Development and Characterization of High Efficacy Cell-Penetrating Peptide via Modulation of the Histidine and Arginine Ratio for Gene Therapy

Endosomal Escape and Nuclear Localization: Critical Barriers for Therapeutic Nucleic Acids

Therapeutic nucleic acids (TNAs) including antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) have emerged as promising treatment strategies for a wide variety of diseases, offering the potential to modulate gene expression with a high degree of specificity. These small, synthetic nucleic acid-like molecules provide unique advantages over traditional pharmacological agents, including the ability to target previously "undruggable" genes. Despite this promise, several biological barriers severely limit their clinical efficacy. Upon administration, TNAs primarily enter cells through endocytosis, becoming trapped inside membrane-bound vesicles known as endosomes. Studies estimate that only 1-2% of TNAs successfully escape endosomal compartments to reach the cytosol, and in some cases the nucleus, where they bind target mRNA and exert their therapeutic effect. Endosomal entrapment and inefficient nuclear localization are therefore critical bottlenecks in the therapeutic application of TNAs. This review explores the current understanding of TNA endosomal escape and nuclear transport along with strategies aimed at overcoming these challenges, including the use of endosomal escape agents, peptide-TNA conjugates, non-viral delivery vehicles, and nuclear localization signals. By improving both endosomal escape and nuclear localization, significant advances in TNA-based therapeutics can be realized, ultimately expanding their clinical utility.

Alkylated RALA-Derived Peptides for Efficient Gene Delivery

RALA is an amphipathic cationic peptide demonstrated to be a low-toxicity and high-efficiency delivery platform for the systemic delivery of nucleic acid therapeutics. This work reports three RALA-derived peptides modified with N-terminal palmitic acid, engineered through amino acid substitutions and truncated sequences. All three peptides have good nucleic acid encapsulation, release and uptake, biocompatibility, and endolysosome escape. The siRNA transfection efficiency is about 90%, and the silencing rate of GA (C16-GLFWHHHARLARALARHLARALRA) exceeds that of lipofectamine 2000 (siRNA concentration = 50 nM). Truncating the peptide chain while retaining a certain amount of arginine ensures an effective particle size. Replacing glutamic acid with three histidines ensures an effective zeta potential and accelerates the endosome escape process through the proton sponge phenomenon. Introducing phenylalanine enhances the carrier-cell interaction. We believe that they are powerful carriers of siRNA therapy and may have good application prospects in treating various diseases.

Nucleic acid drugs: recent progress and future perspectives

High efficacy, selectivity and cellular targeting of therapeutic agents has been an active area of investigation for decades. Currently, most clinically approved therapeutics are small molecules or protein/antibody biologics. Targeted action of small molecule drugs remains a challenge in medicine. In addition, many diseases are considered 'undruggable' using standard biomacromolecules. Many of these challenges however, can be addressed using nucleic therapeutics. Nucleic acid drugs (NADs) are a new generation of gene-editing modalities characterized by their high efficiency and rapid development, which have become an active research topic in new drug development field. However, many factors, including their low stability, short half-life, high immunogenicity, tissue targeting, cellular uptake, and endosomal escape, hamper the delivery and clinical application of NADs. Scientists have used chemical modification techniques to improve the physicochemical properties of NADs. In contrast, modified NADs typically require carriers to enter target cells and reach specific intracellular locations. Multiple delivery approaches have been developed to effectively improve intracellular delivery and the in vivo bioavailability of NADs. Several NADs have entered the clinical trial recently, and some have been approved for therapeutic use in different fields. This review summarizes NADs development and evolution and introduces NADs classifications and general delivery strategies, highlighting their success in clinical applications. Additionally, this review discusses the limitations and potential future applications of NADs as gene therapy candidates.

Synthesis and characterisation of a nucleotide based pro-drug formulated with a peptide into a nano-chemotherapy for colorectal cancer

Recent studies in colorectal cancer patients (CRC) have shown that increased resistance to thymidylate synthase (TS) inhibitors such as 5-fluorouracil (5-FU), reduce the efficacy of standard of care (SoC) treatment regimens. The nucleotide pool cleanser dUTPase is highly expressed in CRC and is an attractive target for potentiating anticancer activity of chemotherapy. The purpose of the current work was to investigate the activity of P1, P4-di(2',5'-dideoxy-5'-selenouridinyl)-tetraphosphate (P4-SedU2), a selenium-modified symmetrically capped dinucleoside with prodrug capabilities that is specifically activated by dUTPase. Using mechanochemistry, P4-SedU2 and the corresponding selenothymidine analogue P4-SeT2 were prepared with a yield of 19% and 30% respectively. The phosphate functionality facilitated complexation with the amphipathic cell-penetrating peptide RALA to produce nanoparticles (NPs). These NPs were designed to deliver P4-SedU2 intracellularly and thereby maximise in vivo activity. The NPs demonstrated effective anti-cancer activity and selectivity in the HCT116 CRC cell line, a cell line that overexpresses dUTPase; compared to HT29 CRC cells and NCTC-929 fibroblast cells which have reduced levels of dUTPase expression. In vivo studies in BALB/c SCID mice revealed no significant toxicity with respect to weight or organ histology. Pharmacokinetic analysis of blood serum showed that RALA facilitates effective delivery and rapid internalisation into surrounding tissues with NPs eliciting lower plasma Cmax than the equivalent injection of free P4-SedU2, translating the in vitro findings. Tumour growth delay studies have demonstrated significant inhibition of growth dynamics with the tumour doubling time extended by >2weeks. These studies demonstrate the functionality and action of a new pro-drug nucleotide for CRC.

Food-Derived Peptides: Beneficial CNS Effects and Cross-BBB Transmission Strategies

Food-derived peptides, as dietary supplements, have significant effects on promoting brain health and relieving central nervous system (CNS) diseases. However, the blood-brain barrier (BBB) greatly limits their in-brain bioavailability. Thus, overcoming the BBB to target the CNS is a major challenge for bioactive peptides in the prevention and treatment of CNS diseases. This review discusses improvement in the neuroprotective function of food-derived active peptides in CNS diseases, as well as the source of BBB penetrating peptides (BBB-shuttles) and the mechanism of transmembrane transport. Notably, this review also discusses various peptide modification methods to overcome the low permeability and stability of the BBB. Lipification, glycosylation, introduction of disulfide bonds, and cyclization are effective strategies for improving the penetration efficiency of peptides through the BBB. This review provides a new prospective for improving their neuroprotective function and developing treatments to delay or even prevent CNS diseases.

In situ transient transfection of 3D cell cultures and tissues, a promising tool for tissue engineering and gene therapy

Various research fields use the transfection of mammalian cells with genetic material to induce the expression of a target transgene or gene silencing. It is a tool widely used in biological research, bioproduction, and therapy. Current transfection protocols are usually performed on 2D adherent cells or suspension cultures. The important rise of new gene therapies and regenerative medicine in the last decade raises the need for new tools to empower the in situ transfection of tissues and 3D cell cultures. This review will present novel in situ transfection methods based on a chemical or physical non-viral transfection of cells in tissues and 3D cultures, discuss the advantages and remaining gaps, and propose future developments and applications.

Self-Assembly of Peptide-Lipid Nanoparticles for the Efficient Delivery of Nucleic Acids

A transfection formulation is successfully developed to deliver nucleic acids by adding an auxiliary lipid (DOTAP) to the peptide, and the transfection efficiency of pDNA reaches 72.6%, which is close to Lipofectamine 2000. In addition, the designed KHL peptide-DOTAP complex exhibits good biocompatibility by cytotoxicity and hemolysis analysis. The mRNA delivery experiment indicates that the complex had a 9- or 10-fold increase compared with KHL or DOTAP alone. Intracellular localization shows that KHL/DOTAP can achieve good endolysosomal escape. Our design provides a new platform for improving the transfection efficiency of peptide vectors.

Aspartate beta-hydroxylase domain containing 1 as a prognostic marker associated with immune infiltration in skin cutaneous melanoma

BACKGROUND

Skin cutaneous melanoma (SKCM) is an extremely malignant tumor and accounts for the majority of skin cancer deaths. Aspartate beta-hydroxylase domain containing 1 (ASPHD1) may participate in cancer progression through controlling α-ketoglutarate-dependent dioxygenases. However, its role in skin cutaneous melanoma (SKCM) has not been well studied.

METHODS

The gene expression data of ASPDH1 and differentially expressed genes (DEGs) from TCGA and GTEx were evaluated, and verified via the GEO database. Then, we performed GO/KEGG, GSEA, PPI network analysis to analyze the functional implications of the DEGs related to ASPHD1. Then, the association between the ASPHD1 expression and clinical parameters was investigated by Cox regression analysis. Subsequently, the survival time of SKCM patients was evaluated by plotting Kaplan-Meier curves. Moreover, we investigated the correlation between the ASPHD1 expression and lymphocytic infiltration by using the data from TISIDB and TIMER 2.0. Next, we explored the association between ASPHD1 expression and drug sensitivity. Finally, we validate the expression differences by analyzing the results of qPCR, Western blot from human normal epidermal melanocytes and melanoma cells, and immunohistochemistry (IHC) from non-tumor skin as well as melanoma tissues.

RESULTS

The ASPHD1 expression level was significantly upregulated in several cancers, including SKCM especially SKCM-metastasis tissues, and patients with an increased ASPHD1 expression had longer overall survival time than low expression ones. The functional enrichment analysis of ASPHD1-related DEGs showed an association with cell development regulation and tumorigenic pathways. Furthermore, the increased ASPHD1 expression level was associated with the level of immunostimulors, immunoinhibitors, chemokines, and TILs, such as CD4⁺, CD8⁺ T cell, mast cell, Th2 cell, and dendritic cell. More interesting, we found that ASPHD1 expression was tightly associated with CTLA4 and CD276 which are immune checkpoint markers. Moreover, the upregulated expression of ASPHD1 exhibited higher IC50 values for 24 chemotherapy drugs, including doxorubicin, and masitinib. Finally, the differential expression of ASPHD1 in SKCM was validated by the results of qPCR, Western blot, and IHC.

CONCLUSION

The expression of ASPHD1 in SKCM patients is closely related to patient survival. ASPHD1 may participate in the regulation of tumor immune microenvironment. Additionally, it may serve as a prognostic biomarker for SKCM and future in-depth studies are necessary to explore its value.

Elastin-Derived VGVAPG Fragment Decorated Cell-Penetrating Peptide with Improved Gene Delivery Efficacy

Cell-penetrating peptides (CPPs) are attractive non-viral gene delivery vectors due to their high transfection capacity and safety. Previously, we have shown that cell-penetrating peptide RALA can be a promising gene delivery vector for chronic wound regeneration application. In this study, we engineered a novel peptide called RALA-E by introducing elastin-derived VGVAPG fragment into RALA, in order to target the elastin-binding protein on the cell surface and thus improve delivery efficacy of RALA. The transfection efficiency of RALA-E was evaluated by transfecting the HEK-293T and HeLa cell lines cells with RALA-E/pDNA complexes and the flow-cytometry results showed that RALA-E significantly increased the transfection efficiency by nearly 20% in both cell lines compared to RALA. Inhibition of pDNA transfection on HEK-293T cells via chlorpromazine, genistein and mβCD showed that the inhibition extent in transfection efficiency was much less for RALA-E group compared to RALA group. In addition, RALA-E/miR-146a complexes showed up to 90% uptake efficiency in macrophages, and can escape from the endosome and enter the nucleus to inhibit the expression of inflammation genes. Therefore, the developed RALA-E peptide has high potential as a safe and efficient vector for gene therapy application.

Application of Peptides in Construction of Nonviral Vectors for Gene Delivery

Gene therapy, which aims to cure diseases by knocking out, editing, correcting or compensating abnormal genes, provides new strategies for the treatment of tumors, genetic diseases and other diseases that are closely related to human gene abnormalities. In order to deliver genes efficiently to abnormal sites in vivo to achieve therapeutic effects, a variety of gene vectors have been designed. Among them, peptide-based vectors show superior advantages because of their ease of design, perfect biocompatibility and safety. Rationally designed peptides can carry nucleic acids into cells to perform therapeutic effects by overcoming a series of biological barriers including cellular uptake, endosomal escape, nuclear entrance and so on. Moreover, peptides can also be incorporated into other delivery systems as functional segments. In this review, we referred to the biological barriers for gene delivery in vivo and discussed several kinds of peptide-based nonviral gene vectors developed for overcoming these barriers. These vectors can deliver different types of genetic materials into targeted cells/tissues individually or in combination by having specific structure-function relationships. Based on the general review of peptide-based gene delivery systems, the current challenges and future perspectives in development of peptidic nonviral vectors for clinical applications were also put forward, with the aim of providing guidance towards the rational design and development of such systems.

Comparing Variants of the Cell-Penetrating Peptide sC18 to Design Peptide-Drug Conjugates

Herein, the design and synthesis of peptide-drug conjugates (PDCs) including different variants of the cell-penetrating peptide sC18 is presented. We first generated a series of novel sequence mutants of sC18 having either amino acid deletions and/or substitutions, and then tested their biological activity. The effects of histidine substituents were found to be not meaningful for sC18 uptake and cell selectivity. Moreover, building a nearly perfect amphipathic structure within a shortened sC18 derivative provided a peptide that was highly membrane-active, but also too cytotoxic. As a result, the most promising analog was sC18^ΔE, which stands out due to its higher uptake efficacy compared to parent sC18. In the last set of experiments, we let the peptides react with the cytotoxic drug doxorubicin by Thiol-Michael addition to form novel PDCs. Our results indicate that sC18^ΔE could be a more efficient drug carrier than parent sC18 for biomedical applications. However, cellular uptake using endocytosis and resulting entrapment of cargo inside vesicles is still a major critical step to overcome in CPP-containing peptide-drug development.

Efficient Induction of Antigen-Specific CD8+ T-Cell Responses by Cationic Peptide-Based mRNA Nanoparticles

A major determinant for the success of mRNA-based vaccines is the composition of the nanoparticles (NPs) used for formulation and delivery. Cationic peptides represent interesting candidate carriers for mRNA, since they have been shown to efficiently deliver nucleic acids to eukaryotic cells. mRNA NPs based on arginine-rich peptides have previously been demonstrated to induce potent antigen-specific CD8+ T-cell responses. We therefore compared the histidine-rich amphipathic peptide LAH4-L1 (KKALLAHALHLLALLALHLAHALKKA) to the fully substituted arginine variant (LAH4-L1R) for their capacity to formulate mRNA and transfect dendritic cells (DCs). Although both peptides encapsulated mRNA to the same extent, and showed excellent uptake in DCs, the gene expression level was significantly higher for LAH4-L1. The LAH4-L1–mRNA NPs also resulted in enhanced antigen presentation in the context of MHC I compared to LAH4-L1R in primary murine CD103+ DCs. Both peptides induced DC maturation and inflammasome activation. Subsequent ex vivo stimulation of OT-I splenocytes with transfected CD103+ DCs resulted in a high proportion of polyfunctional CD8+ T cells for both peptides. In addition, in vivo immunization with LAH4-L1 or LAH4-L1R–mRNA NPs resulted in proliferation of antigen-specific T cells. In conclusion, although LAH4-L1 outperformed LAH4-L1R in terms of transfection efficiency, the immune stimulation ex vivo and in vivo was equally efficient.

Special Issue: Biopolymer-Based Materials for Biomedical Engineering

In the field of tissue engineering and regenerative medicine (TERM), the use of traditional biomaterials capable of integrating the host tissue to promote the healing and regenerative process while it degrades has become less and less a focus of inspiration [...].