The combined action of IL-15 and IL-12 gene transfer can induce tumor cell rejection without T and NK cell involvement

Noncovalently particle-anchored cytokines with prolonged tumor retention safely elicit potent antitumor immunity

Preclinical studies have shown that immunostimulatory cytokines elicit antitumor immune responses but their clinical use is limited by severe immune-related adverse events upon systemic administration. Here, we report a facile and versatile strategy for noncovalently anchoring potent Fc-fused cytokine molecules to the surface of size-discrete particles decorated with Fc-binding peptide for local administration. Following intratumoral injection, particle-anchored Fc cytokines exhibit size-dependent intratumoral retention. The 1-micrometer particle prolongs intratumoral retention of Fc cytokine for over a week and has minimal systemic exposure, thereby eliciting antitumor immunity while eliminating systemic toxicity caused by circulating cytokines. In addition, the combination of these particle-anchored cytokines with immune checkpoint blockade antibodies safely promotes tumor regression in various syngeneic tumor models and genetically engineered murine tumor models and elicits systemic antitumor immunity against tumor rechallenge. Our formulation strategy renders a safe and tumor-agnostic approach that uncouples cytokines' immunostimulatory properties from their systemic toxicities for potential clinical application.

The implications of nitric oxide metabolism in the treatment of glial tumors

Glial tumors are the most common intracranial malignancies. Unfortunately, despite such a high prevalence, patients' prognosis is usually poor. It is related to the high invasiveness, tendency to relapse and the resistance of tumors to traditional methods of treatment. An important link in the aspect of these issues may be nitric oxide (NO) metabolism. It is a very complex mechanism with multidirectional effects on the neoplastic process. Depending on the concentration axis, it can both exert pro-tumor action as well as contribute to the inhibition of tumorigenesis. The latest observations show that the control of its metabolism can be very helpful in the development of new methods of treating gliomas, as well as in increasing the effectiveness of the agents currently used. The influence of nitric oxide and nitric oxide synthase (NOS) activity on glioma stem cells seem to be of particular importance. The use of specific inhibitors may allow the reduction of tumor growth and its tendency to relapse. Another important feature of GSCs is their conditioning of glioma resistance to traditional forms of treatment. Recent studies have shown that modulation of NO metabolism can suppress this effect, preventing the induction of radio and chemoresistance. Moreover, nitric oxide is involved in the regulation of a number of immune mechanisms. Adequate modulation of its metabolism may contribute to the induction of an anti-tumor response in the patients' immune system.

Immunological Effects and Viral Gene Expression Determine the Efficacy of Oncolytic Measles Vaccines Encoding IL-12 or IL-15 Agonists

Tumor-targeted immunomodulation using oncolytic viral vectors is currently being investigated as a promising strategy in cancer therapy. In a previous study, we showed that a measles virus Schwarz vaccine strain (MeVac) vector encoding an interleukin-12 fusion protein (FmIL-12) is an effective immunotherapy in the MC38cea murine colon adenocarcinoma model. We hypothesized that MeVac encoding interleukin-15 may mediate enhanced T and NK cell responses and thus increase the therapeutic efficacy, especially in NK cell-controlled tumors. Therefore, we generated MeVac vectors encoding an interleukin-15 superagonist, FmIL-15. Replication and oncolytic capacity, transgene expression, and functionality of MeVac FmIL-15 vectors were validated in vitro. Effects on the tumor immune landscape and therapeutic efficacy of both FmIL-12 and FmIL-15 vectors were studied in the MC38cea and B16hCD46 tumor models. Treatment with MeVac FmIL-15 increased T and NK cell infiltration in both models. However, MeVac FmIL-12 showed more robust viral gene expression and immune activation, resulting in superior anti-tumor efficacy. Based on these results, MeVac encoding a human IL-12 fusion protein was developed for future clinical translation.

IL-15/IL-15Rα/CD80-expressing AML cell vaccines eradicate minimal residual disease in leukemic mice

Engineered autologous acute myeloid leukemia (AML) cells present multiple leukemia-associated and patient-specific antigens and as such hold promise as immunotherapeutic vaccines. However, prior vaccines have not reliably induced effective antileukemic immunity, in part because AML blasts have immune inhibitory effects and lack expression of the critical costimulatory molecule CD80. To enhance induction of leukemia-specific cytolytic activity, 32Dp210 murine AML cells were engineered to express either CD80 alone, or the immunostimulatory cytokine interleukin-15 (IL-15) with its receptor α (IL-15Rα), or heterodimeric IL-15/IL-15Rα together with CD80 and tested as irradiated cell vaccines. IL-15 is a γc-chain cytokine, with unique properties suited to stimulating antitumor immunity, including stimulation of both natural killer and CD8⁺ memory T cells. Coexpression of IL-15 and IL-15Rα markedly increases IL-15 stability and secretion. Non-tumor-bearing mice vaccinated with irradiated 32Dp210-IL-15/IL-15Rα/CD80 and challenged with 32Dp210 leukemia had greater survival than did mice treated with 32Dp210-CD80 or 32Dp210-IL-15/IL-15Rα vaccines, whereas no unvaccinated mice inoculated with leukemia survived. In mice with established leukemia, treatment with 32Dp210-IL-15/IL-15Rα/CD80 vaccination stimulated unprecedented antileukemic immunity enabling 80% survival, an effect that was abrogated by anti-CD8 antibody-mediated depletion in vivo. Because, clinically, AML vaccines are administered as postremission therapy, we established a novel model in which mice with high leukemic burdens were treated with cytotoxic therapy to induce remission (<5% marrow blasts). Postremission vaccination with 32Dp210-IL-15/IL-15Rα/CD80 achieved 50% overall survival in these mice, whereas all unvaccinated mice achieving remission subsequently relapsed. These studies demonstrate that combined expression of IL-15/IL-15Rα and CD80 by syngeneic AML vaccines stimulates effective and long-lasting antileukemic immunity.

Prostate cancer cells enhance interleukin-15-mediated expansion of NK cells

OBJECTIVES

To identify cytokines that can activate and expand NK cells in the presence of prostate cancer cells in order to determine whether these agents may be useful in future intra-tumoural administration in pre-clinical and clinical prostate cancer trials.

MATERIALS AND METHODS

Lymphocytes isolated from normal donor blood were set up in co-cultures with either cancer or non-cancerous prostate cell lines, together with each of the cytokines interleukin (IL)-2, IL-12, IL-15, interferon (IFN)-γ or IL-21 for a period of 7 days. Then, expansion of NK cells, NKT cells and CD8 T cells was measured by flow cytometry and compared with the expansion of the same cells in the absence of prostate cells. The cytotoxic activity of NK cells, as measured by perforin and tumour cell killing, was also assessed. NK cell receptors and their corresponding ligands on prostate tumour cells were analysed to determine whether any of these were modulated by co-culture. The role of the tumour-secreted heat shock proteins HSP90 and HSP70 in the expansion of NK cells in the co-cultures was also investigated because of their effects on NK and CD8 T-cell activation.

RESULTS

We showed that, among a panel of cytokines known to cause NK cell activation and expansion, only IL-15 could actively induce expansion of NK, NKT and CD8 T cells in the presence of prostate cancer cell lines. Furthermore, the expansion of NK cells was far greater (up to 50% greater) in the presence of the cancer cells (LNCaP, PC3) than when lymphocytes were incubated alone. In contrast, non-cancerous cell lines (PNT2 and WPMY-1) did not exert any expansion of NK cells. The cytolytic activity of the NK cells, as measured by perforin, CD107a and killing of tumour cells, was also greatest in co-cultures with IL-15. Examination of NK cell receptors shows that NKG2D is upregulated to a greater degree in the presence of prostate cancer cells, compared with the upregulation with IL-15 in lymphocytes alone. However, blocking of NKG2D does not inhibit the enhanced expansion of NK cells in the presence of tumour cells.

CONCLUSIONS

Among a panel of NK cell-activating cytokines, IL-15 was the only cytokine that could stimulate expansion of NK cells in the presence of prostate cancer cells; therefore IL-15 may be a good candidate for novel future intra-tumoural therapy of the disease.

Anti-PD-1 therapy redirects macrophages from an M2 to an M1 phenotype inducing regression of OS lung metastases

Osteosarcoma (OS) pulmonary metastasis translates into poor patient survival. The implication of PD‐1‐PD‐L1 pathway in the context of NK cells and/or macrophages in OS is unknown. We investigated the effect of anti‐PD‐1 in OS lung metastasis and the role of NK cells and/or macrophages in anti‐PD‐1 responses. A human LM7 OS mouse model was used. Immunohistochemistry for tissues (PD‐L1, caspase‐3, Ki‐67, NK cells, macrophages), and Western blotting for OS lung tumors (p‐Stat3, p‐Erk1/2) was performed. NK and macrophages were assessed using flow cytometry. NK cell and macrophage depletion were conducted using anti‐asialo GM1 and clodrosome, respectively. PD‐L1 expression was observed in human OS cells and OS patient lung metastases. Anti‐PD1 antibody led to a significant decrease in the number of OS lung metastases, enhanced tumor apoptosis, decreased tumor cell proliferation, and p‐STAT‐3/p‐Erk1/2 signaling blockade in OS lung tumors. NK cells and macrophages in OS lung tumors expressed PD‐1 and anti‐PD1 increased NK cell and macrophage tumor infiltration. Increased numbers of antitumor M1 macrophages and decreased pro‐inflammatory M2 macrophages were seen. NK depletion did not affect therapeutic effect of anti‐PD‐1, suggesting that NK cells were not directly involved. However, macrophage depletion significantly compromised anti‐PD1 efficacy, confirming their role in efficacy of anti‐PD‐1 against OS lung metastasis. Our findings suggest that OS lung metastases regression by anti‐PD1 can be attributed to activated tumor M1 macrophages and reduced M2 macrophages. Owing to the co‐relation of M1 macrophages with OS patient outcome, we provide a novel mechanism of PD‐1 blockade and a basis for future clinical trials for anti‐PD‐1 antibodies in OS.

IL-2 and Beyond in Cancer Immunotherapy

The development of the T- and natural killer (NK) cell growth factor IL-2 has been a sentinel force ushering in the era of immunotherapy in cancer. With the advent of clinical grade recombinant IL-2 in the mid-1980s, oncologists could for the first time directly manipulate lymphocyte populations with systemic therapy. By itself, recombinant IL-2 can induce clinical responses in up to 15% of patients with metastatic cancer or renal cell carcinoma. When administered with adoptively transferred tumor-reactive lymphocytes, IL-2 promotes T cell engraftment and response rates of up to 50% in metastatic melanoma patients. Importantly, these IL-2-driven responses can yield complete and durable responses in a subset of patients. However, the use of IL-2 is limited by toxicity and concern of the expansion of T regulatory cells. To overcome these limitations and improve response rates, other T cell growth factors, including IL-15 and modified forms of IL-2, are in clinical development. Administering T cell growth factors in combination with other agents, such as immune checkpoint pathway inhibitors, may also improve efficacy. In this study, we review the development of T- and NK cell growth factors and highlight current combinatorial approaches based on these reagents.

Nitric oxide donors increase PVR/CD155 DNAM-1 ligand expression in multiple myeloma cells: role of DNA damage response activation

Background

DNAX accessory molecule-1 (DNAM-1) is an activating receptor constitutively expressed by macrophages/dendritic cells and by T lymphocytes and Natural Killer (NK) cells, having an important role in anticancer responses; in this regard, combination therapies able to enhance the expression of DNAM-1 ligands on tumor cells are of therapeutic interest. In this study, we investigated the effect of different nitric oxide (NO) donors on the expression of the DNAM-1 ligand Poliovirus Receptor/CD155 (PVR/CD155) in multiple myeloma (MM) cells.

Methods

Six MM cell lines, SKO-007(J3), U266, OPM-2, RPMI-8226, ARK and LP1 were used to investigate the activity of different nitric oxide donors [DETA-NO and the NO-releasing prodrugs NCX4040 (NO-aspirin) and JS-K] on the expression of PVR/CD155, using Flow Cytometry and Real-Time PCR. Western-blot and specific inhibitors were employed to investigate the role of soluble guanylyl cyclase/cGMP and activation of the DNA damage response (DDR).

Results

Our results indicate that increased levels of nitric oxide can upregulate PVR/CD155 cell surface and mRNA expression in MM cells; in addition, exposure to nitric oxide donors renders myeloma cells more efficient to activate NK cell degranulation and enhances their ability to trigger NK cell-mediated cytotoxicity. We found that activation of the soluble guanylyl cyclase and increased cGMP concentrations by nitric oxide is not involved in the up-regulation of ligand expression. On the contrary, treatment of MM cells with nitric oxide donors correlated with the activation of a DNA damage response pathway and inhibition of the ATM /ATR/Chk1/2 kinase activities by specific inhibitors significantly abrogates up-regulation.

Conclusions

The present study provides evidence that regulation of the PVR/CD155 DNAM-1 ligand expression by nitric oxide may represent an additional immune-mediated mechanism and supports the anti-myeloma activity of nitric oxide donors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1023-5) contains supplementary material, which is available to authorized users.

Interleukin-15: new kid on the block for antitumor combination therapy

Interleukin (IL)-15 is one of the most promising molecules to be used in antitumor immune therapy, as it is able to stimulate the main killer cells of both the innate and adaptive immune system. Although this cytokine can be used as a stand-alone immunotherapeutic agent, IL-15 will probably be most efficient in combination with other strategies to overcome high tumor burden, immune suppression of the tumor microenvironment and/or the short half-life of IL-15. In this review, we will discuss the combination strategies with IL-15 that have been tested to date in different animal tumor models, which include chemotherapy, other immunostimulatory cytokines, targeted therapy, adoptive cell transfer and gene therapy. In addition, we give an overview of IL-15 combination therapies that are currently tested in clinical studies to treat patients with hematological or advanced solid tumors.

Orchestration of angiogenesis by immune cells

It is widely accepted that the tumor microenvironment (TUMIC) plays a major role in cancer and is indispensable for tumor progression. The TUMIC involves many "players" going well beyond the malignant-transformed cells, including stromal, immune, and endothelial cells (ECs). The non-malignant cells can acquire tumor-promoting functions during carcinogenesis. In particular, these cells can "orchestrate" the "symphony" of the angiogenic switch, permitting the creation of new blood vessels that allows rapid expansion and progression toward malignancy. Considerable attention within the context of tumor angiogenesis should focus not only on the ECs, representing a fundamental unit, but also on immune cells and on the inflammatory tumor infiltrate. Immune cells infiltrating tumors typically show a tumor-induced polarization associated with attenuation of anti-tumor functions and generation of pro-tumor activities, among these angiogenesis. Here, we propose a scenario suggesting that the angiogenic switch is an immune switch arising from the pro-angiogenic polarization of immune cells. This view links immunity, inflammation, and angiogenesis to tumor progression. Here, we review the data in the literature and seek to identify the "conductors" of this "orchestra." We also suggest that interrupting the immune → inflammation → angiogenesis → tumor progression process can delay or prevent tumor insurgence and malignant disease.

Human umbilical cord blood-derived mesenchymal stem cells producing IL15 eradicate established pancreatic tumor in syngeneic mice

Mesenchymal stem cells (MSC) represent a new tool for delivery of therapeutic agents to cancer sites because of their strong tropism toward tumors. IL15 has demonstrated a potent antitumor activity in various animal models as well as clinical trials. However, because of its short half-life, effective therapeutic effects usually require a high dose, which often results in undesired side effects; thus, new strategies for overcoming this disadvantage are needed. In this study, human MSCs were isolated from umbilical cord blood as delivery vehicles and transduced with lentivirus vector expressing murine IL15 (MSC-IL15). In vitro assays of lymphocyte activation and proliferation demonstrated that IL15 produced by MSCs was biofunctional. In syngeneic mice bearing Pan02 pancreatic tumors, systemic administration of MSC-IL15 significantly inhibited tumor growth and prolonged the survival of tumor-bearing mice, which were associated with tumor cell apoptosis, and natural killer (NK)- and T-cell accumulation. Furthermore, we confirmed that MSC-IL15 could migrate toward tumor and secreted IL15 in tumor-specific sites. Depletion of NK and CD8(+) T cells abolished the antitumor activity of MSC-IL15, suggesting that NK and CD8(+) T cells play a key role for MSC-IL15-mediated effect. Interestingly, cured mice after MSC-IL15 treatment were resistant to Pan02 pancreatic tumor rechallenge, and adoptive transfer of lymphocytes from cured mice also could cause rejection of Pan02 tumor inoculation in naïve mice, indicating that MSC-IL15 induced tumor-specific T-cell immune memory response. Overall, these data support that MSCs producing IL15 might represent an innovative strategy for therapy of pancreatic tumor.

Enhanced antitumor immunity is elicited by adenovirus-mediated gene transfer of CCL21 and IL-15 in murine colon carcinomas

The chemokine CCL21 is a potent chemoattractant for T cells and dendritic cells. IL-15 elicits powerful antitumor immune responses through the stimulation of natural killer cells. We constructed a CCL21/IL-15-expressing adenovirus (Ad-CCL21-IL-15) and evaluated its antitumor effects in vitro and in vivo. We found that the intratumoral injection of Ad-CCL21-IL-15 into murine colon carcinomas significantly inhibited tumor growth. Splenocytes from mice treated with Ad-CCL21-IL-15 developed tumor-specific cytotoxic T cells and were protected from subsequent challenges with tumor cells. This study indicates that providing cancer therapy by combining CCL21 and IL-15 can induce antitumor immune responses and is an effective strategy for cancer immunotherapy.

A DNA vaccine targeting p42.3 induces protective antitumor immunity via eliciting cytotoxic CD8+T lymphocytes in a murine melanoma model

The p42.3 gene was recently identified and characterized as having tumor-specific and mitosis phase-dependent expression in many types of cancer. This suggested that p42.3 antigen could be used as a target for vaccines against cancers. In this study, we immunized C57BL/6 mice with a DNA vaccine encoding p42.3. We used intramuscular injection with electroporation, either before or after challenge with tumor B16F10 cells. Vaccination with pcDNA3-p42.3 induced some degree of antitumor effect both therapeutically and prophylactically, as evaluated by the inhibition of tumor growth and decrease in tumor weight. Immunized mice showed a high level of specific cytotoxic activity against the p42.3 protein in vivo and had activated CD8 T cells that secreted IFN-γ, perforin, and granzyme B in response to stimulation with the antigen in vitro. Thus, this study presents the DNA vaccination against novel tumor target p42.3 as a promising antitumor modality.

Immunotherapeutic applications of IL-15

IL-15 is a member of the IL-2 family of cytokines, which play a fundamental role in innate and adaptive immune responses. IL-15 has pleiotropic immune-enhancing activities, as it stimulates NK, T and NKT cell proliferation, survival and effector functions. In view of these properties, IL-15 is regarded as a good candidate for cancer immunotherapy. This possibility is reinforced by its low toxicity and efficacy in preclinical tumor models. The use of IL-15 to boost the immune response in HIV infection has also been proposed, although further studies are required to establish potential risks and benefits. Clinical trials of IL-15 have been initiated in cancer patients and in HIV vaccination and will elucidate the potential of IL-15-based immunotherapy. The purpose of this review is to provide an update on the potential applications of IL-15 in cancer immunotherapy and HIV infection.

IL-15 activated human peripheral blood dendritic cell kill allogeneic and xenogeneic endothelial cells via apoptosis

IL-15 is a pleotropic cytokine, which plays an important role in natural killer (NK) cell activity, T cell proliferation, and T cell cytotoxic activity. Dendritic cells (DCs) are the major antigen presenting cells in the immune system and presumed to play an important role in immune recognition of allo and xenotransplantation. We showed that IL-15 activated human peripheral blood DC is cytotoxic to human and porcine aortic endothelial cells. Unlike DCs, CD14+ monocytes show no cytotoxicity against the endothelial cells. This cytotoxic potential of IL-15 activated DC against endothelial cells is dose dependent and increases significantly upon treatment of endothelial cells with inflammatory cytokines like TNF-α or IFN-γ. The cytotoxic potential of IL-15 activated DC is associated with apoptosis of endothelial cells, as indicated by the increased Annexin V staining, caspase activation and loss of mitochondrial membrane potential. Further it was observed that DC mediated cytotoxicity against endothelial cell is mediated via granzyme B possibly secreted by the activated DCs.

Cytokines in cancer immunotherapy

Cytokines are molecular messengers that allow the cells of the immune system to communicate with one another to generate a coordinated, robust, but self-limited response to a target antigen. The growing interest over the past two decades in harnessing the immune system to eradicate cancer has been accompanied by heightened efforts to characterize cytokines and exploit their vast signaling networks to develop cancer treatments. The goal of this paper is to review the major cytokines involved in cancer immunotherapy and discuss their basic biology and clinical applications. The paper will also describe new cytokines in pre-clinical development, combinations of biological agents, novel delivery mechanisms, and potential directions for future investigation using cytokines.

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.

Rapid release of cytoplasmic IL-15 from tumor-associated macrophages is an initial and critical event in IL-12-initiated tumor regression

This study reveals that the IL-15 rapidly released into serum upon IL-12 injection into tumor-bearing mice is critical for the subsequent leukocytic infiltration of the tumor and tumor-bearing tissue. The increase in serum IL-15 occurs within 2 h after IL-12 injection concomitantly with a decrease in cytoplasmic IL-15 in tumor-associated Mphi (TAM). Injection of anti-IL-15 one hour prior to IL-12 abrogates subsequent leukocytic infiltration into the tumor and prevents the IL-12-induced reduction of primary tumor mass and the clearance of metastases. Administration of anti-IL-15 18 h after IL-12 did not have a detectable impact on IL-12-induced leukocytic infiltration of the tumor. Deletion of NK cells had no impact on the IL-12-induced change in the functional phenotype of TAM or on the subsequent initiation of leukocytic infiltration of the tumor. In concert with our previous studies demonstrating that IL-12 reduces tumor-supportive activities of TAM, the current study supports the hypothesis that functional re-programming of TAM not only undermines Mphi support for tumor growth but also contributes to a critical step in the initiation of anti-tumor immune responses. In this context, the functional plasticity and pro-immunogenic potential of TAM may constitute a significant and unappreciated target in existing cytokine therapies.

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.

Interleukin-15 liver gene transfer increases the number and function of IKDCs and NK cells

The surface phenotype CD3-NK1.1+DX5+CD11c(int)B220+GR1- has been recently ascribed to a novel subset of mouse leukocytes termed interferon (IFN)-producing killer dendritic cells (IKDCs) that shares functions with natural killer (NK) cells and DCs. Interleukin-15 (IL-15) is critical for NK cells but its relationship with IKDC remained unexplored. An expression cassette encoding human IL-15 (hIL-15) has been transferred by hydrodynamic injection into the liver of mice, resulting in transient expression of the cytokine that is detectable during the first 48 h. hIL-15 hydrodynamic gene transfer resulted in an expansion of NK cells and IKDCs. Relative expansions of IKDCs were more dramatic in the IL-15 gene-transferred hepatic tissue than in the spleen. Adoptively transferred DX5+ cells comprising both NK cells and IKDCs proliferated in response to hydrodynamic injection of hIL-15, indicating that quantitative increases are at least in part the result of proliferation from already differentiated cells. Expansion is accompanied by enhanced cytolytic activity and increased expression of TRAIL and CD137 (4-1BB), without augmenting interferon-gamma production. The effects of a single hydrodynamic injection surpassed those of two intraperitoneal doses of the recombinant protein. The novel functional link between circulating IL-15 and IKDCs opens new possibilities to study the biology and applications of this minority cell subset.

Synergistic effect of intratumoral IL-12 and TNF-alpha microspheres: systemic anti-tumor immunity is mediated by both CD8+ CTL and NK cells

Neoadjuvant immunotherapy with the combination of intratumoral IL-12 and TNF-alpha encapsulated in poly-lactic acid microspheres (PLAM) generate a greater systemic immune response than either cytokine alone. We sought to examine the effector cells responsible for this synergy using the poorly immunogenic B16 melanoma and MCA205 sarcoma cell lines. Splenocytes from MCA205 bearing mice treated with IL-12 and TNF-alpha PLAM contained significantly more tumor-specific IFN-gamma secreting cells than IL-12 alone. Adoptive transfer of lymphocytes from mice treated by the combination mediated significant tumor regression in mice bearing established pulmonary metastases. In mice bearing bilateral tumors, treatment of the primary with IL-12 and TNF-alpha PLAM, resulted in suppression of contralateral tumor growth. Both the local and distant effects were absent in mice depleted of CD8+ T-cells. In B16 bearing mice with established pulmonary disease, only the combination of intratumoral IL-12 and TNF-alpha resulted in a significant reduction of lung nodules. Both the local and distant effects were eradicated in mice depleted of either CD8+ T-cells or NK cells. The local and sustained release of IL-12 and TNF-alpha using PLAM synergistically activate both a cytotoxic T-cell and NK cell response, although their impact varies with MHC class I expression.

Immunotherapy of cancer by IL-12-based cytokine combinations

Cancer is a multi-faceted disease comprising complex interactions between neoplastic and normal cells. Over the past decade, there has been considerable progress in defining the molecular, cellular and environmental contributions to the pathophysiology of tumor development. Despite these advances, the conventional treatment of patients still generally involves surgery, radiotherapy and/or chemotherapy, and the clinical outcome for many of these efforts remains unsatisfactory. Recent studies have highlighted the feasibility of using immunotherapeutic approaches that seek to enhance host immune responses to developing tumors. These strategies include immunomodulatory cytokines, with TNF-alpha, type I or type II IFNs, IL-2, IL-12, IL-15 and IL-18 being among the most potent inducers of anti-tumor activity in a variety of preclinical studies. More recently, some exciting new cytokines have been characterized, such as IL-21, IL-23, IL-27 and their immunomodulatory and antitumor effects in vitro and in vivo suggest that they may have considerable promise for future immunotherapy protocols. The promise of cytokine therapy does indeed derive from the identification of these novel cytokines but even more fundamentally, the field is greatly benefiting from the ever-expanding amount of preclinical data that convincingly demonstrate synergistic and/or novel biologic effects, which may be achieved through the use of several combinations of cytokines with complementary immune-stimulating capabilities. One cytokine in particular, IL-12, holds considerable promise by virtue of the fact that it plays a central role in regulating both innate and adaptive immune responses, can by itself induce potent anticancer effects, and synergizes with several other cytokines for increased immunoregulatory and antitumor activities. This review discusses the antitumor activity of IL-12, with a special emphasis on its ability to synergize with other cytokines for enhancement of immune effector cell populations and regulation of host-tumor cell interactions and the overall tumor microenvironment.

Inhibition of a vascular ocular tumor growth by IL-12 gene transfer

Ocular tumors such as retinoblastoma and uveal melanoma have devastating effects on vision. Patients with uveal melanoma also have low 5-year survival rates, thus new therapeutic modalities are necessary. As both retinoblastoma and uveal melanoma are highly vascular, we tested application of a gene transduction approach with a potent TH1 cytokine also endowed with strong anti-angiogenic activity, Interleukin-12 (IL-12). Gene transfer into murine 99E1 uveal melanoma-like cells, while having no effects on growth in vitro, essentially blocked subcutaneous tumor growth in vivo without evident signs of toxicity. Orthotopic intraocular injection resulted in invasive tumors that destroyed ocular architecture by the control cells while the IL-12 transduced cells rarely formed tumors. Histological analysis revealed highly invasive and angiogenic tumor growth in the controls and poorly vascularized tumors in the presence of IL-12. The tumor repression effect could be reproduced by a systemic anti-angiogenic effect, where controlateral injection of IL-12 expressing cells strongly repressed growth in tumors formed by parental 99E1 cells. This was associated with significantly lowered tumor vessel densities, a trend toward lower VEGF levels in the lesion, and significantly decreased NK cells in the parental tumors exposed to systemic IL-12. Taken together, our data suggest that IL-12 gene transfer can provide anti-angiogenic effects without toxicity and may be particularly suited for therapy of vascularized ocular tumors.

Cytokine gene transfer for cancer therapy

The possibility of inducing a strong immune response to impair tumor growth by ectopically expressing cytokines, followed by the generation of an antitumor memory raised great hopes and enthusiasm as a therapeutic approach. However, the efficacy of this strategy on established tumor models appeared low and the initial results in the clinics were disappointing. Recently, new evidence indicates that cytokine gene combination or the combined use of cytokine genes with additional gene therapy approaches induces a synergistic effect supporting the use of cytokine gene therapy to improve the clinical outcome for cancer patients.

Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.

Adamantylsulfanyl- and N-adamantylcarboxamido-derivatives of heterocycles and phenols: synthesis, crystal structure, tumor necrosis factor-alpha production-enhancing properties, and theoretical considerations

The synthesis of several adamantylthio heterocycles and S-adamantylated thiocresols is reported. The attack of the adamantyl cation formed from 1-adamantan-1-ol in refluxing trifluoroacetic acid provides the corresponding adamantylsulfanyl compounds. The use of the adamantyl cation in the Ritter reaction gave the number of N-adamantylcarboxamide derivatives of heterocyclic and phenolic compounds. Adamantylsulfanyl heterocycles, contrary to N-adamantylcarboxamido compounds, enhanced the production of tumor necrosis factor alpha (TNF-alpha) in genetically modified murine melanoma cells transduced with the gene for human TNF-alpha. The highest activity, comparable to that of the most-active previously described for 6-methyl-2-[(adamantyl)amino]pyridine, showed 2-thioadamantyl derivatives of pyridine and 6-methylpyridine. The crystal structures of carboxamido and sulfanyl analogues of 2-(1-adamantylamino)pyridine have been studied, and consecutive quantum-chemical calculations have been performed. The low TNF-alpha production stimulatory activity of N-adamantylcarboxamido-pyridine compared to the sulfanyl and amino analogues is postulated to be linked to the conformational rigidity of the former one enhanced by the formation of the intramolecular H-bond. The comparison of the activity of 2-(1-adamantylsulfanyl)-6-methylpyridine and (1-adamantylsulfanyl)-2-methylbenzene proved the importance of the ring N-atom, whereas the differences in activity between bromo and methyl analogues pointed at electronic rather than steric influence of ortho-substituents on the biological activity.

IL-12 and IL-10 expression synergize to induce the immune-mediated eradication of established colon and mammary tumors and lung metastasis

Preclinical studies demonstrated that certain cytokines are potentially useful for the induction of antitumor immune responses. However, their administration in clinical settings was only marginally useful and evoked serious toxicity. In this study, we demonstrate that the combination of autologous inactivated tumor cells expressing IL-12 and IL-10 induced tumor remission in 50-70% of mice harboring large established colon or mammary tumors and spontaneous lung metastases, with the consequent establishment of an antitumor immune memory. Mice treatment with tumor cells expressing IL-12 was only marginally effective, while expression of IL-10 was not effective at all. Administration of the combined immunotherapy stimulated the recruitment of a strong inflammatory infiltrate that correlated with local, increased expression levels of the chemokines MIP-2, MCP-1, IFN-gamma-inducible protein-10, and TCA-3 and the overexpression of IFN-gamma, but not IL-4. The combined immunotherapy was also therapeutically effective on established lung metastases from both colon and mammary tumors. The antitumor effect of the combined immunotherapy was mainly dependent on CD8+ cells although CD4+ T cells also played a role. The production of IFN-gamma and IL-4 by spleen cells and the development of tumor-specific IgG1 and IgG2a Abs indicate that each cytokine stimulated its own Th pathway and that both arms were actively engaged in the antitumor effect. This study provides the first evidence of a synergistic antitumor effect of IL-12 and IL-10 suggesting that a Th1 and a Th2 cytokine can be effectively combined as a novel rational approach for cancer immunotherapy.

Nucleofection is an efficient nonviral transfection technique for human bone marrow-derived mesenchymal stem cells

Viral-based techniques are the most efficient systems to deliver DNA into stem cells because they show high gene transduction and transgene expression in many cellular models. However, the use of viral vectors has several disadvantages mainly involving safety risks. Conversely, nonviral methods are rather inefficient for most primary cells. The Nucleofector technology, a new nonviral electroporation-based gene transfer technique, has proved to be an efficient tool for transfecting hard-to-transfect cell lines and primary cells. However, little is known about the capacity of this technique to transfect adult stem cells. In this study, we applied the Nucleofector technology to engineer human bone marrow- derived mesenchymal stem cells (hMSCs). Using a green fluorescent protein reporter vector, we demonstrated a high transgene expression level using U-23 and C-17 pulsing programs: 73.7%+/-2.9% and 42.5%+/-3.4%, respectively. Cell recoveries and viabilities were 38.7%+/-2.9%, 44.5%+/-3.9% and 91.4%+/-1.3%, 94.31%+/-0.9% for U-23 and C-17, respectively. Overall, the transfection efficiencies were 27.4%+/-2.9% (U-23) and 16.6%+/-1.4% (C-17) compared with 3.6%+/-2.4% and 5.4%+/-3.4% of other nonviral transfection systems, such as FUGENE6 and DOTAP, respectively (p<.005 for all comparisons). Nucleofection did not affect the immunophenotype of hM-SCs, their normal differentiation potential, or ability to inhibit T-cell alloreactivity. Moreover, the interleukin-12 gene could be successfully transfected into hMSCs, and the immunomodulatory cytokine was produced in great amount for at least 3 weeks without impairment of its biological activity. In conclusion, nucleofection is an efficient nonviral transfection technique for hMSCs, which then may be used as cellular vehicles for the delivery of biological agents.

Enhancement of Interleukin-12 Gene-Based Tumor Immunotherapy by the Reduced Secretion of p40 Subunit and the Combination with Farnesyltransferase Inhibitor

Interleukin-12 (IL-12) gene was shown to produce both IL-12 and p40 subunit. The excess production of the p40 subunit as a natural antagonist of IL-12 is a major obstacle of IL-12 gene-based cancer therapy. We previously reported that IL-12N220L gene, which selectively reduces the secretion of the p40 subunit, induces long-lasting stronger type 1 helper T cells (T(H)1) and cytotoxic T lymphocyte (CTL) immunity in hepatitis C virus (HCV) E2 DNA vaccination model and higher protection from challenge with tumor cells expressing E2 than IL-12 in a prophylactic setting. Here, we demonstrated that intratumoral injection of IL-12N220L-expressing adenovirus showed better tumor growth inhibition and higher survival rate than that of IL-12 or granulocyte macrophage-colony stimulating factor (GM-CSF)-expressing adenovirus in a therapeutic setting. In particular, the mice cured by IL-12N220L treatment were protected against intravenous rechallenge of the same tumor cells better than those by IL-12 treatment. In addition, the enhanced antitumor activity of IL-12N220L was confirmed in B16F10 lung metastasis model, which correlated with the frequency of tumor-specific interferon (IFN)-gamma-secreting cells. When tested in CT26/NP tumor that expresses influenza nucleoprotein (NP) as a tumor antigen, IL-12N220L induced stronger NP-specific T(H)1 and CTL responses than IL-12, particularly at a later time point, indicating the generating long-term tumor-specific memory T-cell responses. Moreover, the potent antitumor effects of IL-12N220L were further augmented by combination with chemotherapy using farnesyltransferase inhibitor (FTI), LB42908. Taken together, our results suggest that IL-12N220L is superior to IL-12 in cancer immunotherapy, which can be further enhanced by combination with chemotherapy.

Sequential Immunogene Therapy with Interleukin-12– and Interleukin-15–Engineered Neuroblastoma Cells Cures Metastatic Disease in Syngeneic Mice

Purpose: To investigate the potential synergistic effects of Neuro2a neuroblastoma cells engineered with IL-12 and/or IL-15 genes in improving survival of syngeneic mice bearing neuroblastoma metastatic disease.

Experimental Design: Neuro2a cells engineered with interleukin (IL)-12 (Neuro2a/IL-12), IL-15 (Neuro2a/IL-15), or both cytokines (Neuro2a/IL-12/IL-15) were injected s.c. in syngeneic A/J mice challenged i.v. with Neuro2a parental cells (Neuro2apc) using different schedules of administration in either preventive or therapeutic settings.

Results: A single injection of Neuro2a/IL-12 or Neuro2a/IL-15 cells induced resistance to a subsequent i.v. Neuro2apc challenge in 45% and 28% of mice, respectively. Neuro2a/IL-12/IL-15 cells protected 28% of mice, showing no synergistic effect. However, sequential vaccination with Neuro2a/IL-12 (day −30) followed by Neuro2a/IL-15 (day −15) protected 71% of mice from subsequent challenge with Neuro2apc. A single dose of Neuro2a/IL-12 prolonged the mean survival time of mice bearing established metastatic neuroblastoma from 21 ± 3 to 46 ± 27 days but failed to cure mice, whereas Neuro2a/IL-15 or Neuro2a/IL-12/IL-15 were ineffective. However, sequential vaccination with Neuro2a/IL-12 (day +3) followed by Neuro2a/IL-15 (day +13) cured 43% of mice as assessed by histologic analysis of different organs from long-term surviving mice. CTL activity against Neuro2apc cells was observed in splenocytes from treated mice, and CD8+ T-cell depletion abrogated the therapeutic effect of vaccination.

Conclusions: Sequential vaccination with IL-12- and IL-15-engineered neuroblastoma cells induced optimal preventive and therapeutic effects, which may be related to the Th1 priming effect of IL-12 followed by the enhancement of CD8+ T-cell responses and their maintenance mediated by IL-15.

Recruitment of STAT3 for production of IL-10 by colon carcinoma cells induced by macrophage-derived IL-6

The immunosuppressive cytokine IL-10 is associated with poor prognosis in colon cancer. Although macrophages are involved in antitumor defenses, production of IL-10 by tumor cells may permit malignant cells escape to cell-mediated immune defenses. To investigate interactions between macrophages and tumor cells in humans, we cultured macrophages isolated from patients and tested the effect of these macrophages on the production of IL-10 by several tumor cell lines. Macrophages were isolated from pleural effusions of patients with malignancy and from noncancer control patients. We demonstrated that culture supernatants of macrophages from both sources strongly stimulated IL-10 production by the three different human colon adenocarcinoma cell lines, Colo 205, Colo 320, and HT29. Recombinant IL-6, but not IL-10, TNF-alpha, and IFN-alpha, stimulated the secretion of IL-10 by colon tumor cells. mAbs against IL-6 and IL-6R prevented the effect of macrophage culture supernatants and of rIL-6, respectively, on the production of IL-10 by the three cell lines. Cocultures of macrophages and colon cancer cells showed that these tumor cells first stimulated macrophages to produce IL-6, which was then followed by IL-6-induced IL-10 production by colon cancer cells. Finally, we showed that IL-10 gene regulation was mediated by STAT3, which was phosphorylated after the binding of IL-6 to IL-6R. This is the first demonstration that IL-6, secreted by macrophages, can induce a STAT3-mediated IL-10 production by colon tumor cells.

Immunoprevention of HER-2/neu Transgenic Mammary Carcinoma through an Interleukin 12-Engineered Allogeneic Cell Vaccine

This study evaluated the ability of cytokine-engineered allogeneic (H-2(q)) HER-2/neu-positive cells to prevent tumor development in mammary cancer-prone virgin female BALB/c (H-2(d)) mice transgenic for the transforming rat HER-2/neu oncogene (BALB-neuT mice). Repeated vaccinations with cells engineered to release interleukin (IL)-2, IL-12, IL-15, or IFN-gamma showed that IL-12-engineered cell vaccines had the most powerful immunopreventive activity, with >80% of 1-year-old BALB-neuT mice free of tumors. On the contrary all of the untreated mice and all of the mice vaccinated with IL-12-engineered cells lacking either HER-2/neu or allogeneic antigens developed mammary carcinomas within 22 or 33 weeks, respectively. Whole mount, histology, immunohistochemistry, and gene expression profile analysis showed that vaccination with IL-12-engineered cells maintained 26-week mammary glands free of neoplastic growth, with a gene expression profile that clustered with that of untreated preneoplastic glands. The IL-12-engineered cell vaccine elicited a high production of IFN-gamma and IL-4 and a strong anti-HER-2/neu antibody response. Immune protection was lost or markedly impaired in BALB-neuT mice lacking IFN-gamma or antibody production, respectively. The protection afforded by the IL-12-engineered cell vaccine was equal to that provided by the systemic administration of recombinant IL-12 in combination with HER-2/neu H-2(q) cell vaccine. However, IL-12-engineered cell vaccine induced much lower circulating IL-12 and IFN-gamma, and therefore lower potential side effects and systemic toxicity.

Paracrine release of IL-12 stimulates IFN-gamma production and dramatically enhances the antigen-specific T cell response after vaccination with a novel peptide-based cancer vaccine

Interleukin-12 can act as a potent adjuvant for T cell vaccines, but its clinical use is limited by toxicity. Paracrine administration of IL-12 could significantly enhance the response to such vaccines without the toxicity associated with systemic administration. We have developed a novel vaccine delivery system (designated F2 gel matrix) composed of poly-N-acetyl glucosamine that has the dual properties of a sustained-release delivery system and a potent adjuvant. To test the efficacy of paracrine IL-12, we incorporated this cytokine into F2 gel matrix and monitored the response of OT-1 T cells in an adoptive transfer model. Recipient mice were vaccinated with F2 gel/SIINFEKL, F2 gel/SIINFEKL/IL-12 (paracrine IL-12), or F2 gel/SIINFEKL plus systemic IL-12 (systemic IL-12). Systemic levels of IL-12 were lower in paracrine IL-12-treated mice, suggesting that paracrine administration of IL-12 may be associated with less toxicity. However, paracrine administration of IL-12 was associated with an enhanced Ag-specific T cell proliferative and functional response. Furthermore, paracrine IL-12 promoted the generation of a stable, functional memory T cell population and was associated with protection from tumor challenge. To study the mechanisms underlying this enhanced response, wild-type and gene-deficient mice were used. The enhanced immune response was significantly reduced in IFN-gamma(-/-) and IL-12R beta 2(-/-) recipient mice suggesting that the role of IL-12 is mediated, at least in part, by host cells. Collectively, the results support the potential of F2 gel matrix as a vaccine delivery system and suggest that sustained paracrine release of IL-12 has potential clinical application.

Prevention of angiogenesis by naked DNA IL-12 gene transfer: angioprevention by immunogene therapy

IL-12 is thought to induce a cytokine cascade with antiangiogenic effects mediated by IFN-gamma and angiostatic CXCR3 chemokine ligands. Naked DNA intramuscular injection of an expression vector plasmid producing IL-12 resulted in significant, well-tolerated elevation of serum IL-12 levels. Injection of the IL-12 plasmid at least 2 days, and up to 20 days, before subcutaneous injection of matrigel with angiogenic factors resulted in strong prevention of angiogenesis in both C57/bl and nude mice. A single injection of the IL-12 plasmid contemporarily with the matrigel or 2 days after resulted in partial, statistically not significant, inhibition. Control plasmid injection did not affect either angiogenesis or angiogenesis inhibition by IL-12 protein in vivo. Angiogenesis inhibition was observed in NK cell-depleted C57/bl and nude mice as well as in IFN-gamma(-/-) and CXCR3(-/-) knockout mice, indicating that NK- and/or T-cell-initiated IFN-gamma-chemokine cascades were not involved in the angiogenesis inhibition observed in vivo. Finally, IL-12 plasmid DNA gene transfer significantly prevented the growth and vascularization of highly angiogenic KS-Imm Kaposi's sarcoma and TS/A murine mammary carcinoma tumors in nude and/or syngeneic mice. These data suggest that a preventive gene therapy approach using antiangiogenic cytokines can effectively inhibit tumor angiogenesis and KS, representing an example of angioimmunoprevention.

Tumor cells engineered with IL-12 and IL-15 genes induce protective antibody responses in nude mice

IL-12 and IL-15 stimulate T, B, and NK cell functions through independent mechanisms, and cooperative effects of these cytokines have been reported. The human MHC class I-negative small cell lung cancer cell line, N592, genetically engineered to secrete IL-15, N592/IL-15, showed a reduced tumor growth rate, while N592 cells engineered with IL-12, N592/IL-12, grew similarly to the wild-type N592, N592 parental cells (N592pc), in nude mice. However, N592 cells coexpressing both cytokines, N592/IL-12/IL-15 cells, were completely rejected by 100% of nude mice. Here we show that 60% of nude mice rejecting N592/IL-12/IL-15 cells were resistant to N592pc rechallenge. SCID mice rejected N592/IL-12/IL-15 cells, but did not develop resistance to N592pc rechallenge, suggesting a role of Ab responses. Among nude mice rejecting N592/IL-12/IL-15 cells, those developing resistance to N592pc rechallenge had significantly higher titers of anti-N592 IgG2b Abs than nonresistant nude mice. Induction of an Ig class switch in nude mice was related to the expression of IFN-gamma and CD40 ligand in the draining lymph nodes. An IgG2b, anti-N592 mAb, derived from N592/IL-12/IL-15-immunized nude mice splenocytes induced significant protection against N592pc, while an IgM mAb was ineffective. The protective IgG2b mAb, but not the IgM mAb, triggered Ab-dependent cell-mediated cytotoxicity by nude mouse splenocytes against N592pc. These data indicate that IL-12 and IL-15 synergistically trigger innate, immunity-mediated, anti-tumor effects, resulting in cytotoxic IgG Ab responses in T cell-deficient mice. Protective Ab responses may relate to both direct actions of IL-12 and IL-15 on B cells and to the activation of an innate immunity-B cell cross-talk.

Interleukin-12-induced cytotoxicity against syngeneic B cell lymphomas of SJL/J mice

The B cell lymphomas (RCS) that develop spontaneously in 90% of aging SJL/J mice stimulate syngeneic CD4+ Vbeta16+ Th2 cells to produce cytokines, such as IL-4 and IL-5, which promote lymphoma growth. Although RCS cells express a unique superantigen (vSAg) encoded by an endogenous MMTV (Mtv-29) provirus that also elicits IFN-gamma production from naïve syngeneic lymphoid cells, there is no development of RCS-specific cytotoxicity. However, addition of IL-12 to co-cultures of SJL spleen and irradiated (gamma-)RCS cells resulted in the appearance of effector cells that killed RCS and NK-susceptible target cells. Antibody depletion studies revealed at least two types of RCS/IL-12-induced cytotoxic cells: (1) NK cells (Asialo GM1+) and (2) CD8+ CTL. Despite high titers of IFN-gamma in the SN of co-culture of SJL spleen and gamma-RCS cells, cytotoxicity only developed if IL-12 was also included in the co-cultures. The results of RNAse protection assays and multi-parameter FACS analysis demonstrated an upregulation of IFN-gamma and decrease in IL-4 by activated Th cells in co-cultures with IL-12. These results indicate that inclusion of IL-12 in primary co-cultures of SJL spleen and gamma-RCS cells influences the qualitative nature of the response to favor use of RCS-responsive Th1 rather than Th2 cells to facilitate the production of cytotoxic effector cells. Results of in vivo experiments support this hypothesis, as judged by tumor growth assays and FACS analysis of the tumor cell content of lymphoid tissues. Inhibition of lymphoma growth was observed in mice given gamma-RCS/IL-12-induced effector cells prior to injection of viable RCS cells. These results demonstrate that IL-12 can be used to alter the host immune response leading to induction of cytotoxic effector cells that inhibit the development and/or progressive growth of otherwise resistant B cell lymphomas in SJL/J mice.

p53 and PTEN/MMAC1/TEP1 gene therapy of human prostate PC-3 carcinoma xenograft, using transferrin-facilitated lipofection gene delivery strategy

We previously reported that supplementation of a cationic liposome with transferrin (Tf) greatly enhanced lipofection efficiency (P.-W. Cheng, Hum. Gene Ther. 1996;7:275-282). In this study, we examined the efficacy of p53 and PTEN tumor suppressor gene therapy in a mouse xenograft model of human prostate PC-3 carcinoma cells, using a vector consisting of dimyristoyloxypropyl-3-dimethylhydroxyethyl ammonium bromide (DMRIE)-cholesterol (DC) and Tf. When the volume of the tumors grown subcutaneously in athymic nude mice reached 50-60 mm(3), three intratumoral injections of the following four formulations were performed during week 1 and then during week 3: (1) saline, (2) DC + Tf + pCMVlacZ, (3) DC + Tf + pCMVPTEN, and (4) DC + Tf + pCMVp53 (standard formulation). There was no significant difference in tumor volume and survival between group 1 and group 2 animals. As compared with group 1 controls, group 3 animals had slower tumor growth during the first 3 weeks but thereafter their tumor growth rate was similar to that of the controls. By day 2 posttreatment, group 4 animals had significantly lower tumor volume relative to initial tumor volume as well as controls at the comparable time point. Also, animals treated with p53 survived longer. Treatment with DC, Tf, pCMVp53, DC + pCMVp53, or Tf + pCMVp53 had no effect on tumor volume or survival. Expression of p53 protein and apoptosis were detected in tumors treated with the standard formulation, thus associating p53 protein expression and apoptosis with efficacy. However, p53 protein was expressed in only a fraction of the tumor cells, suggesting a role for bystander effects in the efficacy of p53 gene therapy. We conclude that intratumoral gene delivery by a nonviral vector consisting of a cationic liposome and Tf can achieve efficacious p53 gene therapy of prostate cancer.

Neutrophils as a key cellular target for angiostatin: implications for regulation of angiogenesis and inflammation

Angiostatin effectively blocks tumor angiogenesis through still poorly understood mechanisms. Given the close association between immune and vascular regulation, we investigated the effects of angiostatin on angiogenesis-associated leukocytes. Angiostatin inhibited the migration of monocytes and, even more markedly, neutrophils. Angiostatin blocked chemotaxis of neutrophils to CXCR2 chemokine receptor agonists (IL-8, MIP-2, and GROalpha), formyl-Met-Leu-Phe (fMLP), and 12-O-tetradecanoylphorbol 13-acetate, and repressed fMLP-induced mitochondrial activity. Two different angiostatin forms (kringles 1-4 and 1-3) were effective, whereas whole plasminogen had no effect. IL-8, MIP-2, and GROalpha induced intense angiogenic reactions in vivo, but no angiogenic response to these factors was observed in neutropenic mice, demonstrating an essential role for neutrophils. Angiostatin potently inhibited chemokine-induced angiogenesis in vivo, and consistent with in vitro observations, both angiostatin forms were active and whole plasminogen had little effect. Angiostatin inhibition of angiogenesis in vivo was accompanied by a striking reduction in the number of recruited leukocytes. In vivo, the inflammatory agent lipopolysaccharide also induced extensive leukocyte infiltration and angiogenesis that were blocked by angiostatin. Neutrophils expressed mRNAs for ATP synthase and angiomotin, two known angiostatin receptors. These data show that angiostatin directly inhibits neutrophil migration and neutrophil-mediated angiogenesis and indicate that angiostatin might inhibit inflammation.

The IL-15R alpha chain signals through association with Syk in human B cells

The alpha-chain of the IL-15R (IL-15Ralpha) serves as the specific, high-affinity receptor for IL-15. It is expressed by lymphoid and nonlymphoid cells, including B cell lymphoma lines. In this study, we have further explored IL-15Ralpha-mediated signaling in activated primary B cells and in Raji cells, a human B-lymphoblastoid cell line which expresses the IL-15Ralpha and IL-2Rgamma chains, but lacks the IL-2Rbeta chain. Stimulation of Raji cells with IL-15 induces their proliferation and rescues them from C2-ceramide-induced apoptosis. By immunoprecipitation and Western blotting, we show that treatment of Raji cells and activated primary B cells with IL-15 induces coprecipitation of Syk kinase with the IL-15Ralpha chain. Upon association, the activated Syk kinase phosphorylates the IL-15Ralpha chain as well as phospholipase Cgamma, which coprecipitates with Syk. Furthermore, transfection of Raji cells with stem-loop Syk antisense oligonucleotides prevents IL-15Ralpha and phospholipase Cgamma phosphorylation as well as the inhibition of apoptosis by IL-15. Mutation of a defined region of the intracellular signaling portion of IL-15Ralpha (Tyr227) abrogates both the IL-15Ralpha/Syk association and IL-15Ralpha phosphorylation. Taken together, this suggests that Syk kinase physically and functionally associates with the IL-15Ralpha chain in B cells and that Syk plays a key role in mediating IL-15-induced signal transduction, thus accounting for the distinct functional consequences of IL-15 vs IL-2 binding to B cells.

Neutrophils in anti-cancer immunological strategies: old players in new games

This review highlights the new "immunological identity" of neutrophils within the cytokine network and their role in biology of diseases, particularly in tumor biology. The latest preclinical evidence of their involvement in anti-cancer immunotherapeutic and prophylactic strategies will be discussed with particular reference to the real possibilities of transferring experimental results to a clinical setting.

IL-12 gene therapy for cancer: in synergy with other immunotherapies

In preclinical models of cancer, gene therapy with interleukin 12 (IL-12) has reached unprecedented levels of success when combined with immunotherapy approaches such as gene transfer of other cytokines and/or chemokines, costimulatory molecules or adoptive cell therapy. These combinations have been found to produce synergistic rather than additive effects. Meanwhile, IL-12 gene therapy is beginning clinical testing as a single agent, but combination strategies are at hand.