Intracellular Degradation of SARS-CoV-2 N-Protein Caused by Modular Nanotransporters Containing Anti-N-Protein Monobody and a Sequence That Recruits the Keap1 E3 Ligase

The proper viral assembly relies on both nucleic acids and structural viral proteins. Thus a biologically active agent that provides the degradation of one of these key proteins and/or destroys the viral factory could suppress viral replication efficiently. The nucleocapsid protein (N-protein) is a key protein for the SARS-CoV-2 virus. As a bioactive agent, we offer a modular nanotransporter (MNT) developed by us, which, in addition to an antibody mimetic to the N-protein, contains an amino acid sequence for the attraction of the Keap1 E3 ubiquitin ligase. This should lead to the subsequent degradation of the N-protein. We have shown that the functional properties of modules within the MNT permit its internalization into target cells, endosome escape into the cytosol, and binding to the N-protein. Using flow cytometry and western blotting, we demonstrated significant degradation of N-protein when A549 and A431 cells transfected with a plasmid coding for N-protein were incubated with the developed MNTs. The proposed MNTs open up a new approach for the treatment of viral diseases.

Modular Nanotransporters Delivering Biologically Active Molecules to the Surface of Mitochondria

Treatment of various diseases, in particular cancer, usually requires the targeting of biologically active molecules at a selected subcellular compartment. We modified our previously developed modular nanotransporters (MNTs) for targeting mitochondria. The new MNTs are capable of binding to the protein predominantly localized on the outer mitochondrial membrane, Keap1. These MNTs possessing antiKeap1 monobody co-localize with mitochondria upon addition to the cells. They efficiently interact with Keap1 both in solution and within living cells. A conjugate of the MNT with a photosensitizer, chlorin e6, demonstrated significantly higher photocytotoxicity than chlorin e6 alone. We assume that MNTs of this kind can improve efficiency of therapeutic photosensitizers and radionuclides emitting short-range particles.

Prospects of Using Protein Engineering for Selective Drug Delivery into a Specific Compartment of Target Cells

A large number of proteins are successfully used to treat various diseases. These include natural polypeptide hormones, their synthetic analogues, antibodies, antibody mimetics, enzymes, and other drugs based on them. Many of them are demanded in clinical settings and commercially successful, mainly for cancer treatment. The targets for most of the aforementioned drugs are located at the cell surface. Meanwhile, the vast majority of therapeutic targets, which are usually regulatory macromolecules, are located inside the cell. Traditional low molecular weight drugs freely penetrate all cells, causing side effects in non-target cells. In addition, it is often difficult to elaborate a small molecule that can specifically affect protein interactions. Modern technologies make it possible to obtain proteins capable of interacting with almost any target. However, proteins, like other macromolecules, cannot, as a rule, freely penetrate into the desired cellular compartment. Recent studies allow us to design multifunctional proteins that solve these problems. This review considers the scope of application of such artificial constructs for the targeted delivery of both protein-based and traditional low molecular weight drugs, the obstacles met on the way of their transport to the specified intracellular compartment of the target cells after their systemic bloodstream administration, and the means to overcome those difficulties.

An Approach to Evaluate the Effective Cytoplasmic Concentration of Bioactive Agents Interacting with a Selected Intracellular Target Protein

To compare the effectiveness of various bioactive agents reversibly acting within a cell on a target intracellular macromolecule, it is necessary to assess effective cytoplasmic concentrations of the delivered bioactive agents. In this work, based on a simple equilibrium model and the cellular thermal shift assay (CETSA), an approach is proposed to assess effective concentrations of both a delivered bioactive agent and a target protein. This approach was tested by evaluating the average concentrations of nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated-protein 1 (Keap1) proteins in the cytoplasm for five different cell lines (Hepa1, MEF, RAW264.7, 3LL, and AML12) and comparing the results with known literature data. The proposed approach makes it possible to analyze both binary interactions and ternary competition systems; thus, it can have a wide application for the analysis of protein-protein or molecule-protein interactions in the cell. The concentrations of Nrf2 and Keap1 in the cell can be useful not only in analyzing the conditions for the activation of the Nrf2 system, but also for comparing the effectiveness of various drug delivery systems, where the delivered molecule is able to interact with Keap1.

Exploiting active nuclear import for efficient delivery of Auger electron emitters into the cell nucleus

BACKGROUND

The most attractive features of Auger electrons (AEs) in cancer therapy are their extremely short range and sufficiently high linear energy transfer (LET) for a majority of them. The cytotoxic effects of AE emitters can be realized only in close vicinity to sensitive cellular targets and they are negligible if the emitters are located outside the cell. The nucleus is considered the compartment most sensitive to high LET particles. Therefore, the use of AE emitters could be most useful in specific recognition of a cancer cell and delivery of AE emitters into its nucleus.

PURPOSE

This review describes the studies aimed at developing effective anticancer agents for the delivery of AE emitters to the nuclei of target cancer cells. The use of peptide-based conjugates, nanoparticles, recombinant proteins, and other constructs for AE emitter targeted intranuclear delivery as well as their advantages and limitations are discussed.

CONCLUSION

Transport from the cytoplasm to the nucleus along with binding to the cancer cell is one of the key stages in the delivery of AE emitters; therefore, several constructs for exploitation of this transport have been developed. The transport is carried out through a nuclear pore complex (NPC) with the use of specific amino acid nuclear localization sequences (NLS) and carrier proteins named importins, which are located in the cytosol. Therefore, the effectiveness of NLS-containing delivery constructs designed to provide energy-dependent transport of AE emitter into the nuclei of cancer cells also depends on their efficient entry into the cytosol of the target cell.

Epidermal Growth Factor Receptor: Key to Selective Intracellular Delivery

Epidermal growth factor receptor (EGFR) is an integral surface protein mediating cellular response to a number of growth factors. Its overexpression and increased activation due to mutations is one of the most common traits of many types of cancer. Development and clinical use of the agents, which block EGFR activation, became a prime example of the personalized targeted medicine. However, despite the obvious success in this area, cancer cure remains unattainable in most cases. Because of that, as well as the result of the search for possible ways to overcome the difficulties of treatment, a huge number of new treatment methods relying on the use of EGFR overexpression and its changes to destroy cancer cells. Modern data on the structure, functioning, and intracellular transport of EGFR, its natural ligands, as well as signaling cascades triggered by the EGFR activation, peculiarities of the EGFR expression and activation in oncological disorders, as well as applied therapeutic approaches aimed at blocking EGFR signaling pathway are summarized and analyzed in this review. Approaches to the targeted delivery of various chemotherapeutic agents, radionuclides, immunotoxins, photosensitizers, as well as the prospects for gene therapy aimed at cancer cells with EGFR overexpression are reviewed in detail. It should be noted that increasing attention is being paid nowadays to the development of multifunctional systems, either carrying several different active agents, or possessing several environment-dependent transport functions. Potentials of the systems based on receptor-mediated endocytosis of EGFR and their possible advantages and limitations are discussed.

Soluble Cyanobacterial Carotenoprotein as a Robust Antioxidant Nanocarrier and Delivery Module

To counteract oxidative stress, antioxidants including carotenoids are highly promising, yet their exploitation is drastically limited by the poor bioavailability and fast photodestruction, whereas current delivery systems are far from being efficient. Here we demonstrate that the recently discovered nanometer-sized water-soluble carotenoprotein from Anabaena sp. PCC 7120 (termed AnaCTDH) transiently interacts with liposomes to efficiently extract carotenoids via carotenoid-mediated homodimerization, yielding violet–purple protein samples. We characterize the spectroscopic properties of the obtained pigment–protein complexes and the thermodynamics of liposome–protein carotenoid transfer and demonstrate the delivery of carotenoid echinenone from AnaCTDH into liposomes with an efficiency of up to 70 ± 3%. Most importantly, we show efficient carotenoid delivery to membranes of mammalian cells, which provides protection from reactive oxygen species (ROS). Incubation of neuroblastoma cell line Tet21N in the presence of 1 μM AnaCTDH binding echinenone decreased antimycin A ROS production by 25% (p < 0.05). The described carotenoprotein may be considered as part of modular systems for the targeted antioxidant delivery.

New Recombinant Carriers Binding Specifically to the Epidermal Growth Factor Receptor

New recombinant carriers-modular nanotransporters (MNTs)-with N-terminal ligand module to the epidermal growth factor receptor (EGFR) were developed and characterized. Human epidermal growth factor (hEGF) and antibody-like protein Z₁₉₀₇ were used as a ligand module. We demonstrated that MNTs are able to internalize in a receptor-specific manner into the target cancer cells and to accumulate in the target cell nuclei. Conjugation of MNTs with the Auger electron emitter ¹¹¹In significantly enhanced the cytotoxic effect of ¹¹¹In on the target cells. It was found that the transfer of EGF from the C-terminus to the N-terminus of the MNT enhanced the proliferation of target cells, whereas the use of Z₁₉₀₇ did not have a similar effect.

Targeted Delivery of 111In Into the Nuclei of EGFR Overexpressing Cells via Modular Nanotransporters With Anti-EGFR Affibody

Since cell nucleus is one of the most vulnerable compartments, the maximum therapeutic effect from a variety of locally acting agents, such as photosensitizers, alfa-emitters, Auger electron emitters, will be expected when they get there. Therefore, the targeted delivery of these agents into the nuclei of target tumor cells is necessary for their anticancer effects and minimization of side effects. Modular nanotransporters (MNT) are artificial polypeptides comprising several predefined modules that recognize target cell, launching their subsequent internalization, escape from endosomes, and transport the drug load to the nucleus. This technology significantly enhances the cytotoxicity of locally acting drugs in vitro and in vivo. Epidermal growth factor receptors (EGFR) are useful molecular targets as they are overexpressed in glioblastoma, head-and-neck cancer, bladder cancer, and other malignancies. Here, we examined the possibility of using internalizable anti-EGFR affibody as an EGFR-targeting MNT module for drug transport into the cancer cell nuclei. It binds to both murine and human EGFR facilitating preclinical studies. We showed that MNT with affibody on the N-terminus (MNT_N-affibody) effectively delivered the Auger electron emitter ¹¹¹In to target cell nuclei and had pronounced cytotoxic efficacy against EGFR-overexpressing human A431 epidermoid carcinoma cells. Using EGFR-expressing human adenocarcinoma MCF-7 cells, we demonstrated that in contrast to MNT with N-terminal epidermal growth factor (EGF), MNT_N-affibody and MNT with EGF on the C-terminus did not stimulate cancer cell proliferation.

Structural peculiarities of keto-carotenoids in water-soluble proteins revealed by simulation of linear absorption

To prevent irreversible damage caused by an excess of incident light, the photosynthetic machinery of many cyanobacteria uniquely utilizes the water-soluble orange carotenoid protein (OCP) containing a single keto-carotenoid molecule. This molecule is non-covalently embedded into the two OCP domains which are interconnected by a flexible linker. The phenomenon of OCP photoactivation, causing significant changes in carotenoid absorption in the orange and red form of OCP, is currently being thoroughly studied. Numerous additional spectral forms of natural and synthetic OCP-like proteins have been unearthed. The optical properties of carotenoids are strongly determined by the interaction of their electronic states with vibrational modes, the surrounding protein matrix, and the solvent. In this work, the effects of the pigment-protein interaction and vibrational relaxation in OCP were studied by computational simulation of linear absorption. Taking into account Raman spectroscopy data and applying the multimode Brownian oscillator model as well as the cumulant expansion technique, we have calculated a set of characteristic microparameters sufficient to demarcate different carotenoid states in OCP forms, using the model carotenoids spheroidene and spheroidenone in methanol/acetone solution as benchmarks. The most crucial microparameters, which determine the effect of solvent and protein environment, are the Huang-Rhys factors and the frequencies of C[double bond, length as m-dash]C and C-C stretching modes, the low-frequency mode and the FWHM due to inhomogeneous line broadening. Considering the difference of linear absorption between spheroidene and spheroidenone, which remarkably resembles the photoinduced changes of OCP absorption, and applying quantum chemical calculations, we discuss structural and functional determinants of carotenoid binding proteins.

Antitumor Activity of Auger Electron Emitter 111In Delivered by Modular Nanotransporter for Treatment of Bladder Cancer With EGFR Overexpression

Gamma-ray emitting ¹¹¹In, which is extensively used for imaging, is also a source of short-range Auger electrons (AE). While exhibiting negligible effect outside cells, these AE become highly toxic near DNA within the cell nucleus. Therefore, these radionuclides can be used as a therapeutic anticancer agent if delivered precisely into the nuclei of tumor target cells. Modular nanotransporters (MNTs) designed to provide receptor-targeted delivery of short-range therapeutic cargoes into the nuclei of target cells are perspective candidates for specific intracellular delivery of AE emitters. The objective of this study was to evaluate the in vitro and in vivo efficacy of ¹¹¹In attached MNTs to kill human bladder cancer cells overexpressing epidermal growth factor receptor (EGFR). The cytotoxicity of ¹¹¹In delivered by the EGFR-targeted MNT (¹¹¹In-MNT) was greatly enhanced on EJ-, HT-1376-, and 5637-expressing EGFR bladder cancer cell lines compared with ¹¹¹In non-targeted control. In vivo microSPECT/CT imaging and antitumor efficacy studies revealed prolonged intratumoral retention of ¹¹¹In-MNT with t½ = 4.1 ± 0.5 days as well as significant dose-dependent tumor growth delay (up to 90% growth inhibition) after local infusion of ¹¹¹In-MNT in EJ xenograft-bearing mice.

Targeted Intracellular Delivery of Antibodies: The State of the Art

A dominant area of antibody research is the extension of the use of this mighty experimental and therapeutic tool for the specific detection of molecules for diagnostics, visualization, and activity blocking. Despite the ability to raise antibodies against different proteins, numerous applications of antibodies in basic research fields, clinical practice, and biotechnology are restricted to permeabilized cells or extracellular antigens, such as membrane or secreted proteins. With the exception of small groups of autoantibodies, natural antibodies to intracellular targets cannot be used within living cells. This excludes the scope of a major class of intracellular targets, including some infamous cancer-associated molecules. Some of these targets are still not druggable via small molecules because of large flat contact areas and the absence of deep hydrophobic pockets in which small molecules can insert and perturb their activity. Thus, the development of technologies for the targeted intracellular delivery of antibodies, their fragments, or antibody-like molecules is extremely important. Various strategies for intracellular targeting of antibodies via protein-transduction domains or their mimics, liposomes, polymer vesicles, and viral envelopes, are reviewed in this article. The pitfalls, challenges, and perspectives of these technologies are discussed.

MNT Optimization for Intracellular Delivery of Antibody Fragments

We studied the possibility of optimizing modular nanotransporters (MNTs) for the intracellular delivery of antibody fragments into the nuclei of cells of a specified type. Basic MNT with a reduced size retaining the desired functions was obtained, and the principal possibility of obtaining an MNT carrying an antibody fragment by microbiological synthesis was shown.

Development and evaluation of a new modular nanotransporter for drug delivery into nuclei of pathological cells expressing folate receptors

PURPOSE

Modular nanotransporters (MNTs) are artificial multifunctional systems designed to facilitate receptor-specific transport from the cell surface into the cell nucleus through inclusion of polypeptide domains for accomplishing receptor binding and internalization, as well as sequential endosomal escape and nuclear translocation. The objective of this study was to develop a new MNT targeted at folate receptors (FRs) for precise delivery of therapeutic cargo to the nuclei of FR-positive cells and to evaluate its potential, particularly for delivery of therapeutic agents (eg, the Auger electron emitter ¹¹¹In) into the nuclei of target cancer cells.

METHODS

A FR-targeted MNT was developed by site-specific derivatization of ligand-free MNT with maleimide-polyethylene glycol-folic acid. The ability of FR-targeted MNT to accumulate in target FR-expressing cells was evaluated using flow cytometry, and intracellular localization of this MNT was assessed using confocal laser scanning microscopy of cells. The cytotoxicity of the ¹¹¹In-labeled FR-targeted MNT was evaluated on HeLa and U87MG cancer cell lines expressing FR. In vivo micro-single-photon emission computed tomography/CT imaging and antitumor efficacy studies were performed with intratumoral injection of ¹¹¹In-labeled FR-targeted MNT in HeLa xenograft-bearing mice.

RESULTS

The resulting FR-targeted MNT accumulated in FR-positive HeLa cancer cell lines specifically and demonstrated the ability to reach its target destination - the cell nuclei. ¹¹¹In-labeled FR-targeted MNT demonstrated efficient and specific FR-positive cancer cell eradication. A HeLa xenograft in vivo model revealed prolonged retention of ¹¹¹In delivered by FR-targeted MNT and significant tumor growth delay (up to 80% growth inhibition).

CONCLUSION

The FR-targeted MNT met expectations of its ability to deliver active cargo into the nuclei of target FR-positive cells efficiently and specifically. As a result of this finding the new FR-targeted MNT approach warrants broad evaluation.

Preparation, cytotoxicity, and in vivo antitumor efficacy of 111In-labeled modular nanotransporters

PURPOSE

Modular nanotransporters (MNTs) are a polyfunctional platform designed to achieve receptor-specific delivery of short-range therapeutics into the cell nucleus by receptor-mediated endocytosis, endosome escape, and targeted nuclear transport. This study evaluated the potential utility of the MNT platform in tandem with Auger electron emitting 111In for cancer therapy.

METHODS

Three MNTs developed to target either melanocortin receptor-1 (MC1R), folate receptor (FR), or epidermal growth factor receptor (EGFR) that are overexpressed on cancer cells were modified with p-SCN-Bn-NOTA and then labeled with 111In in high specific activity. Cytotoxicity of the 111In-labeled MNTs was evaluated on cancer cell lines bearing the appropriate receptor target (FR: HeLa, SK-OV-3; EGFR: A431, U87MG.wtEGFR; and MC1R: B16-F1). In vivo micro-single-photon emission computed tomography/computed tomography imaging and antitumor efficacy studies were performed with intratumoral injection of MC1R-targeted 111In-labeled MNT in B16-F1 melanoma tumor-bearing mice.

RESULTS

The three NOTA-MNT conjugates were labeled with a specific activity of 2.7 GBq/mg with nearly 100% yield, allowing use without subsequent purification. The cytotoxicity of 111In delivered by these MNTs was greatly enhanced on receptor-expressing cancer cells compared with 111In nontargeted control. In mice with B16-F1 tumors, prolonged retention of 111In by serial imaging and significant tumor growth delay (82% growth inhibition) were found.

CONCLUSION

The specific in vitro cytotoxicity, prolonged tumor retention, and therapeutic efficacy of MC1R-targeted 111In-NOTA-MNT suggest that this Auger electron emitting conjugate warrants further evaluation as a locally delivered radiotherapeutic, such as for ocular melanoma brachytherapy. Moreover, the high cytotoxicity observed with FR- and EGFR-targeted 111In-NOTA-MNT suggests further applications of the MNT delivery strategy should be explored.

Radiolabeling and in vitro evaluation of (67)Ga-NOTA-modular nanotransporter--a potential Auger electron emitting EGFR-targeted radiotherapeutic

INTRODUCTION

Modular nanotransporters (MNTs) are vehicles designed to transport drugs from the cell surface via receptor-mediated endocytosis and endosomal escape to nucleus. Hence their conjugation to Auger electron emitters, can cause severe cell killing, by nuclear localization. Herein we evaluate the use of MNT as a platform for targeted radiotherapy with (67)Ga.

METHODS

EGF was the targeting ligand on the MNT, and NOTA was selected for its radiolabeling with (67)Ga. In the radiolabeling study we dealt with the precipitation of MNT (pI 5.7) at the labeling pH (4.5-5.5) of (67)Ga. Cellular and nuclei uptake of (67)Ga-NOTA-MNT by the A431 cell line was determined. Its specific cytotoxicity was compared to that of (67)Ga-EDTA, (67)Ga-NOTA-BSA and (67)Ga-NOTA-hEGF, in A431 and U87MGWTT, cell lines, by clonogenic assay. Dosimetry studies were also performed.

RESULTS

(67)Ga-NOTA-MNT was produced with 90% yield and specific activity of 25.6mCi/mg. The in vitro kinetics revealed an increased uptake over 24h. 55% of the internalized radioactivity was detected in the nuclei at 1h. The cytotoxicity of (67)Ga-NOTA-MNT on A431 cell line was 17 and 385-fold higher when compared to non-specific (67)Ga-NOTA-BSA and (67)Ga-EDTA. While its cytotoxic potency was 13 and 72-fold higher when compared to (67)Ga-NOTA-hEGF in the A431 and the U87MGWTT cell lines, respectively, validating its nuclear localization. The absorbed dose, for 63% cell killing, was 8Gy, confirming the high specific index of (67)Ga.

CONCLUSION

These results demonstrate the feasibility of using MNT as a platform for single cell kill targeted radiotherapy by Auger electron emitters.

Microdistribution of MC1R-targeted polyplexes in murine melanoma tumor tissue

Targeted sodium-iodide symporter (NIS) gene transfer can be considered as a promising approach for diagnostics of specific types of cancer. For this purpose we used targeted polyplexes based on PEI-PEG-MC1SP block-copolymer containing MC1SP-peptide, a ligand specific for melanocortin receptor-1 (MC1R) overexpressed on melanoma cells. Targeted polyplexes demonstrated enhanced NIS gene transfer compared to non-targeted (lacking MC1SP) ones in vitro. Using dorsal skinfold chamber and intravital microscopy we evaluated accumulation and microdistribution of quantum dot-labeled polyplexes in tumor and normal subcutaneous tissues up to 4 h after intravenous injection. Polyplexes demonstrated significantly higher total accumulation in tumor tissue in comparison with subcutaneous ones (control). Targeted and non-targeted polyplexes extravasated and penetrated into the tumor tissue up to 20 μm from the vessel walls. In contrast, in normal subcutaneous tissue polyplexes penetrated not more than 3 μm from the vessel walls with the level of extravasated polyplexes 400-fold less than in tumor. Accumulated polyplexes in tumor tissue caused NIS gene expression. Subsequent (123)I(-) intravenous injection resulted in 6.8 ± 1.1 and 4.5 ± 0.8% ID/g (p < 0.001) iodide accumulation in tumors in the case of targeted and non-targeted polyplexes, respectively, as was shown using SPECT/CT.

Modular nanotransporters: a versatile approach for enhancing nuclear delivery and cytotoxicity of Auger electron-emitting 125I

Background

This study evaluates the potential utility of a modular nanotransporter (MNT) for enhancing the nuclear delivery and cytotoxicity of the Auger electron emitter ¹²⁵I in cancer cells that overexpress the epidermal growth factor receptor (EGFR).

Methods

MNTs are recombinant multifunctional polypeptides that we have developed for achieving selective delivery of short-range therapeutics into cancer cells. MNTs contain functional modules for receptor binding, internalization, endosomal escape and nuclear translocation, thereby facilitating the transport of drugs from the cell surface to the nucleus. The MNT described herein utilized EGF as the targeting ligand and was labeled with ¹²⁵I using N-succinimidyl-4-guanidinomethyl-3-[¹²⁵I]iodobenzoate (SGMIB). Membrane binding, intracellular and nuclear accumulation kinetics, and clonogenic survival assays were performed using the EGFR-expressing A431 epidermoid carcinoma and D247 MG glioma cell lines.

Results

[¹²⁵I]SGMIB-MNT bound to A431 and D247 MG cells with an affinity comparable to that of native EGF. More than 60% of internalized [¹²⁵I]SGMIB-MNT radioactivity accumulated in the cell nuclei after a 1-h incubation. The cytotoxic effectiveness of [¹²⁵I]SGMIB-MNT compared with ¹²⁵I-labeled bovine serum albumin control was enhanced by a factor of 60 for D247 MG cells and more than 1,000-fold for A431 cells, which express higher levels of EGFR.

Conclusions

MNT can be utilized to deliver ¹²⁵I into the nuclei of cancer cells overexpressing EGFR, significantly enhancing cytotoxicity. Further evaluation of [¹²⁵I]SGMIB-MNT as a targeted radiotherapeutic for EGFR-expressing cancer cells appears warranted.

Subcellular trafficking and transfection efficacy of polyethylenimine-polyethylene glycol polyplex nanoparticles with a ligand to melanocortin receptor-1

We have synthesized and investigated properties of new PEI-PEG-based polyplexes containing MC1SP-peptide, a ligand specific for melanocortin receptor-1 (targeted polyplexes), and control polyplexes without this ligand peptide (non-targeted polyplexes). The targeted polyplexes demonstrated receptor-mediated transfection of Cloudman S91 (clone M-3) murine melanoma cells that was more efficient than with the non-targeted ones. Transfection with the targeted polyplexes was inhibited by chlorpromazine, an inhibitor of the clathrin-mediated endocytosis pathway, and, to a lesser extent, by filipin III or nystatin, inhibitors of the lipid-raft endocytosis pathway, whereas transfection with the non-targeted polyplexes was inhibited mainly by nystatin or filipin III. The targeted polyplexes caused significantly higher in vivo transfection of melanoma tumor cells after intratumoral administration compared to the non-targeted control. The targeted polyplexes carrying the HSVtk gene, after ganciclovir administration, more efficiently inhibited melanoma tumor growth and prolonged the lifespan of DBA/2 tumor-bearing mice compared to the non-targeted ones. Packed targeted polyplexes appeared and accumulated in the melanoma cells 6h earlier than the non-targeted ones. The targeted polyplexes enter into the nuclei of the melanoma cells more rapidly than the non-targeted control, and this difference may also be attributed to processes of receptor-mediated endocytosis. We believe that these data may be useful for the optimization of polyplex systems.

Modular nanotransporters: a multipurpose in vivo working platform for targeted drug delivery

Background

Modular nanotransporters (MNT) are recombinant multifunctional polypeptides created to exploit a cascade of cellular processes, initiated with membrane receptor recognition to deliver selective short-range and highly cytotoxic therapeutics to the cell nucleus. This research was designed for in vivo concept testing for this drug delivery platform using two modular nanotransporters, one targeted to the α-melanocyte-stimulating hormone (αMSH) receptor overexpressed on melanoma cells and the other to the epidermal growth factor (EGF) receptor overexpressed on several cancers, including glioblastoma, and head-and-neck and breast carcinoma cells.

Methods

In vivo targeting of the modular nanotransporter was determined by immuno-fluorescence confocal laser scanning microscopy and by accumulation of ¹²⁵I-labeled modular nanotransporters. The in vivo therapeutic effects of the modular nanotransporters were assessed by photodynamic therapy studies, given that the cytotoxicity of photosensitizers is critically dependent on their delivery to the cell nucleus.

Results

Immunohistochemical analyses of tumor and neighboring normal tissues of mice injected with multifunctional nanotransporters demonstrated preferential uptake in tumor tissue, particularly in cell nuclei. With ¹²⁵I-labeled MNT{αMSH}, optimal tumor:muscle and tumor:skin ratios of 8:1 and 9.8:1, respectively, were observed 3 hours after injection in B16-F1 melanoma-bearing mice. Treatment with bacteriochlorin p-MNT{αMSH} yielded 89%–98% tumor growth inhibition and a two-fold increase in survival for mice with B16-F1 and Cloudman S91 melanomas. Likewise, treatment of A431 human epidermoid carcinoma-bearing mice with chlorin e₆- MNT{EGF} resulted in 94% tumor growth inhibition compared with free chlorin e₆, with 75% of animals surviving at 3 months compared with 0% and 20% for untreated and free chlorin e₆-treated groups, respectively.

Conclusion

The multifunctional nanotransporter approach provides a new in vivo functional platform for drug development that could, in principle, be applicable to any combination of cell surface receptor and agent (photosensitizers, oligonucleotides, radionuclides) requiring nuclear delivery to achieve maximum effectiveness.

Abstract 5485: Modular nanotransporters: a chimeric multi-functional platform for drug delivery in vivo

A major challenge in the development of specific and effective targeted treatments is the paradoxical situation: one needs to exploit surface molecular targets for achieving tumor selectivity and nevertheless needs to deliver the therapeutic inside the target cell, e.g. to the cell nucleus because subcellular targeting is generally required for maximizing the therapeutic effect.

We created modular nanotransporters (MNT) unifying these 2 contradictory features into one chimeric macromolecule consisting of:- (i) an internalizable ligand module, (ii) a module with nuclear localization sequence, (iii) an endosomolytic module, and (iv) a carrier module. The modules retained their functions within the MNT: they showed high-affinity interactions with target receptors and alpha/beta-importin dimers, and form holes in lipid bilayers at endosomal pH. Anti-cancer therapeutics (photosensitizers, alpha-particle emitting radionuclides) carried by MNT acquired 20-3000 times greater cytotoxicity and cell specificity if compared with free therapeutics.

Herein, we have demonstrated in vivo that MNT possess a unique combination of properties compared with other scaffolds for drug delivery such as antibodies, nanoparticles, and liposomes. The MNT can be freeze-dried and reconstituted without loss of activity. Different modules can be inserted into the MNT in order to impart them with a specific set of capabilities; the modules are interchangeable, so they can be adapted for different cell types and/or different subcellular targets. The MNT can be used for the delivery of many types of therapeutics; they demonstrate low toxicity and low induction of delayed type hypersensitivity in mice. The MNT accumulated in murine tumors with high tumor: non-tumor ratios and displayed preferential accumulation in the subcellular compartment of choice, e.g. the cell nucleus. And finally, anti-cancer therapeutics carried by MNT acquired significantly greater cytotoxicity and cell specificity compared with free therapeutics.

We think that the MNT represent a new platform for targeted drug delivery that could be applied to the treatment of aberrant cell populations characterized by up regulation of a receptor for which there is a known ligand.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5485.