Targeting Tumor-associated Macrophages Research Articles

Targeting tumor-associated macrophages to reverse antitumor drug resistance.

Currently, antitumor drugs show limited clinical outcomes, mainly due to adaptive resistance. Clinical evidence has highlighted the importance of the tumor microenvironment (TME) and tumor-associated macrophages (TAMs) in tumor response to conventional antitumor drugs. Preclinical studies show that TAMs following antitumor agent can be reprogrammed to an immunosuppressive phenotype and proangiogenic activities through different mechanisms, mediating drug resistance and poor prognosis. Potential extrinsic inhibitors targeting TAMs repolarize to an M1-like phenotype or downregulate proangiogenic function, enhancing therapeutic efficacy of anti-tumor therapy. Moreover, pharmacological modulation of macrophages that restore the immune stimulatory characteristics is useful to reshaping the tumor microenvironment, thus further limiting tumor growth. This review aims to introduce macrophage response in tumor therapy and provide a potential therapeutic combination strategy of TAM-targeting immunomodulation with conventional antitumor drugs.

A bioactive nanocomposite integrated specific TAMs target and synergistic TAMs repolarization for effective cancer immunotherapy

Reactive oxygen species (ROS) generated from photosensitizers exhibit great potential for repolarizing immunosuppressive tumor-associated macrophages (TAMs) toward the anti-tumor M1 phenotype, representing a promising cancer immunotherapy strategy. Nevertheless, their effectiveness in eliminating solid tumors is generally limited by the instability and inadequate TAMs-specific targeting of photosensitizers. Here, a novel core-shell integrated nano platform is proposed to achieve a coordinated strategy of repolarizing TAMs for potentiating cancer immunotherapy. Colloidal mesoporous silica nanoparticles (CMSN) are fabricated to encapsulate photosensitizer-Indocyanine Green (ICG) to improve their stability. Then ginseng-derived exosome (GsE) was coated on the surface of ICG/CMSN for targeting TAMs, as well as repolarizing TAMs concurrently, named ICG/CMSN@GsE. As expected, with the synergism of ICG and GsE, ICG/CMSN@GsE exhibited better stability, mild generation of ROS, favorable specificity toward M2-like macrophages, enhancing drug retention in tumors and superior TAMs repolarization potency, then exerted a potent antitumor effect. In vivo, experiment results also confirm the synergistic suppression of tumor growth accompanied by the increased presence of anti-tumor M1-like macrophages and maximal tumor damage. Taken together, by integrating the superiorities of TAMs targeting specificity and synergistic TAMs repolarization effect into a single nanoplatform, ICG/CMSN@GsE can readily serve as a safe and high-performance nanoplatform for enhanced cancer immunotherapy.

Dual roles of HK3 in regulating the network between tumor cells and tumor-associated macrophages in neuroblastoma

Neuroblastoma (NB) is the most common and deadliest extracranial solid tumor in children. Targeting tumor-associated macrophages (TAMs) is a strategy for attenuating tumor-promoting states. The crosstalk between cancer cells and TAMs plays a pivotal role in mediating tumor progression in NB. The overexpression of Hexokinase-3 (HK3), a pivotal enzyme in glucose metabolism, has been associated with poor prognosis in NB patients. Furthermore, it correlates with the infiltration of M2-like macrophages within NB tumors, indicating its significant involvement in tumor progression. Therefore, HK3 not only directly regulates the malignant biological behaviors of tumor cells, such as proliferation, migration, and invasion, but also recruits and polarizes M2-like macrophages through the PI3K/AKT-CXCL14 axis in neuroblastoma. The secretion of lactate and histone lactylation alterations within tumor cells accompanies this interaction. Additionally, elevated expression of HK3 in M2-TAMs was found at the same time. Modulating HK3 within M2-TAMs alters the biological behavior of tumor cells, as demonstrated by our in vitro studies. This study highlights the pivotal role of HK3 in the progression of NB malignancy and its intricate regulatory network with M2-TAMs. It establishes HK3 as a promising dual-functional biomarker and therapeutic target in combating neuroblastoma.

Enhancing anticancer activity of macrophages through rational drug combinations.

Targeting tumor-associated macrophages (TAMs) is an emerging approach being tested in multiple clinical trials. TAMs, depending on their differentiation state, can exhibit pro- or antitumorigenic functions. For example, the M2-like phenotype represents a protumoral state that can stimulate tumor growth, angiogenesis, metastasis, therapy resistance, and immune evasion by expressing immune checkpoint proteins. In this issue of the JCI, Vaccaro and colleagues utilized an innovative drug screen approach to demonstrate that targeting driver oncogenic signaling pathways concurrently with anti-CD47 sensitizes tumor cells, causing them to undergo macrophage-induced phagocytosis. The combination treatment altered expression of molecules on the tumor cells that typically limit phagocytosis. It also reprogrammed macrophages to an M1-like antitumor state. Moreover, the approach was generalizable to tumor cells with different oncogenic pathways, opening the door to precision oncology-based rationale combination therapies that have the potential to improve outcomes for patients with oncogene-driven lung cancers and likely other cancer types.

Abstract SY37-03: Leveraging the complexities of tumor associated macrophages for effective anti-cancer therapy

Abstract Macrophages are innate immune cells that play a critical role in host defense and maintaining tissue homeostasis, however their infiltration into tumors is associated with disease progression and resistance to therapy. Tumor associated macrophages (TAMs) represent a significant proportion of solid tumors, including breast cancer. TAMs play a major role in tumorigenesis as they can enhance tumor cell growth, angiogenesis and metastasis. In addition, TAMs can inhibit anti-tumor responses of T cells. Our recent work has shown that removal or conversion of TAMs to an anti-tumor phenotype enhances chemo- and immuno-therapy establishing TAMs as targets for anti-cancer therapy. Using high-dimensional single-cell and multi-omics profiling of murine and human breast tumors we reveal multiple subsets of TAMs with distinct transcriptional and activity profiles that correlate with progression of disease and response to therapy. This work has revealed the complexity of TAMs and major gaps in our knowledge of the functional and phenotypic characterization of TAM subsets associated with cancer, before and after treatment. Here we will discuss the complexity of TAMs in solid tumors including characterizing TAM subsets, location, and crosstalk with neighboring cells, as well as novel TAM-modulating strategies and combinations that are likely to enhance current therapies and overcome chemo- and immuno-therapy resistance. Our findings support the idea that targeting TAMs offers great potential to enhance both chemo- and immuno-therapy. Citation Format: Jennifer L. Guerriero. Leveraging the complexities of tumor associated macrophages for effective anti-cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY37-03.

Abstract 6521: Macrophage-targeting immunotherapy enhances chemotherapy response in primary and metastatic triple-negative breast cancer models

Abstract Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks targeted treatment options. While immune checkpoint blockade leads to significant benefits in the treatment of TNBC when in combination with chemotherapy, recurrence, metastasis, and chemoresistance still remain major challenges. The purpose of this study was to assess the ability of a colony-stimulating factor 1 receptor inhibitor (CSF-1Ri) to shift the phenotype of the tumor microenvironment (TME) in murine models of TNBC, and the potential benefit of such in enhancing standard of care chemotherapy. We focused on targeting tumor-associated macrophages (TAMs) as they are the most abundant immune infiltrate in the TNBC TME and are associated with worsening overall survival (OS) and metastasis free survival (MFS). Targeting TAMs, specifically M2-like TAMs, has been shown to inhibit tumor progression and improve OS in the clinic. We selected pexidartinib (PLX) as the CSF-1Ri of choice, given its translational potential (FDA approved) and gemcitabine (GEM) as chemotherapy, given its ability to target myeloid derived suppressor cells and M2-like TAMs. For primary TNBC we employed 4T1 mammary carcinoma cells transfected with luciferase reporter gene in BALB/c mice as an immunocompetent model. Mice were injected with 100,000 cells in the 4th mammary fat pad, and tumors established over the course of fifteen days. Mice were then exposed to daily administrations of PLX (8 mg/kg), and weekly administrations of GEM (60 mg/kg). Tumor volumes were recorded every other day. The TME was analyzed with flow cytometry (FC), immunohistochemistry (IHC), and multiplex immunofluorescence (mIF). For the metastatic model, mice were inoculated with 100,000 4T1-luc cells in the flank. On day six, mice were exposed to treatments as outlined above. Mice underwent survival surgery to remove the primary tumor on day thirteen and were then treated with adjuvant therapy. Metastasis and OS were tracked. FC analysis indicated only combination therapy (11.8% ± 2.1) significantly decreased total TAMs compared to vehicle (22% ± 2) in the primary tumor. Combination therapy also showed the greatest depletion of M2-like TAMs (2.2% ± 0.6), with a significant decrease compared to both vehicle (15.6% ± 0.4) and GEM (6.6% ± 0.9). This TME modulation was confirmed using IHC and mIF. After four cycles of treatment, combination therapy (232.9 mm3 ± 130.8) had a significant effect on tumor burden compared to GEM alone (369.7 mm3 ± 165.8), indicating a correlation between tumor phenotype and therapeutic benefit. Furthermore, combination therapy led to the greatest prolongation of MFS and OS in the resection model, indicating that combination therapy has efficacy in the neoadjuvant and adjuvant setting. In conclusion, targeting TAMs in TNBC primes the tumor for combination with chemotherapy in TNBC. Citation Format: Matthew Emilio Fernandez, Yasir Alshehry, Laura Graham, Jennifer E. Koblinski, Harry D. Bear, Doug H. Sweet, Sandro R. da Rocha. Macrophage-targeting immunotherapy enhances chemotherapy response in primary and metastatic triple-negative breast cancer models [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 6521.

Abstract 486: Paclitaxel nanoformulation attenuates pancreatic tumor desmoplasia and alter tumor immune responses

Abstract Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer with a 5-year survival rate of less than 13% due to the lack of effective diagnostic/therapeutic modalities. Paclitaxel (PTX) has been tested in pancreatic cancer (PanCa) therapy with marginally better clinical outcomes, but remains limited by its poor hemocompatibility, biodistribution, and intracellular accumulation in tumor cells. Gemcitabine (GEM) is the most effective therapy for PanCa. However, it shows only a marginal survival benefit of 6 months. The poor therapy response is attributed to high desmoplasia, unfavorable tumor microenvironment (TME), and excessive recruitment of immune suppressive cells. We have recently engineered a multi-layered Pluronic F127 and polyvinyl alcohol stabilized and poly-L-lysine coated paclitaxel loaded poly(lactic-co-glycolic acid) nanoparticle formulation (PPNPs), which effectively inhibits pancreatic tumor. In this study, we demonstrate that PPNPs effectively sensitize tumor cells to GEM via attenuation of tumor desmoplasia. Our findings also show that PPNPs synergize GEM therapy response in cell lines and in vivo mouse models. Mechanistically, PPNPs target the TME via inhibition of the sonic hedgehog (SHH) pathway and other oncogenic signaling axis that inhibits bidirectional tumor-stromal cell interaction as determined by qPCR and Western blot analyses. In addition, PPNPs effectively target tumor-associated macrophages (TAM) by repolarizing M2 into M1 phenotype via inhibiting expression of M2 markers and an increase in M1 markers in mouse macrophage cell line RAW264.7. M2 polarization of RAW264.7 cells were induced by culture with IL-4 (20 ng/mL) in the presence of PPNPs or vehicle control. Furthermore, PPNPs effectively increase phagocytic capacity in murine macrophages as determined by phagocytosis assay (Vybrant Phagocytosis Assay Kit). In conclusion, we observed that our novel PPNP nano formulation effectively targets TME, and facilitates GEM uptake by inhibiting the activation of SHH signaling and reprograming the tumor immune surveillance mechanisms. This study suggests that PPNPs have great potential for future clinical use in management of pancreatic cancer. Citation Format: Vivek K. Kashyap, Godwin P. Darkwah, Neeraj Chauhan, Mohammed Sikander, Eswara N. Ghali, Meghana Kolli, Bilal B. Hafeez, Murali M. Yallapu, Subhash C. Chauhan. Paclitaxel nanoformulation attenuates pancreatic tumor desmoplasia and alter tumor immune responses [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 486.

Abstract 103: Prostate cancer bone metastasis: Therapeutic targeting of tumor associated macrophages

Abstract Introduction: Castration-resistant bone metastatic prostate cancer is a morbid and deadly disease with an exceedingly low response rates to available immunotherapies. Understanding the mechanisms behind immune evasion and tumor progression is critical to improving therapy. Historically, bone metastases have been challenging to model in the laboratory. Our foundational work was built upon fresh patient samples taken directly from the operating room for analysis across multiple platforms: IHC, single cell expression profiling, and spatial transcriptomics. We compared tumors from patients with bone metastatic disease to tumors from patients with disease localized to the prostate. Our work (Cancer Cell, 2021 and Nature Communications, 2023) has consistently pointed towards dysregulated myeloid populations within the tumor microenvironment, particularly TREM2+ tumor associated macrophages (TAMs), as key drivers of disease progression. Methods: Our patient samples and murine pre-clinical models of prostate cancer highlighted several specifically upregulated molecules and pathways in TAMs. Here we focus on TAMs in vitro and in vivo using a new and genetically tractable myeloid model to interrogate the mechanistic role of key pathways, and how they may contribute to T-cell immune suppression. The ER-Hoxb8 system of conditional myeloid differentiation permitted the generation of isogenic cell lines to interrogate the roles of key molecules TREM2, MSR1, APOE, and MERTK through overexpression or CRISPR/Cas9 knockout. Results: Using a system of co-culture in vitro, we quantified the role of these proteins in suppressing T-cell proliferation and cytokine production, as well as their role in TAM differentiation and function. In vivo, these lines were co-injected subcutaneously with syngeneic RM1-BM3 tumor cells to quantify their effect on tumor growth and T-cell suppression in vivo. In addition to localized subcutaneous tumors, bone metastatic disease was established by intracardiac injection. Furthermore, established tumors were treated with TAM-directed small molecule therapy (e.g., MERTK inhibition) as well as immune checkpoint inhibition (anti-PD1) alone, and in combination. Conclusions: TAMs are immune suppressive myeloid cells that are not found in normal tissues. They are specifically recruited to tumors and highly enriched in bone metastatic disease. Transcriptomic analyses highlighted signaling pathways potentially amenable to productive therapeutic targeting. The ER-Hoxb8 system was highly effective in generating a genetically tractable model of TAM for study in vitro and in vivo. Our work supports the hypothesis that the specific targeting of TAMs, by focusing on critical signaling pathways, can be effective in the treatment of pre-clinical models of prostate cancer. This new approach merits further study as a potential strategy for the treatment of patients with bone metastases. Citation Format: Hanyu Zhang, Shenglin Mei, Nathan E. Jeffries, Douglas M. Dahl, Chin-Lee Wu, Philip J. Saylor, David B. Sykes. Prostate cancer bone metastasis: Therapeutic targeting of tumor associated macrophages [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 103.

Bacterial protoplast-derived nanovesicles carrying CRISPR-Cas9 tools re-educate tumor-associated macrophages for enhanced cancer immunotherapy

The CRISPR-Cas9 system offers substantial potential for cancer therapy by enabling precise manipulation of key genes involved in tumorigenesis and immune response. Despite its promise, the system faces critical challenges, including the preservation of cell viability post-editing and ensuring safe in vivo delivery. To address these issues, this study develops an in vivo CRISPR-Cas9 system targeting tumor-associated macrophages (TAMs). We employ bacterial protoplast-derived nanovesicles (NVs) modified with pH-responsive PEG-conjugated phospholipid derivatives and galactosamine-conjugated phospholipid derivatives tailored for TAM targeting. Utilizing plasmid-transformed E. coli protoplasts as production platforms, we successfully load NVs with two key components: a Cas9-sgRNA ribonucleoprotein targeting Pik3cg, a pivotal molecular switch of macrophage polarization, and bacterial CpG-rich DNA fragments, acting as potent TLR9 ligands. This NV-based, self-assembly approach shows promise for scalable clinical production. Our strategy remodels the tumor microenvironment by stabilizing an M1-like phenotype in TAMs, thus inhibiting tumor growth in female mice. This in vivo CRISPR-Cas9 technology opens avenues for cancer immunotherapy, overcoming challenges related to cell viability and safe, precise in vivo delivery.

Small Molecule Immunomodulators as Next-Generation Therapeutics for Glioblastoma.

Glioblastoma (GBM), the most aggressive astrocytic glioma, remains a therapeutic challenge despite multimodal approaches. Immunotherapy holds promise, but its efficacy is hindered by the highly immunosuppressive GBM microenvironment. This review underscores the urgent need to comprehend the intricate interactions between glioma and immune cells, shaping the immunosuppressive tumor microenvironment (TME) in GBM. Immunotherapeutic advancements have shown limited success, prompting exploration of immunomodulatory approaches targeting tumor-associated macrophages (TAMs) and microglia, constituting a substantial portion of the GBM TME. Converting protumor M2-like TAMs to antitumor M1-like phenotypes emerges as a potential therapeutic strategy for GBM. The blood-brain barrier (BBB) poses an additional challenge to successful immunotherapy, restricting drug delivery to GBM TME. Research efforts to enhance BBB permeability have mainly focused on small molecules, which can traverse the BBB more effectively than biologics. Despite over 200 clinical trials for GBM, studies on small molecule immunomodulators within the GBM TME are scarce. Developing small molecules with optimal brain penetration and selectivity against immunomodulatory pathways presents a promising avenue for combination therapies in GBM. This comprehensive review discusses various immunomodulatory pathways in GBM progression with a focus on immune checkpoints and TAM-related targets. The exploration of such molecules, with the capacity to selectively target key immunomodulatory pathways and penetrate the BBB, holds the key to unlocking new combination therapy approaches for GBM.

IRG1 restrains M2 macrophage polarization and suppresses intrahepatic cholangiocarcinoma progression via the CCL18/STAT3 pathway.

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant and aggressive cancer whose incidence and mortality continue to increase, whereas its prognosis remains dismal. Tumor-associated macrophages (TAMs) promote malignant progression and immune microenvironment remodeling through direct contact and secreted mediators. Targeting TAMs has emerged as a promising strategy for ICC treatment. Here, we revealed the potential regulatory function of immune responsive gene 1 (IRG1) in macrophage polarization. We found that IRG1 expression remained at a low level in M2 macrophages. IRG1 overexpression can restrain macrophages from polarizing to the M2 type, which results in inhibition of the proliferation, invasion, and migration of ICC, whereas IRG1 knockdown exerts the opposite effects. Mechanistically, IRG1 inhibited the tumor-promoting chemokine CCL18 and thus suppressed ICC progression by regulating STAT3 phosphorylation. The intervention of IRG1 expression in TAMs may serve as a potential therapeutic target for delaying ICC progression.

Tumor-Associated Macrophage Targeting of Nanomedicines in Cancer Therapy.

The tumor microenvironment (TME) is pivotal in tumor growth and metastasis, aligning with the "Seed and Soil" theory. Within the TME, tumor-associated macrophages (TAMs) play a central role, profoundly influencing tumor progression. Strategies targeting TAMs have surfaced as potential therapeutic avenues, encompassing interventions to block TAM recruitment, eliminate TAMs, reprogram M2 TAMs, or bolster their phagocytic capabilities via specific pathways. Nanomaterials including inorganic materials, organic materials for small molecules and large molecules stand at the forefront, presenting significant opportunities for precise targeting and modulation of TAMs to enhance therapeutic efficacy in cancer treatment. This review provides an overview of the progress in designing nanoparticles for interacting with and influencing the TAMs as a significant strategy in cancer therapy. This comprehensive review presents the role of TAMs in the TME and various targeting strategies as a promising frontier in the ever-evolving field of cancer therapy. The current trends and challenges associated with TAM-based therapy in cancer are presented.

Abstract B122: 2 for 1: Targeting tumor-associated macrophages and cancer cells with a novel MERTK-targeting antibody-drug conjugate (ADC)

Abstract MERTK, a member of the TAM family receptor tyrosine kinases, is overexpressed in various solid and hematologic cancers. MERTK signaling drives multiple processes such as proliferation, survival, invasion and drug resistance. Furthermore, MERTK is expressed on M2 tumor-associated macrophages (TAMs), playing a role in the production of immunosuppressive cytokines and efferocytosis. Within normal tissue, MERTK is also expressed in the retinal pigment epithelium (RPE). Our RNA-DRIVErTM platform identified MERTK as a key driver of metastatic progression and thus a potentially potent target for therapeutic intervention. Our MERTK-targeting humanized monoclonal antibody, RGX-019, is internalized by both MERTK-expressing cancer cells and macrophages. In M2 macrophages, RGX-019 induced expression of pro-inflammatory M1 macrophage type cytokines. To effectively target MERTK in both cancer cells and immune-suppressive macrophages, we developed an MMAE antibody drug conjugate (ADC). Here, we assessed the anti-tumor efficacy and retinal safety of RGX-019-MMAE and examined MERTK expression in both solid and hematologic cancers. RGX-019-MMAE induced cytotoxicity against MERTK-expressing cancer cells and mediated bystander anti-tumor efficacy in vitro. In xenograft models, RGX-019-MMAE demonstrated robust anti-tumor efficacy, including complete tumor regressions in various cancers such as TNBC, melanoma, and multiple myeloma. Anti-tumor efficacy of RGX-019-MMAE was associated with improved overall survival. RGX-019-MMAE suppressed syngeneic tumor growth in a mouse model expressing human MERTK extracellular domain, and lacked anti-tumor efficacy in animals not expressing human MERTK. Anti-tumor efficacy was associated with reduced M2 macrophage levels in tumors. Given that RGX-019 only binds human but not murine MERTK, these findings suggest that RGX-019-MMAE targets the host tumor microenvironment to mediate anti-tumor efficacy. Immunohistochemical analysis revealed broad MERTK expression in multiple human cancers with highest expression detected in ovarian, NSCLC, and urothelial cancers. In primary AML samples, significantly higher expression was detected in M5 subtype samples, those with PTPN11 mutations or t(9;11) translocations. Higher MERTK expression in AML correlated with significantly worse patient survival. MERTK in the RPE is involved in maintenance of retinal homeostasis. After a 28-day treatment with RGX-019-MMAE, we observed no signs of retinal degeneration in a transgenic mouse expressing human MERTK extracellular domain. The lack of retinal toxicity can be explained by the partial agonist activity of RGX-019 and absence of MMAE cytotoxicity against non-proliferating RPE cells. The substantial anti-tumor efficacy of RGX-019-MMAE in multiple aggressive tumors, along with the limited expression in normal tissues, reveal MERTK as a promising novel target for an ADC approach. Our findings support the continued advancement of RGX-019-MMAE for the treatment of solid and hematologic cancers through targeting of both TAMs and cancer cells. Citation Format: Shugaku Takeda, PuiChi Lo, Daniel Schefer, Maryam Siddiqui, Anudishi Tyagi, Venkata Lokesh Battula, Abhishek Maiti, Sohail Tavazoie, Masoud Tavazoie, David Martin Darst, Isabel Kurth. 2 for 1: Targeting tumor-associated macrophages and cancer cells with a novel MERTK-targeting antibody-drug conjugate (ADC) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B122.

Tailoring the surface charges of iron-crosslinked dextran nanogels towards improved tumor-associated macrophage targeting

Tumor-associated macrophages (TAMs) have emerged as therapeutic interests in cancer nanomedicine because TAMs play a pivotal role in the immune microenvironment of solid tumors. Dextran and its derived nanocarriers are among the most promising nanomaterials for TAM targeting due to their intrinsic affinities towards macrophages. Various dextran-based nanomaterials have been developed to image TAMs. However, the effects of physiochemical properties especially for surface charges of dextran nanomaterials on TAM-targeting efficacy were ambiguous in literature. To figure out the surface charge effects on TAM targeting, here we developed a facile non-covalent self-assembly strategy to construct oppositely charged dextran nanogels (NGs) utilizing the coordination interaction of ferric ions, chlorine e6 (Ce6) dye and three dextran derivatives, diethylaminoethyl-, sulfate sodium- and carboxymethyl-dextran. The acquired dextran NGs exhibit different charges but similar hydrodynamic size, Ce6 loading and mechanical stiffness, which enables a side-by-side comparison of the effects of NG surface charges on TAM targeting monitored by the Ce6 fluorescence imaging. Compared with negative NGs, the positive NG clearly displays a superior TAM targeting in murine breast cancer model. This study identifies that positively charged dextran NG could be a promising approach to better engineer nanomedicine towards an improved TAM targeting.

Targeting tumor-associated macrophage: an adjuvant strategy for lung cancer therapy.

The emergence of immunotherapy has revolutionized the treatment landscape for various types of cancer. Nevertheless, lung cancer remains one of the leading causes of cancer-related mortality worldwide due to the development of resistance in most patients. As one of the most abundant groups of immune cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play crucial and complex roles in the development of lung cancer, including the regulation of immunosuppressive TME remodeling, metabolic reprogramming, neoangiogenesis, metastasis, and promotion of tumoral neurogenesis. Hence, relevant strategies for lung cancer therapy, such as inhibition of macrophage recruitment, TAM reprograming, depletion of TAMs, and engineering of TAMs for drug delivery, have been developed. Based on the satisfactory treatment effect of TAM-targeted therapy, recent studies also investigated its synergistic effect with current therapies for lung cancer, including immunotherapy, radiotherapy, chemotherapy, anti-epidermal growth factor receptor (anti-EGFR) treatment, or photodynamic therapy. Thus, in this article, we summarized the key mechanisms of TAMs contributing to lung cancer progression and elaborated on the novel therapeutic strategies against TAMs. We also discussed the therapeutic potential of TAM targeting as adjuvant therapy in the current treatment of lung cancer, particularly highlighting the TAM-centered strategies for improving the efficacy of anti-programmed cell death-1/programmed cell death-ligand 1 (anti-PD-1/PD-L1) treatment.

The Streptococcus virulence protein PepO triggers anti-tumor immune responses by reprograming tumor-associated macrophages in a mouse triple negative breast cancer model

BackgroundThe efficacy of current surgery and chemotherapy for triple negative breast cancer (TNBC) is limited due to heterogenous and immunosuppressive tumor microenvironment (TME). Tumor associated macrophages (TAMs), which are regarded as an M2 tumor-promoting phenotype, are crucial in the development of the immunosuppressive TME. Targeting TAM reprograming is a promising strategy in anti-tumor therapy since reprogramming techniques provide the opportunity to actively enhance the antitumor immunological activity of TAM in addition to eliminating their tumor-supportive roles, which is rarely applied in TNBC clinically. However, how to drive M2 macrophages reprogramming into M1 with high potency remains a challenge and the molecular mechanisms how M2 macrophages polarized into M1 are poorly understood. Here, we identified a new immunoregulatory molecular PepO that was served as an immunoregulatory molecule governed the transformation of tumor-promoting M2 to tumor-inhibitory M1 cells and represented an effective anti-tumor property.ResultsAt the present study, we identified a new immunoregulatory molecular PepO, as a harmless immunoregulatory molecule, governed the transformation of tumor-promoting M2 to tumor-inhibitory M1 cells efficiently. PepO-primed M2 macrophages decreased the expression of tumor-supportive molecules like Arg-1, Tgfb, Vegfa and IL-10, and increased the expression of iNOS, Cxcl9, Cxcl10, TNF-α and IL-6 to inhibit TNBC growth. Moreover, PepO enhanced the functions of macrophages related to cell killing, phagocytosis and nitric oxide biosynthetic process, thereby inhibiting the development of tumors in vivo and in vitro. Mechanistically, PepO reprogramed TAMs toward M1 by activating PI3K-AKT-mTOR pathway via TLR4 and suppressed the function of M2 by inhibiting JAK2-STAT3 pathway via TLR2. The PI3K inhibitor LY294002 abrogated the role of PepO in switching M2 macrophages into M1 and in inhibiting TNBC growth in vivo. And PepO failed to govern the M2 macrophages to reprogram into M1 macrophages and inhibit TNBC when TLR2 or TLR4 was deficient. Moreover, PepO enhanced the antitumor activity of doxorubicin and the combination exerted a synergistic effect on TNBC suppression.ConclusionsOur research identified a possible macrophage-based TNBC immunotherapeutic approach and suggested a novel anticancer immunoregulatory molecular called PepO.

Nebulized Therapy of Early Orthotopic Lung Cancer by Iron-Based Nanoparticles: Macrophage-Regulated Ferroptosis of Cancer Stem Cells.

Cancer stem cells (CSCs) within protumorigenic microlesions are a critical driver in the initiation and progression of early stage lung cancer, where immune cells provide an immunosuppressive niche to strengthen the CSC stemness. As the mutual interactions between CSCs and immune cells are increasingly recognized, regulating the immune cells to identify and effectively eliminate CSCs has recently become one of the most attractive therapeutic options, especially for abundant tumor-associated macrophages (TAMs). Herein, we developed a nebulized nanocatalytic medicine strategy in which iron-based nanoparticle-regulated TAMs effectively target CSC niches and trigger CSC ferroptosis in the early stage of lung cancer. Briefly, the iron-based nanoparticles can effectively accumulate in lung cancer microlesions (minimum 122 μm in diameter) through dextran-mediated TAM targeting by nebulization administration, and as a result, nanoparticle-internalized TAMs can play a predominant role of the iron factory in elevating the iron level surrounding CSC niches and destroying redox equilibrium through downregulating glucose-6-phosphate metabolite following their lysosomal degradation and iron metabolism. The altered microenvironment results in the enhanced sensitivity of CSCs to ferroptosis due to their high expression of the CD44 receptor mediating iron endocytosis. In an orthotopic mouse model of lung cancer, the initiation and progression of early lung cancer are significantly suppressed through ferroptosis-induced stemness reduction of CSCs by nebulization administration. This work presents a nebulized therapeutic strategy for early lung cancer through modulation of communications between TAMs and CSCs, which is expected to be a general approach for regulating primary microlesions and micrometastatic niches of lung cancer.

Mannose-functionalization of reconstituted high-density lipoprotein nanoparticles improves payload delivery and enhances M2-to-M1 phenotype reprogramming of RAW 264.7 macrophages polarized by B16-F10 melanoma cells

The targeting and conversion of the immunosuppressive (M2) tumor-associated macrophages (TAMs) to an immunostimulatory (M1) phenotype can induce tumor regression in advanced melanoma. We have previously characterized and reported the ability of reconstituted high-density lipoprotein nanoparticles (rHDL NPs) functionalized with DSPE-PEG-mannose (DPM) to deliver payload to macrophages. Herein, we investigate the modulation of macrophage phenotype and payload delivery mechanisms of the rHDL-DPM NPs in RAW 264.7 murine macrophages exposed to the conditioned medium (CM) from murine B16-F10 melanoma cells. The rHDL-DPM NPs loaded with the Stimulator of Interferon genes agonist, DMXAA, reduced protein levels of M2 markers. Through the mannose moiety, the rHDL-DPM-DMXAA NPs enhanced the production of interferon β and CXCL10 compared to the free DMXAA in the B16-F10 CM-educated RAW 264.7 macrophages. Compared to their non-mannosylated counterpart, the rHDL-DPM NPs delivered their payload more efficiently to the B16-F10 CM-educated RAW 264.7 macrophages. Mechanistically, both the scavenger receptor type B class 1 (SR-B1) and the mannose receptor (CD206) facilitated payload delivery to the macrophages via endocytic and non-endocytic mechanisms. Finally, the CM from rHDL-DPM-DMXAA NPs -treated macrophages enhanced paclitaxel (paclitaxel)-mediated cytotoxicity in B16-F10 cells. Together, these in vitro findings demonstrate the potential of the mannose-functionalized rHDL NPs in improving the targeting of M2-like TAMs and treatment outcomes when combined with immunotherapy or PTX in B16-F10 melanoma in vivo models.

Outer Membrane Vesicle-Based Nanohybrids Target Tumor-Associated Macrophages to Enhance Trained Immunity-Related Vaccine-Generated Antitumor Activity.

Trained immunity refers to the innate immune system building memory-like features in response to subsequent infections and vaccinations. Compared with classical tumor vaccines, trained immunity-related vaccines (TIrV) are independent of tumor-specific antigens. Bacterial outer membrane vesicles (OMVs) contain an abundance of PAMPs and have the potential to act as TIrV-inducer, but face challenges in endotoxin tolerance, systemic delivery, long-term training, and trained tumor-associated macrophage (TAM)-mediated antitumor phagocytosis. Here, we developed an OMV-based TIrV, OMV nanohybrids (OMV-SIRPα@CaP/GM-CSF) for exerting vaccine-enhanced antitumor activity. In the bone marrow, GM-CSF-assisted OMVs trained bone marrow progenitor cells and monocytes, which were inherited by TAMs. In tumor tissues, SIRPα-Fc-assisted OMVs triggered TAM-mediated phagocytosis. This TIrV can be identified by metabolic and epigenetic rewiring using transposase-accessible chromatin (ATAC) and transcriptome sequencing. Furthermore, we found that the TIrV-mediated antitumor mechanism in MC38 tumor model (TAM-hot & T cell-cold) is trained immunity and activated T cell response, whereas in B16-F10 tumor model (T cell-hot & TAM-cold) is primarily mediated by trained immunity. Our study not only developed and identified OMV-based TIrV, but also investigated the trained immunity signatures and therapeutic mechanisms, providing a basis for further vaccination strategies. This article is protected by copyright. All rights reserved.

The Roles and Targeting of Tumor-Associated Macrophages.

Tumor-associated macrophages (TAMs) are the most abundant infiltrating immune cells in the tumor microenvironment (TME) and play an important role in tumor progression. Clinically, the increase of TAMs infiltration is linked to poor prognosis of patients with various cancer types. Multiple studies have demonstrated that reducing or reprogramming TAMs can inhibit the occurrence or development of tumors. Therefore, TAMs have been identified as novel targets for the treatment of cancer therapy. In this review, the origin, polarization, roles, and targeting of TAMs in malignancies, are discussed.