Small Peptide Ligands for Targeting EGFR in Triple Negative Breast Cancer Cells

Development of injectable upconversion nanoparticle-conjugated doxorubicin theranostics electrospun nanostructure for targeted photochemotherapy in breast cancer

Nanotheranostic-based photochemotherapies with targeted drug delivery have considerably surfaced in cancer therapy. In the presented work, polyethyleneimine-coated upconversion nanoparticles were engineered to conjugate covalently with doxorubicin. Upconversion nanoparticles (UCNP)-Doxorubicin (DOX)/synthesized epidermal growth factor receptor-targeting peptide blended with polymer composite was electrospun and formulated as the injectable dosage form. The size of the UCNP and the nanofiber diameter were assessed as 26.75 ± 1.54 and 162 ± 2.82 nm, respectively. The optimized ratio of dopants resulted in UCNP photoluminescence with maximum emission intensity at around 800 nm upon 980 nm excitation wavelength. The paramagnetic nature of UCNPs and amide conjugation with the drug was confirmed analytically. The loading capacity of UCNP for doxorubicin was determined to be 54.56%, while nanofibers exhibited 98.74% capacity to encapsulate UCNP-DOX. The release profile of UCNP-DOX from nanofiber formulation ranged from sustained to controlled, with relative enhancement in acidic conditions. The nanofiber demonstrated good mechanical strength, robust swelling, and degradation rate. Biocompatibility tests showed more than 90% cell viability on L929 and NIH/3T3 cell lines with UCNP-DOX@NF/pep nanoformulation. The IC50 values of 2.15 ± 0.54, 2.87 ± 0.67, and 3.42 ± 0.45 μg/mL on MDA-MB-231, 4T1, and MCF-7 cancer cell line, respectively, with a significant cellular uptake, has been reported. The UCNP protruded a ≈62.7°C temperature rise within 5 min of 980 nm laser irradiation and a power density of 0.5 W cm-2. The nanoformulation induced reactive oxygen species of 65.67% ± 3.21% and apoptosis by arresting the cell cycle sub-G1 phase. The evaluation conveys the effectiveness of the developed injectable theranostic delivery system in cancer therapy.

Tuning Peptide-Based Nanofibers for Achieving Selective Doxorubicin Delivery in Triple-Negative Breast Cancer

Introduction

The design of delivery tools that efficiently transport drugs into cells remains a major challenge in drug development for most pathological conditions. Triple-negative breast cancer (TNBC) is a very aggressive subtype of breast cancer with poor prognosis and limited effective therapeutic options.

Purpose

In TNBC treatment, chemotherapy remains the milestone, and doxorubicin (Dox) represents the first-line systemic treatment; however, its non-selective distribution causes a cascade of side effects. To address these problems, we developed a delivery platform based on the self-assembly of amphiphilic peptides carrying several moieties on their surfaces, aimed at targeting, enhancing penetration, and therapy.

Methods

Through a single-step self-assembly process, we used amphiphilic peptides to obtain nanofibers decorated on their surfaces with the selected moieties. The surface of the nanofiber was decorated with a cell-penetrating peptide (gH625), an EGFR-targeting peptide (P22), and Dox bound to the cleavage sequence selectively recognized and cleaved by MMP-9 to obtain on-demand drug release. Detailed physicochemical and cellular analyses were performed.

Results

The obtained nanofiber (NF-Dox) had a length of 250 nm and a diameter of 10 nm, and it was stable under dilution, ionic strength, and different pH environments. The biological results showed that the presence of gH625 favored the complete internalization of NF-Dox after 1h in MDA-MB 231 cells, mainly through a translocation mechanism. Interestingly, we observed the absence of toxicity of the carrier (NF) on both healthy cells such as HaCaT and TNBC cancer lines, while a similar antiproliferative effect was observed on TNBC cells after the treatment with the free-Dox at 50 µM and NF-Dox carrying 7.5 µM of Dox.

Discussion

We envision that this platform is extremely versatile and can be used to efficiently carry and deliver diverse moieties. The knowledge acquired from this study will provide important guidelines for applications in basic research and biomedicine.

Gemcitabine-Lipid Conjugate and ONC201 Combination Therapy Effectively Treats Orthotopic Pancreatic Tumor-Bearing Mice

Gemcitabine (GEM) is a nucleoside analogue approved as a first line of therapy for pancreatic ductal adenocarcinoma (PDAC). However, rapid metabolism by plasma cytidine deaminase leading to the short half-life, intricate intracellular metabolism, ineffective cell uptake, and swift development of chemoresistance downgrades the clinical efficacy of GEM. ONC201 is a small molecule that inhibits the Akt and ERK pathways and upregulates the TNF-related apoptosis-inducing ligand (TRAIL), which leads to the reversal of both intrinsic and acquired GEM resistance in PDAC treatment. Moreover, the pancreatic cancer cells that were able to bypass apoptosis after treatment of ONC201 get arrested in the G1-phase, which makes them highly sensitive to GEM. To enhance the in vivo stability of GEM, we first synthesized a disulfide bond containing stearate conjugated GEM (lipid-GEM), which makes it sensitive to the redox tumor microenvironment (TME) comprising high glutathione levels. In addition, with the help of colipids 1,2-dioleoyl-glycero-3-phosphocholine (DOPC), cholesterol, and 1,2-distearoyl-glycero-3-phosphoethanolamine-poly(ethylene glycol)-2000 (DSPE-PEG 2000), we were able to synthesize the lipid-GEM conjugate and ONC201 releasing liposomes. A cumulative drug release study confirmed that both ONC201 and GEM showed sustained release from the formulation. Since MUC1 is highly expressed in 70-90% PDAC, we conjugated a MUC1 binding peptide in the liposomes which showed higher cytotoxicity, apoptosis, and cellular internalization by MIA PaCa-2 cells. A biodistribution study further confirmed that the systemic delivery of the liposomes through the tail vein resulted in a higher accumulation of drugs in orthotopic PDAC tumors in NSG mice. The IHC of the excised tumor grafts further confirmed the higher apoptosis and lower metastasis and cell proliferation. Thus, our MUC1 targeting binary drug-releasing liposomal formulation showed higher drug payload, enhanced plasma stability, and accumulation of drugs in the pancreatic orthotopic tumor and thus is a promising therapeutic alternative for the treatment of PDAC.

Surface-functionalised polymeric nanoparticles for breast cancer treatment: processes and advances

The World Health Organization (WHO) reported that of all the non-communicable diseases, cancer is considered the second cause of death worldwide. This has driven the big pharma companies to prioritise anticancer products in their pipeline. In addition, research has focused on exploration of new anticancer molecules and design of suitable dosage forms to achieve effective drug delivery to the tumour site. Nanotechnology is a valuable tool to build nano delivery systems with controlled and targeted drug release properties. Nanoparticles can be fabricated by robust, scalable and economic techniques using various polymers. Moreover, specific functional groups can be introduced to the surface of nanoparticles enabling targeting to a specific tissue; besides, they exhibit versatile drug release patterns according to the rate of polymer degradation. This review outlines the processes and advances in surface functionalisation of nanoparticles employed for treatment of breast cancer. The therapeutic molecules, the polymers used to fabricate nanoparticles, the techniques used to prepare the nanoparticles have been reviewed with a focus on the processes employed to functionalise these nanoparticles with suitable ligands to target different types of breast cancer.

Purinergic signaling promotes premature senescence

Extracellular ATP activates P2 purinergic receptors. Whether purinergic signaling is functionally coupled to cellular senescence is largely unknown. We find that oxidative stress induced release of ATP and caused senescence in human lung fibroblasts. Inhibition of P2 receptors limited oxidative stress-induced senescence, while stimulation with exogenous ATP promoted premature senescence. Pharmacological inhibition of P2Y11 receptor (P2Y11R) inhibited premature senescence induced by either oxidative stress or ATP, while stimulation with a P2Y11R agonist was sufficient to induce cellular senescence. Our data show that both extracellular ATP and a P2Y11R agonist induced calcium (Ca++) release from the endoplasmic reticulum (ER) and that either inhibition of phospholipase C or intracellular Ca++ chelation impaired ATP-induced senescence. We also find that Ca++ that was released from the ER, following ATP-mediated activation of phospholipase C, entered mitochondria in a manner dependent on P2Y11R activation. Once in mitochondria, excessive Ca++ promoted the production of reactive oxygen species in a P2Y11R-dependent fashion, which drove development of premature senescence of lung fibroblasts. Finally, we show that conditioned medium derived from senescent lung fibroblasts, which were induced to senesce through the activation of ATP/P2Y11R-mediated signaling, promoted the proliferation of triple-negative breast cancer cells and their tumorigenic potential by secreting amphiregulin. Our study identifies the existence of a novel purinergic signaling pathway that links extracellular ATP to the development of a protumorigenic premature senescent phenotype in lung fibroblasts that is dependent on P2Y11R activation and ER-to-mitochondria calcium signaling.

Design of siRNA Bioconjugates for Efficient Control of Cancer-Associated Membrane Receptors

Research on siRNA delivery has seen tremendous growth over the past few decades. As one of the major delivery strategies, siRNA bioconjugates offer the potential to enhance and extend the pharmacological properties of siRNAs while minimizing toxicity. In this paper, we suggest the development of a siRNA conjugate platform with peptides and proteins that are ligands of target receptors for cancer treatment. The siRNA bioconjugates target and block the receptor membrane proteins, enter the cells through receptor-mediated endocytosis, and inhibit the expression of that same target membrane receptor, thereby doubly controlling the function of the membrane proteins. The three kinds of bioconjugates targeting CD47, PD-L1, and EGFR were synthesized via two different copper-free click chemistry reactions. Results showed the cellular uptake of each conjugate, reduction of target gene expression, and efficient functional control of receptor proteins. This platform provides an effective approach for regulating membrane proteins in various diseases beyond cancer.

5,10,15,20-Tetrakis(pentafluorophenyl)porphyrin as a Functional Platform for Peptide Stapling and Multicyclisation

Polyfluorinated aromatic reagents readily react with thiolates via nucleophilic aromatic substitution (SN Ar) and provide excellent scaffolds for peptide cyclisation. Here we report a robust and versatile platform for peptide stapling and multicyclisation templated by 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin, opening the door to the next generation of functional scaffolds for 3D peptide architectures. We demonstrate that stapling and multicyclisation occurs with a range of non-protected peptides under peptide-compatible conditions, exhibiting chemoselectivity and wide-applicability. Peptides containing two cysteine residues are readily stapled, and the remaining perfluoroaryl groups permit the introduction of a second peptide in a modular fashion to access bicyclic peptides. Similarly, peptides with more than two cysteine residues can afford multicyclic products containing up to three peptide 'loops'. Finally, we demonstrate that a porphyrin-templated stapled peptide containing the Skin Penetrating and Cell Entering (SPACE) peptide affords a skin cell penetrating conjugate with intrinsic fluorescence.

Glucose oxidase virus-based nanoreactors for smart breast cancer therapy

BACKGROUND

Breast cancer is the most common malignant tumor disease and the leading cause of female mortality. The evolution of nanomaterials science opens the opportunity to improve traditional cancer therapies, enhancing therapy efficiency and reducing side effects.

METHODS AND MAJOR RESULTS

Herein, protein cages conceived as enzymatic nanoreactors were designed and produced by using virus-like nanoparticles (VLPs) from Brome mosaic virus (BMV) and containing the catalytic activity of glucose oxidase (GOx) enzyme. The GOx enzyme was encapsulated into the BMV capsid (VLP-GOx), and the resulting enzymatic nanoreactors were coated with human serum albumin (VLP-GOx@HSA) for breast tumor cell targeting. The effect of the synthesized GOx nanoreactors on breast tumor cell lines was studied in vitro. Both nanoreactor preparations VLP-GOx and VLP-GOx@HSA showed to be highly cytotoxic for breast tumor cell cultures. Cytotoxicity for human embryonic kidney cells was also found. The monitoring of nanoreactor treatment on triple-negative breast cancer cells showed an evident production of oxygen by the catalase antioxidant enzyme induced by the high production of hydrogen peroxide from GOx activity.

CONCLUSIONS AND IMPLICATIONS

The nanoreactors containing GOx activity are entirely suitable for cytotoxicity generation in tumor cells. The HSA functionalization of the VLP-GOx nanoreactors, a strategy designed for selective cancer targeting, showed no improvement in the cytotoxic effect. The GOx containing enzymatic nanoreactors seems to be an interesting alternative to improve the current cancer therapy. In vivo studies are ongoing to reinforce the effectiveness of this treatment strategy.

Peptide-Based Therapeutics in Cancer Therapy

A monster called cancer is still one of the most challenging human problems and one of the leading causes of death in the world. Different types of treatment methods are used for cancer therapy; however, there are challenges such as high cost and harmful side effects in using these methods. Recent years have witnessed a surge in the development of therapeutic peptides for a wide range of diseases, notably cancer. Peptides are preferred over antibiotics, radiation therapy, and chemotherapy in the treatment of cancer due to a number of aspects, including flexibility, easy modification, low immunogenicity, and inexpensive cost of production. The use of therapeutic peptides in cancer treatment is a novel and intriguing strategy. These peptides provide excellent prospects for targeted drug delivery because of their high selectivity, specificity, small dimensions, good biocompatibility, and simplicity of modification. Target specificity and minimal toxicity are benefits of therapeutic peptides. Additionally, peptides can be used to design antigens or adjuvants for vaccine development. Here, types of therapeutic peptides for cancer therapy will be discussed, such as peptide-based cancer vaccines and tumor-targeting peptides (TTP) and cell-penetrating peptides (CPP).

Fabrication of a Dual-Targeted Liposome-Coated Mesoporous Silica Core-Shell Nanoassembly for Targeted Cancer Therapy

Nanoparticles have been suggested as drug-delivery systems for chemotherapeutic drugs to allow for controlled drug release profiles and selectivity to target cancer cells. In addition, nanoparticles can be used for the in situ generation and amplification of reactive oxygen species (ROS), which have been shown to be a promising strategy for cancer treatment. Thus, a targeted nanoscale drug-delivery platform could be used to synergistically improve cancer treatment by the action of chemotherapeutic drugs and ROS generation. Herein, we propose a promising chemotherapy strategy where the drug-loaded nanoparticles generate high doses of ROS together with the loaded ROS-generating chemotherapeutic drugs, which can damage the mitochondria and activate cell death, potentiating the therapeutic outcome in cancer therapy. In the present study, we have developed a dual-targeted drug-delivery nanoassembly consisting of a mesoporous silica core loaded with the chemotherapeutic, ROS-generating drug, paclitaxel (Px), and coated with a liposome layer for controlled drug release. Two different lung cancer-targeting ligands, folic acid and peptide GE11, were used to target the overexpressed nonsmall lung cancer receptors to create the final nanoassembly (MSN@Px) L-GF. Upon endocytosis by the cancer cells, the liposome layer was degraded by the intracellular lipases, and the drug was rapidly released at a rate of 65% within the first 20 h. In vitro studies confirmed that this nanoassembly was 8-fold more effective in cancer therapy compared to the free drug Px.

Design of Highly Fluorinated Peptides for Cell-based 19F NMR

The design of imaging agents with high fluorine content is essential for overcoming the challenges associated with signal detection limits in 19F MRI-based molecular imaging. In addition to perfluorocarbon and fluorinated polymers, fluorinated peptides offer an additional strategy for creating sequence-defined 19F magnetic resonance imaging (MRI) imaging agents with a high fluorine signal. Our previously reported unstructured trifluoroacetyllysine-based peptides possessed good physiochemical properties and could be imaged at high magnetic field strength. However, the low detection limit motivated further improvements in the fluorine content of the peptides as well as removal of nonspecific cellular interactions. This research characterizes several new highly fluorinated synthetic peptides composed of highly fluorinated amino acids. 19F NMR analysis of peptides TB-1 and TB-9 led to highly overlapping, intense fluorine resonances and acceptable aqueous solubility. Flow cytometry analysis and fluorescence microscopy further showed nonspecific binding could be removed in the case of TB-9. As a preliminary experiment toward developing molecular imaging agents, a fluorinated EGFR-targeting peptide (KKKFFKK-βA-YHWYGYTPENVI) and an EGFR-targeting protein complex E1-DD bioconjugated to TB-9 were prepared. Both bioconjugates maintained good 19F NMR performance in aqueous solution. While the E1-DD-based imaging agent will require further engineering, the success of cell-based 19F NMR of the EGFR-targeting peptide in A431 cells supports the potential use of fluorinated peptides for molecular imaging.

Knockdown of PTK7 Reduces the Oncogenic Potential of Breast Cancer Cells by Impeding Receptor Tyrosine Kinase Signaling

Protein tyrosine kinase 7 (PTK7), a catalytically defective receptor tyrosine kinase (RTK), is often upregulated in various cancers. This study aimed to validate PTK7 as a target for breast cancer (BC) and investigate its oncogenic signaling mechanism. BC tissue analysis showed significantly elevated PTK7 mRNA levels, especially in refractory triple-negative breast cancer (TNBC) tissues, compared with normal controls. Similarly, BC cell lines exhibited increased PTK7 expression. Knockdown of PTK7 inhibited the proliferation of T-47D and MCF-7 hormone-receptor-positive BC cell-lines and of HCC1187, MDA-MB-231, MDA-MB-436, and MDA-MB-453 TNBC cells. PTK7 knockdown also inhibited the adhesion, migration, and invasion of MDA-MB-231, MDA-MB-436, and MDA-MB-453 cells, and reduced the phosphorylation levels of crucial oncogenic regulators including extracellular signal-regulated kinase (ERK), Akt, and focal adhesion kinase (FAK). Furthermore, PTK7 interacts with fibroblast growth factor receptor 1 (FGFR1) and epidermal growth factor receptor (EGFR) expressed in MDA-MB-231 cells. Knockdown of PTK7 decreased the growth-factor-induced phosphorylation of FGFR1 and EGFR in MDA-MB-231 cells, indicating its association with RTK activation. In conclusion, PTK7 plays a significant role in oncogenic signal transduction by enhancing FGFR1 and EGFR activation, influencing BC tumorigenesis and metastasis. Hence, PTK7 represents a potential candidate for targeted BC therapy, including TNBC.

Current research status of anti-cancer peptides: Mechanism of action, production, and clinical applications

The escalating rate of cancer cases, together with treatment deficiencies and long-term side effects of currently used cancer drugs, has made this disease a global burden of the 21st century. The number of breast and lung cancer patients has sharply increased worldwide in the last few years. Presently, surgical treatment, radiotherapy, chemotherapy, and immunotherapy strategies are used to cure cancer, which cause severe side effects, toxicities, and drug resistance. In recent years, anti-cancer peptides have become an eminent therapeutic strategy for cancer treatment due to their high specificity and fewer side effects and toxicity. This review presents an updated overview of different anti-cancer peptides, their mechanisms of action and current production strategies employed for their manufacture. In addition, approved and under clinical trials anti-cancer peptides and their applications have been discussed. This review provides updated information on therapeutic anti-cancer peptides that hold great promise for cancer treatment in the near future.

A computational and laboratory approach for the investigation of interactions of peptide conjugated natural terpenes with EpHA2 receptor

CONTEXT

Ephrin type A receptor 2 (EphA2) is a well-known drug target for cancer treatment due to its overexpression in numerous types of cancers. Thus, it is crucial to determine the binding interactions of this receptor with both the ligand-binding domain (LBD) and the kinase-binding domain (KBD) through a targeted approach in order to modulate its activity. In this work, natural terpenes with inherent anticancer properties were conjugated with short peptides YSAYP and SWLAY that are known to bind to the LBD of EphA2 receptor. We examined the binding interactions of six terpenes (maslinic acid, levopimaric acid, quinopimaric acid, oleanolic, polyalthic, and hydroxybetulinic acid) conjugated to the above peptides with the ligand-binding domain (LBD) of EphA2 receptor computationally. Additionally, following the "target-hopping approach," we also examined the interactions of the conjugates with the KBD. Our results indicated that most of the conjugates showed higher binding interactions with the EphA2 kinase domain compared to LBD. Furthermore, the binding affinities of the terpenes increased upon conjugating the peptides with the terpenes. In order to further investigate the specificity toward EphA2 kinase domain, we also examined the binding interactions of the terpenes conjugated to VPWXE (x = norleucine), as VPWXE has been shown to bind to other RTKs. Our results indicated that the terpenes conjugated to SWLAY in particular showed high efficacy toward binding to the KBD. We also designed conjugates where in the peptide portion and the terpenes were separated by a butyl (C4) group linker to examine if the binding interactions could be enhanced. Docking studies showed that the conjugates with linkers had enhanced binding with the LBD compared to those without linkers, though binding remained slightly higher without linkers toward the KBD. As a proof of concept, maslinate and oleanolate conjugates of each of the peptides were then tested with F98 tumor cells which are known to overexpress EphA2 receptor. Results indicated that the oleanolate-amido-SWLAY conjugates were efficacious in reducing the cell proliferation of the tumor cells and may be potentially developed and further studied for targeting tumor cells overexpressing the EphA2 receptor. To test if these conjugates could bind to the receptor and potentially function as kinase inhibitors, we conducted SPR analysis and ADP-Glo assay. Our results indicated that OA conjugate with SWLAY showed the highest inhibition.

METHODS

Docking studies were carried out using AutoDock Vina, v.1.2.0; Molecular Dynamics and MMGBSA calculations were carried out through Schrodinger Software DESMOND.

Bacterial delivery of therapeutic proteins to the nuclei of cancer cells

Targeting nucleic targets with therapeutic proteins would enhance the treatment of hard-to-treat cancers. However, exogenous proteins are excluded from the nucleus by both the cellular and nuclear membranes. We have recently developed Salmonella that deliver active proteins into the cytoplasm of cancer cells. Here, we hypothesized that bacterially delivered proteins accumulate within nuclei, nuclear localization sequences (NLSs) increase delivery, and bacterially delivered proteins kill cancer cells. To test this hypothesis, we developed intranuclear delivering (IND) Salmonella and quantified the delivery of three model proteins. IND Salmonella delivered both ovalbumin and green fluorescent protein to nuclei of MCF7 cancer cells. The amount of protein in nuclei was linearly dependent on the amount delivered to the cytoplasm. The addition of a NLSs increased both the amount of protein in each nucleus and the number of nuclei that received protein. Delivery of Omomyc, a protein inhibitor of the nuclear transcript factor, Myc, altered cell physiology, and significantly induced cell death. These results show that IND Salmonella deliver functional proteins to the nucleus of cancerous cells. Extending this method to other transcription factors will increase the number of accessible targets for cancer therapy.

Dual Targeted Delivery of Liposomal Hybrid Gold Nano-Assembly for Enhanced Photothermal Therapy against Lung Carcinomas

The delivery and accumulation of therapeutic drugs into cancer cells without affecting healthy cells are a major challenge for antitumor therapy. Here, we report the synthesis of a liposomal hybrid gold nano-assembly with enhanced photothermal activity for lung cancer treatment. The core components of the nano-assembly include gold nanorods coated with a mesoporous silica shell that offers an excellent drug-loading surface for encapsulation of doxorubicin. To enhance the photothermal capacity of nano-assembly, IR 780 dye was loaded inside a thermo-sensitive liposome, and then, the core nano-assembly was wrapped within the liposome, and GE-11 peptide and folic acid were conjugated onto the surface of the liposome to give the final nano-assembly [(GM@Dox) LI]-PF. The dual targeting approach of [(GM@Dox) LI]-PF leads to enhanced cellular uptake and improves the accumulation of nano-assemblies in cancer cells that overexpress the epidermal growth factor receptor and folate. The exposure of near-infrared laser irradiation can trigger photothermal-induced structural disruption of the nano-assembly, which allows for the precise and controllable release of Dox at targeted sites. Additionally, chemo-photothermal therapy was shown to be 11 times more effective in cancer cell treatment when compared to Dox alone. Our systematic study suggests that the nano-assemblies facilitate the cancer cells undergoing apoptosis via an intrinsic mitochondrial pathway that can be directly triggered by the chemo-photothermal treatment. This study offers an appealing candidate that holds great promise for synergistic cancer treatment.

Development of Cyclic Peptides Targeting the Epidermal Growth Factor Receptor in Mesenchymal Triple-Negative Breast Cancer Subtype

Triple-negative breast cancer (TNBC) is an aggressive malignancy characterized by the lack of expression of estrogen and progesterone receptors and amplification of human epidermal growth factor receptor 2 (HER2). Being the Epidermal Growth Factor Receptor (EGFR) highly expressed in mesenchymal TNBC and correlated with aggressive growth behavior, it represents an ideal target for anticancer drugs. Here, we have applied the phage display for selecting two highly specific peptide ligands for targeting the EGFR overexpressed in MDA-MB-231 cells, a human TNBC cell line. Molecular docking predicted the peptide-binding affinities and sites in the extracellular domain of EGFR. The binding of the FITC-conjugated peptides to human and murine TNBC cells was validated by flow cytometry. Confocal microscopy confirmed the peptide binding specificity to EGFR-positive MDA-MB-231 tumor xenograft tissues and their co-localization with the membrane EGFR. Further, the peptide stimulation did not affect the cell cycle of TNBC cells, which is of interest for their utility for tumor targeting. Our data indicate that these novel peptides are highly specific ligands for the EGFR overexpressed in TNBC cells, and thus they could be used in conjugation with nanoparticles for tumor-targeted delivery of anticancer drugs.

Current therapeutic approaches and promising perspectives of using bioengineered peptides in fighting chemoresistance in triple-negative breast cancer

Breast cancer is a collation of malignancies that manifest in the mammary glands at the early stages. Among breast cancer subtypes, triple-negative breast cancer (TNBC) shows the most aggressive behavior, with apparent stemness features. Owing to the lack of response to hormone therapy and specific targeted therapies, chemotherapy remains the first line of the TNBC treatment. However, the acquisition of resistance to chemotherapeutic agents increase therapy failure, and promotes cancer recurrence and distant metastasis. Invasive primary tumors are the birthplace of cancer burden, though metastasis is a key attribute of TNBC-associated morbidity and mortality. Targeting the chemoresistant metastases-initiating cells via specific therapeutic agents with affinity to the upregulated molecular targets is a promising step in the TNBC clinical management. Exploring the capacity of peptides as biocompatible entities with the specificity of action, low immunogenicity, and robust efficacy provides a principle for designing peptide-based drugs capable of increasing the efficacy of current chemotherapy agents for selective targeting of the drug-tolerant TNBC cells. Here, we first focus on the resistance mechanisms that TNBC cells acquire to evade the effect of chemotherapeutic agents. Next, the novel therapeutic approaches employing tumor-targeting peptides to exploit the mechanisms of drug resistance in chemorefractory TNBC are described.

Effect of the Size and Shape of Dendronized Iron Oxide Nanoparticles Bearing a Targeting Ligand on MRI, Magnetic Hyperthermia, and Photothermia Properties—From Suspension to In Vitro Studies

Functionalized iron oxide nanoparticles (IONPs) are increasingly being designed as a theranostic nanoplatform combining specific targeting, diagnosis by magnetic resonance imaging (MRI), and multimodal therapy by hyperthermia. The effect of the size and the shape of IONPs is of tremendous importance to develop theranostic nanoobjects displaying efficient MRI contrast agents and hyperthermia agent via the combination of magnetic hyperthermia (MH) and/or photothermia (PTT). Another key parameter is that the amount of accumulation of IONPs in cancerous cells is sufficiently high, which often requires the grafting of specific targeting ligands (TLs). Herein, IONPs with nanoplate and nanocube shapes, which are promising to combine magnetic hyperthermia (MH) and photothermia (PTT), were synthesized by the thermal decomposition method and coated with a designed dendron molecule to ensure their biocompatibility and colloidal stability in suspension. Then, the efficiency of these dendronized IONPs as contrast agents (CAs) for MRI and their ability to heat via MH or PTT were investigated. The 22 nm nanospheres and the 19 nm nanocubes presented the most promising theranostic properties (respectively, r2 = 416 s−1·mM−1, SARMH = 580 W·g−1, SARPTT = 800 W·g−1; and r2 = 407 s−1·mM−1, SARMH = 899 W·g−1, SARPTT = 300 W·g−1). MH experiments have proven that the heating power mainly originates from Brownian relaxation and that SAR values can remain high if IONPs are prealigned with a magnet. This raises hope that heating will maintain efficient even in a confined environment, such as in cells or in tumors. Preliminary in vitro MH and PTT experiments have shown the promising effect of the cubic shaped IONPs, even though the experiments should be repeated with an improved set-up. Finally, the grafting of a specific peptide (P22) as a TL for head and neck cancers (HNCs) has shown the positive impact of the TL to enhance IONP accumulation in cells.

Bioconjugation studies of an EGF-R targeting ligand on dendronized iron oxide nanoparticles to target head and neck cancer cells

A major challenge in nanomedicine is designing nanoplatforms (NPFs) to selectively target abnormal cells to ensure early diagnosis and targeted therapy. Among developed NPFs, iron oxide nanoparticles (IONPs) are good MRI contrast agents and can be used for therapy by hyperthermia and as radio-sensitizing agents. Active targeting is a promising method for selective IONPs accumulation in cancer tissues and is generally performed by using targeting ligands (TL). Here, a TL specific for the epidermal growth factor receptor (EGFR) is bound to the surface of dendronized IONPs to produce nanostructures able to specifically recognize EGFR-positive FaDu and 93-Vu head and neck cancer cell lines. Several parameters were optimized to ensure a high coupling yield and to adequately quantify the amount of TL per nanoparticle. Nanostructures with variable amounts of TL on the surface were produced and evaluated for their potential to specifically target and be thereafter internalized by cells. Compared to the bare NPs, the presence of the TL at the surface was shown to be effective to enhance their internalization and to play a role in the total amount of iron present per cell.

Magneto-Nanomechanical Array Biosensor for Ultrasensitive Detection of Oncogenic Exosomes for Early Diagnosis of Cancers

Exosomes are a class of nanoscale vesicles secreted by cells, which contain abundant information closely related to parental cells. The ultrasensitive detection of cancer-derived exosomes is highly significant for early non-invasive diagnosis of cancer. Here, an ultrasensitive nanomechanical sensor is reported, which uses a magnetic-driven microcantilever array to selectively detect oncogenic exosomes. A magnetic force, which can produce a far greater deflection of microcantilever than that produced by the intermolecular interaction force even with very low concentrations of target substances, is introduced. This method reduced the detection limit to less than 10 exosomes mL^-1 . Direct detection of exosomes in the serum of patients with breast cancer and in healthy people showed a significant difference. This work improved the sensitivity by five orders of magnitude as compared to that of traditional nanomechanical sensing based on surface stress mode. This method can be applied parallelly for highly sensitive detection of other microorganisms (such as bacteria and viruses) by using different probe molecules, which can provide a supersensitive detection approach for cancer diagnosis, food safety, and SARS-CoV-2 infection.

Identification of a novel peptide ligand for the cancer-specific receptor mutation EGFRvIII using high-throughput sequencing of phage-selected peptides

We report here the selection and characterization of a novel peptide ligand using phage display targeted against the cancer-specific epidermal growth factor tyrosine kinase receptor mutation variant III (EGFRvIII). This receptor is expressed in several kinds of cancer: ovarian cancer, breast cancer and glioblastoma, but not in normal tissues. A 12-mer random peptide library was screened against EGFRvIII. Phage-selected peptides were sequenced in high-throughput by next generation sequencing (NGS), and their diversity was studied to identify highly abundant clones expected to bind with the highest affinities to EGFRvIII. The enriched peptides were characterized and their binding capacity towards stable cell lines expressing EGFRvIII, EGFR wild type (EGFR WT), or a low endogenous level of EGFR WT was confirmed by flow cytometry analysis. The best peptide candidate, VLGREEWSTSYW, was synthesized, and its binding specificity towards EGFRvIII was validated in vitro. Additionally, computational docking analysis suggested that the identified peptide binds selectively to EGFRvIII. The novel VLGREEWSTSYW peptide is thus a promising EGFRvIII-targeting agent for future applications in cancer diagnosis and therapy.

Functional ligands for improving anticancer drug therapy: current status and applications to drug delivery systems

Conventional chemotherapy lacking target selectivity often leads to severe side effects, limiting the effectiveness of chemotherapy. Therefore, drug delivery systems ensuring both selective drug release and efficient intracellular uptake at the target sites are highly demanded in chemotherapy to improve the quality of life of patients with low toxicity. One of the effective approaches for tumor-selective drug delivery is the adoption of functional ligands that can interact with specific receptors overexpressed in malignant cancer cells. Various functional ligands including folic acid, hyaluronic acid, transferrin, peptides, and antibodies, have been extensively explored to develop tumor-selective drug delivery systems. Furthermore, cell-penetrating peptides or ligands for tight junction opening are also actively pursued to improve the intracellular trafficking of anticancer drugs. Sometimes, multiple ligands with different roles are used in combination to enhance the cellular uptake as well as target selectivity of anticancer drugs. In this review, the current status of various functional ligands applicable to improve the effectiveness of cancer chemotherapy is overviewed with a focus on their roles, characteristics, and preclinical/clinical applications.

BODIPYs in PDT: A Journey through the Most Interesting Molecules Produced in the Last 10 Years

Over the past 30 years, photodynamic therapy (PDT) has shown great development. In the clinical setting the few approved molecules belong almost exclusively to the porphyrin family; but in the scientific field, in recent years many researchers have been interested in other families of photosensitizers, among which BODIPY has shown particular interest. BODIPY is the acronym for 4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene, and is a family of molecules well-known for their properties in the field of imaging. In order for these molecules to be used in PDT, a structural modification is necessary which involves the introduction of heavy atoms, such as bromine and iodine, in the beta positions of the pyrrole ring; this change favors the intersystem crossing, and increases the ¹O₂ yield. This mini review focused on a series of structural changes made to BODIPYs to further increase ¹O₂ production and bioavailability by improving cell targeting or photoactivity efficiency.

Design, synthesis, in vitro biological assessment and molecular modeling insights for novel 3-(naphthalen-1-yl)-4,5-dihydropyrazoles as anticancer agents with potential EGFR inhibitory activity

Currently, the humanity is in a fierce battle against various health-related challenges especially those associated with human malignancies. This created the urge to develop potent and selective inhibitors for tumor cells through targeting specific oncogenic proteins possessing crucial roles in cancer progression and survive. In this respect, new series of pyrazole-thiazol-4-one hybrids (9a–p) were synthesized as potential anticancer agents. All the synthesized molecules exhibited potent antiproliferative actions against breast cancer (BC) T-47D and MDA-MB-231 cell lines with IC₅₀ ranges 3.14–4.92 and 0.62–58.01, respectively. Moreover, the most potent anti-proliferative counterparts 9g and 9k were assessed against EGFR. They displayed nanomolar inhibitory activity, IC₅₀ 267 ± 12 and 395 ± 17 nM, respectively. Worth noting, both compounds 9g and 9k induced apoptosis in MDA-MB-231 cells, and resulted in a cell cycle arrest at G2/M phase. Furthermore, an in silico analysis including docking and molecular dynamic simulations was performed.

A Small Peptide Increases Drug Delivery in Human Melanoma Cells

Melanoma is the most fatal type of skin cancer and is notoriously resistant to chemotherapies. The response of melanoma to current treatments is difficult to predict. To combat these challenges, in this study, we utilize a small peptide to increase drug delivery to melanoma cells. A peptide library array was designed and screened using a peptide array-whole cell binding assay, which identified KK-11 as a novel human melanoma-targeting peptide. The peptide and its D-amino acid substituted analogue (VPWxEPAYQrFL or D-aa KK-11) were synthesized via a solid-phase strategy. Further studies using FITC-labeled KK-11 demonstrated dose-dependent uptake in human melanoma cells. D-aa KK-11 significantly increased the stability of the peptide, with 45.3% remaining detectable after 24 h with human serum incubation. Co-treatment of KK-11 with doxorubicin was found to significantly enhance the cytotoxicity of doxorubicin compared to doxorubicin alone, or sequential KK-11 and doxorubicin treatment. In vivo and ex vivo imaging revealed that D-aa KK-11 distributed to xenografted A375 melanoma tumors as early as 5 min and persisted up to 24 h post tail vein injection. When co-administered, D-aa KK-11 significantly enhanced the anti-tumor activity of a novel nNOS inhibitor (MAC-3-190) in an A375 human melanoma xenograft mouse model compared to MAC-3-190 treatment alone. No apparent systemic toxicities were observed. Taken together, these results suggest that KK-11 may be a promising human melanoma-targeted delivery vector for anti-melanoma cargo.

SH003 and Docetaxel Show Synergistic Anticancer Effects by Inhibiting EGFR Activation in Triple-Negative Breast Cancer

Although many anticancer drugs have been developed for triple-negative breast cancer (TNBC) treatment, there are no obvious therapies. Moreover, the combination of epidermal growth factor receptor- (EGFR-) targeted therapeutics and classical chemotherapeutic drugs has been assessed in clinical trials for TNBC treatment, but those are not yet approved. Our serial studies for newly developed herbal medicine named SH003 provide evidence of its broad effectiveness in various cancers, especially on TNBC. The current study demonstrates a synergic effect of combinatorial treatment of SH003 and docetaxel (DTX) by targeting EGFR activation. The combinatorial treatment reduced the viability of both BT-20 and MDA-MB-231 TNBC cells, displaying the synergism. The combination of SH003 and DTX also caused the synergistic effect on apoptosis. Mechanistically, the cotreatment of SH003 and DTX inhibited phosphorylation of EGFR and AKT in both BT-20 and MDA-MB-231 cells. Moreover, our xenograft mouse tumor growth assays showed the inhibitory effect of the combinatorial treatment with no effect on body weight. Our immunohistochemistry confirmed its inhibition of EGFR phosphorylation in vivo. Collectively, combinatorial treatment of SH003 and DTX has a synergistic anticancer effect at a relatively low concentration by targeting EGFR in TNBC, indicating safety and efficacy of SH003 as adjuvant combination therapy with docetaxel. Thus, it is worth testing the combinatorial effect in clinics for treating TNBC.

Ligand-mediated nanomedicines against breast cancer: a review

Ligand-mediated targeting represents the cutting edge in precision-guided therapy for several diseases. Surface engineering of nanomedicines with ligands exhibiting selective or tailored affinity for overexpressed biomolecules of a specific disease may increase therapeutic efficiency and reduce side effects and recurrence. This review focuses on newly developed approaches and strategies to improve treatment and overcome the mechanisms associated with breast cancer resistance.

Biodistribution and Activity of EGFR Targeted Polymeric Micelles Delivering a New Inhibitor of DNA Repair to Orthotopic Colorectal Cancer Xenografts with Metastasis

The disruption of polynucleotide kinase/phosphatase (PNKP) in colorectal cancer (CRC) cells deficient in phosphatase and tensin homolog (PTEN) is expected to lead to the loss of cell viability by a process known as synthetic lethality. In previous studies, we have reported on the encapsulation of a novel inhibitor of PNKP, namely, A83B4C63, in polymeric micelles and its activity in slowing the growth of PTEN-deficient CRC cells as well as subcutaneous xenografts. In this study, to enhance drug delivery and specificity to CRC tumors, the surface of polymeric micelles carrying A83B4C63 was modified with GE11, a peptide targeting epidermal growth factor receptor (EGFR) overexpressed in about 70% of CRC tumors. Using molecular dynamics (MD) simulations, we assessed the binding site and affinity of GE11 for EGFR. The GE11-modified micelles, tagged with a near-infrared fluorophore, showed enhanced internalization by EGFR-overexpressing CRC cells in vitro and a trend toward increased primary tumor homing in an orthotopic CRC xenograft in vivo. In line with these observations, the GE11 modification of polymeric micelles was shown to positively contribute to the improved therapeutic activity of encapsulated A83B4C63 against HCT116-PTEN^-/- cells in vitro and that of orthotopic CRC xenograft in vivo. In conclusion, our results provided proof of principle evidence for the potential benefit of EGFR targeted polymeric micellar formulations of A83B4C63 as monotherapeutics for aggressive and metastatic CRC tumors but at the same time highlighted the need for the development of EGFR ligands with improved physiological stability and EGFR binding.

A Dual-Reporter Platform for Screening Tumor-Targeted Extracellular Vesicles

Extracellular vesicle (EV)-mediated transfer of biomolecules plays an essential role in intercellular communication and may improve targeted drug delivery. In the past decade, various approaches to EV surface modification for targeting specific cells or tissues have been proposed, including genetic engineering of parental cells or postproduction EV engineering. However, due to technical limitations, targeting moieties of engineered EVs have not been thoroughly characterized. Here, we report the bioluminescence resonance energy transfer (BRET) EV reporter, PalmReNL-based dual-reporter platform for characterizing the cellular uptake of tumor-homing peptide (THP)-engineered EVs, targeting PDL1, uPAR, or EGFR proteins expressed in MDA-MB-231 breast cancer cells, simultaneously by bioluminescence measurement and fluorescence microscopy. Bioluminescence analysis of cellular EV uptake revealed the highest binding efficiency of uPAR-targeted EVs, whereas PDL1-targeted EVs showed slower cellular uptake. EVs engineered with two known EGFR-binding peptides via lipid nanoprobes did not increase cellular uptake, indicating that designs of EGFR-binding peptide conjugation to the EV surface are critical for functional EV engineering. Fluorescence analysis of cellular EV uptake allowed us to track individual PalmReNL-EVs bearing THPs in recipient cells. These results demonstrate that the PalmReNL-based EV assay platform can be a foundation for high-throughput screening of tumor-targeted EVs.

Poly-Lysine Dendritic Nanocarrier to Target Epidermal Growth Factor Receptor Overexpressed Breast Cancer for Methotrexate Delivery

A fourth generation poly-lysine dendritic nanocarrier (P₄LDN)-based targeted chemotherapy for breast cancer is attempted by incorporating an epidermal growth factor receptor (EGFR)-specific short peptide E2 (ARSHVGYTGAR) and the drug methotrexate (MTX) into a nanocarrier system. The drug is incorporated into the nanocarrier using a cathepsin B cleavable spacer: glycine–phenylalanine–leucine–glycine (GFLG). The in vitro analysis of the time-dependent drug release, binding and internalization ability, and the cytotoxic nature showed that this drug delivery system (DDS) is highly effective. The efficacy analysis using non-obese diabetic/severe combined immunodeficiency (NOD-SCID) mice also showed that compared to the control group, the DDS can effectively reduce tumor volume. The mice that received the DDS appeared to gain weight more rapidly than the free drug, which suggests that the dendrimer is more easily tolerated by mice than the free drug.

Incorporation of Endosomolytic Peptides with Varying Disruption Mechanisms into EGFR-Targeted Protein Conjugates: The Effect on Intracellular Protein Delivery and EGFR Specificity in Breast Cancer Cells

Intracellular delivery of protein therapeutics remains a significant challenge limiting the majority of clinically available protein drugs to extracellular targets. Strategies to deliver proteins to subcellular compartments have traditionally relied on cell-penetrating peptides, which can drive enhanced internalization but exhibit unreliable activity and are rarely able to target specific cells, leading to off-target effects. Moreover, few design rules exist regarding the relative efficacy of various endosomal escape strategies in proteins. Accordingly, we developed a simple fusion modification approach to incorporate endosomolytic peptides onto epidermal growth factor receptor (EGFR)-targeted protein conjugates and performed a systematic comparison of the endosomal escape efficacy, mechanism of action, and capacity to maintain EGFR-targeting specificity of conjugates modified with four different endosomolytic sequences of varying modes of action (Aurein 1.2, GALA, HA2, and L17E). Use of the recently developed Gal8-YFP assay indicated that the fusion of each endosomolytic peptide led to enhanced endosomal disruption. Additionally, the incorporation of each endosomolytic peptide increased the half-life of the internalized protein and lowered lysosomal colocalization, further supporting the membrane-disruptive capacity. Despite this, only EGFR-targeted conjugates modified with Aurein 1.2 or GALA maintained EGFR specificity. These results thus demonstrated that the choice of endosomal escape moiety can substantially affect targeting capability, cytotoxicity, and bioactivity and provided important new insights into endosomolytic peptide selection for the design of targeted protein delivery systems.

In Silico Studies of Tumor Targeted Peptide-Conjugated Natural Products for Targeting Over-Expressed Receptors in Breast Cancer Cells Using Molecular Docking, Molecular Dynamics and MMGBSA Calculations

In this work, in silico studies were carried out for the design of diterpene and polyphenol-peptide conjugates to potentially target over-expressed breast tumor cell receptors. Four point mutations were induced into the known tumor-targeting peptide sequence YHWYGYTPQN at positions 1, 2, 8 and 10, resulting in four mutated peptides. Each peptide was separately conjugated with either chlorogenate, carnosate, gallate, or rosmarinate given their known anti-tumor activities, creating dual targeting compounds. Molecular docking studies were conducted with the epidermal growth factor receptor (EGFR), to which the original peptide sequence is known to bind, as well as the estrogen receptor (ERα) and peroxisome proliferator-activated receptor (PPARα) using both Autodock Vina and FireDock. Based on docking results, peptide conjugates and peptides were selected and subjected to molecular dynamics simulations. MMGBSA calculations were used to further probe the binding energies. ADME studies revealed that the compounds were not CYP substrates, though most were Pgp substrates. Additionally, most of the peptides and conjugates showed MDCK permeability. Our results indicated that several of the peptide conjugates enhanced binding interactions with the receptors and resulted in stable receptor-ligand complexes; Furthermore, they may successfully target ERα and PPARα in addition to EGFR and may be further explored for synthesis and biological studies for therapeutic applications.

Assessment of CAR-T cell-mediated cytotoxicity in 3D microfluidic cancer co-culture models for combination therapy

Chimeric antigen receptor (CAR)-T cell therapy is efficacious against many haematological malignancies, but challenges remain when using this cellular immunotherapy for treating solid tumours. Classical 2D in vitro models fail to recapitulate the complexity of the tumour microenvironment, whilst in vivo models, such as patient-derived xenografts, are costly and labour intensive. Microfluidic technologies can provide miniaturized solutions to assess CAR-T therapies in 3D complex preclinical models of solid tumours. Here, we present a novel microfluidic immunoassay for the evaluation of CAR-T cell cytotoxicity and targeting specificity on 3D spheroids containing cancer cells and stromal cells. Monitoring the interaction between CAR-T cells and spheroid co-cultures, we show that CAR-T cells home towards target-expressing cancer cells and elicit a cytotoxic effect. Testing CAR-T cells in combination therapies, we show that CAR-T cell cytotoxicity is enhanced with anti-PD-L1 therapy and carboplatin chemotherapy. We propose this proof-of-concept microfluidic immunoassay as a material-saving, pre-clinical screening tool for quantification of cell therapy efficacy.

In silico studies of interactions of peptide-conjugated cholesterol metabolites and betulinic acid with EGFR, LDR, and N-terminal fragment of CCKA receptors

In this work, we designed three new ligands by conjugating cholesterol metabolites 3-hydroxy-5-cholestenoic acid (3-HC) and 3-oxo-4-cholestenoic acid (3-OC) and the natural tri-terpenoid betulinic acid with the tumor-targeting peptide YHWYGYTPQNVI. Molecular interactions with the unconjugated peptide and the conjugates were examined with three receptors that are commonly overexpressed in pancreatic adenocarcinoma cells using ligand docking and molecular dynamics. This study demonstrated the utility of the designed conjugates as a valuable scaffold for potentially targeting EGFR and LDLR receptors. Our results indicate that the conjugates showed strong binding affinities and formation of stable complexes with EGFR, while the unconjugated peptide, BT-peptide conjugate, an 3-HC-peptide conjugate showed the formation of fairly stable complexes with LDLR receptor. For EGFR, two receptor kinase domains were explored. Interactions with the N-terminal domain of CCKA-R were relatively weaker. For LDLR, binding occurred in the beta-propeller region. For the N-terminal fragment of CCKA-R, the conjugates induced significant conformational changes in the receptor. The molecular dynamic simulations for 100 ns demonstrate that BT-peptide conjugates and the unconjugated peptide had the highest binding and formed the most stable complexes with EGFR. RMSD and trajectory analyses indicate that these molecules transit to a dynamically stable configuration in most cases within 60 ns. NMA analysis indicated that amongst the conjugates that showed relatively higher interactions with the respective receptors, the highest potential for deformability was seen for the N-terminal-47 amino acid region of the CCKA-R receptor with and the lowest for the LDLR-receptor. Thus, the newly designed compounds may be evaluated in the future toward developing drug delivery materials for targeting tumor cells overexpressing LDLR or EGFR.

Peptide-Based Drug Delivery Systems

Peptide-based drug delivery systems have many advantages when compared to synthetic systems in that they have better biocompatibility, biochemical and biophysical properties, lack of toxicity, controlled molecular weight via solid phase synthesis and purification. Lysosomes, solid lipid nanoparticles, dendrimers, polymeric micelles can be applied by intravenous administration, however they are of artificial nature and thus may induce side effects and possess lack of ability to penetrate the blood-brain barrier. An analysis of nontoxic drug delivery systems and an establishment of prospective trends in the development of drug delivery systems was needed. This review paper summarizes data, mainly from the past 5 years, devoted to the use of peptide-based carriers for delivery of various toxic drugs, mostly anticancer or drugs with limiting bioavailability. Peptide-based drug delivery platforms are utilized as peptide–drug conjugates, injectable biodegradable particles and depots for delivering small molecule pharmaceutical substances (500 Da) and therapeutic proteins. Controlled drug delivery systems that can effectively deliver anticancer and peptide-based drugs leading to accelerated recovery without significant side effects are discussed. Moreover, cell penetrating peptides and their molecular mechanisms as targeting peptides, as well as stimuli responsive (enzyme-responsive and pH-responsive) peptides and peptide-based self-assembly scaffolds are also reviewed.

Novel Peptide Therapeutic Approaches for Cancer Treatment

Peptides are increasingly being developed for use as therapeutics to treat many ailments, including cancer. Therapeutic peptides have the advantages of target specificity and low toxicity. The anticancer effects of a peptide can be the direct result of the peptide binding its intended target, or the peptide may be conjugated to a chemotherapy drug or radionuclide and used to target the agent to cancer cells. Peptides can be targeted to proteins on the cell surface, where the peptide–protein interaction can initiate internalization of the complex, or the peptide can be designed to directly cross the cell membrane. Peptides can induce cell death by numerous mechanisms including membrane disruption and subsequent necrosis, apoptosis, tumor angiogenesis inhibition, immune regulation, disruption of cell signaling pathways, cell cycle regulation, DNA repair pathways, or cell death pathways. Although using peptides as therapeutics has many advantages, peptides have the disadvantage of being easily degraded by proteases once administered and, depending on the mode of administration, often have difficulty being adsorbed into the blood stream. In this review, we discuss strategies recently developed to overcome these obstacles of peptide delivery and bioavailability. In addition, we present many examples of peptides developed to fight cancer.

Multiple strategies for the treatment of invasive breast carcinoma: A comprehensive prospective

In this review, we emphasize on evolving therapeutic strategies and advances in the treatment of breast cancer (BC). This includes small-molecule inhibitors under preclinical and clinical investigation, phytoconstituents with antiproliferative potential, targeted therapies as antibodies and antibody-drug conjugates (ADCs), vaccines as immunotherapeutic agents and peptides as a novel approach inhibiting the interaction of oncogenic proteins. We provide an update of molecules under different phases of clinical investigation which aid in the identification of loopholes or shortcomings that can be overcomed with future breast cancer research.

The Chemokine-Based Peptide, CXCL9(74-103), Inhibits Angiogenesis by Blocking Heparan Sulfate Proteoglycan-Mediated Signaling of Multiple Endothelial Growth Factors

Simple Summary

Major angiogenic growth factors activate downstream signaling cascades by interacting with both receptor tyrosine kinases (RTKs) and cell surface proteoglycans, such as heparan sulfate proteoglycans (HSPGs). As current anti-angiogenesis regimens in cancer are often faced with resistance, alternative therapeutic strategies are highly needed. The aim of our study was to investigate the impact on angiogenic signaling when we interfered with growth factor-HSPG interactions using a CXCL9 chemokine-derived peptide with high affinity for HS.

Abstract

Growth factors such as vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and epidermal growth factor (EGF) are important angiogenesis-mediating factors. They exert their effects not only through their respective receptor tyrosine kinases (RTKs), but they also require molecular pairing with heparan sulfate proteoglycans (HSPGs). Angiogenic growth factors and their signaling pathways are commonly targeted in current anti-angiogenic cancer therapies but have unfortunately insufficient impact on patient survival. Considering their obvious role in pathological angiogenesis, HS-targeting drugs have become an appealing new strategy. Therefore, we aimed to reduce angiogenesis through interference with growth factor-HS binding and downstream signaling using a CXCL9-derived peptide with a high affinity for glycosaminoglycans (GAGs), CXCL9(74-103). We showed that CXCL9(74-103) reduced EGF-, VEGF165- and FGF-2-mediated angiogenic processes in vitro, such as endothelial cell proliferation, chemotaxis, adhesion and sprouting, without exerting cell toxicity. CXCL9(74-103) interfered with growth factor signaling in diverse ways, e.g., by diminishing VEGF165 binding to HS and by direct association with FGF-2. The dependency of CXCL9(74-103) on HS for binding to HMVECs and for exerting its anti-angiogenic activity was also demonstrated. In vivo, CXCL9(74-103) attenuated neovascularization in the Matrigel plug assay, the corneal cauterization assay and in MDA-MB-231 breast cancer xenografts. Additionally, CXCL9(74-103) reduced vascular leakage in the retina of diabetic rats. In contrast, CXCL9(86-103), a peptide with low GAG affinity, showed no overall anti-angiogenic activity. Altogether, our results indicate that CXCL9(74-103) reduces angiogenesis by interfering with multiple HS-dependent growth factor signaling pathways.

Peptide-Conjugated Nano Delivery Systems for Therapy and Diagnosis of Cancer

Peptides are strings of approximately 2-50 amino acids, which have gained huge attention for theranostic applications in cancer research due to their various advantages including better biosafety, customizability, convenient process of synthesis, targeting ability via recognizing biological receptors on cancer cells, and better ability to penetrate cell membranes. The conjugation of peptides to the various nano delivery systems (NDS) has been found to provide an added benefit toward targeted delivery for cancer therapy. Moreover, the simultaneous delivery of peptide-conjugated NDS and nano probes has shown potential for the diagnosis of the malignant progression of cancer. In this review, various barriers hindering the targeting capacity of NDS are addressed, and various approaches for conjugating peptides and NDS have been discussed. Moreover, major peptide-based functionalized NDS targeting cancer-specific receptors have been considered, including the conjugation of peptides with extracellular vesicles, which are biological nanovesicles with promising ability for therapy and the diagnosis of cancer.

Delivery of doxorubicin loaded P18 conjugated-poly(2-ethyl-oxazoline)-DOPE nanoliposomes for targeted therapy of breast cancer

Breast cancer, a heterogeneous disease, has the highest incidence rate and is a major cause of death in females worldwide. Drug delivery by using nanotechnology has shown great promise for improving cancer treatment. Nanoliposomes are known to have enhanced accumulation ability in tumors due to prolonged systemic circulation. Peptide 18 (P18), a tumor homing peptide targeting keratin-1 (KRT-1), was previously shown to have high binding affinity towards breast cancer cells. In this study, we investigate the ability of P18 conjugated PEtOx-DOPE nanoliposomes (P18-PEtOx-DOPE) for the targeted delivery of doxorubicin to AU565 breast cancer model. Toxicology studies of PEtOx-DOPE nanoliposomes performed on normal breast epithelial cells (MCF10A), showed minimal toxicity. Doxorubicin delivery by P18-PEtOx-DOPE to AU565 cells induces cytotoxicity in a dose and time dependent manner causing mitotic arrest in G2/M phase at 24 h. Anti-cancer activity of P18-PEtOx-DOPE-DOX nanoliposomes on AU565 cells was detected by Annexin V/PI apoptosis assay. In terms of in vivo antitumor efficacy, P18-PEtOx-DOPE-DOX nanoliposomes administration to AU565 CD-1 nu/nu mice model showed significant decrease in tumor volume suggesting that DOX delivered by these nanoliposomes elicited a strong antitumor response comparable to the free delivery of doxorubicin. Overall, our results offered preclinical proof for the use of P18-PEtOx-DOPE-DOX nanoliposomes in KRT-1⁺ breast cancer therapy.

Targeted Liposomal Chemotherapies to Treat Triple-Negative Breast Cancer

Simple Summary

Triple-negative breast cancers (TNBCs) are mainly treated with standard chemotherapies. Combined therapies have been demonstrated as a promising treatment strategy in clinics. The aim of this study was to develop a new formulation of combined chemotherapies facilitated with a targeted delivery vehicle. We found that the mertansine and gemcitabine with different anti-cancer mechanisms resulted in high cytotoxicity in TNBC cells. The in vivo evaluations using two TNBC xenograft models confirmed the anti-tumor efficacy, i.e., significantly reduced tumor growth rate. Furthermore, the antibody-tagged liposomes effectively delivered the therapeutic drugs to TNBC tumor, which could reduce the side effects. This study is highly translational and the targeted liposomal drug formulation can be further investigated in future clinical trials for TNBC treatment.

Abstract

Triple-negative breast cancers (TNBCs) are highly aggressive and recurrent. Standard cytotoxic chemotherapies are currently the main treatment options, but their clinical efficacies are limited and patients usually suffer from severe side effects. The goal of this study was to develop and evaluate targeted liposomes-delivered combined chemotherapies to treat TNBCs. Specifically, the IC₅₀ values of the microtubule polymerization inhibitor mertansine (DM1), mitotic spindle assembly defecting taxane (paclitaxel, PTX), DNA synthesis inhibitor gemcitabine (GC), and DNA damage inducer doxorubicin (AC) were tested in both TNBC MDA-MB-231 and MDA-MB-468 cells. Then we constructed the anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) tagged liposomes and confirmed its TNBC cell surface binding using flow cytometry, internalization with confocal laser scanning microscopy, and TNBC xenograft targeting in NSG female mice using In Vivo Imaging System. The safe dosage of anti-EGFR liposomal chemotherapies, i.e., <20% body weight change, was identified. Finally, the in vivo anti-tumor efficacy studies in TNBC cell line-derived xenograft and patient-derived xenograft models revealed that the targeted delivery of chemotherapies (mertansine and gemcitabine) can effectively inhibit tumor growth. This study demonstrated that the targeted liposomes enable the new formulations of combined therapies that improve anti-TNBC efficacy.

pH-Controlled Protein Orthogonal Ligation Using Asparaginyl Peptide Ligases

Peptide asparaginyl ligases (PALs) catalyze transpeptidation at the Asn residue of a short Asn-Xaa₁-Xaa₂ tripeptide motif. Due to their high catalytic activity toward the P1-Asn substrates at around neutral pH, PALs have been used extensively for peptide ligation at asparaginyl junctions. PALs also bind to aspartyl substrates, but only when the ^γCOOH of P1-Asp remains in its neutral, protonated form, which usually requires an acidic pH. However, this limits the availability of the amine nucleophile and, consequently, the ligation efficiency at aspartyl junctions. Because of this perceived inefficiency, the use of PALs for Asp-specific ligation remains largely unexplored. We found that PAL enzymes, such as VyPAL2, display appreciable catalytic activities toward P1-Asp substrates at pH 4-5, which are at least 2 orders of magnitude higher than that of sortase A, making them practically useful for both intra- and intermolecular ligations. This also allows sequential ligations, first at Asp and then at Asn junctions, because the newly formed aspartyl peptide bond is resistant to the ligase at the pH used for asparaginyl ligation in the second step. Using this pH-controlled orthogonal ligation method, we dually labeled truncated sfGFP with a cancer-targeting peptide and a doxorubicin derivative at the respective N- and C-terminal ends in the N-to-C direction. In addition, a fluorescein tag and doxorubicin derivative were tagged to an EGFR-targeting affibody in the C-to-N direction. This study shows that the pH-dependent catalytic activity of PAL enzymes can be exploited to prepare multifunction protein biologics for pharmacological applications.

Role of inflammatory microenvironment: potential implications for improved breast cancer nano-targeted therapy

Tumor cells, inflammatory cells and chemical factors work together to mediate complex signaling networks, which forms inflammatory tumor microenvironment (TME). The development of breast cancer is closely related to the functional activities of TME. This review introduces the origins of cancer-related chronic inflammation and the main constituents of inflammatory microenvironment. Inflammatory microenvironment plays an important role in breast cancer growth, metastasis, drug resistance and angiogenesis through multifactorial mechanisms. It is suggested that inflammatory microenvironment contributes to providing possible mechanisms of drug action and modes of drug transport for anti-cancer treatment. Nano-drug delivery system (NDDS) becomes a popular topic for optimizing the design of tumor targeting drugs. It is seen that with the development of therapeutic approaches, NDDS can be used to achieve drug-targeted delivery well across the biological barriers and into cells, resulting in superior bioavailability, drug dose reduction as well as off-target side effect elimination. This paper focuses on the review of modulation mechanisms of inflammatory microenvironment and combination with nano-targeted therapeutic strategies, providing a comprehensive basis for further research on breast cancer prevention and control.

Molecular Targeting of Epidermal Growth Factor Receptor (EGFR) and Vascular Endothelial Growth Factor Receptor (VEGFR)

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) are two extensively studied membrane-bound receptor tyrosine kinase proteins that are frequently overexpressed in many cancers. As a result, these receptor families constitute attractive targets for imaging and therapeutic applications in the detection and treatment of cancer. This review explores the dynamic structure and structure-function relationships of these two growth factor receptors and their significance as it relates to theranostics of cancer, followed by some of the common inhibition modalities frequently employed to target EGFR and VEGFR, such as tyrosine kinase inhibitors (TKIs), antibodies, nanobodies, and peptides. A summary of the recent advances in molecular imaging techniques, including positron emission tomography (PET), single-photon emission computerized tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and optical imaging (OI), and in particular, near-IR fluorescence imaging using tetrapyrrolic-based fluorophores, concludes this review.

Development of targeted therapy therapeutics to sensitize triple-negative breast cancer chemosensitivity utilizing bacteriophage phi29 derived packaging RNA

Background

To date, triple-negative breast cancer (TNBC) treatment options are limited because of the loss of target receptors and, as a result, are only managed with chemotherapy. What is worse is that TNBC is frequently developing resistance to chemotherapy. By using small interfering RNA (siRNA)-based therapeutics, our recent work demonstrated X-box-binding protein 1 (XBP1) was linked to human epidermal growth factor receptor 2 positive (HER2+) breast cancer development and chemoresistance. Given the instability, off-target effects, net negative charge, and hydrophobicity of siRNA in vivo utilization and clinical transformation, its use in treatment is hampered. Thus, the development of a siRNA-based drug delivery system (DDS) with ultra-stability and specificity is necessary to address the predicament of siRNA delivery.

Results

Here, we assembled RNase resistant RNA nanoparticles (NPs) based on the 3WJ structure from Phi29 DNA packaging motor. To improved targeted therapy and sensitize TNBC to chemotherapy, the RNA NPs were equipped with an epidermal growth factor receptor (EGFR) targeting aptamer and XBP1 siRNA. We found our RNA NPs could deplete XBP1 expression and suppress tumor growth after intravenous administration. Meanwhile, RNA NPs treatment could promote sensitization to chemotherapy and impede angiogenesis in vivo.

Conclusions

The results further demonstrate that our RNA NPs could serve as an effective and promising platform not only for siRNA delivery but also for chemotherapy-resistant TNBC therapy.

Anti-EGFR antibody-drug conjugate for triple-negative breast cancer therapy

Triple-negative breast cancers (TNBCs) are highly aggressive, metastatic and recurrent. Cytotoxic chemotherapies with limited clinical benefits and severe side effects are the standard therapeutic strategies, but, to date, there is no efficacious targeted therapy. Literature and our data showed that epidermal growth factor receptor (EGFR) is overexpressed on TNBC cell surface and is a promising oncological target. The objective of this study was to develop an antibody-drug conjugate (ADC) to target EGFR+ TNBC and deliver high-potency drug. First, we constructed an ADC by conjugating anti-EGFR monoclonal antibody with mertansine which inhibits microtubule assembly via linker Sulfo-SMCC. Second, we confirmed the TNBC-targeting specificity of anti-EGFR ADC by evaluating its surface binding and internalization in MDA-MB-468 cells and targeting to TNBC xenograft in subcutaneous mouse mode. The live-cell and live-animal imaging with confocal laser scanning microscopy and In Vivo Imaging System (IVIS) confirmed the TNBC-targeting. Finally, both in vitro toxicity assay and in vivo anti-cancer efficacy study in TNBC xenograft models showed that the constructed ADC significantly inhibited TNBC growth, and the pharmacokinetics study indicated its high circulation stability. This study indicated that the anti-EGFR ADC has a great potential to against TNBC.

Homing Peptides for Cancer Therapy

Tumor-homing peptides are widely used for improving tumor selectivity of anticancer drugs and imaging agents. The goal is to increase tumor uptake and reduce accumulation at nontarget sites. Here, we describe current approaches for tumor-homing peptide identification and validation, and provide comprehensive overview of classes of tumor-homing peptides undergoing preclinical and clinical development. We focus on unique mechanistic features and applications of a recently discovered class of tumor-homing peptides, tumor-penetrating C-end Rule (CendR) peptides, that can be used for tissue penetrative targeting of extravascular tumor tissue. Finally, we discuss unanswered questions and future directions in the field of development of peptide-guided smart drugs and imaging agents.