Evaluation of toxicity following electrically mediated interleukin-12 gene delivery in a B16 mouse melanoma model

Non-clinical evaluation of pmIL12 gene therapy for approval of the phase I clinical study

Immunotherapeutic drugs are promising medicines for cancer treatment. A potential candidate for immunotherapy is interleukin-12 (IL-12), a cytokine well known for its ability to mediate antitumor activity. We developed a plasmid encoding human IL-12 devoid of an antibiotic resistance gene (phIL12). For the approval of phase I clinical trials in basal cell carcinoma (BCC), the regulatory agency requires non-clinical in vivo testing of the pharmacodynamic, pharmacokinetic and toxicological properties of the plasmid. As human IL-12 is not biologically active in mice, a mouse ortholog of the plasmid phIL12 (pmIL12) was evaluated. The evaluation demonstrated the antitumor effectiveness of the protein accompanied by immune cell infiltration. The plasmid was distributed throughout the body, and the amount of plasmid diminished over time in all organs except the skin around the tumor. The therapy did not cause any detectable systemic toxicity. The results of the non-clinical evaluation demonstrated the safety and efficacy of the pmIL12/phIL12 GET, and on the basis of these results, approval was obtained for the initiation of a phase I clinical study in BCC.

IL-12 and PD-1 peptide combination gene therapy for the treatment of melanoma

Interleukin-12 (IL-12) gene electrotransfer (GET) delivery is highly effective in inducing long-term, complete regression in mouse and human melanoma and other solid tumors. Therapeutic efficacy is enhanced by immune checkpoint inhibitors, and the combination of IL-12 plasmid GET (pIL-12 GET) and anti-programmed cell death protein 1 (PD-1) monoclonal antibodies has reached clinical trials. In this study, we designed peptides and plasmids encoding the mouse homologs of the pembrolizumab and nivolumab programmed cell death 1 ligand 1 (PD-L1) binding regions. We hypothesized that intratumor autocrine/paracrine peptide expression would block PD-1/PD-L1 binding and provide cancer patients with an effective and cost-efficient treatment alternative. We demonstrated that the mouse homolog to pembrolizumab was effective at blocking PD-1/PD-L1 in vitro. After intratumor plasmid delivery, both peptides bound PD-L1 on tumor cells. We established that plasmid DNA delivery to tumors in vivo or to tumor cells in vitro upregulated several immune modulators and PD-L1 mRNA and protein, potentiating this therapy. Finally, we tested the combination of pIL-12 GET therapy and peptide plasmids. We determined that pIL-12 GET therapeutic efficacy could be enhanced by combination with the plasmid encoding the pembrolizumab mouse homolog.

Pulsed Electric Fields in Oncology: A Snapshot of Current Clinical Practices and Research Directions from the 4th World Congress of Electroporation

The 4th World Congress of Electroporation (Copenhagen, 9-13 October 2022) provided a unique opportunity to convene leading experts in pulsed electric fields (PEF). PEF-based therapies harness electric fields to produce therapeutically useful effects on cancers and represent a valuable option for a variety of patients. As such, irreversible electroporation (IRE), gene electrotransfer (GET), electrochemotherapy (ECT), calcium electroporation (Ca-EP), and tumour-treating fields (TTF) are on the rise. Still, their full therapeutic potential remains underappreciated, and the field faces fragmentation, as shown by parallel maturation and differences in the stages of development and regulatory approval worldwide. This narrative review provides a glimpse of PEF-based techniques, including key mechanisms, clinical indications, and advances in therapy; finally, it offers insights into current research directions. By highlighting a common ground, the authors aim to break silos, strengthen cross-functional collaboration, and pave the way to novel possibilities for intervention. Intriguingly, beyond their peculiar mechanism of action, PEF-based therapies share technical interconnections and multifaceted biological effects (e.g., vascular, immunological) worth exploiting in combinatorial strategies.

The effectiveness of calcium electroporation combined with gene electrotransfer of a plasmid encoding IL-12 is tumor type-dependent

Introduction

In calcium electroporation (CaEP), electroporation enables the cellular uptake of supraphysiological concentrations of Ca2+, causing the induction of cell death. The effectiveness of CaEP has already been evaluated in clinical trials; however, confirmatory preclinical studies are still needed to further elucidate its effectiveness and underlying mechanisms. Here, we tested and compared its efficiency on two different tumor models to electrochemotherapy (ECT) and in combination with gene electrotransfer (GET) of a plasmid encoding interleukin-12 (IL-12). We hypothesized that IL-12 potentiates the antitumor effect of local ablative therapies as CaEP and ECT.

Methods

The effect of CaEP was tested in vitro as well as in vivo in murine melanoma B16-F10 and murine mammary carcinoma 4T1 in comparison to ECT with bleomycin. Specifically, the treatment efficacy of CaEP with increasing calcium concentrations alone or in combination with IL-12 GET in different treatment protocols was investigated. We closely examined the tumor microenvironment by immunofluorescence staining of immune cells, as well as blood vessels and proliferating cells.

Results

In vitro, CaEP and ECT with bleomycin reduced cell viability in a dose-dependent manner. We observed no differences in sensitivity between the two cell lines. A dose-dependent response was also observed in vivo; however, the efficacy was better in 4T1 tumors than in B16-F10 tumors. In 4T1 tumors, CaEP with 250 mM Ca resulted in more than 30 days of growth delay, which was comparable to ECT with bleomycin. In contrast, adjuvant peritumoral application of IL-12 GET after CaEP prolonged the survival of B16-F10, but not 4T1-bearing mice. Moreover, CaEP with peritumoral IL-12 GET modified tumor immune cell populations and tumor vasculature.

Conclusions

Mice bearing 4T1 tumors responded better to CaEP in vivo than mice bearing B16-F10 tumors, even though a similar response was observed in vitro. Namely, one of the most important factors might be involvement of the immune system. This was confirmed by the combination of CaEP or ECT with IL-12 GET, which further enhanced antitumor effectiveness. However, the potentiation of CaEP effectiveness was also highly dependent on tumor type; it was more pronounced in poorly immunogenic B16-F10 tumors compared to moderately immunogenic 4T1 tumors.

Chemotherapy and Physical Therapeutics Modulate Antigens on Cancer Cells

Cancer cells possess specific properties, such as multidrug resistance or unlimited proliferation potential, due to the presence of specific proteins on their cell membranes. The release of proliferation-related proteins from the membrane can evoke a loss of adaptive ability in cancer cells and thus enhance the effects of anticancer therapy. The upregulation of cancer-specific membrane antigens results in a better outcome of immunotherapy. Moreover, cytotoxic T-cells may also become more effective when stimulated ex-vivo toward the anticancer response. Therefore, the modulation of membrane proteins may serve as an interesting attempt in anticancer therapy. The presence of membrane antigens relies on various physical factors such as temperature, exposure to radiation, or drugs. Therefore, changing the tumor microenvironment conditions may lead to cancer cells becoming sensitized to subsequent therapy. This paper focuses on the therapeutic approaches modulating membrane antigens and enzymes in anticancer therapy. It aims to analyze the possible methods for modulating the antigens, such as pharmacological treatment, electric field treatment, photodynamic reaction, treatment with magnetic field or X-ray radiation. Besides, an overview of the effects of chemotherapy and immunotherapy on the immunophenotype of cancer cells is presented. Finally, the authors review the clinical trials that involved the modulation of cell immunophenotype in anticancer therapy.

Intratumoral electroporation of plasmid encoded IL-12 and membrane-anchored anti-CD3 increases systemic tumor immunity

Intratumoral delivery of plasmid IL 12 via electroporation (IT tavo EP) induces localized expression of IL 12 leading to regression of treated and distant tumors with durable responses and minimal toxicity. A key driver in amplifying this local therapy into a systemic response is the magnitude and composition of immune infiltrate in the treated tumor. While intratumoral IL 12 typically increases the density of CD3+ tumor infiltrating lymphocytes (TIL), this infiltrate is composed of a broad range of T cell subsets, including activated tumor specific T cells, less functional bystander T cells, as well as suppressive T regulatory cells. To encourage a more favorable on treatment tumor microenvironment, we explored combining this IL 12 therapy with an intratumoral polyclonal T cell stimulator membrane anchored anti CD3 to productively engage a diverse subset of lymphocytes including the non reactive and suppressive T cells. This study highlighted that combined intratumoral electroporation of IL 12 and membrane anchored anti CD3 plasmids can enhance cytokine production, T cell cytotoxicity, and proliferation while limiting the suppressive capacity within the TME. These collective anti tumor effects not only improve regression of treated tumors but drive systemic immunity with control of non treated contralateral tumors in vivo. Moreover, combination of IL 12 and anti CD3 restored the function of TIL isolated from a melanoma patient actively progressing on PD 1 checkpoint inhibitor therapy. This DNA encodable polyclonal T cell stimulator (membrane anchored anti CD3 plasmid) may represent a key addition to intratumoral IL-12 therapies in the clinic.

Electrical Stimulation for Immune Modulation in Cancer Treatments

Immunotherapy is becoming a very common treatment for cancer, using approaches like checkpoint inhibition, T cell transfer therapy, monoclonal antibodies and cancer vaccination. However, these approaches involve high doses of immune therapeutics with problematic side effects. A promising approach to reducing the dose of immunotherapeutic agents given to a cancer patient is to combine it with electrical stimulation, which can act in two ways; it can either modulate the immune system to produce the immune cytokines and agents in the patient's body or it can increase the cellular uptake of these immune agents via electroporation. Electrical stimulation in form of direct current has been shown to reduce tumor sizes in immune-competent mice while having no effect on tumor sizes in immune-deficient mice. Several studies have used nano-pulsed electrical stimulations to activate the immune system and drive it against tumor cells. This approach has been utilized for different types of cancers, like fibrosarcoma, hepatocellular carcinoma, human papillomavirus etc. Another common approach is to combine electrochemotherapy with immune modulation, either by inducing immunogenic cell death or injecting immunostimulants that increase the effectiveness of the treatments. Several therapies utilize electroporation to deliver immunostimulants (like genes encoded with cytokine producing sequences, cancer specific antigens or fragments of anti-tumor toxins) more effectively. Lastly, electrical stimulation of the vagus nerve can trigger production and activation of anti-tumor immune cells and immune reactions. Hence, the use of electrical stimulation to modulate the immune system in different ways can be a promising approach to treat cancer.

Non-Clinical In Vitro Evaluation of Antibiotic Resistance Gene-Free Plasmids Encoding Human or Murine IL-12 Intended for First-in-Human Clinical Study

Interleukin 12 (IL-12) is a key cytokine that mediates antitumor activity of immune cells. To fulfill its clinical potential, the development is focused on localized delivery systems, such as gene electrotransfer, which can provide localized delivery of IL-12 to the tumor microenvironment. Gene electrotransfer of the plasmid encoding human IL-12 is already in clinical trials in USA, demonstrating positive results in the treatment of melanoma patients. To comply with EU regulatory requirements for clinical application, which recommend the use of antibiotic resistance gene-free plasmids, we constructed and developed the production process for the clinical grade quality antibiotic resistance gene-free plasmid encoding human IL-12 (p21-hIL-12-ORT) and its ortholog encoding murine IL-12 (p21-mIL-12-ORT). To demonstrate the suitability of the p21-hIL-12-ORT or p21-mIL-12-ORT plasmid for the first-in-human clinical trial, the biological activity of the expressed transgene, its level of expression and plasmid copy number were determined in vitro in the human squamous cell carcinoma cell line FaDu and the murine colon carcinoma cell line CT26. The results of the non-clinical evaluation in vitro set the basis for further in vivo testing and evaluation of antitumor activity of therapeutic molecules in murine models as well as provide crucial data for further clinical trials of the constructed antibiotic resistance gene-free plasmid in humans.

Next-Generation Immunotherapy Approaches in Melanoma

PURPOSE OF REVIEW

For patients with metastatic melanoma, immune checkpoint inhibition has drastically changed outcomes. Here, we review the current and next generations of immune-based anti-cancer therapeutics for patients with metastatic melanoma.

RECENT FINDINGS

The need for new anti-cancer therapeutics in patients with metastatic melanoma who have progression of disease despite immune checkpoint blockade is evident. Several novel agents are expected to have FDA approval within the next few years, as they have yielded impressive responses. Despite these optimistic agents, the field of immuno-oncology continues to expand and produce agents with novel mechanisms of action. The next generation of immunotherapy is based upon years of thoroughly researched immuno-oncology. Many of these agents are currently being evaluated in early phase clinical trials, and much of the preliminary data looks promising.

Gene electrotransfer of IL-2 and IL-12 plasmids effectively eradicated murine B16.F10 melanoma

Gene therapy has become an important approach for treating cancer, and electroporation represents a technology for introducing therapeutic genes into a cell. An example of cancer gene therapy relying on gene electrotransfer is the use of immunomodulatory cytokines, such as interleukin 2 (IL-2) and 12 (IL-12), which directly stimulate immune cells at the tumour site. The aim of our study was to determine the effects of gene electrotransfer with two plasmids encoding IL-2 and IL-12 in vitro and in vivo. Two different pulse protocols, known as EP1 (600 V/cm, 5 ms, 1 Hz, 8 pulses) and EP2 (1300 V/cm, 100 µs, 1 Hz, 8 pulses), were assessed in vitro for application in subsequent in vivo experiments. In the in vivo experiment, gene electrotransfer of pIL-2 and pIL-12 using the EP1 protocol was performed in B16.F10 murine melanoma. Combined treatment of tumours using pIL2 and pIL12 induced significant tumour growth delay and 71% complete tumour regression. Furthermore, in tumours coexpressing IL-2 and IL-12, increased accumulation of dendritic cells and M1 macrophages was obtained along with the activation of proinflammatory signals, resulting in CD4 + and CD8 + T-lymphocyte recruitment and immune memory development in the mice. In conclusion, we demonstrated high antitumour efficacy of combined IL-2 and IL-12 gene electrotransfer protocols in low-immunogenicity murine B16.F10 melanoma.

Localized Interleukin-12 for Cancer Immunotherapy

Interleukin-12 (IL-12) is a potent, pro-inflammatory type 1 cytokine that has long been studied as a potential immunotherapy for cancer. Unfortunately, IL-12's remarkable antitumor efficacy in preclinical models has yet to be replicated in humans. Early clinical trials in the mid-1990's showed that systemic delivery of IL-12 incurred dose-limiting toxicities. Nevertheless, IL-12's pleiotropic activity, i.e., its ability to engage multiple effector mechanisms and reverse tumor-induced immunosuppression, continues to entice cancer researchers. The development of strategies which maximize IL-12 delivery to the tumor microenvironment while minimizing systemic exposure are of increasing interest. Diverse IL-12 delivery systems, from immunocytokine fusions to polymeric nanoparticles, have demonstrated robust antitumor immunity with reduced adverse events in preclinical studies. Several localized IL-12 delivery approaches have recently reached the clinical stage with several more at the precipice of translation. Taken together, localized delivery systems are supporting an IL-12 renaissance which may finally allow this potent cytokine to fulfill its considerable clinical potential. This review begins with a brief historical account of cytokine monotherapies and describes how IL-12 went from promising new cure to ostracized black sheep following multiple on-study deaths. The bulk of this comprehensive review focuses on developments in diverse localized delivery strategies for IL-12-based cancer immunotherapies. Advantages and limitations of different delivery technologies are highlighted. Finally, perspectives on how IL-12-based immunotherapies may be utilized for widespread clinical application in the very near future are offered.

Electroporation-Based Treatments in Small Animal Veterinary Oral and Maxillofacial Oncology

Electroporation is a method of inducing an increase in permeability of the cell membrane through the application of an electric field and can be used as a delivery method for introducing molecules of interest (e.g., chemotherapeutics or plasmid DNA) into cells. Electroporation-based treatments (i.e., electrochemotherapy, gene electrotransfer, and their combinations) have been shown to be safe and effective in veterinary oncology, but they are currently mostly recommended for the treatment of those solid tumors for which clients have declined surgery and/or radiotherapy. Published data show that electroporation-based treatments are also safe, simple, fast and cost-effective treatment alternatives for selected oral and maxillofacial tumors, especially small squamous cell carcinoma and malignant melanoma tumors not involving the bone in dogs. In these patients, a good local response to treatment is expected to result in increased survival time with good quality of life. Despite emerging evidence of the clinical efficacy of electroporation-based treatments for oral and maxillofacial tumors, further investigation is needed to optimize treatment protocols, improve clinical data reporting and better understand the mechanisms of patients' response to the treatment.

Intratumoral delivery of tavokinogene telseplasmid yields systemic immune responses in metastatic melanoma patients

BACKGROUND

Interleukin 12 (IL-12) is a pivotal regulator of innate and adaptive immunity. We conducted a prospective open-label, phase II clinical trial of electroporated plasmid IL-12 in advanced melanoma patients (NCT01502293).

PATIENTS AND METHODS

Patients with stage III/IV melanoma were treated intratumorally with plasmid encoding IL-12 (tavokinogene telseplasmid; tavo), 0.5 mg/ml followed by electroporation (six pulses, 1500 V/cm) on days 1, 5, and 8 every 90 days in the main study and additional patients were treated in two alternative schedule exploration cohorts. Correlative analyses for programmed death-ligand 1 (PD-L1), flow cytometry to assess changes in immune cell subsets, and analysis of immune-related gene expression were carried out on pre- and post-treatment samples from study patients, as well as from additional patients treated during exploration of additional dosing schedules beyond the pre-specified protocol dosing schedule. Response was measured by study-specific criteria to maximize detection of latent and potentially transient immune responses in patients with multiple skin lesions and toxicities were graded by the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0).

RESULTS

The objective overall response rate was 35.7% in the main study (29.8% in all cohorts), with a complete response rate of 17.9% (10.6% in all cohorts). The median progression-free survival in the main study was 3.7 months while the median overall survival was not reached at a median follow up of 29.7 months. A total of 46% of patients in all cohorts with uninjected lesions experienced regression of at least one of these lesions and 25% had a net regression of all untreated lesions. Transcriptomic and immunohistochemistry analysis showed that immune activation and co-stimulatory transcripts were up-regulated but there was also increased adaptive immune resistance.

CONCLUSIONS

Intratumoral Tavo was well tolerated and led to systemic immune responses in advanced melanoma patients. While tumor regression and increased immune infiltration were observed in treated as well as untreated/distal lesions, adaptive immune resistance limited the response.

Up-regulation of TIMP-3 and RECK decrease the invasion and metastasis ability of colon cancer

BACKGROUND AND STUDY AIMS

Although the function of microRNA21 (miR-21) in the invasion and metastasis of colon cancer has been extensively studied, the mechanisms of invasion and migration related pathways between and its targets are still not elucidated. This study explored the mechanisms of the pathway between miR-21 and the target genes in vitro and in vivo.

MATERIALS AND METHODS

We transfected pmiRZip21 or Leti3 into colon cancer cells. The levels of miR-21 expression, mRNA transcription and protein of target genes were analysed by TaqMan microRNA assays, RT-PCR and western blot, respectively. Scratch migration and trans-well assays were used to evaluate metastasis and invasion. To build a subcutaneous tumour animal model, detect the level of miR-21 and the target genes and then identify the mechanisms in vivo.

RESULTS

MiR-21 expression levels in colon cancer cells transfected with pmiRZip21 in vivo or in vitro were decreased (P < 0.05). The mRNA and protein levels of TIMP-3 and RECK were up-regulated after inhibiting miR-21 in vitro and in vivo (P < 0.05), but those of BMPR-II and PCDH17 were not. In pmiRZip21-transfected colon cancer cells, invasion and migration were significantly decreased both in vitro and vivo (P < 0.05).

CONCLUSIONS

Up-regulation of TIMP-3 and RECK, by inhibiting miR-21 expression can decrease tumour invasion and metastasis ability in vitro and in vivo, and has potential as a possible target site in anti-tumour therapy. More effects in vivo have to be investigated in further research.

Pre-clinical investigation of the synergy effect of interleukin-12 gene-electro-transfer during partially irreversible electropermeabilization against melanoma

BACKGROUND

Melanoma is a very aggressive skin tumor that can be cured when diagnosed and treated in its early stages. However, at the time of identification, the tumor is frequently in a metastatic stage. Intensive research is currently ongoing to improve the efficacy of the immune system in eliminating cancer cells. One approach is to boost the activation of cytotoxic T cells by IL-12 cytokine that plays a central role in the activation of the immune system. In parallel, physical methods such as electropermeabilization-based treatments are currently under investigation and show promising results.

METHODS

In this study, we set electrical parameters to induce a partial-irreversible electropermeabilization (pIRE) of melanoma to induce a sufficient cell death and potential release of tumor antigens able to activate immune cells. This protocol mimics the situation where irreversible electropermeabilization is not fully completed. Then, a peritumoral plasmid IL-12 electrotransfer was combined with pIRE treatment. Evaluation of the tumor growth and survival was performed in mouse strains having a different immunological background (C57Bl/6 (WT), nude and C57Bl6 (TLR9-/-)).

RESULTS

pIRE treatment induced apoptotic cell death and a temporary tumor growth delay in all mouse strains. In C57Bl/6 mice, we showed that peritumoral plasmid IL-12 electrotransfer combined with tumor pIRE treatment induced tumor regression correlating with a local secretion of IL-12 and IFN-γ. This combined treatment induced a growth delay of distant tumors and prevented the emergence of a second tumor in 50% of immunocompetent mice.

CONCLUSIONS

The combination of pIL-12 GET and pIRE not only enhanced survival but could bring a curative effect in wild type mice. This two-step treatment, named Immune-Gene Electro-Therapy (IGET), led to a systemic activation of the adaptive immune system and the development of an anti-tumor immune memory.

IL-12 Gene Electrotransfer Triggers a Change in Immune Response within Mouse Tumors

Metastatic melanoma is an aggressive skin cancer with a relatively low survival rate. Immune-based therapies have shown promise in the treatment of melanoma, but overall complete response rates are still low. Previous studies have demonstrated the potential of plasmid IL-12 (pIL-12) delivered by gene electrotransfer (GET) to be an effective immunotherapy for melanoma. However, events occurring in the tumor microenvironment following delivery have not been delineated. Therefore, utilizing a B16F10 mouse melanoma model, we evaluated changes in the tumor microenvironment following delivery of pIL-12 using different GET parameters or injection of plasmid alone. The results revealed a unique immune cell composition after intratumoral injection of pIL-12 GET. The number of immune memory cells was markedly increased in pIL-12 GET melanoma groups compared to control group. This was validated using flow cytometry to analyze peripheral blood mononuclear cells as well as delineating immune cell content using immunohistochemistry. Significant differences in multiple cell types were observed, including CD8⁺ T cells, regulatory T cells and myeloid cells, which were induced to mount a CD8⁺PD1^- T cells immune response. Taken together, these findings suggest a basic understanding of the sequence of immune activity following pIL-12 GET and also illuminates that adjuvant immunotherapy can have a positive influence on the host immune response to cancer.

Clinically Usable Interleukin 12 Plasmid without an Antibiotic Resistance Gene: Functionality and Toxicity Study in Murine Melanoma Model

Plasmids, which are currently used in interleukin 12 (IL-12) gene electrotransfer (GET) clinical trials in the USA, contain antibiotic resistance genes and are thus, according to the safety recommendation of the European Medicines Agency (EMA), not suitable for clinical trials in the EU. In the current study, our aim was to prepare an IL-12 plasmid without an antibiotic resistance gene and test its functionality and toxicity after GET in a preclinical B16F10 mouse melanoma model. The antibiotic resistance-free plasmid encoding the human IL-12 fusion gene linked to the p21 promoter, i.e., p21-hIL-12-ORT, was constructed using operator-repressor titration (ORT) technology. Next, the expression profile of the plasmid after GET was determined in B16F10 cells and tumors. Additionally, blood chemistry, hematological and histological changes, and antitumor response were evaluated after GET of the plasmid in melanoma tumors. The results demonstrated a good expression and safety profile of the p21-hIL-12-ORT GET and indications of efficacy. We hope that the obtained results will help to accelerate the transfer of this promising treatment from preclinical studies to clinical application in the EU.

Melanoma treatment with intratumoral electroporation of tavokinogene telseplasmid (pIL-12, tavokinogene telseplasmid)

Tumors evade detection and/or clearance by the immune system via multiple mechanisms. IL-12 is a potent immunomodulatory cytokine that plays a central role in immune priming. However, systemic delivery of IL-12 can result in life-threatening toxicity and therefore has shown limited efficacy at doses that can be safely administered. We developed an electroporation technique to produce highly localized IL-12 expression within tumors leading to regression of both treated and untreated lesions in animal models and in patients with a favorable safety profile. Furthermore, intratumoral tavokinogene telseplasmid electroporation can drive cellular immune responses, converting 'cold' tumors into 'hot' tumors. Clinical trials are ongoing to determine whether intratumoral tavokinogene telseplasmid electroporation synergizes with checkpoint blockade therapy in immunologically cold tumors predicted not to respond to PD-1 antibody monotherapy.

The promising alliance of anti-cancer electrochemotherapy with immunotherapy

Anti-tumor electrochemotherapy, which consists in increasing anti-cancer drug uptake by means of electroporation, is now implanted in about 140 cancer treatment centers in Europe. Its use is supported by the English National Institute for Health and Care Excellence for the palliative treatment of skin metastases, and about 13,000 cancer patients were treated by this technology by the end of 2015. Efforts are now focused on turning this local anti-tumor treatment into a systemic one. Electrogenetherapy, that is the electroporation-mediated transfer of therapeutic genes, is currently under clinical evaluation and has brought excitement to enlarge the anti-cancer armamentarium. Among the promising electrogenetherapy strategies, DNA vaccination and cytokine-based immunotherapy aim at stimulating anti-tumor immunity. We review here the interests and state of development of both electrochemotherapy and electrogenetherapy. We then emphasize the potent beneficial outcome of the combination of electrochemotherapy with immunotherapy, such as immune checkpoint inhibitors or strategies based on electrogenetherapy, to simultaneously achieve excellent local debulking anti-tumor responses and systemic anti-metastatic effects.

Safety and efficacy of tumor-targeted interleukin 12 gene therapy in treated and non-treated, metastatic lesions

The ability to control the immune system to actively attack tumor tissues will be a marvelous weapon to combat the persistent attack of cancer. Unfortunately, safe and effective methods to gain this control are not yet available as cancer therapies. To overcome the impediments to this control, tumor-targeted (tt) Interleukin 12 (IL-12) plasmid DNA can be safely delivered to accessible tumors, and these treatments can induce antitumor immune responses in both the treated and untreated tumors. Here, electroporationmediated ttIL-12 pDNA treatments are shown to be safe and well tolerated in a dose escalation study in canines bearing naturally-occurring neoplasms. The final patient in the dose-escalation study received up to 3,800 μg pDNA distributed among five separate squamous cell carcinoma tumors in doses equivalent to those administered in a Phase I trial with wildtype IL-12 pDNA. Not a single severe adverse event occurred in any patient at any of the five dose levels, and only minor, transient changes were noted in any tested parameter. Clinical response analysis and immune marker mRNA detection of treated and non-treated lesions suggest that ttIL-12 pDNA treatments in only a few tumors can elicit antitumor immune responses in the treated lesions as well as distant metastatic lesions. These observations and results demonstrate that ttIL-12 pDNA can be safely administered at clinical levels, and these treatments can affect both treated and nontreated, metastatic lesions.

Safe and effective treatment of spontaneous neoplasms with interleukin 12 electro-chemo-gene therapy

Electroporation improves the anti-tumour efficacy of chemotherapeutic and gene therapies. Combining electroporation-mediated chemotherapeutics with interleukin 12 (IL-12) plasmid DNA produces a strong yet safe anti-tumour effect for treating primary and refractory tumours. A previously published report demonstrated the efficacy of a single cycle of IL-12 plasmid DNA and bleomycin in canines, and, similarly, this study further demonstrates the safety and efficacy of repeated cycles of chemotherapy plus IL-12 gene therapy for long-term management of aggressive tumours. Thirteen canine patients were enrolled in this study and received multiple cycles of electro-chemo-gene therapy (ECGT) with IL-12 pDNA and either bleomycin or gemcitabine. ECGT treatments are very effective for inducing tumour regression via an antitumour immune response in all tested histotypes except for sarcomas, and these treatments can quickly eradicate or debulk large squamous cell carcinomas. The versatility of ECGT allows for response-based modifications which can overcome treatment resistance for affecting refractory lesions. Importantly, not a single severe adverse event was noted even in animals receiving the highest doses of chemotherapeutics and IL12 pDNA over multiple treatment cycles. This report highlights the safety, efficacy and versatility of this treatment strategy. The data reveal the importance of inducing a strong anti-tumour response for successfully affecting not only the treated tumours, but also non-treated metastatic tumours. ECGT with IL12 pDNA plus chemotherapy is an effective strategy for treating multiple types of spontaneous cancers including large, refractory and multiple tumour burdens.

Gene electrotransfer clinical trials

Plasmid or non-viral gene therapy offers an alternative to classic viral gene delivery that negates the need for a biological vector. In this case, delivery is enhanced by a variety of approaches including lipid or polymer conjugation, particle-mediated delivery, hydrodynamic delivery, ultrasound or electroporation. Electroporation was originally used as a laboratory tool to deliver DNA to bacterial and mammalian cells in culture. Electrode development allowed this technique to be modified for in vivo use. After preclinical therapeutic studies, clinical delivery of cell impermeant chemotherapeutic agents progressed to clinical delivery of plasmid DNA. One huge benefit of this delivery technique is its malleability. The pulse protocol used for plasmid delivery can be fine-tuned to control the levels and duration of subsequent transgene expression. This fine-tuning allows transgene expression to be tailored to each therapeutic application. Effective and appropriate expression induces the desired clinical response that is a critical component for any gene therapy. This chapter focuses on clinical trials using in vivo electroporation or electrotransfer as a plasmid delivery method. The first clinical trial was initiated in 2004, and now more than fifty trials use electric fields for gene delivery. Safety and tolerability has been demonstrated by several groups, and early clinical efficacy results are promising in both cancer therapeutic and infectious disease vaccine applications.

Intricacies for posttranslational tumor-targeted cytokine gene therapy

The safest and most effective cytokine therapies require the favorable accumulation of the cytokine in the tumor environment. While direct treatment into the neoplasm is ideal, systemic tumor-targeted therapies will be more feasible. Electroporation-mediated transfection of cytokine plasmid DNA including a tumor-targeting peptide-encoding sequence is one method for obtaining a tumor-targeted cytokine produced by the tumor-bearing patient's tissues. Here, the impact on efficacy of the location of targeting peptide, choice of targeting peptide, tumor histotype, and cytokine utilization are studied in multiple syngeneic murine tumor models. Within the same tumor model, the location of the targeting peptide could either improve or reduce the antitumor effect of interleukin (IL)12 gene treatments, yet in other tumor models the tumor-targeted IL12 plasmid DNAs were equally effective regardless of the peptide location. Similarly, the same targeting peptide that enhances IL12 therapies in one model fails to improve the effect of either IL15 or PF4 for inhibiting tumor growth in the same model. These interesting and sometimes contrasting results highlight both the efficacy and personalization of tumor-targeted cytokine gene therapies while exposing important aspects of these same therapies which must be considered before progressing into approved treatment options.

Evaluation of p21 promoter for interleukin 12 radiation induced transcriptional targeting in a mouse tumor model

BACKGROUND

Radiation induced transcriptional targeting is a gene therapy approach that takes advantage of the targeting abilities of radiotherapy by using radio inducible promoters to spatially and temporally limit the transgene expression. Cyclin dependent kinase inhibitor 1 (CDKN1A), also known as p21, is a crucial regulator of the cell cycle, mediating G1 phase arrest in response to a variety of stress stimuli, including DNA damaging agents like irradiation. The aim of the study was to evaluate the suitability of the p21 promoter for radiation induced transcriptional targeting with the objective to test the therapeutic effectiveness of the combined radio-gene therapy with p21 promoter driven therapeutic gene interleukin 12.

METHODS

To test the inducibility of the p21 promoter, three reporter gene experimental models with green fluorescent protein (GFP) under the control of p21 promoter were established by gene electrotransfer of plasmid DNA: stably transfected cells, stably transfected tumors, and transiently transfected muscles. Induction of reporter gene expression after irradiation was determined using a fluorescence microplate reader in vitro and by non-invasive fluorescence imaging using fluorescence stereomicroscope in vivo. The antitumor effect of the plasmid encoding the p21 promoter driven interleukin 12 after radio-gene therapy was determined by tumor growth delay assay and by quantification of intratumoral and serum levels of interleukin 12 protein and intratumoral concentrations of interleukin 12 mRNA.

RESULTS

Using the reporter gene experimental models, p21 promoter was proven to be inducible with radiation, the induction was not dose dependent, and it could be re-induced. Furthermore radio-gene therapy with interleukin 12 under control of the p21 promoter had a good antitumor therapeutic effect with the statistically relevant tumor growth delay, which was comparable to that of the same therapy using a constitutive promoter.

CONCLUSIONS

In this study p21 promoter was proven to be a suitable candidate for radiation induced transcriptional targeting. As a proof of principle the therapeutic value was demonstrated with the radio-inducible interleukin 12 plasmid providing a synergistic antitumor effect to radiotherapy alone, which makes this approach feasible for the combined treatment with radiotherapy.

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

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

IL-12 based gene therapy in veterinary medicine

The use of large animals as an experimental model for novel treatment techniques has many advantages over the use of laboratory animals, so veterinary medicine is becoming an increasingly important translational bridge between preclinical studies and human medicine. The results of preclinical studies show that gene therapy with therapeutic gene encoding interleukin-12 (IL-12) displays pronounced antitumor effects in various tumor models. A number of different studies employing this therapeutic plasmid, delivered by either viral or non-viral methods, have also been undertaken in veterinary oncology. In cats, adenoviral delivery into soft tissue sarcomas has been employed. In horses, naked plasmid DNA has been delivered by direct intratumoral injection into nodules of metastatic melanoma. In dogs, various types of tumors have been treated with either local or systemic IL-12 electrogene therapy. The results of these studies show that IL-12 based gene therapy elicits a good antitumor effect on spontaneously occurring tumors in large animals, while being safe and well tolerated by the animals. Hopefully, such results will lead to further investigation of this therapy in veterinary medicine and successful translation into human clinical trials.

Electroporation based gene therapy--from the bench to the bedside

A critical aspect of gene transfer is effective delivery of the transgene to the appropriate target. Electrically mediated delivery (electroporation) of plasmid DNA has been accepted as a viable approach to achieve effective delivery. One promising area is delivering plasmid DNA to skin. Gene transfer to the skin with electroporation is currently being evaluated for its potential for inducing angiogenesis for wound healing and for delivering DNA vaccines to the skin. Experiments utilizing a plasmid encoding for vascular endothelial growth factor has demonstrated how wound healing could be accelerated. In another study, delivery of a plasmid encoding Hepatitis B surface antigen have demonstrated that high antibody titers can be induced after two applications (prime/boost). Our laboratory has also examined the use of electroporation to delivery plasmid DNA encoding various cytokines as a potential therapy for melanoma. The plasmid is injected directly into the tumor followed by the administration of electroporation. Extensive preclinical work provided the rationale for a Phase I proof of concept first in human trial in patients with accessible cutaneous melanoma metastases. Biopsies of treated lesions showed significant necrosis of melanoma cells within the tumor as well as IL-12 expression. Lymphocytic infiltrate was observed in biopsies from patients in several cohorts. Clinical evidence of responses in untreated lesions suggested there was a systemic response following therapy was observed. Since this trial several other clinical studies utilizing electroporation to deliver plasmid DNA have been initiated. It is clear that this delivery approach has tremendous potential to facilitate the translation of gene transfer protocols from the bench to the bedside.

Pre-clinical toxicity assessment of tumor-targeted interleukin-12 low-intensity electrogenetherapy

This study's goal was to assess the safety of tumor-targeted interleukin-12 (ttIL-12) when administered by electrogenetherapy in C3H/HeJ mice by identifying an initial safe dose for human dose escalation schemes, toxicity target organs, markers of toxicity, and toxicity reversibility. Tumor-free mice receiving two doses of 0.45% NaCl, 1 μg ttIL-12 DNA in 0.45% NaCl or 5 μg ttIL-12 DNA in 0.45% NaCl, 10 days apart combined with low-intensity electroporation were compared with non-treatment controls over time. All mice had blood cell counts, serum chemistry profiles, plasma interleukin-12 and IFNγ determinations, necropsy and multi-organ histopathology. Mild treatment-associated changes included electroporation-associated muscle changes that resolved by 30 days; decreased total white blood cell counts and infectious disease in the 5 μg ttIL-12 group, but not in the 1 μg group, and liver changes in ttIL-12 groups that correlated with alanine transaminase levels and resolved by 30 days. Dystrophic cardiac calcification seen in older, 5 μg ttIL-12-treated mice was the only serious toxicity. Based on these results and the lack of any effect on wound healing when combined with surgery, low-intensity electrogenetherapy with ttIL-12 appears to be safe and well tolerated.

Bioelectric applications for treatment of melanoma

Two new cancer therapies apply bioelectric principles. These methods target tumor structures locally and function by applying millisecond electric fields to deliver plasmid DNA encoding cytokines using electrogene transfer (EGT) or by applying rapid rise-time nanosecond pulsed electric fields (nsPEFs). EGT has been used to locally deliver cytokines such as IL-12 to activate an immune response, resulting in bystander effects. NsPEFs locally induce apoptosis-like effects and affect vascular networks, both promoting tumor demise and restoration of normal vascular homeostasis. EGT with IL-12 is in melanoma clinical trials and nsPEFs are used in models with B16F10 melanoma in vitro and in mice. Applications of bioelectrics, using conventional electroporation and extensions of it, provide effective alternative therapies for melanoma.

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.

Electrodelivery of drugs into cancer cells in the presence of poloxamer 188

In the present study it is shown that poloxamer 188, added before or immediately after an electrical pulse used for electroporation, decreases the number of dead cells and at the same time does not reduce the number of reversible electropores through which small molecules (cisplatin, bleomycin, or propidium iodide) can pass/diffuse. It was suggested that hydrophobic sections of poloxamer 188 molecules are incorporated into the edges of pores and that their hydrophilic parts act as brushy pore structures. The formation of brushy pores may reduce the expansion of pores and delay the irreversible electropermeability. Tumors were implanted subcutaneously in both flanks of nude mice using HeLa cells, transfected with genes for red fluorescent protein and luciferase. The volume of tumors stopped to grow after electrochemotherapy and the use of poloxamer 188 reduced the edema near the electrode and around the subcutaneously growing tumors.

Electrodelivery of drugs into cancer cells in the presence of poloxamer 188

In the present study it is shown that poloxamer 188, added before or immediately after an electrical pulse used for electroporation, decreases the number of dead cells and at the same time does not reduce the number of reversible electropores through which small molecules (cisplatin, bleomycin, or propidium iodide) can pass/diffuse. It was suggested that hydrophobic sections of poloxamer 188 molecules are incorporated into the edges of pores and that their hydrophilic parts act as brushy pore structures. The formation of brushy pores may reduce the expansion of pores and delay the irreversible electropermeability. Tumors were implanted subcutaneously in both flanks of nude mice using HeLa cells, transfected with genes for red fluorescent protein and luciferase. The volume of tumors stopped to grow after electrochemotherapy and the use of poloxamer 188 reduced the edema near the electrode and around the subcutaneously growing tumors.

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.

Physiological effects of high- and low-voltage pulse combinations for gene electrotransfer in muscle

Gene transfer by electroporation is gaining momentum now that high-level, long-term expression of transgenes is being obtained. Several different pulse regimens are efficient, yet little information is available about the physiological muscular response to gene electrotransfer. This paper provides a comprehensive evaluation of the physiological and molecular effects on host tissue after DNA electrotransfer. We have tested several pulse regimens with special emphasis on the pulse combination of a short (100 microsec) high-voltage (HV) pulse followed by a long low-voltage (LV) pulse used for DNA electrotransfer, comparing it with 8 HV pulses designed to ensure extensive permeabilization of the muscle membrane. Using both mouse and rat skeletal muscle tissue, we investigated cell permeabilization by the 51Cr-labeled EDTA assay, lactate dehydrogenase release, Na+ and Ca2+ influx, K+ efflux, ATP release, and water content, as well as muscle function both in vivo and ex vivo, Hsp70 induction, and histology. In all these assays, the HVLV pulse combination gave rise to minimal disturbance of cell function, in all cases significantly different from results when using 8 HV pulses. The evaluated parameters were normalized after 1 week. The addition of DNA caused significantly more transmembrane exchange, and this may be due to entrance of the DNA through the membrane. In conclusion, this study comprehensively documents the immediate effects of DNA electrotransfer and shows that only slight cell disturbances occur with the HVLV pulses used for gene transfer. This is highly important, as minimal perturbation of cell physiology is essential for efficient transgene expression.

Electroporation for the delivery of DNA-based vaccines and immunotherapeutics: current clinical developments

Electroporation (EP) has been used in basic research for the past 25 years to aid in the transfer of DNA into cells in vitro. EP in vivo enhances transfer of DNA vaccines and therapeutic plasmids to the skin, muscle, tumors, and other tissues resulting in high levels of expression, often with serological and clinical benefits. The recent interest in nonviral gene transfer as treatment options for a vast array of conditions has resulted in the refinement and optimization of EP technology. Current research has revealed that EP can be successfully used in many species, including humans. Clinical trials are currently under way. Herein, the transition of EP from basic science to clinical trials will be discussed.

Phase I trial of interleukin-12 plasmid electroporation in patients with metastatic melanoma

PURPOSE

Gene-based immunotherapy for cancer is limited by the lack of safe, efficient, reproducible, and titratable delivery methods. Direct injection of DNA into tissue, although safer than viral vectors, suffers from low gene transfer efficiency. In vivo electroporation, in preclinical models, significantly enhances gene transfer efficiency while retaining the safety advantages of plasmid DNA.

PATIENTS AND METHODS

A phase I dose escalation trial of plasmid interleukin (IL)-12 electroporation was carried out in patients with metastatic melanoma. Patients received electroporation on days 1, 5, and 8 during a single 39-day cycle, into metastatic melanoma lesions with six 100-mus pulses at a 1,300-V/cm electric field through a penetrating six-electrode array immediately after DNA injection. Pre- and post-treatment biopsies were obtained at defined time points for detailed histologic evaluation and determination of IL-12 protein levels.

RESULTS

Twenty-four patients were treated at seven dose levels, with minimal systemic toxicity. Transient pain after electroporation was the major adverse effect. Post-treatment biopsies showed plasmid dose proportional increases in IL-12 protein levels as well as marked tumor necrosis and lymphocytic infiltrate. Two (10%) of 19 patients with nonelectroporated distant lesions and no other systemic therapy showed complete regression of all metastases, whereas eight additional patients (42%) showed disease stabilization or partial response.

CONCLUSION

This report describes the first human trial, to our knowledge, of gene transfer utilizing in vivo DNA electroporation. The results indicated this modality to be safe, effective, reproducible, and titratable.

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.

Taking electroporation-based delivery of DNA vaccination into humans: a generic clinical protocol

We are presently aware of two early-phase DNA vaccine clinical trials in humans using electroporation-enhanced vaccine delivery. Moreover, two phase I immunogenetherapy studies are in progress and several tolerability studies have been performed on healthy volunteers. We have used knowledge from these studies to compose a template for clinical protocols involving electroporation-mediated gene delivery. In this template the emphasis will be on aspects related to electroporation. In addition, we will discuss general topics concerning electroporation-augmented DNA vaccination in human subjects.

Gentherapie

Die Gentherapie ist eine junge Wissenschaft, die Nukleinsäuren zur Therapie einsetzt (Hengge u. Bardenheuer 2004). Die somatische Gentherapie befasst sich mit der Behandlung von somatischen (Körper-)Zellen (⧁ Tab. 4.1.1), wobei das therapeutische Gen ein im Organismus benötigtes Protein kodiert.

Multidisciplinary management of special melanoma situations: oligometastatic disease and bulky nodal sites

Potentially resectable, advanced stage melanoma in the form of extensive palpable adenopathy or limited systemic metastases presents a significant challenge but also offers the prospect of long-term disease control. Although surgical resection is the mainstay of therapy, involvement of a multidisciplinary team is required for optimal management of these special situations. These patients need to be evaluated preoperatively by the team, discussed at a multidisciplinary conference, and treated by experienced physicians with access to the full spectrum of modern surgical and oncologic therapy. Surgical resection is generally extensive and may require en bloc resection of important anatomic structures. Adjuvant radiation or systemic therapy is required in many patients to help achieve durable regional and systemic control of disease. In addition, novel therapies, such as neoadjuvant chemotherapy, targeted therapies, or investigational intralesional therapies, may ultimately play a role in the management of these difficult clinical situations and require further evaluation, as preliminary studies show some encouraging results.

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.

Electroporation-mediated gene therapy

Non-viral gene transfer is markedly enhanced by the application of in vivo electroporation. Electroporation is a safe and efficient system to introduce genes to a wide variety of tissues, including skeletal muscle, tumors, kidney, liver and skin. Electroporation has been demonstrated to be effective in numerous disease models. This review focuses on the principles of electroporation and the target tissues employed for gene therapy. Based on the accumulation of positive results, the first clinical study for the treatment of malignant melanoma is now underway, and preclinical studies have suggested that electroporation is useful as a gene therapy protocol.

Feasibility of employing model-based optimization of pulse amplitude and electrode distance for effective tumor electropermeabilization

In electrochemotherapy (ECT) electropermeabilization, parameters (pulse amplitude, electrode setup) need to be customized in order to expose the whole tumor to electric field intensities above permeabilizing threshold to achieve effective ECT. In this paper, we present a model-based optimization approach toward determination of optimal electropermeabilization parameters for effective ECT. The optimization is carried out by minimizing the difference between the permeabilization threshold and electric field intensities computed by finite element model in selected points of tumor. We examined the feasibility of model-based optimization of electropermeabilization parameters on a model geometry generated from computer tomography images, representing brain tissue with tumor. Continuous parameter subject to optimization was pulse amplitude. The distance between electrode pairs was optimized as a discrete parameter. Optimization also considered the pulse generator constraints on voltage and current. During optimization the two constraints were reached preventing the exposure of the entire volume of the tumor to electric field intensities above permeabilizing threshold. However, despite the fact that with the particular needle array holder and pulse generator the entire volume of the tumor was not permeabilized, the maximal extent of permeabilization for the particular case (electrodes, tissue) was determined with the proposed approach. Model-based optimization approach could also be used for electro-gene transfer, where electric field intensities should be distributed between permeabilizing threshold and irreversible threshold-the latter causing tissue necrosis. This can be obtained by adding constraints on maximum electric field intensity in optimization procedure.