Inhibition of tumor growth by NK1.1+ cells and CD8+ T cells activated by IL-15 through receptor beta/common gamma signaling in trans

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.

Poly(I:C) Treatment Prevents Skin Tumor Formation in the Preclinical HPV8 Transgenic Mouse Model

Actinic keratoses and cutaneous squamous cell carcinomas are associated with infections with human papillomavirus of genus beta (betaHPV) in immunosuppressed patients. To date, targeted therapy against betaHPV-associated skin cancer does not exist because of the large number of betaHPV without defined high-risk types. In this study, we hypothesized that the activation of innate antiviral immunity in the skin, asymptomatically infected with betaHPV, induces an antitumor response by in situ autovaccination and prevents the formation of betaHPV-associated skin cancer. To test this, we used the preclinical keratin-14-HPV8 transgenic mouse model, which develops skin tumors after mechanical wounding. Remarkably, treatment with the antiviral immune response activating polyinosinic-polycytidylic acid (poly[I:C]) completely prevented cutaneous tumor growth. The induction of the IFN-induced genes Cxcl10 and Ifit1 by poly(I:C) depended on MDA5 activation. Increased numbers of total and activated CD4 and CD8 T cells were detected in poly(I:C)-treated skin. T cells were found in the skin of poly(I:C)-treated mice but not in the skin tumors of untreated mice. T-cell depletion showed a predominant role of CD4 T cells in poly(I:C)-mediated tumor prevention. Our findings identify the MDA5 ligand poly(I:C) as a promising candidate for in situ autovaccination approaches, which might serve as a treatment strategy against betaHPV-related skin diseases.

An Oncolytic Virus Expressing IL15/IL15Rα Combined with Off-the-Shelf EGFR-CAR NK Cells Targets Glioblastoma

IL15 is a pleiotropic cytokine with multiple roles that improve immune responses to tumor cells. Oncolytic viruses (OV) specifically lyse tumors and activate immune responses. Systemic administration of IL15 or its complex with the IL15Rα and chimeric antigen receptor (CAR) natural killer (NK) cells are currently being tested in the clinic. Here, we generated a herpes simplex 1-based OV-expressing human IL15/IL15Rα sushi domain fusion protein (named OV-IL15C), as well as off-the-shelf EGFR-CAR NK cells, and studied their monotherapy and combination efficacy in vitro and in multiple glioblastoma (GBM) mouse models. In vitro, soluble IL15/IL15Rα complex was secreted from OV-IL15C-infected GBM cells, which promoted GBM cytotoxicity and improved survival of NK and CD8+ T cells. Frozen, readily available off-the-shelf EGFR-CAR NK cells showed enhanced killing of tumor cells compared with empty vector-transduced NK cells. In vivo, OV-IL15C significantly inhibited tumor growth and prolonged survival of GBM-bearing mice in the presence of CD8+ T cells compared with parental OV. OV-IL15C plus EGFR-CAR NK cells synergistically suppressed tumor growth and significantly improved survival compared with either monotherapy, correlating with increased intracranial infiltration and activation of NK and CD8+ T cells and elevated persistence of CAR NK cells in an immunocompetent model. Collectively, OV-IL15C and off-the-shelf EGFR-CAR NK cells represent promising therapeutic strategies for GBM treatment to improve the clinical management of this devastating disease. SIGNIFICANCE: The combination of an oncolytic virus expressing the IL15/IL15Rα complex and frozen, ready-to-use EGFR-CAR NK cells elicits strong antitumor responses in glioblastoma.

Biological effects of IL-15 on immune cells and its potential for the treatment of cancer

Interleukin-15 (IL-15) has recently emerged as a novel immunomodulatory cytokine in cancer immunotherapy. IL-15 has the potential to reject and destroy cancer cells in the tumor microenvironment by expanding and activating natural killer (NK), natural killer T (NKT), and memory (m) CD8+T cells. Due to the feasible outcomes obtained from preclinical studies and phase 1/2 clinical trials, IL-15-based therapy, including chimeric antigen receptor (CAR) T cell or CAR NK cell infusion following in vitro expansion in the presence of IL-15, used in combination with checkpoint inhibitors and other therapy may extend to clinical practice in the future. It is also important to understand the biological characteristics of IL-15 to ensure the maximal benefit of therapeutic strategies. Here, we summarize the current development of IL-15 in the following areas: anti-tumor mechanisms in the tumor microenvironment, advances in IL-15-based therapy itself or in combination with other methods, including biological agents, monoclonal antibodies, and adoptive immunotherapy.

Electrotransfer of IL-15/IL-15Rα Complex for the Treatment of Established Melanoma

Simple Summary

The stimulation of the immune system through the administration of immunomodulatory agents such as cytokines has the potential to be an effective anti-cancer therapy. Obtaining the correct dose is an important aspect with respect to minimizing toxicity and obtaining the desired effect. A method to decrease the toxicity of this type of treatment is to replace the high-dose recombinant protein injections by using DNA expressing genes for one or more of these anti-cancer agents. In this current study, we have evaluated the delivery of interleukin-15 and its receptor in the form of plasmid DNA in a mouse melanoma model. We utilize a delivery approach that can deliver plasmid DNA in a manner that results in the desired level of expression being produced and induces a potent anti-tumor response as well as an immune memory response.

Abstract

Gene electrotransfer (GET) is a safe, reliable, and effective method of delivering plasmid DNA (pDNA) to solid tumors. GET has been previously used to deliver interleukin-15 (IL-15) to mouse melanoma, resulting in long-term tumor regression and the survival of a percentage of treated animals after challenge. To enhance this effect, we evaluated modulating the expression levels of IL-15 and co-expressing its receptor, IL-15Rα. GET was used to deliver plasmids encoding IL-15 and IL-15Rα to established B16.F10 tumors on days 0, 4, and 7. Two delivery protocols that yielded different expression profiles were utilized. Mice that were tumor-free for 50 days were then challenged with B16.F10 cells on the opposite flank and monitored for an additional 50 days. The amount of IL-15 expressed and the presence or absence of IL-15Rα in the treated tumors did not significantly affect the tumor regression and long-term survival. Upon challenge, however, low levels of IL-15 were more protective and resulted in a greater production of anti-tumor cytokines such as IFN-γ and MIP-1β and a greater amount of CD11b+ and CD3e+ cells infiltrating tumors. While mice with high levels of IL-15 showed CD11b+ and CD3e+ cell infiltrate, there was a substantial presence of NK cells that was absent in other treated groups. We can conclude that the level of IL-15 expressed in tumors after GET is an important determinant of the therapeutic outcome, a finding that will help us finetune this type of therapy.

Immunobiology of the IL-15/IL-15Rα complex as an antitumor and antiviral agent

Interleukin (IL)-15 is essential for natural killer (NK), NKT and memory (m) CD8⁺ T cell development and function, and is currently under investigation as an immunotherapeutic agent for the treatment of cancer. Recently, the creation of IL-15 superagonist by complexing IL-15 and its high affinity receptor alpha (IL-15 Rα) in solution, inspired by the natural trans-presentation of IL-15, advances the potential of IL-15-based tumor immunotherapy. IL-15 superagonist shows promising advantages over monomeric IL-15 such as sustaining high circulating concentrations due to prolonged half-life and more potently stimulating NK and CD8⁺ T effector lymphocytes. So far, there are three different forms of recombinant IL-15 superagonist fusion protein based on configurational modifications. Gene therapy using engineered cells co-expressing IL-15/IL-15 Rα complex for cancer treatment is also emerging. All forms have demonstrated efficacy in causing tumor regression in animal studies, which provides strong rationale for advancing IL-15 superagonist through clinical trials. To date, there are fourteen phase I/II IL-15 superagonist trials in cancer patients and one phase I trial in HIV patients. Information generated by ongoing trials regarding the toxicity and efficacy of IL-15 superagonist is awaited. Finally, we elaborate on immunotoxicity caused by IL-15 superagonist in preclinical studies and discuss important safety considerations.

Tethered IL-15 augments antitumor activity and promotes a stem-cell memory subset in tumor-specific T cells

Adoptive immunotherapy retargeting T cells to CD19 via a chimeric antigen receptor (CAR) is an investigational treatment capable of inducing complete tumor regression of B-cell malignancies when there is sustained survival of infused cells. T-memory stem cells (T_SCM) retain superior potential for long-lived persistence, but challenges exist in manufacturing this T-cell subset because they are rare among circulating lymphocytes. We report a clinically relevant approach to generating CAR⁺ T cells with preserved T_SCM potential using the Sleeping Beauty platform. Because IL-15 is fundamental to T-cell memory, we incorporated its costimulatory properties by coexpressing CAR with a membrane-bound chimeric IL-15 (mbIL15). The mbIL15-CAR T cells signaled through signal transducer and activator of transcription 5 to yield improved T-cell persistence independent of CAR signaling, without apparent autonomous growth or transformation, and achieved potent rejection of CD19⁺ leukemia. Long-lived T cells were CD45RO^negCCR7⁺CD95⁺, phenotypically most similar to T_SCM, and possessed a memory-like transcriptional profile. Overall, these results demonstrate that CAR⁺ T cells can develop long-term persistence with a memory stem-cell phenotype sustained by signaling through mbIL15. This observation warrants evaluation in clinical trials.

IL-15 receptor alpha as the magic wand to boost the success of IL-15 antitumor therapies: The upswing of IL-15 transpresentation

Interleukin (IL)-15 as a stand-alone therapy can activate the antitumor functions of immune effector cells resulting in significant tumor regression. Interestingly, combining IL-15 with the α-moiety of its receptor (IL-15Rα), also called IL-15 transpresentation, increases the in vivo half-life of IL-15 and enhances binding of IL-15 with cells expressing the IL-15Rβγ, such as NK cells and CD8⁺ T cells. These features enlarge the signal transmission of IL-15, resulting in improved proliferation and antitumor activities of both NK cells and CD8⁺ T cells, eventually leading to enhanced killing of tumor cells. In this review, we discuss the antitumor strategies in which this IL-15 transpresentation mechanism is implemented, that are currently under preclinical investigation. Furthermore, we give an overview of the studies in which the IL-15/IL-15Rα complexes are combined with other antitumor therapies. The promising results in these preclinical studies have incited several clinical trials to test the safety and efficacy of IL-15 transpresentation strategies to treat both hematological and advanced solid tumors.

Mucosal-associated invariant T cells from patients with tuberculosis exhibit impaired immune response

OBJECTIVES

To identify factors which regulate MAIT cell response to Mycobacterium tuberculosis antigens, and to investigate the role of MAIT cells in patients with active tuberculosis.

METHODS

Immune response of MAIT cells to M. tuberculosis antigens were compared between patients with active TB and healthy controls by flow cytometry and RNA sequencing.

RESULTS

IFN-γ response of MAIT cells to M. tuberculosis lysates was dramatically improved by signal 3 cytokine IL-15 (p = 0.0002). Patients with active TB exhibited highly reduced IFN-γ production in MAIT cells stimulated with M. tuberculosis lysates/IL-15 compared with healthy controls (p < 0.0001) and individuals with latent TB infection (p = 0.0008). RNA sequencing of flow-sorted MAIT cells from patients with TB and healthy controls identified numerous differentially expressed genes, and the expression of genes that encode IFN-γ, TNF-α, IL-17F, granulysin and granzyme B were all down-regulated in patients with TB. MAIT cells from patients with TB has significantly lower expression of γc receptor than those from healthy controls under condition of Mtb lysates/IL-15 stimulation (p = 0.0028). Blockade of both γc and IL-2Rβ receptors resulted in highly reduced frequency of IFN-γ-producing MAIT cells (79.4%) (p = 0.0011).

CONCLUSIONS

MAIT cells from patients with active TB exhibited impaired cytokine and cytotoxic response to M. tuberculosis antigens.

Dendritic cell-derived interleukin-15 is crucial for therapeutic cancer vaccine potency

IL-15 supports improved antitumor immunity. How to best incorporate IL-15 into vaccine formulations for superior cancer immunotherapy remains a challenge. DC-derived IL-15 (DCIL-15) notably has the capacity to activate DC, to substitute for CD4⁺ Th and to potentiate vaccine efficacy making IL-15-based therapies attractive treatment options. We observed in transplantable melanoma, glioma and metastatic breast carcinoma models that DCIL-15-based DNA vaccines in which DC specifically express IL-15 and simultaneously produce tumor Aghsp70 were able to mediate potent therapeutic efficacy that required both host Batf3⁺ DC and CD8⁺ T cells. In an inducible Braf^V600E/Pten-driven murine melanoma model, DCIL-15 (not rIL-15)-based DNA vaccines elicited durable therapeutic CD8⁺ T cell-dependent antitumor immunity. DCIL-15 was found to be superior to rIL-15 in "licensing" both mouse and human DC, and for activating CD8⁺ T cells. Such activation occurred even in the presence of Treg, without a need for CD4⁺ Th, but was IL-15/IL-15Rα-dependent. A single low-dose of DCIL-15 (not rIL-15)-based DC vaccines induced therapeutic antitumor immunity. CD14⁺ DC emigrating from human skin explants genetically-immunized by IL-15 and Aghsp70 were more effective than similar DC emigrating from the explants genetically-immunized by Aghsp70 in the presence of rIL-15 in expressing membrane-bound IL-15/IL-15Rα and activating CD8⁺ T cells. These results support future clinical use of DCIL-15 as a therapeutic agent in battling cancer.

Myxoma virus expressing a fusion protein of interleukin-15 (IL15) and IL15 receptor alpha has enhanced antitumor activity

Myxoma virus, a rabbit poxvirus, can efficiently infect various types of mouse and human cancer cells. It is a strict rabbit-specific pathogen, and is thought to be safe as a therapeutic agent in all non-rabbit hosts tested including mice and humans. Interleukin-15 (IL15) is an immuno-modulatory cytokine with significant potential for stimulating anti-tumor T lymphocytes and NK cells. Co-expression of IL15 with the α subunit of IL15 receptor (IL15Rα) greatly enhances IL15 stability and bioavailability. Therefore, we engineered a new recombinant myxoma virus (vMyx-IL15Rα-tdTr), which expresses an IL15Rα-IL15 fusion protein plus tdTomato red fluorescent reporter protein. Permissive rabbit kidney epithelial (RK-13) cells infected with vMyx-IL15Rα-tdTr expressed and secreted the IL15Rα-IL15 fusion protein. Functional activity was confirmed by demonstrating that the secreted fusion protein stimulated proliferation of cytokine-dependent CTLL-2 cells. Multi-step growth curves showed that murine melanoma (B16-F10 and B16.SIY) cell lines were permissive to vMyx-IL15Rα-tdTr infection. In vivo experiments in RAG1-/- mice showed that subcutaneous B16-F10 tumors treated with vMyx-IL15Rα-tdTr exhibited attenuated tumor growth and a significant survival benefit for the treated group compared to the PBS control and the control viruses (vMyx-IL15-tdTr and vMyx-tdTr). Immunohistological analysis of the subcutaneous tumors showed dramatically increased infiltration of NK cells in vMyx-IL15Rα-tdTr treated tumors compared to the controls. In vivo experiments with immunocompetent C57BL/6 mice revealed a strong infiltrate of both NK cells and CD8+ T cells in response to vMyx-IL15Rα-tdTr, and prolonged survival. We conclude that delivery of IL15Rα-IL15 in a myxoma virus vector stimulates both innate and adaptive components of the immune system.

Tumor targeting of the IL-15 superagonist RLI by an anti-GD2 antibody strongly enhances its antitumor potency

Immunocytokines (ICKs) targeting cytokines to the tumor environment using antibodies directed against a tumor-associated antigen often have a higher therapeutic index than the corresponding unconjugated cytokines. Various ICKs displaying significant antitumoral effects in several murine tumor models have already been developed, and some of them, in particular interleukin (IL)-2-based ICKs, are in Phase II clinical trials. Although sharing common biological activities with IL-2 in vitro, IL-15 is now considered as having a better potential in antitumor immunotherapeutical strategies and has been shown to be less toxic than IL-2 in preclinical studies. We previously developed the fusion protein RLI, linking a soluble form of human IL-15Rα-sushi+ domain to human IL-15. RLI showed better biological activities than IL-15 in vitro as well as higher antitumoral effects in vivo in murine and human cancer models. Here, we investigated, in the context of an ICK, the effect of associating RLI with an antibody targeting the GD2 ganglioside, a validated tumoral target expressed on many neurectodermal tumors. Anti-GD2-RLI fully retained the cytokine potential of RLI and the antibody effector functions (antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity). It displayed strong antitumor activities in two syngeneic cancer models in immunocompetent mice (subcutaneous EL4 and metastatic NXS2). Its therapeutic potency was higher than those of RLI and anti-GD2 alone or in combination. We suggest that this is related to its bifunctional (cytokine and antibody) nature.

Small cell lung cancer tumour cells induce regulatory T lymphocytes, and patient survival correlates negatively with FOXP3+ cells in tumour infiltrate

Small cell lung cancer (SCLC) kills at least one person every 2 hr in the United Kingdom. Some patients do relatively well but most have rapidly progressive disease. There is no effective treatment and overall 2-year survival is less than 5%. Patients with SCLC have poorly understood local and systemic immune defects and can be immunocompromised. As CD4(+) T lymphocytes coordinate and regulate immunity, a better understanding of interactions between SCLC tumour cells and CD4(+) T cells may lead to effective molecular immunotherapy. We show that some, but not all, SCLC tumour cell lines secrete molecules that induce IL-10 secretion by and de novo differentiation of functional CD4(+)CD25(+)FOXP3(+)CD127(lo)Helios(-) regulatory T (Treg) cells in healthy blood lymphocytes. FOXP3(+) T cells were found in SCLC tumour biopsies, and patients with higher ratios of FOXP3(+) cells in tumour infiltrates have a worse survival rate. The inhibitory effect of SCLC tumour cells was not affected by blocking IL-10 receptor or TGF-β signalling but was partially reversed by blocking IL-15, which is reported to be involved in human Treg cells induction. IL-15 was secreted by SCLC cells that inhibited CD4(+) T-cell proliferation and was present in SCLC biopsy tumour cells. These novel findings demonstrate that SCLC tumour cells can induce CD4(+) T-cell-mediated immunosuppression. This gives a potential mechanism by which SCLC tumour cells may downregulate local and systemic immune responses and contribute to poor patient survival. Our data suggest that IL-15 and Treg cells are potential new therapeutic targets to improve immune response and patient survival in SCLC.

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.

IL-15, in synergy with RAE-1ɛ, stimulates TCR-independent proliferation and activation of CD8(+) T cells

CD8(+) T cells play critical roles in immunosurveillance by killing malignant or virally infected cells. Interleukin 15 (IL-15) is a critical cytokine for promoting proliferation and the effector capacity of CD8(+) T cells, and has been used to support the growth of CD8(+) T cells in cellular therapies of neoplastic diseases. Recent studies have shown that IL-15, in synergy with other cytokines, such as IL-6, enhances the T-cell receptor (TCR)-independent proliferation and function of CD8(+) T cells. The aim of the present study was to investigate the role of BaF3-mb15-RAE cells in stimulating mouse CD8(+) T cells. BaF3 cells were cultured and B16F10 cells were grown in DMEM. MTT assay was used to detect the proliferation of CD8(+) T cells. Cells were analyzed using flow cytometry. The results showed that IL-15 synergistically acts with another T-cell stimulatory molecule, RAE1ɛ, to potently promote the proliferation of CD8(+) T cells, induce CD8(+) T-cell activation and enhance granzyme B and interferon-γ (IFN-γ) production in the absence of signaling via the TCR. Moreover, IL-15 in combination with RAE1ɛ resulted in a cooperative effect on CD8(+) T-cell-mediated cytotoxicity against B16F10 tumor cells. Thus, results of the present study showed that IL-15, in synergy with RAE1ɛ, enhances the TCR-independent effector function of CD8(+) T cells in vitro, which may be useful in the cellular immunotherapy of cancer.

Constitutive STAT5 activation correlates with better survival in cervical cancer patients treated with radiation therapy

PURPOSE

Constitutively activated signal transducers and activators of transcription (STAT) factors, in particular STAT1, STAT3, and STAT5, have been detected in a wide variety of human primary tumors and have been demonstrated to directly contribute to oncogenesis. However, the expression pattern of these STATs in cervical carcinoma is still unknown, as is whether or not they have prognostic significance. This study investigated the expression patterns of STAT1, STAT3, and STAT5 in cervical cancer and their associations with clinical outcomes in patients treated with radical radiation therapy.

METHODS AND MATERIALS

A total of 165 consecutive patients with International Federation of Gynecology and Obstetrics (FIGO) Stages IB to IVA cervical cancer underwent radical radiation therapy, including external beam and/or high-dose-rate brachytherapy between 1989 and 2002. Immunohistochemical studies of their formalin-fixed, paraffin-embedded tissues were performed. Univariate and multivariate analyses were performed to identify and to evaluate the effects of these factors affecting patient survival.

RESULTS

Constitutive activations of STAT1, STAT3, and STAT5 were observed in 11%, 22%, and 61% of the participants, respectively. While STAT5 activation was associated with significantly better metastasis-free survival (p < 0.01) and overall survival (p = 0.04), STAT1 and STAT3 activation were not. Multivariate analyses showed that STAT5 activation, bulky tumor (≥ 4 cm), advanced stage (FIGO Stages III and IV), and brachytherapy (yes vs. no) were independent prognostic factors for cause-specific overall survival. None of the STATs was associated with local relapse. STAT5 activation (odds ratio = 0.29, 95% confidence interval = 0.13-0.63) and advanced stage (odds ratio = 2.54; 95% confidence interval = 1.03-6.26) were independent predictors of distant metastasis.

CONCLUSIONS

This is the first report to provide the overall expression patterns and prognostic significance of specific STATs in cervical carcinoma. Our results indicate that constitutive STAT5 activation correlates with better metastasis-free survival and overall survival in cervical cancer patients who have received radiation therapy.

Immune response in ovarian cancer: how is the immune system involved in prognosis and therapy: potential for treatment utilization

Ovarian cancer is one of the leading causes of cancer-related death among women. Resistance to the disease occurs in more than 70% of the cases even after treated with chemotherapy agents such as paclitaxel- and platinum-based agents. The immune system is increasingly becoming a target for intense research in order to study the host's immune response against ovarian cancer. T cell populations, including NK T cells and Tregs, and cytokines have been associated with disease outcome, indicating their increasing clinical significance, having been associated with prognosis and as markers of disease progress, respectively. Harnessing the immune system capacity in order to induce antitumor response remains a major challenge. This paper examines the recent developments in our understanding of the mechanisms of development of the immune response in ovarian cancer as well as its prognostic significance and the existing experience in clinical studies.

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

The innate immune system is crucial for host defense and immunosurveillance against pathogens and tumor cells. IL-15 is a pleiotropic cytokine with important effects on cells of the innate and adaptive immune systems. The NK cell- and CD8(+) T cell-mediated functions of IL-15 against tumor cells have been well documented. However, it has not been established whether IL-15 has innate anti-tumor functions independent of these cells. Here, we explored the innate anti-tumor potential of IL-15 using a B16F10 melanoma tumor model. IL-15tg mice exhibited significantly more resistance to tumor growth and metastasis compared to B6 mice, and to IL-15(-/-) mice, which exhibited increased susceptibility to B16F10 challenge. In vivo depletion of NK cells and CD8(+) T cells abrogated the innate resistance to B16F10 cells in B6 but not in IL-15tg mice. In addition, lung macrophages from IL-15tg mice produced significantly higher levels of NO and IL-12 compared with macrophages from B6 or IL-15(-/-) mice. To examine whether IL-15 has innate anti-tumor activity independent of NK cells and CD8(+) T cells, we developed Ad-Op-hIL-15; this resulted in significantly higher levels of biologically active hIL-15. Delivery of Ad-Op-hIL-15 into RAG-2(-/-)/gamma(c)(-/-) mice significantly suppressed tumor burden in the lungs compared with the control adenovirus vector. Our results show that IL-15 can have innate anti-tumor activity independent of NK cells and CD8(+) T cells and the common gamma(c)R.

High antitumor activity of RLI, an interleukin-15 (IL-15)-IL-15 receptor alpha fusion protein, in metastatic melanoma and colorectal cancer

Interleukin (IL)-15 has an important role in tumor immunosurveillance and has a contemplated use in tumor immunotherapy. We have previously engineered the fusion protein RLI, composed of the NH(2)-terminal (amino acids 1-77, sushi+) domain of IL-15 receptor alpha coupled via a linker to IL-15, and shown that it displayed far better efficacy than IL-15 in vitro. In this report, we investigated in vivo whether RLI would be a better alternative than IL-15 and IL-2 for cancer treatment using two distinct animal models. B16F10 mouse melanoma cells were injected in C57BL/6 mice either i.v. or intrasplenically for lung or liver metastasis, respectively. HCT-116 human colorectal cancer cells were injected in the cecum of nude mice. We show that RLI has a higher efficiency than IL-15 or IL-2 to reduce lung and liver metastasis and enhance survival in the mouse B16F10 melanoma model, a result that was associated with a higher half-life in vivo. We also found that the antitumoral effect of RLI was completely abolished by in vivo depletion of natural killer cells using anti-asialoGM1 antibody. Moreover, RLI was also efficient to reduce by 50% tumor growth and the progression of metastasis of human colon carcinoma cells in an orthotopic nude mouse model. The fusion protein RLI has revealed strong anticancer effect in two different cancer models overcoming the limited effect of IL-15 by increasing its bioavailability and efficiency. These findings hold significant importance for the use of RLI as a potential adjuvant/therapeutic.

Expression of IL-15RA or an IL-15/IL-15RA fusion on CD8+ T cells modifies adoptively transferred T-cell function in cis

IL-15 and IL-15 receptor alpha (IL-15RA) play a significant role in multiple aspects of T-cell biology. However, given the evidence that IL-15RA can present IL-15 in trans, the functional capacity of IL-15RA expressed on CD8(+) T cells to modify IL-15 functions in cis is currently unclear. In the current study, we explore the functional consequences of IL-15RA, expression on T cells using a novel method to transfect naive CD8(+) T cells. We observed that RNA nucleofection led to highly efficient, non-toxic, and rapid manipulation of protein expression levels in unstimulated CD8(+) T cells. We found that transfection of unstimulated CD8(+) T cells with IL-15RA RNA led to enhanced viability of CD8(+) T cells in response to IL-15. Transfection with IL-15RA enhanced IL-15-mediated phosphorylation of STAT5 and also promoted IL-15-mediated proliferation in vivo of adoptively transferred naïve CD8(+) T cells. We demonstrated that IL-15RA can present IL-15 via cis-presentation on CD8(+) T cells. Finally, we showed that transfection with a chimeric construct linking IL-15 to IL-15RA cell autonomously enhances the viability and proliferation of primary CD8(+) T cells and cytotoxic potential of antigen-specific CD8(+) T cells. The clinical implications of the current study are discussed.