Role of IL-21 in immune-regulation and tumor immunotherapy

Co-expression of IL-21-Enhanced NKG2D CAR-NK cell therapy for lung cancer

BACKGROUND

Adoptive cell therapy has achieved great success in treating hematological malignancies. However, the production of chimeric antigen receptor T (CAR-T) cell therapy still faces various difficulties. Natural killer (NK)-92 is a continuously expandable cell line and provides a promising alternative for patient's own immune cells.

METHODS

We established CAR-NK cells by co-expressing natural killer group 2 member D (NKG2D) and IL-21, and evaluated the efficacy of NKG2D-IL-21 CAR-NK cells in treating lung cancer in vitro and in vivo.

RESULTS

Our data suggested that the expression of IL-21 effectively increased the cytotoxicity of NKG2D CAR-NK cells against lung cancer cells in a dose-dependent manner and suppressed tumor growth in vitro and in vivo. In addition, the proliferation of NKG2D-IL-21 CAR-NK cells were enhanced while the apoptosis and exhaustion of these cells were suppressed. Mechanistically, IL-21-mediated NKG2D CAR-NK cells function by activating AKT signaling pathway.

CONCLUSION

Our findings provide a novel option for treating lung cancer using NKG2D-IL-21 CAR-NK cell therapy.

A deep learning approach based on multi-omics data integration to construct a risk stratification prediction model for skin cutaneous melanoma

PURPOSE

Skin cutaneous melanoma (SKCM) is a highly aggressive melanocytic carcinoma whose high heterogeneity and complex etiology make its prognosis difficult to predict. This study aimed to construct a risk subtype typing model for SKCM.

METHODS

The study proposes a deep learning framework combining early fusion feature autoencoder (AE) and late fusion feature AE for risk subtype prediction of SKCM. The deep learning framework integrates mRNA, miRNA, and DNA methylation data of SKCM patients from The Cancer Genome Atlas (TCGA), and clusters the screened multi-omics features associated with survival prognosis to identify risk subtypes. Differential expression analysis and functional enrichment analysis were performed between risk subtypes, while SVM classifiers were constructed between differentially expressed genes (DEGs) obtained by Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression screening and risk subtype labels inferred from multi-omics data, and the predictive robustness of risk subtypes inferred from the risk subtype classification prediction model was validated using two independent datasets.

RESULTS

The deep learning framework that combined early fusion feature AE with late fusion feature AE distinguished the two best risk subtypes compared to the multi-omics integration approach with single strategy AE or PCA. A promising C-index (C-index = 0.748) and a significant difference in survival (log-rank P value = 4.61 × 10-9) were found between the identified risk subtypes. The DEGs with the top significance values together with differentially expressed miRNAs provided the biological interpretation of risk subtypes on SKCM. Finally, the framework was applied to predict risk subtypes in two independent test datasets of SKCM patients, all of which showed good predictive power (C-index > 0.680) and significant survival differences (log-rank P value < 0.01).

CONCLUSION

The SKCM risk subtypes identified by integrating multi-omics data based on deep learning can not only improve the understanding of the molecular mechanisms of SKCM, but also provide clinicians with assistance in treatment decisions.

Immunogenetic variations predict immune-related adverse events for PD-1/PD-L1 inhibitors

BACKGROUND

PD-1/PD-L1 inhibitors have brought remarkable benefits but can cause profound immune-related adverse events (irAEs). The host immunogenetic background is likely to play a role in irAE susceptibility. In this study, we aimed to identify potential immunogenetic biomarkers to predict irAEs.

METHODS

Patients with solid tumours receiving PD-1/PD-L1 blockade were recruited and followed up. Genes considered pivotal contributors to tumour-immunity and autoimmune diseases were screened out via protein-protein interaction network and Cytoscape. Consequently, thirty-nine variants in eighteen genes were genotyped using the multiplex genotyping assay. Association analysis between genetic variants and irAEs as well as irAEs-free survival was performed.

RESULTS

Four immunogenetic variants as predictive biomarkers of irAEs were identified. The C allele of Mitogen-Activated Protein Kinase 1 (MAPK1) rs3810610 (odds ratio [OR] = 1.495, 95% confidence interval [CI] = 1.093-2.044, P = 0.012) was a risk predictor while the A allele of PTPRC rs6428474 (OR = 0.717, 95% CI = 0.521-0.987, P = 0.041) was a protective factor for all-grade irAEs. The A allele of ADAD1 rs17388568 (OR = 2.599, 95% CI = 1.355-4.983, P = 0.003) increased the risk while the G allele of IL6 rs1800796 (OR = 0.425, 95% CI = 0.205-0.881, P = 0.018) protected patients from high-grade irAEs. Significant immunogenetic variants reached a similar tendency in PD-1 blockade or lung cancer subgroups. In multivariate Cox regression analysis, the MAPK1 rs3810610 was an independent factor regarding all-grade irAEs-free survival (CC versus CT or TT: hazard ratio [HR] = 0.71, 95% CI = 0.52-0.99, P = 0.042). ADAD1 rs17388568 (AA versus AG or GG: HR = 0.11, 95% CI = 0.025-0.49, P = 0.004) and IL6 rs1800796 (GG or GC versus CC: HR = 3.10, 95% CI = 1.315-7.29, P = 0.01) were independent variables for high-grade irAEs-free survival.

CONCLUSION

We first identified several immunogenetic polymorphisms associated with irAEs and irAEs-free survival in PD-1/PD-L1 blockade-treated tumour patients, and they may serve as potential predictive biomarkers.

Autoimmune genetic risk variants as germline biomarkers of response to melanoma immune-checkpoint inhibition

Immune-checkpoint inhibition (ICI) treatments improve outcomes for metastatic melanoma; however, > 60% of treated patients do not respond to ICI. Current biomarkers do not reliably explain ICI resistance. Given the link between ICI and autoimmunity, we investigated if genetic susceptibility to autoimmunity modulates ICI efficacy. In 436 patients with metastatic melanoma receiving single line ICI or combination treatment, we tested 25 SNPs, associated with > 2 autoimmune diseases in recent genome-wide association studies, for modulation of ICI efficacy. We found that rs17388568-a risk variant for allergy, colitis and type 1 diabetes-was associated with increased anti-PD-1 response, with significance surpassing multiple testing adjustments (OR 0.26; 95% CI 0.12-0.53; p = 0.0002). This variant maps to a locus of established immune-related genes: IL2 and IL21. Our study provides first evidence that autoimmune genetic susceptibility may modulate ICI efficacy, suggesting that systematic testing of autoimmune risk loci could reveal personalized biomarkers of ICI response.

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.

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.

Association between IL-21 gene rs907715 polymorphisms and Graves' disease in a Southern Chinese population

Interleukin-21 (IL-21) is a pleiotropic cytokine linking innate and adaptive immune responses, which has been reported to play a key role in multiple autoimmune diseases. The aim of the present case-control study was to investigate the genetic association between single nucleotide polymorphisms (SNPs) of rs907715 within the IL-21 gene and Graves’ disease (GD) in a Southern Chinese population. A total of 211 patients with GD and 212 control subjects were recruited for the study. IL-21 gene rs907715 polymorphisms were detected by direct DNA sequencing. The results indicated that the frequencies of the GG genotype and the G allele in GD patients were significantly increased when compared with the frequencies in the controls (P=6.7×10⁻³ and P=2.0×10⁻⁵, respectively). In addition, the frequency of the AA genotype was much lower in the patient group when compared with the control group (16.6 vs. 34.0%; P=4.0×10⁻⁵). Furthermore, the G allele of rs907715 was associated with relapse in GD patients. These observations indicated that polymorphisms of IL-21/rs907715 may affect the susceptibility to GD in a Southern Chinese population. The G allele was significantly associated with an increased risk of GD development, whereas the A allele may lower the susceptibility to GD.

Recombinant IL-21 and anti-CD4 antibodies cooperate in syngeneic neuroblastoma immunotherapy and mediate long-lasting immunity

IL-21 is an immune-enhancing cytokine, which showed promising results in cancer immunotherapy. We previously observed that the administration of anti-CD4 cell-depleting antibody strongly enhanced the anti-tumor effects of an IL-21-engineered neuroblastoma (NB) cell vaccine. Here, we studied the therapeutic effects of a combination of recombinant (r) IL-21 and anti-CD4 monoclonal antibodies (mAb) in a syngeneic model of disseminated NB. Subcutaneous rIL-21 therapy at 0.5 or 1 μg/dose (at days 2, 6, 9, 13 and 15 after NB induction) had a limited effect on NB development. However, coadministration of rIL-21 at the two dose levels and a cell-depleting anti-CD4 mAb cured 28 and 70 % of mice, respectively. Combined immunotherapy was also effective if started 7 days after NB implant, resulting in a 30 % cure rate. Anti-CD4 antibody treatment efficiently depleted CD4(+) CD25(high) Treg cells, but alone had limited impact on NB. Combination immunotherapy by anti-CD4 mAb and rIL-21 induced a CD8(+) cytotoxic T lymphocyte response, which resulted in tumor eradication and long-lasting immunity. CD4(+) T cells, which re-populated mice after combination immunotherapy, were required for immunity to NB antigens as indicated by CD4(+) T cell depletion and re-challenge experiments. In conclusion, these data support a role for regulatory CD4(+) T cells in a syngeneic NB model and suggest that rIL-21 combined with CD4(+) T cell depletion reprograms CD4(+) T cells from immune regulatory to anti-tumor functions. These observations open new perspectives for the use of IL-21-based immunotherapy in conjunction with transient CD4(+) T cell depletion, in human metastatic NB.

Understanding the immunodeficiency in chronic lymphocytic leukemia: potential clinical implications

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Although significant advances have been made in the treatment of CLL in the last decade, it remains incurable. Treatments may be too toxic for some elderly patients, who constitute most of the individuals with this disease, and there remain subgroups of patients for which this therapy has minimal activity. This article summarizes the current understanding of the immune defects in CLL. It also examines the potential clinical implications of these findings.

Monoclonal antibody therapy of pancreatic cancer with cetuximab: potential for immune modulation

Pancreatic cancer is a devastating disease, with a median survival of around 6 months for patients with stage IV disease. The epidermal growth factor receptor (EGFR, or HER1) belongs to the erbB receptor tyrosine kinase family. HER1-mediated cell signaling has been shown to play a major role in promoting tumor proliferation, angiogenesis, metastasis, and evasion of apoptosis. Over-expression of HER1 is observed in multiple human malignancies, including colorectal, lung, breast and pancreatic cancers. In pancreatic carcinoma, over-expression of HER1 is observed in greater than 70% of patients and is associated with a poor prognosis and a significant decrease in survival. Cetuximab (Erbitux) is a chimeric monoclonal antibody (mAb) that binds to the extracellular domain of the HER1 molecule preventing ligand binding and promoting internalization and subsequent degradation of the HER1 receptor. Cetuximab has shown anti-tumor activity either alone or in combination with other agents and is currently FDA approved for use in both squamous cell carcinoma of the head and neck (SCCHN) and colorectal carcinoma. Research efforts continue to elucidate a possible role for cetuximab in the treatment of pancreatic cancer. Despite promising preclinical work, phase II and phase III clinical trials have failed to consistently show efficacy of cetuximab treatment in advanced pancreatic cancer either alone or in combination with cytotoxic agents. Alternative approaches to HER1 blockade and mAbs including immune modulation with cytokines might be necessary in order to improve the efficacy of mAbs in pancreatic cancer therapy.

In vivo intracellular oxygen dynamics in murine brain glioma and immunotherapeutic response of cytotoxic T cells observed by fluorine-19 magnetic resonance imaging

Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC) molecules, combined with quantitative ¹⁹F spin-lattice relaxation rate (R₁) measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS) GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R₁ of ¹⁹F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO₂) was ascertained. Three days after tumor implantation, mice were treated with 2×10⁷ cytotoxic T cells intravenously. At day five, a transient spike in pO₂ was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO₂ was causally related to the T cells infiltration. Surprisingly, the pO₂ spike was detected even though few (∼4×10⁴) T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models.

Interleukin-21 has activity in patients with metastatic melanoma: a phase II study

PURPOSE

We report a multicenter phase II study of patients with metastatic melanoma (MM), evaluating the efficacy, toxicity, progression-free survival (PFS), immunogenicity, and biomarker profile of interleukin-21 (IL-21).

PATIENTS AND METHODS

Patients with no prior systemic therapy and with limited-disease MM were treated with IL-21 by using three different dosing regimens. Cohort 1 received 50 μg/kg per day by outpatient intravenous bolus injection for 5 days of each week during weeks 1, 3, and 5 of an 8-week cycle. Cohort 2 received 30 μg/kg per day on the same schedule, and cohort 3 received 50 μg/kg per day for 5 days of each week during weeks 1 and 3 of a 6-week cycle.

RESULTS

Forty patients were enrolled: three in cohort 1, 30 in cohort 2, and seven in cohort 3. Two patients in cohort 1 and four in cohort 3 had dose-limiting toxicities; all other patients were treated with a dose of 30 μg/kg per day. Common adverse events were fatigue, rash, diarrhea, nausea, and myalgia. Overall response rate (ORR) was 22.5%, with nine confirmed partial responses (median response duration, 5.3 months); 16 had stable disease (median response duration, 5.3 months). ORR did not appear to depended on IL-21 receptor expression or BRAF mutation status. The median PFS was 4.3 months and median overall survival (OS) was 12.4 months (95% CI, 10.09 to 17.81 months).

CONCLUSION

The ORR to IL-21 is 22.5% for first-line MM and warrants further investigation. The favorable PFS and OS suggest that this is an active agent in comparison to both historical NCIC Clinical Trials Group data and data from meta-analysis of Cooperative Group phase II trials.

An integrated disease/pharmacokinetic/pharmacodynamic model suggests improved interleukin-21 regimens validated prospectively for mouse solid cancers

Interleukin (IL)-21 is an attractive antitumor agent with potent immunomodulatory functions. Yet thus far, the cytokine has yielded only partial responses in solid cancer patients, and conditions for beneficial IL-21 immunotherapy remain elusive. The current work aims to identify clinically-relevant IL-21 regimens with enhanced efficacy, based on mathematical modeling of long-term antitumor responses. For this purpose, pharmacokinetic (PK) and pharmacodynamic (PD) data were acquired from a preclinical study applying systemic IL-21 therapy in murine solid cancers. We developed an integrated disease/PK/PD model for the IL-21 anticancer response, and calibrated it using selected “training” data. The accuracy of the model was verified retrospectively under diverse IL-21 treatment settings, by comparing its predictions to independent “validation” data in melanoma and renal cell carcinoma-challenged mice (R²>0.90). Simulations of the verified model surfaced important therapeutic insights: (1) Fractionating the standard daily regimen (50 µg/dose) into a twice daily schedule (25 µg/dose) is advantageous, yielding a significantly lower tumor mass (45% decrease); (2) A low-dose (12 µg/day) regimen exerts a response similar to that obtained under the 50 µg/day treatment, suggestive of an equally efficacious dose with potentially reduced toxicity. Subsequent experiments in melanoma-bearing mice corroborated both of these predictions with high precision (R²>0.89), thus validating the model also prospectively in vivo. Thus, the confirmed PK/PD model rationalizes IL-21 therapy, and pinpoints improved clinically-feasible treatment schedules. Our analysis demonstrates the value of employing mathematical modeling and in silico-guided design of solid tumor immunotherapy in the clinic.

Among the many potential drugs explored within the scope of cancer immunotherapy are selected cytokines which possess promising immune-boosting properties. Yet, the natural involvement of these proteins in multiple, often contradicting biological processes can complicate their use in the clinic. The cytokine interleukin (IL)-21 is no exception: while its strength as an anticancer agent has been established in several animal studies, response rates in melanoma and renal cell carcinoma patients remain low. To help guide the design of effective IL-21 therapy, we have developed a mathematical model that bridges between the complex biology of IL-21 and its optimal clinical use. Our model integrates data from preclinical studies under diverse IL-21 treatment settings, and was validated by extensive experiments in tumor-bearing mice. Model simulations predicted that beneficial, clinically practical IL-21 therapy should be composed of low-dose schedules, and/or schedules in which several partial doses are administered rather than a single complete dose. These findings were subsequently confirmed in mice with melanoma. Thus, future testing of these strategies in solid cancer patients can be a promising starting point for improving IL-21 therapy. Our model can thus provide a computational platform for rationalizing IL-21 regimens and streamlining its clinical development.

Role of common-gamma chain cytokines in NK cell development and function: perspectives for immunotherapy

NK cells are components of the innate immunity system and play an important role as a first-line defense mechanism against viral infections and in tumor immune surveillance. Their development and their functional activities are controlled by several factors among which cytokines sharing the usage of the common cytokine-receptor gamma chain play a pivotal role. In particular, IL-2, IL-7, IL-15, and IL-21 are the members of this family predominantly involved in NK cell biology. In this paper, we will address their role in NK cell ontogeny, regulation of functional activities, development of specialized cell subsets, and acquisition of memory-like functions. Finally, the potential application of these cytokines as recombinant molecules to NK cell-based immunotherapy approaches will be discussed.

Interactions between the immune system and cancer: a brief review of non-spatial mathematical models

We briefly review spatially homogeneous mechanistic mathematical models describing the interactions between a malignant tumor and the immune system. We begin with the simplest (single equation) models for tumor growth and proceed to consider greater immunological detail (and correspondingly more equations) in steps. This approach allows us to clarify the necessity for expanding the complexity of models in order to capture the biological mechanisms we wish to understand. We conclude by discussing some unsolved problems in the mathematical modeling of cancer-immune system interactions.

Immune modulation with interleukin-21

Interleukin 21 (IL-21) is produced by activated CD4(+) T cells. The IL-21R shares the common receptor gamma-chain with IL-2, IL-4, IL-7, IL-9, and IL-15, is widely expressed on immune cells, and mediates a variety of effects on the immune system. IL-21 enhances the proliferation, antigen-induced activation, clonal expansion, IFN-gamma production, and cytotoxicity of NK cells and T cells. The antitumor actions of IL-21 have been variously attributed to NK cell and CD8(+) T cell cytotoxicity, CD4(+) T cell help, NKT cells, and the antiangiogenic properties induced by IFN-gamma secretion. In clinical trials IL-21 has been well tolerated and induces a unique pattern of immune activation. IL-21 is therefore an excellent candidate for use in immune therapy.

Differential effects of IL-2 and IL-21 on expansion of the CD4+ CD25+ Foxp3+ T regulatory cells with redundant roles in natural killer cell mediated antibody dependent cellular cytotoxicity in chronic lymphocytic leukemia

CD4(+) CD25(+) regulatory T cells are expanded in solid and hematological malignancies including chronic lymphocytic leukemia (CLL). Several cytokines and co-stimulatory molecules are required for generation, survival and maintenance of their suppressive effect. We and others have shown direct cytotoxic effect of the novel common gamma chain cytokine interleukin (IL)-21 on primary B cells from CLL patients. Since members of this family of cytokines are known to exhibit their effects on diverse immune cells, we have examined the effects of IL-21 on CLL patient derived regulatory T cell (Treg) induction, expansion and the inhibitory effect on natural killer cells in vitro. We demonstrate here the expression of IL-21 receptor in CD4(+)CD25(High) regulatory cells from CLL patients. In contrast to IL-2, the IL-21 cytokine failed to mediate expansion of regulatory T cells or induced expression of Foxp3 in CD4(+)CD25(Intermediate) or CD4(+)CD25(Dim/-) T cells in whole blood derived from CLL patients. Interestingly, in contrast to their differential effects on expansion of the CD4(+)CD25(+)Foxp3(+)T cells, IL-2 and IL-21 exhibited a redundant role in Treg mediated suppression of NK cell mediated antibody dependent cytotoxicity function. Given the infusion related toxicities and pro-survival effect of IL-2 in CLL, these studies provide a rationale to explore IL-21 as an alternate gamma chain cytokine in CLL therapy.

Interleukin-21 restrains tumor growth and induces a substantial increase in the number of circulating tumor-specific T cells in a murine model of malignant melanoma

New strategies of immunotherapy are currently being evaluated, and the combination of chemo- and immunotherapy has shown promising results. The cytokine interleukin-21 (IL-21) is known to enhance immune function, and in this study we have investigated its ability to boost the efficacy of chemoimmunotherapy-cyclophosphamide and adoptive cell transfer (ACT)-in the B16-OVA/OT-I murine model of malignant melanoma. Subcutaneous B16-OVA tumors were established in C57BL/6J mice 8 days before adoptive transfer of tumor-specific OT-I T cells. In addition to cyclophosphamide and ACT, one group of mice received daily injections of murine IL-21 (mIL-21). Mice treated with mIL-21 had more tumor-specific T cells in the circulation 4 and 7 days following ACT (P=0.004 and P=0.002, respectively). Importantly, mIL-21 and ACT controlled tumor growth instantly and more effectively than ACT alone (P=0.001, day 4)-an effect that persisted up to 5 days after the last mIL-21 injection. We conclude that mIL-21 enhances chemoimmunotherapy: it amplifies the number of tumor-specific T cells in the circulation and also stunts early tumor growth.

Immunotherapy of neuroblastoma by an Interleukin-21-secreting cell vaccine involves survivin as antigen

AIM

IL-21 is the most recently identified member of the IL-2 cytokine family. Here we studied the therapeutic efficacy of IL-21-gene-modified cells (Neuro2a/IL-21) in a syngeneic metastatic neuroblastoma (NB) model.

MATERIALS AND METHODS

Neuro2a/IL-21 cells were tested as subcutaneous (sc) vaccine both in prophylactic and therapeutic settings. Depletion studies, cytotoxicity assay and immunohistochemical analyses were carried out to evaluate the mechanisms involved in tumor rejection.

RESULTS

When injected sc in syngeneic A/J mice viable Neuro2a/IL-21 cells were rejected and induced resistance to a subsequent iv challenge with Neuro2a parental cells (Neuro2a/pc), suggesting the involvement of an immune response. More importantly, in mice bearing Neuro2a/pc micrometastases, a single sc injection of Neuro2a/IL-21 cells significantly increased the mean tumor-free survival of treated animals (43 vs. 22 days) and cured 14% of them. The administration of two or three doses of Neuro2a/IL-21 cell vaccine further increased the mean survival time to 54 and 75 days, and the cure rate to 27 and 33%, respectively, whereas the use of unmodified Neuro2a or mock-transfected cells had no effect. In vivo cell subset depletion and a Winn-assay indicated the involvement of CD8 + CTLs. Immunohistochemical analysis indicated a reduction of CD31+ and VEGFR2+ microvessels in late metastases from therapeutically vaccinated mice. A role of survivin as antigen was suggested by in vitro assays using survivin-synthetic CTL-epitopes.

CONCLUSIONS

Our present data indicate that IL-21-secreting NB cells are effective as therapeutic vaccine in mice bearing metastatic NB, through a specific CTL response involving survivin as antigen, and suggest a potential interest for IL-21 in NB immuno-gene therapy.

Dendritic cell maturation with poly(I:C)-based versus PGE2-based cytokine combinations results in differential functional characteristics relevant to clinical application

In vitro maturation of dendritic cells (DCs) for cancer immunotherapy may be accomplished by cytokine cocktails containing prostaglandin E2 (PGE2). More recently, a poly(I:C)-based protocol has been proposed as a potentially superior alternative because of a strong induction of interleukin (IL)-12 secretion by resulting DCs. As optimal DC maturation represents a crucial issue for cancer vaccination trials, we performed a systematic and comprehensive comparison of both protocols with respect to important indicators of DC function. Although both methods yielded phenotypically mature DCs, transcriptional profiling revealed a substantially higher number of differentially regulated genes after poly(I:C)-based than PGE2-based maturation. Several of these are involved in immunologic processes, indicating that both DC types exhibit subtle, but distinct, molecular properties. Up-regulation of genes encoding the T-cell-attracting chemokines CXCL9, 10, and 11 in poly(I:C)-DC but not PGE2-DC was confirmed on a protein level. Although poly(I:C)-based maturation induced substantial IL-12p70 secretion, poly(I:C)-DC also secreted low levels of IL-10 and showed a significantly higher expression of functionally active indoleamine-2,3-dioxygenase than PGE2-DC, which might mediate immune inhibitory functions. Nonetheless, the number of peptide-specific T cells tended to be higher after in vitro priming with poly(I:C)-DC compared with PGE2-DC. Finally, PGE2-DC displayed superior migratory abilities, which are essential for in vivo applications. In summary, we have identified previously unrecognized shared and distinct molecular features of DCs matured by 2 commonly used protocols that lead to subtle, but significant, immunologic features of the resulting cells relevant to clinical applications.

Aberrant expression of the Th2 cytokine IL-21 in Hodgkin lymphoma cells regulates STAT3 signaling and attracts Treg cells via regulation of MIP-3alpha

The malignant Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (HL) are derived from mature B cells, but have lost a considerable part of the B cell-specific gene expression pattern. Consequences of such a lineage infidelity for lymphoma pathogenesis are currently not defined. Here, we report that HRS cells aberrantly express the common cytokine-receptor gamma-chain (gamma(c)) cytokine IL-21, which is usually restricted to a subset of CD4(+) T cells, and the corresponding IL-21 receptor. We demonstrate that IL-21 activates STAT3 in HRS cells, up-regulates STAT3 target genes, and protects HRS cells from CD95 death receptor-induced apoptosis. Furthermore, IL-21 is involved in up-regulation of the CC chemokine macrophage-inflammatory protein-3alpha (MIP-3alpha) in HRS cells. MIP-3alpha in turn attracts CCR6(+)CD4(+)CD25(+)FoxP3(+)CD127(lo) regulatory T cells toward HRS cells, which might favor their immune escape. Together, these data support the concept that aberrant expression of B lineage-inappropriate genes plays an important role for the biology of HL tumor cells.

Angiostatic activity of the antitumor cytokine interleukin-21

Interleukin-21 (IL-21) is a recently described immunoregulatory cytokine. It has been identified as a very potent immunotherapeutic agent in several cancer types in animal models, and clinical studies are ongoing. IL-21 belongs to the type I cytokine family of which other members, ie, IL-2, IL-15, and IL-4, have been shown to exert activities on vascular endothelial cells (ECs). We hypothesized that IL-21, in addition to inducing the antitumor immune response, also inhibits tumor angiogenesis. In vitro experiments showed a decrease of proliferation and sprouting of activated ECs after IL-21 treatment. We found that the IL-21 receptor is expressed on vascular ECs. Furthermore, in vivo studies in the chorioallantoic membrane of the chick embryo and in mouse tumors demonstrated that IL-21 treatment disturbs vessel architecture and negatively affects vessel outgrowth. Our results also confirm the earlier suggested angiostatic potential of IL-2 in vitro and in vivo. The angiostatic effect of IL-21 is confirmed by the decrease in expression of angiogenesis-related genes. Interestingly, IL-21 treatment of ECs leads to a decrease of Stat3 phosphorylation. Our research shows that IL-21 is a very powerful antitumor compound that combines the induction of an effective antitumor immune response with inhibition of tumor angiogenesis.

Tumor microenvironment and immune escape

This article describes the multiple escape mechanisms used by tumor cells to avoid T-cell-mediated recognition and destruction. The discussion focuses on escape mechanisms that may result from changes at the level of TA-specific cytotoxic T lymphocytes and tumor cells in the tumor microenvironment. Specifically, we discuss the negative impact of regulatory T cells and T-cell apoptosis on the tumor antigen-specific cytotoxic T lymphocyte response. We also discuss changes in the expression of histocompatibility antigens by tumor cells, which may affect tumor cell-immune cell interactions.

IL-21 induces in vivo immune activation of NK cells and CD8(+) T cells in patients with metastatic melanoma and renal cell carcinoma

PURPOSE

Human interleukin-21 (IL-21) is a class I cytokine previously reported in clinical studies on immune responsive cancers. Here we report the effects of systemic IL-21 therapy on the immune system in two phase 1 trials with this novel cytokine.

EXPERIMENTAL DESIGN

Recombinant IL-21 was administered by intravenous bolus injection at dose levels from 1 to 100 microg/kg using two planned treatment regimens: thrice weekly for 6 weeks (3/week); or once daily for five consecutive days followed by nine dose-free days (5 + 9). The following biomarkers were studied in peripheral blood mononuclear cells (PBMC) during treatment: phosphorylation of STAT3, alterations in the composition of leukocyte subsets, ex vivo cytotoxicity, expression of effector molecules in enriched CD8(+) T cells and CD56(+) NK cells by quantitative RT-PCR, and gene array profiling of CD8(+) T cells.

RESULTS

Effects of IL-21 were observed at all dose levels. In the 5 + 9 regimen IL-21 induced a dose dependent decrease in circulating NK cells and T cells followed by a return to baseline in resting periods. In both CD8(+) T cells and CD56(+) NK cells we found up-regulation of perforin and granzyme B mRNA. In addition, full transcriptome analysis of CD8(+) T cells displayed changes in several transcripts associated with increased cell cycle progression, cellular motility, and immune activation. Finally, cytotoxicity assays showed that IL-21 enhanced the ability of NK cells to kill sensitive targets ex vivo.

CONCLUSIONS

IL-21 was biologically active at all dose levels administered with evidence of in vivo NK cell and CD8(+) T cell activation.