CD47/SIRPα blocking peptide identification and synergistic effect with irradiation for cancer immunotherapy

Insights into therapeutic peptides in the cancer-immunity cycle: Update and challenges

Immunotherapies hold immense potential for achieving durable potency and long-term survival opportunities in cancer therapy. As vital biological mediators, peptides with high tissue penetration and superior selectivity offer significant promise for enhancing cancer immunotherapies (CITs). However, physicochemical peptide features such as conformation and stability pose challenges to their on-target efficacy. This review provides a comprehensive overview of recent advancements in therapeutic peptides targeting key steps of the cancer-immunity cycle (CIC), including tumor antigen presentation, immune cell regulation, and immune checkpoint signaling. Particular attention is given to the opportunities and challenges associated with these peptides in boosting CIC within the context of clinical progress. Furthermore, possible future developments in this field are also discussed to provide insights into emerging CITs with robust efficacy and safety profiles.

Modulating macrophage-mediated programmed cell removal: An attractive strategy for cancer therapy

Macrophage-mediated programmed cell removal (PrCR) is crucial for the identification and elimination of needless cells that maintain tissue homeostasis. The efficacy of PrCR depends on the balance between pro-phagocytic "eat me" signals and anti-phagocytic "don't eat me" signals. Recently, a growing number of studies have shown that tumourigenesis and progression are closely associated with PrCR. In the tumour microenvironment, PrCR activated by the "eat me" signal is counterbalanced by the "don't eat me" signal of CD47/SIRPα, resulting in tumour immune escape. Therefore, targeting exciting "eat me" signalling while simultaneously suppressing "don't eat me" signalling and eventually inducing macrophages to produce effective PrCR will be a very attractive antitumour strategy. Here, we comprehensively review the functions of PrCR-activating signal molecules (CRT, PS, Annexin1, SLAMF7) and PrCR-inhibiting signal molecules (CD47/SIRPα, MHC-I/LILRB1, CD24/Siglec-10, SLAMF3, SLAMF4, PD-1/PD-L1, CD31, GD2, VCAM1), the interactions between these molecules, and Warburg effect. In addition, we highlight the molecular regulatory mechanisms that affect immune system function by exciting or suppressing PrCR. Finally, we review the research advances in tumour therapy by activating PrCR and discuss the challenges and potential solutions to smooth the way for tumour treatment strategies that target PrCR.

Tumor-associated macrophages: A sentinel of innate immune system in tumor microenvironment gone haywire

The tumor microenvironment (TME) is a critical determinant in the initiation, progression, and treatment outcomes of various cancers. Comprising of cancer-associated fibroblasts (CAF), immune cells, blood vessels, and signaling molecules, the TME is often likened to the soil supporting the seed (tumor). Among its constituents, tumor-associated macrophages (TAMs) play a pivotal role, exhibiting a dual nature as both promoters and inhibitors of tumor growth. This review explores the intricate relationship between TAMs and the TME, emphasizing their diverse functions, from phagocytosis and tissue repair to modulating immune responses. The plasticity of TAMs is highlighted, showcasing their ability to adopt either protumorigenic or anti-tumorigenic phenotypes based on environmental cues. In the context of cancer, TAMs' pro-tumorigenic activities include promoting angiogenesis, inhibiting immune responses, and fostering metastasis. The manuscript delves into therapeutic strategies targeting TAMs, emphasizing the challenges faced in depleting or inhibiting TAMs due to their multifaceted roles. The focus shifts towards reprogramming TAMs to an anti-tumorigenic M1-like phenotype, exploring interventions such as interferons, immune checkpoint inhibitors, and small molecule modulators. Noteworthy advancements include the use of CSF1R inhibitors, CD40 agonists, and CD47 blockade, demonstrating promising results in preclinical and clinical settings. A significant section is dedicated to Chimeric Antigen Receptor (CAR) technology in macrophages (CAR-M cells). While CAR-T cells have shown success in hematological malignancies, their efficacy in solid tumors has been limited. CAR-M cells, engineered to infiltrate solid tumors, are presented as a potential breakthrough, with a focus on their development, challenges, and promising outcomes. The manuscript concludes with the exploration of third-generation CAR-M technology, offering insight into in-vivo reprogramming and nonviral vector approaches. In conclusion, understanding the complex and dynamic role of TAMs in cancer is crucial for developing effective therapeutic strategies. While early-stage TAM-targeted therapies show promise, further extensive research and larger clinical trials are warranted to optimize their targeting and improve overall cancer treatment outcomes.

An in-situ peptide-antibody self-assembly to block CD47 and CD24 signaling enhances macrophage-mediated phagocytosis and anti-tumor immune responses

Targeted immunomodulation for reactivating innate cells, especially macrophages, holds great promise to complement current adaptive immunotherapy. Nevertheless, there is still a lack of high-performance therapeutics for blocking macrophage phagocytosis checkpoint inhibitors in solid tumors. Herein, a peptide-antibody combo-supramolecular in situ assembled CD47 and CD24 bi-target inhibitor (PAC-SABI) is described, which undergoes biomimetic surface propagation on cancer cell membranes through ligand-receptor binding and enzyme-triggered reactions. By simultaneously blocking CD47 and CD24 signaling, PAC-SABI enhances the phagocytic ability of macrophages in vitro and in vivo, promoting anti-tumor responses in breast and pancreatic cancer mouse models. Moreover, building on the foundation of PAC-SABI-induced macrophage repolarization and increased CD8+ T cell tumor infiltration, sequential anti-PD-1 therapy further suppresses 4T1 tumor progression, prolonging survival rate. The in vivo construction of PAC-SABI-based nano-architectonics provides an efficient platform for bridging innate and adaptive immunity to maximize therapeutic potency.

Targeting the CD47/SIRPα pathway in malignancies: recent progress, difficulties and future perspectives

Since its initial report in 2015, CD47 has garnered significant attention as an innate immune checkpoint, raising expectations to become the next "PD-1." The optimistic early stages of clinical development spurred a flurry of licensing deals for CD47-targeted molecules and company mergers or acquisitions for related assets. However, a series of setbacks unfolded recently, starting with the July 2023 announcement of discontinuing the phase 3 ENHANCE study on Magrolimab plus Azacitidine for higher-risk myelodysplastic syndromes (MDS). Subsequently, in August 2023, the termination of the ASPEN-02 program, assessing Evorpacept in combination with Azacitidine in MDS patients, was disclosed due to insufficient improvement compared to Azacitidine alone. These setbacks have cast doubt on the feasibility of targeting CD47 in the industry. In this review, we delve into the challenges of developing CD47-SIRPα-targeted drugs, analyze factors contributing to the mentioned setbacks, discuss future perspectives, and explore potential solutions for enhancing CD47-SIRPα-targeted drug development.

Deciphering the performance of macrophages in tumour microenvironment: a call for precision immunotherapy

Macrophages infiltrating tumour tissues or residing in the microenvironment of solid tumours are known as tumour-associated macrophages (TAMs). These specialized immune cells play crucial roles in tumour growth, angiogenesis, immune regulation, metastasis, and chemoresistance. TAMs encompass various subpopulations, primarily classified into M1 and M2 subtypes based on their differentiation and activities. M1 macrophages, characterized by a pro-inflammatory phenotype, exert anti-tumoural effects, while M2 macrophages, with an anti-inflammatory phenotype, function as protumoural regulators. These highly versatile cells respond to stimuli from tumour cells and other constituents within the tumour microenvironment (TME), such as growth factors, cytokines, chemokines, and enzymes. These stimuli induce their polarization towards one phenotype or another, leading to complex interactions with TME components and influencing both pro-tumour and anti-tumour processes.This review comprehensively and deeply covers the literature on macrophages, their origin and function as well as the intricate interplay between macrophages and the TME, influencing the dual nature of TAMs in promoting both pro- and anti-tumour processes. Moreover, the review delves into the primary pathways implicated in macrophage polarization, examining the diverse stimuli that regulate this process. These stimuli play a crucial role in shaping the phenotype and functions of macrophages. In addition, the advantages and limitations of current macrophage based clinical interventions are reviewed, including enhancing TAM phagocytosis, inducing TAM exhaustion, inhibiting TAM recruitment, and polarizing TAMs towards an M1-like phenotype. In conclusion, while the treatment strategies targeting macrophages in precision medicine show promise, overcoming several obstacles is still necessary to achieve an accessible and efficient immunotherapy.

The biological roles of CD47 in ovarian cancer progression

Ovarian cancer is one of the most lethal malignant tumors, characterized by high incidence and poor prognosis. Patients relapse occurred in 65-80% after initial treatment. To date, no effective treatment has been established for these patients. Recently, CD47 has been considered as a promising immunotherapy target. In this paper, we reviewed the biological roles of CD47 in ovarian cancer and summarized the related mechanisms. For most types of cancers, the CD47/Sirpα immune checkpoint has attracted the most attention in immunotherapy. Notably, CD47 monoclonal antibodies and related molecules are promising in the immunotherapy of ovarian cancer, and further research is needed. In the future, new immunotherapy regimens targeting CD47 can be applied to the clinical treatment of ovarian cancer patients.

Development of small molecule drugs targeting immune checkpoints

Immune checkpoint inhibitors (ICIs) are used to relieve and refuel anti-tumor immunity by blocking the interaction, transcription, and translation of co-inhibitory immune checkpoints or degrading co-inhibitory immune checkpoints. Thousands of small molecule drugs or biological materials, especially antibody-based ICIs, are actively being studied and antibodies are currently widely used. Limitations, such as anti-tumor efficacy, poor membrane permeability, and unneglected tolerance issues of antibody-based ICIs, remain evident but are thought to be overcome by small molecule drugs. Recent structural studies have broadened the scope of candidate immune checkpoint molecules, as well as innovative chemical inhibitors. By way of comparison, small molecule drug-based ICIs represent superior oral bioavailability and favorable pharmacokinetic features. Several ongoing clinical trials are exploring the synergetic effect of ICIs and other therapeutic strategies based on multiple ICI functions, including immune regulation, anti-angiogenesis, and cell cycle regulation. In this review we summarized the current progression of small molecule ICIs and the mechanism underlying immune checkpoint proteins, which will lay the foundation for further exploration.

Immunomodulatory Peptides for Tumor Treatment

Peptides exhibit various biological activities, including biorecognition, cell targeting, and tumor penetration, and can stimulate immune cells to elicit immune responses for tumor immunotherapy. Peptide self-assemblies and peptide-functionalized nanocarriers can reduce the effect of various biological barriers and the degradation by peptidases, enhancing the efficiency of peptide delivery and improving antitumor immune responses. To date, the design and development of peptides with various functionalities have been extensively reviewed for enhanced chemotherapy; however, peptide-mediated tumor immunotherapy using peptides acting on different immune cells, to the knowledge, has not yet been summarized. Thus, this work provides a review of this emerging subject of research, focusing on immunomodulatory anticancer peptides. This review introduces the role of peptides in the immunomodulation of innate and adaptive immune cells, followed by a link between peptides in the innate and adaptive immune systems. The peptides are discussed in detail, following a classification according to their effects on different innate and adaptive immune cells, as well as immune checkpoints. Subsequently, two delivery strategies for peptides as drugs are presented: peptide self-assemblies and peptide-functionalized nanocarriers. The concluding remarks regarding the challenges and potential solutions of peptides for tumor immunotherapy are presented.

Discovery of a novel small molecule as CD47/SIRPα and PD-1/PD-L1 dual inhibitor for cancer immunotherapy

BACKGROUND

Targeting the tumor microenvironment (TME) has emerged as a promising strategy in cancer treatment, particularly through the utilization of immune checkpoint blockade (ICB) agents such as PD-1/PD-L1 inhibitors. Despite partial success, the presence of tumor-associated macrophages (TAMs) contributes to an immunosuppressive TME that fosters tumor progression, and diminishes the therapeutic efficacy of ICB. Blockade of the CD47/SIRPα pathway has proven to be an effective intervention, that restores macrophage phagocytosis and yields substantial antitumor effects, especially when combined with PD-1/PD-L1 blockade. Therefore, the identification of small molecules capable of simultaneously blocking CD47/SIRPα and PD-1/PD-L1 interactions has remained imperative.

METHODS

SMC18, a small molecule with the capacity of targeting both SIRPα and PD-L1 was obtained using MST. The efficiency of SMC18 in interrupting CD47/SIRPα and PD-1/PD-L1 interactions was tested by the blocking assay. The function of SMC18 in enhancing the activity of macrophages and T cells was tested using phagocytosis assay and co-culture assay. The antitumor effects and mechanisms of SMC18 were investigated in the MC38-bearing mouse model.

RESULTS

SMC18, a small molecule that dual-targets both SIRPα and PD-L1 protein, was identified. SMC18 effectively blocked CD47/SIRPα interaction, thereby restoring macrophage phagocytosis, and disrupted PD-1/PD-L1 interactions, thus activating Jurkat cells, as evidenced by increased secretion of IL-2. SMC18 demonstrated substantial inhibition of MC38 tumor growths through promoting the infiltration of CD8+ T and M1-type macrophages into tumor sites, while also priming the function of CD8+ T cells and macrophages. Moreover, SMC18 in combination with radiotherapy (RT) further improved the therapeutic efficacy.

CONCLUSION

Our findings suggested that the small molecule compound SMC18, which dual-targets the CD47/SIRPα and PD-1/PD-L1 pathways, could be a candidate for promoting macrophage- and T-cell-mediated phagocytosis and immune responses in cancer immunotherapy.

Macrophage: Hidden Criminal in Therapy Resistance

BACKGROUND

Although substantial efforts have been made by researchers to develop drugs, a disappointing reality is that the emergence of drug resistance is an unavoidable reality for the majority of patients. In recent years, emerging evidence suggests a connection between drug resistance and immune dysregulation.

SUMMARY

As a ubiquitously distributed, versatile innate immune cell, macrophages play essential roles in maintaining tissue homeostasis in a steady state. Nevertheless, it is becoming aware that macrophages undermine the action of therapeutic drugs across various disease types. Reprogramming macrophage function has been proven to be effective in restoring patient responsiveness to treatment. Herein, we comprehensively reviewed how macrophages respond to drugs and the mechanisms by which they contribute to treatment unresponsiveness in cancer, inflammatory diseases, and metabolic diseases. In addition, future prospects in macrophage-based combination therapy were discussed.

KEY MESSAGES

Targeting macrophages is a promising strategy for overcoming drug resistance in immune disorders.

Development of LAG-3/FGL1 blocking peptide and combination with radiotherapy for cancer immunotherapy

Aside from antibodies, peptides show great potential as immune checkpoint inhibitors (ICIs) due to several advantages, such as better tumor penetration and lower cost. Lymphocyte-activation gene 3 (LAG-3) is an immune checkpoint which can induce T cell dysfunction through interaction with its soluble ligand fibrinogen like protein-1 (FGL1). Here, we found that LAG-3 expression was higher than programmed cell death protein 1 (PD-1) in multiple human cancers by TCGA databases, and successfully identified a LAG-3 binding peptide LFP-6 by phage display bio-panning, which specifically blocks the interaction of LAG-3/FGL1 but not LAG-3/MHC-II. Subsequently, d-amino acids were introduced to substitute the N- and C-terminus of LFP-6 to obtain the proteolysis-resistant peptide LFP-D1, which restores T cell function in vitro and inhibits tumor growth in vivo. Further, a bispecific peptide LFOP targeting both PD-1/PD-L1 and LAG-3/FGL1 was designed by conjugating LFP-D1 with PD-1/PD-L1 blocking peptide OPBP-1(8-12), which activates T cell with enhanced proliferation and IFN-γ production. More importantly, LFOP combined with radiotherapy significantly improve the T cell infiltration in tumor and elevate systemic antitumor immune response. In conclusion, we developed a novel peptide blocking LAG-3/FGL1 which can restore T cell function, and the bispecific peptide synergizes with radiotherapy to further enhance the antitumor immune response.

Immunotherapies of acute myeloid leukemia: Rationale, clinical evidence and perspective

Acute myeloid leukemia (AML) is a prevalent hematological malignancy that exhibits a wide array of molecular abnormalities. Although traditional treatment modalities such as chemotherapy and allogeneic stem cell transplantation (HSCT) have become standard therapeutic approaches, a considerable number of patients continue to face relapse and encounter a bleak prognosis. The emergence of immune escape, immunosuppression, minimal residual disease (MRD), and other contributing factors collectively contribute to this challenge. Recent research has increasingly highlighted the notable distinctions between AML tumor microenvironments and those of healthy individuals. In order to investigate the potential therapeutic mechanisms, this study examines the intricate transformations occurring between leukemic cells and their surrounding cells within the tumor microenvironment (TME) of AML. This review classifies immunotherapies into four distinct categories: cancer vaccines, immune checkpoint inhibitors (ICIs), antibody-based immunotherapies, and adoptive T-cell therapies. The results of numerous clinical trials strongly indicate that the identification of optimal combinations of novel agents, either in conjunction with each other or with chemotherapy, represents a crucial advancement in this field. In this review, we aim to explore the current and emerging immunotherapeutic methodologies applicable to AML patients, identify promising targets, and emphasize the crucial requirement to augment patient outcomes. The application of these strategies presents substantial therapeutic prospects within the realm of precision medicine for AML, encompassing the potential to ameliorate patient outcomes.

The pathogenic role of succinate-SUCNR1: a critical function that induces renal fibrosis via M2 macrophage

BACKGROUND

Renal fibrosis significantly contributes to the progressive loss of kidney function in chronic kidney disease (CKD), with alternatively activated M2 macrophages playing a crucial role in this progression. The serum succinate level is consistently elevated in individuals with diabetes and obesity, both of which are critical factors contributing to CKD. However, it remains unclear whether elevated succinate levels can mediate M2 polarization of macrophages and contribute to renal interstitial fibrosis.

METHODS

Male C57/BL6 mice were administered water supplemented with 4% succinate for 12 weeks to assess its impact on renal interstitial fibrosis. Additionally, the significance of macrophages was confirmed in vivo by using clodronate liposomes to deplete them. Furthermore, we employed RAW 264.7 and NRK-49F cells to investigate the underlying molecular mechanisms.

RESULTS

Succinate caused renal interstitial macrophage infiltration, activation of profibrotic M2 phenotype, upregulation of profibrotic factors, and interstitial fibrosis. Treatment of clodronate liposomes markedly depleted macrophages and prevented the succinate-induced increase in profibrotic factors and fibrosis. Mechanically, succinate promoted CTGF transcription via triggering SUCNR1-p-Akt/p-GSK3β/β-catenin signaling, which was inhibited by SUCNR1 siRNA. The knockdown of succinate receptor (SUCNR1) or pretreatment of anti-CTGF(connective tissue growth factor) antibody suppressed the stimulating effects of succinate on RAW 264.7 and NRK-49F cells.

CONCLUSIONS

The causative effects of succinate on renal interstitial fibrosis were mediated by the activation of profibrotic M2 macrophages. Succinate-SUCNR1 played a role in activating p-Akt/p-GSK3β/β-catenin, CTGF expression, and facilitating crosstalk between macrophages and fibroblasts. Our findings suggest a promising strategy to prevent the progression of metabolic CKD by promoting the excretion of succinate in urine and/or using selective antagonists for SUCNR1.

Fish oil-based microemulsion can efficiently deliver oral peptide blocking PD-1/PD-L1 and simultaneously induce ferroptosis for cancer immunotherapy

Peptide immune checkpoint inhibitors in cancer immunotherapy have attracted great attention recently, but oral delivery of these peptides remains a huge challenge due to the harsh gastrointestinal environment, large molecular size, high hydrophilic, and poor transmembrane permeability. Here, for the first time, a fish oil-based microemulsion was developed for oral delivery of programmed death-1/programmed cell death-ligand 1 (PD-1/PD-L1) blocking model peptide, OPBP-1. The delivery system was characterized, in vitro and in vivo studies were conducted to evaluate its overall implication. As a result, this nutraceutical microemulsion was easily formed without the need of co-surfactants, and it appeared light yellow, transparent, good flowability with a particle size of 152 ± 0.73 nm, with a sustained drug release manner of 56.45 ± 0.36% over 24 h and a great stability within the harsh intestinal environment. It enhanced intestinal drug uptake and transportation over human intestinal epithelial Caco-2 cells, and drastically elevated the oral peptide bioavailability of 4.1-fold higher than that of OPBP-1 solution. Meanwhile, the mechanism of these dietary droplets permeated over the intestinal enterocytic membrane was found via clathrin and caveolae-mediated endocytic pathways. From the in vivo studies, the microemulsion facilitated the infiltration of CD8+ T lymphocytes in tumors, with increased interferon-γ (IFN-γ) secretion. Thus, it manifested a promising immune anti-tumor effect and significantly inhibited the growth of murine colonic carcinoma (CT26). Furthermore, it was found that the fish oil could induce ferroptosis in tumor cells and exhibited synergistic effect with OPBP-1 for cancer immunotherapy. In conclusion, this fish oil-based formulation demonstrated great potential for oral delivery of peptides with its natural property in reactive oxygen species (ROS)-related ferroptosis of tumor cells, which provides a great platform for functional green oral delivery system in cancer immunotherapy.

Discovery of Anti-CD47 Peptides as Innate Immune Checkpoint Inhibitors

Cancer immunotherapy targeting adaptive immune cells has been attracting considerable interest due to its great success in treating multiple cancers. Recently, there is also increasing interest in agents that can stimulate innate immune cell activities. Immune checkpoint inhibitors targeting innate immune cells can block inhibitory interactions ('don't eat me' signals) between tumor cells and phagocytes. CD47 is a transmembrane protein overexpressed in various cancers and acts as a potent 'do not eat me' signal that contributes to the immune evasion of cancer cells. Anti-CD47 peptides that can bind to CD47 and block CD47/SIRPα interaction were discovered using a novel phage display biopanning strategy. Anti-CD47 peptides enhanced the macrophage-mediated phagocytosis of NCI-H82 tumor cells in vitro. Unlike anti-CD47 antibodies, these peptides do not induce the agglutination of RBCs. Moreover, anti-CD47 peptides exhibit high specificity for MC-38 cancer cells expressing CD47. CMP-22 peptide showed the ability to increase the antitumor activity of doxorubicin and extends the survival of CT26 tumor-bearing mice. The discovered anti-CD47 peptides can be considered potential candidates for cancer immunotherapy by blocking the CD47/SIRPα interaction, especially in combination with chemotherapy, to elicit synergistic effects.

A novel CD47-blocking peptide fused to pro-apoptotic KLA repeat inhibits lung cancer growth in mice

CD47 is highly expressed in many tumor tissues and induces immune evasion by interaction with SIRP-alpha (signal regulatory protein-alpha) expressed on tumor-associated macrophages. In this study, we identified a novel CD47-blocking peptide VK17 by phage display technique. A pro-apoptotic VK30 peptide was obtained after VK17 was fused to KLA amino acid repeat at C-termini. The VK30 was specifically bound to CD47 on lung cancer cells, and subsequently inducing lung cancer cell apoptosis. Meanwhile, the expression of Bax was increased, whereas the expression of Bcl-2 and Ki-67 were reduced in the VK30-treated lung cancer cells. In addition, VK30 effectively improved the phagocytic activity of macrophages against VK30-pretreated lung cancer cells. Combinational treatment of lung cancer cells with blocking antibody anti-CD47 and VK30 additively enhanced VK30 binding to CD47, subsequently increasing lung cancer cell apoptosis and macrophage phagocytosis. Intraperitoneal administration of 2 mg/kg VK30 induced effective trafficking of VK30 into tumor tissues, and suppressing lung cancer cell growth in mice, associated with increased tumor cell apoptosis, macrophage activation and phagocytosis in vivo. The expression of CD47 was reduced in the VK30-treated tumor tissues and the expression level was positively correlated to tumor size. In addition, VK30 reduced the infiltration of CD11b+Ly6G+ neutrophils and CD11b+Ly6C+Ly6G+ granulocytic myeloid-derived suppressor cells (Gr-MDSCs) in tumor tissues, associated with suppressed expression of tumorigenic IL-6 and TNF-alpha from these cell types. Thereby, VK30 exerted anti-tumor effects in mice through inducing tumor cell apoptosis and macrophage phagocytosis. VK30 would be a novel therapeutic peptide in lung cancer immunotherapy.

CD47Binder: Identify CD47 Binding Peptides by Combining Next-Generation Phage Display Data and Multiple Peptide Descriptors

CD47/SIRPα pathway is a new breakthrough in the field of tumor immunity after PD-1/PD-L1. While current monoclonal antibody therapies targeting CD47/SIRPα have demonstrated some anti-tumor effectiveness, there are several inherent limitations associated with these formulations. In the paper, we developed a predictive model that combines next-generation phage display (NGPD) and traditional machine learning methods to distinguish CD47 binding peptides. First, we utilized NGPD biopanning technology to screen CD47 binding peptides. Second, ten traditional machine learning methods based on multiple peptide descriptors and three deep learning methods were used to build computational models for identifying CD47 binding peptides. Finally, we proposed an integrated model based on support vector machine. During the five-fold cross-validation, the integrated predictor demonstrated specificity, accuracy, and sensitivity of 0.755, 0.764, and 0.772, respectively. Furthermore, an online bioinformatics tool called CD47Binder has been developed for the integrated predictor. This tool is readily accessible on http://i.uestc.edu.cn/CD47Binder/cgi-bin/CD47Binder.pl .

Tumor-associated macrophages: an effective player of the tumor microenvironment

Cancer progression is primarily caused by interactions between transformed cells and the components of the tumor microenvironment (TME). TAMs (tumor-associated macrophages) make up the majority of the invading immune components, which are further categorized as anti-tumor M1 and pro-tumor M2 subtypes. While M1 is known to have anti-cancer properties, M2 is recognized to extend a protective role to the tumor. As a result, the tumor manipulates the TME in such a way that it induces macrophage infiltration and M1 to M2 switching bias to secure its survival. This M2-TAM bias in the TME promotes cancer cell proliferation, neoangiogenesis, lymphangiogenesis, epithelial-to-mesenchymal transition, matrix remodeling for metastatic support, and TME manipulation to an immunosuppressive state. TAMs additionally promote the emergence of cancer stem cells (CSCs), which are known for their ability to originate, metastasize, and relapse into tumors. CSCs also help M2-TAM by revealing immune escape and survival strategies during the initiation and relapse phases. This review describes the reasons for immunotherapy failure and, thereby, devises better strategies to impair the tumor-TAM crosstalk. This study will shed light on the understudied TAM-mediated tumor progression and address the much-needed holistic approach to anti-cancer therapy, which encompasses targeting cancer cells, CSCs, and TAMs all at the same time.

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.

The cross-talk between macrophages and tumor cells as a target for cancer treatment

Macrophages represent an important component of the innate immune system. Under physiological conditions, macrophages, which are essential phagocytes, maintain a proinflammatory response and repair damaged tissue. However, these processes are often impaired upon tumorigenesis, in which tumor-associated macrophages (TAMs) protect and support the growth, proliferation, and invasion of tumor cells and promote suppression of antitumor immunity. TAM abundance is closely associated with poor outcome of cancer, with impediment of chemotherapy effectiveness and ultimately a dismal therapy response and inferior overall survival. Thus, cross-talk between cancer cells and TAMs is an important target for immune checkpoint therapies and metabolic interventions, spurring interest in it as a therapeutic vulnerability for both hematological cancers and solid tumors. Furthermore, targeting of this cross-talk has emerged as a promising strategy for cancer treatment with the antibody against CD47 protein, a critical macrophage checkpoint recognized as the "don't eat me" signal, as well as other metabolism-focused strategies. Therapies targeting CD47 constitute an important milestone in the advancement of anticancer research and have had promising effects on not only phagocytosis activation but also innate and adaptive immune system activation, effectively counteracting tumor cells' evasion of therapy as shown in the context of myeloid cancers. Targeting of CD47 signaling is only one of several possibilities to reverse the immunosuppressive and tumor-protective tumor environment with the aim of enhancing the antitumor response. Several preclinical studies identified signaling pathways that regulate the recruitment, polarization, or metabolism of TAMs. In this review, we summarize the current understanding of the role of macrophages in cancer progression and the mechanisms by which they communicate with tumor cells. Additionally, we dissect various therapeutic strategies developed to target macrophage-tumor cell cross-talk, including modulation of macrophage polarization, blockade of signaling pathways, and disruption of physical interactions between leukemia cells and macrophages. Finally, we highlight the challenges associated with tumor hypoxia and acidosis as barriers to effective cancer therapy and discuss opportunities for future research in this field.

Tumour-associated macrophages: versatile players in the tumour microenvironment

Tumour-Associated Macrophages (TAMs) are one of the pivotal components of the tumour microenvironment. Their roles in the cancer immunity are complicated, both pro-tumour and anti-cancer activities are reported, including not only angiogenesis, extracellular matrix remodeling, immunosuppression, drug resistance but also phagocytosis and tumour regression. Interestingly, TAMs are highly dynamic and versatile in solid tumours. They show anti-cancer or pro-tumour activities, and interplay between the tumour microenvironment and cancer stem cells and under specific conditions. In addition to the classic M1/M2 phenotypes, a number of novel dedifferentiation phenomena of TAMs are discovered due to the advanced single-cell technology, e.g., macrophage-myofibroblast transition (MMT) and macrophage-neuron transition (MNT). More importantly, emerging information demonstrated the potential of TAMs on cancer immunotherapy, suggesting by the therapeutic efficiency of the checkpoint inhibitors and chimeric antigen receptor engineered cells based on macrophages. Here, we summarized the latest discoveries of TAMs from basic and translational research and discussed their clinical relevance and therapeutic potential for solid cancers.

Design of a novel chimeric peptide via dual blockade of CD47/SIRPα and PD-1/PD-L1 for cancer immunotherapy

Although immune checkpoint inhibition has been shown to effectively activate antitumor immunity in various tumor types, only a small subset of patients can benefit from PD-1/PD-L1 blockade. CD47 expressed on tumor cells protects them from phagocytosis through interaction with SIRPα on macrophages, while PD-L1 dampens T cell-mediated tumor killing. Therefore, dual targeting PD-L1 and CD47 may improve the efficacy of cancer immunotherapy. A chimeric peptide Pal-DMPOP was designed by conjugating the double mutation of CD47/SIRPα blocking peptide (DMP) with the truncation of PD-1/PD-L1 blocking peptide OPBP-1(8-12) and was modified by a palmitic acid tail. Pal-DMPOP can significantly enhance macrophage-mediated phagocytosis of tumor cells and activate primary T cells to secret IFN-γ in vitro. Due to its superior hydrolysis-resistant activity as well as tumor tissue and lymph node targeting properties, Pal-DMPOP elicited stronger anti-tumor potency than Pal-DMP or OPBP-1(8-12) in immune-competent MC38 tumor-bearing mice. The in vivo anti-tumor activity was further validated in the colorectal CT26 tumor model. Furthermore, Pal-DMPOP mobilized macrophage and T-cell anti-tumor responses with minimal toxicity. Overall, the first bispecific CD47/SIRPα and PD-1/PD-L1 dual-blockade chimeric peptide was designed and exhibited synergistic anti-tumor efficacy via CD8+ T cell activation and macrophage-mediated immune response. The strategy could pave the way for designing effective therapeutic agents for cancer immunotherapy.

[Radix Tetrastigme Polysaccharide Promotes Antitumor Immune Response in Lewis Lung Cancer Mice]

BACKGROUND

Lung cancer has a high incidence and mortality rate, but the treatment of lung cancer still lacks low toxicity and efficient anti-tumor drugs. Polysaccharide from radix tetrastigme has development value in anti-tumor treatment methods. This study was to observe the effect of polysaccharide from radix tetrastigme on immune response of Lewis lung cancer mice and explore its molecular mechanism.

METHODS

Lewis lung cancer mouse models were established and randomly grouped. The spleen polypeptide group was intragastric with 50 mg/kg spleen polypeptide, and the radix tetrastigme polysaccharide low, medium and high dose groups were intragastric with 62.5, 125 and 250 mg/kg radix tetrastigme polysaccharide, respectively, and the model group and the control group were intragastric with equivolume normal saline. Tumor formation and metastasis were compared. Haematoxylin-eosin (HE) staining was used to observe the pathological changes of tumor cells. Macrophage phagocytosis, apoptosis, M1/M2 polarization, T cell subsets and cytokine levels in peripheral blood were detected by flow cytometry. The proliferation activity of macrophages was detected by methyl thiazolyldiphenyl tetrazolium (MTT) assay. Dendritic cell (DC) antigen presenting function was detected by chlorophenol red-β-D-galactopyranoside (CPRG) method. Tumor tissue differentiation antigen cluster 47 (CD47) mRNA and protein expression and macrophage signal regulatory protein α (SIRRP α) expression were detected by real time quantitative polymerase chain reaction (RT-qPCR) and Western blot (WB).

RESULTS

The tumor inhibition rates and anti-metastasis rates in the 3-dose radix tetrastigme polysaccharide group and the spleen polypeptide group were higher than those in the model group, and the pathological injury of tumor tissue were severer, and the positive rate of phagocytosis of ink by macrophages and the efficiency of phagocytosis of tumor cells were increased; the apoptosis rate of macrophages was decreased; the proliferation activity of macrophages, polarization ratio of macrophages to M1 type, DC antigen presenting ability, CD4+, CD4+/CD8+ levels were increased; the level of serum tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and the expression of tumor tissue CD47, macrophage SH2-containing protein tyrosine phosphatase 1 (SHP-1), SH2-containing protein tyrosine phosphatase 2 (SHP-2), and phosphorylation signal regulatory protein α (p-SIRPα) were decreased, and the differences were statistically significant (P<0.05). There were no significant differences in the above indexes between low-dose radix tetrastigme polysaccharide group and spleen polypeptide group (P>0.05), and the effects of radix tetrastigme polysaccharide were dose-dependent.

CONCLUSIONS

Radix tetrastigme polysaccharide can inhibit tumor growth, metastasis and immune response in Lewis lung cancer mice, and its mechanism may be related to inhibiting SIRP/CD47 signaling pathway.

Macrophage-Based Therapeutic Strategies in Hematologic Malignancies

Macrophages are types of immune cells, with ambivalent functions in tumor growth, which depend on the specific environment in which they reside. Tumor-associated macrophages (TAMs) are a diverse population of immunosuppressive myeloid cells that play significant roles in several malignancies. TAM infiltration in malignancies has been linked to a poor prognosis and limited response to treatments, including those using checkpoint inhibitors. Understanding the precise mechanisms through which macrophages contribute to tumor growth is an active area of research as targeting these cells may offer potential therapeutic approaches for cancer treatment. Numerous investigations have focused on anti-TAM-based methods that try to eliminate, rewire, or target the functional mediators released by these cells. Considering the importance of these strategies in the reversion of tumor resistance to conventional therapies and immune modulatory vaccination could be an appealing approach for the immunosuppressive targeting of myeloid cells in the tumor microenvironment (TME). The combination of reprogramming and TAM depletion is a special feature of this approach compared to other clinical strategies. Thus, the present review aims to comprehensively overview the pleiotropic activities of TAMs and their involvement in various stages of cancer development as a potent drug target, with a focus on hematologic tumors.

New hope for tumor immunotherapy: the macrophage-related "do not eat me" signaling pathway

The "do not eat me" signaling pathway is extremely active in tumor cells, providing a means for these cells to elude macrophage phagocytosis and escape immune surveillance. Representative markers of this pathway, such as CD47 and CD24, are highly expressed in numerous tumors. The interaction of SIRPα with CD47 reduces the accumulation of non-myosin ⅡA on the cell membrane. The combination of CD24 and Siglec10 ultimately leads to the recruitment of SHP-1 or SHP-2 to reduce signal transduction. Both of them weaken the ability of macrophages to engulf tumor cells. Blocking the mutual recognition between CD47-SIRPα or CD24-Siglec10 using large molecular proteins or small molecular drugs represents a promising avenue for tumor immunotherapy. Doing so can inhibit signal transduction and enhance macrophage clearance rates of cancer cells. In this paper, we summarize the characteristics of the drugs that affect the "do not eat me" signaling pathway via classical large molecular proteins and small molecule drugs, which target the CD47-SIRPα and CD24-Siglec10 signaling pathways, which target the CD47-SIRPα and CD24-Siglec10 signaling pathways. We expect it will offer insight into the development of new drugs centered on blocking the "do not eat me" signaling pathway.

Current research status of anti-cancer peptides: Mechanism of action, production, and clinical applications

The escalating rate of cancer cases, together with treatment deficiencies and long-term side effects of currently used cancer drugs, has made this disease a global burden of the 21st century. The number of breast and lung cancer patients has sharply increased worldwide in the last few years. Presently, surgical treatment, radiotherapy, chemotherapy, and immunotherapy strategies are used to cure cancer, which cause severe side effects, toxicities, and drug resistance. In recent years, anti-cancer peptides have become an eminent therapeutic strategy for cancer treatment due to their high specificity and fewer side effects and toxicity. This review presents an updated overview of different anti-cancer peptides, their mechanisms of action and current production strategies employed for their manufacture. In addition, approved and under clinical trials anti-cancer peptides and their applications have been discussed. This review provides updated information on therapeutic anti-cancer peptides that hold great promise for cancer treatment in the near future.

Discovery of a novel dual-targeting D-peptide to block CD24/Siglec-10 and PD-1/PD-L1 interaction and synergize with radiotherapy for cancer immunotherapy

BACKGROUND

Aside from immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1), intervention of CD47/Sirpα mediated 'don't eat me' signal between macrophage and tumor cell is considered as a promising therapeutic approach for cancer immunotherapy. Compared with CD47, the novel immune checkpoint CD24/Siglec-10 can also deliver 'don't eat me' signal and CD24 shows much lower expression level in normal tissue which might avoid unwanted side effects.

METHODS

Cell-based phage display biopanning and D-amino acid modification strategy were used to identify the CD24/Siglec-10 blocking peptide. Cell-based blocking assay and microscale thermophoresis assay were used to validate the blocking and binding activities of the peptide. Phagocytosis and co-culture assays were used to explore the in vitro function of the peptide. Flow cytometry was performed to assess the immune microenvironment after the peptide treatment in vivo.

RESULTS

A CD24/Siglec-10 blocking peptide (CSBP) with hydrolysis-resistant property was identified. Surprisingly, we found that CSBP could not only block the interaction of CD24/Siglec-10 but also PD-1/PD-L1. CSBP could induce the phagocytosis of tumor cell by both the macrophages and monocytic myeloid-derived suppressor cells (M-MDSCs), which can further activate CD8⁺ T cells. Besides, combination of radiotherapy and CSBP synergistically reduced tumor growth and altered the tumor microenvironment in both anti-PD-1-responsive MC38 and anti-PD-1-resistant 4T1 tumor models.

CONCLUSIONS

In summary, this is the first CD24/Siglec-10 blocking peptide which blocked PD-1/PD-L1 interaction as well, functioned via enhancing the phagocytosis of tumor cells by macrophages and M-MDSCs, and elevating the activity of CD8⁺ T cells for cancer immunotherapy.

Targeting immune checkpoints on tumor-associated macrophages in tumor immunotherapy

Unprecedented breakthroughs have been made in cancer immunotherapy in recent years. Particularly immune checkpoint inhibitors have fostered hope for patients with cancer. However, immunotherapy still exhibits certain limitations, such as a low response rate, limited efficacy in certain populations, and adverse events in certain tumors. Therefore, exploring strategies that can improve clinical response rates in patients is crucial. Tumor-associated macrophages (TAMs) are the predominant immune cells that infiltrate the tumor microenvironment and express a variety of immune checkpoints that impact immune functions. Mounting evidence indicates that immune checkpoints in TAMs are closely associated with the prognosis of patients with tumors receiving immunotherapy. This review centers on the regulatory mechanisms governing immune checkpoint expression in macrophages and strategies aimed at improving immune checkpoint therapies. Our review provides insights into potential therapeutic targets to improve the efficacy of immune checkpoint blockade and key clues to developing novel tumor immunotherapies.

Cancer immune exclusion: breaking the barricade for a successful immunotherapy

Immunotherapy has changed the course of cancer treatment. The initial steps were made through tumor-specific antibodies that guided the setup of an antitumor immune response. A new and successful generation of antibodies are designed to target immune checkpoint molecules aimed to reinvigorate the antitumor immune response. The cellular counterpart is the adoptive cell therapy, where specific immune cells are expanded or engineered to target cancer cells. In all cases, the key for achieving positive clinical resolutions rests upon the access of immune cells to the tumor. In this review, we focus on how the tumor microenvironment architecture, including stromal cells, immunosuppressive cells and extracellular matrix, protects tumor cells from an immune attack leading to immunotherapy resistance, and on the available strategies to tackle immune evasion.

The CD47-SIRPα axis is a promising target for cancer immunotherapies

Cluster of differentiation 47(CD47) is a transmembrane protein that is ubiquitously found on the surface of many cells in the body and uniquely overexpressed by both solid and hematologic malignant cells. CD47 interacts with signal-regulatory protein α (SIRPα), to trigger a "don't eat me" signal and thereby achieve cancer immune escape by inhibiting macrophage-mediated phagocytosis. Thus, blocking the CD47-SIRPα phagocytosis checkpoint, for release of the innate immune system, is a current research focus. Indeed, targeting the CD47-SIRPα axis as a cancer immunotherapy has shown promising efficacies in pre-clinical outcomes. Here, we first reviewed the origin, structure, and function of the CD47-SIRPα axis. Then, we reviewed its role as a target for cancer immunotherapies, as well as the factors regulating CD47-SIRPα axis-based immunotherapies. We specifically focused on the mechanism and progress of CD47-SIRPα axis-based immunotherapies and their combination with other treatment strategies. Finally, we discussed the challenges and directions for future research and identified potential CD47-SIRPα axis-based therapies that are suitable for clinical application.

Anti-Tumor Strategies by Harnessing the Phagocytosis of Macrophages

Macrophages are essential for the human body in both physiological and pathological conditions, engulfing undesirable substances and participating in several processes, such as organism growth, immune regulation, and maintenance of homeostasis. Macrophages play an important role in anti-bacterial and anti-tumoral responses. Aberrance in the phagocytosis of macrophages may lead to the development of several diseases, including tumors. Tumor cells can evade the phagocytosis of macrophages, and "educate" macrophages to become pro-tumoral, resulting in the reduced phagocytosis of macrophages. Hence, harnessing the phagocytosis of macrophages is an important approach to bolster the efficacy of anti-tumor treatment. In this review, we elucidated the underlying phagocytosis mechanisms, such as the equilibrium among phagocytic signals, receptors and their respective signaling pathways, macrophage activation, as well as mitochondrial fission. We also reviewed the recent progress in the area of application strategies on the basis of the phagocytosis mechanism, including strategies targeting the phagocytic signals, antibody-dependent cellular phagocytosis (ADCP), and macrophage activators. We also covered recent studies of Chimeric Antigen Receptor Macrophage (CAR-M)-based anti-tumor therapy. Furthermore, we summarized the shortcomings and future applications of each strategy and look into their prospects with the hope of providing future research directions for developing the application of macrophage phagocytosis-promoting therapy.

Gold Nanorods and Polymer Micelles Mediated Dual TLR Stimulators Delivery System CPG@Au NRs/M-R848 Regulate Macrophages Reprogramming and DC Maturation for Enhanced Photothermal Immunotherapy of Melanoma

Synergistic photothermal immunotherapy has emerged as a favorable therapeutic approach to fight cancer. However, design of an effective photothermal immunotherapy system to suppress tumor growth and simultaneously inhibit tumor metastases continues to be a challenge. Here a dual toll-like receptor agonists delivery system CPG@Au NRs/m-R848 for combined photothermal immunotherapy of melanoma is developed. CPG@Au NRs/m-R848 displays strong antitumor effects by promoting maturation of dendritic cells (DCs) and reprogramming of M2 macrophages into M1 phenotype. Moreover, immunogenic cell death (ICD) induced by photothermal ablation of Au NRs could synergistically produce in situ vaccination effect with CPG ODN and R848, generating systemic and lasting antitumor immunity. It is further proved that CPG@Au NRs/m-R848 treatment inhibits tumor growth in bilateral B16F10 tumors model by eliciting CD8+ T cell response. Overall, this work suggests that this strategy hold great potential in tumor immunotherapy by regulating tumor-associated macrophage polarization, triggering DCs maturation and inducing ICD.

Precision Delivery of Dual Immune Inhibitors Loaded Nanomodulator to Reverse Immune Suppression for Combinational Photothermal-Immunotherapy

Although photothermal therapy (PTT) can noninvasively kill tumor cells and exert synergistic immunological effects, the immune responses are usually harmed due to the lack of cytotoxic T cells (CTLs) pre-infiltration and co-existing of intricate immunosuppressive tumor microenvironment (TME), including the programmed cell death ligand 1 (PD-L1)/cluster of differentiation 47 (CD47)/regulatory T cells (Tregs)/M2-macrophages overexpression. Indoleamine 2, 3-dioxygenase inhibitor (NLG919) or bromodomain extra-terminal inhibitor (OTX015) holds great promise to reprogram suppressive TME through different pathways, but their collaborative application remains a formidable challenge because of the poor water solubility and low tumor targeting. To address this challenge, a desirable nanomodulator based on dual immune inhibitors loaded mesoporous polydopamine nanoparticles is designed. This nanomodulator exhibits excellent biocompatibility and water solubility, PTT, and bimodal magnetic resonance/photoacoustic imaging abilities. Owing to enhanced permeability and retention effect and tumor acidic pH-responsiveness, both inhibitors are precisely delivered and locally released at tumor sites. Such a nanomodulator significantly reverses the immune suppression of PD-L1/CD47/Tregs, promotes the activation of CTLs, regulates M2-macrophages polarization, and further boosts combined therapeutic efficacy, inducing a strong immunological memory. Taken together, the nanomodulator provides a practical approach for combinational photothermal-immunotherapy, which may be further broadened to other "immune cold" tumors.

Tumor-Associated Macrophage Subsets: Shaping Polarization and Targeting

The tumor microenvironment (TME) is a critical regulator of tumor growth, progression, and metastasis. Among the innate immune cells recruited to the tumor site, macrophages are the most abundant cell population and are present at all stages of tumor progression. They undergo M1/M2 polarization in response to signals derived from TME. M1 macrophages suppress tumor growth, while their M2 counterparts exert pro-tumoral effects by promoting tumor growth, angiogenesis, metastasis, and resistance to current therapies. Several subsets of the M2 phenotype have been observed, often denoted as M2a, M2b, M2c, and M2d. These are induced by different stimuli and differ in phenotypes as well as functions. In this review, we discuss the key features of each M2 subset, their implications in cancers, and highlight the strategies that are being developed to harness TAMs for cancer treatment.

Building on the backbone of CD47-based therapy in cancer: Combination strategies, mechanisms, and future perspectives

Described as a "don't eat me" signal, CD47 becomes a vital immune checkpoint in cancer. Its interaction with signal regulatory protein alpha (SIRPα) prevents macrophage phagocytosis. In recent years, a growing body of evidences have unveiled that CD47-based combination therapy exhibits a superior anti-cancer effect. Latest clinical trials about CD47 have adopted the regimen of collaborating with other therapies or developing CD47-directed bispecific antibodies, indicating the combination strategy as a general trend of the future. In this review, clinical and preclinical cases about the current combination strategies targeting CD47 are collected, their underlying mechanisms of action are discussed, and ideas from future perspectives are shared.

The DNA damage response pathway regulates the expression of the immune checkpoint CD47

CD47 is a cell surface ligand expressed on all nucleated cells. It is a unique immune checkpoint protein acting as "don't eat me" signal to prevent phagocytosis and is constitutively overexpressed in many tumors. However, the underlying mechanism(s) for CD47 overexpression is not clear. Here, we show that irradiation (IR) as well as various other genotoxic agents induce elevated expression of CD47. This upregulation correlates with the extent of residual double-strand breaks (DSBs) as determined by γH2AX staining. Interestingly, cells lacking mre-11, a component of the MRE11-RAD50-NBS1 (MRN) complex that plays a central role in DSB repair, or cells treated with the mre-11 inhibitor, mirin, fail to elevate the expression of CD47 upon DNA damage. On the other hand, both p53 and NF-κB pathways or cell-cycle arrest do not play a role in CD47 upregualtion upon DNA damage. We further show that CD47 expression is upregulated in livers harvested from mice treated with the DNA-damage inducing agent Diethylnitrosamine (DEN) and in cisplatin-treated mesothelioma tumors. Hence, our results indicate that CD47 is upregulated following DNA damage in a mre-11-dependent manner. Chronic DNA damage response in cancer cells might contribute to constitutive elevated expression of CD47 and promote immune evasion.

Natural peptides for immunological regulation in cancer therapy: Mechanism, facts and perspectives

Cancer incidence and mortality rates are increasing annually. Treatment with surgery, chemotherapy and radiation therapy (RT) is unsatisfactory because many patients have advanced disease at the initial diagnosis. However, the emergence of immunotherapy promises to be an effective strategy to improve the outcome of advanced tumors. Immune checkpoint antibodies, which are at the forefront of immunotherapy, have had significant success but still leave some cancer patients without benefit. For more cancer patients to benefit from immunotherapy, it is necessary to find new drugs and combination therapeutic strategies to improve the outcome of advanced cancer patients and achieve long-term tumor control or even eradication. Peptides are promising choices for tumor immunotherapy drugs because they have the advantages of low production cost, high sequence selectivity, high tissue permeability, low toxicity and low immunogenicity etc., and the adjuvant matching and technologies like nanotechnology can further optimize the effects of peptides. In this review, we present the current status and mechanisms of research on peptides targeting multiple immune cells (T cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), regulatory T cells (Tregs)) and immune checkpoints in tumor immunotherapy; and we summarize the current status of research on peptide-based tumor immunotherapy in combination with other therapies including RT, chemotherapy, surgery, targeted therapy, cytokine therapy, adoptive cell therapy (ACT) and cancer vaccines. Finally, we discuss the current status of peptide applications in mRNA vaccine delivery.

SHP2 deneddylation mediates tumor immunosuppression in colon cancer via the CD47/SIRPα axis

SIPRα on macrophages binds with CD47 to resist proengulfment signals, but how the downstream signal of SIPRα controls tumor-infiltrating macrophages (TIMs) is still poorly clarified. Here, we report that the CD47/signal regulatory protein α (SIRPα) axis requires the deneddylation of tyrosine phosphatase SHP2. Mechanistically, Src homology region 2-containing protein tyrosine phosphatase 2 (SHP2) was constitutively neddylated on K358 and K364 sites; thus, its autoinhibited conformation was maintained. In response to CD47-liganded SIRPα, SHP2 was deneddylated by sentrin-specific protease 8 (SENP8), which led to the dephosphorylation of relevant substrates at the phagocytic cup and subsequent inhibition of macrophage phagocytosis. Furthermore, neddylation inactivated myeloid-SHP2 and greatly boosted the efficacy of colorectal cancer (CRC) immunotherapy. Importantly, we observed that supplementation with SHP2 allosteric inhibitors sensitized immune treatment-resistant CRC to immunotherapy. Our results emphasize that the CRC subtype that is unresponsive to immunotherapy relies on SIRPαhiSHP2hiNEDD8lo TIMs and highlight the need to further explore the strategy of SHP2 targeting in CRC therapy.

The landscape overview of CD47-based immunotherapy for hematological malignancies

Extensive clinical and experimental evidence suggests that macrophages play a crucial role in cancer immunotherapy. Cluster of differentiation (CD) 47, which is found on both healthy and malignant cells, regulates macrophage-mediated phagocytosis by sending a "don't eat me" signal to the signal regulatory protein alpha (SIRPα) receptor. Increasing evidence demonstrates that blocking CD47 interaction with SIRPα can enhance cancer cell clearance by macrophages. Additionally, inhibition of CD47/SIRPα interaction can increase antigen cross-presentation, leading to T-cell priming and an activated adaptive antitumor immune response. Therefore, inhibiting CD47/SIRPα axis has a significant impact on tumor immunotherapy. Studies on CD47 monoclonal antibodies are at the forefront of research, and impressive results have been obtained. Nevertheless, hematotoxicity, especially anemia, has become the most common adverse effect of the CD47 monoclonal antibody. More specific targeted drugs (i.e., bispecific antibodies, SIRPα/Fc fusion protein antibodies, and small-molecule inhibitors) have been developed to reduce hematotoxicity. Here, we review the present usage of CD47 antagonists for the treatment of lymphomas and hematologic neoplasms from the perspectives of structure, function, and clinical trials, including a comprehensive overview of the drugs in development.

Reprogramming the tumor microenvironment with biotechnology

The tumor microenvironment (TME) is a unique environment that is developed by the tumor and controlled by tumor-induced interactions with host cells during tumor progression. The TME includes immune cells, which can be classified into two types: tumor- antagonizing and tumor-promoting immune cells. Increasing the tumor treatment responses is associated with the tumor immune microenvironment. Targeting the TME has become a popular topic in research, which includes polarizing macrophage phenotype 2 into macrophage phenotype 1 using Toll-like receptor agonists with cytokines, anti-CD47, and anti-SIPRα. Moreover, inhibiting regulatory T cells through blockades and depletion restricts immunosuppressive cells in the TME. Reprogramming T cell infiltration and T cell exhaustion improves tumor infiltrating lymphocytes, such as CD8⁺ or CD4⁺ T cells. Targeting metabolic pathways, including glucose, lipid, and amino acid metabolisms, can suppress tumor growth by restricting the absorption of nutrients and adenosine triphosphate energy into tumor cells. In conclusion, these TME reprogramming strategies exhibit more effective responses using combination treatments, biomaterials, and nanoparticles. This review highlights how biomaterials and immunotherapy can reprogram TME and improve the immune activity.

Clinical Significance of Signal Regulatory Protein Alpha (SIRPα) Expression in Hepatocellular Carcinoma

BACKGROUND

Signal regulatory protein alpha (SIRPα), expressed in the macrophage membrane, inhibits phagocytosis of tumor cells via CD47/SIRPα interaction, which acts as an immune checkpoint factor in cancers. This study aimed to clarify the clinical significance of SIRPα expression in hepatocellular carcinoma (HCC).

METHODS

This study analyzed SIRPα expression using RNA sequencing data of 372 HCC tissues from The Cancer Genome Atlas (TCGA) and immunohistochemical staining of our 189 HCC patient cohort. The correlation between SIRPα expression and clinicopathologic factors, patient survival, and intratumor infiltration of immune cells was investigated.

RESULTS

Overall survival (OS) was significantly poorer with high SIRPα expression than with low expression in both TCGA and our cohort. High SIRPα expression correlated with lower recurrence-free survival (RFS) in our cohort. High SIRPα expression was associated with higher rates of microvascular invasion and lower serum albumin levels and correlated with greater intratumor infiltration of CD68-positive macrophages and myeloid-derived suppressor cells (MDSCs). Multivariate analysis showed that SIRPα expression and high infiltration of CD8-positive T cells and MDSCs were predictive factors for both RFS and OS. Patients with high SIRPα expression and infiltration of CD8-positive T cells and MDSCs had significantly lower RFS and OS rates. In spatial transcriptomics sequencing, SIRPα expression was significantly correlated with CD163 expression.

CONCLUSIONS

High SIRPα expression in HCC indicates poor prognosis, possibly by inhibiting macrophage phagocytosis of tumor cells, promoting MDSC infiltration and inducing antitumor immunity. Treatment alternatives using SIRPα blockage should be considered in HCC as inhibiting macrophage antitumor immunity and MDSCs.

Targeted Delivery of PD-L1-Derived Phosphorylation-Mimicking Peptides by Engineered Biomimetic Nanovesicles to Enhance Osteosarcoma Treatment

Osteosarcoma is a rare malignant bone-originating tumor that usually occurs in young people. Programmed cell death 1 ligand 1 (PD-L1), an immune checkpoint protein, is highly expressed in osteosarcoma tissues. Several recent studies have indicated that the tumor-related role of PD-L1 in tumors, especially non-plasma membrane (NPM)-localized PD-L1, is not limited to immune regulation in osteosarcoma. Here, mass spectrometry analysis is combined with RNA-seq examination to identify the intracellular binding partners of PD-L1 and elucidate the underlying mechanism of its action. It is found that the NPM-localized PD-L1 interacted with Insulin-like growth factor binding protein-3 (IGFBP3) to promote osteosarcoma tumor growth by activating mTOR signaling. This interaction is enforced after phosphoglyceratekinase1 (PGK1)-mediated PD-L1 phosphorylation. Based on these findings, a phosphorylation-mimicking peptide is designed from PD-L1 and it is encapsulated with a Cyclic RGD (cRGD)-modified red blood cell membrane (RBCM) vesicle (Peptide@cRGD-M). The Peptide@cRGD-M precisely delivers the PD-L1-derived phosphorylation-mimicking peptide into osteosarcoma lesions and significantly promotes its therapeutic effect on the tumor. Therefore, this investigation not only highlights the function of NPM-localized PD-L1, but also uses an engineering approach to synthesize a small molecular peptide capable of inhibiting osteosarcoma growth.

Human CD47-Derived Cyclic Peptides Enhance Engulfment of mAb-Targeted Melanoma by Primary Macrophages

CD47 on healthy cells, cancer cells, and even engineered particles can inhibit phagocytic clearance by binding SIRPα on macrophages. To mimic and modulate this interaction with peptides that could be used as soluble antagonists or potentially as bioconjugates to surfaces, we made cyclic "nano-Self" peptides based on the key interaction loop of human CD47. Melanoma cells were studied as a standard preclinical cancer model and were antibody-opsonized to adhere to and activate engulfment by primary mouse macrophages. Phagocytosis in the presence of soluble peptides showed cyclic > wildtype > scrambled activity, with the same trend observed with human cells. Opsonized cells that were not engulfed adhered tightly to macrophages, with opposite trends to phagocytosis. Peptide activity is nonetheless higher in human versus mouse assays, consistent with species differences in CD47-SIRPα. Small peptides thus function as soluble antagonists of a major macrophage checkpoint.

Oxygen-boosted biomimetic nanoplatform for synergetic phototherapy/ferroptosis activation and reversal of immune-suppressed tumor microenvironment

Photodynamic therapy (PDT) induces apoptosis of cancer cells by generating cytotoxic reactive oxygen species, the therapeutic effect of which, however, is impeded by intrinsic/inducible apoptosis-resistant mechanisms in cancer cells and hypoxia of tumor microenvironment (TME); also, PDT-induced anti-tumor immunity activation is insufficient. To deal with these obstacles, a novel biomimetic nanoplatform is fabricated for the precise delivery of photosensitizer chlorin e6 (Ce6), hemin and PEP20 (CD47 inhibitory peptide), integrating oxygen-boosted PDT, ferroptosis activation and CD47-SIRPα blockade. Hemin's catalase-mimetic activity alleviates TME hypoxia and enhances PDT. The nanoplatform activates ferroptosis via both classical (down-regulating glutathione peroxidase 4 pathway) and non-classical (inducing Fe²⁺ overload) modes. Besides the role of hemin in consuming glutathione and up-regulating heme oxygenase-1 expression, interestingly, we observe that Ce6 enhance ferroptosis activation via both classical and non-classical modes. The anti-cancer immunity is reinforced by combining PEP20-mediated CD47-SIRPα blockade and PDT-mediated T cell activation, efficiently suppressing primary tumor growth and metastasis. PEP20 has been revealed for the first time to sensitize ferroptosis by down-regulating system Xc^-. This work sheds new light on the mechanisms of PDT-ferroptosis activation interplay and bridges immunotherapy and ferroptosis activation, laying the theoretical foundation for novel combinational modes of cancer treatment.

Combining ablative radiotherapy and anti CD47 monoclonal antibody improves infiltration of immune cells in tumor microenvironments

Radiotherapy as an anti-tumor treatment can stimulate the immune system. However, irradiated tumor cells express CD47 to escape the anti-tumor immune response. Anti- CD47 Immunotherapy is a possible way to tackle this problem. This study evaluated the effect of single high dose radiotherapy combined with an anti-CD47 monoclonal antibody (αCD47 mAb) in CT26 tumor‐bearing BALB/c mice. We assessed the tumors volume and survival in mice 60 days after tumor implantation. Also, immune cell changes were analyzed by flow cytometry in tumors, lymph nodes, and spleen. Combination therapy enhanced the anti-tumor response in treated mice by increasing CD8+ T cells and M1 macrophages and decreasing M2 macrophages and myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment (TME). Also, our results showed that combination therapy increased survival time in mice compared to other groups. Furthermore, tumor volumes remarkably decreased in mice that received a single high dose RT plus αCD47 mAb. In conclusion, we showed that combining RT and αCD47 mAb improved the immune cell population in TME, regressed tumor growth, and increased survival in tumor-bearing mice.

CD47 as a promising therapeutic target in oncology

CD47 is ubiquitously expressed on the surface of cells and plays a critical role in self-recognition. By interacting with SIRPα, TSP-1 and integrins, CD47 modulates cellular phagocytosis by macrophages, determines life span of individual erythrocytes, regulates activation of immune cells, and manipulates synaptic pruning during neuronal development. As such, CD47 has recently be regarded as one of novel innate checkpoint receptor targets for cancer immunotherapy. In this review, we will discuss increasing awareness about the diverse functions of CD47 and its role in immune system homeostasis. Then, we will discuss its potential therapeutic roles against cancer and outlines, the possible future research directions of CD47- based therapeutics against cancer.

Macrophages in Glioblastoma Development and Therapy: A Double-Edged Sword

Glioblastoma (GBM) is one of the leading lethal tumors, featuring aggressive malignancy and poor outcome to current standard temozolomide (TMZ) or radio-based therapy. Developing immunotherapies, especially immune checkpoint inhibitors, have improved patient outcomes in other solid tumors but remain fatigued in GBM patients. Emerging evidence has shown that GBM-associated macrophages (GAMs), comprising brain-resident microglia and bone marrow-derived macrophages, act critically in boosting tumor progression, altering drug resistance, and establishing an immunosuppressive environment. Based on its crucial role, evaluations of the safety and efficacy of GAM-targeted therapy are ongoing, with promising (pre)clinical evidence updated. In this review, we summarized updated literature related to GAM nature, the interplay between GAMs and GBM cells, and GAM-targeted therapeutic strategies.