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

GEN-1 immunotherapy for the treatment of ovarian cancer

GEN-1 is a gene-based immunotherapy, comprising a human IL-12 gene expression plasmid and a synthetic plasmid delivery system, delivered intraperitoneally (ip.) to produce local and persistent levels of a pleiotropic immunocytokine, IL-12, at the tumor site in patients with advanced ovarian cancer. The goal of local and persistent IL-12 delivery is to remodel the highly immunosuppressive tumor microenvironment to favor immune stimulation while avoiding serious systemic toxicities, a major limitation of recombinant IL-12 therapy. Safe and sustained local production of IL-12 and related immunocytokines at the tumor site could produce potentially more favorable immunological changes in the tumor microenvironment and antitumor responses than a bolus systemic delivery of recombinant IL-12. Treatment safety, clinical benefits and biological activity of GEN-1 ip. in patients with ovarian cancer and in representative animal models are described.

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.

Preclinical Biodistribution and Safety Evaluation of a pbi-shRNA STMN1 Lipoplex after Subcutaneous Delivery

Stathmin-1 (STMN1) is a microtubule-destabilizing protein which is overexpressed in cancer. Its overexpression is associated with poor prognosis and also serves as a predictive marker to taxane therapy. We have developed a proprietary bi-functional shRNA (bi-shRNA) platform to execute RNA interference (RNAi)-mediated gene silencing and a liposome-carrier complex to systemically deliver the pbi-shRNA plasmids. In vitro and in vivo testing demonstrated efficacy and specificity of pbi-shRNA plasmid in targeting STMN1 (Phadke, A. P., Jay, C. M., Wang, Z., Chen, S., Liu, S., Haddock, C., Kumar, P., Pappen, B. O., Rao, D. D., Templeton, N. S., et al. (2011). In vivo safety and antitumor efficacy of bifunctional small hairpin RNAs specific for the human Stathmin 1 oncoprotein. DNA Cell Biol. 30, 715-726.). Biodistribution and toxicology studies in bio-relevant Sprague Dawley rats with pbi-shRNA STMN1 lipoplex revealed that the plasmid DNA was delivered to a broad distribution of organs after a single subcutaneous injection. Specifically, plasmid was detected within the first week using QPCR (threshold 50 copies plasmid/1 µg genomic DNA) at the injection site, lung, spleen, blood, skin, ovary (limited), lymph nodes, and liver. It was not detected in the heart, testis or bone marrow. No plasmid was detected from any organ 30 days after injection. Treatment was well tolerated. Minimal inflammation/erythema was observed at the injection site. Circulating cytokine response was also examined by ELISA. The IL-6 levels were induced within 6 h then declined to the vehicle control level 72 h after the injection. TNFα induction was transiently observed 4 days after the DNA lipoplex treatment. In summary, the pbi-shRNA STMN1 lipoplex was well tolerated and displayed broad distribution after a single subcutaneous injection. The pre-clinical data has been filed to FDA and the pbi-shRNA STMN1 lipoplex is being investigated in a phase I clinical study.

Radiation-enhanced Endostatin Gene Expression and Effects of Combination Treatment

Targeting cells that support tumor growth by administering potent angiogenesis inhibitors is currently an area of intense interest. In the present study, a unique plasmid vector for the mouse endostatin gene, pXLG-mEndo, was constructed and evaluated with and without radiation using the Lewis lung carcinoma (LLC) cell line. The physical properties of the expressed endostatin protein were validated by PCR, gel electrophoresis, and Western blot. Enzyme-linked immunosorbent and immunocytochemical analyses for the therapeutic gene demonstrated that transfected LLC cells secreted the protein into the medium. Exposure of the cells to 2 gray (Gy) γ-rays reduced the time to reach the maximum expression level of the endostatin gene and also increased the amount of secreted endostatin protein (P<0.001). Biological activity of the endostatin was demonstrated by the inhibition of tube formation by human umbilical vein endothelial cells (HUVEC). Based on 3 H-thymidine incorporation, endostatin expression significantly depressed DNA synthesis in HUVEC and LLC cells compared to controls transfected with parental vector or no vector (P>0.005). In addition, radiation increased the efficiency of endostatin-mediated inhibition of both cell types over a 3-day period post-exposure (P<0.05 or less). Intratumoral injection of 100 μg pXLG-mEndo combined with 10 Gy radiation significantly delayed LLC tumor growth, especially when each modality was delivered twice (P<0.05 or less compared to all other groups). No toxicity was observed. These findings are very promising and suggest that endostatin therapy with a plasmid vector, such as pXLG-mEndo, may enhance the efficacy of radiotherapy for lung cancer.

Preclinical safety and tolerability of a repeatedly administered human leishmaniasis DNA vaccine

The leishmaniases are a complex of vector-borne diseases caused by protozoan parasites of the genus Leishmania. LEISHDNAVAX is a multi-antigen, T-cell epitope-enriched DNA vaccine candidate against human leishmaniasis. The vaccine candidate has been proven immunogenic and showed prophylactic efficacy in preclinical studies. Here, we describe the safety testing of LEISHDNAVAX in naive mice and rats, complemented by the demonstration of tolerability in Leishmania-infected mice. Biodistribution and persistence were examined following single and repeated intradermal (i.d.) administration to rats. DNA vectors were distributed systemically but did not accumulate upon repeated injections. Although vector DNA was cleared from most other tissues within 60 days after the last injection, it persisted in skin at the site of injection and in draining lymph nodes. Evaluation of single-dose and repeated-dose toxicity of the vaccine candidate after i.d. administration to naive, non-infected mice did not reveal any safety concerns. LEISHDNAVAX was also well tolerated in Leishmania-infected mice. Taken together, our results substantiate a favorable safety profile of LEISHDNAVAX in both naive and infected animals and thus, support the initiation of clinical trials for both preventive and therapeutic applications of the vaccine.

Synergistic antitumoral effect of IL-12 gene cotransfected with antiangiogenic genes for angiostatin, endostatin, and saxatilin

Previously, it was reported that the cotransfection of angiostatin K1-3, endostatin, and saxatilin genes using cationic liposomes significantly inhibited tumor progression. IL-12 is a well-known immune modulator that promotes Th1-type antitumor immune responses and also induces antiangiogenic effects. In this study, we have examined the antitumoral function of the IL-12 gene cotransfected with antiangiogenic genes for angiostatin K1-3, endostatin, and saxatilin by O,O'-dimyristyl-N-lysyl glutamate (DMKE) cationic liposomes in a mouse tumor model. According to our results, the administration of the IL-12 gene or the genes for angiostatin K1-3, endostatin, and saxatilin exhibited effective inhibition of B16BL6 melanoma growth in mice. In particular, intravenous administration of the IL-12 gene along with intratumoral administration of the three antiangiogenic genes synergistically inhibited the B16BL6 tumor growth. These results suggest that systemically expressed IL-12 enhances antitumoral efficacy of locally expressed antiangiogenic proteins.

Antitumor effects of recombinant antivascular protein ABRaA-VEGF121 combined with IL-12 gene therapy

Development and neoplastic progression strongly rely on tumor microenvironment cells. Various kinds of cells that form such tumor milieu play substantial roles in angiogenesis and immunosuppression. Attempts to inhibit tumor vascularization alter tumor milieu and enhance immune response against the tumor. Anticancer therapeutic strategy bringing together antiangiogenic and immunostimulating agents has emerged as a promising approach. We here investigated whether therapy directed against preexisting vessels, combined with an immunomodulatory factor would be equally effective in arresting tumor growth. To this goal, we investigated the effectiveness of ABRaA-vascular endothelial growth factor isoform 121 (VEGF₁₂₁), an antivascular drug constructed by us. It is a fusion protein composed of VEGF₁₂₁, and abrin A chain (translation-inhibiting toxin). We used it in combination with interleukin (IL-12) gene therapy and tried to inhibit B16-F10 melanoma tumor growth. ABRaA-VEGF₁₂₁ is a chimeric recombinant protein capable of destroying tumor vasculature and triggering necrosis in the vicinity of damaged vessels. IL-12 cytokine, in turn, activates both specific and non-specific immune responses. Our results demonstrate that combination of ABRaA-VEGF₁₂₁ antivascular agent with immunostimulatory cytokine IL-12 indeed inhibits tumor growth more effectively than either agent alone, leading to complete cure of ca. 20 % mice. Post-therapeutic analysis of tumors excised from mice treated with combination therapy showed decreased numbers of blood microvessels in the tumor microenvironment, lowered numbers of regulatory T lymphocytes, as well as showed higher levels of CD4⁺ and CD8⁺ as compared to control mice. It seems that bringing together antivascular strategy and the action of immunostimulating agents indeed inhibits growth of tumors.

Interleukin-12 gene adjuvant increases the immunogenicity of virus-like particles of human papillomavirus type 16 regional variant strain

Objectives

To analyze the immunogenicity of virus-like particles (VLP) of human papillomavirus type 16 (HPV16) isolated in East China and the adjuvant potential of interleukin-12 (IL-12).

Methods

The variant HPV16 L1VLP expressed in sf9 insect cells were purified with cesium chloride gradient centrifugation. BALB/c mice were vaccinated with VLP (L1N), VLP with Freund's adjuvant (L1A) or VLP with IL-12 recombinant plasmid (L1P). HPV16 VLP specific IgG and IFN-γ level in the serum were detected by ELISA, and the percentage of CD4⁺ and CD8⁺ in spleen cells was detected with flow cytometry.

Results

The titers of serum IgG antibodies in vaccinated groups were higher than in negative control and the serum antibodies mainly recognized conformation-dependent HPV16 VLP epitopes. Splenic CD4⁺ and CD8⁺ T cell subsets increased after vaccination in every experimental group, and CD8⁺ increased obviously in L1P group. The ratio of CD4⁺/CD8⁺ decreased in L1P group and increased in the other two groups, compared to control group. Vaccination induced specific secretion of IFN-γ in the serum of vaccinated group (p < 0.05), especially in the L1P group.

Conclusions

VLP of HPV16 variant strain isolated in East China could induce humoral immunity and cellular immunity in mice, and IL-12 recombinant plasmid can enhance cellular immunity.

Pharmacokinetics of combined gene therapy expressing constitutive human GM-CSF and hyperthermia-regulated human IL-12

Background

An adenovirus that expresses both interleukin (IL)-12 and granulocyte-macrophage colony-stimulating-factor (GM-CSF) has been proven to be very effective in treating several tumors, but causes serious normal tissue toxicities.

Methods

In this study, a novel adenoviral vector was constructed by placing the human GM-CSF gene under the control of the CMV-IE promoter and human IL-12 gene under the control of heat shock protein 70B gene promoter. Both hGM-CSF and hIL-12 expressions in virus-infected tumor cells were analyzed in vitro and in vivo when underlying single or multiple rounds of hyperthermia.

Results

We observed constitutive high expression of human GM-CSF and heat-induced expression of human IL-12 after a single round of hyperthermia post viral infection. The heat-induced hIL-12 expression exhibited a pulse-like pattern with a peak at 24 hrs followed by a decline 48 hrs post heat stress. Repeated heat treatment was more effective in inducing hIL-12 expression than a one-time heat treatment. Interestedly, we also observed that constitutive expression of hGM-CSF could be stimulated by heat stress in tested tumor cells.

Conclusion

Our study provided a novel strategy for combined gene therapy that allows constitutive expression of a non-toxic gene such as GM-CSF and heat-induced expression of a toxic gene such as IL-12. In addition, our study also showed that hyperthermia can be used to trigger gene expression in temporal and special manner.

Therapeutic effect of recombinant plasmid-encoded human interleukin-12 in tumor-bearing mice

The aim of this study was to investigate the effects of gene therapy using a recombinant plasmid encoding human interleukin-12 (rIL-12, pcDNA6-p70) on transplanted tumors in mice. Tumor-bearing mice were transplanted with sarcoma‑180 (S-180) cells and randomly divided into three groups of 10 mice with each group receiving a separate treatment. Following this, pcDNA6-p70 (dissolved in purified water; 100 µg/mouse), cyclophosphamide (dissolved in 0.9% saline; 40 mg/kg) or 0.9% saline (100 µl/mouse) was directly injected into the tumors on the 4th, 7th, 10th, 14th and 17th days following transplantation of the S-180 cells. Mice survival time was monitored and surviving mice were sacrificed on the 21st day. In addition to survival time, tumor volume, NK cell activity, spleen lymphocyte proliferation and IFN-γ production were investigated. The mice were also monitored for any adverse effects regarding the administration of pcDNA6-p70. Our results demonstrated that pcDNA6-p70 prolongs the survival time of tumor-bearing mice, decreases tumor size (P<0.01) and increases the proliferative response of spleen cells, the activity of NK cells and the serum level of IFN-γ. There were no significant adverse effects caused by the administration of pcDNA6-p70. The results of the present study support the hypothesis that gene therapy using the rIL-12 plasmid exerts a therapeutic effect in tumor models by triggering antitumor cellular immunity.

Treatment of disseminated ovarian cancer using nonviral interleukin-12 gene therapy delivered intraperitoneally

BACKGROUND

The poor prognosis associated with ovarian cancer is primarily the result of delayed diagnosis and the lack of an effective treatment for advanced disease. Use of novel immunotherapy strategies are being evaluated that work to enhance local and systemic immune responses against cancer cells and can possibly work together with traditional cytotoxic chemotherapy regimens to produce more effective treatment options.

METHODS

In the present study, we describe a gene-based therapy whereby the anticancer cytokine interleukin-12 gene (pmIL-12) is formulated with a synthetic polymeric delivery vehicle (PPC) and administered intraperitoneally into a mouse model of disseminated ovarian cancer.

RESULTS

The administration of pmIL-12/PPC in tumor-bearing mice was associated with a shift towards a Th1 immune state, including significant increases in murine IL-12 (mIL-12) and interferon (IFN)-gamma (mIFN-gamma) in ascites fluid, with little change in systemic levels of these proteins. The mIL-12 protein was detectable for several days and could be reintroduced with subsequent injections. We show that treatment delayed the onset of ascites formation and improved survival in a dose-dependent manner. A significant decrease in vascular endothelial growth factor was associated with pmIL-12/PPC delivery and believed to play a predominant role in inhibiting ascites accumulation. Administration of pmIL-12/PPC was associated with minimal toxicity and, when combined with standard chemotherapies, resulted in additive improvement in survival.

CONCLUSIONS

Taken together, these results suggest that pmIL-12/PPC may be an effective strategy for inhibiting progression of disseminated ovarian cancer and may offer a new option for treatment of advanced disease that can be used to complement standard therapies.

Quantitative real-time PCR study on persistence of pDNA vaccine pVax-Hsp60 TM814 in beef muscles

Background

Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.

Methods

A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 10⁹ copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.

Results

Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.

Conclusion

Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials.

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.

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.

Preclinical safety and biodistribution of adenovirus-based cancer vaccines after intradermal delivery

The recombinant adenoviral (Ad) vector is being considered as a cancer vaccine platform because it efficiently induces immune responses to tumor antigens by intradermal immunization. The aims of this study were to evaluate the potential toxicities and biodistribution after a single dose or six weekly intradermal doses of Ad2/gp100v2 and Ad2/MART-1v2, which encode tumor-associated antigens gp100 and MelanA/MART-1, respectively. The only dose-related toxicities associated with intradermal administration of these Ad vectors were inflammatory cell infiltrates in the draining lymph nodes and injection sites that persisted 83 days after administration. The biodistribution of Ad DNA as detected by real-time polymerase chain reaction was largely confined to the injection sites and draining lymph nodes of mice treated with either a single dose or multiple doses of Ad vector and in the spleens of mice treated with multiple doses of Ad vector. Adenoviral DNA was transiently detected in the bone marrow, lung, or blood of only one animal for each site and was below the limit of assay quantification (<10 copies/microg DNA). The vector persisted in the skin and lymph nodes as long as 92 days after the last dose. We conclude that Ad vectors delivered by intradermal administration provide a safe, genetic vaccine delivery platform that induces desirable immune responses at the immunization sites and the lymph nodes that, ultimately, result in immune responses specific to the tumor antigens.

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.

Nasal IL-12p70 DNA Prevents and Treats Intestinal Allergic Diarrhea

OVA-induced allergic diarrhea occurs as a consequence of over-expression of Th1 inhibitory IL-12p40 monomers and homodimers in the large intestine, establishing a dominant Th2-type environment. In this study, we demonstrate that intranasally administered murine IL-12p70 naked DNA expression plasmids resulted in the synthesis of corresponding cytokine in the large intestinal CD11c(+) dendritic cells, leading to the inhibition of Ag-specific Th2-type response for the prevention of allergic diarrhea and the suppression of clinical symptoms including OVA-specific IgE Ab synthesis. The nasal IL-12p70 DNA treatment proved effective even after the establishment of allergic diarrhea. These results suggest that the mucosal administration of naked IL-12p70 DNA plasmid should be considered as a possible preventive and therapeutic treatment for Th2 cell-mediated food allergic diseases in the intestinal tract.

Human endostatin gene transfer, either naked or with liposome, has the same inhibitory effect on growth of mouse liver tumor cells in vivo

AIM: To explore a safe and efficient strategy of tumor therapy using anti-angiogenetic agents.

METHODS: Endostatin gene with a signal sequence of human IgG γ chain was amplified by PCR and cloned into pVAX1 plasmid which was the only vector authorized by FDA in clinical trial to construct a recombinant plasmid named as pVAX-sEN. The recombinant plasmid was detected with Eco I/Kpn I and DNA sequencing. BALB/c mice bearing hepatocarcinoma cell line H22 were treated with naked pVAX-sEN or liposome-DNA complex in which the dose of DNA and the ratio of DNA and liposome were different from each other. To compare the efficiency of gene transfection, expression of endostatin at the treated tumor site was assayed with ELISA. To investigate the effect of pVAX1-sEN on hepatocellular carcinoma, pVAX-sEN either naked or in liposome-DNA complex was injected into BALB/c mice bearing H22, then the diameter of tumors was measured, microvessel density was detected by immunohistochemistry, endostatin expression in vivo was assayed at different time points.

RESULTS: DNA sequencing showed the endostatin gene with the signal peptide was correctly cloned. In situ gene expression assay indicated that both the ratio of DNA and liposome and the dose of DNA could affect the gene transfection efficiency. Interestingly, naked pVAX-sEN had a similar in situ endostatin expression to pVAX-sEN with liposome. Animal experiments showed that pVAX-sEN together with pVAX-sEN-liposome complex could efficiently suppress the growth of mouse hepatoma cells.

CONCLUSION: Naked endostatin plasmid intratumoral injection can get a similar gene transfection efficiency to liposome-DNA complex when used in situ.

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.

Gene transfer vector biodistribution: pivotal safety studies in clinical gene therapy development

Techniques allowing for gene transfer vectors biodistribution investigation, in the frame of preclinical gene therapy development, are exposed. Emphasis is given on validation and test performance assessment. In the second part, specific gene vector distribution properties are reviewed (adenovirus, AAV, plasmid, retroviruses, herpes-derived vectors, germline transmission risks). The rationale for biodistribution by quantitative PCR, animal study and result interpretation is discussed. The importance and pivotal role of biodistribution study in gene transfer medicine development is shown through the determination of target organs for toxicity, germline transmission assessment and determination of risks of shedding and spreading of vectors in the gene transfer recipient and the environment.

Metabolic kinetics of foreign plasmid DNA uptake via gastrointestinal tract in mice

AIM: To analyse the changes of foreign plasmid copies in different tissues after uptake via gastrointestinal tract and to evaluate the possibility of foreign plasmid integrating on the host genome.

METHODS: Samples including lung, kidney, spleen, mesenteric lymph node, thymus, gonads, feces, duodenum, large intestine, blood and liver were obtained 1, 3, 6, 24, and 48 h and 3, 6 wk after oral administration of 200 mg plasmid pcDNA3s. PCR technique was used to detect the distribution and kinetics of plasmid in different tissues. Genomic DNA was assayed for integrated plasmid by PCR after purification of high-molecular-weight genomic DNA away from free plasmid by using gel electrophoresis.

RESULTS: Plasmid could be detected in almost all tissues 1 h after oral administration and the copies of plasmid in tissues changed with time. Foreign plasmid could be detected only in kidney and blood at sixth week time. Foreign plasmid mainly as fragment survived in vivo.

CONCLUSION: Foreign plasmid can be absorbed by gastrointestinal tract and distribute in different tissues quickly, surviving as the form of fragment. Foreign plasmid DNA probably integrates into the host genome via the gastrointestinal tract.