Landscape phages and their fusion proteins targeted to breast cancer cells

Characterisation of the cell and molecular biological effect of peptide-based daunorubicin conjugates developed for targeting pancreatic adenocarcinoma (PANC-1) cell line

Pancreatic adenocarcinoma is one of the tumours with the worst prognosis, with a 5-year survival rate of 5-10%. Our aim was to find and optimise peptide-based drug conjugates with daunorubicin (Dau) as the cytotoxic antitumour agent. When conjugated with targeting peptides, the side effect profile and pharmacokinetics of Dau can be improved. The targeting peptide sequences (e.g. GSSEQLYL) we studied were originally selected by phage display. By Ala-scan technique, we identified that position 6 in the parental sequence (Dau=Aoa-LRRY-GSSEQLYL-NH2, ConjA) could be modified without the loss of antitumour activity (Dau=Aoa-LRRY-GSSEQAYL-NH2, Conj03: 14. 9% viability). Our results showed that the incorporation of p-chloro-phenylalanine (Dau=Aoa-LRRY-GSSEQF(pCl)YL-NH2, Conj16) further increased the antitumour potency (10-5 M: 9.7% viability) on pancreatic adenocarcinoma cells (PANC-1). We found that conjugates containing modified GSSEQLYL sequences could be internalised to PANC-1 cells and induce cellular senescence in the short term and subsequent apoptotic cell death. Furthermore, the cardiotoxic effect of Dau was markedly reduced in the form of peptide conjugates. In conclusion, Conj16 had the most effective antitumor activity on PANC-1 cells, which makes this conjugate promising for developing new targeted therapies without cardiotoxic effects.

Dual ligand-targeted Pluronic P123 polymeric micelles enhance the therapeutic effect of breast cancer with bone metastases

Bone metastasis secondary to breast cancer negatively impacts patient quality of life and survival. The treatment of bone metastases is challenging since many anticancer drugs are not effectively delivered to the bone to exert a therapeutic effect. To improve the treatment efficacy, we developed Pluronic P123 (P123)-based polymeric micelles dually decorated with alendronate (ALN) and cancer-specific phage protein DMPGTVLP (DP-8) for targeted drug delivery to breast cancer bone metastases. Doxorubicin (DOX) was selected as the anticancer drug and was encapsulated into the hydrophobic core of the micelles with a high drug loading capacity (3.44%). The DOX-loaded polymeric micelles were spherical, 123 nm in diameter on average, and exhibited a narrow size distribution. The in vitro experiments demonstrated that a pH decrease from 7.4 to 5.0 markedly accelerated DOX release. The micelles were well internalized by cultured breast cancer cells and the cell death rate of micelle-treated breast cancer cells was increased compared to that of free DOX-treated cells. Rapid binding of the micelles to hydroxyapatite (HA) microparticles indicated their high affinity for bone. P123-ALN/DP-8@DOX inhibited tumor growth and reduced bone resorption in a 3D cancer bone metastasis model. In vivo experiments using a breast cancer bone metastasis nude model demonstrated increased accumulation of the micelles in the tumor region and considerable antitumor activity with no organ-specific histological damage and minimal systemic toxicity. In conclusion, our study provided strong evidence that these pH-sensitive dual ligand-targeted polymeric micelles may be a successful treatment strategy for breast cancer bone metastasis.

Phage-Displayed Mimotopes of SARS-CoV-2 Spike Protein Targeted to Authentic and Alternative Cellular Receptors

The evolution of the SARS-CoV-2 virus during the COVID-19 pandemic was accompanied by the emergence of new heavily mutated viral variants with increased infectivity and/or resistance to detection by the human immune system. To respond to the urgent need for advanced methods and materials to empower a better understanding of the mechanisms of virus’s adaptation to human host cells and to the immuno-resistant human population, we suggested using recombinant filamentous bacteriophages, displaying on their surface foreign peptides termed “mimotopes”, which mimic the structure of viral receptor-binding sites on the viral spike protein and can serve as molecular probes in the evaluation of molecular mechanisms of virus infectivity. In opposition to spike-binding antibodies that are commonly used in studying the interaction of the ACE2 receptor with SARS-CoV-2 variants in vitro, phage spike mimotopes targeted to other cellular receptors would allow discovery of their role in viral infection in vivo using cell culture, tissue, organs, or the whole organism. Phage mimotopes of the SARS-CoV-2 Spike S1 protein have been developed using a combination of phage display and molecular mimicry concepts, termed here “phage mimicry”, supported by bioinformatics methods. The key elements of the phage mimicry concept include: (1) preparation of a collection of p8-type (landscape) phages, which interact with authentic active receptors of live human cells, presumably mimicking the binding interactions of human coronaviruses such as SARS-CoV-2 and its variants; (2) discovery of closely related amino acid clusters with similar 3D structural motifs on the surface of natural ligands (FGF1 and NRP1), of the model receptor of interest FGFR and the S1 spike protein; and (3) an ELISA analysis of the interaction between candidate phage mimotopes with FGFR3 (a potential alternative receptor) in comparison with ACE2 (the authentic receptor).

Detection of cancer stem cells by EMT-specific biomarker-based peptide ligands

The occurrence of epithelial-mesenchymal transition (EMT) within tumors, which enables invasion and metastasis, is linked to cancer stem cells (CSCs) with drug and radiation resistance. We used two specific peptides, F7 and SP peptides, to detect EMT derived cells or CSCs. Human tongue squamous carcinoma cell line-SAS transfected with reporter genes was generated and followed by spheroid culture. A small molecule inhibitor-Unc0642 and low-dose ionizing radiation (IR) were used for induction of EMT. Confocal microscopic imaging and fluorescence-activated cell sorting analysis were performed to evaluate the binding ability and specificity of peptides. A SAS xenograft mouse model with EMT induction was established for assessing the binding affinity of peptides. The results showed that F7 and SP peptides not only specifically penetrated into cytoplasm of SAS cells but also bound to EMT derived cells and CSCs with high nucleolin and vimentin expression. In addition, the expression of CSC marker and the binding of peptides were increased in tumors isolated from Unc0642/IR-treated groups. Our study demonstrates the potential of these peptides for detecting EMT derived cells or CSCs and might provide an alternative isolation method for these subpopulations within the tumor in the future.

Potential anticancer activity of a new pro-apoptotic peptide-thioctic acid gold nanoparticle platform

Targeted nanoparticle platforms designed to induce cell death by apoptosis can bypass the resistance mechanisms of cancer cells. With this in mind we have constructed a new cancer-targeting peptide-functionalized nanoparticle using gold nanoparticles (AuNPs) and a thioctic acid-DMPGTVLP peptide (TA-peptide) conjugate. Morphological analysis of the nanoparticles by transmission electron microscopy showed average diameters of about 3.52 nm and 26.2 nm for the AuNP core and shell, respectively. Strong affinity toward the nucleolin receptors of breast cancer cell lines MCF-7 and T47D was observed for the TA-peptide gold nanoparticles (TAP@AuNPs) based on IC₅₀ values. Furthermore, the nanoparticles showed excellent hemocompatibility. Quantitative results of atomic absorption showed improved uptake of TAP@AuNPs. Treatment of the cells with TAP@AuNPS resulted in greater release of cytochrome c following caspase-3/7 activation compared with free TA-peptide. The cytosolic level of adenosine triphosphate for TAP@AuNPs was higher than in controls. Higher anti-tumor efficiency was observed for TAP@AuNPs than TA-peptide compared with phosphate-buffered saline after intratumoral injection in tumor-bearing mice. It can be concluded that the design and development of a receptor-specific peptide-AuNP platform will be valuable for theranostic applications in cancer nanomedicine.

Proteomic Evaluation of Plasma Membrane Fraction Prepared from a Mouse Liver and Kidney Using a Bead Homogenizer: Enrichment of Drug-Related Transporter Proteins

Quantifying the protein levels of drug transporters in plasma membrane fraction helps elucidate the function of these transporters. In this study, we conducted a proteomic evaluation of enriched drug-related transporter proteins in plasma membrane fraction prepared from mouse liver and kidney tissues using the membrane protein extraction kit and a bead homogenizer. Crude and plasma membrane fractions were prepared using either the Dounce or bead homogenizer, and protein levels were determined using quantitative proteomics. In liver tissues, the plasma membrane fractions were more enriched in transporter proteins than the crude membrane fractions; the average enrichment ratios of plasma-to-crude membrane fractions were 3.31 and 6.93 using the Dounce and bead homogenizers, respectively. The concentrations of transporter proteins in plasma membrane fractions determined using the bead homogenizer were higher than those determined using the Dounce homogenizer. Meanwhile, in kidney tissues, the plasma membrane fractions were enriched in transporters localized in the brush-border membrane to the same degree for both the homogenizers; however, the membrane fractions obtained using either homogenizer were not enriched in Na^+/K⁺-ATPase and transporters localized in the basolateral membrane. These results indicate that fractionation, using the bead homogenizer, yielded transporter-enriched plasma membrane fractions from mouse liver and kidney tissues; however, no enrichment of basolateral transporters was observed in plasma membrane fractions prepared from kidney tissues.

Combinatorial Avidity Selection of Mosaic Landscape Phages Targeted at Breast Cancer Cells-An Alternative Mechanism of Directed Molecular Evolution

Low performance of actively targeted nanomedicines required revision of the traditional drug targeting paradigm and stimulated the development of novel phage-programmed, self-navigating drug delivery vehicles. In the proposed smart vehicles, targeting peptides, selected from phage libraries using traditional principles of affinity selection, are substituted for phage proteins discovered through combinatorial avidity selection. Here, we substantiate the potential of combinatorial avidity selection using landscape phage in the discovery of Short Linear Motifs (SLiMs) and their partner domains. We proved an algorithm for analysis of phage populations evolved through multistage screening of landscape phage libraries against the MDA-MB-231 breast cancer cell line. The suggested combinatorial avidity selection model proposes a multistage accumulation of Elementary Binding Units (EBU), or Core Motifs (CorMs), in landscape phage fusion peptides, serving as evolutionary initiators for formation of SLiMs. Combinatorial selection has the potential to harness directed molecular evolution to create novel smart materials with diverse novel, emergent properties.

Phage Display Technology and its Applications in Cancer Immunotherapy

Background:

Phage display is an effective technology for generation and selection targeting protein for a variety of purpose, which is based on a direct linkage between the displayed protein and the DNA sequence encoding it and utilized in selecting peptides, improving peptides affinity and indicating protein-protein interactions. Phage particles displaying peptide have the potential to apply in the identification of cell-specific targeting molecules, identification of cancer cell surface biomarkers, identification anti-cancer peptide, and the design of peptide-based anticancer therapy.

Method/Results:

Literature searches, reviews and assessments about Phage were performed in this review from PubMed and Medline databases.

Conclusion:

The phage display technology is an inexpensive method for expressing exogenous peptides, generating unique peptides that bind any given target and investigating protein-protein interactions. Due to the powerful ability to insert exogenous gene and display exogenous peptides on the surface, phages may represent a powerful peptide delivery system that can be utilized to develop rapid, efficient, safe and inexpensive cancer therapy methods.

Phage Ligands for Identification of Mesenchymal-Like Breast Cancer Cells and Cancer-Associated Fibroblasts

Epithelial to mesenchymal transition (EMT) is believed to be crucial for primary tumors to escape their original residence and invade and metastasize. To properly define EMT, there is a need for ligands that can identify this phenomenon in tumor tissue and invivo. A phage-display selection screening was performed to select novel binding phage peptides for identification of EMT in breast cancer. Epithelial breast cancer cell line, MCF-7 was transformed to mesenchymal phenotype by TGF-β treatment and was used for selection. Breast fibroblasts were used for subtractive depletion and breast cancer metastatic cell lines MDA-MB-231, T47D-shNMI were used for specificity assay. The binding peptides were identified, and their binding capacities were confirmed by phage capture assay, phage-based ELISA, immunofluorescence microscopy. The phage peptide bearing the 7-amino acid sequence, LGLRGSL, demonstrated selective binding to EMT phenotypic cells (MCF-7/TGF-β and MDA-MB-231) as compared to epithelial subtype, MCF-7, T47D and breast fibroblasts (Hs578T). The selected phage was also able to identify metastatic breast cancer tumor in breast cancer tissue microarray (TMA). These studies suggest that the selected phage peptide LGLRGSL identified by phage-display library, showed significant ability to bind to mesenchymal-like breast cancer cells/ tissues and can serve as a novel probe/ligand for metastatic breast cancer diagnostic and imaging.

The Improved Delivery to Breast Cancer Based on a Novel Nanocarrier Modified with High-Affinity Peptides Discovered by Phage Display

Ligand-targeted nanosystems have the potential to realize site-specific tumor therapy and alleviate unwanted side effects of many chemotherapeutic agents, and one of the most key issues seems to be the construction of an effective nanocarrier. Based on different processes of phage display techniques, 38 cell-binding peptides and 32 cell-internalizing peptides are discovered. Four of these ligand peptides [FIPFDPMSMRWE (FIP), NASSFPTNSRWA (NAS), GLHTSATNLYLH (GLH), and ALAVAPSRWWNE (ALA), respectively] exhibit high affinity to MCF7 human breast cancer cells. Among them, NAS and ALA are reported for the first time, whose affinities are 20.6 and 76.3 times that of the random peptide control, respectively. Both NAS and ALA modifications to doxorubicin-loaded lipid nanosytems [LP(DOX)] show stronger tumor inhibition, longer animal survival time, and less body weight loss, compared to unmodified or control peptide modified nanosystems, on an MCF7 tumor-bearing mouse model. In conclusion, the cell-binding peptide NAS and cell-internalizing peptide ALA can be used for ligand-targeted delivery of antitumor drugs. It seems that the in vivo antitumor effect of these ligand-targeted nanosystems is closely related to their ligand-cell affinity, but fairly tolerant of the ligand types.

Landscape Phage: Evolution from Phage Display to Nanobiotechnology

The development of phage engineering technology has led to the construction of a novel type of phage display library-a collection of nanofiber materials with diverse molecular landscapes accommodated on the surface of phage particles. These new nanomaterials, called the "landscape phage", serve as a huge resource of diagnostic/detection probes and versatile construction materials for the preparation of phage-functionalized biosensors and phage-targeted nanomedicines. Landscape-phage-derived probes interact with biological threat agents and generate detectable signals as a part of robust and inexpensive molecular recognition interfaces introduced in mobile detection devices. The use of landscape-phage-based interfaces may greatly improve the sensitivity, selectivity, robustness, and longevity of these devices. In another area of bioengineering, landscape-phage technology has facilitated the development and testing of targeted nanomedicines. The development of high-throughput phage selection methods resulted in the discovery of a variety of cancer cell-associated phages and phage proteins demonstrating natural proficiency to self-assemble into various drug- and gene-targeting nanovehicles. The application of this new "phage-programmed-nanomedicines" concept led to the development of a number of cancer cell-targeting nanomedicine platforms, which demonstrated anticancer efficacy in both in vitro and in vivo experiments. This review was prepared to attract the attention of chemical scientists and bioengineers seeking to develop functionalized nanomaterials and use them in different areas of bioscience, medicine, and engineering.

Engineering T7 bacteriophage as a potential DNA vaccine targeting delivery vector

Background

DNA delivery with bacteriophage by surface-displayed mammalian cell penetrating peptides has been reported. Although, various phages have been used to facilitate DNA transfer by surface displaying the protein transduction domain of human immunodeficiency virus type 1 Tat protein (Tat peptide), no similar study has been conducted using T7 phage.

Methods

In this study, we engineeredT7 phage as a DNA targeting delivery vector to facilitate cellular internalization. We constructed recombinant T7 phages that displayed Tat peptide on their surface and carried eukaryotic expression box (EEB) as a part of their genomes (T7-EEB-Tat).

Results

We demonstrated that T7 phage harboring foreign gene insertion had packaged into infective progeny phage particles. Moreover, when mammalian cells that were briefly exposed to T7-EEB-Tat, expressed a significant higher level of the marker gene with the control cells infected with the wide type phage without displaying Tat peptides.

Conclusion

These data suggested that the potential of T7 phage as an effective delivery vector for DNA vaccine transfer.

Autonomous self-navigating drug-delivery vehicles: from science fiction to reality

Low efficacy of targeted nanomedicines in biological experiments enforced us to challenge the traditional concept of drug targeting and suggest a paradigm of ‘addressed self-navigating drug-delivery vehicles,’ in which affinity selection of targeting peptides and vasculature-directed in vivo phage screening is replaced by the migration selection, which explores ability of ‘promiscuous’ phages and their proteins to migrate through the tumor-surrounding cellular barriers, using a ‘hub and spoke’ delivery strategy, and penetrate into the tumor affecting the diverse tumor cell population. The ‘self-navigating’ drug-delivery paradigm can be used as a theoretical and technical platform in design of a novel generation of molecular medications and imaging probes for precise and personal medicine.

[Formula: see text]

Paradigm shift in bacteriophage-mediated delivery of anticancer drugs: from targeted 'magic bullets' to self-navigated 'magic missiles'

INTRODUCTION

New phage-directed nanomedicines have emerged recently as a result of the in-depth study of the genetics and structure of filamentous phage and evolution of phage display and phage nanobiotechnology. This review focuses on the progress made in the development of the cancer-targeted nanomaterials and discusses the trends in using phage as a bioselectable molecular navigation system. Areas covered: The merging of phage display technologies with nanotechnology in recent years has proved promising in different areas of medicine and technology, such as medical diagnostics, molecular imaging, vaccine development and targeted drug/gene delivery, which is the focus of this review. The authors used data obtained from their research group and sourced using Science Citation Index (Web of Science) and NCBI PubMed search resources. Expert opinion: First attempts of adapting traditional concepts of direct targeting of tumor using phage-targeted nanomedicines has shown minimal improvements. With discovery and study of biological and technical barriers that prevent anti-tumor drug delivery, a paradigm shift from traditional drug targeting to nanomedicine navigation systems is required. The advanced bacteriophage-driven self-navigation systems are thought to overcome those barriers using more precise, localized phage selection methods, multi-targeting 'promiscuous' ligands and advanced multifunctional nanomedicine platforms.

Tumor-targeting peptides from combinatorial libraries

Cancer is one of the major and leading causes of death worldwide. Two of the greatest challenges in fighting cancer are early detection and effective treatments with no or minimum side effects. Widespread use of targeted therapies and molecular imaging in clinics requires high affinity, tumor-specific agents as effective targeting vehicles to deliver therapeutics and imaging probes to the primary or metastatic tumor sites. Combinatorial libraries such as phage-display and one-bead one-compound (OBOC) peptide libraries are powerful approaches in discovering tumor-targeting peptides. This review gives an overview of different combinatorial library technologies that have been used for the discovery of tumor-targeting peptides. Examples of tumor-targeting peptides identified from each combinatorial library method will be discussed. Published tumor-targeting peptide ligands and their applications will also be summarized by the combinatorial library methods and their corresponding binding receptors.

Promiscuous tumor targeting phage proteins

Cancer cell-specific targeting ligands against numerous cancer cell lines have been selected previously and used as ligands for cell-specific delivery of chemotherapies and various nanomedicines. However, tumor heterogeneity is one recognized problem hampering clinical translation of targeted anti-cancer medicines. Therefore, a novel class of targeting ligands is required that recognize receptors expressed between a variety of cancer phenotypes, identified here as 'promiscuous' ligands. In this work, promiscuous phage fusion proteins were first identified by a novel selection scheme to enrich for pan-cancer cell binding abilities, as indicated by conserved structural motifs identified previously in other cancer types. Additionally, peptide sequences containing a combination of motifs were identified to modulate binding. A panel of phage fusion proteins was studied for their specificity and selectivity for lung and pancreatic cancer cells. Phage displaying the fusion peptides GSLEEVSTL or GEFDELMTM, the two predominate clones with greatest binding ability, were used to modify preformed, doxorubicin-loaded, liposomes. These modified liposomes increased cytotoxicity up to 8.1-fold in several cancer cell lines when compared with unmodified liposomal doxorubicin. Taken together, these data indicate that promiscuous phage proteins, selected against different cancer cell lines, can be used as targeting ligands for treatment of heterogeneous tumor populations.

Selection of Lung Cancer-Specific Landscape Phage for Targeted Drug Delivery

Cancer cell-specific diagnostic or therapeutic tools are commonly believed to significantly increase the success rate of cancer diagnosis and targeted therapies. To extend the repertoire of available cancer cell-specific phage fusion proteins and study their efficacy as navigating moieties, we used two landscape phage display libraries f8/8 and f8/9 displaying an 8- or 9-mer random peptide fusion to identify a panel of novel peptide families that are specific to Calu-3 cells. Using a phage capture assay, we showed that two of the selected phage clones, ANGRPSMT and VNGRAEAP (phage and their recombinant proteins are named by the sequence of the fusion peptide), are selective for the Calu-3 cell line in comparison to phenotypically normal lung epithelial cells and distribute into unique subcellular fractions.

Bifunctional fused polypeptide inhibits the growth and metastasis of breast cancer

Breast cancer is the most common cancer and the leading cause of cancer-related death among women worldwide, with urgent need to develop new therapeutics. Targeted therapy is a promising strategy for breast cancer therapy. Stromal-derived factor-1/CXC chemokine receptor 4 (CXCR4) has been implicated in the metastasis of breast cancer, which renders it to be therapeutic target. This study aimed to evaluate the anticancer effect of fused TAT- DV1-BH3 polypeptide, an antagonist of CXCR4, and investigate the underlying mechanism for the cancer cell-killing effect in the treatment of breast cancer in vitro and in vivo. This results in a potent inhibitory effect of fused TAT-DV1-BH3 polypeptide on tumor growth and metastasis in nude mice bearing established MDA-MB-231 tumors. Fused TAT-DV1-BH3 polypeptide inhibited the proliferation of MDA-MB-231 and MCF-7 cells but did not affect that of HEK-293 cells. The fused TAT-DV1-BH3 polypeptide colocalized with mitochondria and exhibited a proapoptotic effect through the regulation of caspase-9 and -3. Furthermore, the fused TAT-DV1-BH3 polypeptide suppressed the migration and invasion of the highly metastatic breast cancer cell line MDA-MB-231 in a concentration-dependent manner. Notably, the DV1-mediated inhibition of the stromal-derived factor-1/CXCR4 pathway contributed to the antimetastasis effect, evident from the reduction in the level of phosphoinositide 3 kinase and matrix metalloproteinase 9 in MDA-MB-231 cells. Collectively, these results indicate that the apoptosis-inducing effect and migration- and invasion-suppressing effect explain the tumor regression and metastasis inhibition in vivo, with the involvement of caspase- and CXCR4-mediated signaling pathway. The data suggest that the fused TAT-DV1-BH3 polypeptide is a promising agent for the treatment of breast cancer, and more studies are warranted to fully elucidate the therapeutic targets and molecular mechanism.

Beyond phage display: non-traditional applications of the filamentous bacteriophage as a vaccine carrier, therapeutic biologic, and bioconjugation scaffold

For the past 25 years, phage display technology has been an invaluable tool for studies of protein-protein interactions. However, the inherent biological, biochemical, and biophysical properties of filamentous bacteriophage, as well as the ease of its genetic manipulation, also make it an attractive platform outside the traditional phage display canon. This review will focus on the unique properties of the filamentous bacteriophage and highlight its diverse applications in current research. Particular emphases are placed on: (i) the advantages of the phage as a vaccine carrier, including its high immunogenicity, relative antigenic simplicity and ability to activate a range of immune responses, (ii) the phage's potential as a prophylactic and therapeutic agent for infectious and chronic diseases, (iii) the regularity of the virion major coat protein lattice, which enables a variety of bioconjugation and surface chemistry applications, particularly in nanomaterials, and (iv) the phage's large population sizes and fast generation times, which make it an excellent model system for directed protein evolution. Despite their ubiquity in the biosphere, metagenomics work is just beginning to explore the ecology of filamentous and non-filamentous phage, and their role in the evolution of bacterial populations. Thus, the filamentous phage represents a robust, inexpensive, and versatile microorganism whose bioengineering applications continue to expand in new directions, although its limitations in some spheres impose obstacles to its widespread adoption and use.

Combinatorial synthesis and screening of cancer cell-specific nanomedicines targeted via phage fusion proteins

Active tumor targeting of nanomedicines has recently shown significant improvements in the therapeutic activity of currently existing drug delivery systems, such as liposomal doxorubicin (Doxil/Caelyx/Lipodox). Previously, we have shown that isolated pVIII major coat proteins of the fd-tet filamentous phage vector, containing cancer cell-specific peptide fusions at their N-terminus, can be used as active targeting ligands in a liposomal doxorubicin delivery system in vitro and in vivo. Here, we show a novel major coat protein isolation procedure in 2-propanol that allows spontaneous incorporation of the hydrophobic protein core into preformed liposomal doxorubicin with minimal damage or drug loss while still retaining the targeting ligand exposed for cell-specific targeting. Using a panel of 12 structurally unique ligands with specificity toward breast, lung, and/or pancreatic cancer, we showed the feasibility of pVIII major coat proteins to significantly increase the throughput of targeting ligand screening in a common nanomedicine core. Phage protein-modified Lipodox samples showed an average doxorubicin recovery of 82.8% across all samples with 100% of protein incorporation in the correct orientation (N-terminus exposed). Following cytotoxicity screening in a doxorubicin-sensitive breast cancer line (MCF-7), three major groups of ligands were identified. Ligands showing the most improved cytotoxicity included: DMPGTVLP, ANGRPSMT, VNGRAEAP, and ANDVYLD showing a 25-fold improvement (p < 0.05) in toxicity. Similarly DGQYLGSQ, ETYNQPYL, and GSSEQLYL ligands with specificity toward a doxorubicin-insensitive pancreatic cancer line (PANC-1) showed significant increases in toxicity (2-fold; p < 0.05). Thus, we demonstrated proof-of-concept that pVIII major coat proteins can be screened in significantly higher throughput to identify novel ligands displaying improved therapeutic activity in a desired cancer phenotype.

Bio-mimetic nanostructure self-assembled from Au@Ag heterogeneous nanorods and phage fusion proteins for targeted tumor optical detection and photothermal therapy

Nanomaterials with near-infrared (NIR) absorption have been widely studied in cancer detection and photothermal therapy (PTT), while it remains a great challenge in targeting tumor efficiently with minimal side effects. Herein we report a novel multifunctional phage-mimetic nanostructure, which was prepared by layer-by-layer self-assembly of Au@Ag heterogenous nanorods (NRs) with rhodamine 6G, and specific pVIII fusion proteins. Au@Ag NRs, first being applied for PTT, exhibited excellent stability, cost-effectivity, biocompatibility and tunable NIR absorption. The fusion proteins were isolated from phage DDAGNRQP specifically selected from f8/8 landscape phage library against colorectal cancer cells in a high-throughput way. Considering the definite charge distribution and low molecular weight, phage fusion proteins were assembled on the negatively charged NR core by electrostatic interactions, exposing the N-terminus fused with DDAGNRQP peptide on the surface. The fluorescent images showed that assembled phage fusion proteins can direct the nanostructure into cancer cells. The nanostructure was more efficient than gold nanorods and silver nanotriangle-based photothermal agents and was capable of specifically ablating SW620 cells after 10 min illumination with an 808 nm laser in the light intensity of 4 W/cm(2). The prepared nanostructure would become an ideal reagent for simutaneously targeted optical imaging and PTT of tumor.

Selection of pancreatic cancer cell-binding landscape phages and their use in development of anticancer nanomedicines

It is hypothesized that the use of targeted drug delivery systems can significantly improve the therapeutic index of small molecule chemotherapies by enhancing accumulation of the drugs at the site of disease. Phage display offers a high-throughput approach for selection of the targeting ligands. We have successfully isolated phage fusion proteins selective and specific for PANC-1 pancreatic cancer cells. Doxorubicin liposomes (Lipodox) modified with tumor-specific phage fusion proteins enhanced doxorubicin uptake specifically in PANC-1 cells as compared with unmodified Lipodox and also compared with normal breast epithelial cells. Phage protein-targeted Lipodox substantially increased the concentration of doxorubicin in the nuclei of PANC-1 cells in spite of P-glycoprotein-mediated drug efflux. The in vitro cytotoxic activity obtained with pancreatic cell-targeted Lipodox was greater than that of unmodified Lipodox. We present a novel and straightforward method for preparing pancreatic tumor-targeted nanomedicines by anchoring pancreatic cancer-specific phage proteins within the liposome bilayer.

Phage protein-targeted cancer nanomedicines

Nanoencapsulation of anticancer drugs improves their therapeutic indices by virtue of the enhanced permeation and retention effect which achieves passive targeting of nanoparticles in tumors. This effect can be significantly enhanced by active targeting of nanovehicles to tumors. Numerous ligands have been proposed and used in various studies with peptides being considered attractive alternatives to antibodies. This is further reinforced by the availability of peptide phage display libraries which offer an unlimited reservoir of target-specific probes. In particular landscape phages with multivalent display of target-specific peptides which enable the phage particle itself to become a nanoplatform creates a paradigm for high throughput selection of nanoprobes setting the stage for personalized cancer management. Despite its promise, this conjugate of combinatorial chemistry and nanotechnology has not made a significant clinical impact in cancer management due to a lack of using robust processes that facilitate scale-up and manufacturing. To this end we proposed the use of phage fusion protein as the navigating modules of novel targeted nanomedicine platforms which are described in this review.

Enhanced tumor delivery and antitumor activity in vivo of liposomal doxorubicin modified with MCF-7-specific phage fusion protein

A novel strategy to improve the therapeutic index of chemotherapy has been developed by the integration of nanotechnology with phage technique. The objective of this study was to combine phage display, identifying tumor-targeting ligands, with a liposomal nanocarrier for targeted delivery of doxorubicin. Following the proof of concept in cell-based experiments, this study focused on in vivo assessment of antitumor activity and potential side-effects of phage fusion protein-modified liposomal doxorubicin. MCF-7-targeted phage-Doxil treatments led to greater tumor remission and faster onset of antitumor activity than the treatments with non-targeted formulations. The enhanced anticancer effect induced by the targeted phage-Doxil correlated with an improved tumor accumulation of doxorubicin. Tumor sections consistently revealed enhanced apoptosis, reduced proliferation activity and extensive necrosis. Phage-Doxil-treated mice did not show any sign of hepatotoxicity and maintained overall health. Therefore, MCF-7-targeted phage-Doxil seems to be an active and tolerable chemotherapy for breast cancer treatment.

FROM THE CLINICAL EDITOR

The authors of this study successfully combined phage display with a liposomal nanocarrier for targeted delivery of doxorubicin using MCF-7-targeted phage-Doxil nanocarriers in a rodent model. The method demonstrated improved efficiency and reduced hepatotoxicity, paving the way to future clinical trials addressing breast cancer.

Targeted delivery of siRNA into breast cancer cells via phage fusion proteins

Nucleic acids, including antisense oligonucleotides, small interfering RNA (siRNA), aptamers, and rybozymes, emerged as versatile therapeutics due to their ability to interfere in a well-planned manner with the flow of genetic information from DNA to protein. However, a systemic use of NAs is hindered by their instability in physiological liquids and inability of intracellular accumulation in the site of action. We first evaluated the potential of cancer specific phage fusion proteins as targeting ligands that provide encapsulation, protection, and navigation of siRNA to the target cell. The tumor-specific proteins were isolated from phages that were affinity selected from a landscape phage library against target breast cancer cells. It was found that fusion phage coat protein fpVIII displaying cancer-targeting peptides can effectively encapsulate siRNAs and deliver them into the cells leading to specific silencing of the model gene GAPDH. Complexes of siRNA and phage protein form nanoparticles (nanophages), which were characterized by atomic force microscopy and ELISA, and their stability was demonstrated by resistance of encapsulated siRNA to degradation by serum nucleases. The phage protein/siRNA complexes can make a new type of highly selective, stable, active, and physiologically acceptable cancer nanomedicine.