Control of cell penetration enhancer shielding and endosomal escape-kinetics crucial for efficient and biocompatible siRNA delivery

Although cationic liposomes are efficient carriers for nucleic acid delivery, their toxicity often hampers the clinical translation. Polyethylene glycol (PEG) coating has been largely used to improve their stability and reduce toxicity. Nevertheless, it has been found to decrease the transfection process. In order to exploit the advantages of cationic liposomes and PEG decoration for nucleic acid delivery, liposomes decorated with tetraArg-[G-1]-distearoyl glycerol (Arg4-DAG) dendronic oligo-cationic lipid enhancer (OCE) and PEG-lipid have been investigated. Non decorated or OCE-decorated lipoplexes (OCEfree-LPX and OCE-LPX, respectively) were obtained by lipid film hydration using oligonucleotide (ON) solutions. PEG and OCE/PEG decorated lipoplexes (PEG-OCEfree-LPX and PEG-OCE-LPX, respectively) were obtained by post-insertion of 2 or 5 kDa PEG-DSPE on preformed lipoplexes. The OCE decoration yielded lipoplexes with size of about 240 nm, 84% loading efficiency at 10 N/P ratio, ten times higher than OCEfree-LPX, and prevented the ON release when incubated with physiological heparin concentration or with plasma. The PEG decoration reduced the zeta potential, enhanced the lipoplex stability in serum and decreased both hemolysis and cytotoxicity, while it did not affect the lipoplex size and ON loading. With respect to OCEfree-LPX, the OCE-LPX remarkably associated with cells and were taken up by different cancer cell lines (HeLa and MDA-MB-231). Interestingly, 2 or 5 kDa PEG decoration did not reduce either the cell interaction or the cell up-take of the cationic lipoplexes. With siRNA as a payload, OCE enabled efficient internalization, but endosomal release was hampered. Post-transfection treatment with the lysosomotropic drug chloroquine allowed to identify the optimal time point for endosomal escape. Chloroquine treatment after 12 to 20 h of LPX pre-incubation enabled siRNA mediated target knockdown indicating that this is the time window of endo-lysosomal processing. This indicates that OCE can protect siRNA from lysosomal degradation for up to 20 h, as shown by these rescue experiments.

Degradable Bottlebrush Polypeptides and the Impact of their Architecture on Cell Uptake, Pharmacokinetics, and Biodistribution In Vivo

Bottlebrush polymers are highly promising as unimolecular nanomedicines due to their unique control over the critical parameters of size, shape and chemical function. However, since they are prepared from biopersistent carbon backbones, most known bottlebrush polymers are non-degradable and thus unsuitable for systemic therapeutic administration. Herein, we report the design and synthesis of novel poly(organo)phosphazene-g-poly(α-glutamate) (PPz-g-PGA) bottlebrush polymers with exceptional control over their structure and molecular dimensions (Dh ≈ 15-50 nm). These single macromolecules show outstanding aqueous solubility, ultra-high multivalency and biodegradability, making them ideal as nanomedicines. While well-established in polymer therapeutics, it has hitherto not been possible to prepare defined single macromolecules of PGA in these nanosized dimensions. A direct correlation was observed between the macromolecular dimensions of the bottlebrush polymers and their intracellular uptake in CT26 colon cancer cells. Furthermore, the bottlebrush macromolecular structure visibly enhanced the pharmacokinetics by reducing renal clearance and extending plasma half-lives. Real-time analysis of the biodistribution dynamics showed architecture-driven organ distribution and enhanced tumor accumulation. This work, therefore, introduces a robust, controlled synthesis route to bottlebrush polypeptides, overcoming limitations of current polymer-based nanomedicines and, in doing so, offers valuable insights into the influence of architecture on the in vivo performance of nanomedicines.

A Comparison of the Impact of Restrictive Diets on the Gastrointestinal Tract of Mice

The rate of gut inflammatory diseases is growing in modern society. Previously, we showed that caloric restriction (CR) shapes gut microbiota composition and diminishes the expression of inflammatory factors along the gastrointestinal (GI) tract. The current project aimed to assess whether prominent dietary restrictive approaches, including intermittent fasting (IF), fasting-mimicking diet (FMD), and ketogenic diet (KD) have a similar effect as CR. We sought to verify which of the restrictive dietary approaches is the most potent and if the molecular pathways responsible for the impact of the diets overlap. We characterized the impact of the diets in the context of several dietary restriction-related parameters, including immune status in the GI tract; microbiota and its metabolites; bile acids (BAs); gut morphology; as well as autophagy-, mitochondria-, and energy restriction-related parameters. The effects of the various diets are very similar, particularly between CR, IF, and FMD. The occurrence of a 50 kDa truncated form of occludin, the composition of the microbiota, and BAs distinguished KD from the other diets. Based on the results, we were able to provide a comprehensive picture of the impact of restrictive diets on the gut, indicating that restrictive protocols aimed at improving gut health may be interchangeable.

Investigating 3R In Vivo Approaches for Bio-Distribution and Efficacy Evaluation of Nucleic Acid Nanocarriers: Studies on Peptide-Mimicking Ionizable Lipid

Formulations based on ionizable amino-lipids have been put into focus as nucleic acid delivery systems. Recently, the in vitro efficacy of the lipid formulation OH4:DOPE has been explored. However, in vitro performance of nanomedicines cannot correctly predict in vivo efficacy, thereby considerably limiting pre-clinical translation. This is further exacerbated by limited access to mammalian models. The present work proposes to close this gap by investigating in vivo nucleic acid delivery within simpler models, but which still offers physiologically complex environments and also adheres to the 3R guidelines (replace/reduce/refine) to improve animal experiments. The efficacy of OH4:DOPE as a delivery system for nucleic acids is demonstrated using in vivo approaches. It is shown that the formulation is able to transfect complex tissues using the chicken chorioallantoic membrane model. The efficacy of DNA and mRNA lipoplexes is tested extensively in the zebra fish (Danio rerio) embryo which allows the screening of biodistribution and transfection efficiency. Effective transfection of blood vessel endothelial cells is seen, especially in the endocardium. Both model systems allow an efficacy screening according to the 3R guidelines bypassing the in vitro-in vivo gap. Pilot studies in mice are performed to correlate the efficacy of in vivo transfection.

Endothelial Retargeting of AAV9 In Vivo

Adeno-associated viruses (AAVs) are frequently used for gene transfer and gene editing in vivo, except for endothelial cells, which are remarkably resistant to unmodified AAV-transduction. AAVs are retargeted here toward endothelial cells by coating with second-generation polyamidoamine dendrimers (G2) linked to endothelial-affine peptides (CNN). G2CNN AAV9-Cre (encoding Cre recombinase) are injected into mTmG-mice or mTmG-pigs, cell-specifically converting red to green fluorescence upon Cre-activity. Three endothelial-specific functions are assessed: in vivo quantification of adherent leukocytes after systemic injection of - G2CNN AAV9 encoding 1) an artificial adhesion molecule (S1FG) in wildtype mice (day 10) or 2) anti-inflammatory Annexin A1 (Anxa1) in ApoE-/- mice (day 28). Moreover, 3) in Cas9-transgenic mice, blood pressure is monitored till day 56 after systemic application of G2CNN AAV9-gRNAs, targeting exons 6-10 of endothelial nitric oxide synthase (eNOS), a vasodilatory enzyme. G2CNN AAV9-Cre transduces microvascular endothelial cells in mTmG-mice or mTmG-pigs. Functionally, G2CNN AAV9-S1FG mediates S1FG-leukocyte adhesion, whereas G2CNN AAV9-Anxa1-application reduces long-term leukocyte recruitment. Moreover, blood pressure increases in Cas9-expressing mice subjected to G2CNN AAV9-gRNAeNOS . Therefore, G2CNN AAV9 may enable gene transfer in vascular and atherosclerosis models.

CD47-targeted cancer immunogene therapy: Secreted SIRPα-Fc fusion protein eradicates tumors by macrophage and NK cell activation

CD47 protects healthy cells from macrophage attack by binding to signal regulatory protein α (SIRPα), while its upregulation in cancer prevents immune clearance. Systemic treatment with CD47 antibodies requires a weakened Fc-mediated effector function or lower CD47-binding affinity to prevent side effects. Our approach combines “the best of both worlds,” i.e., maximized CD47 binding and full Fc-mediated immune activity, by exploiting gene therapy for paracrine release. We developed a plasmid vector encoding for the secreted fusion protein sCV1-hIgG1, comprising highly efficient CD47-blocking moiety CV1 and Fc domain of human immunoglobulin G1 (IgG1) with maximized immune activation. sCV1-hIgG1 exhibited a potent bystander effect, blocking CD47 on all cells via fusion protein secreted from only a fraction of cells or when transferring transfection supernatant to untransfected cells. The CpG-free plasmid ensured sustained secretion of sCV1-hIgG1. In orthotopic human triple-negative breast cancer in CB17-severe combined immunodeficiency (SCID) mice, ex vivo transfection significantly delayed tumor growth and eradicated one-third of tumors. In intratumoral transfection experiments, CD47 blockage and increased migration of macrophages into the tumor were observed within 17 h of a single injection. Natural killer (NK) cell-mediated lysis of sCV1-hIgG1-expressing cells was demonstrated in vitro. Taken together, this approach also opens the opportunity to block, in principle, any immune checkpoints.

Surface Modification of E. coli Outer Membrane Vesicles with Glycosylphosphatidylinositol-Anchored Proteins: Generating Pro/Eukaryote Chimera Constructs

Extracellular vesicles produced by different types of cells have recently attracted great attention, not only for their role in physiology and pathology, but also because of the emerging applications in gene therapy, vaccine production and diagnostics. Less well known than their eukaryotic counterpart, also bacteria produce extracellular vesicles, in the case of the Gram-negative E. coli the main species is termed outer membrane vesicles (OMVs). In this study, we show for the first time the functional surface modification of E. coli OMVs with glycosylphosphatidylinositol (GPI)-anchored protein, exploiting a process variably described as molecular painting or protein engineering in eukaryotic membranes, whereby the lipid part of the GPI anchor inserts in cell membranes. By transferring the process to bacterial vesicles, we can generate a hybrid of perfectly eukaryotic proteins (in terms of folding and post-translational modifications) on a prokaryotic platform. We could demonstrate that two different GPI proteins can be displayed on the same OMV. In addition to fluorescent marker proteins, cytokines, growth factors and antigens canb be potentially transferred, generating a versatile modular platform for a novel vaccine strategy.

Combined Chemisorption and Complexation Generate siRNA Nanocarriers with Biophysics Optimized for Efficient Gene Knockdown and Air-Blood Barrier Crossing

Current nucleic acid (NA) nanotherapeutic approaches face challenges because of shortcomings such as limited control on loading efficiency, complex formulation procedure involving purification steps, low load of NA cargo per nanoparticle, endosomal trapping, and hampered release inside the cell. When combined, these factors significantly limit the amount of biologically active NA delivered per cell in vitro, delivered dosages in vivo for a prolonged biological effect, and the upscalability potential, thereby warranting early consideration in the design and developmental phase. Here, we report a versatile nanotherapeutic platform, termed auropolyplexes, for improved and efficient delivery of small interfering RNA (siRNA). Semitelechelic, thiolated linear polyethylenimine (PEI) was chemisorbed onto gold nanoparticles to endow them with positive charge. A simple two-step complexation method offers tunable loading of siRNA at concentrations relevant for in vivo studies and the flexibility for inclusion of multiple functionalities without any purification steps. SiRNA was electrostatically complexed with these cationic gold nanoparticles and further condensed with polycation or polyethyleneglycol-polycation conjugates. The resulting auropolyplexes ensured complete complexation of siRNA into nanoparticles with a high load of ∼15,500 siRNA molecules/nanoparticle. After efficient internalization into the tumor cell, an 80% knockdown of the luciferase reporter gene was achieved. Auropolyplexes were applied intratracheally in Balb/c mice for pulmonary delivery, and their biodistribution were studied spatio-temporally and quantitatively by optical tomography. Auropolyplexes were well tolerated with ∼25% of the siRNA dose remaining in the lungs after 24 h. Importantly, siRNA was released from auropolyplexes in vivo and a fraction also crossed the air-blood barrier, which was then excreted via kidneys, whereas >97% of gold nanoparticles were retained in the lung. Linear PEI-based auropolyplexes offer a combination of successful endosomal escape and better biocompatibility profile in vivo. Taken together, combined chemisorption and complexation endow auropolyplexes with crucial biophysical attributes, enabling a versatile and upscalable nanogold-based platform for siRNA delivery in vitro and in vivo.

Luminescent and fluorescent triple reporter plasmid constructs for Wnt, Hedgehog and Notch pathway

Tracking the activity of signalling pathways is a fundamental method for basic science, as well as in cancer- and pharmaceutical research. The developmental pathways Wnt, Hedgehog and Notch are frequently deregulated in cancers and represent a valuable target for the discovery of novel anticancer compounds. Here we present reporter systems for tracking activity of these pathways by using specific promoter elements driving the expression of either sensitive luciferases or fluorescent proteins. A high level of sensitivity was obtained using the luciferase reporter genes for firefly (FLuc), secreted Gaussia (GLuc) and synthetic NanoLuc (NLuc). As fluorescent reporter proteins, mTurqouise2, tdTomato and iRFP720 were chosen. Specificity of pathway activity was validated by co-transfection with pathway activating genes, showing significant response to induction. In addition, multi-gene plasmids were cloned, allowing the detection of all three pathways by one vector. By using the multi-gene vector 3P-Luc (wnt-NLuc, hedgehog-FLuc, Notch-GLuc), we could unambiguously demonstrate the crosstalk between pathways, while excluding cross reactivity of luciferase substrates. First studies with synthetic compounds confirmed the applicability of the system for future drug screening approaches.

Peptide-Targeted Polyplexes for Aerosol-Mediated Gene Delivery to CD49f-Overexpressing Tumor Lesions in Lung

Peptide ligands can enhance delivery of nucleic acid-loaded nanoparticles to tumors by promoting their cell binding and internalization. Lung tumor lesions accessible from the alveolar side can be transfected, in principle, using gene vectors delivered as an aerosol. The cell surface marker CD49f (Integrin α6) is frequently upregulated in metastasizing, highly aggressive tumors. In this study, we utilize a CD49f binding peptide coupled to linear polyethylenimine (LPEI) promoting gene delivery into CD49f-overexpressing tumor cells in vitro and into lung lesions in vivo. We have synthesized a molecular conjugate based on LPEI covalently attached to the CD49f binding peptide CYESIKVAVS via a polyethylene glycol (PEG) spacer. Particles formed with plasmid DNA were small (<200 nm) and could be aerosolized without causing major aggregation or particle loss. In vitro, CD49f targeting significantly improved plasmid uptake and reporter gene expression on both human and murine tumor cell lines. For evaluation in vivo, localization and morphology of 4T1 murine triple-negative breast cancer tumor lesions in the lung of syngeneic BALB/c mice were identified by MRI. Polyplexes applied via intratracheal aerosolization were well tolerated and resulted in measurable transgene activity of the reporter gene firefly luciferase in tumor areas by bioluminescence imaging (BLI). Transfectability of tumors correlated with their accessibility for the aerosol. With CD49f-targeted polyplexes, luciferase activity was considerably increased and was restricted to the tumor area.

Mechanistic profiling of the release kinetics of siRNA from lipidoid-polymer hybrid nanoparticles in vitro and in vivo after pulmonary administration

Understanding the release kinetics of siRNA from nanocarriers, their cellular uptake, their in vivo biodistribution and pharmacokinetics is a fundamental prerequisite for efficient optimisation of the design of nanocarriers for siRNA-based therapeutics. Thus, we investigated the influence of composition on the siRNA release from lipid-polymer hybrid nanoparticles (LPNs) consisting of cationic lipidoid 5 (L₅) and poly(DL-lactic-co-glycolic acid) (PLGA) intended for pulmonary administration. An array of siRNA-loaded LPNs was prepared by systematic variation of: (i) the L₅ content (10-20%, w/w), and (ii) the L₅:siRNA ratio (10,1-30:1, w/w). For comparative purposes, L₅-based lipoplexes, L₅-based stable nucleic acid lipid nanoparticles (SNALPs). and dioleoyltrimethylammoniumpropane (DOTAP)-modified LPNs loaded with siRNA were also prepared. Release studies in buffer and lung surfactant-containing medium showed that siRNA release is dependent on the presence of both surfactant and heparin (a displacing agent) in the release medium, since these interact with the lipid shell structure thereby facilitating decomplexation of L₅ and siRNA, as evident from the retarded siRNA release when the L₅ content and the L₅:siRNA ratio were increased. This confirms the hypothesis that siRNA loaded in LPNs is predominantly present as complexes with the cationic lipid and primarily is located near the particle surface. Cellular uptake and tolerability studies in the human macrophage cell line THP-1 and the type I-like human alveolar epithelial cell line hAELVi, which together represents a monolayer-based barrier model of lung epithelium, indicated that uptake of LPNs was much higher in THP-1 cells in agreement with their primary clearance role. In vivo biodistributions of formulations loaded with Alexa Fluor® 750-labelled siRNA after pulmonary administration in mice were compared by using quantitative fluorescence imaging tomography. The L₅-modified LPNs, SNALPs and DOTAP-modified LPNs displayed significantly increased lung retention of siRNA as compared to L₅-based lipoplexes, which had a biodistribution profile comparable to that of non-loaded siRNA, for which >50% of the siRNA dose permeated the air-blood barrier within 6 h and subsequently was excreted via the kidneys. Hence, the enhanced lung retention upon pulmonary administration of siRNA-loaded LPNs represents a promising characteristic that can be used to control the delivery of the siRNA cargo to lung tissue for local management of disease.

Combination of Hypoglycemia and Metformin Impairs Tumor Metabolic Plasticity and Growth by Modulating the PP2A-GSK3β-MCL-1 Axis

Tumor cells may adapt to metabolic challenges by alternating between glycolysis and oxidative phosphorylation (OXPHOS). To target this metabolic plasticity, we combined intermittent fasting, a clinically feasible approach to reduce glucose availability, with the OXPHOS inhibitor metformin. In mice exposed to 24-h feeding/fasting cycles, metformin impaired tumor growth only when administered during fasting-induced hypoglycemia. Synergistic anti-neoplastic effects of the metformin/hypoglycemia combination were mediated by glycogen synthase kinase 3β (GSK3β) activation downstream of PP2A, leading to a decline in the pro-survival protein MCL-1, and cell death. Mechanistically, specific activation of the PP2A-GSK3β axis was the sum of metformin-induced inhibition of CIP2A, a PP2A suppressor, and of upregulation of the PP2A regulatory subunit B56δ by low glucose, leading to an active PP2A-B56δ complex with high affinity toward GSK3β.

Synthesis of Polyethylenimine-Based Nanocarriers for Systemic Tumor Targeting of Nucleic Acids

Nucleic acid-based therapies offer the option to treat tumors in a highly selective way, while toxicity towards healthy tissue can be avoided when proper delivery vehicles are used. We have recently developed carrier systems based on linear polyethylenimine, which after chemical coupling of protein- or peptide-based ligands can form nanosized polyplexes with plasmid DNA (pDNA) or RNA and deliver their payload into target cells by receptor-mediated endocytosis. This chapter describes the synthesis of LPEI from a precursor polymer and the current coupling techniques and purification procedure for peptide conjugates with linear polyethylenimine. A protocol is also given for the formation and characterization of polyplexes formed with LPEI conjugate and pDNA.

Firefly Luciferase-Based Reporter Gene Assay for Investigating Nanoparticle-Mediated Nucleic Acid Delivery

Investigation of nanoparticle-mediated nucleic acid delivery is a key step for the development of nucleic acid-based nanotherapeutics. Using luciferases as reporter genes, the efficiency of gene delivery can be quantified in a highly sensitive way based on bioluminescence measurements. Here we describe a robust assay to quantify the activity of exogenously produced firefly luciferase and its normalization by the total protein amount (bicinchoninic acid assay, BCA) in the cells. The method describes preparation of firefly luciferase assay buffer (F-LAB) along with BCA assay and employment of the optimized firefly luciferase assay for investigating in vitro gene delivery by polyplex and lipoplex nanoparticles. Reusability of F-LAB for ease of usage (by freezing and reusing it for luciferase assay) is also demonstrated.

Systemic tumor-targeted sodium iodide symporter (NIS) gene therapy of hepatocellular carcinoma mediated by B6 peptide polyplexes

BACKGROUND

Nonviral polymer-based gene transfer represents an adaptable system for tumor-targeted gene therapy because various design strategies of shuttle systems, together with the mechanistic concept of active tumor targeting, lead to improved gene delivery vectors resulting in higher tumor specificity, efficacy and safety.

METHODS

Using the sodium iodide symporter (NIS) as a theranostic gene, nonviral gene delivery vehicles based on linear polyethylenimine (LPEI), polyethylene glycol (PEG) and coupled to the synthetic peptide B6 (LPEI-PEG-B6), which specifically binds to tumor cells, were investigated in a hepatocellular carcinoma xenograft model for tumor selectivity and transduction efficiency.

RESULTS

In vitro incubation of three different tumor cell lines with LPEI-PEG-B6/NIS resulted in significant increase in iodide uptake activity compared to untargeted and empty vectors. After establishment of subcutaneous HuH7 tumors, NIS-conjugated nanoparticles were injected intravenously followed by analysis of radioiodide biodistribution using ¹²³ I-scintigraphy showing significant perchlorate-sensitive iodide accumulation in tumors of LPEI-PEG-B6/NIS-treated mice (8.0 ± 1.5% ID/g ¹²³ I; biological half-life of 4 h). After four cycles of repetitive polyplex/¹³¹ I applications, a significant delay of tumor growth was observed, which was associated with markedly improved survival in the therapy group.

CONCLUSIONS

These results clearly demonstrate that systemic in vivo NIS gene transfer using nanoparticle vectors coupled to B6 tumor targeting ligand is capable of inducing tumor-specific radioiodide uptake. This promising gene therapy approach opens the exciting prospect of NIS-mediated radionuclide therapy in metastatic cancer, together with the possibility of combining several targeting ligands to enhance selective therapeutic efficacy in a broad field of cancer types with various receptor expression profiles.

Bacterial ghosts as adjuvant to oxaliplatin chemotherapy in colorectal carcinomatosis

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers and a major cause of cancer mortality worldwide. At late stage of the disease CRC often shows (multiple) metastatic lesions in the peritoneal cavity which cannot be efficiently targeted by systemic chemotherapy. This is one major factor contributing to poor prognosis. Oxaliplatin is one of the most commonly used systemic treatment options for advanced CRC. However, drug resistance - often due to insufficient drug delivery - is still hampering successful treatment. The anticancer activity of oxaliplatin includes besides DNA damage also a strong immunogenic component. Consequently, the aim of this study was to investigate the effect of bacterial ghosts (BGs) as adjuvant immunostimulant on oxaliplatin efficacy. BGs are empty envelopes of gram-negative bacteria with a distinct immune-stimulatory potential. Indeed, we were able to show that the combination of BGs with oxaliplatin treatment had strong synergistic anticancer activity against the CT26 allograft, resulting in prolonged survival and even a complete remission in this murine model of CRC carcinomatosis. This synergistic effect was based on an enhanced induction of immunogenic cell death and activation of an efficient T-cell response leading to long-term anti-tumor memory effects. Taken together, co-application of BGs strengthens the immunogenic component of the oxaliplatin anticancer response and thus represents a promising natural immune-adjuvant to chemotherapy in advanced CRC.

Novel PAMAM-PEG-Peptide Conjugates for siRNA Delivery Targeted to the Transferrin and Epidermal Growth Factor Receptors

The transferrin (TfR) and epidermal growth factor receptors (EGFR) are known to be overexpressed on the surface of a wide variety of tumor cells. Therefore, the peptides B6 (TfR specific) and GE11 (targeted to the EGFR) were linked to the PAMAM (polyamidoamine) structure via a polyethylenglycol (PEG) 2 kDa chain with the aim of improving the silencing capacity of the PAMAM-based dendriplexes. The complexes showed an excellent binding capacity to the siRNA with a maximal condensation at nitrogen/phosphate (N/P) 2. The nanoparticles formed exhibited hydrodynamic diameters below 200 nm. The zeta potential was always positive, despite the complexes containing the PEG chain in the structure showing a drop of the values due to the shielding effect. The gene silencing capacity was assayed in HeLa and LS174T cells stably transfected with the eGFPLuc cassette. The dendriplexes containing a specific anti luciferase siRNA, assayed at different N/P ratios, were able to mediate a mean decrease of the luciferase expression values of 14% for HeLa and 20% in LS174T cells, compared to an unspecific siRNA-control. (p < 0.05). In all the conditions assayed, dendriplexes resulted to be non-toxic and viability was always above 75%.

Reintroducing the Sodium-Iodide Symporter to Anaplastic Thyroid Carcinoma

BACKGROUND

Anaplastic thyroid carcinoma (ATC), the most aggressive form of thyroid cancer, is unresponsive to radioiodine therapy. The current study aimed to extend the diagnostic and therapeutic application of radioiodine beyond the treatment of differentiated thyroid cancer by targeting the functional sodium-iodide symporter (NIS) to ATC.

METHODS

The study employed nanoparticle vectors (polyplexes) based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG) and coupled to the synthetic peptide GE11 as an epidermal growth factor receptor (EGFR)-specific ligand in order to target a NIS-expressing plasmid (LPEI-PEG-GE11/NIS) to EGFR overexpressing human thyroid carcinoma cell lines. Using ATC xenograft mouse models, transfection efficiency by ¹²³I scintigraphy and potential for systemic radioiodine therapy after systemic polyplex application were evaluated.

RESULTS

In vitro iodide uptake studies in SW1736 and Hth74 ATC cells, and, for comparison, in more differentiated follicular (FTC-133) and papillary (BCPAP) thyroid carcinoma cells demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS that correlated well with EGFR expression levels. After systemic polyplex injection, in vivo ¹²³I gamma camera imaging revealed significant tumor-specific accumulation of radioiodine in an SW1736 and an Hth74 xenograft mouse model. Radioiodine accumulation was found to be higher in SW1736 tumors, reflecting in vitro results, EGFR expression levels, and results from ex vivo analysis of NIS staining. Administration of ¹³¹I in LPEI-PEG-GE11/NIS-treated SW1736 xenograft mice resulted in significantly reduced tumor growth associated with prolonged survival compared to control animals.

CONCLUSIONS

The data open the exciting prospect of NIS-mediated radionuclide imaging and therapy of ATC after non-viral reintroduction of the NIS gene. The high tumor specificity after systemic application makes the strategy an attractive alternative for the treatment of highly metastatic ATC.

Multimodal Fluorescence and Bioluminescence Imaging Reveals Transfection Potential of Intratracheally Administered Polyplexes for Breast Cancer Lung Metastases

Local delivery of anticancer agents or gene therapeutics to lung tumors can circumvent side effects or accumulation in non-target organs, but accessibility via the alveolar side of the blood-air barrier remains challenging. Polyplexes based on plasmid and linear polyethylenimine (LPEI) transfect healthy lung tissue when applied intravenously (i.v.) in the mouse, but direct delivery into the lungs results in low transfection of lung tissue. Nevertheless, LPEI could offer the potential to transfect lung tumors selectively, if accessible from the alveolar side. This study combined near infrared fluorescent protein 720 (iRFP720) and firefly luciferase as reporter genes for detection of tumor lesions and transfection efficiency of LPEI polyplexes, after intratracheal microspraying in mice bearing 4T1 triple negative breast cancer lung metastases. Simultaneous flow cytometric analysis of iRFP720 and enhanced green fluorescent protein expression in vitro demonstrated the potential to combine these reporter genes within transfection studies. Polyplex biophysics was characterized by single nanoparticle tracking analysis (NTA) to monitor physical integrity after microspraying in vitro. 4T1 cells were transduced with iRFP720-encoding lentivirus and evaluated by flow cytometry for stable iRFP720 expression. Growth of 4T1-iRFP720 cells was monitored in Balb/c mice by tomographic near infrared imaging, tissue and tumor morphology by computed tomography and magnetic resonance imaging. In 4T1-iRFP720 tumor-bearing mice, intratracheal administration of luciferase-encoding plasmid DNA by LPEI polyplexes resulted in successful tumor transfection, as revealed by bioluminescence imaging.

Imaging and targeted therapy of pancreatic ductal adenocarcinoma using the theranostic sodium iodide symporter (NIS) gene

The theranostic sodium iodide symporter (NIS) gene allows detailed molecular imaging of transgene expression and application of therapeutic radionuclides. As a crucial step towards clinical application, we investigated tumor specificity and transfection efficiency of epidermal growth factor receptor (EGFR)-targeted polyplexes as systemic NIS gene delivery vehicles in an advanced genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC) that closely reflects human disease. PDAC was induced in mice by pancreas-specific activation of constitutively active KrasG12D and deletion of Trp53. We used tumor-targeted polyplexes (LPEI-PEG-GE11/NIS) based on linear polyethylenimine, shielded by polyethylene glycol and coupled with the EGFR-specific peptide ligand GE11, to target a NIS-expressing plasmid to high EGFR-expressing PDAC. In vitro iodide uptake studies in cell explants from murine EGFR-positive and EGFR-ablated PDAC lesions demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS. In vivo 123I gamma camera imaging and three-dimensional high-resolution 124I PET showed significant tumor-specific accumulation of radioiodide after systemic LPEI-PEG-GE11/NIS injection. Administration of 131I in LPEI-PEG-GE11/NIS-treated mice resulted in significantly reduced tumor growth compared to controls as determined by magnetic resonance imaging, though survival was not significantly prolonged. This study opens the exciting prospect of NIS-mediated radionuclide imaging and therapy of PDAC after systemic non-viral NIS gene delivery.

Transient Hepatic Overexpression of Insulin-Like Growth Factor 2 Induces Free Cholesterol and Lipid Droplet Formation

Although insulin-like growth factor 2 (IGF2) has been reported to be overexpressed in steatosis and steatohepatitis, a causal role of IGF2 in steatosis development remains elusive. Aim of our study was to decipher the role of IGF2 in steatosis development. Hydrodynamic gene delivery of an Igf2 plasmid used for transient Igf2 overexpression employing codon-optimized plasmid DNA resulted in a strong induction of hepatic Igf2 expression. The exogenously delivered Igf2 had no influence on endogenous Igf2 expression. The downstream kinase AKT was activated in Igf2 animals. Decreased ALT levels mirrored the cytoprotective effect of IGF2. Serum cholesterol was increased and sulfo-phospho-vanillin colorimetric assay confirmed lipid accumulation in Igf2-livers while no signs of inflammation were observed. Interestingly, hepatic cholesterol and phospholipids, determined by thin layer chromatography, and free cholesterol by filipin staining, were specifically increased. Lipid droplet (LD) size was not changed, but their number was significantly elevated. Furthermore, free cholesterol, which can be stored in LDs and has been reported to be critical for steatosis progression, was elevated in Igf2 overexpressing mice. Accordingly, Hmgcr/HmgCoAR was upregulated. To have a closer look at de novo lipid synthesis we investigated expression of the lipogenic transcription factor SREBF1 and its target genes. SREBF1 was induced and also SREBF1 target genes were slightly upregulated. Interestingly, the expression of Cpt1a, which is responsible for mitochondrial fatty acid oxidation, was induced. Hepatic IGF2 expression induces a fatty liver, characterized by increased cholesterol and phospholipids leading to accumulation of LDs. We therefore suggest a causal role for IGF2 in hepatic lipid accumulation.

Assessment of Raman spectroscopy as a fast and non-invasive method for total stratum corneum thickness determination of pig skin

Determination of total stratum corneum (SC) thickness is necessary to construct accurate SC drug concentration depth profiles that are used to evaluate the skin absorption of locally acting active components. Currently, different established methods such as the microscopic or gravimetric approach, estimation via transepidermal water loss or NIR densitometry are used. However, some of them represent time consuming strategies. In the present study, Raman spectroscopy was assessed as a non-invasive and fast method for total SC thickness estimation. All techniques employed in this study yielded comparable results with SC values of 11.15 ± 1.52 μm derived from Raman experiments, 10.22 ± 2.64 μm from NIR densitometry measurements and 10.91 ± 2.03 μm from light microscopy studies suggesting Raman spectroscopy as an appropriate and rapid method for total SC thickness determination. As a further objective of the study, the storage conditions of the skin samples during Raman measurements and the impact of keeping the skin on the cartilage during NIR densitometry measurements were investigated. Skin samples can be stored dry during Raman measurements, if immediate measurement is not feasible. Furthermore, skin samples for NIR densitometry studies should be kept on the cartilage during the stripping procedure to avoid SC thickness underestimation.

De-targeting by miR-143 decreases unwanted transgene expression in non-tumorigenic cells

MicroRNA dysregulation often results in the development and progression of cancer. miR-143 is ubiquitously expressed in most human and murine tissues but downregulated in many cancer types. This differential miRNA expression can be utilized for targeted cancer gene therapies. Multiple copies of the miR-143 complementary target sequence were inserted into the 3'UTR of plasmid vectors encoding either for different reporter genes or for the therapeutic gene TNFα. With these transgenes, we analyzed the miR-143-dependent gene expression in cancer cells and normal cells. Moreover, we investigated miR-143-regulated luciferase expression in an NMRI nude/HUH7 xenograft mouse model using a nonviral carrier system for in vivo transfections. We showed low and high levels of miR-143 in cancer cells and normal cells, respectively, leading to a differential gene expression of the reporters and the therapeutic TNFα. According to the miR-143 levels, the luciferase reporter gene expression was silenced in the mouse lungs but not in HUH7 tumors. Thus, we utilized the differential miR-143 expression in healthy and cancerous tissues to de-target the lung by specifically targeting the tumor in an in vivo HUH7 xenograft mouse model. The use of an miR-143-regulated therapeutic transgene may present a promising approach for cancer gene therapy.

Systemic image-guided liver cancer radiovirotherapy using dendrimer-coated adenovirus encoding the sodium iodide symporter as theranostic gene

Currently, major limitations for the clinical application of adenovirus-mediated gene therapy are high prevalence of neutralizing antibodies, widespread expression of the coxsackie-adenovirus receptor (CAR), and adenovirus sequestration by the liver. In the current study, we used the sodium iodide symporter (NIS) as a theranostic gene to investigate whether coating of adenovirus with synthetic dendrimers could be useful to overcome these hurdles in order to develop adenoviral vectors for combination of systemic oncolytic virotherapy and NIS-mediated radiotherapy.

METHODS

We coated replication-deficient (Ad5-CMV/NIS) (CMV is cytomegalovirus) and replication-selective (Ad5-E1/AFP-E3/NIS) adenovirus serotype 5 carrying the hNIS gene with poly(amidoamine) dendrimers generation 5 (PAMAM-G5) in order to investigate transduction efficacy and altered tropism of these coated virus particles by (123)I scintigraphy and to evaluate their therapeutic potential for systemic radiovirotherapy in a liver cancer xenograft mouse model.

RESULTS

After dendrimer coating, Ad5-CMV/NIS demonstrated partial protection from neutralizing antibodies and enhanced transduction efficacy in CAR-negative cells in vitro. In vivo (123)I scintigraphy of nude mice revealed significantly reduced levels of hepatic transgene expression after intravenous injection of dendrimer-coated Ad5-CMV/NIS (dcAd5-CMV/NIS). Evasion from liver accumulation resulted in significantly reduced liver toxicity and increased transduction efficiency of dcAd5-CMV/NIS in hepatoma xenografts. After PAMAM-G5 coating of the replication-selective Ad5-E1/AFP-E3/NIS, a significantly enhanced oncolytic effect was observed after intravenous application (virotherapy) that was further increased by additional treatment with a therapeutic dose of (131)I (radiovirotherapy) and was associated with markedly improved survival.

CONCLUSION

These results demonstrate efficient liver detargeting and tumor retargeting of adenoviral vectors after coating with synthetic dendrimers, thereby representing a promising innovative strategy for systemic NIS gene therapy. Moreover, our study-based on the function of NIS as a theranostic gene allowing the noninvasive imaging of NIS expression by (123)I scintigraphy-provides detailed characterization of in vivo vector biodistribution and localization, level, and duration of transgene expression, essential prerequisites for exact planning and monitoring of clinical gene therapy trials that aim to individualize the NIS gene therapy concept.

Generation of a tumor- and tissue-specific episomal non-viral vector system

Background

A key issue for safe and reproducible gene therapy approaches is the autologous and tissue-specific expression of transgenes. Tissue-specific expression in vivo is either achieved by transfer vectors that deliver the gene of interest into a distinct cell type or by use of tissue-specific expression cassettes. Here we present the generation of non-viral, episomally replicating vectors that are able to replicate in a tissue specific manner thus allowing tissue specific transgene expression in combination with episomal replication. The episomal replication of the prototype vector pEPI-1 and its derivatives depends exclusively on a transcription unit starting from a constitutively active promoter extending into the scaffold/matrix attachment region (S/MAR).

Results

Here, we exchanged the constitutive promoter in the pEPI derivative pEPito by the tumor specific alpha fetoprotein (AFP) or the muscle specific smooth muscle 22 (SM22) promoter leading to specific transgene expression in AFP positive human hepatocellular carcinoma (HUH7) and in a SM22 positive cell line, respectively. The incorporation of the hCMV enhancer element into the expression cassette further boosted the expression levels with both promoters. Tissue specific-replication could be exemplary proven for the smooth muscle protein 22 (SM22) promoter in vitro. With the AFP promoter-driven pEPito vector hepatocellular carcinoma-specific expression could be achieved in vivo after systemic vector application together with polyethylenimine as transfection enhancer.

Conclusions

In this study we present an episomal plasmid system designed for tissue specific transgene expression and replication. The human AFP-promoter in combination with the hCMV enhancer element was demonstrated to be a valuable tissue-specific promoter for targeting hepatocellular carcinomas with non-viral gene delivery system, and tissue specific replication could be shown in vitro with the muscle specific SM22 promoter. In combination with appropriate delivery systems, the tissue specific pEPito vector system will allow higher tissue-specificity with less undesired side effects and is suitable for long term transgene expression in vivo within gene therapeutical approaches.

Adenoviral vectors coated with PAMAM dendrimer conjugates allow CAR independent virus uptake and targeting to the EGF receptor

Adenovirus type 5 (Ad) is an efficient gene vector with high gene transduction potential, but its efficiency depends on its native cell receptors coxsackie- and adenovirus receptor (CAR) for cell attachment and α(v)β(3/5) integrins for internalization. To enable transduction of CAR negative cancer cell lines, we have coated the negatively charged Ad by noncovalent charge interaction with cationic PAMAM (polyamidoamine) dendrimers. The specificity for tumor cell infection was increased by targeting the coated Ad to the epidermal growth factor receptor using the peptide ligand GE11, which was coupled to the PAMAM dendrimer via a 2 kDa PEG spacer. Particles were examined by measuring surface charge and size, the degree of coating was determined by transmission electron microscopy. The net positive charge of PAMAM coated Ad enhanced cellular binding and uptake leading to increased transduction efficiency, especially in low to medium CAR expressing cancer cell lines using enhanced green fluorescent protein or luciferase as transgene. While PAMAM coated Ad allowed for efficient internalization, coating with linear polyethylenimine induced excessive particle aggregation, elevated cellular toxicity and lowered transduction efficiency. PAMAM coating of Ad enabled successful transduction of cells in vitro even in the presence of neutralizing antibodies. Taken together, this study clearly proves noncovalent, charge-based coating of Ad vectors with ligand-equipped dendrimers as a viable strategy for efficient transduction of cells otherwise refractory to Ad infection.

Synthesis of polyethylenimine-based nanocarriers for systemic tumor targeting of nucleic acids

Nucleic acid-based therapies offer the option to treat tumors in a highly selective way, while toxicity towards healthy tissue can be avoided when proper delivery vehicles are used. We have recently developed carrier systems based on linear polyethylenimine, which after chemical coupling of proteinous or peptidic ligands can form nanosized polyplexes with plasmid DNA or RNA and deliver their payload into target cells by receptor-mediated endocytosis. This chapter describes the synthesis of linear PEI (LPEI) from a precursor polymer and the current coupling techniques and purification procedure for peptide conjugates with linear polyethylenimine. A protocol is also given for the formation and characterization of polyplexes formed with LPEI conjugate and plasmid DNA.

In vivo imaging enables high resolution preclinical trials on patients' leukemia cells growing in mice

Background

Xenograft mouse models represent helpful tools for preclinical studies on human tumors. For modeling the complexity of the human disease, primary tumor cells are by far superior to established cell lines. As qualified exemplary model, patients’ acute lymphoblastic leukemia cells reliably engraft in mice inducing orthotopic disseminated leukemia closely resembling the disease in men. Unfortunately, disease monitoring of acute lymphoblastic leukemia in mice is hampered by lack of a suitable readout parameter.

Design and Methods

Patients’ acute lymphoblastic leukemia cells were lentivirally transduced to express the membrane-bound form of Gaussia luciferase. In vivo imaging was established in individual patients’ leukemias and extensively validated.

Results

Bioluminescence in vivo imaging enabled reliable and continuous follow-up of individual mice. Light emission strictly correlated to post mortem quantification of leukemic burden and revealed a logarithmic, time and cell number dependent growth pattern. Imaging conveniently quantified frequencies of leukemia initiating cells in limiting dilution transplantation assays. Upon detecting a single leukemia cell within more than 10,000 bone marrow cells, imaging enabled monitoring minimal residual disease, time to tumor re-growth and relapse. Imaging quantified therapy effects precisely and with low variances, discriminating treatment failure from partial and complete responses.

Conclusions

For the first time, we characterized in detail how in vivo imaging reforms preclinical studies on patient-derived tumors upon increasing monitoring resolution. In the future, in vivo imaging will enable performing precise preclinical studies on a broad range of highly demanding clinical challenges, such as treatment failure, resistance in leukemia initiating cells, minimal residual disease and relapse.

Tuning nanoparticle uptake: live-cell imaging reveals two distinct endocytosis mechanisms mediated by natural and artificial EGFR targeting ligand

Therapeutic nanoparticles can be directed to cancer cells by incorporating selective targeting ligands. Here, we investigate the epidermal growth factor receptor (EGFR)-mediated endocytosis of gene carriers (polyplexes) either targeted with natural EGF or GE11, a short synthetic EGFR-binding peptide. Highly sensitive live-cell fluorescence microcopy with single particle resolution unraveled the existence of two different uptake mechanisms; EGF triggers accelerated nanoparticle endocytosis due to its dual active role in receptor binding and signaling activation. For GE11, an alternative EGFR signaling independent, actin-driven pathway is presented.

Porcine ear necrosis syndrome: a preliminary investigation of putative infectious agents in piglets and mycotoxins in feed

The aim of this study was to identify the causative factors of porcine ear necrosis syndrome (PENS) in 72 pigs, 5.5-10 weeks in age housed on nine farms. Biopsy samples of ear pinnae were collected from all piglets for bacteriology, histopathology and in situ hybridization for porcine circovirus type 2 (PCV2). At the same time, serum samples were taken for serological analysis and viral PCR, and feed was sampled for mycotoxin analysis. The initial lesion of PENS seemed to be a focal epidermal necrosis. Streptococci were isolated from 44 and staphylococci from 36 pinnae. PCV2 could not be detected by in situ hybridization or qPCR. Seven piglets were positive for porcine reproductive and respiratory syndrome virus, and one for Mycoplasma suis. One piglet had antibodies against Sarcoptes scabiei var. suis. No infectious agents were found in 15 samples. Positive virology and parasitology were often found alongside positive bacteriology. Deoxynivalenol, zearalenone and ergot alkaloids were detected in feed. The findings suggest that PENS is multifactorial in origin and that although infectious agents can be involved in the development of the syndrome they are not the exclusive triggering factor.

PolyIC GE11 polyplex inhibits EGFR-overexpressing tumors

Phage display has identified the dodecapeptide YHWYGYTPQNVI (GE11) as a ligand that binds to the epidermal growth factor receptor (EGFR) but does not activate the receptor. Here, we compare the EGFR binding affinities of GE11, EGF, and their polyethyleneimine-polyethyleneglycol (PEI-PEG) conjugates. We found that although GE11 by itself does not exhibit measurable affinity to the EGFR, tethering it to PEI-PEG increases its affinity markedly, and complex formation with polyinosine/cytosine (polyIC) further enhances the affinity to the submicromolar range. PolyIC/PPGE11 has a similar strong antitumor effect against EGFR overexpressing tumors in vitro and in vivo, as polyIC/polyethyleneimine-polyetheleneglycol-EGF (polyIC/PP-EGF). Absence of EGFR activation, as previously shown by us and easier production of GE11 and GE11 conjugates, confer polyIC/PPGE11 a significant advantage over similar EGF-based polyplexes as a potential therapy of EGFR overexpressing tumors.

Synthesis of linear polyethylenimine and use in transfection

Linear polyethylenimine (LPEI) is an efficient transfection reagent for a broad range of cell lines and primary cells and is also useful for local or systemic gene delivery in vivo. In contrast to many other nonviral transfection methods, LPEI is less dependent on mitosis and also transfects postmitotic cells. Transfections can be performed with a simple protocol, as described here. The presence of serum (up to 10%) during transfection does not markedly decrease transfection efficiency, but it significantly reduces toxicity, especially to primary cells. This is a major advantage compared to most lipidic transfection systems. Toxicity can also be kept to a minimum using low, optimized amounts of the transfection reagent. However, LPEI can be quite toxic when applied at elevated doses in vitro or in vivo. LPEI is a fully synthetic product that can be easily synthesized from rather inexpensive precursors and is suitable for large-scale transfections. This protocol describes the synthesis of LPEI from a precursor polymer and the generation of DNA/LPEI polyplexes. Transfection protocols for cells adherent to tissue culture dishes or grown in suspension are given, as are in vivo applications.

Sustained, high transgene expression in liver with plasmid vectors using optimized promoter-enhancer combinations

BACKGROUND

Plasmid-based gene therapy approaches often lack long-term transgene expression in vivo as a result of silencing or loss of the vector. One way to overcome these limitations is to combine nonsilenced promoters with strong enhancers.

METHODS

In the present study, we combine murine or human cytomegalovirus (CMV)-derived enhancer elements with the human elongation factor 1α (EF1α) promoter in a plasmid backbone devoid of potentially immunostimulating cytosine-guanine repeat sequences. Luciferase transgene activity was monitored in mouse liver after hydrodynamic plasmid delivery.

RESULTS

Luciferase activity of a CMV-promoter driven plasmid rapidly declined within days, whereas the activity of the EF1α driven plasmid remained high for 2 weeks (murine enhancer) and detectable for > 80 days (human enhancer). Expression levels clearly correlated with higher plasmid copy number found in the liver at 2 months after gene delivery. Furthermore, we developed a novel synthetic CMV-EF1α hybrid promoter (SCEP) combining the high activity of CMV and sustained activity of EF1α promoter. The SCEP led to a constitutive three-fold increase in expression levels compared to the EF1α promoter in vivo.

CONCLUSIONS

This novel combination of enhancer and promoter element with optimized plasmid backbones will pave the way for more efficient nonviral approaches in gene therapy.

Liposome based systems for systemic siRNA delivery: stability in blood sets the requirements for optimal carrier design

siRNA therapeutics are currently regarded as promising candidates to make a leap forward in the search for treatments of various hard to cure diseases. In order to exploit the full potential of siRNA based therapeutics, development of delivery systems that can efficiently guide the siRNA molecules to their target without major side effects will be the key to success. Lipid based delivery systems, originating from earlier research in the fields of gene delivery, are the most studied candidates for siRNA delivery. Here we discuss the requirements that need to be met by these siRNA delivery systems to ensure adequate stability after systemic application and subsequent deposition in the target tissue. The encountered hurdles in the blood stream and the solutions proposed in literature are discussed.

Image-guided tumor-selective radioiodine therapy of liver cancer after systemic nonviral delivery of the sodium iodide symporter gene

We reported the induction of tumor-selective iodide uptake and therapeutic efficacy of (131)I in a hepatocellular carcinoma (HCC) xenograft mouse model, using novel polyplexes based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG), and coupled with the epidermal growth factor receptor-specific peptide GE11 (LPEI-PEG-GE11). The aim of the current study in the same HCC model was to evaluate the potential of biodegradable nanoparticle vectors based on pseudodendritic oligoamines (G2-HD-OEI) for systemic sodium iodide symporter (NIS) gene delivery and to compare efficiency and tumor specificity with LPEI-PEG-GE11. Transfection of HCC cells with NIS cDNA, using G2-HD-OEI, resulted in a 44-fold increase in iodide uptake in vitro as compared with a 22-fold increase using LPEI-PEG-GE11. After intravenous application of G2-HD-OEI/NIS HCC tumors accumulated 6-11% ID/g (123)I (percentage of the injected dose per gram tumor tissue) with an effective half-life of 10 hr (tumor-absorbed dose, 281 mGy/MBq) as measured by (123)I scintigraphic gamma camera or single-photon emission computed tomography computed tomography (SPECT CT) imaging, as compared with 6.5-9% ID/g with an effective half-life of only 6 hr (tumor-absorbed dose, 47 mGy/MBq) for LPEI-PEG-GE11. After only two cycles of G2-HD-OEI/NIS/(131)I application, a significant delay in tumor growth was observed with markedly improved survival. A similar degree of therapeutic efficacy had been observed after four cycles of LPEI-PEG-GE11/(131)I. These results clearly demonstrate that biodegradable nanoparticles based on OEI-grafted oligoamines show increased efficiency for systemic NIS gene transfer in an HCC model with similar tumor selectivity as compared with LPEI-PEG-GE11, and therefore represent a promising strategy for NIS-mediated radioiodine therapy of HCC.

Disconnecting the yin and yang relation of epidermal growth factor receptor (EGFR)-mediated delivery: a fully synthetic, EGFR-targeted gene transfer system avoiding receptor activation

The epidermal growth factor receptor (EGFR) is upregulated within a high percentage of solid tumors and hence is an attractive target for tumor-targeted therapies including gene therapy. The natural EGFR ligand epidermal growth factor (EGF) has been used for this purpose, despite the risk of mitogenic effects due to EGFR activation. We have developed a fully synthetic, EGFR-targeted gene delivery system based on PEGylated linear polyethylenimine (LPEI), allowing evaluation of different EGFR-binding peptides in terms of transfection efficiency and EGFR activation. Peptide sequences directly derived from the human EGF molecule enhanced transfection efficiency with concomitant EGFR activation. Only the EGFR-binding peptide GE11, which has been identified by phage display technique, showed specific enhancement of transfection on EGFR-overexpressing tumor cells including glioblastoma and hepatoma, but without EGFR activation. EGFR targeting led to high levels of cell association of fluorescently labeled polyplexes after only 30 min of incubation. EGF pretreatment of cells induced enhanced cellular internalization of all polyplex types tested, pointing at generally enhanced macropinocytosis. EGF polyplexes diminished cell surface expression of EGFR for up to 4 hr, whereas GE11 polyplexes did not. In a clinically relevant orthotopic prostate cancer model, intratumorally injected GE11 polyplexes were superior in inducing transgene expression when compared with untargeted polyplexes.

Live in vivo imaging of Egr-1 promoter activity during neonatal development, liver regeneration and wound healing

BACKGROUND

The zinc finger transcription factor Egr-1 (Early growth response 1) is central to several growth factors and represents an important activator of target genes not only involved in physiological processes like embryogenesis and neonatal development, but also in a variety of pathophysiological processes, for example atherosclerosis or cancer. Current options to investigate its transcription and activation in vivo are end-point measurements that do not provide insights into dynamic changes in the living organism.

RESULTS

We developed a transgenic mouse (Egr-1-luc) in which the luciferase reporter gene is under the control of the murine Egr-1 promoter providing a versatile tool to study the time course of Egr-1 activation in vivo. In neonatal mice, bioluminescence imaging revealed a high Egr-1 promoter activity reaching basal levels three weeks after birth with activity at snout, ears and paws. Using a model of partial hepatectomy we could show that Egr-1 promoter activity and Egr-1 mRNA levels were increased in the regenerating liver. In a model of wound healing, we demonstrated that Egr-1 promoter activity was upregulated at the site of injury.

CONCLUSION

Taken together, we have developed a transgenic mouse model that allows real time in vivo imaging of the Egr-1 promoter activity. The ability to monitor and quantify Egr-1 activity in the living organism may facilitate a better understanding of Egr-1 function in vivo.

Development of a lyophilized plasmid/LPEI polyplex formulation with long-term stability--A step closer from promising technology to application

Cationic polymer/DNA complexes are limited by their instability in aqueous suspensions and usually have to be freshly prepared prior to administration. Thus, the development of isotonic lyophilized polyplex formulations with long-term stability is a desirable goal. Polyplexes based on 22kDa linear polyethylenimine were prepared using a micro-mixer method. Freeze-thawing and lyophilization were performed on a pilot scale freeze-drier. Several excipients (trehalose, sucrose, lactosucrose, dextran, hydroxypropylbetadex or povidone and combinations thereof) at varying concentrations were evaluated for their stabilizing potential against freezing and dehydration induced stresses. For stability testing the lyophilized samples were stored for 6 weeks at 2-8°C, 20°C and 40°C, respectively. Polyplex samples were characterized for particle size, zeta potential, their in vitro transfection efficiency and metabolic activity in Neuro2A cells. In addition, liquid samples were investigated for turbidity and number of sub-visible particles and solid samples were analyzed for residual moisture content, glass transition temperature and sample morphology. L-histidine buffer pH 6.0 was selected as effective buffer. In isotonic formulations with 14% lactosucrose, 10% hydroxypropylbetadex/6.5% sucrose or 10% povidone/6.3% sucrose, particle size was <170nm for all formulations and did not change after storage for 6weeks at 40°C. Polyplexes formulated with lactosucrose or hydroxypropylbetadex/sucrose showed high transfection efficiencies and cellular metabolic activities. Absence of large aggregates was indicated by turbidity and subvisible particle number measurements. The current standard limits for particulate contamination for small volume parenterals were met for all formulations. All samples were amorphous with low residual moisture levels (<1.3%) and high glass transition temperatures (>90°C).

EGFR-homing dsRNA activates cancer-targeted immune response and eliminates disseminated EGFR-overexpressing tumors in mice

PURPOSE

The cause of most cancer deaths is incurable dissemination of cancer cells into vital organs. Current systemic therapies for disseminated cancers provide limited efficacy and are often accompanied by toxic side effects. We have recently shown that local application of epidermal growth factor receptor (EGFR)-targeted polyinosine-cytosine (polyIC) eradicates preestablished EGFR-overexpressing tumors. Here we show for the first time the high efficiency of systemic application of polyIC/melittin-polyethyleneimine-polyethyleneglycol-EGF (polyIC/MPPE) in combination with human immune cells.

EXPERIMENTAL DESIGN

Cancer-targeted activation of immune cells was examined in vitro and in vivo following transfection with polyIC/MPPE. The therapeutic efficiency of the strategy was then examined on disseminated EGFR-overexpressing tumors grown in severe combined immunodeficient (SCID) mice.

RESULTS

Intravenous delivery of polyIC/MPPE followed by intraperitoneal injection of peripheral blood mononuclear cells induced the complete cure of SCID mice with preestablished disseminated EGFR-overexpressing tumors, with no adverse toxic effects. The immune cells and the cytokines they produce are localized to the tumor site of the treated animal and contribute decisively to the demise of the tumor cells. The immune system homes to the tumors, due to the chemokines produced by the internalized polyIC.

CONCLUSION

The EGFR-homing vector loaded with polyIC can be used to treat and possibly cure patients with disseminated EGFR-overexpressing tumors. The possibility of adopting this strategy to treat other tumors that express a protein capable of ligand induced internalization is discussed.

The establishment of an up-scaled micro-mixer method allows the standardized and reproducible preparation of well-defined plasmid/LPEI polyplexes

Polyplexes based on linear polyethylenimine (LPEI) and plasmid DNA are known as efficient non-viral gene delivery systems. However, the requirement for freshly prepared complexes prior to administration due to their instability in aqueous suspension poses the risk of batch-to-batch variations. Therefore, the aim of the study was the establishment of a reproducible and up-scalable method for the preparation of well-defined polyplexes. Polyplexes consisting of pCMVLuc plasmid and 22 kDa linear polyethylenimine (LPEI) were prepared by classical pipetting or with a micro-mixer method using different mixing speeds and plasmid DNA concentrations (20-400 μg/mL). The z-average diameter of the polyplexes was measured by dynamic light scattering. Metabolic activity and transfection efficiency was evaluated on murine neuroblastoma cells after transfection with polyplexes. When varying mixing speeds of the micro-mixer, polyplex size (59-197 nm) and polydispersity index (0.05-0.19) could be directly controlled. The z-average diameter (65-170 nm) and polydispersity index (0.05-0.22) of the polyplexes increased with increasing plasmid DNA concentration (20-400 μg/mL). The established up-scaled micro-mixer method allows the standardized and reproducible preparation of well-defined, transfection-competent plasmid/LPEI polyplexes with high reproducibility.