IL-15 has innate anti-tumor activity independent of NK and CD8 T cells

TS-2021, a third-generation oncolytic adenovirus that carried Ki67 promoter, TGF-β2 5'UTR, and IL-15 against experimental glioblastoma

Oncolytic virotherapy is a promising therapeutic approach for glioblastoma (GBM) treatment, although the outcomes are partially satisfactory. Hence, more effective strategies are needed urgently to modify therapeutic viruses to enhance their efficiency and safety in killing tumor cells and improve the survival rate of GBM patients. This study generated a new-generation oncolytic adenovirus Ad5 KT-E1A-IL-15 (TS-2021) and evaluated its antitumor efficacy. Ex vivo analyses revealed Ki67 and TGF-β2 co-localized in GBM cells. In addition, TS-2021 selectively replicated in GBM cells, which was dependent on the expression of Ki67 and TGF-β2. The immunocompetent mice model of GBM demonstrated the in vivo efficacy of TS-2021 by inhibiting tumor growth and improving survival proficiently. Notably, TS-2021 effectively reduced MMP3 expression by inactivating the MKK4/JNK pathway, thereby reducing tumor invasiveness. Altogether, the findings of the present study highlight that TS-2021 can effectively target GBM cells expressing high levels of Ki67 and TGF-β2, exerting potent antitumor effects. Additionally, it can improve efficacy and suppress tumor invasiveness by inhibiting the MKK4/JNK/MMP3 pathway. Thus our study demonstrates the efficiency of the novel TS-2021 in the mouse model and provides a potential therapeutic option for patients with GBM.

Mesenchymal stem cells loaded with Ad5-Ki67/IL-15 enhance oncolytic adenovirotherapy in experimental glioblastoma

The conventional treatment strategy for glioblastoma multiforme (GBM) is surgical resection followed by radiotherapy and chemotherapy. Oncolytic adenovirotherapy is a promising alternative to conventional treatment. It provides a strategic combination of direct tumor-specific cell lysis and antitumor immune promotion. Despite advances in oncolytic adenovirotherapy, limitations remain, including the host's antiviral immune response and insufficient viral infiltration into the tumor. Mesenchymal stem cells (MSCs) have emerged as innovative vehicles due to their ability to home to tumors and protect oncolytic adenovirus (oAd) from the host antiviral immune system. We developed an Ad5-Ki67/IL-15 driven by the Ki67 promoter and armed with IL-15. Using this construction, viral replication is related to Ki67 expression in GBM cells. Thus, MSCs with background Ki67 expression can help deliver higher levels of oncolytic viruses and can strike a balance between viral load and cell viability. Using in vitro assay, MSCs loaded with Ad5-Ki67/IL-15 (MSC-Ad5) were shown to exert anti-glioblastoma efficacy. Compared to previous attempts at direct intratumoral injection of high doses of viruses, MSCs loaded with lower doses of viruses exerted stronger therapeutic effects and promoted macrophage/microglia infiltration in a Vivo model. Collectively, our results suggest that the use of MSCs as vehicles of oAd is a promising strategy and deserves further investigation for the treatment of GBM.

Interleukin-15 augments NK cell-mediated ADCC of alemtuzumab in patients with CD52+ T-cell malignancies

Interleukin-15 (IL-15) monotherapy substantially increases the number and activity of natural killer (NK) cells and CD8+ T cells but has not produced clinical responses. In a xenograft mouse model, IL-15 enhanced the NK cell-mediated antibody-dependent cell cytotoxicity (ADCC) of the anti-CD52 antibody alemtuzumab and led to significantly more durable responses than alemtuzumab alone. To evaluate whether IL-15 potentiates ADCC in humans, we conducted a phase 1 single-center study of recombinant human IL-15 and alemtuzumab in patients with CD52-positive mature T-cell malignances. We gave IL-15 subcutaneously 5 days per week for 2 weeks in a 3 + 3 dose escalation scheme (at 0.5, 1, and 2 μg/kg), followed by standard 3 times weekly alemtuzumab IV for 4 weeks. There were no dose-limiting toxicities or severe adverse events attributable to IL-15 in the 11 patients treated. The most common adverse events were lymphopenia (100%), alemtuzumab-related infusion reactions (90%), anemia (90%), and neutropenia (72%). There were 3 partial and 2 complete responses, with an overall response rate of 45% and median duration of response 6 months. Immediately after 10 days of IL-15, there was a median 7.2-fold increase in NK cells and 2.5-fold increase in circulating CD8+ T cells, whereas the number of circulating leukemic cells decreased by a median 38% across all dose levels. Treatment with IL-15 was associated with increased expression of NKp46 and NKG2D, markers of NK-cell activation, and increased ex vivo ADCC activity of NK cells, whereas inhibitory receptors PD1 and Tim3 were decreased. This trial was registered at www.clinicaltrials.gov as #NCT02689453.

Efficacy of a novel double-controlled oncolytic adenovirus driven by the Ki67 core promoter and armed with IL-15 against glioblastoma cells

Background

Glioblastoma (GBM) is an immunosuppressive, highly vascular and devastating malignant brain tumor. Even with progressive combination treatment that includes surgery, radiotherapy, and chemotherapy, the prognosis for GBM patients is still extremely poor. Oncolytic adenovirus (OAd) can specifically replicate in GBM cells, permitting the rapid copy of the therapeutic genes it carries. Moreover, E1A is an essential gene in adenoviral replication and is the first gene expressed upon viral infection. E1A expression can be regulated by the Ki67 promoter, while the CMV promoter drives therapeutic gene expression. However, the efficacy of a double-controlled OAd driven by the Ki67 core promoter and armed with IL-15 against GBM cells has not been investigated.

Methods

Fluorescence microscopy was performed to evaluate infection ability in the viruses. Cell viability was detected by CCK-8 assay. Levels of cytokines in different supernatants were determined by ELISA, and IL-15 gene expression was measured by RT-PCR. Angiogenic capacity was analyzed by tube formation assay.

Results

We successfully constructed a double-controlled oncolytic adenovirus driven by the Ki67 core promoter and armed with IL-15 that selectively infected and killed GBM cells while sparing normal cells. The adenoviruses prime IL-15 gene expression to significantly enhance anti-GBM efficacy through effective activation of microglial cells. Moreover, OAd not only directly inhibits angiogenesis but exhibits potent antiangiogenic capacity mediated by the reduction of VEGF secretion.

Conclusions

These results provide new insight into the effects of a novel double-controlled OAd driven by the Ki67 core promoter and armed with IL-15 in glioblastoma treatment, which may help in the development of novel therapies in solid tumors.

Natural Killer Cell-Based Cancer Immunotherapy: A Review on 10 Years Completed Clinical Trials

NK cell cancer immunotherapy is an emerging anti-tumour therapeutic strategy that explores NK cell stimulation. In this review, we address strategies developed to circumvent limitations to clinical application of NK cell-based therapies, and comprehensively review the design and results of clinical trials conducted in the past 10 years (2008-2018) to test their therapeutic potential. NK cell-based immunotherapy of solid cancers remains controversial, but merit further detailed investigation.

Interleukin-15 suppresses gastric cancer liver metastases by enhancing natural killer cell activity in a murine model

Interleukin (IL)-15 is a promising cytokine for cancer immunotherapy as it is a critical factor for the proliferation and activation of natural killer (NK) cells. Previous studies have suggested critical roles of IL-15 in tumor invasion and metastasis. However, the association between IL-15 and liver metastasis of gastric cancer (LMGC) remains unknown. The present study investigated the therapeutic efficacy of recombinant mouse IL-15 (rmIL-15) in murine LMGC models, in which stable green fluorescent protein (GFP)-expressing MKN45 cells (MKN45-GFP cells) were injected into the spleen parenchyma of mice for liver metastasis. At different treatments (high dose group: 2.5 µg of rmIL-15; low dose group: 0.2 µg of rmIL-15; control group: PBS), it was found that rmIL-15 decreased the formation of liver metastasis sites. Additionally, this treatment lead to improved survival of mice following tumor cell transplantation. Treatment with a high dose of rmIL-15 provided greater therapeutic efficacy by prolonged survival of the mice compared with low dose group and control group. It was found that NK cells isolated from the liver that received the high dose of rmIL-15 showed stronger cytotoxic activity compared with the other two groups on the target cells. These findings hold significant importance for the use of IL-15 as a potential adjuvant/therapeutic for liver metastasis from gastric cancer.

The role of nitric oxide in melanoma

Nitric oxide (NO) is a small gaseous signaling molecule that mediates its effects in melanoma through free radical formation and enzymatic processes. Investigations have demonstrated multiple roles for NO in melanoma pathology via immune surveillance, apoptosis, angiogenesis, melanogenesis, and on the melanoma cell itself. In general, elevated levels of NO prognosticate a poor outcome for melanoma patients. However, there are processes where the relative concentration of NO in different environments may also serve to limit melanoma proliferation. This review serves to outline the roles of NO in melanoma development and proliferation. As demonstrated by multiple in vivo murine models and observations from human tissue, NO may promote melanoma formation and proliferation through its interaction via inhibitory immune cells, inhibition of apoptosis, stimulation of pro-tumorigenic cytokines, activation of tumor associated macrophages, alteration of angiogenic processes, and stimulation of melanoma formation itself.

Characterization of Breast Cancer Preclinical Models Reveals a Specific Pattern of Macrophage Polarization

Drug discovery efforts have focused on the tumor microenvironment in recent years. However, few studies have characterized the stroma component in patient-derived xenografts (PDXs) and genetically engineered mouse models (GEMs). In this study, we characterized the stroma in various models of breast cancer tumors in mice. We performed transcriptomic and flow cytometry analyses on murine populations for a series of 25 PDXs and the two most commonly used GEMs (MMTV-PyMT and MMTV-erBb2). We sorted macrophages from five models. We then profiled gene expression in these cells, which were also subjected to flow cytometry for phenotypic characterization. Hematopoietic cell composition, mostly macrophages and granulocytes, differed between tumors. Macrophages had a specific polarization phenotype related to their M1/M2 classification and associated with the expression of genes involved in the recruitment, invasion and metastasis processes. The heterogeneity of the stroma component of the models studied suggests that tumor cells modify their microenvironment to satisfy their needs. Our observations suggest that such models are of relevance for preclinical studies.

Combined therapy with CTL cells and oncolytic adenovirus expressing IL-15-induced enhanced antitumor activity

Addition of immunoregulation factor to an oncolytic adenovirus being constructed is a developmental step in tumor gene therapy; however, cytokine IL-15 has not been frequently used as a potential cancer therapy agent. Here, we constructed an E2F-1 promoter oncolytic adenovirus based on type 5 adenovirus, which induces viral replication and proliferation in targeted tumor cells. We inserted the IL-15 gene into the E3 region of the model and found that human IL-15 expressing oncolytic adenovirus (Ad-E2F/IL15) shows a more intense antitumor effect than simple oncolytic viruses (Ad-E2F) do. Precisely because IL-15 can activate natural killer (NK) cells, CD8(+)T cells, and other immune cells, in antitumor therapy, Ad-E2F/IL15 was used in combination with cytotoxic T lymphocytes (CTL) to create a virus that can induce IL-15 gene expression while lysing tumors and stimulating the activity and function of adoptive immune cells. The therapeutic effect of this therapy is clearly stronger than that of a single application of oncolytic viruses or CTL, and hence, it could be a potential new tumor therapy.

Interleukin-15 is required for immunosurveillance and immunoprevention of HER2/neu-driven mammary carcinogenesis

Introduction

We previously demonstrated that HER2/neu-driven mammary carcinogenesis can be prevented by an interleukin-12 (IL-12)-adjuvanted allogeneic HER2/neu-expressing cell vaccine. Since IL-12 can induce the release of interleukin-15 (IL-15), in the present study we investigated the role played by IL-15 in HER2/neu driven mammary carcinogenesis and in its immunoprevention.

Methods

HER2/neu transgenic mice with homozygous knockout of IL-15 (here referred to as IL15KO/NeuT mice) were compared to IL-15 wild-type HER2/neu transgenic mice (NeuT) regarding mammary carcinogenesis, profile of peripheral blood lymphocytes and splenocytes and humoral and cellular responses induced by the vaccine.

Results

IL15KO/NeuT mice showed a significantly earlier mammary cancer onset than NeuT mice, with median latency times of 16 and 20 weeks respectively, suggesting a role for IL-15 in cancer immunosurveillance. Natural killer (NK) and CD8+ lymphocytes were significantly lower in IL15KO/NeuT mice compared to mice with wild-type IL-15. The IL-12-adjuvanted allogeneic HER2/neu-expressing cell vaccine was still able to delay mammary cancer onset but efficacy in IL-15-lacking mice vanished earlier: all vaccinated IL15KO/NeuT mice developed tumors within 80 weeks of age (median latency of 53 weeks), whereas more than 70 % of vaccinated NeuT mice remained tumor-free up to 80 weeks of age. Vaccinated IL15KO/NeuT mice showed less necrotic tumors with fewer CD3+ lymphocyes and lacked perforin-positive infiltrating cells compared to NeuT mice. Concerning the anti-vaccine antibody response, antibody titer was unaffected by the lack of IL-15, but less antibodies of IgM and IgG1 isotypes were found in IL15KO/NeuT mice. A lower induction by vaccine of systemic interferon-gamma (IFN-γ) and interleukin-5 (IL-5) was also observed in IL15KO/NeuT mice when compared to NeuT mice. Finally, we found a lower level of CD8+ memory cells in the peripheral blood of vaccinated IL15KO/NeuT mice compared to NeuT mice.

Conclusions

We demonstrated that IL-15 has a role in mammary cancer immunosurveillance and that IL-15-regulated NK and CD8+ memory cells play a role in long-lasting immunoprevention, further supporting the potential use of IL-15 as adjuvant in immunological strategies against tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0588-x) contains supplementary material, which is available to authorized users.

IL-15 suppresses colitis-associated colon carcinogenesis by inducing antitumor immunity

IL-15 regulates the development, survival, and proliferation of multiple innate and adaptive immune cells and plays a dual role, inducing both tumor cell growth and antitumor immunity. However, the role of IL-15 in inflammation-induced cancer remains unclear. To explore this, we have compared the colon carcinoma burden of Il15^-/- and Il15rα ^-/- mice with wild type (WT) mice after induction of colitis-associated colon carcinogenesis utilizing the AOM/DSS model. Compared to WT mice, Il15^-/- but not Il15rα ^-/- mice showed reduced survival, along with higher tumor incidence, colon weight, and tumor size. This suggests that low affinity IL-15 signaling via the shared IL-2Rβ/γc decreases the risk for developing colitis-associated cancer. CD11c-Il15 mice, in which IL-15 expression is reconstituted in Il15^-/- mice under the control of the CD11c-promoter, showed that selective reconstitution of IL-15 in antigen-presenting cells restored the CD8⁺ T and NK cell compartments, serum levels of IFNγ, G-CSF, IL-10, and CXCL1 and reduced tumor burden. After demonstrating IL-15 expression in human colorectal cancer (CRC) cells in situ, we investigated the role of this cytokine in the modulation of key colonic oncogenic pathways in the tumor. While these pathways were found to be unaltered in the absence of IL-15, tumor transcriptome analysis showed that the loss of IL-15 upregulates key inflammatory mediators associated with colon cancer progression, such as IL-1β, IL-22, IL-23, Cxcl5, and Spp1. These findings provide evidence that IL-15 suppresses colitis-associated colon carcinogenesis through regulation of antitumor cytotoxicity, and modulation of the inflammatory tumor micromilieu.

Interleukin-15 modulates adipose tissue by altering mitochondrial mass and activity

Interleukin-15 (IL-15) is an immunomodulatory cytokine that affects body mass regulation independent of lymphocytes; however, the underlying mechanism(s) involved remains unknown. In an effort to investigate these mechanisms, we performed metabolic cage studies, assessed intestinal bacterial diversity and macronutrient absorption, and examined adipose mitochondrial activity in cultured adipocytes and in lean IL-15 transgenic (IL-15tg), overweight IL-15 deficient (IL-15-/-), and control C57Bl/6 (B6) mice. Here we show that differences in body weight are not the result of differential activity level, food intake, or respiratory exchange ratio. Although intestinal microbiota differences between obese and lean individuals are known to impact macronutrient absorption, differing gut bacteria profiles in these murine strains does not translate to differences in body weight in colonized germ free animals and macronutrient absorption. Due to its contribution to body weight variation, we examined mitochondrial factors and found that IL-15 treatment in cultured adipocytes resulted in increased mitochondrial membrane potential and decreased lipid deposition. Lastly, IL-15tg mice have significantly elevated mitochondrial activity and mass in adipose tissue compared to B6 and IL-15-/- mice. Altogether, these results suggest that IL-15 is involved in adipose tissue regulation and linked to altered mitochondrial function.

The absence or overexpression of IL-15 drastically alters breast cancer metastasis via effects on NK cells, CD4 T cells, and macrophages

IL-15 is a cytokine that can affect many immune cells, including NK cells and CD8 T cells. In several tumor models, IL-15 delays primary tumor formation and can prevent or reduce metastasis. In this study, we have employed a model of breast cancer metastasis to examine the mechanism by which IL-15 affects metastasis. When breast tumor cells were injected i.v. into IL-15(-/-), C57BL/6, IL-15 transgenic (TG) and IL-15/IL-15Rα-treated C57BL/6 mice, there were high levels of metastasis in IL-15(-/-) mice and virtually no metastasis in IL-15 TG or IL-15-treated mice. In fact, IL-15(-/-) mice were 10 times more susceptible to metastasis, whereas IL-15 TG mice were at least 10 times more resistant to metastasis when compared with control C57BL/6 mice. Depletion of NK cells from IL-15 TG mice revealed that these cells were important for protection from metastasis. When NK cells were depleted from control C57BL/6 mice, these mice did not form as many metastatic foci as IL-15(-/-) mice, suggesting that other cell types may be contributing to metastasis in the absence of IL-15. We then examined the role of CD4 T cells and macrophages. In IL-15(-/-) mice, in vivo depletion of CD4 T cells decreased metastasis. The lack of IL-15 in IL-15(-/-) mice, and possibly the Th2-polarized CD4 T cells, was found to promote the formation of M2 macrophages that are thought to contribute to metastasis formation. This study reveals that whereas IL-15 effects on NK cells are important, it also has effects on other immune cells that contribute to metastasis.

Delivery of interleukin-15 to B16 melanoma by electroporation leads to tumor regression and long-term survival

Electroporation (EP) is a method used to physically deliver therapeutic molecules such as plasmid DNA directly to tissues. It has been used safely and successfully in clinical studies and preclinical cancer models to deliver genes to a variety of tissues. In cancer research cytokine therapy is emerging as a promising tool that can be used to boost the host response to tumor antigens. The delivery of cytokines as recombinant proteins can result in toxicity and other adverse effects; however the delivery of cytokine genes using EP has been shown to be safe and effective. Interleukin 15 (IL-15) is a cytokine that promotes the innate as well as the adaptive immune response to cancer cells and bacterial pathogens. In this study we used EP to deliver a human IL-15 plasmid (phIL-15) directly to tumors to examine its anti-cancer effects. B16.F10 melanoma tumors were induced in C57BL/6J mice and phIL-15 was delivered three times over the course of a week. Expression of the transgene, tumor volume, long-term survival and resistance to challenge were monitored in these animals. Delivery of IL-15 plasmid by EP resulted in increased IL-15 expression within the tumor compared to the injection only control. This expression peaked at 12 to 18 hours after the first delivery and was sustained at lower levels after the second and third deliveries. The delivery of the phIL-15 resulted in tumor regression, long-term survival and greater protection against tumor recurrence when cancer cells were reintroduced compared to control plasmid. From these results we can conclude that the delivery of IL-15 plasmid to tumors using EP is a promising avenue to investigate for its anti-tumor effects, however more work needs to be done to increase the stability of the gene once it is delivered and to elucidate the anti-tumor mechanism.

Interleukin-15 suppresses hepatitis B virus replication via IFN-β production in a C57BL/6 mouse model

BACKGROUND

Interleukin-15 (IL-15) is a pleiotropic cytokine known to modulate both innate and adaptive immunity. It is suggested that IL-15 may play an important role in the regulation of immune response to hepatitis B virus (HBV).

AIMS

We investigated whether IL-15 could modulate the immune response to HBV.

METHODS

A mouse model for HBV tolerance was established by hydrodynamical injection of pAAV/HBV1.2 plasmid into C57BL/6 mice. This HBV-carrier mouse was simultaneously hydrodynamically injected with either an IL-15-expression plasmid pLIVE-IL-15 or a mock control vector pLIVE-EGFP. The serum levels of HBsAg and HBeAg were measured by radioimmunoassay.

RESULTS

Hydrodynamic injection of the plasmid pLIVE-IL-15 resulted in sustained high level of IL-15 in mouse serum, along with the markedly decreased serum HBsAg and HBeAg titres and liver HBV DNA levels. IL-15 also induced anti-HBV activity in T cell- and B cell-deficient Rag1(-/-) mice. Interestingly, despite an increase in NK cell numbers in both spleen and liver of IL-15 treated mice, the anti-HBV effect of IL-15 was neither dependent on presence of NK cells nor on production of IFN-γ. Furthermore, IL-15 could exert anti-HBV function independent of the common IL-2γ(c) R. Lastly, we found that IFN-β expression in the liver and serum was significantly up-regulated by liver expression of IL-15, and blockade of IFN-β function abrogated the anti-HBV activity of IL-15.

CONCLUSIONS

Liver over-expression of IL-15 may suppress HBV replication in an IFN-β-dependent manner.

Interleukin-15 treatment induces weight loss independent of lymphocytes

Obesity is a chronic inflammatory condition characterized by activation and infiltration of proinflammatory immune cells and a dysregulated production of proinflammatory cytokines. While known as a key regulator of immune natural killer (NK) cell function and development, we have recently demonstrated that reduced expression of the cytokine Interleukin-15 (IL-15) is closely linked with increased body weight and adiposity in mice and humans. Previously, we and others have shown that obese individuals have lower circulating levels of IL-15 and NK cells. Lean IL-15 overexpressing (IL-15 tg) mice had an accumulation in adipose NK cells compared to wildtype and NK cell deficient obese IL-15^−/− mice. Since IL-15 induces weight loss in IL-15^−/− and diet induced obese mice and has effects on various lymphocytes, the aim of this paper was to determine if lymphocytes, particularly NK cells, play a role in IL-15 mediated weight loss. Acute IL-15 treatment resulted in an increased accumulation of NK, NKT, and CD3⁺ T cells in adipose tissue of B6 mice. Mice depleted of NK and NKT cells had similar weight loss comparable to controls treated with IL-15. Finally, IL-15 treatment induces significant weight loss in lymphocyte deficient RAG2^−/−γc^−/− mice independent of food intake. Fat pad cross-sections show decreased pad size with cytokine treatment is due to adipocyte shrinkage. These results clearly suggest that IL-15 mediates weight loss independent of lymphocytes.

IL-15 can signal via IL-15Rα, JNK, and NF-κB to drive RANTES production by myeloid cells

IL-15 plays many important roles within the immune system. IL-15 signals in lymphocytes via trans presentation, where accessory cells such as macrophages and dendritic cells present IL-15 bound to IL-15Rα in trans to NK cells and CD8(+) memory T cells expressing IL-15/IL-2Rβ and common γ chain (γ(c)). Previously, we showed that the prophylactic delivery of IL-15 to Rag2(-/-)γ(c)(-/-) mice (mature T, B, and NK cell negative) afforded protection against a lethal HSV-2 challenge and metastasis of B16/F10 melanoma cells. In this study, we demonstrated that in vivo delivery of an adenoviral construct optimized for the secretion of human IL-15 to Rag2(-/-)γ(c)(-/-) mice resulted in significant increases in spleen size and cell number, leading us to hypothesize that IL-15 signals differently in myeloid immune cells compared with lymphocytes, for which IL-15/IL-2Rβ and γ(c) expression are essential. Furthermore, treatment with IL-15 induced RANTES production by Rag2(-/-)γ(c)(-/-) bone marrow cells, but the presence of γ(c) did not increase bone marrow cell sensitivity to IL-15. This IL-15-mediated RANTES production by Rag2(-/-)γ(c)(-/-) bone marrow cells occurred independently of the IL-15/IL-2Rβ and Jak/STAT pathways and instead required IL-15Rα signaling as well as activation of JNK and NF-κB. Importantly, we also showed that the trans presentation of IL-15 by IL-15Rα boosts IL-15-mediated IFN-γ production by NK cells but reduces IL-15-mediated RANTES production by Rag2(-/-)γ(c)(-/-) myeloid bone marrow cells. Our data clearly show that IL-15 signaling in NK cells is different from that of myeloid immune cells. Additional insights into IL-15 biology may lead to novel therapies aimed at bolstering targeted immune responses against cancer and infectious disease.

Interleukin-15 treatment improves glucose homeostasis and insulin sensitivity in obese mice

The prevalence of metabolic diseases associated with obesity, such as type 2 diabetes, continues to rise along with obesity rates. Recently, obesity has been described as an inflammatory condition, suggesting a link between the dysregulation in proinflammatory cytokine production and the aetiology of these metabolic diseases. While known as an immunomodulatory cytokine, Interleukin-15 (IL-15) has been shown to have effects on adipose tissue and induce weight loss in diet-induced obese mice. As weight loss improves glucose homeostasis, the goal of this study was to determine whether IL-15 impacts glucose regulation in a mouse model of diet-induced obesity. Our data demonstrate that IL-15 treatment significantly improves insulin sensitivity and glucose and insulin responses to an oral glucose challenge compared to obese counterparts and/or lean controls. These results show that IL-15 may be a novel therapeutic target for the treatment of obesity and its associated abnormal glucose regulation.

Expressing human interleukin-15 from oncolytic vesicular stomatitis virus improves survival in a murine metastatic colon adenocarcinoma model through the enhancement of anti-tumor immunity

In this study, we sought to enhance the potency of an oncolytic virus, vesicular stomatitis virus (VSV), by inserting a transgene encoding a highly secreted version of human interleukin-15 (IL-15). IL-15 has shown promise as an immunotherapeutic cytokine, as it is able to enhance both natural killer (NK) and T-cell responses, but it has not yet been tested as a therapeutic transgene in the context of viral oncolysis. The transgene was modified to ensure enhanced secretion of IL-15 from infected cells, leading to strong localized expression from infected CT-26 tumors in vivo. This localized expression in the tumor microenvironment led to a clear enhancement to anti-tumoral T-cell responses and enhanced survival, while additional IL-15 administration systemically failed to further enhance the therapy. Overall, the transient localized expression of IL-15 in the tumour by an oncolytic virus was able to induce stronger anti-tumoral immunity in a murine model of colon carcinoma.

Antitumoral efficacy by systemic delivery of heparin conjugated polyethylenimine-plasmid interleukin-15 complexes in murine models of lung metastasis

Gene therapy shows promising application in cancer therapy, but the lack of an ideal gene delivery system is still a tough challenge for cancer gene therapy. Previously, we prepared a novel cationic nanogel, heparin-polyethylenimine (HPEI), which had potential application in gene delivery. In the present study, we constructed a plasmid with high expression efficiency of interleukin-15 (IL15) and investigated the effects HPEI-plasmid IL15 (HPEI-pIL15) complexes on the distribution level of the lung. We then evaluated the anticancer effect of HPEI-pIL15 complexes on lung metastases of B16-F10 melanoma and CT26 colon carcinoma. These results demonstrated that intravenous injection of the HPEI-pIL15 complex exhibited the highest plasmid distribution level in the lung compared with that of PEI2K-pIL15 and PEI25K-pIL15, and mice treated with HPEI-pIL15 had a lower tumor metastasis index compared with other treatment groups. Moreover, the number of natural killer cells, which were intermingled among the tumor cells, and the level of tumor necrosis factor-α and interferon-γ in the serum also increased in the pIL15-treated mice. Furthermore, the cytotoxic activity of spleen cells also increased significantly in the HPEI-pIL15 group. In addition, induction of apoptosis and inhibition of cell proliferation in lung tumor foci in the HPEI-pIL15 group was observed. Taken together, treating lung metastasis cancer with the HPEI nanogels delivered by plasmid IL15 might be a new and interesting cancer gene therapy protocol.

T cells expanded in presence of IL-15 exhibit increased antioxidant capacity and innate effector molecules

Persistence of effector cytotoxic T lymphocytes (CTLs) during an immunological response is critical for successfully controlling a viral infection or tumor growth. Various cytokines are known to play an important part in regulating the immune response. The IL-2 family of cytokines that includes IL-2 and IL-15 are known to function as growth and survival factors for antigen-experienced T cells. IL-2 and IL-15 possess similar properties, including the ability to induce T cell proliferation. Whereas long-term IL-2 exposure has been shown to promote apoptosis and limit CD8(+) memory T cell survival and proliferation, it is widely believed that IL-15 can inhibit apoptosis and helps maintain a memory CD8(+) T-cell population. However, mechanisms for superior outcomes for IL-15 as compared to IL-2 are still under investigation. Our data shows that human T cells cultured in the presence of IL-15 exhibit increased expression of anti-oxidant molecules glutathione reductase (GSR), thioredoxin reductase 1 (TXNDR1), peroxiredoxin (PRDX) and superoxide dismutase (SOD). An increased expression of cell-surface thiols, intracellular glutathione, and thioredoxins was also noted in IL-15 cultured T cells. Additionally, IL-15 cultured T cells showed an increase in cytolytic effector molecules. Apart from increased level of Granzyme A and Granzyme B, IL-15 cultured T cells exhibited increased accumulation of reactive oxygen (ROS) and reactive nitrogen species (RNS) as compared to IL-2 cultured T cells. Overall, this study suggests that T cells cultured in IL-15 show increased persistence not only due to levels of anti-apoptotic proteins, but also due to increased anti-oxidant levels, which is complimented by increased cytolytic effector functions.

Side population cells isolated from hepatic carcinoma cell lines escape being killed by NK cells from NOD/SCID mice

AIM: To examine whether side population (SP) cells isolated from hepatic carcinoma cell lines can escape being killed by NK cells from NOD/SCID mice.

METHODS: Sorted natural killer (NK) cells from NOD/SCID mice were seeded in dishes and cultured for three days in the presence of 25 ng/mL IL-2 and IL-15 to activate cells. SP cells and main population (MP) cells were sorted with the FACSAria from Huh7 and PLC/REF/5 cell lines and co-cultured with activated NK cells for 12 hours. Cell apoptosis was evaluated by annexin V/7-AAD staining and flow cytometry.

RESULTS: There are no significant differences in cell viability and apoptosis between MP cells and SP cells from Huh7 and PLC/REF/5 cell lines (all P > 0.05). However, the proportions of annexin V+/7-AAD+ cells in MP cells co-cultured with NK cells were significantly higher than those in MP cells cultured alone and SP cells co-cultured with NK cells (Huh7: 8.43 ± 1.56 vs4.33 ± 1.36, 4.41 ± 0.70; PLC/PRF/5: 7.89 ± 1.53 vs 5.47 ± 1.04, 4.94 ± 0.95, all P < 0.05).

CONCLUSION: SP cells isolated from Huh7 and PLC/REF/5 cells could probably escape being killed by activated NK cells from NOD/SCID mice.