Inhibition of established subcutaneous and metastatic murine tumors by intramuscular electroporation of the interleukin-12 gene

Electrogene therapy with interleukin-12 in canine mast cell tumors

BACKGROUND

Mast cell tumors (MCT) are the most common malignant cutaneous tumors in dogs with extremely variable biological behaviour. Different treatment approaches can be used in canine cutaneous MCT, with surgical excision being the treatment of choice. In this study, electrogene therapy (EGT) as a new therapeutic approach to canine MCTs, was established. MATERIALS AND METHODS.: Eight dogs with a total of eleven cutaneous MCTs were treated with intratumoral EGT using DNA plasmid encoding human interleukin-12 (IL-12). The local response to the therapy was evaluated by repeated measurements of tumor size and histological examination of treated tumors. A possible systemic response was assessed by determination of IL-12 and interferon- γ (IFN-γ) in patients' sera. The occurence of side effects was monitored with weekly clinical examinations of treated animals and by performing basic bloodwork, consisting of the complete bloodcount and determination of selected biochemistry parameters.

RESULTS

Intratumoral EGT with IL-12 elicits significant reduction of treated tumors' size, ranging from 13% to 83% (median 50%) of the initial tumor volume. Additionally, a change in the histological structure of treated nodules was seen. There was a reduction in number of malignant mast cells and inflammatory cell infiltration of treated tumors. Systemic release of IL-12 in four patients was detected, without any noticeable local or systemic side effects.

CONCLUSIONS

These data suggest that intratumoral EGT with plasmid encoding IL-12 may be useful in the treatment of canine MCTs, exerting a local antitumor effect.

Controlled systemic release of interleukin-12 after gene electrotransfer to muscle for cancer gene therapy alone or in combination with ionizing radiation in murine sarcomas

BACKGROUND

The present study aimed to evaluate the antitumor effectiveness of systemic interleukin (IL)-12 gene therapy in murine sarcoma models, and to evaluate its interaction with the irradiation of tumors and metastases. To avoid toxic side-effects of IL-12 gene therapy, the objective was to achieve the controlled release of IL-12 after intramuscular gene electrotransfer.

METHODS

Gene electrotransfer of the plasmid pORF-mIL12 was performed into the tibialis cranialis in A/J and C57BL/6 mice. Systemic release of the IL-12 was monitored in the serum of mice after carrying out two sets of intramuscular IL-12 gene electrotransfer of two different doses of plasmid DNA. The antitumor effectiveness of IL-12 gene electrotransfer alone or in combination with local tumor or lung irradiation with X-rays, was evaluated on subcutaneous SA-1 and LPB tumors, as well as on lung metastases.

RESULTS

A synergistic antitumor effect of intramuscular gene electrotransfer combined with local tumor irradiation was observed as a result of the systemic distribution of IL-12. The gene electrotransfer resulted in up to 28% of complete responses of tumors. In combination with local tumor irradiation, the curability was increased by up to 100%. The same effect was observed for lung metastases, where a potentiating factor of 1.3-fold was determined. The amount of circulating IL-12 was controlled by the number of repeats of gene electrotransfer and by the amount of the injected plasmid.

CONCLUSIONS

The present study demonstrates the feasibility of treatment by IL-12 gene electrotransfer combined with local tumor or lung metastases irradiation on sarcoma tumors for translation into the clinical setting.

Delivery of DNA into muscle for treating systemic diseases: advantages and challenges

An efficient and safe method to deliver DNA in vivo is a requirement for several purposes, such as the study of gene function and gene therapy applications. Among the different nonviral delivery methods currently under investigation, in vivo DNA electrotransfer has proven to be one of the most efficient and simple methods. This technique is a physical method of gene delivery consisting of a local application of electric pulses after injection of DNA. This technique can be applied to almost any tissue of a living animal, including tumors, skin, liver, kidney, artery, retina, cornea, or even brain, but the focus of this review will be on electrotransfer of plasmid DNA into skeletal muscle and its possible therapeutic uses for systemic diseases. Skeletal muscle is a good target for electrotransfer of DNA because of the following features: a large volume of easily accessible tissue, an endocrine organ capable of expressing several local and systemic factors, and muscle fibers as postmitotic cells have a long lifespan, which allows long-term gene expression. In this review, we will describe the main characteristics of DNA electrotransfer, including toxicity and safety issues related to this technique. We will focus on the important possible therapeutic applications of electrotransfer for systemic diseases demonstrated in animal models in the recent years, in the fields of monogenic diseases, tissue-specific diseases, metabolic disorders, immune-system-related diseases, and cancer. Finally, we will discuss the advantages and challenges of this technique.

Efficient electrotransfection into canine muscle

Two different types of electroporation protocols have been developed for efficient electrotransfer of plasmid DNA into skeletal muscle of experimental animals. At first, only low voltage electric pulses have been used, but lately, a combination of high and low voltage pulses has been suggested as more efficient. Up to date, in dogs, this type of electroporation protocol has never been used for muscle targeted plasmid DNA electrotransfection. In this study, we used two different DNA plasmids, one encoding green fluorescent protein and one encoding human interleukin-12. Five different electroporation protocols were evaluated. Three of them featured different combinations of high and low voltage pulses, and two were performed with delivery of low voltage pulses only. Our study shows that combination of 1 high voltage pulse (600 V/cm, 100 mus), followed by 4 low voltage pulses (80 V/cm, 100 ms, 1 Hz) yielded in the same transfection efficiency as the standard trains of low voltage pulses. However, this protocol is performed quicker and, thus, more suitable for potential use in clinical practice. In addition, it yielded in detectable systemic expression of human interleukin-12. Electrotransfer of either of the plasmids was associated with only mild and transitory local side effects, without clinically detectable systemic side effects. The results indicate that electrotransfection is a feasible, effective, and safe method for muscle targeted gene therapy in dogs, which could have potential for clinical applications in veterinary medicine of small animals.

Function of interleukin-20 as a proinflammatory molecule in rheumatoid and experimental arthritis

OBJECTIVE

The pathogenesis of rheumatoid arthritis (RA) reflects an ongoing imbalance between proinflammatory and antiinflammatory cytokines. Interleukin-20 (IL-20) has proinflammatory properties for keratinocytes. In this study, we sought to determine whether IL-20 is involved in RA.

METHODS

We analyzed IL-20 levels in synovial fluid from RA patients. IL-20 and its receptors were detected in RA synovial fibroblasts (RASFs), using immunohistochemical staining. The effect of IL-20 on endothelial cells, neutrophils, and RASFs was investigated using MTT and migration assays. The expression of IL-20 and its receptors in healthy rats and in rats with collagen-induced arthritis (CIA) was also analyzed. Soluble IL-20 receptor type I (sIL-20RI) or sIL-20RII was administered to rats with CIA by intramuscular electroporation, and the severity of arthritis was monitored.

RESULTS

RA patients expressed significantly higher levels of synovial fluid IL-20 than did the rheumatic disease controls. IL-20 and its receptors were expressed in the synovial membranes and RASFs. IL-20 induced RASFs to secrete monocyte chemoattractant protein 1, IL-6, and IL-8, and it promoted neutrophil chemotaxis, RASF migration, and endothelial cell proliferation. Both IL-20 and IL-20RI were up-regulated in the rat CIA model. In vivo, electroporated sIL-20RI plasmid DNA decreased the severity of arthritis in the rats with CIA.

CONCLUSION

IL-20 was up-regulated in the synovial fluid of RA patients and acted as a chemokine that attracted the migration of neutrophils and RASFs in vitro. The rat CIA model demonstrated that IL-20 was involved in the pathogenesis of arthritis, because sIL-20RI significantly reduced arthritis in rats with CIA. Thus, IL-20 may modulate the incidence and severity of arthritis and play important roles at local sites of inflammation.

Electroporation for targeted gene transfer

The utilisation of nonviral gene delivery methods has been increasing steadily, however, a drawback has been the relative low efficiency of gene transfer with naked DNA compared with viral delivery methods. In vivo electroporation, which has previously been used clinically to deliver chemotherapeutic agents, also enhances the delivery of plasmid DNA and has been used to deliver plasmids to several tissue types, particularly muscle and tumour. Recently, a large number of preclinical studies for a variety of therapeutic modalities have demonstrated the potential of electrically mediated gene transfer. Although clinical trials using gene transfer with in vivo electroporation have not as yet been realised, the tremendous growth of this technology suggests that the first trials will soon be initiated.

Analysis of humoral immunity of hepatitis D virus DNA vaccine generated in mice by using different dosage, gene gun immunization, and in vivo electroporation

BACKGROUND

Hepatitis D virus (HDV) DNA vaccine can produce Th1 and cytotoxic T-cell immune responses but only a low anti-HDV antibody titer is generated with a large hepatitis D antigen (L-HDAg) construct. In contrast, DNA vaccine expressing small hepatitis D antigen (S-HDAg) can generate a high titer of anti-HDV antibodies. Whether the low humoral immunity of L-HDAg DNA vaccine is due to inadequate dosage or can be ameliorated by other modes of immunization needs further evaluation.

METHODS

Plasmid (p25L) encoding L-HDAg and plasmid (pS/p25L) coexpressing hepatitis B surface antigen (HBsAg) and L-HDAg were used in this study. We compared the humoral response generated in mice using different plasmid DNA dosages and modes of immunization, including gene gun and in vivo electroporation (EP).

RESULTS

Intramuscular injection with a high dose of plasmid DNA (10 mg/kg) produced strong antibodies to HBsAg earlier than the usual dose did, but did not augment the anti-HDV response. Gene gun DNA immunization could not provide a better humoral immune response to HDV. EP DNA immunization had a higher anti-HDV seroconversion rate of 80%, but the anti-HDV antibody responses were generally weak (titer < or = 400:1).

CONCLUSION

The low humoral immunogenicity of DNA vaccine with L-HDAg cannot be ameliorated by different dosage, gene gun immunization, or in vivo EP intramuscular injection. DNA vaccine with a L-HDAg construct may not be a candidate HDV vaccine to generate anti-HDV humoral immunity.

Gene therapy for spinal fusion

Spinal fusion will continue to be an important part of the surgical treatment of spinal pathology for the foreseeable future. Traditional challenges to successful spinal fusion surgery include autograft donor site morbidity and pseudoarthrosis. Recent advances in the understanding of the biology of bone formation have allowed the development of therapeutic biologics. Although recombinant bone morphogenetic proteins delivered to the arthrodesis site will stimulate fusion, these proteins have been less successful in more challenging fusion situations (posterolateral), require supraphysiologic doses to promote fusion in humans, and are quite expensive. Gene therapy may represent the easiest method for the application of bone-forming biologic agents to promote spinal fusion. Both in vivo and ex vivo techniques of delivery of therapeutic genes have been used effectively to promote fusion in lower animals. Considerable research is required to identify gene therapy techniques and vectors with acceptable safety profiles and high fusion rates.

IL-24 inhibits the growth of hepatoma cells in vivo

The interleukin (IL)-24/melanoma differentiation associated gene-7 (mda-7) is a member of the IL-10 cytokine family. Introduction of the IL-24 gene into a variety of cancer cells suppresses their growth. It has not been shown, however, whether IL-24 can suppress the growth of hepatoma cells. The purpose of this study was to determine whether the mouse (m)IL-24 gene would suppress hepatoma cells in vivo after being delivered via intramuscular electroporation. After mice were given a subcutaneous dorsal injection of ML-1 hepatoma cells, the mIL-24 gene was delivered and suppressed tumor growth. On day 140, 60% of the mIL-24-treated mice (n=10) and 0% (n=10) of the untreated control mice had survived. We also generated a mouse-hepatoma model by injecting ML-1 cells into the spleen, which resulted in tumor metastasis in the liver. Intramuscular electroporation of mIL-24 also inhibited hepatoma-cell growth in the liver. On day 50, 90% of the experimental mice (n=10) and 40% (n=10) of the control mice had survived. Liver tumors in surviving experimental mice were 50% smaller than those in control mice. IL-24 also inhibited tumor vascularization. These results suggest that IL-24 has potential therapeutic value for hepatoma

Electric pulse-mediated gene delivery to various animal tissues

Electroporation designates the use of electric pulses to transiently permeabilize the cell membrane. It has been shown that DNA can be transferred to cells through a combined effect of electric pulses causing (1) permeabilization of the cell membrane and (2) an electrophoretic effect on DNA, leading the polyanionic molecule to move toward or across the destabilized membrane. This process is now referred to as DNA electrotransfer or electro gene transfer (EGT). Several studies have shown that EGT can be highly efficient, with low variability both in vitro and in vivo. Furthermore, the area transfected is restricted by the placement of the electrodes, and is thus highly controllable. This has led to an increasing use of the technology to transfer reporter or therapeutic genes to various tissues, as evidenced from the large amount of data accumulated on this new approach for non-viral gene therapy, termed electrogenetherapy (EGT as well). By transfecting cells with a long lifetime, such as muscle fibers, a very long-term expression of genes can be obtained. A great variety of tissues have been transfected successfully, from muscle as the most extensively used, to both soft (e.g., spleen) and hard tissue (e.g., cartilage). It has been shown that therapeutic levels of systemically circulating proteins can be obtained, opening possibilities for using EGT therapeutically. This chapter describes the various aspects of in vivo gene delivery by means of electric pulses, from important issues in methodology to updated results concerning the electrotransfer of reporter and therapeutic genes to different tissues.

DNA electrotransfer: its principles and an updated review of its therapeutic applications

The use of electric pulses to transfect all types of cells is well known and regularly used in vitro for bacteria and eukaryotic cells transformation. Electric pulses can also be delivered in vivo either transcutaneously or with electrodes in direct contact with the tissues. After injection of naked DNA in a tissue, appropriate local electric pulses can result in a very high expression of the transferred genes. This manuscript describes the evolution in the concepts and the various optimization steps that have led to the use of combinations of pulses that fit with the known roles of the electric pulses in DNA electrotransfer, namely cell electropermeabilization and DNA electrophoresis. A summary of the main applications published until now is also reported, restricted to the in vivo preclinical trials using therapeutic genes.

Inhibition of Cytotrophoblastic (JEG-3) Cell Invasion by Interleukin 12 Involves an Interferon γ-mediated Pathway

Trophoblast invasion, like tumor invasion, shares common biochemical mechanisms. However, in contrast to tumor invasion of a host tissue, trophoblastic invasion during implantation is strictly regulated, temporospatially. Factors responsible for these important regulatory processes are presently unknown; however, studies indicate that cytokines and growth factors represent in the peri-implantation uterine milieu as the possible candidates. In this study we investigated the role of interleukin (IL) 12 in regulating trophoblast invasion and the expression of trophoblast proteases (matrix metalloprotease (MMP)-2, MMP-9, and urokinase-type plasminogen activators) and their inhibitors (tissue inhibitors of metalloprotease (TIMP) 1, TIMP-2, and plasminogen activator inhibitor (PAI)-1) using an in vitro tissue culture system of human choriocarcinoma cell line JEG-3. Our major findings show an anti-invasive role of IL-12, associated with an inhibitory effect on the proteases but with an opposite up-regulating influence on the protease inhibitor, TIMP-1, whereas TIMP-2 and plasminogen activator inhibitor 1 remained unaltered. Stimulation of JEG-3 cells with IL-12 also induced interferon (IFN)-gamma production, which when neutralized using a monoclonal anti-IFN-gamma antibody, F12, abrogates its ability to down-regulate the MMPs. IL-12 also mediates an IFN-gamma-dependent up-regulation of E-cadherin, thereby implying that alteration in cell-cell adhesion besides regulating the proteases and the inhibitors possibly contributes to the observed anti-invasive role of this cytokine. TIMP-1, although stimulated by IL-12, was found to be unaltered by antibody F12, thereby implying a possibility of an IL-12-dependent-IFN-gamma independent regulation. These findings thereby suggest an important role of IL-12 in modulation of trophoblast proteases and their inhibitors besides regulating cell-cell interactions and invasion during implantation, with far reaching possibilities for understanding the mechanism(s) and regulations of invasion and metastasis.

Combination electro-gene therapy using herpes virus thymidine kinase and interleukin-12 expression plasmids is highly efficient against murine carcinomas in vivo

We report the use of plasmid DNA-mediated combination gene therapy for tumor-bearing mice using in vivo electroporation, also called electro-gene therapy (EGT), that resulted in uncomplicated and complete cures in more than 90% of the mice. Subcutaneously inoculated CT26 tumors in syngeneic BALB/c mice were subjected to repeated EGT treatments consisting of intratumoral co-injection of naked plasmids encoding the cytokine interleukin-12 (IL-12) (p35 and p40 subunits) and the suicide gene herpes simplex virus thymidine kinase (HSV-tk), followed by in vivo electroporation. The early anti-tumor effect was always stronger, and the rate of cure, as seen in the long-term follow-up, was always greater in the groups treated with combination EGT than in those treated with IL-12 or HSV-tk EGT alone. Systemic levels of IL-12 and IFN-gamma increased in both combination and IL-12-alone EGT-treated groups. Moreover, combination EGT for established subcutaneous tumors strongly reduced hematogenous lung metastases and increased survival time when live CT26 tumor cells were injected through the tail vein. Limited experiments on C57/B16 mice with murine melanoma also showed very similar trends. These results suggest that this simple and safe method of plasmid-mediated combination EGT may provide a potentially effective gene therapy for cancer.

Electroporation for gene transfer to skeletal muscles: current status

Naked plasmid DNA can be used to introduce genetic material into a variety of cell types in vivo. However, such gene transfer and expression is generally very low compared with that achieved with viral vectors and so is unsuitable for clinical therapeutic application in most cases. This difference in efficiency has been substantially reduced by the introduction of in vivo electroporation to enhance plasmid delivery to a wide range of tissues including muscle, skin, liver, lung, artery, kidney, retina, cornea, spinal cord, brain, synovium, and tumors. The precise mechanism of in vivo electroporation is uncertain, but appears to involve both electropore formation and an electrophoretic movement of the plasmid DNA. Skeletal muscle is a favored target tissue for three reasons: there is a pressing need to develop effective therapies for muscular dystrophies; skeletal muscle can act as an effective platform for the long-term secretion of therapeutic proteins for systemic distribution; and introduction of DNA vaccines into skeletal muscle promotes strong humoral and cellular immune responses. All of these applications are significantly improved by the application of in vivo electroporation. Importantly, the increased efficiency of plasmid delivery following electroporation is seen in larger species as well as rodents, in contrast to the decreasing efficiencies with increasing body size for simple intramuscular injection of naked plasmid DNA. As this electroporation-enhanced non-viral gene delivery system works well in larger species and avoids the vector-specific immune responses associated with recombinant viruses, the prospects for clinical application are promising.