IL-21 activates both innate and adaptive immunity to generate potent antitumor responses that require perforin but are independent of IFN-gamma

Multiomics Analysis of Interleukin-21 as a Potential Immunologic and Biomarker in Hepatocellular Carcinoma

Interleukin-21 (IL-21) is an important antitumor cytokine that contributes to the proliferation and differentiation of CD8+ T cells. It has been proven to enhance the response to immune checkpoint inhibitors (ICIs) in various solid tumors. However, its role in hepatocellular carcinoma (HCC) has not yet been clarified. In this research, we aimed to investigate the antitumor effect of IL-21 in HCC and its effect on ICI treatment. Through transcriptome sequencing analysis and immunohistochemistry validation, we found that patients with high IL-21 expression had a better prognosis. HCCs with high expression of IL-21 had higher infiltration of CD8+ T cells, increased expression of immune checkpoints, and an improved response to ICI treatment. In conclusion, IL-21 can enhance the efficacy of ICI treatment and improve the prognosis of patients by promoting the infiltration of CD8+ T cells and the expression of immune checkpoint-related genes.

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.

Melanocytotoxic chemicals and their toxic mechanisms

Melanocyte cell death can lead to various melanocyte-related skin diseases including vitiligo and leukoderma. Melanocytotoxic chemicals are one of the most well-known causes of nongenetic melanocyte-related diseases, which induce melanocyte cell death through apoptosis. Various chemicals used in cosmetics, medicine, industry and food additives are known to induce melanocyte cell death, which poses a significant risk to the health of consumers and industrial workers. This review summarizes recently reported melanocytotoxic chemicals and their mechanisms of toxicity in an effort to provide insight into the development of safer chemicals.

Saga of monokines in shaping tumour-immune microenvironment: Origin to execution

Cellular communication mediated by cytokines is an important mechanism dictating immune responses, their cross talk and final immune output. Cytokines play a major role in dictating the immune outcome to cancer by regulating the events of development, differentiation and activation of innate immune cells. Cytokines are pleiotropic in nature, hence understanding their role individually or as member of network cytokines is critical to delineate their role in tumour immunity. Tumour systemically manipulates the immune system to evade and escape immune recognition for their uncontrollable growth and metastasis. The developing tumour comprise a large and diverse set of myeloid cells which are vulnerable to manipulation by the tumour-microenvironment. The innate immune cells of the monocytic lineage skew the fate of the adaptive immune cells and thus dictating cancer elimination or progression. Targeting cells at tumour cite is preposterous owing to their tight network, poor reach and abundance of immunosuppressive mechanisms. Monocytic lineage-derived cytokines (monokines) play crucial role in tumour regression or progression by either directly killing the tumour cells with TNFα or promoting its growth by TGFβ. In addition, the monokines like IL-12, IL-1β, IL-6, IL-10 and TGFβ direct the adaptive immune cells to secrete anti-tumour cytokines, TNFα, IFNγ, perforin and granzyme or pro-tumour cytokines, IL-10 and TGFβ. In this review, we elucidate the roles of monokines in dictating the fate of tumour by regulating responses at various stages of generation, differentiation and activation of immune cells along with the extensive cross talk. We have attempted to delineate the synergy and antagonism of major monokines among themselves or with tumour-derived or adaptive immune cytokines. The review provides an update on the possibilities of placing monokines to potential practical use as cytokine therapy against cancer.

The War Is on: The Immune System against Glioblastoma—How Can NK Cells Drive This Battle?

Natural killer (NK) cells are innate lymphocytes that play an important role in immunosurveillance, acting alongside other immune cells in the response against various types of malignant tumors and the prevention of metastasis. Since their discovery in the 1970s, they have been thoroughly studied for their capacity to kill neoplastic cells without the need for previous sensitization, executing rapid and robust cytotoxic activity, but also helper functions. In agreement with this, NK cells are being exploited in many ways to treat cancer. The broad arsenal of NK-based therapies includes adoptive transfer of in vitro expanded and activated cells, genetically engineered cells to contain chimeric antigen receptors (CAR-NKs), in vivo stimulation of NK cells (by cytokine therapy, checkpoint blockade therapies, etc.), and tumor-specific antibody-guided NK cells, among others. In this article, we review pivotal aspects of NK cells’ biology and their contribution to immune responses against tumors, as well as providing a wide perspective on the many antineoplastic strategies using NK cells. Finally, we also discuss those approaches that have the potential to control glioblastoma—a disease that, currently, causes inevitable death, usually in a short time after diagnosis.

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.

IL-21 Signaling in the Tumor Microenvironment

IL-21 is an immunomodulatory cytokine produced by natural killer (NK) cells and T cells that has pleiotropic roles in immune and nonimmune cells. IL-21 can modulate innate and specific immunity activities. It is a potent stimulator of T and natural killer cell-mediated antitumor immunity but also has pro-inflammatory functions in many tissues and is involved in oncogenesis. It is important to understand IL-21 biology in these different situations to ensure the maximal benefit of therapeutic strategies targeting this cytokine. This chapter summarizes IL-21 characteristics and signaling, its role in immune system components, and its use in cancer immunotherapies.

The connection between the Th17 cell related cytokines and cancer stem cells in cancer: Novel therapeutic targets

Cancer Stem Cells (CSCs) are the subpopulation of cells present in the different types of cancers with capabilities of self-renewal, differentiation, and tumorigenicity when transplanted into an animal host. The research work on the CSC has been providing a promising approach for the improvement of cancer therapies in the future. The CSCs have a close connection with the cytokines related with the T helper 17 (Th17) cell and other factors present in the tumor microenvironment, and these play a pivotal role in tumor progression and metastasis. The properties of CSCs are well defined in various type of tumor which is mainly developed by chemically and spontaneously in murine cancer model but in human defined primarily on acute myeloid leukemia, glioma, and breast cancer. The role of Th1, Th2, Natural Killer cells are well described in the cancer biology, but the Th17 cells are the subset which is recently exploited, and lots of research are going on. In this Review, we summarize current findings of the characteristics and functions of the Th17 cell and its signature cytokines in different cancers and their interconnections with cancer stem cells and with their markers. We have also discussed the functional properties of CSCs and how the CSCs markers can be distinguished from normal stem cells markers. We have also talked about the strategies that are efficiently targeting of CSCs and Th17 cells in different cancers.

The association between interleukin-21 (rs2055979G/T) gene polymorphism and the risk of hepatocellular carcinoma and metastasis in patients with hepatitis C virus

Cancer prevalence is critically increasing worldwide; accordingly, improved prediction and therapeutic tools are necessary. Interleukin (IL)-21 is a potent antitumor cytokine, and the relationship between its gene variations and cancer risk is well established. Nevertheless, so far no study has investigated its role in hepatocellular carcinoma (HCC) progression and metastasis in hepatitis C virus (HCV)-infected people. Therefore, the present investigation was led on 267 Egyptian participants, involving 177 patients with HCV of which 90 patients had HCC (HCC group), 87 patients without HCC (non-HCC group), and 90 unrelated healthy controls. The association between rs2221903A/G and rs2055979G/T of the IL-21 gene and the risk of HCC and metastasis, as well as the clinico-pathological features, were analyzed. While rs2221903A/G polymorphism was not polymorphic in our cohort, patients carrying the genotype TT and allele T of the rs2055979G/T polymorphism had a significantly lower risk of HCC when comparing with HCC group and healthy controls. Also, participants carrying the aforementioned genotype and allele had a significantly lower risk of metastasis when comparing metastatic group with both nonmetastatic group and control group. The rs2055979G/T polymorphism was not significantly associated with clinico-pathological features of HCC. This is the first study to report a relationship between an intronic polymorphism in IL-21 gene and HCC and metastasis risk in the Egyptian people, in addition to identifying a potential new marker for the early detection and treatment of HCC.

The Number of Donor-Specific IL-21 Producing Cells Before and After Transplantation Predicts Kidney Graft Rejection

Interleukin (IL)-21 supports induction and expansion of CD8⁺ T cells, and can also regulate the differentiation of B cells into antibody-producing plasma cells. We questioned whether the number of circulating donor-specific IL-21 producing cells (pc) can predict kidney transplant rejection, and evaluated this in two different patient cohorts. The first analysis was done on pre-transplantation samples of 35 kidney transplant recipients of whom 15 patients developed an early acute rejection. The second study concerned peripheral blood mononuclear cell (PBMC) samples from 46 patients obtained at 6 months after kidney transplantation of whom 13 developed late rejection. Significantly higher frequencies of donor-specific IL-21 pc were found by Elispot assay in both patients who developed early and late rejection compared to those without rejection. In addition, low frequencies of donor-specific IL-21 pc were associated with higher rejection-free survival. Moreover, low pre-transplant donor-specific IL-21 pc numbers were associated with the absence of anti-HLA antibodies. Donor-reactive IL-21 was mainly produced by CD4⁺ T cells, including CD4⁺ follicular T helper cells. In conclusion, the number of donor-specific IL-21 pc is associated with an increased risk of both early and late rejection, giving it the potential to be a new biomarker in kidney transplantation.

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.

Cytokines in Cancer Immunotherapy

Cytokines that control the immune response were shown to have efficacy in preclinical murine cancer models. Interferon (IFN)-α is approved for treatment of hairy cell leukemia, and interleukin (IL)-2 for the treatment of advanced melanoma and metastatic renal cancer. In addition, IL-12, IL-15, IL-21, and granulocyte macrophage colony-stimulating factor (GM-CSF) have been evaluated in clinical trials. However, the cytokines as monotherapy have not fulfilled their early promise because cytokines administered parenterally do not achieve sufficient concentrations in the tumor, are often associated with severe toxicities, and induce humoral or cellular checkpoints. To circumvent these impediments, cytokines are being investigated clinically in combination therapy with checkpoint inhibitors, anticancer monoclonal antibodies to increase the antibody-dependent cellular cytotoxicity (ADCC) of these antibodies, antibody cytokine fusion proteins, and anti-CD40 to facilitate tumor-specific immune responses.

The role of CMV in glioblastoma and implications for immunotherapeutic strategies

Controversy surrounds the role of cytomegalovirus (CMV) in glioblastoma (GBM). However, several studies have shown that CMV nucleic acids and proteins are present within GBM tumor tissue. CMV has been implicated in GBM pathogenesis by affecting tumor stem cell factors, angiogenesis and immune pathways. Anti-viral therapy has not been found to definitively improve outcomes for patients with GBM. Several studies have leveraged CMV by targeting CMV antigens using ex-vivo expanded T cells or dendritic cell vaccines. The initial results from these studies are promising and larger studies are underway.

Cytokines in the Treatment of Cancer

Cytokines are major regulators of innate and adaptive immunity that enable cells of the immune system to communicate over short distances. Cytokine therapy to activate the immune system of cancer patients has been an important treatment modality and continues to be a key contributor to current clinical cancer research. Interferon alpha (IFNα) is approved for adjuvant treatment of completely resected high-risk melanoma patients and several refractory malignancies. High-dose interleukin-2 (HDIL-2) is approved for treatment of metastatic renal cell cancer and melanoma, but both agents are currently less commonly used with the development of newer agents. Granulocyte-macrophage colony-stimulating factor (GM-CSF), IFN gamma (IFNγ), IL-7, IL-12, and IL-21 were evaluated in clinical trials and remain part of certain investigational trials. The initial single-agent clinical trials with the long-awaited IL-15 have been completed and combination trials with antitumor antibodies or checkpoint inhibitors (CPIs) have been initiated. However, cytokines in monotherapy have not fulfilled the promise of efficacy seen in preclinical experiments. They are often associated with severe dose-limiting toxicities that are manageable with appropriate dosing and are now better understood to induce immune-suppressive humoral factors, suppressive cells, and cellular checkpoints, without consistently inducing a tumor-specific response. To circumvent these impediments, cytokines are being investigated clinically with new engineered cytokine mutants (superkines), chimeric antibody-cytokine fusion proteins (immunokines), anticancer vaccines, CPIs, and cancer-directed monoclonal antibodies to increase their antibody-dependent cellular cytotoxicity or sustain cellular responses and anticancer efficacy. In this review, we summarize current knowledge and clinical application of cytokines either as monotherapy or in combination with other biological agents. We emphasize a discussion of future directions for research on these cytokines, to bring them to fruition as major contributors for the treatment of metastatic malignancy.

A Two-Phase Expansion Protocol Combining Interleukin (IL)-15 and IL-21 Improves Natural Killer Cell Proliferation and Cytotoxicity against Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue malignancy in children. Despite intensive research in recent decades the prognosis for patients with metastatic or relapsed diseases has hardly improved. New therapeutic concepts in anti-tumor therapy aim to modulate the patient’s immune system to increase its aggressiveness or targeted effects toward tumor cells. Besides surgery, radiotherapy and chemotherapy, immune activation by direct application of cytokines, antibodies or adoptive cell therapy are promising approaches. In the last years, adoptive transfer of natural killer (NK) cells came into the focus of translational medicine, because of their high cytotoxic potential against transformed malignant cells. A main challenge of NK cell therapy is that it requires a high amount of functional NK cells. Therefore, ex vivo NK cell expansion protocols are currently being developed. Many culturing strategies are based on the addition of feeder or accessory cells, which need to be removed prior to the clinical application of the final NK cell product. In this study, we addressed feeder cell-free expansion methods using common γ-chain cytokines, especially IL-15 and IL-21. Our results demonstrated high potential of IL-15 for NK cell expansion, while IL-21 triggered NK cell maturation and functionality. Hence, we established a two-phase expansion protocol with IL-15 to induce an early NK cell expansion, followed by short exposure to IL-21 that boosted the cytotoxic activity of NK cells against RMS cells. Further functional analyses revealed enhanced degranulation and secretion of pro-inflammatory cytokines such as interferon-γ and tumor necrosis factor-α. In a proof of concept in vivo study, we also observed a therapeutic effect of adoptively transferred IL-15 expanded and IL-21 boosted NK cells in combination with image guided high precision radiation therapy using a luciferase-transduced RMS xenograft model. In summary, this two-phased feeder cell-free ex vivo culturing protocol combined efficient expansion and high cytolytic functionality of NK cells for treatment of radiation-resistant RMS.

Activation of the FcgammaReceptorIIIa on human natural killer cells leads to increased expression of functional interleukin-21 receptor

Natural killer (NK) cells are innate immune effector cells that play a crucial role in immune surveillance and the destruction of cancer cells. NK cells express a low-affinity receptor for the Fc or constant region of immunoglobulin G (FcγRIIIa) and multiple cytokine receptors that respond to antibody-coated targets and cytokines in the tumor microenvironment. In the present work, microarray gene expression analysis revealed that the IL-21 receptor (IL-21R) was strongly upregulated following FcR stimulation. The IL-21R was found to be upregulated on FcR-stimulated NK cells at the transcript level as determined by reverse transcription polymerase chain reaction (RT-PCR). Immunoblot analysis revealed that protein expression of the IL-21R peaked at 8 h post-stimulation of the FcR. Inhibition of the mitogen-activated protein kinase (MAPK) pathway downstream of the FcR blocked the induction of IL-21R expression. Increased expression of the IL-21R sensitized NK cells to IL-21 stimulation, as treatment of FcR-stimulated NK cells led to significantly increased phosphorylation of STAT1 and STAT3, as measured by intracellular flow cytometry and immunoblot analysis. Following FcR-stimulation, IL-21-activated NK cells were better able to mediate the lysis of trastuzumab-coated human epidermal growth factor receptor 2 (HER2⁺) SK-BR-3 tumor cells as compared to control-treated cells. Likewise, IL-21-induced NK cell secretion of IFNγ following exposure to antibody-coated tumor cells was enhanced following FcR-stimulation. The analysis of NK cells from patients receiving trastuzumab therapy for HER2⁺ cancer exhibited increased levels of the IL-21R following the administration of antibody suggesting that the presence of monoclonal antibody-coated tumor cells in vivo can stimulate the increased expression of IL-21R on NK cells.

Chitosan nanoparticle-based delivery of fused NKG2D-IL-21 gene suppresses colon cancer growth in mice

Nanoparticles can be loaded with exogenous DNA for the potential expression of cytokines with immune-stimulatory function. NKG2D identifies major histocompatibility complex class I chain-related protein in human and retinoic acid early induced transcript-1 in mouse, which acts as tumor-associated antigens. Biologic agents based on interleukin 21 (IL-21) have displayed antitumor activities through lymphocyte activation. The NKG2D-IL-21 fusion protein theoretically identifies tumor cells through NKG2D moiety and activates T cells through IL-21 moiety. In this study, double-gene fragments that encode the extracellular domains of NKG2D and IL-21 genes were connected and then inserted into the pcDNA3.1(-) plasmid. PcDNA3.1-dsNKG2D-IL-21 plasmid nanoparticles based on chitosan were generated. Tumor cells pretransfected with dsNKG2D-IL-21 gene nanoparticles can activate natural killer (NK) and CD8⁺ T cells in vitro. Serum IL-21 levels were enhanced in mice intramuscularly injected with the gene nanoparticles. DsNKG2D-IL-21 gene nanoparticles accumulated in tumor tissues after being intravenously injected for ~4-24 h. Treatment of dsNKG2D-IL-21 gene nanoparticles also retarded tumor growth and elongated the life span of tumor-bearing mice by activating NK and T cells in vivo. Thus, the dsNKG2D-IL-21 gene nanoparticles exerted efficient antitumor activities and would be potentially used for tumor therapy.

Bioengineered Colorectal Cancer Drugs: Orally Delivered Anti-Inflammatory Agents

Intestinal inflammation is one of the major factors that increase colorectal cancer (CRC) incidence worldwide. Inflammation in the gastrointestinal tract is directly linked to tumor development at the early stages of the disease, thus a key issue toward the prevention and the treatment of colonic neoplasia. Thus, the use of anti-inflammatory drugs has emerged first as a strategy to reduce chronic inflammation in case of many inflammatory bowel diseases (IBD), but it has proven its efficacy by reducing the risk of colonic neoplasia. This comprehensive review highlights the role of chronic inflammation, mainly in IBD, in the development of CRC including molecular and immune mechanisms that have tumorigenic effects. Multiple lines of evidence indicate that several bioactive and phytochemical compounds used as anti-inflammatory drugs have also antitumoral attributes. The uses of orally delivered cytokines and small molecules, as well as key dietary supplementation as anti-inflammatory therapeutics are discussed. In addition, comprehensive knowledge about CRC and intestinal inflammation, and the importance of the intestinal mucosal wall as a mucosal immunological barrier that comes into play during interactions with gut microbiota (pathogens and commensal), luminal secretions (bile acids, and bacterial and epithelial metabolites), and ingested chemicals (food components, high fat content, heterocyclic amines, and low intake of dietary fiber) are underscored. The multifunctionality of several anti-inflammatory drugs opens a line for their application in the treatment and prevention not only in IBD but also in CRC. Current bioengineering approaches for oral delivery of anti-inflammatory agents including cytokines, genetically modified bacteria, or small molecule inhibitors of inflammation directly contribute to the early management of CRC. Limitations of the current therapeutics, which stem from the lack of complete understanding of the complex molecular interactions between the intestinal microbiota, colonic epithelial barrier, and host immune system, are also discussed.

Forced co-expression of IL-21 and IL-7 in whole-cell cancer vaccines promotes antitumor immunity

Genetic modification of whole-cell cancer vaccines to augment their efficacies has a history of over two and a half decades. Various genes and gene combinations, targeting different aspects of immune responses have been tested in pursuit of potent adjuvant effects. Here we show that co-expression of two cytokine members of the common cytokine receptor γ-chain family, IL-21 and IL-7, in whole-cell cancer vaccines boosts antitumor immunity in a CD4⁺ and CD8⁺ T cell-dependent fashion. It also generates effective immune memory. The vaccine-elicited short-term effects positively correlated with enhanced infiltration of CD4⁺ and CD8⁺ effector T cells, and the long-term effects positively correlated with enhanced infiltration of effector memory T cells, especially CD8⁺ effector memory T cells. Preliminary data suggested that the vaccine exhibited good safety profile in murine models. Taken together, the combination of IL-21 and IL-7 possesses potent adjuvant efficacy in whole-cell vaccines. This finding warrants future development of IL-21 and IL-7 co-expressing whole-cell cancer vaccines and their relevant combinatorial regimens.

IL-21 and probiotic therapy improve Th17 frequencies, microbial translocation, and microbiome in ARV-treated, SIV-infected macaques

Increased mortality in antiretroviral (ARV)-treated, HIV-infected individuals has been attributed to persistent immune dysfunction, in part due to abnormalities at the gastrointestinal barrier. In particular, the poor reconstitution of gastrointestinal Th17 cells correlates with residual translocation of dysbiotic, immunostimulatory microflora across a compromised intestinal epithelial barrier. We have previously demonstrated that oral probiotics promote increased intestinal CD4(+) T-cell reconstitution during ARV treatment in a non-human primate model of HIV infection; however, essential mucosal T-cell subsets, such as Th17 cells, had limited recovery. Here, we sought to promote Th17 cell recovery by administering interleukin (IL)-21 to a limited number of ARV-treated, probiotic-supplemented, Simian Immunodeficiency Virus (SIV)-infected pigtailed macaques. We demonstrate that probiotic and IL-21 supplementation of ARVs are associated with enhanced polyfunctional Th17 expansion and reduced markers of microbial translocation and dysbiosis as compared with infected controls receiving ARVs alone. Importantly, treatment resulted in fewer morbidities compared with controls, and was independent of increased immune activation or loss of viral suppression. We propose that combining ARVs with therapeutics aimed at restoring intestinal stasis may significantly improve disease prognosis of ARV-treated, HIV-infected individuals.

IL-21 Signaling in Immunity

IL-21 is a type I cytokine produced by T cells and natural killer T cells that has pleiotropic actions on a wide range of immune and non-immune cell types. Since its discovery in 2000, extensive studies on the biological actions of IL-21 have been performed in vitro and in vivo. Recent reports describing patients with primary immunodeficiency caused by mutations of IL21 or IL21R have further deepened our knowledge of the role of this cytokine in host defense. Elucidation of the molecular mechanisms that mediate IL-21's actions has provided the rationale for targeting IL-21 and IL-21 downstream mediators for therapeutic purposes. The use of next-generation sequencing technology has provided further insights into the complexity of IL-21 signaling and has identified transcription factors and co-factors involved in mediating the actions of this cytokine. In this review, we discuss recent advances in the biology and signaling of IL-21 and how this knowledge can be potentially translated into clinical settings.

The Yin and Yang aspects of IL-27 in induction of cancer-specific T-cell responses and immunotherapy

Accumulating evidences from animal studies have indicated that both endogenous and exogenous IL-27, an IL-12 family of cytokine, can increase antitumor T-cell activities and inhibit tumor growth. IL-27 can modulate Treg responses, and program effector T cells into a unique T-effector stem cell (TSEC) phenotype, which enhances T-cell survival in the tumor microenvironment. However, animal studies also suggest that IL-27 induces molecular pathways such as IL-10, PD-L1 and CD39, which may downregulate tumor-specific T-cell responses. In this review paper, we will discuss the Yin and Yang aspects of IL-27 in the induction of tumor-specific T-cell responses, and the potential impacts of these functions of IL-27 in the design of cancer immunotherapy.

In Vivo Imaging of Natural Killer Cell Trafficking in Tumors

Natural killer cells (NKs) are important effectors of the innate immune system, with marked antitumor activity. Imaging NK trafficking in vivo may be relevant to following up the efficacy of new therapeutic approaches aiming at increasing tumor-infiltrating NKs (TINKs). The specific aims of present study were to efficiently target NKs using a 99mTc-anti-CD56 and to image human NK trafficking in SCID mice bearing human cancer.

METHODS

The anti-CD56 monoclonal antibody (mAb) was radiolabeled with 99mTc, and in vitro quality controls were performed to test labeling efficiency, stability, and binding affinity to CD56. In vivo biodistribution was determined by injecting 5.5 MBq (104 ng) of radiolabeled antibody in the tail vein of SCID mice, which were then sacrificed at 1, 3, 6, and 24 h after injection. Targeting experiments were performed on 2 groups of SCID mice inoculated subcutaneously with increasing numbers of human NKs in the right thigh (from 2.5×10(6) to 40×10(6)) and human granulocytes (CD56-) or anaplastic thyroid cancer (ARO) cells in the contralateral thigh as control. TINK trafficking imaging was achieved by injecting 5.5 MBq of 99mTc-anti-CD56 mAb in SCID mice bearing ARO tumor xenografts in the right thigh, 24 h after being reconstituted with 10(5), 10(6), or 10(7) human NKs.

RESULTS

Anti-CD56 mAb was radiolabeled, achieving a radiochemical purity of more than 97% and a specific activity of 3,700 MBq/mg and retaining biochemical integrity and binding activity. In vivo studies revealed physiologic uptake in the liver and kidneys. Targeting experiments confirmed the specificity of labeled antibody to CD56+ cells. Human NK cells injected in CD1 nude mice accumulated in the ARO tumors within 24 h and were imaged as early as 3 h after intravenous administration of (99m)Tc-anti-CD56.

CONCLUSION

99mTc-anti-CD56 is a promising tool for in vivo imaging of TINK cell trafficking.

Anticancer Cytokines: Biology and Clinical Effects of Interferon-α2, Interleukin (IL)-2, IL-15, IL-21, and IL-12

Efforts over nearly four decades have focused on ways to use cytokines to manipulate the host immune response towards cancer cell recognition and eradication. Significant advances were achieved with interleukin-2 (IL-2) and interferon-α (IFN-α), primarily in the treatment of patients with melanoma and renal cell carcinoma. However, the utility of other cytokines showing promise in the preclinical setting has not been established largely because of toxicity, the complex functionality of each cytokine and the difficulty mimicking in preclinical models the human environment. Here, we review the basic biology and the clinical experiences with IFN-α, IL-2, IL-15, IL-21, and IL-12. We will also review ongoing clinical trials and discuss future directions including potential use of cytokines in combination with other effective immunotherapy approaches that have come of age in recent years.

IL-21: a pleiotropic cytokine with potential applications in oncology

Interleukin- (IL-) 21 is a pleiotropic cytokine that regulates the activity of both innate and specific immunity. Indeed, it costimulates T and natural killer (NK) cell proliferation and function and regulates B cell survival and differentiation and the function of dendritic cells. In addition, IL-21 exerts divergent effects on different lymphoid cell leukemia and lymphomas, as it may support cell proliferation or on the contrary induce growth arrest or apoptosis of the neoplastic lymphoid cells. Several preclinical studies showed that IL-21 has antitumor activity in different tumor models, through mechanism involving the activation of NK and T or B cell responses. Moreover, IL-21's antitumor activity can be potentiated by its combination with other immune-enhancing molecules, monoclonal antibodies recognizing tumor antigens, chemotherapy, or molecular targeted agents. Clinical phase I-II studies of IL-21 in cancer patients showed immune stimulatory properties, acceptable toxicity profile, and antitumor effects in a fraction of patients. In view of its tolerability, IL-21 is also suitable for combinational therapeutic regimens with other agents. This review will summarize the biological functions of IL-21, and address its role in lymphoid malignancies and preclinical and clinical studies of cancer immunotherapy.

Advances in IL-21 biology - enhancing our understanding of human disease

Cytokines play critical roles in regulating the development and function of immune cells. Cytokines function by binding specific multimeric receptor complexes and activating intracellular signaling pathways that often involve JAKs and STATs. In addition to contributing to immunity, when production of cytokines is perturbed, they can contribute to disease. IL-21 is a pleiotropic cytokine produced predominantly by CD4(+) T cells and NKT cells. Gene-targeting studies in mice and in vitro analyses of human and murine lymphocytes have revealed central roles of IL-21 in regulating effector functions of T cells, NK cells and B cells. However, recent discoveries of loss-of function mutations in IL21 or IL21R in humans have unveiled unexpected roles for IL-21 in immune regulation. This review will focus on recent advances in IL-21 biology that have highlighted its critical role in normal immunity and how dysregulated IL-21 production can lead to immunodeficiency and autoimmune conditions.

Extending the lifespan and efficacies of immune cells used in adoptive transfer for cancer immunotherapies-A review

Cells used in adoptive cell-transfer immunotherapies against cancer include dendritic cells (DCs), natural-killer cells, and CD8⁺ T-cells. These cells may have limited efficacy due to their lifespan, activity, and immunosuppressive effects of tumor cells. Therefore, increasing longevity and activity of these cells may boost their efficacy. Four cytokines that can extend immune effector-cell longevity are IL-2, IL-7, IL-21, and IL-15. This review will discuss current knowledge on effector-cell lifespans and the mechanisms by which IL-2, IL-7, IL-15, and IL-21 can extend effector-cell longevity. We will also discuss how lifespan and efficacy of these cells can be regulated to allow optimal clinical benefits.

The future of glioblastoma therapy: synergism of standard of care and immunotherapy

The current standard of care for glioblastoma (GBM) is maximal surgical resection with adjuvant radiotherapy and temozolomide (TMZ). As the 5-year survival with GBM remains at a dismal <10%, novel therapies are needed. Immunotherapies such as the dendritic cell (DC) vaccine, heat shock protein vaccines, and epidermal growth factor receptor (EGFRvIII) vaccines have shown encouraging results in clinical trials, and have demonstrated synergistic effects with conventional therapeutics resulting in ongoing phase III trials. Chemoradiation has been shown to have synergistic effects when used in combination with immunotherapy. Cytotoxic ionizing radiation is known to trigger pro-inflammatory signaling cascades and immune activation secondary to cell death, which can then be exploited by immunotherapies. The future of GBM therapeutics will involve finding the place for immunotherapy in the current treatment regimen with a focus on developing strategies. Here, we review current GBM therapy and the evidence for combination of immune checkpoint inhibitors, DC and peptide vaccines with the current standard of care.

The IL-2 cytokine family in cancer immunotherapy

The use of cytokines from the IL-2 family (also called the common γ chain cytokine family) such as interleukin (IL)-2, IL-7, IL-15, and IL-21 to activate the immune system of cancer patients is one of the most important areas of current cancer immunotherapy research. The infusion of IL-2 at low or high doses for multiple cycles in patients with metastatic melanoma and renal cell carcinoma was the first successful immunotherapy for cancer proving that the immune system could completely eradicate tumor cells under certain conditions. The initial clinical success observed in some IL-2-treated patients encouraged further efforts focused on developing and improving the application of other IL-2 family cytokines (IL-4, IL-7, IL-9, IL-15, and IL-21) that have unique biological effects playing important roles in the development, proliferation, and function of specific subsets of lymphocytes at different stages of differentiation with some overlapping effects with IL-2. IL-7, IL-15, and IL-21, as well as mutant forms or variants of IL-2, are now also being actively pursued in the clinic with some measured early successes. In this review, we summarize the current knowledge on the biology of the IL-2 cytokine family focusing on IL-2, IL-15 and IL-21. We discuss the similarities and differences between the signaling pathways mediated by these cytokines and their immunomodulatory effects on different subsets of immune cells. Current clinical application of IL-2, IL-15 and IL-21 either as single agents or in combination with other biological agents and the limitation and potential drawbacks of these cytokines for cancer immunotherapy are also described. Lastly, we discuss the future direction of research on these cytokines, such as the development of new cytokine mutants and variants for improving cytokine-based immunotherapy through differential binding to specific receptor subunits.

Tumor-associated antigen/IL-21-transduced dendritic cell vaccines enhance immunity and inhibit immunosuppressive cells in metastatic melanoma

Dendritic cell (DC)-based vaccine approaches are being actively evaluated for developing immunotherapeutic agents against cancers. In this study, we investigated the use of engineered DCs expressing transgenic tumor-associated antigen hgp100 and the regulatory cytokine interleukin-21, namely DC-hgp100/mIL-21, as a therapeutic vaccine against melanoma. Tumor-bearing mice were injected intratumorally with transgenic DCs followed by three booster injections. Transgenic DC-hgp100/mIL-21 showed significant reduction in primary tumor growth and metastasis compared with DC-hgp100 alone and DC-mIL-21 alone. In vivo depletion of specific immune cell types (CD8(+) T, CD4(+) T and Natural killer (NK)-1.1(+) cells) effectively blocked the protective effect of this combinational vaccine. In adoptive transfer experiments, a survival rate of nearly 90% was observed at 60 days post-tumor inoculation for the combinational vaccine group. In contrast, all mice in the DC-hgp100 and DC-mIL-21-only groups died within 43-46 days after tumor challenge. Considerably increased levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, granulocyte macrophage colony-stimulating factor (GM-CSF) and cytotoxic T lymphocytes (CTLs) were detected with the combination vaccine group compared with other individual treatment groups. In comparison with the DC-hgp100 or mIL-21 groups, the combinational DC-hgp100/mIL-21 vaccine also drastically suppressed the myeloid-derived suppressor cells (MDSCs) and T-regulatory (Treg) cell populations. Our findings suggest that a combinational DC- and gene-based hgp100 and mIL-21 vaccine therapy strategy warrants further evaluation as a clinically relevant cancer vaccine approach for human melanoma patients.

IL-21 promotes CD4 T cell responses by phosphatidylinositol 3-kinase-dependent upregulation of CD86 on B cells

The cytokine IL-21 is a potent immune modulator with diverse mechanisms of action on multiple cell types. IL-21 is in clinical use to promote tumor rejection and is an emerging target for neutralization in the setting of autoimmunity. Despite its clinical potential, the biological actions of IL-21 are not yet fully understood and the full range of effects of this pleiotropic cytokine are still being uncovered. In this study, we identify a novel role for IL-21 as an inducer of the costimulatory ligand CD86 on B lymphocytes. CD86 provides critical signals through T cell–expressed CD28 that promote T cell activation in response to Ag engagement. Expression levels of CD86 are tightly regulated in vivo, being actively decreased by regulatory T cells and increased in response to pathogen-derived signals. In this study, we demonstrate that IL-21 can trigger potent and sustained CD86 upregulation through a STAT3 and PI3K-dependent mechanism. We show that elevated CD86 expression has functional consequences for the magnitude of CD4 T cell responses both in vitro and in vivo. These data pinpoint CD86 upregulation as an additional mechanism by which IL-21 can elicit immunomodulatory effects.

Interleukin (IL)-21 promoter polymorphism increases the risk of thyroid cancer in Chinese population

Polymorphisms in Interleukin (IL)-21 have been researched in several cancers, but the association between IL-21 polymorphisms and thyroid cancer remains unclarified. This case-control study explored the role of five tagSNPs (rs12508721C>T, rs907715G>A, rs13143866G>A, rs2221903A>G and rs4833837A>G) in IL-21 gene in thyroid cancer development. IL-21 genotypes were examined in 615 thyroid cancer patients and 600 controls in Chinese population, and the associations with the risk of thyroid cancer were estimated by logistic regression. Moreover, the potential role of rs12508721C>T in thyroid cancer was further explored by biochemical assays. Compared with the rs12508721CC genotype, CT genotype presented a significantly decreased risk of thyroid cancer (adjusted odds ratios [OR]=0.72; 95%CI=0.57-0.94), the TT carriers had a further decreased risk of thyroid cancer (OR=0.56; 95%CI=0.41-0.87). Furthermore, our quantitative real-time PCR and Enzyme-linked immunosorbent assay (ELISA) results demonstrated that the presence of rs12508721T allele led to more IL-21 expression. However, no significant difference was found in genotype frequencies for other four sites between cases and controls. These findings suggested that rs12508721 polymorphism in IL-21 might be a genetic modifier for the development of thyroid cancer.

Signal transducer and activator of transcription 3 (STAT3) mutations underlying autosomal dominant hyper-IgE syndrome impair human CD8(+) T-cell memory formation and function

BACKGROUND

The capacity of CD8(+) T cells to control infections and mediate antitumor immunity requires the development and survival of effector and memory cells. IL-21 has emerged as a potent inducer of CD8(+) T-cell effector function and memory development in mouse models of infectious disease. However, the role of IL-21 and associated signaling pathways in protective CD8(+) T-cell immunity in human subjects is unknown.

OBJECTIVE

We sought to determine which signaling pathways mediate the effects of IL-21 on human CD8(+) T cells and whether defects in these pathways contribute to disease pathogenesis in patients with primary immunodeficiencies caused by mutations in components of the IL-21 signaling cascade.

METHODS

Human primary immunodeficiencies resulting from monogenic mutations provide a unique opportunity to assess the requirement for particular molecules in regulating human lymphocyte function. Lymphocytes from patients with loss-of-function mutations in signal transducer and activator of transcription 1 (STAT1), STAT3, or IL-21 receptor (IL21R) were used to assess the respective roles of these genes in human CD8(+) T-cell differentiation in vivo and in vitro.

RESULTS

Mutations in STAT3 and IL21R, but not STAT1, led to a decrease in multiple memory CD8(+) T-cell subsets in vivo, indicating that STAT3 signaling, possibly downstream of IL-21R, regulates the memory cell pool. Furthermore, STAT3 was important for inducing the lytic machinery in IL-21-stimulated naive CD8(+) T cells. However, this defect was overcome by T-cell receptor engagement.

CONCLUSION

The IL-21R/STAT3 pathway is required for many aspects of human CD8(+) T-cell behavior but in some cases can be compensated by other signals. This helps explain the relatively mild susceptibility to viral disease observed in STAT3- and IL-21R-deficient subjects.

Diagnostic value of interleukin 21 and carcinoembryonic antigen levels in malignant pleural effusions

The aim of this study was to evaluate the diagnostic value of interleukin 21 (IL-21) and carcinoembryonic antigen (CEA) in tuberculous pleural effusions (TPEs) and malignant pleural effusions (MPEs). Pleural effusion samples from 103 patients were classified on the basis of diagnosis as TPE (n=51) and MPE (n=52). The concentration of IL-21 was determined by ELISA. Lactate dehydrogenase (LDH), adenosine dehydrogenase (ADA) and CEA levels were also determined in all patients. A significant difference was observed in the levels of ADA and CEA (P<0.01), but not in the levels of LDH (P>0.05) between TPE and MPE. The concentration of IL-21 in MPE was significantly higher compared to TPE (P<0.01). With a threshold value of 4.32 pg/ml, IL-21 had a sensitivity of 76.9% (40/52) and a specificity of 80.4% (41/51). Combined detection of IL-21 and CEA had a sensitivity of 69.2% (36/52) and a specificity of 92.2% (47/51). These two markers can contribute to the differential diagnosis of MPEs.

NK cell-based immunotherapy for malignant diseases

Natural killer (NK) cells play critical roles in host immunity against cancer. In response, cancers develop mechanisms to escape NK cell attack or induce defective NK cells. Current NK cell-based cancer immunotherapy aims to overcome NK cell paralysis using several approaches. One approach uses expanded allogeneic NK cells, which are not inhibited by self histocompatibility antigens like autologous NK cells, for adoptive cellular immunotherapy. Another adoptive transfer approach uses stable allogeneic NK cell lines, which is more practical for quality control and large-scale production. A third approach is genetic modification of fresh NK cells or NK cell lines to highly express cytokines, Fc receptors and/or chimeric tumor-antigen receptors. Therapeutic NK cells can be derived from various sources, including peripheral or cord blood cells, stem cells or even induced pluripotent stem cells (iPSCs), and a variety of stimulators can be used for large-scale production in laboratories or good manufacturing practice (GMP) facilities, including soluble growth factors, immobilized molecules or antibodies, and other cellular activators. A list of NK cell therapies to treat several types of cancer in clinical trials is reviewed here. Several different approaches to NK-based immunotherapy, such as tissue-specific NK cells, killer receptor-oriented NK cells and chemically treated NK cells, are discussed. A few new techniques or strategies to monitor NK cell therapy by non-invasive imaging, predetermine the efficiency of NK cell therapy by in vivo experiments and evaluate NK cell therapy approaches in clinical trials are also introduced.

The cytokines IL-21 and GM-CSF have opposing regulatory roles in the apoptosis of conventional dendritic cells

Interleukin-21 (IL-21) has broad actions on T and B cells, but its actions in innate immunity are poorly understood. Here we show that IL-21 induced apoptosis of conventional dendritic cells (cDCs) via STAT3 and Bim, and this was inhibited by granulocyte-macrophage colony-stimulating factor (GM-CSF). ChIP-Seq analysis revealed genome-wide binding competition between GM-CSF-induced STAT5 and IL-21-induced STAT3. Expression of IL-21 in vivo decreased cDC numbers, and this was prevented by GM-CSF. Moreover, repetitive α-galactosylceramide injection of mice induced IL-21 but decreased GM-CSF production by natural killer T (NKT) cells, correlating with decreased cDC numbers. Furthermore, adoptive transfer of wild-type CD4+ T cells caused more severe colitis with increased DCs and interferon-γ (IFN-γ)-producing CD4+ T cells in Il21r(-/-)Rag2(-/-) mice (which lack T cells and have IL-21-unresponsive DCs) than in Rag2(-/-) mice. Thus, IL-21 and GM-CSF exhibit cross-regulatory actions on gene regulation and apoptosis, regulating cDC numbers and thereby the magnitude of the immune response.

IL-21 gene polymorphism is associated with the prognosis of breast cancer in Chinese populations

Interleukin (IL)-21, which is secreted by activated CD4(+) T cells and NKT cells, has been found to be able to influence the humoral and cell-mediated immune responses and have potent antitumor activity in animal models. This study was to investigate the impact of genetic polymorphisms in IL-21 on survival of breast cancer. Four TagSNPs of IL-21 (rs12508721C>T, rs907715G>A, rs13143866G>A, rs2221903A>G) were selected and then genotyped in 891 patients with breast cancer in Eastern and Southern Chinese populations. We then examined the associations between these SNPs and overall survival. Potential function of rs12508721C>T and association between this variation and breast cancer prognosis were further studied. Overall, 121 of the patients had died over the followed-up period of 5 years. The IL-21 rs12508721T allele predicted longer five-year survival (HR = 0.347, 95 % CI = 0.187-0.644, P < 0.0001) in the discovery cohort, the independent validation cohort (HR = 0.429, 95 % CI = 0.244-0.755, P = 0.012), and combined group (HR = 0.447, 95 % CI = 0.301-0.667, P < 0.0001). Furthermore, our luciferase assay revealed that rs12508721T variant allele had a higher transcription activity and the RT-PCR and ELISA assay showed that rs12508721 variant genotypes (CT and TT) carriers have more IL-21 expression than CC carriers (P < 0.05). Our present study established a robust association between the functional polymorphism (rs12508721C>T) in IL-21 and prognosis of breast cancer, indicating that this polymorphism may be a potential biomarker for prognosis of breast cancer.

Depigmenting effect of Kojic acid esters in hyperpigmented B16F1 melanoma cells

The depigmenting effect of kojic acid esters synthesized by the esterification of kojic acid using Rhizomucor miehei immobilized lipase was investigated in B16F1 melanoma cells. The depigmenting effect of kojic acid and kojic acid esters was evaluated by the inhibitory effect of melanin formation and tyrosinase activity on alpha-stimulating hormone- (α-MSH-) induced melanin synthesis in B16F1 melanoma cells. The cellular tyrosinase inhibitory effect of kojic acid monooleate, kojic acid monolaurate, and kojic acid monopalmitate was found similar to kojic acid at nontoxic doses ranging from 1.95 to 62.5 μg/mL. However, kojic acid monopalmitate gave slightly higher inhibition to melanin formation compared to other inhibitors at doses ranging from 15.63 to 62.5 μg/mL. Kojic acid and kojic acid esters also show antioxidant activity that will enhance the depigmenting effect. The cytotoxicity of kojic acid esters in B16F1 melanoma cells was significantly lower than kojic acid at high doses, ranging from 125 and 500 μg/mL. Since kojic acid esters have lower cytotoxic effect than kojic acid, it is suggested that kojic acid esters can be used as alternatives for a safe skin whitening agent and potential depigmenting agents to treat hyperpigmentation.

Robust tumor immunity to melanoma mediated by interleukin-9-producing T cells

Interleukin-9 is a T cell cytokine that acts through a γC-family receptor on target cells. We determined that T cells from mice deficient in the T_H17 pathway genes ROR-γ and IL-23R produced abundant IL-9, and observed significant growth inhibition of B16F10 melanoma tumor in these mice. IL-9 blocking antibodies reversed this tumor growth inhibition, and enhanced tumor growth in normal mice. IL9R^−/− mice showed accelerated tumor growth, while administration of rIL-9 to tumor bearing mice inhibited tumor growth. Adoptive transfer of tumor antigen-specific T_H9 cells blocked tumor growth; this was reversed by anti-IL-9. Exogenous rIL-9 inhibited tumor growth in Rag1^−/− mice, but not in mast cell deficient mice, suggesting a T cell independent process. Finally, we found T_H9 cells in normal human skin and blood, and low IL-9 production from melanoma tumor infiltrating lymphocytes. These results suggest a role for IL-9 in tumor immunity, and suggest therapeutic strategies.

The role of antigen-specific and non-specific immunotherapy in the treatment of cancer

Immunotherapy in the treatment of cancer is increasing, particularly with the recent FDA approval of sipuleucel-T and ipilimumab. The efficacy of anti-tumor immunotherapies has been modest compared to their theoretical and pre-clinical promise. This review evaluates the promise and pitfalls of immunotherapy and highlight some of the obstacles to improving anti-tumor immunotherapy: the need for technical refinement of therapies, the need for an increased understanding of how best to combine therapies with traditional cytotoxic therapies, the inability of patients to mount an effective immune response either due to disease burden or tumor induced immune suppression, the significant toxicities associated with many immunotherapies, and the lack of strongly immunogenic antigens required by many therapies. Further, antigen-non-specific immunotherapies, including cytokines such as interleukins and interferons, immuno-stimulatory agents such as CpG oligonucleotides, or BCG, antibodies targeted against receptors such as the agonistic CD40 or inhibitory CTLA-4 antibodies, and enzyme inhibitors such as those targeting cyclo-oxygenase or indolamine-2,3-dioxygenase are discussed. In addition, potential mechanisms of these therapies such as direct anti-tumor effects, reversal of immune suppression, activation of innate immunity, and antigen-non-specific T-cell activation are reviewed. We also appraise the potential of these antigen-non-specific therapies to overcome some of the previously described pitfalls of immunotherapy. Lastly, we discuss a recent series of studies from our laboratory demonstrating the importance of antigen-non-specific 'bystander activation' of memory T-lymphocytes by immunomodulatory therapies such as interleukin-2 and the antigen-non-specific anti-tumor effects of these cells.

Involvement of interleukin-21 in the regulation of colitis-associated colon cancer

IL-21 expression is increased in the gut of patients with colitis-associated colon cancer, and genetic ablation or antibody neutralization of IL-21 reduces tumor size and inflammation in mice treated with dextran sulfate sodium and azoxymethane.

Chronic inflammation is a major driving force in the development of cancer in many tissues, but the array of factors involved in this neoplastic transformation are not well understood. We have investigated the role of interleukin (IL)-21 in colitis-associated colon cancer (CAC), as this cytokine is overexpressed in the gut mucosa of patients with ulcerative colitis (UC), a chronic inflammatory disease associated with colon cancer. IL-21 was increased in the gut of patients with UC-associated colon cancer, and in mice with CAC induced by azoxymethane (AOM) and dextran sulfate sodium (DSS). After AOM+DSS treatment, IL-21 KO mice showed reduced mucosal damage, reduced infiltration of T cells, and diminished production of IL-6 and IL-17A. IL-21–deficient mice also developed fewer and smaller tumors compared with wild-type (WT) mice. Absence of IL-21 reduced signal transducer and activator of transcription 3 activation in tumor and stromal cells. Administration of a neutralizing IL-21 antibody to WT mice after the last DSS cycle decreased the colonic T cell infiltrate and the production of IL-6 and IL-17A and reduced the number of tumors. These observations indicate that IL-21 amplifies an inflammatory milieu that promotes CAC, and suggest that IL-21 blockade may be useful in reducing the risk of UC-associated colon cancer.

Reprogramming CD19-specific T cells with IL-21 signaling can improve adoptive immunotherapy of B-lineage malignancies

Improving the therapeutic efficacy of T cells expressing a chimeric antigen receptor (CAR) represents an important goal in efforts to control B-cell malignancies. Recently an intrinsic strategy has been developed to modify the CAR itself to improve T-cell signaling. Here we report a second extrinsic approach based on altering the culture milieu to numerically expand CAR(+) T cells with a desired phenotype, for the addition of interleukin (IL)-21 to tissue culture improves CAR-dependent T-cell effector functions. We used electrotransfer of Sleeping Beauty system to introduce a CAR transposon and selectively propagate CAR(+) T cells on CD19(+) artificial antigen-presenting cells (aAPC). When IL-21 was present, there was preferential numeric expansion of CD19-specific T cells which lysed and produced IFN-γ in response to CD19. Populations of these numerically expanded CAR(+) T cells displayed an early memory surface phenotype characterized as CD62L(+)CD28(+) and a transcriptional profile of naïve T cells. In contrast, T cells propagated with only exogenous IL-2 tended to result in an overgrowth of CD19-specific CD4(+) T cells. Furthermore, adoptive transfer of CAR(+) T cells cultured with IL-21 exhibited improved control of CD19(+) B-cell malignancy in mice. To provide coordinated signaling to propagate CAR(+) T cells, we developed a novel mutein of IL-21 bound to the cell surface of aAPC that replaced the need for soluble IL-21. Our findings show that IL-21 can provide an extrinsic reprogramming signal to generate desired CAR(+) T cells for effective immunotherapy.

Interleukins and cancer immunotherapy

Cancer is a complex disease with interactions between normal and neoplastic cells. Since current therapies for cancer largely rely on drugs or radiation that kill dividing cells or block cell division, these treatments may have severe side effects on normal proliferating cells in patients with cancer. Therefore, the potential for treatment of cancer patients by immunologic approaches, which may be specific for tumors and will not injure most normal cells, has great promise. Cancer immunotherapy aims to augment the weak host immune response to developing tumors. One strategy is to utilize cytokines such as IL-2. More recently, several exciting new interleukins have been characterized that have considerable promise for future immunotherapy. The promise of cancer immunotherapy largely depends upon the identification of these novel interleukins. This review provides an overview of the antitumor effects of relatively new interleukins as potential therapeutic agents applicable for cancer immunotherapy.

Classes and prediction of cell-penetrating peptides

The classical view on how peptides enter cells has been changed due to the development in the research field of cell-penetrating peptides (CPPs). During the last 15 years, more than 100 peptide sequences have been published to enter cells and also to bring different biological cargoes with them. Here, we present an overview of CPPs, mainly trying to analyze their common properties yielding the prediction of their cell-penetrating properties. Furthermore, examples of recent research, ideas on classification and uptake mechanisms, as well as a summary of the therapeutic potential of CPPs are presented.

Novel gamma-chain cytokines as candidate immune modulators in immune therapies for cancer

Cytokines that signal through the common-gamma chain are potent growth factors for T cells and natural killer cells. Interleukin (IL)-2, the gammac prototype, can mediate antitumor effects as a single agent or in the context of multimodality regimens but is limited by side effects and a propensity for expansion of regulatory T cells. IL-7, IL-15, and IL-21 each possess properties that can be exploited in the context of immunotherapy for cancer. Each has been demonstrated to mediate potent vaccine adjuvant effects in tumor models, and each can enhance the effectiveness of adoptive immunotherapies. Although the overlap among the agents is significant, IL-7 is uniquely immunorestorative and preferentially augments reactivity of naive populations, IL-15 potently augments reactivity of CD8 memory cells and natural killer cells, and IL-21 preferentially expands the inflammatory Th17 subset and may limit terminal differentiation of effector CD8 cells. Clinical trials of IL-7 and IL-21 have already been completed and, so far, demonstrate safety and biologic activity of these agents. Clinical trials of IL-15 are expected soon. Ultimately, these agents are expected to be most effective in the context of multimodal immunotherapy regimens, and careful clinical trial design will be needed to efficiently identify the proper doses, regimens, and settings in which to exploit their biologic properties for therapeutic gain.