Dendritic Cells in Irradiated Mice Trigger the Functional Plasticity and Antitumor Activity of Adoptively Transferred Tc17 Cells via IL12 Signaling

RORγT agonists as immune modulators in anticancer therapy

RORγT is a transcription factor that directs the development of Th17 lymphocytes and other IL-17-expressing cells (e.g., Tc17 and ILC3 cells). These cells are involved in the body's defense against pathogenic bacteria and fungi, but they also participate in maintaining the proinflammatory environment in some autoimmune diseases and play a role in the immune system's response to cancer. Similar to other members of the nuclear receptor superfamily, the activity of RORγT is regulated by low-molecular-weight ligands. Therefore, extensive efforts have been dedicated to identifying inverse agonists that diminish the activity of this receptor and subsequently inhibit the development of autoimmune diseases. Unfortunately, in the pursuit of an ideal inverse agonist, the development of agonists has been overlooked. It is important to remember that these types of compounds, by stimulating lymphocytes expressing RORγT (Th17 and Tc17), can enhance the immune system's response to tumors. In this review, we present recent advancements in the biology of RORγT agonists and their potential application in anticancer therapy.

IFNγ-IL-17+ CD8 T cells contribute to immunosuppression and tumor progression in human hepatocellular carcinoma

IL-17-producing CD8 (Tc17) T cells have been shown to play an important role in infection and chronic inflammation, however their implications in hepatocellular carcinoma (HCC) remain elusive. In this study, we performed cytometry by time-of-flight (CyTOF) and revealed the distinctive immunological phenotypes of two IFNγ⁺ and IFNγ^- Tc17 subsets that were preferentially enriched in human HCC. Single-cell RNA-sequencing analysis further revealed regulatory circuits governing the different phenotypes of these Tc17 subsets. In particular, we discovered that IFNγ^- Tc17 subset demonstrated pro-tumoral characteristics and expressed higher levels of CCL20. This corresponded to increased tumor infiltration of T regulatory cells (Treg) validated by immunohistochemistry in another independent HCC cohort, demonstrating the immunosuppressive functions of IFNγ^- Tc17 subset. Most importantly, higher intra-tumoral proportions of IFNγ^- Tc17 were associated with poorer prognosis in patients with HCC and this was further validated in The Cancer Genome Atlas (TCGA) HCC cohort. Taken together, this compendium of transcriptomic and proteomic data of Tc17 subsets sheds light on the immunosuppressive phenotypes of IFNγ^- Tc17 and its implications in HCC progression.

PD-1 limits differentiation and plasticity of Tc17 cells

Blockade of surface co-inhibitory receptor programmed cell death-1 (PD-1; CD279) has been established as an important immunotherapeutic approach to treat malignancies. On a cellular level, PD-1 is demonstrated to be of particular importance in inhibiting differentiation and effector function of cytotoxic Tc1 cells (CTLs). Nevertheless, the role of PD-1 in modulating interleukin (IL)-17-producing CD8⁺ T-cells (Tc17 cells), which generally display suppressed cytotoxic nature, is not well understood. To evaluate the impact of PD-1 in Tc17 responses, we examined its functioning using different in vitro and in vivo models. Upon activation of CD8⁺ T-cells in Tc17 environment, we found that PD-1 was rapidly expressed on the surface of CD8⁺ T-cells and triggered a T-cell-internal mechanism that inhibited the expression of IL-17 and Tc17-supporting transcription factors pSTAT3 and RORγt. Expression of type17-polarising cytokine IL-21 and the receptor for IL-23 were also suppressed. Intriguingly, adoptively transferred, PD-1^-/- Tc17 cells were highly efficient in rejection of established B16 melanoma in vivo and displayed Tc1 like characteristics ex vivo. When using IL-17A-eGFP reporter mice for in vitro fate tracking, IL-17A-eGFP expressing cells lacking PD-1 signaling upon re-stimulation with IL-12 quickly acquired Tc1 characteristics such as IFN-γ, and granzyme B expression, implicating lineage independent upregulation of CTL-characteristics that are needed for tumor control. In line with plasticity characteristics, absence of PD-1 signaling in Tc17 cells increased the expression of the stemness and persistence-associated molecules TCF1 and BCL6. Thus, PD-1 plays a central role in the specific suppression of Tc17 differentiation and its plasticity in relation to CTL-driven tumor rejection, which provides further explanation as to why the blockade of PD-1 is such an efficient therapeutic target for inducing tumor rejection.

Effects of Chemotherapy on Neuroinflammation, Neuronal Damage, Neurogenesis, and Behavioral Performance in Bone Marrow Transplantation Recipient Mice

As bone marrow transplant (BMT) is gradually applied to the study of central nervous system (CNS) disease, it is needed to investigate the proper dose of chemotherapy to eradicate bone marrow cells while bringing little damage to brain. In the present study, we established a BMT model with varied busulfan and cyclophosphamide (Bu-Cy) dosages. The recipient mice's chimera rate, neuronal death, neuroinflammation, and behavioral functions were all investigated. Chimerism of peripheral blood cells was shown to rise with Bu-Cy treatment doses, with 60.7% in the Bu(20 mg/kg)/Cy(100 mg/kg) group and 93.0% in the Bu(35 mg/kg)/Cy(100 mg/kg) group. Recipients with Bu(35 mg/kg)/Cy(100 mg/kg) therapy had brain injury, increased neuroinflammation, diminished neurogenesis and cognitive abnormalities, whereas animals given a lesser dosage had no such brain damages. Conclusively, considering the chimerism and the possibility to damage brain, we recommend Bu(20 mg/kg)/Cy(100 mg/kg) is the ideal dose in BMT for studying CNS diseases in the C57/BL6 mouse strain.

Adoptive transfer of IL-4 reprogrammed Tc17 cells elicits anti-tumor immunity through functional plasticity

Ability of IL-17-producing CD8⁺ T cells (Tc17) to transform into cytotoxic anti-tumor effectors makes them a promising candidate for immune effector cell (IEC) therapy. However, key factors regulating Tc17 reprograming remain poorly defined, hindering translation of Tc17-based IEC use from bench to bedside. We probed the effects of multiple cytokines and underlying signaling pathways on Tc17 cells and identified pivotal role for IL-4 and PI3K/AKT in promoting Tc17 transformation into cytotoxic IFN-γ-producing IECs, an effect dependent on Eomes expression. IL-4 not only triggered Tc17 cytotoxicity, but also induced cell expansion, which significantly improved the antitumor potential of Tc17 cells compared to that of IFN-γ-producing CD8⁺ T cells (Tc1) in a murine model. Furthermore, IL-4/AKT signaling drove the upregulation of the T-cell receptor-associated transmembrane adaptor 1 (Trat1) in Tc17 cells to promote IL-4-induced T-cell receptor stabilization and Tc17 cytotoxicity. Finally, we proposed a possible procedure to expand human Tc17 from peripheral blood of cancer patients, and confirmed the function of IL-4 in Tc17 reprogramming. Collectively, these results document a novel IL-4/AKT/Eomes/Trat1 axis that promotes expansion and transformation of Tc17 cells into cytotoxic effectors with a therapeutic potential. IL-4 priming of Tc17 cells should be further explored as a cell therapy engineering strategy to generate IECs to augment anti-tumor responses. This article is protected by copyright. All rights reserved.

IL12 integrated into the CAR exodomain converts CD8+ T cells to poly-functional NK-like cells with superior killing of antigen-loss tumors

Chimeric antigen receptor (CAR)-redirected T cell therapy often fails to control tumors in the long term due to selecting cancer cells that downregulated or lost CAR targeted antigen. To reprogram the functional capacities specifically of engineered CAR T cells, we inserted IL12 into the extracellular moiety of a CD28-ζ CAR; both the CAR endodomain and IL12 were functionally active, as indicated by antigen-redirected effector functions and STAT4 phosphorylation, respectively. The IL12-CAR reprogrammed CD8⁺ T cells toward a so far not recognized natural killer (NK) cell-like signature and a CD94⁺CD56⁺CD62L^high phenotype closely similar, but not identical, to NK and cytokine induced killer (CIK) cells. In contrast to conventional CAR T cells, IL12-CAR T cells acquired antigen-independent, human leukocyte antigen E (HLA-E) restricted cytotoxic capacities eliminating antigen-negative cancer cells in addition to eliminating cancer cells with CAR cognate antigen. Simultaneous signaling through both the CAR endodomain and IL12 were required for inducing maximal NK-like cytotoxicity; adding IL12 to conventional CAR T cells was not sufficient. Antigen-negative tumors were attacked by IL12-CAR T cells, but not by conventional CAR T cells. Overall, we present a prototype of a new family of CARs that augments tumor recognition and elimination through expanded functional capacities by an appropriate cytokine integrated into the CAR exodomain.

Exosome-mediated cellular crosstalk within the tumor microenvironment upon irradiation

Radiotherapy is one of the most effective treatment methods for various solid tumors. Bidirectional signal transduction between cancer cells and stromal cells within the irradiated microenvironment is important in cancer development and treatment responsiveness. Exosomes, initially considered as “garbage bins” for unwanted from cells, are now understood to perform a variety of functions in interactions within the tumor microenvironment. Exosome-mediated regulation processes are rebuilt under the irradiation stimuli, because the exosome production, uptake, and contents are markedly modified by irradiation. In turn, irradiation-modified exosomes may modulate the cell response to irradiation through feedback regulation. Here, we review current knowledge and discuss the roles of exosome-mediated interactions between cells under radiotherapy conditions.

Gut microbiota modulate dendritic cell antigen presentation and radiotherapy-induced antitumor immune response

Alterations in gut microbiota impact the pathophysiology of several diseases, including cancer. Radiotherapy (RT), an established curative and palliative cancer treatment, exerts potent immune modulatory effects, inducing tumor-associated antigen (TAA) cross-priming with antitumor CD8+ T cell elicitation and abscopal effects. We tested whether the gut microbiota modulates antitumor immune response following RT distal to the gut. Vancomycin, an antibiotic that acts mainly on gram-positive bacteria and is restricted to the gut, potentiated the RT-induced antitumor immune response and tumor growth inhibition. This synergy was dependent on TAA cross presentation to cytolytic CD8+ T cells and on IFN-γ. Notably, butyrate, a metabolite produced by the vancomycin-depleted gut bacteria, abrogated the vancomycin effect. In conclusion, depletion of vancomycin-sensitive bacteria enhances the antitumor activity of RT, which has important clinical ramifications.

The Roles of CD8+ T Cell Subsets in Antitumor Immunity

Effector CD8⁺ T cells are typically thought to be a homogenous group of cytotoxic cells that produce interferon-(IFN) γ. However, recent findings have challenged this notion because multiple subsets of CD8⁺ T cells have been described, each with distinct effector functions and cytotoxic potential. These subsets, referred to as the Tc subsets, have also been detected in tumor microenvironments (TMEs), where they potentially influence the antitumor response and patient outcomes. In this review, we highlight the prevalence and roles of Tc subsets in the TME. We also discuss their therapeutic applications in the context of adoptive immunotherapy to treat cancer.

IL6 Fuels Durable Memory for Th17 Cell-Mediated Responses to Tumors

The accessibility of adoptive T-cell transfer therapies (ACT) is hindered by the cost and time required for product development. Here we describe a streamlined ACT protocol using Th17 cells expanded only 4 days ex vivo. While shortening expansion compromised cell yield, this method licensed Th17 cells to eradicate large tumors to a greater extent than cells expanded longer term. Day 4 Th17 cells engrafted, induced release of multiple cytokines including IL6, IL17, MCP-1, and GM-CSF in the tumor-bearing host, and persisted as memory cells. IL6 was a critical component for efficacy of these therapies via its promotion of long-term immunity and resistance to tumor relapse. Mechanistically, IL6 diminished engraftment of FoxP3⁺ donor T cells, corresponding with robust tumor infiltration by donor effector over regulatory cells for the Day 4 Th17 cell product relative to cell products expanded longer durations ex vivo. Collectively, this work describes a method to rapidly generate therapeutic T-cell products for ACT and implicates IL6 in promoting durable immunity of Th17 cells against large, established solid tumors. SIGNIFICANCE: An abbreviated, 4-day ex vivo expansion method licenses Th17 cells to confer long-lived immunity against solid malignancies via induction of systemic IL6 in the host.See related commentary by Fiering and Ho, p. 3795.

Low-Dose Total Body Irradiation Can Enhance Systemic Immune Related Response Induced by Hypo-Fractionated Radiation

A systemic immune related response (SIME) of radiotherapy has been occasionally observed on metastatic tumors, but the clinical outcomes remain poor. Novel treatment approaches are therefore needed to improve SIME ratio. We used a combination of hypo-fractionated radiation therapy (H-RT) with low-dose total body irradiation (L-TBI) in a syngeneic mouse model of breast and colon carcinoma. The combination therapy of H-RT and L-TBI potentially enhanced SIME by infiltration of CD8⁺ T cell and altering the immunosuppressive microenvironment in non-irradiated subcutaneous tumor lesions. The frequency of IFN-γ, as a tumor-specific CD8⁺ T cells producing, significantly inhibited the secondary tumor growth of breast and colon. Our findings suggest that L-TBI could serve as a potential therapeutic agent for metastatic breast and colon cancer and, together with H-RT, their therapeutic potential is enhanced significantly.

Tissue Resident CD8 Memory T Cell Responses in Cancer and Autoimmunity

Resident memory (T_RM) cells are a distinct tissue-localized T cell lineage that is crucial for protective immunity in peripheral tissues. While a great deal of effort has focused on defining their role in immunity to infections, studies now reveal T_RM cells as a vital component of the host immune response to cancer. Characterized by cell-surface molecules including CD103, CD69, and CD49a, T_RM-like tumor-infiltrating lymphocytes (TILs) can be found in a wide range of human cancers, where they portend improved prognosis. Recent studies in mouse tumor models have shown that T_RM cells are induced by cancer vaccines delivered in peripheral tissue sites, or by the depletion of regulatory T cells. Such tumor-specific T_RM cells are recognized as both necessary and sufficient for long-lived protection against tumors in peripheral tissue locations. T_RM responses against tumor/self-antigens can concurrently result in the development of pathogenic T_RM responses to self, with a growing number of autoimmune diseases and inflammatory pathologies being attributed to T_RM responses. This review will recount the path to discovering the importance of resident memory CD8 T cells as they pertain to cancer immunity. In addition to highlighting key studies that directly implicate T_RM cells in anti-tumor immunity, we will highlight earlier work that implicitly suggested their importance. Informed by studies in infectious disease models, and instructed by a clear role for T_RM cells in autoimmunity, we will discuss strategies for therapeutically promoting T_RM responses in settings where they don't naturally occur.

Interleukin‑17A and heparanase promote angiogenesis and cell proliferation and invasion in cervical cancer

Interleukin‑17A (IL‑17A) is a CD4 T-cell-derived pro-inflammatory cytokine that is involved in human cervical tumorigenesis. Heparanase (HPSE) is an endo-glycosidase expressed in mammals, which has been confirmed to be associated with cervical cancer invasion. In the present study, it was hypothesized that IL‑17A and HPSE are key proteins promoting tumor angiogenesis and cell proliferation and invasion in cervical cancer. The expression of IL‑17A and HPSE in cervical cancer tissues was detected by immunohistochemical staining. In addition, the expression of IL‑17A and HPSE was down- and upregulated via RNAi and human recombinant proteins, and MTT and Transwell assays were performed to examine cervical cancer cell proliferation and invasion, respectively. Flow cytometry analysis was also performed to detect cell cycle distribution, and the levels of target mRNA and protein were evaluated by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. IL‑17A and HPSE were highly expressed in cervical cancer tissues, and microvessel density was notably higher in the IL‑17A-positive group. IL‑17A and/or HPSE recombinant protein promoted the proliferation and invasion of cervical cancer cells, increased the proportion of cells in the G2/M phase, and enhanced the mRNA and protein expression of human papillomavirus E6, P53, vascular endothelial growth factor and CD31, whereas downregulation of IL‑17A and/or HPSE exerted the opposite effects. Furthermore, downregulation of IL‑17A and/or HPSE was found to inhibit the expression of nuclear factor (NF)-κB P65. In summary, IL‑17A and HPSE may promote tumor angiogenesis and cell proliferation and invasion in cervical cancer, possibly via the NF-κB signaling pathway. These findings may lead to the identification of new diagnostic markers and therapeutic targets.

Role of immune system in tumor progression and carcinogenesis

Tumor micro-environment has potential to customize the behavior of the immune cell according to their need. In immune-eliminating phase, immune cells eliminate transformed cells but after tumor establishment innate and adaptive immune cells synergistically provide shelter as well as fulfill their requirement that helps in progression. In between eliminating and establishment phase, equilibrium and escaping phase regulate the immune cells response. During immune-escaping, (1) the antigenic response generated is either inadequate, or focused entirely on tolerance, and (2) immune response generated is specific and effective, but the tumor skips immune recognition. In this review, we are discussing the critical role of immune cells and their cytokines before and after the establishment of tumor which might play a critical role during immunotherapy.

Gut microbiota modulates adoptive cell therapy via CD8α dendritic cells and IL-12

Adoptive T cell therapy (ACT) is a promising new modality for malignancies. Here, we report that adoptive T cell efficacy in tumor-bearing mice is significantly affected by differences in the native composition of the gut microbiome or treatment with antibiotics, or by heterologous fecal transfer. Depletion of bacteria with vancomycin decreased the rate of tumor growth in mice from The Jackson Laboratory receiving ACT, whereas treatment with neomycin and metronidazole had no effect, indicating the role of specific bacteria in host response. Vancomycin treatment induced an increase in systemic CD8α+ DCs, which sustained systemic adoptively transferred antitumor T cells in an IL-12-dependent manner. In subjects undergoing allogeneic hematopoietic cell transplantation, we found that oral vancomycin also increased IL-12 levels. Collectively, our findings demonstrate an important role played by the gut microbiota in the antitumor effectiveness of ACT and suggest potentially new avenues to improve response to ACT by altering the gut microbiota.

The microbiome in anti-cancer therapy

The commensal microbiome constitutes an important modulator of host physiology and risk of disease, including cancer development and progression. Lately, the microbiome has been suggested to modulate the efficacy of anti-cancer treatment. Examples include chemotherapy and total body irradiation-induced barrier function disruption, leading to microbial efflux that drives activation of anti-tumorigenic T cells; Microbiome-driven release of reactive oxygen species contributing to the efficacy of platinum salts; and microbiome-induced immune priming promoting the anti-tumor effects of alkylating chemotherapy and immune checkpoint inhibitors. Furthermore, selected commensals are able to colonize solid tumors. This 'tumor microbiome' may further impact local tumor responses to treatment and potentially be harnessed for tumor-specific targeting and therapeutic delivery. In this review, we present recent advances in understanding of the intricate role of microbiome in modulating efficacy of a number of anti-cancer treatments, and discuss how anti-cancer treatment approaches utilizing the tumor microbiome may enhance oncological treatment efficacy.

Murine Th17 cells utilize IL-2 receptor gamma chain cytokines but are resistant to cytokine withdrawal-induced apoptosis

Adoptive cellular therapy (ACT) with the Th17 subset of CD4⁺ T cells can cure established melanoma in preclinical models and holds promise for treating human cancer. However, little is known about the growth factors necessary for optimal engraftment and anti-tumor activity of Th17 cells. Due to the central role of IL-2 receptor gamma chain (IL2Rγ-chain) cytokines (IL-2, IL-7, and IL-15) in the activity and persistence of many T cell subsets after adoptive transfer, we hypothesized that these cytokines are important for Th17 cells. We found that Th17 cells proliferated in response to IL-2, IL-7, and IL-15 in vitro. However, in contrast to many other T cell subsets, including conventionally activated CD8⁺ T cells, we found that Th17 cells were resistant to apoptosis in the absence of IL2Rγ-chain cytokines. To determine whether Th17 cells utilize IL2Rγ-chain cytokines in vivo, we tracked Th17 cell engraftment after adoptive transfer with or without cytokine depletion. Depletion of IL-7 and/or IL-2 decreased initial engraftment, while depletion of IL-15 did not. Supplementation of IL-2 increased initial Th17 engraftment. To assess the clinical relevance of these findings, we treated melanoma-bearing mice with Th17 cell adoptive transfer and concurrent cytokine depletion or supplementation. We found that simultaneous depletion of IL-2 and IL-7 decreased therapeutic efficacy, depletion of IL-15 had no effect, and IL-2 supplementation increased therapeutic efficacy. Our results show that Th17 cells are responsive to IL2Rγ-chain cytokines, and provide insight into the application of these cytokines for Th17-based therapeutic strategies.

Th17 cells are refractory to senescence and retain robust antitumor activity after long-term ex vivo expansion

Adoptive immunotherapy for solid tumors relies on infusing large numbers of T cells to mediate successful antitumor responses in patients. While long-term rapid-expansion protocols (REPs) produce sufficient numbers of CD8⁺ T cells for treatment, they also cause decline in the cell's therapeutic fitness. In contrast, we discovered that IL-17-producing CD4⁺ T cells (Th17 cells) do not require REPs to expand 5,000-fold over 3 weeks. Also, unlike Th1 cells, Th17 cells do not exhibit hallmarks of senescence or apoptosis, retaining robust antitumor efficacy in vivo. Three-week-expanded Th17 cells eliminated melanoma as effectively as Th17 cells expanded for 1 week when infused in equal numbers into mice. However, treating mice with large recalcitrant tumors required the infusion of all cells generated after 2 or 3 weeks of expansion, while the cell yield obtained after 1-week expansion was insufficient. Long-term-expanded Th17 cells also protected mice from tumor rechallenge including lung metastasis. Importantly, 2-week-expanded human chimeric antigen receptor-positive (CAR⁺) Th17 cells also retained their ability to regress human mesothelioma, while CAR⁺ Th1 cells did not. Our results indicate that tumor-reactive Th17 cells are an effective cell therapy for cancer, remaining uncompromised when expanded for a long duration owing to their resistance to senescence.

The differentiation and plasticity of Tc17 cells are regulated by CTLA-4-mediated effects on STATs

As the blockade of inhibitory surface-molecules such as CTLA-4 on T cells has led to recent advances in antitumor immune therapy, there is great interest in identifying novel mechanisms of action of CD8⁺ T cells to evoke effective cytotoxic antitumor responses. Using in vitro and in vivo models, we investigated the molecular pathways underlying the CTLA-4-mediated differentiation of IL-17-producing CD8⁺ T cells (Tc17 cells) that strongly impairs cytotoxicity. Our studies demonstrate that Tc17 cells lacking CTLA-4 signaling have limited production of STAT3-target gene products such as IL-17, IL-21, IL-23R and RORγt. Upon re-stimulation with IL-12, these cells display fast downregulation of Tc17 hallmarks and acquire Tc1 characteristics such as IFNγ and TNF-α co-expression, which is known to correlate with tumor control. Indeed, upon adoptive transfer, these cells were highly efficient in the antigen-specific rejection of established OVA-expressing B16 melanoma in vivo. Mechanistically, in primary and re-stimulated Tc17 cells, STAT3 binding to the IL-17 promoter was strongly augmented by CTLA-4, associated with less binding of STAT5 and reduced relative activation of STAT1 which is known to block STAT3 activity. Inhibiting CTLA-4-induced STAT3 activity reverses enhancement of signature Tc17 gene products, rendering Tc17 cells susceptible to conversion to Tc1-like cells with enhanced cytotoxic potential. Thus, CTLA-4 critically shapes the characteristics of Tc17 cells by regulating relative STAT3 activation, which provides new perspectives to enhance cytotoxicity of antitumor responses.

CAR T Cell Therapy: A Game Changer in Cancer Treatment

The development of novel targeted therapies with acceptable safety profiles is critical to successful cancer outcomes with better survival rates. Immunotherapy offers promising opportunities with the potential to induce sustained remissions in patients with refractory disease. Recent dramatic clinical responses in trials with gene modified T cells expressing chimeric antigen receptors (CARs) in B-cell malignancies have generated great enthusiasm. This therapy might pave the way for a potential paradigm shift in the way we treat refractory or relapsed cancers. CARs are genetically engineered receptors that combine the specific binding domains from a tumor targeting antibody with T cell signaling domains to allow specifically targeted antibody redirected T cell activation. Despite current successes in hematological cancers, we are only in the beginning of exploring the powerful potential of CAR redirected T cells in the control and elimination of resistant, metastatic, or recurrent nonhematological cancers. This review discusses the application of the CAR T cell therapy, its challenges, and strategies for successful clinical and commercial translation.

TGF-β and IL-21 cooperatively stimulate activated CD8(+) T cells to differentiate into Tc17 cells

TGF-β together with IL-21 or IL-6 can drive the differentiation of naïve CD8(+) T cells into IL-17-producing CD8(+) T cells. These IL-17-producing CD8(+) T cells are termed Tc17 cells. Tc17 cells preserve plasticity under various conditions in vitro and in vivo. IFN-γ-producing CD8(+) T cells are termed Tc1 cells. However, Tc1 cells are considered relatively stable. In the present study, we show that the combination of TGF-β plus IL-21, but not IL-6, converts Tc1 cells into Tc17 cells; this conversion is associated with elevated RORα, RORγt, and Batf mRNA levels. These results indicate that Tc1 cells are skewed to the Tc17 cell phenotype under TGF-β plus IL-21-polarizing conditions. Furthermore, IL-6R is expressed on naïve, but not activated, CD8(+) T cells. In contrast, IL-21R is expressed on both naïve and activated CD8(+) T cells. Thus, differential expression profiles of IL-6R and IL-21R on naïve and activated CD8(+) T cells may be one mechanism by which TGF-β plus IL-21, but not IL-6, can drive activated CD8(+) T cells to differentiate into IL-17-producing cells. Taken together, these results provide a novel viewpoint for the plasticity of Tc1 cells.

Toll-like receptor agonist therapy can profoundly augment the antitumor activity of adoptively transferred CD8(+) T cells without host preconditioning

Background

Lymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial components, such as LPS, are key mediators of total body irradiation (TBI) enhancement, but our ability to strategically use these toll-like receptor (TLR) agonists to bolster the potency of T cell-based therapies for cancer remains elusive. Herein, we used TLR4 agonist LPS as a tool to address how and when to use TLR agonists to effectively improve cancer immunotherapy.

Methods

To determine the mechanisms of how innate immune activation via lymphodepletion potentiated antitumor T cell immunity, we utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were preconditioned with 5Gy TBI and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8⁺ T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated based on tumor growth and the phenotype of recovered splenocytes by flow cytometry. We also evaluated the role of non-toxic and clinically used TLR4 and TLR9 agonists—monophosphoryl lipid A (MPL) and CpG Oligodeoxynucleotide (CpG ODN), respectively— for ACT therapy.

Results

Here we report that while exogenous administration of LPS was able to enhance adoptively transferred CD8⁺ T cells’ tumor destruction, LPS treatment alone did not replace individual components of the tripartite ACT regimen, or obviate TBI. Moreover, we found that sequentially administering LPS during or one day prior to ACT therapy compromised tumor regression. In contrast, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred tumor-specific CD8⁺ T cells over host CD4⁺ T cells. We also found that non-toxic TLR agonists MPL and CpG potentiated the antitumor activity of infused CD8⁺ T cells. Finally, TBI was no longer needed to regress tumors in mice who were depleted of host CD4⁺ T cells, given a tripartite ACT regimen and then treated with low dose LPS.

Conclusions

Collectively, our results identify how and when to administer TLR agonists to augment T cell-based immunotherapy in the absence or presence of host preconditioning for treatment of advanced malignancies. Our findings have clinical implications for the design of next generation immune-based therapies for patients with cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0110-8) contains supplementary material, which is available to authorized users.

Exploiting IL-17-producing CD4+ and CD8+ T cells to improve cancer immunotherapy in the clinic

Cancer immunotherapy is one the most effective approaches for treating patients with tumors, as it bolsters the generation and persistence of memory T cells. In preclinical work, it has been reported that adoptively transferred CD4+ and CD8+ lymphocytes that secrete IL-17A (i.e., Th17 and Tc17 cells) regress tumors to a greater extent than IFN-γ(+)Th1 or Tc1 cells in vivo. Herein, we review the mechanisms underlying how infused Th17 and Tc17 cells regress established malignancies in clinically relevant mouse models of cancer. We also discuss how unique signaling cues--such as co-stimulatory molecules (ICOS and 41BB), cytokines (IL-12 and IL-23) or pharmaceutical reagents (Akt inhibitors, etc.)--can be exploited to bolster the therapeutic potential of IL-17(+) lymphocytes with an emphasis on using this knowledge to improve next-generation clinical trials for patients with cancer.

Harnessing the Microbiome to Enhance Cancer Immunotherapy

The microbiota plays a key role in regulating the innate and adaptive immune system. Herein, we review the immunological aspects of the microbiota in tumor immunity in mice and man, with a focus on toll-like receptor (TLR) agonists, vaccines, checkpoint modulators, chemotherapy, and adoptive T cell transfer (ACT) therapies. We propose innovative treatments that may safely harness the microbiota to enhance T cell-based therapies in cancer patients. Finally, we highlight recent developments in tumor immunotherapy, particularly novel ways to modulate the microbiome and memory T cell responses to human malignancies.