Tumor Microenvironment Research Articles

New insights into the role of the CHI3L2 protein in invasive ductal breast carcinoma

AbstractChitinase-like proteins have multiple biological functions that promote tumor growth, angiogenesis and metastasis. Expression of CHI3L2, which is similar in structure to CHI3L1, is detected in glioma cells and tumor-associated macrophages (TAMs) in glioma and breast cancer. However, its exact role remains unclear. We analyzed the expression of CHI3L2 in 74 invasive ductal breast carcinoma (IDC) tumors, breast cancer and macrophages cell cultures using immunohistochemistry, immunofluorescence, Western blot and PCR methods. Clinicopathologic data were included in the analysis. The results obtained show that CHI3L2 expression decreases with increasing degree of tumor grade and negative status of estrogen (ER) and progesterone receptors (PR). Furthermore, CHI3L2 is significantly and positively correlated with phosphorylation of STAT-3 and ERK1/2 signaling pathways, but negatively correlated with macrophage infiltration. CHI3L2 is expressed both in the cytoplasm of cancer cells and in macrophages and may regulate STAT-3 and ERK1/2 phosphorylation in breast cancer cell lines. Analysis of the clinicopathologic data revealed that CHI3L2 levels had no effect on patient survival. CHI3L2 expression may be specific for cancer cells in IDC and involved in cross-talk with the tumor microenvironment. Our study has shown that IDC cancer cells express the CHI3L2 protein, possibly indicating a novel function of this protein.

Cutaneous T cell lymphoma atlas reveals malignant TH2 cells supported by a B cell-rich tumor microenvironment

AbstractCutaneous T cell lymphoma (CTCL) is a potentially fatal clonal malignancy of T cells primarily affecting the skin. The most common form of CTCL, mycosis fungoides, can be difficult to diagnose, resulting in treatment delay. We performed single-cell and spatial transcriptomics analysis of skin from patients with mycosis fungoides-type CTCL and an integrated comparative analysis with human skin cell atlas datasets from healthy and inflamed skin. We revealed the co-optation of T helper 2 (TH2) cell-immune gene programs by malignant CTCL cells and modeling of the tumor microenvironment to support their survival. We identified MHC-II+ fibroblasts and dendritic cells that can maintain TH2 cell-like tumor cells. CTCL tumor cells are spatially associated with B cells, forming tertiary lymphoid structure-like aggregates. Finally, we validated the enrichment of B cells in CTCL and its association with disease progression across three independent patient cohorts. Our findings provide diagnostic aids, potential biomarkers for disease staging and therapeutic strategies for CTCL.

Tumor microenvironment remodeling after neoadjuvant chemoradiotherapy in local advanced rectal cancer revealed by single-cell RNA sequencing

Tumor microenvironment remodeling after neoadjuvant chemoradiotherapy in local advanced rectal cancer revealed by single-cell RNA sequencing

IL-2/anti-IL-2 antibody complexes augment immune responses to therapeutic cancer vaccines

One driver of the high failure rates of clinical trials for therapeutic cancer vaccines is likely the inability to sufficiently engage conventional dendritic cells (cDCs), the antigen-presenting cell (APC) subset that is specialized in priming antitumor T cells. Here, we demonstrate that, relative to vaccination with an injectable mesoporous silica rod (MPS) vaccine alone (Vax), combining MPS vaccines with CD122-biased IL-2/anti-IL-2 antibody complexes (IL-2cx) drives ~3-fold expansion of cDCs at the vaccination sites, vaccine-draining lymph nodes, and spleens of treated mice. Furthermore, relative to Vax alone, Vax+IL-2cx led to a ~3-fold increase in the numbers of CD8 + T cells and ~15-fold increase in the numbers of NK cells at the vaccination site. Notably, with both the model protein antigen OVA as well as various peptide neoantigens, Vax+IL-2cx induced ~5 to 30-fold greater numbers of circulating antigen-specific CD8 + T cells relative to Vax alone. We further demonstrate that Vax+IL-2cx leads to significantly improved efficacy in the MC38 colon carcinoma model relative to either monotherapy alone, driving complete regressions in 50% of mice in a cDC-dependent manner. Relative to vaccine alone, Vax+IL-2cx led to comparable numbers of CD8 + T cells, but markedly greater numbers of NK cells and activated cDCs in the B16F10 melanoma tumor microenvironment post-therapy. Taken together, these findings suggest that the administration of factors that engage both the cDC-CD8 + T cell and cDC-NK cell axes can boost the potency of therapeutic cancer vaccines.

Abstract B015: Targeting CX3CL1 transforms a cold tumor microenvironment into a hot one by enhancing T cells and DCs locally and systemically

Abstract Intratumoral heterogeneity (ITH) is associated with immunotherapy failure and a weaker anti- tumor immune response. Using a series of carcinogen-induced tumor (CIT) squamous cell skin carcinoma cell lines, our lab has sought to identify tumor-intrinsic factors—particularly chemokines and cytokines—which can have a “dominant negative” effect on the immune microenvironment when present within a heterogeneous tumor. We identified CX3CL1 as a one such critical mediator of a cold (T cell low) immune microenvironment and found that tumors containing as few as 10% CX3CL1high tumor cells exhibit a diminished T cell response compared to tumors which lack CX3CL1high tumor cells. We predicted that targeting CX3CL1 could therefore transform a cold tumor microenvironment (TME) into an inflammatory hot (T cell high) TME. Supporting this, we found that CRISPR-Cas9-mediated deletion of CX3CL1 in a tumor cell line that typically gives rise to cold tumors led to higher T cell infiltration and fewer immunosuppressive macrophages in the TME of CX3CL1-/- tumors. Building on this, we further explored T cell populations in the TME and found that CX3CL1-/- tumors had significantly increased activation and decreased exhaustion markers on T cells. Flow cytometry analysis showed higher expression of CD44 on effector CD4 T cells and an increase in the number of activated CD44+ PD1low CD4 T cells. By contrast, the frequency of CD4 T cells which were PD1High TIM3+ and PD1High TIM3+ TIGIT+ which represent a likely exhausted effector CD4 population was lower in CX3CL1-/- tumors than in counterpart control tumors. An interrogation of DC subsets in the TME further revealed a higher number of cDC1 and cDC2 populations in CX3CL1−/− tumors. To determine the effect of tumor-produced CX3CL1 on immune activity in lymphoid organs, we investigated T cell and DC markers in the spleen and tumor-draining lymph nodes during early tumor development. Spleens harvested 10 days after tumor injection showed higher infiltration of cDC1 CCR7+ and cDC2 CCR7+ mature DCs in CX3CL1-/- tumor-bearing mice. Thus, in the absence of tumor-produced CX3CL1, both cDC1 and cDC2 dendritic cell subsets attain more mature phenotypes in both the TME and the spleen. At the same time point, tumor-draining lymph nodes also exhibited a shift in immune cell composition characterized by an increased frequency of T cells, particularly CD4+ T cells, and a decreased frequency of B cells. Moreover, the percentage of PD1+ CD8 cells was also higher, indicating better priming and activation of CD8 T cells via DCs in tumor-draining lymph nodes. These findings indicate that tumor-produced CX3CL1 drives a cold immune microenvironment through both tumor-localized and systemic effects. These studies suggest therapeutically targeting CX3CL1 particularly in tumors where tumor cells produce high levels of CX3CL1 holds promise to transform a cold TME into a hot immune inflammatory TME and potentiate better anti-tumor immunity. Citation Format: Piyush Chaudhary, Savannah Hughes, Joshua Tay, Robert Letchworth, Miho Tanaka, Melissa Reeves. Targeting CX3CL1 transforms a cold tumor microenvironment into a hot one by enhancing T cells and DCs locally and systemically [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B015.

Abstract A017: HER2 overexpression initiates breast tumorigenesis non-cell-autonomously by altering energy metabolism in the tissue microenvironment

Abstract Breast cancer is the most common cancer globally, with approximately 70% of pre-malignant breast tumors, known as ductal carcinoma in situ (DCIS), and 20% of invasive breast tumors overexpressing human epidermal growth factor receptor 2 (HER2). While the biological role of HER2 in invasive breast cancer has been extensively studied, its impact on breast cancer stem cells (BCSCs) and early-stage tumorigenesis, particularly within the tumor microenvironment, remains unclear. Here, we explore the role of HER2 overexpression in driving cellular events within the tumor microenvironment during the premalignant stage of breast tumorigenesis, using in vitro, in vivo, and ex vivo models. We conducted multi-omics analyses on mammary ducts from a HER2+ breast cancer mouse model at the pre-cancerous stage. Our results showed that HER2/Neu overexpression alters glucose and lipid metabolism and pentose phosphate pathway in mammary epithelial cells. Ex vivo organ culture of mammary ducts confirmed that these metabolic changes lead to increased reactive oxygen species (ROS) levels within the tumor microenvironment suggesting that oxidative stress and subsequent DNA damage are early events in HER2-driven tumorigenesis. Immunostaining of histological sections from mouse mammary glands further revealed that elevated oxidative stress and DNA damage not only in HER2+ cells but also in neighboring HER2- cells. Moreover, whole genome sequencing of tumor cells confirmed that both HER2+ and HER2- tumor cells have similar mutational burden. This suggests a non-cell-autonomous effect, where HER2 overexpression in one cell population affects the tumor microenvironment and adjacent cells, contributing to early-stage cancer development. To investigate the involvement of BCSCs during tumor initiation, we performed mammosphere assays on primary cells from HER2+ mouse models and clinical DCIS samples. Our findings showed that neither BCSCs nor their cells of origin express HER2 in both DCIS samples and murine mammary glands and tumors. This suggests that HER2 overexpression may not directly drive BCSC formation but rather creates a genotoxic microenvironment that facilitates the transformation of HER2- cell populations through a non-cell-autonomous mechanism. In summary, our findings indicate that HER2 overexpression contributes to the creation of a genotoxic tumor microenvironment by altering cellular energy metabolism and increasing ROS levels. This, in turn, may lead to the transformation of BCSCs in HER2- cell populations during early breast tumorigenesis. Understanding the role of HER2 overexpression in shaping the tumor microenvironment could provide new insights into therapeutic and preventive strategies against breast cancer. Citation Format: Sevim B. Gurler, Oliver Wagstaff, Lili Dimitrova, Fuhui Chen, Robert Pedley, William Weston, Ian J. Donaldson, Brian A. Telfer, David Novo, Kyriaki Pavlou, George Taylor, Yaqing Ou, Kaye Williams, Andrew Gilmore, Keith Brennan, Ahmet Ucar. HER2 overexpression initiates breast tumorigenesis non-cell-autonomously by altering energy metabolism in the tissue microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A017.

Abstract B028: The Role of cDC1 Gene Signatures in gastric cancer prognosis and immune microenvironment modulation

Abstract Background and Aim: Gastric cancer (GC) continues to be a major global health burden, with a growing body of evidence highlighting the critical role of conventional type 1 dendritic cells (cDC1s) within the tumor microenvironment. This study aims to elucidate the prognostic significance of cDC1-associated genes—CD141, XCR1, CLEC9A, CADM1, and BTLA—in gastric cancer, as well as to explore the biological mechanisms that underpin their effects on patient outcomes. Materials and Methods: We conducted a comprehensive analysis of RNA- seq data from The Cancer Genome Atlas (TCGA-STAD) and Gene Expression Omnibus (GEO) datasets, focusing on the expression profiles of five cDC1-related genes. Patients were stratified into high and low expression groups based on a defined cDC1 gene signature. To assess the impact of these signatures, we utilized gene set variation analysis (GSVA) to examine relevant oncogenic pathways and performed Kaplan-Meier survival analysis along with Cox proportional hazards modeling to evaluate their prognostic value. Results: Our findings demonstrate that patients exhibiting a high cDC1-related gene signature had significantly worse overall and disease-free survival within the TCGA-STAD cohort. Further analysis revealed marked differences in CD8+ T cell infiltration and cytotoxic activity between the high and low cDC1 signature groups. Additionally, the high cDC1 signature group was strongly associated with upregulated expression of immune checkpoint proteins and the activation of oncogenic pathways, indicating a highly immunosuppressive tumor microenvironment. Conclusions: This study suggests that the cDC1-related gene signature may serve as a potent prognostic biomarker in gastric cancer, offering new insights into the complex interactions between the tumor and immune microenvironment. These results could pave the way for innovative therapeutic strategies that target the immune landscape in gastric cancer, potentially improving patient outcomes. Citation Format: Song-hee han. The Role of cDC1 Gene Signatures in gastric cancer prognosis and immune microenvironment modulation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B028.

Abstract B034: Engineering the tumor microenvironment: Patient-specific microphysiological systems of the head and neck cancer tumor microenvironment

Abstract Introduction: Survival rates in advanced head and neck cancer (HNC) remain poor with no clinically approved biomarkers to predict treatment efficacy. HNC is a highly heterogenous disease and the lack of available models that capture patient heterogeneity and the complexity of the tumor microenvironment (TME) contributes to these poor patient outcomes. Microphysiological systems (MPS) are complex multicellular in vitro models that can recapitulate three-dimensional organ structure and function. The low cell number requirements for MPS permits the creation of patient-specific TME models, where all the cell types can be isolated from a single piece of tumor tissue. These patient-specific MPS represent a promising strategy for elucidating the contribution of the TME to treatment resistance, predicting the best treatment for each patient and improving patient outcomes in HNC. Here, we report a patient-specific MPS that contains multiple TME compartments and recapitulates patient heterogeneity. Methods: Tumor tissue was collected from patients with oral cavity carcinoma undergoing standard of care surgery followed by radiation or chemoradiation. Tissue from each patient was digested and tumor infiltrating leukocytes (TIL) were isolated using CD45 magnetic beads, while epithelial cells and fibroblasts were expanded in culture using specific media formulations. Tissue was also snap frozen for single cell RNA sequencing analysis. To build the MPS, a custom designed microfluidic device was filled with a hydrogel matrix containing patient-matched TIL, fibroblasts and epithelial spheroids to mimic the solid tumor. Lumens molded from the hydrogel were seeded with blood or lymphatic endothelial cells to create vasculature. Multiple replicate MPS can be built from each patient, which are cultured in an optimized media formulation to support the multiple primary cell types. Patient-specific MPS were treated with radiation or cisplatin + radiation to mimic the treatment the patient received. Multiple orthogonal endpoints were measured including tumor cell migration and viability, cytokine secretion and angiogenesis. Single cell sequencing was also performed on the original tumor tissue and matched MPS. Results: We have successfully created patient-specific models of the HNC TME. Single cell RNA sequencing analysis of the MPS suggests that cellular heterogeneity is being retained. Patient characteristics varied between MPS with some patient TME MPS showing highly migratory tumor cells or angiogenic responses. Treatment responses were measured for each patient-specific MPS and ongoing work will characterize the contributions of the TME to treatment resistance. These data demonstrate the feasibility of using patient-specific MPS to investigate the contribution of the TME to treatment response and resistance and lays important groundwork for using MPS to identify patient treatment responses. Citation Format: Adeel Ahmed, Marcos Lares, Fauzan Ahmed, Adam R. Burr, Paul M. Harari, David J. Beebe, Sheena C. Kerr. Engineering the tumor microenvironment: Patient-specific microphysiological systems of the head and neck cancer tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B034.

Abstract C021: Tumor-associated microbiota suppresses anti-tumor immunity by driving cDC1 dysfunction in lung cancer

Abstract Type 1 conventional dendritic cells (cDC1s) are critical for initiating and sustaining tumor-reactive CD8 T cells; lack of functional cDC1s is a key driver for failed tumor immunosurveillance and immunotherapy. However, what factors cause the cDC1 insufficiency in the tumor microenvironment (TME) remain poorly understood. Commensal microbiota has emerged as a key regulator of TME and the efficacy of cancer immunotherapies. Nonetheless, most studies have focused on the intestinal microbiome; it remains underexplored whether and how the local microbiota within tumors influences the anti-cancer immunity. Using the autochthonous Kras LSL-G12D/+ ; p53 flox/flox (KP) mouse model of lung cancer, we found an increased local bacterial burden and altered bacterial composition associated with lung tumors. Importantly, this local microbiota suppresses the anti-tumor CD8 T cell response both at baseline and in response to ICB therapies. Specifically, single-cell RNA-seq analysis revealed that the microbiota shapes the functional subsets of tumor-reactive CD8 T cells. Bacterial depletion promotes the accumulation of stem-like Tpex cells (precursor of exhausted T cells) in the TME, which serve as a reservoir of effector CD8 T cells and mediate an effective response upon ICB treatment. To distinguish the function of the local microbiota within TME from the distal gut microbiota, we developed a new method of aerosolized antibiotic treatment, which selectively ablates the intra-tumoral lung microbiota while preserving the intact gut microbiota. Using this approach, we demonstrated that removal of the intra-tumoral lung microbiota markedly improves the tumor-reactive T cell response and sensitizing “cold” lung tumors to ICB therapies. Mechanistically, we identified cDC1s as a central player in microbiota-mediated suppression of anti-tumor immunity. Local microbiota diminishes cDC1 quality and quantity in the lung TME, resulting in impaired T cell priming and Tpex maintenance. At the molecular level, our data revealed that bacterial products derived from the local microbiota induce type I interferon expression in tumor-associated myeloid cells and enhance GM-CSF production from cancer cells: chronic type I interferon and GM-CSF signaling acts cooperatively to reduce the functional cDC1 population. Combining in vitro cDC1 assays, competitive bone marrow chimera experiments and cDC1-specific knockout models, we establish the causal relationships between the local microbiota, IFN-I and GM-CSF signaling in cDC1s, and the tumor response to ICB. Altogether, our study uncovered a dominant role of tumor-associated microbiota in inhibiting cDC1s and suppressing anti-tumor immunity through type I IFN and GM-CSF dependent pathways in lung cancer. Our findings not only identify the intra-tumoral microbiota as a critical therapeutic target for lung cancer treatment, but also provide new insights into the tissue-specific, context-dependent regulatory mechanisms of cDC1s in the TME. Citation Format: Qiang Dong, Chengcheng Jin. Tumor-associated microbiota suppresses anti-tumor immunity by driving cDC1 dysfunction in lung cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C021.

Abstract B037: Expression of MRTFA facilitates an immunosuppressive tumor microenvironment via upregulation of VSIR

Abstract Breast cancer, the second highest cause of cancer-related deaths in women, accounts for 31% of female cancer diagnoses. African American women have lower survival rates than White American women, influenced by both biological factors (age, family history, genetic factors, tumor biology) and social determinants (socio-economic status, insurance status, health care access). However, precise biological determinants remain unclear. The primary reason for breast cancer mortality is metastasis to organs like the lung, liver, and brain, with transcription factors playing a key role in this process. Myocardin related transcription factor A/B (MRTFA/B) are co-activators of serum-response factor (SRF), and the MRTF-SRF complex promotes breast cancer cell migration, invasion, and metastasis by regulating genes involved in actin cytoskeleton remodeling. MRTFA also supports tumor growth by modulating cancer-associated fibroblasts (CAFs) and remodeling the extracellular matrix (ECM) in the tumor microenvironment. While the pro-metastatic role of MRTFA/B is established in vitro and in mice, their impact on human cancer progression and metastasis requires further investigation. Therefore, understanding MRTFA's role in breast cancer metastasis is crucial for improving patient outcomes, making it essential to investigate MRTFA/B expression patterns in both tumor cells and the tumor microenvironment (TME). To explore the clinical, demographic, tumor-intrinsic, and tumor microenvironmental patterns of MRTFA/B’s expression and activation, we utilized multiplex imaging methods on multiple racially diverse tissue microarrays (TMA) and bioinformatics analyses of The Cancer Genome Atlas (TCGA), Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), and available single-cell RNA sequencing datasets. Strikingly, MRTFA expression levels were higher in African American patients than in White American patients. Next, we investigated MRTFA expression patterns in the TME by using single-cell sequencing databases and found more abundant MRTFA expression in dendritic cells (DCs) within the TME compared to any other cell subtype. Moreover, our multiplex-imaging of tumor microarray (TMA) samples showed prominent MRTFA expression in HLA-DRA+CD45+ cells, indicative of antigen-presenting cells (APC). Notably, public single-cell RNA sequencing data indicated that breast cancer DCs strongly express the V-set immunoregulatory receptor (VSIR), an immune checkpoint protein, implying the immunosuppressive nature of the TME and we found that this increased VSIR expression is mediated by the MRTF-SRF complex. These findings suggest that DCs expressing MRTFA in breast cancer microenvironment contribute to creating the immunosuppressive TME via upregulation of VSIR expression, resulting in racial breast cancer disparities. Citation Format: Kihak Lee, Stephanie M. Wilk, Alexa M. Gajda, Mohamed Haloul, Virgilia Macias, Elizabeth L. Wiley, Zhengjia Chen, Xinyi Liu, Xiaowei Wang, Maria Sverdlov, Kent F. Hoskins, Ekrem Emrah Er. Expression of MRTFA facilitates an immunosuppressive tumor microenvironment via upregulation of VSIR [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B037.

Abstract C033: Identifying and targeting prostate cancer therapy resistance mechanisms driven by the tumor microenvironment

Abstract Background: Prostate cancer is a prevalent malignancy in men, with treatment resistance posing a significant challenge to successful cure. Acquired Resistance to Therapy (ART) arises from two main components: (1) Tumor Microenvironment (TME) and (2) mutations or epigenetic changes at gene level within the tumor cells themselves. While most cancer therapies target the intrinsic biology of cancer cells, growing evidence indicates that these treatments can also harm the stromal cells within TME, potentially driving ART. The biology of ART may vary based on the types of treatments, cell types, and organ locations. Thus, this study aims to dissect ART components driven by TME-mediated cellular processes in a comprehensive manner. Hypothesis: We propose that cancer therapies induce stress responses in non-cancerous cells within the TME. These stress responses involve the secretion of cytokines, mediators, and growth factors, which we term Stress Response Secretory Programs (SRSPs). We further hypothesize that targeting SRSPs could overcome ART that helps to improve treatment specificity and efficacy. Materials and Methods: We employed comprehensive single-cell profiling of common metastatic sites included liver, prostate, lung, bone, lymph node and spleen in preclinical models to identify secreted proteins and dysregulated pathways caused by genotoxic therapies. In vitro, we evaluated treatment resistance in murine prostate epithelial cell lines (Myc-CAP) by exposing them to conditioned media (CM) from irradiated murine fibroblasts (F4M2), using cell growth assays. Results: Single-cell RNA sequencing of organ samples revealed significant expressions of SRSPs and increased inflammatory responses in liver and prostate fibroblasts as well as other stromal cells treated with carboplatin. In vitro, CM from irradiated F4M2 cells enhanced cell proliferation and survival of Myc-CAP cells in response to docetaxel treatment. Conclusion: Our findings highlight the crucial role of SRSPs in mediating ART through interactions within the TME, which alter tumor cell phenotypes. Targeting these SRSPs holds potential for overcoming treatment resistance and improving therapeutic outcomes, underscoring the need to consider TME complexity in cancer treatment strategies. Citation Format: Tony Lok Heng Chu, Armand Bankhead, Ilsa Coleman, Sander Frank, Peter S. Nelson, Tarana Arman. Identifying and targeting prostate cancer therapy resistance mechanisms driven by the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C033.

Abstract B016: Utilizing gene expression profiles (GEP) to assess tumor microenvironment (TME) and response to immunotherapy

Abstract Background: Despite the success of anti-PD-1/PD-L1 immunotherapies, outcomes for lung cancer patients remain suboptimal. There is a critical need to incorporate multi-omics data focused on the tumor microenvironment (TME) to enhance patient selection and treatment individualization. This study aimed to identify predictive and prognostic biomarkers of immunotherapy response by characterizing transcriptional profiles of lung adenocarcinoma patients who underwent genomic profiling at diagnosis. Methods: RNA sequencing data were obtained from 68 lung adenocarcinoma patients who underwent next-generation sequencing with CARIS at our institution. We analyzed gene expression profiles (GEP) comprising 18 inflammatory genes associated with antigen presentation, chemokine expression, cytolytic activity, and adaptive immune resistance, identified as potential biomarkers for immune checkpoint inhibitor (ICI) response (Cristescu et al., 2018). The genes included were CCL5, CD27, CD274 (PD-L1), CD276 (B7-H3), CD8A, CMKLR1, CXCL9, CXCR6, HLA-DQA1, HLA-DRB1, HLA-E, IDO1, LAG3, NKG7, PDCD1LG2 (PD-L2), PSMB10, STAT1, and TIGIT. GEP scores were calculated, and hierarchical clustering identified tumor subsets with similar GEPs. Gene set variation analysis was conducted to assess enrichment of cell-cell interaction activities of specific ligand-receptor pairs of immune checkpoint genes, partially overlapping with the 18 GEP genes. Results: Hierarchical clustering identified four distinct GEP clusters: "T cell-inflamed GEP," "T cell-non-inflamed GEP high," "T cell-non-inflamed GEP medium," and "T cell-non-inflamed low GEP," with average scores of 0.18 (N=9, 13%), 0.11 (N=29, 43%), 0.08 (N=19, 28%), and 0.04 (N=11, 16%), respectively. The gene scores among these clusters showed significant differences (P = 3.3e-09). Additionally, analysis of specific ligand-receptor pairs of immune checkpoint genes (PD1/PD-L1, PD-L2; CTLA4/CD28, CD80, CD86; ICOS/ICOSLG; TIM3/GAL9; SIRP1/CD47) showed consistent positive enrichment in the “T cell-inflamed” cluster, with no or negative enrichment in the “T cell-non-inflamed” clusters. This suggests active immune checkpoint interactions in clusters with high GEP scores. Conclusion: We identified four different clusters among tissues from patients with NSCLC based on GEP scoring highlighting differences in immune activation and TME makeup, which may play a role in predicting response to immunotherapies. Our results suggest that GEP may provide information on identifying optimal immunotherapeutic approaches based on TME. Our findings underscore the importance of using biomarker-guided strategies to improve patient selection for precision immunotherapy approaches in lung cancer. Citation Format: Changde Cheng, Doug Welsch, Kayla F. Goliwas, Jessy Deshane, Sameer Deshmukh, Sanad Ahlushki, Yanis Boumber, Darshan Shimoga Chandrashekar, Alexander C. Mackinnon, Aakash Desai. Utilizing gene expression profiles (GEP) to assess tumor microenvironment (TME) and response to immunotherapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B016.

Abstract C049: Implementing human bone marrow organoids to interrogate microenvironmental influences on the efficacy of blood cancer immunotherapies

Abstract Cancers perpetuate immunosuppressive niches that fuel progression and hinder the clinical utility of immunotherapies. Pre-clinical validation of immunotherapies often relies on 2D models that lack spatial complexity, or mouse models that do not fully recapitulate the human tumor microenvironment (TME). We recently developed a human induced pluripotent stem cell (iPSC)-derived bone marrow organoid platform, creating a robust system to interrogate cancer-stroma cross talk. Here, we further develop the model to create the first in vitro system for evaluation of blood cancer immunotherapies in a human tissue environment. We focused on targeting myeloproliferative neoplasms (MPNs) – chronic blood cancers affecting ∼400,000 individuals in the US that are currently largely incurable. 1/3 of MPNs are driven by a mutation in calreticulin (mutCALR), and the mutCALR oncoprotein is displayed on the cell surface of disease-initiating stem cells and fibrosis-driving megakaryocytes. MPNs are characterized by pronounced inflammation and fibrosis (“myelofibrosis”). Therapeutic antibodies have entered first-in-human trials, and we recently presented pre-clinical data for the first mutCALR-directed CAR-T cell therapy. However, it is unclear how the TME may limit the efficiency of these agents. To address this, we first tested the utility of the organoid platform to evaluate target killing of leukemic cell lines and cells from patients using the anti-CD33 antibody-drug conjugate (ADC) gemtuzumab. The ADC showed good penetration and potent target cell killing in organoids, with only minimal reduction in efficacy in TGFβ-rich/fibrotic microenvironments. We then developed more sophisticated ‘chimeroids’ comprising the iPSC organoid scaffold engrafted with malignant stem cells plus CAR-Ts. Addition of mutCALR-directed CAR-Ts induced highly selective killing of mutCALR+ stem/progenitor cells with minimal toxicity to non-malignant cells including niche cells (n=5 donors), replicating the highly specific and robust killing seen in 2D cultures. To evaluate the impact of TME perturbations on CAR-T phenotype and function, we generated a scRNAseq dataset of 161,970 cells from ‘healthy’ and ‘myelofibrotic’ organoids engrafted with patient-derived mutCALR+ cells plus CAR-Ts, pre-stimulating organoids with two immunoregulatory cytokines highly abundant in myelofibrosis -TGFβ and Galectin-1. CAR- Ts exposed to mutCALR+ cells showed a 2x expansion of CD8+ effector memory cells, with significant enrichment of IFNγ, TNFα and IL-2 signaling gene-sets. The proportion of immunosuppressive Tregs increased in a high TGFβ TME, but not with Galectin-1. Ongoing analyses are further interrogating crosstalk between CAR-T, target cells, and niche components, and exploring the pro-inflammatory impact of CAR-T killing on the marrow niche – a potential mediator of delayed hematopoietic recovery. These studies demonstrate the utility of human organoids to evaluate blood cancer-targeting immunotherapies within a relevant human TME, with broad relevance for mechanistic and translational studies. Citation Format: Zoë C. Wong, Yuqi Shen, Alex Rampotas, Isaac Gannon, Charlotte Brierley, Camelia Benlabiod, Nawshad Hayder, Eleanor Murphy, Aude-Anaïs Olijnik, Claire Roddie, Martin Pulé, Adam J. Mead, Abdullah O. Khan, Bethan Psaila. Implementing human bone marrow organoids to interrogate microenvironmental influences on the efficacy of blood cancer immunotherapies [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C049.

Abstract B033: Identification of cell-specific DNA methylation alterations in the breast tumor microenvironment

Abstract The tumor microenvironment (TME) comprises diverse cell types whose interactions are crucial for cancer progression. Traditional bulk tissue analyses mask cell-type-specific epigenetic changes that may drive disease progression. We used DNA methylation data and a reference- based cell-type deconvolution algorithm — hierarchical tumor immune microenvironment epigenetic deconvolution (HiTIMED) — to quantify cell types in the TME. Then, we employed CellDMC, a statistical interaction testing framework that can use cell type proportions in conjunction with differential methylation analysis to identify cell-specific differential methylation. Genome-scale DNA methylation profiles from breast cancer tissue (n=609) and normal breast tissue (n=230) samples were accessed in GEO and GTEx. Our novel approach leverages bulk DNA methylation data to infer cell-type-specific epigenetic landscapes, circumventing challenges and limitations associated with direct single-cell methylation profiling, such as high costs and technical variability. Reference-based computational tools allow us to dissect complex tissue compositions and reveal distinct methylation patterns and pathways that may be unique to individual cell types, providing insights that are not discernible from traditional bulk tumor analysis approaches. Compared with nontumor normal samples, we identified significant DNA methylation alterations (FDR≤0.05) across tumor, stromal, endothelial, epithelial, lymphocytes, and myeloid cells in breast tumors. Tumor cells exhibited the highest number, 8,510, differentially methylated cytosines (DMCs) with 1,966 of these unique to tumor cells. Stromal, endothelial, and epithelial cells also showed considerable methylation alterations, with a total of 530, 440, 339 DMCs, respectively, with 5 DMCs unique to epithelial cells. Despite lower immune cell proportions in our samples, we identified 104 lymphocyte specific DMCs and 185 myeloid specific DMCs, with 14 and 20 DMCs unique to these cell types respectively. The unique DMCs identified in each cell type suggest distinct epigenetic landscapes that may drive specific cellular functions and interactions within the TME. Importantly, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the annotated cell-type-specific DMCs revealed distinct pathways that were not apparent in the pathway analysis of bulk tumor versus normal tissue, underscoring the value of examining epigenetic alterations at the cell-type level. Our findings highlight the opportunity to leverage DNA-based cell typing with DNA methylation data to discern cell-specific molecular alterations. By focusing on cell-type-specific alterations, we can better understand the epigenetic mechanisms driving TME crosstalk, such as the activation of stromal cells and the modulation of immune responses by tumor cells. Our findings underscore the need for targeted therapeutic strategies that consider the unique epigenetic landscapes of individual cell types within the TME, offering new avenues for improving cancer treatment outcomes. Citation Format: Barbara Karakyriakou, Brock C. Christensen, Lucas A. Salas. Identification of cell-specific DNA methylation alterations in the breast tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B033.

Abstract B047: Understanding the role of cancer-associated adipocytes in breast tumor microenvironment to delineate the relationship between obesity and cancer

Abstract Obesity has emerged as a prominent risk factor for the development of malignant tumors. However, the existing literature on the role of adipocytes in the tumor microenvironment (TME) to elucidate the correlation between obesity and cancer remains insufficient. Here, we aim to investigate the formation of cancer-associated adipocytes (CAAs) and their contribution to tumor growth using mouse models harboring dysfunctional adipocytes. Our results reveal that the activation of YAP/TAZ signaling in CAAs induces adipocyte dedifferentiation and the formation of a malignant TME. The additional deletion of YAP/TAZ significantly led to tumor regression by mitigating adipokine secretion such as Lipocalin2 and TNFα. Furthermore, mice fed a high- fat diet exhibit increased YAP/TAZ expression in their adipose tissues. Treatment with the YAP/TAZ inhibitor, verteporfin, suppressed tumor progression, highlighting its efficacy against mice with metabolic dysregulation. These findings provide insights into the key mediators of CAA transformation and their significance in developing a TME. Our study extends to the impact of maladaptive adipocytes as a TME component. We gather multi-omics results including single-nucleus RNA sequencing and spatial transcriptomics (Xenium) to identify the CAA population in the peritumoral region. CAAs are found to modulate the TME via interacting with multiple immune cells, especially macrophages. Xenium result visualizes the proximity between CAAs and macrophages, indicating their cellular interaction. Additionally, our in-vitro co- culture system shows that CAAs recruit macrophages more effectively compared to normal adipocytes. Overall, we strive to understand the importance of adipocyte quality in forming a malignant TME and ultimately introduce therapeutic strategies targeting the tumor microenvironment, especially adipocytes. Citation Format: Yaechan Song, Hee Ju Na, Han Woong Lee. Understanding the role of cancer-associated adipocytes in breast tumor microenvironment to delineate the relationship between obesity and cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B047.

Abstract B031: Lean adipocyte-derived lipid decreases metastatic potential of breast cancer cells

Abstract Obesity rates are increasing globally, making it of critical importance to study obesity-linked diseases. Breast cancer is the most common cancer in women, and obesity is associated with both increased incidence and metastatic progression of breast cancer. Metastasis formation depends on a cancer cell leaving the primary site, migrating through the bloodstream, and establishing new growth in a distant site. Both metastasizing cell-intrinsic and metastatic site-dependent factors can help to regulate the effectiveness of this process; however, it is unknown whether obesity-linked metastasis depends on changes to the metastasizing cell and/or changes to the distant metastatic site. This study aims to characterize how the lean versus obese tumor microenvironment impacts breast cancer metastasis and identify adipocyte-derived molecules that modulate the metastatic potential of breast cancer cells. We and others have shown that obesity leads to increased metastasis formation in mouse models of orthotopic breast cancer. However, my preliminary data show that an obese metastatic site is not sufficient to increase metastasis formation in an intravenous injection model of metastasis, emphasizing the importance of the primary tumor microenvironment in programming breast cancer cells for metastasis. Cancer cell stemness helps to mediate metastasis formation and can be assessed in vitro with the mammosphere assay. Importantly, my data demonstrate that a secreted lipid from lean, but not obese, adipocytes potently inhibits the ability of breast cancer cells to form mammospheres. Furthermore, this inhibition induces a G1/S cell cycle arrest. Together, these data suggest that lean adipocytes in the breast cancer tumor microenvironment act in a paracrine manner to decrease the metastatic potential of breast cancer cells. My work demonstrates the role of adipocytes in the regulation of metastasis in breast cancer and provides important insight into the role of the tumor microenvironment in mediating metastasis in lean versus obese conditions. Citation Format: Abigail E. Jackson, Keren I Hilgendorf. Lean adipocyte-derived lipid decreases metastatic potential of breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B031.

Abstract A020: Elevated extracellular glucose level in tumor microenvironment by hyperglycemia increases glycolysis rate, stiffness, contractility, and motility of breast cancer cells through the cAMP-RhoA-Rock and AMPK-YAP-RhoA axes to promote metastasis

Abstract Glucose is a preferred nutrient for most cells, including cancer cells. The tumor microenvironment is both hypoxic and hypoglycemic. Glucose levels in tumors are ten times lower than in normal tissues due to poor vascularization and high glucose consumption by cancer cells, which adapt to hypoglycemia. Obesity, often accompanied by hyperglycemia, hyperinsulinemia, and hypertriglyceridemia, is linked to increased breast cancer metastasis. High extracellular glucose levels have been shown to promote cancer cell motility, though the mechanisms remain unclear. Given cancer cells' reliance on aerobic glycolysis (the Warburg effect), we hypothesized that hyperglycemia in obesity promotes cancer metastasis by modulating glucose metabolism and related cell mechanics pathways. Using Triple-Negative Breast Cancer (TNBC) cells, we found that elevated extracellular glucose levels increase glycolysis, activating the RhoA GTPase signaling pathway. This results in greater cell stiffness and contractility, correlating with increased motility. Our unpublished data, which I will present, validate these findings in obese-TNBC mouse models and further elucidate the glycolysis-mediated activation of the RhoA-ROCK axis. We also identified a novel long-term effect of hyperglycemia in promoting metastasis via transcriptional regulation of the AMPK-YAP-RhoA axis. To confirm hyperglycemia's pro-metastatic effects, we developed two obese-TNBC mouse models using diet-induced obesity (DIO) in NSG and C57BL/6J mice with orthotopic implantation of human and mouse TNBC cells, respectively. RhoA GTPase activity was measured with a GTP-RhoA FRET sensor or pull-down assay. Cell stiffness was assessed using our innovative parallel microfiltration (PMF) assay or Atomic Force Microscopy (AFM). We disrupted glucose uptake by knocking out glucose transporter 3 (GLUT3) via CRISPR/Cas9 or using a GLUT3-selective inhibitor, G3iA. Cell motility was measured by scratch wound-healing and invasion assays. Bulk RNA-seq identified differentially expressed genes under high glucose conditions in human breast cancer cells. Our results show increased lung metastasis of breast cancer cells under hyperglycemic conditions in vivo. Besides the previously reported cAMP-RhoA-ROCK axis, we discovered the glycolysis-AMPK-YAP axis also regulates RhoA-ROCK activity transcriptionally. GLUT3 inhibition activated AMPK, reduced F-actin levels via the AMPK-VASP axis, and decreased non-muscle myosin activity through the AMPK-YAP-RhoA axis. These changes in cell mechanics correlated with reduced motility. Our study suggests that targeting glucose metabolism and cell mechanics could be a novel approach to inhibit cancer metastasis, particularly in obese patients. Citation Format: Tae-Hyung Kim, Aadil Q Bhat, Jun-Yong Choe, Donghoon Yoon. Elevated extracellular glucose level in tumor microenvironment by hyperglycemia increases glycolysis rate, stiffness, contractility, and motility of breast cancer cells through the cAMP-RhoA-Rock and AMPK-YAP-RhoA axes to promote metastasis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A020.

Abstract C002: CKLF attracts CCR4-expressing CD4+ cells to foster immune repression and tumor aggressiveness in MYCN-driven neuroblastoma

Abstract Neuroblastoma, especially those with aberrant MYCN activation, often harbor an immunosuppressive microenvironment to fuel malignant growth and trigger treatment resistance. Despite this knowledge, there are no effective strategies to tackle this problem. Here we combined analyses of human neuroblastoma with live tracking and functional studies of the tumor microenvironment (TME) in zebrafish. We identified chemokine-like factor (CKLF) as a key driver of MYCN-mediated immunosuppression and neuroblastoma aggression. We showed that human MYCN-activated neuroblastoma upregulates and secretes CKLF, which is a reliable predictor of poor patient survival. Analysis of primary patient samples demonstrates a strong positive association between MYCN and CKLF expression in neuroblastoma cells together with the enrichment of FOXP3+ T cells in the TME. Taking advantage of in vivo zebrafish models of MYCN-driven neuroblastoma that resemble human high-risk disease, we demonstrated that cklf overexpression in zebrafish neural crest cells induces an immunosuppressive TME while promoting rapid tumor onset and progression. We also demonstrated that as early as the premalignant stage, tumor cells secrete CKLF to attract CCR4-expressing Cd4+ cells to induce immunosuppression and tumor aggression. Conversely, genetic depletion of cklf in tumor cells reduces the recruitment of Cd4+ cells to the TME while increasing cytotoxic Cd8+ and natural killer cells infiltration, inhibiting neuroblastoma development in zebrafish. Our work provides the first example that MYCN can activate CKLF to allure CD4+ immune cells to the TME and incite immunosuppression, positioning CKLF as a potential novel immunotherapeutic target for the treatment of MYCN-driven high-risk neuroblastoma. Citation Format: Xiaodan Qin, Hui Feng, Andrew Lam, Xu Zhang, Satyaki Sengupta, Bryan Iorgulescu, Sanjukta Das, Zhenwei Zhou, Tao Zuo, Grace Meara, Madison Rager, Alexander Floru, Hongru Ni, Chinyere Kemet, Divya Veerapaneni, Daniel Kashy, Liang Lin, Kenneth Lloyd, Lauren Kwok, Kaylee Smith, Raghavendar Nagaraju, Rob Meijers, Craig Ceol, Ching-Ti Liu, Sanda Alexandrescu, Catherine J. Wu, Derin Keskin, Rani George. CKLF attracts CCR4-expressing CD4+ cells to foster immune repression and tumor aggressiveness in MYCN-driven neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C002.

Abstract IA019: Regulation of EMT tumor states by stromal cells

Abstract Epithelial-to-mesenchymal transition (EMT) is a reversible process during which epithelial cells lose their epithelial characteristics and acquire mesenchymal features, that are important for tumor initiation, progression, stemness, metastasis, and therapy resistance. Different EMT states, each with distinct functional properties, have been identified across various tumor models. These EMT states reside within specific physical niches, characterized by unique stromal cell populations. Understanding the cellular interactions within the tumor microenvironment (TME) and their influence on EMT could lead to novel therapeutic strategies. To understand how the TME regulates the distinct tumor states, we performed single-cell RNA sequencing of the tumor cells and their TME in mouse cancer models presenting EMT. We identified distinct subsets of cancer-associated fibroblasts (CAFs), macrophages, neutrophils, endothelial cells, pericytes, adipocytes, dendritic cells, mast cells, Schwann cells, and T cells in different tumor types. To unravel how TME-tumor cell interactions regulates EMT, we used different bioinformatic approaches to identify ligand-receptor pairs that are likely to organize the tumor niche and to regulate tumor transition states. In vitro treatment of tumor cells with some of these ligands demonstrated their EMT-promoting effects. These findings provide novel mechanistic insights on the crosstalk between tumor cells and the surrounding TME, that may have important implications for anti-cancer therapy. Citation Format: Cédric Blanpain. Regulation of EMT tumor states by stromal cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr IA019.

Abstract B018: Multifaceted pro-metastatic role of IL-17 signaling in modulating the tumor microenvironment of colorectal cancer

Abstract Colorectal cancer (CRC) ranks second in mortality and advanced CRCs are resistant to current immunotherapies and prone to metastasis, which necessitates research into enhancing innate and adaptive anti-cancer immune responses. Chronic inflammation mediated by cytokines like IL6 and notably, IL17 activates the oncogenic pathways in cancer cells, promoting sporadic and inflammatory CRC. What is unknown, is the ability of cytokines to control tumor microenvironment (TME) via cell type specific mechanisms to increase cancer progression, metastasis and/or therapy resistance. Increased levels of IL17A in CRC portends poor prognosis indicating its potential involvement into metastasis. However, the role of IL17 signaling in TME in the process of CRC progression and metastasis remains enigmatic. We utilized different models of CRC progression and metastasis, as well as variety of genetic mice models and therapeutic interventions. First, using a model of colitis-associated cancer we found that “late” IL17A neutralization decreases tumor burden, possibly acting through regulation of ferroptosis, NK cells mediated cytotoxicity, as well as myeloid cells and chemokine network essential for the control of immunosuppressive TME. Next, models of CRC metastasis, including those based on MC38 cells and APTAK cancerous organoids, showed that IL17A neutralization reduces metastasis growth. Also, FACS analysis revealed that IL17A promotes the recruitment of tumor- associated macrophages and other key myeloid subsets into the metastatic liver environment. Further research, using mice with conditional knockout of IL17RC receptor in myeloid cells (Il17rc f/f -LysMCre) or hepatocytes (Il17rc f/f -AlbCre) also showed significance of IL17 signaling activation in CRC metastasis through two distinct mechanisms. Employing different techniques, from FACS, immunohistochemistry, to RNAseq and scRNAseq data analysis, we observed that local hepatic activation of IL17RC signaling recruits neutrophils and reduces infiltration of cytotoxic CD8+T and NK cells to the metastatic niche supporting tumor growth, while myeloid IL17RC signaling reshapes TME, including macrophages and neutrophils, enhancing CRC metastasis. Our research indicates that IL17 signaling plays a multifaceted pathogenic role in CRC progression by operating in at least several cell types, providing new insights into the basic biology of CRC metastasis and potentially illuminating the design and improvement of CRC treatment strategies. Citation Format: Katarzyna Chojnacka, Katrina Mae Reyes, Hana Tomizawa, Sergei Grivennikov. Multifaceted pro-metastatic role of IL-17 signaling in modulating the tumor microenvironment of colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B018.