Biomedical subjects

R Kircheis

Publications and source records attributed to R Kircheis.

At least 19 recordsLinked to original sources

PubMed2003

Nonviral gene transfer into fetal mouse livers (a comparison between the cationic polymer PEI and naked DNA).

We investigated the efficacy and safety of the cationic polymer polyethylenimine (PEI) as a potential tool for intrauterine gene delivery into livers of fetal mice in the last trimester of pregnancy (E17.5). Using luciferase as a reporter gene, transferrin-conjugated and ligand-free PEI/DNA complexes (containing 3 microg DNA) with varying PEI-nitrogen/DNA-phosphate (N/P) ratios and different PEI forms, branched (800, 25 kDa) and linear (22 kDa), were compared with naked DNA. Transgene expression was measured 48 h after administration of PEI/DNA complexes or naked DNA. Highest luciferase activity (9.8 x 10(3) relative light units (RLU)/mg of tissue protein) was observed with ligand-free PEI22/DNA mixtures at N/P 6.0. In addition, this formulation was associated with very low toxicity as compared to the other PEI/DNA-injected groups. Using beta-galactosidase as a reporter gene, transfection of single, but also small, clusters of cells was demonstrated throughout the liver. Injection of 3 microg naked DNA resulted in an 11-fold lower transgene expression value (0.9 x 10(3) RLU/mg of tissue protein) as compared to PEI22/DNA complexes. However, the administration of higher concentrated naked DNA (9 microg) into fetal livers yielded expression levels of 3.2 x 10(4) RLU/mg of tissue protein, a more than three-fold increase compared to PEI22/DNA complexes. Furthermore, the gene transfer efficacy of concentrated naked DNA was approximately 40 times higher in fetuses than in adults (0.8 x 10(3) RLU/mg of tissue protein), indicating that fetal tissue is especially amenable to the uptake and expression of naked DNA.

3T3 Cells↗

PubMed2003

Tissue-dependent factors affect gene delivery to tumors in vivo.

Systemic application of surface-shielded transferrin-polyethylenimine/DNA complexes leads to predominant DNA uptake and gene expression in Neuro2a tumors in syngeneic A/J mice. Similarly, high expression levels were found in Huh-7 and HepG2 human tumor xenografts in SCID mice after systemic application of surface-shielded EGF-PEG-PEI/DNA complexes. Significant DNA uptake but low gene expression were found in the M-3 melanoma while no DNA uptake and no gene expression were found in KB, 518A2, A549, and SW480 xenograft tumor models. To elucidate the reasons for these differences, the tumors were analyzed for vascularization and infiltration of macrophages. Neuro2a, Huh-7, and HepG2 tumors are well vascularized, with a high density of partially immature blood vessels and low numbers of infiltrating macrophages. The M-3 melanoma is well vascularized correlating with significant DNA uptake, however, necrosis and intensive infiltration by macrophages lead to rapid degradation of DNA. In contrast, the KB, 518A2, A549, and SW480 tumors are poorly vascularized, correlating with undetectable DNA uptake and gene expression. Using two different vector systems the data indicate that gene delivery to tumors in vivo is affected by tissue-dependent factors. Uptake of DNA into the tumor depends on vascularization of the tumor, while necrosis and macrophage infiltration may facilitate degradation of the DNA.

Animals↗

PubMed2002

Tumor-targeted gene delivery: an attractive strategy to use highly active effector molecules in cancer treatment.

We have developed surface-shielded ligand-polycation based gene delivery systems which are able to target gene expression to distant tumors after systemic application. Tumor-specific targeting is achieved by (1) incorporation of cell-binding ligands; and (2) shielding of the complexes from non-specific interactions with blood components and non-target cells. Shielding of polycation/DNA complexes can be achieved by coating with either polyethylene glycol or by incorporating the ligand transferrin at high densities. Following systemic application, surface-shielded DNA complexes coding for a highly active, yet highly toxic cytokine, tumor necrosis factor-alpha (TNFalpha), localized gene expression to distant tumors, resulting in hemorrhagic tumor necrosis and inhibition of tumor growth. TNFalpha activity was confined to the tumor without systemic TNF-related toxicity. These results indicate that targeted gene delivery may be an attractive strategy to use highly potent molecules in cancer treatment.

Animals↗

PubMed2001

Design and gene delivery activity of modified polyethylenimines.

The polycation polyethylenimine (PEI) has recently been widely employed for the design of DNA delivery vehicles. Gene delivery using PEI involves condensation of DNA into compact particles, uptake into the cells, release from the endosomal compartment into the cytoplasm, and uptake of the DNA into the nucleus. Particularly for in vivo gene delivery, optimal coordination and timing between DNA complexation for protection of the DNA from nucleases and the disassembly of the complexes is essential. For in vivo application, DNA complexes have to pass a variety of anatomical and physiological barriers, and an environment of biological fluids and extracellular matrix before reaching their targets. Furthermore, targeted gene delivery is seriously hampered by non-specific interactions with non-target cells. Strategies have been developed to protect transfection complexes from non-specific interactions and to increase target specificity and gene expression.

Animals↗

PubMed2001

Functional maturation of dendritic cells by exposure to CD40L transgenic tumor cells, fibroblasts or keratinocytes.

Tumor antigen pulsed dendritic cells (DCs) can induce anti-tumor immunity. We studied strategies for the reliable generation of such a tumor vaccine by functional maturation of DCs via interaction of CD40 with its ligand (CD40L, CD154). Exposure of immature DCs to CD40L transgenic cells, soluble recombinant human CD40L molecules or lipopolysaccharide induced expression of the co-stimulatory molecules, CD80 and CD86, and supported an allogeneic mixed leukocyte reaction. In contrast, the release of IL-12, an important mediator of anti-tumor immunity, and antigen-specific expansion and IFNgamma secretion of lymphocytes, was strongly triggered only by DCs exposed to CD40L transgenic cells.

Antigens, CD↗

PubMed2001

Tumor targeting with surface-shielded ligand--polycation DNA complexes.

Incorporation of the receptor binding ligands transferrin (Tf) or epidermal growth factor (EGF) into DNA/polyethylenimine (PEI) complexes was found to enhance gene transfer into tumor cell lines in a receptor-dependent manner. In systemic applications, the surface charge of DNA complexes dominated the in vivo characteristics of gene transfer. Administration of surface-shielded Tf-polycation/DNA complexes into the tail vein of A/J mice resulted in preferential gene delivery into distantly growing subcutaneous Neuro2a tumors. In contrast, application of positively charged DNA/PEI complexes directed gene transfer primarily to the lung. Two alternatives of masking the surface charge of complexes were accomplished. In the first case, shielding was obtained by covalently coating of DNA/Tf-PEI complexes with polyethylene glycol (PEG). Alternatively, incorporation of sufficient Tf protein into the DNA complexes resulted in charge shielding even without PEGylation. In the latter case lower-molecular weight polycations (25 kDa PEI for Tf-PEI complexes, or 32 kDa polylysine for AVET complexes) were used.

Animals↗

PubMed2001

Polyethylenimine/DNA complexes shielded by transferrin target gene expression to tumors after systemic application.

Systemic application of positively charged polycation/DNA complexes has been shown to result in predominant gene expression in the lungs. Targeting gene expression to other sites, eg distant tumors, is hampered by nonspecific interactions largely due to the positive surface charge of transfection complexes. In the present study we show that the positive surface charge of PEI (25 kDa branched or 22 kDa linear)/DNA complexes can be efficiently shielded by covalently incorporating transferrin at sufficiently high densities in the complex, resulting in a dramatic decrease in nonspecific interactions, eg with erythrocytes, and decreased gene expression in the lung. Systemic application of transferrin-shielded PEI/DNA complexes into A/J mice bearing subcutaneously growing Neuro2a tumors via the tail vein resulted in preferential (100- to 500-fold higher) luciferase reporter gene expression in distant tumors as compared with the major organs including the lungs. Tumor targeting is also demonstrated by DNA uptake and beta-galactosidase gene expression in tumor cells. Assessing DNA distribution following systemic application significant amounts of DNA were found in the liver and tumor. However, in the liver, DNA was mainly taken up by Kupffer cells and degraded without significant transgene expression. In the tumor, DNA was associated mainly with tumor cells and frequently found near structures which resemble primitive blood vessels.

Animals↗

PubMed2000

Xenogenization by tetanus toxoid loading into lymphoblastoid cell lines and primary human tumor cells mediated by polycations and liposomes.

We explored the potential of the xenogenization concept as an adjuvant procedure in anti-tumor immunity. To mediate effective loading we used polyarginine (pArg) molecules of various degrees of polymerization, cationic liposomes, or chimeric molecules of transferrin (Tf) and the polycation polyethyleneimine (PEI). Tetanus toxoid (TT) was loaded onto primary human leukemia cells, culture adapted primary human neuroblastoma cells, and human lymphoblastoid cell lines (LCLs) with high efficiency by all procedures. Trypsin treatment of loaded cells provided evidence that only liposomes and Tf-PEI mediated internalization of TT. Lymphocytes primed with xenogenized LCLs and challenged with unmodified LCLs showed increased IFNgamma secretion compared with lymphocytes primed with non-xenogenized LCLs.

B-Lymphocytes↗

PubMed2000

Liposomes containing interferon-gamma as adjuvant in tumor cell vaccines.

PURPOSE: Liposomal systems may be useful as a cytokine supplement in tumor cell vaccines by providing a cytokine reservoir at the antigen presentation site. Here, we examined the effect of liposome incorporation of mIFNgamma on its potency as adjuvant in an established tumor cell vaccination protocol in the murine B16 melanoma model. Adjuvanticity of the mIFNgamma-liposomes was compared to that achieved by mIFNgamma-gene transfection of the B16 tumor cells. Furthermore, we studied whether liposomal incorporation of mIFNgamma indeed increases the residence time of the cytokine at the vaccination site. METHODS: C57B1/6 mice were immunized with i) irradiated IFNgamma-gene transfected B16 melanoma cells or ii) irradiated wild type B16 cells supplemented with (liposomal) mIFNgamma, followed by a challenge with viable B16 cells. The residence time of the (liposomal) cytokine at the subcutaneous (s.c.) vaccination site was monitored using radiolabeled mIFNgamma and liposomes. RESULTS: Immunization with irradiated tumor cells admixed with liposomal mIFNgamma generated comparable protection against B16 challenge as immunization with mIFNgamma-gene modified tumor cells. Irradiated tumor cells admixed with soluble mIFNgamma did not generate any protective responses. Radiolabeling studies indicated that free mIFNgamma rapidly cleared from the s.c. injection site. Association of [125I]-mIFNgamma with liposomes increased the local residence time substantially: liposomal association of mIFNgamma resulted in a prolonged local residence time of the cytokine as reflected by a 4-fold increase of the area under the curve. The amount of released cytokine in the optimal dose range corresponds to the amount released by the gene-transfected cells. Moderate but significant CTL-activity against B16 cells was found for mice immunized with irradiated cells supplemented with mIFNgamma-liposomes compared to untreated control animals. CONCLUSIONS: Prolonged presence of mIFNgamma at the site of antigen presentation is crucial for the generation of systemic immune responses in the B16 melanoma model. These studies show that liposomal encapsulation of cytokines is an attractive strategy for paracrine cytokine delivery in tumor vaccine development.

Adjuvants, Immunologic↗

PubMed2000

Interleukin-2 gene-modified allogeneic melanoma cell vaccines can induce cross-protection against syngeneic tumors in mice.

Vaccination using well-characterized allogeneic tumor cell lines expressing standardized doses of immunostimulatory cytokines is an attractive alternative for autologous gene-transfected tumor cell vaccines. In the present study, we show that vaccination with irradiated allogeneic K1 735 (H-2k) or B16F10 (H-2b) melanoma cells induces a moderate degree of cross-protection against the M-3 melanoma (H-2d) in DBA/2 mice. Cross-protection against the syngeneic tumor was markedly improved when the allogeneic vaccines were transfected with the interleukin-2 (IL-2) gene. The IL-2 gene-modified allogeneic vaccines were effective for prophylactic vaccination against subsequent tumor challenge and for therapeutic vaccination against pre-existing tumor deposits, with efficacies that were comparable with that of the IL-2 gene-modified syngeneic vaccines. Cross-protection correlated with the cytotoxic activity of splenocytes against M-3 targets. Allogeneic vaccination was not effective in another model, against the B16F10 melanoma in C57BL/6 mice, irrespective of genetic modification with the IL-2 or granulocyte-macrophage colony-stimulating factor genes.

Animals↗

PubMed1999

Liposomes as cytokine-supplement in tumor cell-based vaccines.

Subcutaneous vaccination of C57bl/6 mice with irradiated B16 melanoma cells supplemented with liposomal interleukin-2 (IL2) or murine interferon-gamma (mIFNgamma), resulted in systemic protection in 50% of the animals, against a subsequent tumor cell challenge in a dose dependent manner. The protective efficacy was comparable to the efficacy of cytokine gene-modified cells as tumor vaccine, whereas irradiated B16 cells supplemented with soluble cytokine did not result in protective responses. In vivo evidence was obtained that the beneficial effects mediated by liposome incorporation of the cytokine are the result of a depot function of the liposomal cytokine supplement at the vaccination site. In can be concluded that liposomal delivery of cytokines offers an attractive alternative to cytokine-gene transfection of tumor cells for therapeutic vaccination protocols.

Animals↗

PubMed1999

PEGylated DNA/transferrin-PEI complexes: reduced interaction with blood components, extended circulation in blood and potential for systemic gene delivery.

We investigated the in vitro and in vivo properties of DNA/transferrin-polyethylenimine (800 kDa) complexes before and after covalent coupling of poly(ethylene glycol) (PEG). Upon incubation with plasma, the positively charged non-PEGylated DNA complexes form aggregates. Plasma proteins such as IgM, fibrinogen, fibronectin and complement C3 were found to bind to non-PEGylated DNA complexes. At DNA concentrations relevant for in vivo gene delivery a strong aggregation of erythrocytes was also observed. PEGylation of the complexes strongly reduces plasma protein binding and erythrocyte aggregation. Furthermore, PEGylated complex size was stabilized and had a reduced surface charge. Prolonged circulation in the blood of the PEGylated complexes was also observed when injected intravenously. In tumor bearing mice, application of non-PEGylated complexes through the tail vein resulted in reporter gene expression in tail and lung, but severe toxicity was observed in some mice. In contrast, PEGylated complexes mediated reporter gene transfer to the tumor without significant toxicity.

Animals↗

PubMed1999

Development of transferrin-polycation/DNA based vectors for gene delivery to melanoma cells.

We describe the comparison of non-viral polycation transfection reagents, adenovirus-enhanced transferrinfection (AVET), polyethylenimine (PEI800) and transferrin-conjugated PEI800 (Tf-PEI800) in their ability to transfect murine and primary human melanoma cell lines. Expression of a reporter gene, cell surface marker and secreted protein (interleukin-2) was assessed for each vector system. Testing for luciferase reporter gene expression in murine and primary human cell lines, AVET and Tf-PEI800, both showed high levels of expression and comparable activity. Furthermore, when the melanoma cell line B16F10 was transfected with a cell surface marker up to approximately 97% of the cells expressed the protein on the cell surface. Assessing the levels of secreted IL-2 in murine cell lines, AVET/IL-2, Tf-PEI800/IL-2 and PEI800/IL-2 all expressed high levels of the cytokine (up to 20 microg IL-2/10(6) cells/24 h). In primary human melanoma cell lines, AVET/IL-2 transfected cells secreted more IL-2 than cells transfected with either Tf-PEI800/IL-2 or PEI800/IL-2. In murine melanoma cell culture experiments, positively charged PEI800/DNA and Tf-PEI800/DNA complexes gave similar transfection efficiencies. However, when subcutaneous tumors in mice were injected with the luciferase reporter gene complexed with either Tf-PEI800 or AVET, higher transfection activity was measured in the tumors as compared to ligand free PEI800/DNA complexes.

Adenoviridae↗

PubMed1998

Increase of proliferation rate and enhancement of antitumor cytotoxicity of expanded human CD3+ CD56+ immunologic effector cells by receptor-mediated transfection with the interleukin-7 gene.

Cytokine-induced killer (CIK) cells have been shown to eradicate established tumors in a SCID mouse-human lymphoma model. CIK cells depend on exogenous addition of cytokines such as interleukin-2 (IL-2), interleukin-7 (IL-7) or interleukin-12 (IL-12) for proliferation. In this study, we used the adenovirus-enhanced CD3 receptor-mediated gene transfer for transfection with the IL-7 gene. An episomally replicating plasmid was used containing cDNA of the human IL-7 gene under the control of a CMV promoter for transfection of CIK cells. Biosynthesis of IL-7 was demonstrated by RT-PCR, an enzyme-linked immunosorbent assay (ELISA) and using a bioassay. Transfected cells produced IL-7 in the range between 200 and 1100 pg/10(6) cells in 24 h. IL-7 was shown to be biologically active, since transfected CIK cells showed an improved proliferation rate as compared with nontransfected cells. Expression of IL-7 altered the secretion of other cytokines by CIK cells, in particular the production of TNF alpha increased after transfection. In contrast, nontransfected CIK cells fed with IL-7 showed no increase in TNF alpha secretion. No significant differences were found in expression of surface antigens linked to the cytotoxic activity of CIK cells. Cytotoxic activity against various tumor cell lines (eg renal cell carcinoma, malignant melanoma and colon carcinoma) was tested. Transfected cells possessed a significantly higher cytotoxic activity as compared with nontransfected cells. Receptor-mediated gene transfer effectively delivers expression plasmids for therapeutic genes into CIK cells and CIK cells transfected with an IL-7 gene expression construct may be valuable for adoptive immunotherapy.

Adenoviridae↗

PubMed1998

The size of DNA/transferrin-PEI complexes is an important factor for gene expression in cultured cells.

Under physiological salt concentration, plasmid DNA complexed with transferrin-conjugated or unmodified polyethylenimine (PEI, 800 kDa) forms huge (up to > 1000 nm) aggregates, unless the individual components are mixed at a highly positive nitrogen/phosphate (N/P) charge ratio. At low ionic strengths, however, small particles with an average size of 40 nm are formed over a broad range of N/P ratios. Interestingly, in transfection experiments these small particles result in a 10-fold (B16F10 cells) to more than 100-fold (Neuro2A cells, K562 cells) reduced luciferase gene expression efficiency in comparison to the large complexes formed in physiological salt solutions. Limited transport of the small particles to the cell surfaces is one possible reason for this effect. Application of the small particles in more concentrated form and over extended periods of time improves transfection activity. Reduced intracellular release may be another explanation for the decreased transfection efficiency; incubation with chloroquine or incorporation of the endosomolytic peptide INF5 into the small complexes enhances gene expression approximately 10-fold. Analysis of gene expression at the cellular level using a green fluorescence protein reporter gene and flow cytometry revealed that the differences in overall gene expression largely result from different intensities per expressing cell, while the difference in the percentage of expressing cells is less substantial.

Animals↗

PubMed1998

Cytokine gene-modified tumor cells for prophylactic and therapeutic vaccination: IL-2, IFN-gamma, or combination IL-2 + IFN-gamma.

Murine melanoma cells were engineered to express interleukin-2 (IL-2), interferon-gamma (IFN-gamma) or both cytokines at various dose levels by means of the adenovirus-enhanced transferrinfection (AVET) method. The gene-modified cells were tested for their potency to induce an antitumor immune response in two experimental settings with different tumor load. In a prophylactic vaccination model, both IL-2 and IFN-gamma showed a dose-dependent protection against tumor cell challenge in two melanoma models. In the therapeutic vaccination model, where mice with measurable tumors were treated, immunization with IL-2 or IFN-gamma gene-modified cells led to complete tumor regression in 30% or 20% of the tumor-bearing animals respectively. The combination of IL-2 + IFN-gamma resulted in complete tumor regression in up to 50% of the tumor-bearing mice.

Animals↗

PubMed1998

Sustained cytokine delivery for anticancer vaccination: liposomes as alternative for gene-transfected tumor cells.

Vaccination with tumor cells genetically engineered to produce interleukin (IL)-2 is an attractive strategy to enhance antitumor immune responses. The improved antitumor immunity upon vaccination with IL-2 gene-modified tumor cells may be due to the prolonged presence of the cytokine at the vaccination site. Because liposomes have been used for sustained delivery of a variety of agents, we compared the protective effect of vaccines consisting of IL-2 gene-modified B16 melanoma cells to that of vaccines composed of IL-2 liposomes and irradiated melanoma cells. The results indicate that both approaches equally protect against a lethal challenge with B16 melanoma cells. More than 20% of the protected animals developed vitiligo at the vaccination and/or tumor challenge site.

Animals↗

PubMed1997

Lymphocyte apoptosis: induction by gene transfer techniques.

Efficient gene transfer of lymphocytes has been shown to be extremely difficult. The molecular background for this gene transfer resistance is not completely understood. We reasoned that apoptosis may play a role in this gene transfer resistance of lymphocytes. We show that transfection of lymphocytes via nonviral vectors leads to induction of apoptosis in a significant proportion of cells. Since apoptosis may be mediated via the TNF alpha and TNF alpha receptor pathway, we studied the amount of TNF secreted by transfected lymphocytes. The percentage of apoptotic lymphocytes correlated well with TNF alpha secretion. TNF secretion was dependent on the gene transfection method used. High amounts of TNF secretion were detected using receptor-mediated gene transfer and lipofection. In contrast, only low amounts of TNF were detected after electroporation and retroviral gene transfer. In receptor-mediated gene transfer, TNF secretion was due to the use of anti-CD3 antibody. Induction of apoptosis and increase in necrosis was blocked using an anti-TNF antibody. This blockage led to a significant increase in the proliferation rate of lymphocytes transfected with the interleukin-2 or interleukin-7 gene. In conclusion, gene transfer techniques led to TNF secretion, apoptosis and necrosis of lymphocytes. This could be blocked using an anti-TNF antibody. Blockage of apoptosis after gene transfer should have an impact on the use of lymphocytes transfected with cytokine genes as immunologic effector cells in cancer gene therapy protocols.

Antibodies, Monoclonal↗