Tumor-associated Macrophages Cells Research Articles

Correlation of enriched specific subset of immune cells nearby tumor associated macrophage (TAM) with pathologic complete response (pCR) of concurrent chemoradiotherapy followed by nivolumab in locally advanced rectal cancer (LARC).

58 Background: We previously reported tumor-infiltrating lymphocyte (TIL) dynamics predictive of pCR in microsatellite-stable (MSS) LARC. In the current analysis, we investigate whether an immune cell-to-cell spatial network may predict pCR in MSS LARC. Methods: VOLTAGE study is a phase I/II study to evaluate the efficacy of chemoradiotherapy (CRT) followed by nivolumab and subsequent surgery in LARC pts. H&E images and multiplex immunofluorescence (mIF) images containing a total of 35 markers for T cells, TAM, Myeloid-derived suppressor cells, and Dendritic cells were analyzed with the Lunit SCOPE platform (Lunit, Republic of Korea). The proportion of T cells among all DAPI-positive (-pos) cells in a 50-micrometer radius centered on the TAM cells was counted. Results: In the samples of MSS LARC pts gathered at baseline, pre-treatment (n=38), TIL density in tumor microenvironment (TME) analyzed by H&E images was significantly correlated with the proportions of CD8-pos, CD4-pos, and FOXP3-pos cells (coefficient [coeff] 0.635, 0.482, and 0.580, respectively), but loosely correlated with PDL1-pos, PD1-pos, and CTLA4-pos cells (coeff 0.255, 0.174, and 0.180, respectively). Interestingly, intratumoral TIL density was more strongly correlated with TAM markers such as CD68 (coeff 0.269), compared to stromal TIL density (coeff 0.086). pCR rate was 28.9% in all MSS LARC, with baseline TIL density in TME predicting pCR with area under the receiver operating characteristic curve (AUROC) of 0.636 (p = 0.101). Interestingly, the ratio of baseline PDL1-pos cell proportion nearby CD68-pos cells, over that in all TME area (hereafter referred to as 'TAM-PDL1-proximity score') showed the best predictive performance for pCR, with an AUROC of 0.768 (p = 0.005). At the optimal cutoff of 1.66 times TAM-PDL1-proximity score, pCR rates for pts ≥ the cutoff and < the cutoff were 44% (11/25) and 0% (0/13), respectively (p = 0.006). Conclusions: PDL1-expressing immune cells nearby tumor associated macrophages before treatment is a promising predictive biomarker for pCR of neoadjuvant CRT followed by nivolumab in MSS LARC.

Photosensitive and dual-targeted chromium nanoparticle delivering small interfering RNA YTHDF1 for molecular-targeted immunotherapy in liver cancer

Tumor-associated macrophages (TAMs) are a promising target for cancer immunotherapy, but delivering therapeutic agents to TAMs within the tumor microenvironment (TME) is challenging. In this study, a photosensitive, dual-targeting nanoparticle system (M.RGD@Cr-CTS-siYTHDF1 NPs) was developed. The structure includes a shell of DSPE-modified RGD peptides targeting integrin receptors on tumor cells and carboxymethyl mannose targeting CD206 receptors on macrophages, with a core of chitosan adsorbing m6A reading protein YTHDF1 siRNA and chromium nanoparticles (Cr NPs). The approach is specifically designed to target TAM and cancer cells, utilizing the photothermal effect of Cr NPs to disrupt the TME and deliver siYTHDF1 to TAM. In experiments with tumor-bearing mice, M.RGD@Cr-CTS-siYTHDF1 NPs, when exposed to laser irradiation, effectively killed tumor cells, disrupted the TME, delivered siYTHDF1 to TAMs, silenced the YTHDF1 gene, and shifted the STAT3-STAT1 equilibrium by reducing STAT3 and enhancing STAT1 expression. This reprogramming of TAMs towards an anti-tumor phenotype led to a pro-immunogenic TME state. The strategy also suppressed immunosuppressive IL-10 production, increased expression of immunostimulatory factors (IL-12 and IFN-γ), boosted CD8 + T cell infiltration and M1-type TAMs, and reduced Tregs and M2-type TAMs within the TME. In conclusion, the dual-targeting M.RGD@Cr-CTS-siYTHDF1 NPs, integrating dual-targeting capabilities with photothermal therapy (PTT) and RNA interference, offer a promising approach for molecular targeted cancer immunotherapy with potential for clinical application.Graphical

Single-cell transcriptomics reveal distinct immune-infiltrating phenotypes and macrophage–tumor interaction axes among different lineages of pituitary neuroendocrine tumors

BackgroundPituitary neuroendocrine tumors (PitNETs) are common gland neoplasms demonstrating distinctive transcription factors. Although the role of immune cells in PitNETs has been widely recognized, the precise immunological environment and its control over tumor cells are poorly understood.MethodsThe heterogeneity, spatial distribution, and clinical significance of macrophages in PitNETs were analyzed using single-cell RNA sequencing (scRNA-seq), bulk RNA-seq, spatial transcriptomics, immunohistochemistry, and multiplexed quantitative immunofluorescence (QIF). Cell viability, cell apoptosis assays, and in vivo subcutaneous xenograft experiments have confirmed that INHBA-ACVR1B influences the process of tumor cell apoptosis.ResultsThe present study evaluated scRNA-seq data from 23 PitNET samples categorized into 3 primary lineages. The objective was to explore the diversity of tumors and the composition of immune cells across these lineages. Analyzed data from scRNA-seq and 365 bulk RNA sequencing samples conducted in-house revealed the presence of three unique subtypes of tumor immune microenvironment (TIME) in PitNETs. These subtypes were characterized by varying levels of immune infiltration, ranging from low to intermediate to high. In addition, the NR5A1 lineage is primarily associated with the subtype characterized by limited infiltration of immune cells. Tumor-associated macrophages (TAMs) expressing CX3CR1+, C1Q+, and GPNMB+ showed enhanced contact with tumor cells expressing NR5A1 + , TBX19+, and POU1F1+, respectively. This emphasizes the distinct interaction axes between TAMs and tumor cells based on their lineage. Moreover, the connection between CX3CR1+ macrophages and tumor cells via INHBA-ACVR1B regulates tumor cell apoptosis.ConclusionsIn summary, the different subtypes of TIME and the interaction between TAM and tumor cells offer valuable insights into the control of TIME that affects the development of PitNET. These findings can be utilized as prospective targets for therapeutic interventions.

Tumor-associated macrophage subtypes on cancer immunity along with prognostic analysis and SPP1-mediated interactions between tumor cells and macrophages.

Tumor-associated macrophages (TAM) subtypes have been shown to impact cancer prognosis and resistance to immunotherapy. However, there is still a lack of systematic investigation into their molecular characteristics and clinical relevance in different cancer types. Single-cell RNA sequencing data from three different tumor types were used to cluster and type macrophages. Functional analysis and communication of TAM subpopulations were performed by Gene Ontology-Biological Process and CellChat respectively. Differential expression of characteristic genes in subpopulations was calculated using zscore as well as edgeR and Wilcoxon rank sum tests, and subsequently gene enrichment analysis of characteristic genes and anti-PD-1 resistance was performed by the REACTOME database. We revealed the heterogeneity of TAM, and identified eleven subtypes and their impact on prognosis. These subtypes expressed different molecular functions respectively, such as being involved in T cell activation, apoptosis and differentiation, or regulating viral bioprocesses or responses to viruses. The SPP1 pathway was identified as a critical mediator of communication between TAM subpopulations, as well as between TAM and epithelial cells. Macrophages with high expression of SPP1 resulted in poorer survival. By in vitro study, we showed SPP1 mediated the interactions between TAM clusters and between TAM and tumor cells. SPP1 promoted the tumor-promoting ability of TAM, and increased PDL1 expression and stemness of tumor cells. Inhibition of SPP1 attenuated N-cadherin and β-catenin expression and the activation of AKT and STAT3 pathway in tumor cells. Additionally, we found that several subpopulations could decrease the sensitivity of anti-PD-1 therapy in melanoma. SPP1 signal was a critical pathway of communication between macrophage subtypes. Some specific macrophage subtypes were associated with immunotherapy resistance and prognosis in some cancer types.

Integrated Analysis Construct a Tumor-Associated Macrophage Novel Signature with Promising Implications in Predicting the Prognosis and Immunotherapeutic Response of Gastric Cancer Patients.

Gastric cancer (GC) remains one of the most prevalent malignant tumors worldwide. At present, tumor-associated macrophages (TAMs) are essential in the progression, metastasis, and drug resistance of tumors. Therefore, TAMs can be a crucial target for tumor treatment. We intended to investigate the TAM characteristics in GC and develop a risk signature based on TAM to predict the prognosis of GC patients. The single-cell RNA sequencing (scRNA-seq) and bulk RNA-seq data were acquired from a publicly available database. We utilized the Seurat pipeline to process the scRNA-seq data and determine TAM cell types using marker genes. Univariate Cox regression analysis was utilized to examine TAM-related prognostic genes, and then we employed Lasso-Cox regression analysis, and Multivariate Cox regression analysis established a novel risk profile to forecast the clinical value of the model with a new nomogram combining risk profiles and clinicopathological characteristics. The current study employed scRNA-seq data to identify five TAM clusters in GC, among which four were significantly associated with GC prognosis. Accordingly, we further developed a TAM-related risk signature utilizing nine genes. After evaluation, our model accurately predicted the prognosis of gastric cancer. Generally, GC patients with low TAMS scores exhibited a more favorable prognosis, greater benefits from immunotherapy, and higher levels of immune cell infiltration. The prognosis of GC can be effectively predicted by TAM-based risk signatures, and the signature may provide a new perspective for comprehensively guiding clinical diagnosis, prediction, and immunotherapy for gastric cancer.

Complement Activation and Up-Regulated Expression of Anaphylatoxin C3a/C3aR in Glioblastoma: Deciphering the Links with TGF-β and VEGF.

The complement (C) innate immune system has been shown to be activated in the tumor microenvironment of various cancers. The C may support tumor growth by modulating the immune response and promoting angiogenesis through the actions of C anaphylatoxins (e.g., C5a, C3a). The C has important double-edged sword functions in the brain, but little is known about its role in brain tumors. Hence, we analyzed the distribution and the regulated expression of C3a and its receptor C3aR in various primary and secondary brain tumors. We found that C3aR was dramatically upregulated in Grade 4 diffuse gliomas, i.e., glioblastoma multiforme, IDH-wildtype (GBM) and astrocytoma, IDH-mutant, Grade 4, and was much less expressed in other brain tumors. C3aR was observed in tumor-associated macrophages (TAM) expressing CD68, CD18, CD163, and the proangiogenic VEGF. Robust levels of C3a were detected in the parenchyma of GBM as a possible result of Bb-dependent C activation of the alternative C pathway. Interestingly, in vitro models identified TGF-β1 as one of the most potent growth factors that upregulate VEGF, C3, and C3aR in TAM (PMA-differentiated THP1) cell lines. Further studies should help to delineate the functions of C3a/C3aR on TAMs that promote chemotaxis/angiogenesis in gliomas and to explore the therapeutic applications of C3aR antagonists for brain tumors.

Exploring Monocytes-Macrophages in Immune Microenvironment of Glioblastoma for the Design of Novel Therapeutic Strategies

Gliomas are primary malignant brain tumors. These tumors seem to be more and more frequent, not only because of a true increase in their incidence, but also due to the increase in life expectancy of the general population. Among gliomas, malignant gliomas and more specifically glioblastomas (GBM) are a challenge in their diagnosis and treatment. There are few effective therapies for these tumors, and patients with GBM fare poorly, even after aggressive surgery, chemotherapy, and radiation. Over the last decade, it is now appreciated that these tumors are composed of numerous distinct tumoral and non-tumoral cell populations, which could each influence the overall tumor biology and response to therapies. Monocytes have been proved to actively participate in tumor growth, giving rise to the support of tumor-associated macrophages (TAMs). In GBM, TAMs represent up to one half of the tumor mass cells, including both infiltrating macrophages and resident brain microglia. Infiltrating macrophages/monocytes constituted ~ 85% of the total TAM population, they have immune functions, and they can release a wide array of growth factors and cytokines in response to those factors produced by tumor and non-tumor cells from the tumor microenvironment (TME). A brief review of the literature shows that this cell population has been increasingly studied in GBM TME to understand its role in tumor progression and therapeutic resistance. Through the knowledge of its biology and protumoral function, the development of therapeutic strategies that employ their recruitment as well as the modulation of their immunological phenotype, and even the eradication of the cell population, can be harnessed for therapeutic benefit. This revision aims to summarize GBM TME and localization in tumor niches with special focus on TAM population, its origin and functions in tumor progression and resistance to conventional and experimental GBM treatments. Moreover, recent advances on the development of TAM cell targeting and new cellular therapeutic strategies based on monocyte/macrophages recruitment to eradicate GBM are discussed as complementary therapeutics.

“Two birds with one stone” strategy for the lung cancer therapy with bioinspired AIE aggregates

Aggregation-induced emission luminogens (AIEgens) have emerged as novel phototherapeutic agents with high photostability and excellent performance to induce photodynamic and/or photothermal effects. In this study, a zwitterion-type NIR AIEgens C41H37N2O3S2 (named BITT) with biomimetic modification was utilized for lung cancer therapy. The tumor-associated macrophage (TAM)-specific peptide (CRV) was engineered into the lung cancer cell-derived exosomes. The CRV-engineered exosome membranes (CRV-EM) were obtained to camouflage the BITT nanoparticles (CEB), which targeted both lung cancer cells and TAMs through homotypic targeting and TAM-specific peptide, respectively. The camouflage with CRV-EM ameliorated the surface function of BITT nanoparticles, which facilitated the cellular uptake in both cell lines and induced significant cell death in the presence of laser irradiations in vitro and in vivo. CEB showed improved circulation lifetime and accumulations in the tumor tissues in vivo, which induced efficient photodynamic and photothermal therapy. In addition, CEB induced the tumor microenvironment remodeling as indicated by the increase of CD8 + and CD4 + T cells, as well as a decrease of M2 TAM and Myeloid-derived suppressor cells (MDSCs). Our work developed a novel style of bioinspired AIE aggregates, which could eliminate both lung cancer cells and TAMs, and remodel the tumor environments to achieve an efficient lung cancer therapy. To the best of our knowledge, we are the first to use this style of bioinspired AIE aggregates for photo-mediated immunotherapy in lung cancer therapy.

ETV1 inhibition depressed M2 polarization of tumor-associated macrophage and cell process in gastrointestinal stromal tumor via down-regulating PDE3A.

M2-type polarization of tumor associated-macrophage (TAM) is involved in the malignancy of gastrointestinal stromal tumor (GIST) progression. ETS variant 1 (ETV1) has been previously validated to regulate GIST pathogenesis. Our study intended to explore the role and mechanism of ETV1 in mediating the M2-polarization of TAM in GIST progression. First, we analyzed the correlation between ETV1 expression and M2-polarization in GIST tissues. IL-4 was used to treat THP-1-derived TAM cells and IL-4-stimulated TAM were co-cultured with GIST-T1 cells to mimic the GIST microenvironment. A loss-of-function assay was performed to explore the role of ETV1. Results showed that ETV1 elevation was positively correlated with M2-polarization. IL-4-induced TAM promoted ETV1 expression, silencing ETV1 inhibited proliferation, invasion and KIT activation in IL-4-treated GIST cells, while cell apoptosis was enhanced. Besides, co-culture of ETV1-silenced GIST cells significantly depressed M2-polarization in TAM, presented as decreased levels of CD206, Agr-1 and cytokines, as well as the proportion of CD206-positive TAM. PDE3A was positively correlated with ETV1 and M2-polarization. Overexpressing PDE3A reversed the inhibitory effects of ETV1 silencing. Generally, ETV1 inhibition depressed M2-polarization of TAM in GIST and its promotion on pathological aggravation via down-regulating PDE3A. This evidence may provide a new target for GIST regulation.

Prostacyclin Released by Cancer-Associated Fibroblasts Promotes Immunosuppressive and Pro-Metastatic Macrophage Polarization in the Ovarian Cancer Microenvironment.

Metastasis of high-grade ovarian carcinoma (HGSC) is orchestrated by soluble mediators of the tumor microenvironment. Here, we have used transcriptomic profiling to identify lipid-mediated signaling pathways encompassing 41 ligand-synthesizing enzymes and 23 cognate receptors in tumor, immune and stroma cells from HGSC metastases and ascites. Due to its strong association with a poor clinical outcome, prostacyclin (PGI2) synthase (PTGIS) is of particular interest in this signaling network. PTGIS is highly expressed by cancer-associated fibroblasts (CAF), concomitant with elevated PGI2 synthesis, whereas tumor-associated macrophages (TAM) exhibit the highest expression of its surface receptor (PTGIR). PTGIR activation by PGI2 agonists triggered cAMP accumulation and induced a mixed-polarization macrophage phenotype with altered inflammatory gene expression, including CXCL10 and IL12A repression, as well as reduced phagocytic capability. Co-culture experiments provided further evidence for the interaction of CAF with macrophages via PGI2, as the effect of PGI2 agonists on phagocytosis was mitigated by cyclooxygenase inhibitors. Furthermore, conditioned medium from PGI2-agonist-treated TAM promoted tumor adhesion to mesothelial cells and migration in a PTGIR-dependent manner, and PTGIR activation induced the expression of metastasis-associated and pro-angiogenic genes. Taken together, our study identifies a PGI2/PTGIR-driven crosstalk between CAF, TAM and tumor cells, promoting immune suppression and a pro-metastatic environment.

Telomere-Associated Changes in Nuclear Architecture of Cancer-Associated Macrophage-like Cells in Liquid Biopsies from Melanoma Patients.

During phagocytosis, tumor-associated macrophages (TAMs) can incorporate genetic material from tumor cells. The incorporation of extra genetic material may be responsible for advanced malignant behavior observed in some TAMs, making TAMs potentially important players in cancer progression. More recently, similar cells were described in the blood as cancer-associated macrophage-like cells (CAMLs). CAMLs may be equivalent to TAMs cells in the blood, and they express macrophage markers. However, their origin is still unclear. In a previous study, we showed for the first time the distinct telomere 3D structure of circulating tumor cells (CTCs) in melanoma and other cancers. In the present pilot study, we investigated, comparatively, the 3D telomere structure of CAMLs, CTCs and leucocytes from nine melanoma patients with metastatic cutaneous melanoma stage IV. CTC capture was performed by size-based filtration followed by cytological and immunocytological evaluation. Three-dimensional Quantitative Fluorescent in situ Hybridization was performed to measure differences in five 3D telomere parameters. Telomere parameters, such as number, length, telomere aggregates, nuclear volume, and a/c ratio, were compared among different cellular types (CTCs, CAMLs, and normal leucocytes). Three telomere parameters were significantly different between CAMLs and leucocytes. The combination of two telomere parameters (telomere length against the number of telomeres) resulted in the identification of two CAMLs subpopulations with different levels of genomic instability. Those populations were classified as profile 1 and 2. Profile 2, characterized by a high number of short telomeres, was observed in four of the nine melanoma patients. To our knowledge, this is the first pilot study to investigate 3D telomere parameters as hallmarks of nuclear architecture in CAMLs’ population in comparison to leucocytes from the same patient. Further studies involving a larger patient sample size are necessary to validate these findings and explore their potential prognostic value.

Molecular mechanism of CD163+ tumor-associated macrophage (TAM)-derived exosome-induced cisplatin resistance in ovarian cancer ascites

BackgroundStudies have found that tumor-associated macrophages (TAMs) in the malignant ascites of patients with serous ovarian cancer exhibit a mixed polarization phenotype and highly variable expression of the surface marker CD163. The exosomes secreted by mesenchymal cells can be taken up by tumor cells, affecting the malignant biological behavior of them.MethodsUsing reverse transcription-polymerase chain reaction (RT-PCR) to detect the genes expression of drug resistance related factors cancer stem cells (CSCs)/multidrug resistance (MDR)/epithelial-mesenchymal transition (EMT) after CD163+ TAMs exosomes in ovarian cancer ascites co-cultured with A2780 and A2780/cis-diamminedichloroplatinum (DDP). Differences of the level of miR-221-3p expression between CD163+ TAMs cells (M2) and peripheral blood mononuclear cells M0 detect by microarray screening, and bioinformatics analysis predicts that its target gene is ADAMTS6. Western blot (WB) and immunohistochemical detection of ADAMTS6 expression level in epithelial ovarian cancer (EOC) clinical sample tissues, and analysis of the ADAMTS6 expression in ovarian cancer tissues and its correlation with clinicopathological factors. WB was used to detect the expression of AKT pathway and downstream EMT-related molecules [SNAIL1, ZEB1, Vimentin (VIM)] after co-culture of CD163+ TAMs exosomes with ovarian cancer cell lines A2780, A2780/DDP. WB detects the expression of EGFR and TGF-β1 upstream molecules of the AKT signaling pathway (AKT-pAKT) and downstream EMT molecules (SNAIL1, ZEB1, VIM) after overexpression of ADAMTS6 in A2780 and A2780/DDP.ResultsWe demonstrated that after CD163+ TAM exosomes were taken up by EOC cells, the highly expressed miR-221-3p could downregulate the level of ADAMTS6, further activate the AKT signaling pathway, and increase the expression of EMT transcription factors SNAIL1 and ZEB1 and the mesothelial marker VIM. Decreased expression of the epithelial marker E-cadherin induced EMT, triggering a switch to a CSC-like phenotype and MDR, thereby promoting EOC cell proliferation, adhesion, migration, and resistance. Compared with benign ovarian tumors, ADAMTS6 expression was low in EOC tissues and was closely related to the clinical stage, age, and survival curve of ovarian cancer patients.ConclusionsOverexpression of ADAMTS6 reduced the IC50 of cisplatin in ovarian cancer cells. The mechanism may be related to the inhibition of EMT mediated by the EGFR/TGF-β/AKT pathway of EOC cells, which has potential value in the treatment of ovarian cancer.

Spindle pole body component 25 and platelet-derived growth factor mediate crosstalk between tumor-associated macrophages and prostate cancer cells.

Tumor-associated macrophages (TAMs) are involved in the growth of prostate cancer (PrC), while the molecular mechanisms underlying the interactive crosstalk between TAM and PrC cells remain largely unknown. Platelet-derived growth factor (PDGF) is known to promote mesenchymal stromal cell chemotaxis to the tumor microenvironment. Recently, activation of spindle pole body component 25 (SPC25) has been shown to promote PrC cell proliferation and is associated with PrC stemness. Here, the relationship between SPC25 and PDGF in the crosstalk between TAM and PrC was investigated. Significant increases in both PDGF and SPC25 levels were detected in PrC specimens compared to paired adjacent normal prostate tissues. A significant correlation was detected between PDGF and SPC25 levels in PrC specimens and cell lines. SPC25 increased PDGF production and tumor cell growth in cultured PrC cells and in xenotransplantation. Mechanistically, SPC25 appeared to activate PDGF in PrC likely through Early Growth Response 1 (Egr1), while the secreted PDGF signaled to TAM through PDGFR on macrophages and polarized macrophages, which, in turn, induced the growth of PrC cells likely through their production and secretion of transforming growth factor β1 (TGFβ1). Thus, our data suggest that SPC25 triggers the crosstalk between TAM and PrC cells via SPC25/PDGF/PDGFR/TGFβ1 receptor signaling to enhance PrC growth.

Abstract 2053: Phenotypic and functional analyses of response of lung tumor-associated myeloid cells to systemic oncolytic virotherapy

Abstract Introduction: Oncolytic virotherapy represents a promising cancer treatment modality. One of the appeals of oncolytic virotherapy approaches is the capacity of viruses to change tumor microenvironment, frequently interpreted as de-polarization of tumor-associated macrophages (TAMs) from highly pro-tumorigenic to less pro-tumorigenic phenotypes. The goal of this study was to analyze how systemic therapy with oncolytic adenovirus AVID-317 modulates complexity, phenotypes, and pro-tumorigenic function of tumor-associated myeloid cells in a mouse model of orthotopic metastatic lung cancer. Methods: We utilized single cell RNAseq and a 37-marker mass-cytometry (Cy-TOF) analyses to explore phenotypic and functional states of distinct myeloid cell populations in the lungs of tumor-bearing mice before and after virotherapy. We further performed correlation analyses to reveal functional contribution of each identified myeloid cell population to tumor control or tumor progression after virotherapy on a large groups of mice treated with the virus (N=43) or buffer (N=23). Summary of the results: Our phenotypic immunoprofiling identified 13 discrete TAM and DCs cell populations and 5 discrete populations of granulocytic cells, which were present in the lungs of lung tumor-bearing mice prior to virotherapy treatment. We found that in all TAM populations, the expression of CD274, ARG1, IL-10, and surprisingly, CD127 correlated with a higher tumor burden. In 7 out of 13 TAM populations, virotherapy further increased the expression of these pro-tumorigenic markers. Moreover, virotherapy led to a significant increase in the abundance of TAMs that correlated with tumor burden increase. In addition, in response to virotherapy, TAMs increased the expression of pro-tumorigenic growth factors. These data indicate the virotherapy indeed activated TAMs but did not trigger their de-polarization to lesser pro-tumorigenic phenotypes. To find whether virus-induced tumor cell death may drive TAM activation, we next treated tumor-bearing mice with a UV-inactivated AVID-317 virus that lacks the capacity of killing tumor cells. Our analyses confirmed that virus-mediated tumor cells death but not the exposure of TAMs to the virus drives TAM activation. Conclusion: Our analyses showed that oncolytic virotherapy activates TAMs, which in response produce pro-tumorigenic growth factors that may promote tumor progression. Our findings do not support the universal assumption of de-polarization of TAMs to a lesser pro-tumorigenic phenotypes in response to oncolytic virotherapy. The clinical success of oncolytic virotherapy will require careful consideration of the TAM activation in response to virotherapy and finding effective drug combinations to suppress pro-tumorigenic function of myeloid cells prior to administration of viruses with potent anti-tumor activity. Citation Format: Svetlana Atasheva, Jia Yao, Dmitry Shayakhmetov. Phenotypic and functional analyses of response of lung tumor-associated myeloid cells to systemic oncolytic virotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2053.

Abstract 3123: Cancer-associated fibroblasts and tumor-associated macrophages cooperate to promote TGF-β1-dependent NFkB activation and IL6 production and immune escape

Abstract The individual contribution of tumor-associated macrophages (TAM) and cancer-associated fibroblasts (CAF), and their precursors mesenchymal stromal cells (MSC) to a pro-tumorigenic and immune-suppressive tumor microenvironment (TME) in neuroblastoma (NB) is well known. However, whether and how they could cooperate has not been studied in this cancer. This important question, in the context of current immunotherapies for NB, has been addressed here in complementary studies evaluating the TME landscape in primary human NB tumors and examining the production of cytokines/chemokines and the activation of signaling pathways in NB cells in the presence of human monocytes and MSC-CAF in vitro and in vivo. A multiplex immunohistochemistry evaluation of 17 untreated human NB tumors demonstrated the presence of MSC-CAF and TAM representing between 0.5% to 7.4% and 0.4% to 8.4% of the total cell population respectively. MSC-CAF were predominantly present in the stroma around NB cells, while TAM diffusely infiltrated tumors. There was a paucity of infiltrating T cells and NK cells (0.7% and 0.1% of total cells, respectively) in all tumors. MSC-CAF promoted in vitro the survival of human monocytes and TAM through their production of IL6 and soluble IL6 receptor. When co-cultured with NB cells, MSC-CAF and monocytes increased the production of pro-tumorigenic cytokines/chemokines like TGFβ1, IL6, IL8, IL10, CCL2/MCP-1 and induced a high expression in MYCN amplified NB cells and TME cells. In contrast they did not stimulate the production of anti-tumorigenic cytokines like IFNγ, TNFα and IL12. Among these multiple cytokines, we demonstrated the central role of TGFβ1 which induced the expression of IL6 in NB cells and in MSC-CAF. Mechanistically, we demonstrated that production of IL6 in NB cells was dependent on the activation of NFκB by TGFβ1 via TAK1 and SMAD2 signaling pathways. In contrast, in MSC, the production of IL6 was dependent on the transcriptional activity of SMAD2/SMAD4 but independent of NFκB. Moreover, the significant increase in TGFβ1 production and secretion to a level only observed in co-cultures of MSC-CAF, TAM and NB cells led to inhibition of NK cell-mediated NB cytotoxicity. Increased TGFβ1, NFκB and IL6 activities were also detected in NB tumors implanted in immunodeficient mice in the presence of human MSC-CAF and monocytes and in primary human NB tumors where we observed a direct correlation between pSMAD2, pSTAT3, and the presence of α-SMA positive MSC-CAF. Our results emphasize the importance of the synergistic role of TAM and CAF in promoting immune escape and resistance to immunotherapies, and the need to define the TME of tumors in patients with NB in order to improve immunotherapies. Citation Format: Kevin Louault, Tania Porras, Meng-Hua Lee, Sakunthala Muthugounder, Rebekah Kennedy, Laurence Sarte, Gerardo E. Fernandez, Bruce Pawel, Hiroyuki Shimada, Shahab Asgharzadeh, Yves A. Declerck. Cancer-associated fibroblasts and tumor-associated macrophages cooperate to promote TGF-β1-dependent NFkB activation and IL6 production and immune escape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3123.

SIGLEC15 amplifies immunosuppressive properties of tumor-associated macrophages in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) usually presents infrequent infiltration of T lymphocytes. The known immune-checkpoint inhibitors to date focus on activating T cells and manifest limited effectiveness in PDAC. SIGLEC15 was identified as a novel tumor-associated macrophage (TAM)-related immune-checkpoint in other cancer types, while its immunosuppressive role and clinical significance remained unclear in PDAC. In our study, SIGLEC15 presented immunosuppressive relevance in PDAC via bioinformatic analysis and expressed on TAM and PDAC cells. SIGLEC15+ TAM, rather than SIGLEC15+ PDAC cells or SIGLEC15- TAM, correlated with poor prognosis and immunosuppressive microenvironment in the PDAC microarray cohort. Compared with SIGLEC15- TAM, SIGLEC15+ TAM presented an M2-like phenotype that could be modulated by SIGLEC15 in a tumor cell-dependent manner. In mechanism, SIGLEC15 interacted with PDAC-expressed sialic acid, preferentially α-2, 3 sialic acids, to stimulate SYK phosphorylation in TAM, which further promoted its immunoregulatory cytokines and chemokines production. In vivo, SIGLEC15+ TAM also presented an M2-like phenotype, accelerated tumor growth, and facilitated immunosuppressive microenvironment, which was greatly abolished by SYK inhibitor. Our study highlighted a novel M2-promoting function of SIGLEC15 and strongly suggested SIGLEC15 as a potential immunotherapeutic target for PDAC.

Comparative effects of free doxorubicin, liposome encapsulated doxorubicin and liposome co-encapsulated alendronate and doxorubicin (PLAD) on the tumor immunologic milieu in a mouse fibrosarcoma model.

Background: We have previously shown that alendronate, an amino-bisphosphonate, when reformulated in liposomes, can significantly enhance the efficacy of cytotoxic chemotherapies and help remodel the immunosuppressive tumor microenvironment towards an immune-permissive milieu resulting in increased anticancer efficacy. In addition, we have previously shown that the strong metal-chelating properties of alendronate can be exploited for nuclear imaging of liposomal biodistribution. To further improve anticancer efficacy, a pegylated liposome formulation co-encapsulating alendronate and doxorubicin (PLAD) has been developed. In this study, we examined the effects of PLAD on the tumor immunologic milieu in a mouse fibrosarcoma model in which the tumor microenvironment is heavily infiltrated with tumor-associated macrophages (TAM) that are associated with poor prognosis and treatment resistance.Methods: Doxorubicin biodistribution, characterization of the tumor immunologic milieu, cellular doxorubicin uptake, and tumor growth studies were performed in Balb/c mice bearing subcutaneously implanted WEHI-164 fibrosarcoma cells treated intravenously with PLAD, pegylated liposomal doxorubicin (PLD), free doxorubicin, or vehicle.Results: PLAD delivery resulted in a high level of tumor doxorubicin that was 20 to 30-fold greater than in free doxorubicin treated mice, and non-significantly higher than in PLD treated mice. PLAD also resulted in increased uptake in spleen and slightly lower plasma levels as compared to PLD. Importantly, our results showed that PLAD, and to a lesser extent PLD, shifted cellular drug uptake to TAM and to monocytic myeloid-derived suppressor cells (MDSC), while there was no drug uptake in neutrophilic MDSC or lymphoid cells. Free doxorubicin cellular drug uptake was below detectable levels. PLAD, and to a lesser extent PLD, also induced significant changes in number and functionality of tumor-infiltrating TAM, MDSC, Treg, NKT, and NK cells that are consistent with enhanced antitumor immune responses in the tumor microenvironment. In contrast, free doxorubicin induced moderate changes in the tumor microenvironment that could promote (decreased Treg) or be detrimental to antitumor immune responses (decreased M1 TAM and NK cells). These immune modulatory effects are reflected in the therapeutic study which showed that PLAD and PLD inhibited tumor growth and significantly prolonged survival, while free doxorubicin showed little or no anticancer activity.Conclusion: We show that liposomal delivery of doxorubicin not only alters pharmacokinetics, but also dramatically changes the immune modulatory activity of the drug cargo. In addition, our data support that the PLAD nanotheranostic platform further enhances some immune changes that may act in synergy with its cytotoxic chemotherapy effects.

The Role of Tumor-Associated Macrophages in Hematologic Malignancies.

Simple SummaryTumor-associated macrophages (TAM) represent a leading component of the tumor microenvironment in hematologic malignancies. TAM could display antitumor activity or, conversely, could contribute to tumor growth and survival, depending on their polarization. TAM are polarized towards form M1, with a pro-inflammatory phenotype and an antineoplastic activity, or M2, with an alternately activated phenotype, associated with a poor outcome in patients presenting with leukemia, lymphoma or multiple myeloma. The molecular mechanisms of TAM in different types of hematologic malignancies are different due to the peculiar microenvironment of each disease. TAM could contribute to tumor progression, reduced apoptosis and angiogenesis; a different TAM polarization could explain a reduced treatment response in patients with a similar disease subtype. The aim of our review is to better define the role of TAM in patients with leukemia, lymphoma or multiple myeloma. Finally, we would like to focus on TAM as a possible target for antineoplastic therapy.The tumor microenvironment includes dendritic cells, T-cytotoxic, T-helper, reactive B-lymphoid cells and macrophages; these reactive cells could interplay with malignant cells and promote tumor growth and survival. Among its cellular components, tumor-associated macrophages (TAM) represent a component of the innate immune system and play an important role, especially in hematologic malignancies. Depending on the stimuli that trigger their activation, TAM are polarized towards form M1, contributing to antitumor responses, or M2, associated with tumor progression. Many studies demonstrated a correlation between TAM, disease progression and the patient’s outcome in lymphoproliferative neoplasms, such as Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL), even if with conflicting results. A critical hurdle to overcome is surely represented by the heterogeneity in the choice of the optimal markers and methods used for TAM analysis (gene-expression profile vs. immunohistochemistry, CD163vs. CD68vs. CD163/CD68 double-positive cells). TAM have been recently linked to the development and progression of multiple myeloma and leukemia, with a critical role in the homing of malignant cells, drug resistance, immune suppression and angiogenesis. As such, this review will summarize the role of TAM in different hematologic malignancies, focusing on the complex interplay between TAM and tumor cells, the prognostic value of TAM and the possible TAM-targeted therapeutic strategies.

CAFs Interacting With TAMs in Tumor Microenvironment to Enhance Tumorigenesis and Immune Evasion.

Cancer associated fibroblasts (CAFs) and tumor associated macrophages (TAMs) are among the most important and abundant players of the tumor microenvironment. CAFs as well as TAMs are known to play pivotal supportive roles in tumor growth and progression. The number of CAF or TAM cells is mostly correlated with poor prognosis. Both CAFs and TAMs are in a reciprocal communication with the tumor cells in the tumor milieu. In addition to such interactions, CAFs and TAMs are also involved in a dynamic and reciprocal interrelationship with each other. Both CAFs and TAMs are capable of altering each other’s functions. Here, the current understanding of the distinct mechanisms about the complex interplay between CAFs and TAMs are summarized. In addition, the consequences of such a mutual relationship especially for tumor progression and tumor immune evasion are highlighted, focusing on the synergistic pleiotropic effects. CAFs and TAMs are crucial components of the tumor microenvironment; thus, they may prove to be potential therapeutic targets. A better understanding of the tri-directional interactions of CAFs, TAMs and cancer cells in terms of tumor progression will pave the way for the identification of novel theranostic cues in order to better target the crucial mechanisms of carcinogenesis.

Abstract PS16-16: B-catenin-ccl2 axis regulates breast cancer stem cells via crosstalk between cancer cells and tumor-associated macrophages

Abstract Breast cancer is most frequently diagnosed cancer among women worldwide. Though advance in diagnosis and treatment strategies have prolonged disease-free survival (DFS) and overall survival (OS) for different molecular types of breast cancer patients, many patients initially benefit from chemotherapy but experience recurrence, metastasis, and ultimately death. Breast cancer stem cells (BCSCs) are tumor initiating cells with self-renewal, low differentiation, and high tumorigenicity and metastasis abilities. The ineffectiveness of conventional chemotherapy to eradicate BCSCs frequently results in therapy failure. Therefore, understanding the molecular pathways sustaining BCSC characteristics and targeting BCSCs will ultimately improve breast cancer treatments. Here, we found that activation of β-Catenin directly regulated CCL2 expression at the transcriptional level, and in turn, promoted tumor-associated macrophage (TAM) infiltration and M2 polarization. Moreover, crosstalk between the TAM and breast cancer cells increased secretion of CCL2, which promoted cancer progression by regulating BCSCs characteristics through feedback activation of β-Catenin. The combined inhibition of CCR2 and β-catenin synergistically suppressed breast cancer growth. The results described herein provide novel insights into our understanding how the β-Catenin-CCL2 feedback loop mediates the crosstalk between cancer stem cells and tumor-associated macrophages. They may also facilitate the development of useful therapeutic targets against BCSCs for breast cancer therapy. Citation Format: Hao Liu, Bolin Liu. B-catenin-ccl2 axis regulates breast cancer stem cells via crosstalk between cancer cells and tumor-associated macrophages [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-16.