Long-lasting anti-metastatic efficiency of interleukin 12-encoding plasmid DNA

A novel method for the development of plasmid DNA-loaded nanoliposomes for cancer gene therapy

We aimed to develop a simple yet novel method to prepare plasmid DNA-loaded nanoliposomes for cancer gene therapy. Murine interleukin-12 (mIL-12) pDNA-loaded nanoliposomes were prepared via novel freeze-drying of a monophase solution method. The physicochemical characteristics, cytotoxicity, and transfection efficiency of the prepared nanoliposomes in murine CT-26 colon carcinoma cells were evaluated. Furthermore, tumor progression and survival rate in CT-26 colon carcinoma-bearing BALB/c mice subsequent to direct intratumoral injections were investigated over a period of 40 days. Using this preparation method, nanoliposomes with particle size of around 300 nm and zeta potential of 96.5 mV were obtained. The transmission electron microscope results showed that the liposomes were nano-sized and almost spherical. The agarose gel retardation assay revealed the pDNA encapsulation in the nanoliposomes. The nanoliposomes with 72.4% encapsulation efficiency and low cell toxicity could significantly improve mIL-12 expression by approximately 25-fold relative to the naked mIL-12 pDNA. There was a significant tumor growth inhibition after repeated injections of mIL-12 pDNA-loaded nanoliposomes. This is the first study on the freeze-drying of a monophase solution method as a simple yet novel technique for the preparation of pDNA-loaded nanoliposomes. Given the ease of preparation method and promising in vitro and in vivo characteristics, this investigation demonstrates advances in pDNA lipid formulation for cancer gene therapy.

Effect of mesenchymal stem cells-derived exosomes on tumor microenvironment: Tumor progression versus tumor suppression

Mesenchymal stem cells (MSCs) are multipotent cells with the potential to differentiate into different cell types. Owing to their immunosuppressive and anti-inflammatory properties, they are widely used in regenerative medicine, but they have a dual effect on cancer progression and exert both growth-stimulatory or -inhibitory effects on different cancer types. It has been proposed that these controversial effects of MSC in tumor microenvironment (TME) are mediated by their polarization to proinflammatory or anti-inflammatory phenotype. In addition, they can polarize the immune system cells that in turn influence tumor progression. One of the mechanisms involved in the TME communications is extracellular vesicles (EVs). MSCs, as one of cell populations in TME, produce a large amount of EVs that can influence tumor development. Similar to MSC, MSC-EVs can exert both anti- or protumorigenic effects. In the current study, we will investigate the current knowledge related to MSC role in cancer progression with a focus on the MSC-EV content in limiting tumor growth, angiogenesis, and metastasis. We suppose MSC-EVs can be used as safe vehicles for delivering antitumor agents to TME.

T Cells and Regulated Cell Death: Kill or Be Killed

Cell death plays two major complementary roles in T cell biology: mediating the removal of cells that are targeted by T cells and the removal of T cells themselves. T cells serve as major actors in the adaptive immune response and function by selectively killing cells which are infected or dysfunctional. This feature is highly involved during homeostatic maintenance, and is relied upon and modulated in the context of cancer immunotherapy. The vital recognition and elimination of both autoreactive T cells and cells which are unable to recognize threats is a highly selective and regulated process. Moreover, detection of potential threats will result in the activation and expansion of T cells, which on resolution of the immune response will need to be eliminated. The culling of these T cells can be executed via a multitude of cell death pathways which are used in context-specific manners. Failure of these processes may result in an accumulation of misdirected or dysfunctional T cells, leading to complications such as autoimmunity or cancer. This review will focus on the role of cell death regulation in the maintenance of T cell homeostasis, as well as T cell-mediated elimination of infected or dysfunctional cells, and will summarize and discuss the current knowledge of the cellular mechanisms which are implicated in these processes.

Generation of Expression Plasmids for Angiostatin, Endostatin and Timp-2 for Cancer Gene Therapy

Antiangiogenic therapy may represent a promising approach to cancer treatment. Indeed, the efficacy of endogenous angiogenesis inhibitors, including angiostatin, endostatin and TIMPs, has been demonstrated in many types of solid tumors in animal models. In view of the possible problems associated with long-term administration of inhibitors as recombinant proteins, we propose their delivery as nucleic acids through a gene therapy approach. To this end, eukaryotic expression constructs for murine angiostatin and endostatin as well as human TIMP-2 were generated, and characterized in vitro. All constructs carry the relevant cDNAs under the control of the strong HCMV promoter/enhancer, and cleavable leader signals to allow protein secretion. Expression of the angiogenesis inhibitors was detected by in vitro transcription/translation experiments as well as transfection of 293T cells, followed by Western blotting (WB) or radioimmunoprecipitation analysis of both cell lysates and supernatants (SNs). These constructs might be used for in vivo intramuscular delivery of plasmid DNA and as a set of reagents for the development of retroviral as well as adeno-associated viral (AAV) vectors expressing angiogenesis inhibitors.

Photodynamic agents with anti-metastatic activities

A new concept in multifunctional anticancer agents is demonstrated. Tetrakis-(diisopropyl-guanidino) zinc phthalocyanine (Zn-DIGP) exhibits excellent properties as a photodynamic therapy (PDT) agent, as well as potential anti-metastatic activities in vivo. Zn-DIGP exhibits good cellular uptake and low toxicity in the dark (EC50 > 80 μM) and is well tolerated upon its intravenous injection into mice at 8 mg/kg. Upon photoexcitation with red laser light (660 nm), Zn-DIGP exhibits a high quantum yield for singlet oxygen formation (Φ ≈ 0.51) that results in potent phototoxicity to cell cultures (EC50 ≈ 0.16 μM). Zn-DIGP is also capable of inhibiting the formation of tumor colonies in the lungs of C57BL/6 mice injected with B16F10 cells. Zn-DIGP therefore inhibits cancer growth by both light-dependent and light-independent pathways. The anti-metastatic activities of Zn-DIGP possibly result from its ability to interfere with the signaling between chemokine CXCL10 and the G protein-coupled receptor CXCR3. Zn-DIGP is a competitive inhibitor of CXCR3 activation (IC50 = 3.8 μM) and selectively inhibits downstream events such as CXCL10-activated cell migration. Consistent with the presence of feedback regulation between CXCR3 binding and CXCL10 expression, Zn-DIGP causes overexpression of CXCL10. Interestingly, Zn-DIGP binds to CXCR3 without activating the receptor yet is able to cause endocytosis and degradation of this GPCR. To the best of our knowledge, Zn-DIGP is the first PDT agent that can facilitate the photodynamic treatment of primary tumors while simultaneously inhibiting the formation of metastatic tumor colonies by a light-independent mode of action.

Gene therapy for advanced melanoma: selective targeting and therapeutic nucleic acids

Despite recent advances, the treatment of malignant melanoma still results in the relapse of the disease, and second line treatment mostly fails due to the occurrence of resistance. A wide range of mutations are known to prevent effective treatment with chemotherapeutic drugs. Hence, approaches with biopharmaceuticals including proteins, like antibodies or cytokines, are applied. As an alternative, regimens with therapeutically active nucleic acids offer the possibility for highly selective cancer treatment whilst avoiding unwanted and toxic side effects. This paper gives a brief introduction into the mechanism of this devastating disease, discusses the shortcoming of current therapy approaches, and pinpoints anchor points which could be harnessed for therapeutic intervention with nucleic acids. We bring the delivery of nucleic acid nanopharmaceutics into perspective as a novel antimelanoma therapeutic approach and discuss the possibilities for melanoma specific targeting. The latest reports on preclinical and already clinical application of nucleic acids in melanoma are discussed.

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.

Antitumor activity of small double-stranded oligodeoxynucleotides targeting telomerase RNA in malignant melanoma cells

Human telomerase RNA (hTR) is an intrinsic component of telomerase enzyme. Small interfering RNAs (siRNAs) and single-stranded antisense oligonucleotides have been used previously for silencing of the hTR. The objective of this study was to investigate the effect of partially double-stranded oligodeoxynucleotides (ODNs), in vitro and in vivo in comparison to single-stranded antisense ODNs and siRNAs. ODNs were designed on the basis of structural properties of an ODN from previous studies on HIV, to target the hTR in the human cervical carcinoma HeLa cell line and mouse telomerase RNA (mTR) in the murine metastatic melanoma B16-F10 cell line, respectively. Our results indicate that ODNs were able to inhibit the hTR by 68% and the mTR by 81% in the respective cell lines. This correlated with ODN-mediated rapid inhibition of cell proliferation and induction of apoptosis excluding slow effects on telomerase function. The inhibition of the hTR was decreased by knock-down of the cellular RNases H suggesting their contribution. Furthermore, we showed a reduction in numbers of metastases by 70% after intravenous administration of ODN-transfected B16-F10 cells in C57BL/6 mice. Our study demonstrates the potential utility of these hairpin-loop-structured ODNs as a different group of nucleic acids for telomerase-based antiproliferative strategies.

Electroporation-mediated IL-12 gene therapy in a transplantable canine cancer model

Interleukin-12 (IL-12) is effective in treating many types of rodent tumors, but has been unsuccessful in most human clinical trials, suggesting that animal models of more clinical relevance are required for evaluating human cancer immunotherapy. Herein, we report on the effectiveness of gene therapy with plasmid encoding human IL-12 (pIL-12) through in vivo electroporation in the treatment of beagles with a canine tumor, the canine transmissible venereal tumor (CTVT). The optimal electroporation conditions for gene transfer into CTVTs were tested by luciferase activity and determined to be a voltage of 200 V and duration of 50 msec, with the number of shocks set at 10 pulses, and the use of an electrode with 2 needles. Under these conditions, intratumoral administration of as little as 0.1 mg pIL-12 followed by electroporation significantly inhibited the growth of well-established tumors and eventually led to complete tumor regression. Furthermore, local pIL-12 treatment also induced a strong systemic effect that prevented new tumor growth and cured established tumors at distant locations. Intratumoral administration of pIL-12 greatly elevated the IL-12 level in the tumor masses, but produced only a trace amount in the serum. A high level of IFN-gamma mRNA was also detected in the treated tumor masses. pIL-12 gene therapy attracted significantly more lymphocytes infiltrating the tumors, including CD4(+) and CD8(+) T cells, and the surface expression of MHC I and MHC II molecules on CTVT cells was greatly increased after pIL-12 therapy. This treatment also induced apoptosis of the tumor cells as detected by Annexin V. More importantly, delivery of pIL-12 with intratumoral electroporation did not result in any detectable toxicity in the dogs. We conclude that intratumoral electroporation of the pIL-12 gene could cause profound immunologic host responses and efficiently treat CTVT in beagle dogs. The results also indicate that CTVT is an excellent large animal cancer model for testing immunogene therapies mediated by electroporation.

Effects of IL-12 gene therapy on spontaneous transgenic and transplanted breast tumors

Cytokines are promising agents for cancer therapy due to their activity at low concentrations. We used a naked IL-12 DNA expression vector to achieve long-term systemic cytokine expression to inhibit breast tumor growth in MMTVneu transgenic and transplanted models. Constant low levels of IL-12 produced by this protocol provided effective tumor growth inhibition of both tumor models without adverse effects.

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.

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.

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.

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

PURPOSE

Interleukin-12 (IL-12) has potential as an immunotherapeutic agent for the treatment of cancer but is unfortunately associated with toxicity. Delivery of a plasmid encoding IL-12 with electroporation induces an antitumor effect in the B16 mouse melanoma model without serious side effects. To translate this observation to the clinic, an evaluation of toxicity was done in the mouse model.

EXPERIMENTAL DESIGN

Weight change, tumor response, blood chemistry and hematology values, and serum IL-12 levels were evaluated. Multiple tissues were analyzed histopathologically.

RESULTS

A pronounced reduction in tumor volume, including a large percentage of complete regressions, was observed after electrically mediated gene therapy. No significant increases in serum IL-12 levels were detected. Tumor-bearing mice showed an increased number of atypical hematology values when compared with normal naive controls. Statistically significant differences in chemistry and hematology values were observed sporadically in most of the standard chemistry and hematology categories in all groups. The only histopathologic abnormality specific to the animals receiving both plasmid and electroporation was inflammation associated with the kidney at the last time point.

CONCLUSIONS

In general, mice that received both plasmid and electroporation showed the least abnormal histopathologic findings and were found to be in the best health, reflecting the reduced burden of disease. No significant toxic effects due to the IL-12 gene therapy were observed.

Intratumoral injection of DNA encoding human interleukin 12 into patients with metastatic melanoma: clinical efficacy

Plasmid DNA encoding human interleukin 12 (IL-12) was produced under GMP conditions and injected into lesions of nine patients with malignant melanoma (stage IV) previously treated with both standard and nonstandard therapies. The treatment was based on efficacy in preclinical studies with melanoma in mice and gray horses. The DNA was applied in cycles, three injections per cycle, for up to seven cycles. Three therapy arms comprised low (2 mg), medium (4 mg), and high (10 to 20 mg) amounts of total DNA. The therapy was well tolerated. Three of nine patients experienced a clinical response: two stable disease and one complete remission. One patient receiving a low dose of DNA experienced a long-lasting stabilization of the disease for more than 3 years, whereas the other two responders received high doses of DNA. All patients but one (patient 9) experienced a transient response at the intratumoral injection site. Immunohistochemical staining of responder sections showed local reduction of angiogenesis and lymphocyte infiltrations. All patients, in particular the clinical and local responders (patients 3, 7, and 8), exhibited an antigen-specific immune response against MAGE-1 and MART-1, which in some cases preexisted. Biopsies of responders showed some increase in IL-12, IP-10, and IFN-(). Serum levels revealed fluctuations. The results show that intratumoral injection of DNA produced some beneficial clinical effect. DNA encoding a cytokine may be useful as a therapeutic or adjuvant against various human cancers.

Antibodies from a DNA peptide vaccination decrease the brain amyloid burden in a mouse model of Alzheimer's disease

The neuropathology of Alzheimer's disease(AD) is characterized by the accumulation of amyloid peptide Abeta in the brain derived from proteolytic cleavage of the amyloid precursor protein (APP). Vaccination of mice with plasmid DNA coding for the human Abeta42 peptide together with low doses of preaggregated peptide induced antibodies with detectable titers after only 2 weeks. One serum was directed against the four aminoterminal amino acids DAEF and differs from previously described ones. Both immune sera and monoclonal antibodies solubilized preformed aggregates of Abeta42 in vitro and recognized amyloid plaques in brain sections of mice transgenic for human APP. Passive immunization of transgenic AD mice caused a significant and rapid reduction in brain amyloid plaques within 24 h. The combined DNA peptide vaccine may prove useful for active immunization with few inoculations and low peptide dose which may prevent the recently described inflammatory reactions inpatients. The monoclonal antibodies are applicable for passive immunization studies and may lead to a therapy of AD.

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

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

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

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

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

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

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

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.

In vivo elimination of CD25+ regulatory T cells leads to tumor rejection of B16F10 melanoma, when combined with interleukin-12 gene transfer

CD4(+)CD25(+) T cells are an important population that plays a crucial role in the maintenance of peripheral self-tolerance. Recently, it was shown that the elimination of these cells by in vivo administration of anti-CD25 monoclonal antibody (mAb) caused the regression of highly immunogenic tumors in syngeneic mice. In this study, we examined whether B16F10 melanoma cells regressed with the elimination of CD25(+) regulatory T cells. We found the melanoma cells were not affected at all by in vivo anti-CD25 mAb administration alone but tumor rejection resulted in all mice when the administration was combined with IL-12 gene transfer to tumor cells. In vivo, depletion of natural killer (NK) cells or CD8(+) T cells cancelled the tumor rejection. NK-cell depletion allowed IL-12-transfected B16F10 melanoma (B16/IL-12) to grow from an early stage and resulted in a more rapid tumor growth of B16/IL-12 than that in mice without administration of anti-CD25 mAb. On the other hand, CD8(+) T-cell depletion did not affect the tumor growth in the early phase but allowed B16/IL-12 to grow in rather a late phase and resulted in almost the same degree of tumor growth as in mice without administration of anti-CD25 mAb. In a previous study, we showed that the elimination of CD4(+) T cells enhanced the antitumor effect of B16/IL-12 and induced vitiligo-like coat color alteration. Therefore, we also examined the frequency of the change to a vitiligo-like coat color in mice showing tumor rejection caused by CD25(+) T-cell elimination to compare with the mechanism enhancing the antitumor effects by cell elimination. The elimination of CD25(+) T cells did not induce vitiligo-like coat color changes, though that of CD4(+) T cells induced the change in 60% of mice. Furthermore, we confirmed that elimination of CD25(+) T cells did not affect the T-helper (Th) 1/Th2 cytokine profile, while that of CD4(+)T cells abrogated the Th2 cytokines (IL-4 and IL-10) and resulted in a Th1-dominant cytokine profile in the tumor-draining lymph nodes (TDLNs) of B16/IL-12-bearing mice. These results indicate that in vivo depletion of CD25(+) regulatory T cells is a potent useful adjuvant in immunotherapy of B16F10 melanoma, when combined with IL-12 gene transfer and that the enhancement of the antitumor effect by CD25(+) T-cell depletion is mediated through CD8(+) T cells and may differ from the enhancing mechanism caused by CD4(+) T-cell depletion.

IP-10-encoding plasmid DNA therapy exhibits anti-tumor and anti-metastatic efficiency

We report here that the interferon-induced protein of 10 kDa (IP-10 or CXCL10) elicits strong anti-tumor and anti-metastatic responses in mice when administered by plasmid DNA. Intratumoral but not intramuscular IP-10 DNA inoculation resulted in reduced tumor formation of malignant melanoma (B16F10) and Lewis lung carcinoma (LL/2) in C57BL/6 mice. In addition, plasmid DNA-encoding IP-10 substantially reduced the establishment of metastases when injected systemically by the intramuscular route. In contrast to the primary tumor model, the anti-metastatic effect of DNA-encoding IP-10 was primarily mediated by NK cells. Compared to DNA-encoding interleukin-12 (IL-12), therapy with DNA-encoding IP-10 exhibits lower efficacy against primary melanoma tumors but equivalent efficacy against primary Lewis lung tumors and against B16F10 lung metastasis formation. Co-administration of DNA-encoding IP-10 and IL-12 enhanced the anti-tumor activity of IL-12 in the lung metastasis model but had little effect in the local treatment of established subcutaneous tumors. Interestingly, treatment of nude mice lacking T lymphocytes with DNA-encoding IP-10 or IL-12 still resulted in a pronounced reduction of tumor growth or metastasis formation.

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

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

IL-12 gene therapy using an electrically mediated nonviral approach reduces metastatic growth of melanoma

Interleukin-12 (IL-12) has been evaluated in both preclinical and clinical immunotherapy protocols as a potential therapy for melanoma. However, delivery of IL-12 in the form of recombinant protein can result in severe toxicity, and gene therapy has had limited success against B16.F10 murine melanoma. This study investigated the therapeutic effect of delivering a plasmid encoding IL-12 followed by electroporation on primary and secondary tumors. Three treatments of intratumoral (i.t.) plasmid injection and electroporation resulted in 80% of mice with B16.F10 melanoma tumors being tumor free for >100 days (cure). The "cured animals" were resistant to challenge with B16 cells. In a separate experiment, B16 cells were injected on the opposite flank of the treated tumor on the day of treatment. Eighty-seven percent of control mice developed a distant tumor while only 43.8% of mice receiving two or three i.t. electroporation treatments developed a distant tumor. For examination of tumor development in the lungs, mice were injected intravenously with B16.F10 cells then treated with i.m. injections of plasmid with or without electroporation. Only 37.5% of mice receiving i.m. injections and electroporation developed nodules in the lungs compared to 87.5% of mice in the no-treatment group. The results show that administration of a plasmid encoding IL-12 with electroporation has a therapeutic effect on primary tumors as well as distant tumors and metastases.

Antimetastatic effect of an immunomodulatory arabinomannan extracted from Mycobacterium tuberculosis strain Aoyama B, Z-100, through the production of interleukin-12

In this study, the role of interleukin (IL)-12 on the antimetastatic effect of Z-100 was investigated using wild-type C57BL/6 mice or IL-12p40 knockout (IL-12p40 KO) mice inoculated with highly metastatic B16F10 melanoma. When C57BL/6 mice were inoculated with B16F10 melanoma (2x10(5) cells/mouse i.v.), Z-100 (10 mg/kg i.p.) significantly suppressed the pulmonary metastasis of B16F10 melanoma 14 d after tumor inoculation. On the other hand, the antimetastatic effect of Z-100 was not observed in IL-12p40 KO mice inoculated with B16F10 melanoma. These results indicate that IL-12 is essentially required for the appearance of the antimetastatic effect of Z-100. Since helper T (Th) 2 cell responses have been reported to have a role in tumor metastasis, the regulatory effect of Z-100 on the immune balance of Th1/Th2 cell responses was investigated. In both C57BL/6 mice and IL-12p40 KO mice bearing B16F10 melanoma, Th1 cytokine production (IL-2, interferon-gamma) was significantly suppressed as compared with those in normal mice. On the other hand, Th2 cytokine production (IL-4, IL-10) in these mice was increased. The administration of Z-100 (10 mg/kg i.p.) in C57BL/6 mice bearing B16F10 melanoma improved the balance of Th1/Th2 cell responses from the Th2-dominant state to the normal state. However, the improvement of Th1/Th2 cell responses by Z-100 was not observed in IL-12p40 KO mice bearing the same tumors. In addition, Z-100 significantly increased IL-12 production by macrophages in a concentration-dependent manner, while Z-100 significantly decreased IL-10 production by these cells in vitro. These results suggested that up-regulation of IL-12 production and down-regulation of IL-10 production by Z-100 are related to the improvement of Th1/Th2 cell responses from the Th2-dominant state to the normal state, which resulted in suppression of tumor metastasis.

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

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

A combination of plasmid DNAs encoding murine fetal liver kinase 1 extracellular domain, murine interleukin-12, and murine interferon-gamma inducible protein-10 leads to tumor regression and survival in melanoma-bearing mice

The vascular endothelial growth factor (VEGF) and its interaction with the vascular endothelial growth factor receptor 2 [VEGFR2/murine fetal liver kinase 1 (Flk-1), human kinase domain receptor] are an important angiogenic pathway leading to tumor vascularization. A plasmid DNA encoding the complete extracellular domain (ECD) of murine Flk-1 including the endogenous signal sequence was designed as a possible competitor of the receptor to sequester VEGF. The plasmid DNA was used to treat B16F10 cell-induced subcutaneous melanomas in syngeneic mice. The Flk-1 ECD-encoding plasmid DNA injected intramuscularly did not lead to tumor reduction. However, intratumoral injection caused a dose-dependent reduction and significant retardation of tumor growth. Blood vessels analyzed by immunohistochemistry with anti-CD31 antibodies as indicators of vascularization appeared smaller in diameter after treatment. A combination of Flk-1 ECD and DNA encoding murine interleukin-12 or murine interferon-gamma inducible protein-10 improved the effect, leading to tumor regression and long-term survival of the mice.

Non-viral and hybrid vectors in human gene therapy: an update

Non-viral DNA vectors have several advantages over viral vectors. For example, virus production is expensive and there are safety concerns regarding viral manipulations. In addition, the size of the delivered plasmid is limited by the size of the viral capsid, whereas this is not a problem with non-viral vectors. The major disadvantage of using non-viral DNA delivery vectors, compared with their viral counterparts, is the low transfection efficiency. This has resulted in low levels of usage in clinical trials. Consequently, the majority of research into non-viral gene therapy has been focused on developing more efficient vectors.

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.

IL-12 plasmid delivery by in vivo electroporation for the successful treatment of established subcutaneous B16.F10 melanoma

Interleukin-12 (IL-12) has been used in numerous immunotherapy protocols against melanoma. However, delivery of IL-12 in the form of recombinant protein can result in severe toxicity, and gene therapy has had limited success against B16.F10 murine melanoma. The purpose of this study was to examine the effectiveness of in vivo electroporation for the delivery of plasmid DNA encoding IL-12 as an antitumor agent against B16.F10 melanoma. We treated mice bearing established B16.F10 melanoma tumors with intratumoral (i.t.) or intramuscular (i.m.) injections of a plasmid encoding IL-12, followed by in vivo electroporation. For i.t. treatments, we used an applicator containing six penetrating electrodes to deliver 1500-V/cm, 100-micros pulses. We administered i.m. pulses with an applicator containing four penetrating electrodes delivering 100-V/cm, 20-ms pulses. The i.t. treatment resulted in the cure of 47% of tumor-bearing mice, and 70% of cured mice were resistant to challenge with B16.F10 cells. The i.m. treatment did not result in tumor regression. We found that i.t. treatment resulted in increased levels of IL-12 and interferon-gamma (IFN-gamma) within the tumors, the influx of lymphocytes into the tumors, and reduction in vascularity. Neither i.m. nor i.t. treatment was successful against B16.F10 tumors in a nude mouse model, supporting a role for T cells in regression of this tumor model.

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.

Gene gun-mediated oral mucosal transfer of interleukin 12 cDNA coupled with an irradiated melanoma vaccine in a hamster model: successful treatment of oral melanoma and distant skin lesion

Malignant melanoma involving the oral cavity has a highly metastatic potential. Curative surgery is required to resect extensive oral tissues and often results in dysfunction as well as a severe cosmetic deformity in patients with the disease. An alternative technology for the local and sustained delivery of cytokines for cancer immunotherapy has been shown to induce tumor regression, suppression of metastasis, and development of systemic antitumor immunity. However, local immunization of the oral cavity has not previously been studied. In this study, we examined the efficacy of particle-mediated oral gene transfer on luciferase and green fluorescent protein production. The results showed that these proteins were more significantly expressed in oral mucosa than the skin, stomach, liver, and muscle. Using an established oral melanoma model in hamsters, particle-mediated oral gene gun therapy with interleukin (IL) 12 cDNA was then conducted. The results indicated that direct bombardment of mouse IL-12 cDNA suppressed tumor formation and improved the survival rate. The skin tumor model created by inoculation of melanoma cells was also significantly inhibited by the oral bombardment of IL-12 cDNA coupled with an irradiated melanoma vaccine administrated to the oral mucosa, compared to treatment with a percutaneous vaccine. IL-12 gene gun therapy, combined with an oral mucosal vaccine, induced interferon-gamma mRNA expression in the host spleen for a long time. These results suggest that immunization of oral mucosa may induce systemic antitumor immunity more efficiently than immunization of the skin and that oral mucosa may be one of the most suitable tissues for cancer gene therapy by means of particle-mediated gene transfer.

Immune rejection of a large sarcoma following cyclophosphamide and IL-12 treatment requires both NK and NK T cells and is associated with the induction of a novel NK T cell population

Combined immunotherapy with cyclophosphamide (Cy) and IL-12, but not IL-12 alone, stimulates eradication of a large established solid tumor (20 mm), MCA207, a methylcholanthrene-induced murine sarcoma. In these studies we demonstrate that NK1.1(+) cells and CD1d-dependent NK T cells each play important yet distinct roles in regression of a large tumor in response to Cy and IL-12, and we define a novel NK T cell subset, selectively increased by this treatment. Mice depleted of NK1.1(+) cells demonstrated more rapid initial tumor growth and prolonged tumor regression following treatment, but tumors were eventually eradicated. In contrast, initial tumor regression following therapy was unimpaired in CD1d(-/-) mice, which are deficient in most NK T cells, but tumors recurred. No tumor regression occurred following Cy and IL-12 therapy in CD1d(-/-) mice that were depleted of NK1.1(+) cells. We found that Cy and IL-12 induced the selective increase in liver and spleen lymphocytes of a unique NK T subpopulation (DX5(+)NK1.1(-)CD3(+)). These cells were not induced by treatment in CD1d(-/-) mice. Our studies demonstrate a contribution of both NK and NK T cells to the Cy- and IL-12-stimulated anti-tumor response. We describe the selective induction of a distinct NK T cell subset by Cy and IL-12 therapy, not seen following IL-12 therapy alone, which we suggest may contribute to the successful anti-tumor response induced by this immunotherapeutic regimen.

DNA vaccination against La Crosse virus

For the development of effective conventional vaccines or DNA vaccines against viruses, the availability of suitable animal models is an essential prerequisite. For many recently emerging zoonotic viruses, suitable animal models are still missing. We have established a novel small animal model for DNA vaccines using mice lacking a functional interferon-alpha/beta receptor (IFNAR-1). IFNAR-1-deficient mice are highly susceptible to many different viruses despite their ability to mount a normal humoral and cellular immune response. Taking advantage of this animal model, we show that mice can be completely protected from lethal challenge with a single injection of plasmid DNA encoding the viral envelope proteins G1 and G2. By contrast, vaccination with a plasmid encoding the internal nucleocapsid protein N had little effect. In an effort to enhance the protective immune response to N we assessed the efficacy of vaccination with plasmid DNA encoding N in combination with a plasmid encoding the cytokine IL-12 as adjuvant. IL-12 enhanced the survival of mice following viral challenge, but the effect was independent of N indicating the involvement of components of the innate immune system such as NK cells.

Mechanism of protection against influenza A virus by DNA vaccine encoding the hemagglutinin gene

Influenza A virus with its two major antigenic surface proteins hemagglutinin (HA) and neuraminidase (NA) is a widely used model to study DNA immunizations in mice and other animals. Natural protection against influenza A virus infection is mediated by antibodies, which mostly are not protective against antigenic shift or drift variants of the original virus. Therefore, it would be a major task to induce a protective cellular immune response to more conserved proteins or epitopes. Injection of plasmid encoding a viral antigen is known to induce cellular as well as humoral immunity. In this study we investigate the mechanism of protection after intramuscular vaccination of C57Bl/6 mice with a DNA vaccine encoding HA of influenza A/PR/8/34. After a single injection, only a small percentage of mice survive the lethal challenge with homologous virus. The amount of protection can be doubled by applying a booster injection. Furthermore, by coinjection of plasmids encoding cytokines GM-CSF and IL-12, respectively, nearly all of the mice are protected. Mice with specific defects in the cellular immune response [perforin knockout (P-/-) mice] and in the humoral immune response [IgD/IgM knockout (muMT) mice], respectively, have been immunized with HA DNA with or without cytokine DNA. Protection could only be induced in P-/- mice, whereas muMT mice succumbed to the infection. Moreover, when muMT mice were infected with only 0.75 x50% lethal dose they died all the same, whereby mice that had been depleted of CD8+ T cells before infection showed an even greater progression of illness. Altogether these results demonstrate that antibodies mediate protection after immunization with plasmid coding for HA of influenza A virus, and that booster immunizations and coinjection of plasmids encoding GM-CSF or IL-12 can improve this protection.

Interleukin 12 gene transfer into skin distant from the tumor site elicits antimetastatic effects equivalent to local gene transfer

We have reported that particle-mediated interleukin 12 (IL-12) gene transfer into the skin overlying the local tumor inhibits systemic metastases. To further characterize this effect, we compared the antitumor and antimetastatic effects of IL-12 cDNA delivered at the local tumor site versus at a site distant from the primary tumor, in a spontaneous metastasis model of LLC-F5 tumor. Local IL-12 gene delivery into the skin overlying the intradermal tumor (local IL-12 treatment) on days 7, 9, and 11 after tumor implantation resulted in the most suppression of the growth of the primary LLC-F5 tumor, whereas IL-12 gene transfer into the skin distant from the tumor (distant IL-12 treatment) was less effective. In contrast, both local IL-12 and distant IL-12 treatment, followed by tumor excision, inhibited lung metastases to a similar extent, resulting in significantly extended survival of test mice. The results of in vivo studies using depleting anti-asialo GM1 antibody and anti-CD4/anti-CD8 monoclonal antibodies, or neutralizing anti-interferon gamma (IFN-gamma) monoclonal antibody demonstrated that natural killer (NK) cells, CD8(+) T cells, and IFN-gamma contributed to the antimetastatic effects in both treatment groups. Furthermore, the levels of mRNA expression of vascular endothelial growth factor and matrix methalloproteinase 9 at the tumor microenvironment were suppressed after both local and distant IL-12 treatment. These results suggest that the current particle-mediated IL-12 gene delivery in the spontaneous LLC-F5 metastasis model can confer antimetastatic activities, irrespective of the gene transfection site, via a combination of several mechanisms involving CD8(+) T cells, NK cells, IFN-gamma, and antiangiogenesis.

Intradermal delivery of interleukin-12 plasmid DNA by in vivo electroporation

Gene therapy depends on safe and efficient gene delivery. The skin is an attractive target for gene delivery because of its accessibility. Recently, in vivo electroporation has been shown to enhance expression after injection of plasmid DNA. In this study, we examined the use of electroporation to deliver plasmid DNA to cells of the skin in order to demonstrate that localized delivery can result in increased serum concentrations of a specific protein. Intradermal injection of a plasmid encoding luciferase resulted in low levels of expression. However, when injection was combined with electroporation, expression was significantly increased. When performing this procedure with a plasmid encoding interleukin-12, the induced serum concentrations of gamma-interferon were as much as 10 fold higher when electroporation was used. The results presented here demonstrate that electroporation can be used to augment the efficiency of direct injection of plasmid DNA to skin.

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

The cooperative antitumor effects of IL-12 and IL-15 gene transfer were studied in the N592 MHC class I-negative small cell lung cancer cell line xenotransplanted in nude mice. N592 cells engineered to secrete IL-15 displayed a significantly reduced tumor growth kinetics, and a slightly reduced tumor take rate, while N592 engineered with IL-12 displayed only minor changes in their growth in nude mice. However, N592 cells producing both cytokines were completely rejected, and produced a potent local bystander effect, inducing rejection of coinjected wild-type tumor cells. N592/IL-12/IL-15 cells were completely and promptly rejected also in NK-depleted nude mice, while in granulocyte-depleted animals a slight delay in the rejection process was observed. Immunohistochemical analyses of the N592/IL-12/IL-15 tumor area in intact nude mice revealed the presence of infiltrating macrophages, granulocytes, and NK cells, and expression of inducible NO synthase and of secondary cytokines such as IL-1beta, TNF-alpha, and IFN-gamma, and at higher levels GM-CSF, macrophage-inflammatory protein-2, and monocyte chemoattractant protein-1. In NK cell-depleted nude mice, numerous macrophages and granulocytes infiltrated the tumor, and a strong expression of macrophage-inflammatory protein-2 and inducible NO synthase was also observed. Finally, macrophages cocultured with N592/IL-12/IL-15 produced NO in vitro, and inhibited tumor cell growth, further suggesting their role as effector cells in this model.

Soluble biodegradable polymer-based cytokine gene delivery for cancer treatment

Transgene expression and tumor regression after direct injection of plasmid DNA encoding cytokine genes, such as mIL-12 and mIFN-gamma, remain very low. The objective of this study is to develop nontoxic biodegradable polymer-based cytokine gene delivery systems, which should enhance mIL-12 expression, increasing the likelihood of complete tumor elimination. We synthesized poly[alpha-(4-aminobutyl)-l-glycolic acid] (PAGA), a biodegradable nontoxic polymer, by melting condensation. Plasmids used in this study encoded luciferase (pLuc) and murine interleukin-12 (pmIL-12) genes. PAGA/plasmid complexes were prepared at different (+/-) charge ratios and characterized in terms of particle size, zeta potential, osmolality, surface morphology, and cytotoxicity. Polyplexes prepared by complexing PAGA with pmIL-12 as well as pLuc were used for transfection into cultured CT-26 colon adenocarcinoma cells as well as into CT-26 tumor-bearing BALB/c mice. The in vitro and in vivo transfection efficiency was determined by luciferase assay (for pLuc), enzyme-linked immunosorbent assay (for mIL-12, p70, and p40), and reverse transcriptase-polymerase chain reaction (RT-PCR) (for Luc and mIL-12 p35). PAGA condensed and protected plasmids from nuclease degradation. The mean particle size and zeta potential of the polyplexes prepared in 5% (w/v) glucose at 3:1 (+/-) charge ratio were approximately 100 nm and 20 mV, respectively. The surface characterization of polyplexes as determined by atomic force microscopy showed complete condensation of DNA with an ellipsoidal structure in Z direction. The levels of mIL-12 p40, mIL-12 p70, and mIFN-gamma were significantly higher for PAGA/pmIL-12 complexes compared to that of naked pmIL-12. This is in good agreement with RT-PCR data, which showed significant levels of mIL-12 p35 expression. The PAGA/pmIL-12 complexes did not induce any cytotoxicity in CT-26 cells as evidenced by 3-¿4, 5-dimethylthiazol-2-yl¿-2,5-diphenyltetrazolium bromide assay and showed enhanced antitumor activity in vivo compared to naked pmIL-12. PAGA/pmIL-12 complexes are nontoxic and significantly enhance mIL-12 expression at mRNA and protein levels both in vitro and in vivo.

Interleukin-12 induces efficient lysis of natural killer-sensitive and natural killer-resistant human osteosarcoma cells: the synergistic effect of interleukin-2

Previously we demonstrated that some osteosarcoma cell lines varied greatly in their susceptibility to natural killer (NK) cell lysis in vitro. The expression of CD54 and CD58 adhesion molecules on their surface appeared to influence their vulnerability, and the tumour necrosis factor-alpha (TNF-alpha)-induced positive modulation of CD54 increased osteosarcoma susceptibility in vitro. This study investigated whether peripheral blood mononuclear cells from normal healthy donors could be activated by interleukin (IL)-12 and IL-2, separately or in combination, to lyse osteosarcoma cell lines in vitro, as evaluated by using a microcytotoxicity test. In addition, we analysed (by flow cytometry) whether this function correlated with modifications of the CD2, CD11a, CD11b and CD18 molecules, which are involved in the adhesion of effector cells to the counter-receptors (CD54 and CD58) on osteosarcomas. This study demonstrates that incubation with IL-12 and/or IL-2 triggered NK cell cytolytic activity against osteosarcoma targets and that cytolytic activity was enhanced to a greater extent when lymphocytes were incubated simultaneously with a combination of IL-12 and IL-2. The density of CD18 and CD2 molecules involved in NK adhesion was also up-modulated following cytokine incubation. These changes in the density of adhesion molecules can be involved in the increased lytic activity of effector lymphocytes and in the modification of their binding capacity to osteosarcoma target cells.

DNA vaccines

The premise that DNA coding for antigens produces proteins to stimulate the immune system when inoculated directly into muscle tissues, has the immense attractions of simplicity, versatility and economy. When other vaccination approaches are experiencing practical problems, meeting such challenges as AIDS and malaria, considerable attention has focused on DNA vaccines with entire conferences and a flood of commercial companies devoted to exploring the possibilities. A number of clinical trials for both infectious diseases and cancer have already commenced, even though a number of major issues have to be resolved.

Regulation of T-helper-1 versus T-helper-2 activity and enhancement of tumor immunity by combined DNA-based vaccination and nonviral cytokine gene transfer

Intramuscular (i.m.) injections of a plasmid encoding human carcinoembryonic antigen (CEA) elicited both humoral and cellular immune responses in mice, but only partial inhibition of the growth of transplanted syngeneic CEA-positive P815 tumor cells (CEA/P815). Coinjection of the CEA vector with a vector encoding either interferon-gamma (IFN gamma) or IL-12 promoted IgG2a isotype anti-CEA antibody production, anti-CEA/P815 CTL activity and greater resistance to CEA/P815 tumor challenge. As well, CEA/P815-stimulated IFN gamma secretion in vitro was increased, but IL-4 diminished, consistent with a T-helper type 1 (Th1) response. In contrast, coinjection of the CEA vector with an IL-4 vector increased IgG1 production, but reduced CTL activity and resistance to tumor challenge. The latter treatment inhibited CEA/P815-dependent IFN gamma production but enhanced IL-4 secretion, consistent with a Th type 2 (Th2) response. Antitumor immunity was enhanced when the CEA and IL-12 plasmids were coinjected at the same muscle site, but not at separate sites despite increased serum IL-12 levels. Though the tumor cells expressed neomycin phosphotransferase, mice immunized with vectors encoding that protein (without CEA) were not protected against tumor growth, and produced no CTLs except for low levels when coinjected with an IL-12 vector. Thus, we show that immunity elicited by DNA vaccination against CEA can be biased to a protective type (high Th1 and CTL activity) or nonprotective type (high Th2 and low CTL activity) by i.m. coinjection of cytokine-expressing plasmids. IL-12 appears to act locally, but not systemically, through an adjuvant effect.

Enhanced protection against viral infection by co-administration of plasmid DNA coding for viral antigen and cytokines in mice

BACKGROUND

DNA vaccines have been shown to induce protective immunity against viral infections in different animal models. We have recently demonstrated that DNA vaccine induced protective immunity against influenza A virus and La Crosse virus (LACV) is primarily mediated by humoral immune response.

OBJECTIVE

The goal of this study was to investigate whether administration of DNA coding for cytokines such as interleukin 12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF) could increase the protective immune response induced by vaccination with DNA coding for viral antigens.

STUDY DESIGN

For the influenza A virus or LACV model, C57BL/6 or interferon-alpha/beta receptor (IFNAR-1)-deficient mice, respectively, were vaccinated once or twice with 100 micrograms of DNA encoding viral antigens. At the same time plasmid DNAs (100 micrograms) coding either for mouse GM-CSF or mouse IL-12 were administered. The mice were subsequently challenged with a lethal dose of influenza A virus or LACV and monitored for clinical symptoms (weight loss) and survival.

RESULTS

To achieve a high degree of protection (70% survival) two injections of DNA encoding the influenza A virus surface protein hemagglutinin (HA) were required. Intriguingly, administration of DNA coding for IL-12 alone also led to a pronounced protective effect against virus challenge. Co-administration of DNAs encoding IL-12 and HA significantly increased the protective immunity against influenza A virus, while IL-12 expression did not improve protection upon vaccination with DNA coding for the internal nucleocapsid protein N of LACV. Co-injection of DNA coding for mouse GM-CSF and HA also showed an adjuvant effect.

CONCLUSIONS

The data clearly indicate that co-administration of DNA encoding cytokines such as IL-12 and GM-CSF with DNA coding for viral antigens has adjuvant effects on the protective immune response against different viral pathogens.