nuclear factor-kappaB (NF-kappaB) pathway. Indeed TRAF-2, TRAF-6, and TRAF-3 are E3 ubiquitin ligases that form K63-linked ubiquitin polymers. Therefore signaling via TNF family receptors, IL1R, IL-18R, T-cell receptor (TCR), and Toll-like receptors (TLR) use this type of post-translational modification. Specific enzymes exist (DUBs) that deactivate this system, degrading K63 polyubiquitin chains. Interestingly, mice deficient in these deubiquitinases develop autoimmunity and inflammation. In carcinogenesis, the K63 polyubiquitin pathway is possibly critical for inflammation-driven tumor promotion. The pathway is also critically involved in costimulation of tumor immunity/immunotherapy as well as in the biology of malignant cells themselves. The elements of this new signaling paradigm offer the opportunity for therapeutic exploitation and drug discovery.
PDF
