Matrix-Targeting Immunotherapy Controls Tumor Growth and Spread by Switching Macrophage Phenotype.

The interplay between cancer cells and immune cells is a key determinant of tumor survival. Here, we uncovered how tumors exploit the immunomodulatory properties of the extracellular matrix to create a microenvironment that enables their escape from immune surveillance. Using orthotopic grafting of mammary tumor cells in immunocompetent mice and autochthonous models of breast cancer, we discovered how tenascin-C, a matrix molecule absent from most healthy adult tissues but expressed at high levels and associated with poor patient prognosis in many solid cancers, controls the immune status of the tumor microenvironment. We found that, although host-derived tenascin-C promoted immunity via recruitment of proinflammatory, antitumoral macrophages, tumor-derived tenascin-C subverted host defense by polarizing tumor-associated macrophages toward a pathogenic, immune-suppressive phenotype. Therapeutic monoclonal antibodies that blocked tenascin-C activation of Toll-like receptor 4 reversed this phenotypic switch in vitro and reduced tumor growth and lung metastasis in vivo, providing enhanced benefit in combination with anti-PD-L1 over either treatment alone. Combined tenascin-C:macrophage gene-expression signatures delineated a significant survival benefit in people with breast cancer. These data revealed a new approach to targeting tumor-specific macrophage polarization that may be effective in controlling the growth and spread of breast tumors.

Internal Affairs: Tenascin-C as a Clinically Relevant, Endogenous Driver of Innate Immunity.

To protect against danger, the innate immune system must promptly and accurately sense alarm signals, and mount an appropriate response to restore homeostasis. One endogenous trigger of immunity is tenascin-C, a large hexameric protein of the extracellular matrix. Upregulated upon tissue injury and cellular stress, tenascin-C is expressed during inflammation and tissue remodeling, where it influences cellular behavior by interacting with a multitude of molecular targets, including other matrix components, cell surface proteins, and growth factors. Here, we discuss how these interactions confer upon tenascin-C distinct immunomodulatory capabilities that make this matrix molecule necessary for efficient tissue repair. We also highlight in vivo studies that provide insight into the consequences of misregulated tenascin-C expression on inflammation and fibrosis during a wide range of inflammatory diseases. Finally, we examine how its unique expression pattern and inflammatory actions make tenascin-C a viable target for clinical exploitation in both diagnostic and therapeutic arenas.

Investigating cell-type specific functions of tenascin-C.

The extracellular matrix molecule tenascin-C (TNC) has received a lot of attention since its discovery 30 years ago because of its multiple roles in tissue repair, and in pathologies such as chronic inflammation, fibrosis, and cancer. Mouse models with high or no TNC expression have enabled the validation of key roles for TNC in immunity and angiogenesis. In parallel, many approaches including primary cell or organ cultures have shed light on the cellular and molecular mechanisms by which TNC exerts its multiple actions in vivo. Here, we will describe assays that investigate its antiadhesive properties and that measure the effect of TNC on the actin cytoskeleton, cell survival, proliferation, and migration. We will also describe assays to assess the impact of TNC on endothelial and immune cells in cell and organ culture, and to compare the responses of fibroblasts from normal and diseased tissues.

Mapping tenascin-C interaction with toll-like receptor 4 reveals a new subset of endogenous inflammatory triggers.

Pattern recognition underpins innate immunity; the accurate identification of danger, including infection, injury, or tumor, is key to an appropriately targeted immune response. Pathogen detection is increasingly well defined mechanistically, but the discrimination of endogenous inflammatory triggers remains unclear. Tenascin-C, a matrix protein induced upon tissue damage and expressed by tumors, activates toll-like receptor 4 (TLR4)-mediated sterile inflammation. Here we map three sites within tenascin-C that directly and cooperatively interact with TLR4. We also identify a conserved inflammatory epitope in related proteins from diverse families, and demonstrate that its presence targets molecules for TLR detection, while its absence enables escape of innate immune surveillance. These data reveal a unique molecular code that defines endogenous proteins as inflammatory stimuli by marking them for recognition by TLRs.

Association of Distinct Fine Specificities of Anti-Citrullinated Peptide Antibodies With Elevated Immune Responses to Prevotella intermedia in a Subgroup of Patients With Rheumatoid Arthritis and Periodontitis.

OBJECTIVE: In addition to the long-established link with smoking, periodontitis (PD) is a risk factor for rheumatoid arthritis (RA). This study was undertaken to elucidate the mechanism by which PD could induce antibodies to citrullinated peptides (ACPAs), by examining the antibody response to a novel citrullinated peptide of cytokeratin 13 (CK-13) identified in gingival crevicular fluid (GCF), and comparing the response to 4 other citrullinated peptides in patients with RA who were well-characterized for PD and smoking. METHODS: The citrullinomes of GCF and periodontal tissue from patients with PD were mapped by mass spectrometry. ACPAs of CK13 (cCK13), tenascin-C (cTNC5), vimentin (cVIM), α-enolase (CEP-1), and fibrinogen ß (cFIBß) were examined by enzyme-linked immunosorbent assay in patients with RA (n = 287) and patients with osteoarthritis (n = 330), and cross-reactivity was assessed by inhibition assays. RESULTS: A novel citrullinated peptide cCK13-1 (444 TSNASGR-Cit-TSDV-Cit-RP458 ) identified in GCF exhibited elevated antibody responses in RA patients (24%). Anti-cCK13-1 antibody levels correlated with anti-cTNC5 antibody levels, and absorption experiments confirmed this was not due to cross-reactivity. Only anti-cCK13-1 and anti-cTNC5 were associated with antibodies to the periodontal pathogen Prevotella intermedia (P = 0.05 and P = 0.001, respectively), but not with antibodies to Porphyromonas gingivalis arginine gingipains. Levels of antibodies to CEP-1, cFIBß, and cVIM correlated with each other, and with smoking and shared epitope risk factors in RA. CONCLUSION: This study identifies 2 groups of ACPA fine specificities associated with different RA risk factors. One is predominantly linked to smoking and shared epitope, and the other links anti-cTNC5 and cCK13-1 to infection with the periodontal pathogen P intermedia.

Serum Amyloid P Component (SAP) Interactome in Human Plasma Containing Physiological Calcium Levels.

The pentraxin serum amyloid P component (SAP) is secreted by the liver and found in plasma at a concentration of approximately 30 mg/L. SAP is a 25 kDa homopentamer known to bind both protein and nonprotein ligands, all in a calcium-dependent manner. The function of SAP is unclear but likely involves the humoral innate immune system spanning the complement system, inflammation, and coagulation. Also, SAP is known to bind to the generic structure of amyloid deposits and possibly to protect them against proteolysis. In this study, we have characterized the SAP interactome in human plasma containing the physiological Ca2+ concentration using SAP affinity pull-down and co-immunoprecipitation experiments followed by mass spectrometry analyses. The analyses resulted in the identification of 33 proteins, of which 24 were direct or indirect interaction partners not previously reported. The SAP interactome can be divided into categories that include apolipoproteins, the complement system, coagulation, and proteolytic regulation.