Identification of novel human CC chemokine receptor 8 (CCR8) antagonists via the synthesis of naphthalene amide and sulfonamide isosteres.

The human CC chemokine receptor 8 (CCR8) has been extensively pursued as target for the treatment of various inflammatory disorders. More recently, the importance of CCR8 in the tumor microenvironment has been demonstrated, spurring the interest in CCR8 antagonism as therapeutic strategy in immuno-oncology. On a previously described naphthalene sulfonamide with CCR8 antagonistic properties, the concept of isosterism was applied, leading to the discovery of novel CCR8 antagonists with IC50 values in the nM range in both the CCL1 competition binding and CCR8 calcium mobilization assay. The excellent CCR8 antagonistic activity of the most potent congeners was rationalized by homology molecular modeling.

Unveiling the structural mechanisms of nonpeptide ligand recognition and activation in human chemokine receptor CCR8.

The human CC chemokine receptor 8 (CCR8) is an emerging therapeutic target for cancer immunotherapy and autoimmune diseases. Understanding the molecular recognition of CCR8, particularly with nonpeptide ligands, is valuable for drug development. Here, we report three cryo-electron microscopy structures of human CCR8 complexed with Gi trimers in the ligand-free state or activated by nonpeptide agonists LMD-009 and ZK 756326. A conserved Y1.39Y3.32E7.39 motif in the orthosteric binding pocket is shown to play a crucial role in the chemokine and nonpeptide ligand recognition. Structural and functional analyses indicate that the lack of conservation in Y1143.33 and Y1724.64 among the CC chemokine receptors could potentially contribute to the selectivity of the nonpeptide ligand binding to CCR8. These findings present the characterization of the molecular interaction between a nonpeptide agonist and a chemokine receptor, aiding the development of therapeutics targeting related diseases through a structure-based approach.

Development of a cellular model to study CCR8 signaling in tumor-infiltrating regulatory T cells.

The human CC chemokine receptor 8 (CCR8) is specifically expressed on tumor-infiltrating regulatory T cells (TITRs) and is a promising drug target for cancer immunotherapy. However, the role of CCR8 signaling in TITR biology and the effectiveness of CCR8 small molecule antagonists as TITR-targeting immunotherapy remain subjects of ongoing debate. In this work, we generated a novel cellular model of TITRs by culturing peripheral blood mononuclear cell-derived regulatory T cells in medium containing tumor cell-conditioned medium, CD3/CD28 activator, interleukin-2 and 1α,25-dihydroxyvitamin D3. This cellular model (named TITR mimics) highly and stably expressed a series of TITR signature molecules, including CCR8, FOXP3, CD30, CD39, CD134, CD137, TIGIT and Tim-3. Moreover, TITR mimics displayed robust in vitro immunosuppressive activity. To unravel the functional role of CCR8 in TITR mimics, a chemotaxis assay was performed showing strong and CCR8-specific migration toward CCL1, the natural chemokine agonist of CCR8. However, either stimulation (with CCL1) or blocking (with the small molecule antagonist NS-15) of CCR8 signaling did not affect the immunosuppressive activity, proliferation and survival of TITR mimics. Collectively, our work provides a method for the generation of TITR mimics in vitro, which can be used to study TITR biology and to evaluate drug candidates targeting TITRs. Furthermore, our findings suggest that CCR8 signaling primarily regulates migration of these cells.

MiR-184-5p represses neuropathic pain by regulating CCL1/CCR8 signaling interplay in the spinal cord in diabetic mice.

BACKGROUND: Diabetic neuropathic pain (DNP) is a serious complication for diabetic patients involving nervous system. MicroRNAs (miRNAs) are small-noncoding RNAs which are dysregulated in neuropathic pain, and might be critical molecules for pain treatment. Our previous study has shown miR-184-5p was significantly downregulated in DNP. Therefore, the mechanism of miR-184-5p in DNP was investigated in this study. METHODS: A DNP model was established through streptozotocin (STZ). The pharmacological tools were injected intrathecally, and pain behavior was evaluated by paw withdrawal mechanical thresholds (PWMTs). Bioinformatics analysis, Dual-luciferase reporter assay and fluorescence-in-situ-hybridization (FISH) were used to seek and confirm the potential target genes of miR-184-5p. The expression of relative genes and proteins was analyzed by quantitative reverse transcriptase real-time PCR (qPCR) and western blotting. RESULTS: MiR-184-5p expression was down-regulated in spinal dorsal on days 7 and 14 after STZ, while intrathecal administration of miR-184-5p agomir attenuates neuropathic pain induced by DNP and intrathecal miR-184-5p antagomir induces pain behaviors in naïve mice. Chemokine CC motif ligand 1 (CCL1) was found to be a potential target of miR-184-5p and the protein expression of CCL1 and the mRNA expression of CCR8 were up-regulated in spinal dorsal on days 7 and 14 after STZ. The luciferase reporter assay and FISH demonstrated that CCL1 is a direct target of miR-184-5p. MiR-184-5p overexpression attenuated the expression of CCL1/CCR8 in DNP; intrathecal miR-184-5p antagomir increased the expression of CCL1/CCR8 in spinal dorsal of naïve mice. CONCLUSION: This research illustrates that miR-184-5p alleviates DNP through the inhibition of CCL1/CCR8 signaling expression.

Structural basis of antibody inhibition and chemokine activation of the human CC chemokine receptor 8.

The C-C motif chemokine receptor 8 (CCR8) is a class A G-protein coupled receptor that has emerged as a promising therapeutic target in cancer. Targeting CCR8 with an antibody has appeared to be an attractive therapeutic approach, but the molecular basis for chemokine-mediated activation and antibody-mediated inhibition of CCR8 are not fully elucidated. Here, we obtain an antagonist antibody against human CCR8 and determine structures of CCR8 in complex with either the antibody or the endogenous agonist ligand CCL1. Our studies reveal characteristic antibody features allowing recognition of the CCR8 extracellular loops and CCL1-CCR8 interaction modes that are distinct from other chemokine receptor - ligand pairs. Informed by these structural insights, we demonstrate that CCL1 follows a two-step, two-site binding sequence to CCR8 and that antibody-mediated inhibition of CCL1 signaling can occur by preventing the second binding event. Together, our results provide a detailed structural and mechanistic framework of CCR8 activation and inhibition that expands our molecular understanding of chemokine - receptor interactions and offers insight into the development of therapeutic antibodies targeting chemokine GPCRs.

CD4+CCR8+ Tregs in ovarian cancer: a potential effector Tregs for immune regulation.

BACKGROUND: Tregs are key drivers of immunosuppression in solid tumors. As an important chemokine receptor on Tregs, the regulatory effect of CCR8 on tumor immunity has received more and more attention. However, the current research on CCR8 in the immune microenvironment of ovarian cancer has not been clear. METHODS: Bioinformatics analysis was used to compare the transcriptome differences between CD4+ T cells in the peripheral circulation and infiltrated in ovarian tumor tissues. RT-PCR was used to detect the expression levels of chemokine receptor-related differential genes on CD4+ T cells in peripheral blood and ovarian tumor tissues. Multiparameter flow cytometry was used to detect the proportion and phenotypic characteristics of CD4+CCR8+ Tregs and CD4+CCR8- Tregs in different sample types. The expression level of CCR8 ligands was detected at multiple levels. To explore the important role of CCR8-CCL1 and CCR8-CCL18 axis in the migration and invasion of CD4+CCR8+ Tregs into ovarian tumor tissues by establishing a chemotaxis system in vitro. RESULTS: In this study, significantly different gene expression profiles were found between peripheral circulating CD4+ T cells and infiltrating CD4+ T cells in ovarian tumor tissues, in which chemokine-chemokine receptor signaling pathway was significantly enriched in all three groups of differential genes. The expression level of CCR8 in infiltrating CD4+ T cells of ovarian cancer tissue was significantly higher than that in peripheral blood of healthy controls and ovarian cancer patients, and high expression of CCR8 was significantly correlated with advanced tumor stage and poor differentiation. CD4+CCR8+ Tregs are the main type of infiltrating CD4+ Tregs in ovarian tumor tissues, which have stronger immunosuppressive phenotypes, secrete more inhibitory cytokines and have stronger proliferation ability. The ligands CCL1 and CCL18 corresponding to CCR8 were significantly overexpressed in ovarian tumor tissues, and the CCR8-CCL1 and CCR8-CCL18 axis played a key role in the migration and infiltration of CD4+CCR8+ Tregs into ovarian tumor tissues. CONCLUSIONS: The results of this study may help to understand the phenotypic characteristics and recruitment process of Tregs in the tumor, and provide new ideas for improving the immunosuppressive status of the ovarian cancer microenvironment.

Oxamate enhances the efficacy of CAR-T therapy against glioblastoma via suppressing ectonucleotidases and CCR8 lactylation.

BACKGROUND: Chimeric antigen receptor (CAR)-T immunotherapy fails to treat solid tumors due in part to immunosuppressive microenvironment. Excess lactate produced by tumor glycolysis increases CAR-T immunosuppression. The mechanism of lactate inducing the formation of immunosuppressive microenvironment remains to be further explored. METHODS: Immunocyte subpopulations and molecular characteristics were analyzed in the orthotopic xenografts of nude mice using flow cytometry assay and immunohistochemical staining after oxamate, a lactate dehydrogenase A (LDHA) inhibitor, and control T or CAR-T cells injection alone or in combination. RT-qPCR, western blot, flow cytometry, immunofluorescence, luciferase reporter assay, chromatin immunoprecipitation and ELISA were performed to measure the effect of lactate on the regulation of CD39, CD73 and CCR8 in cultured glioma stem cells, CD4 + T cells or macrophages. RESULTS: Oxamate promoted immune activation of tumor-infiltrating CAR-T cells through altering the phenotypes of immune molecules and increasing regulatory T (Treg) cells infiltration in a glioblastoma mouse model. Lactate accumulation within cells upregulated CD39, CD73 and CCR8 expressions in both lactate-treated cells and glioma stem cells-co-cultured CD4 + T cells and macrophages, and intracellular lactate directly elevated the activities of these gene promotors through histone H3K18 lactylation. CONCLUSIONS: Utilizing lactate generation inhibitor not only reprogramed glucose metabolism of cancer stem cells, but also alleviated immunosuppression of tumor microenvironment and reduced tumor-infiltrating CAR-Treg cells, which may be a potential strategy to enhance CAR-T function in glioblastoma therapy.

Synthesis and structure-activity relationship study of phenoxybenzylpiperazine analogues as CCR8 agonists.

CCR8 agonists hold promise for the treatment of various auto-immune diseases. Despite the fact that phenoxybenzylpiperazine derivatives are known to be endowed with CCR8 agonistic activity, systematic structure-activity relationship studies have not been reported. In this study, ZK756326, a previously disclosed CCR8 agonist, was divided in various fragments and each subunit was subjected to structural modifications. All newly synthesized analogues were evaluated in a CCR8 calcium mobilization assay, revealing that only limited structural variation was tolerated in both phenyl rings and at the benzylic position. In contrast, various linkers gave analogues with good CCR8 agonistic potency. In addition, the presence of small substituents on the piperazinyl moiety or the exchange of the piperazinyl for a piperidinyl group afforded compounds with promising CCR8 agonism, with the most potent congener being 10-fold more potent than ZK756326.

A Novel Prognostic Biomarker CCR8 for Gastric Cancer and Anti-CCR8 Blockade Attenuate the Immunosuppressive Capacity of Tregs In Vitro.

Objective: To investigate the immunotherapeutic roles and functions of C-C Motif Chemokine Receptor 8 (CCR8) molecule in gastric cancer (GC). Materials and Methods: Clinicopathological features of 95 GC cases were collected by a follow-up survey. The expression level of CCR8 was measured by immunohistochemistry (IHC) staining and analyzed with the cancer genome atlas database. The relationship between CCR8 expression and Clinicopathological features of GC cases was evaluated by univariate and multivariate analysis. Flow cytometry was used to determine the expression of cytokines and the proliferation of CD4+ regulator T cells (Tregs) and CD8+ T cells. Results: An upregulated expression of CCR8 in GC tissues was associated with tumor grade, nodal metastasis, and overall survival (OS). Tumor-infiltrated Tregs with higher expression of CCR8 produced more IL10 molecules in vitro. In addition, anti-CCR8 blocking downregulated IL10 expression produced by CD4+ Tregs, and reversed the suppression by Tregs on the secretion and proliferation of CD8+ T cells. Conclusion: CCR8 molecule could be a prognostic biomarker for GC cases and a therapeutic target for immune treatments.

Discovery of a Potent and Selective CCR8 Small Molecular Antagonist IPG7236 for the Treatment of Cancer.

Recently, there has been increasing evidence indicating that the CC chemokine receptor 8 (CCR8) plays an important role in mediating the recruitment and immunosuppressive function of regulatory T (Treg) cells in the tumor microenvironment. Therefore, the development of a specific CCR8 antagonist presents a potential therapeutic strategy against cancer. Despite a few small molecules having been reported as CCR8 antagonists, none has progressed to the clinical stage. Herein, we described a potent and selective CCR8 antagonist (compound 1, IPG7236) as the first small molecule to advance to the clinical stage. IPG7236 demonstrated an anti-cancer effect via modulating Treg and cytotoxic T (CD8+ T) cells. IPG7236 alone or in combination with PD-1 antibody exhibited significant tumor suppression effects in the mouse xenograft model of human breast cancer. IPG7236 is a promising clinical candidate that targets CCR8 with excellent in vitro ADMET properties, pharmacokinetics, safety profiles, and in vivo efficacy.

Differential expression of CCR8 in tumors versus normal tissue allows specific depletion of tumor-infiltrating T regulatory cells by GS-1811, a novel Fc-optimized anti-CCR8 antibody.

The presence of T regulatory (Treg) cells in the tumor microenvironment is associated with poor prognosis and resistance to therapies aimed at reactivating anti-tumor immune responses. Therefore, depletion of tumor-infiltrating Tregs is a potential approach to overcome resistance to immunotherapy. However, identifying Treg-specific targets to drive such selective depletion is challenging. CCR8 has recently emerged as one of these potential targets. Here, we describe GS-1811, a novel therapeutic monoclonal antibody that specifically binds to human CCR8 and is designed to selectively deplete tumor-infiltrating Tregs. We validate previous findings showing restricted expression of CCR8 on tumor Tregs, and precisely quantify CCR8 receptor densities on tumor and normal tissue T cell subsets, demonstrating a window for selective depletion of Tregs in the tumor. Importantly, we show that GS-1811 depleting activity is limited to cells expressing CCR8 at levels comparable to tumor-infiltrating Tregs. Targeting CCR8 in mouse tumor models results in robust anti-tumor efficacy, which is dependent on Treg depleting activity, and synergizes with PD-1 inhibition to promote anti-tumor responses in PD-1 resistant models. Our data support clinical development of GS-1811 to target CCR8 in cancer and drive tumor Treg depletion in order to promote anti-tumor immunity.

Blocking CCL8-CCR8-Mediated Early Allograft Inflammation Improves Kidney Transplant Function.

BACKGROUND: In kidney transplantation, early allograft inflammation impairs long-term allograft function. However, precise mediators of early kidney allograft inflammation are unclear, making it challenging to design therapeutic interventions. METHODS: We used an allogeneic murine kidney transplant model in which CD45.2 BALB/c kidneys were transplanted to CD45.1 C57BL/6 recipients. RESULTS: Donor kidney resident macrophages within the allograft expanded rapidly in the first 3 days. During this period, they were also induced to express a high level of Ccl8, which, in turn, promoted recipient monocyte graft infiltration, their differentiation to resident macrophages, and subsequent expression of Ccl8. Enhanced graft infiltration of recipient CCR8+ T cells followed, including CD4, CD8, and γδ T cells. Consequently, blocking CCL8-CCR8 or depleting donor kidney resident macrophages significantly inhibits early allograft immune cell infiltration and promotes superior short-term allograft function. CONCLUSIONS: Targeting the CCL8-CCR8 axis is a promising measure to reduce early kidney allograft inflammation.

The Chemokine Receptor CCR8 Is a Target of Chimeric Antigen T Cells for Treating T Cell Malignancies.

Chimeric antigen receptor (CAR) T cells have been successfully used in the therapy of B cell leukemia and lymphoma, but still have many challenges in their use for treating T cell malignancies, such as the lack of unique tumor antigens, their limitation of T cell expansion, and the need for third party donors or genome editing. Therefore, we need to find novel targets for CAR T cell therapy to overcome these challenges. Here, we found that both adult T-cell leukemia/lymphoma (ATLL) patients and ATLL cells had increased CCR8 expression but did not express CD7. Moreover, targeting CCR8 in T cells did not impair T cell expansion in vitro. Importantly, anti-CCR8 CAR T cells exhibited antitumor effects on ATLL- and other CCR8-expressing T-ALL cells in vitro and in vivo, and prolonged the survival of ATLL and Jurkat tumor-bearing mouse models. In conclusion, these collective results show that anti-CCR8 CAR T cells possess strong antitumor activity and represent a promising therapeutic approach for ATLL and CCR8+ tumors.

C8Mab-2: An Anti-Mouse C-C Motif Chemokine Receptor 8 Monoclonal Antibody for Immunocytochemistry.

C-C motif chemokine receptor 8 (CCR8) is a G protein-coupled receptor predominantly expressed in regulatory T (Treg) and T helper 2 cells. The evidence that CCR8 expression in Treg is increased in cancers, CCR8 increases migration activity of Treg, and CCR8 induces the anti-apoptotic activity in T cell leukemia and lymphoma suggests that CCR8 is associated with cancer development. Thus, developing a specific monoclonal antibody (mAb) for CCR8 is useful for diagnostic and therapeutic purposes and the anti-CCR8 mAb becomes a remarkable experimental tool for basic research. We previously developed an anti-mouse CCR8 (mCCR8) mAb called C8Mab-2 (rat IgG2b, kappa) that was applicable to flow cytometric analysis for both endogenous and exogenous mCCR8. This study showed that C8Mab-2 and recombinant C8Mab-2 (recC8Mab-2) were specifically bound to exogenously expressed mCCR8 in mCCR8-overexpressed Chinese hamster ovary-K1 cells. In addition, we found that C8Mab-2 and recC8Mab-2 recognized endogenous mCCR8 in P388 (a mouse lymphocyte-like cell line) and J774-1 cells (a mouse macrophage-like cell line). These data demonstrate that C8Mab-2 and recC8Mab-2 are useful for immunocytochemical analysis.

Microglia/macrophage-derived human CCL18 promotes glioma progression via CCR8-ACP5 axis analyzed in humanized slice model.

Factors released from glioma-associated microglia/macrophages (GAMs) play a crucial role in glioblastoma multiforme (GBM) progression. Here, we study the importance of CCL18, a cytokine expressed in human but not in rodent GAMs, as a modulator of glioma growth. Since CCL18 signaling could not be studied in classical mouse glioma models, we developed an approach by transplanting induced pluripotent stem cell-derived human microglia and human glioma cells into mouse brain slices depleted of their intrinsic microglia. We observe that CCL18 promotes glioma cell growth and invasion. Chemokine (C-C motif) receptor 8 (CCR8) is identified as a functional receptor for CCL18 on glioma cells, and ACP5 (acid phosphatase 5) is revealed as an important part of the downstream signaling cascade for mediating glioma growth. We conclude, based on the results from an in vitro, ex vivo humanized glioma model and an in vivo GBM model that microglia/macrophage-derived CCL18 promotes glioma growth.

Tumor-derived exosomes drive pre-metastatic niche formation in lung via modulating CCL1+ fibroblast and CCR8+ Treg cell interactions.

BACKGROUND: Since the lung is one of the most common sites for cancer metastasis, it could provide a suitable microenvironment for pre-metastatic niche (PMN) formation to facilitate tumor cell colonization. Regulatory T cells (Tregs) are an immunosuppressive cell type found ubiquitously in tumors and may play a crucial role in PNM formation. In this study, we investigated tumor-derived exosome (TDE)-induced Treg differentiation in the lung PMN as well as the underlying mechanisms. METHODS: TDEs were isolated from the Lewis lung carcinoma cell line (LLC-exo) and their effects on mouse pulmonary fibroblasts was investigated in vitro as well as on lung tumor formation and metastasis in a pre-injected mouse model. Immune cell populations in the lung were analyzed by flow cytometry. Expression of CCL1 and CCR8 was evaluated by immunofluorescence staining, qRT-PCR and Western blot analyses. Cytokine expression was measured using mouse cytokine arrays and ELISA. RESULTS: The number of CD4+ FoxP3+ Tregs was significantly increased in lungs in a LLC-exo pre-injected mouse model. Lung fibroblasts secreted increased amounts of CCL1 after co-culture with LLC-exo, which induced Treg differentiation by activating its specific receptor CCR8, ultimately contributing to the establishment of an immunologically tolerant PMN. Moreover, inhibiting the release of LLC-exo by GW4869, or blocking the CCL1-CCR8 axis using AZ084, suppressed Tregs differentiation and tumor metastasis in the lung. CONCLUSIONS: Collectively, our study provides a novel mechanism by which Tregs are activated to form an immunologically tolerant PMN and demonstrates a critical link among lung fibroblasts, Tregs and metastatic tumor cells.

C8Mab-3: An Anti-Mouse CCR8 Monoclonal Antibody for Immunocytochemistry.

The C-C motif chemokine receptor 8 (CCR8) is highly expressed in regulatory T cells. CCR8 is also expressed in many cancers and is associated with those progression. The development of monoclonal antibodies (mAbs) for CCR8 leads to cancer immunotherapy and elucidation of unknown mechanisms of CCR8-dependent cancer progression. In this study, we have developed an anti-mouse CCR8 (mCCR8) mAb (clone C8Mab-3, rat IgG1, kappa) using the Cell-Based Immunization and Screening (CBIS) method. We revealed that C8Mab-3 and its recombinant antibody (recC8Mab-3) bind to mCCR8-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/mCCR8), but not to the parental CHO-K1 cells, in flow cytometry. In addition, C8Mab-3 and recC8Mab-3 reacted to P388 (a mouse lymphocyte-like cell) and J774-1 (a mouse macrophage-like cell), which express endogenous mCCR8. C8Mab-3 also detected exogenous and endogenous mCCR8 using immunocytochemistry. These results suggest that C8Mab-3, developed using the CBIS method, is useful for immunocytochemistry against exogenous and endogenous mCCR8.

The impact of CCR8+ regulatory T cells on cytotoxic T cell function in human lung cancer.

Regulatory T cells (Tregs) suppress the host immune response and maintain immune homeostasis. Tregs also promote cancer progression and are involved in resistance to immune checkpoint inhibitor treatments. Recent studies identified selective CCR8 expression on tumor-infiltrating Tregs; CCR8+ Tregs have been indicated as a possible new target of cancer immunotherapy. Here, we investigated the features of CCR8+ Tregs in lung cancer patients. CCR8+ Tregs were highly activated and infiltration of CCR8+ Tregs in tumors was associated with poor prognosis in lung cancer patients. We also investigated their immune suppressive function, especially the influence on cytotoxic T lymphocyte cell function. The Cancer Genome Atlas analysis revealed that CD8 T cell activities were suppressed in high CCR8-expressing tumors. Additionally, depletion of CCR8+ cells enhanced CD8 T cell function in an ex vivo culture of lung tumor-infiltrating cells. Moreover, CCR8+ Tregs, but not CCR8- Tregs, induced from human PBMCs markedly suppressed CD8 T cell cytotoxicity. Finally, we demonstrated the therapeutic effect of targeting CCR8 in a murine model of lung cancer. These findings reveal the significance of CCR8+ Tregs for immunosuppression in lung cancer, especially via cytotoxic T lymphocyte cell suppression, and suggest the potential value of CCR8-targeted therapy for cancer treatment.

CCR8-targeted specific depletion of clonally expanded Treg cells in tumor tissues evokes potent tumor immunity with long-lasting memory.

Foxp3-expressing CD25+CD4+ regulatory T cells (Tregs) are abundant in tumor tissues. Here, hypothesizing that tumor Tregs would clonally expand after they are activated by tumor-associated antigens to suppress antitumor immune responses, we performed single-cell analysis on tumor Tregs to characterize them by T cell receptor clonotype and gene-expression profiles. We found that multiclonal Tregs present in tumor tissues predominantly expressed the chemokine receptor CCR8. In mice and humans, CCR8+ Tregs constituted 30 to 80% of tumor Tregs in various cancers and less than 10% of Tregs in other tissues, whereas most tumor-infiltrating conventional T cells (Tconvs) were CCR8- CCR8+ tumor Tregs were highly differentiated and functionally stable. Administration of cell-depleting anti-CCR8 monoclonal antibodies (mAbs) indeed selectively eliminated multiclonal tumor Tregs, leading to cure of established tumors in mice. The treatment resulted in the expansion of CD8+ effector Tconvs, including tumor antigen-specific ones, that were more activated and less exhausted than those induced by PD-1 immune checkpoint blockade. Anti-CCR8 mAb treatment also evoked strong secondary immune responses against the same tumor cell line inoculated several months after tumor eradication, indicating that elimination of tumor-reactive multiclonal Tregs was sufficient to induce memory-type tumor-specific effector Tconvs. Despite induction of such potent tumor immunity, anti-CCR8 mAb treatment elicited minimal autoimmunity in mice, contrasting with systemic Treg depletion, which eradicated tumors but induced severe autoimmune disease. Thus, specific removal of clonally expanding Tregs in tumor tissues for a limited period by cell-depleting anti-CCR8 mAb treatment can generate potent tumor immunity with long-lasting memory and without deleterious autoimmunity.