Targeting CD47: the achievements and concerns of current studies on cancer immunotherapy

CD47: the next checkpoint target for cancer immunotherapy

Cancer immunotherapy using checkpoint blockade has brought about a paradigm shift in the treatment of advanced-stage cancers. Unfortunately, not all patients benefit from these therapies, paving the way for other immune checkpoints to be targeted. CD47, a 'marker-of-self' protein that is overexpressed broadly across tumor types, is emerging as a novel potent macrophage immune checkpoint for cancer immunotherapy. Recently, CD47 blockade by Hu5F9-G4 has shown promise combined with Rituximab in non-Hodgkin's lymphoma. Here we review the complex structure and various physiological functions of CD47 and their implications in cancer biology. Further, this review considers future directions and challenges in advancing this promising target platform to widespread therapeutic use.

Pharmacologic targeting of renal ischemia-reperfusion injury using a normothermic machine perfusion platform

Normothermic machine perfusion (NMP) is an emerging modality for kidney preservation prior to transplantation. NMP may allow directed pharmacomodulation of renal ischemia-reperfusion injury (IRI) without the need for systemic donor/recipient therapies. Three proven anti-IRI agents not in widespread clinical use, CD47-blocking antibody (αCD47Ab), soluble complement receptor 1 (sCR1), and recombinant thrombomodulin (rTM), were compared in a murine model of kidney IRI. The most effective agent was then utilized in a custom NMP circuit for the treatment of isolated porcine kidneys, ascertaining the impact of the drug on perfusion and IRI-related parameters. αCD47Ab conferred the greatest protection against IRI in mice after 24 hours. αCD47Ab was therefore chosen as the candidate agent for addition to the NMP circuit. CD47 receptor binding was demonstrated by immunofluorescence. Renal perfusion/flow improved with CD47 blockade, with a corresponding reduction in oxidative stress and histologic damage compared to untreated NMP kidneys. Tubular and glomerular functional parameters were not significantly impacted by αCD47Ab treatment during NMP. In a murine renal IRI model, αCD47Ab was confirmed as a superior anti-IRI agent compared to therapies targeting other pathways. NMP enabled effective, direct delivery of this drug to porcine kidneys, although further efficacy needs to be proven in the transplantation setting.

Improved Antitumor Efficacy of Chimeric Antigen Receptor T Cells that Secrete Single-Domain Antibody Fragments

Chimeric antigen receptor (CAR) T-cell therapy is effective in the treatment of cancers of hematopoietic origin. In the immunosuppressive solid tumor environment, CAR T cells encounter obstacles that compromise their efficacy. We developed a strategy to address these barriers by having CAR T cells secrete single-domain antibody fragments [variable heavy domain of heavy chain antibodies (VHH) or nanobodies] that can modify the intratumoral immune landscape and thus support CAR T-cell function in immunocompetent animals. VHHs are small in size and able to avoid domain swapping when multiple nanobodies are expressed simultaneously-features that can endow CAR T cells with desirable properties. The secretion of an anti-CD47 VHH by CAR T cells improves engagement of the innate immune system, enables epitope spreading, and can enhance the antitumor response. CAR T cells that secrete anti-PD-L1 or anti-CTLA-4 nanobodies show improved persistence and demonstrate the versatility of this approach. Furthermore, local delivery of secreted anti-CD47 VHH-Fc fusions by CAR T cells at the tumor site limits their systemic toxicity. CAR T cells can be further engineered to simultaneously secrete multiple modalities, allowing for even greater tailoring of the antitumor immune response.

Microbiota-derived SSL6 enhances the sensitivity of hepatocellular carcinoma to sorafenib by down-regulating glycolysis

Enhancing the sensitivity of hepatocellular carcinoma (HCC) cells to sorafenib (SFN) is an essential clinical bottleneck to be solved. Here we report that the expression of CD47 negatively correlated with HCC sensitivity to SFN. The microbiota-derived Staphylococcal superantigen-like protein 6 (SSL6) inhibited CD47 and promoted SFN-induced apoptosis of HCC cells Huh-7 and MHCC97H. Mechanistically, the sensitivity of HCC cells to SFN was inhibited by elevated Warburg effect (glycolysis), and SSL6 down-regulated PI3K/Akt-mediated glycolysis by blocking CD47. Knockdown of CD47 also dampened glycolysis and sensitized HCC cells to SFN. Moreover, SFN-resistant HCC cells exhibited enhanced glycolysis and CD47 expression. SSL6 significantly re-sensitized the resistant HCC cells to SFN. More importantly, we identified the anti-tumor effect of SSL6 in combination with SFN in HCC-bearing mice. Our results clarify the mechanism by which SSL6 enhances SFN sensitivity in HCC cells, providing a molecular basis for combination targeted therapy with microbiota-derived SSL6 to treat HCC.

Lipid-based phagocytosis nanoenhancer for macrophage immunotherapy

Tumor associated macrophages (TAMs) play an important role in initiating the immunosuppressive environment that negatively impacts the immunotherapy efficacy and has long been linked with cancer progression. On the other hand, activated macrophages display immense phagocytic potential and can be used as an effector cell for cancer therapy. But, activating TAMs to effectively phagocytose cancer cells is challenging. Cancer cells upregulate CD47, a "don't eat me" receptor that ligates with SIRPα present on macrophages to downregulate the phagocytosis. Since phagocytosis is a physical phenomenon based on engulfment of aberrant cells, we hypothesized that the phagocytic function of macrophages can be enhanced by blocking both CD47 and SIRPα in tandem and at the same time, engaging both macrophages and cancer cells can favor increased macrophage-cancer cellular interactions. Here, we demonstrate that a simple approach of anti-CD47 and anti-SIRPα antibodies conjugated lipid-based phagocytosis nanoenhancer (LPN) can perform both of these functions. The LPNs were stable in both physiological and biologically relevant conditions, bound to both macrophages and cancer cells and significantly enhanced phagocytosis of cancer cells as compared to combination of free antibodies. LPN treatment showed significant tumor growth inhibition and increased survival in B16F10 melanoma tumor bearing mice with no systemic toxicity. Mechanistic analysis of efficacy revealed an increase in intra-tumoral infiltration of effector T cells and NK cells. Cytokine analysis revealed increased secretion of intracellular iNOS, a hallmark of activated macrophages. This study shows that LPN can simultaneously block both CD47 and SIRPα and can effectively engage macrophage and cancer cell in close proximity. Combining these facets provide a simple approach to enhance phagocytosis and improve anti-cancer macrophage immunotherapy.

Preclinical development of a novel CD47 nanobody with less toxicity and enhanced anti-cancer therapeutic potential

BACKGROUND

CD47, the integrin-related protein, plays an important role in immune resistance and escape of tumor cells. Antibodies blocking the CD47/SIRPα signal pathway can effectively stimulate macrophage-mediated phagocytosis of tumor cells, which becomes a promising approach for tumor immunotherapy. Nanobodies (Nbs) derived from camelid animals are emerging as a new force in antibody therapy.

RESULTS

HuNb1-IgG4, an innovative anti-CD47 nanobody, was developed with high affinity and specificity. It effectively enhanced macrophage-mediated phagocytosis of tumor cells in vitro and showed potent anti-ovarian and anti-lymphoma activity in vivo. Importantly, HuNb1-IgG4 did not induce the agglutination of human red blood cells (RBCs) in vitro and exhibited high safety for hematopoietic system in cynomolgus monkey. In addition, HuNb1-IgG4 could be produced on a large scale in CHO-S cells with high activity and good stability. Also, we established anti-CD47/CD20 bispecific antibody (BsAb) consisted of HuNb1 and Rituximab, showing more preference binding to tumor cells and more potent anti-lymphoma activity compared to HuNb1-IgG4.

CONCLUSIONS

Both of HuNb1-IgG4 and anti-CD47/CD20 BsAb are potent antagonists of CD47/SIRPα pathway and promising candidates for clinical trials.

Hydrogel-Based Controlled Drug Delivery for Cancer Treatment: A Review

As an emerging drug carrier, hydrogels have been widely used for tumor drug delivery. A hydrogel drug carrier can cause less severe side effects than systemic chemotherapy and can achieve sustained delivery of a drug at tumor sites. In addition, hydrogels have excellent biocompatibility and biodegradability and lower toxicity than nanoparticle carriers. Smart hydrogels can respond to stimuli in the environment (e.g., heat, pH, light, and ultrasound), enabling in situ gelation and controlled drug release, which greatly enhance the convenience and efficiency of drug delivery. Here, we summarize the different sizes of hydrogels used for cancer treatment and their related delivery routes, discuss the design strategies for stimuli-responsive hydrogels, and review the research concerning smart hydrogels reported in the past few years.

Inducing Tumor Suppressive Microenvironments through Genome Edited CD47-/- Syngeneic Cell Vaccination

Tumors can escape from the immune system by overexpressing CD47 and other checkpoint blockades. CD47 is expressed ubiquitously by all cells in the body, posing an obstacle for CD47 blocking treatments due to their systemic toxicity. We performed a study to determine how the tumor microenvironment changes after vaccination with genome edited CD47-/- syngeneic tumor cells. We discovered that inactivated CD47-depleted mouse melanoma cells can protect mice from melanoma. Our animal study indicated that 33% of vaccinated mice remained tumor-free, and 100% of mice had 5-fold reduced growth rates. The characterization of immunomodulatory effects of the vaccine revealed a highly anti-tumorigenic and homogenous microenvironment after vaccination. We observed consistently that in the tumors that failed to respond to vaccines, there were reduced natural killer cells, elevated regulatory T cells, M2-type macrophages, and high PD-L1 expression in these cells. These observations suggested that the tumor microenvironments became more suppressive to tumor growth after vaccination, suggesting a potential new immunotherapy for solid tumors.

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.

CD47 blockade augmentation of trastuzumab antitumor efficacy dependent on antibody-dependent cellular phagocytosis

The HER2-specific monoclonal antibody (mAb), trastuzumab, has been the mainstay of therapy for HER2+ breast cancer (BC) for approximately 20 years. However, its therapeutic mechanism of action (MOA) remains unclear, with antitumor responses to trastuzumab remaining heterogeneous and metastatic HER2+ BC remaining incurable. Consequently, understanding its MOA could enable rational strategies to enhance its efficacy. Using both murine and human versions of trastuzumab, we found its antitumor activity dependent on Fcγ receptor stimulation of tumor-associated macrophages (TAMs) and antibody-dependent cellular phagocytosis (ADCP), but not cellular cytotoxicity (ADCC). Trastuzumab also stimulated TAM activation and expansion, but did not require adaptive immunity, natural killer cells, and/or neutrophils. Moreover, inhibition of the innate immune ADCP checkpoint, CD47, significantly enhanced trastuzumab-mediated ADCP and TAM expansion and activation, resulting in the emergence of a unique hyperphagocytic macrophage population, improved antitumor responses, and prolonged survival. In addition, we found that tumor-associated CD47 expression was inversely associated with survival in HER2+ BC patients and that human HER2+ BC xenografts treated with trastuzumab plus CD47 inhibition underwent complete tumor regression. Collectively, our study identifies trastuzumab-mediated ADCP as an important antitumor MOA that may be clinically enabled by CD47 blockade to augment therapeutic efficacy.

CD47-SIRPα Signaling Induces Epithelial-Mesenchymal Transition and Cancer Stemness and Links to a Poor Prognosis in Patients with Oral Squamous Cell Carcinoma

Background: Oral squamous cell carcinoma (OSCC), with high mortality rates, is one of the most diagnosed head and neck cancers. Epithelial-to-mesenchymal transition (EMT) and the generation of cancer stem cells (CSCs) are two keys for therapy-resistance, relapse, and distant metastasis. Accumulating evidence indicates that aberrantly expressed cluster of differentiation (CD)47 is associated with cell-death evasion and metastasis; however, the role of CD47 in the generation of CSCs in OSCC is not clear. Methods: We investigated the functional roles of CD47 in OSCC cell lines SAS, TW2.6, HSC-3, and FaDu using the bioinformatics approach, immunoblotting, immunofluorescence staining, and assays for cellular migration, invasion, colony, and orosphere formation, as well as radiosensitivity. Results: We demonstrated increased expression of CD47 in OSCC patients was associated with an estimated poorly survival disadvantage (p = 0.0391) and positively correlated with the expression of pluripotency factors. Silencing CD47 significantly suppressed cell viability and orosphere formation, accompanied by a downregulated expression of CD133, SRY-Box transcription factor 2 (SOX2), octamer-binding transcription factor 4 (OCT4), and c-Myc. In addition, CD47-silenced OSCC cells showed reduced EMT, migration, and clonogenicity reflected by increased E-cadherin and decreased vimentin, Slug, Snail, and N-cadherin expression. Conclusion: Of therapeutic relevance, CD47 knockdown enhanced the anti-OSCC effect of radiotherapy. Collectively, we showed an increased CD47 expression promoted the generation of CSCs and malignant OSCC phenotypes. Silencing CD47, in combination with radiation, could provide an alternative and improved therapeutic efficacy for OSCC patients.

Drug delivery to macrophages: A review of targeting drugs and drug carriers to macrophages for inflammatory diseases

Macrophages play a key role in defending against foreign pathogens, healing wounds, and regulating tissue homeostasis. Driving this versatility is their phenotypic plasticity, which enables macrophages to respond to subtle cues in tightly coordinated ways. However, when this coordination is disrupted, macrophages can aid the progression of numerous diseases, including cancer, cardiovascular disease, and autoimmune disease. The central link between these disorders is aberrant macrophage polarization, which misguides their functional programs, secretory products, and regulation of the surrounding tissue microenvironment. As a result of their important and deterministic roles in both health and disease, macrophages have gained considerable attention as targets for drug delivery. Here, we discuss the role of macrophages in the initiation and progression of various inflammatory diseases, summarize the leading drugs used to regulate macrophages, and review drug delivery systems designed to target macrophages. We emphasize strategies that are approved for clinical use or are poised for clinical investigation. Finally, we provide a prospectus of the future of macrophage-targeted drug delivery systems.

Epithelial CD47 is critical for mucosal repair in the murine intestine in vivo

CD47 is a ubiquitously expressed transmembrane glycoprotein that regulates inflammatory responses and tissue repair. Here, we show that normal mice treated with anti-CD47 antibodies, and Cd47-null mice have impaired intestinal mucosal wound healing. Furthermore, intestinal epithelial cell (IEC)-specific loss of CD47 does not induce spontaneous immune-mediated intestinal barrier disruption but results in defective mucosal repair after biopsy-induced colonic wounding or Dextran Sulfate Sodium (DSS)-induced mucosal damage. In vitro analyses using primary cultures of CD47-deficient murine colonic IEC or human colonoid-derived IEC treated with CD47-blocking antibodies demonstrate impaired epithelial cell migration in wound healing assays. Defective wound repair after CD47 loss is linked to decreased epithelial β1 integrin and focal adhesion signaling, as well as reduced thrombospondin-1 and TGF-β1. These results demonstrate a critical role for IEC-expressed CD47 in regulating mucosal repair and raise important considerations for possible alterations in wound healing secondary to therapeutic targeting of CD47.

The role of the transmembrane glycoprotein CD47 in healing injured intestinal mucosa is unclear. Here, the authors show that selective loss of CD47 in the murine intestinal epithelium results in defective mucosal repair after colonic wounding, with suggested impaired cell migration in vitro.

Monoclonal Antibodies in Dermatooncology-State of the Art and Future Perspectives

Monoclonal antibodies (mAbs) targeting specific proteins are currently the most popular form of immunotherapy used in the treatment of cancer and other non-malignant diseases. Since the first approval of anti-CD20 mAb rituximab in 1997 for the treatment of B-cell malignancies, the market is continuously booming and the clinically used mAbs have undergone a remarkable evolution. Novel molecular targets are constantly emerging and the development of genetic engineering have facilitated the introduction of modified mAbs with improved safety and increased capabilities to activate the effector mechanisms of the immune system. Next to their remarkable success in hematooncology, mAbs have also an already established role in the treatment of solid malignancies. The recent development of mAbs targeting the immune checkpoints has opened new avenues for the use of this form of immunotherapy, also in the immune-rich milieu of the skin. In this review we aim at presenting a comprehensive view of mAbs' application in the modern treatment of skin cancer. We present the characteristics and efficacy of mAbs currently used in dermatooncology and summarize the recent clinical trials in the field. We discuss the side effects and strategies for their managing.

Sprayable gel for postsurgical immunotherapy

Background

Surgery remains the first option to treat most solid tumors. However, despite the development of surgical techniques, the elimination of tumor recurrence after surgery remains a challenge.

Design

In a recent study published in Nature Nanotechnology, we described an in-situ-sprayed gel for local delivery of bioresponsive and immunotherapeutic calcium carbonate nanoparticles encapsulated with anti-CD47 antibodies (aCD47@CaCO₃) to the surgical site after surgery. CaCO₃ nanoparticles react with H⁺ in the surgical wound site, eliciting an immunosupportive tumor microenvironment after surgery. Meanwhile, the subsequently released aCD47 blocks the ‘don’t eat me’ signal expressed on cancer cells to increase the phagocytosis of cancer cells by macrophages and activate T-cell-mediated antitumor immune responses.

Conclusion

The engineered immunotherapeutic gel could activate both innate and adaptive immune responses systemically after local treatment, effectively destroying the remaining cancer cells and reducing tumor recurrence.

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An in-situ-sprayed immunotherapeutic scaffold was engineered for convenient postsurgical treatment.

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The regulated acidic tumor microenvironment to elicit immunosupportive responses.

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Local, bioresponsive delivery of immunotherapeutics to tumor improves effect and reduces toxicity.

Thrombospondin 1 and Its Diverse Roles as a Regulator of Extracellular Matrix in Fibrotic Disease

Thrombospondin 1 (TSP1) is a matricellular extracellular matrix protein that has diverse roles in regulating cellular processes important for the pathogenesis of fibrotic diseases. We will present evidence for the importance of TSP1 control of latent transforming growth factor beta activation in renal fibrosis with an emphasis on diabetic nephropathy. Other functions of TSP1 that affect renal fibrosis, including regulation of inflammation and capillary density, will be addressed. Emerging roles for TSP1 N-terminal domain regulation of collagen matrix assembly, direct effects of TSP1-collagen binding, and intracellular functions of TSP1 in mediating endoplasmic reticulum stress responses in extracellular matrix remodeling and fibrosis, which could potentially affect renal fibrogenesis, will also be discussed. Finally, we will address possible strategies for targeting TSP1 functions to treat fibrotic renal disease.

Bioresponsive Protein Complex of aPD1 and aCD47 Antibodies for Enhanced Immunotherapy

Despite the promising efficacy of immune checkpoint blockade (ICB) in treating many types of cancers, the clinical benefits have often been restricted by the low objective response rates and systemic immune-related adverse events. Here, a bioresponsive ICB treatment is developed based on the reactive oxygen species (ROS)-sensitive protein complex for controlled sequential release of anti- "don't eat me" signal antibody (aCD47) and antiprogrammed cell death protein 1 (aPD1), by leveraging the abundant ROS in the tumor microenvironment (TME). These protein complexes can also act as scavengers of ROS in the TME to reverse the immunosuppressive responses, thereby enhancing antitumor efficacy in vivo. In a melanoma cancer model, the synergistic antitumor efficacy was achieved, which was accompanied by enhanced T cell immune responses together with reduced immunosuppressive responses.

Antibody-Directed Therapies: Toward a Durable and Tolerable Treatment Platform for CTCL

Cutaneous T-cell lymphomas (CTCL) are a rare group of heterogeneous disorders characterized by cutaneous involvement of monoclonal T-lymphocytes. Although indolent at early stages, CTCL can confer significant morbidity, and mortality when advanced. There is an unmet need for tolerable and durable treatments with antibodies recently gaining promise. Here we review approved systemic therapies and discuss select antibodies in development.

Programmable bacteria induce durable tumor regression and systemic antitumor immunity

Synthetic biology is driving a new era of medicine through the genetic programming of living cells^1,2. This transformative approach allows for the creation of engineered systems that intelligently sense and respond to diverse environments, ultimately adding specificity and efficacy that extends beyond the capabilities of molecular-based therapeutics^3–6. One particular focus area has been the engineering of bacteria as therapeutic delivery systems to selectively release therapeutic payloads in vivo^7–11. Here, we engineered a non-pathogenic E. coli to specifically lyse within the tumor microenvironment and release an encoded nanobody antagonist of CD47 (CD47nb)¹², an anti-phagocytic receptor commonly overexpressed in several human cancers^13,14. We show that delivery of CD47nb by tumor-colonizing bacteria increases activation of tumor-infiltrating T cells, stimulates rapid tumor regression, prevents metastasis, and leads to long-term survival in a syngeneic tumor model. Moreover, we report that local injection of CD47nb bacteria stimulates systemic tumor antigen–specific immune responses that reduce the growth of untreated tumors – providing, to the best of our knowledge, the first demonstration of an abscopal effect induced by an engineered bacterial immunotherapy. Thus, engineered bacteria may be used for safe and local delivery of immunotherapeutic payloads leading to systemic antitumor immunity.

Targeting CD47 as a cancer therapeutic strategy: the cutaneous T-cell lymphoma experience

PURPOSE OF REVIEW

To describe the relevance of CD47 in the tumor microenvironment and summarize data on anti-CD47 therapies, including its role in cutaneous T-cell lymphoma (CTCL).

RECENT FINDINGS

CD47 is expressed on all normal cells and targets SIRPα on the surface of myeloid cells. However, CD47 is found to be overexpressed on cancer cells. CD47-SIRPα interaction inhibits macrophage phagocytosis, allowing cancer cells to escape immune surveillance. Current focus in immunotherapy has been targeted toward inhibiting CD47-SIRPα interaction via anti-CD47 antibodies. This activates innate immunity, promoting cancer cell destruction by macrophages. It also activates adaptive immunity resulting in antigen-presentation, mostly by dendritic cells, leading to antitumor cytotoxic reactions. Current CD47 antagonists undergoing clinical trials include Hu5F9 (an anti-CD47 antibody that directly inhibits the CD47-SIRPα interaction) and TTI-621, (a fusion protein composed of CD47 binding domain of human SIRPα and linked to the Fc region of IgG1). These agents have continued to show strong efficacy against solid and hematological tumors.

SUMMARY

In the CTCL tumor microenvironment, increased immune checkpoint inhibition expression via CD47 bound to SIRPα correlates with a more advanced disease state. Continued success in treating these patients requires further studies on CD47 antagonists, specifically when combined with other antibodies.

Tumor Microenvironment-Activatable Prodrug Vesicles for Nanoenabled Cancer Chemoimmunotherapy Combining Immunogenic Cell Death Induction and CD47 Blockade

Chemoimmunotherapy is reported to activate a robust T cell antitumor immune response by triggering immunogenic cell death (ICD), which has initiated a number of clinical trials. However, current chemoimmunotherapy is restricted to a small fraction of patients due to low drug delivery efficacy and immunosuppression within the tumor microenvironment. A tumor microenvironment-activatable prodrug vesicle for cancer chemoimmunotherapy using ICD is herein reported. The prodrug vesicles are engineered by integrating an oxaliplatin (OXA) prodrug and PEGylated photosensitizer (PS) into a single nanoplatform, which show tumor-specific accumulation, activation, and deep penetration in response to the tumoral acidic and enzymatic microenvironment. It is demonstrated that codelivery of OXA prodrug and PS can trigger ICD of the tumor cells by immunogenic cells killing. The combination of prodrug vesicle-induced ICD with Î ± CD47-mediated CD47 blockade further facilitates dendritic cell (DC) maturation, promotes antigen presentation by DCs, and eventually propagates the antitumor immunity of ICD. CD47 blockade and ICD induction efficiently inhibit the growth of both primary and abscopal tumors, suppress tumor metastasis, and prevent tumor recurrence. Collectively, these results imply that boosting antitumor immunity using ICD induction and suppressing tumor immune evasion via CD47 blockade might be promising for improved cancer chemoimmunotherapy.

Functional genomics: paving the way for more successful cancer immunotherapy

Immunotherapies have revolutionized cancer treatment. Immunotherapy is effective for the treatment of a wide range of cancer types and can mediate complete and durable tumor regression. Nonetheless, the field still faces many significant challenges, such as the need for personalized therapeutic strategies and better biomarkers, the difficulty of selecting the right combination therapy, and resistance to currently available immunotherapies. Both cancer and host immunity comprise significantly diverse and complex ecosystems, making immunogenomics an ideal field for functional genomics analysis. In this review, we describe the cancer-immunity cycle, how cancer cells manage to evade immune attack and the current hurdles in the path of cancer immunotherapy. Then, we discuss how functional genomics approaches can pave the way for more successful cancer immunotherapies.

In situ sprayed bioresponsive immunotherapeutic gel for post-surgical cancer treatment

Cancer recurrence after surgical resection remains a significant cause of treatment failure. Here, we have developed an in situ formed immunotherapeutic bioresponsive gel that controls both local tumour recurrence after surgery and development of distant tumours. Briefly, calcium carbonate nanoparticles pre-loaded with the anti-CD47 antibody are encapsulated in the fibrin gel and scavenge H⁺ in the surgical wound, allowing polarization of tumour-associated macrophages to the M1-like phenotype. The released anti-CD47 antibody blocks the 'don't eat me' signal in cancer cells, thereby increasing phagocytosis of cancer cells by macrophages. Macrophages can promote effective antigen presentation and initiate T cell mediated immune responses that control tumour growth. Our findings indicate that the immunotherapeutic fibrin gel 'awakens' the host innate and adaptive immune systems to inhibit both local tumour recurrence post surgery and potential metastatic spread.

Autoimmunity-associated intronic SNP (rs2281808) detected by a simple phenotypic assay: Unique case or broader opportunity?

Multiple genome-wide association studies have shown that the single-nucleotide polymorphism (SNP) rs2281808 TT variant, present within the signal regulatory protein gamma (SIRPG) gene, is associated with autoimmune diseases, such as type 1 diabetes. SIRPγ is the only SIRP expressed on T cells. The role of SIRPγ in human T-cells or the effect of the TT variant are poorly understood. In this short report, we demonstrate the rather unusual finding that this intronic SNP is associated with a reduction of SIRPγ expression on T cells, both in healthy subjects as well as patients with type 1 diabetes. Using this information, we propose that a simple flow cytometric detection of SIRPγ could be a potential diagnostic testing approach for the presence of SNP in the appropriate clinical context.

A multi-functional macrophage and tumor targeting gene delivery system for the regulation of macrophage polarity and reversal of cancer immunoresistance

To achieve effective tumor eradication using anti-tumor immunotherapies, a fusion peptide functionalized gene delivery system for macrophage and tumor targeting delivery of the plasmid DNA encoding the IL-12 gene (pDNA IL-12) was prepared for macrophage re-polarization as well as reversal of cancer immunosuppression. A fusion peptide containing the tuftsin sequence that can interact with Fc receptors and neuropilin-1, and hyaluronic acid (HA) that can interact with CD44 were introduced into the delivery system by self-assembly to form peptide/hyaluronic acid/protamine/CaCO3/DNA nanoparticles (PHNP) with both macrophage targeting and tumor targeting capabilities. PHNP provides an efficient immunoregulation on J774A.1 cells to shift the anti-inflammatory M2 phenotype to the anti-tumor M1 phenotype with enhanced secretion of pro-inflammatory cytokines and increased expression of M1 markers. Owing to the improved delivery efficiency caused by the fusion peptide and HA, the transfection mediated by multi-functional PHNP can up-regulate IL-12 as well as down-regulate IL-10 and IL-4 more effectively as compared with the nanoparticles without HA and/or peptide decoration. More importantly, the gene delivery system can also deliver pDNA IL-12 to targeted cancerous HeLa cells to realize the secretion of IL-12. PHNP not only enables tumorous cells to produce pDNA IL-12, but also down-regulates CD47 and up-regulate CD80 and HLA-1 in the malignant cells, indicating that the gene delivery system can effectively reverse tumor induced immunosuppression.

Notch Signaling Modulates Macrophage Polarization and Phagocytosis Through Direct Suppression of Signal Regulatory Protein α Expression

The Notch pathway plays critical roles in the development and functional modulation of myeloid cells. Previous studies have demonstrated that Notch activation promotes M1 polarization and phagocytosis of macrophages; however, the downstream molecular mechanisms mediating Notch signal remain elusive. In an attempt to identify Notch downstream targets in bone marrow-derived macrophages (BMDMs) using mass spectrometry, the signal regulatory protein α (SIRPα) appeared to respond to knockout of recombination signal-binding protein Jk (RBP-J), the critical transcription factor of Notch pathway, in macrophages. In this study, we validated that Notch activation could repress SIRPα expression likely via the Hes family co-repressors. SIRPα promoted macrophage M2 polarization, which was dependent on the interaction with CD47 and mediated by intracellular signaling through SHP-1. We provided evidence that Notch signal regulated macrophage polarization at least partially through SIRPα. Interestingly, Notch signal regulated macrophage phagocytosis of tumor cells through SIRPα but in a SHP-1-independent way. To access the translational value of our findings, we expressed the extracellular domains of the mouse SIRPα (mSIRPα^ext) to block the interaction between CD47 and SIRPα. We demonstrated that the soluble mSIRPα^ext polypeptides could promote M1 polarization and increase phagocytosis of tumor cells by macrophages. Taken together, our results provided new insights into the molecular mechanisms of notch-mediated macrophage polarization and further validated SIRPα as a target for tumor therapy through modulating macrophage polarization and phagocytosis.

CD47 promotes ovarian cancer progression by inhibiting macrophage phagocytosis

Targeting CD47 efficiently enhances macrophage phagocytosis in both physiological and pathological conditions. Anti-CD47 antibodies have been shown to inhibit the progression of several types of cancer. However, the mechanism of anti-CD47 monoclonal antibody (mAb) treatment remains controversial. In this study, we confirmed that CD47 protein is highly expressed in ovarian cancer, and is correlated with poor clinical characteristics and prognosis. CD47 knockdown in the ovarian cancer cell line, SK-OV-3, promoted phagocytosis by macrophages in vitro and inhibited tumor growth in vivo. These data combined suggest that CD47 inhibition is a potential strategy for cancer treatment. Using an anti-CD47 mAb, we found that CD47 inhibition in both SK-OV-3 cells and primary cancer cells was able to recapitulate our knockdown results and led to an increase in the number of infiltrating macrophages. In addition, the CD133⁺ tumor initiating cells expressed a high level of CD47, and anti-CD47 mAb treatment was able to trigger the phagocytosis of this cell population. In conclusion, our results indicate that CD47 inhibits macrophage phagocytosis of ovarian cancer cells, and down-regulation of CD47 or inhibiting CD47 by mAb was able to reverse the negative effect. Thus, CD47 antibody therapy may be a promising strategy to treat ovarian cancer.

A novel bispecific antibody fusion protein co-targeting EGFR and CD47 with enhanced therapeutic index

OBJECTIVE

To promote targeting specificity of anti-CD47 agents, we have constructed a novel bispecific antibody fusion protein against EGFR and CD47, which may minimize the "off-target" effects caused by CD47 expression on red blood cells.

RESULTS

The novel bispecific antibody fusion protein, denoted as Bi-SP could simultaneously bind to EGFR and CD47 and exhibited potent phagocytosis-stimulation effects in vitro. Bi-SP treatment with a low dose more effectively inhibited tumor growth than either EGFR-targeting antibody, Pan or the SIRPα variant-Fc (SIRPαV-Fc) in the A431 xenograft tumor model. In addition, the treatment with Bi-SP produced less red blood cell (RBC) losses than the SIRPαV-Fc treatment, suggesting its potential use for minimizing RBC toxicity in therapy.

CONCLUSIONS

Bi-SP with improved therapeutic index has the potential to treat CD47+ and EGFR+ cancers in clinics.

SIRPα-CD47 Immune Checkpoint Blockade in Anticancer Therapy

Inhibitory immune checkpoint blockade has been one of the most significant advances in anticancer therapy of the past decade. Research so far has largely focused on improving adaptive immune functions, but recent studies have indicated that the signal-regulatory protein (SIRP)α-CD47 pathway, a phagocytosis checkpoint in macrophages and other innate immune cells, may be an interesting therapeutic target. Here, we summarize current knowledge about SIRPα-CD47 blockade, and highlight key issues for future investigations. These include the targeting of prophagocytic receptors (Fc receptors or otherwise) to complement SIRPα-CD47 blockade, the understanding of constraints on phagocytosis other than the SIRPα-CD47 checkpoint and the contribution of immune cells other than macrophages. A better understanding of how SIRPα-CD47 blockade works may aid in identifying patients suitable for this therapy, avoiding potential toxicities and designing optimal combination therapies.

New Strategies Using Antibody Combinations to Increase Cancer Treatment Effectiveness

Antibodies have proven their high value in antitumor therapy over the last two decades. They are currently being used as the first-choice to treat some of the most frequent metastatic cancers, like HER2⁺ breast cancers or colorectal cancers, currently treated with trastuzumab (Herceptin) and bevacizumab (Avastin), respectively. The impressive therapeutic success of antibodies inhibiting immune checkpoints has extended the use of therapeutic antibodies to previously unanticipated tumor types. These anti-immune checkpoint antibodies allowed the cure of patients devoid of other therapeutic options, through the recovery of the patient’s own immune response against the tumor. In this review, we describe how the antibody-based therapies will evolve, including the use of antibodies in combinations, their main characteristics, advantages, and how they could contribute to significantly increase the chances of success in cancer therapy. Indeed, novel combinations will consist of mixtures of antibodies against either different epitopes of the same molecule or different targets on the same tumor cell; bispecific or multispecific antibodies able of simultaneously binding tumor cells, immune cells or extracellular molecules; immunomodulatory antibodies; antibody-based molecules, including fusion proteins between a ligand or a receptor domain and the IgG Fab or Fc fragments; autologous or heterologous cells; and different formats of vaccines. Through complementary mechanisms of action, these combinations could contribute to elude the current limitations of a single antibody which recognizes only one particular epitope. These combinations may allow the simultaneous attack of the cancer cells by using the help of the own immune cells and exerting wider therapeutic effects, based on a more specific, fast, and robust response, trying to mimic the action of the immune system.

Thrombospondin-1, Free Radicals, and the Coronary Microcirculation: The Aging Conundrum

SIGNIFICANCE

Successful matching of cardiac metabolism to perfusion is accomplished primarily through vasodilation of the coronary resistance arterioles, but the mechanism that achieves this effect changes significantly as aging progresses and involves the contribution of reactive oxygen species (ROS). Recent Advances: A matricellular protein, thrombospondin-1 (Thbs-1), has been shown to be a prolific contributor to the production and modulation of ROS in large conductance vessels and in the peripheral circulation. Recently, the presence of physiologically relevant circulating Thbs-1 levels was proven to also disrupt vasodilation to nitric oxide (NO) in coronary arterioles from aged animals, negatively impacting coronary blood flow reserve.

CRITICAL ISSUES

This review seeks to reconcile how ROS can be successfully utilized as a substrate to mediate vasoreactivity in the coronary microcirculation as "normal" aging progresses, but will also examine how Thbs-1-induced ROS production leads to dysfunctional perfusion and eventual ischemia and why this is more of a concern in advancing age.

FUTURE DIRECTIONS

Current therapies that may effectively disrupt Thbs-1 and its receptor CD47 in the vascular wall and areas for future exploration will be discussed. Antioxid. Redox Signal. 27, 785-801.

A drug development perspective on targeting tumor-associated myeloid cells

Despite decades of research, cancer remains a devastating disease and new treatment options are needed. Today cancer is acknowledged as a multifactorial disease not only comprising of aberrant tumor cells but also the associated stroma including tumor vasculature, fibrotic plaques, and immune cells that interact in a complex heterotypic interplay. Myeloid cells represent one of the most abundant immune cell population within the tumor stroma and are equipped with a broad functional repertoire that promotes tumor growth by suppressing cytotoxic T cell activity, stimulating neoangiogenesis and tissue remodeling. Therefore, myeloid cells have become an attractive target for pharmacological intervention. In this review, we summarize the pharmacological approaches to therapeutically target tumor-associated myeloid cells with a focus on advanced programs that are clinically evaluated. In addition, for each therapeutic strategy, the preclinical rationale as well as advantages and challenges from a drug development perspective are discussed.