Modulation Of Tumor-associated Macrophages Research Articles

β,β-Dimethylacrylalkannin, a Natural Naphthoquinone, Inhibits the Growth of Hepatocellular Carcinoma Cells by Modulating Tumor-Associated Macrophages.

Tumor-associated macrophages (TAMs) are pivotal in the tumor microenvironment (TME) of hepatocellular carcinoma (HCC), influencing various stages from initiation to metastasis. Understanding the role of TAMs in HCC is crucial for developing novel therapeutic strategies. Macrophages exhibit plasticity, resulting in M1 and M2 phenotypes, with M1 macrophages displaying antitumor properties and M2 macrophages promoting tumor progression. Targeting TAMs to alter their polarization could offer new avenues for HCC treatment. β,β-dimethylacrylalkannin (DMAKN), a natural naphthoquinone, has gained attention for its antitumor properties. However, its impact on TAMs modulation remains unclear. This study investigates DMAKN's modulation of TAMs and its anti-HCC activity. Using an in vitro model with THP-1 cells, we induced M1 macrophages with LPS/IFN-γ and M2 macrophages with IL-4/IL-13, confirming polarization with specific markers. Co-culturing these macrophages with HCC cells showed that M1 cells inhibited HCC growth, while M2 cells promoted it. Screening for non-toxic DMAKN concentrations revealed its ability to induce M1 polarization and enhance LPS/IFN-γ-induced M1 macrophages, both showing anti-HCC effects. Conversely, DMAKN suppressed IL-4/IL-13-induced M2 polarization, inhibiting M2 macrophages' promotion of HCC cell viability. In summary, DMAKN induces and enhances M1 polarization while inhibiting M2 polarization of macrophages, thereby inhibiting HCC cell growth. These findings suggest that DMAKN has the potential to regulate TAMs in HCC, offering promise for future therapeutic development.

Research advances on signaling pathways regulating the polarization of tumor-associated macrophages in lung cancer microenvironment.

Lung cancer (LC) is one of the most common cancer worldwide. Tumor-associated macrophages (TAMs) are important component of the tumor microenvironment (TME) and are closely related to the stages of tumor occurrence, development, and metastasis. Macrophages are plastic and can differentiate into different phenotypes and functions under the influence of different signaling pathways in TME. The classically activated (M1-like) and alternatively activated (M2-like) represent the two polarization states of macrophages. M1 macrophages exhibit anti-tumor functions, while M2 macrophages are considered to support tumor cell survival and metastasis. Macrophage polarization involves complex signaling pathways, and blocking or regulating these signaling pathways to enhance macrophages' anti-tumor effects has become a research hotspot in recent years. At the same time, there have been new discoveries regarding the modulation of TAMs towards an anti-tumor phenotype by synthetic and natural drug components. Nanotechnology can better achieve combination therapy and targeted delivery of drugs, maximizing the efficacy of the drugs while minimizing side effects. Up to now, nanomedicines targeting the delivery of various active substances for reprogramming TAMs have made significant progress. In this review, we primarily provided a comprehensive overview of the signaling crosstalk between TAMs and various cells in the LC microenvironment. Additionally, the latest advancements in novel drugs and nano-based drug delivery systems (NDDSs) that target macrophages were also reviewed. Finally, we discussed the prospects of macrophages as therapeutic targets and the barriers to clinical translation.

Targeted reprogramming of tumor-associated macrophages for overcoming glioblastoma resistance to chemotherapy and immunotherapy

The resistance of glioblastoma multiforme (GBM) to standard chemotherapy is primarily attributed to the existence of tumor-associated macrophages (TAMs) in the GBM microenvironment, particularly the anti-inflammatory M2 phenotype. Targeted modulation of M2-TAMs is emerging as a promising strategy to enhance chemotherapeutic efficacy. However, combination TAM-targeted therapy with chemotherapy faces substantial challenges, notably in terms of delivery efficiency and targeting specificity. In this study, we designed a pH-responsive hierarchical brain-targeting micelleplex loaded with temozolomide (TMZ) and resiquimod (R848) for combination chemo-immunotherapy against GBM. This delivery system, termed PCPA&PPM@TR, features a primary Angiopep-2 decoration on the outer layer via a pH-cleavable linker and a secondary mannose analogue (MAN) on the middle layer. This pH-responsive hierarchical targeting strategy enables effective BBB permeability while simultaneous GBM- and TAMs-targeting delivery. GBM-targeted delivery of TMZ induces alkylation and triggers an anti-GBM immune response. Concurrently, TAM-targeted delivery of R848 reprograms their phenotype from M2 to pro-inflammatory M1, thereby diminishing GBM resistance to TMZ and amplifying the immune response. In vivo studies demonstrated that targeted modulation of TAMs using PCPA&PPM@TR significantly enhanced anti-GBM efficacy. In summary, this study proposes a promising brain-targeting delivery system for the targeted modulation of TAMs to combat GBM.

The Role of Astrocytes in Promoting Glioblastoma Pathogenicity

For this review, we study the ways that astrocytes lead to increased glioblastoma (GBM) cancer cell survival by interacting with the tumor microenvironment (TME). GBM cells exploit and alter surrounding somatic cells, such as astrocytes, to fuel their growth and metastasis. Astrocytes are the most abundant cells in the central nervous system (CNS) and occupy important roles in maintaining the blood-brain barrier and stabilizing synapses. Tumor-associated astrocytes (TAAs) help tumor progression by interacting with players of the TME. In summary, astrocytes support GBM pathogenicity by transferring mitochondria and cholesterol and directly promoting immunosuppression through the modulation of tumor-associated macrophages (TAMs). Targeting non-GBM cells such as astrocytes, which directly promotes its development, could become a new option for treating the lethal GBM disease. A further understanding of the interaction involved in astrocyte-driven GBM pathogenicity could identify promising molecular targets and effective strategies against GBM.

IL4I1 in M2-like macrophage promotes glioma progression and is a promising target for immunotherapy.

Glioma is the prevailing malignant intracranial tumor, characterized by an abundance of macrophages. Specifically, the infiltrating macrophages often display the M2 subtype and are known as tumor-associated macrophages (TAMs). They have a critical role in promoting the oncogenic properties of tumor cells. Interleukin-4-induced-1 (IL4I1) functions as an L-phenylalanine oxidase, playing a key part in regulating immune responses and the progression of various tumors. However, there is limited understanding of the IL4I1-mediated cross-talk function between TAMs and glioma cell in the glioma microenvironment. TCGA, GTEx, and HPA databases were applied to assess the IL4I1 expression, clinical characteristics, and prognostic value of pan-cancer. The link between IL4I1 levels and the prognosis, methylation, and immune checkpoints (ICs) in gliomas were explored through Kaplan-Meier curve, Cox regression, and Spearman correlation analyses. The IL4I1 levels and their distribution were investigated by single-cell analysis and the TIMER 2 database. Additionally, validation of IL4I1 expression was performed by WB, RT-qPCR, IHC, and IF. Co-culture models between glioma cells and M2-like macrophages were used to explore the IL4I1-mediated effects on tumor growth, invasion, and migration of glioma cells. Moreover, the function of IL4I1 on macrophage polarization was evaluated by ELISA, RT-qPCR, WB, and siRNA transfection. Both transcriptome and protein levels of IL4I1 were increased obviously in various tumor types, and correlated with a dismal prognosis. Specifically, IL4I1 was implicated in aggressive progression and a dismal prognosis for patients with glioma. A negative association was noticed between the glioma grade and DNA promoter methylation of IL4I1. Enrichment analyses in glioma patients suggested that IL4I1 was linked to cytokine and immune responses, and was positively correlated with ICs. Single-cell analysis, molecular experiments, and in vitro assays showed that IL4I1 was significantly expressed in TAMs. Importantly, co-culture models proved that IL4I1 significantly promoted the invasion and migration of glioma cells, and induced the polarization of M2-like macrophages. IL4I1 could be a promising immunotherapy target for selective modulation of TAMs and stands as a novel macrophage-related prognostic biomarker in glioma.

The modulation of tumor-associated macrophages via natural nanomodulators by neutralizing the acidic tumor microenvironment for tumor treatment

A nano-modulator is developed that inhibits tumor growth by modulating the tumor acidic microenvironment and the polarization of tumor-associated macrophages for cancer therapy.

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.

Zinc-c-di-AMP nanoparticles target and suppress tumors via endothelial STING activation and tumor associated macrophage reinvigoration

Abstract Mounting evidence indicates that the stimulator of interferon genes (STING) pathway is critical for the effectiveness of standard cancer treatments. However, systemic delivery of STING agonists remains a challenge due to poor tumor-targeting and unwanted toxicities. Here we describe a robust tumor-targeted STING agonist, ZnCDA, formed by the encapsulation of bacterial-derived cyclic dimeric adenosine monophosphate (CDA) in nanoscale coordination polymers. Intravenously injected ZnCDA prolonged CDA circulation and efficiently targeted tumors, mediating robust antitumor effects in a diverse set of preclinical cancer models. Moreover, endothelial STING activation promotes the accumulation of ZnCDA in the tumor tissues by amplifying the enhanced permeability and retention (EPR) effect. In this study, we discover that type I IFN is not required for the antitumor effects of STING agonism by ZnCDA, indicating that differentially formulated STING activators may suppress tumor growth in different ways. Using metal- or dye-labelled nanoparticles, we identified a group of tumor-associated macrophages (TAMs) as the cellular target of ZnCDA in the tumor immune microenvironment. RNA-seq analysis indicated the modulation of TAMs for antigen processing and presentation via STING activation. We further showed that TAMs with ZnCDA uptake promoted an antitumor T cell response. Lastly, we utilized two immunologically “cold” tumor models, a fragment Panc02-SIY pancreatic cancer model and an intracranial GL261 glioma model, both of which represent intractable fatal human cancers, to provide a proof-of-concept strategy for combining ZnCDA with immune checkpoint blockade or radiotherapy in aggressive, difficult-to-treat tumors. a grant from the Ludwig Foundation and an NIH grant (R01CA262508) to R.R.W., NIH grants (R01CA223184 and R01CA216436) to W.L. and NIH grants (R35CA232109 and R01AI141333) to J.P.Y.T. A.P. is the recipient of a Walter Benjamin scholarship provided by the German Research Foundation (Deutsche Forschungsgemeinschaft). J.B. was supported by a Clinical Therapeutics Training Grant (T32GM007019).

Modulation of tumor-associated macrophages in colitis-associated colorectal cancer.

Intestinal macrophages are the most abundant immune cells in the small and large intestine, which maintain intestinal homeostasis by clearing invading bacteria and dead cells, secreting anti-inflammatory cytokines, and inducing tolerance to symbiotic bacteria and food particles. In addition, as antigen-presenting cells, they also participate in eliciting adaptive immune responses through bridging innate immune responses. After the intestinal homeostasis is disrupted, the damaged or apoptotic intestinal epithelial cells cannot be effectively cleared, and the infection of exogenous pathogens and leakage of endogenous antigens lead to persistent intestinal inflammation. Long-term chronic inflammation is one of the important causes of colitis-associated carcinogenesis (CAC). Tumor microenvironment (TME) is gradually formed around tumor cells, in which tumor associated macrophage (TAMs) is not only the builder, but also regulated by TME. This review just briefly summarized the role of intestinal macrophages under physiological and pathological inflammatory and cancerous conditions, and current therapeutic strategies for intestinal diseases targeting macrophages.

Osteosarcoma exocytosis of soluble LGALS3BP mediates macrophages toward a tumoricidal phenotype.

This study aimed to elucidate the interactions between osteosarcoma (OS) and M1 macrophages infiltrated into the tumor microenvironment and to explore the underlying mechanisms whereby M1 macrophages influence the growth of OS, so that novel treatments of OS can be developed. A transwell co-culture system, an indirect conditioned medium culture system and two orthotopic bearing OS models were established to assess for the interplay between M1 macrophages and OS. We found that the co-culture of M1 macrophages with OS cells significantly inhibited the growth of the tumor cells by inducing apoptosis. Furthermore, HSPA1L secreted by M1 macrophages exerted this anti-tumor effect through the IRAK1 and IRAK4 pathways. LGALS3BP secreted by OS cells bound to the ligand LGALS3 on M1 macrophages and thereby induced the secretion of Hspa11 via Akt phosphorylation. In vivo experiments demonstrated that the culture supernatant of OS-stimulated M1 macrophages significantly inhibited the growth of OS, whereas silencing Lgals3bp promoted the progression of OS. In conclusion, OS modifies the phenotype of tumor-associated macrophages (TAMs) and thereby influences the apoptosis of OS cells through soluble factors. The modulation of TAMs may be a promising and effective therapeutic approach in OS.

Tumor-associated macrophages (TAMs) modulate response to HER2-targeted agents in a humanized mouse model of breast cancer.

Tumor-associated macrophages (TAM) may participate to antitumor activity of anti-HER2-targeted therapies (Pertuzumab, Trastuzumab) in breast cancers harbouring HER-2 overexpression through antibody-dependent phagocytosis. Additive antitumor effect of concurrent cytotoxic chemotherapies, including Paclitaxel, may be counterbalanced by alteration in TAM infiltrate. The aim of this study is to evaluate the role of TAM in tumor response to anti-HER2-targeted therapies and chemotherapy in an experimental model of HER2-amplified breast cancer. A xenograft mouse model was built by subcutaneous injection of the SKBR-3 human HER2-amplified breast cancer cell line in Hu-CD34+ mice. Animals were randomized to receive weekly administration of Cremophor (control), Trastuzumab+Pertuzumab (TP), and Paclitaxel+Trastuzumab+Pertuzumab (PTP) with or without macrophage depletion with clodronate (C). At week 4, mice were euthanised and tumors were harvested for immunohistochemical analysis of TAM infiltration (RBP-J CD163 and CD68 for M1, M2, and overall TAM, respectively). Tumor size was significantly lower in mice treated with TP, PTP, and PTP+C as compared to control, while no meaningful difference was observed in the TP+C arm. Analysis of TAM infiltrate showed significantly lower CD68 and CD163 expression in PTP, TP+C, and PTP+C as compared to TP and control arm. RBP-J expression was significantly decreased in mice treated with clodronate depletion. Activity of TP is modulated by TAM infiltrate, that is inhibited by concurrent administration of Paclitaxel. To enhance the effect of anti-HER2-targeted therapies and minimize chemotherapy-related side effects, modulation of TAM should be considered in novel therapeutic combinations.

Targeting tumor-associated macrophages for cancer immunotherapy.

Tumor-associated macrophages (TAMs) are one of the most abundant immune components in the tumor microenvironment and play a plethora of roles in regulating tumorigenesis. Therefore, the therapeutic targeting of TAMs has emerged as a new paradigm for immunotherapy of cancer. Herein, the review summarizes the origin, polarization, and function of TAMs in the progression of malignant diseases. The understanding of such knowledge leads to several distinct therapeutic strategies to manipulate TAMs to battle cancer, which include those to reduce TAM abundance, such as depleting TAMs or inhibiting their recruitment and differentiation, and those to harness or boost the anti-tumor activities of TAMs such as blocking phagocytosis checkpoints, inducing antibody-dependent cellular phagocytosis, and reprogramming TAM polarization. In addition, modulation of TAMs may reshape the tumor microenvironment and therefore synergize with other cancer therapeutics. Therefore, the rational combination of TAM-targeting therapeutics with conventional therapies including radiotherapy, chemotherapy, and other immunotherapies is also reviewed. Overall, targeting TAMs presents itself as a promising strategy to add to the growing repertoire of treatment approaches in the fight against cancer, and it is hopeful that these approaches currently being pioneered will serve to vastly improve patient outcomes and quality of life.

Ferroptosis-Strengthened Metabolic and Inflammatory Regulation of Tumor-Associated Macrophages Provokes Potent Tumoricidal Activities.

Modulation of tumor-associated macrophages (TAMs) holds promise for cancer treatment, mainly relying on M1 signaling activation and pro-inflammatory promotion. Nevertheless, the antitumor activity is often limited by the anti-inflammatory factors in the tumor microenvironment. Moreover, the metabolic function of TAMs is also critical to tumor progression. However, there are a few strategies that can simultaneously regulate both inflammatory and metabolic functions to achieve safe and potent antitumor activation of TAMs. Herein, we demonstrate that an iron-based metal organic framework nanoparticle and a ferroptosis-inducing agent synergistically induce mitochondrial alternation in TAMs, resulting in a radical metabolic switch from mitochondrial oxidative phosphorylation to glycolysis, which is resistant to anti-inflammatory stimuli challenge. The ferroptosis stress strengthened by the nanoformulation also drives multiple pro-inflammatory signaling pathways, enabling macrophage activation with potent tumoricidal activities. The ferroptosis-strengthened macrophage regulation strategy present in this study paves the way for TAM-centered antitumoral treatment to overcome the limitations of conventional methods.

A dual macrophage polarizer conjugate for synergistic melanoma therapy

Tumor associated macrophages (TAMs) play a paradoxical role in the fate of aggressive tumors like melanoma. Immune modulation of TAMs from the tumor-permissive M2 phenotype to antitumoral M1 phenotype is an emerging attractive approach in melanoma therapy. Resiquimod is a TLR7/8 agonist that shifts the polarization of macrophages towards M1 phenotype. Bexarotene (BEX) is a retinoid that induce the expression of phagocytic receptors in macrophages besides its ability to downregulate the M2 polarization. However, the clinical use of both agents is hindered by poor pharmacokinetic properties. Here, for the first time we repurposed BEX based on its immunomodulatory properties and combined it with RES by designing hyaluronic acid (HA) conjugates of both drugs that act synergistically as a dual macrophage polarizer to promote the M1 phenotype and suppress the M2 phenotype. This combination enhanced the macrophage secretion of proinflammatory cytokines (IL-6 and TNF-α), while suppressing the production of tumor promoting cytokine CCL22. It enhanced the macrophage phagocytic ability and showed superior inhibitory effects against B16F10 cells. In vivo studies on a mouse melanoma model confirmed the superiority of the dual conjugate compared to the single HA-drug conjugates in suppressing the tumor growth. Immunoprofiling of the excised tumors revealed a significant increase in the M1/M2 ratio of TAMs in mice treated with the dual conjugate. Our intravenously injectable HA conjugate of RES and BEX provides a promising immunotherapeutic combination strategy for resetting the M1/M2 ratio, supporting the tumoricidal activity of TAMs for effective melanoma treatment.

Role of Tumor-Associated Myeloid Cells in Breast Cancer.

Stromal immune cells constitute the tumor microenvironment. These immune cell subsets include myeloid cells, the so-called tumor-associated myeloid cells (TAMCs), which are of two types: tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs). Breast tumors, particularly those in human epidermal growth factor receptor 2 (HER-2)-positive breast cancer and triple-negative breast cancer, are solid tumors containing immune cell stroma. TAMCs drive breast cancer progression via immune mediated, nonimmune-mediated, and metabolic interactions, thus serving as a potential therapeutic target for breast cancer. TAMC-associated breast cancer treatment approaches potentially involve the inhibition of TAM recruitment, modulation of TAM polarization/differentiation, reduction of TAM products, elimination of MDSCs, and reduction of MDSC products. Furthermore, TAMCs can enhance or restore immune responses during cancer immunotherapy. This review describes the role of TAMs and MDSCs in breast cancer and elucidates the clinical implications of TAMs and MDSCs as potential targets for breast cancer treatment.

Abstract PR22: Collagen scavenging alters macrophage phenotype in pancreatic cancer

Abstract A hallmark of pancreatic tumors is their highly desmoplastic stroma composed of fibroblasts, immune cells and a dense network of collagen fibers. Pancreatic tumor-associated macrophages are considered M2 macrophages and are thought to support tumor progression through the engagement of multiple mechanisms that promote immune tolerance. Another well-documented role of M2 macrophages is the remodeling of the tumor stroma via collagen production and degradation, with the latter being mediated by mannose receptor (Mrc1)-mediated endocytosis of collagen. Given our previous work showing that protein scavenging by tumor cells can be utilized as a nutrient delivery mechanism, we set out to investigate the functional significance of collagen scavenging by macrophages. We have found that, in M2 macrophages, Mrc1-mediated collagen internalization and subsequent lysosomal degradation leads to a metabolic reprogramming that is characterized by the accumulation of collagen-derived intracellular free amino acids and an increase in arginine biosynthesis. The increase in arginine levels results in a significant upregulation of inducible nitric oxide synthase (iNOS) and arginase 1 (ARG1), giving rise to an M1/M2 hybrid macrophage. Moreover, iNOS+ARG1+ double-positive macrophages are present in the microenvironment of pancreatic tumors. The functional contribution of this cell population to pancreatic tumorigenesis is being investigated. Our findings suggest a new modality for the functional modulation of tumor-associated macrophages through the coupling of extracellular matrix remodeling to protein scavenging. This abstract is also being presented as Poster A58. Citation Format: Madeleine M. LaRue, Jane Cullis, Dafna Bar-Sagi. Collagen scavenging alters macrophage phenotype in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr PR22.

Low-dose glucocorticoids suppresses ovarian tumor growth and metastasis in an immunocompetent syngeneic mouse model.

Ovarian cancer has the highest mortality rate among gynecologic malignancies. Despite chemotherapy and surgical debulking options, ovarian cancer recurs and disseminates frequently with a poor prognosis. We previously reported a novel role of glucocorticoids (GCs) in metastatic ovarian cancer by upregulating microRNA-708. In this study, we used an immunocompetent syngeneic mouse model and further evaluated the effect and optimal dosages of GCs in treating metastatic ovarian cancer. The treatment of C57BL/6-derived ovarian cancer ID-8 cells with a synthetic GC, dexamethasone (DEX), induced the expression of microRNA-708, leading to decreased cell migration and invasion through targeting Rap1B. Administration of DEX at a low dose, as low as 5 μg/kg body weight, inhibited the primary tumor size and abdominal metastasis in mice bearing ID-8 cell-derived ovarian tumors. In the treated primary tumors, microRNA-708 was upregulated, whereas some proinflammatory cytokines, namely interleukin (IL)-1β and IL-18, were downregulated. The number of tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment were reduced. Overall, our study shows that low-dose GCs can suppress ovarian cancer progression and metastasis likely through not only the upregulation of the metastasis suppressor microRNA-708, but also the modulation of TAMs and MDSCs in the tumor microenvironment.

Novel role of semaphorin 3A in the growth and progression of hepatocellular carcinoma

Semaphorin3A(SEMA3A), a secretory protein, is a founding member of the semaphorin family and functions in both the biological behavior of tumor cells and the modulation of tumor-associated macrophages. However, the role of SEMA3A in hepatocellular carcinoma(HCC) is still not well established. In the present study, we investigated the expression levels of SEMA3A in 80HCC tissues and cell lines, using RT-qPCR, western blotting and immunohistochemistry. Expression profile analysis revealed that SEMA3A was significantly overexpressed in human HCC patients and positively correlated with the metastatic potential of HCC cells. Lentiviral transfection into PLC/PRF/5 and HCCLM3 cells was performed to stably upregulate and downregulate the expression of SEMA3A in HCC cells. Cell Counting Kit-8(CCK-8), wound-healing and invasion assays revealed that SEMA3A promoted the proliferation and migration of HCC cells invitro. Proteome profiler antibody microarray analysis revealed that overexpression of SEMA3A in HCC cells induced a significant increase in the expression levels of gelsolin-like capping protein(CapG), galectin-3, enolase2 and epithelial cell adhesion molecule(EpCAM). Furthermore, the upregulation of SEMA3A in HCC cells promoted tumor growth and progression in an HCC mouse model. These results indicate that SEMA3A enhances CapG, galectin-3, enolase2 and EpCAM expression to promote HCC progression and is a potential therapeutic target for HCC.

Modulation of Tumor-Associated Macrophages (TAM) Phenotype by Platelet-Activating Factor (PAF) Receptor.

Platelet-activating factor (PAF) plays an important role in the pathogenesis of several types of tumors. The biological effects of PAF are mediated by the PAF receptor (PAFR), which can be expressed by tumor cells and host cells that infiltrate the tumor microenvironment. In the present study, we investigated the role of PAFR expressed by leukocytes that infiltrate two types of tumors, one that expresses PAFR (TC-1 carcinoma) and another that does not express the receptor (B16F10 melanoma) implanted in mice that express the receptor or not (PAFR KO). It was found that both tumors grew significantly less in PAFR KO than in wild-type (WT) mice. Analysis of the leukocyte infiltration shown in PAFR KO increased the frequency of neutrophils (Gr1+) and of CD8+ lymphocytes in B16F10 tumors and of CD4+ lymphocytes in TC-1 tumors. PAFR KO also had a higher frequency of M1-like (CD11c+) and lower M2-like (CD206+) macrophages infiltrated in both tumors. This was confirmed in macrophages isolated from the tumors that showed higher iNOS, lower arginase activity, and lower IL10 expression in PAFR KO tumors than WT mice. These data suggest that in the tumor microenvironment, endogenous PAF-like activity molecules bind PAFR in macrophages which acquire an M2-like profile and this promotes tumor growth.

Abstract A17: Modulation of tumor-associated macrophages towards an antitumor phenotype

Abstract An effective anti-tumor immune response is a potentially powerful tool to be deployed against cancer. While the concept of manipulating the immune system to attack cancer cells has been pursued for nearly a century, the main focus has been on manipulating the adaptive immune system, primarily T-cells. While this approach has recently been met with some significant successes, there is also a growing appreciation of the innate immune system in mediating tumor reduction and elimination. In fact, tumor associated macrophages (TAMs) are the most abundant immune population in a tumor. Although M1 macrophages have potent anti-tumor activity, TAMs are phenotypically polarized to M2 macrophages, which support tumors. Clinically, a high tumor density of TAMs has been associated with chemoresistance and a worse clinical outcome. Using a tool, BH3 profiling, that is unique to the Letai Laboratory, we have identified that macrophage phenotype can alter the sensitivity of tumor cells to apoptotic signaling, and in doing so, affect their response to chemotherapy. The Letai Laboratory has developed a unique and novel assay to predict a cancer cell's response to chemotherapy called BH3 profiling. BH3 profiling is used to determine whether a cell is relatively close to the threshold of apoptosis (“primed” for death), or relatively far from the threshold (“unprimed”). We have found that the priming of cancer cells, as measured by BH3 profiling, is by itself a predictor of clinical response to conventional chemotherapy. Using the BH3 profiling strategy, we show for the first time that conditioned media (CM) from M1 macrophages “primes” tumor cells, which correlates to their increased chemosensitivity. Interestingly, we have found some tumor cells to be resistant to CM from M1 macrophages. We have performed gene expression analysis on these two phenotypes of tumor cells, to uncover why some, but not others, are sensitive to M1 macrophages. We are working to validate these findings, as it will be important to know who will benefit from TAM modulation clinically. Additionally, we are working with a novel compound that we have shown modulates TAMs to an anti-tumor phenotype in vivo and induces rapid tumor regression in an immunocompetent mouse model of breast cancer. These results suggest modulating TAMs towards an anti-tumor phenotype may have great promise for cancer therapy. Finally, we are investigating strategies to convert M2 TAMs to a M1 phenotype. We have initiated a high throughput screen (HTS) at the Institute of Chemistry and Cell Biology (ICCB) – Longwood, at Harvard Medical School, to identify small molecules that polarize macrophages to an anti-tumor phenotype. We have identified several interesting small molecules and are working to validate their clinical significance. Citation Format: Jennifer L. Guerriero, Anthony Letai. Modulation of tumor-associated macrophages towards an antitumor phenotype. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A17. doi:10.1158/1538-7445.CHTME14-A17