Biomedical subjects

Ralf Kircheis

Publications and source records attributed to Ralf Kircheis.

6 recordsLinked to original sources

PubMed2004

Targeted nucleic acid delivery into tumors: new avenues for cancer therapy.

Unique properties of tumors, such as abnormalities in the cell cycle and apoptosis, migration and metastasis, neoangiogenesis or unique antigen profiles are targets for therapeutic anti-cancer strategies. Beyond the selection of such strategies, additional specificity for the targeted tumor tissue can be accomplished in cancer gene therapy in several ways. Upon systemic administration, appropriately packaged therapeutic nucleic acid may be preferentially transported into the tumor tissue (targeted delivery); formulation can mediate the intracellular uptake of the nucleic acid into the nucleus of target cells only (transductional targeting); and/or the use of specific promotor/enhancer elements can restrict transcription of therapeutic genes to the target cells only (transcriptional targeting). Options for physical and biological targeting of nucleic acid formulations into tumors and therapeutic approaches are reviewed.

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PubMed2003

Tumor-targeted gene therapy: strategies for the preparation of ligand-polyethylene glycol-polyethylenimine/DNA complexes.

Surface-shielded DNA delivery systems have been synthesized with virus-like characteristics that target gene expression into distant tumor tissues. Polyethylenimine (PEI)/DNA complexes ('polyplexes') conjugated with the cell-binding ligand transferrin (Tf) or epidermal growth factor (EGF) were used to achieve receptor-mediated endocytosis. The surface charge of the complexes was masked by covalently linking PEI to polyethylene glycol (PEG). Three alternatives for generating these surface-shielded formulations were utilized, attaching ligand and PEG molecules to PEI either before or after DNA complex formation. The stabilized formulations could be ultra-concentrated, stored frozen, and applied systemically after thawing. Intravenous injection of Tf-PEG-coated polyplexes resulted in gene transfer to subcutaneous Neuro2a neuroblastoma tumors of syngeneic A/J mice; EGF-PEG-coated polyplexes were intravenously applied for targeting human hepatocellular carcinoma xenografts in SCID mice. In these models, luciferase marker gene expression levels in tumor tissues were 10- to 100-fold higher than in other organ tissues. Repeated systemic application of Tf-PEG-PEI/DNA complexes encoding tumor necrosis factor alpha (TNF-alpha) into tumor-bearing mice induced tumor necrosis and inhibition of tumor growth in three murine tumor models of different tissue origin (Neuro2a, M-3 or B16 melanoma).

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PubMed2003

Technology evaluation: TNFerade, GenVec.

TNFerade is a new gene therapy drug under development by GenVec that employs a replication-deficient adenovector carrying the gene for human tumor necrosis factor (TNF)-alpha, regulated by a radiation-sensitive promoter. TNFerade is currently undergoing phase II trials for the potential treatment of cancer.

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PubMed2002

Tumor-targeted gene delivery of tumor necrosis factor-alpha induces tumor necrosis and tumor regression without systemic toxicity.

We have recently developed surface-shielded transferrin-polyethylenimine (Tf-PEI)/DNA delivery systems that target reporter gene expression to distant tumors after systemic application. In the present study, we used surface-shielded Tf-PEI/DNA complexes for delivering the gene for a highly potent cytokine, tumor necrosis factor-alpha (TNFalpha). TNFalpha is known for its ability to induce hemorrhagic tumor necrosis and tumor regression. However, the therapeutic application of TNFalpha is hampered by its high systemic toxicity dictating the need to target TNFalpha activity to the tumor. Systemic application of surface-shielded Tf-PEI complexes with the TNFalpha gene resulted in preferential expression of TNFalpha in the tumor without detectable TNFalpha serum levels, in contrast to the application of nontargeted complexes. Tumor-targeted TNFalpha gene delivery induced pronounced hemorrhagic tumor necrosis and inhibition of tumor growth in three murine tumor models of different tissue origins, Neuro2a neuroblastoma, MethA fibrosarcoma, and M-3 melanoma, with complete tumor regressions observed in the MethA model. No systemic TNF-related toxicity was observed due to the localization of the TNFalpha activity to the tumor. Targeted gene therapy may be an attractive strategy applicable to highly active, yet toxic, molecules such as TNFalpha.

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PubMed2002

Specific systemic nonviral gene delivery to human hepatocellular carcinoma xenografts in SCID mice.

Systemic tumor-targeted gene delivery is attracting increasing attention as a promising alternative to conventional therapeutical strategies. To be considered as a viable option, however, the respective transgene has to be administered with high tumor specificity. Here, we describe novel polyethylenimine (PEI)-based DNA complexes, shielded by covalent attachment of polyethylene glycol (PEG), that make use of epidermal growth factor (EGF) as a ligand for targeting gene delivery to EGF receptor-expressing human hepatocellular carcinoma (HCC) cells. In vitro transfection of luciferase reporter DNA resulted in high levels of gene expression in the human HCC cell lines Huh-7 and HepG2. An excess of free EGF during transfection clearly reduced expression levels, indicating a specific EGF receptor-mediated uptake of the DNA particles. Following intravenous injection into human HCC xenograft-bearing SCID mice, luciferase expression was predominantly found in the tumor, with levels up to 2 logs higher than in the liver, which was the highest expressing major organ. Histologic investigation showed reporter gene expression (beta-galactosidase) localized to tumor cells. Assessing DNA distribution within the tumor by immunofluorescence microscopy, rhodamine-labelled transgene DNA was found to be mainly associated with HCC cells. In the liver, DNA was taken up almost exclusively by Kupffer cells and, as indicated by the low expression, subsequently degraded. In conclusion, we have shown that intravenous injection of PEGylated EGF-containing DNA/PEI complexes allows for highly specific expression of a transgene in human HCC tumors.

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PubMedDate not supplied

Novel shielded transferrin-polyethylene glycol-polyethylenimine/DNA complexes for systemic tumor-targeted gene transfer.

Tumor-targeting DNA complexes which can readily be generated by the mixing of stable components and freeze-thawed would be very advantageous for their subsequent application as medical products. Complexes were generated by the mixing of plasmid DNA, linear polyethylenimine (PEI22, 22 kDa) as the main DNA condensing agent, PEG-PEI (poly(ethylene glycol)-conjugated PEI) for surface shielding, and Tf-PEG-PEI (transferrin-PEG-PEI) to provide a ligand for receptor-mediated cell uptake. Within the shielding conjugates, PEG chains of varying size (5, 20, or 40 kDa) were conjugated with either linear PEI22 (22 kDa) or branched PEI25 (25 kDa). The three polymer components were mixed together at various ratios with DNA; particle size, surface charge, in vitro transfection activity, and systemic gene delivery to tumors was investigated. In general, increasing the proportion of shielding conjugate in the complex reduced surface charge, particle size, and in vitro transfection efficiency in transferrin receptor-rich K562 cells. The particle size or surface charge of the complexes containing the PEG-PEI conjugate did not significantly change after freeze-thawing, while complexes without the shielding conjugate aggregated. Complexes containing PEG-PEI conjugate efficiently transfected K562 cells after freeze-thawing. Furthermore the systemic application of freeze-thawed complexes exhibited in vivo tumor targeted expression. For complexes containing the luciferase reporter gene the highest expression was found in tumor tissue of mice. An optimum formulation for in vivo application, PEI22/Tf-PEG-PEI/PEI22-PEG5, containing plasmid DNA encoding for the tumor necrosis factor (TNF-alpha), inhibited tumor growth in three different murine tumor models. These new DNA complexes offer simplicity and convenience, with tumor targeting activity in vivo after freeze-thawing.

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