Targeting Treg Research Articles

Cytotoxic T lymphocyte-associated protein 4 antibody aggrandizes antitumor immune response of oncolytic virus M1 via targeting regulatory T cells.

Oncolytic virotherapies are perceived as remarkable immunotherapies coming into view and represent highly promising cancer treatments, yet to figure out its specific immune responses and underlying barriers remains critical. Albeit recent studies have demonstrated that oncolytic viruses (OVs) could fine tune tumor microenvironment (TME) to elicit tumor suppression mainly due to effective T-cell responses, the interaction between suppressive T cells and OVs is barely undetermined. Herein, we found that regulatory T cells (Treg cells) were increased in the TME following systemic administration of oncolytic virus M1 along with the higher expression of relative cytokines and chemokines in both mouse RM-1 prostatic carcinoma model and mouse B16F10 melanoma model. Besides, Treg cells expressed high levels of CD25 post-M1 treatment, and its suppressive effect on CD8+ T cells was also elevated. Depletion of Treg cells in M1-treated groups significantly reinforced antitumor effect of M1. Specific targeting of Treg cells using cytotoxic T lymphocyte-associated protein 4 (CTLA-4) antibody (Ab) in combination with M1 treatment elicited a more profound tumor suppression and longer overall survival time than M1 alone in both tumor models. Moreover, CTLA-4 Ab further aggrandized antitumor immune response elicited by M1, including increased infiltration of CD45+ immune cells and CD8+ or CD4+ T lymphocytes, decreased ratio of Treg cells to CD4+ T lymphocytes, the intensified lymphocytotoxicity and elevated secretion of cytotoxic cytokines like interferon-γ, granzyme B and perforin. Therefore, our findings constituted a suggestive evidence that targeting Treg cells in M1-based oncolytic virotherapy may achieve a highly response in clinical cancer research.

To Go or Not to Go?-Targeting Tregs Traveling in Tumors.

Regulatory T cells (Treg) are one of the major impediments to effective antitumor immunity and successful immunotherapy. Elevated intratumoral Treg frequencies, observed in a variety of malignancies, have been associated with poor prognosis. In this issue of Cancer Research, two studies underscore the potential of harnessing the unique migratory profile of tumor-infiltrating Tregs to selectively eliminate these cells without compromising peripheral tolerance. Both studies identify surface migratory receptors, CCR8 by Campbell and colleagues and GPR15 by Adamczyk and colleagues, as selective markers of intratumoral Tregs in tumor-bearing mice and patients with cancer. Genetic deletion of GPR15 or antibody-mediated depletion of CCR8 was found to preferentially decrease tumor-infiltrating Tregs and substantially delayed tumor progression. Together, these two studies highlight the significance of migratory molecules in intratumoral Tregs and propose two potential selective targets for preferential elimination of tumor-associated "pathogenic" Tregs, which can be hijacked to enhance the response to immunotherapy.See related articles by Adamczyk et al., p. 2970 and Campbell et al., p. 2983.

Targeting Treg cells with GITR activation alleviates resistance to immunotherapy in murine glioblastomas

Immune checkpoint blockers (ICBs) have failed in all phase III glioblastoma (GBM) trials. Here, we show that regulatory T (Treg) cells play a key role in GBM resistance to ICBs in experimental gliomas. Targeting glucocorticoid-induced TNFR-related receptor (GITR) in Treg cells using an agonistic antibody (αGITR) promotes CD4 Treg cell differentiation into CD4 effector T cells, alleviates Treg cell-mediated suppression of anti-tumor immune response, and induces potent anti-tumor effector cells in GBM. The reprogrammed GBM-infiltrating Treg cells express genes associated with a Th1 response signature, produce IFNγ, and acquire cytotoxic activity against GBM tumor cells while losing their suppressive function. αGITR and αPD1 antibodies increase survival benefit in three experimental GBM models, with a fraction of cohorts exhibiting complete tumor eradication and immune memory upon tumor re-challenge. Moreover, αGITR and αPD1 synergize with the standard of care treatment for newly-diagnosed GBM, enhancing the cure rates in these GBM models.

Reducing the immunosuppressive tumor microenvironment enhances photoimmunotherapy efficacy.

Reducing the immunosuppressive tumor microenvironment enhances photoimmunotherapy efficacy.

Exosomal miR-208b related with oxaliplatin resistance promotes Treg expansion in colorectal cancer

Oxaliplatin resistance is a challenge in the treatment of colorectal cancer (CRC) patients. Regulatory T cells (Tregs) are well known for their immunosuppressive roles, and targeting Tregs is an effective way to improve chemosensitivity. Exosome-delivered microRNA (miRNA) might be used as a potential biomarker for predicting chemosensitivity. However, the relationship between Tregs and exosomal miRNAs remains largely unknown. TaqMan low-density array was performed to screen the differentially expressed serum miRNAs from pooled serum of patients who had FOLFOX treatment. Differential expression was validated using qRT-PCR in individual samples. Exosomes were isolated by sequential differential centrifugation, and they were verified by transmission electron microscopy. The RNA and protein levels were determined by quantitative real-time PCR and western blotting. A mouse xenograft model was adopted to evaluate the correlation between exosome-derived miR-208b and Tregs in vivo. We demonstrated that circulating miR-208b is a non-invasive marker for predicting FOLFOX sensitivity in CRC. miR-208b in colon cancer was secreted by tumor cells in the pattern of exosomes, and oxaliplatin-resistant cells showed the most obvious phenomenon of miR-208b increase. Colon cancer cell-secreted miR-208b was sufficiently delivered into recipient T cells to promote Treg expansion by targeting programmed cell death factor 4 (PDCD4). Furthermore, in vivo studies indicated that Treg expansion mediated by cancer cell-secreted miR-208b resulted in tumor growth and oxaliplatin resistance. Our results demonstrate that tumor-secreted miR-208b promotes Treg expansion by targeting PDCD4, and it may be related to a decrease of oxaliplatin-based chemosensitivity in CRC. These findings highlight a potential role of exosomal miR-208b as a predictive biomarker for oxaliplatin-based therapy response, and they provide a novel target for immunotherapy.

Fc-Optimized Anti-CCR8 Antibody Depletes Regulatory T Cells in Human Tumor Models.

FOXP3+ regulatory T cells (Treg) play a critical role in mediating tolerance to self-antigens and can repress antitumor immunity through multiple mechanisms. Therefore, targeted depletion of tumor-resident Tregs is warranted to promote effective antitumor immunity while preserving peripheral homeostasis. Here, we propose the chemokine receptor CCR8 as one such optimal tumor Treg target. CCR8 was expressed by Tregs in both murine and human tumors, and unlike CCR4, a Treg depletion target in the clinic, CCR8 was selectively expressed on suppressive tumor Tregs and minimally expressed on proinflammatory effector T cells (Teff). Preclinical mouse tumor modeling showed that depletion of CCR8+ Tregs through an FcyR-engaging anti-CCR8 antibody, but not blockade, enabled dose-dependent, effective, and long-lasting antitumor immunity that synergized with PD-1 blockade. This depletion was tumor Treg-restricted, sparing CCR8+ T cells in the spleen, thymus, and skin of mice. Importantly, Fc-optimized, nonfucosylated (nf) anti-human CCR8 antibodies specifically depleted Tregs and not Teffs in ex vivo tumor cultures from primary human specimens. These findings suggest that anti-CCR8-nf antibodies may deliver optimal tumor-targeted Treg depletion in the clinic, providing long-term antitumor memory responses while limiting peripheral toxicities. SIGNIFICANCE: These findings show that selective depletion of regulatory T cells with an anti-CCR8 antibody can improve antitumor immune responses as a monotherapy or in combination with other immunotherapies. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/11/2983/F1.large.jpg.

GPR15 Facilitates Recruitment of Regulatory T Cells to Promote Colorectal Cancer.

Colorectal cancer is one of the most frequent malignancies worldwide. Despite considerable progress in early detection and treatment, there is still an unmet need for novel antitumor therapies, particularly in advanced colorectal cancer. Regulatory T cells (Treg) are increased in the peripheral blood and tumor tissue of patients with colorectal cancer. Recently, transient ablation of tumor-associated Tregs was shown to foster CD8+ T-cell-mediated antitumoral immunity in murine colorectal cancer models. However, before considering therapies on targeting Tregs in patients with cancer, detailed knowledge of the phenotype and features of tumor-associated Tregs is indispensable. Here, we demonstrate in a murine model of inflammation-induced colorectal cancer that tumor-associated Tregs are mainly of thymic origin and equipped with a specific set of molecules strongly associated with enhanced migratory properties. Particularly, a dense infiltration of Tregs in mouse and human colorectal cancer lesions correlated with increased expression of the orphan chemoattractant receptor GPR15 on these cells. Comprehensive gene expression analysis revealed that tumor-associated GPR15+ Tregs have a Th17-like phenotype, thereby producing IL17 and TNFα. Gpr15 deficiency repressed Treg infiltration in colorectal cancer, which paved the way for enhanced antitumoral CD8+ T-cell immunity and reduced tumorigenesis. In conclusion, GPR15 represents a promising novel target for modifying T-cell-mediated antitumoral immunity in colorectal cancer. SIGNIFICANCE: The G protein-coupled receptor 15, an unconventional chemokine receptor, directs Tregs into the colon, thereby modifying the tumor microenvironment and promoting intestinal tumorigenesis.See related commentary by Chakraborty and Zappasodi, p. 2817.

Advances in Human Immune System Mouse Models for Personalized Treg-Based Immunotherapies.

Immunodeficient mice engrafted with a functional human immune system [Human immune system (HIS) mice] have paved the way to major advances for personalized medicine and translation of immune-based therapies. One prerequisite for advancing personalized medicine is modeling the immune system of individuals or disease groups in a preclinical setting. HIS mice engrafted with peripheral blood mononuclear cells have provided fundamental insights in underlying mechanisms guiding immune activation vs. regulation in several diseases including cancer. However, the development of Graft-vs.-host disease restrains relevant long-term studies in HIS mice. Alternatively, engraftment with hematopoietic stem cells (HSCs) enables mimicking different disease stages, however, low frequencies of HSCs in peripheral blood of adults impede engraftment efficacy. One possibility to overcome those limitations is the use of patient-derived induced pluripotent stem cells (iPSCs) reprogrammed into HSCs, a challenging process which has recently seen major advances. Personalized HIS mice bridge research in mice and human diseases thereby facilitating the translation of immunomodulatory therapies. Regulatory T cells (Tregs) are important mediators of immune suppression and thereby contribute to tumor immune evasion, which has made them a central target for cancer immunotherapies. Importantly, studying Tregs in the human immune system in vivo in HIS mice will help to determine requirements for efficient Treg-targeting. In this review article, we discuss advances on personalized HIS models using reprogrammed iPSCs and review the use of HIS mice to study requirements for efficient targeting of human Tregs for personalized cancer immunotherapies.

Transcriptional regulation of VEGFA expression in T-regulatory cells from breast cancer patients.

The initiation of new bloodvessel formation (neo-angiogenesis) is one of the primary requirements for the establishment of tumor. As the tumor grows beyond a certain size, a hypoxic-condition arises in the inner core of tumor, triggering the release of chemokines, which attract T-regulatory (Treg) cells in the tumor-site. The presence of FOXP3, a lineage-specific transcription factor, expressing Treg cells in various types of tumor implements immunosuppressive and tumor-promoting strategies. One such strategy is the invitation of endothelial cells for neo-vascularization in the tumor site. Here we report that as the disease progresses, Treg cells from breast cancer patients are capable of secreting high-amount of VEGFA. The VEGFA promoter lacks Treg-specific transcription factor FOXP3 binding site. FOXP3 in associationwith locus-specific transcription factor STAT3 binds to VEGFA promoter to induce its transcription in Treg cells obtained from breast cancer patients. Treg cell-secreted VEGFA induces neo-angiogenesis from endothelial cells under in-vitro conditions. Targeting Tregs in mice with breast tumor reduces tumor growth as well as the level of neo-angiogenesis in the tumor tissue.

Regulatory T cell targeting in cancer: Emerging strategies in immunotherapy.

The adaptive immune system is modulated by an important subset of CD4+ T lymphocytes called Treg cells that function in maintaining immune homeostasis by preventing excessive immune activation. Both deficiency and overactivation of Treg cell function can result in disease pathology. While loss of Treg function can lead to autoimmunity, an overabundance of Treg activity can promote tumorigenesis. Blocking and/or depleting Tregs has emerged as a viable strategy to enhance antitumor immunity. A major limitation underlying the limited efficacy observed with Treg therapies in the clinic is lack of selective targeting, often attributed to concurrent depletion of antitumor effector T-cell populations. Novel approaches to improve the specificity of Treg targeting in the context of cancer include the use of T-cell receptor mimic antibodies, bispecific antibodies, and near-infrared photoimmunotherapy. Next-generation technology platforms and transcriptomic/computational-based screening methods have been recently developed to identify preferential Treg targets. Herein, we highlight key advancements and challenges pertaining to the development of novel Treg targeting cancer therapeutics and discuss ongoing clinical trials evaluating next-generation Treg therapies for solid tumors.

Heterogeneity of Regulatory T Cells in B-Cell Non-Hodgkin Lymphoma

Introduction: Regulatory T cells (Tregs), a highly immunosuppressive subset of CD4 T cells, are enriched in B-cell non-Hodgkin lymphoma (NHL) and constitute a barrier to potent antitumor immune responses. Despite extensive studies, the significance of tumor-infiltrating Tregs on disease outcome is unclear and while Tregs may express co-inhibitory and co-stimulatory receptors, the role of intratumoral Tregs in the context of immune checkpoint therapy remains elusive. Emerging evidence suggests heterogeneity among Tregs and their suppressive capacities in cancer, emphasizing the need for additional markers to identify highly suppressive Tregs. Therefore, an in-depth characterization of Treg heterogeneity in NHL could provide important insight into the disease pathogenesis and have implications for rational drug design. Methods: Expression of checkpoint receptors in Tregs was characterized by fluorescence flow cytometry and mass cytometry analysis of single-cell suspensions from diffuse large B-cell lymphoma (DLBCL; n = 16), follicular lymphoma (FL; n = 8), mantle cell lymphoma (MCL; n = 10), marginal zone lymphoma (MZL; n = 2), chronic lymphocytic lymphoma (CLL; n = 7), as well as tonsils (n = 8) and peripheral blood (n = 4) from healthy donors. Functional characterization of intratumoral Tregs was performed by a proliferation assay using FACS-sorted Tregs as suppressor cells and autologous CellTrace Violet-labelled T effector cells as responder cells. Single-cell RNA sequencing (scRNA-seq) was performed on FACS-sorted CD4 T cells from 3 DLBCL, 3 FL and 3 healthy donor tonsils using the 10X Genomics single cell 5' based library construction and VDJ libraries for TCR-sequencing. Additionally, for simultaneous profiling of phenotypic features with the mRNA expression in single cells, Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITEseq) was applied. The Treg compartment was characterized by clustering into distinct transcriptional Treg states and differential expression of marker genes. Results: TIGIT and CTLA-4 were identified as common markers of intratumoral Tregs, in addition to FOXP3 and CD25. Unsupervised computational analysis revealed two distinct Treg subsets, based on contrasting expression of PD-1, OX40, CD226 and ICOS (Figure 1A). One subset displayed a checkpoint receptorlow phenotype that corresponded to peripheral blood Tregs. The second subset had a checkpoint receptorhigh phenotype with elevated levels of PD-1, OX40, ICOS, TIGIT, CTLA-4 and increased levels of activation markers CD28, CD69 and CD95/Fas. The frequency of checkpoint receptorhigh Tregs was significantly increased in NHL tumors, compared to PBMCs and tonsils from healthy donors. FL tumors had the highest frequency of Tregs with receptorhigh phenotype among the NHL entities (median frequency of 86%, range 71-92%) and DLBCL had the highest donor-to-donor variation (median frequency of 77%, range 35-98%) (Figure 1B). This phenotypic heterogeneity of the Treg compartment reflected different suppressive capacities of the two subsets. Checkpoint receptorhigh Tregs were more potent mediators of immunosuppression in terms of suppressing the proliferation of autologous effector CD4 and CD8 T cells (Figure 1C). Furthermore, transcriptomic analysis of CD4 T cells by scRNA-seq and CITEseq revealed distinct transcriptomic signatures of the checkpoint receptorhigh and -receptorlow subsets. In addition, a third subset of Tregs, characterized by increased expression of LAG3 and immunosuppression-associated genes (CTLA-4, IL10, CD38, KLRB1) but lack of FOXP3, was identified (Figure 1D-E). Analysis of scTCR-sequences to compare TCR repertoires and to identify developmental trajectories will further add to our knowledge of intratumoral Tregs. Conclusions: These results reveal heterogeneity within the Treg compartment in NHL based on expression of checkpoint receptors, transcriptional profiles and suppressive capacities. As intratumoral Treg phenotypes differ from peripheral blood Tregs, this presents new therapeutic opportunities. Specific targeting of intratumoral Tregs would lead to stronger antitumor effects while limiting immune-related adverse events. A deeper understanding of Treg heterogeneity within the tumor microenvironment could therefore open new paths for rational design of immune checkpoint therapy. Disclosures Kolstad: Merck: Research Funding; Nordic Nanovector: Membership on an entity's Board of Directors or advisory committees, Research Funding. Alizadeh:Janssen: Consultancy; Genentech: Consultancy; Pharmacyclics: Consultancy; Chugai: Consultancy; Celgene: Consultancy; Gilead: Consultancy; Roche: Consultancy; Pfizer: Research Funding.

Orca-T, a Precision Treg-Engineered Donor Product, Prevents Acute Gvhd with Less Immunosuppression in an Early Multicenter Experience with Myeloablative HLA-Matched Transplants

Orca-T, a Precision Treg-Engineered Donor Product, Prevents Acute Gvhd with Less Immunosuppression in an Early Multicenter Experience with Myeloablative HLA-Matched Transplants

Foxp3+ Regulatory T Cell Depletion after Nonablative Oligofractionated Irradiation Boosts the Abscopal Effects in Murine Malignant Mesothelioma.

Increasing evidence indicates that local hypofractionated radiotherapy (LRT) can elicit both immunogenic and immunosuppressive local and systemic immune responses. We thus hypothesized that blockade of LRT-induced immunosuppressive responses could augment the antitumor effects and induce an abscopal response. In this study, we found that the upregulation of Foxp3+ regulatory T cells (Tregs) in the mesothelioma tumor microenvironment after nonablative oligofractionated irradiation significantly limited the success of irradiation. Using DEREG mice, which allow conditional and efficient depletion of Foxp3+ Tregs by diphtheria toxin injection, we observed that transient Foxp3+ Treg depletion immediately after nonablative oligofractionated irradiation provided synergistic local control and biased the T cell repertoire toward central and effector memory T cells, resulting in long-term cure. Furthermore, this combination therapy showed significant abscopal effect on the nonirradiated tumors in a concomitant model of mesothelioma through systemic activation of cytotoxic T cells and enhanced production of IFN-γ and granzyme B. Although local control was preserved with one fraction of nonablative irradiation, three fractions were required to generate the abscopal effect. PD-1 and CTLA-4 were upregulated on tumor-infiltrating CD4+ and CD8+ T cells in irradiated and nonirradiated tumors, suggesting that immune checkpoint inhibitors could be beneficial after LRT and Foxp3+ Treg depletion. Our findings are applicable to the strategy of immuno-radiotherapy for generating optimal antitumor immune responses in the clinical setting. Targeting Tregs immediately after a short course of irradiation could have a major impact on the local response to irradiation and its abscopal effect.

Nonhuman Primate Testing of the Impact of Different Regulatory T Cell Depletion Strategies on Reactivation and Clearance of Latent Simian Immunodeficiency Virus.

Regulatory T cells (Tregs) may be key contributors to the HIV/SIV latent reservoir, since they harbor high levels of HIV/SIV; reverse CD4+ T cell immune activation status, increasing the pool of resting CD4+ T cells; and impair CD8+ T cell function, favoring HIV persistence. We tested the hypothesis that Treg depletion is a valid intervention toward an HIV cure by depleted Tregs in 14 rhesus macaque (RM) controllers infected with SIVsab, the virus that naturally infects sabaeus monkeys, through different strategies: administration of an anti-CCR4 immunotoxin, two doses of an anti-CD25 immunotoxin (interleukin-2 with diphtheria toxin [IL-2-DT]), or two combinations of both. All of these treatments resulted in significant depletion of the circulating Tregs (>70%) and their partial depletion in the gut (25%) and lymph nodes (>50%). The fractions of CD4+ T cells expressing Ki -67 increased up to 80% in experiments containing IL-2-DT and only 30% in anti-CCR4-treated RMs, paralleled by increases in the inflammatory cytokines. In the absence of ART, plasma virus rebounded to 103 vRNA copies/ml by day 10 after IL-2-DT administration. A large but transient boost of the SIV-specific CD8+ T cell responses occurred in IL-2-DT-treated RMs. Such increases were minimal in the RMs receiving anti-CCR4-based regimens. Five RMs received IL-2-DT on ART, but treatment was discontinued because of high toxicity and lymphopenia. As such, while all treatments depleted a significant proportion of Tregs, the side effects in the presence of ART prevent their clinical use and call for different Treg depletion approaches. Thus, based on our data, Treg targeting as a strategy for HIV cure cannot be discarded.IMPORTANCE Regulatory T cells (Tregs) can decisively contribute to the establishment and persistence of the HIV reservoir, since they harbor high levels of HIV/SIV, increase the pool of resting CD4+ T cells by reversing their immune activation status, and impair CD8+ T cell function, favoring HIV persistence. We tested multiple Treg depletion strategies and showed that all of them are at least partially successful in depleting Tregs. As such, Treg depletion appears to be a valid intervention toward an HIV cure, reducing the size of the reservoir, reactivating the virus, and boosting cell-mediated immune responses. Yet, when Treg depletion was attempted in ART-suppressed animals, the treatment had to be discontinued due to high toxicity and lymphopenia. Therefore, while Treg targeting as a strategy for HIV cure cannot be discarded, the methodology for Treg depletion has to be revisited.

Abstract 4532: Preclinical evaluation of JTX-1811, an anti-CCR8 antibody with enhanced ADCC activity, for preferential depletion of tumor-infiltrating regulatory T cells

Abstract Introduction: Immune checkpoint blockade (ICB) has revolutionized the treatment of many cancers, still most patients do not respond to PD-1 or CTLA-4 inhibitors. Thus, new Immuno-Oncology (IO) therapies that could potentially benefit non-responding patients are greatly needed. Jounce has generated cell type-specific gene signatures as a means of probing The Cancer Genome Atlas and other large datasets for novel IO targets. Regulatory T cells (Tregs) are one attractive cell type for targeting as they may contribute to resistance to ICB. While Tregs are critical for immune homeostasis and preventing tissue damage, they are often present in large numbers within tumors where they may suppress anti-tumor immunity. Therapeutic strategies that specifically deplete tumor-infiltrating Tregs (TITRs) while sparing peripheral and normal tissue Tregs are highly desirable. Using a Treg gene signature, we have a found a strong correlation with TITRs and CCR8 (C-C motif chemokine receptor 8) across multiple tumor types. CCR8 may be differentiated from other known Treg targets in this regard, as its expression was found to be highly selective to TITRs. Methods and Results: We first assessed CCR8 levels on TITRs across multiple tumor types and compared expression to Tregs in normal colon tissue or peripheral blood. On average, peripheral blood Tregs had nearly undetectable CCR8 expression and normal colon tissue Tregs showed 4 to 5-fold lower levels of CCR8 than TITRs. We then generated a panel of monoclonal antibodies (mAbs) that bind specifically to CCR8, but not other family members, and block CCR8 signaling induced by its ligand CCL1. The ability of these mAbs to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) of target cells expressing CCR8 was tested. When target cells expressed CCR8 at levels equivalent to normal tissue Tregs no ADCC activity was observed. In contrast, when cells expressed CCR8 at levels equivalent to TITRs, robust ADCC was observed, but only using antibodies in which the human IgG1 Fc was afucosylated. Thus, afucosylated anti-CCR8 antibodies demonstrated a therapeutic window whereby TITRs but not normal tissue Tregs could be depleted. An Fc competent, mouse-specific, anti-CCR8 antibody showed single agent tumor growth inhibition across several murine tumor models - including models in which anti-PD-1 was ineffective. Anti-CCR8 was a potent combination partner with anti-PD-1 resulting in 50% complete tumor regressions in PD-1 resistant models. Conclusions: Based on these pre-clinical data JTX-1811, a high affinity CCR8-specific humanized monoclonal antibody with enhanced ADCC activity, is being developed for the selective depletion of tumor-infiltrating Tregs. JTX-1811 may be useful in PD-1 resistant settings and may restore the activity of PD-1 inhibitors in the setting of primary or acquired resistance to ICB. Citation Format: Fabien Dépis, Changyun Hu, Jessica Weaver, Lara McGrath, Boris Klebanov, Joshua Buggé, Ben Umiker, Christine Fregeau, Dhruvkumar Upadhyay, Anirudh Singh, Chang-Ai Xu, Vikki Spaulding, Michelle Priess, Masie Wong, Seema Naheed, Yan Zhang, Kristin Legendre, Edward C. Stack, Alessandro Mora, Margaret Willer, Kristan Meetze, Monica Gostissa, Michael A. Meehl, Donald R. Shaffer. Preclinical evaluation of JTX-1811, an anti-CCR8 antibody with enhanced ADCC activity, for preferential depletion of tumor-infiltrating regulatory T cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4532.

Primary breast tumours but not lung metastases induce protective anti-tumour immune responses after Treg-depletion

Although metastatic disease is responsible for the majority of cancer deaths, tests of novel immunotherapies in mouse tumour models often focus on primary tumours without determining whether these therapies also target metastatic disease. This study examined the impact of depleting Foxp3+ regulatory T cells (Treg), on lung metastases, using a mouse model of breast cancer. After Treg-depletion, generation of an immune response to the primary tumour was a critical determinant for limiting development of metastasis. Indeed, resection of the primary tumour abrogated any effect of Treg-depletion on metastases. In addition, whilst the immune response, generated by the primary tumour, prevented metastases development, it had little impact on controlling established disease. Collectively, the data indicate that metastatic cells in the lung are not controlled by immune responses induced by the primary tumour. These findings indicate that targeting Tregs alone will not suffice for treating lung metastases.

PD47-05 REGULATORY T CELLS PLAY A KEY ROLE IN BLADDER CANCER DEVELOPMENT

You have accessJournal of UrologyBladder Cancer: Basic Research & Pathophysiology IV (PD47)1 Apr 2020PD47-05 REGULATORY T CELLS PLAY A KEY ROLE IN BLADDER CANCER DEVELOPMENT Karen Wheeler*, Niannan Ji, Neelam Mukherjee, and Robert Svatek Karen Wheeler*Karen Wheeler* More articles by this author , Niannan JiNiannan Ji More articles by this author , Neelam MukherjeeNeelam Mukherjee More articles by this author , and Robert SvatekRobert Svatek More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000934.05AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Regulatory T cells (Treg) are vital in the development and maintenance of immune tolerance. They function to dampen immune responses and their dysfunction leads to autoimmune disease. Treg are known to play key roles in the development of cancers including lung, breast, head and neck, and others. They are believed to aid the tumors in immune evasion. In bladder cancer (BCa), clinical studies have shown an increase in Treg in patients’ tumors or peripheral blood correlates with a worse prognosis. Herein we determine whether Treg play a key role in the development of BCa. METHODS: Female wild type C57BL/6 mice or transgenic DEREG mice (express a diptheria toxin [DT] receptor whenever Foxp3, the driver of a Treg phenotype, is expressed) were used. Metastatic cancer was induced by injecting 0.5 x 106 MB49 bladder tumor cells via tail vein into mice on the day of surgery. Orthotopic (bladder) cancer was induced by catheterizing the bladders of female mice and injecting poly-L-lysine followed by 0.08x106 MB49 cells at day 0. Treg were depleted in DEREG mice with administration of 50g/kg DT given intraperitoneally every 4 days. Mice were sacrificed at days 21-26 and bladders, lungs, and bladder draining lymph nodes (BLN) were harvested for weight and flow cytometric analysis. RESULTS: In mice that received both orthotopic and intravenous bladder tumor challenge, Treg were increased in the bladder tumors but not the lymph nodes or lung (Fig 1). In DEREG mice challenged with orthotopic BCa, depletion of Treg with DT administration abrogated the development of BCa (Fig 2A). Additionally, Treg depleted mice had an increase in the number and percentage of antigen specific CD8+ T cells in the bladder draining lymph nodes as well as an increase in activated CD4+ T cells (Fig 2B). CONCLUSIONS: Regulatory T cells are necessary for BCa development in the orthotopic model of BCa. Treg appear to function in an antigen-specific manner, but pan-T cell activation cannot be excluded. Development of immunotherapy targeting Treg in the bladder may represent a novel cancer therapeutic. Source of Funding: AUA Care Foundation Award, CPRIT Training Grant © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e927-e927 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Karen Wheeler* More articles by this author Niannan Ji More articles by this author Neelam Mukherjee More articles by this author Robert Svatek More articles by this author Expand All Advertisement PDF downloadLoading ...

Targeting the immunosuppressive tumor microenvironment: Synergistic effect of low-dose IL12 in combination with dual immune checkpoint inhibition in a preclinical model of ovarian cancer.

7 Background: Epithelial ovarian cancer (OC) is the most lethal gynecologic cancer with ~22,000 women diagnosed annually in the US. The impact of immune checkpoint inhibition (ICI) in the treatment of solid tumors has been significant. However, the response rates for OC are low ranging from 11-15%. It is critical to explore strategies to enhance the efficacy of ICI immunotherapy in OC. Targeting immunosuppressive factors and cells within the tumor microenvironment (TME) represents a feasible approach. The use of IL12 is attractive because induces potent antitumor activity by targeting myeloid cells and lymphocytes. However its clinical application has been hindered by its potential systemic toxicity. Here we explore the use of low dose intraperitoneal IL12 to enhance the antitumor activity of dual ICI in OC. Methods: Mice bearing ID8-VEGF tumors implanted intraperitoneally received either anti-PD1 alone or dual ICI treatment of anti-PD1 plus anti-CTLA4 with or without low dose IL12. Ascites accumulation was used as surrogate for tumor progression and determined by assessing weight increase. Blood and ascites were analyzed by flow cytometry for frequency of PMN-MDSC, M-MDSC, and activated T cells. Results: Low dose IL12 alone induced a significant delay in ascites accumulation when compared to untreated controls or mice treated with PD1 monotherapy or dual ICI. Addition of IL12 to dual ICI resulted in significant tumor regression and extended survival benefit compared to dual ICI alone. A synergistic effect of IL12 was not observed when combined with PD1 monotherapy. Antitumor responses associated with a marked decrease in the frequency of M-MDSC in blood and a decrease in both PMN- and M-MDSC in ascites. Decrease in MDSC associated with elevated levels of activated T cells. Conclusions: Low dose IL12 can induce regression of ID8-VEGF tumors. However, durable responses were only observed when IL12 was added to dual ICI. This suggests that IL12 can induce changes in the TME, particularly on MDSC, that can potentiate the antitumor activity of dual ICI. Our findings also suggest a crucial role of CTLA4 blockade perhaps via Treg targeting.

Immune checkpoint molecules in pregnancy: Focus on regulatory Tcells.

Regulatory T (Treg) cells are a specialized subpopulation of Tcells that plays critical roles in the maintenance of immune homeostasis. Although efforts have been done, their role in human pregnancy is not fully understood. Numerous studies reported the presence of Treg cells throughout gestation by promoting maternal-fetal tolerance and fetal development. Furthermore, Treg population is heterogeneous as it is expressing different immune checkpoint molecules favoring immune suppressive function. Therefore, better understanding of the heterogeneity and function of Treg cells during pregnancy is critical for an effective immune intervention. Latest evidence has shown that several immune checkpoint molecules are closely associated with pregnancy outcome via multiple inhibitory mechanisms. Majority of these studies demonstrated the modulatory effects of immune checkpoint molecules on effector T-cell immunity, but their effects on Treg activation and function are still an enigma. In this review, we emphasize the potential influence of multiple immune checkpoint molecules, including CTLA-4, PD-1, Tim-3, LAG-3, and TIGIT, either in membrane or soluble form, on the function of decidual and peripheral Treg cells during pregnancy. Additionally, we discuss the promising future of targeting Treg cells via immune checkpoint molecules for pregnancy maintenance and prevention of complicated pregnancies.

Regulatory T Cells in the Tumor Microenvironment.

Regulatory T cells (Tregs) are an immunosuppressive subpopulation of CD4+ T cells that are endowed with potent suppressive activity and function to limit immune activation and maintain homeostasis. These cells are identified by the hallmark transcription factor FOXP3 and the high-affinity interleukin-2 (IL-2) receptor chain CD25. Tregs can be recruited to and persist within the tumor microenvironment (TME), acting as a potent barrier to effective antitumor immunity. This chapter will discuss [i] the history and hallmarks of Tregs; [ii] the recruitment, development, and persistence of Tregs within the TME; [iii] Treg function within TME; asnd [iv] the therapeutic targeting of Tregs in the clinic. This chapter will conclude with a discussion of likely trends and future directions.