Cytokine gene therapy of cancer using gene gun technology: superior antitumor activity of interleukin-12

A combined radio-immunotherapy regimen eradicates late-stage tumors in mice

Background

The majority of experimental approaches for cancer immunotherapy are tested against relatively small tumors in tumor-bearing mice, because in most cases advanced cancers are resistant to the treatments. In this study, we asked if even late-stage mouse tumors can be eradicated by a rationally designed combined radio-immunotherapy (CRI) regimen.

Methods

CRI consisted of local radiotherapy, intratumoral IL-12, slow-release systemic IL-2 and anti- CTLA-4 antibody. Therapeutic effects of CRI against several weakly immunogenic and immunogenic mouse tumors including B78 melanoma, MC38 and CT26 colon carcinomas and 9464D neuroblastoma were evaluated. Immune cell depletion and flow cytometric analysis were performed to determine the mechanisms of the antitumor effects.

Results

Tumors with volumes of 2,000 mm3 or larger were eradicated by CRI. Flow analyses of the tumors revealed reduction of T regulatory (Treg) cells and increase of CD8/Treg ratios following CRI. Rapid shrinkage of the treated tumors did not require T cells, whereas T cells were involved in the systemic effect against the distant tumors. Cured mice developed immunological memory.

Conclusions

These findings underscore that rationally designed combination immunotherapy regimens can be effective even against large, late-stage tumors.

Interleukin-12: Structure, Function, and Its Impact in Colorectal Cancer

Interleukin 12 (IL-12) is a heterodimer consisting of 2 subunits, p35 and p40, with unique associations and interacting functions with its family members. IL-12 is one of the most important cytokines regulating the immune system response and is integral to adaptive immunity. IL-12 has shown marked therapeutic potential in a variety of tumor types. This review therefore summarizes the characteristics of IL-12 and its application in tumor treatment, focusing on its antitumor effects in colorectal cancer (CRC) and potential radiosensitization mechanisms. We aim to provide a current reference for IL-12 and other potential CRC treatment strategies.

IL-27 Improves Prophylactic Protection Provided by a Dead Tumor Cell Vaccine in a Mouse Melanoma Model

The protocol used to induce cell death for generating vaccines from whole tumor cells is a critical consideration that impacts vaccine efficacy. Here we compared how different protocols used to induce cell death impacted protection provided by a prophylactic whole tumor cell vaccine in a mouse melanoma model. We found that melanoma cells exposed to γ-irradiation or lysis combined with UV-irradiation (LyUV) provided better protection against tumor challenge than lysis only or cells exposed to UV-irradiation. Furthermore, we found that the immunoregulatory cytokine, IL-27 enhanced protection against tumor growth in a dose-dependent manner when combined with either LyUV or γ-irradiated whole tumor cell vaccine preparations. Taken together, this data supports the use of LyUV as a potential protocol for developing whole tumor cell prophylactic cancer vaccines. We also showed that IL-27 can be used at low doses as a potent adjuvant in combination with LyUV or γ-irradiation treated cancer cells to improve the protection provided by a prophylactic cancer vaccine in a mouse melanoma model.

Interleukin-12 as an in situ cancer vaccine component: a review

Interleukin-12 (IL-12) is a type I cytokine involved in both innate and adaptive immunity that stimulates T and natural killer cell activity and induces interferon gamma production. IL-12 has been identified as a potential immunotherapeutic component for combinatorial cancer treatments. While IL-12 has successfully been used to treat a variety of cancers in mice, it was associated with toxicity when administered systemically in cancer patients. In this review, we discuss the research findings and progress of IL-12 used in combination with other cancer treatment modalities. We describe different methods of IL-12 delivery, both systemic and local, and ultimately highlight the potential of an in situ vaccination approach for minimizing toxicities and providing antitumor efficacy. This review offers a basis for pursuing an in situ vaccine approach that may eventually allow IL-12 to be more readily integrated as an immunotherapy into the clinical treatment of cancers.

Bioengineered Colorectal Cancer Drugs: Orally Delivered Anti-Inflammatory Agents

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

The role of the cytokines IL-27 and IL-35 in cancer

The cancer-immune interaction is a fast growing field of research in biology, where the goal is to harness the immune system to fight cancer more effectively. In the present paper we review recent work of the interaction between T cells and cancer. CD8+ T cells are activated by IL-27 cytokine and they kill tumor cells. Regulatory T cells produce IL-35 which promotes cancer cells by enhancing angiogenesis, and inhibit CD8+ T cells via TGF-β production. Hence injections of IL-27 and anti-IL-35 are both potentially anti-tumor drugs. The models presented here are based on experimental mouse experiments, and their simulations agree with these experiments. The models are used to suggest effective schedules for drug treatment.

Mathematical modeling of interleukin-27 induction of anti-tumor T cells response

Interleukin-12 is a pro-inflammatory cytokine which promotes Th1 and cytotoxic T lymphocyte activities, such as Interferon- secretion. For this reason Interleukin-12 could be a powerful therapeutic agent for cancer treatment. However, Interleukin-12 is also excessively toxic. Interleukin-27 is an immunoregulatory cytokine from the Interleukin-12 family, but it is not as toxic as Interleukin-12. In recent years, Interleukin-27 has been considered as a potential anti-tumor agent. Recent experiments in vitro and in vivo have shown that cancer cells transfected with IL-27 activate CD8⁺ T cells to promote the secretion of anti-tumor cytokines Interleukin-10, although, at the same time, IL-27 inhibits the secretion of Interferon- by CD8⁺ T cells. In the present paper we develop a mathematical model based on these experimental results. The model involves a dynamic network which includes tumor cells, CD8⁺ T cells and cytokines Interleukin-27, Interleukin-10 and Interferon-. Simulations of the model show how Interleukin-27 promotes CD8⁺ T cells to secrete Interleukin-10 to inhibit tumor growth. On the other hand Interleukin-27 inhibits the secretion of Interferon- by CD8⁺ T cells which somewhat diminishes the inhibition of tumor growth. Our numerical results are in qualitative agreement with experimental data. We use the model to design protocols of IL-27 injections for the treatment of cancer and find that, for some special types of cancer, with a fixed total amount of drug, within a certain range, continuous injection has better efficacy than intermittent injections in reducing the tumor load while the treatment is ongoing, although the decrease in tumor load is only temporary.

Paclitaxel-conjugated PEG and arginine-grafted bioreducible poly (disulfide amine) micelles for co-delivery of drug and gene

We developed a paclitaxel-conjugated polymeric micelle, ABP-PEG3.5k-Paclitaxel (APP) consisting of poly (ethylene glycol) (PEG) and arginine-grafted poly (cystaminebisacrylamide-diaminohexane) (ABP) for the co-delivery of gene and drug. The APP polymer self-assembled into cationic polymeric micelles with a critical micelle concentration (CMC) value of approximately 0.062 mg/mL, which was determined from measurements of the UV absorption of pyrene. The micelles have an average size of about 3 nm and a zeta potential of about +14 mV. Due to the positive surface charge, APP micelles formed polyplexes with plasmid DNA approximately 200 nm in diameter. The luciferase gene and mouse interleukin-12 (IL-12) gene was used to monitor gene delivery potency. APP polyplexes showed increased gene delivery efficiency and cellular uptake with higher anticancer potency than paclitaxel alone. These results demonstrate that an APP micelle-based delivery system is well suitable for the co-delivery of gene and drug.

Gene therapy with tumor-specific promoter mediated suicide gene plus IL-12 gene enhanced tumor inhibition and prolonged host survival in a murine model of Lewis lung carcinoma

Background

Gene therapy is a promising therapeutic approach for cancer. Targeted expression of desired therapeutic proteins within the tumor is the best approach to reduce toxicity and improve survival. This study is to establish a more effective and less toxic gene therapy of cancer.

Methods

Combined gene therapy strategy with recombinant adenovirus expressing horseradish peroxidase (HRP) mediated by human telomerase reverse transcriptase (hTERT) promoter (AdhTERTHRP) and murine interleukin-12 (mIL-12) under the control of Cytomegalovirus (CMV) promoter (AdCMVmIL-12) was developed and evaluated against Lewis lung carcinoma (LLC) both in vivo and in vitro. The mechanism of action and systemic toxicities were also investigated.

Results

The combination of AdhTERTHRP/indole-3-acetic acid (IAA) treatment and AdCMVmIL-12 resulted in significant tumor growth inhibition and survival improvement compared with AdhTERTHRP/IAA alone (tumor volume, 427.4 ± 48.7 mm³ vs 581.9 ± 46.9 mm³, p = 0.005 on day 15; median overall survival (OS), 51 d vs 33 d) or AdCMVmIL-12 alone (tumor volume, 362.2 ± 33.8 mm³ vs 494.4 ± 70.2 mm³, p = 0.046 on day 12; median OS, 51 d vs 36 d). The combination treatment stimulated more CD4⁺ and CD8⁺ T lymphocyte infiltration in tumors, compared with either AdCMVmIL-12 alone (1.3-fold increase for CD4⁺ T cells and 1.2-fold increase for CD8⁺ T cells, P < 0.01) or AdhTERTHRP alone (2.1-fold increase for CD4⁺ T cells and 2.2-fold increase for CD8⁺ T cells, P < 0.01). The apoptotic cells in combination group were significantly increased in comparison with AdCMVmIL-12 alone group (2.8-fold increase, P < 0.01) or AdhTERTHRP alone group (1.6-fold increase, P < 0.01). No significant systematic toxicities were observed.

Conclusions

Combination gene therapy with AdhTERTHRP/IAA and AdCMVmIL-12 could significantly inhibit tumor growth and improve host survival in LLC model, without significant systemic adverse effects.

Transfection of living HeLa cells with fluorescent poly-cytosine encapsulated Ag nanoclusters

The fluorescence of silver clusters encapsulated by single stranded oligo-DNA (24 cytosine base pairs, C(24):Ag(n)) was used to monitor the transfection of this new silver/DNA fluorophore inside living HeLa cells. For this, the C(24):Ag(n) molecules were complexed with a commercially available transfection reagent Lipofectamine and the internalization of C(24):Ag(n) was followed with confocal fluorescence microscopy. Bright near-infrared fluorescence was observed from inside the transfected HeLa cells, when exciting with 633 nm excitation, opening up the possibility for the use of these C(24):Ag(n) clusters for biological labelling and imaging of living cells and for monitoring the transfection process with limited harm to the living cells.

IL-12 and IL-27 sequential gene therapy via intramuscular electroporation delivery for eliminating distal aggressive tumors

Eradication of residual malignancies and metastatic tumors via a systemic approach is the key for successfully treating cancer and increasing cancer patient survival. Systemic administration of IL-12 protein in an acute large dose is effective but toxic. Systemic administration of IL-12 gene by persistently expressing a low level of IL-12 protein may reduce the systemic toxicity but only eradicates IL-12-sensitive tumors. In this study, we discovered that sequential administration of IL-12- and IL-27-encoding DNA, referred to as sequential IL-12-->IL-27 (IL-12 administration followed by IL-27 administration 10 d after) gene therapy, not only eradicated IL-12-sensitive CT26 tumors from 100% of mice but also eradicated the highly malignant 4T1 tumors from 33% of treated mice in multiple independent experiments. This IL-12-->IL-27 sequential gene therapy is not only superior to IL-12-encoding plasmid DNA given a total of two times at a 10-d interval sequential gene therapy for eliminating tumors but also for inducing CTL activity, increasing T cell infiltration into tumors, and yielding a large number of tumor-specific IFN-gamma-positive CD8 T cells. Notably, depletion of either T or NK cells during the IL-27 treatment phase reverses tumor eradication, suggesting an NK cell requirement for this sequential gene therapy-mediated tumor eradication. Both reversal of the administration sequence and coadministration of IL-12 and IL-27 impaired tumor eradication in 4T1 tumor-bearing mice. This IL-12-->IL-27 sequential gene therapy, via sequential administration of IL-12- and IL-27-encoding plasmid DNA into tumor-bearing mice through i.m. electroporation, provides a simple but effective approach for eliminating inaccessible residual tumors.

Identification of a 17beta-hydroxysteroid dehydrogenase type 12 pseudogene as the source of a highly restricted BALB/c Meth A tumor rejection peptide

Mass spectrometric analysis identified the peptide recognized by a cytotoxic T lymphocyte (CTL) specific for the chemically induced BALB/c Meth A sarcoma as derived from a 17beta-hydroxysteroid dehydrogenase type 12 (Hsd17b12) pseudogene present in the BALB/c genome, but only expressed in Meth A sarcoma. The sequence of the peptide is TYDKIKTGL and corresponds to Hsd17b12(114-122) with threonine instead of isoleucine at codon 114 and is designated Hsd17b12(114T). Immunization of mice with an Hsd17b12(114T) peptide-pulsed dendritic cell-based vaccine or a non-viral plasmid construct expressing the Hsd17b12(114T) peptide protected the mice from lethal Meth A tumor challenge in tumor rejection assays. A Hsd17b12(114-122) peptide-pulsed vaccine was ineffective in inducing resistance in mice to Meth A sarcoma. These results confirm the immunogenicity of the identified tumor peptide, as well as demonstrate the efficacies of these vaccine vehicles. These findings suggest that the role of the human homolog of Hsd17b12, HSD17B12, as a potential human tumor antigen be explored.

Expression of interleukins-23 and 27 leads to successful gene therapy of hepatocellular carcinoma

IL-23 and IL-27 are two novel IL-12 cytokine family members who are quite similar to, but yet clearly distinct from IL-12 in their structures and T-cell stimulatory mechanisms. Here, we demonstrated that either IL-27 or IL-23 has potent antitumor activity in murine models of MM45T.Li hepatocellular carcinoma (HCC). These potent antitumor effects were induced primarily by CD8(+)T cells, secreting IFN-gamma while CD4(+)T cells were also involved as a help of antitumor immunity. However, the antitumor response induced by IL-27 was observed from an early stage of tumor growth whereas that of IL-23 was only evident in the late stage of tumor cell proliferation. IL-23 could induce mice to develop a long-term systemic immunologic memory response against parental MM45T.Li tumors cells, an effect IL-27 was not able to accomplish. CTLs specific for MM45T.Li cells were significantly induced by IL-23, whereas antitumor efficacy mediated by IL-27 and IL-12 involved NK cells, which IL-23 failed to activate. Furthermore, we demonstrated that CD40 expression also plays an important role in the induction of antitumor activities by IL-27, IL-23 or IL-12. Together our data suggest that IL-27 and IL-23 may be two novel and attractive candidate agents to apply to cancer immunotherapy.

Antitumoral activity of transferrin-lipoplexes carrying the IL-12 gene in the treatment of colon cancer

The present study aimed to establish an efficient targeted nonviral strategy for IL-12 gene transfer in colon carcinoma in vivo employing transferrin (Tf)-lipoplexes. Complexes for in vitro experiments were prepared at a 5/1(+/ - ) (lipid/DNA) charge ratio, with the ligand Tf (32 (microg/(microg DNA). Complexes for in vivo experiments contained 144 mM of total lipid (DOTAP/Chol), 60 (microg of pCMVLuc or pCMVIL-12 and 32 (microg of Tf-lipoplexes per microgram of plasmid. For intratumoral studies, CT26 (5 x 105 cells) in 50 microl of PBS were inoculated subcutaneously into the back of the mouse. Treatments began when tumor sizes reached 5-6 mm in diameter. Complexes were injected by a single intratumoral injection in a volume of 50 microl. Our in vitro results indicate that Tf-lipoplexes always mediate higher gene expression in colon (CT26) tumor cells, compared to plain-lipoplexes (without ligand) or naked plasmid. At the same time, CT26 tumor-bearing animals treated with Tf-lipoplexes containing the therapeutic gene IL-12, showed tumor growth inhibition, leading to a complete tumor regression in 75% of the treated mice (p < 0.001), without signs of recurrence. High levels of IL-12 and IFN-gamma were detected in the sera of treated mice. Mice survival also improved considerably by treatment with this system, with a survival rate of 88%, at 23 days post-administration. In summary, in this study we have developed an efficient, targeted cationic lipid-based system for the treatment of colon tumors. The vector has the advantages of ease of preparation and economy, in comparison with commercial transfection reagents, as well as, the possibility of a large scale production.

Cloning and characterization of an adenoviral vector for highly efficient and doxycycline-suppressible expression of bioactive human single-chain interleukin 12 in colon cancer

BACKGROUND

Interleukin-12 (IL-12) is well characterized to induce cellular antitumoral immunity by activation of NK-cells and T-lymphocytes. However, systemic administration of recombinant human IL-12 resulted in severe toxicity without perceptible therapeutic benefit. Even though intratumoral expression of IL-12 leads to tumor regression and long-term survival in a variety of animal models, clinical trials have not yet shown a significant therapeutic benefit. One major obstacle in the treatment with IL-12 is to overcome the relatively low expression of the therapeutic gene without compromising the safety of such an approach. Our objective was to generate an adenoviral vector system enabling the regulated expression of very high levels of bioactive, human IL-12.

RESULTS

High gene expression was obtained utilizing the VP16 herpes simplex transactivator. Strong regulation of gene expression was realized by fusion of the VP16 to a tetracycline repressor with binding of the fusion protein to a flanking tetracycline operator and further enhanced by auto-regulated expression of its fusion gene within a bicistronic promoter construct. Infection of human colon cancer cells (HT29) at a multiplicity of infection (m.o.i.) of 10 resulted in the production of up to 8000 ng/106 cells in 48 h, thus exceeding any published vector system so far. Doxycycline concentrations as low as 30 ng/ml resulted in up to 5000-fold suppression, enabling significant reduction of gene expression in a possible clinical setting. Bioactivity of the human single-chain IL-12 was similar to purified human heterodimeric IL-12. Frozen sections of human colon cancer showed high expression of the coxsackie adenovirus receptor with significant production of human single chain IL-12 in colon cancer biopsies after infection with 3*107 p.f.u. Ad.3r-scIL12. Doxycycline mediated suppression of gene expression was up to 9000-fold in the infected colon cancer tissue.

CONCLUSION

VP16 transactivator-mediated and doxycycline-regulated expression of the human interleukin-12 gene enables highly efficient and tightly controlled cytokine expression in human cancer. These data illustrate the potential of the described adenoviral vector system for the safe and superior expression of therapeutic genes in the treatment of colorectal cancer and other malignancies.

Intratumoral injection of IL-12 plasmid DNA--results of a phase I/IB clinical trial

Effective eradication of established tumor and generation of a lasting systemic immune response are the goals of cancer immunotherapy. The objective of this phase IB study was to assess the safety and toxicity of treatment to metastatic tumor underlying the skin with the DNA encoding interleukin-12 (IL-12). This treatment strategy allowed the patient's own tumor to serve as a source of autologous antigen in the tumor microenvironment. We proposed that IL-12 protein produced by the transfected cells would result in the generation of both a local and systemic antitumor response. The tumor was treated with either three or six intratumoral injections of plasmid containing IL-12 DNA. This treatment strategy resulted in no significant local or systemic toxicity. The treatment did not result in an increase in serum IL-12 protein. The size of the treated lesion decreased significantly (greater than 30%) in five of the 12 patients. However, nontreated subcutaneous lesions or other disease did not decrease in size.

A phase I trial of hyperthermia-induced interleukin-12 gene therapy in spontaneously arising feline soft tissue sarcomas

Interleukin-12 (IL-12), a proinflammatory cytokine, shows anticancer properties. Systemically administered IL-12 causes dose-dependent toxicity. To achieve localized intratumoral gene expression, an adenoviral gene therapy vector with IL-12 controlled by a heat-inducible promoter (heat shock promoter 70B) was developed and tested in a phase I clinical trial in cats with spontaneously arising soft tissue sarcoma. A feasibility study was done in 16 cats with soft tissue sarcoma using murine IL-12 and/or enhanced green fluorescent protein adenoviral vectors under cytomegalovirus or heat shock promoter 70 control. Subsequently, we conducted a phase I clinical trial using an adenoviral feline IL-12 construct in 13 cats with soft tissue sarcoma. The soft tissue sarcomas were irradiated (48 Gy/16 fractions) followed by intratumoral injection of adenovirus. Twenty-four hours postinjection, tumors were heated (41 degrees C, 60 min). Tumor expression of feline IL-12 and IFN-gamma was determined. Cats were monitored for systemic toxicity. For the murine IL-12 construct, an association was noted between viral dose and murine IL-12 levels within tumor, whereas serum levels were minimal. Mild toxicity was noted at 10(11) plaque-forming units (pfu). With the feline IL-12 construct, high levels of feline IL-12 mRNA were detected in tumor biopsies with low or absent IFN-gamma mRNA following gene therapy. Hematologic and hepatic toxicities were noted at the highest viral doses and were associated with detection of IFN-gamma mRNA in tumor. It is possible to localize gene expression and limit systemic toxicity of IL-12 using the hyperthermia-induced gene therapy approach. The maximum tolerated dose of the feline IL-12 adenoviral vector was 10(10) pfu/tumor as dose-limiting toxicities were noted at the 4 x 10(10) pfu dose.

Anti-tumor activity of mesenchymal stem cells producing IL-12 in a mouse melanoma model

Mesenchymal stem cells (MSCs) represent a new tool for delivery of therapeutic agents to tumor cells. In this study, we have evaluated the anti-tumor activity of human MSCs stably transduced with a retroviral vector expressing the cytokine interleukin-12 (IL-12) in a mouse melanoma model. Application of MSC(IL-12) but not control MSCs strongly reduced the formation of lung metastases of B16F10 melanoma cells. The activity of the MSC(IL-12) cells was dependent on the presence of natural killer (NK) cells in this experimental setting. Further, MSC(IL-12) cells elicited a pronounced retardation of tumor growth and led to prolonged survival when injected into established subcutaneous melanoma in a therapeutic regimen. The therapeutic effect of the MSC(IL-12) was in part mediated by CD8(+) T cells, while NK cells and CD4(+) T cells appeared to play a minor role. The anti-tumor effect of MSC(IL-12) cells was of similar efficiency as observed for application of naked plasmid DNA encoding IL-12. The presented data demonstrate that these two different strategies can induce a similar therapeutic anti-tumor efficacy in the mouse melanoma tumor model.

Review: novel nonviral delivery approaches for interleukin-12 protein and gene systems: curbing toxicity and enhancing adjuvant activity

It has become increasingly apparent that the ability to generate an optimal host immune response requires effective cross talk between the innate and adaptive components of the immune system. Pro-inflammatory cytokines, in particular those that can induce a danger signal, often called signal 3, are crucial in this role of initiating and augmenting the presentation of exogenous antigen to T cells by dendritic cells. Interleukin-12 (IL-12) in particular has been defined as a "signal 3" cytokine required for the antigen cross priming. Given this unique interactive function, a significant amount of work has been performed to define possible therapeutic applications for IL-12. Systemic IL-12 administration can clearly act as a potent adjuvant for postvaccination T cell responses in a variety of diseases. As an example, in the cancer setting, systemic IL-12 is capable of suppressing tumor growth, metastasis, and angiogenesis in vivo. IL-12, however, has been associated with significant dose- and schedule-dependent toxicity in early clinical trials, results that have proven to be a major obstacle to its clinical application. Recent research has focused on decreasing the toxicity of IL-12 using different delivery approaches, including virus-based and gene-modified cell-based delivery. Although effective, these approaches also have limitations, including the generation of neutralizing antibodies, in addition to lacking the simplicity and versatility required for universal clinical application. Thus, there is a significant interest in the development of alternative delivery approaches for IL-12 administration that can overcome these issues. Several nonviral delivery approaches for IL-12 protein or gene expression vectors are being defined, including alum, liposomes, and polymer-based delivery. These developing approaches have shown promising adjuvant effects with significantly lessened systemic toxicity. This article discusses the potential capabilities of these nonvirus-based IL-12 delivery systems in different disease settings, including allergy, infection, and cancer.

Interleukin-23 and interleukin-27 exert quite different antitumor and vaccine effects on poorly immunogenic melanoma

Recent studies revealed that two novel interleukin (IL)-12-related cytokines, IL-23 and IL-27, have potent antitumor activities. However, the antitumor effects were mainly evaluated in relatively highly immunogenic tumors and have not been fully evaluated against nonimmunogenic or poorly immunogenic tumors. In this study, we investigated the antitumor efficacies of IL-23 and IL-27 on poorly immunogenic B16F10 melanoma and found that the antitumor responses mediated by IL-23 and IL-27 were clearly different. In syngeneic mice, mouse single-chain (sc) IL-23-transfected B16F10 (B16/IL-23) tumors exhibited almost the same growth curve as B16F10 parental tumor about until day 20 after tumor injection and then showed growth inhibition or even regression. In contrast, scIL-27-transfected B16F10 (B16/IL-27) tumors exhibited significant retardation of tumor growth from the early stage. In vivo depletion assay revealed that the antitumor effect of B16/IL-23 was mainly mediated by CD8+ T cells and IFN-gamma whereas that of B16/IL-27 mainly involved natural killer cells and was independent of IFN-gamma. We also found that antitumor effects of B16/IL-23 and B16/IL-27 were synergistically enhanced by treatment with IL-18 and IL-12, respectively. Furthermore, B16/IL-23-vaccinated mice developed protective immunity against parental B16F10 tumors but B16/IL-27-vaccinated mice did not. When combined with prior in vivo depletion of CD25+ T cells, 80% of B16/IL-23-vaccinated mice completely rejected subsequent tumor challenge. Finally, we showed that the systemic administration of neither IL-23 nor IL-27 induced such intense toxicity as IL-12. Our data support that IL-23 and IL-27 might play a role in future cytokine-based immunotherapy against poorly immunogenic tumors.

Analysis of Antitumor Activity Elicited by Vaccination with Combinations of Interleukin-12 DNA with gp100 DNA or the Chemokine CCL21In Vivo

The antitumor efficacy of human melanoma-associated antigen (hgp100) and chemokine CCL21 in combination with interleukin-12 (IL-12) was evaluated in a syngeneic melanoma mouse model. The rationale for this approach was based on previous studies showing that the efficacy of IL-12 therapy in melanoma patients correlated with the presence of antibodies against tumor-associated antigens. We have previously shown that application of xenogeneic human gp100 DNA (hgp100 DNA) is protective against mouse B16 melanoma. Furthermore, the chemokine CCL21 has the ability to chemoattract both dendritic cells (DCs) and T lymphocytes. We show here that intratumoral injection of IL-12-encoding DNA (IL-12 DNA) in combination with hgp100- encoding DNA (hgp100 DNA) into tumor-bearing mice led to a strong antitumor effect. Coapplication of IL- 12 DNA with CCL21-encoding DNA (CCL21 DNA) or recombinant CCL21 (recCCL21) protein also showed some efficacy. Triple therapy with IL-12 DNA, hgp100 DNA, and CCL21 DNA, however, showed less effect on tumor growth than double therapy with IL-12 DNA and hgp100 DNA. These findings open a new route of investigation of IL-12 and gp100 or other tumor-associated antigens in the immunotherapy of a variety of tumors.

Administration route- and immune cell activation-dependent tumor eradication by IL12 electrotransfer

Injection of DNA via electric pulses into targeted tissues is referred to as electrotransfer. Intratumoral electrotransfer of the IL12 gene is more effective than intramuscular electrotransfer of the same gene in the eradication of established tumors. To understand the underlying immunological mechanisms, T cell infiltration, CTL activity, inhibition of angiogenesis, and transgene expression were analyzed using immunohistochemistry, fluorescence-based CTL analysis, Northern blot, and ELISA. In addition, the therapeutic effects of IL12 gene therapy were determined in immunocompetent, immune-cell-depleted, and immunodeficient mice. We found that intratumoral, but not intramuscular, electrotransfer of the IL12 gene induces CD8+ T cell infiltration, CTL activity, and tumor eradication. Tumor eradication by intratumoral IL12 gene electrotransfer requires both NK and T cells. The absence of either cell type will abrogate the intratumoral IL12 gene therapy-induced tumor eradication. Such a requirement explains why tumors cannot be eradicated by intramuscular electrotransfer of the IL12 gene. Only NK-cell-dependent, and not T-cell-dependent, anti-tumor effects are induced by intramuscular administration. Together, these results suggest that NK cells play an important role in both administration routes, mediating tumor growth inhibition, but T cells are specifically activated by intratumoral IL12 gene electrotransfer and not by the intramuscular route.

Immunization with adenoviral vectors carrying recombinant IL-12 and E7 enhanced the antitumor immunity to human papillomavirus 16-associated tumor

OBJECTIVE

Human papillomavirus (HPV) infection play a significant role in cervical carcinogenesis, and HPV oncoprotein E7 has important functions in the formation and maintenance of cervical cancers. Interleukin-12 (IL-12) has been reported to induce cellular immune responses, and has also been demonstrated to suppress the growth of tumors and the expression of E7. Here, we investigate the utility of adenovirus E7 (AdE7) and adenovirus IL-12 (AdIL-12) for protection against TC-1 tumor using an animal model.

METHODS

The antitumor effects induced by AdIL-12 and/or E7 were assessed by measurements of tumor size. E7-specific antibody and INF-gamma production in sera were measured, as were T-helper cell proliferative responses. Cytotoxic T-lymphocytes (CTL) and T cell subset depletion studies were also performed.

RESULTS

Infection of tumor sites with a combination of AdIL-12 and AdE7 resulted in an antitumor effect which was significantly more profound than that which resulted from singular infections with either AdIL-12 or AdE7. Combined infection resulted in regression of 9-mm-sized tumors in approximately 80% of our experimental animals as compared to the PBS group. Serum levels of E7-specific antibody and INF-gamma production, as well as T-helper cell proliferative responses, were found to be significantly higher in coinfected with AdIL-12 and AdE7 group than in single infection with either AdIL-12 or AdE7 group. CTL responses only exhibited by the AdIL-12 and AdE7 coinjected group suggested that these tumor suppression effects were mediated primarily by CD8+ and, to a lesser degree, by CD4+ T cells.

CONCLUSION

Combined injection with adenovirus carrying IL-12 and E7 induced significant antitumor immunity against TC-1 tumors. They may prove useful in clinical applications for the treatment of HPV-associated tumors.

Immunization with adenoviral vectors carrying recombinant IL-12 and E7 enhanced the antitumor immunity against human papillomavirus 16-associated tumor

PURPOSE

Human papillomavirus (HPV) infection has a significant role in cervical carcinogenesis, and HPV oncoprotein E7 plays an important part in the formation and maintenance of cervical cancer. Interleukin-12 (IL-12) has been reported to induce a cellular immune response, and to suppress the tumor growth and the E7 production. Here we describe the use of adenoviral delivery of the HPV 16 E7 subunit (AdE7) along with adenoviral delivery of IL-12 (AdIL-12) in mice with HPV-associated tumors.

MATERIALS AND METHODS

Mice were injected with TC-1 cells to establish TC-1 tumor, and then they were immunized with AdIL-12 and/or AdE7 intratumorally. The anti tumor effects induced by AdIL-12 and/or E7 were evaluated by measuring the size of the tumor. E7-specific antibody and INF-gamma production in sera, and the T-helper cell proliferative responses were then measured. Cytotoxic T-lymphocyte (CTL) and T cell subset depletion studies were also performed.

RESULTS

Combined AdIL-12 and AdE7 infection at the tumor sites significantly enhanced the antitumor effects more than that of AdIL-12 or AdE7 single infection. This combined infection resulted in regression of the 9 mm sized tumors in 80% of animals as compare to the PBS group. E7-specific antibody and INF-gamma production in the sera, and the T-helper cell proliferative responses were significantly higher with coinfection of AdIL-12 and AdE7 than with AdIL-12 or AdE7 alone. CTL response induced by AdIL-12 and AdE7 in the coinjected group suggested that tumor suppression was mediated by mostly CD8+ and only a little by the CD4+ T cells.

CONCLUSION

IL-12 and E7 application using adenovirus vector showed antitumor immunity effects against TC-1 tumor, and this system could be use in clinical applications for HPV-associated cancer.

Human cancer gene therapy with cytokine gene-modified cells

Cytokines can impede tumour growth and activate innate and adaptive immune responses, leading to elimination of cancer cells. For many years, it was believed that systemic administration of recombinant cytokines might become a standard treatment of different cancer types. However, due to a high toxicity of therapeutic doses and a low efficacy, even in combination with chemotherapy, this strategy is generally not accepted. On the other hand, cancer gene therapy approaches utilising cells modified with cytokine genes seem to represent a novel promising approach. For the last decade, numerous Phase I and II clinical trials evaluating different therapies based on cytokine gene-modified cells have been carried out. In the early studies, several strategies have been shown to improve clinical outcomes and induce strong antitumour immune responses. Recently, a few prospective, randomised, Phase III clinical trials have been initiated in order to finally determine the efficacy of particular cancer immunogene therapy strategies. This article reviews the present status and perspectives of clinical trials of cancer immunotherapies utilising cytokine gene-modified cells.

Anti-angiogenic therapies in cancer clinical trials

Strategies involving vasculature have widely been acknowledged to have therapeutic potential in the management of cancer and other diseases. Based on a large body of evidence from preclinical studies and early clinical trials there is considerable optimism that anti-angiogenesis and vascular targeting will be a major clinical therapy. This review considers some 30 anti-angiogenic and vascular targeting agents that are currently in cancer clinical trials and highlights specific problems relating to the assessment of the activity of these agents in patients, trial design, potential toxicities and resistance mechanisms.

CpG immunostimulatory oligodeoxynucleotide 1826 enhances antitumor effect of interleukin 12 gene-modified tumor vaccine in a melanoma model in mice

PURPOSE

The effectiveness of interleukin (IL)-12-secreting tumor vaccines in the treatment of mouse tumors could be enhanced by concurrent application of cytokines and costimulatory molecules. We investigated the therapeutic potential of IL-12 gene-transduced melanoma vaccine in combination with CpG immunostimulatory oligodeoxynucleotide (ODN) 1826, an adjuvant known to favor development of Th1-biased immune response, in a B78-H1 (B78) melanoma model in mice.

EXPERIMENTAL DESIGN

Mice injected with B78 melanoma cells were treated with irradiated IL-12 gene-transduced B78 cells [B78/IL-12(X)] and/or ODN 1826. Mechanisms responsible for the antitumor effects of the treatment were investigated using fluorescence-activated cell sorter analysis, a standard (51)Cr releasing assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and ELISA.

RESULTS

Single injection of B78/IL-12(X) cells had no effect on tumor growth, whereas seven consecutive daily injections of ODN 1826 markedly inhibited tumor progression with occasional curative effects. When used in combination, B78/IL-12(X) cells and ODN 1826 caused additional tumor growth reduction and eradication of tumors in 62% of treated mice. The combined treatment activated local inflammatory response against tumor but also induced systemic antitumor immunity. In vitro studies have shown that when used together, B78/IL-12(X) cells and ODN 1826 induced a potent Th1 response and suggested the role of IFN-gamma in activation of the host immune response. The antitumor effects in double-treated mice were accompanied by the development of cytotoxic effectors in the spleen and activation of macrophages.

CONCLUSIONS

The results provided the evidence that the combination of IL-12 gene-modified melanoma vaccine and ODN 1826 induces synergistically systemic and local antitumor immunity.

Intratumoral Administration of a Recombinant Canarypox Virus Expressing Interleukin 12 in Patients with Metastatic Melanoma

The aim of this study was to evaluate the tolerability and activity of intratumoral administered human interleukin 12 encoded by a vector derived from the canarypox virus (ALVAC-IL-12). Nine patients with surgically incurable metastatic melanoma who had subcutaneous nodules available for injection were enrolled. ALVAC-IL-12 was administered by intratumoral injection on days 1, 4, 8, and 11. Tumor nodules greater than 2 cm in diameter were injected with 2 x 10(6) median tissue culture infectious doses (TCID(50)), and smaller tumors were injected with 1 x 10(6) TCID(50). The total dose per patient per time point ranged from 1 x 10(6) to 4 x 10(6) TCID(50). Toxicity was mild to moderate and consisted of inflammatory reactions at the injection site and fever associated with chills, myalgia, and fatigue. No dose-limiting toxicities occurred. Increases in IL-12 mRNA, and also increases in interferon gamma mRNA, were observed in ALVAC-IL-12-injected tumors compared with saline-injected control tumors in four of the nine patients. ALVAC-IL-12-injected tumors were also characterized by T cell infiltration. Three patients demonstrated increases in serum IL-12 and in interferon gamma levels. All patients developed neutralizing IgG antibody to the canarypox vector. One patient manifested a complete response of injected subcutaneous metastases and uninjected in-transit metastases. The intratumoral injection of ALVAC-IL-12 at these dose levels and according to this schedule was well tolerated and resulted in measurable biologic response in patients with metastatic melanoma.

IL-12 cDNA direct injection: antimetastatic effect from a single injection in a murine hepatic metastases model

BACKGROUND

Interleukin 12 (IL-12) gene therapy is an effective antitumor agent in local and metastatic murine tumor models. We sought to evaluate the antimetastatic effect of IL-12 cDNA in a liver metastases model.

MATERIALS AND METHODS

A liver metastases model was induced by creating a "primary" splenic tumor through inoculation of 1 x 10(5) TS/A adenocarcinoma cells directly into the inferior pole of the spleen in female BALB/c mice. On day 4, 50 microg of IL-12 cDNA or control plasmid DNA was injected into splenic tumor, followed by splenectomy on day 8. Mice were sacrificed on day 25 to assess liver tumor burden. IL-12 mRNA and mIL-12 and IFN-gamma protein levels were assessed after IL-12 injection. Peripheral blood CD4+, CD8+, and NK cells were quantified on day 14 using FACS. To determine the significance of site of cytokine DNA injection, IL-12 cDNA was injected on day 4 into splenic tumor or into the non-involved spleen after isolation of the inferior and superior portions of the spleen, respectively, with surgical clips. Splenectomy was performed on day 8 and sacrifice was performed on day 25.

RESULTS

IL-12 mRNA was detected in the liver 8 h after injection, with a peak at 24 h. After splenic injection, protein levels of IL-12 and IFN-gamma were detectable in the liver and spleen 24 h after treatment. IL-12 and IFN-gamma were not detectable in control animals. In the peripheral blood, there was a marked increase in NK cells (13% of total lymphocytes versus 4%, control) and in the CD4+/CD8+ ratio (5.5 versus 1.9). At day 25, there was a marked antimetastatic effect after IL-12 injection into either splenic tumor [liver:body weight, 6.2 versus 10.9 (control), P = 0.007] or non-involved spleen (6.8 g versus 10.7 g, P = 0.005). There was no difference in the antimetastatic effect between animals injected into splenic tumor or non-involved spleen (P = 0.3).

CONCLUSION

Injection with a single dose of IL-12 cDNA into splenic tumor or non-involved spleen resulted in a profound antimetastatic effect. Splenic IL-12 injection results in mRNA expression in the liver, protein expression in the liver and spleen, and a marked increase in NK cells and the CD4+/CD8+ ratio in peripheral blood.

Treatment of experimental breast cancer using interleukin-12 gene therapy combined with anti–vascular endothelial growth factor receptor-2 antibody

We have shown previously that interleukin-12 (IL-12) gene therapy induced strong antitumor effects in several syngeneic murine tumor models including 4T1 mammary adenocarcinoma. Antiangiogenic treatment with a monoclonal antibody (mAb) directed against the vascular endothelial growth factor receptor-2 (VEGFR-2) is another promising treatment approach that can cause transient suppression of tumor growth. We hypothesized that the combination of IL-12 gene therapy and anti-VEGFR-2 mAb will achieve better antitumor and antimetastatic effects against 4T1 adenocarcinoma than each treatment alone via implementation of different mechanisms. Administration of anti-VEGFR-2 mAb into BALB/c mice bearing s.c. 4T1 tumors induced significant suppression of tumor growth, as did intratumoral administration of naked IL-12 DNA. The combined treatment with anti-VEGFR-2 mAb and IL-12 DNA resulted in significantly enhanced inhibition of tumor growth as compared with each treatment alone. This combination was also effective against spontaneous lung metastases. In T-cell–deficient nude mice, both IL-12 DNA and anti-VEGFR-2 mAb were effective in suppressing tumor growth. In T-cell- and natural killer cell–deficient scid/beige mice, only anti-VEGFR-2 mAb was effective, suggesting that natural killer cells are involved in the antitumor effects induced by IL-12 DNA. In both types of immunodeficient mice, the combination of anti-VEGFR-2 mAb and IL-12 DNA was as effective in suppressing 4T1 tumor growth as anti-VEGFR-2 mAb alone. Antitumor effects of anti-VEGFR-2 mAb were associated with the inhibition of angiogenesis within the tumors, whereas the antiangiogenic effect of IL-12 gene therapy was not detected. Our results show a therapeutic benefit of combining IL-12 gene therapy and anti-VEGFR-2 mAb for cancer treatment.

Potent antitumor activity of interleukin-27

Although much promising data that interleukin (IL)-12 could be a powerful therapeutic agent against cancer were reported in animal models, its excessive toxicity has become a problem for its clinical application. IL-27 is a novel IL-12 family member that plays a role in the early regulation of T helper cell 1 initiation, including induction of T-bet and IL-12 receptor beta 2 expression. In the present study, we have evaluated the antitumor activity of IL-27 against a murine tumor model of colon carcinoma C26. C26 cells, which were transduced with the single-chain IL-27 cDNA and became secreting IL-27 (C26-IL-27), exhibited minimal tumor growth in vivo, and all of the mice inoculated with these cells survived healthily with complete tumor remission. Inoculation of mice with C26-IL-27 induced enhanced IFN-gamma production and cytotoxic T-lymphocyte activity against C26 tumor in spleen cells. Recovered mice from the inoculation showed a tumor-specific protective immunity to the following challenge with parental C26 tumor. The antitumor activity of IL-27 was almost diminished in nude mice, and depletion of CD8(+) T cells and neutralization of IFN-gamma in immunocompetent mice reduced greatly the antitumor activity. Moreover, the antitumor activity was abolished in T-bet-deficient mice, whereas it was observed unexpectedly in mice deficient of signal transducer and activator of transcription (STAT) 4. These results suggest that IL-27 has potent abilities to induce tumor-specific antitumor activity and protective immunity and that the antitumor activity is mediated mainly through CD8(+) T cells, IFN-gamma, and T-bet but not through STAT4.

Candidate Genes Associated with Tumor Regression Mediated by Intratumoral Il-12 Electroporation Gene Therapy

Interleukin-12 (IL-12) is one of the most effective cytokines for treating malignancy. Intratumoral delivery of the murine Il-12 gene, using electroporation, has been found effective in inducing regression of established tumors in mice, and more effective than intramuscular injection of this gene by electroporation, but what is not known is the molecular mechanism by which IL-12 exerts an antitumor effect. To define these candidate genes, the gene expression profiles of tumors treated with and without intratumoral Il-12 electroporation gene therapy were analyzed by cDNA array. Mig (Cxcl9), Stat1, and IRF7 are the three genes that are the most altered at the level of expression after administration of Il-12 via intratumoral electroporation, when subjected to further characterization by Northern blot, Western blot, and immunostaining. The results from Northern blot and immunostaining analyses indicate that intratumoral delivery of the murine Il-12 gene via electroporation induces accumulation of IRF7 in the nuclei of tumor cells and upregulates Mig and Stat1 expression by 15- and 5-fold, respectively, compared to intratumoral electroporation of control plasmid DNA. Intramuscular injection of the same Il-12 gene using electroporation upregulates Mig and Stat1 by only 6- and 2.9-fold, respectively, but does not induce any IRF7 accumulation in the nuclei. Further functional analyses of Mig indicate that expression in tumors can induce CD4+ but not CD8+ T cell infiltration. Further functional analysis of Stat1 indicates that a lack of Stat1 expression inhibits the Il-12-mediated induction of IP10, a known antiangiogenic gene. These data suggest that these three genes may positively correlate with the antitumor efficacy of intratumoral Il-12 electroporation gene therapy.

A model for the analysis of nonviral gene therapy

Further understanding of the mechanisms involved in cellular and intracellular delivery of transgene is needed to produce clinical applications of gene therapy. The compartmental and computational model designed in this work is integrated with data from previous experiments to quantitatively estimate rate constants of plasmid translocation across cellular barriers in transgene delivery in vitro. The experimental conditions between two cellular studies were held constant, varying only the cell type, to investigate how the rates differed between cell lines. Two rate constants were estimated per barrier for active transport and passive diffusion. Translocation rates of intact plasmid across the cytoplasmic and nuclear barriers varied between cell lines. CV1 cells were defined by slower rates (0.23 h(-1) cytoplasmic, 0.08 h(-1) nuclear) than those of the HeLa cells (1.87 h(-1) cytoplasmic, 0.45 h(-1) nuclear). The nuclear envelope was identified as a rate-limiting barrier by comparing the rate of intact plasmid translocation at each barrier. Slower intact plasmid translocation in CV1 cells was correlated with a reduced absolute capacity for transgene efficiency in comparison with HeLa cells. HeLa cells were three times more efficient than CV1 cells at producing green fluorescent protein per intact plasmid delivered to the nucleus. Mathematical modeling coordinated with experimental studies can provide detailed, quantitative understanding of nonviral gene therapy.

Safety of interleukin-12 gene therapy against cancer: a murine biodistribution and toxicity study

As a prerequisite for a human clinical trial using interleukin (IL)-12 gene therapy, the biodistribution and safety of IL-12, administered as an intradermal naked DNA injection, was evaluated in mice. The pNGVL3-mIL12 plasmid used in this study is a nonviral vector designed to induce a high level of IL-12 protein expression during a transient transfection of the host cell. The biodistribution was evaluated by a polymerase chain reaction (PCR) assay that is capable of detecting less than 100 copies of the plasmid in the context of host DNA. Twenty-four hours after three intradermal injections of 0.5 microg or 5 microg of pNGVL3-mIL12 plasmid, the plasmid was detectable in various internal organs, the blood, and the injection site. The plasmid was detectable in the gonads of only one animal at the high-dose treatment 24 hr after the injections. In the majority of the organs the plasmid was undetectable throughout the study. Possible side effects were monitored by histology and clinical chemistry, and the level of IL-12 protein expression was assessed by enzyme-linked immunosorbent assay (ELISA). No treatment-related histologic abnormalities were detected and the blood chemistry parameters showed no toxicity. The IL-12 protein was undetectable at all times at the injection site and interferon (IFN)-gamma levels at the injection site and in the serum were at background levels. The results of this murine safety study indicate that based on the distribution pattern of the plasmid in the body and the undetectable toxicities in the tissues, the use of the pNGVL3-hIL12 plasmid in cancer gene therapy clinical trials can be considered as safe.

Advantages and limitations of particle-mediated transfection (gene gun) in cancer immuno-gene therapy using IL-10, IL-12 or B7-1 in murine tumor models

BACKGROUND

Previous studies have shown that particle-mediated transfection (PMT; gene gun) is an efficient method of non-viral gene transfer. We have examined the advantages and limitations of PMT in cancer immuno-gene therapy using IL-10, IL-12 or B7-1, all of which have been shown to be effective in murine tumor models using retroviral vectors.

METHODS

Murine cell lines (MCA205, MCA207, NIH-3T3) were treated with in vitro PMT, liposome-mediated transfection (LMT) or retroviral transfection. In vivo PMT was also examined for in vivo experiments using C57BL/6.

RESULTS

Transfection efficiency and cytokine expression of PMT were similar to those of LMT, another non-viral approach, in culture when murine adherent cells were used. Tumor establishment of MCA205 was suppressed when they were transfected with the mIL-12 and/or mB7-1 gene using PMT in vitro. In a treatment of established tumor, vaccination with tumor cells transfected with an IL-12 gene suppressed tumor growth, whereas a B7-1 gene was not effective. When an IL-10 gene was used to supply a high level of expression for antitumor effects, neither in vitro nor in vivo PMT could suppress even tumor establishment. These failures appear to be caused by the characteristics of PMT which allows high, but transient, expression of transfected genes.

CONCLUSIONS

Particle-mediated transfection is a useful non-viral transfection method in a system which does not require high-level gene expression for a prolonged time of period.

Differential effects of age on chicken heterophil functional activation by recombinant chicken interleukin-2

Interleukin-2 (IL-2) exercises an array of biological effects on many cells including the functional activation of cells of the innate immune response. Heterophils, the avian equivalent of the neutrophil, function as professional phagocytes to aid in regulation of innate host defenses. The objective of the present studies was to examine the effects of recombinant chicken IL-2 (rChIL-2) on functional activities of heterophils from chickens during the first 3 weeks after hatch. Peripheral blood heterophils were isolated and incubated with either COS cell-derived rChIL-2 or supernatants from mock-transfected COS cells. rChIL-2 had no effect on the functional activities of heterophils from day-of-hatch chickens, but significantly increased the phagocytosis and bactericidal activity of heterophils from 7- and 14-day-old chickens. rChIL-2 induced no direct stimulation of the respiratory burst by heterophils, but primed heterophils from 7- and 14-day-old birds for an enhanced respiratory burst in response to phorbol ester stimulation. Lastly, rChIL-2 had neither direct nor priming effects on heterophil degranulation. The enhancing effects on heterophil functional activity by rChIL-2 were abated by a neutralizing anti-chicken IL-2 mAb and were therefore specific for this cytokine. These results show that rChIL-2 can directly activate chicken heterophils to exert effector functions, and that heterophil activation by rChIL-2 is also an age-dependent event.

Cytokine gene therapy for cancer with naked DNA

Plasmid DNA vectors (naked DNA) can easily be purified and transferred in vivo by intramuscular or intradermal injection. Naked DNA is stable in vivo, and long-term expression of the encoded protein is seen without chromosomal integration. Gene gun-mediated delivery of an expression plasmid is slightly more complicated but more efficient. These techniques have been applied to DNA vaccination or cytokine gene therapy for various diseases, including infections, autoimmune disorders, and cancer. We review cytokine gene therapy for cancer with naked DNA in animal models and present our preliminary data on gene gun-mediated in vivo transfection with the interleukin-12 gene in a murine renal cancer model. Because of its safety, simplicity, and low cost, cytokine gene therapy with naked DNA may become an important cancer treatment.

Fas-Fas ligand signaling pathway mediates an interleukin-12-induced rejection of a murine prostate tumor system

BACKGROUND

Recent data suggest that anti-tumor activities of interleukin-12 (IL-12) involve the induction of apoptosis. Fas (APO-1/CD95) is a type I membrane protein that is capable of initiating an apoptosis signaling pathway when bound to its ligand (FasL). We undertook this study to test the hypothesis that Fas-FasL-mediated apoptosis plays a role in IL-12-induced tumor regression.

METHODS

An mIL-12 expression vector driven by cytomegalovirus promoter was used to express murine IL-12 cDNA in the RM-9 murine prostate carcinoma cell line. Control RM-9 cells and RM-9 cells stably transfected with IL-12 gene (RM-9-IL12) were inoculated subcutaneously in 4- to 6-week-old male C57BL/J6 mice. Tumor size was measured every 3 days. Western blot and immunohistochemical assays were used to evaluate Fas and FasL protein expression. In situ fluorescent end labeling was used to label apoptotic cells.

RESULTS

IL-12-expressing RM-9 prostate carcinoma cells transplanted into C57BL/J6 mice grew more slowly than control RM-9 cells and vector control RM-9-Luc cells. The average survival time of the RM-9-IL12 mice was longer than 53 days, whereas the mean survival for mice transplanted with control RM-9 cells was only 16 days. Apoptotic cells were more numerous in RM-9-IL12 tumors: 10.3% vs. 1.5% in control (P = 0.001). Fas and FasL proteins were increased approximately twofold in the RM-9-IL12 tumors compared with the RM-9 control tumors as determined by Western blot and immunohistochemical analyses (P < 0.05).

CONCLUSION

The Fas-FasL-mediated apoptosis pathway may contribute to the IL-12-induced rejection of prostate carcinoma.

Biodegradable polymer-based interleukin-12 gene delivery: role of induced cytokines, tumor infiltrating cells and nitric oxide in anti-tumor activity

The objective of this study was to investigate the role of induced cytokines, tumor infiltrating cells and nitric oxide (NO) in anti-tumor activity upon intratumoral injection of free and condensed plasmid DNA encoding murine interleukin-12 (pmIL-12) into BALB/c mice bearing subcutaneous tumors. Poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) was used for complex formation with pmIL-12 in presence of 5% (w/v) glucose. Upon characterization, PAGA/pmIL-12 (3/1, +/-) complexes were found to be most effective in gene transfer and were used consistently throughout this study. The levels of mIL-12 p70 and induced cytokines were determined by ELISA in the supernatant of the cultured tumors of the CT-26 subcutaneous tumor bearing BALB/c female mice 48 h after intratumoral injection of PAGA/pmIL-12 complexes and naked pmIL-12. The levels of IL-12, IFN-gamma, TNF-alpha and NO were higher for the PAGA/pmIL-12 complexes than those for the naked pmIL-12, PAGA alone and 5% glucose injected groups. The relative presence of natural killer (NK) cells, CD4(+) T cells, and antigen presenting cells, such as macrophages and dendritic cells determined using immunohistochemistry was higher for PAGA/pmIL-12 complexes compared with naked pmIL-12. The presence of CMV promoter in plasmid encoding IL-12 cDNAs did not induce any type I interferon response. There was a significant improvement in the survival rate and the inhibition of tumor growth after repeated injections of PAGA/pmIL-12 complexes.

Tumor regression of human and murine melanoma after intratumoral injection of IL-12-encoding plasmid DNA in mice

DNA coding for murine interleukin 12 (IL-12) prevents the formation of B16-melanoma metastasis when administered intramuscularly. Here, the antitumor effect of IL-12-encoding DNA on established mouse B16 melanoma and human melanoma tumors was investigated in vivo using two animal models: B16 melanoma in C57B/6 mice and human melanoma in nude mice. In B16 melanoma, intratumoral injections of IL-12-encoding DNA resulted in highly significant growth retardation when compared with mice injected with control vector. In the case of the human melanoma model, treatment with DNA coding for IL-12 induced regression of tumors in all cases, with complete disappearance of the tumor in two out of five animals. DNA treatment did not induce systemic side-effects. In the animals injected with control vector the human melanoma tumors grew expansively. The therapeutic effect of the DNA injection was mediated in part by natural killer (NK) cells as shown by NK-depletion experiments. An antivascular effect of IL-12 treatment was evident in histological examination with endothelial thickening and abrupt changes in vessel diameters. These results suggest that intratumoral plasmid DNA coding for IL-12 holds some promise as a new therapeutic tool for accessible melanoma lesions and should be tested in clinical trial.

Safety toxicity study of plasmid-based IL-12 therapy in Cynomolgus monkeys

We have investigated the potential toxicity of hlL-12 DNA plasmid formulated with 5% polyvinylpyrrolidone (PVP) administered twice weekly via subcutaneous injections to Cynomolgus monkeys for four weeks, and have evaluated recovery from any effects of the test article over a four-week treatment-free period. Doses of the formulated hIL-12 plasmid were selected based on anti-tumour efficacy studies previously conducted in mice. The duration of the study and the frequency of dosing were designed to support clinical trials. No clinical signs indicative of an adverse effect of administration of formulated hIL-12 plasmid were observed. There were no apparent effects of the formulated hIL-12 plasmid on body weights or on serum chemistry, haematology, coagulation or urinalysis parameters. No treatment-elated ocular abnormalities were evident. In addition, examination of the electrocardiograms from all monkeys at the pre-study, week-4, and week-8 time points did not reveal any treatment-related effects. No treatment-related gross lesions were noted at days 28 or 57. Slight histopathological changes associated with high doses of PVP vehicle were observed at both time points. These results suggested that the administration of formulated hIL-12 plasmid at a dose level up to 18 mg kg(-1) dose twice per week for four weeks to experimentally naïve Cynomolgus monkeys did not result in significant toxicity. These results support further testing of this gene therapy in clinical trials.