Tumor-targeting peptides from combinatorial libraries

Peptides for microbe-induced cancers: latest therapeutic strategies and their advanced technologies

Cancer is a significant global health concern associated with multiple distinct factors, including microbial and viral infections. Numerous studies have elucidated the role of microorganisms, such as Helicobacter pylori (H. pylori), as well as viruses for example human papillomavirus (HPV), hepatitis B virus (HBV), and hepatitis C virus (HCV), in the development of human malignancies. Substantial attention has been focused on the treatment of these microorganism- and virus-associated cancers, with promising outcomes observed in studies employing peptide-based therapies. The current paper provides an overview of microbe- and virus-induced cancers and their underlying molecular mechanisms. We discuss an assortment of peptide-based therapies which are currently being developed, including tumor-targeting peptides and microbial/viral peptide-based vaccines. We describe the major technological advancements that have been made in the design, screening, and delivery of peptides as anticancer agents. The primary focus of the current review is to provide insight into the latest research and development in this field and to provide a realistic glimpse into the future of peptide-based therapies for microbe- and virus-induced neoplasms.

Identification and anticoagulant mechanisms of novel factor XIa inhibitory peptides by virtual screening of a in silico generated deep-sea peptide database

The objective of this study was to identify novel anticoagulant peptides from the deep-sea using multiple in silico methods, and to investigate their inhibitory activity and molecular mechanisms. A deep-sea peptide database was firstly constructed by performing virtual proteolysis on protein sequences from animals inhabiting deep-sea hydrothermal vents and cold seeps. Candidate anticoagulant peptides were identified through molecular docking and binding free energy screening against FXIa as the target. Two novel anticoagulant peptides, PRNIF (IC50 = 0.67 mM) and GNDRCL (IC50 = 1.52 mM), were identified, and their anticoagulant activities were verified in vitro. PRNIF was demonstrated to be a noncompetitive inhibitor of FXIa, and caused significant prolongation of thrombin time (TT) and activated partial thromboplastin time (APTT), whereas GNDRCL markedly prolonged the APTT only. Molecular dynamics simulations demonstrated considerable conformational shifts of both anticoagulant peptides when bound to the active sites of FXIa. The lowest energy binding poses of the FXIa-peptide complexes for PRNIF and GNDRCL exhibited comparable numbers of hydrogen bonds and binding free energies. However, occupancy analysis revealed completely distinct stability characteristics of the hydrogen bond interactions. The conserved residue Asp569 in the S1 pocket of FXIa formed strong and stable hydrogen bonds as well as a salt bridge with the arginine residues of PRNIF, which were not observed in the FXIa-GNDRCL complex. To our knowledge, PRNIF represented the first FXIa inhibitory peptide derived from the deep-sea, which may contribute to the development and utilization of deep-sea peptides resources. Two deep-sea peptides may potentially serve as an alternative food-derived ingredient that could be utilized for thrombosis prevention.

Ascorbate: a forgotten component in the cytotoxicity of Cu(II) ATCUN peptide complexes

In 1983, Linus Pauling and colleagues reported about enhanced antitumor activity of the Cu(II) complex of the simplest ATCUN (amino terminal Cu(II) and Ni(II)-binding motif) peptide (NH2-Gly-Gly-His-COOH, GGH) in the presence of ascorbate as an additive. In the following 4 decades, structural modifications of this complex were implemented, however, anticancer activity could not be significantly increased. This has led to neglecting the ATCUN motif and its Cu(II) complexes as potential chemotherapeutic agents. Furthermore, the addition of ascorbate with its positive effect on the anticancer activity has fallen into oblivion. In this work, we compared Cu(II) GGH with Cu(II) ATCUN peptides bearing β-Ala instead of Gly at the 2nd position of the peptide sequence regarding their in vitro complex stability and cytotoxicity (MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and annexin V-FITC (fluorescein isothiocyanate) apoptosis assay) towards three cancer cell lines (AGS, HeLa and NCI-N87). Such an exchange of amino acids led to an up to three-fold higher cytotoxic effect in the presence of ascorbate. We thus achieved a significant increase in the otherwise moderate cytotoxicity of Cu(II) ATCUN-like complexes. Lipophilicity assays (n-octanol/water coefficient, log P values) of the studied complexes were used to evaluate differences in the antiproliferative activity.

Facile Peptide Macrocyclization and Multifunctionalization via Cyclen Installation

Cyclen-peptide bioconjugates are usually prepared in multiple steps that require individual preparation and purification of the cyclic peptide and hydrophilic cyclen derivatives. An efficient strategy is discovered for peptide cyclization and functionalization toward lanthanide probe via three components intermolecular crosslinking on solid-phase peptide synthesis with high conversion yield. Multifunctionality can be conferred by introducing different modular parts or/and metal ions on the cyclen-embedded cyclopeptide. As a proof-of-concept, a luminescent Eu3+ complex and a Gd3+-based contrasting agent for in vitro optical imaging and in vivo magnetic resonance imaging, respectively, are demonstrated through utilizing this preparation of cyclen-embedded cyclic arginylglycylaspartic acid (RGD) peptide.

Enhancing siRNA cancer therapy: Multifaceted strategies with lipid and polymer-based carrier systems

Cancers are increasing in prevalence and many challenges remain for their treatment, such as chemoresistance and toxicity. In this context, siRNA-based therapeutics have many potential advantages for cancer therapies as a result of their ability to reduce or prevent expression of specific cancer-related genes. However, the direct delivery of naked siRNA is hindered by issues like enzymatic degradation, insufficient cellular uptake, and poor pharmacokinetics. Hence, the discovery of a safe and efficient delivery vehicle is essential. This review explores various lipid and polymer-based delivery systems for siRNA in cancer treatment. Both polymers and lipids have garnered considerable attention as carriers for siRNA delivery. While all of these systems protect siRNA and enhance transfection efficacy, each exhibits its unique strengths. Lipid-based delivery systems, for instance, demonstrate high entrapment efficacy and utilize cost-effective materials. Conversely, polymeric-based delivery systems offer advantages through chemical modifications. Nonetheless, certain drawbacks still limit their usage. To address these limitations, combining different materials in formulations (lipid, polymer, or targeting agent) could enhance pharmaceutical properties, boost transfection efficacy, and reduce side effects. Furthermore, co-delivery of siRNA with other therapeutic agents presents a promising strategy to overcome cancer resistance. Lipid-based delivery systems have been demonstrated to encapsulate many therapeutic agents and with high efficiency, but most are limited in terms of the functionalities they display. In contrast, polymeric-based delivery systems can be chemically modified by a wide variety of routes to include multiple components, such as release or targeting elements, from the same materials backbone. Accordingly, by incorporating multiple materials such as lipids, polymers, and/or targeting agents in RNA formulations it is possible to improve the pharmaceutical properties and therapeutic efficacy while reducing side effects. This review focuses on strategies to improve siRNA cancer treatments and discusses future prospects in this important field.

Emerging and Biological Concepts in Pediatric High-Grade Gliomas

Primary central nervous system tumors are the most frequent solid tumors in children, accounting for over 40% of all childhood brain tumor deaths, specifically high-grade gliomas. Compared with pediatric low-grade gliomas (pLGGs), pediatric high-grade gliomas (pHGGs) have an abysmal survival rate. The WHO CNS classification identifies four subtypes of pHGGs, including Grade 4 Diffuse midline glioma H3K27-altered, Grade 4 Diffuse hemispheric gliomas H3-G34-mutant, Grade 4 pediatric-type high-grade glioma H3-wildtype and IDH-wildtype, and infant-type hemispheric gliomas. In recent years, we have seen promising advancements in treatment strategies for pediatric high-grade gliomas, including immunotherapy, CAR-T cell therapy, and vaccine approaches, which are currently undergoing clinical trials. These therapies are underscored by the integration of molecular features that further stratify HGG subtypes. Herein, we will discuss the molecular features of pediatric high-grade gliomas and the evolving landscape for treating these challenging tumors.

Encoding and display technologies for combinatorial libraries in drug discovery: The coming of age from biology to therapy

Drug discovery is a sophisticated process that incorporates scientific innovations and cutting-edge technologies. Compared to traditional bioactivity-based screening methods, encoding and display technologies for combinatorial libraries have recently advanced from proof-of-principle experiments to promising tools for pharmaceutical hit discovery due to their high screening efficiency, throughput, and resource minimization. This review systematically summarizes the development history, typology, and prospective applications of encoding and displayed technologies, including phage display, ribosomal display, mRNA display, yeast cell display, one-bead one-compound, DNA-encoded, peptide nucleic acid-encoded, and new peptide-encoded technologies, and examples of preclinical and clinical translation. We discuss the progress of novel targeted therapeutic agents, covering a spectrum from small-molecule inhibitors and nonpeptidic macrocycles to linear, monocyclic, and bicyclic peptides, in addition to antibodies. We also address the pending challenges and future prospects of drug discovery, including the size of screening libraries, advantages and disadvantages of the technology, clinical translational potential, and market space. This review is intended to establish a comprehensive high-throughput drug discovery strategy for scientific researchers and clinical drug developers.

Placenta-targeted Treatment Strategies for Preeclampsia and Fetal Growth Restriction: An Opportunity and Major Challenge

The placenta plays a crucial role in maintaining normal pregnancy. The failure of spiral artery remodeling (SAR) is a key factor leading to placental ischemia and poor perfusion which is strongly associated with obstetric diseases, including preeclampsia (PE) and fetal growth restriction (FGR). Existing interventions for PE and FGR are limited and termination of pregnancy is inevitable when the maternal or fetus condition deteriorates. Considering the safety of the mother and fetus, treatments that may penetrate the placental barrier and harm the fetus are not accepted. Developing targeted treatment strategies for these conditions is urgent and necessary. With the proven efficacy of targeted therapy in treating conditions such as endometrial cancer and trophoblastic tumors, research on placental dysfunction continues to deepen. This article reviews the studies on placenta-targeted treatment and drug delivery strategies, summarizes the characteristics proposes corresponding improvement measures in targeted treatment, provides solutions for existing problems, and makes suggestions for future studies.

Intelligent Biomaterialomics: Molecular Design, Manufacturing, and Biomedical Applications

Materialomics integrates experiment, theory, and computation in a high-throughput manner, and has changed the paradigm for the research and development of new functional materials. Recently, with the rapid development of high-throughput characterization and machine-learning technologies, the establishment of biomaterialomics that tackles complex physiological behaviors has become accessible. Breakthroughs in the clinical translation of nanoparticle-based therapeutics and vaccines have been observed. Herein, recent advances in biomaterials, including polymers, lipid-like materials, and peptides/proteins, discovered through high-throughput screening or machine learning-assisted methods, are summarized. The molecular design of structure-diversified libraries; high-throughput characterization, screening, and preparation; and, their applications in drug delivery and clinical translation are discussed in detail. Furthermore, the prospects and main challenges in future biomaterialomics and high-throughput screening development are highlighted.

Synthesis and biological evaluation of EGFR binding peptides for near-infrared photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that involves photoimmunotherapy drug injection and NIR light exposure. In NIR-PIT, antibodies are commonly used as target-directed molecules carrying IRDye700DX (IR700). However, antibodies have disadvantages, such as high cost, complex development strategies, and poor tumor penetration. In contrast, peptides have lower production costs, can be easy to chemically synthesize and modify, and can also be used for tumor-targeting like antibodies. In this study, we developed a novel PIT drug using a peptide as the target-directed molecule. Epidermal growth factor receptor (EGFR) was selected as the target, and monovalent and bivalent EGFR-binding peptides were synthesized. The bivalent peptide showed sufficient binding to EGFR-positive cells, and a bivalent peptide-IR700 conjugate with a long linker induced morphological changes in EGFR-positive cells. Additionally, the drug significantly reduced cell viability in vitro in an NIR light-dose- and drug-concentration-dependent manner. These results indicate the feasibility of NIR-PIT in treating cancer using peptide-based drugs.

Peptide-based non-viral gene delivery: A comprehensive review of the advances and challenges

Gene therapy is the most effective treatment option for diseases, but its effectiveness is affected by the choice and design of gene carriers. The genes themselves have to pass through multiple barriers in order to enter the cell and therefore require additional vectors to carry them inside the cell. In gene therapy, peptides have unique properties and potential as gene carriers, which can effectively deliver genes into specific cells or tissues, protect genes from degradation, improve gene transfection efficiency, and enhance gene targeting and biological responsiveness. This paper reviews the research progress of peptides and their derivatives in the field of gene delivery recently, describes the obstacles encountered by foreign materials to enter the interior of the cell, and introduces the following classes of functional peptides that can carry materials into the interior of the cell, and assist in transmembrane translocation of carriers, thus breaking through endosomal traps to enable successful entry of genetic materials into the nucleus of the cell. The paper also discusses the combined application of peptide vectors with other vectors to enhance its transfection ability, explores current challenges encountered by peptide vectors, and looks forward to future developments in the field.

Recent Progress in Peptide-Based Molecular Probes for Disease Bioimaging

Recent strides in molecular pathology have unveiled distinctive alterations at the molecular level throughout the onset and progression of diseases. Enhancing the in vivo visualization of these biomarkers is crucial for advancing disease classification, staging, and treatment strategies. Peptide-based molecular probes (PMPs) have emerged as versatile tools due to their exceptional ability to discern these molecular changes with unparalleled specificity and precision. In this Perspective, we first summarize the methodologies for crafting innovative functional peptides, emphasizing recent advancements in both peptide library technologies and computer-assisted peptide design approaches. Furthermore, we offer an overview of the latest advances in PMPs within the realm of biological imaging, showcasing their varied applications in diagnostic and therapeutic modalities. We also briefly address current challenges and potential future directions in this dynamic field.

A lncRNA Dleu2-encoded peptide relieves autoimmunity by facilitating Smad3-mediated Treg induction

Micropeptides encoded by short open reading frames (sORFs) within long noncoding RNAs (lncRNAs) are beginning to be discovered and characterized as regulators of biological and pathological processes. Here, we find that lncRNA Dleu2 encodes a 17-amino-acid micropeptide, which we name Dleu2-17aa, that is abundantly expressed in T cells. Dleu2-17aa promotes inducible regulatory T (iTreg) cell generation by interacting with SMAD Family Member 3 (Smad3) and enhancing its binding to the Foxp3 conserved non-coding DNA sequence 1 (CNS1) region. Importantly, the genetic deletion of Dleu2-17aa in mice by start codon mutation impairs iTreg generation and worsens experimental autoimmune encephalomyelitis (EAE). Conversely, the exogenous supplementation of Dleu2-17aa relieves EAE. Our findings demonstrate an indispensable role of Dleu2-17aa in maintaining immune homeostasis and suggest therapeutic applications for this peptide in treating autoimmune diseases.

Bioscreening specific peptide-expressing phage and its application in sensitive dual-mode immunoassay of SARS-CoV-2 spike antigen

Biorecognition components with high affinity and selectivity are vital in bioassay to diagnose and treat epidemic disease. Herein a phage display strategy of combining single-amplification-panning with non-amplification-panning was developed, by which a phage displaying cyclic heptapeptide ACLDWLFNSC (peptide J4) with good affinity and specificity to SARS-CoV-2 spike protein (SP) was identified. Molecular docking suggests that peptide J4 binds to S2 subunit by hydrogen bonding and hydrophobic interaction. Then the J4-phage was used as the capture antibody to establish phage-based chemiluminescence immunoassay (CLIA) and electrochemical impedance spectroscopy (EIS) analytical systems. The as-proposed dual-modal immunoassay platform exhibited good sensitivity and reliability in SARS-CoV-2 SP and pseudovirus assay. The limit of detection for SARS-CoV-2 SP by EIS immunoassay is 0.152 pg/mL, which is dramatically lower than that of 42 pg/mL for J4-phage based CLIA. Further, low to 40 transducing units (TU)/mL, 10 TU/mL SARS-CoV-2 pseudoviruses can be detected by the proposed J4-phage based CLIA and electrochemical immunosensor, respectively. Therefore, the as-developed dual mode immunoassays are potential methods to detect SARS-CoV-2. It is also expected to explore various phages with specific peptides to different targets for bioanalysis.

A simple method for developing lysine targeted covalent protein reagents

Peptide-based covalent probes can target shallow protein surfaces not typically addressable using small molecules, yet there is a need for versatile approaches to convert native peptide sequences into covalent binders that can target a broad range of residues. Here we report protein-based thio-methacrylate esters-electrophiles that can be installed easily on unprotected peptides and proteins via cysteine side chains, and react efficiently and selectively with cysteine and lysine side chains on the target. Methacrylate phosphopeptides derived from 14-3-3-binding proteins irreversibly label 14-3-3σ via either lysine or cysteine residues, depending on the position of the electrophile. Methacrylate peptides targeting a conserved lysine residue exhibit pan-isoform binding of 14-3-3 proteins both in lysates and in extracellular media. Finally, we apply this approach to develop protein-based covalent binders. A methacrylate-modified variant of the colicin E9 immunity protein irreversibly binds to the E9 DNAse, resulting in significantly higher thermal stability relative to the non-covalent complex. Our approach offers a simple and versatile route to convert peptides and proteins into potent covalent binders.

Toward tryptathionine-stapled one-bead-one-compound (OBOC) libraries: solid phase synthesis of a bioactive octretoate analog

New somatostatin analogs are highly desirable for diagnosing and treating neuroendocrine tumors (NETs). Here we describe the solid-phase synthesis of a new octreotate (TATE) analog where the disulfide bond is replaced with a tryptathionine (Ttn) staple as part of an effort to prototyping a one-bead-one-compound (OBOC) library of Ttn-stapled peptides. Library design provides the potential for on- and off-bead screening. To validate our method, we labelled Ttn-TATE with a fluorescent dye to demonstrate binding to soluble somatostatin receptor subtype-2 and staining of Ar42J rat prostate cancer cells. By exploring this staple in the context of a ligand of known affinity, this method paves the way for an OBOC library construction of bioactive octreotate analogs and, more broadly speaking, tryptathionine-staped peptide macrocycles.

Recent strategies of carbon dot-based nanodrugs for enhanced emerging antitumor modalities

Nanomaterial-based cancer therapy has recently emerged as a new therapeutic modality with the advantages of minimal invasiveness and negligible normal tissue toxicity over traditional cancer treatments. However, the complex microenvironment and self-protective mechanisms of tumors have suppressed the therapeutic effect of emerging antitumor modalities, which seriously hindered the transformation of these modalities to clinical settings. Due to the excellent biocompatibility, unique physicochemical properties and easy surface modification, carbon dots, as promising nanomaterials in the biomedical field, can effectively improve the therapeutic effect of emerging antitumor modalities as multifunctional nanoplatforms. In this review, the mechanism and limitations of emerging therapeutic modalities are described. Further, the recent advances related to carbon dot-based nanoplatforms in overcoming the therapeutic barriers of various emerging therapies are systematically summarized. Finally, the prospects and potential obstacles for the clinical translation of carbon dot-based nanoplatforms in tumor therapy are also discussed. This review is expected to provide a reference for nanomaterial design and its development for the efficacy enhancement of emerging therapeutic modalities.

Construction and Applications of Mammalian Cell-Based DNA-Encoded Peptide/Protein Libraries

DNA-encoded peptide/protein libraries are the starting point for protein evolutionary modification and functional peptide/antibody selection. Different display technologies, protein directed evolution, and deep mutational scanning (DMS) experiments employ DNA-encoded libraries to provide sequence variations for downstream affinity- or function-based selections. Mammalian cells promise the inherent post-translational modification and near-to-natural conformation of exogenously expressed mammalian proteins and thus are the best platform for studying transmembrane proteins or human disease-related proteins. However, due to the current technical bottlenecks of constructing mammalian cell-based large size DNA-encoded libraries, the advantages of mammalian cells as screening platforms have not been fully exploited. In this review, we summarize the current efforts in constructing DNA-encoded libraries in mammalian cells and the existing applications of these libraries in different fields.

Biopanning of specific peptide for SARS-CoV-2 nucleocapsid protein and enzyme-linked immunosorbent assay-based antigen assay

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread worldwide which triggered serious public health issues. The search for rapid and accurate diagnosis, effective prevention, and treatment is urgent. The nucleocapsid protein (NP) of SARS-CoV-2 is one of the main structural proteins expressed and most abundant in the virus, and is considered a diagnostic marker for the accurate and sensitive detection of SARS-CoV-2. Herein, we report the screening of specific peptides from the pIII phage library that bind to SARS-CoV-2 NP. The phage monoclone expressing cyclic peptide N1 (peptide sequence, ACGTKPTKFC, with C&C bridged by disulfide bonding) specifically recognizes SARS-CoV-2 NP. Molecular docking studies reveal that the identified peptide is bound to the "pocket" region on the SARS-CoV-2 NP N-terminal domain mainly by forming a hydrogen bonding network and through hydrophobic interaction. Peptide N1 with the C-terminal linker was synthesized as the capture probe for SARS-CoV-2 NP in ELISA. The peptide-based ELISA was capable of assaying SARS-CoV-2 NP at concentrations as low as 61 pg/mL (∼1.2 pM). Furthermore, the as-proposed method could detect the SARS-CoV-2 virus at limits as low as 50 TCID₅₀ (median tissue culture infective dose)/mL. This study demonstrates that selected peptides are powerful biomolecular tools for SARS-CoV-2 detection, providing a new and inexpensive method of rapidly screening infections as well as rapidly diagnosing coronavirus disease 2019 patients.

A Bispecific Peptide-Polymer Conjugate Bridging Target-Effector Cells to Enhance Immunotherapy

Peptide-based immune checkpoint inhibitors exhibit remarkable therapeutic benefits although their application is hindered by quick blood clearance and low affinity with receptors. The modification of the peptides into artificial antibodies is an ideal platform to solve these problems, and one of the optional pathways is the conjugation of peptides with a polymer. More importantly, the bridging effect, mediated by bispecific artificial antibodies, could promote the interaction of cancer cells and T cells, which will benefit cancer immunotherapy. Herein, a bispecific peptide-polymer conjugate (octa PEG-PD1-PDL1) is prepared by simultaneously conjugating PD1-binding and PDL1-binding peptides onto 8-arm-PEG. octa PEG-PD1-PDL1 bridges T cells and cancer cells and thus enhances T cell-mediated cytotoxicity against cancer cells. Meanwhile, the tumor-targeting octa PEG-PD1-PDL1 increases the infiltration of cytotoxic T lymphocytes in tumors and reduces their exhaustion. It effectively activates the tumor immune microenvironment and exerts a potent antitumor effect against CT26 tumor models with a tumor inhibition rate of 88.9%. This work provides a novel strategy to enhance tumor immunotherapy through conjugating bispecific peptides onto a hyperbranched polymer to effectively engage target-effector cells.

Linking peptide-oriented surface imprinting magnetic nanoparticle with carbon nanotube-based fluorescence signal output device for ultrasensitive detection of glycoprotein

Determination of trace glycoprotein has important guiding significance in clinical diagnosis and is usually achieved by immunoaffinity. However, immunoaffinity possesses inherent drawbacks, such as poor probability of high-quality antibodies, instability of biological reagents, and harmfulness of chemical labels to the body. Herein, we propose an innovative method of peptide-oriented surface imprinting to fabricate artificial antibody for recognition of glycoprotein. By integrating peptide-oriented surface imprinting and PEGylation, an innovative hydrophilic peptide-oriented surface imprinting magnetic nanoparticle (HPIMN) was successfully fabricated with human epidermal growth factor receptor-2 (HER2) as a model glycoprotein template. In addition, we further prepared a novel boronic acid-modified/fluorescein isothiocyanate-loaded/polyethylene glycol-covered carbon nanotube (BFPCN) as fluorescence signal output device, which was loaded with numerous fluorescent molecules could specifically label the cis-diol of glycoprotein at physiological pH via boronate-affinity interaction. To prove the practicability, we proposed a HPIMN-BFPCN strategy, in which the HPIMN first selectively captured the HER2 due to the molecular imprinted recognition and then the BFPCN specific labeled the exposed cis-diol of HER2 based on the boronate-affinity reaction. The HPIMN-BFPCN strategy exhibited ultrahigh sensitivity with limit of detection of 14 fg mL^-1 and was successfully used in the determination of HER2 in spiked sample with recovery and relative standard deviation in the range of 99.0%-103.0% and 3.1%-5.6%, respectively. Therefore, we believe that the novel peptide-oriented surface imprinting has great potential to become an universal strategy for fabrication of recognition units for other protein biomarkers, and the synergy sandwich assay could become a powerful tool in prognosis evaluation and clinical diagnosis of glycoprotein-related diseases.

Evolving strategies and application of proteins and peptide therapeutics in cancer treatment

Several proteins and peptides have therapeutic potential and can be used for cancer therapy. By binding to cell surface receptors and other indicators uniquely linked with or overexpressed on tumors compared to healthy tissue, protein biologics enhance the active targeting of cancer cells, as opposed to the passive targeting of cells by conventional small-molecule chemotherapeutics. This study focuses on peptide medications that exist to slow or stop tumor growth and the spread of cancer, demonstrating the therapeutic potential of peptides in cancer treatment. As an alternative to standard chemotherapy, peptides that selectively kill cancer cells while sparing healthy tissue are developing. A mountain of clinical evidence supports the efficacy of peptide-based cancer vaccines. Since a single treatment technique may not be sufficient to produce favourable results in the fight against cancer, combination therapy is emerging as an effective option to generate synergistic benefits. One example of this new area is the use of anticancer peptides in combination with nonpeptidic cytotoxic drugs or the combination of immunotherapy with conventional therapies like radiation and chemotherapy. This review focuses on the different natural and synthetic peptides obtained and researched. Discoveries, manufacture, and modifications of peptide drugs, as well as their contemporary applications, are summarized in this review. We also discuss the benefits and difficulties of potential advances in therapeutic peptides.

Generation of peptides using phage display technology for cancer diagnosis and molecular imaging

Cancer is one of the leading causes of mortality worldwide; nearly 10 million people died from it in 2020. The high mortality rate results from the lack of effective screening approaches where early detection cannot be achieved, reducing the chance of early intervention to prevent cancer development. Non-invasive and deep-tissue imaging is useful in cancer diagnosis, contributing to a visual presentation of anatomy and physiology in a rapid and safe manner. Its sensitivity and specificity can be enhanced with the application of targeting ligands with the conjugation of imaging probes. Phage display is a powerful technology to identify antibody- or peptide-based ligands with effective binding specificity against their target receptor. Tumour-targeting peptides exhibit promising results in molecular imaging, but the application is limited to animals only. Modern nanotechnology facilitates the combination of peptides with various nanoparticles due to their superior characteristics, rendering novel strategies in designing more potent imaging probes for cancer diagnosis and targeting therapy. In the end, a myriad of peptide candidates that aimed for different cancers diagnosis and imaging in various forms of research were reviewed.

Gex2SGen: Designing Drug-like Molecules from Desired Gene Expression Signatures

Drug-induced gene expression profiling provides a lot of useful information covering various aspects of drug discovery and development. Most importantly, this knowledge can be used to discover drugs' mechanisms of action. Recently, deep learning-based drug design methods are in the spotlight due to their ability to explore huge chemical space and design property-optimized target-specific drug molecules. Recent advances in accessibility of open-source drug-induced transcriptomic data along with the ability of deep learning algorithms to understand hidden patterns have opened opportunities for designing drug molecules based on desired gene expression signatures. In this study, we propose a deep learning model, Gex2SGen (Gene Expression 2 SMILES Generation), to generate novel drug-like molecules based on desired gene expression profiles. The model accepts desired gene expression profiles in a cell-specific manner as input and designs drug-like molecules which can elicit the required transcriptomic profile. The model was first tested against individual gene-knocked-out transcriptomic profiles, where the newly designed molecules showed high similarity with known inhibitors of the knocked-out target genes. The model was next applied on a triple negative breast cancer signature profile, where it could generate novel molecules, highly similar to known anti-breast cancer drugs. Overall, this work provides a generalized method, where the method first learned the molecular signature of a given cell due to a specific condition, and designs new small molecules with drug-like properties.

Design and synthesis of novel N-terminal peptides of integrin and aminopeptidase are new finding for anticancer activity

The short peptides, containing the amino acid sequence asparagine-glycine-arginine (NGR) and arginine-glycine-aspartic acid (RGD), possess the strong binding ability to N (APN/CD13) aminopeptidase receptor and integrin proteins involved in antitumor properties are overexpressed. A novel short N-terminal modified hexapeptides P1 and P2 was designed and synthesized using the Fmoc-chemistry solid phase peptide synthesis protocol. Notably, the cytotoxicity of the MTT assay demonstrated the viability of normal and cancer cells up to lower peptide concentrations. Interestingly, both peptides show good anticancer activities against the four cancer cells and normal cells namely, Hep-2, HepG2, MCF-7, A375, and Vero and compared with standard drugs, doxorubicin and paclitaxel. Additionally, in silico studies were applied to predict the binding sites and binding orientation of the peptides for potential anticancer targets. Steady-state fluorescence measurements showed that peptide P1 exhibits preferential interactions with POPC/POPG anionic bilayers rather than the zwitterionic POPC lipid bilayers and peptide P2, did not show any preferential interaction with lipids bilayers. But impressively, peptide P2 shows anticancer activity due to the NGR/RGD motif. Circular dichroism studies demonstrated that the peptide's secondary structure changes only minimally upon binding to the anionic lipid bilayers.

Localized Instillation Enables In Vivo Screening of Targeting Peptides Using One-Bead One-Compound Technology

The One-Bead One-Compound (OBOC) library screening is an efficient technique for identifying targeting peptides. However, due to the relatively large bead size, it is challenging for the OBOC method to be applied for in vivo screening. Herein, we report an in vivo Localized Instillation Beads library (LIB) screening method to discover targeting peptides with the OBOC technique. Inspired by localized instillation, we constructed a cavity inside of a transplanted tumor of a mouse. Then, the OBOC heptapeptide library was injected and incubated inside the tumor cavity. After an efficient elution process, the retained beads were gathered, from which three MDA-MB-231 tumor-targeting heptapeptides were discovered. It was verified that the best peptide had 1.9-fold higher tumor accumulation than the commonly used targeting peptide RGD in vivo. Finally, two targeting proteins were discovered as potential targets of our targeting peptide to the MDA-MB-231 tumor. The in vivo LIB screening method expands the scope of OBOC peptide screening applications to discover targeting peptides in vivo feasibly and reliably.

Ophthalmic Solution of Smart Supramolecular Peptides to Capture Semaphorin 4D against Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss in working age population. Intravitreal injection of anti-VEGF antibody is widely used in clinical practice. However, about 27% of patients show poor response to anti-VEGF therapy and about 50% of these patients continue to have macular thickening. Frequent intravitreal injections of antibody may increase the chance of endophthalmitis and cause visual loss or even blindness once happened. Therefore, there is a greatly urgent need for novel noninvasive target to treat DR clinically. Here, the formulation of a smart supramolecular peptide (SSP) eye drop for DR treatment that is effective via specifically identifying and capturing soluble semaphorin 4D (sSema4D), a strongly pro-angiogenesis and exudates factor, is reported. The SSP nanostructures encapsulate sSema4D so that all biological effects mediated by three receptors of sSema4D are inhibited, thereby significantly alleviating pathological retinal angiogenesis and exudates in DR. Moreover, it is found that combination of SSPs eye drop and anti-VEGF injection shows better therapeutic effect over anti-VEGF treatment alone. Overall, SSP eye drop provide an alternative and effective method for noninvasive treatment for DR.

Delivery of Theranostic Nanoparticles to Various Cancers by Means of Integrin-Binding Peptides

Active targeting of tumors is believed to be the key to efficient cancer therapy and accurate, early-stage diagnostics. Active targeting implies minimized off-targeting and associated cytotoxicity towards healthy tissue. One way to acquire active targeting is to employ conjugates of therapeutic agents with ligands known to bind receptors overexpressed onto cancer cells. The integrin receptor family has been studied as a target for cancer treatment for almost fifty years. However, systematic knowledge on their effects on cancer cells, is yet lacking, especially when utilized as an active targeting ligand for particulate formulations. Decoration with various integrin-targeting peptides has been reported to increase nanoparticle accumulation in tumors ≥ 3-fold when compared to passively targeted delivery. In recent years, many newly discovered or rationally designed integrin-binding peptides with excellent specificity towards a single integrin receptor have emerged. Here, we show a comprehensive analysis of previously unreviewed integrin-binding peptides, provide diverse modification routes for nanoparticle conjugation, and showcase the most notable examples of their use for tumor and metastases visualization and eradication to date, as well as possibilities for combined cancer therapies for a synergetic effect. This review aims to highlight the latest advancements in integrin-binding peptide development and is directed to aid transition to the development of novel nanoparticle-based theranostic agents for cancer therapy.

Targeted delivery of liposomal chemoimmunotherapy for cancer treatment

Chemoimmunotherapy that utilizes the immunomodulatory effect of chemotherapeutics has shown great promise for treating poorly immunogenic solid tumors. However, there remains a significant room for improving the synergy between chemotherapy and immunotherapy, including the efficient, concurrent delivery of chemotherapeutics and immunomodulators into tumors. Here, we report the use of metabolic glycan labeling to facilitate cancer-targeted delivery of liposomal chemoimmunotherapy. 4T1 triple-negative breast cancer cells can be metabolically labeled with azido groups for subsequently targeted conjugation of dibenzocycoloctyne (DBCO)-bearing liposomes loaded with doxorubicin and imiquimod (R837) adjuvant via efficient click chemistry. The encased doxorubicin can induce the immunogenic death of cancer cells and upregulate the expression of CD47 and calreticulin on the surface of cancer cells, while R837 can activate dendritic cells for enhanced processing and presentation of tumor antigens. Targeted delivery of liposomes encapsulating doxorubicin and R837 to 4T1 tumors, enabled by metabolic glycan labeling and click chemistry, showed the promise to reshape the immunosuppressive tumor microenvironment of solid tumors. This cancer-targetable liposomal chemoimmunotherapy could provide a new approach to improving conventional chemotherapy.

iRGD-grafted N-trimethyl chitosan-coated protein nanotubes enhanced the anticancer efficacy of curcumin and melittin

Curcumin (Cur) and Melittin (Mel) are two natural extracts that have been shown anti-tumor effects. However, their applications are limited due to poor oral bioavailability and the lack of tumor-targeting property. Here, we developed a novel nanocomposite that enabled the co-delivery of Cur and Mel, which consists of α-lactalbumin protein nanotubes (NTs), positively charged N,N,N-trimethyl chitosan (TMC), and a tumor-targeting cyclic peptide iRGD. The results showed that NTs/Cur-TMC-Mel-iRGD incorporated the advantages of each component, for instance, effective compounds loading by NTs, improved cellular uptake by TMC, prolonged accumulation in tumors by iRGD as well as synergistic anti-tumor effects of Cur and Mel. In the tumor-bearing mice, NTs/Cur-TMC-Mel-iRGD treatment remarkably induced cancer cell apoptosis while inhibiting cell proliferation, leading to suppressed tumor growth. Besides, no obvious adverse effects were observed in the blood physiology and tissue histology. Overall, our study provided an effective strategy for co-delivering Cur and Mel, which has a potential for translational clinical research aiming to treat solid tumors.

Cu and Zn Interactions with Peptides Revealed by High-Resolution Mass Spectrometry

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by abnormal extracellular amyloid-beta (Aβ) peptide depositions in the brain. Among amorphous aggregates, altered metal homeostasis is considered a common risk factor for neurodegeneration known to accelerate plaque formation. Recently, peptide-based drugs capable of inhibiting amyloid aggregation have achieved unprecedented scientific and pharmaceutical interest. In response to metal ions binding to Aβ peptide, metal chelation was also proposed as a therapy in AD. The present study analyzes the interactions formed between NAP octapeptide, derived from activity-dependent neuroprotective protein (ADNP), amyloid Aβ(9–16) fragment and divalent metal ions such as Cu and Zn. The binding affinity studies for Cu and Zn ions of synthetic NAP peptide and Aβ(9–16) fragment were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ion trap mass spectrometry (ESI-MS) and atomic force microscopy (AFM). Both mass spectrometric methods confirmed the formation of metal–peptide complexes while the AFM technique provided morphological and topographic information regarding the influence of metal ions upon peptide crystallization. Our findings showed that due to a rich histidine center, the Aβ(9–16) fragment is capable of binding metal ions, thus becoming stiff and promoting aggregation of the entire amyloid peptide. Apart from this, the protective effect of the NAP peptide was found to rely on the ability of this octapeptide to generate both chelating properties with metals and interactions with Aβ peptide, thus stopping its folding process.

Tachyplesin and CyLoP-1 as efficient anti-mycobacterial peptides: A novel finding

Mycobacterium tuberculosis is an etiological agent of tuberculosis (TB) known to be a highly contagious disease and is the major cause of mortality from a single infectious agent worldwide. Emergence of multi-drug resistant and extremely drug resistant strains of M. tuberculosis has made TB management extremely challenging eliciting the urgent need for alternative therapeutics. Peptide based therapeutic strategies are an emerging area that can be employed as a prospective alternative to the currently existing therapeutic regime for TB treatment. Here, we are reporting the anti-mycobacterial activity of two peptides, Tachyplesin and CyLoP-1, derived from marine horseshoe crab and snake toxin respectively, with potent anti-mycobacterial activity against various mycobacterium species. Both the peptides exhibit appreciable antimicrobial and anti-biofilm activities against mycobacterium species with minimum cytotoxicity towards macrophage cells. They are also effective in eliminating mycobacterium cells from infected macrophage cells. Tachyplesin acts on mycobacterium cells in a lytic manner with outer membrane disruption confirmed by propidium iodide uptake with slight membrane depolarization and reactive oxygen species (ROS) production. CyLoP-1, on the other hand, does not rupture the mycobacterium cells even at high concentrations. It seems to follow intracellular pathway of killing mycobacterium cells by production of more ROS and membrane depolarization. Both the peptides do not lead to apoptotic way of mycobacterium cell death. These results suggest an effective peptide-based antimicrobial strategy for development of future anti-TB therapeutics.

ADAMTS4-specific MR probe to assess aortic aneurysms in vivo using synthetic peptide libraries

The incidence of abdominal aortic aneurysms (AAAs) has substantially increased during the last 20 years and their rupture remains the third most common cause of sudden death in the cardiovascular field after myocardial infarction and stroke. The only established clinical parameter to assess AAAs is based on the aneurysm size. Novel biomarkers are needed to improve the assessment of the risk of rupture. ADAMTS4 (A Disintegrin And Metalloproteinase with ThromboSpondin motifs 4) is a strongly upregulated proteoglycan cleaving enzyme in the unstable course of AAAs. In the screening of a one-bead-one-compound library against ADAMTS4, a low-molecular-weight cyclic peptide is discovered with favorable properties for in vivo molecular magnetic resonance imaging applications. After identification and characterization, it's potential is evaluated in an AAA mouse model. The ADAMTS4-specific probe enables the in vivo imaging-based prediction of aneurysm expansion and rupture.

Anti-cancer peptide-based therapeutic strategies in solid tumors

BACKGROUND

Nowadays, conventional medical treatments such as surgery, radiotherapy, and chemotherapy cannot cure all types of cancer. A promising approach to treat solid tumors is the use of tumor-targeting peptides to deliver drugs or active agents selectively.

RESULT

Introducing beneficial therapeutic approaches, such as therapeutic peptides and their varied methods of action against tumor cells, can aid researchers in the discovery of novel peptides for cancer treatment. The biomedical applications of therapeutic peptides are highly interesting. These peptides, owing to their high selectivity, specificity, small dimensions, high biocompatibility, and easy modification, provide good opportunities for targeted drug delivery. In recent years, peptides have shown considerable promise as therapeutics or targeting ligands in cancer research and nanotechnology.

CONCLUSION

 This study reviews a variety of therapeutic peptides and targeting ligands in cancer therapy. Initially, three types of tumor-homing and cell-penetrating peptides (CPPs) are described, and then their applications in breast, glioma, colorectal, and melanoma cancer research are discussed.

The landscape of receptor-mediated precision cancer combination therapy via a single-cell perspective

Mining a large cohort of single-cell transcriptomics data, here we employ combinatorial optimization techniques to chart the landscape of optimal combination therapies in cancer. We assume that each individual therapy can target any one of 1269 genes encoding cell surface receptors, which may be targets of CAR-T, conjugated antibodies or coated nanoparticle therapies. We find that in most cancer types, personalized combinations composed of at most four targets are then sufficient for killing at least 80% of tumor cells while sparing at least 90% of nontumor cells in the tumor microenvironment. However, as more stringent and selective killing is required, the number of targets needed rises rapidly. Emerging individual targets include PTPRZ1 for brain and head and neck cancers and EGFR in multiple tumor types. In sum, this study provides a computational estimate of the identity and number of targets needed in combination to target cancers selectively and precisely.

Peptide-based delivery of therapeutics in cancer treatment

Current delivery strategies for cancer therapeutics commonly cause significant systemic side effects due to required high doses of therapeutic, inefficient cellular uptake of drug, and poor cell selectivity. Peptide-based delivery systems have shown the ability to alleviate these issues and can significantly enhance therapeutic loading, delivery, and cancer targetability. Peptide systems can be tailor-made for specific cancer applications. This review describes three peptide classes, targeting, cell penetrating, and fusogenic peptides, as stand-alone nanoparticle systems, conjugations to nanoparticle systems, or as the therapeutic modality. Peptide nanoparticle design, characteristics, and applications are discussed as well as peptide applications in the clinical space.

A Novel Peptide as a Specific and Selective Probe for Klebsiella pneumoniae Detection

Klebsiella pneumoniae is infamous for generating hospital-acquired infections, many of which are difficult to treat due to the bacterium’s multidrug resistance. A sensitive and robust detection method of K. pneumoniae can help prevent a disease outbreak. Herein, we used K. pneumoniae cells as bait to screen a commercially available phage-displayed random peptide library for peptides that could be used to detect K. pneumoniae. The biopanning-derived peptide TSATKFMMNLSP, named KP peptide, displayed a high selectivity for the K. pneumoniae with low cross-reactivity to related Gram-negative bacteria. The specific interaction between KP peptide and K. pneumoniae lipopolysaccharide resulted in the peptide’s selectivity against K. pneumoniae. Quantitative analysis of this interaction by enzyme-linked immunosorbent assay revealed that the KP peptide possessed higher specificity and sensitivity toward K. pneumoniae than commercially available anti-Klebsiella spp. antibodies and could detect K. pneumoniae at a detection limit of 10⁴ CFU/mL. These results suggest that KP peptide can be a promising alternative to antibodies in developing a biosensor system for K. pneumoniae detection.

EGFR-Targeted Photodynamic Therapy

The epidermal growth factor receptor (EGFR) plays a pivotal role in the proliferation and metastatization of cancer cells. Aberrancies in the expression and activation of EGFR are hallmarks of many human malignancies. As such, EGFR-targeted therapies hold significant potential for the cure of cancers. In recent years, photodynamic therapy (PDT) has gained increased interest as a non-invasive cancer treatment. In PDT, a photosensitizer is excited by light to produce reactive oxygen species, resulting in local cytotoxicity. One of the critical aspects of PDT is to selectively transport enough photosensitizers to the tumors environment. Accordingly, an increasing number of strategies have been devised to foster EGFR-targeted PDT. Herein, we review the recent nanobiotechnological advancements that combine the promise of PDT with EGFR-targeted molecular cancer therapy. We recapitulate the chemistry of the sensitizers and their modes of action in PDT, and summarize the advantages and pitfalls of different targeting moieties, highlighting future perspectives for EGFR-targeted photodynamic treatment of cancer.

Peptide probes with high affinity to target protein selection by phage display and characterization using biophysical approaches

Herein, phage display was utilized to screen the affinity of peptides against dihydrofolate reductase and a positive peptide was obtained, and the verification of the affinity was tested by multiple in vitro biophysical methods.

Genetically Engineered Cellular Membrane Vesicles as Tailorable Shells for Therapeutics

Benefiting from the blooming interaction of nanotechnology and biotechnology, biosynthetic cellular membrane vesicles (Bio-MVs) have shown superior characteristics for therapeutic transportation because of their hydrophilic cavity and hydrophobic bilayer structure, as well as their inherent biocompatibility and negligible immunogenicity. These excellent cell-like features with specific functional protein expression on the surface can invoke their remarkable ability for Bio-MVs based recombinant protein therapy to facilitate the advanced synergy in poly-therapy. To date, various tactics have been developed for Bio-MVs surface modification with functional proteins through hydrophobic insertion or multivalent electrostatic interactions. While the Bio-MVs grow through genetically engineering strategies can maintain binding specificity, sort orders, and lead to strict information about artificial proteins in a facile and sustainable way. In this progress report, the most current technology of Bio-MVs is discussed, with an emphasis on their multi-functionalities as "tailorable shells" for delivering bio-functional moieties and therapeutic entities. The most notable success and challenges via genetically engineered tactics to achieve the new generation of Bio-MVs are highlighted. Besides, future perspectives of Bio-MVs in novel bio-nanotherapy are provided.

Quantitatively mapping the interaction of HER2 and EGFR on cell membranes with peptide probes

Human epidermal growth factor receptor-2 (HER2) is a member of the epidermal growth factor receptor (HER) family that is involved in various biological processes such as cell proliferation, survival, differentiation, migration and invasion. It generally functions in the form of homo-/hetero-dimers or oligomers with other HER family members. Although its essential roles in cellular activities have been widely recognized, questions concerning the spatial distribution of HER2 on the membranes and the interactions between it and other ErbB family members remain obscure. Here, we obtained a high-quality dSTORM image of HER2 nanoscale clusters recognized by peptide probes, and found that HER2 forms clusters containing different numbers of molecules on cell membranes. Moreover, we found that HER2 and EGFR formed hetero-oligomers on non-stimulated cell membranes, whereas EGF stimulation reduced the degree of heteromerization, suggesting that HER2 and EGFR hetero-oligomers may inhibit the activation of EGFR. Collectively, our work revealed the clustered distribution of HER2 and quantified the changes of the interaction between HER2 and EGFR in the resting and active states at the single molecular level, which promotes a deeper understanding of the protein-protein interaction on cell membranes.

Nanoparticles modified with vasculature-homing peptides for targeted cancer therapy and angiogenesis imaging

The two major challenges in cancer treatment include lack of early detection and ineffective therapies with various side effects. Angiogenesis is the key process in the growth, survival, invasiveness, and metastasis of many of cancerous tumors. Imaging of the angiogenesis could lead to diagnosis of tumors in the early stage and evaluation of the therapeutic responses. Angiogenic blood vessels express specific molecular markers different from normal blood vessels (in level or kind). This fact would make the tumor vasculature a suitable site to target therapeutics and imaging agents within the tumor. Surface modified nanoparticles using peptide ligands with high binding affinity to the vasculature markers, provide efficient delivery of therapeutic and imaging agents, while avoiding undesirable side effects. In this review, we discuss discoveries of various tumor targeting peptides useful for tumor angiogenesis imaging and targeted therapy with emphasis on surface modified nanomedicines using vasculature targeting peptides.

Computational Design of Structured and Functional Peptide Macrocycles

Structure-based computational design methods have been developed to create proteins in silico with diverse shapes and sizes that accurately fold in vitro, from 7-residue macrocycles to megadalton-scale self-assembling nanomaterials. Precise control over protein shape has further enabled design and optimization of functional therapeutic proteins, including agonists, antagonists, enzymes, and vaccines. Computational design of functional peptides of smaller size presents a persistent challenge, with few successful examples to date. Herein we describe validated general methods for computational design of peptides using the Rosetta molecular modeling suite and discuss outstanding challenges and future directions.

TRIOMPHE: Transcriptome-Based Inference and Generation of Molecules with Desired Phenotypes by Machine Learning

One of the most challenging tasks in the drug-discovery process is the efficient identification of small molecules with desired phenotypes. In this study, we propose a novel computational method for omics-based de novo drug design, which we call TRIOMPHE (transcriptome-based inference and generation of molecules with desired phenotypes). We investigated the correlation between chemically induced transcriptome profiles (reflecting cellular responses to compound treatment) and genetically perturbed transcriptome profiles (reflecting cellular responses to gene knock-down or gene overexpression of target proteins) in terms of ligand-target interactions. Subsequently, we developed novel machine learning methods to generate the chemical structures of new molecules with desired transcriptome profiles in the framework of a variational autoencoder. The use of desired transcriptome profiles enables the automatic design of molecules that are likely to have bioactivities for target proteins of interest. We showed that our methods can generate chemically valid molecules that are likely to have biological activities on 10 target proteins; moreover, they can outperform previous methods that had the same objective. Our omics-based structure generator is expected to be useful for the de novo design of drugs for a variety of target proteins.

Targeted nanostructured lipid carrier containing galangin as a promising adjuvant for improving cytotoxic effects of chemotherapeutic agents

Resistance to chemotherapeutic drugs is the main limitation of cancer therapy. The combination use of chemotherapeutic agents and galangin (a naturally active flavonoid) amplifies the effectiveness of cancer treatment. This study aimed to prepare arginyl-glycyl-aspartic acid (RGD) containing nanostructured lipid carrier (NLC-RGD) to improve the bioavailability of galangin and explore its ability in improving the cytotoxic effects of doxorubicin (DOX). Galangin-loaded NLC-RGD was prepared by hot homogenization method and characterized by diverse techniques. Then, cytotoxicity, uptake, and apoptosis induction potential of prepared nanoparticles beside the DOX were evaluated on A549 lung cancer cells. Finally, the expression level of some ABC transporter genes was evaluated in galangin-loaded NLC-RGD-treated cells. Nanoparticles with appropriate characteristics of the delivery system (size: 120 nm, polydispersity index: 0.23, spherical morphology, and loading capacity: 59.3 mg/g) were prepared. Uptake experiments revealed that NLC-RGD promotes the accumulation of galangin into cancerous cells by integrin-mediated endocytosis. Results also showed higher cytotoxicity and apoptotic effects of DOX + galangin-loaded NLC-RGD in comparison to DOX + galangin. Gene expression analysis demonstrated that galangin-loaded NLC-RGD downregulates ABCB1, ABCC1, and ABCC2 more efficiently than galangin. These findings indicated that delivery of galangin by NLC-RGD makes it an effective adjuvant to increase the efficacy of chemotherapeutic agents in cancer treatment.

An in vivo selection-derived d-peptide for engineering erythrocyte-binding antigens that promote immune tolerance

When displayed on erythrocytes, peptides and proteins can drive antigen-specific immune tolerance. Here, we investigated a straightforward approach based on erythrocyte binding to promote antigen-specific tolerance to both peptides and proteins. We first identified a robust erythrocyte-binding ligand. A pool of one million fully d-chiral peptides was injected into mice, blood cells were isolated, and ligands enriched on these cells were identified using nano-liquid chromatography-tandem mass spectrometry. One round of selection yielded a murine erythrocyte-binding ligand with an 80 nM apparent dissociation constant, K _d We modified an 83-kDa bacterial protein and a peptide antigen derived from ovalbumin (OVA) with the identified erythrocyte-binding ligand. An administration of the engineered bacterial protein led to decreased protein-specific antibodies in mice. Similarly, mice given the engineered OVA-derived peptide had decreased inflammatory anti-OVA CD8⁺ T cell responses. These findings suggest that our tolerance-induction strategy is applicable to both peptide and protein antigens and that our in vivo selection strategy can be used for de novo discovery of robust erythrocyte-binding ligands.

Engineering of an EpCAM-targeting cyclic peptide to improve the EpCAM-mediated cellular internalization and tumor accumulation of a peptide-fused antibody

Fusion of a target-specific peptide to a full-length antibody (Ab) can result in a peptide-Ab fusion protein with additional specificity and enhanced activity. We recently developed an intracellular pan-RAS-targeting cytosol-penetrating antibody, RT22-ep59, in which a tumor-specific targeting ability was achieved via the fusion of an epithelial cell adhesion molecule (EpCAM) targeting cyclic peptide (ep133). Here, the aim was to enhance EpCAM-mediated endocytosis and tumor accumulation of the peptide-fused RAS-targeting Ab. Accordingly, we engineered a cyclic peptide (from ep133) that has stronger affinity for EpCAM by using yeast surface display technology and then rationally designed cyclic peptides in the Ab-fused form to enhance colloidal stability. The finally engineered EpCAM-targeting cyclic peptide (ep₆)-fused Ab, ep₆Ras37, has ∼10-fold stronger affinity (K_D ≈ 1.9 nM) for EpCAM than that of RT22-ep59, without deterioration of biophysical properties. Compared with the parental antibody (RT22-ep59), ep₆Ras37 more efficiently reached the cytosol of EpCAM-expressing cells and showed greater preferential tumor homing and accumulation in mice bearing EpCAM-expressing LoVo xenograft tumors. Thus, the high-affinity EpCAM-targeting peptide ensures efficient cellular internalization and better tumor accumulation of the peptide-fused Ab.