CD47 Augments Fas/CD95-mediated Apoptosis

Targeting "don't eat me" signal: breast cancer immunotherapy

PURPOSE

Breast cancer ranks as the most prevalent cancer type impacting women globally, both in terms of incidence and mortality rates, making it a major health concern for females. There's an urgent requirement to delve into new cancer treatment methods to improve patient survival rates.

METHODS

Immunotherapy has gained recognition as a promising area of research in the treatment of breast cancer, with targeted immune checkpoint therapies demonstrating the potential to yield sustained clinical responses and improve overall survival rates. Presently, the predominant immune checkpoints identified on breast cancer cells include CD47, CD24, PD-L1, MHC-I, and STC-1, among others. Nevertheless, the specific roles of these various immune checkpoints in breast carcinogenesis, metastasis, and immune evasion have yet to be comprehensively elucidated. We conducted a comprehensive review of the existing literature pertaining to breast cancer and immune checkpoint inhibitors, providing a summary of findings and an outlook on future research directions.

RESULTS

This article reviews the advancements in research concerning each immune checkpoint in breast cancer and their contributions to immune evasion, while also synthesizing immunotherapy strategies informed by these mechanisms. Furthermore, it anticipates future research priorities, thereby providing a theoretical foundation to guide immunotherapy as a potential interventional approach for breast cancer treatment.

CONCLUSION

Knowledge of immune checkpoints will drive the creation of novel cancer therapies, and future breast cancer research will increasingly emphasize personalized treatments tailored to patients' specific tumor characteristics.

Regulating islet stress responses through CD47 activation

AIMS/HYPOTHESIS

Diabetes is a global health burden characterised by incremental beta cell loss. Islet transplantation is a recognised treatment for individuals with type 1 diabetes and hypoglycaemia unawareness but broader application is constrained by limited islet survival and function post-transplantation. The underlying molecular mechanisms that induce beta cell dysfunction and demise remain unclear, and therapeutic agents that protect against cellular loss and maintain insulin secretion are in demand as potential treatment options. CD47 is a cell surface protein implicated in cellular stress responses but its role in beta cell function remains relatively unexplored. We hypothesised that modulating CD47 expression would demonstrate a cytoprotective effect in beta cells.

METHODS

We used primary murine islets with/without genetic deletion of CD47, as well as human islets and MIN6 cells subjected to pharmacological disruption of CD47 signalling (siRNA or blocking antibody). Metabolic stress was induced in cells by exposure to hypoxia, hyperglycaemia or thapsigargin, and markers of the unfolded protein response, cell survival and insulin secretory function were assessed. Human pancreases from individuals with and without diabetes were examined for evidence of CD47 signalling.

RESULTS

Expression of CD47 and its high affinity ligand thrombospondin-1 (TSP1) was robustly upregulated by exogenous stressors. Limiting CD47 signalling improved markers of senescence, apoptosis, endoplasmic reticulum stress, unfolded protein response, self-renewal and autophagy, and maintained insulin secretory responses. We also found concurrent upregulated expression of CD47 and senescence markers in the endocrine pancreas of aged donors and those with type 2 diabetes. Both CD47 and TSP1 expression were increased in pancreases of humans with type 1 diabetes, as were plasma levels of TSP1.

CONCLUSIONS/INTERPRETATION

Our study provides key insights into the essential role of CD47 as a novel regulator of islet dysfunction, regulating cytoprotective responses to stress. CD47 may contribute to beta cell damage during the development of diabetes and failure of islet transplant function. Therefore, limiting CD47 activation may be a potential therapeutic tool in conditions where islet function is inadequate.

Refolding of the recombinant IgV domain of CD47 from E. coli for NMR studies

CD47 is a widely expressed integrin-associated transmembrane protein that regulates many macrophage functions, including phagocytosis. Since many cancer cells overexpress CD47 to evade the immune system, targeting CD47 has been proposed as a strategy to enhance macrophage-mediated destruction of cancer cells. Consequently, developing antagonists that block the CD47-SIRPα interaction has drawn attention. However, the exclusive use of eukaryotic cell culture to produce CD47-IgV precludes isotope enrichment of the domain. This prevents the use of solution NMR as a tool for identifying CD47 inhibitors. Here, we describe a two-step refolding protocol for the CD47-IgV domain from inclusion bodies produced in E. coli. The yield of CD47-IgV is ∼30 mg/L of culture. The refolded domain interacts with the anti-CD47 antibody B6H12 with an affinity similar to glycosylated CD47-IgV produced in mammalian cells and binds the IgV domain of SIRPα. The method allowed us to produce 15N and 13C enriched CD47-IgV for NMR. The chemical shift assignments of the CD47-IgV domain backbone atoms confirmed that the refolded protein has the same secondary structure as the crystal structure of CD47-IgV produced in mammalian cells. Furthermore, NMR data showed refolded CD47-IgV interacts with SIRPα-IgV similarly to glycosylated CD47-IgV. The application of this method can advance the progress of biochemical investigations of the interaction between CD47-IgV and SIRPα and will be useful for the discovery of antibodies, small molecules, and peptides targeting the CD47/SIRPα axis in vivo.

CD47 as a potent target in cancer immunotherapy: A review

Cancer is the second-highest cause of death worldwide. Accordingly, finding new cancer treatments is of great interest to researchers. The current platforms to fight cancer such as chemotherapy, radiotherapy, and surgery are limited in efficacy, especially in the metastatic setting. In this war against cancer, the immune system is a powerful ally, but tumor cells often outsmart it through alternative pathways. Cluster of differentiation 47 (CD47), a protein that normally prevents healthy cells from being attacked by immune cells, is often overexpressed on cancer cells. This makes CD47 a prime target for immunotherapy. Blocking of CD47 has the potential to unleash the immune system's cell populations-such as myeloid cells, macrophages, and T cells-to allow the immune system to discover and destroy cancer cells more successfully. In this review, we aimed to provide the latest information and findings about the roles of CD47 in the regulation of various cellular pathways and, thus, the importance of CD47 as a potential target in cancer therapy.

Evaluation of thrombospondin 1 as a novel biomarker in pediatric-onset systemic lupus erythematosus

OBJECTIVE

This study aimed to assess the potential of thrombospondin 1 (TBS-1) as a biomarker for pediatric-onset systemic lupus erythematosus (pSLE) and investigated its association with clinical characteristics and other laboratory tests in pSLE.

METHODS

A total of 112 pSLE and 50 age-matched and gender-matched healthy controls (HCs) were recruited in this study from January 2022 to June 2023 at West China Second University Hospital, Sichuan university. Plasma TBS-1 levels were measured, and clinical and laboratory findings were collected from the medical database.

RESULTS

The plasma TBS-1 level was significantly lower in pSLE patients (26778 ng/mL, IQR: 9875-59011) compared to HCs (100583 ng/mL, IQR: 58327-189547) (P < 0.0001). ROC analysis demonstrated that TBS-1 could effectively differentiate pSLE patients and HCs (AUC: 0.845, 95%CI: 0.785-0.905, P < 0.0001) with an optimal cut-off was 49,937 ng/mL, yielding a sensitivity of 84% and specificity of 70.5% based on the Youden index. Compared to TBS-1 positive patients, TBS-1 negative patients exhibited significant reductions in hemoglobin, IgM, and fibrinogen levels.

CONCLUSION

In light of the current data, the efficacy of TBS-1 as a biomarker in pSLE diverged from its performance in adult SLE. In summary, TBS-1 shows potential as a biomarker for pSLE, particularly in hematological manifestations. Further investigations are essential to delve into the immunomodulatory roles of TBS-1 in the autoimmune pathways of pSLE.

Deciphering the role of CD47 in cancer immunotherapy

BACKGROUND

Immunotherapy has emerged as a novel strategy for cancer treatment following surgery, radiotherapy, and chemotherapy. Immune checkpoint blockade and Chimeric antigen receptor (CAR)-T cell therapies have been successful in clinical trials. Cancer cells evade immune surveillance by hijacking inhibitory pathways via overexpression of checkpoint genes. The Cluster of Differentiation 47 (CD47) has emerged as a crucial checkpoint for cancer immunotherapy by working as a "don't eat me" signal and suppressing innate immune signaling. Furthermore, CD47 is highly expressed in many cancer types to protect cancer cells from phagocytosis via binding to SIRPα on phagocytes. Targeting CD47 by either interrupting the CD47-SIRPα axis or combing with other therapies has been demonstrated as an encouraging therapeutic strategy in cancer immunotherapy. Antibodies and small molecules that target CD47 have been explored in pre- and clinical trials. However, formidable challenges such as the anemia and palate aggregation cannot be avoided because of the wide presentation of CD47 on erythrocytes.

AIM OF VIEW

This review summarizes the current knowledge on the regulation and function of CD47, and provides a new perspective for immunotherapy targeting CD47. It also highlights the clinical progress of targeting CD47 and discusses challenges and potential strategies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of targeting CD47 in cancer immunotherapy, it also augments the concept of combination immunotherapy strategies by employing both innate and adaptive immune responses.

Tolerating CD47

Cluster of differentiation 47 (CD47) occupies the outer membrane of human cells, where it binds to soluble and cell surface receptors on the same and other cells, sculpting their topography and resulting in a pleiotropic receptor-multiligand interaction network. It is a focus of drug development to temper and accentuate CD47-driven immune cell liaisons, although consideration of on-target CD47 effects remain neglected. And yet, a late clinical trial of a CD47-blocking antibody was discontinued, existent trials were restrained, and development of CD47-targeting agents halted by some pharmaceutical companies. At this point, if CD47 can be exploited for clinical advantage remains to be determined. Herein an airing is made of the seemingly conflicting actions of CD47 that reflect its position as a junction connecting receptors and signalling pathways that impact numerous human cell types. Prospects of CD47 boosting and blocking are considered along with potential therapeutic implications for autoimmune diseases and cancer.

The role of CD47 in non-neoplastic diseases

CD47 is a 50 kDa five-spanning membrane receptor that plays a crucial role in multiple cellular processes, including myeloid cell activation, neutrophils transmigration, vascular remodeling, leukocyte adhesion and trans-endothelial migration. Recent studies have revealed that CD47 is a highly expressed anti-phagocytic signal in several types of cancer, and therefore, blocking of CD47 has shown an effective therapeutic potential in cancer immunotherapy. In addition, CD47 has been found to be involved in a complex interplay with microglia and other types of cells, and increasing evidence indicates that CD47 can be targeted as part of immune modulatory strategies for non-neoplastic diseases as well. In this review, we focus on CD47 and its role in non-neoplastic diseases, including neurological disorders, atherosclerosis and autoimmune diseases. In addition, we discuss the major challenges and potential remedies associated with CD47-SIRPα-based immunotherapies.

Targeting CXCR4 and CD47 Receptors: An Overview of New and Old Molecules for a Biological Personalized Anticancer Therapy

Biological therapy, with its multifaceted applications, has revolutionized the treatment of tumors, mainly due to its ability to exclusively target cancer cells and reduce the adverse effects on normal tissues. This review focuses on the therapies targeting the CXCR4 and CD47 receptors. We surveyed the results of early clinical trials testing compounds classified as nonpeptides, small peptides, CXCR4 antagonists or specific antibodies whose activity reduces or completely blocks the intracellular signaling pathways and cell proliferation. We then examined antibodies and fusion proteins against CD47, the receptor that acts as a “do not eat me” signal to phagocytes escaping immune surveillance. Despite these molecules being tested in early clinical trials, some drawbacks are emerging that impair their use in practice. Finally, we examined the ImmunoGenic Surrender mechanism that involves crosstalk and co-internalization of CXCR4 and CD47 upon engagement of CXCR4 by ligands or other molecules. The favorable effect of such compounds is dual as CD47 surface reduction impact on the immune response adds to the block of CXCR4 proliferative potential. These results suggest that a combination of different therapeutic approaches has more beneficial effects on patients’ survival and may pave the way for new accomplishments in personalized anticancer therapy.

Loss of CD47 alters CD8+ T cell activation in vitro and immunodynamics in mice

CD47 has established roles in the immune system for regulating macrophage phagocytosis and lymphocyte activation, with growing evidence of its cell-intrinsic regulatory roles in natural killer and CD8+ T cells. CD47 limits antigen-dependent cytotoxic activities of human and murine CD8+ T cells, but its role in T cell activation kinetics remains unclear. Using in vitro and in vivo models, we show here that CD47 differentially regulates CD8+ T cell responses to short- versus long-term activation. Although CD47 was not required for T cell development in mice and early activation in vitro, short-term stimuli elevated pathogen-reactive gene expression and enhanced proliferation and the effector phenotypes of Cd47-deficient relative to Cd47-sufficient CD8+ T cells. In contrast, persistent TCR stimulation limited the effector phenotypes of Cd47 -/- CD8+ T cells and enhanced their apoptosis signature. CD8+ T cell expansion and activation in vivo induced by acute lymphocytic choriomeningitis virus (LCMV) infection did not differ in the absence of CD47. However, the frequency and effector phenotypes of Cd47-/- CD8+ T cells were constrained in chronic LCMV-infected as well as in mice bearing B16 melanoma tumors. Therefore, CD47 regulates CD8+ T cell activation, proliferation, and fitness in a context-dependent manner.

Targeting macrophages in hematological malignancies: recent advances and future directions

Emerging evidence indicates that the detection and clearance of cancer cells via phagocytosis induced by innate immune checkpoints play significant roles in tumor-mediated immune escape. The most well-described innate immune checkpoints are the "don't eat me" signals, including the CD47/signal regulatory protein α axis (SIRPα), PD-1/PD-L1 axis, CD24/SIGLEC-10 axis, and MHC-I/LILRB1 axis. Molecules have been developed to block these pathways and enhance the phagocytic activity against tumors. Several clinical studies have investigated the safety and efficacy of CD47 blockades, either alone or in combination with existing therapy in hematological malignancies, including myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), and lymphoma. However, only a minority of patients have significant responses to these treatments alone. Combining CD47 blockades with other treatment modalities are in clinical studies, with early results suggesting a synergistic therapeutic effect. Targeting macrophages with bispecific antibodies are being explored in blood cancer therapy. Furthermore, reprogramming of pro-tumor macrophages to anti-tumor macrophages, and CAR macrophages (CAR-M) demonstrate anti-tumor activities. In this review, we elucidated distinct types of macrophage-targeted strategies in hematological malignancies, from preclinical experiments to clinical trials, and outlined potential therapeutic approaches being developed.

CD47-SIRPα Controls ADCC Killing of Primary T Cells by PMN Through a Combination of Trogocytosis and NADPH Oxidase Activation

Immunotherapies targeting the “don’t eat me” myeloid checkpoint constituted by CD47 SIRPα interaction have promising clinical potential but are limited by toxicities associated with the destruction of non-tumor cells. These dose-limiting toxicities demonstrate the need to highlight the mechanisms of anti–CD47-SIRPα therapy effects on non-tumor CD47-bearing cells. Given the increased incidence of lymphopenia in patients receiving anti-CD47 antibodies and the strong ADCC (antibody-dependent cellular cytotoxicity) effector function of polymorphonuclear cells (PMNs), we investigated the behavior of primary PMNs cocultured with primary T cells in the presence of anti-CD47 mAbs. PMNs killed T cells in a CD47-mAb–dependent manner and at a remarkably potent PMN to T cell ratio of 1:1. The observed cytotoxicity was produced by a novel combination of both trogocytosis and a strong respiratory burst induced by classical ADCC and CD47-SIRPα checkpoint blockade. The complex effect of the CD47 blocking mAb could be recapitulated by combining its individual mechanistic elements: ADCC, SIRPα blockade, and ROS induction. Although previous studies had concluded that disruption of SIRPα signaling in PMNs was limited to trogocytosis-specific cytotoxicity, our results suggest that SIRPα also tightly controls activation of NADPH oxidase, a function demonstrated during differentiation of immature PMNs but not so far in mature PMNs. Together, our results highlight the need to integrate PMNs in the development of molecules targeting the CD47-SIRPα immune checkpoint and to design agents able to enhance myeloid cell function while limiting adverse effects on healthy cells able to participate in the anti-tumor immune response.

CXCR4/CXCL12 Activities in the Tumor Microenvironment and Implications for Tumor Immunotherapy

Simple Summary

Chemokines are small soluble proteins that control and regulate cell trafficking within and between tissues by binding to their receptors. Among them, CXCL12 and its receptor CXCR4 appeared with ancestral vertebrates, are expressed almost ubiquitously, and play essential roles in embryogenesis and organogenesis. In addition, CXCL12 and CXCR4 are involved in antigen recognition by T and B cells and in shaping the tumor microenvironment (TME), mainly towards dampening immune responses. New data indicate that CXCR4 interacts with the surface protein CD47 in a novel form of immunosurveillance, called ImmunoGenic Surrender (IGS). Following the co-internalization of CXCR4 and CD47 in tumor cells, macrophages phagocytose them and cross-present their antigens to the adaptive immune system, leading to tumor rejection in a fraction of mice. All of these specific activities of CXCL12 and CXCR4 in antigen presentation might be complementary to current immunotherapies.

Abstract

CXCR4 is a G-Protein coupled receptor that is expressed nearly ubiquitously and is known to control cell migration via its interaction with CXCL12, the most ancient chemokine. The functions of CXCR4/CXCL12 extend beyond cell migration and involve the recognition and disposal of unhealthy or tumor cells. The CXCR4/CXCL12 axis plays a relevant role in shaping the tumor microenvironment (TME), mainly towards dampening immune responses. Notably, CXCR4/CXCL12 cross-signal via the T and B cell receptors (TCR and BCR) and co-internalize with CD47, promoting tumor cell phagocytosis by macrophages in an anti-tumor immune process called ImmunoGenic Surrender (IGS). These specific activities in shaping the immune response might be exploited to improve current immunotherapies.

CD47 and thrombospondin-1 regulation of mitochondria, metabolism, and diabetes

Thrombospondin-1 (TSP1) is the prototypical member of a family of secreted proteins that modulate cell behavior by engaging with molecules in the extracellular matrix and with receptors on the cell surface. CD47 is widely displayed on many, if not all, cell types and is a high-affinity TSP1 receptor. CD47 is a marker of self that limits innate immune cell activities, a feature recently exploited to enhance cancer immunotherapy. Another major role for CD47 in health and disease is to mediate TSP1 signaling. TSP1 acting through CD47 contributes to mitochondrial, metabolic, and endocrine dysfunction. Studies in animal models found that elevated TSP1 expression, acting in part through CD47, causes mitochondrial and metabolic dysfunction. Clinical studies established that abnormal TSP1 expression positively correlates with obesity, fatty liver disease, and diabetes. The unabated increase in these conditions worldwide and the availability of CD47 targeting drugs justify a closer look into how TSP1 and CD47 disrupt metabolic balance and the potential for therapeutic intervention.

Functions of Thrombospondin-1 in the Tumor Microenvironment

The identification of thrombospondin-1 as an angiogenesis inhibitor in 1990 prompted interest in its role in cancer biology and potential as a therapeutic target. Decreased thrombospondin-1 mRNA and protein expression are associated with progression in several cancers, while expression by nonmalignant cells in the tumor microenvironment and circulating levels in cancer patients can be elevated. THBS1 is not a tumor suppressor gene, but the regulation of its expression in malignant cells by oncogenes and tumor suppressor genes mediates some of their effects on carcinogenesis, tumor progression, and metastasis. In addition to regulating angiogenesis and perfusion of the tumor vasculature, thrombospondin-1 limits antitumor immunity by CD47-dependent regulation of innate and adaptive immune cells. Conversely, thrombospondin-1 is a component of particles released by immune cells that mediate tumor cell killing. Thrombospondin-1 differentially regulates the sensitivity of malignant and nonmalignant cells to genotoxic stress caused by radiotherapy and chemotherapy. The diverse activities of thrombospondin-1 to regulate autophagy, senescence, stem cell maintenance, extracellular vesicle function, and metabolic responses to ischemic and genotoxic stress are mediated by several cell surface receptors and by regulating the functions of several secreted proteins. This review highlights progress in understanding thrombospondin-1 functions in cancer and the challenges that remain in harnessing its therapeutic potential.

Thrombospondin-1 CD47 Signalling: From Mechanisms to Medicine

Recent advances provide evidence that the cellular signalling pathway comprising the ligand-receptor duo of thrombospondin-1 (TSP1) and CD47 is involved in mediating a range of diseases affecting renal, vascular, and metabolic function, as well as cancer. In several instances, research has barely progressed past pre-clinical animal models of disease and early phase 1 clinical trials, while for cancers, anti-CD47 therapy has emerged from phase 2 clinical trials in humans as a crucial adjuvant therapeutic agent. This has important implications for interventions that seek to capitalize on targeting this pathway in diseases where TSP1 and/or CD47 play a role. Despite substantial progress made in our understanding of this pathway in malignant and cardiovascular disease, knowledge and translational gaps remain regarding the role of this pathway in kidney and metabolic diseases, limiting identification of putative drug targets and development of effective treatments. This review considers recent advances reported in the field of TSP1-CD47 signalling, focusing on several aspects including enzymatic production, receptor function, interacting partners, localization of signalling, matrix-cellular and cell-to-cell cross talk. The potential impact that these newly described mechanisms have on health, with a particular focus on renal and metabolic disease, is also discussed.

[On the inflammatory origins of AMD]

Age-related macular degeneration (AMD) is a complex, highly heritable, multifactorial disease caused by the interplay of age and genetic and environmental risk factors. No treatment has yet been found to treat the slowly progressing atrophic form of AMD. All forms of AMD are invariably associated with an accumulation of mononuclear phagocytes (MP) in the subretinal space, a family of cells that include inflammatory and resident macrophages. We here present an overview of the inflammatory process occurring in AMD and discuss the origin of MPs and the consequences of their accumulation in the subretinal space. Finally, we will review the role played by the established risk factors for AMD to promote the switch from beneficial inflammation in early stage to a deleterious inflammation in the advanced stage of the disease.

CD47 (Cluster of differentiation 47): an anti-phagocytic receptor with a multitude of signaling functions

CD47 is a tumor-associated antigen best known for its ability to bind counter-receptors on the surface of professional phagocytes as an immune-evasion strategy. ⁣Recently, CD47 has been shown to play a role as a signaling receptor, involving a number of cell physiological processes.⁣⁣ This review provides a comprehensive survey of the signaling pathways triggered by CD47 ligand-mediated cell death in tumor cells. Such an understanding should lead to improvement of CD47-targeted anti-tumor therapeutics able to both neutralize the anti-phagocytic role and trigger autonomous tumor cell death.

Tumoral and paratumoral NK cells and CD8+ T cells of esophageal carcinoma patients express high levels of CD47

In a limited number of human malignancies, anti-CD47 therapy leads to the rapid clearance of tumor cells by macrophages. In esophageal squamous cell carcinoma, anti-CD47 treatment has shown promising results in vitro. However, the CD47 expression pattern in tumor-infiltrating lymphocytes (TILs), which are associated with prolonged overall survival and serve as a positive prognostic factor, is largely unknown. In this study, a total of 36 tissue samples from the tumor, peritumoral tissue, and adjacent healthy esophageal tissue was obtained from 12 esophageal carcinoma (EC) patients, and the surface expression of CD47 was evaluated in natural killer (NK) cells, CD8⁺ T cells, and the nonlymphocyte cell fraction. We found that the proportions of the evaluated cells and their CD47-expressing populations were comparable across the analyzed tissue compartments. However, the proportions of CD47-expressing populations in the analyzed tissue compartments were significantly higher in NK cells and CD8⁺ T cells than in the nonlymphocyte cell fraction. Importantly, the intensity of CD47 staining was also significantly higher in the tested immune cells than in the nonlymphocyte cell fraction. High expression of CD47 in tissue-infiltrating NK cells and CD8⁺ T cells in EC patients can, therefore, affect the efficacy of anti-CD47 therapy in EC.

The 10q26 Risk Haplotype of Age-Related Macular Degeneration Aggravates Subretinal Inflammation by Impairing Monocyte Elimination

A minor haplotype of the 10q26 locus conveys the strongest genetic risk for age-related macular degeneration (AMD). Here, we examined the mechanisms underlying this susceptibility. We found that monocytes from homozygous carriers of the 10q26 AMD-risk haplotype expressed high amounts of the serine peptidase HTRA1, and HTRA1 located to mononuclear phagocytes (MPs) in eyes of non-carriers with AMD. HTRA1 induced the persistence of monocytes in the subretinal space and exacerbated pathogenic inflammation by hydrolyzing thrombospondin 1 (TSP1), which separated the two CD47-binding sites within TSP1 that are necessary for efficient CD47 activation. This HTRA1-induced inhibition of CD47 signaling induced the expression of pro-inflammatory osteopontin (OPN). OPN expression increased in early monocyte-derived macrophages in 10q26 risk carriers. In models of subretinal inflammation and AMD, OPN deletion or pharmacological inhibition reversed HTRA1-induced pathogenic MP persistence. Our findings argue for the therapeutic potential of CD47 agonists and OPN inhibitors for the treatment of AMD.

Role of CD47 in Hematological Malignancies

CD47, or integrin-associated protein, is a cell surface ligand expressed in low levels by nearly all cells of the body. It plays an integral role in various immune responses as well as autoimmunity, by sending a potent "don't eat me" signal to prevent phagocytosis. A growing body of evidence demonstrates that CD47 is overexpressed in various hematological malignancies and its interaction with SIRPα on the phagocytic cells prevents phagocytosis of cancer cells. Additionally, it is expressed by different cell types in the tumor microenvironment and is required for establishing tumor metastasis. Overexpression of CD47 is thus often associated with poor clinical outcomes. CD47 has emerged as a potential therapeutic target and is being investigated in various preclinical studies as well as clinical trials to prove its safety and efficacy in treating hematological neoplasms. This review focuses on different therapeutic mechanisms to target CD47, either alone or in combination with other cell surface markers, and its pivotal role in impairing tumor growth and metastatic spread of various types of hematological malignancies.

Development of AO-176, a Next-Generation Humanized Anti-CD47 Antibody with Novel Anticancer Properties and Negligible Red Blood Cell Binding

Inhibitors of adaptive immune checkpoints have shown promise as cancer treatments. CD47 is an innate immune checkpoint receptor broadly expressed on normal tissues and overexpressed on many tumors. Binding of tumor CD47 to signal regulatory protein alpha (SIRPα) on macrophages and dendritic cells triggers a "don't eat me" signal that inhibits phagocytosis enabling escape of innate immune surveillance. Blocking CD47/SIRPα interaction promotes phagocytosis reducing tumor burden in numerous xenograft and syngeneic animal models. We have developed a next-generation humanized anti-CD47 antibody, AO-176, that not only blocks the CD47/SIRPα interaction to induce tumor cell phagocytosis, but also induces tumor cytotoxicity in hematologic and solid human tumor cell lines, but not normal noncancerous cells, by a cell autonomous mechanism (not ADCC). AO-176 also binds preferentially to tumor versus many normal cell types. In particular, AO-176 binds negligibly to RBCs in contrast to tumor cells, even at high concentrations up to 200 μg/mL and does not agglutinate RBCs up to 1 mg/mL in vitro These properties are expected not only to decrease the antigen sink, but also to minimize on-target clinical adverse effects observed following treatment with other reported RBC-binding anti-CD47 antibodies. When tested in cynomolgus monkeys, AO-176 was well tolerated with no adverse effects. Finally, we show that AO-176 demonstrates dose-dependent antitumor activity in tumor xenograft models. Taken together, the unique properties and antitumor activity of our next-generation anti-CD47 antibody, AO-176, distinguishes it from other CD47/SIRPα axis targeting agents in clinical development.

The Neuro-Immune-Regulators (NIREGs) Promote Tissue Resilience; a Vital Component of the Host's Defense Strategy against Neuroinflammation

An effective protective inflammatory response in the brain is crucial for the clearance of pathogens (e.g. microbes, amyloid fibrils, prion^SC) and should be closely regulated. However, the CNS seems to have limited tissue resilience to withstand the detrimental effects of uncontrolled inflammation compromising functional recovery and tissue repair. Newly described neuro-immune-regulators (NIREGs) are functionally related proteins regulating the severity and duration of the host inflammatory response. NIREGs such as CD200, CD47 and CX3CL1 are vital for increasing tissue resilience and are constitutively expressed by neurons. The interaction with co-receptors (CD200R, CD172a, CX3CR1) will maintain microglia in the resting phenotype, directing aggressive microglia phenotype and limiting bystander injuries. Neurons can also express many of the complement NIREGs (CD55, CD46, CD59 and factor H). Neurons and glia also express suppressor of cytokine signaling proteins (SOCS) down regulating janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway and to lead to the polarization of microglia towards anti-inflammatory phenotype. Other NIREGs such as serine protease inhibitors (serpins) and thrombomodulin (CD141) inhibit neurotoxic systemic coagulation proteins such as thrombin. The unfolded protein response (UPR) detects misfolded proteins and other stressors to prevent irreversible cell injury. Microglial pattern recognition receptors (PRR) (TREM-2, CR3, FcγR) are important to clear apoptotic cells and cellular debris but in non-phlogystic manner through inhibitory signaling pathways. The TYRO3, Axl, Mer (TAM) tyrosine receptor kinases activated by Gas 6 and PROS1 regulate inflammation by inhibiting Toll like receptors (TLR) /JAK-STAT activation and contribute to NIREG's functions.

ATP-Decorated Mesoporous Silica for Biomineralization of Calcium Carbonate and P2 Purinergic Receptor-Mediated Antitumor Activity against Aggressive Lymphoma

Adenosine triphosphate (ATP) is an important transmitter that mediates various biological effects via purinergic receptors (P2 receptors) in cancer. We investigated the antitumor activity of ATP-decorated and doxorubicin (DOX)-loaded mesoporous silica with biomineralization of calcium carbonate against a highly aggressive and metastatic murine lymphoma called Dalton's lymphoma (DL). Our results suggest that this nanocomposite has unique effects with respect to the morphology and properties of calcium carbonate on the surface of the nanoparticle. DOX in the nanoparticles was prevented from quick release via the interactions of the phosphate group present on ATP and calcium carbonate. This construct is significantly tumoricidal against parental and DOX-resistant DL cells and is thus a promising candidate for applications in drug delivery. The composite nanomaterial has excellent biocompatibility with higher uptake and acts via the participation of the purinergic receptor P2X7. The nanocomposite induces significantly higher apoptosis in tumor cells compared with DOX alone. Treatment of DL-bearing mice with the construct significantly reduces tumor burden, in addition to augmenting the lifespan of tumor-bearing mice as demonstrated by a sustained healthy life of the animals and improved histopathological parameters.

The Roles of Thrombospondins in Hemorrhagic Stroke

Hemorrhagic stroke is a devastating cerebrovascular disease with significant morbidity and mortality worldwide. Thrombospondins (TSPs), as matricellular proteins, belong to the TSP family which is comprised of five members. All TSPs modulate a variety of cellular functions by binding to various receptors. Recently, TSPs gained attention in the area of hemorrhagic stroke, especially TSP-1. TSP-1 participates in angiogenesis, the inflammatory response, apoptosis, and fibrosis after hemorrhagic stroke through binding to various molecules including but not limited to CD36, CD47, and TGF-β. In this review, we will discuss the roles of TSPs in hemorrhagic stroke and focus primarily on TSP-1.

CD47 deficiency improves neurological outcomes of traumatic brain injury in mice

CD47 is a receptor for signal-regulatory protein alpha (SIRPα) in self-recognition by the innate immune system, and a receptor of thrombospondin-1 (TSP-1) contributing to vascular impairment in response to stress. However, the roles of CD47 in traumatic brain injury (TBI) have not been investigated. In this study we aimed to test our hypothesis that CD47 mediates early neutrophil brain infiltration and late brain vascular remodeling after TBI. Mice were subjected to TBI using a controlled cortical impact (CCI) device. We examined early phase neutrophil infiltration, and late phase brain vessel density, pro-angiogenic markers VEGF and Ang-1 protein expression, neurological function deficits and lesion volumes for up to three weeks after TBI. Our results show that mice deficient in CD47 (CD47 Knockout) had significantly less brain neutrophil infiltration at 24h, upregulated VEGF expression in peri-lesion cortex at 7 and 14days, and increased blood vessel density at 21days after TBI, compared to wild type (WT) mice. CD47 knockout also significantly decreased sensorimotor function deficits and reduced brain lesion volume at 21days after TBI. We conclude that CD47 may play pathological roles in brain neutrophil infiltration, progression of brain tissue damage, impairment of cerebrovascular remodeling and functional recovery after TBI.

Downregulation of STAT3 phosphorylation enhances tumoricidal effect of IL-15-activated dendritic cell against doxorubicin-resistant lymphoma and leukemia via TNF-α

Although disputed by some, increasing evidence suggests that TNF-α synergies with traditional chemotherapeutic drugs to exert a heightened antitumor effect. The present study investigated the antitumor efficacy of recombinant IL-15 in combination with the STAT3 inhibitor cucurbitacin-I in a doxorubicin-resistant murine lymphoma model. The significance of the work is to understand and design effective strategies in doxorubicin resistant lymphomas. TNF-α is downregulated in dendritic cells from mice with Dalton's lymphoma and shows an inverse relationship with disease progression. Doxorubicin-resistant DL cells have elevated levels of Bcl-2 and Mcl-1 and increased phosphorylation of STAT3. These cells are refractory to dendritic cell derived TNF-α. Doxorubicin resistant Dalton's lymphoma is susceptible to dendritic cell derived TNF-α upon stimulation with the STAT3 inhibitor cucurbitacin-I, which downregulates STAT3 and other survival molecules. The combined treatment of low dose of cucurbitacin-I and rIL-15 is ineffective in mice with doxorubicin resistant Dalton's lymphoma, but a similar therapy prolongs the survival of mice transplanted with parental Dalton's lymphoma. Doxorubicin resistant Dalton's lymphoma responds to therapy with high doses of cucurbitacin-I and rIL-15. Dendritic cell derived from mice responded positively to the therapy and regained their tumoricidal properties with respect to growth inhibition and killing of DL tumor cells. Similar to DL, DC derived from CML patients are impaired in TNF-α expression and are unable to restrict the growth of drug-resistant lymphoma and leukemia cells. This combination approach could be used as a new therapeutic strategy for aggressive and highly metastatic doxorubicin resistant lymphoma.

CD47 signaling pathways controlling cellular differentiation and responses to stress

CD47 is a widely expressed integral membrane protein that serves as the counter-receptor for the inhibitory phagocyte receptor signal-regulatory protein-α (SIRPα) and as a signaling receptor for the secreted matricellular protein thrombospondin-1. Recent studies employing mice and somatic cells lacking CD47 have revealed important pathophysiological functions of CD47 in cardiovascular homeostasis, immune regulation, resistance of cells and tissues to stress and chronic diseases of aging including cancer. With the emergence of experimental therapeutics targeting CD47, a more thorough understanding of CD47 signal transduction is essential. CD47 lacks a substantial cytoplasmic signaling domain, but several cytoplasmic binding partners have been identified, and lateral interactions of CD47 with other membrane receptors play important roles in mediating signaling resulting from the binding of thrombospondin-1. This review addresses recent advances in identifying the lateral binding partners, signal transduction pathways and downstream transcription networks regulated through CD47 in specific cell lineages. Major pathways regulated by CD47 signaling include calcium homeostasis, cyclic nucleotide signaling, nitric oxide and hydrogen sulfide biosynthesis and signaling and stem cell transcription factors. These pathways and other undefined proximal mediators of CD47 signaling regulate cell death and protective autophagy responses, mitochondrial biogenesis, cell adhesion and motility and stem cell self-renewal. Although thrombospondin-1 is the best characterized agonist of CD47, the potential roles of other members of the thrombospondin family, SIRPα and SIRPγ binding and homotypic CD47 interactions as agonists or antagonists of signaling through CD47 should also be considered.

CD47: A Cell Surface Glycoprotein Which Regulates Multiple Functions of Hematopoietic Cells in Health and Disease

Interactions between cells and their surroundings are important for proper function and homeostasis in a multicellular organism. These interactions can either be established between the cells and molecules in their extracellular milieu, but also involve interactions between cells. In all these situations, proteins in the plasma membranes are critically involved to relay information obtained from the exterior of the cell. The cell surface glycoprotein CD47 (integrin-associated protein (IAP)) was first identified as an important regulator of integrin function, but later also was shown to function in ways that do not necessarily involve integrins. Ligation of CD47 can induce intracellular signaling resulting in cell activation or cell death depending on the exact context. By binding to another cell surface glycoprotein, signal regulatory protein alpha (SIRPα), CD47 can regulate the function of cells in the monocyte/macrophage lineage. In this spotlight paper, several functions of CD47 will be reviewed, although some functions may be more briefly mentioned. Focus will be on the ways CD47 regulates hematopoietic cells and functions such as CD47 signaling, induction of apoptosis, and regulation of phagocytosis or cell-cell fusion.

Activated CD47 regulates multiple vascular and stress responses: implications for acute kidney injury and its management

Ischemia-reperfusion injury (IRI) remains a significant source of early and delayed renal transplant failure. Therapeutic interventions have yet to resolve this ongoing clinical challenge although the reasons for this remain unclear. The cell surface receptor CD47 is widely expressed on vascular cells and in tissues. It has one known soluble ligand, the stress-released matricellular protein thrombospondin-1 (TSP1). The TSP1-CD47 ligand receptor axis controls a number of important cellular processes, inhibiting survival factors such as nitric oxide, cGMP, cAMP, and VEGF, while activating injurious pathways such as production of reactive oxygen species. A role of CD47 in renal IRI was recently revealed by the finding that the TSP1-CD47 axis is induced in renal tubular epithelial cells (RTEC) under hypoxia and following IRI. The absence of CD47 in knockout mice increases survival, mitigates RTEC damage, and prevents subsequent kidney failure. Conversely, therapeutic blockade of TSP1-CD47 signaling provides these same advantages to wild-type animals. Together, these findings suggest an important role for CD47 in renal IRI as a proximate promoter of injury and as a novel therapeutic target.

Role of CD47 and Signal Regulatory Protein Alpha (SIRPα) in Regulating the Clearance of Viable or Aged Blood Cells

SUMMARY

The ubiquitously expressed cell surface glycoprotein CD47 is expressed by virtually all cells in the host, where it can function to regulate integrin-mediated responses, or constitute an important part of the erythrocyte band 3/Rh multi-protein complex. In addition, CD47 can protect viable cells from being phagocytosed by macrophages or dendritic cells. The latter mechanism is dependent on the interaction between target cell CD47 and SIRPα on the phagocyte. In this context, SIRPα functions to inhibit prophagocytic signaling from Fcγ receptors, complement receptors, and LDL receptor-related protein-1 (LRP-1), but not scavenger receptors. The expression level and/or distribution of CD47 may be altered on the surface of apoptotic/senescent cells, rendering the phagocytosis inhibitory function of the CD47/SIRPα interaction reduced or eliminated. Instead, the interaction between these 2 proteins may serve to enhance the binding of apoptotic/senescent target cells to the phagocyte to promote phagocytosis.

Trauma patients' elevated tumor necrosis related apoptosis inducing ligand (TRAIL) contributes to increased T cell apoptosis

Immunosuppression resulting from excessive post-trauma apoptosis of hyperactivated T cells is controversial. TRAIL mediated T cell apoptosis decreases highly activated T cells' responses. Caspase-10, a particular TRAIL target, was increased in trauma patients' T cells with concomitantly elevated plasma TRAIL levels. These patients' T cells developed anergy, implicating increased TRAIL-mediated T cell apoptosis in post-trauma T cell anergy. Control T cells cultured with patients' sera containing high TRAIL levels increased their caspase-10 activity and apoptosis. Stimulated primary T cells are TRAIL apoptosis resistant. Increased plasma thrombospondin-1 and T cell expression of CD47, a thrombospondin-1 receptor, preceded patients' T cell anergy. CD47 triggering of T cells increased their sensitivity to TRAIL-induced apoptosis. Augmentation of T cell TRAIL-induced apoptosis was secondary to CD47 triggered activation of the Src homology-containing phosphatase-1 (SHP-1) and was partially blocked by a SHP-1 inhibitor. We suggest that combined post-trauma CD47 triggering, SHP-1 mediated NFκB suppression, and elevated TRAIL levels increase patients' CD47 expressing T cell apoptosis, thus contributing to subsequent T cell anergy.

Activation of parenchymal CD47 promotes renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) contributes to decreased allograft function and allograft rejection in transplanted kidneys. Thrombospondin-1 is a stress protein typically secreted in response to hypoxia and the ligand activator for the ubiquitously expressed receptor CD47. The function of activated CD47 in IRI remains completely unknown. Here, we found that both CD47 and its ligand thrombospondin-1 were upregulated after renal IRI in mice. CD47-knockout mice were protected against renal dysfunction and tubular damage, suggesting that the development of IRI requires intact CD47 signaling. Chimeric CD47-knockout mice engrafted with wild-type hematopoietic cells had significantly lower serum creatinine and less tubular damage than wild-type controls after IRI, suggesting that CD47 signaling in parenchymal cells predominantly mediates renal damage. Treatment with a CD47-blocking antibody protected mice from renal dysfunction and tubular damage compared with an isotype control. Taken together, these data imply that CD47 on parenchymal cells promotes injury after renal ischemia and reperfusion. Therefore, CD47 blockade may have therapeutic potential to prevent or suppress ischemia-reperfusion-mediated damage.

CD47(low) status on CD4 effectors is necessary for the contraction/resolution of the immune response in humans and mice

How do effector CD4 T cells escape cell death during the contraction of the immune response (IR) remain largely unknown. CD47, through interactions with thrombospondin-1 (TSP-1) and SIRP-α, is implicated in cell death and phagocytosis of malignant cells. Here, we reported a reduction in SIRP-α-Fc binding to effector memory T cells (T(EM)) and in vitro TCR-activated human CD4 T cells that was linked to TSP-1/CD47-induced cell death. The reduced SIRP-α-Fc binding (CD47(low) status) was not detected when CD4 T cells were stained with two anti-CD47 mAbs, which recognize distinct epitopes. In contrast, increased SIRP-α-Fc binding (CD47(high) status) marked central memory T cells (T(CM)) as well as activated CD4 T cells exposed to IL-2, and correlated with resistance to TSP-1/CD47-mediated killing. Auto-aggressive CD4 effectors, which accumulated in lymph nodes and at mucosal sites of patients with Crohn's disease, displayed a CD47(high) status despite a high level of TSP-1 release in colonic tissues. In mice, CD47 (CD47(low) status) was required on antigen (Ag)-specific CD4 effectors for the contraction of the IR in vivo, as significantly lower numbers of Ag-specific CD47(+/+)CD4 T cells were recovered when compared to Ag-specific CD47(-/-) CD4 T cells. In conclusion, we demonstrate that a transient change in the status of CD47, i.e. from CD47(high) to CD47(low), on CD4 effectors regulates the decision-making process that leads to CD47-mediated cell death and contraction of the IR while maintenance of a CD47(high) status on tissue-destructive CD4 effectors prevents the resolution of the inflammatory response.

The expression of sonic hedgehog in diabetic wounds following treatment with poly(methacrylic acid-co-methyl methacrylate) beads

The expression of native sonic hedgehog (Shh) was significantly increased in poly(methacrylic acid-co-methyl methacrylate) bead (MAA) treated wounds at day 4 compared to both poly(methyl methacrylate) bead (PMMA) treated and untreated wounds in diabetic db/db mice. MAA beads also increased the expression of the Shh transcription factor Gli3 at day 4. Previously, topical application of MAA beads (45 mol % methacrylic acid) improved wound closure and blood vessel density in excisional wounds in these mice, while PMMA beads did not. Gene expression within the granulation tissue of healing wounds was studied to provide insight into the mechanism of vessel formation and wound healing in the presence of MAA beads. In addition to the increased expression of Shh, MAA-treated wounds had increased expression of osteopontin (OPN), IL-1β and TNF-α, (at day 7) similar to the previously reported MAA response of macrophage-like and endothelial cells in vitro.

The matricellular protein thrombospondin-1 globally regulates cardiovascular function and responses to stress via CD47

Matricellular proteins play diverse roles in modulating cell behavior by engaging specific cell surface receptors and interacting with extracellular matrix proteins, secreted enzymes, and growth factors. Studies of such interactions involving thrombospondin-1 have revealed several physiological functions and roles in the pathogenesis of injury responses and cancer, but the relatively mild phenotypes of mice lacking thrombospondin-1 suggested that thrombospondin-1 would not be a central player that could be exploited therapeutically. Recent research focusing on signaling through its receptor CD47, however, has uncovered more critical roles for thrombospondin-1 in acute regulation of cardiovascular dynamics, hemostasis, immunity, and mitochondrial homeostasis. Several of these functions are mediated by potent and redundant inhibition of the canonical nitric oxide pathway. Conversely, elevated tissue thrombospondin-1 levels in major chronic diseases of aging may account for the deficient nitric oxide signaling that characterizes these diseases, and experimental therapeutics targeting CD47 show promise for treating such chronic diseases as well as acute stress conditions that are associated with elevated thrombospondin-1 expression.

Programmed cell removal: a new obstacle in the road to developing cancer

The development of cancer involves mechanisms by which aberrant cells overcome normal regulatory pathways that limit their numbers and their migration. The evasion of programmed cell death is one of several key early events that need to be overcome in the progression from normal cellular homeostasis to malignant transformation. Recently, we provided evidence in mouse and human cancers that successful cancer clones must also overcome programmed cell removal. In this Opinion article, we explore the role of programmed cell removal in both normal and neoplastic cells, and we place this pathway in the context of the initiation of programmed cell death.

Therapeutic Targeting of CD47 to Modulate Tissue Responses to Ischemia and Radiation

CD47 is a widely expressed cell surface receptor that serves as a counter-receptor for signal regulatory protein-α and as a receptor for the secreted matricellular protein thrombospondin-1. Thrombospondin-1 signaling through CD47 regulates cellular signaling pathways that control cell survival, growth, motility, mitochondrial biogenesis, arterial vasoactive responses to physiologic vasodilators and blood flow, and responsiveness to growth factors. Studies employing mice lacking either thrombospondin-1 or CD47 have revealed an important role for this receptor-ligand interaction in tissue responses to injury and stress. These null mice show enhanced recovery from soft tissue fixed ischemic injuries, ischemia reperfusion injuries, and radiation injuries. These studies have led to development of antisense strategies to locally or globally suppress CD47 gene expression. A translation-blocking CD47 morpholino improves tissue survival in skin flap and hindlimb fixed ischemia models, full thickness skin grafts, and a liver ischemia/reperfusion model of organ transplantation in mice. Furthermore, the benefits of morpholino treatment extend to aged mice and mice with dysregulated fat metabolism that characteristically exhibit impaired recovery from ischemic injuries. Activity of the morpholino was also demonstrated for treatment of ischemic injury in miniature pigs. Treatment with the CD47 morpholino protects mice from major effects of ionizing radiation including alopecia, deterioration of muscle function, soft tissue and cutaneous fibrosis, and loss of hematopoietic stem cells in bone marrow. Remarkably, the same treatment does not protect tumors but instead enhances their ablation by irradiation. We discuss prospects for further development of CD47 antisense therapeutics for clinical applications including reconstructive surgery, organ transplantation, angioplasty, and cancer.

Thrombospondin-1: multiple paths to inflammation

Inflammation is a defensive process against tissue injury. Once this self-protective strategy is initiated, an effective resolution of the process is crucial to avoid major and unnecessary tissue damage. If the underlying event inducing inflammation is not addressed and homeostasis is not restored, this process can become chronic and lead to angiogenesis and carcinogenesis. Thrombospondin-1 (TSP-1) is a matricellular protein involved in angiogenesis, cancer, and inflammation. The effects of TSP-1 have been studied in many preclinical tumor models, and mimetic peptides are being tested in cancer clinical trials. However, the molecular mechanisms explaining its role in inflammatory processes are not well understood. This paper will discuss the role of TSP-1 in inflammation and its interaction with key receptors that may explain its functions in that process. Recent literature will be reviewed showing novel mechanisms by which this multifaceted protein could modulate the inflammatory process and impact its resolution.

Correlation of BRCA1, TXR1 and TSP1 mRNA expression with treatment outcome to docetaxel-based first-line chemotherapy in patients with advanced/metastatic non-small-cell lung cancer

BACKGROUND

We explored the predictive significance of BRCA1, TXR1 and TSP1 expression in non-small-cell lung cancer (NSCLC) patients treated with docetaxel in association with cisplatin or gemcitabine.

METHODS

To analyse BRCA1, TXR1 and TSP1 mRNA expression from microdissected primary tumours of 131 patients with stage IIIB (wet) and IV NSCLC, RT-qPCR was used.

RESULTS

The mRNA levels of TXR1/TSP1 were inversely correlated (Spearman's test: -0.37; P=0.001). Low TXR1 mRNA levels were associated with higher response rate (RR; P=0.018), longer median progression-free survival (PFS; P=0.029) and median overall survival (mOS P=0.003), whereas high TSP1 expression was correlated with higher RR (P=0.035), longer PFS (P<0.001) and mOS (P<0.001). Higher BRCA1 mRNA expression was associated with higher RR (P=0.028) and increased PFS (P=0.021), but not mOS (P=0.4). Multivariate analysis demonstrated that low TXR1/high TSP1 expression was an independent factor for increased PFS (HR 0.49; 95% CI 0.32-0.76; P<0.001) and mOS (HR 0.37; 95% CI 0.2-0.58; P<0.001), whereas high BRCA1 expression was correlated with increased PFS (HR 0.53; 95% CI 0.37-0.78; P=0.001).

CONCLUSIONS

These data indicate that TXR1/TSP1 and BRCA1 expression could be used for the prediction of taxanes' resistance in the treatment of NSCLC.

The regulation of the CNS innate immune response is vital for the restoration of tissue homeostasis (repair) after acute brain injury: a brief review

Neurons and glia respond to acute injury by participating in the CNS innate immune response. This involves the recognition and clearance of "not self " pathogens and "altered self " apoptotic cells. Phagocytic receptors (CD14, CD36, TLR-4) clear "not self" pathogens; neurons and glia express "death signals" to initiate apoptosis in T cells.The complement opsonins C1q, C3, and iC3b facilitate the clearance of apoptotic cells by interacting with CR3 and CR4 receptors. Apoptotic cells are also cleared by the scavenger receptors CD14, Prs-R, TREM expressed by glia. Serpins also expressed by glia counter the neurotoxic effects of thrombin and other systemic proteins that gain entry to the CNS following injury. Complement pathway and T cell activation are both regulated by complement regulatory proteins expressed by glia and neurons. CD200 and CD47 are NIRegs expressed by neurons as "don't eat me" signals and they inhibit microglial activity preventing host cell attack. Neural stem cells regulate T cell activation, increase the Treg population, and suppress proinflammatory cytokine expression. Stem cells also interact with the chemoattractants C3a, C5a, SDF-1, and thrombin to promote stem cell migration into damaged tissue to support tissue homeostasis.

Radioprotection in normal tissue and delayed tumor growth by blockade of CD47 signaling

Radiation-induced damage of normal tissues restricts the therapeutic doses of ionizing radiation that can be delivered to tumors and thereby limits the effectiveness of radiotherapy. Thrombospondin-1 signaling through its cell surface receptor CD47 limits recovery from several types of stress, and mice lacking either gene are profoundly resistant to radiation injury. We describe strategies to protect normal tissues from radiation damage using CD47 or thrombospondin-1 antibodies, a CD47-binding peptide, or antisense suppression of CD47. A morpholino oligonucleotide targeting CD47 confers radioresistance to human endothelial cells in vitro and protects soft tissue, bone marrow, and tumor-associated leukocytes in irradiated mice. In contrast, CD47 suppression in mice bearing melanoma or squamous lung tumors prior to irradiation result in 89% and 71% smaller tumors, respectively. Thus, inhibiting CD47 signaling maintains the viability of normal tissues following irradiation while increasing the radiosensitivity of tumors.

Thrombospondin-1/CD47 blockade following ischemia-reperfusion injury is tissue protective

BACKGROUND

Nitric oxide has prosurvival effects that can limit ischemia-reperfusion injuries. However, the matrix glycoprotein thrombospondin-1 is induced following ischemia-reperfusion injury and limits nitric oxide signaling by engaging its cell surface receptor CD47. In this article, the authors examine whether postinjury blocking of this inhibitory signal can protect from ischemia-reperfusion injury in a rat flap model.

METHODS

A total of 40 tissue flaps were created in rats based solely on the deep inferior epigastric vessels. Microvascular clamps were used to create 45 minutes of ischemia time to the flaps. The flaps were then treated using a monoclonal antibody to CD47 or an isotype-matched control immunoglobulin G1 5 or 30 minutes after clamp removal. Twenty-four or 72 hours postoperatively, the necrotic area of the flap was determined, and serum, deep inferior epigastric vessels, and flaps were harvested for analysis from five rats in each respective group.

RESULTS

Treatment with a CD47 antibody 5 minutes after reperfusion significantly reduces flap necrosis compared with immunoglobulin G1 control (9 percent versus 43 percent; p < 0.01). The protective effect is even more dramatic when treatment is delayed until 30 minutes after reperfusion (10 percent versus 88 percent for control; p < 0.01). Markers of neutrophil and endothelial cell activation along with total leukocytes are reduced in CD47 antibody-treated flaps, as are tissue malondialdehyde levels. Levels of cyclic guanosine monophosphate are elevated 72 hours postoperatively in the CD47 antibody-treated deep inferior epigastric vessels versus the control flaps.

CONCLUSIONS

Therapies targeting the thrombospondin-1 receptor CD47 offer potential for increasing tissue survival in ischemia-reperfusion injuries. The ability to protect when given after ischemia-reperfusion injury enables a broader clinical applicability.

Decreased CD47 expression during spontaneous apoptosis targets neutrophils for phagocytosis by monocyte-derived macrophages

BACKGROUND

Neutrophils (PMN) are the primary leukocyte responders during acute inflammation. After migrating into the tissues, PMN undergo programmed cell death (apoptosis) and are subsequently removed via phagocytosis by resident macrophages during the resolution phase. Efficient phagocytosis of apoptotic neutrophils is necessary for successful resolution. CD47 plays a critical role in mediating the phagocytic response, although its role in the phagocytosis of apoptotic PMN is incompletely understood.

AIMS

In the present study we tested the hypotheses that CD47 modulates the targeting of apoptotic PMN for phagocytosis, and that this process is altered in neonatal PMN.

STUDY DESIGN

Adult and neonatal PMN were examined for their expression of CD47. To investigate CD47-mediated functions, apoptotic adult and neonatal PMN were co-cultured with monocyte-derived macrophages (MDM) and the phagocytic index was determined using a flow cytometry-based assay.

RESULTS

We observed lower basal surface CD47 levels on neonatal vs. adult PMN. In both groups, spontaneous apoptosis led to decreased surface and total cellular CD47 expression. Adult and neonatal MDM ingested apoptotic neonatal target PMN more avidly than apoptotic adult target PMN. Masking of surface CD47 on PMN with a monoclonal antibody enhanced MDM phagocytic activity.

CONCLUSIONS

Our results suggest that age-dependent expression of CD47 on PMN may account for differences in their ingestion by macrophages and in the resolution of inflammation.