Tumor-associated Macrophages Populations Research Articles

Abstract IA008: Dissecting innate immune mechanisms of resistance to immune checkpoint blockade therapy in bladder cancer

Abstract We have explored the TME of bladder cancer (BC) leveraging single-cell RNA sequencing (scRNAseq) and clinical trial data to ascertain the complexity of tumor-infiltrated immune ecllls in BC. As a first step we identify distinct tumor-associated macrophage (TAM) populations associated with immune checkpoint blockade (ICB) response and resistance. Through plasma cytokine profiling, in vitro assays, and spatial analyses, we uncover novel cytokine-driven axes influencing these TAM populations and their impact on T cells, offering insights into enhancing anti-tumor T cell immunity in BC. Second, we investigate the potential of urine-derived cells (UDCs) as surrogates for monitoring the BC TME. Our scRNAseq atlas of BC patient UDCs reveals a diverse composition of immune cell populations, strikingly transcriptionally similar to tumor immune cells and containing immune subsets absent or rare in peripheral blood, suggesting their utility as biomarkers for response to therapeutic intervention. Collectively, these findings provide new insights into the immune landscape of BC and provide putative targets to enhance existing immunotherapy strategies in BC. Citation Format: Nina Bhardwaj. Dissecting innate immune mechanisms of resistance to immune checkpoint blockade therapy in bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr IA008.

Abstract 163: Role of macrophages in the development of ovarian cancer stem-like cells during chemotherapy

Abstract Ovarian cancer is a poorly understood disease with 75% death rate when identified after metastasis. Drug resistance and tumor recurrence are likely due to cancer stem-like cells (CSCs) that evade chemotherapy and induce relapse with phenotypes that are distinct from bulk tumor cells. It remains unclear how CSCs facilitate relapse and what role the tumor microenvironment (TME) plays in this process. Our preliminary data show that a secreted cytokine, tumor necrosis factor-like weak inducer of apoptosis (TWEAK), and its receptor Fn14 are overexpressed in ovarian tumors and increase after chemotherapy. TWEAK is a strong inducer of stem cell features and enhances survival of CSCs during chemotherapy exposure. The source of TWEAK has not been clarified, although clinical data from human ovarian tumors show that TWEAK mRNA was primarily observed in a subset of infiltrating immune cells known as tumor associated macrophages (TAMs). When we evaluated TWEAK expression in cells found in the ovarian TME, including PBMC and THP-1-derived macrophages, IMR-90 activated fibroblasts, and ovarian cancer cell lines, we found that PBMC macrophages were the primary source of TWEAK production. Since cytotoxic chemotherapy can enrich for different TAM populations, we propose that TWEAK producing TAMs support CSC survival and expansion and contribute to the high rate of relapse in ovarian cancer patients. We further found that treatment with a small molecule inhibitor of TAM polarization leads to decreased TWEAK production, fewer CSCs, and prolonged remission in mouse models of ovarian cancer relapse as compared to vehicle. Currently we are testing whether knockout of Fn14 in ovarian cancer cells co-cultured with TAMs reduces stem cell features dependent on TWEAK-Fn14 signaling. Identification of immune populations responsible for TWEAK production could lead to new therapeutic strategies for patients with high rates of relapse. Citation Format: Luisjesus S. Cruz, Denay Stevenson, Mikella Robinson, Steffy Mathew, Isabella Amador, Gregory Jordan, Carrie D. House. Role of macrophages in the development of ovarian cancer stem-like cells during chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 163.

Abstract 5485: Spatial characterization of the immunosuppressive tumor microenvironment in estrogen receptor positive breast cancer at single cell level

Abstract We characterized immune cell exclusion in estrogen receptor positive (ER+) breast cancer through the study of spatial relationships among various subsets of cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), and other immune cells using a novel in-situ spatial transcriptomic technology. ER+ breast cancer is the most common breast cancer subtype. While endocrine therapy and immune checkpoint inhibitors have considerably reduced relapse and mortality for breast cancer patients, tumor resistance to treatment remains a major challenge. The tumor microenvironment (TME) plays an important role in this mechanism of resistance. Our previous spatial proteomic analysis of ER+ breast FFPE samples demonstrated the intricate relationship between tumor and immunosuppressive cells such as CAFs and TAMs via the CXCR4-CXCL12 axis associated with the exclusion of CD8 T cells from the TME. However, the limited number of antibodies in the panel made it challenging to investigate the diversity of those CAF and TAM populations and better understand their contribution to T cell exclusion. For this purpose, we further characterized the TME of 4 human ER+ breast cancer FFPE cores using the Xenium in-situ transcriptomic platform with a breast cancer-focused panel of 280 genes from 10x Genomics plus 100 additional genes selected from literature and publicly available single cell datasets to delineate CAF and TAM sub-populations. Image analysis enabled the quantification and spatial mapping of the target genes within each cell boundary. Cells were manually annotated through unsupervised clustering of over 1 million cells. The cell phenotyping analysis allowed us to annotate major cell types including tumor cells, macrophages, T cells and fibroblasts. With our curated panel, we further characterized CAF and TAM sub-populations by identifying myofibroblastic CAFs (myCAFs), inflammatory CAFs (iCAFs), and antigen-presenting CAFs (apCAFs) in addition to M1 and M2-like macrophages as reported in the literature. We then performed spatial neighborhood analysis based on the similarity of the cell type composition in the vicinity of each cell. The results showed that myCAFs and M2-like macrophages are found in proximity to tumor cells and may play a role in T-cell exclusion. In addition, iCAFs mainly express CXCL12, a chemokine known to attract immunosuppressive cells such as regulatory T cells and M2-like macrophages as well as repel cytotoxic T cells from infiltrating the tumor via the CXCR4-CXCL12 axis. Overall, our work shows the potential of spatial transcriptomics to elucidate the spatial distribution of cells and their contribution to the immunosuppressive TME, which may enable researchers to improve understanding of tumor biology and drug target discovery efforts. Citation Format: Julien Tessier, Sandra Curras-Alonso, Joon Sang Lee, Fabien Delahaye, Hong Ma, Katie Malley, Dinesh Bangari, Donald Jackson, Angela Hadjipanayis. Spatial characterization of the immunosuppressive tumor microenvironment in estrogen receptor positive breast cancer at single cell level [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5485.

Riboflavin-LSD1 axis participates in the in vivo tumor-associated macrophage morphology in human colorectal liver metastases

Tumor-associated macrophages (TAMs) are key components of the tumor microenvironment (TME). In colorectal liver metastasis (CLM), TAM morphology correlates with prognosis, with smaller TAMs (S-TAMs) conferring a more favorable prognosis than larger TAMs (L-TAMs). However, the metabolic profile of in vivo human TAM populations remains unknown. Multiparametric flow cytometry was used to freshly isolate S- and L-TAMs from surgically resected CLM patients (n = 14S-, 14L-TAMs). Mass spectrometry-based metabolomics analyses were implemented for the metabolic characterization of TAM populations. Gene expression analysis and protein activity were used to support the biochemical effects of the enzyme–substrate link between riboflavin and (lysine-specific demethylase 1A, LSD1) with TAM morphologies. L-TAMs were characterized by a positive correlation and a strong association between riboflavin and TAM morphologies. Riboflavin in both L-TAMs and in-vitro M2 polarized macrophages modulates LSD1 protein expression and activity. The inflammatory stimuli promoted by TNFα induced the increased expression of riboflavin transporter SLC52A3 and LSD1 in M2 macrophages. The modulation of the riboflavin-LSD1 axis represents a potential target for reprogramming TAM subtypes, paving the way for promising anti-tumor therapeutic strategies.

Histidine-rich glycoprotein in metabolic dysfunction-associated steatohepatitis-related disease progression and liver carcinogenesis.

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously non-alcoholic fatty liver disease (NAFLD), is a leading cause of chronic liver disease worldwide. In 20%-30% of MASLD patients, the disease progresses to metabolic dysfunction-associated steatohepatitis (MASH, previously NASH) which can lead to fibrosis/cirrhosis, liver failure as well as hepatocellular carcinoma (HCC). Here we investigated the role of histidine-rich glycoprotein (HRG), a plasma protein produced by hepatocytes, in MASLD/MASH progression and HCC development. The role of HRG was investigated by morphological, cellular, and molecular biology approaches in (a) HRG knock-out mice (HRG-/- mice) fed on a CDAA dietary protocol or a MASH related diethyl-nitrosamine/CDAA protocol of hepatocarcinogenesis, (b) THP1 monocytic cells treated with purified HRG, and (c) well-characterized cohorts of MASLD patients with or without HCC. In non-neoplastic settings, murine and clinical data indicate that HRG increases significantly in parallel with disease progression. In particular, in MASLD/MASH patients, higher levels of HRG plasma levels were detected in subjects with extensive fibrosis/cirrhosis. When submitted to the pro-carcinogenic protocol, HRG-/- mice showed a significant decrease in the volume and number of HCC nodules in relation to decreased infiltration of macrophages producing pro-inflammatory mediators, including IL-1β, IL-6, IL-12, IL-10, and VEGF as well as impaired angiogenesis. The histopathological analysis (H-score) of MASH-related HCC indicate that the higher HRG positivity in peritumoral tissue significantly correlates with a lower overall patient survival and an increased recurrence. Moreover, a significant increase in HRG plasma levels was detected in cirrhotic (F4) patients and in patients carrying HCC vs. F0/F1 patients. Murine and clinical data indicate that HRG plays a significant role in MASLD/MASH progression to HCC by supporting a specific population of tumor-associated macrophages with pro-inflammatory response and pro-angiogenetic capabilities which critically support cancer cell survival. Furthermore, our data suggest HRG as a possible prognostic predictor in HCC patients with MASLD/MASH-related HCCs.

Novel tumor-associated macrophage populations and subpopulations by single cell RNA sequencing.

Tumor-associated macrophages (TAMs) are present in almost all solid tumor tissues. 16They play critical roles in immune regulation, tumor angiogenesis, tumor stem cell activation, tumor invasion and metastasis, and resistance to therapy. However, it is unclear how TAMs perform these functions. With the application of single-cell RNA sequencing (scRNA-seq), it has become possible to identify TAM subpopulations associated with distinct functions. In this review, we discuss four novel TAM subpopulations in distinct solid tumors based on core gene signatures by scRNA-seq, including FCN1 +, SPP1 +, C1Q + and CCL18 + TAMs. Functional enrichment and gene expression in scRNA-seq data from different solid tumor tissues found that FCN1 + TAMs may induce inflammation; SPP1 + TAMs are potentially involved in metastasis, angiogenesis, and cancer cell stem cell activation, whereas C1Q + TAMs participate in immune regulation and suppression; And CCL18 + cells are terminal immunosuppressive macrophages that not only have a stronger immunosuppressive function but also enhance tumor metastasis. SPP1 + and C1Q + TAM subpopulations can be further divided into distinct populations with different functions. Meanwhile, we will also present emerging evidence highlighting the separating macrophage subpopulations associated with distinct functions. However, there exist the potential disconnects between cell types and subpopulations identified by scRNA-seq and their actual function.

SPP1+ TAM subpopulations in tumor microenvironment promote intravasation and metastasis of head and neck squamous cell carcinoma.

Macrophages are heterogeneous cells that play multifaceted roles in cancer progression and metastasis. However, the phenotypic diversity of tumor-associated macrophages (TAMs) in head and neck squamous carcinomas (HNSCC) remains poorly characterized. Here, we comprehensively analyzed the HNSCC single-cell transcriptomic dataset (GSE172577) and identified 5 subsets of myeloid-driven cells as TAMs using Seurat. Deciphering the lineage trajectory of TAMs, we revealed that FCN1+ TAMs could give rise to pro-angiogenesis SPP1+CCL18+ and SPP1+FOLR2+ populations through SPP1-CCL18+ and CXCL9+CXCL10+ TAMs. SPP1+CCL18+ and SPP1+FOLR2+ TAMs harbored pro-angiogenic and metastatic transcriptional programs and were correlated with poor survival of HNSCC patients. Our immunostaining examination revealed that infiltration of SPP1+ TAMs is associated with lymph node metastasis and poor prognosis in patients with HNSCC. Cell-cell communication analysis implied that SPP1+ TAM populations may employ SPP1 signaling to activate metastasis-related ECs. In vitro and in vivo studies, we demonstrated that SPP1hi TAMs enhanced tumor intravasation and metastasis in HNSCC in a manner dependent on the secretion of SPP1, CCL18, and CXCL8. Taken together, our study characterized the cellular heterogeneity of TAM populations and identified two SPP1+ TAM populations that play key roles in HNSCC intravasation and metastasis and serve as predictive markers for patients with HNSCC.

CD74 + Leukemia-Associated Macrophages Supporess T Cell Immune Surveillance and Promote Leukemic Cell Growth in Acute Myeloid Leukemia

The bone marrow microenvironment plays a pivotal role in the recurrence of acute myeloid leukemia (AML). However, the exact mechanisms are not fully understood. Single-cell technologies have emerged as powerful tools for unraveling the immune microenvironment in leukemia. In this study, utilizing scRNA-seq on a cohort of 13 paired AML patients, we have unveiled a distinctive subcluster of tumor-associated macrophages (TAMs) linked to relapse leukemia. To explore the heterogeneity of the bone marrow microenvironment during the progression of AML, we conducted a scRNA-seq analysis on bone marrow cells obtained from 13 paired AML patients at the time of diagnosis (DX) and relapse (RE) (Figure 1A). Employing UMAP for dimensionality reduction, we detected multiple subclusters and observed a notable rise in the Macrophage CD74 cluster in all paired RE patients, suggesting a pivotal role of CD74+ TAMs in AML relapse (Figure 1B-C). Furthermore, CD274, FOS, TGFβ1, and CD163, recognized as markers of M2 macrophages, were significantly enriched in the CD74+ TAMs population (Figure 1D). Intriguingly, a higher proportion of CD74+ TAMs correlated with unfavorable outcomes in TCGA database (Figure 1E). Meanwhile, we found that the ligand macrophage migration inhibitory factor (MIF) of CD74 was associated with poor prognosis of AML (Figure 1F). To investigate the association of CD74+ TAMs with AML cells, Gene Set Variation Analysis (GSVA) was employed and revealed restrained pathways related to T cell function (Figure 2A). Through in vitro experiments on patient samples, we found that CD74+TAM can inhibit the proliferation of T cells and the secretion of IFN-γ. Further monoclonal antibody block experiments unveiled that this inhibitory effect might be attributed to the heightened expression of PD-L1, TGFβ1, and IL-10 by the macrophages (Figure 2B-C). In conclusion, we have substantiated the inhibitory role of CD74+ TAMs on T cells, which hampers their ability to engage in effective tumor killing. To elucidate the interplay between CD74+ TAMs and AML cells, we examined the gene expression profile of cytokines, noting a significant increase in the expression level of IL-6 within the CD74+ TAMs subclusters of the RE group (Figure 3A). Furthermore, upon co-culture with CD74+ TAMs, THP-1 cells exhibited notable activation of IL-6 related pathways (Figure 3B). The injection of CD74+ TAMs resulted in heightened AML initiation and poorer survival in patient-derived xenograft (PDX) model, which was reversed by blocking the IL-6-IL-6R axis (Figure 3C-D). These findings collectively confirm that IL-6 secreted by CD74+ TAMs fosters the malignancy and drug resistance of AML cells. Subsequently, MLL-AF9-induced AML mouse model was employed to explore the spatial interplay between CD74+ TAMs, AML cells and T cells. Immunofluorescence (IF) analysis of mouse bone marrow tissue revealed that after chemotherapy, the proximity between AML cells and CD74+ TAMs decreased (Figure 4A-B). Conversely, the presence of T cells surrounding CD74+ TAMs increased (Figure 4C-D). These findings indicate that CD74+ TAMs can inhibit T cell function and directly influence AML cells within the tumor microenvironment. In summary, our study revealed a notable rise in the proportion of TAMs expressing CD74 in relapsed AML patients. These CD74+ TAMs were found to facilitate leukemia progression while concurrently inhibiting T cell immune surveillance in the context of AML. Thus, our findings indicate that CD74+ TAMs represent a distinct type of macrophages associated with AML relapse.

TMIC-39. PERIVASCULAR CONTAINMENT OF T CELLS IN IDH-MUTANT ASTROCYTOMA ASSOCIATES WITH HIGH ABUNDANCE OF GEMISTOCYTIC TUMOR CELLS AND IMMUNE STIMULATORY MICROGLIA

Abstract Isocitrate dehydrogenase mutant (IDHmt) astrocytoma is considered a T cell-deficient tumor, yet little is known regarding the underlying mechanism that drives T cell exclusion. To this end, we have systematically characterized the IDHmt astrocytoma immune microenvironment. We used multiplex immunofluorescence stainings (n=75; 1293 regions), bulk (n=152) and single nucleus RNA-sequencing (snRNAseq) (n=8) alongside spatial proteomics and RNA sequencing (n=12; 72 regions of interest) on samples from one patient cohort from the Erasmus Medical Center in the Netherlands, enabling integrative spatially resolved multi-omics analysis. We identified three spatially distinct T cell distributions in IDHmt astrocytoma: perivascular accumulation of T cells (T cell cuffs); presence of T cells in the tumor stroma; and absence of T cells. T cells were most frequently present in cuffs. Notably, T cell cuffs were characterized by a high abundance of a histologically distinct tumor cell type called gemistocytes. Conversely, we find gemistocyte high regions to be enriched for T cell cuffs, B cells and tumor associated macrophages (TAMs). Gemistocyte high tumors have an increased expression of immune cell migration and activation programs. SnRNAseq demonstrates that these programs originate from TAMs and T cells. Interestingly, we find that gemistocytic tumor cells form a transcriptionally distinct tumor cell sub-cluster of the astrocyte-like tumor cell state that expresses CD44. Spatial transcriptomics consequently confirmed that gemistocytes co-occurred with a population of immune stimulatory microglia that expresses the CD44-ligand Secreted Phosphoprotein 1 (SPP1), the chemo-attractants CCL3, CCL4 and CCL4L2, and markers for reactive microglia. In summary, we systematically uncovered a previously unrecognized cellular network between T cells, gemistocytic tumor cells and a subpopulation of immune-stimulatory microglia. This spatially confined population of TAMs, together with gemistocytic tumor cells, harbors signatures associated with astrogliosis, a CNS-specific mechanism of T cell exclusion, and thus may explain the perivascular confinement of T cells.

Radiomics Correlation to CD68+ Tumor-Associated Macrophages in Clear Cell Renal Cell Carcinoma

Introduction: Renal cell carcinoma (RCC) is the ninth most common cancer worldwide, with clear cell RCC (ccRCC) being the most frequent histological subtype. The tumor immune microenvironment (TIME) of ccRCC is an important factor to guide treatment, but current assessments are tissue-based, which can be time-consuming and resource-intensive. In this study, we used radiomics extracted from clinically performed computed tomography (CT) as a noninvasive surrogate for CD68 tumor-associated macrophages (TAMs), a significant component of ccRCC TIME. Methods: TAM population was measured by CD68+/PanCK+ ratio and tumor-TAM clustering was measured by normalized K function calculated from multiplex immunofluorescence (mIF). A total of 1,076 regions on mIF slides from 78 patients were included. Radiomic features were extracted from multiphase CT of the ccRCC tumor. Statistical machine learning models, including random forest, Adaptive Boosting, and ElasticNet, were used to predict TAM population and tumor-TAM clustering. Results: The best models achieved an area under the ROC curve of 0.81 (95% CI: [0.69, 0.92]) for TAM population and 0.77 (95% CI: [0.66, 0.88]) for tumor-TAM clustering, respectively. Conclusion: Our study demonstrates the potential of using CT radiomics-derived imaging markers as a surrogate for assessment of TAM in ccRCC for real-time treatment response monitoring and patient selection for targeted therapies and immunotherapies.

Abstract IA019: Metabolic adaptations in renal cell carcinoma

Abstract Clear cell renal cell carcinoma (ccRCC) is characterized by deregulated hypoxic signaling, metabolic defects, and a complex tumor microenvironment (TME) highly enriched in both lymphoid and myeloid immune subsets. Loss of the oxygen sensing gene, von Hippel Lindau (VHL), is a critical early event in ccRCC pathogenesis and promotes stabilization of hypoxia inducible (transcription) factors (HIF) that upregulate pro-growth signaling pathways, including angiogenesis and aerobic glycolysis. However, whether Vhl loss in cancer cells impacts the frequency, energetic requirements, or other functional properties of immune subsets in the TME remains unclear. Here, using Vhl WT and Vhl KO in vivo murine kidney cancer models, we found that Vhl KO tumors across multiple clones were slower growing and promoted increased immune cell infiltration in the TME. Enhanced proinflammatory signatures in tumor associated macrophage (TAM) subsets from Vhl deficient tumors were also observed, and these features were rescued when Vhl was reintroduced to the cancer cells. Moreover, in vivo quantification of the PET tracer and glucose analog, [18F]fluorodeoxyglucose (FDG), revealed that both myeloid derived suppressor cells (MDSC) and TAM populations from Vhl KO tumors consume more glucose than myeloid subsets from Vhl intact tumors. Notably, Vhl loss did not confer increased glucose uptake in cancer cells or lymphoid subsets in vivo. Overall, these data are consistent with enhanced metabolism and proinflammatory properties observed in the myeloid compartment of human ccRCC and highlight cancer cell intrinsic mechanisms driving environmental reprograming as a means of shaping the immune landscape in ccRCC. Citation Format: W. Kimryn Rathmell. Metabolic adaptations in renal cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr IA019.

Abstract A012: Investigating the heterogeneity and clinical significance of tumor-associated macrophages in renal cell carcinoma milieu

Abstract Background: Tumor-associated macrophages (TAMs) exert a range of immunomodulatory functions in the tumor microenvironment (TME) and have been considered key regulators of tumor development. The interactions of TAMs with cancer and stromal cells in the TME have been shown to promote and sustain tumor progression; however, TAMs are largely phenotypically and functionally heterogeneous. Studies at a single-cell level are therefore necessary to understand biological and clinical relevance of heterogeneity of TAMs. Objective: To investigate the heterogeneity of TAM populations in renal cell carcinoma (RCC), the most common form of Kidney cancer, and to determine their connections to patient outcome. Methods and Results: We leverage single-cell RNA sequencing analysis of six primary RCC tumors and three Lung metastatic clear cell RCC (ccRCC) tumors, from which we identified eight TAM and two monocyte clusters shared across all nine patient tissue samples. Differential gene expression and pathway analyses revealed distinct subsets of upregulated genes and cellular pathways activated in each subpopulation. Survival analysis using gene signatures characteristic of each TAM population in datasets of ccRCC tumors (n=533) from TCGA revealed two subpopulations associated with poor patient outcome in ccRCC. Of these, one subpopulation, which we labelled as TAM-8, was characterized by upregulation of pro-inflammatory cytokines, chemokines, and growth factors such as CCL20, CXCL8, and IL1A/B. To our knowledge, this TAM population has not been described in RCC previously. We performed additional in silico functional analyses to further characterize the function of TAM-8 subpopulation, which indicated an active role in promoting immune cell infiltration and angiogenesis via various pro-inflammatory signaling pathways. Conclusion: This study provides new insight into the heterogeneity of TAM populations in RCC and defines CCL20/CXCL8/IL1High TAM-8 population as a potential driver of poor outcome and a candidate therapeutic target. Citation Format: Evelyn M. Zavacky, Minjun Kim, Ariel Madrigal, Zohreh Mehrjoo, Jonathon Spicer, Simon Tanguay, Fadi Brimo, Hamed Najafabadi, Yasser Riazalhosseini. Investigating the heterogeneity and clinical significance of tumor-associated macrophages in renal cell carcinoma milieu [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr A012.

Clearance of senescent macrophages ameliorates tumorigenesis in KRAS-driven lung cancer.

The accumulation of senescent cells in the tumor microenvironment can drive tumorigenesis in a paracrine manner through the senescence-associated secretory phenotype (SASP). Using a new p16-FDR mouse line, we show that macrophages and endothelial cells are the predominant senescent cell types in murine KRAS-driven lung tumors. Through single cell transcriptomics, we identify a population of tumor-associated macrophages that express a unique array of pro-tumorigenic SASP factors and surface proteins and are also present in normal aged lungs. Genetic or senolytic ablation of senescent cells, or macrophage depletion, result in a significant decrease in tumor burden and increased survival in KRAS-driven lung cancer models. Moreover, we reveal the presence of macrophages with senescent features in human lung pre-malignant lesions, but not in adenocarcinomas. Taken together, our results have uncovered the important role of senescent macrophages in the initiation and progression of lung cancer, highlighting potential therapeutic avenues and cancer preventative strategies.

Integrated analysis of intratumoral biomarker and tumor-associated macrophage to improve the prognosis prediction in cancer patients

BackgroundThe lack of effective and accurate predictive indicators remains a major bottleneck for the improvement of the prognosis of patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Hepatitis B virus X (HBx) has been widely suggested as a critical pathogenic protein for HBV-driven liver carcinogenesis, while tumor-associated macrophage (TAM) infiltration is also closely related to the tumorigenesis and progression of HCC. However, few studies have determined whether combining HBx expression with TAM populations could increase the accuracy of prognostic prediction for HBV-related HCC.MethodsThe study cohort enrolling 251 patients with HBV-related HCC was randomly split into a training and a validation group (ratio 1:1). The expression levels of HBx and TAM marker CD68 in HCC samples were detected by immunohistochemistry. Kaplan–Meier curves, Cox regression and Harrell’s concordance index (C-index) analysis were conducted to evaluate the prognostic significance of these indicators alone or in combination.ResultsThe expression level of HBx was strongly correlated with CD68+ TAM infiltration in HCC tissues. Elevated HBx or CD68 expression indicated poorer overall survival (OS) and progression-free survival (PFS) after hepatectomy, and both of them were independent risk factors for postoperative survival. Meanwhile, patients with both high HBx and CD68 levels had worst clinical outcomes. Moreover, integrating HBx and CD68 expression with clinical indicators (tumor size and micro-vascular invasion) showed the best prognostic potential with highest C-index value for survival predictivity, and this proposed model also performed better than several conventional classifications of HCC.ConclusionCombining the expression of intratumoral HBx, CD68+ TAM population and clinical variables could enable better prognostication for HBV-related HCC after hepatectomy, thus providing novel insights into developing more effective clinical prediction model based on both molecular phenotypes and tumor-immune microenvironment.

Aerobic Exercise Alters the Melanoma Microenvironment and Modulates ERK5 S496 Phosphorylation.

Exercise changes the tumor microenvironment by remodeling blood vessels and increasing infiltration by cytotoxic immune cells. The mechanisms driving these changes remain unclear. Herein, we demonstrate that exercise normalizes tumor vasculature and upregulates endothelial expression of VCAM1 in YUMMER 1.7 and B16F10 murine models of melanoma but differentially regulates tumor growth, hypoxia, and the immune response. We found that exercise suppressed tumor growth and increased CD8+ T-cell infiltration in YUMMER but not in B16F10 tumors. Single-cell RNA sequencing and flow cytometry revealed exercise modulated the number and phenotype of tumor-infiltrating CD8+ T cells and myeloid cells. Specifically, exercise caused a phenotypic shift in the tumor-associated macrophage population and increased the expression of MHC class II transcripts. We further demonstrated that ERK5 S496A knock-in mice, which are phosphorylation deficient at the S496 residue, "mimicked" the exercise effect when unexercised, yet when exercised, these mice displayed a reversal in the effect of exercise on tumor growth and macrophage polarization compared with wild-type mice. Taken together, our results reveal tumor-specific differences in the immune response to exercise and show that ERK5 signaling via the S496 residue plays a crucial role in exercise-induced tumor microenvironment changes. See related Spotlight by Betof Warner, p. 1158.

A subpopulation of CD146+ macrophages enhances antitumor immunity by activating the NLRP3 inflammasome.

As one of the main tumor-infiltrating immune cell types, tumor-associated macrophages (TAMs) determine the efficacy of immunotherapy. However, limited knowledge about their phenotypically and functionally heterogeneous nature restricts their application in tumor immunotherapy. In this study, we identified a subpopulation of CD146+ TAMs that exerted antitumor activity in both human samples and animal models. CD146 expression in TAMs was negatively controlled by STAT3 signaling. Reducing this population of TAMs promoted tumor development by facilitating myeloid-derived suppressor cell recruitment via activation of JNK signaling. Interestingly, CD146 was involved in the NLRP3 inflammasome-mediated activation of macrophages in the tumor microenvironment, partially by inhibiting transmembrane protein 176B (TMEM176B), an immunoregulatory cation channel. Treatment with a TMEM176B inhibitor enhanced the antitumor activity of CD146+ TAMs. These data reveal a crucial antitumor role of CD146+ TAMs and highlight the promising immunotherapeutic approach of inhibiting CD146 and TMEM176B.

Targeting molecular cross-talk between tumor cells and tumor associated macrophage as therapeutic strategy in triple negative breast cancer

Triple-negative Breast cancer (TNBC) is a subtype of breast cancer (BC) that lacks expression for ER/PR/Her2 receptors and is associated with aggressive disease pathogenesis and the worst prognosis among other subtypes of BC. Accumulating evidence-based studies indicate the high immunogenic ability of TNBC tumors and the applicability of immunotherapeutic strategies to overcome therapy resistance and tumor recurrence in TNBC patients. However, not all TNBC patients respond equally well to current immunotherapies that mainly target the adaptive immune system for tumor rejection. Recent studies are contemplating the efficacy of tumor-associated macrophage (TAM) targeted therapies since these subpopulations of cells comprise one of the major components of tumor-infiltrating immune cells (TIIs) in the TNBC tumor microenvironment (TME) and play an essential role in priming the adaptive immune response mediators towards both antitumorigenic and pro-tumorigenic response facilitated by intercellular cross-talk between tumor cells and TAM populations present within TNBC-TME. The present review discusses these molecular mechanisms and their consequence on the progression of TNBC tumors. Also, the therapeutic strategies targeting candidate genes/pathways involved in molecular cross-talk between TAM-TNBC cells and their impact on the development and progression of TNBC tumors are also discussed.

Uncovering mechanisms of response of pembrolizumab and lenvatinib for the treatment of platinum-resistant high grade serous ovarian cancer.

TPS5619 Background: Despite initial response to conventional platinum-containing therapies, the majority of high grade serous ovarian cancer (HGSOC) patients will eventually develop treatment resistance. Despite interest for immune checkpoint inhibitor alternatives, pembrolizumab monotherapy is poor with objective response rates (ORR) ranging between 4.1 - 10%. Poor response may be linked to higher expression of immunosuppressive factors (e.g. VEGF, TGF-β) in the tumor microenvironment (TME). In an immunosuppressive TME, monotherapy with PD-1 inhibitors can induce T-cell dysfunction and apoptosis, leading to innate resistance to pembrolizumab. Preclinical studies of other tumors have demonstrated that lenvatinib can improve T-cell activation and reduce the tumor-associated macrophage population and TGF-β/VEGF/FGF-signaling. In HGSOC, mechanisms of resistance to pembrolizumab and whether this resistance can be overcome by the addition of lenvatinib remain unknown. The objective of this investigation is to uncover the immunologic basis and synergistic mechanisms of action underlying clinical efficacy of pembrolizumab and lenvatinib in HGSOC. Specifically, we will evaluate the dynamic changes in proliferative and dysfunctional T-cell populations in the peritoneal TME (p-TME) of HGSOC patients receiving monotherapy with pembrolizumab or lenvatinib followed by combination therapy. Methods: All patients will receive a cycle of monotherapy (pembrolizumab 200 mg IV every 3 weeks or lenvatinib 20 mg po daily) followed by combination therapy (both) up to 35 cycles. Enrolled patients will receive intra-peritoneal port placement for serial peritoneal fluid evaluations (cycle 0 day 1, cycle 0 day 8, cycle 1 day 8, cycle 2 day 1, cycle 3 day 1, cycle 5 day 1, then day 1 of every 3rd cycle) for multichannel flow cytometry and single-cell RNA sequencing. Our primary translational objective is to estimate both the individual and combined effects of pembrolizumab and lenvatinib on T-cell dysfunction (PD1+ CD38+) and proliferation (ki67+) in the p-TME using multichannel flow cytometry on the peritoneal fluid. Secondary clinical objective is ORR. Secondary translational objectives include individual and synergistic effects of monotherapy and combination therapy on T-cell effector function, T-cell memory, and myeloid cell subpopulations. Exploratory objectives include evaluating the dynamic changes in immune and non-immune cells in the p-TME for exceptional responders and non-responders using single cell RNA sequencing. Key eligibility criteria include 1) histologic diagnosis of high grade serous ovarian, peritoneal, or fallopian tube cancer 2) platinum-resistant disease and 3) no prior lenvatinib therapy. The trial is open with 10 patients enrolled at the time of submission. Clinical trial information: NCT05114421 .

Evaluation of a CD206-Targeted Peptide for PET Imaging of Macrophages in Syngeneic Mouse Models of Cancer.

Tumor-associated macrophages (TAMs) are large phagocytic cells that play numerous roles in cancer biology and are an important component of the relationship between immune system response and tumor progression. The peptide, RP832c, targets the Mannose Receptor (CD206) expressed on M2-like macrophages and is cross-reactive to both human and murine CD206. Additionally, it exhibits therapeutic properties through its ability to shift the population of TAMs from an M2-like (protumor) toward an M1-like phenotype (antitumor) and has demonstrated promise in inhibiting tumor resistance in PD-L1 unresponsive melanoma murine models. In addition, it has shown inhibition in bleomycin-induced pulmonary fibrosis through interactions with CD206 macrophages.1,2 Our work aims to develop a novel CD206 positron emission tomography (PET) imaging probe based on RP832c (Kd = 5.64 μM) as a direct, noninvasive method for the assessment of TAMs in mouse models of cancer. We adapted RP832c to incorporate the chelator DOTA to allow for radiolabeling with the PET isotope 68Ga (t1/2 = 68 min; ß+ = 89%). In vitro stability studies were conducted in mouse serum up to 3 h. The in vitro binding characteristics of [68Ga]RP832c to CD206 were determined by a protein plate binding assay and Surface Plasmon Resonance (SPR). PET imaging and biodistribution studies were conducted in syngeneic tumor models. Stability studies in mouse serum demonstrated that 68Ga remained complexed up to 3 h (less than 1% free 68Ga). Binding affinity studies demonstrated high binding of [68Ga]RP832c to mouse CD206 protein and that the binding of the tracer was able to be blocked significantly when incubated with a blocking solution of native RP832c. PET imaging and biodistribution studies in syngeneic tumor models demonstrated uptake in tumor and CD206 expressing organs of [68Ga]RP832c. A significant correlation was found between the percentage of CD206 present in each tumor imaged with [68Ga]RP832c and PET imaging mean standardized uptake values in a CT26 mouse model of cancer. The data shows that [68Ga]RP832c represents a promising candidate for macrophage imaging in cancer and other diseases.

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.