1396 Antibody blockade of the immunoinhibitory receptor Siglec 10 polarizes tumor associated myeloid cells and promotes anti-tumor immunity

Tumor-Associated Macrophages in the Cutaneous SCC Microenvironment Are Heterogeneously Activated

The immune checkpoint inhibitor blockade takes advantage of the specific receptor-ligand interactions between immune and tumor cells. However, the immunosuppressive microenvironment has been largely ignored, which likely contribute to low efficacy and resistance in immune therapies. Our studies demonstrate that TGF-β signaling in tumor-associated myeloid cells isessential in systemic immune suppression and metastatic progression. Using mouse models of breast cancer metastasis, we further uncover that miR130a and 145 are critical in regulating TGF-β signaling in myeloid cells. miR130a and 145 are down-regulated in these myeloid cells, leading to increased TGF-β RII. Ectopic expression of miR-130a and miR-145 in the myeloid cells decrease tumor metastasis. This is mediated through a downregulation of type 2 cytokines in myeloid cells and an increase in IFNgamma-producing cytotoxic CD8 T lymphocytes. Lastly, miR-130a and miR-145 mimics improve systemic anti-tumor immunity and inhibit metastasis in preclinical mouse models. Another important mechanism in myeloid-mediated immune suppression involves a decreased expression of Lamin A/C, nuclear lamina proteins that prominently interact with heterochromatin. Lamin A/C knockout in myeloid cells leads to H3K4me3-mediated upregulation of Gfi1 and C/EBPϵ,critical transcription factors responsible for granulocytic lineage differentiation. In addition, loss of Lamin A/C attenuates antigen-presentation and compromises host anti-tumor immunity. These mechanistic understandings provide options to reprogram tumor-associated myeloid cells by altering the cytokine milieu and metastatic microenvironment, thus enhancing host antitumor immunity. Citation Format: Hiroki Ishii, Christine Hollander, Tim Greten, Li Yang. Mechanisms of tumor-associated myeloid cells in modulating host immune microenvironment and metastatic progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4500.

192 Background: STAT3 transcription factor is a critical mediator of signaling by IL-6, a cytokine promoting aggressive, castration-resistant prostate cancers (CPRCs). Importantly, STAT3 activation propagates from cancer cells to the tumor-associated immune cells, thereby generating immunosuppressive and proangiogenic tumor microenvironment. Janus kinase inhibitors provide an attractive method for disrupting IL-6/Jak/STAT3 signaling in both cancer and immune cells to amplify therapeutic effects. Methods: We tested the effect of selective Jak2 inhibitor, SAR302503, in xenotransplanted DU145 CPRCs and the tumor-associated myeloid immune cells in NSG mice. Results: Our initial results confirmed verified that oral gavage of 75 to 100 mg/kg SAR302503 results in dose-dependent inhibition of Jak2 phosphorylation in lysates from whole s.c. growing DU145 tumors within 18 h after treatment. Repeated daily treatment using SAR302503 (75 mg/kg) reduced phosphorylation of both Jak2 and STAT3, induced cancer cell death and significantly reduced growth of aggressive DU145 tumors. More detailed flow cytometric analysis revealed confirmed STAT3 inhibition in cancer cells and even greater extent in tumor-associated myeloid cells. SAR302503 did not reduce the total percentage of tumor-infiltrating myeloid cells. However, it promoted maturation of myeloid-derived suppressor cells. Conclusions: Our findings indicate that SAR302503 can potentially induce both direct and immune-mediated effects on castration-resistant prostate tumors. These preliminary results merit further studies in syngeneic tumor models that will assess whether Jak2/STAT3 inhibition can disrupt immunosuppressive and/or angiogenic functions of prostate cancer-associated myeloid cells. Further, these results may support clinical examination of SAR302503 either alone or in combination with other immunomodulatory therapies for metastatic CPRC.

<div>Abstract<p>The increased presence of myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) in tumor tissue has been extensively reported. However, their role in the regulation of hyaluronan (HA) metabolism in the tumor microenvironment has not been established. Here we describe a novel function of tumor-associated myeloid cells related to the enhanced breakdown of extracellular HA in human bladder cancer tissue, leading to the accumulation of small HA fragments with molecular weight (MW) <20 kDa. Increased fragmentation of extracellular HA and accumulation of low molecular weight HA (LMW-HA) in tumor tissue was associated with elevated production of multiple inflammatory cytokines, chemokines, and angiogenic factors. The fragmentation of HA by myeloid cells was mediated by the membrane-bound enzyme hyaluronidase 2 (Hyal2). Increased numbers of Hyal2<sup>+</sup>CD11b<sup>+</sup> myeloid cells were detected in the tumor tissue as well as in the peripheral blood of patients with bladder cancer. Coexpression of CD33 suggested that these cells belong to monocytic myeloid-derived suppressor cells. The HA-degrading function of Hyal2-expressing MDSCs could be enhanced by exposure to tumor-conditioned medium, and IL1β was identified as one of the factors involved in the stimulation of Hyal2 activity. CD44-mediated signaling played an important role in the regulation of HA-degrading activity of Hyal2-expressing myeloid cells, as the engagement of CD44 receptor with specific mAb triggered translocation of Hyal2 enzyme to the cellular surface and stimulated secretion of IL1β. Taken together, this work identifies Hyal2-expressing tumor-associated myeloid cells as key players in the accumulation of LMW-HA in the tumor microenvironment and cancer-related inflammation and angiogenesis.</p>Significance:<p>This study identifies Hyal2-expressing tumor-associated myeloid cells of monocyte–macrophage lineage as contributors to hyaluronan degradation in bladder cancer tissue, leading to accumulation of inflammatory and proangiogenic low molecular weight hyaluronan fragments.</p></div>

The tumor microenvironment plays a pivotal role in orchestrating tumor initiation, progression, and spreading, as well as response to therapy. Myeloid immune cells infiltrating tumors are integral component of the TME. While it would be expected that immune cells exert mainly a protective role for the host against tumor, it is now well established that tumor cells can strongly influence the functions of immune cells, subverting their biological properties and enabling them to support the neoplastic growth. Tumor-associated macrophages (TAMs) and neutrophils (TANs), together with myeloid derived suppressor cells (MDSCs) are the most representative myeloid cells infiltrating tumors. They are a very heterogeneous entity of cells regulating diverse aspects of cancer biology, directly supporting cancer growth and survival, angiogenesis, metastasis as well as immunosuppression. Given these premises, innovative anti-cancer approaches consider targeting of myeloid cells an essential aspect for the success of the therapy. Here, we will review the main characteristics of tumor-associated myeloid cells and their role in promoting tumor growth and dissemination. In addition, we will briefly address the therapeutic possibilities based on targeting of these cells.

BackgroundMyeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) are critical negative regulators of immunity in cancer.1 2 Understanding factors which regulate these cells could result in the identification of new...

Therapeutic approaches that engage immune cells to treat cancer are becoming increasingly utilized in the clinics and demonstrated durable clinical benefit in several solid tumor types. Most of the current immunotherapies focus on manipulating T cells, however, the tumor microenvironment (TME) is abundantly infiltrated by a heterogeneous population of tumor-associated myeloid cells, including tumor-associated macrophages (TAMs), tumor-associated dendritic cells (TADCs), tumor-associated neutrophils (TANs), and myeloid-derived suppressor cells (MDSCs). Educated by signals perceived in the TME, these cells often acquire tumor-promoting properties ultimately favoring disease progression. Upon appropriate stimuli, myeloid cells can exhibit cytoxic, phagocytic, and antigen-presenting activities thereby bolstering antitumor immune responses. Thus, depletion, reprogramming or reactivation of myeloid cells to either directly eradicate malignant cells or promote antitumor T-cell responses is an emerging field of interest. In this review, we briefly discuss the tumor-promoting and tumor-suppressive roles of myeloid cells in the TME, and describe potential therapeutic strategies in preclinical and clinical development that aim to target them to further expand the range of current treatment options.

Tumor-associated myeloid cells (TAMCs) play a crucial role in orchestrating the dynamics of the tumor immune microenvironment. This heterogeneous population encompasses myeloid-derived suppressor cells, tumor-associated macrophages and dendritic cells, all of which contribute to the establishment of an immunosuppressive milieu that fosters tumor progression. Tumor-derived exosomes (TEXs), small extracellular vesicles secreted by tumor cells, have emerged as central mediators in intercellular communication within the tumor microenvironment. In this comprehensive review, we explore the intricate mechanisms through which TEXs modulate immune-suppressive effects on TAMCs and their profound implications in cancer progression. We delve into the multifaceted ways in which TEXs influence TAMC functions, subsequently affecting tumor immune evasion. Furthermore, we elucidate various therapeutic strategies aimed at targeting TEX-mediated immune suppression, with the ultimate goal of bolstering antitumor immunity.

Background: Laminin subunit gamma 1 (LAMC1) protein is associated with tumor cell invasion and metastasis. However, its role in kidney cancer remains unclear. In this work, we sought to probe the expression as well as its carcinogenic mechanisms of LAMC1 in kidney renal papillary cell carcinoma (KIRP) and kidney renal clear cell carcinoma (KIRC). Methods: Public databases including TIMER, Oncomine, UALCAN, TISIDB, TCGA, Kaplan–Meier plotter, UCSC Xena, cBioPortal, SurvivalMeth, KEGG, GeneMANIA, Metascape, GSCALite and GDSC were adopted, and the expression, clinical pathological correlation, prognostic signatures, dominant factors influencing LAMC1 expression, DNA methylation levels, gene mutations, copy number variations, functional networks, and drug sensitivity were analyzed. Expression of LAMC1 protein in clinical KIRP and KIRC was validated using tissue array. Results: LAMC1 expression in KIRP and KIRC were significantly higher than those in normal tissues. High LAMC1 expression indicated poor overall survival in KIRP patients and better overall survival in KIRC patients. Through the univariate and multivariate Cox analysis, we found that high LAMC1 expression was a potential independent marker for poor prognosis in KIRP, however it implied a better prognosis in KIRC by univariate Cox analysis. In addition, the LAMC1 expression in KIRP and KIRC was negatively correlated with methylation levels of LAMC1 DNA. Interestingly, LAMC1 expression was positively correlated with the infiltration of CD8+ T cells, dendritic cells and neutrophils in KIRP; however, it was positively correlated with the infiltration of CD4+ T cells, macrophages and neutrophils but negatively correlated with B cells in KIRC. Moreover, high level of CD8+ T cells is beneficial for KIRC prognosis but opposite for KIRP. LAMC1 may participate in signaling pathways involved in formation of adherens junction and basement membrane in KIRP and KIRC, and the high expression of LAMC1 is resistant to most drugs or small molecules of the Genomics of Drug Sensitivity in Cancer database. Conclusion: Enhanced LAMC1 expression suggests a poor prognosis in KIRP while a better prognosis in KIRC, and these opposite prognostic signatures of LAMC1 may be related to different immune microenvironments.

Background: Methods to perturb tumor-associated myeloid cell function are being actively pursued to overcome these challenges in immunotherapy and search for a cure. CD11b is a potential therapeutic target to modulate suppressive myeloid derived cells and induce tumor-reactive T-cell responses. However, CD11b can bind to multiple carbohydrate ligands that trigger a variety of myeloid cell functions like adhesion, migration, and even phagocytosis and proliferation. This has created a major challenge to understand the molecular basis by which CD11b converts differences in receptor-ligand binding into subsequent immune signaling responses, and to use this knowledge for therapeutic development. Methods: This study investigated a previously reported carbohydrate ligand, BG34-200, that showed anti-tumor effect through modulating CD11b+ cells. Applying modern approaches of peptide microarray, multi-parameter FACS analysis, cellular/molecular immunological technology, advanced microscopic imaging, and transgenic mouse models of solid cancers, we studied the BG34-200-CD11b carbohydrate-protein engagement and immunological changes it triggered in the context of solid cancers including osteosarcoma, melanoma and pancreatic cancer. Results: Our results show that BG34-200 can mediate direct, specific, multi-site and multivalent binding to integrin CD11b to trigger cellular differentiation in a suppressive tumor-associated myeloid cell subset. In melanoma, osteosarcoma, and pancreatic cancer, we detected this rare myeloid cell subset in blood, which displayed an inflammatory monocyte phenotype and exhibited immunosuppressive behavior. BG34-200-CD11b engagement could induce differentiation of these tumor-associated inflammatory monocytes into dendritic cells by inducing phagocytosis that effectively trigger F-actin cytoskeletal rearrangement and intrinsic ICAM-1 clustering important for antigen presentation and effector T cell stimulation. Conclusions: Our findings improve understanding of molecular basis by which CD11b converts difference in carbohydrate ligands into subsequent immune signaling responses, may lead to development of safe and novel therapies modulating myeloid derived cell function for immunotherapy of solid cancers. Citation Format: Mei Zhang. Carbohydrate-CD11b engagement enhances differentiation of tumor-associated myeloid cells in immunotherapy of solid cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4420.

The activation of 41BB costimulatory signals by agonistic Abs enhances the expansion and function of tumor-infiltrating lymphocytes (TILs) for treating cancer patients with adoptive cell therapy. However, the impact of 41BB agonism is not limited to enhancing the activity of T cells, and the mechanism by which additional activation of this costimulatory axis in tumor-associated myeloid cells is poorly understood. In this study, we describe that the intratumoral administration of 41BB agonistic Abs led to increases in CD8 T cell infiltration followed by tumor regression in murine models. We found that granulocytes and monocytes rapidly replaced macrophages and dendritic cells in tumors following administration of anti-41BB Abs. Overall, myeloid cells from anti-41BB-treated tumors had an improved capacity to stimulate T cells in comparison with control-treated tumors. In human coculture systems, we demonstrated that the agonism of the 41BB-41BBL axis enhanced costimulatory signals and effector functions among APC and autologous TILs. Overall, these findings suggest that the effect of 41BB agonistic Abs are supported by additional costimulatory signals from tumor-associated myeloid cells,v leading to enhanced TIL expansion and function.

Suppressive myeloid cells represent a significant barrier to the generation of productive antitumor immune responses to many solid tumors. Eliminating or reprogramming suppressive myeloid cells to abrogate tumor-associated immune suppression is a promising therapeutic approach. We asked whether treatment of established aggressive disseminated pancreatic cancer with the immunotherapeutic attenuated Toxoplasma gondii vaccine strain CPS would trigger tumor-associated myeloid cells to generate therapeutic antitumor immune responses. CPS treatment significantly decreased tumor-associated macrophages and markedly increased dendritic cell infiltration of the pancreatic tumor microenvironment. Tumor-resident macrophages and dendritic cells, particularly cells actively invaded by CPS, increased expression of costimulatory molecules CD80 and CD86 and concomitantly boosted their production of IL12. CPS treatment increased CD4(+) and CD8(+) T-cell infiltration into the tumor microenvironment, activated tumor-resident T cells, and increased IFNγ production by T-cell populations. CPS treatment provided a significant therapeutic benefit in pancreatic tumor-bearing mice. This therapeutic benefit depended on IL12 and IFNγ production, MyD88 signaling, and CD8(+) T-cell populations. Although CD4(+) T cells exhibited activated effector phenotypes and produced IFNγ, CD4(+) T cells as well as natural killer cells were not required for the therapeutic benefit. In addition, CD8(+) T cells isolated from CPS-treated tumor-bearing mice produced IFNγ after re-exposure to pancreatic tumor antigen, suggesting this immunotherapeutic treatment stimulated tumor cell antigen-specific CD8(+) T-cell responses. This work highlights the potency and immunotherapeutic efficacy of CPS treatment and demonstrates the significance of targeting tumor-associated myeloid cells as a mechanism to stimulate more effective immunity to pancreatic cancer.

The leukocyte immunoglobulin-like receptor (LILR) family comprises a set of paired immunomodulatory receptors expressed among human myeloid and lymphocyte cell populations. While six members of LILR subfamily A (LILRA) associate with membrane adaptors to signal via immunoreceptor tyrosine-based activating motifs (ITAM), LILR subfamily B (LILRB) members signal via multiple cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIM). Ligand specificity of some LILR family members has been studied in detail, but new perspective into the immunoregulatory aspects of this receptor family in human myeloid cells has been limited. LILRB receptors and the murine ortholog, paired immunoglobulin-like receptor B (PIRB), have been shown to negatively regulate maturation pathways in myeloid cells including mast cells, neutrophils, dendritic cells, as well as B cells. Our laboratory further demonstrated in mouse models that PIRB regulated functional development of myeloid-derived suppressor cell and the formation of a tumor-permissive microenvironment. Based on observations from the literature and our own studies, our laboratory is focusing on how LILRs modulate immune homeostasis of human myeloid cells and how these pathways may be targeted in disease states. Integrity of this pathway in tumor microenvironments, for example, permits a myeloid phenotype that suppresses antitumor adaptive immunity. This review presents the evidence supporting a role of LILRs as myeloid cell regulators and ongoing efforts to understand the functional immunology surrounding this family.

Tumor-associated myeloid cells (TAMCs) are an abundant, phenotypically plastic cell population that is critical for initiating a robust antitumor response. To properly combat cancer cells, TAMCs must sense and transduce both soluble and vital biophysical cues imparted by the dense extracellular matrix (ECM) of the tumor microenvironment (TME). Despite ample research enumerating the deleterious effects of a primary tumor's ECM on TAMCs' functionality, few studies have evaluated the contribution of mechanosensitive cation channel(s) underlying these detrimental changes. Our study aimed to evaluate the significance of the mechanosensitive cation channel PIEZO1 in TAMCs' phenotype and effector functionality. To do so, we generated CD11b-conditional Piezo1 knockout mice, orthotopically inoculated them with rhabdomyosarcoma 76-9, an aggressive syngeneic rhabdomyosarcoma cell line, and evaluated tumor burden, pan-immune compartment changes, and intrinsic myeloid and lymphoid transcriptomic and functional changes. Genetic deletion of Piezo1 in CD11b-expressing cells significantly hindered primary and metastatic tumor burden. Intratumorally, we observe enhanced infiltration of CD11b+ dendritic cells (DCs) and CD8+, but not CD4+, T cells. This phenotype was driven by CD11b+ DCs that have undergone transcriptional changes related to improved antigen presentation and T cell activation. Despite being canonically inefficient cross-presenters in the wildtype state, Piezo1 KO CD11b+ DCs, specifically the cDC2A subpopulation, efficiently cross-prime CD8+ T cells on exposure to exogenous particulate antigens. Here, we report for the first time an association between mechanosensation and cross-presentation by cDC2A cells. Our findings may be impactful to improving the continued development of DC vaccines whose success hinges on proper antigen processing and presentation to cytotoxic T cells in the TME.

Arginase I (ARG1) is a cytosolic enzyme that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. The association of ARG1 with cancer has mostly been focused on the ARG1 released by tumor-associated myeloid cells in tumor microenvironment. However, the role of ARG1 expressed in cancer cells is unclear. Here, we showed that the expression of ARG1 in human breast cancer (BC) is related to a good prognosis in BC patients. Overexpression of ARG1 suppresses BC cell proliferation and migration in vitro and xenograft tumor growth and development in mouse models. Furthermore, ARG1 expression down-regulates the expression of p-AKT, leading to the de-activation of AKT signal pathway in BC cells. Thus, our results established that in contrast to the role of ARG1 released from tumor-associated myeloid cells in tumor microenvironment that promotes tumor immune escape, ARG1 expressed in BC cells suppresses AKT signaling pathway and functions as a tumor suppressor.