Agonistic anti-CD137 antibody treatment leads to antitumor response in mice with liver cancer

Radiolabelling and preclinical characterisation of [89Zr]Zr-Df-ATG-101 bispecific to PD-L1/4-1BB

PURPOSE

ATG-101, a bispecific antibody that simultaneously targets the immune checkpoint PD-L1 and the costimulatory receptor 4-1BB, activates exhausted T cells upon PD-L1 crosslinking. Previous studies demonstrated promising anti-tumour efficacy of ATG-101 in preclinical models. Here, we labelled ATG-101 with 89Zr to confirm its tumour targeting effect and tissue biodistribution in a preclinical model. We also evaluated the use of immuno-PET to study tumour uptake of ATG-101 in vivo.

METHODS

ATG-101, anti-PD-L1, and an isotype control were conjugated with p-SCN-Deferoxamine (Df). The Df-conjugated antibodies were radiolabelled with 89Zr, and their radiochemical purity, immunoreactivity, and serum stability were assessed. We conducted PET/MRI and biodistribution studies on [89Zr]Zr-Df-ATG-101 in BALB/c nude mice bearing PD-L1-expressing MDA-MB-231 breast cancer xenografts for up to 10 days after intravenous administration of [89Zr]Zr-labelled antibodies. The specificity of [89Zr]Zr-Df-ATG-101 was evaluated through a competition study with unlabelled ATG-101 and anti-PD-L1 antibodies.

RESULTS

The Df-conjugation and [89Zr]Zr -radiolabelling did not affect the target binding of ATG-101. Biodistribution and imaging studies demonstrated biological similarity of [89Zr]Zr-Df-ATG-101 and [89Zr]Zr-Df-anti-PD-L1. Tumour uptake of [89Zr]Zr-Df-ATG-101 was clearly visualised using small-animal PET imaging up to 7 days post-injection. Competition studies confirmed the specificity of PD-L1 targeting in vivo.

CONCLUSION

[89Zr]Zr-Df-ATG-101 in vivo distribution is dependent on PD-L1 expression in the MDA-MB-231 xenograft model. Immuno-PET with [89Zr]Zr-Df-ATG-101 provides real-time information about ATG-101 distribution and tumour uptake in vivo. Our data support the use of [89Zr]Zr-Df-ATG-101 to assess tumour and tissue uptake of ATG-101.

Therapeutic Strategies in BRAF V600 Wild-Type Cutaneous Melanoma

There have been many recent advances in melanoma therapy. While 50% of melanomas have a BRAF mutation and are a target for BRAF inhibitors, the remaining 50% are BRAF wild-type. Immune checkpoint inhibitors targeting PD-1, cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and lymphocyte activated gene-3 (Lag-3) are all approved for the treatment of patients with advanced BRAF wild-type melanoma; however, treatment of this patient population following initial immune checkpoint blockade is a current therapeutic challenge given the lack of other efficacious options. Here, we briefly review available US FDA-approved therapies for BRAF wild-type melanoma and focus on developing treatment avenues for this heterogeneous group of patients. We review the basics of genomic features of both BRAF mutant and BRAF wild-type melanoma as well as efforts underway to develop new targeted therapies involving the mitogen-activated protein kinase (MAPK) pathway for patients with BRAF wild-type tumors. We then focus on novel immunotherapies, including developing checkpoint inhibitors and agonists, cytokine therapies, oncolytic viruses and tumor-infiltrating lymphocytes, all of which represent potential therapeutic avenues for patients with BRAF wild-type melanoma who progress on currently approved immune checkpoint inhibitors.

The Roles of Myeloid-Derived Suppressor Cells in Liver Disease

Liver disease-related mortality is a major cause of death worldwide. Hepatic innate and adaptive immune cells play diverse roles in liver homeostasis and disease. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells. MDSCs can be broadly divided into monocytic MDSCs and polymorphonuclear or granulocytic MDSCs, and they functionally interact with both liver parenchymal and nonparenchymal cells, such as hepatocytes and regulatory T cells, to impact liver disease progression. The infiltration and activation of MDSCs in liver disease can be regulated by inflammatory chemokines and cytokines, tumor-associated fibroblasts, epigenetic regulation factors, and gut microbiota during liver injury and cancer. Given the pivotal roles of MDSCs in advanced liver diseases, they can be targeted to treat primary and metastatic liver cancer, liver generation, alcoholic and nonalcoholic liver disease, and autoimmune hepatitis. Currently, several treatments such as the antioxidant and anti-inflammatory agent berberine are under preclinical and clinical investigation to evaluate their therapeutic efficacy on liver disease and their effect on MDSC infiltration and function. Phenotypic alteration of MDSCs in different liver diseases that are in a model-dependent manner and lack special markers for distinct MDSCs are challenges for targeting MDSCs to treat liver disease. Multi-omics study is an option to uncover the features of disease-specific MDSCs and potential gene or protein targets for liver disease treatment. In summary, MDSCs play important roles in the pathogenesis and progression of liver disease by regulating both intrahepatic innate and adaptive immune responses.

The role of immune checkpoints in antitumor response: a potential antitumor immunotherapy

Immunotherapy aims to stimulate the immune system to inhibit tumor growth or prevent metastases. Tumor cells primarily employ altered expression of human leukocyte antigen (HLA) as a mechanism to avoid immune recognition and antitumor immune response. The antitumor immune response is primarily mediated by CD8+ cytotoxic T cells (CTLs) and natural killer (NK) cells, which plays a key role in the overall anti-tumor immune response. It is crucial to comprehend the molecular events occurring during the activation and subsequent regulation of these cell populations. The interaction between antigenic peptides presented on HLA-I molecules and the T-cell receptor (TCR) constitutes the initial signal required for T cell activation. Once activated, in physiologic circumstances, immune checkpoint expression by T cells suppress T cell effector functions when the antigen is removed, to ensures the maintenance of self-tolerance, immune homeostasis, and prevention of autoimmunity. However, in cancer, the overexpression of these molecules represents a common method through which tumor cells evade immune surveillance. Numerous therapeutic antibodies have been developed to inhibit immune checkpoints, demonstrating antitumor activity with fewer side effects compared to traditional chemotherapy. Nevertheless, it's worth noting that many immune checkpoint expressions occur after T cell activation and consequently, altered HLA expression on tumor cells could diminish the clinical efficacy of these antibodies. This review provides an in-depth exploration of immune checkpoint molecules, their corresponding blocking antibodies, and their clinical applications.

Soluble CD137 and risk of hepatocellular carcinoma: nested case-control studies in cohorts in Shanghai and Singapore

BACKGROUND

The majority of hepatocellular carcinoma (HCC) cases occur in the presence of cirrhosis. Biomarkers of cirrhosis-associated immune dysfunction such as CD8+ T cell cytokines could aid HCC risk assessment.

METHODS

CD8+ T cell cytokines were determined in pre-diagnostic serum in two studies including 315 HCC case-control pairs in the Shanghai Cohort Study (SCS) and 197 pairs in the Singapore Chinese Health Study (SCHS). Conditional logistic regression was used to estimate odds ratio (OR) and 95% confidence interval (CI) for HCC with levels of five cytokines-soluble CD137 (sCD137), soluble Fas (sFas), perforin, macrophage inflammatory protein 1-beta (MIP-1β), and tumour necrosis factor alpha (TNF-α).

RESULTS

sCD137 levels were significantly higher in HCC cases than controls in both cohorts (Ps < 0.001). Compared with the lowest quartile, multivariable-adjusted ORs (95% CI) of HCC for the highest sCD137 quartile were 3.79 (1.73, 8.30) in the SCS and 3.49 (1.44, 8.48) in the SCHS. The sCD137-HCC association was independent of hepatitis B seropositivity and follow-up time. No other cytokine was consistently associated with HCC risk.

CONCLUSION

sCD137 was associated with higher risk of HCC in two studies nested in general population cohorts. sCD137 may be a long-term risk marker of HCC development.

Delivering co-stimulatory tumor necrosis factor receptor agonism for cancer immunotherapy: past, current and future perspectives

The tumor necrosis factor superfamily (TNFSF) and their receptors (TNFRSF) are important regulators of the immune system, mediating proliferation, survival, differentiation, and function of immune cells. As a result, their targeting for immunotherapy is attractive, although to date, under-exploited. In this review we discuss the importance of co-stimulatory members of the TNFRSF in optimal immune response generation, the rationale behind targeting these receptors for immunotherapy, the success of targeting them in pre-clinical studies and the challenges in translating this success into the clinic. The efficacy and limitations of the currently available agents are discussed alongside the development of next generation immunostimulatory agents designed to overcome current issues, and capitalize on this receptor class to deliver potent, durable and safe drugs for patients.

Circulating CD137+ T Cell Levels Are Correlated with Response to Pembrolizumab Treatment in Advanced Head and Neck Cancer Patients

Pembrolizumab, an anti-PD-1 antibody, has been approved as first-line treatment for recurrent or metastatic head and neck squamous cell carcinoma ((R/M) HNSCC). However, only a minority of patients benefit from immunotherapy, which highlights the need to identify novel biomarkers to optimize treatment strategies. CD137⁺ T cells have been identified as tumour-specific T cells correlated with immunotherapy responses in several solid tumours. In this study, we investigated the role of circulating CD137⁺ T cells in (R/M) HNSCC patients undergoing pembrolizumab treatment. PBMCs obtained from 40 (R/M) HNSCC patients with a PD-L1 combined positive score (CPS) ≥1 were analysed at baseline via cytofluorimetry for the expression of CD137, and it was found that the percentage of CD3⁺CD137⁺ cells is correlated with the clinical benefit rate (CBR), PFS, and OS. The results show that levels of circulating CD137⁺ T cells are significantly higher in responder patients than in non-responders (p = 0.03). Moreover, patients with CD3⁺CD137⁺ percentage ≥1.65% had prolonged OS (p = 0.02) and PFS (p = 0.02). Multivariate analysis, on a combination of biological and clinical parameters, showed that high levels of CD3⁺CD137⁺ cells (≥1.65%) and performance status (PS) = 0 are independent prognostic factors of PFS (CD137⁺ T cells, p = 0.007; PS, p = 0.002) and OS (CD137⁺ T cells, p = 0.006; PS, p = 0.001). Our results suggest that levels of circulating CD137⁺ T cells could serve as biomarkers for predicting the response of (R/M) HNSCC patients to pembrolizumab treatment, thus contributing to the success of anti-cancer treatment.

Targeting tumor-associated macrophages in hepatocellular carcinoma: biology, strategy, and immunotherapy

Hepatocellular carcinoma (HCC), one of the most malignant tumors, is characterized by its stubborn immunosuppressive microenvironment. As one of the main members of the tumor microenvironment (TME) of HCC, tumor-associated macrophages (TAMs) play a critical role in its occurrence and development, including stimulating angiogenesis, enhancing immunosuppression, and promoting the drug resistance and cancer metastasis. This review describes the origin as well as phenotypic heterogeneity of TAMs and their potential effects on the occurrence and development of HCC and also discusses about various adjuvant therapy based strategies that can be used for targeting TAMs. In addition, we have highlighted different treatment modalities for TAMs based on immunotherapy, including small molecular inhibitors, immune checkpoint inhibitors, antibodies, tumor vaccines, adoptive cellular immunotherapy, and nanocarriers for drug delivery, to explore novel combination therapies and provide feasible therapeutic options for clinically improving the prognosis and quality of life of HCC patients.

Macrophage and monocyte subsets as new therapeutic targets in cancer immunotherapy

The introduction of immune checkpoint inhibitors (ICIs) for the treatment of solid cancers dramatically turned the tables in clinical routine. However, therapy success is still limited with up to 70% of non-responders in patients with ICI treatment. Traditionally, most immunotherapy approaches aim at directly stimulating anti-tumor T cell responses. More recently, tumor-associated macrophages have come into focus due to their predominance in solid tumors. Intensive cross-talk with tumor cells and immune as well as stromal cells within the tumor microenvironment can drive either pro- or anti-tumorigenic macrophage phenotypes. In turn, tumor-associated macrophages strongly shape cytokine and metabolite levels in the tumor microenvironment and thus are central players in anti-tumor immunity. Thus, ambivalent macrophage populations exist which raises therapeutic possibilities to either enhance or diminish their functionality. However, molecular signals controlling tumor-associated macrophage polarization are incompletely understood. Gaining in-depth understanding of monocyte/macrophage properties both in circulation and within distinct tumor microenvironments would (i) allow the development of new therapeutic approaches, and (ii) could additionally aid our understanding of underlying mechanisms limiting current therapy with the option of combinatorial therapies to increase efficacy. In this review, we summarize recent data addressing heterogeneity of tumor-associated macrophage populations and we discuss strategies to target macrophages using known molecular pathways with the potential for straight-forward clinical application.

4-1BB: A promising target for cancer immunotherapy

Immunotherapy, powered by its relative efficacy and safety, has become a prominent therapeutic strategy utilized in the treatment of a wide range of diseases, including cancer. Within this class of therapeutics, there is a variety of drug types such as immune checkpoint blockade therapies, vaccines, and T cell transfer therapies that serve the purpose of harnessing the body’s immune system to combat disease. Of these different types, immune checkpoint blockades that target coinhibitory receptors, which dampen the body’s immune response, have been widely studied and established in clinic. In contrast, however, there remains room for the development and improvement of therapeutics that target costimulatory receptors and enhance the immune response against tumors, one of which being the 4-1BB (CD137/ILA/TNFRSF9) receptor. 4-1BB has been garnering attention as a promising therapeutic target in the setting of cancer, amongst other diseases, due to its broad expression profile and ability to stimulate various signaling pathways involved in the generation of a potent immune response. Since its discovery and demonstration of potential as a clinical target, major progress has been made in the knowledge of 4-1BB and the development of clinical therapeutics that target it. Thus, we seek to summarize and provide a comprehensive update and outlook on those advancements in the context of cancer and immunotherapy.

Cowpea Mosaic Virus and Natural Killer Cell Agonism for In Situ Cancer Vaccination

We have previously shown the plant virus Cowpea mosaic virus (CPMV) to be an efficacious in situ cancer vaccine, providing elimination of tumors and tumor-specific immune memory. Additionally, we have shown that CPMV recruits Natural Killer (NK) cells within the tumor microenvironment. Here we aimed to determine whether a combination of CPMV and anti-4-1BB monoclonal antibody agonist to stimulate tumor-resident and CPMV-recruited NK cells is an effective dual therapy approach to improve NK cell function and in situ cancer vaccination efficacy. Using murine models of metastatic colon carcinomatosis and intradermal melanoma, intratumorally administered CPMV + anti-4-1BB dual therapy provided a robust antitumor response, improved elimination of primary tumors, and reduced mortality compared to CPMV and anti-4-1BB monotherapies. Additionally, on tumor rechallenge there was significant delay/prevention of tumor development and improved survival, highlighting that the CPMV + anti-4-1BB dual therapy enables potent and durable antitumor efficacy.

Circulating CD137+ T Cells Correlate with Improved Response to Anti-PD1 Immunotherapy in Patients with Cancer

PURPOSE

CD137 molecule is expressed by activated lymphocytes, and in patients with cancer identifies the tumor-reactive T cells. In solid tumors, high levels of circulating CD137+ T cells are associated with the clinical response and the disease-free status. Here, we examined the role of the CD137+ T cells in the improvement of patients' selection for immunotherapy treatment.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells derived from 109 patients with metastatic cancer (66 patients for the identification cohort and 43 for the validation cohort) were analyzed for the expression of CD3, CD4, CD8, CD137, and PD1 molecules before the beginning of anti-PD1 therapy. Twenty healthy donors were used as control. The soluble form of CD137 (sCD137) was also analyzed. The CD137+ T cell subsets and the sCD137 were correlated with the clinicopathologic characteristics. The distribution of CD137+ T cells was also examined in different tumor settings.

RESULTS

The percentage of CD137+ T cells was higher in healthy donors and in those patients with a better clinical status (performance status = 0-1, n°metastasis≤2) and these high levels were ascribed to the CD8+CD137+ T cell population. The high frequency of CD137+ and CD8+CD137+ T cells resulted as a prognostic factor of overall survival (OS) and progression-free survival (PFS), respectively, and were confirmed in the validation cohort. High levels of CD3+CD137+PD1+ lymphocytes were associated with a low number of metastasis and longer survival. Instead, the high concentration of the immunosuppressive sCD137 in the serum is associated with a lower PFS and OS. In tumor bed, patients with a complete response showed a high percentage of CD137+ and CD8+ T cells.

CONCLUSIONS

We propose the CD137+ T subset as an immune biomarker to define the wellness status of the immune system for successful anticancer immunotherapy.

CD137 agonist potentiates the abscopal efficacy of nanoparticle-based photothermal therapy for melanoma

Despite the promise of immunotherapy such as the immune checkpoint inhibitors (ICIs) anti-PD-1 and anti-CTLA-4 for advanced melanoma, only 26%-52% of patients respond, and many experience grade III/IV immune-related adverse events. Motivated by the need for an effective therapy for patients non-responsive to clinically approved ICIs, we have developed a novel nanoimmunotherapy that combines locally administered Prussian blue nanoparticle-based photothermal therapy (PBNP-PTT) with systemically administered agonistic anti-CD137 monoclonal antibody therapy (aCD137). PBNP-PTT was administered at various thermal doses to melanoma cells in vitro, and was combined with aCD137 in vivo to test treatment effects on melanoma tumor progression, animal survival, immunological protection against tumor rechallenge, and hepatotoxicity. When administered at a melanoma-specific thermal dose, PBNP-PTT elicits immunogenic cell death (ICD) in melanoma cells and upregulates markers associated with antigen presentation and immune cell co-stimulation in vitro. Consequently, PBNP-PTT eliminates primary melanoma tumors in vivo, yielding long-term tumor-free survival. However, the antitumor immune effects generated by PBNP-PTT cannot eliminate secondary tumors, despite significantly slowing their growth. The addition of aCD137 enables significant abscopal efficacy and improvement of survival, functioning through activated dendritic cells and tumor-infiltrating CD8⁺ T cells, and generates CD4⁺ and CD8⁺ T cell memory that manifests in the rejection of tumor rechallenge, with no long-term hepatotoxicity. This study describes for the first time a novel and effective nanoimmunotherapy combination of PBNP-PTT with aCD137 mAb therapy for melanoma.

Boosting antitumor response with PSMA-targeted immunomodulatory VLPs, harboring costimulatory TNFSF ligands and GM-CSF cytokine

Therapeutic strategies based on immunomodulation have improved cancer therapy. Most approaches target co-stimulatory pathways or the inhibition of immunosuppressive mechanisms, to enhance immune response and overcome the immune tolerance of tumors. Here, we propose a novel platform to deliver targeted immunomodulatory signaling, enhancing antitumor response. The platform is based on virus-like particles derived from lentiviral capsids. These particles may be engineered to harbor multifunctional ligands on the surface that drive tropism to the tumor site and deliver immunomodulatory signaling, boosting the antitumor response. We generated virus-like particles harboring a PSMA-ligand, TNFSF co-stimulatory ligands 4-1BBL or OX40L, and a membrane-anchored GM-CSF cytokine. The virus-like particles are driven to PSMA-expressing tumors and deliver immunomodulatory signaling from the TNFSF surface ligands and the anchored GM-CSF, inducing T cell proliferation, inhibition of regulatory T cells, and potentiating elimination of tumor cells. The PSMA-targeted particles harboring immunomodulators enhanced antitumor activity in immunocompetent challenged mice and may be explored as a potential tool for cancer immunotherapy.

Soluble CD137 is a novel serum marker of liver cirrhosis in patients with hepatitis C and alcohol-associated disease etiology

Defective T-cell functions play a role in the persistence of HCV infection. Activated T cells express CD137, which costimulates antivirus T-cell responses, and this activity is antagonized by soluble CD137 (sCD137). Here, we show that in sera of 81 patients with chronic HCV, sCD137 levels did not correlate with measures of viral infection, and did not decline after virus eradication using direct-acting antivirals. Thus, serum sCD137 was similar in patients infected with HCV and in uninfected controls. Of note, in HCV patients with liver cirrhosis and patients with mostly alcohol-associated liver cirrhosis, sCD137 was increased. A negative association of sCD137 and albumin existed in both cohorts. sCD137 concentrations were similar in hepatic and portal vein blood excluding the liver as the origin of higher levels. Recombinant sCD137 reduced Th1 and Th2 but not Th17 cell polarization in vitro, and accordingly lowered IFN-γ, TNF, and IL-13 in cell media. Serum sCD137 is associated with inflammatory states, and positively correlated with serum TNF in cirrhotic HCV patients following virus eradication. Our study argues against a role of sCD137 in HCV infection and suggests a function of sCD137 in liver cirrhosis, which yet has to be defined.

Directing T-Cell Immune Responses for Cancer Vaccination and Immunotherapy

Cancer vaccination and immunotherapy revolutionised the treatment of cancer, a result of decades of research into the immune system in health and disease. However, despite recent breakthroughs in treating otherwise terminal cancer, only a minority of patients respond to cancer immunotherapy and some cancers are largely refractive to immunotherapy treatment. This is due to numerous issues intrinsic to the tumour, its microenvironment, or the immune system. CD4+ and CD8+ αβ T-cells emerged as the primary effector cells of the anti-tumour immune response but their function in cancer patients is often compromised. This review details the mechanisms by which T-cell responses are hindered in the setting of cancer and refractive to immunotherapy, and details many of the approaches under investigation to direct T-cell function and improve the efficacy of cancer vaccination and immunotherapy.

Anti-tumor effects of RTX-240: an engineered red blood cell expressing 4-1BB ligand and interleukin-15

Recombinant agonists that activate co-stimulatory and cytokine receptors have shown limited clinical anticancer utility, potentially due to narrow therapeutic windows, the need for coordinated activation of co-stimulatory and cytokine pathways and the failure of agonistic antibodies to recapitulate signaling by endogenous ligands. RTX-240 is a genetically engineered red blood cell expressing 4-1BBL and IL-15/IL-15Rα fusion (IL-15TP). RTX-240 is designed to potently and simultaneously stimulate the 4-1BB and IL-15 pathways, thereby activating and expanding T cells and NK cells, while potentially offering an improved safety profile through restricted biodistribution. We assessed the ability of RTX-240 to expand and activate T cells and NK cells and evaluated the in vivo efficacy, pharmacodynamics and tolerability using murine models. Treatment of PBMCs with RTX-240 induced T cell and NK cell activation and proliferation. In vivo studies using mRBC-240, a mouse surrogate for RTX-240, revealed biodistribution predominantly to the red pulp of the spleen, leading to CD8 + T cell and NK cell expansion. mRBC-240 was efficacious in a B16-F10 melanoma model and led to increased NK cell infiltration into the lungs. mRBC-240 significantly inhibited CT26 tumor growth, in association with an increase in tumor-infiltrating proliferating and cytotoxic CD8 + T cells. mRBC-240 was tolerated and showed no evidence of hepatic injury at the highest feasible dose, compared with a 4-1BB agonistic antibody. RTX-240 promotes T cell and NK cell activity in preclinical models and shows efficacy and an improved safety profile. Based on these data, RTX-240 is now being evaluated in a clinical trial.

Selective SIRPα blockade reverses tumor T cell exclusion and overcomes cancer immunotherapy resistance

T cell exclusion causes resistance to cancer immunotherapies via immune checkpoint blockade (ICB). Myeloid cells contribute to resistance by expressing signal regulatory protein-α (SIRPα), an inhibitory membrane receptor that interacts with ubiquitous receptor CD47 to control macrophage phagocytosis in the tumor microenvironment. Although CD47/SIRPα-targeting drugs have been assessed in preclinical models, the therapeutic benefit of selectively blocking SIRPα, and not SIRPγ/CD47, in humans remains unknown. We report a potent synergy between selective SIRPα blockade and ICB in increasing memory T cell responses and reverting exclusion in syngeneic and orthotopic tumor models. Selective SIRPα blockade stimulated tumor nest T cell recruitment by restoring murine and human macrophage chemokine secretion and increased anti-tumor T cell responses by promoting tumor-antigen crosspresentation by dendritic cells. However, nonselective SIRPα/SIRPγ blockade targeting CD47 impaired human T cell activation, proliferation, and endothelial transmigration. Selective SIRPα inhibition opens an attractive avenue to overcoming ICB resistance in patients with elevated myeloid cell infiltration in solid tumors.

CD137+ T-Cells: Protagonists of the Immunotherapy Revolution

Simple Summary

The CD137 receptor is expressed by activated antigen-specific T-cells. CD137⁺ T-cells were identified inside TILs and PBMCs of different tumor types and have proven to be the naturally occurring antitumor effector cells, capable of expressing a wide variability in terms of TCR specificity against both shared and neoantigenic tumor-derived peptides. The aim of this review is thus summarizing and highlighting their role as drivers of patients’ immune responses in anticancer therapies as well as their potential role in future and current strategies of immunotherapy.

Abstract

The CD137 receptor (4-1BB, TNF RSF9) is an activation induced molecule expressed by antigen-specific T-cells. The engagement with its ligand, CD137L, is capable of increasing T-cell survival, proliferation, and cytokine production. This allowed to identify the CD137⁺ T-cells as the real tumor-specific activated T-cell population. In fact, these cells express various TCRs that are specific for a wide range of tumor-derived peptides, both shared and neoantigenic ones. Moreover, their prevalence in sites close to the tumor and their unicity in killing cancer cells both in vitro and in vivo, raised particular interest in studying their potential role in different strategies of immunotherapy. They indeed showed to be a reliable marker able to predict patient’s outcome to immune-based therapies as well as monitor their response. In addition, the possibility of isolating and expanding this population, turned promising in order to generate effector antitumor T-cells in the context of adoptive T-cell therapies. CD137-targeting monoclonal antibodies have already shown their antitumor efficacy in cancer patients and a number of clinical trials are thus ongoing to test their possible introduction in different combination approaches of immunotherapy. Finally, the intracellular domain of the CD137 receptor was introduced in the anti-CD19 CAR-T cells that were approved by FDA for the treatment of pediatric B-cell leukemia and refractory B-cell lymphoma.

T-cell agonists in cancer immunotherapy

Cancer cells can evade immune surveillance in the body. However, immune checkpoint inhibitors can interrupt this evasion and enhance the antitumor activity of T cells. Other mechanisms for promoting antitumor T-cell function are the targeting of costimulatory molecules expressed on the surface of T cells, such as 4-1BB, OX40, inducible T-cell costimulator and glucocorticoid-induced tumor necrosis factor receptor. In addition, CD40 targets the modulation of the activation of antigen-presenting cells, which ultimately leads to T-cell activation. Agonists of these costimulatory molecules have demonstrated promising results in preclinical and early-phase trials and are now being tested in ongoing clinical trials. In addition, researchers are conducting trials of combinations of such immune modulators with checkpoint blockade, radiotherapy and cytotoxic chemotherapeutic drugs in patients with advanced tumors. This review gives a comprehensive picture of the current knowledge of T-cell agonists based on their use in recent and ongoing clinical trials.

Targeting the 4-1BB costimulatory molecule through single chain antibodies promotes the human T-cell response

Background

Adoptive T-cell therapy (ACT) using autologous tumor-reactive T lymphocytes has considerable potential for cancer immunotherapy. In ACT, T cells are isolated from cancer patients and then stimulated and expanded in vitro by cytokines and costimulatory molecules. 4-1BB is an important costimulatory protein belonging to the TNF receptor superfamily. It is involved in T-cell survival, proliferation and activation. Agonistic anti-4-1BB monoclonal antibodies have been introduced as appropriate tools for ACT.

Methods

Here, various single-chain fragment variable (scFv) antibodies were used to activate T cells isolated from peripheral blood via immune magnetic isolation. The T cells were stimulated with IL-2 and anti-CD-3 mAb and then treated with agonistic anti-4-1BB scFvs. The results showed the remarkable effects of anti-41BB scFvs on the functional properties of T cells, including their activation, proliferation and cytokine production. The flow cytometry analysis revealed a considerable increase in the expression of the T-cell activation marker CD69. Moreover, T-cell proliferation was evidenced in treated cells by CFSE labeling compared to the control groups.

Result

Anti-4-1BB scFvs significantly increased IFN-γ and IL-2 mRNA and protein expression in T cells, but exhibited no stimulatory effect on IL-4 expression. These findings show that anti-4-1BB scFvs could evoke a Type I immune response.

Conclusions

Our results demonstrate that targeting the 4-1BB molecule using agonistic scFvs could be an effective strategy for T-cell stimulation as part of an ACT approach to cancer treatment.

Expression of costimulatory and inhibitory receptors in FoxP3+ regulatory T cells within the tumor microenvironment: Implications for combination immunotherapy approaches

The unprecedented success of immune checkpoint inhibitors has given rise to a rapidly growing number of immuno-oncology agents undergoing preclinical and clinical development and an exponential increase in possible combinations. Defining a clear rationale for combinations by identifying synergies between immunomodulatory pathways has therefore become a high priority. Immunosuppressive regulatory T cells (Tregs) within the tumor microenvironment (TME) represent a major roadblock to endogenous and therapeutic tumor immunity. However, Tregs are also essential for the maintenance of immunological self-tolerance, and share many molecular pathways with conventional T cells including cytotoxic T cells, the primary mediators of tumor immunity. Hence the inability to specifically target and neutralize Tregs within the TME of cancer patients without globally compromising self-tolerance poses a significant challenge. Here we review recent advances in the characterization of tumor-infiltrating Tregs with a focus on costimulatory and inhibitory receptors. We discuss receptor expression patterns, their functional role in Treg biology and mechanistic insights gained from targeting these receptors in preclinical models to evaluate their potential as clinical targets. We further outline a framework of parameters that could be used to refine the assessment of Tregs in cancer patients and increase their value as predictive biomarkers. Finally, we propose modalities to integrate our increasing knowledge on Treg phenotype and function for the rational design of checkpoint inhibitor-based combination therapies. Such combinations have great potential for synergy, as they could concomitantly enhance cytotoxic T cells and inhibit Tregs within the TME, thereby increasing the efficacy of current cancer 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.

Adoptive Cell Transfer: Is it a Promising Immunotherapy for Colorectal Cancer?

The last decade has witnessed significant advances in the adoptive cell transfer (ACT) technique, which has been appreciated as one of the most promising treatments for patients with cancer. Utilization of ACT can enhance the function of the immune system or improve the specificity and persistence of transferred cells. Various immune cells including T lymphocytes, natural killer cells, dendritic cells, and even stem cells can be used in the ACT despite their different functional mechanisms. Colorectal cancer (CRC) is among the most common malignancies and causes millions of deaths worldwide every year. In this review, we discuss the status and perspective of the ACT in the treatment of CRC.

Overcoming Tumor-Induced Immune Suppression: From Relieving Inhibition to Providing Costimulation with T Cell Agonists

Recent advancements in T-cell biology and antibody engineering have opened doors to significant improvements in cancer immunotherapy. Initial success with monoclonal antibodies targeting key receptors that inhibit T-cell function such as cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death-ligand 1 (PD-1) have demonstrated the potency of this new class of therapy, highlighted by long-term complete responses for metastatic cancers once thought incurable. However, only a subset of patients responds to checkpoint blockade because of a multitude of factors, including an immunosuppressive tumor microenvironment and the mutational burden of the cancer. Novel antibodies, as well as ligand-immunoglobulin fusion proteins that target costimulatory immune receptors, are being developed and tested in clinical trials to further enhance the anti-tumor immune response. Many of these costimulatory receptors are in the tumor necrosis factor receptor superfamily (TNFRSF) and are expressed on multiple immune cell types, including inhibitory cells. While TNFRSFs signal through common pathways, the outcome of targeting different receptors depends on the functional status of the cell types expressing the relevant receptors. In this review, we discuss the current state of targeted costimulatory immunotherapy.

Mouse models of hepatocellular carcinoma: an overview and highlights for immunotherapy research

Mouse models are the basis of preclinical and translational research in hepatocellular carcinoma (HCC). Multiple methods exist to induce tumour formation in mice, including genetically engineered mouse models, chemotoxic agents, intrahepatic or intrasplenic injection of tumour cells and xenograft approaches. Additionally, as HCC generally develops in the context of diseased liver, methods exist to induce liver disease in mice to mimic viral hepatitis, fatty liver disease, fibrosis, alcohol-induced liver disease and cholestasis. Similar to HCC in humans, response to therapy in mouse models is monitored with imaging modalities such as CT or MRI, as well as additional techniques involving bioluminescence. As immunotherapy is increasingly applied to HCC, mouse models for these approaches are required for preclinical data. In studying cancer immunotherapy, it is important to consider aspects of antitumour immune responses and to produce a model that mimics the complexity of the immune system. This Review provides an overview of the different mouse models of HCC, presenting techniques to prepare an HCC mouse model and discussing different approaches to help researchers choose an appropriate model for a specific hypothesis. Specific aspects of immunotherapy research in HCC and the applied mouse models in this field are also highlighted.

Therapeutic vaccination with 4-1BB co-stimulation eradicates mouse acute myeloid leukemia

Immunomodulatory therapies can effectively control haematological malignancies. Previously we reported the effectiveness of combination immunotherapies that centre on 4-1BB-targeted co-stimulation of CD8 + T cells, particularly when simultaneously harnessing the immune adjuvant properties of Natural Killer T (NKT) cells. The objective of this study was to assess the effectiveness of agonistic anti-4-1BB antibody-based combination therapy against two aggressive forms of acute myeloid leukemia (AML). Anti-4-1BB treatment alone resulted in transient suppression of established AML-ETO9a tumor growth in 50% of mice, however the majority of these mice subsequently succumbed to disease. Combining alpha-galactosylceramide (α-GalCer)-loaded tumor cell vaccination with anti-4-1BB antibody treatment increased the proportion of responding mice to 100%, and protection led to long-term, tumor-free survival, demonstrating complete eradication of AML. This finding was extended to established mixed lymphocytic leukemia (MLL)-AF9 tumors, whereby vaccine plus anti-4-1BB combination similarly resulted in 100% protection. The addition of anti-PD-1 to anti-4-1BB treatment, although improving survival outcomes compared to anti-4-1BB alone, was not as effective as NKT cell vaccination. The effectiveness of 4-1BB combination therapies was dependent on IFN-γ signaling within host cells, but not tumors. Vaccine plus anti-4-1BB therapy elicited potent generation of functional effector and memory CD8 + T cells in all tumor-associated organs. Therapy induced KLRG1+ effector CD8 T cells were the most effective at controlling disease. We show that combining NKT cell-targeting vaccination with anti-4-1BB provides excellent therapeutic responses against AML and MLL in mice, and these results will guide ongoing efforts in finding immunotherapeutic solutions against acute myeloid leukemias.

The promise and challenges of immune agonist antibody development in cancer

Immune cell functions are regulated by co-inhibitory and co-stimulatory receptors. The first two generations of cancer immunotherapy agents consist primarily of antagonist antibodies that block negative immune checkpoints, such as programmed cell death protein 1 (PD1) and cytotoxic T lymphocyte protein 4 (CTLA4). Looking ahead, there is substantial promise in targeting co-stimulatory receptors with agonist antibodies, and a growing number of these agents are making their way through various stages of development. This Review discusses the key considerations and potential pitfalls of immune agonist antibody design and development, their differentiating features from antagonist antibodies and the landscape of agonist antibodies in clinical development for cancer treatment.

Hepatic irradiation persistently eliminates liver resident NK cells

Hepatic irradiation for the treatment of hepatobiliary malignancies often indirectly damages liver tissue and promotes the development of liver fibrosis. However, little is known concerning the effects of hepatic irradiation on the liver immune system, including natural killer (NK) cells. The aim of this study was therefore to investigate how hepatic irradiation influences the functions and characteristics of liver resident NK cells. An established murine hepatic irradiation model was used to examine the specific effects of hepatic irradiation on immune cell populations and metastasis. This analysis demonstrated that hepatic irradiation decreased the number of liver resident NK cells (DX5^–TRAIL⁺), but did not affect the total NK number or proportions of NK cells in the liver or spleen. This effect was correlated with the hepatic irradiation dose. Surprisingly, the liver resident NK population had not recovered by two months after hepatic irradiation. We also found that hepatic irradiation limited the cytotoxic effects of liver-derived lymphocytes against a mouse hepatoma cell line and promoted hepatic metastases in an in vivo model, although adoptive transfer of activated NK cells could alleviate metastatic growth. Finally, we demonstrated that hepatic irradiation disrupted the development of liver-resident NK cells, even after the adoptive transfer of precursor cells from the bone marrow, liver, and spleen, suggesting that irradiation had altered the developmental environment of the liver. In summary, our data demonstrated that hepatic irradiation abolished the DX5^–TRAIL⁺ liver-resident NK cell population and dampened antitumor activities in the liver for at least two months. Additionally, hepatic irradiation prevented differentiation of precursor cells into liver-resident NK cells.

Immune checkpoint blockade in advanced hepatocellular carcinoma: an update and critical review of ongoing clinical trials

Systemic treatments for advanced hepatocellular carcinoma (HCC) are evolving rapidly and several multi-targeted tyrosine kinase inhibitors have demonstrated a survival advantage over best supportive care. Despite these treatment advances, the majority of HCC patients will progress on tyrosine kinase inhibitor therapy. Preclinical data indicate that interference with immune checkpoint molecules results in HCC growth suppression. Several clinical trials applying monoclonal antibodies to immune checkpoint molecules have demonstrated durable antitumor activity in advanced HCC patients. As such, pivotal clinical trials are now in progress to assess if these agents will alter the natural history of the disease and further extend the overall survival of advanced HCC patients. This manuscript will review the current status of immune checkpoint blockade in patients with advanced HCC.

Immunotherapy for hepatocellular carcinoma patients: is it ready for prime time?

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and the second most common cause of cancer death worldwide. Current treatment options for patients with intermediate and advanced HCC are limited, and there is an unmet need for novel therapeutic approaches. HCC is an attractive target for immunomodulation therapy, since it arises in an inflammatory milieu due to hepatitis B and C infections and cirrhosis. However, a major barrier to the development and success of immunotherapy in patients with HCC is the liver's inherent immunosuppressive function. Recent advances in the field of cancer immunology allowed further characterization of immune cell subsets and function, and created new opportunities for therapeutic modulation of the immune system. In this review, we present the different immune cell subsets involved in potential immune modulation of HCC, discuss their function and clinical relevance, review the variety of immune therapeutic agents currently under investigation in clinical trials, and outline future research directions.

Exploring Synergy in Combinations of Tumor-Derived Vaccines That Harbor 4-1BBL, OX40L, and GM-CSF

Recent studies have demonstrated that combination of modulatory immune strategies may potentiate tumor cell elimination. Most strategies rely on the use of monoclonal antibodies that can block cell surface receptors to overcome tumor-induced immunosuppression or acting as costimulatory ligands to boost activation of T cells. In this study, we evaluate the use of combinations of genetically modified tumor-derived cell lines that harbor the costimulatory T cell ligands 4-1BB ligand, OX40L, and the cytokine GM-CSF. The aim of these treatments is to boost the activation of T cells and the elimination of cancer cells. These tumor-derived cells are able to activate or reinforce T cell activation, thereby generating a potent and specific antitumor response. We developed a high-content in vitro imaging assay that allowed us to investigate synergies between different tumor-derived cells expressing modulatory immune molecules, as well as the influence on effector T cells to achieve tumor cell death. These results were then compared to the results of in vivo experiments in which we challenged immunocompetent animals using the B16F10 syngeneic model of melanoma in C57BL6 mice. Our results suggest that there is a substantial therapeutic benefit to using combinations of syngeneic tumor vaccines that express immune modulators. In addition, we observed that combinations of tumor-derived cells that expressed costimulatory ligands and GM-CSF induced a long-term protective effect by preventing cancer development in both cured and rechallenged animals.

Metabolism-associated danger signal-induced immune response and reverse immune checkpoint-activated CD40+ monocyte differentiation

Adaptive immunity is critical for disease progression and modulates T cell (TC) and antigen-presenting cell (APC) functions. Three signals were initially proposed for adaptive immune activation: signal 1 antigen recognition, signal 2 co-stimulation or co-inhibition, and signal 3 cytokine stimulation. In this article, we propose to term signal 2 as an immune checkpoint, which describes interactions of paired molecules leading to stimulation (stimulatory immune checkpoint) or inhibition (inhibitory immune checkpoint) of an immune response. We classify immune checkpoint into two categories: one-way immune checkpoint for forward signaling towards TC only, and two-way immune checkpoint for both forward and reverse signaling towards TC and APC, respectively. Recently, we and others provided evidence suggesting that metabolic risk factors (RF) activate innate and adaptive immunity, involving the induction of immune checkpoint molecules. We summarize these findings and suggest a novel theory, metabolism-associated danger signal (MADS) recognition, by which metabolic RF activate innate and adaptive immunity. We emphasize that MADS activates the reverse immune checkpoint which leads to APC inflammation in innate and adaptive immunity. Our recent evidence is shown that metabolic RF, such as uremic toxin or hyperhomocysteinemia, induced immune checkpoint molecule CD40 expression in monocytes (MC) and elevated serum soluble CD40 ligand (sCD40L) resulting in CD40⁺ MC differentiation. We propose that CD40⁺ MC is a novel pro-inflammatory MC subset and a reliable biomarker for chronic kidney disease severity. We summarize that CD40:CD40L immune checkpoint can induce TC and APC activation via forward stimulatory, reverse stimulatory, and TC contact-independent immune checkpoints. Finally, we modeled metabolic RF-induced two-way stimulatory immune checkpoint amplification and discussed potential signaling pathways including AP-1, NF-κB, NFAT, STAT, and DNA methylation and their contribution to systemic and tissue inflammation.

TNFSF9 exerts an inhibitory effect on hepatocellular carcinoma

OBJECTIVE

Tumor necrosis factor superfamily member 9 (TNFSF9), also known as 4-1BBL and CD137L, has been implicated in cancer immunotherapy due to its function as a T-cell co-stimulator. We aimed to investigate the role of TNFSF9 in the cancer pathogenesis in hepatocellular carcinoma (HCC).

METHODS

TNFSF9 expression was examined by immunohistochemistry in 106 pairs of HCC and adjacent non-tumorous tissues, and by quantitative polymerase chain reaction and Western blot in HCC cell lines. The impact of TNFSF9 on the proliferation, migration and invasion of HCC cells was determined using the 3-(4,5-diethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) and transwell assays in vitro. We also assessed the influence of TNFSF9 on the growth and metastasis of HCC tumors in an orthotopic mouse model of human HCC.

RESULTS

TNFSF9 expression was downregulated in approximately 70% of HCC tissues. A decreased expression of TNFSF9 was also consistently observed in all the four HCC cell lines. Either the overexpression of TNFSF9 or treatment with recombinant TNFSF9 protein could significantly inhibit the proliferation, migration and invasion of Huh7 and SMMC-7721 HCC cells in vitro. The inhibitory effect of TNFSF9 on HCC was further confirmed in vivo. Mice orthotopically transplanted with TNFSF9-overexpressing Huh7 cells developed significantly smaller tumors with less intrahepatic metastasis and distant metastasis compared with the control group.

CONCLUSIONS

TNFSF9 may be a tumor suppressor in HCC. Based on its immune stimulatory aspect and the tumor inhibition property, TNFSF9 may be a promising therapeutic target for HCC.

Alloantigen gene transfer to hepatocytes promotes tolerance to pancreatic islet graft by inducing CD8+ regulatory T cells

BACKGROUND & AIMS

Induction of donor-specific immune tolerance is a good alternative to chronic life-long immunosuppression for transplant patients. Donor major histocompatibility complex (MHC) molecules represent the main targets of the allogeneic immune response of transplant recipients. Liver targeted gene transfer with viral vectors induces tolerance toward the encoded antigen. The aim of this work was to determine whether alloantigen gene transfer to hepatocytes induces tolerance and promotes graft acceptance.

METHODS

C57BL/6 (H-2b) mice were treated with adeno-associated viral (AAV) vector targeting the expression of the MHC class I molecule H-2K^d to hepatocytes, before transplantation with fully allogeneic pancreatic islet from BALB/c mice (H-2d).

RESULTS

AAV H-2K^d treated mice were tolerant to the alloantigen, as demonstrated by its long-term expression by the hepatocytes, even after a highly immunogenic challenge with an adenoviral vector. After chemical induction of diabetes, the AAV treated mice had significantly delayed rejection of fully allogeneic pancreatic islet grafts, with more than 40% of recipients tolerant (>100days). AAV-mediated expression of H-2K^d in the liver induced the local expansion of CD8⁺ T lymphocytes with allo-specific suppressive properties. The adoptive transfer of these liver-generated CD8⁺ Tregs into naive diabetic mice promoted the long-term survival of allogeneic pancreatic islet grafts.

CONCLUSION

AAV-mediated long-term expression of a single MHC class I molecule in the liver induces the generation of a subset of allo-specific CD8⁺ Treg cells, which promote tolerance toward fully allogeneic graft. Liver gene transfer represents a promising strategy for in vivo induction of donor-specific tolerance.

LAY SUMMARY

The liver has a special immune system, biased toward tolerance. In this study, we investigated the possibility of harnessing this property of the liver to induce tolerance to an allogeneic transplantation. We demonstrate for the first time that the in vivo gene transfer of an allogeneic antigen with an adeno-associated viral vector to mouse hepatocytes induces the expansion of a population of CD8⁺ regulatory T lymphocytes. These Tregs are then instrumental in preventing the rejection of allogeneic pancreatic islets transplanted in these animals. Allogeneic transplantation is the main treatment for the end-stage diseases of a number of organs. Life-long immunosuppressive treatments are still required to limit graft rejection, and these treatments exhibit serious side effects. Our present findings open a new avenue for promoting allo-specific tolerance via in vivo induction of CD8⁺ Treg expansion.

A Multifunctional Role for Adjuvant Anti-4-1BB Therapy in Augmenting Antitumor Response by Chimeric Antigen Receptor T Cells

Adoptive immunotherapy utilizing chimeric antigen receptor (CAR) T cells has demonstrated high success rates in hematologic cancers, but results against solid malignancies have been limited to date, due in part to the immunosuppressive tumor microenvironment. Activation of the 4-1BB (CD137) pathway using an agonistic α-4-1BB antibody is known to provide strong costimulatory signals for augmenting and diversifying T-cell responses. We therefore hypothesized that a combination of α-4-1BB and CAR T-cell therapy would result in improved antitumor responses. Using a human-Her2 self-antigen mouse model, we report here that α-4-1BB significantly enhanced CAR T-cell efficacy directed against the Her2 antigen in two different established solid tumor settings. Treatment also increased the expression of IFNγ and the proliferation marker Ki67 in tumor-infiltrating CAR T cells when combined with α-4-1BB. Strikingly, α-4-1BB significantly reduced host immunosuppressive cells at the tumor site, including regulatory T cells and myeloid-derived suppressor cells, correlating with an increased therapeutic response. We conclude that α-4-1BB has a multifunctional role for enhancing CAR T-cell responses and that this combination therapy has high translational potential, given current phase I/II clinical trials with α-4-1BB against various types of cancer. Cancer Res; 77(6); 1296-309. ©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.

Protective effects of agonistic anti-4-1BB antibody on the development of imiquimod-induced psoriasis-like dermatitis in mice

Agonistic anti-4-1BB antibodies (Abs) play a central role in immunomodulatory conditions that control the pathogenesis of immune-mediated autoimmune and allergic diseases. However, the effects of agonistic anti-4-1BB Abs have not been examined in an experimental mouse model of psoriasis. Therefore, we investigated the protective effects of agonistic anti-4-1BB Abs, using imiquimod (IMQ)-induced psoriasis-like dermatitis in mice, a condition histologically and clinically similar to human psoriasis. We found that administration of agonistic anti-4-1BB Abs (10mg/kg) significantly alleviated the severity of IMQ-induced psoriasis-like skin inflammation in mice, with reduced histologic symptoms, including inflammatory infiltration, parakeratosis, and hyperkeratosis. Subsequent analyses revealed that the production of Th17 cytokines (IL-17A and IL-23) in the serum and skin of IMQ-induced mice was significantly inhibited by agonistic anti-4-1BB Abs (10mg/kg), although Th1 cytokines (TNF-α and IFN-γ) were not. Moreover, administration of agonistic anti-4-1BB Abs (10mg/kg) induced a relative increase of CD4(+)FoxP3(+) regulatory T (Treg) cells in the spleen and draining lymph node (DLN). Taken together, our data provide evidence that agonistic anti-4-1BB Abs possesses immunosuppressive properties in IMQ-induced psoriasis-like skin inflammation, providing insight into the immunomodulatory effect of agonistic anti-4-1BB Abs for psoriasis immunotherapy.

Mouse models of liver cancer: Progress and recommendations

To clarify the pathogenesis of hepatocellular carcinoma (HCC) and investigate the effects of potential therapies, a number of mouse models have been developed. Subcutaneous xenograft models are widely used in the past decades. Yet, with the advent of in vivo imaging technology, investigators are more and more concerned with the orthotopic models nowadays. Genetically engineered mouse models (GEM) have greatly facilitated studies of gene function in HCC development. Recently, GEM of miR-122 and miR-221 provided new approaches for better understanding of the in vivo functions of microRNA in hepatocarcinogenesis. Chemically induced liver tumors in animals share many of the morphological, histogenic, and biochemical features of human HCC. Yet, the complicated and obscure genomic alternation restricts their applications. In this review, we highlight both the frequently used mouse models and some emerging ones with emphasis on their merits or defects, and give advises for investigators to chose a “best-fit” animal model in HCC research.

Combinatorial approach to cancer immunotherapy: strength in numbers

Immune-checkpoint blockade therapy with antibodies targeting CTLA-4 and PD-1 has revolutionized melanoma treatment by eliciting responses that can be remarkably durable and is now advancing to other malignancies. However, not all patients respond to immune-checkpoint inhibitors. Extensive preclinical evidence suggests that combining immune-checkpoint inhibitors with other anti-cancer treatments can greatly improve the therapeutic benefit. The first clinical success of the combinatorial approach to cancer immunotherapy was demonstrated using a dual-checkpoint blockade with CTLA-4 and PD-1 inhibitors, which resulted in accelerated FDA approval of this therapeutic regimen. In this review, we discuss the combinations of current and emerging immunotherapeutic agents in clinical and preclinical development and summarize the insights into potential mechanisms of synergistic anti-tumor activity gained from animal studies. These promising combinatorial partners for the immune-checkpoint blockade include therapeutics targeting additional inhibitory receptors of T cells, such as TIM-3, LAG-3, TIGIT, and BTLA, and agonists of T cell costimulatory receptors 4-1BB, OX40, and GITR, as well as agents that promote cancer cell recognition by the immune system, such as tumor vaccines, IDO inhibitors, and agonists of the CD40 receptor of APCs. We also review the therapeutic potential of regimens combining the immune-checkpoint blockade with therapeutic interventions that have been shown to enhance immunogenicity of cancer cells, including oncolytic viruses, RT, epigenetic therapy, and senescence-inducing therapy.

Expression of the inhibitory Ly49E receptor is not critically involved in the immune response against cutaneous, pulmonary or liver tumours

Natural killer (NK) lymphocytes are part of the innate immune system and are important in immune protection against tumourigenesis. NK cells display a broad repertoire of activating and inhibitory cell surface receptors that regulate NK cell activity. The Ly49 family of NK receptors is composed of several members that recognize major histocompatibility complex class I (MHC-I) or MHC-I-related molecules. Ly49E is a unique inhibitory member, being triggered by the non-MHC-I-related protein urokinase plasminogen activator (uPA) in contrast to the known MHC-I-triggering of the other inhibitory Ly49 receptors. Ly49E also has an uncommon expression pattern on NK cells, including high expression on liver DX5⁻ NK cells. Furthermore, Ly49E is the only Ly49 member expressed by epidermal γδ T cells. As γδ T cells and/or NK cells have been shown to be involved in the regulation of cutaneous, pulmonary and liver malignancies, and as uPA is involved in tumourigenesis, we investigated the role of the inhibitory Ly49E receptor in the anti-tumour immune response. We demonstrate that, although Ly49E is highly expressed on epidermal γδ T cells and liver NK cells, this receptor does not play a major role in the control of skin tumour formation or in lung and liver tumour development.

Immune checkpoint inhibitors for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer deaths worldwide, and advanced HCC generally caries a poor prognosis. The treatment of advanced disease is limited to sorafenib, which provides only a limited improvement in survival, and novel therapies are, thus, sorely needed. Among emerging alternative approaches, immune checkpoint inhibitors are a particularly promising treatment modality. In this review, we summarize current knowledge of the mechanisms for the two primary targets of immune checkpoint inhibitors and discuss the relevance of these pathways to the immunology of HCC. We also review the state of ongoing and forthcoming trials of immune checkpoint blockade in HCC.

Progress in surgical and nonsurgical approaches for hepatocellular carcinoma treatment

BACKGROUND

Hepatocellular carcinoma (HCC) is a complex and heterogeneous malignancy, frequently occurs in the setting of a chronically diseased organ, with multiple confounding factors making its management challenging. HCC represents one of the leading causes of cancer-related mortality globally with a rising trend of incidence in some of the developed countries, which indicates the need for better surgical and nonsurgical management strategies.

DATA SOURCES

PubMed database was searched for relevant articles in English on the issue of HCC management.

RESULTS

Surgical resection represents a potentially curative option for appropriate candidates with tumors detected at earlier stages and with well-preserved liver function. The long-term outcome of surgery is impaired by a high rate of recurrence. Surgical approaches are being challenged by local ablative therapies such as radiofrequency ablation and microwave ablation in selected patients. Liver transplantation offers potential cure for HCC and also correction of underlying liver disease, and minimizes the risk of recurrence, but is reserved for patients within a set of criteria proposed for a prudent allocation in the shortage of donor organs. Transcatheter locoregional therapies have become the palliative standard allowing local control for intermediate stage patients with noninvasive multinodular or large HCC who are beyond the potentially curative options. The significant survival benefit with the multikinase inhibitor sorafenib for advanced HCC has shifted the direction of research regarding systemic treatment toward molecular therapies targeting the disregulated pathways of hepatocarcinogenesis. Potential benefit is suggested from simultaneous or sequential multimodal therapies, and optimal combinations are being investigated. Despite the striking progress in preclinical studies of HCC immunotherapy and gene therapy, extensive clinical trials are required to achieve successful clinical applications of these innovative approaches.

CONCLUSION

Treatment decisions have become increasingly complex for HCC with the availability of multiple surgical and nonsurgical therapeutic options and require a comprehensive, multidisciplinary approach.

An adenoviral cancer vaccine co-encoding a tumor associated antigen together with secreted 4-1BBL leads to delayed tumor progression

Previous studies have shown promising results when using an agonistic anti-4-1BB antibody treatment against established tumors. While this is promising, this type of treatment can induce severe side effects. Therefore, we decided to incorporate the membrane form of 4-1BB ligand (4-1BBL) in a replicative deficient adenovirus vaccine expressing the invariant chain (Ii) adjuvant fused to a tumor associated antigen (TAA). The Ii adjuvant increases and prolongs TAA specific CD8+ T cells as previously shown and local expression of 4-1BBL was chosen to avoid the toxicity associated with systemic antibody administration. Furthermore, adenovirus encoded 4-1BBL expression has previously been successfully used to enhance responses toward Plasmodium falciparum and Influenza A antigens. We showed that the incorporation of 4-1BBL in the adenovirus vector led to surface expression of 4-1BBL on antigen presenting cells, but it did not enhance T cell responses in mice towards the Ii linked antigen. In tumor-bearing mice, our vaccine was found to decrease the frequency of TAA specific CD8+ T cells, but this difference did not alter the therapeutic efficacy. In order to reconcile our findings with the previous reports of increased anti-cancer efficacy using systemically delivered 4-1BB agonists, we incorporated a secreted version of 4-1BBL (Fc-4-1BBL) in our vaccine and co-expressed it with the Ii linked to TAA. In tumor bearing mice, this vaccine initially delayed tumor growth and slightly increased survival compared to the vaccine expressing the membrane form of 4-1BBL. Accordingly, secreted 4-1BBL co-encoded with the Ii linked antigen may offer a simplification compared to administration of drug and vaccine separately.

Immunotherapy in hepatocellular carcinoma: Primed to make a difference?

Advanced hepatocellular carcinoma (HCC) carries a dismal prognosis and the current treatment is limited to sorafenib, an agent with modest benefit. Preclinical data have indicated that several immunologic mechanisms are at play to promote HCC development and growth while impairing effective antitumor immune surveillance. Several novel approaches geared toward manipulating the immune response to HCC have suggested a therapeutic benefit in early-stage clinical trials, indicating a real potential to augment tumor-specific immunity and improve outcomes in patients with this disease. In the current study, the authors reviewed the barriers to an effective immune response against HCC and contemporary clinical investigations that may be "primed" to alter the natural history of HCC.

Emerging roles of myeloid derived suppressor cells in hepatic inflammation and fibrosis

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of immune cells that are potent suppressors of immune responses. MDSC emerge in various compartments in the body, such as blood, bone marrow or spleen, especially in conditions of cancer, infections or inflammation. MDSC usually express CD11b, CD33, and low levels of human leukocyte antigen-DR in humans or CD11b and Gr1 (Ly6C/G) in mice, and they can be further divided into granulocytic or monocytic MDSC. The liver is an important organ for MDSC induction and accumulation in hepatic as well as extrahepatic diseases. Different hepatic cells, especially hepatic stellate cells, as well as liver-derived soluble factors, including hepatocyte growth factor and acute phase proteins (SAA, KC), can promote the differentiation of MDSC from myeloid cells. Importantly, hepatic myeloid cells like neutrophils, monocytes and macrophages fulfill essential roles in acute and chronic liver diseases. Recent data from patients with liver diseases and animal models linked MDSC to the pathogenesis of hepatic inflammation, fibrosis and hepatocellular carcinoma (HCC). In settings of acute hepatitis, MDSC can limit immunogenic T cell responses and subsequent tissue injury. In patients with chronic hepatitis C, MDSC increase and may favor viral persistence. Animal models of chronic liver injury, however, have not yet conclusively clarified the involvement of MDSC for hepatic fibrosis. In human HCC and mouse models of liver cancer, MDSC are induced in the tumor environment and suppress anti-tumoral immune responses. Thus, the liver is a primary site of MDSC in vivo, and modulating MDSC functionality might represent a promising novel therapeutic target for liver diseases.

Hepatic myeloid-derived suppressor cells in cancer

Myeloid-derived suppressor cells are key components of tumor-induced immune suppression. They are composed of a heterogeneous population of immature myeloid cells that abrogates innate and adaptive immune responses. Myeloid-derived suppressor cells accumulate not only in peripheral blood, secondary lymphoid organs and tumors, but also in the liver in preclinical tumor models and in hepatocellular carcinoma patients. The liver, continuously exposed to food and microbial antigens from the intestine, avoids autoimmune damage through the use of specialized mechanisms of immune tolerance. In the context of cancer, myeloid-derived suppressor cells profit the intrinsic tolerogenic properties of the liver to accumulate and exert various immune-suppressive and tumor-promoting mechanisms which go from inducing immune cell dysfunction to supporting the generation of liver metastases. In this review, we seek to describe the phenotype, function, accumulation and therapeutic targeting of hepatic myeloid-derived suppressor cells both in preclinical settings and in the context of human hepatocellular carcinoma.

4-1BB Agonists: Multi-Potent Potentiators of Tumor Immunity

Immunotherapy is a rapidly expanding field of oncology aimed at targeting, not the tumor itself, but the immune system combating the cancerous lesion. Of the many approaches currently under study to boost anti-tumor immune responses; modulation of immune co-receptors on lymphocytes in the tumor microenvironment has thus far proven to be the most effective. Antibody blockade of the T cell co-inhibitory receptor cytotoxic T lymphocyte antigen-4 (CTLA-4) has become the first FDA approved immune checkpoint blockade; however, tumor infiltrating lymphocytes express a diverse array of additional stimulatory and inhibitory co-receptors, which can be targeted to boost tumor immunity. Among these, the co-stimulatory receptor 4-1BB (CD137/TNFSF9) possesses an unequaled capacity for both activation and pro-inflammatory polarization of anti-tumor lymphocytes. While functional studies of 4-1BB have focused on its prominent role in augmenting cytotoxic CD8 T cells, 4-1BB can also modulate the activity of CD4 T cells, B cells, natural killer cells, monocytes, macrophages, and dendritic cells. 4-1BB’s expression on both T cells and antigen presenting cells, coupled with its capacity to promote survival, expansion, and enhanced effector function of activated T cells, has made it an alluring target for tumor immunotherapy. In contrast to immune checkpoint blocking antibodies, 4-1BB agonists can both potentiate anti-tumor and anti-viral immunity, while at the same time ameliorating autoimmune disease. Despite this, 4-1BB agonists can trigger high grade liver inflammation which has slowed their clinical development. In this review, we discuss how the underlying immunobiology of 4-1BB activation suggests the potential for therapeutically synergistic combination strategies in which immune adverse events can be minimized.

Current concepts of immune based treatments for patients with HCC: from basic science to novel treatment approaches

The recent approval of two immune checkpoint inhibitors for the treatment of malignant melanoma has sparked great interest by physicians and basic scientists searching for novel therapeutics for GI cancer. Chronic inflammation is recognised as a major risk factor for the development of hepatocellular carcinoma (HCC) and makes this type of cancer a potentially ideal target for an immune based treatment approach. Further evidence for a critical role of immune responses in patients with HCC is derived from the fact that immune signatures and profiles predict patients' outcome as well as the fact that tumour-induced spontaneous antitumour immunity can be detected. In addition ablative therapies can lead to changes in the number, phenotype and function of different immune cell subsets, which correlate with patients' survival. Various HCC-specific mouse models have been developed, which improve our understanding of hepatocarcinogenesis and tumour-immune cell interactions, and lead to the development of novel immune based treatment approaches, which are currently being evaluated in preclinical and in early clinical settings. Immune checkpoint blockade along with adoptive immune cell therapy and vaccine approaches are currently being evaluated either alone or in combination with other treatments. Here, we provide an overview for the rationale of immunotherapy in HCC, summarise ongoing studies and provide a perspective for immune based approaches in patients with HCC.