Inhibition of TGF-β1 signaling promotes central memory T cell differentiation

Tertiary lymphoid structures in cancer: immune mechanisms and clinical implications

Cancer is a major cause of death globally, and traditional treatments often have limited efficacy and adverse effects. Immunotherapy has shown promise in various malignancies but is less effective in tumors with low immunogenicity or immunosuppressive microenvironment, especially sarcomas. Tertiary lymphoid structures (TLSs) have been associated with a favorable response to immunotherapy and improved survival in cancer patients. However, the immunological mechanisms and clinical significance of TLS in malignant tumors are not fully understood. In this review, we elucidate the composition, neogenesis, and immune characteristics of TLS in tumors, as well as the inflammatory response in cancer development. An in-depth discussion of the unique immune characteristics of TLSs in lung cancer, breast cancer, melanoma, and soft tissue sarcomas will be presented. Additionally, the therapeutic implications of TLS, including its role as a marker of therapeutic response and prognosis, and strategies to promote TLS formation and maturation will be explored. Overall, we aim to provide a comprehensive understanding of the role of TLS in the tumor immune microenvironment and suggest potential interventions for cancer treatment.

New insights into the stemness of adoptively transferred T cells by γc family cytokines

T cell-based adoptive cell therapy (ACT) has exhibited excellent antitumoral efficacy exemplified by the clinical breakthrough of chimeric antigen receptor therapy (CAR-T) in hematologic malignancies. It relies on the pool of functional T cells to retain the developmental potential to serially kill targeted cells. However, failure in the continuous supply and persistence of functional T cells has been recognized as a critical barrier to sustainable responses. Conferring stemness on infused T cells, yielding stem cell-like memory T cells (TSCM) characterized by constant self-renewal and multilineage differentiation similar to pluripotent stem cells, is indeed necessary and promising for enhancing T cell function and sustaining antitumor immunity. Therefore, it is crucial to identify TSCM cell induction regulators and acquire more TSCM cells as resource cells during production and after infusion to improve antitumoral efficacy. Recently, four common cytokine receptor γ chain (γc) family cytokines, encompassing interleukin-2 (IL-2), IL-7, IL-15, and IL-21, have been widely used in the development of long-lived adoptively transferred TSCM in vitro. However, challenges, including their non-specific toxicities and off-target effects, have led to substantial efforts for the development of engineered versions to unleash their full potential in the induction and maintenance of T cell stemness in ACT. In this review, we summarize the roles of the four γc family cytokines in the orchestration of adoptively transferred T cell stemness, introduce their engineered versions that modulate TSCM cell formation and demonstrate the potential of their various combinations. Video Abstract.

Methionine enkephalin(MENK) upregulated memory T cells in anti-influenza response

Novel prophylactic drugs and vaccination strategies for protection against influenza virus should induce specific effector T-cell immune responses in pulmonary airways and peripheral lymphoid organs. Designing approaches that promote T-cell-mediated responses and memory T-cell differentiation would strengthen host resistance to respiratory infectious diseases. The results of this study showed that pulmonary delivery of MENK via intranasal administration reduced viral titres, upregulated opioid receptor MOR and DOR, increased the proportions of T-cell subsets including CD8+ T cells, CD8+ TEM cells, NP/PA-effector CD8+ TEM cells in bronchoalveolar lavage fluid and lungs, and CD4+/CD8+ TCM cells in lymph nodes to protect mice against influenza viral challenge. Furthermore, we demonstrated that, on the 10th day of infection, the proportions of CD4+ TM and CD8+ TM cells were significantly increased, which meant that a stable TCM and TEM lineage was established in the early stage of influenza infection. Collectively, our data suggested that MENK administered intranasally, similar to the route of natural infection by influenza A virus, could exert antiviral activity through upregulating T-cell-mediated adaptive immune responses against influenza virus.

Improved memory CD8 T cell response to delayed vaccine boost is associated with a distinct molecular signature

Effective secondary response to antigen is a hallmark of immunological memory. However, the extent of memory CD8 T cell response to secondary boost varies at different times after a primary response. Considering the central role of memory CD8 T cells in long-lived protection against viral infections and tumors, a better understanding of the molecular mechanisms underlying the changing responsiveness of these cells to antigenic challenge would be beneficial. We examined here primed CD8 T cell response to boost in a BALB/c mouse model of intramuscular vaccination by priming with HIV-1 gag-encoding Chimpanzee adenovector, and boosting with HIV-1 gag-encoding Modified Vaccinia virus Ankara. We found that boost was more effective at day(d)100 than at d30 post-prime, as evaluated at d45 post-boost by multi-lymphoid organ assessment of gag-specific CD8 T cell frequency, CD62L-expression (as a guide to memory status) and in vivo killing. RNA-sequencing of splenic gag-primed CD8 T cells at d100 revealed a quiescent, but highly responsive signature, that trended toward a central memory (CD62L⁺) phenotype. Interestingly, gag-specific CD8 T cell frequency selectively diminished in the blood at d100, relative to the spleen, lymph nodes and bone marrow. These results open the possibility to modify prime/boost intervals to achieve an improved memory CD8 T cell secondary response.

CTLs Get SMAD When Pathogens Tell Them Where to Go

Vaccines protect against infections by eliciting both Ab and T cell responses. Because the immunity wanes as protective epitopes get modified by accruing mutations, developing strategies for immunization against new variants is a major priority for vaccine development. CTLs eliminate cells that support viral replication and provide protection against new variants by targeting epitopes from internal viral proteins. This form of protection has received limited attention during vaccine development, partly because reliable methods for directing pathogen-specific memory CD8 T cells to vulnerable tissues are currently unavailable. In this review we examine how recent studies expand our knowledge of mechanisms that contribute to the functional diversity of CTLs as they respond to infection. We discuss the role of TGF-β and the SMAD signaling cascade during genetic programming of pathogen-specific CTLs and the pathways that promote formation of a newly identified subset of terminally differentiated memory CD8 T cells that localize in the vasculature.

SMAD4 and TGFβ are architects of inverse genetic programs during fate-determination of antiviral CTLs

Transforming growth factor β (TGFβ) is an important differentiation factor for cytotoxic T lymphocytes (CTLs) and alters the expression levels of several of homing receptors during infection. SMAD4 is part of the canonical signaling network used by members of the transforming growth factor family. For this study, genetically modified mice were used to determine how SMAD4 and TGFβ receptor II (TGFβRII) participate in transcriptional programming of pathogen-specific CTLs. We show that these molecules are essential components of opposing signaling mechanisms, and cooperatively regulate a collection of genes that determine whether specialized populations of pathogen-specific CTLs circulate around the body, or settle in peripheral tissues. TGFβ uses a canonical SMAD-dependent signaling pathway to downregulate Eomesodermin (EOMES), KLRG1, and CD62L, while CD103 is induced. Conversely, in vivo and in vitro data show that EOMES, KLRG1, CX₃CR1, and CD62L are positively regulated via SMAD4, while CD103 and Hobit are downregulated. Intravascular staining also shows that signaling via SMAD4 promotes formation of long-lived terminally differentiated CTLs that localize in the vasculature. Our data show that inflammatory molecules play a key role in lineage determination of pathogen-specific CTLs, and use SMAD-dependent signaling to alter the expression levels of multiple homing receptors and transcription factors with known functions during memory formation.

IL-27 Improves Adoptive CD8+ T Cells Antitumor Activity via Enhancing Cells Survival and Memory T Cells Differentiation

IL-27 is an anti-inflammatory cytokine that triggers enhanced antitumor immunity, particularly cytotoxic T lymphocyte responses. In the present study, we sought to develop IL-27 into a therapeutic adjutant for adoptive T-cell therapy using our well-established models. We have found that IL-27 directly improved the survival status and cytotoxicity of adoptive OT-1 CD8⁺ T cells in vitro and in vivo. Meanwhile, IL-27 treatment programs memory T cells differentiation in CD8⁺ T cells, characterized by up regulation of genes associated with T cell memory differentiation (T-bet, Eomes, Blimp1 and Ly6C). Additionally, we engineered the adoptive OT-1 CD8⁺ T cells to deliver IL-27. In mice, the established tumors treated with OT-1 CD8⁺ T-IL-27 were completely rejected, which demonstrated that IL-27 delivered via tumor antigen-specific T cells enhance adoptive T cells cancer immunity. To our knowledge, this is the first application of CD8⁺ T cells as a vehicle to deliver IL-27 to treat tumors. Thus, these studies demonstrate IL-27 is a feasible approach for enhancing CD8⁺ T cells anti-tumor immunity and can be used as a therapeutic adjutant for T cell adoptive transfer to treat cancer.

Effects of Radiation on the Tumor Microenvironment

A malignant tumor consists of malignant cells as well as a wide array of normal host tissues including stroma, vasculature, and immune infiltrate. The interaction between cancer and these host tissues is critical as these host tissues play a variety of roles in supporting or resisting disease progression. Radiotherapy (RT) has direct effects on malignant cells, but, also, critically important effects on these other components of the tumor microenvironment (TME). Given the growing role of immune checkpoint inhibitors and other immunotherapy strategies, understanding how RT affects the TME, particularly the immune compartment, is essential to advance RT in this new era of cancer therapy. The interactions between RT and the TME are complex, affecting the innate and adaptive arms of the immune system. RT can induce both proinflammatory effects and immune suppressive effects that can either promote or impede antitumor immunity. It is likely that the initial proinflammatory effects of RT eventually lead to rebound immune-suppression as chronic inflammation sets in. The exact kinetics and nature of how RT changes the TME likely depends on timing, dose, fractionation, site irradiated, and tumor type. With increased understanding of the effects of RT on the TME, in the future it is likely that we will be able to personalize RT by varying the dose, site, and timing of intervention to generate the desired response to partner with immunotherapy strategies.

Autologous cervical tumor lysate pulsed dendritic cell stimulation followed by cisplatin treatment abrogates FOXP3+ cells in vitro

Objective

Dendritic cells (DCs) are administered as immunotherapeutic adjuvants after the completion of standard treatment in most settings. However, our Phase I trial indicated that one patient out of four, who received autologous tumor lysate-pulsed dendritic cell (TLDC) also received cisplatin chemotherapy and experienced complete regression of her lung lesion, continuing to be disease free till date. Hence, the objective of our current study is to evaluate the sustenance or augmentation of immune responses when autologous human papillomavirus positive cervical tumor lysate pulsed DC- are combined with cisplatin, using co-culture assays in vitro.

Methods

Before treatment, peripheral blood and punch biopsy samples were collected from 23 cervical cancer patients after obtaining an informed consent. DC functionality was confirmed through phenotypic and functional assays using autologous peripheral blood mononuclear cells as responders. For cisplatin experiments, the drug was added at 150, 200 (clinical dose equivalent), and 400 µM concentrations to DCs alone or DC-T cell co-cultures. Phenotypic assessment and functional characterization of DCs was done using flow cytometry. Cytokine enzyme-linked immunosorbent assay and interferon (IFN)-γ enzyme-linked immune absorbent spot assays were also performed.

Results

The functionality of TLDCs was not compromised upon cisplatin treatment in vitro even at the highest (400 μM) concentration. Even though cisplatin treatment reduced the secretion of IFN-γ and interleukin (IL)-12p40 in co-cultures stimulated with TLDCs, this effect was not significant (p>0.05). A doubling of IFN-γ secretion following cisplatin treatment was observed in at least one of three independent experiments. Additional experiments showed a reduction in both FOXP3+ regulatory T cells and IL-10 levels.

Conclusion

Our results provide evidence that cisplatin treatment may be given after autologous TLDC administration to maintain or improve a productive anti-tumor response in vaccinated patients.

TGF-β signaling in cell fate control and cancer

Members of the transforming growth factor-β (TGF-β) family regulate cell fate decisions during early embryonic development and tissue homeostasis in the adult. Deregulation of TGF-β family signaling contributes to developmental anomalies, fibrotic disorders, tumorigenesis and immune diseases. TGF-β exerts a wide spectrum of cellular functions by activating canonical (SMAD-dependent) or non-canonical (SMAD-independent) pathways in a cell type-specific and context-dependent manner. Here, we focus on recent advances in the understanding of the mechanisms and functions of SMAD and non-SMAD pathways in physiology and pathology.

TGFβ Programs Central Memory Differentiation in Ex Vivo-Stimulated Human T Cells

The adoptive transfer of ex vivo-expanded T cells is a promising approach to treat several malignancies. Several lines of evidence support that the infusion of T cells with early memory features, capable of expanding and persisting after transfer, are associated with better outcomes. We report herein that exposure to exogenous TGFβ during human T-cell stimulation ex vivo leads to the accumulation of early/central memory (Tcm) cells. Exposure to TGFβ suppressed the expression of BLIMP-1, a key orchestrator of effector T-cell differentiation, and led to the upregulation of the memory-associated transcription factor ID3. Accordingly, this was associated with an early memory transcriptional signature in both CD4⁺ and CD8⁺ T-cell subsets. The T cells stimulated in the presence of TGFβ expanded normally, and displayed polyfunctional features and no suppressive activity. The adoptive transfer of ex vivo-stimulated T cells into immunodeficient mice confirmed that TGFβ-conditioned cells had an enhanced capacity to persist and mediate xenogeneic graft-versus-host disease, as predicted by their early T-cell memory phenotype. Chimeric antigen receptor-expressing T cells generated in the presence of exogenous TGFβ were cytotoxic and more effective at controlling tumor growth in immunodeficient animals. This work unveils a new role for TGFβ in memory T-cell differentiation and indicates that TGFβ signaling may be harnessed to program Tcm differentiation in the context of ex vivo T-cell stimulation for adoptive immunotherapy in humans.

Blockade of TGF-β signaling: a potential target for cancer immunotherapy?

Introduction: Malignant tumors often escape surveillance and eventual destruction by the host immune system through a variety of strategies including production of transforming growth factor (TGF)-β. Because of its generally immunosuppressive role, TGF-β has emerged as a promising therapeutic target in cancer immunotherapy. Areas covered: This article looks at specific mechanisms of how TGF-β controls the function of various immune cell subsets in the tumor microenvironment and focusses on T-cells. Various inhibition tools of TGF-β signaling and potential targets of therapeutic intervention are assessed along with the recent progress in combining TGF-β blockade and immune-mediated therapies. To round off the article, a summary of results from clinical trials is provided in which TGF-β blockade has shown therapeutic benefit for patients. Expert opinion: Data from preclinical models have shown that blocking TGF-β signaling can overcome resistance mechanisms and in combination with immune-checkpoint therapies, can yield additive or synergistic anti-tumor responses. The future of immunooncology will therefore be based on combination trials. Since response rates may critically depend on both cancer type and stage, selection of only those patients who can benefit from combinatorial immunotherapy regimens is of utmost importance.

Traditional Chinese medicine as targeted treatment for epithelial-mesenchymal transition-induced cancer progression

The epithelial-mesenchymal transition (EMT) program, which loosens cell-cell adhesion complexes, endows cells with enhanced migratory and invasive properties. Furthermore, this process facilitates both the development of drug resistance and immunosuppression by tumor cells, which preclude the successful treatment of cancer. Recent research has demonstrated that many signaling pathways are involved in EMT progression. In addition, cancer stem cells (CSCs), vasculogenic mimicry (VM) and the tumor-related immune microenvironment all play important roles in tumor formation. However, there are few reports on the relationships between EMT and these factors. In addition, in recent years, traditional Chinese medicine (TCM) has developed a unique system for treating cancer. In this review, we summarize the crucial signaling pathways associated with the EMT process in cancer patients and discuss the interconnections between EMT and other molecular factors (such as CSCs, VM, and the tumor-related immune microenvironment). We attempt to identify common regulators that might be potential therapeutic targets to thereby optimize tumor treatment. In addition, we outline recent research on TCM approaches that target EMT and thereby provide a foundation for further research on the exact mechanisms by which TCMs affect EMT in cancer.

Focal Irradiation and Systemic TGFβ Blockade in Metastatic Breast Cancer

Purpose: This study examined the feasibility, efficacy (abscopal effect), and immune effects of TGFβ blockade during radiotherapy in metastatic breast cancer patients.Experimental Design: Prospective randomized trial comparing two doses of TGFβ blocking antibody fresolimumab. Metastatic breast cancer patients with at least three distinct metastatic sites whose tumor had progressed after at least one line of therapy were randomized to receive 1 or 10 mg/kg of fresolimumab, every 3 weeks for five cycles, with focal radiotherapy to a metastatic site at week 1 (three doses of 7.5 Gy), that could be repeated to a second lesion at week 7. Research bloods were drawn at baseline, week 2, 5, and 15 to isolate PBMCs, plasma, and serum.Results: Twenty-three patients were randomized, median age 57 (range 35-77). Seven grade 3/4 adverse events occurred in 5 of 11 patients in the 1 mg/kg arm and in 2 of 12 patients in the 10 mg/kg arm, respectively. Response was limited to three stable disease. At a median follow up of 12 months, 20 of 23 patients are deceased. Patients receiving the 10 mg/kg had a significantly higher median overall survival than those receiving 1 mg/kg fresolimumab dose [hazard ratio: 2.73 with 95% confidence interval (CI), 1.02-7.30; P = 0.039]. The higher dose correlated with improved peripheral blood mononuclear cell counts and a striking boost in the CD8 central memory pool.Conclusions: TGFβ blockade during radiotherapy was feasible and well tolerated. Patients receiving the higher fresolimumab dose had a favorable systemic immune response and experienced longer median overall survival than the lower dose group. Clin Cancer Res; 24(11); 2493-504. ©2018 AACR.

Bifunctional immune checkpoint-targeted antibody-ligand traps that simultaneously disable TGFβ enhance the efficacy of cancer immunotherapy

A majority of cancers fail to respond to immunotherapy with antibodies targeting immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed death-1 (PD-1)/PD-1 ligand (PD-L1). Cancers frequently express transforming growth factor-β (TGFβ), which drives immune dysfunction in the tumor microenvironment by inducing regulatory T cells (Tregs) and inhibiting CD8⁺ and T_H1 cells. To address this therapeutic challenge, we invent bifunctional antibody-ligand traps (Y-traps) comprising an antibody targeting CTLA-4 or PD-L1 fused to a TGFβ receptor II ectodomain sequence that simultaneously disables autocrine/paracrine TGFβ in the target cell microenvironment (a-CTLA4-TGFβRIIecd and a-PDL1-TGFβRIIecd). a-CTLA4-TGFβRIIecd is more effective in reducing tumor-infiltrating Tregs and inhibiting tumor progression compared with CTLA-4 antibody (Ipilimumab). Likewise, a-PDL1-TGFβRIIecd exhibits superior antitumor efficacy compared with PD-L1 antibodies (Atezolizumab or Avelumab). Our data demonstrate that Y-traps counteract TGFβ-mediated differentiation of Tregs and immune tolerance, thereby providing a potentially more effective immunotherapeutic strategy against cancers that are resistant to current immune checkpoint inhibitors.

Bifunctional immune checkpoint-targeted antibody-ligand traps that simultaneously disable TGFβ enhance the efficacy of cancer immunotherapy

A majority of cancers fail to respond to immunotherapy with antibodies targeting immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed death-1 (PD-1)/PD-1 ligand (PD-L1). Cancers frequently express transforming growth factor-β (TGFβ), which drives immune dysfunction in the tumor microenvironment by inducing regulatory T cells (Tregs) and inhibiting CD8+ and TH1 cells. To address this therapeutic challenge, we invent bifunctional antibody-ligand traps (Y-traps) comprising an antibody targeting CTLA-4 or PD-L1 fused to a TGFβ receptor II ectodomain sequence that simultaneously disables autocrine/paracrine TGFβ in the target cell microenvironment (a-CTLA4-TGFβRIIecd and a-PDL1-TGFβRIIecd). a-CTLA4-TGFβRIIecd is more effective in reducing tumor-infiltrating Tregs and inhibiting tumor progression compared with CTLA-4 antibody (Ipilimumab). Likewise, a-PDL1-TGFβRIIecd exhibits superior antitumor efficacy compared with PD-L1 antibodies (Atezolizumab or Avelumab). Our data demonstrate that Y-traps counteract TGFβ-mediated differentiation of Tregs and immune tolerance, thereby providing a potentially more effective immunotherapeutic strategy against cancers that are resistant to current immune checkpoint inhibitors.

Expansion of tumor-infiltrating lymphocytes and their potential for application as adoptive cell transfer therapy in human breast cancer

Adoptive cell transfer (ACT) of ex vivo expanded tumor-infiltrating lymphocytes (TILs) has been successful in treating a considerable proportion of patients with metastatic melanoma. In addition, some patients with several other solid tumors were recently reported to have benefited clinically from such ACT. However, it remains unclear whether ACT using TILs is broadly applicable in breast cancer, the most common cancer in women. In this study, the utility of TILs as an ACT source in breast cancers was explored by deriving TILs from a large number of breast cancer samples and assessing their biological potentials. We successfully expanded TILs ex vivo under a standard TIL culture condition from over 100 breast cancer samples, including all breast cancer subtypes. We also found that the information about the percentage of TIL and presence of tertiary lymphoid structure in the tumor tissues could be useful for estimating the number of obtainable TILs after ex vivo culture. The ex vivo expanded TILs contained a considerable level of central memory phenotype T cells (about 20%), and a large proportion of TIL samples were reactive to autologous tumor cells in vitro. Furthermore, the in vitro tumor-reactive autologous TILs could also function in vivo in a xenograft mouse model implanted with the primary tumor tissue. Collectively, these results strongly indicate that ACT using ex vivo expanded autologous TILs is a feasible option in treating patients with breast cancer.

New insights into the role of EMT in tumor immune escape

Novel immunotherapy approaches have provided durable remission in a significant number of cancer patients with cancers previously considered rapidly lethal. Nonetheless, the high degree of nonresponders, and in some cases the emergence of resistance in patients who do initially respond, represents a significant challenge in the field of cancer immunotherapy. These issues prompt much more extensive studies to better understand how cancer cells escape immune surveillance and resist immune attacks. Here, we review the current knowledge of how cellular heterogeneity and plasticity could be involved in shaping the tumor microenvironment (TME) and in controlling antitumor immunity. Indeed, recent findings have led to increased interest in the mechanisms by which cancer cells undergoing epithelial‐mesenchymal transition (EMT), or oscillating within the EMT spectrum, might contribute to immune escape through multiple routes. This includes shaping of the TME and decreased susceptibility to immune effector cells. Although much remains to be learned on the mechanisms at play, cancer cell clones with mesenchymal features emerging from the TME seem to be primed to face immune attacks by specialized killer cells of the immune system, the natural killer cells, and the cytotoxic T lymphocytes. Recent studies investigating patient tumors have suggested EMT as a candidate predictive marker to be explored for immunotherapy outcome. Promising data also exist on the potential utility of targeting these cancer cell populations to at least partly overcome such resistance. Research is now underway which may lead to considerable progress in optimization of treatments.

The Lysine Methyltransferase G9a in Immune Cell Differentiation and Function

G9a (KMT1C, EHMT2) is a lysine methyltransferase (KMT) whose primary function is to di-methylate lysine 9 of histone H3 (H3K9me2). G9a-dependent H3K9me2 is associated with gene silencing and acts primarily through the recruitment of H3K9me2-binding proteins that prevent transcriptional activation. Gene repression via G9a-dependent H3K9me2 is critically required in embryonic stem (ES) cells for the development of cellular lineages by repressing expression of pluripotency factors. In the immune system, lymphoid cells such as T cells and innate lymphoid cells (ILCs) can differentiate from a naïve state into one of several effector lineages that require both activating and repressive mechanisms to maintain the correct gene expression program. Furthermore, the long-term immunity to re-infection is mediated by memory T cells, which also require specific gene expression and repression to maintain a quiescent state. In this review, we examine the molecular machinery of G9a-dependent functions, address the role of G9a in lymphoid cell differentiation and function, and identify potential functions of T cells and ILCs that may be controlled by G9a. Together, this review will highlight the dynamic nature of G9a-dependent H3K9me2 in the immune system and shed light on the nature of repressive epigenetic modifications in cellular lineage choice.

Regulation of Innate and Adaptive Immunity by TGFβ

Immune regulation by cytokines is crucial in maintaining immune homeostasis, promoting responses to infection, resolving inflammation, and promoting immunological memory. Additionally, cytokine responses drive pathology in immune-mediated disease. A crucial cytokine in the regulation of all aspects of an immune response is transforming growth factor beta (TGFβ). Although best known as a crucial regulator of T cell responses, TGFβ plays a vital role in regulating responses mediated by virtually every innate and adaptive immune cell, including dendritic cells, B cells, NK cells, innate lymphoid cells, and granulocytes. Here, we review our current knowledge of how TGFβ regulates the immune system, highlighting the multifunctional nature of TGFβ and how its function can change depending on location and context of action.

T-cell-expressed proprotein convertase FURIN inhibits DMBA/TPA-induced skin cancer development

Proprotein convertases (PCSK) have a critical role in the body homeostasis as enzymes responsible for processing precursor proteins into their mature forms. FURIN, the first characterized member of the mammalian PCSK family, is overexpressed in multiple malignancies and the inhibition of its activity has been considered potential cancer treatment. FURIN has also an important function in the adaptive immunity, since its deficiency in T cells causes an impaired peripheral immune tolerance and accelerates immune responses. We addressed whether deleting FURIN from the immune cells would strengthen anticancer responses by subjecting mouse strains lacking FURIN from either T cells or macrophages and granulocytes to the DMBA/TPA two-stage skin carcinogenesis protocol. Unexpectedly, deficiency of FURIN in T cells resulted in enhanced and accelerated development of tumors, whereas FURIN deletion in macrophages and granulocytes had no effect. The epidermises of T-cell-specific FURIN deficient mice were significantly thicker with more proliferating Ki67+ cells. In contrast, there were no differences in the numbers of the T cells. The flow cytometric analyses of T-cell populations in skin draining lymph nodes showed that FURIN T-cell KO mice have an inherent upregulation of early activation marker CD69 as well as more CD4⁺CD25⁺Foxp3⁺ positive T regulatory cells. In the early phase of tumor promotion, T cells from the T-cell-specific FURIN knockout animals produced more interferon gamma, whereas at later stage the production of Th2- and Th17-type cytokines was more prominent than in wild-type controls. In conclusion, while PCSK inhibitors are promising therapeutics in cancer treatment, our results show that inhibiting FURIN specifically in T cells may promote squamous skin cancer development.

Stimulation of Natural Killer Cell-Mediated Tumor Immunity by an IL15/TGFβ-Neutralizing Fusion Protein

The clinical efficacy of immune cytokines used for cancer therapy is hampered by elements of the immunosuppressive tumor microenvironment such as TGFβ. Here we demonstrate that FIST15, a recombinant chimeric protein composed of the T-cell-stimulatory cytokine IL15, the sushi domain of IL15Rα and a TGFβ ligand trap, can overcome immunosuppressive TGFβ to effectively stimulate the proliferation and activation of natural killer (NK) and CD8⁺ T cells with potent antitumor properties. FIST15-treated NK and CD8⁺ T cells produced more IFNγ and TNFα compared with treatment with IL15 and a commercially available TGFβ receptor-Fc fusion protein (sTβRII) in the presence of TGFβ. Murine B16 melanoma cells, which overproduce TGFβ, were lysed by FIST15-treated NK cells in vitro at doses approximately 10-fold lower than NK cells treated with IL15 and sTβRII. Melanoma cells transduced to express FIST15 failed to establish tumors in vivo in immunocompetent murine hosts and could only form tumors in beige mice lacking NK cells. Mice injected with the same cells were also protected from subsequent challenge by unmodified B16 melanoma cells. Finally, mice with pre-established B16 melanoma tumors responded to FIST15 treatment more strongly compared with tumors treated with control cytokines. Taken together, our results offer a preclinical proof of concept for the use of FIST15 as a new class of biological therapeutics that can coordinately neutralize the effects of immunosuppressive TGFβ in the tumor microenvironment while empowering tumor immunity. Cancer Res; 76(19); 5683-95. ©2016 AACR.

Favorable prognostic influence of T-box transcription factor Eomesodermin in metastatic renal cell cancer patients

T-box transcription factors, T-box expressed in T cells (T-bet) encoded by Tbx21 and Eomesodermin (Eomes), drive the differentiation of effector/memory T cell lineages and NK cells. The aim of the study was to determine the prognostic influence of the expression of these transcription factors in peripheral blood (pB) in a cohort of 41 metastatic (m) RCC patients before receiving sorafenib treatment and to analyze their association with the immunophenotype in pB. In contrast to Tbx21, in the multivariate analysis including clinical features, Eomes mRNA expression was identified as an independent good prognostic factor for progression-free survival (PFS, p = 0.042) and overall survival (OS, p = 0.001) in addition to a favorable ECOG performance status (p = 0.01 and p = 0.008, respectively). Eomes expression correlated positively not only with expression of Tbx21 and TGFβ1 mRNA, but also with mRNA expression of the activation marker ICOS, and with in vivo activated HLA-DR(+) T cells. Eomes expression was negatively associated with TNFα-producing T cells. On protein level, Eomes was mainly expressed by CD56(+)CD3(-) NK cells in pB. In conclusion, we identified a higher Eomes mRNA expression as an independent good prognostic factor for OS and PFS in mRCC patients treated with sorafenib.

TGF-β1 induces erlotinib resistance in non-small cell lung cancer by down-regulating PTEN

BACKGROUND

TKI-acquired resistance is a tough obstacle for effectively treating NSCLC patients with EGFR mutant characteristics. T790M mutations and MET amplifications account for 70% of the acquired resistance, but the causes for the remaining 30% need elucidation.

METHODS

We detected TGF-β1and PTEN expression levels in 51 NSCLC patients undergoing EGFR-TKI treatment using Immunohistochemistry (IHC) assay. We examined erlotinib sensitivity, apoptosis rate, and invasion ability in PC-9 cells and PC-9/TGF-β1 cells with CCK-8, flow cytometry, and trans-well assays. We examined and analyzed the AKT and ERK pathways' expression levels using western blot.

RESULTS

High TGF-β1 and low PTEN expression levels were correlated with poor EGFR-TKI sensitivity and overall survival in 51 NSCLC samples. In vitro analysis revealed that TGF-β1 could reduce erlotinib sensitivity, increase anti-apoptosis ability and invasive characteristic in TKI-sensitive PC-9 cell lines by down-regulating PTEN and activating the Akt and ERK pathways.

CONCLUSIONS

The results suggest that TGF-β1 demonstrated another acquired erlotinib resistance by down-regulating PTEN expression.

Transforming growth factor-β signaling is constantly shaping memory T-cell population

The long-term maintenance of memory T cells is essential for successful vaccines. Both the quantity and the quality of the memory T-cell population must be maintained. The signals that control the maintenance of memory T cells remain incompletely identified. Here we used two genetic models to show that continuous transforming growth factor-β signaling to antigen-specific T cells is required for the differentiation and maintenance of memory CD8(+) T cells. In addition, both infection-induced and microbiota-induced inflammation impact the phenotypic and functional identity of memory CD8(+) T cells.

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.