Tumor-infiltrating Tregs Research Articles

Glut3 promotes cellular O-GlcNAcylation as a distinctive tumor-supportive feature in Treg cells.

Regulatory T cells (Tregs) establish dominant immune tolerance but obstruct tumor immune surveillance, warranting context-specific mechanistic insights into the functions of tumor-infiltrating Tregs (TIL-Tregs). We show that enhanced posttranslational O-linked N-acetylglucosamine modification(O-GlcNAcylation) of cellular factors is a molecular feature that promotes a tumor-specific gene expression signature and distinguishes TIL-Tregs from their systemic counterparts. We found that altered glucose utilization through the glucose transporter Glut3 is a major facilitator of this process. Treg-specific deletion of Glut3 abrogates tumor immune tolerance, while steady-state immune homeostasis remains largely unaffected in mice. Furthermore, by employing mouse tumor models and human clinical data, we identified the NF-κB subunit c-Rel as one such factor that, through Glut3-dependent O-GlcNAcylation, functionally orchestrates gene expression in Tregs at tumor sites. Together, these results not only identify immunometabolic alterations and molecular events contributing to fundamental aspects of Treg biology, specifically at tumor sites but also reveal tumor-specific cellular properties that can aid in the development of Treg-targeted cancer immunotherapies.

Inhibition of UBE2N in regulatory T-cells boosts immunity against cancer.

Regulatory T (Treg) cells prevent autoimmunity and facilitate cancer immune evasion. Depletion of Tregs is a promising cancer therapy, but risks of autoimmune reactions hamper its clinical translation. Here, we demonstrate that temporally induced deletion of Ube2n in Tregs (Ube2n Treg-KO ) of adult mice results in a robust expansion and activation of cytotoxic CD8 + T-cells in response to cancer cell challenges, producing a long-lasting survival benefit without autoimmune complications. The anti-tumor effect persists following adoptive T-cell transfer to T-cell-deficient Rag1-knockout mice. Single-cell transcriptomic analysis revealed that UBE2N deletion shifted immunosuppressive Tregs to effector-like T-cells. This shift is characterized by the downregulation of c-Myc target genes, resembling that observed in tumor-infiltrating Tregs of melanoma patients. Further analyses confirm that UBE2N maintains c-Myc protein stability via suppression of K48-Ubiquitin-mediated proteasomal degradation. Taken together, our studies uncover a hitherto unexplored and potentially druggable UBE2N/c-Myc signaling axis to eradicate Treg-enabled cancer immune escape.

The CCR6-CCL20 Axis Promotes Regulatory T-cell Glycolysis and Immunosuppression in Tumors.

Regulatory T cells (Treg) are important players in the tumor microenvironment. However, the mechanisms behind their immunosuppressive effects are poorly understood. We found that CCR6-CCL20 activity in tumor-infiltrating Tregs is associated with greater glycolytic activity and ablation of Ccr6 reduced glycolysis and lactic acid production while increasing compensatory glutamine metabolism. Immunosuppressive activity toward CD8+ T cells was abrogated in Ccr6-/- Tregs due to reduction in activation-induced glycolysis. Furthermore, Ccr6-/- mice exhibited improved survival across multiple tumor models compared to wild-type mice and Treg and CD8+ T-cell depletion abrogated the improvement. In addition, Ccr6 ablation further promoted the efficacy of anti-PD-1 therapy in a preclinical glioma model. Follow-up knockdown of Ccl20 with siRNA also demonstrated improvement in antitumor efficacy. Our results unveil CCR6 as a marker and regulator of Treg-induced immunosuppression and identify approaches to target the metabolic determinants of Treg immunosuppressive activity.

Dynamic Foxp3-chromatin interaction controls tunable Treg cell function.

Nuclear factor Foxp3 determines regulatory T (Treg) cell fate and function via mechanisms that remain unclear. Here, we investigate the nature of Foxp3-mediated gene regulation in suppressing autoimmunity and antitumor immune response. Contrasting with previous models, we find that Foxp3-chromatin binding is regulated by Treg activation states, tumor microenvironment, and antigen and cytokine stimulations. Proteomics studies uncover dynamic proteins within Foxp3 proximity upon TCR or IL-2 receptor signaling in vitro, reflecting intricate interactions among Foxp3, signal transducers, and chromatin. Pharmacological inhibition and genetic knockdown experiments indicate that NFAT and AP-1 protein Batf are required for enhanced Foxp3-chromatin binding in activated Treg cells and tumor-infiltrating Treg cells to modulate target gene expression. Furthermore, mutations at the Foxp3 DNA-binding domain destabilize the Foxp3-chromatin association. These representative settings delineate context-dependent Foxp3-chromatin interaction, suggesting that Foxp3 associates with chromatin by hijacking DNA-binding proteins resulting from Treg activation or differentiation, which is stabilized by direct Foxp3-DNA binding, to dynamically regulate Treg cell function according to immunological contexts.

Prognostic value of tumor-infiltrating lymphocytes and PD-L1 expression in esophageal squamous cell carcinoma.

Tumor cells (TC) participate in tumor progression by altering the immune responses in the tumor microenvironment. However, the clinical relevance and prognostic effect of PD-L1 expression and tumor-infiltrating lymphocytes (TILs) in esophageal squamous cell carcinoma (ESCC) are unknown. The purpose of this study was to investigate the interactions and clinical significance of PD-L1 expression and TILs in ESCC. Tissue specimens were collected from 126 patients with ESCC who underwent curative esophagectomy. Immunohistochemical analysis and multiplex immunofluorescence for CD4, CD8, CD25, FOXP3, and PD-L1 in the tumor were used to identify multiple tumor-infiltrating immune cells (TIIC), Tregs, and TC. PD-L1 was expressed in tumor cells (PD-L1 TC). PD-L1 TIIC and PD-L1 TC affected the biological behavior of TC. The positive expression rate of PD-L1 TC and CD8+ TILs was 27.8% (35/126) and 31.7% (40/126), respectively. Kaplan-Meier analysis showed that overall survival (OS) was significantly associated with decreased CD8+ TILs and PD-L1 TC-positive expression, which promote ESCC progression and metastasis. Tumor depth, CD8, and PD-L1 TC were independent prognostic factors in ESCC, and a predictive nomogram with these three risk factors improved the accuracy of predicting OS in patients with ESCC after surgical resection. The conjoint analysis of multiple immune-related factors is beneficial for stratifying patient survival risk.

ICOS-expressing Regulatory T Cells Influence the Composition of Antitumor CTL Populations.

The role of ICOS in antitumor T cell responses and overall tumor progression has been controversial. In this study, we compared tumor progression in mice lacking ICOS selectively in regulatory T (Treg) cells or in all T cells. Using an experimental melanoma lung metastasis model, we found that Treg cell-specific ICOS knockout reduces the overall tumor burden compared with Cre control mice, with increased CD4+-to-Treg cell and CD8+-to-Treg cell ratios in the tumor. In contrast, there was no difference in the tumor burden in mice lacking ICOS in all of the T cell compartments. This suggests a dual role of ICOS costimulation in promoting protumor and antitumor T cell responses. Consistent with reduced tumor burden, we found that Treg cell-specific deletion of ICOS leads to an increase of CD8+ CTLs that express high levels of granzyme B and perforin. Moreover, single-cell transcriptome analysis revealed an increase of Ly108+Eomeshi CD8+ T cells at the cost of the Ly108+T-bethi subset in Treg cell-specific knockout mice. These results suggest that ICOS-expressing Treg cells suppress the CTL maturation process at the level of Eomes upregulation, a critical step known to drive perforin expression and cytotoxicity. Collectively, our data imply that cancer immunotherapies using ICOS agonist Abs may work better in Treg cell-low tumors or when they are combined with regimens that deplete tumor-infiltrating Treg cells.

Diet restriction enhances the effect of immune checkpoint block by inhibiting the intratumoralmTORC1/B7-H3 axis.

Immune checkpoint blockade therapy has demonstrated significant therapeutic efficacy in certain cancer types; however, the impact of dietary restriction remains scarcely reported in this context. This study aimed to investigate the influence of dietary restriction on anti-PDL-1 therapy and the interplay of immune cells within this context. Using an anti-PDL-1 regimen combined with dietary restrictions, tumor progression was assessed in LLC-bearing mice. Flow cytometry was employed to analyze immune cell infiltration and differentiation levels within the tumor microenvironment. The expression of mTORC1/B7-H3 in tumors subjected to dietary restriction was also examined. LLC tumors with elevated B7-H3 expression were validated in mice to determine its inhibitory effect on immune cell proliferation and differentiation. A CD3/B7-H3 chimeric antibody was developed for therapeutic intervention in B7-H3 overexpressing tumors, with subsequent T cell responses assessed through flow cytometry. Dietary restriction potentiated the effect of anti-PDL1 therapy by suppressing the intratumorally mTORC1/B7-H3 axis. In vivo experiments demonstrated that elevated B7-H3 expression in tumors reduced infiltration and activation of CD8 + T cells within the tumor, while it did not affect tumor-infiltrating Tregs. In vitro studies revealed that high B7-H3 expression influenced the proliferation and activation of CD8 + T cells within a Coculture system. The constructed CD3/B7-H3 chimeric antibody prominently activated TCR within B7-H3 overexpressing tumors and impeded tumor progression. The findings suggest that dietary restriction enhances the efficacy of immune checkpoint blockade by modulating the intratumoral mTORC1/B7-H3 axis.

Targeting tumor-infiltrating CCR8+ regulatory T cells induces antitumor immunity through functional restoration of CD4+ Tconvs and CD8+ T cells in colorectal cancer

BackgroundChemokine (C-C motif) receptor 8 (CCR8) is a chemokine receptor selectively expressed on tumor-infiltrating regulatory T cells (Tregs). Strong immunosuppression mediated by CCR8+ Tregs observed in breast and lung malignancies suggest for their functional significance in cancer therapy. To date, detailed characterization of tumor-infiltrating CCR8+ Tregs cells in colorectal cancer (CRC) is limited.MethodsTo study the presence and functional involvement of CCR8+ Tregs in CRC, we analyzed the proportions of CCR8-expressing T cells in different T cell subsets in tumor and adjacent normal tissues and peripheral blood mononuclear cells (PBMCs) from CRC patients by Flow cytometry. Also, we compared the distribution of CCR8+ T cells in malignant tissues and peripheral lymphoid organs from a subcutaneous CRC murine model. Bioinformatic analysis was performed to address the significance of CCR8 expression levels in CRC prognosis, immune regulatory gene expression profiles and potential molecular mechanisms associated with CCR8+ Tregs in CRC tumors. Further, we administrated an anti-CCR8 monoclonal antibody to CT26 tumor-bearing mice and examined the antitumor activity of CCR8-targeted therapy both in vivo and in an ex vivo confirmative model.ResultsHere, we showed that Tregs was predominantly presented in the tumors of CRC patients (13.4 ± 5.8, p < 0.0001) and the CRC subcutaneous murine model (35.0 ± 2.6, p < 0.0001). CCR8 was found to be preferentially expressed on these tumor-infiltrating Tregs (CRC patients: 63.6 ± 16.0, p < 0.0001; CRC murine model: 65.3 ± 9.5, p < 0.0001), which correlated with poor survival. We found that majority of the CCR8+ Tregs expressed activation markers and exhibited strong suppressive functions. Treatment with anti-CCR8 antibody hampered the growth of subcutaneous CRC tumor through effectively restoring the anti-tumor immunity of CD4+ conventional T cells (CD4+ Tconvs) and CD8+ T cells, which was confirmed in the ex vivo examinations.ConclusionsCollectively, these findings illustrate the importance of CCR8+ Tregs for an immunosuppressive microenvironment in CRC tumors by functional inhibition of CD4+ Tconvs and CD8+ T cells, and suggest for the applicable value of CCR8-targeted therapy for CRC.

Anti-TNFR2 Antibody-Conjugated PLGA Nanoparticles for Targeted Delivery of Adriamycin in Mouse Colon Cancer.

High levels of tumor necrosis factor receptor type II (TNFR2) are preferentially expressed by immunosuppressive CD4+Foxp3+ regulatory T cells (Tregs), especially those present in the tumor microenvironment, as initially reported by us. There is compelling evidence that targeting TNFR2 markedly enhances antitumor immune responses. Furthermore, a broad spectrum of human cancers also expresses TNFR2, while its expression by normal tissue is very limited. We thus hypothesized that TNFR2 may be harnessed for tumor-targeted delivery of chemotherapeutic agents. In this study, we performed a proof-of-concept study by constructing a TNFR2-targeted PEGylated poly(dl-lactic-co-glycolic acid) (PLGA-PEG) nanodrug delivery system [designated as TNFR2-PLGA-ADR (Adriamycin)]. The results of invitro study showed that this TNFR2-targeted delivery system had the properties in cellular binding and cytotoxicity toward mouse colon cancer cells. Further, upon intravenous injection, TNFR2-PLGA-ADR could efficiently accumulate in MC38 and CT26 mouse colon tumor tissues and preferentially bind with tumor-infiltrating Tregs. Compared with ADR and ISO-PLGA-ADR, the invivo antitumor effect of TNFR2-PLGA-ADR was markedly enhanced, which was associated with a decrease of TNFR2+ Tregs and an increase of IFNγ+CD8+ cytotoxic T lymphocytes in the tumor tissue. Therefore, our results clearly show that targeting TNFR2 is a promising strategy for designing tumor-specific chemoimmunotherapeutic agent delivery system.

Mapping the complexity and diversity of tertiary lymphoid structures in primary and peritoneal metastatic gastric cancer

BackgroundTertiary lymphoid structures (TLSs) are thought to stimulate antitumor immunity and positively impact prognosis and response to immune checkpoint blockade. In gastric cancers (GCs), however, TLSs are predominantly found in...

Dynamic network biomarker of treg cells differentiation critical state with neoadjuvant treatment in LUSC.

e20063 Background: Regulatory T cells (Tregs) suppress immune responses and can promote tumor growth and metastasis during cancer progression. Studies have shown that tumor-infiltrating Tregs upregulate inhibitory gene programs after immune checkpoint blockade therapy. Targeting Tregs is believed to be a valuable approach to enhance the effectiveness of immunotherapy. However, the precise role of Tregs in the tumor microenvironment, their connection to treatment resistance mechanisms, and how changes in their immune activity impact tumor treatment are still not well understood. Methods: Single-cell data and clinical information were obtained from the Gene Expression Omnibus database with the accession number GSE176021 for 4 patients diagnosed with lung squamous cell carcinoma (LUSC) who received neoadjuvant anti-PD-1 therapy, including 2 patients with major pathologic response (MPR) and 2 patients with non-MPR. BioTIP was employed to identify critical transition signals of the Treg cell differentiation trajectory constructed by Monocle2. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set variation analysis were performed to understand biological processes and pathways. Additionally, potential transcription factors were identified using Single-Cell rEgulatory Network Inference and Clustering, and CellChat analysis was conducted to evaluate possible interactions among cell populations. Results: The study constructed a pseudo-temporal differentiation trajectory of Tregs in LUSC patients, and Treg subpopulations during the critical transition period were identified based on the dynamic network biomarker method. Notably, subpopulations of Treg cells clustering MPR or non-MPR samples were located at different ends of the differentiation trajectory, showing variations in Treg-related pathways and transcription factor regulation. The critical transition subpopulation exhibited high expression of glycolysis, TCA cycle, and natural killer cell receptors, along with upregulation of the CEBPB transcription factor activity and downregulation of ARNTL activity. SELPLG-SELL, CD99-CD99, and MHC-II-CD4 were identified as potential key signals that may affect therapeutic effect, primarily influencing cell adhesion, the immune suppressive activity of Treg cells, and T cell response. Conclusions: In conclusion, this study utilized single-cell data analysis to uncover the dynamic regulation of Treg cells in LUSC, identifying critical transition Treg subpopulations. Notably, our findings suggest the involvement of the transcription factors CEBPB and ARNTL in regulating Treg activity. These novel insights shed light on potential strategies for targeted therapies and provide valuable information regarding resistance mechanisms associated with Treg cells.

Efficacy and safety of LM-108, an anti-CCR8 monoclonal antibody, in combination with an anti-PD-1 antibody in patients with gastric cancer: Results from phase 1/2 studies.

2504 Background: Targeting tumor-infiltrating regulatory T cells (Tregs) is a potential approach to overcome immunotherapy resistance in the treatment of cancers. LM-108 is a novel Fc-optimized, anti-CCR8 monoclonal antibody that selectively depletes tumor-infiltrating Tregs. Here we report a pooled analysis of results from 3 phase 1/2 studies (NCT05199753; NCT05255484; NCT05518045) to evaluate the efficacy and safety of LM-108 in combination with anti-PD-1 therapy in patients with gastric cancer. Methods: Eligible patients with gastric cancer treated with LM-108 in combination with an anti-PD-1 antibody were included in the analysis. Patients received intravenous LM-108 at dose levels of 3 mg/kg Q2W, 6 mg/kg Q3W, or 10 mg/kg Q3W plus an anti-PD-1 antibody (intravenous pembrolizumab 200 mg Q3W or 400 mg Q6W or toripalimab 240 mg Q3W). The primary endpoint was investigator-assessed ORR per RECIST v1.1. The secondary endpoints included safety, other efficacy outcomes, and biomarkers analysis. Data cutoff date for the pooled analysis was December 25, 2023. Results: Forty-eight patients with gastric cancer (median age: 60.5 years; male: 72.9%) from China, USA, and Australia were treated ≥ 1 dose of LM-108 in combination with pembrolizumab or toripalimab. Most (n = 47, 97.9%) patients had received at least 1 prior anticancer treatment, and 43 (89.6%) had received prior anti-PD-1 therapy. Treatment-related adverse events (TRAEs) occurred in 39 (81.3%) patients, in which the most common events (≥15%) were alanine transaminase increased (25.0%), aspartate transaminase increased (22.9%), white blood cell decreased (22.9%), anemia (16.7%). Grade ≥ 3 TRAEs occurred in 18 (37.5%) patients, the most common events (≥ 4%) were anemia (8.3%), lipase increased (4.2%), rash (4.2%), and lymphocyte count decreased (4.2%). Among 36 efficacy-evaluable patients across all regimens, ORR was 36.1% (95% CI 20.8%–53.8%) and DCR was 72.2% (95% CI 54.8%–85.8%). The median PFS was 6.53 months (95% CI 2.96–NA). Among 11 patients whose disease had progressed on first-line treatment, ORR was 63.6% (95% CI 30.8%–89.1%) and DCR was 81.8% (95% CI 48.2%–97.7%). Of the 11 patients who progressed on first-line treatment, 8 had high CCR8 expression. Among these 8 patients, ORR was 87.5% and DCR was 100%, with 1 CR, 6 PR, and 1 SD observed. Conclusions: LM-108 in combination with an anti-PD-1 antibody showed promising antitumor activity in patients with gastric cancer that was resistance to anti-PD-1 therapy. The combination therapy was well tolerated. These results support further evaluation of LM-108 in CCR8 positive gastric cancer. Clinical trial information: NCT05199753 ; NCT05255484 ; NCT05518045 .

Density of tumor-infiltrating NK and Treg cells is associated with 5 years progression-free and overall survival in resected lung adenocarcinoma

Surgical resection of pulmonary adenocarcinoma is considered to be curative but progression-free survival (PFS) has remained highly variable. Antitumor immune response may be important, however, the prognostic significance of tumor-infiltrating natural killer (NK) and regulatory T (Treg) lymphocytes is uncertain. Resected pulmonary adenocarcinoma tissues (n = 115) were studied by immunohistochemical detection of NKp46 and FoxP3 positivity to identify NK and Treg cells, respectively. Association of cell densities with clinicopathological features and progression-free survival (PFS) as well as overall survival (OS) were analyzed with a follow-up time of 60 months. Both types of immune cells were accumulated predominantly in tumor stroma. NK cell density showed association with female gender, non-smoking and KRAS wild-type status. According to Kaplan-Meier analysis, PFS and OS proved to be longer in patients with high NK or Treg cell densities (p = 0.0293 and p = 0.0375 for PFS, p = 0.0310 and p = 0.0448 for OS, respectively). Evaluating the prognostic effect of the combination of NK and Treg cell density values revealed that PFS and OS were significantly longer in NKhigh/Treghigh cases compared to the other groups combined (p = 0.0223 and p = 0.0325, respectively). Multivariate Cox regression analysis indicated that high NK cell density was independent predictor of longer PFS while high NK and high Treg cell densities both proved significant predictors of longer OS. The NKhigh/Treghigh combination also proved to be an independent prognostic factor for both PFS and OS. In conclusion, NK and Treg cells can be components of the innate and adaptive immune response at action against progression of pulmonary adenocarcinoma.

CD74 supports accumulation and function of regulatory T cells in tumors

Regulatory T cells (Tregs) are plastic cells playing a pivotal role in the maintenance of immune homeostasis. Tregs actively adapt to the microenvironment where they reside; as a consequence, their molecular and functional profiles differ among tissues and pathologies. In tumors, the features acquired by Tregs remains poorly characterized. Here, we observe that human tumor-infiltrating Tregs selectively overexpress CD74, the MHC class II invariant chain. CD74 has been previously described as a regulator of antigen-presenting cell biology, however its function in Tregs remains unknown. CD74 genetic deletion in human primary Tregs reveals that CD74KO Tregs exhibit major defects in the organization of their actin cytoskeleton and intracellular organelles. Additionally, intratumoral CD74KO Tregs show a decreased activation, a drop in Foxp3 expression, a low accumulation in the tumor, and consistently, they are associated with accelerated tumor rejection in preclinical models in female mice. These observations are unique to tumor conditions as, at steady state, CD74KO-Treg phenotype, survival, and suppressive capacity are unaffected in vitro and in vivo. CD74 therefore emerges as a specific regulator of tumor-infiltrating Tregs and as a target to interfere with Treg anti-tumor activity.

PPAR delta promotes tumor-infiltrating Treg plasticity

Abstract Regulatory T-cells (Tregs) accumulate within the tumor microenvironment and are exploited to suppress anti-tumor immune responses. Lipid metabolism has been implicated as a regulator of Treg function. Unexpextedly, we found the master regulator of fatty acid catabolism PPARd as a Treg-intrinsic switch that restricts tumor growth by inducing Treg plasticity. Activation of PPARd in Tregs specifically leads to inflammatory reprograming of the tumor immune microenvironment without adverse effects in the periphery. We identified PPARd-induced transcriptional, epigenetic and metabolic alterations in Tregs that drive this plasticity response. Finally, using an inducible model of PPARd gain-of-function in Tregs, we demonstrate therapeutic potential of targeting this transcription factor to enhance immunotherapy against cancer. Collectively, these results indicate that inducing Treg plasticity in tumors can be harnessed to promote anti-tumor immunity.

Abstract 6350: 2MW4691, a novel CCR8/CTLA-4 bispecific antibody, displays potent anti-tumor efficacy by specifically depeleting tumor-infiltrating Tregs and blocking CTLA-4 signaling on CD8+ T cells

Abstract Background: Regulatory T cells (Tregs) are one of the representative immunosuppressive cells playing a critical role in tumor microenvironment by suppressing anti-tumor immune responses. A great many Treg-depleting therapeutics targeting CTLA-4, CCR8, and CD25 are currently being investigated in clinical trials, and the overwhelming majority of these studies showed systemic toxicity or limited efficacy. Novel modalities favoring tumor-infiltrating Tregs depletion are urgently needed. Here, a CCR8/CTLA-4 bispecific antibody 2MW4691 with inequivalent target arm affinities was developed to specifically deplete tumor-infiltrating Tregs and block CTLA-4 signaling on CD8+ T cells. Methods: Single-cell RNA sequencing data collection and computational analysis were applied to investigate CCR8 and CTLA-4 gene expression profiles in tumor-infiltrating Tregs. 2MW4691 was generated by combining parental bivalent anti-CCR8 and anti-CTLA-4 antibodies with different target arm affinities. CCR8 and CTLA-4 single and double-positive cells were used to evaluate the binding and blocking abilities of 2MW4691. Human FcγRIIIa receptor system, NK cells, and hPBMCs were used to assess the ADCC activity of 2MW4691. hCCR8/hCTLA-4 double transgenic mouse syngeneic models were used to evaluate the anti-tumor efficacy of 2MW4691 in vivo. A repeat dose administration study was performed in cynomolgus monkeys to evaluate the pharmacokinetic and toxicity profiles of 2MW6471. Results: Single-cell RNA sequencing analysis confirmed the co-expression of CCR8 and CTLA-4 in tumor-infiltrating Tregs of NSCLC patients. 2MW4691 was designed as a tetravalency symmetric structure with high binding affinity to CCR8 and low binding affinity to CTLA-4, which resulted in strong ADCC activity towards CCR8 single and CCR8/CTLA4 double-positive cells, but limited ADCC activity towards CTLA-4 single positive cells in cell-based assays. In the staphylococcal enterotoxin B stimulation assay, 2MW4691 promoted T-cell activation, suggesting that it maintained the ability to block CTLA-4-mediated downstream signaling from its parental anti-CTLA-4 antibody. In vivo, 2MW4691 exhibited potent anti-tumor efficacy in hCCR8 or hCTLA4 humanized mice bearing MC38 tumors. Further, the advantage in tumor inhibition of 2MW4691 compared with its parental antibodies was proved in the hCCR8/hCTLA-4 double knock-in mouse model. In the NHP study, 2MW4691 exhibited good pharmacokinetic and safety profiles with negligible impact on peripheral T cells. Conclusion: 2MW4691 demonstrated superior anti-tumor efficacy compared with its parental antibodies in CDX models and favorable tolerability in NHPs. The encouraging preclinical results support further evaluation of 2MW4691 in clinical trials. Citation Format: Cuicui Guo, Xiaodong Dai, Xiumei Xiong, Hongqin Liu, Xiaowei Cen, Hai Wu, Jinchao Zhang, Xun Gui. 2MW4691, a novel CCR8/CTLA-4 bispecific antibody, displays potent anti-tumor efficacy by specifically depeleting tumor-infiltrating Tregs and blocking CTLA-4 signaling on CD8+ T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6350.

Abstract 4123: Attenuating breast cancer metastasis with BCL-XL-targeting PROTACs

Abstract B-cell lymphoma X-large (BCL-XL) emerges as a significant player in cancer progression. In our recent findings, we unveil the efficacy of proteolysis-targeting chimeras (PROTACs) directed against BCL-XL, demonstrating their capacity to not only eliminate cancer cells but also target tumor-induced regulatory T cells (TI-Tregs). Notably, BCL-XL's role in promoting breast cancer metastasis extends beyond its anti-apoptotic function. We posit that BCL-XL-targeting PROTACs (BCL-XL-Ps) hold promise for treating metastatic breast cancer. Their potential lies in directly eliminating circulating tumor cells during vulnerable stages and/or triggering anti-cancer immunity through Treg cell depletion. Our experiments underscore the potency of IAP-based PROTACs in facilitating BCL-XL degradation via the ubiquitin-proteasome system (UPS) while mitigating on-target platelet toxicity. Treatment of breast cancer-bearing mice with these compounds demonstrates a tangible reduction in breast cancer metastasis to the lungs. Additionally, our studies reveal a significant depletion of tumor-infiltrating Tregs in mice treated with BCL-XL-Ps. While affirming BCL-XL as a viable therapeutic target for breast cancer metastasis, further exploration into the mechanisms behind BCL-XL-P targeting is imperative. Our future endeavors will be devoted to unraveling whether our BCL-XL-Ps effectively target both tumor-intrinsic BCL-XL, potentially inducing tumor cell death, and tumor-infiltrating Tregs, thereby fostering an adaptive immune response against the tumor cells. Citation Format: Madison E. Carelock, Peiyi Zhang, Mo Jiao, Umasankar De, Zeng Jin, Rachel M. Stump, Sarah G. Williams, Guangrong Zheng, Weizhou Zhang. Attenuating breast cancer metastasis with BCL-XL-targeting PROTACs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4123.

Abstract 4079: EGL-001 is a novel immunocytokine designed to specifically target and disarm T regulatory cells in the tumor microenvironment

Abstract Introduction Immune checkpoint blockade (ICB) therapies targeting PD-1/PD-L1 or CTLA-4 have greatly improved clinical outcome in many cancers. However, multiple mechanisms of resistance to ICB severely limit the number of patients experiencing long-term survival benefits. Overcoming resistance to ICB represents a significant challenge for drug development. Regulatory T cells (Tregs) in the tumor microenvironment (TME) prevent effector T cells (Teffs) from mounting a productive immune response and have been implicated in ICB resistance. Novel therapeutic strategies aimed at disarming Tregs in the TME could restore anti-tumor responses and sensitize patients to ICB therapy. Treg survival is dependent on interleukin-2 (IL-2), which signals in Tregs via the high affinity IL-2 receptor (IL-2R). Tumor-associated Tregs differentiate from tumor-associated Teffs and from peripheral Tregs by higher expression of CD25, the IL-2R alpha chain. Tregs in the TME also express higher surface levels of CTLA-4 as compared to peripheral Tregs. Thus, CD25 and CTLA-4 overexpression could allow preferential targeting of tumor-associated Tregs. Methods and Results We used single-cell RNA sequencing data from cancer patients and flow cytometry analysis of human tumor samples to verify that CD25 and CTLA-4 are selectively overexpressed in tumor-associated Tregs as compared with peripheral Tregs or other T cells. Based on these findings, we developed EGL-001, a novel immunocytokine (ICK) comprising a humanized IgG1 directed against CTLA-4 fused to a Treg-specific IL-2R antagonist IL-2 mutein, to selectively target tumor infiltrating Tregs. EGL-001 IgG1 moiety binds membrane CTLA-4, as demonstrated by flow cytometry, and competes with CTLA-4-CD80/86 interaction, as evaluated by ELISA. EGL-001 IL-2 mutein moiety binds to CD25, as demonstrated by bio-layer interferometry, and specifically blocks high-affinity IL-2R signaling in Tregs. Signaling blockade is further potentiated by a CTLA-4 dependent CD25 downmodulation process evidenced by confocal microscopy and flow cytometry. We demonstrate that EGL-001 unique tumor-associated Treg-targeted dual mechanism of action results in increased Treg apoptosis and decreased Treg frequencies in multiple in vitro, ex vivo and in vivo systems. Importantly, EGL-001 only minimally affects IL-2 signaling and survival of Teffs, which are then expected to be unleashed from Treg cell-mediated suppression. Accordingly, EGL-001 induces anti-tumor responses in mice in combination with anti-PD1 therapy. Conclusions EGL-001 is an ICK with a novel and unique mechanism of action combining ICB and Treg selective IL-2 starvation, designed to specifically disarm and deplete tumor-associated Tregs. Based on our preclinical data, EGL-001 is being developed as a cancer immunotherapeutic to improve patients’ response to ICB and counteract ICB resistance. Citation Format: Fiorella Kotsias, Caroline Janot-Sardet, Pamela Pamela Caudana, Erica Russo, Marine Dubois, Andres Zucchetti, Mercedes Tkach, Sebastien Lemoine, Ilgar Z. Mamedov, Alvaro Lladser, Jordan Denizeau, Annalisa Meola, Christine Sedlik, Edith Borcoman, Felix Rey, Pablo Guardado-Calvo, Bernard Vanhove, Monica Gostissa, Eliane PIaggio. EGL-001 is a novel immunocytokine designed to specifically target and disarm T regulatory cells in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4079.

Lymphatic endothelial cell-mediated accumulation of CD177+Treg cells suppresses antitumor immunity in human esophageal squamous cell carcinoma

ABSTRACT Regulatory T (Treg) cells are critical in shaping an immunosuppressive microenvironment to favor tumor progression and resistance to therapies. However, the heterogeneity and function of Treg cells in esophageal squamous cell carcinoma (ESCC) remain underexplored. We identified CD177 as a tumor-infiltrating Treg cell marker in ESCC. Interestingly, expression levels of CD177 and PD-1 were mutually exclusive in tumor Treg cells. CD177+ Treg cells expressed high levels of IL35, in association with CD8+ T cell exhaustion, whereas PD-1+ Treg cells expressed high levels of IL10. Pan-cancer analysis revealed that CD177+ Treg cells display increased clonal expansion compared to PD-1+ and double-negative (DN) Treg cells, and CD177+ and PD-1+ Treg cells develop from the same DN Treg cell origin. Importantly, we found CD177+ Treg cell infiltration to be associated with poor overall survival and poor response to anti-PD-1 immunotherapy plus chemotherapy in ESCC patients. Finally, we found that lymphatic endothelial cells are associated with CD177+ Treg cell accumulation in ESCC tumors, which are also decreased after anti-PD-1 immunotherapy plus chemotherapy. Our work identifies CD177+ Treg cell as a tumor-specific Treg cell subset and highlights their potential value as a prognostic marker of survival and response to immunotherapy and a therapeutic target in ESCC.

Targeting tumor-infiltrating tregs for improved antitumor responses.

Immunotherapies have revolutionized the landscape of cancer treatment. Regulatory T cells (Tregs), as crucial components of the tumor immune environment, has great therapeutic potential. However, nonspecific inhibition of Tregs in therapies may not lead to enhanced antitumor responses, but could also trigger autoimmune reactions in patients, resulting in intolerable treatment side effects. Hence, the precision targeting and inhibition of tumor-infiltrating Tregs is of paramount importance. In this overview, we summarize the characteristics and subpopulations of Tregs within tumor microenvironment and their inhibitory mechanisms in antitumor responses. Furthermore, we discuss the current major strategies targeting regulatory T cells, weighing their advantages and limitations, and summarize representative clinical trials targeting Tregs in cancer treatment. We believe that developing therapies that specifically target and suppress tumor-infiltrating Tregs holds great promise for advancing immune-based therapies.