Recruitment Of Tumor-associated Macrophages Research Articles

Hyperglycemia-Induced miR-467 Drives Tumor Inflammation and Growth in Breast Cancer.

The tumor microenvironment contains the parenchyma, blood vessels, and infiltrating immune cells, including tumor-associated macrophages (TAMs). TAMs affect the developing tumor and drive cancer inflammation. We used mouse models of hyperglycemia and cancer and specimens from hyperglycemic breast cancer (BC) patients to demonstrate that miR-467 mediates the effects of high blood glucose on cancer inflammation and growth. Hyperglycemic patients have a higher risk of developing breast cancer. We have identified a novel miRNA-dependent pathway activated by hyperglycemia that promotes BC angiogenesis and inflammation supporting BC growth. miR-467 is upregulated in endothelial cells (EC), macrophages, BC cells, and in BC tumors. A target of miR-467, thrombospondin-1 (TSP-1), inhibits angiogenesis and promotes resolution of inflammation. Systemic injections of a miR-467 antagonist in mouse models of hyperglycemia resulted in decreased BC growth (p < 0.001). Tumors from hyperglycemic mice had a two-fold increase in macrophage accumulation compared to normoglycemic controls (p < 0.001), and TAM infiltration was prevented by the miR-467 antagonist (p < 0.001). BC specimens from hyperglycemic patients had increased miR-467 levels, increased angiogenesis, decreased levels of TSP-1, and increased TAM infiltration in malignant breast tissue in hyperglycemic vs. normoglycemic patients (2.17-fold, p = 0.002) and even in normal breast tissue from hyperglycemic patients (2.18-fold increase, p = 0.04). In malignant BC tissue, miR-467 levels were upregulated 258-fold in hyperglycemic patients compared to normoglycemic patients (p < 0.001) and increased 56-fold in adjacent normal tissue (p = 0.008). Our results suggest that miR-467 accelerates tumor growth by inducing angiogenesis and promoting the recruitment of TAMs to drive hyperglycemia-induced cancer inflammation.

From the Editor’s Desk...

From the Editor’s Desk...

TAp73 represses NF-κB–mediated recruitment of tumor-associated macrophages in breast cancer

Infiltration of tumor-promoting immune cells is a strong driver of tumor progression. Especially the accumulation of macrophages in the tumor microenvironment is known to facilitate tumor growth and to correlate with poor prognosis in many tumor types. TAp73, a member of the p53/p63/p73 family, acts as a tumor suppressor and has been shown to suppress tumor angiogenesis. However, what role TAp73 has in regulating immune cell infiltration is unknown. Here, we report that low levels of TAp73 correlate with an increased NF-κB-regulated inflammatory signature in breast cancer. Furthermore, we show that loss of TAp73 results in NF-κB hyperactivation and secretion of Ccl2, a known NF-κB target and chemoattractant for monocytes and macrophages. Importantly, TAp73-deficient tumors display an increased accumulation of protumoral macrophages that express the mannose receptor (CD206) and scavenger receptor A (CD204) compared to controls. The relevance of TAp73 expression in human breast carcinoma was further accentuated by revealing that TAp73 expression correlates negatively with the accumulation of protumoral CD163+ macrophages in breast cancer patient samples. Taken together, our findings suggest that TAp73 regulates macrophage accumulation and phenotype in breast cancer through inhibition of the NF-κB pathway.

Abstract PS4-37: A pro-tumorigenic mechanism of M2 tumor-associated macrophages (TAM) in triple-negative breast cancer

Abstract Introduction:Triple-Negative Breast Cancer (TNBC) comprises approximately 30% of all breast cancers in Indian women. Given their aggressive nature, TNBCs have high rates of systemic metastasis and mortality with only chemotherapy available for treatment. The success of immunotherapy in solid tumors has raised the hope for their utility in TNBCs as well. But only a subset of patients have a clinical response to check-point inhibitors. The cellular and molecular mechanisms that mediate the immunological response or tolerance are just beginning to be understood. Compared to ER/PR+ breast cancer, TNBC features a unique tumor microenvironment (TME) characterized by a large number of tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs). The density of TILs in and of themselves do not accurately predict response to neoadjuvant chemotherapy or survival. M2 tumor-associated macrophages (M2-TAMs) have been reported to associate with solid tumors to facilitate epithelial to mesenchymal transition (EMT), tumor invasiveness, metastasis, and resistance to therapy. In this study, we have characterized presence of M2-TAM in the TNBC immune environment by examining expression of several biomarkers. Methods:Surgically excised tumor specimens from 88 Indian women with TNBC were accessed from the longitudinal observational series of SJNAHS tissue bank under IERB approved protocols and assayed on nCounter® PanCancer Immune Profiling Panel which comprised of 740 genes and characterises 14 different immune cell types. Transcriptome analysis using Non-negative Matrix factorization (NMF) based unsupervised clustering was done to arrive at stable subtypes characterized by different tumour microenvironments within TNBC. CIEBERSORT tool was used to analyse for distribution of cell types. Identification of macrophages was done by Immunohistochemistry (IHC) for CD68 and CD163 markers in TNBCs and a control group of ER+HER2-.Results:NMF analysis with an enriched immune gene signature of 111 genes, yielded 3 subtypes (ST) (37%, 27% and 36% with relative proportions of ST1, ST2 and ST3) within the TNBC. The three subtypes had distinct survival patterns with ST1 having the best prognosis with enriched TH1 gene signature and ST3 had poorest (log rank p=0.5). On application of this gene signature to TNBC groups in METABRIC and TCGA data, similar pattern emerged with a significant survival pattern of ST 3 having the poorest outcome (p=0.005). A closer examination of ST 3 revealed a signature enriched for M2 macrophages also known as TAM. Immunohistochemistry for Pan macrophage marker CD68 and an M2 specific marker CD163 between TNBC and ER/PR+ revealed difference in the two groups was significantly different (Mann Whitney p=0.03), with TNBC exhibiting 2.4 fold higher expression of CD163. CD 68, was enriched in ST2 and ST3. CD163 which is an M2 specific marker was highest in ST3 as compared to ST 1&amp; 2 (p=0.04). This group also correlated with signal molecules secreted by macrophages containing growth factors, cytokines and chemokines, such as TGF-β, VEGF, IL-10 and CXCL and interleukins like IL4 and IL6 suggestive of TAM recruitment and polarization. It is likely that the TAM enriched subgroup is likely to be unresponsive to PD1/PDL1 inhibitors but could be targeted by novel therapeutic strategies to directly target M2-TAM. In vitro and In vivo analysis to target M2-TAM to evaluate the response to these therapeutic compounds in cell lines as well as a mouse syngeneic model is underway.Conclusions and future directions: As a cell type within the tumor microenvironment, that promotes invasion, M2-TAMs makes an ideal therapeutic target in TNBC. In addition, this sub-type lends itself to easy identification by a simple IHC assay. Citation Format: Aruna Korlimarla, Jyothi Prabhu, Chantirika Ragulan, Gnanapriya Shivakumar, Krisha Desai, Maggie Cheang, Srinath BS, Ravi Diwakar, Sandhya Apachu, Rekha Kumar, TS Sridhar, Savitha RajaRajan, Rohini Kaluve, Annie Alexander, Anguraj Sadanandam. A pro-tumorigenic mechanism of M2 tumor-associated macrophages (TAM) in triple-negative breast cancer [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 PS4-37.

A novel lymphatic pattern promotes metastasis of cervical cancer in a hypoxic tumour-associated macrophage-dependent manner

Lymphatic remodelling in the hypoxic tumour microenvironment (TME) is critically involved in the metastasis of cervical squamous cell carcinoma (CSCC); however, its underlying mechanisms remain unclear. Here, we uncovered a novel lymphatic pattern in the hypoxic TME, wherein lymphatic vessels (LVs) are encapsulated by tumour-associated macrophages (TAMs) to form an interconnected network. We describe these aggregates as LVEM (LVs encapsulated by TAMs) considering their advantageous metastatic capacity and active involvement in early lymph node metastasis (LNM). Mechanistic investigations revealed that interleukin-10 (IL-10) derived from hypoxic TAMs adjacent to LVs was a prerequisite for lymphangiogenesis and LVEM formation through its induction of Sp1 upregulation in lymphatic endothelial cells (LECs). Interestingly, Sp1high LECs promoted the transactivation of C–C motif chemokine ligand 1 (CCL1) to facilitate TAM and tumour cell recruitment, thereby forming a positive feedback loop to strengthen the LVEM formation. Knockdown of Sp1 or blockage of CCL1 abrogated LVEM and consequently attenuated LNM. Notably, CSCCnon-LNM is largely devoid of hypoxic TAMs and the resultant LVEM, which might explain its metastatic delay. These findings identify a novel and efficient metastasis-promoting lymphatic pattern in the hypoxic TME, which might provide new targets for anti-metastasis therapy and prognostic assessment.

Targeting FAPα-expressing tumor-associated mesenchymal stromal cells inhibits triple-negative breast cancer pulmonary metastasis.

Tumor metastasis is the main cause of death in patients with triple-negative breast cancer (TNBC). Bone marrow-derived mesenchymal stem cells (BM-MSCs) have tropism towards tumor tissues, and can be converted into tumor-associated mesenchymal stromal cells (TA-MSCs) to facilitate TNBC metastasis through interactions with tumor-associated macrophages (TAMs). However, the underlying molecular mechanisms are complex and unclear, and effective strategies to suppress tumor metastasis via eliminating TA-MSCs are still lacking. Here, we demonstrate that fibroblast activation protein alpha (FAPα) was overexpressed in TA-MSCs, which prompts TA-MSCs to secrete multiple C-C motif chemokine ligands, promoting C-C motif chemokine receptor 2 (CCR2)+ TAM recruitment and facilitating TAM polarization into the M2 phenotype, thereby promoting TNBC pulmonary metastasis. Z-GP-DAVLBH, an FAPα-activated vinblastine prodrug, induces FAPα+ TA-MSC apoptosis, which significantly suppresses CCR2+ TAM recruitment and polarization, thus inhibiting pulmonary metastasis of orthotopic TNBC cell-derived xenografts and patient-derived xenografts. This study provides insight into an important role of FAPα in mediating TA-MSC-induced TNBC metastasis and provides compelling evidence that targeting TA-MSCs with an FAPα-activated prodrug is a promising strategy for suppressing TNBC metastasis.

Targeting tumor associated macrophages through blockade of GM-CSF sensitizes cholangiocarcinoma to adaptive immunity

Presenter: Luis Ruffolo MD | University of Rochester Background: Cholangiocarcinoma (CCA), is an aggressive malignancy with poor survival and increasing incidence. Immunotherapies offer the promise for better disease control, yet a thorough understanding of mechanisms of T cell exclusion in CCA remains undescribed. Here were report the immunosuppressive priming of the tumor microenvironment (TME) driven by CCA derived Granulocyte-Macrophage-Colony Stimulating Factor (GM-CSF) in a spontaneous model of CCA. Methods: KRAS(G12D); TP53(-/-); Alb-Cre mice (KPPC) develop spontaneous CCA. Disease was monitored with high frequency ultrasonography. Novel murine tumor cell lines were derived from syngeneic KPPC tumors and injected orthotopically. Histology and immunohistochemistry (IHC) staining was performed on mouse and human CCA for stromal and immunophenotypic markers. Murine tumor and immune compartments were processed for flow cytometry analysis. Genomic analysis of tumor and normal parenchyma was performed by quantitative real time polymerase chain reaction (qRT-PCR) and whole exome RNA sequencing (RNA seq). Therapeutic blockade of GM-CSF was achieved by administration of monoclonal antibody (mab), or appropriate control. The study was approved by UCAR and RSRB at the University of Rochester. Results: The human CCA TME is heavily desmoplastic with a predominant myeloid leukocyte infiltrate (CD11b+). CD68+ tumor associated macrophages (TAMs) are the most abundant leukocyte and their presence within the TME correlates with a worse overall survival after resection (p = 0.03). KPPC tumors closely recapitulate human CCA, and are similarly heavily infiltrated with TAMs and myeloid derived suppressor cells (MDSCs). Outside of the TME, myeloid leukocytes are elevated in the peripheral blood, spleen, and bone marrow of tumor bearing mice compared to littermate controls (P < 0.001). qRT-PCR of bulk tumor vs. normal parenchyma demonstrates increased transcription of myelopoietic cytokines, with GM-CSF being 1000 fold overexpressed compared to littermate controls (P < 0.001). Therapeutic blockade with anti-GM-CSF mAb slowed disease growth and onset of metastases, and prolonged survival in spontaneous tumor bearing mice (P = 0.015) (Figure). Flow cytometry analysis of treated and untreated murine CCA tumors demonstrated a significant decrease in TAMs and peripheral blood monocytes. Furthermore, GM-CSF blockade resulted in a reduction in expression of programmed cell death ligand 1 (PD-L1) and arginase (Arg1) by both TAMs and MDSCs within the TME. Concomitantly, CD8+ effector T cells were found to be increased in prevalence compared to untreated tumor bearing mice, and these cells exhibited increased expression of programmed cell death receptor 1 indicative of activation. RNA seq analysis of tumor educated macrophages treated with anti-GM-CSF mAb demonstrated repolarization away from an M2 phenotype, with reduction in CD206, Arg1, PD-L1, PD-L2, and IL6 (all p-values < 0.01). GM-CSF was found to be over expressed by human CCA tumors compared to normal liver, and tumors with a higher expression of GM-CSF conferred a worse overall survival in resected patients (P = 0.008). Conclusion: CCA induces myelopoiesis and recruitment of TAMs and MDSCs resulting in an immunosuppressive TME. GM-CSF is a key driver of myeloid cell production and immunosuppressive programming, and therapeutic blockade of GM-CSF potently inhibits TAMs resulting in enhanced cytotoxic T cell penetration and activation. GM-CSF represents a novel target which should be explored in advanced biliary malignancies.

ILT4 inhibition prevents TAM- and dysfunctional T cell-mediated immunosuppression and enhances the efficacy of anti-PD-L1 therapy in NSCLC with EGFR activation.

Rationale: Immune checkpoint inhibitors (ICIs) against the PD-1/PD-L1 pathway showed limited success in non-small cell lung cancer (NSCLC) patients, especially in those with activating epidermal growth factor receptor (EGFR) mutations. Elucidation of the mechanisms underlying EGFR-mediated tumor immune escape and the development of effective immune therapeutics are urgently needed. Immunoglobulin-like transcript (ILT) 4, a crucial immunosuppressive molecule initially identified in myeloid cells, is enriched in solid tumor cells and promotes the malignant behavior of NSCLC. However, the upstream regulation of ILT4 overexpression and its function in tumor immunity of NSCLC with EGFR activation remains unclear.Methods: ILT4 expression and EGFR phosphorylation in human NSCLC tissues and cell lines were analyzed using immunohistochemistry (IHC), real-time PCR, Western blotting, immunofluorescence, and flow cytometry. The molecular signaling for EGFR-regulated ILT4 expression was investigated using mRNA microarray and The Cancer Genome Atlas (TCGA) database analyses and then confirmed by Western blotting. The regulation of tumor cell proliferation and apoptosis by ILT4 was examined by CCK8 proliferation and apoptosis assays. The impact of ILT4 and PD-L1 on tumor-associated macrophage (TAM) recruitment and polarization was evaluated using Transwell migration assay, flow cytometry, enzyme linked immunosorbent assay (ELISA) and real-time PCR, while their impact on T cell survival and cytotoxicity was analyzed by CFSE proliferation assay, apoptotic assay, flow cytometry, ELISA and cytolytic assay. Tumor immunotherapy models targeting at paired Ig-like receptor B (PIR-B, an ortholog of ILT4 in mouse)/ILT4 and/or PD-L1 were established in C57BL/6 mice inoculated with stable EGFR- overexpressing Lewis lung carcinoma (LLC) cells and in humanized NSG mice inoculated with EGFR mutant, gefitinib-resistant PC9 (PC9-GR) or EGFR-overexpressing wild type H1299 cells. PIR-B and ILT4 inhibition was implemented by infection of specific knockdown lentivirus and PD-L1 was blocked using human/mouse neutralizing antibodies. The tumor growth model was established in NSG mice injected with PIR-B-downregulated LLC cells to evaluate the effect of PIR-B on tumor proliferation. The frequencies and phenotypes of macrophages and T cells in mouse spleens and blood were detected by flow cytometry while those in tumor tissues were determined by IHC and immunofluorescence.Results: We found that ILT4 expression in tumor cells was positively correlated with EGFR phosphorylation in human NSCLC tissues. Using NSCLC cell lines, we demonstrated that ILT4 was upregulated by both tyrosine kinase mutation-induced and epidermal growth factor (EGF)-dependent EGFR activation and subsequent AKT/ERK1/2 phosphorylation. Overexpressed ILT4 in EGFR-activated tumor cells induced TAM recruitment and M2-like polarization, which impaired T cell function. ILT4 also directly inhibited T cell proliferation, cytotoxicity, and IFN-γ expression and secretion. In EGFR-activated cell lines in vitro and in wild-type EGFR-activated C57BL/6 and humanized NSG immunotherapy models in vivo, either ILT4 (PIR-B) or PD-L1 inhibition enhanced anti-tumor immunity and suppressed tumor progression by counteracting TAM- and dysfunctional T cell- induced immuno-suppressive TME; the combined inhibition of both molecules showed the most dramatic tumor retraction. Surprisingly, in EGFR mutant, TKI resistant humanized NSG immunotherapy model, ILT4 inhibition alone rather than in combination with a PD-L1 inhibitor suppressed tumor growth and immune evasion.Conclusions: ILT4 was induced by activation of EGFR-AKT and ERK1/2 signaling in NSCLC cells. Overexpressed ILT4 suppressed tumor immunity by recruiting M2-like TAMs and impairing T cell response, while ILT4 inhibition prevented immunosuppression and tumor promotion. Furthermore, ILT4 inhibition enhanced the efficacy of PD-L1 inhibitor in EGFR wild-type but not in EGFR mutant NSCLC. Our study identified novel mechanisms for EGFR-mediated tumor immune escape, and provided promising immunotherapeutic strategies for patients with EGFR-activated NSCLC.

Immunosuppressive Mechanisms of Tumor-Associated Macrophages: Bioinformatic Analyses and Targeting

In recent years, the treatment of various cancers with immunotherapeutic strategies has revolutionized the classical treatments with chemotherapy or radiation. Such immunotherapeutic strategies are effective only in a subset of cancer patients who were unresponsive to conventional therapies and are not generalized to all cancer types. Several mechanisms have been reported that underlie the failure of the natural anti-tumor immunity or the administered immunotherapeutic agents in the treatment of cancer. Among these mechanisms is the pivotal role played by the immunosuppressive tumor microenvironment (TME). The TME is complex and consists of the stroma, blood vessels, and several cell types that have a direct relationship with the tumor as well as the tumor-relationship with the TME. Among the immunosuppressive cells in the TME are the tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), T regulatory cells (Tregs), and cancer-associated fibroblasts (CAFs). These cells altogether inhibit both innate and the adaptive anti-tumor immune responses. Noteworthy, TAMs represent > 50 % of all the infiltrating cells in the TME and their frequencies correlate with poor prognoses in many cancers. The depletion or inactivation of TAMs has been reported to restore, in large part, the anti-tumor immune response in several cancers. In this review, we discuss (i) the interrelationship between TAMs and cancer stem cells, (ii) the various mechanisms by which TAMs suppress the immune response [e.g., expression of inhibitory receptors and ligands, secretion of immunosuppressive cytokines, secretion of chemokines, secretion of arginase 1, secretion of IDO1 and expression of the triggering receptor expressed on myeloid cells (TREM)], and (iii) targeting TAMs for immunotherapy (e.g., depletion of TAMs, killing of TAMs, inhibition of TAM recruitment, reprogramming of TAMs, targeting Toll-like receptors, inhibition of PI3K gamma, HDAC inhibitors, and inhibition of specific miRNA activities, and targeting TREM and exosomes). In addition, we present bioinformatic analyses that demonstrated that (i) TAM infiltration into many cancers correlated with poor survival (ii) the TAM infiltration was associated with the clinical stages of the cancer and (iii) there is a strong correlation between the TAM infiltrates and various immunosuppressive gene products. Although many clinical studies are underway to inhibit the immunosuppressive functions of TAMs through a variety of mechanisms, by either targeting TAMs alone or in combination with other therapeutics, we present various perspectives that need to be considered for the successful translational application of TAMs targeting alone or in combination with other therapies in the clinic.

Is the C-C Motif Ligand 2-C-C Chemokine Receptor 2 Axis a Promising Target for Cancer Therapy and Diagnosis?

C-C motif ligand 2 (CCL2) was originally reported as a chemical mediator attracting mononuclear cells to inflammatory tissue. Many studies have reported that CCL2 can directly activate cancer cells through a variety of mechanisms. CCL2 can also promote cancer progression indirectly through increasing the recruitment of tumor-associated macrophages into the tumor microenvironment. The role of CCL2 in cancer progression has gradually been understood, and various preclinical cancer models elucidate that CCL2 and its receptor C-C chemokine receptor 2 (CCR2) are attractive targets for intervention in cancer development. However, clinically available drugs that regulate the CCL2–CCR2 axis as anticancer agents are not available at this time. The complete elucidation of not only the oncological but also the physiological functions of the CCL2–CCR2 axis is required for achieving a satisfactory effect of the CCL2–CCR2 axis-targeted therapy.

Tumor derived UBR5 promotes ovarian cancer growth and metastasis through inducing immunosuppressive macrophages

Immunosuppressive tumor microenvironment (TME) and ascites-derived spheroids in ovarian cancer (OC) facilitate tumor growth and progression, and also pose major obstacles for cancer therapy. The molecular pathways involved in the OC-TME interactions, how the crosstalk impinges on OC aggression and chemoresistance are not well-characterized. Here, we demonstrate that tumor-derived UBR5, an E3 ligase overexpressed in human OC associated with poor prognosis, is essential for OC progression principally by promoting tumor-associated macrophage recruitment and activation via key chemokines and cytokines. UBR5 is also required to sustain cell-intrinsic β-catenin-mediated signaling to promote cellular adhesion/colonization and organoid formation by controlling the p53 protein level. OC-specific targeting of UBR5 strongly augments the survival benefit of conventional chemotherapy and immunotherapies. This work provides mechanistic insights into the novel oncogene-like functions of UBR5 in regulating the OC-TME crosstalk and suggests that UBR5 is a potential therapeutic target in OC treatment for modulating the TME and cancer stemness.

Distinct regional ontogeny and activation of tumor associated macrophages in human glioblastoma

Tumor-associated macrophages (TAMs) constitute up to 50% of tumor bulk in glioblastoma (GBM) and play an important role in tumor maintenance and progression. The recently discovered differences between invading tumour periphery and hypoxic tumor core implies that macrophage biology is also distinct by location. This may provide further insight into the observed treatment resistance to immune modulation. We hypothesize that macrophage activation occurs through processes that are distinct in tumor periphery versus core. We therefore investigated regional differences in TAM recruitment and evolution in GBM by combining open source single cell and bulk gene expression data. We used single cell gene expression data from 4 glioblastomas (total of 3589 cells) and 122 total bulk samples obtained from 10 different patients. Cell identity, ontogeny (bone-marrow derived macrophages-BMDM vs microglia), and macrophage activation state were inferred using verified gene expression signatures. We captured the spectrum of immune states using cell trajectory analysis with pseudotime ordering. In keeping with previous studies, TAMs carrying BMDM identity were more abundant in tumor bulk while microglia-derived TAMs dominated the tumor periphery across all macrophage activation states including pre-activation. We note that core TAMs evolve towards a pro-inflammatory state and identify a subpopulation of cells based on a gene program exhibiting strong, opposing correlation with Programmed cell Death-1 (PD-1) signaling, which may correlate to their response to PD-1 inhibition. By contrast, peripheral TAMs evolve towards anti-inflammatory phenotype and contains a population of cells strongly associated with NFkB signaling. Our preliminary analysis suggests important regional differences in TAMs with regard to recruitment and evolution. We identify regionally distinct and potentially actionable cell subpopulations and advocate the need for a multi-targeted approach to GBM therapeutics.

Incorporating Tumor-Associated Macrophages into Engineered Models of Glioma

SummaryTumor progression is profoundly influenced by interactions between cancer cells and the tumor microenvironment (TME). Among the various non-neoplastic cells present, immune cells are critical players in tumor development and have thus emerged as attractive therapeutic targets. Malignant gliomas exhibit a unique immune landscape characterized by high numbers of tumor-associated macrophages (TAMs). Despite encouraging preclinical results, targeting TAMs has yielded limited clinical success as a strategy for slowing glioma progression. The slow translational progress of TAM-targeted therapies is due in part to an incomplete understanding of the factors driving TAM recruitment, differentiation, and polarization. Furthermore, the functions that TAMs adopt in gliomas remain largely unknown. Progress in addressing these gaps requires sophisticated culture platforms capable of capturing key cellular and physical TME features. This review summarizes the current understanding of TAMs in gliomas and highlights the utility of in vitro TME models for investigating TAM-cancer cell cross talk.

SETDB1 promotes glioblastoma growth via CSF-1-dependent macrophage recruitment by activating the AKT/mTOR signaling pathway

BackgroundGlioblastoma is a common disease of the central nervous system (CNS), with high morbidity and mortality. In the infiltrate in the tumor microenvironment, tumor-associated macrophages (TAMs) are abundant, which are important factors in glioblastoma progression. However, the exact details of TAMs in glioblastoma progression have yet to be determined.MethodsThe clinical relevance of SET domain bifurcated 1 (SETDB1) was analyzed by immunohistochemistry, real-time PCR and Western blotting of glioblastoma tissues. SETDB1-induced cell proliferation, migration and invasion were investigated by CCK-8 assay, colony formation assay, wound healing and Transwell assay. The relationship between SETDB1 and colony stimulating factor 1 (CSF-1), as well as TAMs recruitment was examined by Western blotting, real-time PCR and syngeneic mouse model.ResultsOur findings showed that SETDB1 upregulated in glioblastoma and relative to poor progression. Gain and loss of function approaches showed the SETDB1 overexpression promotes cell proliferation, migration and invasion in glioblastoma cells. However, knockdown SETDB1 exerted opposite effects in vitro. Moreover, SETDB1 promotes AKT/mTOR-dependent CSF-1 induction and secretion, which leads to macrophage recruitment in the tumor, resulted in tumor growth.ConclusionOur research clarified that SETDB1 regulates of tumor microenvironment and hence presents a potential therapeutic target for treating glioblastoma.

NT5DC2 knockdown inhibits colorectal carcinoma progression by repressing metastasis, angiogenesis and tumor-associated macrophage recruitment: A mechanism involving VEGF signaling

Colorectal cancer (CRC) is one of the most commonly diagnosed tumors among human worldwide. Angiogenesis and tumor-associated macrophage (TAM) recruitment are closely associated with CRC development. Nevertheless, the mechanisms revealing CRC progression are still not fully understood. 5′-Nucleotidase domain containing 2 (NT5DC2), a member of the NT5DC family, modulates various cellular events to mediate tumor growth, and thus serves as a disgnostic biomarker. Here, we explored the potential of NT5DC2 on tumor progression in CRC. We first found that NT5DC2 expression was significantly up-regulated in CRC tissues and cell lines. CRC patients with higher NT5DC2 expression showed poor overall survival. Furthermore, CRC cell lines stably transfected with shNT5DC2 lentivirus plasmids exhibited markedly reduced cell proliferation, migration and invasion compared with the negative control group. Hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (VEGF-A) expression levels were remarkably reduced in CRC cells with NT5DC2 deletion, along with evidently reduced tube formation in the HUVECs cultured in the collected conditional medium. The expression levels of CC chemokine ligand 2 (CCL2) and its receptor CCR2 were found to be greatly down-regulated in CRC cells transfected with shNT5DC2. Moreover, NT5DC2 knockdown markedly suppressed the activation of protein kinase-B/nuclear transcription factor κB (AKT/NF-κB) signaling in CRC cells. Furthermore, we found that NT5DC2 deletion obviously reduced the TAM recruitments through suppressing CCL2/CCR2 and AKT/NF-κB signaling pathways. Intriguingly, our in vitro experiments demonstrated that VEGF reduction was necessary for shNT5DC2-inhibited cell proliferation, migration, invasion, angiogenesis and TAM recruitment. In vivo studies also confirmed that NT5DC2 knockdown effectively reduced the tumor growth and VEGF expression in a xonegraft mouse model with CRC. Lung metastasis of CRC cells was also hindered by NT5DC2 deletion in vivo. Collectively, our results indicated a previously unrecognized NT5DC2/VEGF/CCL2 axis involved in CRC development and metastasis.

CtBP1 promotes tumour-associated macrophage infiltration and progression in non-small-cell lung cancer.

The progression of lung cancer is majorly facilitated by TAMs (tumour‐associated macrophages). However, how the TAMs infiltrate the NSCLC microenvironment and the associated biochemical are not fully elaborated. Research has revealed that changes in CtBP1 modulates innate immunity. Here, we investigated if CtBP1 facilitates infiltration of TAM and the subsequent progression of NSCLC. Immunohistochemical analysis was carried out in 96 NSCLC patients to estimate the clinicopathological importance of CtBP1 in the disease. CtBP1 overexpression and knockdown were carried out to assess the activity of CtBP1 in NSCLC cells. Elevated expression of CtBP1 correlated positively with TAMs infiltration into NSCLC tissues, induced EMT (epithelial‐mesenchymal transition) in NSCLC cells and modulated the activated NF‐κB signalling pathway leading to increase in CCL2 secretion from NSCLC cells, thus promoting TAM recruitment and polarization. TAM induction and polarization reduced significantly on exhausting p65 in NSCLC cells with CtBP1. Moreover, infiltration of TMAs was reduced remarkably on antagonist‐mediated blocking of CCR2 and impeded the progression of NSCLC in a mouse model. These findings thus show a novel insight into the process of CtBP1‐regulated TAM infiltration in NSCLC.

MiR-148a Affects Polarization of THP-1-Derived Macrophages and Reduces Recruitment of Tumor-Associated Macrophages via Targeting SIRPα.

PurposeThe objective of this study was to investigate the effect of miR-148a on the polarization and recruitment of tumor-associated macrophages (TAMs).MethodsIn human monocyte THP-1 cells, M1 or M2 differentiation was induced by phorbol 12-myristate 13-acetate (PMA) with specific induction supplements and identified using flow cytometry and ELISA. To alter cellular miR-148a expression level, THP-1 cells were transfected with miR-148a mimics or inhibitors. A dual-luciferase assay was used to determine whether miR-148a could directly regulate the expression of signal regulatory protein α (SIRPα). Expression of miR-148a and SIRPα was detected with RT-PCR or Western blot. A co-culture system of THP-1 cells and colorectal cancer SW480 cells was used for TAM induction. The recruitment of macrophage to SW480 cells was measured using chemotaxis assay. In SW480 cells, apoptosis induced by macrophages was detected using flow cytometry and a xenograft assay. Macrophage infiltration was detected by immunofluorescence assay in tumor tissues.ResultsmiR-148a over-expression increased M1-related CD86 expression in THP-1 cells and promoted differentiation to M1-like macrophages. Inhibition of miR-148a increased M2-related CD206 expression and promoted differentiation to M2-like macrophages. In the co-culture system, THP-1 cells were induced to the M2-like state by SW480 cells. The level of miR-148a negatively correlated with the levels of M2-related cytokines. Additionally, miR-148a expression level was negatively associated with macrophage recruitment by colorectal cancer cells. Furthermore, in miR-148a over-expression, the number of macrophages recruited by SW480 cells was reduced. Meanwhile, cancer cell apoptosis induced by macrophages was enhanced. Thus, miR-148a expression was beneficial for the transformation of macrophages, from an immune-suppressive status to an immune-promoting status. These anti-cancer effects of miR-148a were related to the down-regulation of SIRPα in macrophages, directly targeted by miR-148a. A xenograft assay showed that the co-inoculation of macrophages over-expressing miR-148a reduced subcutaneous tumorigenesis and M2 macrophage infiltration.ConclusionmiR-148a promoted the differentiation of M0 macrophages into anti-tumor classical activation type M1, and reduced TAM recruitment by targeting SIRPα to inhibit colorectal cancer cell viability.

EB virus-induced ATR activation accelerates nasopharyngeal carcinoma growth via M2-type macrophages polarization

Chronic inflammation induced by persistent viruses infection plays an essential role in tumor progression, which influenced on the interaction between the tumor cells and the tumor microenvironment. Our earlier study showed that ATR, a key kinase participant in single-stranded DNA damage response (DDR), was obviously activated by Epstein–Barr virus (EBV) in nasopharyngeal carcinoma (NPC). However, how EBV-induced ATR activation promotes NPC by influencing inflammatory microenvironment, such as tumor-associated macrophages (TAMs), remains elusive. In this study, we showed that EBV could promote the expression of p-ATR and M2-type TAMs transformation in clinical NPC specimens. The expression of p-ATR and M2-type TAMs were closely correlated each other and involved in TNM stage, lymph node metastasis and poor prognosis of the patients. In addition, the expression levels of CD68+CD206+, Arg1, VEGF, and CCL22 were increased in EB+ CNE1 cells, and decreased when ATR was inhibited. In the nude mice, EBV-induced ATR activation promoted subcutaneous transplanted tumor growth, higher expression of Ki67 and lung metastasis via M2-type TAMs recruitment. Experimental data also showed that the polarization of M2, the declined tumor necrosis factor-α (TNF-α) and increased transforming growth factor-β (TGF-β) were associated with ATR. Meanwhile, ATR activation could promote PPAR-δ and inhibited c-Jun and p-JNK expression, then downregulate JNK pathway. Collectively, our current study demonstrated the EBV infection could activate the ATR pathway to accelerate the transition of TAMs to M2, suggesting ATR knockdown could be a potential effective treatment strategy for EBV-positive NPC.

Abstract CT171: Phase I study of BLZ945 alone and with spartalizumab (PDR001) in patients (pts) with advanced solid tumors

Abstract Background: CSF-1R signaling regulates the function of tumor-associated macrophages (TAMs) which are poor prognostic indicators in several cancers. In animal models, including intracranial GBM, M-CSF/CSF-1 blockade may reduce TAM recruitment to the tumor microenvironment, inhibit tumor growth, and overcome resistance to PD-1 inhibitors. BLZ945, a highly selective brain penetrant CSF-1R kinase inhibitor, is being explored as single agent and with the anti-PD-1 mAb, spartalizumab. Here we present dose-escalation results from a Phase I/II, open-label study of BLZ945 ± spartalizumab (NCT02829723). Methods: Pts aged ≥18 years with advanced/metastatic solid tumors including GBM, received BLZ945 Q1W (300 mg-1600 mg QD and 600 mg BID), 7d on/7d off (150 mg-300 mg QD), or 4d on/10d off (300 mg-1200 mg QD and 600 mg BID); or BLZ945 Q1W (150 mg-1400 mg QD, 600 mg-800 mg BID) or 4d on/10d off (300 mg-1200 mg QD) + spartalizumab (400 mg IV, Q4W). Phase I objective was to characterize safety, tolerability, antitumor activity and pharmacokinetics (PK) of BLZ945 ± spartalizumab and determine the MTDs and/or RP2Ds using an adaptive Bayesian logistic regression model with overdose control, and considering overall safety including control of ALT/AST, PK, and clinical efficacy. Results: We report 146 pts receiving BLZ945 (77 pts) or the combination (69 pts), 57/43% M/F, median age 57.5 years. DLTs occurred in 7/77 pts in the BLZ945 arm (increases in amylase, lipase, AST, ALP, worsening of elevated amylase, sudden death) and 7/69 pts in the combination arm (increases in amylase, AST, ALT, dizziness, hyperuricemia). Treatment-related AEs (TRAEs) (≥20%) were AST increase (35%), nausea (29%) and vomiting (23%) in the BLZ945 arm and AST increase (38%), ALT increase (25%), vomiting (23%), and nausea (20%) in the combination arm. Gr ≥3 TRAEs were reported in 19/77 (25%) pts in the BLZ945 arm and 23/69 (33%) pts in the combination arm. Median duration of exposure (DOE) was 8 weeks for BLZ945 alone (1.0-66.6) and for the combination (2.1-85.0). BLZ945 half-life was 15hr-24hr, exposure increases were less than dose proportional after 600/700 mg. BLZ945 did not affect spartalizumab PK and vice versa. Overall response assessment (RECIST 1.1) showed a partial response in 1 pt with HNSCC in the combination arm; stable disease was observed in 21/61 (34%) and 22/49 (45%) pts in the BLZ945 and combination arms, respectively. In evaluable pts with relapsed/refractory GBM (n=18: 7 BLZ945 arm, 11 combination arm), 2 partial responses were reported per RANO (1 per arm). Among treated pts with GBM (n=24), the median DOE was 8 weeks, with 7/24 (29%) pts on treatment for &amp;gt;16 weeks. Conclusions: BLZ945 ± spartalizumab showed an acceptable safety pattern; RP2D was declared as 1200 mg (4d on/10d off) for single-agent BLZ945, the MTD was 700 mg (4d on/10d off) for BLZ945 + spartalizumab. Encouraging preliminary antitumor activity was observed in pts with GBM. Citation Format: Chia-Chi Lin, Marta Gil-Martin, Todd M. Bauer, Aung Naing, Darren Wan-Teck Lim, John Sarantopoulos, Ravit Geva, Yuichi Ando, Liqiong Fan, Somesh Choudhury, Pei-Jung Tu, Cornelia Quadt, Armando Santoro. Phase I study of BLZ945 alone and with spartalizumab (PDR001) in patients (pts) with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT171.

P2X7R promotes angiogenesis and tumour-associated macrophage recruitment by regulating the NF-κB signalling pathway in colorectal cancer cells.

Overexpression of P2X7R has been observed in several tumours and is related to cancer advancement and metastasis. However, the role of P2X7R in colorectal cancer (CRC) patients is not well understood. In the current study, overexpression of P2X7R and the effects at the molecular and functional levels in CRC were assessed in a mouse orthotopic model. Functional assays, such as the CCK‐8 assay, wound healing and transwell assay, were used to determine the biological role of P2X7R in CRC cells. CSC‐related genes and properties were detected via sphere formation and real‐time PCR assays. The underlying mechanisms were explored by Western blotting, real‐time PCR and Flow cytometry. In this study, we found that overexpression of P2X7R increases in the in vivo growth of tumours. P2X7R overexpression also increased CD31, VEGF and concurrent angiogenesis. P2X7R up‐regulates aldehyde dehydrogenase‐1 (ALDH1) and CSC characteristics. Transplanted tumour cells with P2X7R overexpression stimulated cytokines to recruit tumour‐associated macrophage (TAMs) to increase the growth of tumours. We also found that the NF‐κB signalling pathway is involved in P2X7R‐induced cytokine up‐regulation. P2X7R promotes NF‐κB–dependent cytokine induction, which leads to TAM recruitment to control tumour growth and advancement and remodelling of the stroma. Our findings demonstrate that P2X7R plays a key role in TAM recruitment, which may be a therapeutic target for CRC patients.