PVRIG is expressed on stem-like T cells in dendritic cell-rich niches in tumors and its blockade may induce immune infiltration in non-inflamed tumors.

Cancers that are poorly immune infiltrated pose a substantial challenge, with current immunotherapies yielding limited clinical success. Stem-like memory T cells (TSCM) have been identified as a subgroup of T cells that possess strong proliferative capacity and that can expand and differentiate following interactions with dendritic cells (DCs). In this study, we explored the pattern of expression of a recently discovered inhibitory receptor PVRIG and its ligand, PVRL2, in the human tumor microenvironment. Using spatial and single-cell RNA transcriptomics data across diverse cancer indications, we found that among the T-cell checkpoints, PVRIG is uniquely expressed on TSCM and PVRL2 is expressed on DCs in immune aggregate niches in tumors. PVRIG blockade could therefore enhance TSCM-DC interactions and efficiently drive T-cell infiltration to tumors. Consistent with these data, following PVRIG blockade in patients with poorly infiltrated tumors, we observed immune modulation including increased tumor T-cell infiltration, T-cell receptor (TCR) clonality, and intratumoral T-cell expansion, all of which were associated with clinical benefit. These data suggest PVRIG blockade as a promising strategy to induce potent antitumor T-cell responses, providing a novel approach to overcome resistance to immunotherapy in immune-excluded tumors.

Characterization of BAY 1905254, an Immune Checkpoint Inhibitor Targeting the Immunoglobulin-Like Domain Containing Receptor 2 (ILDR2).

The immunoglobulin-like domain containing receptor 2 (ILDR2), a type I transmembrane protein belonging to the B7 family of immunomodulatory receptors, has been described to induce an immunosuppressive effect on T-cell responses. Besides its expression in several nonlymphoid tissue types, we found that ILDR2 was also expressed in fibroblastic reticular cells (FRC) in the stromal part of the lymph node. These immunoregulatory cells were located in the T-cell zone and were essential for the recruitment of naïve T cells and activated dendritic cells to the lymph nodes. Previously, it has been shown that an ILDR2-Fc fusion protein exhibits immunomodulatory effects in several models of autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, and type I diabetes. Herein, we report the generation and characterization of a human/mouse/monkey cross-reactive anti-ILDR2 hIgG2 antibody, BAY 1905254, developed to block the immunosuppressive activity of ILDR2 for cancer immunotherapy. BAY 1905254 was shown to promote T-cell activation in vitro and enhance antigen-specific T-cell proliferation and cytotoxicity in vivo in mice. BAY 1905254 also showed potent efficacy in various syngeneic mouse cancer models, and the efficacy was found to correlate with increasing mutational load in the cancer models used. Additive or even synergistic antitumor effects were observed when BAY 1905254 was administered in combination with anti-PD-L1, an immunogenic cell death-inducing chemotherapeutic, or with tumor antigen immunization. Taken together, our data showed that BAY 1905254 is a potential drug candidate for cancer immunotherapy, supporting its further evaluation.

ILDR2 Is a Novel B7-like Protein That Negatively Regulates T Cell Responses.

The B7-like protein family members play critical immunomodulatory roles and constitute attractive targets for the development of novel therapies for human diseases. We identified Ig-like domain-containing receptor (ILDR)2 as a novel B7-like protein with robust T cell inhibitory activity, expressed in immune cells and in immune-privileged and inflamed tissues. A fusion protein, consisting of ILDR2 extracellular domain with an Fc fragment, that binds to a putative counterpart on activated T cells showed a beneficial effect in the collagen-induced arthritis model and abrogated the production of proinflammatory cytokines and chemokines in autologous synovial-like cocultures of macrophages and cytokine-stimulated T cells. Collectively, these findings point to ILDR2 as a novel negative regulator for T cells, with potential roles in the development of immune-related diseases, including autoimmunity and cancer.

The interaction of TIGIT with PVR and PVRL2 inhibits human NK cell cytotoxicity.

NK cell cytotoxicity is controlled by numerous NK inhibitory and activating receptors. Most of the inhibitory receptors bind MHC class I proteins and are expressed in a variegated fashion. It was recently shown that TIGIT, a new protein expressed by T and NK cells binds to PVR and PVR-like receptors and inhibits T cell activity indirectly through the manipulation of DC activity. Here, we show that TIGIT is expressed by all human NK cells, that it binds PVR and PVRL2 but not PVRL3 and that it inhibits NK cytotoxicity directly through its ITIM. Finally, we show that TIGIT counter inhibits the NK-mediated killing of tumor cells and protects normal cells from NK-mediated cytotoxicity thus providing an "alternative self" mechanism for MHC class I inhibition.

Systematic antigenic profiling of hematopoietic antigens on ovarian carcinoma cells identifies membrane proteins for targeted therapy development.

OBJECTIVE: We studied ovarian cancers for the expression of membrane markers of hematopoietic origin. STUDY DESIGN: We used flow cytometry to systematically characterize the expression of more than 30 hematologic antigens on ovarian carcinoma cell lines and to assess their stability under estrogen exposure. The expression of the antigens was validated by a bioinformatics survey and immunohistochemical staining of ovarian cancer specimens. RESULTS: Several antigens were expressed by the majority of the cells, such as CD15, CD71, and CD138, whereas others were found on small and distinct cellular subpopulations. The expression patterns of the different markers were unaffected by estrogen exposure, indicating their stability. CONCLUSION: The antigens described in our work may serve as potential targets for new and existing targeted drugs.

Peptides modulating conformational changes in secreted chaperones: from in silico design to preclinical proof of concept.

Blocking conformational changes in biologically active proteins holds therapeutic promise. Inspired by the susceptibility of viral entry to inhibition by synthetic peptides that block the formation of helix-helix interactions in viral envelope proteins, we developed a computational approach for predicting interacting helices. Using this approach, which combines correlated mutations analysis and Fourier transform, we designed peptides that target gp96 and clusterin, 2 secreted chaperones known to shift between inactive and active conformations. In human blood mononuclear cells, the gp96-derived peptide inhibited the production of TNFalpha, IL-1beta, IL-6, and IL-8 induced by endotoxin by >80%. When injected into mice, the peptide reduced circulating levels of endotoxin-induced TNFalpha, IL-6, and IFNgamma by >50%. The clusterin-derived peptide arrested proliferation of several neoplastic cell lines, and significantly enhanced the cytostatic activity of taxol in vitro and in a xenograft model of lung cancer. Also, the predicted mode of action of the active peptides was experimentally verified. Both peptides bound to their parent proteins, and their biological activity was abolished in the presence of the peptides corresponding to the counterpart helices. These data demonstrate a previously uncharacterized method for rational design of protein antagonists.

Activation of relaxin-related receptors by short, linear peptides derived from a collagen-containing precursor.

In a screening effort based on algorithmic predictions for novel G-protein-coupled receptor (GPCR) peptide activators, we were able to identify and examine two novel peptides (P59 and P74) which are short, linear, and derived from a natural, previously unidentified precursor protein containing a collagen-like repeat. Both peptides seemed to show an apparent cAMP-related effect on CHO-K1 cells transiently transfected with either LGR7 or LGR8, usually after treatment with cAMP-generating forskolin, compared to the same cells treated with forskolin plus relaxin. This activation was not found for the relaxin-3 receptor (GPR135). In a set of follow-up experiments, both peptides were found to stimulate cAMP production, mostly upon initial stimulation of cAMP production by 5 micro M forskolin in cells transfected with either LGR7 or LGR8. In a dye-free cell impedance GPCR activation assay, we were able to show that these peptides were also able to activate a cellular response mediated by these receptors. Although untransfected CHO-K1 cells showed some cellular activation by both relaxin and at least one of our newly discovered peptides, both LGR7- and LGR8-transfected cells showed a stronger response, indicating stimulation of a cellular pathway through activation of these receptors. In conclusion, we were able to show that these newly discovered peptides, which have no similarity to any member of the relaxin-insulin-like peptide family, are potential ligands for the relaxin-related family of receptors and as such might serve as novel candidates for relaxin-related therapeutic indications. Both peptides are linear and were found to be active after being chemically synthesized.

Discovery and validation of novel peptide agonists for G-protein-coupled receptors.

G-protein-coupled receptors (GPCRs) represent an important group of targets for pharmaceutical therapeutics. The completion of the human genome revealed a large number of putative GPCRs. However, the identification of their natural ligands, and especially peptides, suffers from low discovery rates, thus impeding development of therapeutics based on these potential drug targets. We describe the discovery of novel GPCR ligands encrypted in the human proteome. Hundreds of potential peptide ligands were predicted by machine learning algorithms. In vitro screening of selected 33 peptides on a set of 152 GPCRs, including a group of designated orphan receptors, was conducted by intracellular calcium measurements and cAMP assays. The screening revealed eight novel peptides as potential agonists that specifically activated six different receptors in a dose-dependent manner. Most of the peptides showed distinct stimulatory patterns targeted at designated and orphan GPCRs. Further analysis demonstrated a significant in vivo effect for one of the peptides in a mouse inflammation model.

A novel recombinant soluble splice variant of Met is a potent antagonist of the hepatocyte growth factor/scatter factor-Met pathway.

PURPOSE: The Met receptor tyrosine kinase and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), are involved in a wide range of biological activities, including cell proliferation, motility, invasion, and angiogenesis. The HGF/SF-Met signaling pathway is frequently activated in a variety of cancers, and uncontrolled Met activation correlates with highly invasive tumors and poor prognosis. In this study, we investigated the inhibitory effect of a novel soluble splice variant of Met on the HGF/SF-Met pathway. EXPERIMENTAL DESIGN: Using our alternative splicing modeling platform LEADS, we have identified a novel splice variant of the Met receptor, which encodes a truncated soluble form of the receptor. This variant was produced as a recombinant Fc-fused protein named Cgen-241A and was tested in various cell-based assays representing different outcomes of the HGF/SF-Met pathway. RESULTS: Cgen-241A significantly inhibited HGF/SF-induced Met phosphorylation as well as cell proliferation and survival. In addition, Cgen-241A showed a profound inhibitory effect on cell scattering, invasion, and urokinase up-regulation. The inhibitory effects of Cgen-241A were shown in multiple human and nonhuman cell types, representing different modes of Met activation. Furthermore, Cgen-241A showed direct binding to HGF/SF. CONCLUSIONS: Taken together, our results indicate that Cgen-241A is a potent antagonist of the HGF/SF-Met pathway, underlining its potential as a therapeutic agent for the treatment of a wide variety of human malignancies that are dependent on this pathway.

Large-scale protein annotation through gene ontology.

Recent progress in genomic sequencing, computational biology, and ontology development has presented an opportunity to investigate biological systems from a unique perspective, that is, examining genomes and transcriptomes through the multiple and hierarchical structure of Gene Ontology (GO). We report here our development of GO Engine, a computational platform for GO annotation, and analysis of the resultant GO annotations of human proteins. Protein annotation was centered on sequence homology with GO-annotated proteins and protein domain analysis. Text information analysis and a multiparameter cellular localization predictive tool were also used to increase the annotation accuracy, and to predict novel annotations. The majority of proteins corresponding to full-length mRNA in GenBank, and the majority of proteins in the NR database (nonredundant database of proteins) were annotated with one or more GO nodes in each of the three GO categories. The annotations of GenBank and SWISS-PROT proteins are available to the public at the GO Consortium web site.