Cancer Therapy Targeting CD47/SIRPα

Optimizing antibody stability and efficacy in CD47- SIRPα inhibition via computational approaches

CD47, a cell surface protein, serves as a "don't eat me" signal that prevents immune cells from engulfing healthy cells upon its interaction with SIRPα. Cancer cells exploit this mechanism by overexpressing CD47 to evade immune destruction. Blocking the interaction between CD47 and its receptor, SIRPα, is a promising therapeutic strategy. Targeting the interactions between these surface proteins with small molecules is quite challenging, and on the other hand, antibodies offer potential. However, the interactions between antigen (CD47) and antibody (B6H12.2) play a crucial role in this scenario, and increasing the affinity by mutating the interacting residues might impact the inclination and effectiveness of the antibody towards antigen. Thus, this study focuses on designing antibodies with increased affinity and stability towards the antigen compared to the wild-type. Residual scanning calculations were performed to mutate the interacting as well as the hydrophobic residues of the antibody and affinity was assessed. Computational approaches, including antigen-antibody docking studies and molecular dynamics simulations, were employed to evaluate the affinity, stability and therapeutic potential of these modified antibodies.

Microglia membrane-mediated trans-blood-brain barrier prodrug micelles enhance phagocytosis for glioblastoma chemo-immunotherapy

Glioblastoma-associated macrophages & microglia (GAMs) are critical immune cells within the glioblastoma (GBM) microenvironment. Their phagocytosis of GBM cells is crucial for initiating both innate and adaptive immune responses. GBM cells evade this immune attack by upregulating the anti-phagocytic molecule CD47 on their surface. Although CD47 knockdown has shown promise in reducing tumor volume and increasing survival in GBM models, the efficacy of anti-CD47 antibodies remains limited clinically, partly due to the blood-brain tumor barrier (BBTB) and the insufficient pro-phagocytosis efficacy of CD47 blockade alone. Here, we introduce CSSOssMIT@MM-PEP20, a PEP20-linked microglia membrane (MM) camouflaged CSSOssMIT prodrug micelle. The MM targets vascular cell adhesion molecule-1 on the BBTB and enhances the penetration of CSSOssMIT@MM-PEP20 into the GBM tissue. CSSOssMIT@MM-PEP20 disassembles into MM-PEP20 and CSSOssMIT through the proton sponge effect in the acidic microenvironment. MM-PEP20 blocks the CD47-SIRPα axis, disabling the 'don't eat me' signal, while CSSOssMIT releases MIT within tumor cells to promote immunogenic cell death and amplify the 'eat me' signal. In an orthotopic GBM mouse model, CSSOssMIT@MM-PEP20 increased GAMs-mediated phagocytosis of GBM cells by 5.01-fold and enhanced CD8+ T cell infiltration by 8.63-fold, demonstrating significant GBM inhibition. Overall, this study presents a noninvasive strategy to traverse the BBTB and modulate GAMs phagocytosis, thereby facilitating effective anti-GBM chemo-immunotherapy.

Therapeutic strategies targeting CD47-SIRPα signaling pathway in gastrointestinal cancers treatment

Gastrointestinal (GI) cancers are prevalent globally, with leading incidence and mortality rates among malignant tumors. Despite notable advancements in surgical resection, radiotherapy, and chemotherapy, the overall survival rates remain low. Hence, it is imperative to explore alternative approaches that enhance patient outcomes. Cluster of differentiation 47 (CD47), serving as an early diagnostic marker, is predominantly overexpressed in GI cancers and associated with poor prognosis. Targeting the CD47-signal regulatory protein alpha (SIRPα) signaling pathway may provide a novel strategy for GI cancers treatment. This study summarizes current knowledge of the structure and function of CD47 and SIRPα, their roles in signaling pathways, the prognostic significance of CD47, therapeutic strategies targeting the CD47-SIRPα signaling pathway in GI cancer, and highlights key issues for future investigations.

Construction and characterization of a novel secreted MsC-CAR-T cell in solid tumors

The CD47-SIRPα signaling has been acknowledged as a significant immune checkpoint and CD47 blocking has been proved as a potential therapeutic strategy for the treatment of solid tumor. However, the potential application of CAR-T cells secreted antibody fragment simultaneously in solid tumor is rarely explored. In this study, we searched bioinformatic databases and investigated the characteristics of CD47 in solid tumors. Then we consulted bioinformatic databases to design, optimize and construct a novel MsC-CAR which could target MAGE-A1 and self-secrete CD47-scFv. The engineering T cells containing MsC-CAR were transfected, verified and characterized. The tumor-inhibitory role of MsC-CART cells was further determined in vitro and in vivo. The results showed that MsC-CARs were successfully constructed and MsC1-CARs demonstrated the preferable features of recognizing MAGE-A1 and secreting CD47-scFv. Engineering T cells transfecting with MsC1-CAR (MsC1-CART cells) exerted the prominent tumor-inhibitory effectiveness, both in different cancer cell lines and LUAD xenograft tumors. The present data highlighted that MsC1-CART cells elaborately combined the adoptive cellular immunotherapy and immune checkpoint inhibitor therapy, may represent a new direction for the treatment of MAGE-A1 positive solid tumors.

Assessing CD36 and CD47 expression levels in solid tumor indications to stratify patients for VT1021 treatment

Despite the development of cancer biomarkers and targeted therapies, most cancer patients do not have a specific biomarker directly associated with effective treatment options. We have developed VT1021 that induces the expression of thrombospondin-1 (TSP-1) in myeloid-derived suppressor cells (MDSCs) recruited to the tumor microenvironment (TME). Our studies identified CD36 and CD47 as dual biomarkers that can be used as patient stratifying tools and prognostic biomarkers for VT1021 treatment.

Enhancing anti-EGFRvIII CAR T cell therapy against glioblastoma with a paracrine SIRPγ-derived CD47 blocker

A significant challenge for chimeric antigen receptor (CAR) T cell therapy against glioblastoma (GBM) is its immunosuppressive microenvironment, which is densely populated by protumoral glioma-associated microglia and macrophages (GAMs). Myeloid immune checkpoint therapy targeting the CD47-signal regulatory protein alpha (SIRPα) axis induces GAM phagocytic function, but CD47 blockade monotherapy is associated with toxicity and low bioavailability in solid tumors. In this work, we engineer a CAR T cell against epidermal growth factor receptor variant III (EGFRvIII), constitutively secreting a signal regulatory protein gamma-related protein (SGRP) with high affinity to CD47. Anti-EGFRvIII-SGRP CAR T cells eradicate orthotopic EGFRvIII-mosaic GBM in vivo, promoting GAM-mediated tumor cell phagocytosis. In a subcutaneous CD19+ lymphoma mouse model, anti-CD19-SGRP CAR T cell therapy is superior to conventional anti-CD19 CAR T. Thus, combination of CAR and SGRP eliminates bystander tumor cells in a manner that could overcome main mechanisms of CAR T cell therapy resistance, including immune suppression and antigen escape.

Signal Regulatory Protein α Expression in Systemic Vasculitis

OBJECTIVE

Signal regulatory protein α (SIRPα) is found primarily on myeloid cells, including macrophages and neutrophils; binds to CD47; and regulates phagocytosis, antigen presentation, cellular fusion, cell proliferation, and migration. Therefore, SIRPα may be involved in the pathogenesis of autoimmune diseases, including systemic vasculitis. This study aimed to assess SIRPα expression in tissue samples from patients with vasculitis.

METHODS

Immunohistochemical staining for SIRPα was performed on temporal artery (TA), kidney, and lung biopsy samples from patients with giant cell arteritis (GCA), patients with microscopic polyangiitis (MPA), patients with granulomatosis with polyangiitis (GPA), and patients without vasculitis. A score of SIRPα+ expression was calculated, derived from the percentages of monocytes, macrophages, and dendritic cells and neutrophils with different staining intensities in affected tissues.

RESULTS

A total of 46 samples from patients with different vasculitides (GCA, MPA, and GPA) were included in the study. Tissue samples included TA samples from 15 patients with GCA; kidney samples from 11 and 9 patients with GPA and MPA, respectively; and lung samples from 11 patients with GPA. Most tissue samples from patients with active vasculitis (15 of 15 TA samples, 17 of 20 kidney samples, and 9 of 11 lung samples) showed SIRPα staining. SIRPα staining intensity was less in kidney samples compared to TA and lung samples.

CONCLUSION

This study demonstrates high-level expression of SIRPα in macrophages and monocytes in affected tissue in systemic vasculitis. These findings provide a foundation for further studies exploring the role of the SIRPα-CD47 pathway in the pathogenesis of systemic vasculitis and the potential for the blockade of SIRPα and/or the depletion of SIRPα+ cells as treatment of systemic vasculitis.

Breaking the 'don't eat me' signal: in silico design of CD47-directed peptides for cancer immunotherapy

The leading cause of death worldwide is cancer. Although there are various therapies available to treat cancer, finding a successful one can be like searching for a needle in a haystack. Immunotherapy appears to be one of those needles in the haystack of cancer treatment. Immunotherapeutic agents enhance the immune response of the patient's body to tumor cells. One of the immunotherapeutic targets, Cluster of Differentiation 47 (CD47), releases the "don't eat me" signal when it binds to its receptor, Signal Regulatory Protein (SIRPα). Tumor cells use this signal to circumvent the immune system, rendering it ineffective. To stop tumor cells from releasing the "don't eat me" signal, the CD47-SIRPα interaction is specifically targeted in this study. To do so, in silico peptides were designed based on the structural analysis of the interaction between two proteins using point mutations on the interacting residues with the other amino acids. The peptide library was designed and docked on SIRPα using computational tools. Later on, after analyzing the docked complex, the best of them was selected for MD simulation studies of 100 ns. Further analysis after MD studies was carried out to determine the possible potential anti-SIRPα peptides.

Macrophage-engaging peptidic bispecific antibodies (pBsAbs) for immunotherapy via a facile bioconjugation strategy

Bispecific antibodies are artificial molecules that fuse two different antigen-binding sites of monoclonal antibodies into one single entity. They have emerged as a promising next-generation anticancer treatment. Despite the fascinating applications of bispecific antibodies, the design and production of bispecific antibodies remain tedious and challenging, leading to a long R&D process and high production costs. We herein report an unprecedented strategy to cyclise and conjugate tumour-targeting peptides on the surface of a monoclonal antibody to form a novel type of bispecific antibody, namely the peptidic bispecific antibody (pBsAb). Such design combines the merits of highly specific monoclonal antibodies and serum-stable cyclic peptides that endows an additional tumour-targeting ability to the monoclonal antibody for binding with two different antigens. Our results show that the novel pBsAb, which comprises EGFR-binding cyclic peptides and an anti-SIRP-α monoclonal antibody, could serve as a macrophage-engaging bispecific antibody to initiate enhanced macrophage-cancer cell interaction and block the "don't eat me" signal between CD47-SIRP-α, as well as promoting antibody-dependent cellular phagocytosis and 3D cell spheroid infiltration. These findings give rise to a new type of bispecific antibody and a new platform for the rapid generation of new bispecific antibodies for research and potential therapeutic uses.

Macrocycles and macrocyclization in anticancer drug discovery: Important pieces of the puzzle

Increasing disease-related proteins have been identified as novel therapeutic targets. Macrocycles are emerging as potential solutions, bridging the gap between conventional small molecules and biomacromolecules in drug discovery. Inspired by successful macrocyclic drugs of natural origins, macrocycles are attracting more attention for enhanced binding affinity and target selectivity. Due to the conformation constraint and structure preorganization, macrocycles can reach bioactive conformations more easily than parent acyclic compounds. Also, rational macrocyclization combined with sequent structural modification will help improve oral bioavailability and combat drug resistance. This review introduces various strategies to enhance membrane permeability in macrocyclization and subsequent modification, such as N-methylation, intramolecular hydrogen bonding modulation, isomerization, and reversible bicyclization. Several case studies highlight macrocyclic inhibitors targeting kinases, HDAC, and protein-protein interactions. Finally, some macrocyclic agents targeting tumor microenvironments are illustrated.

Shifting the paradigm: engaging multicellular networks for cancer therapy

Most anti-cancer modalities are designed to directly kill cancer cells deploying mechanisms of action (MOAs) centered on the presence of a precise target on cancer cells. The efficacy of these approaches is limited because the rapidly evolving genetics of neoplasia swiftly circumvents the MOA generating therapy-resistant cancer cell clones. Other modalities engage endogenous anti-cancer mechanisms by activating the multi-cellular network (MCN) surrounding neoplastic cells in the tumor microenvironment (TME). These modalities hold a better chance of success because they activate numerous types of immune effector cells that deploy distinct cytotoxic MOAs. This in turn decreases the chance of developing treatment-resistance. Engagement of the MCN can be attained through activation of immune effector cells that in turn kill cancer cells or when direct cancer killing is complemented by the production of proinflammatory factors that secondarily recruit and activate immune effector cells. For instance, adoptive cell therapy (ACT) supplements cancer cell killing with the release of homeostatic and pro-inflammatory cytokines by the immune cells and damage associated molecular patterns (DAMPs) by dying cancer cells. The latter phenomenon, referred to as immunogenic cell death (ICD), results in an exponential escalation of anti-cancer MOAs at the tumor site. Other approaches can also induce exponential cancer killing by engaging the MCN of the TME through the release of DAMPs and additional pro-inflammatory factors by dying cancer cells. In this commentary, we will review the basic principles that support emerging paradigms likely to significantly improve the efficacy of anti-cancer therapy.

From glioma gloom to immune bloom: unveiling novel immunotherapeutic paradigms-a review

In tumor therapeutics, the transition from conventional cytotoxic drugs to targeted molecular therapies, such as those targeting receptor tyrosine kinases, has been pivotal. Despite this progress, the clinical outcomes have remained modest, with glioblastoma patients' median survival stagnating at less than 15 months. This underscores the urgent need for more specialized treatment strategies. Our review delves into the progression toward immunomodulation in glioma treatment. We dissect critical discoveries in immunotherapy, such as spotlighting the instrumental role of tumor-associated macrophages, which account for approximately half of the immune cells in the glioma microenvironment, and myeloid-derived suppressor cells. The complex interplay between tumor cells and the immune microenvironment has been explored, revealing novel therapeutic targets. The uniqueness of our review is its exhaustive approach, synthesizing current research to elucidate the intricate roles of various molecules and receptors within the glioma microenvironment. This comprehensive synthesis not only maps the current landscape but also provides a blueprint for refining immunotherapy for glioma, signifying a paradigm shift toward leveraging immune mechanisms for improved patient prognosis.

Immune Evasion in Cancer Is Regulated by Tumor-Asociated Macrophages (TAMs): Targeting TAMs

Recent advancements in cancer treatment have explored a variety of approaches to address the needs of patients. Recently, immunotherapy has evolved as an efficacious treatment for various cancers resistant to conventional therapies. Hence, significant milestones in immunotherapy were achieved clinically in a large subset of cancer patients. Unfortunately, some cancer types do not respond to treatment, and among the responsive cancers, some patients remain unresponsive to treatment. Consequently, there is a critical need to examine the mechanisms of immune resistance and devise strategies to target immune suppressor cells or factors, thereby allowing for tumor sensitivity to immune cytotoxic cells. M2 macrophages, also known as tumor-associated macrophages (TAMs), are of interest due to their role in suppressing the immune system and influencing antitumor immune responses through modulating T cell activity and immune checkpoint expression. TAMs are associated with signaling pathways that modulate the tumor microenvironment (TME), contributing to immune evasion. One approach targets TAMs, focusing on preventing the polarization of M1 macrophages into the protumoral M2 phenotype. Other strategies focus on direct or indirect targeting of M2 macrophages through understanding the interaction of TAMs with immune factors or signaling pathways. Clinically, biomarkers associated with TAMs' immune resistance in cancer patients have been identified, opening avenues for intervention using pharmacological agents or immunotherapeutic approaches. Ultimately, these multifaceted approaches are promising in overcoming immune resistance and improving cancer treatment outcomes.

Two birds with one stone: human SIRPα nanobodies for functional modulation and in vivo imaging of myeloid cells

Signal-regulatory protein α (SIRPα) expressed by myeloid cells is of particular interest for therapeutic strategies targeting the interaction between SIRPα and the "don't eat me" ligand CD47 and as a marker to monitor macrophage infiltration into tumor lesions. To address both approaches, we developed a set of novel human SIRPα (hSIRPα)-specific nanobodies (Nbs). We identified high-affinity Nbs targeting the hSIRPα/hCD47 interface, thereby enhancing antibody-dependent cellular phagocytosis. For non-invasive in vivo imaging, we chose S36 Nb as a non-modulating binder. By quantitative positron emission tomography in novel hSIRPα/hCD47 knock-in mice, we demonstrated the applicability of 64Cu-hSIRPα-S36 Nb to visualize tumor infiltration of myeloid cells. We envision that the hSIRPα-Nbs presented in this study have potential as versatile theranostic probes, including novel myeloid-specific checkpoint inhibitors for combinatorial treatment approaches and for in vivo stratification and monitoring of individual responses during cancer immunotherapies.

Inhibitory receptor CD47 binding to plasma TSP1 suppresses NK-cell IFN-γ production via activating the JAK/STAT3 pathway during HIV infection

BACKGROUND

Natural killer (NK) cells play an important first-line role against tumour and viral infections and are regulated by inhibitory receptor expression. Among these inhibitory receptors, the expression, function, and mechanism of cluster of differentiation 47 (CD47) on NK cells during human immunodeficiency virus (HIV) infection remain unclear.

METHODS

Fresh peripheral blood mononuclear cells (PBMCs) were collected from people living with HIV (PLWH) and HIV negative controls (NC) subjects. Soluble ligand expression levels of CD47 were measured using ELISA. HIV viral proteins or Toll-like receptor 7/8 (TLR7/8) agonist was used to investigate the mechanisms underlying the upregulation of CD47 expression. The effect of CD47 on NK cell activation, proliferation, and function were evaluated by flow cytometry. RNA-seq was used to identify downstream pathways for CD47 and its ligand interactions. A small molecule inhibitor was used to restore the inhibition of NK cell function by CD47 signalling.

RESULTS

CD47 expression was highly upregulated on the NK cells from PLWH, which could be due to activation of the Toll-like receptor 7/8 (TLR7/8) pathway. Compared with NC subjects, PLWH subjects exhibited elevated levels of CD47 ligands, thrombospondin-1 (TSP1), and counter ligand signal regulatory protein-α (SIRPα). The TSP1-CD47 axis drives the suppression of interferon gamma (IFN-γ) production and the activation of the Janus kinase signal transducer and activator of transcription (JAK-STAT) pathway in NK cells. After treatment with a STAT3 inhibitor, the NK cells from PLWH showed significantly improved IFN-γ production.

CONCLUSIONS

The current data indicate that the binding of the inhibitory receptor CD47 to plasma TSP1 suppresses NK cell IFN-γ production by activating the JAK/STAT3 pathway during HIV infection. Our results suggest that CD47 and its related signalling pathways could be targets for improving NK cell function in people living with HIV.

Opportunities and challenges of CD47-targeted therapy in cancer immunotherapy

Cancer immunotherapy has emerged as a promising strategy for the treatment of cancer, with the tumor microenvironment (TME) playing a pivotal role in modulating the immune response. CD47, a cell surface protein, has been identified as a crucial regulator of the TME and a potential therapeutic target for cancer therapy. However, the precise functions and implications of CD47 in the TME during immunotherapy for cancer patients remain incompletely understood. This comprehensive review aims to provide an overview of CD47's multifaced role in TME regulation and immune evasion, elucidating its impact on various types of immunotherapy outcomes, including checkpoint inhibitors and CAR T-cell therapy. Notably, CD47-targeted therapies offer a promising avenue for improving cancer treatment outcomes, especially when combined with other immunotherapeutic approaches. The review also discusses current and potential CD47-targeted therapies being explored for cancer treatment and delves into the associated challenges and opportunities inherent in targeting CD47. Despite the demonstrated effectiveness of CD47-targeted therapies, there are potential problems, including unintended effects on healthy cells, hematological toxicities, and the development if resistance. Consequently, further research efforts are warranted to fully understand the underlying mechanisms of resistance and to optimize CD47-targeted therapies through innovative combination approaches, ultimately improving cancer treatment outcomes. Overall, this comprehensive review highlights the significance of CD47 as a promising target for cancer immunotherapy and provides valuable insight into the challenges and opportunities in developing effective CD47-targeted therapies for cancer treatment.

Membrane-Mediated Cooperative Interactions of CD47 and SIRPα

The specific binding of the ubiquitous 'marker of self' protein CD47 to the SIRPα protein anchored in the macrophage plasma membrane results in the inhibition of the engulfment of 'self' cells by macrophages and thus constitutes a key checkpoint of our innate immune system. Consequently, the CD47-SIRPα protein complex has been recognized as a potential therapeutic target in cancer and inflammation. Here, we introduce a lattice-based mesoscale model for the biomimetic system studied recently in fluorescence microscopy experiments where GFP-tagged CD47 proteins on giant plasma membrane vesicles bind to SIRPα proteins immobilized on a surface. Computer simulations of the lattice-based mesoscale model allow us to study the biomimetic system on multiple length scales, ranging from single nanometers to several micrometers and simultaneously keep track of single CD47-SIRPα binding and unbinding events. Our simulations not only reproduce data from the fluorescence microscopy experiments but also are consistent with results of several other experiments, which validates our numerical approach. In addition, our simulations yield quantitative predictions on the magnitude and range of effective, membrane-mediated attraction between CD47-SIRPα complexes. Such detailed information on CD47-SIRPα interactions cannot be obtained currently from experiments alone. Our simulation results thus extend the present understanding of cooperative effects in CD47-SIRPα interactions and may have an influence on the advancement of new cancer treatments.

A collagen-binding SIRPαFc fusion protein for targeted cancer immunotherapy

Collagen is abundant but exposed in tumor due to the abnormal tumor blood vessels, thus is considered as a tumor-specific target. The A3 domain of von Willebrand factor (vWF A3) is a kind of collagen-binding domain (CBD) which could bind collagen specifically. Previously we reported a chemosynthetic CBD-SIRPαFc conjugate, which could block CD47 and derived tumor-targeting ability by CBD. CBD-SIRPαFc conjugate represented improved anti-tumor efficacy with increased MHC II+ M1 macrophages, but the uncertain coupling ratio remained a problem. Herein, we produced a vWF A3-SIRPαFc fusion protein through eukaryotic expression system. It was examined at both molecular and cellular levels with its collagen affinity, uninfluenced original affinity to targets and phagocytosis-promoting function compared to unmodified SIRPαFc. Living imaging showed that vWF A3-SIRPαFc fusion protein derived the improved accumulation and retention in tumor than SIRPαFc. In the MC38 allograft model, vWF A3-SIRPαFc demonstrated a superior tumor-suppressing effect, characterized by increased MHC II+ M1 macrophages and T cells (particularly CD4+ T cells). These results revealed that vWF A3-SIRPαFc fusion protein derived tumor-targeting ability, leading to improved anti-tumor immunotherapeutic efficacy compared to SIRPαFc. Altogether, vWF A3 improved the anti-tumor efficacy and immune-activating function of SIRPαFc, supporting targeting tumor collagen as a possible targeted strategy.

CD47 blockade enhances phagocytosis of cardiac cell debris by neutrophils

CD47 is a cell surface protein controlling phagocytotic activity of innate immune cells. CD47 blockade was investigated as an immune checkpoint therapy in cancer treatment, enhancing phagocytosis of tumor cells by macrophages. Anti-CD47 treatment also reduced injury size during reperfused acute myocardial infarction (repAMI) by enhancing phagocytotic acitivity of macrophages. Little is known about the impact of CD47 blockade on neutrophils, representing the main portion of early infiltrating immune cells after repAMI. Therefore, we performed 45 min of cardiac ischemia followed by 24 h of reperfusion, observing a decreased cardiac injury size measured by triphenyl tetrazolium chloride (TTC) Evan's blue staining. We were able to detect this effect with an innovative three-dimensional method based on light sheet fluorescence microscopy (LSFM). This further allowed us a simultaneous analysis of neutrophil infiltration, showing an unaltered amount of injury-associated neutrophils with reduced cardiac injury volume from repAMI. This observation suggests modulated phagocytosis of cell debris by neutrophils. Therefore, we performed flow cytometry analysis, revealing an increased phagocytotic activity of neutrophils in vitro. These findings highlight that CD47 blockade also enhances phagocytosis of cardiac cell debris by neutrophils, which might be an additional protective effect of anti-CD47 treatment after repAMI.

Tuftsin-tailored fusion protein inhibits the growth of circulating gastric tumor cells associated with macrophage phagocytosis

Circulating tumor cells (CTCs) are a major cause of tumor metastasis and resistance to anticancer therapies. To date, no effective low-toxicity chemotherapeutic agents or antibodies have exhibited significant clinical activity against CTCs. Macrophages are important mediators of antitumor immunity. Tuftsin (TF), a tetrapeptide located at residues 289-292 of the CH2 domain of the Fc region of the IgG heavy chain, binds to Nrp-1, a receptor on the surface of macrophages that promotes phagocytosis and induces nonspecific activation of the immune system against tumors. Lidamycin (LDM) is an antitumor chemotherapy agent that is strongly cytotoxic to tumors and can dissociate into an apoprotein (LDP) and active enediyne (AE) in vitro. We previously constructed the fusion protein LDP-TF through genetic engineering and inserted the chromophore AE to produce LDM-TF, which can target macrophages to promote their phagocytic and cytotoxic activity against tumor cells. Preliminary experiments confirmed the anti-tumor activity of LDM-TFs. In this study, we found that LDM-TF effectively inhibited the growth of CTCs of gastric cancer origin and enhanced macrophage phagocytosis both in vivo and in vitro. Tumor cell expression of CD47, which helps to evade phagocytosis by macrophages, was substantially downregulated by LDM-TF. Notably, our in vitro experiments demonstrated that the combination of LDM-TF and anti-CD47 antibodies promoted phagocytosis more than either component alone. Our findings demonstrate the significant inhibitory effect of LDM-TF on the growth of CTCs of gastric cancer origin and suggest that the combination of LDM-TF and anti-CD47 antibodies may exhibit synergistic effects, thereby providing a new option for the clinical treatment of patients with advanced tumors that have metastasized.

[Latest Findings on the Role of CD47 in Tumor Immune Evasion and Related Targeted Therapies]

CD47 is an immunoglobulin that is overexpressed on the surface of a variety of cancer cells. CD47 forms a signaling complex with signal regulatory protein alpha (SIRPα), prompting the escape of cancer cells from macrophage-mediated phagocytosis. In recent years, CD47 has been shown to be highly expressed in many types of solid tumors and is associated with poor prognosis in patients. More and more studies have shown that inhibition of the CD47-SIRPα signaling pathway can promote adaptive immune responses and enhance the phagocytosis of tumor cells by macrophages. Humanized anti-CD47 IgG4 monoclonal antibody has been studied in clinical trials for the treatment of a variety of advanced solid tumors and lymphomas, demonstrating a sound safety profile and achieving partial remission in some patients. In this review we discuss the structure and function of CD47 and the mechanism of CD47 regulation in tumors, summarize the research progress in therapeutic antibody drugs targeting CD47 and a bottleneck in research that targeted drugs are more prone to result in serious adverse effects, and evaluated the potential of the applying CD47-SIRPα signaling pathway in anti-cancer therapy.

Impact of Precision Medicine in Oncology: Immuno-oncology

ABSTRACT

Cancer treatment has dramatically changed over the last decade with the development of immunotherapy. Therapies including immune cytokines, immune checkpoint inhibition, intratumoral therapies, and cellular therapies are already widely used in the oncology clinic. Active development continues in these areas and in the development of vaccines, bispecific therapies, and more refined cellular therapies. In this review, we will examine the role that immune therapy has in cancer treatment and explore areas of future development.

Prognostic Utility of CD47 in Cancer of the Uterine Cervix and the Sensitivity of Immunohistochemical Scores

INTRODUCTION

Cancer of the uterine cervix (CUC) is still one of the most frequent oncological diagnoses in women. The specific interactions between the tumor cells of CUC and the cells and tissues in the tumor microenvironment can affect cancer cells' invasive and metastatic potential and can modulate tumor's progression and death. CD47 is a trans-membranous immunoglobulin, expressed in many cells. It protects the cells from being destroyed by the circulating macrophages.

AIM

We aimed to evaluate the prognostic role of CD47 expressed in the tumor tissues of patients with CUC for tumor progression and to find the most sensitive immunohistochemical score for defining the cut-off significantly associated with tumor biology and progression.

MATERIALS AND METHODS

Paraffin-embedded tumor tissues from 86 patients with CUC were included in the study. Clinico-morphological data for patients, such as age and stage at diagnosis according to FIGO and TNM classification, were obtained from the hospital electronic medical records. Immunohistochemical staining was performed with rabbit recombinant monoclonal CD47 antibody (Clone SP279). The final result was interpreted based on three reporting models in immunohistochemistry: H-score, Allred score and combined score.

RESULTS

The expression of CD47 was higher in tumors limited in the cervix compared with those invading other structures, and it did not depend on the nodal status. The results of immunohistochemical staining were similar regardless of which immunohistochemical method was used. The most significant correlation with TNM stage was observed with the H-score (p = 0.00018). The association with the Allred and combined score was less significant, with p values of 0.0013 and 0.0002, respectively.

CONCLUSION

The expression of CD47 in the cancer cells is prognostic for tumor invasion in the surrounding structures, independent of lymph node engagement. The H-score is the most sensitive immunohistochemical score to describe tumor stage. To the best of our knowledge, this is the first study evaluating the significance of CD47 expression in CUC.

A cancer cell membrane coated nanoparticles-based gene delivery system for enhancing cancer therapy

Gene therapy is a superior therapeutic means in cancer therapy. However, the instability of nucleic acid and the lack of suitable delivery carrier greatly restricts its further development and application. Herein, we coupled low molecular weight polyethyleneimine (LMW PEI) through disulfide bonds, then modified it with manganese dioxide (MnO2) nanosheets and nuclear localization signal peptide (NLS), as a p53 gene carrier, and finally coated it with B16F10 cell membrane to construct a novel gene-carrier system CM@MnO2-PEI-NLS-ss/p53 (M@MPNs/p53). Tumor cell membrane coating endows nanoparticles with homotypic targeting and immune escape capabilities, disulfide-crosslinked LMW-PEI has high transfection efficiency and low toxicity, and NLS peptides enhance nuclear delivery and improve p53 gene delivery efficiency; meanwhile, MnO2 nanosheets oxidize high intracellular concentration of glutathione (GSH), sensitizing p53 gene-mediated antitumor therapy. The results showed that the novel biofilm-camouflaged M@MPNs/p53 nanoparticles had a highly specific targeting effect on homologous cancer cells and could effectively inhibit tumor growth in vitro and in vivo. Besides, MnO2 loading improved p53-mediated tumor regression. This novel gene delivery platform is of great significance in improving gene delivery efficiency and enhancing anti-tumor therapy.

CD47 (don't eat me signal) expression levels and its relationship with clinicopathologic features in early-stage prostate carcinoma

BACKGROUND

Prostate cancer is a cancer with poor host immune response and could be defined as a non-T-cell inflamed tumor. Therefore, immunotherapy treatments could not be included in the treatment of prostate cancer until recently. Inadequate antitumoral response is one of the main reasons why tumor cells multiply rapidly and cause lethal results. It was shown that CD47 molecule, which is secreted at high levels by leukemia cells, reduces macrophage-mediated phagocytosis and thus facilitates escape from the antitumoral immune response. The aim of this study was to show don't eat me signaling in prostate carcinoma tissues and its relationship with macrophage polarization.

MATERIALS AND METHODS

A total of 263 patients with a diagnosis of prostatic adenocarcinoma after radical prostatectomy between 2015 and 2020 at our institute were included in the study. CD47, CD68, and CD163 expression levels were examined immunohistochemically (IHC) in these tissues. The relationship of these expression levels with unfavorable prognostic factors and survival for prostate carcinoma was investigated.

RESULTS

In this study, all the operated prostate carcinoma cases had CD47 expression in tumor tissue, but only 52.5% had a high level of expression. Of 263 prostate cancer tissues, 135 (51.3%) showed high expression of CD68 protein and 189 (71.9%) showed high expression of CD163 protein. There was a statistically strong relationship between CD47, CD68, and CD163.

CONCLUSIONS

The CD47 molecule is basically a molecule that inhibits macrophage activation. CD68 is mostly used for macrophage classification, while CD163 is used for tumor-associated macrophage classification. Unlike others, we IHC examined CD47, CD68, and CD163 expressions in the surgical materials of patients who were operated for prostate carcinoma. In addition, we concluded that strong CD47 expression was closely associated with strong CD68 and CD163 expression in all tumor samples. However, a significant relationship between these expression levels and survival could not be demonstrated.

Circulating inflammatory cells in patients with metastatic breast cancer: Implications for treatment

Adaptive and innate immune cells play a crucial role as regulators of cancer development.

Inflammatory cells in blood flow seem to be involved in pro-tumor activities and contribute to breast cancer progression. Circulating lymphocyte ratios such as the platelet-lymphocytes ratio (PLR), the monocyte-lymphocyte ratio (MLR) and the neutrophil-lymphocyte ratio (NLR) are new reproducible, routinely feasible and cheap biomarkers of immune response. These indexes have been correlated to prognosis in many solid tumors and there is growing evidence on their clinical applicability as independent prognostic markers also for breast cancer.

In this review we give an overview of the possible value of lymphocytic indexes in advanced breast cancer prognosis and prediction of outcome. Furthermore, targeting the immune system appear to be a promising therapeutic strategy for breast cancer, especially macrophage-targeted therapies. Herein we present an overview of the ongoing clinical trials testing systemic inflammatory cells as therapeutic targets in breast cancer.

Overcoming Immunotherapeutic Resistance in PDAC: SIRPα-CD47 blockade

A daily increase in the number of new cases of pancreatic ductal adenocarcinoma remains an issue of contention in cancer research. The data revealed that a global cumulated case of about 500, 000 have been reported. This has made PDAC the fourteenth most occurring tumor case in cancer research. Furthermore, PDAC is responsible for about 466,003 deaths annually, representing the seventh prevalent type of cancer mortality. PDAC has no salient symptoms in its early stages. This has exasperated several attempts to produce a perfect therapeutic agent against PDAC. Recently, immunotherapeutic research has shifted focus to the blockade of checkpoint proteins in the management and of some cancers. Investigations have centrally focused on developing therapeutic agents that could at least to a significant extent block the SIRPα-CD47 signaling cascade (a cascade which prevent phagocytosis of tumors by dendritic cells, via the deactivation of innate immunity and subsequently resulting in tumor regression) with minimal side effects. The concept on the blockade of this interaction as a possible mechanism for inhibiting the progression of PDAC is currently being debated. This review examined the structure--function activity of SIRPα-CD47 interaction while discussing in detail the mechanism of tumor resistance in PDAC. Further, this review details how the blockade of SIRPα-CD47 interaction serve as a therapeutic option in the management of PDAC.

Macrophage Associated Immune Checkpoint CD47 Blocking Ameliorates Endometriosis

Peritoneal macrophages play a significant role in the progression of endometriosis (EM), but their functional differentiation is still unclear, and their phagocytic ability is weak. CD47-SIRPα and PD-L1-PD-1 are considered immune checkpoints associated with macrophage phagocytosis. A specific blockade of these two pathways had been shown to increase the phagocytic clearance of cancer cells by macrophages in most cancers. We hypothesized that targeting CD47/PD-L1 in EM could improve the phagocytosis of macrophages, thereby delaying the progression of EM. From localization to quantification, from mRNA to protein, we comprehensively evaluated the expression of CD47 and PD-L1 in EM. We demonstrated that the CD47 expression in ectopic endometrium from patients with EM was significantly increased, but PD-L1was not. We performed direct co-culture experiments of endometrial stromal cells with macrophages in vitro and in vivo to assess whether ectopic endometrial stromal cells escape macrophage phagocytosis through the CD47-SIRPα signaling pathway. The results showed that targeting CD47 increased the phagocytic capacity of macrophages. Interestingly, we also found that the reduction of CD47 expression promoted apoptosis of ESCs. In conclusion, these data suggested that targeting CD47 can effectively target ectopic endometrial stromal cells through a dual mechanism of increased phagocytosis of macrophages and induced apoptosis of ectopic endometrial stromal cells. Thus, immunotherapy based on the CD47-SIRPa signaling pathway has some potential in treating EM, but further mechanistic studies are needed to explore more effective and specific antibodies.