Systemically inducing trained immunity overcomes solid tumors’ immunosuppressive microenvironment

Multifunctional Ca2+ nanomodulators regulate type I interferon pathway to remodel tumor microenvironment for cancer immunotherapy

Pancreatic cancer is the fourth leading cause of cancer death in the United States with current 5-year survival rates at 6%. Greater than 90% of all pancreatic cancers harbor an activating mutation in codon 12 of the Kras gene (KrasG12D). Protein Kinase C iota (PKCι) has been shown to mediate KrasG12D downstream signaling and acinar-to-ductal metaplasia in an explant model of pancreatic cancer initiation. Additionally, inhibition of PKCι in human pancreatic cancer cells leads to decreased tumor size, angiogenesis, and metastasis in an orthotopic tumor model, suggesting that PKCι plays a role in maintaining the oncogenic phenotype of pancreatic cancer cells. We sought to test the hypothesis that PKCι plays a role development and maintenance of pancreatic cancer using a mouse model of KrasG12D-induced pancreatic cancer. Purpose: To identify the effect of PKCι loss on pancreas function and development of KrasG12D-induced pancreatic cancer. Procedures: Pancreata from mice with pancreas-specific deletion of PKCι, with and without pancreas-specific KrasG12D expression, were analyzed for histological and protein expression alterations. Acinar cells isolated from these transgenic mouse models were subjected to in vitro analyses to determine the role of PKCι in pancreatic cell homeostasis. Results: Mice lacking pancreatic PKCι survived and developed normally. Pancreatic knockout of PKCι expression resulted in a phenotype consistent with a defect in autophagic flux. In vitro analyses of isolated acinar cells supported the hypothesis that PKCι promotes autophagy in pancreatic cells. Autophagy exhibits a dual functionality in pancreatic cancer, acting as a tumor suppressor in normal cells and a tumor promoter in established tumor cells. We sought to determine the effect of PKCι knock-out on both of these cell types in a mouse model of pancreatic cancer. Using the LSL mouse model of K-ras induced pancreatic cancer, we demonstrated that pancreatic loss of PKCι lead to an increase in the number of Pancreatic Intraepithelial (PanIN) lesions formed in young mice. However, these lesions were protected from progressing past the early PanIN1/2 stage such that no mice lacking PKCι developed cancer, even after 1.5 years of age. By contrast, over 50% of mice with wild-type PKCι developed cancer; of those without cancer, many had progressed to the PanIN-3 stage, a stage representative of carcinoma in-situ. These data are similar to that seen in mouse models of pancreatic cancer with genetic inhibition of autophagy. Analysis of PanINs in these mice revealed that those lacking PKCι expressed significantly more P62 protein, a selective autophagy substrate, compared to PanINs with wild-type PKCι, supporting a block in the autophagic flux. These data suggest that PKCι plays an important role in both the initiation and progression of pancreatic cancer, possibly by regulating autophagic flux. Impact: Inhibition of pancreatic PKCι expression prevented progression of PanIN lesions past the early PanIN1/2 stage, resulting in a complete block in cancer development in mouse models of pancreatic cancer. Our preliminary data suggests that PKCι promotes cancer progression by regulating autophagic flux, a process that has been shown to be essential for KrasG12D-mediated pancreatic cancers. Pancreatic cancer is characterized by resistance to current therapies. Novel targets for new and more effective therapies are critical to improve outcomes for patients with this deadly disease. Inhibitors of PKCι are currently in clinical trials for ovarian and lung cancers. Our data supports the feasibility of using PKCι inhibitors for therapy in pancreatic cancer. Citation Format: Kristin S. Inman, Amanda A. Francis, Nicole R. Murray. PKCι in pancreatic cancer development: A possible role for autophagy. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A02.

Objective:Trained immunity of natural killer (NK) cells has shown great potential in the treatment of cancers by eliciting enhanced effector responses to restimulation by cytokines or cancer cells for long time periods after preactivation. However, the human NK cells responsible for the generation and maintenance of trained immunity are largely unknown. We hypothesized that heterogeneous human NK cells would respond differentially to stimulation with a combination of IL-12, IL-15, and IL-18, and that an NK cell subset might exist that is mainly responsible for the induction of trained immunity. On the basis of our hypothesis, we aimed to identify the subset from which cytokine-trained human NK cells originate and to explore possible regulatory targets for drug intervention.Methods:Flow cytometry assays were performed to analyze the functions of cytokine-trained NK cells and examine cell division and protein expression in NK cell subsets. Single-cell RNA sequencing (scRNA-seq) plus TotalSeq™ technology was used to track the heterogeneity of NK cells during the induction of trained immunity.Results:Traditional developmental markers for peripheral NK cells were unable to identify the precursors of human NK cells with trained immunity. Therefore, we used scRNA-seq plus TotalSeq™ technology to track the heterogeneity of NK cells during the induction of trained immunity and identified a unique cluster of CD57−NKG2A+EZH2+IFNG+MKI67+IL12R+IL15R+IL18R+ NK cells. Enrichment and pseudotime trajectory analyses suggested that this cluster of NK cells contained the precursor of trained NK cells. We then used flow cytometry to further investigate the role of EZH2 in trained NK precursors and found that CD57−NKG2A+EZH2+ NK cells had faster cell cycles and an enhanced trained phenotype, and EZH2 inhibition significantly impaired the induction of trained immunity in NK cells. These results suggested that EZH2 is a unique epigenetic marker of precursors of human NK cells with trained immunity.Conclusions:Our work revealed human NK heterogeneity in the induction of trained immunity, identified the precursor subset for trained NK cells, and demonstrated the critical role of EZH2 in the induction of trained immunity in human NK cells.

Despite the remarkable success of immunotherapy in many types of cancer, pancreatic ductal adenocarcinoma has yet to benefit. Innate immune cells are critical to anti-tumor immunosurveillance and recent studies have revealed that these populations possess a form of memory, termed trained innate immunity, which occurs through transcriptomic, epigenetic, and metabolic reprograming. Here we demonstrate that yeast-derived particulate β-glucan, an inducer of trained immunity, traffics to the pancreas, which causes a CCR2-dependent influx of monocytes/macrophages to the pancreas that display features of trained immunity. These cells can be activated upon exposure to tumor cells and tumor-derived factors, and show enhanced cytotoxicity against pancreatic tumor cells. In orthotopic models of pancreatic ductal adenocarcinoma, β-glucan treated mice show significantly reduced tumor burden and prolonged survival, which is further enhanced when combined with immunotherapy. These findings characterize the dynamic mechanisms and localization of peripheral trained immunity and identify an application of trained immunity to cancer.

ABSTRACTAtherosclerosis is a chronic inflammatory disease of the arterial wall that causes cardiovascular disease. Monocyte‐derived macrophages are an important contributor to atherogenesis. Monocytes can become primed for higher responsiveness to secondary, unrelated stimuli—a phenomenon known as trained immunity—a process driven by intracellular metabolic and epigenetic reprogramming. Oxidized low‐density lipoprotein (oxLDL) induces trained immunity by enhancing glycolysis and oxidative phosphorylation (OXPHOS). Glutamine is known to enter the Krebs cycle through glutaminolysis where it can be used for ATP synthesis via OXPHOS. We therefore explored the role of the glutaminolysis pathway in oxLDL‐induced trained immunity. Primary human monocytes from healthy donors were exposed to oxLDL for 24 h, followed by differentiation into macrophages over 6 days in culture medium. Thereafter, cytokine production capacity was assessed by stimulating them with Toll‐like receptor agonist. Co‐administration of the glutaminase inhibitor CB‐839 during oxLDL exposure reduces glutamine anaplerosis. This prevented oxLDL‐induced trained immunity, with diminished cytokine production capacity, associated with a reduced oxygen consumption rate (OCR), and glycolysis rate (ECAR). The role of glutaminolysis for induction of trained immunity was validated genetically, by showing significant associations between several single‐nucleotide polymorphisms in genes related to glutaminolysis and ex vivo cytokine production in oxLDL‐trained monocytes from 243 healthy volunteers. Finally, we identified a positive correlation between glutamate and Krebs cycle metabolites with inflammatory circulating biomarkers and monocyte counts in an independent cohort of 302 obese individuals. Altogether, these data suggest a crucial role of glutaminolysis in the establishment of oxLDL‐induced trained immunity.

Cancer antigens of choice include mutant DNA sequences encoding neo-antigens, selected cancer testis antigens, and differentiation antigens, in addition to viral antigens. Neo-antigens and viral antigens are the most attractive, because the T cell repertoire against these antigens has not been blunted by central thymic tolerance. Optimal vaccine platforms include DNA and RNA vaccines as well as synthetic long peptides and selected prime-boost protocols involving recombinant viruses encoding cancer antigens. The most effective cancer vaccines deliver concentrated antigen to both HLA class I and II molecules of DCs, promoting both CD4 and CD8 T cell responses. Suboptimal antigen selection, suboptimal vaccine design, and an immunosuppressive cancer microenvironment are the root causes of the lack of clinical efficacy of cancer vaccines in many clinical trials. Drugs or physical treatments can mitigate the immunosuppressive cancer microenvironment and include chemotherapeutics, radiation, inhibitors of T cell checkpoints, indoleamine 2,3-dioxygenase (IDO) inhibitors, agonists of selected TNF receptor family members, and inhibitors of undesirable cytokines. The specificity of therapeutic vaccination combined with such immunomodulation offers an attractive avenue for the development of future cancer therapies. Clinical benefit of certain therapeutic cancer vaccines has been established, usually by noting prolonged progression free or overall survival. Reviews of the properties and prospects of cancer vaccines have been listed below (1-3). The addition of one or more immunomodulation strategies may further enhance the potential of therapeutic cancer vaccines, including of those that have been only marginally active due to the immunosuppressive cancer microenvironment. We have established clinical benefit of a cancer vaccine as monotherapy in patients with premalignant disease induced by high risk human papilloma virus. Regression of lesions was associated with a better vaccine-induced immune response against the target antigens of the vaccine. However in patients with cervical cancer the vaccine monotherapy failed to install clinically effective immunity. Recently we showed in a pilot trial that vaccine-induced immunity could be markedly enhanced by combination with standard of care chemotherapy for late stage recurrent or metastatic cervical cancer. Increased levels of myeloid-derived suppressor cells were shown to be depleted by the carboplatin and paclitaxel chemotherapy to the low levels of healthy donors, while T cell numbers in PBMC remained intact. Timed vaccination with a single dose of vaccine at the MDSC nadir during chemotherapy led to a robust vaccine-induced T cell response (4). In a subsequent chemo-immunotherapy trial with three vaccine doses, spaced by three weeks, and in cohorts of patients at four different vaccine doses, the initiation and maintenance of robust tumor-specific T cell responses was confirmed and a broad dose response relationship of tumor-specific T cell responses was noted. Preliminary data on clinical outcomes relative to HPV-specific immune responses will be discussed. In summary, therapeutic benefit of cancer vaccines can be maximized in patients with established cancers by improving vaccine design and by using vaccines in combination with standard chemotherapies. In addition cancer vaccines can establish and/or maintain tumor-specific T cells in combination with checkpoint blockade or other immunomodulatory therapies. Finally, cancer vaccines can also help to sustain and expand adoptively transferred tumor-specific T cells.

Angiogenesis is a critical component of the initiation, maintenance and progression of tumors, and has been the target of extensive drug development. In clinical practice there are several approved and investigational anti-angiogenesis drugs, the majority of which primarily target the VEGF pathway, however their long term effectiveness remains limited. In designing new drug regimens, it is important to consider other known angiogenic factors that likely contribute to the pro-angiogenic phenotype. We evaluated two such factors: thymidine phosphorylase (TP) (aka platelet-derived endothelial cell growth factor, PD-ECGF), an enzyme that can stimulate endothelial cell migration, and angiopoietin 2 (Ang2), a member of the Ang/Tie2 signaling pathway. To target TP, we used a novel, highly specific, orally available small molecule inhibitor, which we had previously designed, named AEAC. To target Ang2, we used an Ang2 neutralizing peptibody, L1-7[N] (provided by CTEP-NCI), which is a genetically engineered peptide-Fc fusion protein that specifically binds Ang2. In a mouse NCI-H460 NSCLC sc xenograft model, AEAC and L1-7[N] produced 33% and 67% reductions, respectively, in tumor growth, and the combination produced a small, but statistically significant further reduction, when compared to either agent used alone. Tumor growth inhibition was paralleled by a reduction in Ki-67 staining. L1-7[N] also produced a large infiltration of macrophages (F4/80+) into the tumors after treatment. We also tested the drug combination in a mouse genetic model of pancreatic neuroendocrine tumors (PNET). PNET are one the few human solid tumors that are clinically responsive to angiogenesis inhibitors used alone. These mice have a conditional knockout of the Men1 gene in the endocrine pancreatic cells (Pdx1-Cre;Men1 mice) mimicking a primary genetic alteration seen in human disease. Men1 KO PNET experiments were initiated when the mice were 10-11 months old, and drug treatment was daily (5 days per week) for 3 weeks. To date, we have not seen any antiangiogenic or antitumor effects of the drugs. Upon sacrifice, the mice were found to have extensive insulinomas, involving around 70% of the entire pancreas. CD31(+) and F4/80(+) cells in the pancreas showed that most of them concentrated inside the PNET, however there was no change after the treatments. Studies are currently underway to determine if higher doses and/or starting treatment at an earlier time would be more efficacious. Citation Format: Evelyn Aranda, Ziqiang Yuan, Steven K. Libutti, Edward L. Schwartz. Antitumor activity of agents targeting the angiogenic factors angiopoietin-2 and thymidine phosphorylase in mouse models of lung and pancreatic neuroendocrine cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1822. doi:10.1158/1538-7445.AM2017-1822

Bacterial infections such as Escherichia coli and necrotic enteritis (NE) caused by Clostridium perfringens (CP) are responsible for significant economic losses in the broiler chicken industry. Our previous studies have involved trying to develop alternatives to antimicrobials and immunoprotective agents to such pathogens. Previously, we demonstrated that delivery of a single dose of oligodeoxynucleotides containing unmethylated cytosine-phosphodiester-guanine motifs (CpG-ODN) can promote antimicrobial immunity against yolk sac infections caused by E. coli and Salmonella by enriching immune compartments and activating immune cells. Recently, we have demonstrated delivery of CpG-ODN twice by the intramuscular (IM) route in neonatal broiler chickens at Days 1 and 4 of age to induce trained immunity and protect against lethal E. coli septicemia later in the grow-out period. The objectives of this study were to explore the ability of CpG-ODN to induce trained immunity in broiler chickens (1) by administering CpG-ODN by the in ovo route and intrapulmonary (IPL) route at hatch and (2) by administering CpG-ODN by the in ovo route and IPL delivery of a CP vaccine at hatch to protect against E. coli infections. Intramuscular (IM) delivery of CpG-ODN twice at Days 1 and 4 of age in neonatal broiler chickens induced trained immunity to protect against NE. Induction of trained immunity in broiler chickens led to a switch in cellular energy metabolism of immune cells from glycolysis to mitochondrial oxidative phosphorylation (OXPHOS) following two administrations of CpG-ODN. We have also demonstrated that delivery of CpG-ODN by the in ovo route followed by delivery of a live CP vaccine by the IPL route at hatch induced trained immunity and significantly (P < 0.0001) protected birds against E. coli septicemia at 27 days of age. Trained immunity was induced in broiler chickens only with administrations of CpG-ODN by the in ovo route followed by the IPL route at hatch or in ovo delivery of CpG-ODN followed by IPL delivery of a live CP vaccine at hatch. These birds were significantly (P < 0.0001) protected against lethal E. coli septicemia and NE later in the production cycle, demonstrating the utility of CpG-ODN for induction of trained immunity and broad-spectrum protection of broiler chickens against common lethal bacterial infections.

Purpose:To dissect the clinical and immunologic features of people living with human immunodeficiency virus (HIV; PLWH) diagnosed with melanoma, who have consistently shown worse outcomes than HIV-negative individuals (PLw/oH) with the same cancer.Experimental Design:We analyzed electronic health records from 1,087 PLWH and 394,437 PLw/oH with melanoma. Demographic and clinical characteristics were compared. Spatial immune transcriptomics (72 immune-related genes) was performed on melanoma tumor samples (n = 11), with downstream validation using multiplex immunofluorescence (mIF; n = 15 PLWH, n = 14 PLw/oH).Results:PLWH were diagnosed at a younger age, had a greater representation of Hispanic and Black individuals, and showed reduced survival. They also had a markedly increased risk of brain metastases. PLWH experienced significant delays in initiating immune checkpoint inhibitor (ICI) therapy and had worse post-ICI survival, even after balancing covariates. Spatial transcriptomics revealed a more immunosuppressive tumor microenvironment in PLWH, with increased transcription of immune checkpoints (PD-1, LAG3) and reduced antigen-presentation markers (HLA-DRB, B2M), along with distinct spatial distributions in tumors and surrounding microenvironments. mIF demonstrated features of an exhausted CD8+ T-cell compartment, including enrichment of PD-1intLAG3− and PD-1intLAG3+ subpopulations and a significant accumulation of myeloid-derived suppressor cells (MDSC; CD11b+ HLA-DR− CD33+).Conclusions:Melanoma in PLWH is associated with distinct clinical and immunologic features, including delayed ICI treatment, reduced survival, and an immunosuppressive microenvironment with exhausted CD8+ T cells and expanded MDSCs. These findings suggest that chronic HIV infection may impair antitumor immunity in melanoma. Targeting the pathways identified here may improve therapeutic responses and outcomes in this population.

Trained immunity, induced by β-glucan in monocytes, is mediated by activating metabolic pathways that result in epigenetic rewiring of cellular functional programs; however, molecular mechanisms underlying these changes remain unclear. Here, we report a key immunometabolic and epigenetic pathway mediated by the miR–9-5p-isocitrate dehydrogenase 3α (IDH3α) axis in trained immunity. We found that β-glucan–trained miR–9-5p–/– monocytes showed decreased IL-1β, IL-6, and TNF-α production after LPS stimulation. Trained miR–9-5p–/– mice produced decreased levels of proinflammatory cytokines upon rechallenge in vivo and had worse protection against Candida albicans infection. miR–9-5p targeted IDH3α and reduced α-ketoglutarate (α-KG) levels to stabilize HIF-1α, which promoted glycolysis. Accumulating succinate and fumarate via miR–9-5p action integrated immunometabolic circuits to induce histone modifications by inhibiting KDM5 demethylases. β-Glucan–trained monocytes exhibited low IDH3α levels, and IDH3α overexpression blocked the induction of trained immunity by monocytes. Monocytes with IDH3α variants from autosomal recessive retinitis pigmentosa patients showed a trained immunity phenotype at immunometabolic and epigenetic levels. These findings suggest that miR–9-5p and IDH3α act as critical metabolic and epigenetic switches in trained immunity.

The prognosis of patients with cancer in which tumor-associated macrophages with a pro-tumoral phenotype are abundant is poor. This includes aggressive forms of non-medullary thyroid carcinoma (NMTC). Trained immunity describes long-term epigenetic and metabolic reprogramming in innate immune cells and their bone marrow progenitors, leading to improved responsiveness, which is currently being explored as a potential new treatment approach in cancer. We aimed to assess whether trained immunity can be induced in myeloidcells of patients with NMTC to enhance the anti-tumor immune response, and whether this effect is tumor-specific or can be elicited in other forms of cancers sharing the immune-mediated pathophysiology, such as colorectal carcinoma (CRC). Peripheral blood and bone marrow were obtained from 53 NMTC patients (39 differentiated and 14 poorly differentiated/anaplastic NMTC) and 13 healthy controls. Peripheral monocytes and bone marrow progenitors were isolated ex vivo, and trained immunity was induced using different stimuli. Cytokine production upon restimulation and expression of cell membrane activation markers were used as biomarkers of cellular activation. In addition, trained immunity was assessed in peripheral monocytes from seven CRC patients. Training of circulating monocytes with β-glucan or interleukin-4 resulted in amplified cytokine production upon restimulation, a hallmark of trained immunity responses. Fold changes of increase in cytokine production were comparable between the NMTC subtypes, CRC, and healthy controls. Flow cytometry showed that training of bone marrow progenitors resulted in macrophages with lower CD206 and CD163 and higher CD86 expression, a profile associated with a less immunosuppressive and more anti-tumoral phenotype. Ex vivo training of monocytes and bone marrow progenitors from patients with NMTC and CRC results in macrophages with increased proinflammatory cytokine production and differentiation toward an anti-tumoral phenotype. This suggests that trained immunity may be exploited as a potential novel treatment strategy for cancer.

Trained immunity is the long-term functional reprogramming of innate immune cells, which results in altered responses toward a secondary challenge. Despite indoxyl sulfate (IS) being a potent stimulus associated with chronic kidney disease (CKD)-related inflammation, its impact on trained immunity has not been explored. Here, we demonstrate that IS induces trained immunity in monocytes via epigenetic and metabolic reprogramming, resulting in augmented cytokine production. Mechanistically, the aryl hydrocarbon receptor (AhR) contributes to IS-trained immunity by enhancing the expression of arachidonic acid (AA) metabolism-related genes such as Arachidonate 5-Lipoxygenase (ALOX5) and ALOX5 Activating Protein (ALOX5AP). Inhibition of AhR during IS training suppresses the induction of IS-trained immunity. Monocytes from end-stage renal disease (ESRD) patients have increased ALOX5 expression and after 6-day training, they exhibit enhanced TNF-α and IL-6 production to LPS. Furthermore, healthy control-derived monocytes trained with uremic sera from ESRD patients exhibit increased production of TNF-α and IL-6. Consistently, IS-trained mice and their splenic myeloid cells had increased production of TNF-α after in vivo and ex vivo LPS stimulation compared to that of control mice. These results provide insight into the role of IS in the induction of trained immunity, which is critical during inflammatory immune responses in CKD patients.

The efficacy of chimeric antigen receptor T (CAR-T) cells for solid tumors remains unsatisfactory due to the limited tumor infiltration and immunosuppressive microenvironment. To overcome these limitations, the genetically engineered recombinant oncolytic adenoviruses (OAVs) that conditionally replicate in tumor cells were developed to modify the tumor microenvironment (TME) to facilitate CAR-T-mediated tumor eradication. Here in the present study, a novel recombinant OAV carrying CCL5, IL12, and IFN-γ controlled by Ki67 promoter was constructed (named AdKi67-C3). The antitumor activity of AdKi67-C3 was tested in vitro and in vivo by using mono administration or combing with CAR-T cells targeting B7H3. It proved that CCL5 expressed by AdKi67-C3 indeed induced more CAR-T migration in vitro and CAR-T infiltration in tumor mass in vivo. Meanwhile, cytokines of IFN-γ and IL12 secreted by AdKi67-C3-infected tumor cells significantly promoted proliferation and persistence of CAR-T cells in vitro and in vivo. In tumor-bearing xenograft mouse models of kidney, prostate or pancreatic cancer, local pretreatment with AdKi67-C3 dramatically enhanced CAR-T cell efficacy and eliminated local and distant tumors. More importantly, mice achieving complete tumor regression resisted to re-challenge with the same tumor cells, suggesting establishment of long-term antitumor immune response. Therefore, OAVs armored with cytokines could be developed as a bioenhancer to defeat the immunosuppressive microenvironment and improve therapeutic efficacy of CAR-T in solid tumors.

Immune checkpoint blockade (ICB) therapy has improved patient survival in a variety of cancers, but its resistance presents a major clinical challenge. It remains unclear whether therapeutic resistance is driven predominantly by refractory clones of cancer cells or by immunosuppressive microenvironment. To address this, we utilized syngeneic transplantation model and performed clonal tracing of cancer cells to monitor the response to ICB. Different cancer clones displayed variable sensitivity to ICB treatment, reflecting intratumoral heterogeneity in therapy response. Furthermore, different recipients manifested distinct resistance mechanisms. ICB-responders developed resistance through selection and expansion of pre-existing ICB-resistant cancer clones, whereas non-responders presented with irresponsive microenvironment rather than dominance of resistant cancer clones. Extrapolation of the tumor-infiltrating immune repertoire revealed that higher IgG and lower IgA strongly correlated with better ICB response. This biomarker was further validated in multiple clinical cohorts. Our approach discriminates different sources of resistance to ICB, and identifies humoral immunity as biomarker of ICB response. Citation Format: Shengqing Gu, Xihao Hu, Xiaoqing Wang, Peng Jiang, Ziyi Li, Nicole Traugh, Xia Bu, Xiaofang Xing, Gordon J. Freeman, Myles Brown, Xiaole S. Liu. Clonal tracing reveals different mechanisms of resistance to immune checkpoint blockade [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 3779.

SummaryToll‐like receptor 10 (TLR10) is the only member of the human Toll‐like receptor family with an inhibitory function on the induction of innate immune responses and inflammation. However, its role in the modulation of trained immunity (innate immune memory) is unknown. In the present study, we assessed whether TLR10 modulates the induction of trained immunity induced by β‐glucan or bacillus Calmette–Guérin (BCG). Interleukin 10 receptor antagonist production was increased upon activation of TLR10 ex vivo after BCG vaccination, and TLR10 protein expression on monocytes was increased after BCG vaccination, whereas anti‐TLR10 antibodies did not significantly modulate β‐glucan or BCG‐induced trained immunity in vitro. A known immunomodulatory TLR10 missense single‐nucleotide polymorphism (rs11096957) influenced trained immunity responses by β‐glucan or BCG in vitro. However, the in vivo induction of trained immunity by BCG vaccination was not influenced by TLR10 polymorphisms. In conclusion, TLR10 has a limited, non‐essential impact on the induction of trained immunity in humans.