VSIG4 interaction with heparan sulfates inhibits VSIG4-complement binding.

V-set and immunoglobulin domain-containing 4 (VSIG4) is a complement receptor of the immunoglobulin superfamily that is specifically expressed on tissue resident macrophages, and its many reported functions and binding partners suggest a complex role in immune function. VSIG4 is reported to have a role in immune surveillance as well as in modulating diverse disease phenotypes such as infections, autoimmune conditions, and cancer. However, the mechanism(s) governing VSIG4's complex, context-dependent role in immune regulation remains elusive. Here, we identify cell surface and soluble glycosaminoglycans, specifically heparan sulfates, as novel binding partners of VSIG4. We demonstrate that genetic deletion of heparan sulfate synthesis enzymes or cleavage of cell-surface heparan sulfates reduced VSIG4 binding to the cell surface. Furthermore, binding studies demonstrate that VSIG4 interacts directly with heparan sulfates, with a preference for highly sulfated moieties and longer glycosaminoglycan chains. To assess the impact on VSIG4 biology, we show that heparan sulfates compete with known VSIG4 binding partners C3b and iC3b. Furthermore, mutagenesis studies indicate that this competition occurs through overlapping binding epitopes for heparan sulfates and complement on VSIG4. Together these data suggest a novel role for heparan sulfates in VSIG4-dependent immune modulation.

CD22-targeted CD28 bispecific antibody enhances antitumor efficacy of odronextamab in refractory diffuse large B cell lymphoma models.

Although many patients with diffuse large B cell lymphoma (DLBCL) may achieve a complete response to frontline chemoimmunotherapy, patients with relapsed/refractory disease typically have poor outcomes. Odronextamab, a CD20xCD3 bispecific antibody that provides "signal 1" through the activation of the T cell receptor/CD3 complex, has exhibited early, promising activity for patients with highly refractory DLBCL in phase 1 trials. However, not all patients achieve complete responses, and many relapse, thus representing a high unmet medical need. Here, we investigated whether adding a costimulatory "signal 2" by engaging CD28 receptors on T cells could augment odronextamab activity. We demonstrate that REGN5837, a bispecific antibody that cross-links CD22-expressing tumor cells with CD28-expressing T cells, enhances odronextamab by potentiating T cell activation and cytolytic function. In preclinical DLBCL studies using human immune system-reconstituted animals, REGN5837 promotes the antitumor activity of odronextamab and induces intratumoral expansion of reprogrammable T cells while skewing away from a dysfunctional state. Although REGN5837 monotherapy shows limited activity and no toxicity in primate studies, it augments T cell activation when dosed in combination with odronextamab. In addition, analysis of non-Hodgkin lymphoma clinical samples reveals an increase in CD28+CD8+ T cells after odronextamab treatment, demonstrating the presence of a population that could potentially be targeted by REGN5837. Collectively, our data demonstrate that REGN5837 can markedly enhance the antitumor activity of odronextamab in preclinical NHL models, and the combination of these two bispecific antibodies may provide a chemotherapy-free approach for the treatment of DLBCL.

Sequence of αPD-1 relative to local tumor irradiation determines the induction of abscopal antitumor immune responses.

Although radiotherapy has been used for over a century to locally control tumor growth, alone it rarely induces an abscopal response or systemic antitumor immunity capable of inhibiting distal tumors outside of the irradiation field. Results from recent studies suggest that combining immune checkpoint blockades to radiotherapy may enhance abscopal activity. However, the treatment conditions and underlying immune mechanisms that consistently drive an abscopal response during radiation therapy combinations remain unknown. Here, we analyzed the antitumor responses at primary and distal tumor sites, demonstrating that the timing of αPD-1 antibody administration relative to radiotherapy determined the potency of the induced abscopal response. Blockade of the PD-1 pathway after local tumor irradiation resulted in the expansion of polyfunctional intratumoral CD8+ T cells, a decrease in intratumoral dysfunctional CD8+ T cells, expansion of reprogrammable CD8+ T cells, and induction of potent abscopal responses. However, administration of αPD-1 before irradiation almost completely abrogated systemic immunity, which associated with increased radiosensitivity and death of CD8+ T cells. The subsequent reduction of polyfunctional effector CD8+ T cells at the irradiated tumor site generated a suboptimal systemic antitumor response and the loss of abscopal responses. Therefore, this report maximizes the potential synergy between radiotherapy and αPD-1 immunotherapy, information that will benefit clinical combinations of radiotherapy and immune checkpoint blockade.

Combination cancer immunotherapy targeting PD-1 and GITR can rescue CD8+ T cell dysfunction and maintain memory phenotype.

Most patients with cancer do not develop durable antitumor responses after programmed cell death protein 1 (PD-1) or programmed cell death ligand 1(PD-L1) checkpoint inhibition monotherapy because of an ephemeral reversal of T cell dysfunction and failure to promote long-lasting immunological T cell memory. Activating costimulatory pathways to induce stronger T cell activation may improve the efficacy of checkpoint inhibition and lead to durable antitumor responses. We performed single-cell RNA sequencing of more than 2000 tumor-infiltrating CD8+ T cells in mice receiving both PD-1 and GITR (glucocorticoid-induced tumor necrosis factor receptor-related protein) antibodies and found that this combination synergistically enhanced the effector function of expanded CD8+ T cells by restoring the balance of key homeostatic regulators CD226 and T cell immunoreceptor with Ig and ITIM domains (TIGIT), leading to a robust survival benefit. Combination therapy decreased CD8+ T cell dysfunction and induced a highly proliferative precursor effector memory T cell phenotype in a CD226-dependent manner. PD-1 inhibition rescued CD226 activity by preventing PD-1-Src homology region 2 (SHP2) dephosphophorylation of the CD226 intracellular domain, whereas GITR agonism decreased TIGIT expression. Unmasking the molecular pathways driving durable antitumor responses will be essential to the development of rational approaches to optimizing cancer immunotherapy.

Ablation of B7-H3 but Not B7-H4 Results in Highly Increased Tumor Burden in a Murine Model of Spontaneous Prostate Cancer.

The costimulatory molecules B7-H3 and B7-H4 are overexpressed in a variety of human tumors and have been hypothesized as possible biomarkers and immunotherapeutic targets. Despite this potential, the predominating uncertainty about their functional implication in tumor-host interaction hampers their evaluation as a target for cancer therapy. By means of a highly physiologic, spontaneous tumor model in mice, we establish a causal link between B7-H3 and host tumor control and found B7-H4 to be redundant.

B7x in the periphery abrogates pancreas-specific damage mediated by self-reactive CD8 T cells.

B7x (B7-H4 or B7S1) is the seventh member of the B7 family, and its in vivo function remains largely unknown. Despite new genetic data linking the B7x gene with autoimmune diseases, how exactly it contributes to peripheral tolerance and autoimmunity is unclear. In this study, we showed that B7x protein was not detected on APCs or T cells in both human and mice, which is unique in the B7 family. Because B7x protein is expressed in some peripheral cells such as pancreatic ß cells, we used a CD8 T cell-mediated diabetes model (AI4αß) in which CD8 T cells recognize an endogenous self-Ag, and found that mice lacking B7x developed more severe diabetes than control AI4αß mice. Conversely, mice overexpressing B7x in the ß cells (Rip-B7xAI4αß) were diabetes free. Furthermore, adoptive transfer of effector AI4αß CD8 T cells induced diabetes in control mice, but not in Rip-B7xAI4αß mice. Mechanistic studies revealed that pathogenic effector CD8 T cells were capable of migrating to the pancreas but failed to robustly destroy tissue when encountering local B7x in Rip-B7xAI4αß mice. Although AI4αß CD8 T cells in Rip-B7xAI4αß and AI4αß mice showed similar cytotoxic function, cell death, and global gene expression profiles, these cells had greater proliferation in AI4αß mice than in RIP-B7xAI4αß mice. These results suggest that B7x in nonlymphoid organs prevents peripheral autoimmunity partially through inhibiting proliferation of tissue-specific CD8 T cells, and that local overexpression of B7x on pancreatic ß cells is sufficient to abolish CD8 T cell-induced diabetes.

Tissue-specific expression of B7x protects from CD4 T cell-mediated autoimmunity.

B7x, an inhibitory member of the B7/CD28 superfamily, is highly expressed in a broad range of nonhematopoietic organs, suggesting a role in maintaining peripheral tolerance. As endogenous B7x protein is expressed in pancreatic islets, we investigated whether the molecule inhibits diabetogenic responses. Transfer of disease-inducing BDC2.5 T cells into B7x-deficient mice resulted in a more aggressive form of diabetes than in wild-type animals. This exacerbation of disease correlated with higher frequencies of islet-infiltrating Th1 and Th17 cells. Conversely, local B7x overexpression inhibited the development of autoimmunity, as crossing diabetes-susceptible BDC2.5/B6(g7) mice to animals overexpressing B7x in pancreatic islets abrogated disease induction. This protection was caused by the inhibition of IFN-γ production by CD4 T cells and not to a skewing or expansion of Th2 or regulatory T cells. The suppressive function of B7x was also supported by observations from another autoimmune model, experimental autoimmune encephalomyelitis, in which B7x-deficient mice developed exacerbated disease in comparison with wild-type animals. Analysis of central nervous system-infiltrating immune cells revealed that the loss of endogenous B7x resulted in expanded Th1 and Th17 responses. Data from these two autoimmune models provide evidence that B7x expression in the periphery acts as an immune checkpoint to prevent tissue-specific autoimmunity.

Tumor associated endothelial expression of B7-H3 predicts survival in ovarian carcinomas.

B7-H3 and B7x are members of the B7 family of immune regulatory ligands that are thought to attenuate peripheral immune responses through co-inhibition. Previous studies have correlated their overexpression with poor prognosis and decreased tumor-infiltrating lymphocytes in various carcinomas including uterine endometrioid carcinomas, and mounting evidence supports an immuno-inhibitory role in ovarian cancer prognosis. We sought to examine the expression of B7-H3 and B7x in 103 ovarian borderline tumors and carcinomas and study associations with clinical outcome. Using immunohistochemical tissue microarray analysis on tumor specimens, we found that 93 and 100% of these ovarian tumors express B7-H3 and B7x, respectively, with expression found predominantly on cell membranes and in cytoplasm. In contrast, only scattered B7-H3- and B7x-positive cells were detected in non-neoplastic ovarian tissues. B7-H3 was also expressed in the endothelium of tumor-associated vasculature in 44% of patients, including 78% of patients with high-stage tumors (FIGO stages III and IV), nearly all of which were high-grade serous carcinomas, and 26% of patients with low-stage tumors (FIGO stages I and II; P<0.001), including borderline tumors. Analysis of cumulative survival time and recurrence incidence revealed that carcinomas with B7-H3-positive tumor vasculature were associated with a significantly shorter survival time (P=0.02) and a higher incidence of recurrence (P=0.03). The association between B7-H3-positive tumor vasculature and poor clinical outcome remained significant even when the analysis was limited to the high-stage subgroup. These results show that ovarian borderline tumors and carcinomas aberrantly express B7-H3 and B7x, and that B7-H3-positive tumor vasculature is associated with high-grade serous histological subtype, increased recurrence and reduced survival. B7-H3 expression in tumor vasculature may be a reflection of tumor aggressiveness and has diagnostic and immunotherapeutic implications in ovarian carcinomas.

In silico and in vivo approach to elucidate the inflammatory complexity of CD14-deficient mice.

The inflammatory phenotype of genetically modified mice is complex, and the role of Gram-negative lipopolysaccharide (LPS) in acute inflammation induced by surgical cannulation trauma, alone or in combination with hemorrhage and resuscitation ("hemorrhagic shock"), is both complex and controversial. We sought to determine if a mathematical model of acute inflammation could elucidate both the phenotype of CD14-deficient (CD14(-/-)) mice--following LPS, cannulation, or hemorrhagic shock--and the role of LPS in trauma/hemorrhage-induced inflammation. A mathematical model of inflammation initially calibrated in wild-type (C57Bl/6) mice subjected to LPS, cannulation, and hemorrhagic shock was recalibrated in CD14(-/-) mice subjected to the same insults, yielding an ensemble of models that suggested specific differences at the cellular and molecular levels (for example, 43-fold lower activation of leukocytes by LPS). The CD14(-/-)-specific model ensemble could account for complex changes in inflammatory analytes in these mice following LPS treatment. Model prediction of similar organ damage in CD14(-/-) and wild-type mice subjected to cannulation alone or with hemorrhagic shock was verified in vivo (similar ALT levels). These studies suggest that LPS-CD14 responses do not cause inflammation in surgical trauma/hemorrhagic shock and demonstrate a novel use of combined in silico and in vivo methods to elucidate the complex inflammatory phenotype of genetically modified animals.

Myc-interacting protein 1 target gene profile: a link to microtubules, extracellular signal-regulated kinase, and cell growth.

To study the role of the transcription factor Myc-interacting protein 1 (MIZ-1) in activating various target genes after induction with the microtubule disrupting agent T113242, we have used small interfering RNA duplexes (siRNAs) to knockdown the expression of MIZ-1. As expected, depletion of MIZ-1 resulted in the inhibition of T113242-dependent activation of the low-density lipoprotein receptor (LDLR) gene in hepatocytes. Cells transfected with MIZ-1 siRNAs also exhibited growth arrest. In addition, inhibition of the extracellular signal-regulated kinase (ERK) pathway inhibited T113242-induced nuclear accumulation of MIZ-1 and activation of LDLR. Gene expression microarray analysis under various induction conditions identified other T113242-activated genes affected by a decrease in MIZ-1 and inhibition of the ERK pathway. We also found that the accumulation of MIZ-1 in the nucleus is influenced by cell-cell contact and/or growth. Taken together, our studies suggest that MIZ-1 regulates a specific set of genes that includes LDLR and that the ERK pathway plays a role in the activation of target promoters by MIZ-1.