Phase I study of recombinant interleukin-21 in patients with metastatic melanoma and renal cell carcinoma

Targeting γc family cytokines with biologics: current status and future prospects

Over the recent decades the market potential of biologics has substantially expanded, and many of the top-selling drugs worldwide are now monoclonal antibodies or antibody-like molecules. The common gamma chain (γc) cytokines, Interleukin (IL-)2, IL-4, IL-7, IL-9, IL-15, and IL-21, play pivotal roles in regulating immune responses, from innate to adaptive immunity. Dysregulation of cell signaling by these cytokines is strongly associated with a range of immunological disorders, which includes cancer as well as autoimmune and inflammatory diseases. Given the essential role of γc cytokines in maintaining immune homeostasis, the development of therapeutic interventions targeting these molecules poses unique challenges. Here, we provide an overview of current biologics targeting either single or multiple γc cytokines or their respective receptor subunits across a spectrum of diseases, primarily focusing on antibodies, antibody-like constructs, and antibody-cytokine fusions. We summarize therapeutic biologics currently in clinical trials, highlighting how they may offer advantages over existing therapies and standard of care, and discuss recent advances in this field. Finally, we explore future directions and the potential of novel therapeutic intervention strategies targeting this cytokine family.

Adjusting the scope of natural killer cells in cancer therapy

Natural killer (NK) cells have evolved to detect abnormalities in tissues arising from infection with pathogens, genomic damage, or transformation and respond rapidly to the production of potent proinflammatory and cytolytic mediators. While this acute proinflammatory response is highly efficient at orchestrating sterilizing immunity to pathogens in a matter of days, cellular transformation often avoids the innate detection mechanisms of NK cells. When cellular transformation results in malignancy, tumor cells and/or the tumor microenvironment can evolve additional mechanisms to circumvent NK cell responses, and cancer is now a dominant disease burden worldwide. Here, we review recent advances in our understanding of the combined relationship between malignancies and natural killer (NK) cells, learn from recent clinical efforts in therapeutically targeting natural killer (NK) cells in cancer and outline some emerging therapeutic concepts that aim to improve the innate immune response against cancer.

Combinatorial immunotherapy with anti-ROR1 CAR NK cells and an IL-21 secreting oncolytic virus against neuroblastoma

Children with recurrent/metastatic neuroblastoma (NB) have a dismal survival (<25%). Novel therapies are desperately needed. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is highly expressed on NB. C021 is a selective oncolytic herpes simplex virus modified to overexpress human interleukin-21 (hIL-21), a cytokine that enhances natural killer (NK) cell cytotoxicity. In the current study, we successfully engineered ex-vivo-expanded NK cells to express a chimeric antigen receptor (CAR) against ROR1 using mRNA electroporation and investigated the efficacy of anti-ROR1-CAR-NK cells combined with C021 in targeting ROR1+ NB. We found that C021-infected NB cells secreted hIL-21 in vitro and in vivo. Compared to the non-cytokine-secreting parental virus C134, C021 significantly enhanced the in vitro cytotoxicity (p < 0.05) of anti-ROR1-CAR-NK cells with increased interferon (IFN)-γ (p < 0.05), granzyme B (p < 0.05), and perforin (p < 0.05) secretion against NB cells. Furthermore, the combination of C021 and anti-ROR1-CAR-NK cells significantly extended the survival of human NB xenografted NSG mice compared to controls (mock NK, ROR1-CAR-NK, C134, C021, C134+ROR1-CAR-NK, and C021+mock NK). Our results suggest that cytokine-secreting oncolytic virus in combination with CAR-NK cells is a novel, effective immunotherapeutic approach for high-risk NB.

GM-CSF and IL-21-armed oncolytic vaccinia virus significantly enhances anti-tumor activity and synergizes with anti-PD1 immunotherapy in pancreatic cancer

Pancreatic cancer is one of the most aggressive cancers and poses significant challenges to current therapies because of its complex immunosuppressive tumor microenvironment (TME). Oncolytic viruses armed with immunoregulatory molecules are promising strategies to overcome limited efficacy and target inaccessible and metastatic tumors. In this study, we constructed a tumor-selective vaccinia virus (VV) with deletions of the TK and A49 genes (VVLΔTKΔA49, VVL-DD) using CRISPR-Cas9-based homologous recombination. VVL-DD exhibited significant tumor selectivity in vitro and anti-tumor potency in vivo in a murine pancreatic cancer model. Then, VVL-DD was armed with an optimal combination of immunomodulatory molecules, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-21 (IL-21), to produce VVL-GL21. VVL-GL21 induced significant tumor regression after intratumoral and systemic administration. Moreover, VVL-GL21 increased the infiltration of dendritic cells (DCs), macrophages, and T cells; induced DC maturation; increased the transition from M2 to M1 macrophages; improved the formation of immune memory; prevented tumor recurrence; and effectively bolstered the immune response against tumors in multiple key immune compartments. Interestingly, mice bearing-pancreatic cancer tumors treated with VVL-GL21 showed anti-tumor immunity against lung and colon cancer tumors. Importantly, treatment with VVL-GL21 enhanced the responsiveness of tumors to the immune checkpoint inhibitor anti-PD1. Taken together, VVL-GL21 remodels the suppressive TME and has powerful anti-tumor activities as monotherapy or in combination with anti-PD1 by intratumoral or systemic delivery for the treatment of pancreatic cancer. VVL-GL21 could be used as a therapeutic cancer vaccine.

Potent antitumor activity of a designed interleukin-21 mimic

Long-standing goals of cancer immunotherapy are to activate cytotoxic antitumor T cells across a broad range of affinities while dampening suppressive regulatory T (Treg) cell responses, but current approaches achieve these goals with limited success. Here, we report a de novo IL-21 mimic, 21h10, designed to have augmented stability and high signaling potency in both humans and mice. In multiple animal models and in ex vivo human melanoma patient derived organotypic tumor spheroids (PDOTS), 21h10 showed robust antitumor activity. 21h10 generates significantly prolonged STAT signaling in vivo compared with native IL-21, and has considerably stronger anti-tumor activity. Toxicities associated with systemic administration of 21h10 could be mitigated by TNFα blockade without compromising antitumor efficacy. In the tumor microenvironment, 21h10 induced highly cytotoxic antitumor T cells from clonotypes with a range of affinities for endogenous tumor antigens, robustly expanding low-affinity cytotoxic T cells and driving high expression of interferon-𝛾 (IFN-𝛾) and granzyme B compared to native IL-21, while increasing the frequency of IFN-𝛾 + Th1 cells and reducing that of Foxp3 + Tregs. As 21h10 has full human/mouse cross-reactivity, high stability and potency, and potentiates low-affinity antitumor responses, it has considerable translational potential.

Intratumoral delivery of lipid nanoparticle-formulated mRNA encoding IL-21, IL-7, and 4-1BBL induces systemic anti-tumor immunity

Local delivery of mRNA-based immunotherapy offers a promising avenue as it enables the production of specific immunomodulatory proteins that can stimulate the immune system to recognize and eliminate cancer cells while limiting systemic exposure and toxicities. Here, we develop and employ lipid-based nanoparticles (LNPs) to intratumorally deliver an mRNA mixture encoding the cytokines interleukin (IL)-21 and IL-7 and the immunostimulatory molecule 4-1BB ligand (Triplet LNP). IL-21 synergy with IL-7 and 4-1BBL leads to a profound increase in the frequency of tumor-infiltrating CD8+ T cells and their capacity to produce granzyme B and IFN-γ, leading to tumor eradication and the development of long-term immunological memory. Mechanistically, the efficacy of the Triplet LNP depends on tumor-draining lymph nodes to tumor CD8+ T-cell trafficking. Moreover, we highlight the therapeutic potential of the Triplet LNP in multiple tumor models in female mice and its superior therapeutic efficacy to immune checkpoint blockade. Ultimately, the expression of these immunomodulators is associated with better overall survival in patients with cancer.

From bench to bedside: the past, present and future of IL-21 immunotherapy

As immunotherapy gains momentum as a promising approach for treating several types of cancer, IL-21 has emerged as the latest discovery within the γ chain cytokine family, known for its decisive effects on innate and adaptive immunity and immunopathology. Through the modulation of immune cells, IL-21 has demonstrated significant anti-tumor effects in preclinical studies. The potential of IL-21 in cancer treatment has been explored in phase I and II clinical trials, where it has been utilized both as monotherapy and in combination with other drug agents. Further investigation, alongside larger studies, is necessary before final evaluation and application of IL-21 as immunotherapy. This review aims to summarize these pre-clinical and clinical studies and to discuss the possible future directions of IL-21 immunotherapy development. Such a study may be helpful to accelerate the process of clinical application for IL21 immunotherapy.

Metabolic adaptations determine whether natural killer cells fail or thrive within the tumor microenvironment

Natural Killer (NK) cells are a top contender in the development of adoptive cell therapies for cancer due to their diverse antitumor functions and ability to restrict their activation against nonmalignant cells. Despite their success in hematologic malignancies, NK cell-based therapies have been limited in the context of solid tumors. Tumor cells undergo various metabolic adaptations to sustain the immense energy demands that are needed to support their rapid and uncontrolled proliferation. As a result, the tumor microenvironment (TME) is depleted of nutrients needed to fuel immune cell activity and contains several immunosuppressive metabolites that hinder NK cell antitumor functions. Further, we now know that NK cell metabolic status is a main determining factor of their effector functions. Hence, the ability of NK cells to withstand and adapt to these metabolically hostile conditions is imperative for effective and sustained antitumor activity in the TME. With this in mind, we review the consequences of metabolic hostility in the TME on NK cell metabolism and function. We also discuss tumor-like metabolic programs in NK cell induced by STAT3-mediated expansion that adapt NK cells to thrive in the TME. Finally, we examine how other approaches can be applied to enhance NK cell metabolism in tumors.

Therapeutic potential of interleukin-21 in cancer

Interleukin-21 (IL-21) is an immunostimulatory cytokine which belongs to the common gamma-chain family of cytokines. It plays an import role in the development, differentiation, proliferation, and activation of immune cells, in particular T and natural killer (NK) cells. Since its discovery in 2000, IL-21 has been shown to regulate both adaptive and immune responses associates with key role in antiviral and antitumor responses. Recent advances indicate IL-21 as a promising target for cancer treatment and encouraging results were obtained in preclinical studies which investigated the potency of IL-21 alone or in combination with other therapies, including monoclonal antibodies, checkpoint inhibitory molecules, oncolytic virotherapy, and adoptive cell transfer. Furthermore, IL-21 showed antitumor effects in the treatment of patients with advanced cancer, with minimal side effects in several clinical trials. In the present review, we will outline the recent progress in IL-21 research, highlighting the potential of IL-21 based therapy as single agent or in combination with other drugs to enhance cancer treatment efficiency.

Interleukin-21 as an adjuvant in cancer immunotherapy: Current advances and future directions

Immunotherapy has revolutionized cancer treatment. However, it's well-recognized that a considerable proportion of patients fail to benefit from immunotherapy, and to improve immunotherapy response is clinically urgent. Insufficient immune infiltration and immunosuppressive tumor microenvironments (TME) are main contributors to immunotherapy resistance. Thus sustaining functional self-renewal capacity for immune cells and subverting immune-suppressive signals are potential strategies for boosting the efficacy of immunotherapy. Interleukin-21 (IL-21), a crucial cytokine, which could enhance cytotoxic function of immune cells and reduces immunosuppressive cells enrichment in TME, shows promising orientations as an immunoadjuvant in tumor immunotherapy. This review focuses on IL-21 in cancer treatment, including function and mechanisms of IL-21, preclinical and clinical studies, and future directions for IL-21-assisted therapies.

Translatability of findings from cynomolgus monkey to human suggests a mechanistic role for IL-21 in promoting immunogenicity to an anti-PD-1/IL-21 mutein fusion protein

AMG 256 is a bi-specific, heteroimmunoglobulin molecule with an anti-PD-1 antibody domain and a single IL-21 mutein domain on the C-terminus. Nonclinical studies in cynomolgus monkeys revealed that AMG 256 administration led to the development of immunogenicity-mediated responses and indicated that the IL-21 mutein domain of AMG 256 could enhance the anti-drug antibody response directed toward the monoclonal antibody domain. Anti-AMG 256 IgE were also observed in cynomolgus monkeys. A first-in-human (FIH) study in patients with advanced solid tumors was designed with these risks in mind. AMG 256 elicited ADA in 28 of 33 subjects (84.8%). However, ADA responses were only robust and exposure-impacting at the 2 lowest doses. At mid to high doses, ADA responses remained low magnitude and all subjects maintained exposure, despite most subjects developing ADA. Limited drug-specific IgE were also observed during the FIH study. ADA responses were not associated with any type of adverse event. The AMG 256 program represents a unique case where nonclinical studies informed on the risk of immunogenicity in humans, due to the IL-21-driven nature of the response.

Biological effects of IL-21 on immune cells and its potential for cancer treatment

Interleukin-21 (IL-21), a member of the IL-2 cytokine family, is one of the most important effector and messenger molecules in the immune system. Produced by various immune cells, IL-21 has pleiotropic effects on innate and adaptive immune responses via regulation of natural killer, T, and B cells. An anti-tumor role of IL-21 has also been reported in the literature, as it may support cell proliferation or on the contrary induce growth arrest or apoptosis of the tumor cell. Anti-tumor effect of IL-21 enhances when combined with other agents that target tumor cells, immune regulatory circuits, or other immune-enhancing molecules. Therefore, understanding the biology of IL-21 in the tumor microenvironment (TME) and reducing its systemic toxic and side effects is crucial to ensure the maximum benefits of anti-tumor treatment strategies. In this review, we provide a comprehensive overview on the biological functions, roles in tumors, and the recent advances in preclinical and clinical research of IL-21 in tumor immunotherapy.

Cytokines and their role as immunotherapeutics and vaccine Adjuvants: The emerging concepts

Cytokines are a protein family comprising interleukins, lymphokines, chemokines, monokines and interferons. They are significant constituents of the immune system, and they act in accordance with specific cytokine inhibiting compounds and receptors for the regulation of immune responses. Cytokine studies have resulted in the establishment of newer therapies which are being utilized for the treatment of several malignant diseases. The advancement of these therapies has occurred from two distinct strategies. The first strategy involves administrating the recombinant and purified cytokines, and the second strategy involves administrating the therapeutics which inhibits harmful effects of endogenous and overexpressed cytokines. Colony stimulating factors and interferons are two exemplary therapeutics of cytokines. An important effect of cytokine receptor antagonist is that they can serve as anti-inflammatory agents by altering the treatments of inflammation disorder, therefore inhibiting the effects of tumour necrosis factor. In this article, we have highlighted the research behind the establishment of cytokines as therapeutics and vaccine adjuvants, their role of immunotolerance, and their limitations.

Engineering cytokines for cancer immunotherapy: a systematic review

Cytokines are pivotal mediators of cell communication in the tumor microenvironment. Multiple cytokines are involved in the host antitumor response, but the production and function of these cytokines are usually dysregulated during malignant tumor progression. Considering their clinical potential and the early successful use of cytokines in cancer immunotherapy, such as interferon alpha-2b (IFNα-2b; IntronA^®) and IL-2 (Proleukin^®), cytokine-based therapeutics have been extensively evaluated in many follow-up clinical trials. Following these initial breakthroughs, however, clinical translation of these natural messenger molecules has been greatly limited owing to their high-degree pleiotropic features and complex biological properties in many cell types. These characteristics, coupled with poor pharmacokinetics (a short half-life), have hampered the delivery of cytokines via systemic administration, particularly because of severe dose-limiting toxicities. New engineering approaches have been developed to widen the therapeutic window, prolong pharmacokinetic effects, enhance tumor targeting and reduce adverse effects, thereby improving therapeutic efficacy. In this review, we focus on the recent progress and competitive landscape in cytokine engineering strategies and preclinical/clinical therapeutics for cancer. In addition, aiming to promote engineered cytokine-based cancer immunotherapy, we present a profound discussion about the feasibility of recently developed methods in clinical medicine translation.

Metabolic hallmarks of natural killer cells in the tumor microenvironment and implications in cancer immunotherapy

Natural killer (NK) cells belong to the early responder group against cancerous cells and viral infection. Emerging evidence reveals that distinct metabolic reprogramming occurs concurrently with activation and memory formation of NK cells. However, metabolism of NK cells is disturbed in the tumor immune microenvironment, which may promote tumor progression while limiting immunotherapy responses. In this review, we highlight how cell metabolism influences NK cell activity, the key molecular regulators of NK cell metabolism, and emerging strategies to alter metabolism to improve cytotoxicity of NK cells to kill tumor cells for cancer patients.

Cancer Immunotherapy Beyond Checkpoint Blockade: JACC: CardioOncology State-of-the-Art Review

Avoidance of immune destruction is recognized as one of the hallmarks of cancer development. Although first predicted as a potential antitumor treatment modality more than 50 years ago, the widespread clinical use of cancer immunotherapies has only recently become a reality. Cancer immunotherapy works by reactivation of a stalled pre-existing immune response or by eliciting a de novo immune response, and its toolkit comprises antibodies, vaccines, cytokines, and cell-based therapies. The treatment paradigm in some malignancies has completely changed over the past 10 to 15 years. Massive efforts in preclinical development have led to a surge of clinical trials testing innovative therapeutic approaches as monotherapy and, increasingly, in combination. Here we provide an overview of approved and emerging antitumor immune therapies, focusing on the rich landscape of therapeutic approaches beyond those that block the canonical PD-1/PD-L1 and CTLA-4 axes and placing them in the context of the latest understanding of tumor immunology.

Roles for macrophage-polarizing interleukins in cancer immunity and immunotherapy

Macrophages are the most abundant and one of the most critical cells of tumor immunity. They provide a bridge between innate and adaptive immunity through releasing cytokines into the tumor microenvironment (TME). A number of interleukin (IL) cytokine family members is involved in shaping the final phenotype of macrophages toward either a classically-activated pro-inflammatory M1 state with anti-tumor activity or an alternatively-activated anti-inflammatory M2 state with pro-tumor activity. Shaping TME macrophages toward the M1 phenotype or recovering this phenotypic state may offer a promising therapeutic approach in patients with cancer. Here, we focus on the impact of macrophage-polarizing ILs on immune cells and IL-mediated cellular cross-interactions within the TME. The key aim of this review is to define therapeutic schedules for addressing ILs in cancer immunotherapy based on their multi-directional impacts in such a milieu. Gathering more knowledge on this area is also important for defining adverse effects related to cytokine therapy and addressing them for reinforcing the efficacy of immunotherapy against cancer.

Engineering interferons and interleukins for cancer immunotherapy

Cytokines are a class of potent immunoregulatory proteins that are secreted in response to various stimuli and act locally to regulate many aspects of human physiology and disease. Cytokines play important roles in cancer initiation, progression, and elimination, and thus, there is a long clinical history associated with the use of recombinant cytokines to treat cancer. However, the use of cytokines as therapeutics has been limited by cytokine pleiotropy, complex biology, poor drug-like properties, and severe dose-limiting toxicities. Nevertheless, cytokines are crucial mediators of innate and adaptive antitumor immunity and have the potential to enhance immunotherapeutic approaches to treat cancer. Development of immune checkpoint inhibitors and combination immunotherapies has reinvigorated interest in cytokines as therapeutics, and a variety of engineering approaches are emerging to improve the safety and effectiveness of cytokine immunotherapy. In this review we highlight recent advances in cytokine biology and engineering for cancer immunotherapy.

Cushing syndrome and glucocorticoids: T-cell lymphopenia, apoptosis, and rescue by IL-21

BACKGROUND

Pediatric endogenous Cushing syndrome (eCs) is mainly caused by pituitary corticotropin-producing adenomas, and most glucocorticoid-dependent effects progressively regress upon tumor removal. eCs reproduces long-term, high-dose glucocorticoid therapy, representing a clean, natural, and unbiased model in which to study glucocorticoid bona fide effects on immunity.

OBJECTIVE

We performed extensive immunologic studies in otherwise healthy pediatric patients with eCs before and 6 to 13 months after tumor resection, as well as in in vitro glucocorticoid-treated control cells.

METHODS

Flow cytometry, immunoblotting, enzyme-linked immunosorbent assay, real-time quantitative PCR, and RNA-Seq techniques were used to characterize patients' and in vitro glucocorticoid treated cells.

RESULTS

Reduced thymic output, decreased naive T cells, diminished proliferation, and increased T-cell apoptosis were detected before surgery; all these defects eventually normalized after tumor removal in patients. In vitro studies also showed increased T-cell apoptosis, with correspondingly diminished NF-κB signaling and IL-21 levels. In this setting, IL-21 addition upregulated antiapoptotic BCL2 expression and rescued T-cell apoptosis in a PI3K pathway-dependent manner. Similar and reproducible findings were confirmed in eCs patient cells as well.

CONCLUSIONS

We identified decreased thymic output and lymphocyte proliferation, together with increased apoptosis, as the underlying causes to T-cell lymphopenia in eCs patients. IL-21 was decreased in both natural and in vitro long-term, high-dose glucocorticoid environments, and in vitro addition of IL-21 counteracted the proapoptotic effects of glucocorticoid therapy. Thus, our results suggest that administration of IL-21 in patients receiving long-term, high-dose glucocorticoid therapy may contribute to ameliorate lymphopenia and the complications associated to it.

The Half-Life-Extended IL21 can Be Combined With Multiple Checkpoint Inhibitors for Tumor Immunotherapy

In the era of immune checkpoint blockade cancer therapy, cytokines have become an attractive immune therapeutics to increase response rates. Interleukin 21 (IL21) as a single agent has been evaluated for cancer treatment with good clinical efficacy. However, the clinical application of IL21 is limited by a short half-life and concern about potential immune suppressive effect on dendritic cells. Here, we examined the antitumor function of a half-life extended IL21 alone and in combination with PD-1 blockade using preclinical mouse tumor models. We also determined the immune mechanisms of combination therapy. We found that combination therapy additively inhibited the growth of mouse tumors by increasing the effector function of type 1 lymphocytes. Combination therapy also increased the fraction of type 1 dendritic cells (DC1s) and M1 macrophages in the tumor microenvironment (TME). However, combination therapy also induced immune regulatory mechanisms, including the checkpoint molecules Tim-3, Lag-3, and CD39, as well as myeloid derived suppressor cells (MDSC). This study reveals the mechanisms of IL21/PD-1 cooperation and shed light on rational design of novel combination cancer immunotherapy.

An engineered IL-21 with half-life extension enhances anti-tumor immunity as a monotherapy or in combination with PD-1 or TIGIT blockade

Interleukin-21 (IL-21) has exhibited anti-tumor activity in preclinical and clinical studies; however, its modest efficacy and short half-time has limited its therapeutic utility as a monotherapy. Therefore, we engineered a fusion protein (IL-21-αHSA) in which a nanobody targeting human serum albumin (HSA) was fused to the C-terminus of rhIL-21. The αHSA nanobody displayed broad species cross-reactivity and bound to a HSA epitope that does not overlap with the FcRn binding site, thus providing a strategic design for half-life extension. The IL-21-αHSA fusion protein showed increased stability compared to rhIL-21, while retaining its bioactivity in a liquid solution for at least 6 months. Moreover, IL-21-αHSA showed a dramatically extended half-life and prolonged exposure in cynomolgus monkeys, with the t_1/2 and AUC nearly 10 and 50 times greater than that of rhIL-21, respectively. Furthermore, IL-21-αHSA displayed enhanced anti-tumor efficacy in two syngeneic mouse models. Notably, IL-21-αHSA increased the anti-tumor effect of programmed cell death protein 1 (PD-1) and T cell immunoglobulin and ITIM domain (TIGIT) blockades when used in combination, with a protection against tumor rechallenge, suggesting the formation of long-term anti-tumor memory response. KEGG analysis identified significantly enriched pathways associated with anti-tumor immune response, with increased expression of genes associated with CD8⁺ T and NK cell cytotoxicity. Overall, these data support further clinical evaluation of IL-21-αHSA as a monotherapy or in combination with immune checkpoint blockades.

The Biological Role and Therapeutic Potential of NK Cells in Hematological and Solid Tumors

NK cells are an attractive target for cancer immunotherapy due to their potent antitumor activity. The main advantage of using NK cells as cytotoxic effectors over T cells is a reduced risk of graft versus host disease. At present, several variants of NK-cell-based therapies are undergoing clinical trials and show considerable effectiveness for hematological tumors. In these types of cancers, the immune cells themselves often undergo malignant transformation, which determines the features of the disease. In contrast, the current use of NK cells as therapeutic agents for the treatment of solid tumors is much less promising. Most studies are at the stage of preclinical investigation, but few progress to clinical trials. Low efficiency of NK cell migration and functional activity in the tumor environment are currently considered the major barriers to NK cell anti-tumor therapies. Various therapeutic combinations, genetic engineering methods, alternative sources for obtaining NK cells, and other techniques are aiming at the development of promising NK cell anticancer therapies, regardless of tumorigenesis. In this review, we compare the role of NK cells in the pathogenesis of hematological and solid tumors and discuss current prospects of NK-cell-based therapy for hematological and solid tumors.

Enhancing a Natural Killer: Modification of NK Cells for Cancer Immunotherapy

Natural killer (NK) cells are potent innate immune system effector lymphocytes armed with multiple mechanisms for killing cancer cells. Given the dynamic roles of NK cells in tumor surveillance, they are fast becoming a next-generation tool for adoptive immunotherapy. Many strategies are being employed to increase their number and improve their ability to overcome cancer resistance and the immunosuppressive tumor microenvironment. These include the use of cytokines and synthetic compounds to bolster propagation and killing capacity, targeting immune-function checkpoints, addition of chimeric antigen receptors (CARs) to provide cancer specificity and genetic ablation of inhibitory molecules. The next generation of NK cell products will ideally be readily available as an “off-the-shelf” product and stem cell derived to enable potentially unlimited supply. However, several considerations regarding NK cell source, genetic modification and scale up first need addressing. Understanding NK cell biology and interaction within specific tumor contexts will help identify necessary NK cell modifications and relevant choice of NK cell source. Further enhancement of manufacturing processes will allow for off-the-shelf NK cell immunotherapies to become key components of multifaceted therapeutic strategies for cancer.

A novel vaccinia virus enhances anti-tumor efficacy and promotes a long-term anti-tumor response in a murine model of colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of mortality and morbidity in the world, and there remains an urgent need to develop long-lasting therapies to treat CRC and prevent recurrence in patients. Oncolytic virus therapy (OVT) has demonstrated remarkable efficacy in a number of different cancer models. Here, we report a novel vaccinia virus (VV)-based OVT for treatment of CRC. The novel VV, based on the recently reported novel VVLΔTKΔN1L virus, was armed with the pleiotropic cytokine interleukin-21 (IL-21) to enhance anti-tumor immune responses stimulated after viral infection of tumor cells. Compared with an unarmed virus, VVLΔTKΔN1L-mIL-21 had a superior anti-tumor efficacy in murine CMT93 subcutaneous CRC models in vivo, mediated mainly by CD8+ T cells. Treatment resulted in development of long-term immunity against CMT93 tumor cells, as evidenced by prevention of disease recurrence. These results demonstrate that VVLΔTKΔN1L-mIL-21 is a promising therapeutic agent for treatment of CRC.

α-Pinene Enhances the Anticancer Activity of Natural Killer Cells via ERK/AKT Pathway

Natural killer (NK) cells are lymphocytes that can directly destroy cancer cells. When NK cells are activated, CD56 and CD107a markers are able to recognize cancer cells and release perforin and granzyme B proteins that induce apoptosis in the targeted cells. In this study, we focused on the role of phytoncides in activating NK cells and promoting anticancer effects. We tested the effects of several phytoncide compounds on NK-92mi cells and demonstrated that α-pinene treatment exhibited higher anticancer effects, as observed by the increased levels of perforin, granzyme B, CD56 and CD107a. Furthermore, α-pinene treatment in NK-92mi cells increased NK cell cytotoxicity in two different cell lines, and immunoblot assays revealed that the ERK/AKT pathway is involved in NK cell cytotoxicity in response to phytoncides. Furthermore, CT-26 colon cancer cells were allografted subcutaneously into BALB/c mice, and α-pinene treatment then inhibited allografted tumor growth. Our findings demonstrate that α-pinene activates NK cells and increases NK cell cytotoxicity, suggesting it is a potential compound for cancer immunotherapy.

A systemically deliverable Vaccinia virus with increased capacity for intertumoral and intratumoral spread effectively treats pancreatic cancer

BACKGROUND

Pancreatic cancer remains one of the most lethal cancers and is refractory to immunotherapeutic interventions. Oncolytic viruses are a promising new treatment option, but current platforms demonstrate limited efficacy, especially for inaccessible and metastatic cancers that require systemically deliverable therapies. We recently described an oncolytic vaccinia virus (VV), VVLΔTKΔN1L, which has potent antitumor activity, and a regime to enhance intravenous delivery of VV by pharmacological inhibition of pharmacological inhibition of PI3 Kinase δ (PI3Kδ) to prevent virus uptake by macrophages. While these platforms improve the clinical prospects of VV, antitumor efficacy must be improved.

METHODS

VVLΔTKΔN1L was modified to improve viral spread within and between tumors via viral B5R protein modification, which enhanced production of the extracellular enveloped virus form of VV. Antitumor immunity evoked by viral treatment was improved by arming the virus with interleukin-21, creating VVL-21. Efficacy, functional activity and synergy with α-programmed cell death protein 1 (α-PD1) were assessed after systemic delivery to murine and Syrian hamster models of pancreatic cancer.

RESULTS

VVL-21 could reach tumors after systemic delivery and demonstrated antitumor efficacy in subcutaneous, orthotopic and disseminated models of pancreatic cancer. The incorporation of modified B5R improved intratumoural accumulation of VV. VVL-21 treatment increased the numbers of effector CD8+ T cells within the tumor, increased circulating natural killer cells and was able to polarize macrophages to an M1 phenotype in vivo and in vitro. Importantly, treatment with VVL-21 sensitized tumors to the immune checkpoint inhibitor α-PD1.

CONCLUSIONS

Intravenously administered VVL-21 successfully remodeled the suppressive tumor-microenvironment to promote antitumor immune responses and improve long-term survival in animal models of pancreatic cancer. Importantly, treatment with VVL-21 sensitized tumors to the immune checkpoint inhibitor α-PD1. Combination of PI3Kδ inhibition, VVL-21 and α-PD1 creates an effective platform for treatment of pancreatic cancer.

Molecular Aspects and Future Perspectives of Cytokine-Based Anti-cancer Immunotherapy

Cytokine-based immunotherapy is a promising field in the cancer treatment, since cytokines, as proteins of the immune system, are able to modulate the host immune response toward cancer cell, as well as directly induce tumor cell death. Since a low dose monotherapy with some cytokines has no significant therapeutic results and a high dose treatment leads to a number of side effects caused by the pleiotropic effect of cytokines, the problem of understanding the influence of cytokines on the immune cells involved in the pro- and anti-tumor immune response remains a pressing one. Immune system cells carry CD makers on their surface which can be used to identify various populations of cells of the immune system that play different roles in pro- and anti-tumor immune responses. This review discusses the functions and specific CD markers of various immune cell populations which are reported to participate in the regulation of the immune response against the tumor. The results of research studies and clinical trials investigating the effect of cytokine therapy on the regulation of immune cell populations and their surface markers are also discussed. Current trends in the development of cancer immunotherapy, as well as the role of cytokines in combination with other therapeutic agents, are also discussed.

Engineered IL-21 Cytokine Muteins Fused to Anti-PD-1 Antibodies Can Improve CD8+ T Cell Function and Anti-tumor Immunity

Inhibitors that block the programmed cell death-1 (PD-1) pathway can potentiate endogenous antitumor immunity and have markedly improved cancer survival rates across a broad range of indications. However, these treatments work for only a minority of patients. The efficacy of anti-PD-1 inhibitors may be extended by cytokines, however, the incorporation of cytokines into therapeutic regimens has significant challenges. In their natural form when administered as recombinant proteins, cytokine treatments are often associated with low response rates. Most cytokines have a short half-life which limits their exposure and efficacy. In addition, cytokines can activate counterregulatory pathways, in the case of immune-potentiating cytokines this can lead to immune suppression and thereby diminish their potential efficacy. Improving the drug-like properties of natural cytokines using protein engineering can yield synthetic cytokines with improved bioavailability and tissue targeting, allowing for enhanced efficacy and reduced off-target effects. Using structure guided engineering we have designed a novel class of antibody-cytokine fusion proteins consisting of a PD-1 targeting antibody fused together with an interleukin-21 (IL-21) cytokine mutein. Our bifunctional fusion proteins can block PD-1/programmed death-ligand 1 (PD-L1) interaction whilst simultaneously delivering IL-21 cytokine to PD-1 expressing T cells. Targeted delivery of IL-21 can improve T cell function in a manner that is superior to anti-PD-1 monotherapy. Fusion of engineered IL-21 variants to anti-PD1 antibodies can improve the drug-like properties of IL-21 cytokine leading to improved cytokine serum half-life allowing for less frequent dosing. In addition, we show that targeted delivery of IL-21 can minimize any potential detrimental effect on local antigen-presenting cells. A highly attenuated IL-21 mutein variant (R9E:R76A) fused to a PD-1 antibody provides protection in a humanized mouse model of cancer that is refractory to anti-PD-1 monotherapy. Collectively, our preclinical data demonstrate that this approach may improve upon and extend the utility of anti-PD-1 therapeutics currently in the clinic.

Glypican-3-Specific CAR T Cells Coexpressing IL15 and IL21 Have Superior Expansion and Antitumor Activity against Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death in the world, and curative systemic therapies are lacking. Chimeric antigen receptor (CAR)-expressing T cells induce robust antitumor responses in patients with hematologic malignancies but have limited efficacy in patients with solid tumors, including HCC. IL15 and IL21 promote T-cell expansion, survival, and function and can improve the antitumor properties of T cells. We explored whether transgenic expression of IL15 and/or IL21 enhanced glypican-3-CAR (GPC3-CAR) T cells' antitumor properties against HCC. We previously optimized the costimulation in GPC3-CARs and selected a second-generation GPC3-CAR incorporating a 4-1BB costimulatory endodomain (GBBz) for development. Here, we generated constructs encoding IL15, IL21, or both with GBBz (15.GBBz, 21.GBBz, and 21.15.GBBz, respectively) and examined the ability of transduced T cells to kill, produce effector cytokines, and expand in an antigen-dependent manner. We performed gene-expression and phenotypic analyses of GPC3-CAR T cells and CRISPR-Cas9 knockout of the TCF7 gene. Finally, we measured GPC3-CAR T-cell antitumor activity in murine xenograft models of GPC3+ tumors. The increased proliferation of 21.15.GBBz T cells was at least in part dependent on the upregulation and maintenance of TCF-1 (encoded by TCF7) and associated with a higher percentage of stem cell memory and central memory populations after manufacturing. T cells expressing 21.15.GBBz had superior in vitro and in vivo expansion and persistence, and the most robust antitumor activity in vivo These results provided preclinical evidence to support the clinical evaluation of 21.15.GPC3-CAR T cells in patients with HCC.

Influence of the Tumor Microenvironment on NK Cell Function in Solid Tumors

Natural killer (NK) cells are a population of innate lymphoid cells playing a pivotal role in host immune responses against infection and tumor growth. These cells have a powerful cytotoxic activity orchestrated by an intricate network of inhibitory and activating signals. The importance of NK cells in controlling tumor growth and in mediating a robust anti-metastatic effect has been demonstrated in different experimental mouse cancer models. Consistently, high density of tumor-infiltrating NK cells has been linked with a good prognosis in multiple human solid tumors. However, there are also tumors that appear to be refractory to NK cell-mediated killing for the presence of an immunosuppressive microenvironment affecting NK cell function. Immunotherapeutic strategies aimed at restoring and increasing the cytotoxic activity of NK cells in solid tumors, including the adoptive transfer of NK and CAR-NK cells, are currently employed in preclinical and clinical studies. In this review, we outline recent advances supporting the direct role of NK cells in controlling expansion of solid tumors and their prognostic value in human cancers. We summarize the mechanisms adopted by cancer cells and the tumor microenvironment to affect NK cell function, and finally we evaluate current strategies to augment the antitumor function of NK cells for the treatment of solid tumors.

T Follicular Helper Cell Subsets and the Associated Cytokine IL-21 in the Pathogenesis and Therapy of Asthma

For many decades, T helper 2 (TH2) cells have been considered to predominantly regulate the pathogenic manifestations of allergic asthma, such as IgE-mediated sensitization, airway hyperresponsiveness, and eosinophil infiltration. However, recent discoveries have significantly shifted our understanding of asthma from a simple TH2 cell-dependent disease to a heterogeneous disease regulated by multiple T cell subsets, including T follicular helper (TFH) cells. TFH cells, which are a specialized cell population that provides help to B cells, have attracted intensive attention in the past decade because of their crucial role in regulating antibody response in a broad range of diseases. In particular, TFH cells are essential for IgE antibody class-switching. In this review, we summarize the recent progress regarding the role of TFH cells and their signature cytokine interleukin (IL)-21 in asthma from mouse studies and clinical reports. We further discuss future therapeutic strategies to treat asthma by targeting TFH cells and IL-21.

Adoptive Transfer of Interleukin-21-stimulated Human CD8+ T Memory Stem Cells Efficiently Inhibits Tumor Growth

Memory stem T (T_SCM) cells, a new subset of memory T cells with self-renewal and multipotent capacities, are considered as a promising candidates for adoptive cellular therapy. However, the low proportion of human T_SCM cells in total CD8⁺ T cells limits their utility. Here, we aimed to induce human CD8⁺ T_SCM cells by stimulating naive precursors with interleukin-21 (IL-21). We found that IL-21 promoted the generation of T_SCM cells, described as CD45RA⁺CD45RO⁻CD62L⁺CCR7⁺CD122⁺CD95⁺ cells, with a higher efficiency than that observed with other common γ-chain cytokines. Upon adoptive transfer into an A375 melanoma mouse model, these lymphocytes mediated much stronger antitumor responses. Further mechanistic analysis revealed that IL-21 activated the Janus kinase signal transducer and activator of transcription 3 pathway by upregulating signal transducer and activator of transcription 3 phosphorylation and consequently promoting the expression of T-bet and suppressor of cytokine signaling 1, but decreasing the expression of eomesodermin and GATA binding protein 3. Our findings provide novel insights into the generation of human CD8⁺ T_SCM cells and reveal a novel potential clinical application of IL-21.

Irradiated Bladder Cancer Cells Expressing both GM-CSF and IL-21 versus Either GM-CSF or IL-21 Alone as Tumor Vaccine in a Mouse Xenograft Model

Previous studies have established the efficacy of irradiated cancer cells overexpressing GM-CSF or IL-21 as a vaccine. Here we examined whether the vaccine efficacy was greater when both factors were overexpressed together. MB49 bladder cancer cells were transfected with expression plasmid pT7TS encoding mouse GM-CSF and human IL-21, and then irradiated with 100 Gy at 4 days later. The cells (1×107 per animal) were injected subcutaneously into C57BL/6 mice at 0, 4, 8, and 12 days after inoculation with MB49 tumor xenografts. Control animals were injected with MB49 cells transfected with pT7TS encoding GM-CSF or IL-21 on its own. Tumor growth was monitored for 45 days and compared among the groups using repeated-measures ANOVA. Vaccination with irradiated MB49 cells did not affect xenograft growth. Vaccination with irradiated cells overexpressing GM-CSF or IL-21 alone significantly inhibited tumor growth and led to significantly more CD4+ CD8+ T cells and fewer CD4+ Foxp3+ T cells in the spleen and xenograft. These effects were even greater following vaccination with irradiated cells overexpressing both GM-CSF and IL-21. Irradiated bladder cancer cells overexpressing both GM-CSF and IL-21 are more effective than cells expressing either factor alone as a vaccine against bladder cancer.

Fueling Cancer Immunotherapy With Common Gamma Chain Cytokines

Adoptive T cell transfer therapy (ACT) using tumor infiltrating lymphocytes or lymphocytes redirected with antigen receptors (CAR or TCR) has revolutionized the field of cancer immunotherapy. Although CAR T cell therapy mediates robust responses in patients with hematological malignancies, this approach has been less effective for treating patients with solid tumors. Additionally, toxicities post T cell infusion highlight the need for safer ACT protocols. Current protocols traditionally expand T lymphocytes isolated from patient tumors or from peripheral blood to large magnitudes in the presence of high dose IL-2 prior to infusion. Unfortunately, this expansion protocol differentiates T cells to a full effector or terminal phenotype in vitro, consequently reducing their long-term survival and antitumor effectiveness in vivo. Post-infusion, T cells face further obstacles limiting their persistence and function within the suppressive tumor microenvironment. Therapeutic manipulation of T cells with common γ chain cytokines, which are critical growth factors for T cells, may be the key to bypass such immunological hurdles. Herein, we discuss the primary functions of the common γ chain cytokines impacting T cell survival and memory and then elaborate on how these distinct cytokines have been used to augment T cell-based cancer immunotherapy.

Overcoming Resistance to Natural Killer Cell Based Immunotherapies for Solid Tumors

Despite advances in the diagnostic and therapeutic modalities, the prognosis of several solid tumor malignancies remains poor. Different factors associated with solid tumors including a varied genetic signature, complex molecular signaling pathways, defective cross talk between the tumor cells and immune cells, hypoxic and immunosuppressive effects of tumor microenvironment result in a treatment resistant and metastatic phenotype. Over the past several years, immunotherapy has emerged as an attractive therapeutic option against multiple malignancies. The unique ability of natural killer (NK) cells to target cancer cells without antigen specificity makes them an ideal candidate for use against solid tumors. However, the outcomes of adoptive NK cell infusions into patients with solid tumors have been disappointing. Extensive studies have been done to investigate different strategies to improve the NK cell function, trafficking and tumor targeting. Use of cytokines and cytokine analogs has been well described and utilized to enhance the proliferation, stimulation and persistence of NK cells. Other techniques like blocking the human leukocyte antigen-killer cell receptors (KIR) interactions with anti-KIR monoclonal antibodies, preventing CD16 receptor shedding, increasing the expression of activating NK cell receptors like NKG2D, and use of immunocytokines and immune checkpoint inhibitors can enhance NK cell mediated cytotoxicity. Using genetically modified NK cells with chimeric antigen receptors and bispecific and trispecific NK cell engagers, NK cells can be effectively redirected to the tumor cells improving their cytotoxic potential. In this review, we have described these strategies and highlighted the need to further optimize these strategies to improve the clinical outcome of NK cell based immunotherapy against solid tumors.

NK Cell-Based Immunotherapy in Cancer Metastasis

Metastasis represents the leading cause of cancer-related death mainly owing to the limited efficacy of current anticancer therapies on advanced malignancies. Although immunotherapy is rendering promising results in the treatment of cancer, many adverse events and factors hampering therapeutic efficacy, especially in solid tumors and metastases, still need to be solved. Moreover, immunotherapeutic strategies have mainly focused on modulating the activity of T cells, while Natural Killer (NK) cells have only recently been taken into consideration. NK cells represent an attractive target for cancer immunotherapy owing to their innate capacity to eliminate malignant tumors in a non-Major Histocompatibility Complex (MHC) and non-tumor antigen-restricted manner. In this review, we analyze the mechanisms and efficacy of NK cells in the control of metastasis and we detail the immunosubversive strategies developed by metastatic cells to evade NK cell-mediated immunosurveillance. We also share current and cutting-edge clinical approaches aimed at unleashing the full anti-metastatic potential of NK cells, including the adoptive transfer of NK cells, boosting of NK cell activity, redirecting NK cell activity against metastatic cells and the release of evasion mechanisms dampening NK cell immunosurveillance.

Human TH9 differentiation is dependent on signal transducer and activator of transcription (STAT) 3 to restrain STAT1-mediated inhibition

BACKGROUND

Patients with loss-of-function (LOF) signal transducer and activator of transcription 3 (STAT3) mutations have dermatitis, enhanced IgE production despite a relative lack of immediate hypersensitivity, recurrent infection, and an increased rate of lymphoma in addition to a number of skeletal and connective tissue abnormalities. Patients with STAT1 gain-of-function (GOF) mutations also have susceptibility to candidiasis and sinopulmonary infection, as well as autoimmunity and squamous cell carcinoma, in addition to even more broad phenotypes.

OBJECTIVE

Because of the link between T_H9 cells and allergic inflammation, autoimmunity, and antitumor surveillance and because evidence shows a role for either STAT3 or STAT1 in T_H9 differentiation conflicts, we sought to determine the status on this lineage of STAT1 GOF and STAT3 LOF mutations in human subjects.

METHODS

We detected IL-9 levels and T_H9 differentiation in patients with STAT3 LOF and STAT1 GOF mutations, together with T_H9 transcript factors, and partially rescued their deficiency in vitro by adding cytokines they lacked or transfecting key molecules.

RESULTS

We found that PBMCs or sorted naive CD4⁺ T cells from patients with STAT3 LOF and STAT1 GOF mutations had impaired T_H9 generation/differentiation. STAT3 inhibition in normal T_H9 cultures diminished early IL-21 induction and late IL-9 production, whereas exogenous IL-21 enhanced T_H9 differentiation, even with STAT3 inhibition, by restoring suppressor of cytokine signaling 3 expression and thus inhibiting excessive phosphorylated signal transducer and activator of transcription (p-STAT) 1 activation. Furthermore, exogenous expression of suppressor of cytokine signaling 3 or either T-bet or STAT1 RNA interference in STAT3 LOF cells partially rescued IL-9 differentiation.

CONCLUSION

Collectively, these results suggest that human T_H9 differentiation depends on normal p-STAT3 and IL-21 production to suppress p-STAT1 activation and T-bet transcription.

Strategies for enhancing adoptive T-cell immunotherapy against solid tumors using engineered cytokine signaling and other modalities

INTRODUCTION

Cancer therapy has been transformed by the demonstration that tumor-specific T-cells can eliminate tumor cells in a clinical setting with minimal long-term toxicity. However, significant success in the treatment of leukemia and lymphoma with T-cells using native receptors or redirected with chimeric antigen receptors (CARs) has not been recapitulated in the treatment of solid tumors. This lack of success is likely related to the paucity of costimulatory and cytokine signaling available in solid tumors, in addition to a range of inhibitory mechanisms.

AREAS COVERED

We summarize the latest developments in engineered T-cell immunotherapy, describe the limitations of these approaches in treating solid tumors, and finally highlight several strategies that may be useful in mediating solid tumor responses in the future, while also ensuring safety of engineered cells.

EXPERT OPINION

CAR-T therapies require further engineering to achieve their potential against solid tumors. Facilitating cytokine signaling in CAR T-cells appears to be essential in achieving better responses. However, the engineering of T-cells with potentially unchecked proliferation and potency raises the question of whether the simultaneous combination of enhancements will prove safe, necessitating continued advancements in regulating CAR-T activity at the tumor site and methods to safely switch off these engineered cells.

IL21 Therapy Combined with PD-1 and Tim-3 Blockade Provides Enhanced NK Cell Antitumor Activity against MHC Class I-Deficient Tumors

Increased expression of coinhibitory molecules such as PD-1 and Tim-3 on NK cells has been demonstrated in advanced cancer patients who harbor MHC class I-deficient tumors. However, even in preclinical models, the antitumor effects of checkpoint blockade on NK cells have not been clearly elucidated. Here, we show that anti-PD-1/anti-Tim-3 treatment suppressed tumor progression in mice bearing MHC class I-deficient tumors, and the suppression was further enhanced by recombinant IL21 (rIL21) treatments through an NK-cell-dependent mechanism. We also show that the intratumoral delivery of rIL21 attracted NK cells to the tumor site in a CXCR3-dependent fashion. A combination of IL21 and checkpoint blockade facilitated the effector function of exhausted NK cells in cancer patients. Given the effects of the checkpoint blockade and rIL21 combination on NK cells infiltrating into MHC class I-deficient tumors, we suggest that the efficacy of checkpoint blockade can be enhanced through the administration of IL21 for advanced cancer patients with MHC class I-low/deficient tumors. Cancer Immunol Res; 6(6); 685-95. ©2018 AACR.

Identification of patient-specific and tumor-shared T cell receptor sequences in renal cell carcinoma patients

A major requirement for cancer immunotherapy is the development of biomarkers for prognosis and for monitoring therapy response. In an attempt to evaluate the immune response of renal cell carcinoma (RCC) patients, tumor lesions and / or blood samples from 12 RCC patients underwent deep T cell receptor (TCR) sequencing. Despite the low number of samples, different TCR distribution patterns could be detected. Most of the RCC patients presented "patient-specific" TCR sequences, and those clonotypes were present at higher frequency in tumor lesions suggesting a specific extravasation from the blood. Comparison among the tumor samples revealed also "patient-shared" TCR patterns. Indeed, a central core of 16 different TCRs were shared by 3 patients, whereas other 6 patients shared between 4 and 6 TCR sequences, with two sub-groups sharing 12 to 17 different clonotypes. The relative frequencies of shared clonotypes were very different varying from < 1% to a maximum of 37% of the total TCR repertoire. These data confirm the presence of tumor-specific TCR within the cancer tissue and suggest the existence of shared epitopes among different patients that might be used as targets for tumor immunotherapy.

Interleukin-21 combined with PD-1 or CTLA-4 blockade enhances antitumor immunity in mouse tumor models

Recent advances in cancer treatment with checkpoint blockade of receptors such as CTLA-4 and PD-1 have demonstrated that combinations of agents with complementary immunomodulatory effects have the potential to enhance antitumor activity as compared to single agents. We investigated the efficacy of immune-modulatory interleukin-21 (IL-21) combined with checkpoint blockade in several syngeneic mouse tumor models. After tumor establishment, mice were administered recombinant mouse IL-21 (mIL-21) alone or in combination with blocking monoclonal antibodies against mouse PD-1 or CTLA-4. In contrast to monotherapy, IL-21 enhanced antitumor activity of mCTLA-4 mAb in four models and anti-PD-1 mAb in two models, with evidence of synergy for one or both of the combination treatments in the EMT-6 and MC38 models. The enhanced efficacy was associated with increased intratumoral CD8+ T cell infiltrates, CD8+ T cell proliferation, and increased effector memory T cells, along with decreased frequency of central memory CD8+ T cells. In vivo depletion of CD8+ T cells abolished the antitumor activities observed for both combination and monotherapy treatments, further supporting a beneficial role for CD8+ T cells. In all studies, the combination therapies were well tolerated. These results support the hypothesis that the combination of recombinant human IL-21 with CTLA-4 or PD-1 monoclonal antibodies could lead to improved outcomes in cancer patients.

Unveil the mysterious mask of cytokine-based immunotherapy for melanoma

Melanoma is the leading cause of death among all skin cancers and its incidence continues to rise rapidly worldwide in the past decades. The available treatment options for melanoma remain limited despite extensive clinical research. Melanoma is an immunogenic tumor and great advances in immunology in recent decades allow for the development of immunotherapeutic agents against melanoma. In recent years, immunotherapy utilizing cytokines has been particularly successful in certain cancers and holds promise for patients with advanced melanoma. In this review, an overview of the current status and emerging perspectives on cytokine immunotherapy for melanoma are discussed in details. Such a study will be helpful to unveil the mysterious mask of cytokine-based immunotherapy for melanoma.

Antibody-Based Cancer Therapy: Successful Agents and Novel Approaches

Since their discovery, antibodies have been viewed as ideal candidates or "magic bullets" for use in targeted therapy in the fields of cancer, autoimmunity, and chronic inflammatory disorders. A wave of antibody-dedicated research followed, which resulted in the clinical approval of a first generation of monoclonal antibodies for cancer therapy such as rituximab (1997) and cetuximab (2004), and infliximab (2002) for the treatment of autoimmune diseases. More recently, the development of antibodies that prevent checkpoint-mediated inhibition of T cell responses invigorated the field of cancer immunotherapy. Such antibodies induced unprecedented long-term remissions in patients with advanced stage malignancies, most notably melanoma and lung cancer, that do not respond to conventional therapies. In this review, we will recapitulate the development of antibody-based therapy, and detail recent advances and new functions, particularly in the field of cancer immunotherapy. With the advent of recombinant DNA engineering, a number of rationally designed molecular formats of antibodies and antibody-derived agents have become available, and we will discuss various molecular formats including antibodies with improved effector functions, bispecific antibodies, antibody-drug conjugates, antibody-cytokine fusion proteins, and T cells genetically modified with chimeric antigen receptors. With these exciting advances, new antibody-based treatment options will likely enter clinical practice and pave the way toward more successful control of malignant diseases.

Adenovirus-mediated interleukin 21 gene transfer enhances antitumor immunity and reduces tumorigenicity of Hepa1-6 in mice

In the present study, adenovirus-mediated interleukin 21 (Ad5-IL-21-EGFP) gene expression was induced in Hepa1–6 cells to investigate whether IL-21 was capable of enhancing antitumor immunity and reducing tumorigenicity of Hepa1–6 in a mouse model. Mice were inoculated intradermally into the right flank with Hepa1–6 cells or Hepa1–6 cells infected with Ad5 or Ad5-IL-21. Four weeks later, the mice were sacrificed humanely, and the tumor volume, tumor weight and mouse spleen index were measured. The levels of IL-21, IL-4 and interferon (IFN)-γ levels in mouse serum and tumor tissues were detected by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. Cell counting kit-8 (CCK-8) assay was used to detect the killing ability of spleen T cells and natural killer (NK) cells, and the proliferation ability of T cells. The expression of IL-21 was confirmed by reverse transcription-polymerase chain reaction, western blot analysis and ELISA assay in Ad5-IL-21-EGFP-infected Hepa1–6 cells. The overexpression of IL-21 significantly reduced the tumorigenicity of Hepa1–6 cells. The tumor volumes and tumor weights in Ad5-IL-21-Hepa1–6 mice were much smaller than those in the Ad5-Hepa1–6 group and Hepa1–6 wild-type group. The immunohistochemistry and ELISA assay demonstrated that IL-21 and IFN-γ levels were much higher while the IL-4 level was much lower in the Ad5-IL-21-Hepa1–6 group than in the other two groups. CCK-8 assay revealed that the killing ability of NK cells and T cells, and the proliferation ability of T cells in Ad5-IL-21-Hepa1–6 mice were higher than in the other two groups; the spleen index of Ad5-IL-21-Hepa1–6 mice was also higher than in the other groups. The data had a significant difference (P<0.01). In conclusion, IL-21 reduces tumorigenicity of Hepa1–6 by a mechanism involving enhanced activation of cell-mediated immunity in tumor-bearing mice.

Improving Adoptive T Cell Therapy: The Particular Role of T Cell Costimulation, Cytokines, and Post-Transfer Vaccination

Adoptive cellular therapy (ACT) is a form of immunotherapy whereby antigen-specific T cells are isolated or engineered, expanded ex vivo, and transferred back to patients. Clinical benefit after ACT has been obtained in treatment of infection, various hematological malignancies, and some solid tumors; however, due to poor functionality and persistence of the transferred T cells, the efficacy of ACT in the treatment of most solid tumors is often marginal. Hence, much effort is undertaken to improve T cell function and persistence in ACT and significant progress is being made. Herein, we will review strategies to improve ACT success rates in the treatment of cancer and infection. We will deliberate on the most favorable phenotype for the tumor-specific T cells that are infused into patients and on how to obtain T cells bearing this phenotype by applying novel ex vivo culture methods. Moreover, we will discuss T cell function and persistence after transfer into patients and how these factors can be manipulated by means of providing costimulatory signals, cytokines, blocking antibodies to inhibitory molecules, and vaccination. Incorporation of these T cell stimulation strategies and combinations of the different treatment modalities are likely to improve clinical response rates further.

Interleukin 21 - its potential role in the therapy of B-cell lymphomas

Interleukin-21 (IL-21), a member of IL-2 cytokine family, has pleotropic biological effects on lymphoid and myeloid cells. During the past 15 years, since the discovery of IL-21, great advances have been made regarding its biological activity and the mechanisms controlling IL-21-mediated cellular responses, especially in hematological malignancies. Preclinical studies have shown that IL-21R is expressed on healthy and neoplastic B-cells and exogenous IL-21 can induce direct apoptosis of IL-21R expressing B-cell non-Hodgkin lymphomas (NHL), making it a potentially attractive anti-lymphoma therapy. However, in some hematological malignancies such as multiple myeloma, Hodgkin lymphoma and Burkitt lymphoma, IL-21 can induce proliferation of neoplastic B-cells. In NHL, the underlying mechanism of cell death was found to be different between the various subtypes, including activation of different JAK/STAT signal transduction pathways or other factors. Immunomodulatory effects of IL-21 have also been reported to contribute to its anti-tumor effects as described by earlier studies in solid tumors and B-cell associated malignancies. These effects are predominantly mediated by IL-21's ability to activate cytolytic activities by NK-cells and CD4⁺/CD8⁺ T-cells. In this review, we provide an overview of IL-21's effects in NHL, results from clinical trials utilizing IL-21, and propose how IL-21 can be therapeutically exploited for treating these lymphomas.

Checkpoint inhibitors and other novel immunotherapies for advanced renal cell carcinoma

The management of advanced renal cell carcinoma (RCC) has dramatically changed over the past decade. Therapies that target the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) pathways have considerably expanded treatment options; however, most patients with advanced RCC still have limited overall survival. Increased understanding of the mechanisms of T cell-antigen recognition and function has led to the development of novel immunotherapies to treat cancer, chief among them inhibitors of checkpoint receptors - molecules whose function is to restrain the host immune response. In 2015, the FDA approved the first checkpoint inhibitor nivolumab for patients with advanced RCC following treatment with antiangiogenic therapy based on improved overall survival compared with the standard of care. Ongoing phase III trials are comparing checkpoint-inhibitor-based combination regimens with antiangiogenesis agents in the first-line setting. The field is evolving rapidly, with many clinical trials already testing several checkpoint inhibitors alone, in combination, or with other targeted therapies. In addition, different novel immune therapies are being investigated including vaccines, T-cell agonists, and chimeric antigen receptor T cells. Determining which patients will benefit from these therapies and which combination approaches will result in better response will be important as this field evolves.

NKTR-214, an Engineered Cytokine with Biased IL2 Receptor Binding, Increased Tumor Exposure, and Marked Efficacy in Mouse Tumor Models

PURPOSE

Aldesleukin, recombinant human IL2, is an effective immunotherapy for metastatic melanoma and renal cancer, with durable responses in approximately 10% of patients; however, severe side effects limit maximal dosing and thus the number of patients able to receive treatment and potential cure. NKTR-214 is a prodrug of conjugated IL2, retaining the same amino acid sequence as aldesleukin. The IL2 core is conjugated to 6 releasable polyethylene glycol (PEG) chains. In vivo, the PEG chains slowly release to generate active IL2 conjugates.

EXPERIMENTAL DESIGN

We evaluated the bioactivity and receptor binding of NKTR-214 and its active IL2 conjugates in vitro; the tumor immunology, tumor pharmacokinetics, and efficacy of NKTR-214 as a single agent and in combination with anti-CTLA-4 antibody in murine tumor models. Tolerability was evaluated in non-human primates.

RESULTS

In a murine melanoma tumor model, the ratio of tumor-killing CD8(+) T cells to Foxp3(+) regulatory T cells was greater than 400 for NKTR-214 compared with 18 for aldesleukin, supporting preferential activation of the IL2 receptor beta over IL2 receptor alpha, due to the location of PEG molecules. NKTR-214 provides a 500-fold greater exposure of the tumor to conjugated IL2 compared with aldesleukin. NKTR-214 showed efficacy as a single agent and provided durable immunity that was resistant to tumor rechallenge in combination with anti-CTLA-4 antibody. NKTR-214 was well tolerated in non-human primates.

CONCLUSIONS

These data support further evaluation of NKTR-214 in humans for a variety of tumor types, adding to the repertoire of potent and potentially curative cancer immunotherapies.