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

Antibody-dependent cellular phagocytosis of tropomyosin receptor kinase C (TrkC) expressing cancer cells for targeted immunotherapy

Conventional cancer therapies such as chemotherapy are non-selective and induce immune system anergy, which lead to serious side effects and tumor relapse. It is a challenge to prime the body's immune system in the cancer-bearing subject to produce cancer antigen-targeting antibodies, as most tumor-associated antigens are expressed abundantly in cancer cells and some of normal cells. This study illustrates how hapten-based pre-immunization (for anti-hapten antibodies production) combined with cancer receptor labeling with hapten antigen constructs can elicit antibody-dependent cellular phagocytosis (ADCP). Thus, the hapten antigen 2,4-dinitrophenol (DNP) was covalently combined with a cancer receptor-binding dipeptide (IYIY) to form a dipeptide-hapten construct (IYIY-DNP, MW = 1322.33) that targets the tropomyosin receptor kinase C (TrkC)-expressed on the surface of metastatic cancer cells. IYIY-DNP facilitated selective association of RAW264.7 macrophages to the TrkC expressing 4T1 cancer cells in vitro, forming cell aggregates in the presence of anti-DNP antibodies, suggesting initiation of anti-DNP antibody-dependent cancer cell recognition of macrophages by the IYIY-DNP. In in vivo, IYIY-DNP at 10 mg/kg suppressed growth of 4T1 tumors in DNP-immunized BALB/c mice by 45% (p < 0.05), when comparing the area under the tumor growth curve to that of the saline-treated DNP-immunized mice. Meanwhile, IYIY-DNP at 10 mg/kg had no effect on TrkC-negative 67NR tumor-bearing mice immunized with DNP. Tumor growth suppression activity of IYIY-DNP in DNP-immunized mice was associated with an increase in the anti-DNP IgG (7.3 × 10⁶ ± 1.6 U/mL) and IgM (0.9 × 10⁶ ± 0.07 U/mL) antibodies after five cycles of DNP treatment, demonstrated potential for hapten-based pre-immunization then treatment with IYIY-DNP to elicit ADCP for improved immunotherapy of TrkC expressing cancers.

Role of Fcγ receptors in HER2-targeted breast cancer therapy

Several therapeutic monoclonal antibodies (mAbs), including those targeting epidermal growth factor receptor, human epidermal growth factor receptor 2 (HER2), and CD20, mediate fragment crystallizable gamma receptor (FcγR)–dependent activities as part of their mechanism of action. These activities include induction of antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP), which are innate immune mechanisms of cancer cell elimination. FcγRs are distinguished by their affinity for the Fc fragment, cell distribution, and type of immune response they induce. Activating FcγRIIIa (CD16A) on natural killer cells plays a crucial role in mediating ADCC, and activating FcγRIIa (CD32A) and FcγRIIIa on macrophages are important for mediating ADCP. Polymorphisms in FcγRIIIa and FcγRIIa generate variants that bind to the Fc portion of antibodies with different affinities. This results in differential FcγR-mediated activities associated with differential therapeutic outcomes across multiple clinical settings, from early stage to metastatic disease, in patients with HER2+ breast cancer treated with the anti-HER2 mAb trastuzumab. Trastuzumab has, nonetheless, revolutionized HER2+ breast cancer treatment, and several HER2-directed mAbs have been developed using Fc glyco-engineering or Fc protein-engineering to enhance FcγR-mediated functions. An example of an approved anti-HER2 Fc-engineered chimeric mAb is margetuximab, which targets the same epitope as trastuzumab, but features five amino acid substitutions in the IgG 1 Fc domain that were deliberately introduced to increase binding to activating FcγRIIIa and decrease binding to inhibitory FcγRIIb (CD32B). Margetuximab enhances Fc-dependent ADCC in vitro more potently than the combination of pertuzumab (another approved mAb directed against an alternate HER2 epitope) and trastuzumab. Margetuximab administration also enhances HER2-specific B cell and T cell–mediated responses ex vivo in samples from patients treated with prior lines of HER2 antibody-based therapies. Stemming from these observations, a worthwhile future goal in the treatment of HER2+ breast cancer is to promote combinatorial approaches that better eradicate HER2+ cancer cells via enhanced immunological mechanisms.

Macrophages in ovarian cancer and their interactions with monoclonal antibody therapies

The unmet clinical need for effective treatments in ovarian cancer has yet to be addressed using monoclonal antibodies (mAbs), which have largely failed to overcome tumour-associated immunosuppression, restrict cancer growth, and significantly improve survival. In recent years, experimental mAb design has moved away from solely targeting ovarian tumours and instead sought to modulate the wider tumour microenvironment (TME). Tumour-associated macrophages (TAMs) may represent an attractive therapeutic target for mAbs in ovarian cancer due to their high abundance and close proximity to tumour cells and their active involvement in facilitating several pro-tumoural processes. Moreover, the expression of several antibody crystallisable fragment (Fc) receptors and broad phenotypic plasticity of TAMs provide opportunities to modulate TAM polarisation using mAbs to promote anti-tumoural phenotypes. In this review, we discuss the role of TAMs in ovarian cancer TME and the emerging strategies to target the contributions of these cells in tumour progression through the rationale design of mAbs.

Emerging immunotherapeutic strategies for the treatment of breast cancer

Immunotherapy has resulted in unprecedented gains in long-term outcomes for many cancer types and has revolutionized the treatment landscape of solid tumor oncology. Checkpoint inhibition in combination with chemotherapy has proven to be effective for the treatment of a subset of advanced triple-negative breast cancer in the first-line setting. This initial success is likely just the tip of the iceberg as there is much that remains unknown about how to best harness the immune system as a therapeutic strategy in all breast cancer subtypes. Therefore, numerous ongoing studies are currently underway to evaluate the safety and efficacy of immunotherapy in breast cancer. In this review, we will discuss emerging immunotherapeutic strategies for breast cancer treatment including the following: (1) Intratumoral therapies, (2) Anti-tumor vaccines, (3) B-specific T-cell engagers, and (4) Chimeric antigen receptor T-cell therapy, and (5) Emerging systemic immunotherapy strategies. For each topic, we will review the existing preclinical and clinical literature, discuss ongoing clinical trials, and highlight future directions in the field.

Mechanisms of Therapeutic Antitumor Monoclonal Antibodies

Monoclonal antibodies (mAb) are a major component of cancer therapy. In this review, we summarize the different therapeutic mAbs that have been successfully developed against various tumor-expressed antigens and examine our current understanding of their different mechanisms of antitumor action. These mechanisms of action (MOA) largely center on the stimulation of different innate immune effector processes, which appear to be principally responsible for the efficacy of most unconjugated mAb therapies against cancer. This is evident in studies of mAbs targeting antigens for hematologic cancers, with emerging data also demonstrating the critical nature of innate immune-mediated mechanisms in the efficacy of anti-HER2 mAbs against solid HER2+ cancers. Although HER2-targeted mAbs were originally described as inhibitors of HER2-mediated signaling, multiple studies have since demonstrated these mAbs function largely through their engagement with Fc receptors to activate innate immune effector functions as well as complement activity. Next-generation mAbs are capitalizing on these MOAs through improvements to enhance Fc-activity, although regulation of these mechanisms may vary in different tumor microenvironments. In addition, novel antibody-drug conjugates have emerged as an important means to activate different MOAs. Although many unknowns remain, an improved understanding of these immunologic MOAs will be essential for the future of mAb therapy and cancer immunotherapy.

Bringing Macrophages to the Frontline against Cancer: Current Immunotherapies Targeting Macrophages

Macrophages are found in all tissues and display outstanding functional diversity. From embryo to birth and throughout adult life, they play critical roles in development, homeostasis, tissue repair, immunity, and, importantly, in the control of cancer growth. In this review, we will briefly detail the multi-functional, protumoral, and antitumoral roles of macrophages in the tumor microenvironment. Our objective is to focus on the ever-growing therapeutic opportunities, with promising preclinical and clinical results developed in recent years, to modulate the contribution of macrophages in oncologic diseases. While the majority of cancer immunotherapies target T cells, we believe that macrophages have a promising therapeutic potential as tumoricidal effectors and in mobilizing their surroundings towards antitumor immunity to efficiently limit cancer progression.

Inter-cellular CRISPR screens reveal regulators of cancer cell phagocytosis

Monoclonal antibody therapies targeting tumour antigens drive cancer cell elimination in large part by triggering macrophage phagocytosis of cancer cells^1-7. However, cancer cells evade phagocytosis using mechanisms that are incompletely understood. Here we develop a platform for unbiased identification of factors that impede antibody-dependent cellular phagocytosis (ADCP) using complementary genome-wide CRISPR knockout and overexpression screens in both cancer cells and macrophages. In cancer cells, beyond known factors such as CD47, we identify many regulators of susceptibility to ADCP, including the poorly characterized enzyme adipocyte plasma membrane-associated protein (APMAP). We find that loss of APMAP synergizes with tumour antigen-targeting monoclonal antibodies and/or CD47-blocking monoclonal antibodies to drive markedly increased phagocytosis across a wide range of cancer cell types, including those that are otherwise resistant to ADCP. Additionally, we show that APMAP loss synergizes with several different tumour-targeting monoclonal antibodies to inhibit tumour growth in mice. Using genome-wide counterscreens in macrophages, we find that the G-protein-coupled receptor GPR84 mediates enhanced phagocytosis of APMAP-deficient cancer cells. This work reveals a cancer-intrinsic regulator of susceptibility to antibody-driven phagocytosis and, more broadly, expands our knowledge of the mechanisms governing cancer resistance to macrophage phagocytosis.

In Situ Tumor Vaccination with Nanoparticle Co-Delivering CpG and STAT3 siRNA to Effectively Induce Whole-Body Antitumor Immune Response

The success of immunotherapy with immune checkpoint inhibitors (ICIs) in a subset of individuals has been very exciting. However, in many cancers, responses to current ICIs are modest and are seen only in a small subsets of patients. Herein, a widely applicable approach that increases the benefit of ICIs is reported. Intratumoral administration of augmenting immune response and inhibiting suppressive environment of tumors-AIRISE-02 nanotherapeutic that co-delivers CpG and STAT3 siRNA-results in not only regression of the injected tumor, but also tumors at distant sites in multiple tumor model systems. In particular, three doses of AIRISE-02 in combination with systemic ICIs completely cure both treated and untreated aggressive melanoma tumors in 63% of mice, while ICIs alone do not cure any mice. A long-term memory immune effect is also reported. AIRISE-02 is effective in breast and colon tumor models as well. Lastly, AIRISE-02 is well tolerated in mice and nonhuman primates. This approach combines multiple therapeutic agents into a single nanoconstruct to create whole-body immune responses across multiple cancer types. Being a local therapeutic, AIRISE-02 circumvents regulatory challenges of systemic nanoparticle delivery, facilitating rapid translation to the clinic. AIRISE-02 is under investigational new drug (IND)-enabling studies, and clinical trials will soon follow.

Physicochemical and functional characterization of trastuzumab-dkst, a trastuzumab biosimilar

Aims: Preclinical comparative similarity studies of trastuzumab-dkst, a Herceptin^® biosimilar, are reported. Materials & methods: Primary sequence and higher order structure and pharmacological mechanisms of action were compared using multiple techniques. Pharmacokinetics and repeat-dose toxicity were assessed in cynomolgus monkeys. Results: Primary structures were identical; secondary and tertiary structures were highly similar. Non-significant differences were observed for charge heterogeneity. Twelve of 13 glycan species were highly similar, with slightly higher total mannose levels in trastuzumab-dkst. FcγR and FcRn binding activity was highly similar. Each drug equally inhibited HER2⁺ cell proliferation, demonstrating equivalent relative potency in mediating HER2⁺ cell cytolysis by antibody-dependent cellular cytotoxicity. Pharmacokinetic and toxicological profiles in cynomolgus monkeys were similar. Conclusion: Trastuzumab-dkst, US-licensed trastuzumab and EU-approved trastuzumab demonstrate high structural and functional similarity.

Combining CD47 blockade with trastuzumab eliminates HER2-positive breast cancer cells and overcomes trastuzumab tolerance

This study demonstrates the efficacy of combining macrophage-checkpoint inhibition with tumor-specific antibodies for cancer immunotherapy. The combination of anti-CD47 (magrolimab) and anti-HER2 (trastuzumab) antibodies eliminated HER2⁺ breast cancer cells with increased efficacy due to the enhancement of antibody-dependent cellular phagocytosis by macrophages, even when the cancer cells were tolerant to trastuzumab-induced antibody-dependent cellular cytotoxicity by natural killer cells. We believe these findings present a promising therapeutic approach for treating HER2⁺ breast cancer patients whose tumors are either sensitive or resistant to trastuzumab treatment, as long as the cells harbor the HER2 trastuzumab-binding epitope. This study supports the notion that combining CD47 blockade with existing macrophage FcR-engaging tumor-specific antibodies may be an effective approach for treating a wide range of cancers.

Trastuzumab, a targeted anti-human epidermal-growth-factor receptor-2 (HER2) monoclonal antibody, represents a mainstay in the treatment of HER2-positive (HER2⁺) breast cancer. Although trastuzumab treatment is highly efficacious for early-stage HER2⁺ breast cancer, the majority of advanced-stage HER2⁺ breast cancer patients who initially respond to trastuzumab acquire resistance to treatment and relapse, despite persistence of HER2 gene amplification/overexpression. Here, we sought to leverage HER2 overexpression to engage antibody-dependent cellular phagocytosis (ADCP) through a combination of trastuzumab and anti-CD47 macrophage checkpoint immunotherapy. We have previously shown that blockade of CD47, a surface protein expressed by many malignancies (including HER2⁺ breast cancer), is an effective anticancer therapy. CD47 functions as a “don’t eat me” signal through its interaction with signal regulatory protein-α (SIRPα) on macrophages to inhibit phagocytosis. Hu5F9-G4 (magrolimab), a humanized monoclonal antibody against CD47, blocks CD47’s “don’t eat me” signal, thereby facilitating macrophage-mediated phagocytosis. Preclinical studies have shown that combining Hu5F9-G4 with tumor-targeting antibodies, such as rituximab, further enhances Hu5F9-G4’s anticancer effects via ADCP. Clinical trials have additionally demonstrated that Hu5F9-G4, in combination with rituximab, produced objective responses in patients whose diffuse large B cell lymphomas had developed resistance to rituximab and chemotherapy. These studies led us to hypothesize that combining Hu5F9-G4 with trastuzumab would produce an anticancer effect in antibody-dependent cellular cytotoxicity (ADCC)-tolerant HER2⁺ breast cancer. This combination significantly suppressed the growth of ADCC-tolerant HER2⁺ breast cancers via Fc-dependent ADCP. Our study demonstrates that combining trastuzumab and Hu5F9-G4 represents a potential new treatment option for HER2⁺ breast cancer patients, even for patients whose tumors have progressed after trastuzumab.

Macrophages, as a Promising Strategy to Targeted Treatment for Colorectal Cancer Metastasis in Tumor Immune Microenvironment

The tumor immune microenvironment plays a vital role in the metastasis of colorectal cancer. As one of the most important immune cells, macrophages act as phagocytes, patrol the surroundings of tissues, and remove invading pathogens and cell debris to maintain tissue homeostasis. Significantly, macrophages have a characteristic of high plasticity and can be classified into different subtypes according to the different functions, which can undergo reciprocal phenotypic switching induced by different types of molecules and signaling pathways. Macrophages regulate the development and metastatic potential of colorectal cancer by changing the tumor immune microenvironment. In tumor tissues, the tumor-associated macrophages usually play a tumor-promoting role in the tumor immune microenvironment, and they are also associated with poor prognosis. This paper reviews the mechanisms and stimulating factors of macrophages in the process of colorectal cancer metastasis and intends to indicate that targeting macrophages may be a promising strategy in colorectal cancer treatment.

Anti-CD47 antibody synergizes with cisplatin against laryngeal cancer by enhancing phagocytic ability of macrophages

Cisplatin is mainly used in late-stage or recurrent laryngeal cancer patients. However, the effect of the chemotherapy is limited due to cisplatin resistance. Therefore, we explored the synergized role of immunosuppressive mediator with cisplatin in laryngeal cancer. Cancer cells isolated from tissues of patients with laryngeal cancer were treated with cisplatin to screen the potential immunosuppressive mediator, whose synergized effects with cisplatin were explored both in vivo and in vitro. CD47 was selected for its high expression in cisplatin-treated laryngeal cancer cells. Blocking CD47 expression using its neutralizing antibody (aCD47) synergized with cisplatin to increase macrophage phagocytosis in a co-culture system of human epithelial type 2 (Hep-2) cancer cells with tumor-associated macrophages (TAMs). Moreover, aCD47 together with cisplatin prevented tumor growth by inhibiting proliferation of cancer cells and the secretion of proinflammatory cytokines, as well as by inducing the apoptosis of cancer cells and phagocytosis of TAMs in a Hep-2-implanted mouse tumor model. aCD47 synergized with cisplatin against laryngeal cancer by enhancing the phagocytic ability of TAMs, and the combined therapy of cisplatin and aCD47 might serve as a novel therapeutic strategy against laryngeal cancer.

SIRPα-specific monoclonal antibody enables antibody-dependent phagocytosis of neuroblastoma cells

Immunotherapy with anti-G_D2 monoclonal antibodies (mAbs) provides some benefits for patients with neuroblastoma (NB). However, the therapeutic efficacy remains limited, and treatment is associated with significant neuropathic pain. Targeting O-acetylated G_D2 (OAcG_D2) by 8B6 mAb has been proposed to avoid pain by more selective tumor cell targeting. Thorough understanding of its mode of action is necessary to optimize this treatment strategy. Here, we found that 8B6-mediated antibody-dependent cellular phagocytosis (ADCP) performed by macrophages is a key effector mechanism. But efficacy is limited by upregulation of CD47 expression on neuroblastoma cells in response to OAcG_D2 mAb targeting, inhibiting 8B6-mediated ADCP. Antibody specific for the CD47 receptor SIRPα on macrophages restored 8B6-induced ADCP of CD47-expressing NB cells and improved the antitumor activity of 8B6 mAb therapy. These results identify ADCP as a critical mechanism for tumor cytolysis by anti-disialoganglioside mAb and support a combination with SIRPα blocking agents for effective neuroblastoma therapy.

The Immunology of Hormone Receptor Positive Breast Cancer

Immune checkpoint blockade (ICB) has revolutionized the treatment of cancer patients. The main focus of ICB has been on reinvigorating the adaptive immune response, namely, activating cytotoxic T cells. ICB has demonstrated only modest benefit against advanced breast cancer, as breast tumors typically establish an immune suppressive tumor microenvironment (TME). Triple-negative breast cancer (TNBC) is associated with infiltration of tumor infiltrating lymphocytes (TILs) and patients with TNBC have shown clinical responses to ICB. In contrast, hormone receptor positive (HR+) breast cancer is characterized by low TIL infiltration and minimal response to ICB. Here we review how HR+ breast tumors establish a TME devoid of TILs, have low HLA class I expression, and recruit immune cells, other than T cells, which impact response to therapy. In addition, we review emerging technologies that have been employed to characterize components of the TME to reveal that tumor associated macrophages (TAMs) are abundant in HR+ cancer, are highly immune-suppressive, associated with tumor progression, chemotherapy and ICB-resistance, metastasis and poor survival. We reveal novel therapeutic targets and possible combinations with ICB to enhance anti-tumor immune responses, which may have great potential in HR+ breast cancer.

Lessons to Learn for Adequate Targeted Therapy Development in Metastatic Colorectal Cancer Patients

Insulin-like growth factor 1 receptor (IGF1R) is a receptor tyrosine kinase that regulates cell growth and proliferation. Upregulation of the IGF1R pathway constitutes a common paradigm shared with other receptor tyrosine kinases such as EGFR, HER2, and MET in different cancer types, including colon cancer. The main IGF1R signaling pathways are PI3K-AKT and MAPK-MEK. However, different processes, such as post-translational modification (SUMOylation), epithelial-to-mesenchymal transition (EMT), and microenvironment complexity, can also contribute to intrinsic and acquired resistance. Here, we discuss new strategies for adequate drug development in metastatic colorectal cancer patients.

Berberine exerts anti-tumor activity in diffuse large B-cell lymphoma by modulating c-myc/CD47 axis

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL) with high clinical heterogeneity and poor prognosis. Immune escape mediated by CD47 overexpression contributes to the limited efficacy of rituximab, an anti-CD20 antibody, which indicates a target to improve the efficacy of DLBCL treatment. Here, we validated berberine, a natural compound, as a suppressor of CD47 and revealed the involved mechanism and biological function in DLBCL. Berberine downregulated the expression of CD47 in DLBCL at the transcriptional level by suppressing c-myc expression. Berberine-induced CD47 inhibition enhanced the phagocytosis of macrophages, thereby eliminating DLBCL cells in vitro and in vivo. Interestingly, berberine enhanced the efficiency of anti-CD47 antibody and rituximab-mediated phagocytosis. Moreover, a novel prognostic model based on the combination of CD47 and CD68, a biomarker of macrophages, was established in DLBCL. Our results highlighted for the first time that berberine could restore macrophage function in the tumor microenvironment, enhance rituximab-mediated phagocytosis and promote anti-CD47 antibody function via suppressing CD47 expression, which revealed a new anti-tumor mechanism of berberine and provided novel insights into the rituximab-based immunochemotherapy and CD47-targeted immunotherapy in DLBCL.

Targeting macrophages in cancer immunotherapy

Immunotherapy is regarded as the most promising treatment for cancers. Various cancer immunotherapies, including adoptive cellular immunotherapy, tumor vaccines, antibodies, immune checkpoint inhibitors, and small-molecule inhibitors, have achieved certain successes. In this review, we summarize the role of macrophages in current immunotherapies and the advantages of targeting macrophages. To better understand and make better use of this type of cell, their development and differentiation characteristics, categories, typical markers, and functions were collated at the beginning of the review. Therapeutic strategies based on or combined with macrophages have the potential to improve the treatment efficacy of cancer therapies.

Harnessing and Enhancing Macrophage Phagocytosis for Cancer Therapy

Cancer immunotherapy has revolutionized the paradigm for the clinical management of cancer. While FDA-approved cancer immunotherapies thus far mainly exploit the adaptive immunity for therapeutic efficacy, there is a growing appreciation for the importance of innate immunity in tumor cell surveillance and eradication. The past decade has witnessed macrophages being thrust into the spotlight as critical effectors of an innate anti-tumor response. Promising evidence from preclinical and clinical studies have established targeting macrophage phagocytosis as an effective therapeutic strategy, either alone or in combination with other therapeutic moieties. Here, we review the recent translational advances in harnessing macrophage phagocytosis as a pivotal therapeutic effort in cancer treatment. In addition, this review emphasizes phagocytosis checkpoint blockade and the use of nanoparticles as effective strategies to potentiate macrophages for phagocytosis. We also highlight chimeric antigen receptor macrophages as a next-generation therapeutic modality linking the closely intertwined innate and adaptive immunity to induce efficacious anti-tumor immune responses.

Immunotherapy as a partner for HER2-directed therapies

Introduction: Existing HER2-targeted therapies modulate the tumor microenvironment and the immunologic response cancer in a favorable way. While these therapies have made dramatic improvements in the treatment and prognosis of HER2-overexpressing malignancies, additional treatment options are still needed.Areas covered: This review covers the immunomodulatory effects of approved HER2-targeted therapies. We discuss the preclinical data that demonstrate an additive effect of the combination of trastuzumab or other HER2-targeting agents with immunomodulatory drugs. Finally, we report the initial studies on the combination of HER2-targeted agents together with immune checkpoint inhibitors or cancer vaccines in breast cancer.Expert opinion: Preclinical data suggest a synergistic effect of HER2-targeted therapy together with both checkpoint inhibitor and cancer vaccine immunotherapy. Results from initial trials with PD-1/PD-L1-blocking therapy together with HER2-targeted therapy have been negative, but responses were seen in patients with PD-L1+ breast cancer. Trastuzumab together with HER2-targeted cancer vaccination has shown benefits in triple negative breast cancer. Further trials are necessary and warranted to confirm the benefit of these combinations.

The role of CD47-SIRPα immune checkpoint in tumor immune evasion and innate immunotherapy

As a transmembrane protein, CD47 plays an important role in mediating cell proliferation, migration, phagocytosis, apoptosis, immune homeostasis, inhibition of NO signal transduction and other related reactions. Upon the interaction of innate immune checkpoint CD47-SIRPα occurrence, they send a "don't eat me" signal to the macrophages. This signal ultimately helps tumors achieve immune escape by inhibiting macrophage contraction to prevent tumor cells from phagocytosis. Therefore, the importance of CD47-SIRPα immune checkpoint inhibitors in tumor immunotherapy has attracted more attention in recent years. Based on the cognitive improvement of the effect with CD47 in tumor microenvironment and tumor characteristics, the pace of tumor treatment strategies for CD47-SIRPα immune checkpoint inhibitors has gradually accelerated. In this review, we introduced the high expression of CD47 in cancer cells to avoid phagocytosis by immune cells and the importance of CD47 in the structure of cancer microenvironment and the maintenance of cancer cell characteristics. Given the role of the innate immune system in tumorigenesis and development, an improved understanding of the anti-tumor process of innate immune checkpoint inhibitors can lay the foundation for more effective combinations with other anti-tumor treatment strategies.

Harnessing NK cells for cancer immunotherapy: immune checkpoint receptors and chimeric antigen receptors

Natural killer (NK) cells, key antitumor effectors of the innate immune system, are endowed with the unique ability to spontaneously eliminate cells undergoing a neoplastic transformation. Given their broad reactivity against diverse types of cancer and close association with cancer prognosis, NK cells have gained considerable attention as a promising therapeutic target for cancer immunotherapy. NK cell-based therapies have demonstrated favorable clinical efficacies in several hematological malignancies but limited success in solid tumors, thus highlighting the need to develop new therapeutic strategies to restore and optimize antitumor activity while preventing tumor immune escape. The current therapeutic modalities yielding encouraging results in clinical trials include the blockade of immune checkpoint receptors to overcome the immune-evasion mechanism used by tumors and the incorporation of tumor-directed chimeric antigen receptors to enhance NK cell antitumor specificity and activity. These observations, together with recent advances in the understanding of NK cell activation within the tumor microenvironment, will facilitate the optimal design of NK cell-based therapy against a broad range of cancers and, more desirably, refractory cancers.

Exploiting Gangliosides for the Therapy of Ewing's Sarcoma and H3K27M-Mutant Diffuse Midline Glioma

Simple Summary

Osteosarcoma, Ewing’s sarcoma, and H3K27M-mutant diffuse midline glioma are rare but aggressive malignancies occurring mainly in children. Due to their rareness and often fatal course, drug development is challenging. Here, we repurposed the existing drugs dinutuximab and eliglustat and investigated their potential to directly target or indirectly modulate the tumor cell-specific ganglioside GD2. Our data suggest that targeting and/or modulating tumor cell-specific GD2 may offer a new therapeutic strategy for the above mentioned tumor entities.

Abstract

The ganglioside GD2 is an important target in childhood cancer. Nevertheless, the only therapy targeting GD2 that is approved to date is the monoclonal antibody dinutuximab, which is used in the therapy of neuroblastoma. The relevance of GD2 as a target in other tumor entities remains to be elucidated. Here, we analyzed the expression of GD2 in different pediatric tumor entities by flow cytometry and tested two approaches for targeting GD2. H3K27M-mutant diffuse midline glioma (H3K27M-mutant DMG) samples showed the highest expression of GD2 with all cells strongly positive for the antigen. Ewing’s sarcoma (ES) samples also showed high expression, but displayed intra- and intertumor heterogeneity. Osteosarcoma had low to intermediate expression with a high percentage of GD2-negative cells. Dinutuximab beta in combination with irinotecan and temozolomide was used to treat a five-year-old girl with refractory ES. Disease control lasted over 12 months until a single partially GD2-negative intracranial metastasis was detected. In order to target GD2 in H3K27M-mutant DMG, we blocked ganglioside synthesis via eliglustat, since dinutuximab cannot cross the blood–brain barrier. Eliglustat is an inhibitor of glucosylceramide synthase, and it is used for treating children with Gaucher’s disease. Eliglustat completely inhibited the proliferation of primary H3K27M-mutant DMG cells in vitro. In summary, our data provide evidence that dinutuximab might be effective in tumors with high GD2 expression. Moreover, disrupting the ganglioside metabolism in H3K27M-mutant DMG could open up a new therapeutic option for this highly fatal cancer.

Macrophage-Mediated Tumor Cell Phagocytosis: Opportunity for Nanomedicine Intervention

Macrophages are one of the most abundant non-malignant cells in the tumor microenvironment, playing critical roles in mediating tumor immunity. As important innate immune cells, macrophages possess the potential to engulf tumor cells and present tumor-specific antigens for adaptive antitumor immunity induction, leading to growing interest in targeting macrophage phagocytosis for cancer immunotherapy. Nevertheless, live tumor cells have evolved to evade phagocytosis by macrophages via the extensive expression of anti-phagocytic molecules, such as CD47. In addition, macrophages also rapidly recognize and engulf apoptotic cells (efferocytosis) in the tumor microenvironment, which inhibits inflammatory responses and facilitates immune escape of tumor cells. Thus, intervention of macrophage phagocytosis by blocking anti-phagocytic signals on live tumor cells or inhibiting tumor efferocytosis presents a promising strategy for the development of cancer immunotherapies. Here, the regulation of macrophage-mediated tumor cell phagocytosis is first summarized, followed by an overview of strategies targeting macrophage phagocytosis for the development of antitumor therapies. Given the potential off-target effects associated with the administration of traditional therapeutics (for example, monoclonal antibodies, small molecule inhibitors), we highlight the opportunity for nanomedicine in macrophage phagocytosis intervention.

Targeting tumor-associated macrophages: A potential treatment for solid tumors

Tumor-associated macrophages (TAMs) in solid tumors exert protumor activities by releasing cytokines or growth factors into the tumor microenvironment. Increasing studies have also shown that TAMs play a key role in tumor progression, such as tumor angiogenesis, immunosuppression, cell proliferation, migration, invasion, and metastasis. A large body of evidence shows that the abundance of TAMs in solid tumors is correlated with poor disease prognosis and resistance to therapies. Therefore, targeting TAMs in solid tumors is considered to be a promising immunotherapeutic strategy. At present, the therapeutic strategies of targeting macrophages mainly include limiting monocyte recruitment, depletion strategies, promoting macrophage phagocytic activity, and induction of macrophage reprogramming. Additionally, targeting TAMs in combination with conventional therapies has been demonstrated to be a promising therapeutic strategy in solid tumors. In the present review, we summarized various TAMs-targeting therapeutic strategies for treating solid tumors. This review also discusses the challenges for targeting TAMs as tumor treatments, the obstacles in clinical trials, and the perspective for the future development of TAMs-targeting therapies for various cancers.

The anti-B7-H4 checkpoint synergizes trastuzumab treatment to promote phagocytosis and eradicate breast cancer

Trastuzumab is a humanized mAb used to treat HER2-overexpressing breast cancer; however its mechanisms remain to be fully elucidated. Previous studies suggest a role for immunity in mediating trastuzumab-specific antitumor effects. This study evaluated the role(s) of trastuzumab and other antibodies on macrophage activation and Ab-dependent cell-mediated phagocytosis (ADCP) of HER2+ breast cancer cells in vitro and in vivo. We employed orthotopic implantation of HER2+ murine breast cancer (BC) cells in immunocompetent mouse models, a human HER2+ BC xenograft in an immune humanized mouse model, and human PDXs involving adoptive transfer of autologous macrophages to simulate an endogenous mammary tumor-immune microenvironment. Our study demonstrated that trastuzumab greatly and consistently increased macrophage frequency and tumor-cell phagocytosis, and that concurrent knockdown of B7-H4 by a neutralizing antibody increased immune cell infiltration and promoted an antitumor phenotype. Furthermore, neoadjuvant trastuzumab therapy significantly upregulated B7-H4 in the cancer-infiltrating macrophages of HER2+ BC patients, which predicted poor trastuzumab response. We suggest that strategies to specifically enhance ADCP activity might be critical to overcoming resistance to HER2 mAb therapies by inhibiting tumor growth and potentially enhance antigen presentation. Furthermore, these results advance the understanding of macrophage plasticity by uncovering a dual role for ADCP in macrophages involving elimination of tumors by engulfing cancer cells while causing a concomitant undesired effect by upregulating immunosuppressive checkpoints.

Bispecific antibody approach for EGFR-directed blockade of the CD47-SIRPα "don't eat me" immune checkpoint promotes neutrophil-mediated trogoptosis and enhances antigen cross-presentation

Cancer cells overexpress CD47 to subvert phagocytic elimination and evade immunogenic processing of cancer antigens. Moreover, CD47 overexpression inhibits the antibody-dependent cellular phagocytosis (ADCP) and cytotoxicity (ADCC) activities of therapeutic anticancer antibodies. Consequently, CD47-blocking antibodies have been developed to overcome the immunoevasive activities of cancer cell-expressed CD47. However, the wide-spread expression of CD47 on normal cells forms a massive "antigen sink" that potentially limits sufficient tumor accretion of these antibodies. Additionally, a generalized blockade of CD47-SIRPα interaction may ultimately lead to unintended cross-presentation of self-antigens potentially promoting autoimmunity. To address these issues, we constructed a bispecific antibody, designated bsAb CD47xEGFR-IgG1, that blocks cancer cell surface-expressed CD47 in an EGFR-directed manner. BsAb CD47xEGFR-IgG1 selectively induced phagocytic removal of EGFR^pos/CD47^pos cancer cells and endowed neutrophils with capacity to kill these cancer cells by trogoptosis; an alternate form of ADCC that disrupts the target cell membrane. Importantly, bsAb CD47xEGFR-IgG1 selectively enhanced phagocytosis and immunogenic processing of EGFR^pos/CD47^pos cancers cells ectopically expressing viral protein CMVpp65. In conclusion, bsAb CD47xEGFR-IgG1 may be useful to reduce on-target/off-tumor effects of CD47-blocking approaches, enhance cancer cell elimination by trogoptosis, and promote adaptive anticancer immune responses.

Dual blockade of CD47 and HER2 eliminates radioresistant breast cancer cells

Although the efficacy of cancer radiotherapy (RT) can be enhanced by targeted immunotherapy, the immunosuppressive factors induced by radiation on tumor cells remain to be identified. Here, we report that CD47-mediated anti-phagocytosis is concurrently upregulated with HER2 in radioresistant breast cancer (BC) cells and RT-treated mouse syngeneic BC. Co-expression of both receptors is more frequently detected in recurrent BC patients with poor prognosis. CD47 is upregulated preferentially in HER2-expressing cells, and blocking CD47 or HER2 reduces both receptors with diminished clonogenicity and augmented phagocytosis. CRISPR-mediated CD47 and HER2 dual knockouts not only inhibit clonogenicity but also enhance macrophage-mediated attack. Dual antibody of both receptors synergizes with RT in control of syngeneic mouse breast tumor. These results provide the evidence that aggressive behavior of radioresistant BC is caused by CD47-mediated anti-phagocytosis conjugated with HER2-prompted proliferation. Dual blockade of CD47 and HER2 is suggested to eliminate resistant cancer cells in BC radiotherapy.

The root cause of drug resistance in HER2-positive breast cancer and the therapeutic approaches to overcoming the resistance

HER2 is a well-known oncogenic receptor tyrosine kinase. HER2 gene amplification occurs in about 20% of breast cancer (BC), which leads to overexpression of HER2 protein, known as HER2-positive BC. Inhibitors of HER2 have significantly improved the prognosis of patients with this subset of BC. Since 1998, seven HER2 inhibitors have been developed to treat this disease. However, drug resistance is common and remains a major unresolved clinical problem. Patients typically show disease progression after some time on treatment. This review discusses the complexity and diversified nature of HER2 signaling, the mechanisms of actions and therapeutic activities of all HER2 inhibitors, the roles of HER2 and other signaling proteins in HER2-positive BC resistant to the inhibitors, the non-cell-autonomous mechanisms of drug resistance, and the heterogeneity of tumor HER2 expression. The review presents the concept that drug resistance in HER2-positive BC results primarily from the inability of HER2 inhibitors to deplete HER2. Emerging therapeutics that are promising for overcoming drug resistance are also discussed.

Stimulation of Oncogene-Specific Tumor-Infiltrating T Cells through Combined Vaccine and αPD-1 Enable Sustained Antitumor Responses against Established HER2 Breast Cancer

PURPOSE

Despite promising advances in breast cancer immunotherapy, augmenting T-cell infiltration has remained a significant challenge. Although neither individual vaccines nor immune checkpoint blockade (ICB) have had broad success as monotherapies, we hypothesized that targeted vaccination against an oncogenic driver in combination with ICB could direct and enable antitumor immunity in advanced cancers.

EXPERIMENTAL DESIGN

Our models of HER2⁺ breast cancer exhibit molecular signatures that are reflective of advanced human HER2⁺ breast cancer, with a small numbers of neoepitopes and elevated immunosuppressive markers. Using these, we vaccinated against the oncogenic HER2Δ16 isoform, a nondriver tumor-associated gene (GFP), and specific neoepitopes. We further tested the effect of vaccination or anti-PD-1, alone and in combination.

RESULTS

We found that only vaccination targeting HER2Δ16, a driver of oncogenicity and HER2-therapeutic resistance, could elicit significant antitumor responses, while vaccines targeting a nondriver tumor-specific antigen or tumor neoepitopes did not. Vaccine-induced HER2-specific CD8⁺ T cells were essential for responses, which were more effective early in tumor development. Long-term tumor control of advanced cancers occurred only when HER2Δ16 vaccination was combined with αPD-1. Single-cell RNA sequencing of tumor-infiltrating T cells revealed that while vaccination expanded CD8 T cells, only the combination of vaccine with αPD-1 induced functional gene expression signatures in those CD8 T cells. Furthermore, we show that expanded clones are HER2-reactive, conclusively demonstrating the efficacy of this vaccination strategy in targeting HER2.

CONCLUSIONS

Combining oncogenic driver targeted vaccines with selective ICB offers a rational paradigm for precision immunotherapy, which we are clinically evaluating in a phase II trial (NCT03632941).

Recent Advancements in CD47 Signal Transduction Pathways Involved in Vascular Diseases

Cardiovascular and cerebrovascular diseases caused by atherosclerosis have a high disability rate and reduce the quality of life of the population. Therefore, understanding the mechanism of atherosclerosis and its control may interfere with the progression of atherosclerosis and thus control the occurrence of diseases closely related to atherosclerosis. TSP-1 is a factor that has been found to have an antiangiogenic effect, and CD47, as the receptor of TSP-1, can participate in the regulation of antiangiogenesis of atherosclerosis. VEGF is an important regulator of angiogenesis, and TSP-1/CD47 can cause VEGF and its downstream expression. Therefore, the TSP-1/CD47/VEGF/VEGFR2 signal may have an important influence on atherosclerosis. In addition, some inflammatory factors, such as IL-1 and NLRP3, can also affect atherosclerosis. This review will be expounded focusing on the pathogenesis and influencing factors of atherosclerosis.

Combined Anti-Cancer Strategies Based on Anti-Checkpoint Inhibitor Antibodies

Therapeutic monoclonal antibodies for the treatment of cancer came of age in 1997, with the approval of anti-CD20 Rituximab. Since then, a wide variety of antibodies have been developed with many different formats and mechanisms of action. Among these, antibodies blocking immune checkpoint inhibitors (ICI) have revolutionized the field, based on the novelty of their concept and their demonstrated efficacy in several types of cancer otherwise lacking effective immunotherapy approaches. ICI are expressed by tumor, stromal or immune cells infiltrating the tumor microenvironment, and negatively regulate anti-tumor immunity. Antibodies against the first discovered ICI, CTLA-4, PD-1 and PD-L1, have shown significant activity in phase III studies against melanoma and other solid cancers, alone or in combination with chemotherapy or radiotherapy. However, not all cancers and not all patients respond to these drugs. Therefore, novel antibodies targeting additional ICI are currently being developed. In addition, CTLA-4, PD-1 and PD-L1 blocking antibodies are being combined with each other or with other antibodies targeting novel ICI, immunostimulatory molecules, tumor antigens, angiogenic factors, complement receptors, or with T cell engaging bispecific antibodies (BsAb), with the aim of obtaining synergistic effects with minimal toxicity. In this review, we summarize the biological aspects behind such combinations and review some of the most important clinical data on ICI-specific antibodies.

Therapeutic modulation of the CD47-SIRPα axis in the pediatric tumor microenvironment: working up an appetite

Evasion of immune surveillance is one of the hallmarks of cancer. Although the adaptive immune system has been targeted via checkpoint inhibition, many patients do not sustain durable remissions due to the heterogeneity of the tumor microenvironment, so additional strategies are needed. The innate immune system has its own set of checkpoints, and tumors have co-opted this system by expressing surface receptors that inhibit phagocytosis. One of these receptors, CD47, also known as the "don't eat me" signal, has been found to be overexpressed by most cancer histologies and has been successfully targeted by antibodies blocking the receptor or its ligand, signal regulatory protein α (SIRPα). By enabling phagocytosis via antigen-presenting cells, interruption of CD47-SIRPα binding leads to earlier downstream activation of the adaptive immune system. Recent and ongoing clinical trials are demonstrating the safety and efficacy of CD47 blockade in combination with monoclonal antibodies, chemotherapy, or checkpoint inhibitors for adult cancer histologies. The aim of this review is to highlight the current literature and research on CD47, provide an impetus for investigation of its blockade in pediatric cancer histologies, and provide a rationale for new combination therapies in these patients.