EZH2 Inhibition Compromises α4-1BB-Mediated Antitumor Efficacy by Reducing the Survival and Effector Programming of CD8+ T Cells

Enhancer of Zeste Homolog 2 (EZH2) inhibitors (EZH2i) are approved to treat certain cancer types. Previous studies have suggested the potential to combine EZH2i with immune checkpoint blockade targeting coinhibitory receptors like PD-(L)1 and CTLA-4, but whether it can also enhance the activity of agents targeting costimulatory receptors is not known. Here, we explore the combination between EZH2i and an agonist antibody targeting the T cell costimulatory receptor 4-1BB (α4-1BB). Our data show that EZH2i compromise the efficacy of α4-1BB in both CT26 colon carcinoma and in an in vivo protein immunization model. We link this to reduced effector survival and increased BIM expression in CD8+ T cells upon EZH2i treatment. These data support the requirement of EZH2 function in 4-1BB-mediated CD8+ T cell expansion and effector programming and emphasize the consideration that must be given when combining such antitumoral therapies.

TNF receptor agonists induce distinct receptor clusters to mediate differential agonistic activity

Monoclonal antibodies (mAb) and natural ligands targeting costimulatory tumor necrosis factor receptors (TNFR) exhibit a wide range of agonistic activities and antitumor responses. The mechanisms underlying these differential agonistic activities remain poorly understood. Here, we employ a panel of experimental and clinically-relevant molecules targeting human CD40, 4-1BB and OX40 to examine this issue. Confocal and STORM microscopy reveal that strongly agonistic reagents induce clusters characterized by small area and high receptor density. Using antibody pairs differing only in isotype we show that hIgG2 confers significantly more receptor clustering than hIgG1 across all three receptors, explaining its greater agonistic activity, with receptor clustering shielding the receptor-agonist complex from further molecular access. Nevertheless, discrete receptor clustering patterns are observed with different hIgG2 mAb, with a unique rod-shaped assembly observed with the most agonistic mAb. These findings dispel the notion that larger receptor clusters elicit greater agonism, and instead point to receptor density and subsequent super-structure as key determinants.

Agonist-induced 4-1BB activation prevents the development of Sjӧgren's syndrome-like sialadenitis in non-obese diabetic mice

Activation of costimulatory receptor 4-1BB enhances T helper 1 (Th1) and CD8 T cell responses in protective immunity, and prevents or attenuates several autoimmune diseases by increasing Treg numbers and suppressing Th17 or Th2 effector response. We undertook this study to elucidate the impact of enforced 4-1BB activation on the development of Sjögren's syndrome (SS)-like sialadenitis in non-obese diabetic (NOD) model of this disease. An anti-4-1BB agnostic antibody was intraperitoneally injected to female NOD mice aged 7 weeks, prior to the disease onset that occurs around 10-11 weeks of age, 3 times weekly for 2 weeks, and the mice were analyzed for SS pathologies at age 11 weeks. The salivary flow rate was markedly higher in the anti-4-1BB-treated NOD mice compared to the IgG-treated controls. Anti-4-1BB treatment significantly reduced the leukocyte infiltration of the submandibular glands (SMGs) and the levels of serum antinuclear antibodies. Flow cytometric analysis showed that the percentages of CD4 T cells, Th17 cells and plasmacytoid dendritic cells among SMG leukocytes were markedly reduced by anti-4-1BB treatment, in conjunction with a reduction in SMG IL-23p19 mRNA levels and serum IL-17 concentrations. Although the proportion of Tregs and IL-10 mRNA levels in SMGs were not altered by 4-1BB activation, IL-10 mRNA levels in salivary gland-draining lymph nodes and serum IL-10 concentrations were both markedly increased. While anti-4-1BB treatment did not affect the amount of Th1 cells and IFNγ mRNA in the SMGs, it increased these measurables in salivary gland-draining lymph nodes. Hence, agonistic activation of 4-1BB impedes the development of SS-like sialadenitis and hyposalivation.

Multimodal Multiplexed Immunoimaging with Nanostars to Detect Multiple Immunomarkers and Monitor Response to Immunotherapies

The overexpression of immunomarker programmed cell death protein 1 (PD-1) and engagement of PD-1 to its ligand, PD-L1, are involved in the functional impairment of cluster of differentiation 8+ (CD8+) T cells, contributing to cancer progression. However, heterogeneities in PD-L1 expression and variabilities in biopsy-based assays render current approaches inaccurate in predicting PD-L1 status. Therefore, PD-L1 screening alone is not predictive of patient response to treatment, which motivates us to simultaneously detect multiple immunomarkers engaged in immune modulation. Here, we have developed multimodal probes, immunoactive gold nanostars (IGNs), that accurately detect PD-L1+ tumor cells and CD8+ T cells simultaneously in vivo, surpassing the limitations of current immunoimaging techniques. IGNs integrate the whole-body imaging of positron emission tomography with high sensitivity and multiplexing of Raman spectroscopy, enabling the dynamic tracking of both immunomarkers. IGNs also monitor response to immunotherapies in mice treated with combinatorial PD-L1 and CD137 agonists and distinguish responders from those nonresponsive to treatment. Our results showed a multifunctional nanoscale probe with capabilities that cannot be achieved with either modality alone, allowing multiplexed immunologic tumor profiling critical for predicting early response to immunotherapies.

An Update on Anti-CD137 Antibodies in Immunotherapies for Cancer

The selective expression of CD137 on cells of the immune system (e.g., T and DC cells) and oncogenic cells in several types of cancer leads this molecule to be an attractive target to discover cancer immunotherapy. Therefore, specific antibodies against CD137 are being studied and developed aiming to activate and enhance anti-cancer immune responses as well as suppress oncogenic cells. Accumulating evidence suggests that anti-CD137 antibodies can be used separately to prevent tumor in some cases, while in other cases, these antibodies need to be co-administered with other antibodies or drugs/vaccines/regents for a better performance. Thus, in this work, we aim to update and discuss current knowledge about anti-cancer effects of anti-CD137 antibodies as mono- and combined-immunotherapies.

Chronic retroviral infection of mice promotes tumor development, but CD137 agonist therapy restores effective tumor immune surveillance

T cell responses are crucial for anti-tumor immunity. In chronic viral infections, anti-tumor T cell responses can be compromised due to various immunological mechanisms, including T cell exhaustion. To study mechanisms of anti-tumor immunity during a chronic viral infection, we made use of the well-established Friend virus (FV) mouse model. Chronically FV-infected mice are impaired in their ability to reject FBL-3 cells-a virus-induced tumor cell line of C57BL/6 origin. Here we aimed to explore therapeutic strategies to overcome the influence of T cell exhaustion during chronic viral infection, and reactivate effector CD8+ and CD4+ T cells to eliminate tumor cells. For T cell stimulation, agonistic antibodies against the tumor necrosis factor receptor (TNFR) superfamily members CD137 and CD134 were used, because they were reported to augment the cytotoxic program of T cells. αCD137 agonistic therapy, but not αCD134 agonistic therapy, resulted in FBL-3 tumor elimination in chronically FV-infected mice. CD137 stimulation significantly enhanced the cytotoxic activity of both CD4+ and CD8+ T cells, which were both required for efficient tumor control. Our study suggests that agonistic antibodies to CD137 can efficiently enhance anti-tumor immunity even in the setting of chronic viral infection, which might have promising therapeutic applications.

Activation of 4-1BB on Liver Myeloid Cells Triggers Hepatitis via an Interleukin-27-Dependent Pathway

Purpose: Agonist antibodies targeting the T-cell costimulatory receptor 4-1BB (CD137) are among the most effective immunotherapeutic agents across preclinical cancer models. In the clinic, however, development of these agents has been hampered by dose-limiting liver toxicity. Lack of knowledge of the mechanisms underlying this toxicity has limited the potential to separate 4-1BB agonist-driven tumor immunity from hepatotoxicity.Experimental Design: The capacity of 4-1BB agonist antibodies to induce liver toxicity was investigated in immunocompetent mice, with or without coadministration of checkpoint blockade, via (i) measurement of serum transaminase levels, (ii) imaging of liver immune infiltrates, and (iii) qualitative and quantitative assessment of liver myeloid and T cells via flow cytometry. Knockout mice were used to clarify the contribution of specific cell subsets, cytokines, and chemokines.Results: We find that activation of 4-1BB on liver myeloid cells is essential to initiate hepatitis. Once activated, these cells produce interleukin-27 that is required for liver toxicity. CD8 T cells infiltrate the liver in response to this myeloid activation and mediate tissue damage, triggering transaminase elevation. FoxP3⁺ regulatory T cells limit liver damage, and their removal dramatically exacerbates 4-1BB agonist-induced hepatitis. Coadministration of CTLA-4 blockade ameliorates transaminase elevation, whereas PD-1 blockade exacerbates it. Loss of the chemokine receptor CCR2 blocks 4-1BB agonist hepatitis without diminishing tumor-specific immunity against B16 melanoma.Conclusions: 4-1BB agonist antibodies trigger hepatitis via activation and expansion of interleukin-27-producing liver Kupffer cells and monocytes. Coadministration of CTLA-4 and/or CCR2 blockade may minimize hepatitis, but yield equal or greater antitumor immunity. Clin Cancer Res; 24(5); 1138-51. ©2018 AACR.

4-1BB Agonist Focuses CD8+ Tumor-Infiltrating T-Cell Growth into a Distinct Repertoire Capable of Tumor Recognition in Pancreatic Cancer

Purpose: Survival for pancreatic ductal adenocarcinoma (PDAC) patients is extremely poor and improved therapies are urgently needed. Tumor-infiltrating lymphocyte (TIL) adoptive cell therapy (ACT) has shown great promise in other tumor types, such as metastatic melanoma where overall response rates of 50% have been seen. Given this success and the evidence showing that T-cell presence positively correlates with overall survival in PDAC, we sought to enrich for CD8+ TILs capable of autologous tumor recognition. In addition, we explored the phenotype and T-cell receptor repertoire of the CD8+ TILs in the tumor microenvironment.Experimental Design: We used an agonistic 4-1BB mAb during the initial tumor fragment culture to provide 4-1BB costimulation and assessed changes in TIL growth, phenotype, repertoire, and antitumor function.Results: Increased CD8+ TIL growth from PDAC tumors was achieved with the aid of an agonistic 4-1BB mAb. Expanded TILs were characterized by an activated but not terminally differentiated phenotype. Moreover, 4-1BB stimulation expanded a more clonal and distinct CD8+ TIL repertoire than IL2 alone. TILs from both culture conditions displayed MHC class I-restricted recognition of autologous tumor targets.Conclusions: Costimulation with an anti-4-1BB mAb increases the feasibility of TIL therapy by producing greater numbers of these tumor-reactive T cells. These results suggest that TIL ACT for PDAC is a potential treatment avenue worth further investigation for a patient population in dire need of improved therapy. Clin Cancer Res; 23(23); 7263-75. ©2017 AACR.

4-1BB agonism: adding the accelerator to cancer immunotherapy

The success of checkpoint inhibitors has validated immunomodulatory agents as a valuable class of anticancer therapeutics. A promising co-stimulatory immunologic target is 4-1BB, or CD137, a member of the tumor necrosis factor receptor superfamily. Ligation of 4-1BB induces an activating signal in CD8(+) T cells and natural killer cells, resulting in increased pro-inflammatory cytokine secretion, cytolytic function, and antibody-dependent cell-mediated cytotoxicity. Targeting 4-1BB with agonistic monoclonal antibody (mAb) therapy demonstrated potent antitumor effects in murine tumor models. While anti-4-1BB mAbs have entered clinical trials, optimal efficacy of 4-1BB-targeted agents will inevitably come from combination therapeutic strategies. Checkpoint blockade is a compelling combination partner for 4-1BB agonism. This novel immunotherapeutic approach has the potential to active antitumor immune effectors by a complementary mechanism: simultaneously "removing the brakes" via blocking inhibitory signaling and "stepping on the accelerator" via co-stimulation. While important considerations should be given to 4-1BB-mediated toxicities, the current understanding of 4-1BB biology suggests it may play a key role in advancing the capabilities of cancer combination therapy.

Combination immunotherapy with 4-1BB activation and PD-1 blockade enhances antitumor efficacy in a mouse model of subcutaneous tumor

BACKGROUND/AIM

The purpose of the present study was to establish an effective immunotherapy by skewing the cosignal balance to be on the positive side by using the combination of monoclonal antibody (mAb) against 4-1BB also known as Cluster of Differentiation (CD) 137 as a co-stimulatory effector and to programmed death-1 (PD-1) to blockade the immune checkpoint.

MATERIALS AND METHODS

Mice implanted with 1×10(5) CT26 cells were treated with anti 4-1BB mAb alone, anti PD-1 mAb alone, or both anti 4-1BB mAb and anti PD-1 mAb. Immune cell populations were analyzed by flow cytometry. Tumor-infiltrating T-cells were evaluated by immunohistochemistry.

RESULTS

Mice treated with the combination therapy had the best antitumor response that resulted in complete tumor rejection. The numbers of CD4(+) interferon (IFN)-γ(+) and CD8(+) IFN-γ(+) T-cells were significantly higher in the combination group. The number of tumor-infiltrating T-cells was significantly increased in the combination therapy.

CONCLUSION

The therapeutic strategy of targeting co-signal molecules has promising clinical applications in the future.

Focal radiation therapy combined with 4-1BB activation and CTLA-4 blockade yields long-term survival and a protective antigen-specific memory response in a murine glioma model

Background

Glioblastoma (GBM) is the most common malignant brain tumor in adults and is associated with a poor prognosis. Cytotoxic T lymphocyte antigen -4 (CTLA-4) blocking antibodies have demonstrated an ability to generate robust antitumor immune responses against a variety of solid tumors. 4-1BB (CD137) is expressed by activated T lymphocytes and served as a co-stimulatory signal, which promotes cytotoxic function. Here, we evaluate a combination immunotherapy regimen involving 4-1BB activation, CTLA-4 blockade, and focal radiation therapy in an immune-competent intracranial GBM model.

Methods

GL261-luciferace cells were stereotactically implanted in the striatum of C57BL/6 mice. Mice were treated with a triple therapy regimen consisted of 4-1BB agonist antibodies, CTLA-4 blocking antibodies, and focal radiation therapy using a small animal radiation research platform and mice were followed for survival. Numbers of brain-infiltrating lymphocytes were analyzed by FACS analysis. CD4 or CD8 depleting antibodies were administered to determine the relative contribution of T helper and cytotoxic T cells in this regimen. To evaluate the ability of this immunotherapy to generate an antigen-specific memory response, long-term survivors were re-challenged with GL261 glioma en B16 melanoma flank tumors.

Results

Mice treated with triple therapy had increased survival compared to mice treated with focal radiation therapy and immunotherapy with 4-1BB activation and CTLA-4 blockade. Animals treated with triple therapy exhibited at least 50% long-term tumor free survival. Treatment with triple therapy resulted in a higher density of CD4⁺ and CD8⁺ tumor infiltrating lymphocytes. Mechanistically, depletion of CD4⁺ T cells abrogated the antitumor efficacy of triple therapy, while depletion of CD8⁺ T cells had no effect on the treatment response.

Conclusion

Combination therapy with 4-1BB activation and CTLA-4 blockade in the setting of focal radiation therapy improves survival in an orthotopic mouse model of glioma by a CD4⁺ T cell dependent mechanism and generates antigen-specific memory.

CD137 is induced by the CD40 signal on chronic lymphocytic leukemia B cells and transduces the survival signal via NF-κB activation

CD137 is a member of the tumor necrosis factor receptor family that is expressed on activated T cells. This molecule provides a co-stimulatory signal that enhances the survival, and differentiation of cells, and has a crucial role in the development of CD8 cytotoxic T cells and anti-tumor immunity. Here we report that CD137 expression is also induced on normal or malignant human B cells by CD40 ligation by its ligand CD154. This CD137 induction was more prominent in chronic lymphocytic leukemia (CLL) cells than in other types of B cells. CD137 stimulation on B cells by its ligand induced the nuclear translocation of p52 (a non-canonical NF-κB factor). In agreement with this finding, expression of the survival factor BCL-XL was upregulated. Consequently, the CD137 signal augmented the survival of CD154-stimulated CLL B cells in vitro. This unexpected induction of CD137 on B cells by CD40 signal may influence the clinical course of CLL.

Co-stimulation through 4-1BB/CD137 improves the expansion and function of CD8(+) melanoma tumor-infiltrating lymphocytes for adoptive T-cell therapy

Adoptive T-cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) can induce tumor regression in up to 50% or more of patients with unresectable metastatic melanoma. However, current methods to expand melanoma TIL, especially the “rapid expansion protocol” (REP) were not designed to enhance the generation of optimal effector-memory CD8⁺ T cells for infusion. One approach to this problem is to manipulate specific co-stimulatory signaling pathways to enhance CD8⁺ effector-memory T-cell expansion. In this study, we determined the effects of activating the TNF-R family member 4-1BB/CD137, specifically induced in activated CD8⁺ T cells, on the yield, phenotype, and functional activity of expanded CD8⁺ T cells during the REP. We found that CD8⁺ TIL up-regulate 4-1BB expression early during the REP after initial TCR stimulation, but neither the PBMC feeder cells in the REP or the activated TIL expressed 4-1BB ligand. However, addition of an exogenous agonistic anti-4-1BB IgG₄ (BMS 663513) to the REP significantly enhanced the frequency and total yield of CD8⁺ T cells as well as their maintenance of CD28 and increased their anti-tumor CTL activity. Gene expression analysis found an increase in bcl-2 and survivin expression induced by 4-1BB that was associated with an enhanced survival capability of CD8⁺ post-REP TIL when re-cultured in the absence or presence of cytokines. Our findings suggest that adding an agonistic anti-4-1BB antibody during the time of TIL REP initiation produces a CD8⁺ T cell population capable of improved effector function and survival. This may greatly improve TIL persistence and anti-tumor activity in vivo after adoptive transfer into patients.

Agonistic anti-4-1BB antibody promotes the expansion of natural regulatory T cells while maintaining Foxp3 expression

The engagement of the 4-1BB (CD137) co-stimulatory pathway promotes the activation and proliferation of conventional CD4(+) T and CD8(+) T cells, but the role of 4-1BB co-stimulation in CD4(+) CD25(+) regulatory T cells (Treg) is less clear. In particular, whether 4-1BB stimulation affects the expression of Foxp3, a master gene for Treg, is unknown. This study demonstrates that co-stimulation of 4-1BB engaged by an agonistic antibody promotes the proliferation of Treg in a dependent manner of low-concentration interleukin-2 in vitro. The 4-1BB-expanded Treg maintain Foxp3 expression and their ability to suppress conventional CD4(+) T cells and their feature to produce no interleukin-2. However, the 4-1BB-expanded Treg produce increased levels of interferon-gamma, whose significance is unknown. Thus, 4-1BB co-stimulation plays a role in the expansion of functional CD4(+) CD25(+) Treg cells without adversely affecting their suppressive activity.

CD134 Costimulation Couples the CD137 Pathway to Induce Production of Supereffector CD8 T Cells That Become IL-7 Dependent

The TNFR superfamily members 4-1BB (CD137) and OX40 (CD134) are costimulatory molecules that potently boost CD8 and CD4 T cell responses. Concomitant therapeutic administration of agonist anti-CD137 and -CD134 mAbs mediates rejection of established tumors and fosters powerful CD8 T cell responses. To reveal the mechanism, the role of CD137 expression by specific CD8 T cells was determined to be essential for optimal clonal expansion and accumulation of effector cells. Nonetheless, dual costimulation induced production of supereffector CD8 T cells when either the specific T cells or the host alone bore CD137. Perhaps surprisingly, the total absence of CD137 prevented anti-CD134 augmentation of supereffector differentiation demonstrating an unappreciated link between these related pathways. Ultimately, it was reasoned that these powerful dual costimulatory responses involved common gamma family members, and we show substantial increases of CD25 and IL-7Ralpha-chain expression by the specific CD8 T cells. To investigate this further, it was shown that IL-7 mediated T cell accumulation, but importantly, a gradual and preferential effect of survival was directed toward supereffector CD8 T cells. In fact, a clear enhancement of effector differentiation was demonstrated to be proportional to the increasing amount of IL-7Ralpha expression by the specific CD8 T cells. Therefore, dual costimulation through CD137 and CD134 drives production and survival of supereffector CD8 T cells through a distinct IL-7-dependent pathway.

[Promotion of the activity of Akt in CD8+ T cells by the crosslink of 3H3, an agonist antibody of 4-1BB]

AIM

To investigate whether 4-1BB could promote the proliferation and survival of CD8(+) T cells proliferation, and the activity of protein kinase B (Akt).

METHODS

Highly purified CD8(+) T cells were separated and stimulated by CD3 antibody. The crosslink of 3H3 and the proliferation and antiapoptosis of CD8(+) T cells were examined.

RESULTS

The crosslink of 3H3 promoted the proliferation and survival of CD8(+) T cells. 4-1BB induced by 3H3 promoted the phosphorylated level and kinase activity of Akt.

CONCLUSION

Akt pathway might participate in 4-1BB which promoted the proliferation and survival of CD8(+) T cells induced by 3H3.