Macrophage-mediated Phagocytosis Research Articles

Cell autonomous functions of CD47 in regulating cellular plasticity and metabolic plasticity.

CD47 is a ubiquitously expressed cell surface receptor, which is widely known for preventing macrophage-mediated phagocytosis by interacting with signal regulatory protein α (SIRPα) on the surface of macrophages. In addition to its role in phagocytosis, emerging studies have reported numerous noncanonical functions of CD47 that include regulation of various cellular processes such as proliferation, migration, apoptosis, differentiation, stress responses, and metabolism. Despite lacking an extensive cytoplasmic signaling domain, CD47 binds to several cytoplasmic proteins, particularly upon engaging with its secreted matricellular ligand, thrombospondin 1. Indeed, the regulatory functions of CD47 are greatly influenced by its interacting partners. These interactions are often cell- and context-specific, adding a further level of complexity. This review addresses the downstream cell-intrinsic signaling pathways regulated by CD47 in various cell types and environments. Some of the key pathways modulated by this receptor include the PI3K/AKT, MAPK/ERK, and nitric oxide signaling pathways, as well as those implicated in glucose, lipid, and mitochondrial metabolism. These pathways play vital roles in maintaining tissue homeostasis, highlighting the importance of understanding the phagocytosis-independent functions of CD47. Given that CD47 expression is dysregulated in a variety of cancers, improving our understanding of the cell-intrinsic signals regulated by this molecule will help advance the development of CD47-targeted therapies.

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.

A first-in-human phase I study of ATG-031, anti-CD24 antibody, in patients with advanced solid tumors or B-cell non-Hodgkin lymphomas (PERFORM).

TPS2691 Background: ATG-031 is a first-in-class humanized cluster of differentiation 24 (CD24) antibody. By disrupting the interaction between CD24, a ‘do not eat me’ signal on cancer cells, and the inhibitory receptor Siglec-10 on tumor-associated macrophages (TAMs), it enhances macrophage-mediated phagocytosis of cancer cells and promotes cytotoxic T cell function in the tumor microenvironment. ATG-031 also triggers antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) towards target tumor cells through its immunoglobulin gamma 1 (IgG1) Fc-dependent effects. Preclinical studies indicated that ATG-031-induced phagocytosis transforms macrophages from a tumor-tolerant M2 phenotype to an antitumor M1 phenotype, significantly inhibiting tumor growth both as monotherapy and synergistically with immune checkpoint inhibitors (ICI) and/or chemotherapies in mouse models. Methods: ATG-031 is undergoing evaluation for safety and preliminary antitumor efficacy in a Phase I, multi-center, open-label clinical study, PERFORM (NCT04986865), in patients with advanced solid tumors or B-cell non-Hodgkin’s lymphoma. The study includes a dose escalation phase and a dose expansion phase. The dose escalation phase enrolls patients with advanced solid tumors (preferred tumor types: lung cancer, breast cancer, ovarian cancer, urothelial cancer, and liver cancer) using a Bayesian Optimal Interval (BOIN) design with 3 to 9 patients at each dose level. A priming dose, defined as an initial lower dose followed by escalation to the full treatment dose, will be applied if Grade ≥2 cytokine release syndrome (CRS) is observed during the dose-limiting toxicity (DLT) period. The dose expansion phase will enroll patients with specific tumor types and will randomize patients into two or more dose levels to determine the recommended Phase II dose (RP2D). The PERFORM study explores an intravenous dose of ATG-031 once every 21 days (1 cycle) to assess DLT during the first two treatment cycles in dose escalation. Key inclusion criteria include histological or cytological confirmation of a solid tumor that has relapsed or has been refractory to standard therapy, at least one measurable lesion per RECIST, and an ECOG performance status of 0 to 1. The study excludes patients with CNS malignancies and those who have experienced Grade ≥3 immune-related adverse events (irAEs) or irAEs leading to prior immunotherapy discontinuation. As of January 2024, 2 sites in the United States have initiated the study, and 4 patients have received ATG-031 treatment at 0.03mg/kg (dose level 1). Clinical trial information: NCT04986865 .

LncRNA IL21-AS1 facilitates tumour progression by enhancing CD24-induced phagocytosis inhibition and tumorigenesis in ovarian cancer

CD24 is overexpressed in various tumours and considered a regulator of cell migration, invasion, and proliferation. Recent studies have found that CD24 on ovarian cancer (OC) and triple-negative breast cancer cells interacts with the inhibitory receptor sialic-acid-binding Ig-like lectin 10 (Siglec-10) on tumour-associated macrophages (TAMs) to inhibit phagocytosis by macrophages. Because of its multiple roles in regulating the immune response and tumorigenesis, CD24 is a very promising therapeutic target. However, the regulatory mechanism of CD24 in OC remains unclear. Here, we found that the long noncoding RNA (lncRNA) IL21-AS1, which was upregulated in OC, inhibited macrophage-mediated phagocytosis and promoted OC cell proliferation and apoptosis inhibition. More importantly, after IL21-AS1 knockdown, a significant survival advantage was observed in mice engrafted with tumours. Mechanistically, we identified IL21-AS1 as a hypoxia-induced lncRNA. Moreover, IL21-AS1 increased HIF1α-induced CD24 expression under hypoxic conditions. In parallel, we found that IL21-AS1 acted as a competing endogenous RNA (ceRNA) for miR-561-5p to regulate CD24 expression. Finally, IL21-AS1 increased CD24 expression in OC and facilitated OC progression. Our findings provide a molecular basis for the regulation of CD24, thus highlighting a potential strategy for targeted treatment of OC.

Combining SiRPα decoy-coengineered T cells and antibodies augments macrophage-mediated phagocytosis of tumor cells.

The adoptive transfer of T cell receptor-engineered (TCR-engineered) T cells (ACT) targeting the HLA-A2-restricted cancer-testis epitope NY-ESO-1157-165 (A2/NY) has yielded favorable clinical responses against several cancers. Two approaches to improve ACT are TCR affinity optimization and T cell coengineering to express immunomodulatory molecules that can exploit endogenous immunity. By computational design we previously developed a panel of binding-enhanced A2/NY-TCRs including A97L, which augmented the in vitro function of gene-modified T cells as compared with WT. Here, we demonstrated higher persistence and improved tumor control by A97L-T cells. In order to harness macrophages in tumors, we further coengineered A97L-T cells to secrete a high-affinity signal regulatory protein α (SiRPα) decoy (CV1) that blocks CD47. While CV1-Fc-coengineered A97L-T cells mediated significantly better control of tumor outgrowth and survival in Winn assays, in subcutaneous xenograft models the T cells, coated by CV1-Fc, were depleted. Importantly, there was no phagocytosis of CV1 monomer-coengineered T cells by human macrophages. Moreover, avelumab and cetuximab enhanced macrophage-mediated phagocytosis of tumor cells in vitro in the presence of CV1 and improved tumor control upon coadministration with A97L-T cells. Taken together, our study indicates important clinical promise for harnessing macrophages by combining CV1-coengineered TCR-T cells with targeted antibodies to direct phagocytosis against tumor cells.

Type III interferon inhibits bladder cancer progression by reprogramming macrophage-mediated phagocytosis and orchestrating effective immune responses

BackgroundInterferons (IFNs) are essential for activating an effective immune response and play a central role in immunotherapy-mediated immune cell reactivation for tumor regression. Type III IFN (λ), related to type...

Targeting the GPI transamidase subunit GPAA1 abrogates the CD24 immune checkpoint in ovarian cancer

CD24 is frequently overexpressed in ovarian cancer and promotes immune evasion by interacting with its receptor Siglec10, present on tumor-associated macrophages, providing a "don't eat me" signal that prevents targeting and phagocytosis by macrophages. Factors promoting CD24 expression could represent novel immunotherapeutic targets for ovarian cancer. Here, using a genome-wide CRISPR knockout screen, we identify GPAA1 (glycosylphosphatidylinositol anchor attachment 1), a factor that catalyzes the attachment of a glycosylphosphatidylinositol (GPI) lipid anchor to substrate proteins, as a positive regulator of CD24 cell surface expression. Genetic ablation of GPAA1 abolishes CD24 cell surface expression, enhances macrophage-mediated phagocytosis, and inhibits ovarian tumor growth in mice. GPAA1 shares structural similarities with aminopeptidases. Consequently, we show that bestatin, a clinically advanced aminopeptidase inhibitor, binds to GPAA1 and blocks GPI attachment, resulting in reduced CD24 cell surface expression, increased macrophage-mediated phagocytosis, and suppressed growth of ovarian tumors. Our study highlights the potential of targeting GPAA1 as an immunotherapeutic approach for CD24+ ovarian cancers.

The IL-7R antagonist lusvertikimab reduces leukemic burden in xenograft ALL via antibody-dependent cellular phagocytosis

AbstractAcute lymphoblastic leukemia (ALL) arises from the uncontrolled proliferation of B-cell precursors (BCP-ALL) or T cells (T-ALL). Current treatment protocols obtain high cure rates in children but are based on toxic polychemotherapy. Novel therapies are urgently needed, especially in relapsed/refractory (R/R) disease, high-risk (HR) leukemias and T-ALL, in which immunotherapy approaches remain scarce. Although the interleukin-7 receptor (IL-7R) plays a pivotal role in ALL development, no IL-7R–targeting immunotherapy has yet reached clinical application in ALL. The IL-7Rα chain (CD127)–targeting IgG4 antibody lusvertikimab (LUSV; formerly OSE-127) is a full antagonist of the IL-7R pathway, showing a good safety profile in healthy volunteers. Here, we show that ∼85% of ALL cases express surface CD127. We demonstrate significant in vivo efficacy of LUSV immunotherapy in a heterogeneous cohort of BCP- and T-ALL patient-derived xenografts (PDX) in minimal residual disease (MRD) and overt leukemia models, including R/R and HR leukemias. Importantly, LUSV was particularly effective when combined with polychemotherapy in a phase 2-like PDX study with CD127high samples leading to MRD-negativity in >50% of mice treated with combination therapy. Mechanistically, LUSV targeted ALL cells via a dual mode of action comprising direct IL-7R antagonistic activity and induction of macrophage-mediated antibody-dependent cellular phagocytosis (ADCP). LUSV–mediated in vitro ADCP levels significantly correlated with CD127 expression levels and the reduction of leukemia burden upon treatment of PDX animals in vivo. Altogether, through its dual mode of action and good safety profile, LUSV may represent a novel immunotherapy option for any CD127+ ALL, particularly in combination with standard-of-care polychemotherapy.

Abstract 2672: GD3 synthase (ST8SIA1) is a key immunomodulator in GD2+ breast cancer cells

Abstract Background: Gangliosides are acidic glycosphingolipids involved in cell adhesion, proliferation, and modulation of signal transduction pathways. It has been reported that tumor-shed gangliosides influence the activity of immune cells, including macrophages, NK cells, and T cells. GD3 synthase (GD3S) is the key enzyme that regulates the biosynthesis of the b and c-series gangliosides, particularly GD3 and GD2, and studies have shown that GD3S is upregulated in most tumors and plays a role in tumor progression. Similarly, we have found GD3S to be significantly upregulated in GD2+ breast cancer stem cells (BCSC) compared to GD2− cells, and the knockdown of this gene prevented tumor formation in mice. Here, we hypothesize that GD3 synthase has an immunomodulatory function in breast cancer (BC) cells through the upregulation of GD2. Methods: We stably overexpressed GD3S in BT549 and MCF-7 breast cancer cell lines by lentiviral transfection and performed CRISPR-Cas9 knockout of GD3S in BT549 and SUM 159 cell lines. We examined the effect of GD3 synthase on macrophage-mediated phagocytosis, NK cell-mediated killing, and T-cell cytotoxicity of BC cells using the live cell imaging system, IncuCyte®. Naxitamab is a US FDA-approved fully humanized anti-GD2 monoclonal antibody for the treatment of neuroblastoma. We evaluated the effects of naxitamab in GD2+ BC cell lines (HCC1395, Hs578T) using the Incucyte, and also examined its effect on in vivo tumor growth using TNBC PDX models. Results: We observed a highly significant decrease in macrophage-mediated phagocytosis (p<0.005; p<0.0001) and NK-mediated killing (p<0.0001; p<0.0001) in BT549 and MCF-7 cell overexpressing GD3S compared to the control cells. Interestingly, we observed a significant increase in phagocytosis in GD3S knockout BT549 and SUM 159 cells (p<0.05; p<0.005) compared to their wild-type counterparts. Moreover, the knockout of GD3S enhanced NK cell-mediated apoptosis in BT549 cells (p<0.001) and T cell killing in BT549 and SUM 159 cells (p<0.0001; p<0.0001). Finally, we found that naxitamab dose-dependently enhances macrophage-mediated phagocytosis and NK cell-mediated apoptosis in HCC1395 and Hs578T BC cells, with 20µg/ml being the most effective concentration in comparison to IgG control (p<0.0001; p<0.0001). In addition, we observed a reduction in tumor volume in naxitamab-treated mice compared to IgG control (p<0.05) Conclusion: GD3 synthase regulates macrophage-mediated phagocytosis, NK cell-induced apoptosis, and T-cell cytotoxicity in BC cells. Naxitamab enhances immune cell killing of breast cancer cells with high GD2 expression. Furthermore, naxitamab inhibited tumor growth in GD2+ TNBC PDX models. Citation Format: Bolutyfe Oderinde, Vivek Anand, Maryam Siddiqui, Anudishi Tyagi, Borgman Jenny, Venkata Lokesh Battula. GD3 synthase (ST8SIA1) is a key immunomodulator in GD2+ breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2672.

Abstract 1537: CD63 acts as a key modulator of tumor progression and innate immune evasion in non-small cell lung cancer

Abstract Introduction: Lung cancer is a major reason for cancer-related mortality worldwide, causing more than two million cancer deaths per year. Over the last decade, new therapies have allowed long-term survival for patients even in advanced stages. However, only a minority of patients benefits from these therapies and patients often grow resistant over time. An important mechanism that contributes to cancer growth and the development of therapy resistances is the cross-talk between cancer cells and their tissue microenvironment, in particular fibroblasts and macrophages. In this context, we explored whether the tetraspanin CD63 - which is commonly found on intra- and extracellular membranes - stimulates cancer growth and mediates pro-tumorigenic functions of the tissue microenvironment in NSCLC. Methods: We analyzed patient tissue via immunohistochemistry and in-situ-hybridization. We deleted CD63 in cancer cell lines (A549, H810, LC19) and primary fibroblasts via CRISPR-Cas9. To assess phagocytosis, we used in vitro EdU assays and adaptive transfer models in vivo, and identified changes in cell signaling via mass spectrometry. We used an in vitro phagocytosis assay to determine the effect of CD63 on cancer cell phagocytosis through macrophages and analyzed the expression of M1 and M2-associated surface markers through flow cytometry upon co-culturing PBMC with cancer cells over one week. Results: In patient sections, cancer tissue did not only express more CD63 on the gene expression and protein level but a stronger CD63 expression also correlated with a denser macrophage infiltrate. Looking for pro-tumorigenic functions, deleting CD63 in three cancer cell lines reduced cancer cell growth both in vitro and in an adaptive transfer model in vivo. Additionally, deleting CD63 impaired the pro-tumorigenic focal adhesion signaling in primary fibroblasts. Concerning the interaction between cancer cells and macrophages, deleting CD63 reduced the macrophage-mediated phagocytosis of cancer cells and co-culturing primary monocytes with CD63-deficient lung cancer cells induced the expression of M1-associated surface markers on the PBMC. Conclusion: In conclusion, these results demonstrate that the tetraspanin CD63 drives NSCLC growth by stimulating cancer cell proliferation - in part by interfering with focal adhesion signaling - and facilitating immune evasion by preventing cancer cell phagocytosis through macrophages and inducing an immunosuppressive phenotype in macrophages. Citation Format: Tristan Lerbs, Lu Cui, Cristabelle De Souza, Reinhard Buettner, Gerlinde Wernig. CD63 acts as a key modulator of tumor progression and innate immune evasion in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1537.

Abstract 6532: Blockade of CD24 sensitizes pancreatic cancer to Kras inhibitors

Abstract Pancreatic ductal adenocarcinoma (PDAC) is predominantly driven by KRAS oncogene. KRAS, long considered an undruggable target, has been targeted by drugs including a KRASG12C inhibitor (G12Ci), AMG 510, which is approved for the treatment of KRASG12C-mutant non-small cell lung cancer (NSCLC). AMG 510 also exhibited promising anticancer activity in human PDAC, with 21% response rate and over 70% patients experiencing certain level of tumor control. However, targeting KRAS oncogenes faces the major challenge of therapy resistance, which severely limited its survival benefit. While multiple studies have elucidated potential resistance mechanisms to G12Ci in lung cancer, the molecular mechanisms underlying resistance in PDAC remains elusive. Here, using KRASG12C-driven mouse PDAC model, we found that similar to the clinical observation, KRASG12C tumors exhibit only partial response to AMG 510 treatment. CyTOF analysis indicates that such tumor persistence following G12Ci treatment occurs even in the presence of conversion from a ‘cold’ pro-tumor immune microenvironment to a ‘hot’ anti-tumor immune environment, as evidenced by the prominent increase in both cytotoxic T cells and M1-like macrophages. Interestingly, we discovered that the expression of CD24, which was recently identified as a new ‘do not eat me’ signal, is significantly upregulated on the surface of persist tumor cells after G12Ci treatment which suppresses the function of anti-tumor macrophages. Anti-CD24 blocking mAb enhanced macrophage-mediated phagocytosis in vitro and significantly sensitizes KRASG12C tumors to AMG 510 treatment in vivo in a macrophage-dependent manner. Similar findings were observed in KRASG12D-driven PDAC model. Our findings identified a novel immune combination to improve the outcome of KRAS targeted therapy in PDAC. Citation Format: Yongkun Wei, Minghui Liu, Er-Yen Yen, Jun Yao, Phuoc T. Nguyen, Xiaofei Wang, Zecheng Yang, Abdelrahman Yousef, Dean Pan, Yanqing Jin, Madelaine S. Theady, Jangho Park, Yiming Cai, Mitsunobu Takeda, Matthew Vasquez, Yong Zhou, Hong Zhao, Andrea Viale, Huamin Wang, Dan Zhao, Ronald A. DePinho, Wantong Yao, Haoqiang Ying. Blockade of CD24 sensitizes pancreatic cancer to Kras inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6532.

Checkpoint CD24 function on tumor and immunotherapy.

CD24 is a protein found on the surface of cells that plays a crucial role in the proliferation, invasion, and spread of cancer cells. It adheres to cell membranes through glycosylphosphatidylinositol (GPI) and is associated with the prognosis and survival rate of cancer patients. CD24 interacts with the inhibitory receptor Siglec-10 that is present on immune cells like natural killer cells and macrophages, leading to the inhibition of natural killer cell cytotoxicity and macrophage-mediated phagocytosis. This interaction helps tumor cells escape immune detection and attack. Although the use of CD24 as a immune checkpoint receptor target for cancer immunotherapy is still in its early stages, clinical trials have shown promising results. Monoclonal antibodies targeting CD24 have been found to be well-tolerated and safe. Other preclinical studies are exploring the use of chimeric antigen receptor (CAR) T cells, antibody-drug conjugates, and gene therapy to target CD24 and enhance the immune response against tumors. In summary, this review focuses on the role of CD24 in the immune system and provides evidence for CD24 as a promising immune checkpoint for cancer immunotherapy.

Discovery and Preclinical Activity of BMS-986351, an Antibody to SIRPα That Enhances Macrophage-mediated Tumor Phagocytosis When Combined with Opsonizing Antibodies.

Increasing the phagocytotic capabilities of tumor-associated macrophages by modulating macrophage-tumor cell surface signaling via the CD47-SIRPα axis is a novel strategy. Molecules targeting CD47 have potential but its ubiquitous expression necessitates higher therapeutic doses to overcome potential antigen sink effects. The restricted expression pattern of SIRPα may limit toxicities and lower doses of the SIRPα antibody BMS-986351 may overcome target mediated drug disposition while maintaining the desired pharmacology.

Characterization of a Myeloid Differentiation Factor 2-Derived Peptide that Facilitates THP-1 Macrophage-Mediated Phagocytosis of Gram-Negative Bacteria.

Myeloid differentiation factor 2 (MD2), the TLR4 coreceptor, has been shown to possess opsonic activity and has been implicated in phagocytosis and intracellular killing of Gram-negative bacteria. However, any MD2 protein segment involved in phagocytosis of Gram-negative bacteria is not yet known. A short synthetic MD2 segment, MD54 (amino acid regions 54 to 69), was shown to interact with a Gram-negative bacterial outer membrane component, LPS, earlier. Furthermore, the MD54 peptide induced aggregation of LPS and facilitated its internalization in THP-1 cells. Currently, it has been investigated if MD2-derived MD54 possesses any opsonic property and role in phagocytosis of Gram-negative bacteria. Remarkably, we observed that MD54 facilitated agglutination of Gram-negative bacteria, Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC BAA-427), but not of Gram-positive bacteria, Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 25923). The MD54-opsonized Gram-negative bacteria internalized within PMA-treated THP-1 cells and were killed over a longer incubation period. However, both internalization and intracellular killing of the MD54-opsonized Gram-negative bacteria within THP-1 phagocytes were appreciably inhibited in the presence of a phagocytosis inhibitor, cytochalasin D. Furthermore, MD54 facilitated the clearance of Gram-negative bacteria E. coli (ATCC 25922) and P. aeruginosa (ATCC BAA-427) from the infected BALB/c mice whereas an MD54 analog, MMD54, was inactive. Overall, for the first time, the results revealed that a short MD2-derived peptide can specifically agglutinate Gram-negative bacteria, act as an opsonin for these bacteria, and facilitate their phagocytosis by THP-1 phagocytes. The results suggest that the MD54 segment could have a crucial role in MD2-mediated host-pathogen interaction involving the Gram-negative bacteria.

The Oncogenic Lipid Sphingosine-1-Phosphate Impedes the Phagocytosis of Tumor Cells by M1 Macrophages in Diffuse Large B Cell Lymphoma.

A total of 30-40% of diffuse large B cell lymphoma (DLBCL) patients will either not respond to the standard therapy or their disease will recur. The first-line treatment for DLBCL is rituximab and combination chemotherapy. This treatment involves the chemotherapy-induced recruitment of tumor-associated macrophages that recognize and kill rituximab-opsonized DLBCL cells. However, we lack insights into the factors responsible for the recruitment and functionality of macrophages in DLBCL tumors. We have studied the effects of the immunomodulatory lipid sphingosine-1-phosphate (S1P) on macrophage activity in DLBCL, both in vitro and in animal models. We show that tumor-derived S1P mediates the chemoattraction of both monocytes and macrophages in vitro and in animal models, an effect that is dependent upon the S1P receptor S1PR1. However, S1P inhibited M1 macrophage-mediated phagocytosis of DLBCL tumor cells opsonized with the CD20 monoclonal antibodies rituximab and ofatumumab, an effect that could be reversed by an S1PR1 inhibitor. Our data show that S1P signaling can modulate macrophage recruitment and tumor cell killing by anti-CD20 monoclonal antibodies in DLBCL. The administration of S1PR1 inhibitors could enhance the phagocytosis of tumor cells and improve outcomes for patients.

Abstract C097: KRASG12C exhibits allele-specific biology in pancreatic cancer and targeting CD24 sensitizes KRASG12C-driven tumors to sotorasib treatment

Abstract Pancreatic adenocarcinoma (PDAC) is predominantly driven by KRAS oncogene. While all oncogenic KRAS mutations result in its hyperactivation, the allele-specific biology of KRAS mutations remain poorly understood. Addressing such issues has become particularly important with the recent advancements in the development of allele-specific and pan-KRAS inhibitors. Among the KRAS inhibitors, KRASG12C inhibitors (G12Ci), Sotorasib and Adagrasib, have been approved for treating KRASG12C-mutant lung cancer. Sotorasib also exhibited promising anticancer activity in human PDAC, with 21% response rate and over 70% patients experiencing certain level of tumor control. However, targeting KRAS oncogenes faces the major challenge of therapy resistance, which severely limited its survival benefit. While multiple studies have elucidated potential resistance mechanisms to G12Ci in lung cancer, the molecular mechanisms underlying its resistance in PDAC remains elusive, largely owing to the scarcity of relevant and faithful preclinical models. Here, we report the generation of a new autochthonous KRASG12C-driven PDAC model (p48Cre; LSL-KrasG12C; p53L/+, KCPC). Compared to the KRASG12D-driven KPC model (p48Cre; LSL-KrasG12D; p53L/+), tumor development in KCPC model is significantly delayed accompanied with corresponding decrease in both KRAS signaling and proliferation in premalignant lesions. As a result, the overall survival of the KCPC model is significantly prolonged compared to the KPC model, indicating allele-specific discrepancy of KRAS mutations during PDAC initiation. However, upon malignant progression, KRASG12C-driven mouse PDAC exhibit similar histopathological and molecular features as KRASG12D-driven tumors. Furthermore, similar to the clinical observation, KCPC tumors exhibit only partial response to Sotorasib treatment. CyTOF analysis indicates that such tumor persistence following G12Ci treatment occurs even in the presence of conversion from a ‘cold’ pro-tumor immune microenvironment to a ‘hot’ anti-tumor immune environment, as evidenced by the prominent increase in both cytotoxic T cells and M1-like macrophages. Interestingly, we discovered that the expression of CD24, which was recently identified as a new ‘do not eat me’ signal, is significantly upregulated on the surface of persist tumor cells, which suppresses the function of anti-tumor macrophages. Treatment with anti-CD24 blocking mAb enhanced macrophage-mediated phagocytosis in vitro and significantly sensitizes KCPC-derived xenograft tumors to Sotorasib treatment in vivo in a macrophage-dependent manner. Similar upregulation of CD24 following KRAS inhibition and therapeutic benefit of co-targeting CD24 and KRAS were also observed in KRASG12D-driven mouse and human PDAC, implicating the potential of such combination in a broader spectrum of KRAS-driven PDAC. Together, our findings revealed the allele-specific function of KRASG12C in the development of PDAC and identified a novel immune combination to improve the outcome of KRAS targeted therapy in PDAC. Citation Format: Yongkun Wei, Minghui Liu, Phuoc T. Nguyen, Dean N. Pan, Wantong Yao, Haoqiang Ying. KRASG12C exhibits allele-specific biology in pancreatic cancer and targeting CD24 sensitizes KRASG12C-driven tumors to sotorasib treatment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C097.

Nitrated T cell epitope linked vaccine targeting CD47 elicits antitumor immune responses and acts synergistically with vaccine targeting PDL1

Despite the clinical breakthrough made by immune checkpoint blockades (ICB) in cancer immunotherapy, immunosuppressed tumor microenvironment (TME) remains a major impediment in the efficacy of ICB immunotherapy. In this study, we constructed a Nitrated T cell epitope (NitraTh) linked vaccine targeting CD47, namely CD47-NitraTh. CD47-NitraTh could repress the progression of tumor by inducing tumor-specific immune response. Furthermore, combination vaccination with CD47-NitraTh and PDL1-NitraTh could reconstruct tumor associated macrophage, enhance macrophage-mediated phagocytosis for tumor cells, and promote the activation of tumor infiltrating T cells. Notably, by activating chemokine signaling pathway, NitraTh based vaccines reversed immunosuppressed TME, resulting in improved therapeutic outcome for tumor. With the advantage of reversing immunosuppressed TME, NitraTh based vaccine seems an optimal immunotherapy strategy for patients who are not sensitive to antibody based ICB.

Single-cell transcriptomics reveals ferrimagnetic vortex iron oxide nanoring-mediated mild magnetic hyperthermia exerts antitumor effects by alleviating macrophage suppression in breast cancer

The potential of Ferrimagnetic vortex iron oxide nanoring-mediated mild magnetic hyperthermia (FVIO-MHT) in solid tumor therapy has been demonstrated. However, the impact of FVIO-MHT on the tumor microenvironment (TME) remains unclear. This study utilized single-cell transcriptome sequencing to examine the alterations in the TME in response to FVIO-MHT in breast cancer. The results revealed the cellular composition within the tumor microenvironment (TME) was primarily modified due to a decrease in tumor cells and an increased infiltration of myeloid cells. Subsequently, an enhancement in active oxygen (ROS) metabolism was observed, indicating oxidative damage to tumor cells. Interestingly, FVIO-MHT reprogrammed the macrophages’ phenotypes, as evidenced by alterations in the transcriptome characteristics associated with both classic and alternative activated phenotypes. And an elevated level of ROS generation and oxidative phosphorylation suggested that activated phagocytosis and inflammation occurred in macrophages. Additionally, cell–cell communication analysis revealed that FVIO-MHT attenuated the suppression between tumor cells and macrophages by inhibiting phagocytic checkpoint and macrophage migration inhibitory factor signaling pathways. Inhibition of B2m, an anti-phagocytosis checkpoint, could promote macrophage-mediated phagocytosis and significantly inhibit tumor growth. These data emphasize FVIO-MHT may promote the antitumor capabilities of macrophages by alleviating the suppression between tumor cells and macrophages.

Macrophage-hitchhiking interleukin-10 plasmid DNA delivery system modulates rheumatoid arthritis microenvironment via the re-polarization of macrophages

Rheumatoid arthritis (RA) is a common chronic inflammatory disease and the current treatments for RA are unsatisfactory due to the buffer barrier from the RA microenvironment. Interleukin-10 (IL-10) was found to be able to modulate rheumatoid arthritis microenvironment (RAM) by the metabolic reprogramming of macrophages. However, its clinical application has proven challenging mainly due to its short half-life, non-ideal targeting efficiency via systemic administration and poor tissue penetration. Taking advantage of the recruitment of macrophages, we constructed an innovative macrophage-hitchhiking IL-10 pDNA delivery system using the peptides bearing nuclear localization signal (NLS) and tuftsin-modified disulfide-crosslinked polymers (bPEI-SS-PEG-T) which was responsive to the intracellular glutathione concentration. Firstly, we formed NLS/DNA complexes via electrostatic interactions to enhance the nuclear entry efficiency. Then NLS/DNA complexes were combined with bPEI-SS-PEG-T to construct bPEI-SS-PEG-T/NLS/DNA NPs with sizes of 168.4 nm and zeta potentials of + 10.9 mV. As the bPEI-SS-PEG-T was biodegradable and the tuftsin peptides enhanced macrophage-mediated phagocytosis, the nanoparticles exhibited lower cytotoxicity and better cellular uptake in addition to higher nuclear entry efficiency, leading to better IL-10 plasmid transfection. In addition, these macrophage-hitchhiking nanoparticles could effectively accumulate at inflammatory sites of RA via intra-peritoneal injection due to the macrophage migration to the inflammatory joints and alleviate symptoms of inflammation in vivo by inducing the re-polarization of macrophages, which might be mediated by the inhibition of mammalian target of rapamycin (mTOR) and the induction of arginase-2 (Arg2). As a result, this macrophage-hitchhiking gene delivery system demonstrated excellent inflammation targeting ability, good nuclear entry ability, high IL-10 plasmid transfection efficiency and great therapeutic efficacy in vivo, which is promising for the treatment of rheumatoid arthritis. Besides, this delivery system also provides a novel strategy for the gene therapy and the gene delivery system design for rheumatoid arthritis and other similar inflammatory diseases from the perspective of the inflammatory microenvironment.

Live-Cell Imaging Quantifies Changes in Function and Metabolic NADH Autofluorescence During Macrophage-Mediated Phagocytosis of Tumor Cells

ABSTRACT Background The immune system has evolved to detect foreign antigens and deliver coordinated responses, while minimizing “friendly fire.” Until recently, studies investigating the behavior of immune cells were limited to static in vitro measurements. Although static measurements allow for real-time imaging, results are often difficult to translate to an in vivo setting. Multiphoton microscopy is an emerging method to capture spatial information on subcellular events and characterize the local microenvironment. Previous studies have shown that multiphoton microscopy can monitor changes in single-cell macrophage heterogeneity during differentiation. Therefore, there is a need to use multiphoton microscopy to monitor molecular interactions during immunological activities like phagocytosis. Here we investigate the correlation between phagocytic function and changes in endogenous optical reporters during phagocytosis. Methods In vitro autofluorescence imaging of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) was used to detect metabolic changes in macrophages during phagocytosis. More specifically, optical redox ratio, mean NADH fluorescence lifetime and ratio of free to protein-bound NADH were used to quantify changes in metabolism. Results Results show that IFN-γ (M1) macrophages showed decreased optical redox ratios and mean NADH lifetime while phagocytosing immunogenic cancer cells compared to metastatic cells. To validate phagocytic function, a fluorescence microscopy-based protocol using a pH-sensitive fluorescent probe was used. Results indicate that M0 and M1 macrophages show similar trends in phagocytic potential. Conclusion Overall, this work demonstrates that in vitro multiphoton imaging can be used to longitudinally track changes in phagocytosis and endogenous metabolic cofactors.