Identification and characterization of a novel peptide ligand of epidermal growth factor receptor for targeted delivery of therapeutics

Epidermal growth factor receptor-targeted (131)I-therapy of liver cancer following systemic delivery of the sodium iodide symporter gene

We recently demonstrated tumor-selective iodide uptake and therapeutic efficacy of radioiodine in neuroblastoma tumors after systemic nonviral polyplex-mediated sodium iodide symporter (NIS) gene delivery. In the present study, we used novel polyplexes based on linear polyethylenimine (LPEI), polyethylene glycol (PEG), and the synthetic peptide GE11 as an epidermal growth factor receptor (EGFR)-specific ligand to target a NIS-expressing plasmid to hepatocellular carcinoma (HCC) (HuH7). Incubation of HuH7 cells with LPEI-PEG-GE11/NIS polyplexes resulted in a 22-fold increase in iodide uptake, which was confirmed in other cancer cell lines correlating well with EGFR expression levels. Using (123)I-scintigraphy and ex vivo γ-counting, HuH7 xenografts accumulated 6.5-9% injected dose per gram (ID/g) (123)I, resulting in a tumor-absorbed dose of 47 mGray/Megabecquerel (mGy/MBq) (131)Iodide ((131)I) after intravenous (i.v.) application of LPEI-PEG-GE11/NIS. No iodide uptake was observed in other tissues. After pretreatment with the EGFR-specific antibody cetuximab, tumoral iodide uptake was markedly reduced confirming the specificity of EGFR-targeted polyplexes. After three or four cycles of polyplex/(131)I application, a significant delay in tumor growth was observed associated with prolonged survival. These results demonstrate that systemic NIS gene transfer using polyplexes coupled with an EGFR-targeting ligand is capable of inducing tumor-specific iodide uptake, which represents a promising innovative strategy for systemic NIS gene therapy in metastatic cancers.

Peptide arrays for screening cancer specific peptides

In this paper, we describe a novel method to screen peptides for specific recognition by cancer cells. Seventy peptides were synthesized on a cellulose membrane in an array format, and a direct method to study the peptide-whole cell interaction was developed. The relative binding affinity of the cells for different peptides with respect to a lead 12-mer p160 peptide, identified by phage display, was evaluated using the CyQUANT fluorescence of the bound cells. Screening allowed identification of at least five new peptides that displayed higher affinity (up to 3-fold) for MDA-MB-435 and MCF-7 human cancer cells compared to the p160 peptide. These peptides showed very little binding to the control (noncancerous) human umbilical vein endothelial cells (HUVECs). Three of these peptides were synthesized separately and labeled with fluorescein isothiocyanate (FITC) to study their uptake and interaction with the cancer and control cells using confocal laser scanning microscopy and flow cytometry. The results confirmed the high and specific affinity of an 11-mer peptide 11 (RGDPAYQGRFL) and a 10-mer peptide 18 (WXEAAYQRFL) for the cancer cells versus HUVECs. Peptide 11 binds different receptors on target cancer cells as its sequence contains multiple recognition motifs, whereas peptide 18 binds mainly to the putative p160 receptor. The peptide array-whole cell binding assay reported here is a complementary method to phage display for further screening and optimization of cancer targeting peptides for cancer therapy and diagnosis.

Development of EGFR-targeted polymer blend nanocarriers for combination paclitaxel/lonidamine delivery to treat multi-drug resistance in human breast and ovarian tumor cells

Multi-drug resistant (MDR) cancer is a significant clinical obstacle and is often implicated in cases of recurrent, nonresponsive disease. Targeted nanoparticles were made by synthesizing a poly(D,L-lactide-co-glycolide)/poly(ethylene glycol)/epidermal growth factor receptor targeting peptide (PLGA/PEG/EGFR-peptide) construct for incorporation in poly(epsilon-caprolactone) (PCL) nanoparticles. MDR was induced in a panel of nine human breast and ovarian cancer cell lines using hypoxia. EGFR-targeted polymer blend nanoparticles were shown to actively target EGFR overexpressing cell lines, especially upon induction of hypoxia. The nanoparticles were capable of sustained drug release. Combination therapy with lonidamine and paclitaxel significantly improved the therapeutic index of both drugs. Treatment with a nanoparticle dose of 1 μM paclitaxel/10 μM lonidamine resulted in less than 10% cell viability for all hypoxic/MDR cell lines and less than 5% cell viability for all normoxic cell lines. Comparatively, treatment with 1 μM paclitaxel alone was the approximate IC₅₀ value of the MDR cells while treatment with lonidamine alone had very little effect. The PLGA/PEG/EGFR-peptide delivery system actively targets a MDR cell by exploiting the expression of EGFR. This system treats MDR by inhibiting the Warburg effect and promoting mitochondrial binding of pro-apoptotic Bcl-2 proteins (lonidamine), while hyperstabilizing microtubules (paclitaxel). This nanocarrier system actively targets a MDR associated phenotype (EGFR receptor overexpression), further enhancing the therapeutic index of both drugs and potentiating the use of lonidamine/paclitaxel combination therapy in the treatment of MDR cancer.

Peptidic tumor targeting agents: the road from phage display peptide selections to clinical applications

Cancer has become the number one cause of death amongst Americans, killing approximately 1,600 people per day. Novel methods for early detection and the development of effective treatments are an eminent priority in medicine. For this reason, isolation of tumor-specific ligands is a growing area of research. Tumor-specific binding agents can be used to probe the tumor cell surface phenotype and to customize treatment accordingly by conjugating the appropriate cell-targeting ligand to an anticancer drug. This refines the molecular diagnosis of the tumor and creates guided drugs that can target the tumor while sparing healthy tissues. Additionally, these targeting agents can be used as in vivo imaging agents that allow for earlier detection of tumors and micrometastasis. Phage display is a powerful technique for the isolation of peptides that bind to a particular target with high affinity and specificity. The biopanning of intact cancer cells or tumors in animals can be used as the bait to isolate peptides that bind to cancer-specific cell surface biomarkers. Over the past 10 years, unbiased biopanning of phage-displayed peptide libraries has generated a suite of cancer targeting peptidic ligands. This review discusses the recent advances in the isolation of cancer-targeting peptides by unbiased biopanning methods and highlights the use of the isolated peptides in clinical applications.

Bio and nanotechnological strategies for tumor-targeted gene therapy

Gene therapy is a new medical approach for the treatment of tumors. For safe and efficient gene therapy, therapeutic genes need to be delivered efficiently into the target tumor cells. Development of gene delivery systems to specifically recognize and target tumor cells and to distinguish them from normal cells, especially in the same tissue or organ, is one of the most important issues regarding the present gene delivery methodologies. The enhanced permeability and retention (EPR) effect using the characteristics of angiogenic tumor blood vessels, as well as gene delivery systems recognizing hyperactivated receptors or intracellular signals, is broadly applied to tumor-targeted gene therapy. In addition, bacterial vectors can be a useful means for targeting hypoxic or anoxic regions of a tumor.

Cell-targeting and cell-penetrating peptides for delivery of therapeutic and imaging agents

This review will discuss the basic concepts concerning the use of cell-targeting peptides (CTPs) and cell-penetrating peptides (CPPs) in the context of nanocarrier technology. It deals with the discovery and subsequent evolution of CTPs and CPPs, issues concerning their interactions with cells and their biodistribution in vivo, and their potential advantages and disadvantages as delivery agents. The article also briefly discusses several specific examples of the use of CTPs or CPPs to assist in the delivery of nanoparticles, liposomes, and other nanocarriers.

HDL-mimicking peptide-lipid nanoparticles with improved tumor targeting

Targeted delivery of intracellularly active diagnostics and therapeutics in vivo is a major challenge in cancer nanomedicine. A nanocarrier should possess long circulation time yet be small and stable enough to freely navigate through interstitial space to deliver its cargo to targeted cells. Herein, it is shown that by adding targeting ligands to nanoparticles that mimic high-density lipoprotein (HDL), tumor-targeted sub-30-nm peptide-lipid nanocarriers are created with controllable size, cargo loading, and shielding properties. The size of the nanocarrier is tunable between 10 and 30 nm, which correlates with a payload of 15-100 molecules of fluorescent dye. Ligand-directed nanocarriers targeting epidermal growth factor receptor (EGFR) are confirmed both in vitro and in vivo. The nanocarriers show favorable circulation time, tumor accumulation, and biodistribution with or without the targeting ligand. The EGFR targeting ligand is proved to be essential for the EGFR-mediated tumor cell uptake of the nanocarriers, a prerequisite of intracellular delivery. The results demonstrate that targeted HDL-mimetic nanocarriers are useful delivery vehicles that could open new avenues for the development of clinically viable targeted nanomedicine.

Targeting the EGF receptor for ovarian cancer therapy

Ovarian carcinoma is the leading cause of death from gynecologic malignancy in the US. Factors such as the molecular heterogeneity of ovarian tumors and frequent diagnosis at advanced stages hamper effective disease treatment. There is growing emphasis on the identification and development of targeted therapies to disrupt molecular pathways in cancer. The epidermal growth factor (EGF) receptor is one such protein target with potential utility in the management of ovarian cancer. This paper will discuss contributions of EGF receptor activation to ovarian cancer pathogenesis and the status of EGF receptor inhibitors and EGF receptor targeted therapies in ovarian cancer treatment.

Environmentally responsive peptides as anticancer drug carriers

The tumor microenvironment provides multiple cues that may be exploited to improve the efficacy of established chemotherapeutics; furthermore, polypeptides are uniquely situated to capitalize on these signals. Peptides provide: 1) a rich repertoire of biologically specific interactions to draw upon; 2) environmentally responsive phase behaviors, which may be tuned to respond to signatures of disease; 3) opportunities to direct self-assembly; 4) control over routes of biodegradation; 5) the option to seamlessly combine functionalities into a single polymer via a one-step biosynthesis. As development of cancer-targeted nanocarriers expands, peptides provide a unique source of functional units that may target disease. This review explores potential microenvironmental physiology indicative of tumors and peptides that have demonstrated an ability to target and deliver to these signals.

Epidermal growth factor receptor-targeted gelatin-based engineered nanocarriers for DNA delivery and transfection in human pancreatic cancer cells

Type B gelatin-based engineered nanocarrier systems (GENS) have been used over the last several years as a non-condensing systemic and oral DNA delivery system. In this study, we have modified the surface of GENS with epidermal growth factor receptor (EGFR)-targeting peptide for gene delivery and transfection in pancreatic cancer cell lines. GENS were prepared by the solvent displacement method and the EGFR-targeting peptide was grafted on the surface using a hetero-bifunctional poly(ethylene glycol) (PEG) spacer. Plasmid DNA, encoding for enhanced green fluorescent protein (GFP), was efficiently encapsulated and protected from degrading enzymes in the control and surface-modified GENS. Upon incubation with EGFR over-expressing Panc-1 human pancreatic adenocarcinoma cells, the peptide-modified nanoparticles were found to be internalized efficiently by receptor-mediated endocytosis. Both quantitative and qualitative transgene expression efficiencies were significantly enhanced when plasmid DNA was administered with EGFR-targeted GENS relative to the control-unmodified gelatin or PEG-modified gelatin nanoparticle systems. Based on these preliminary results, EGFR-targeted GENS show tremendous promise as a safe and effective gene delivery vector with the potential to treat pancreatic cancer.

Selection of phage-displayed peptides that bind to a particular ligand-bound antibody

Phage-displayed peptides that selectively bind to aldolase catalytic antibody 93F3 when bound to a particular 1,3-diketone hapten derivative have been developed using designed selection strategies with libraries containing 7-12 randomized amino acid residues. These phage-displayed peptides discriminated the particular 93F3-diketone complex from ligand-free 93F3 and from 93F3 bound to other 1,3-diketone hapten derivatives. By altering the selection procedures, phage-displayed peptides that bind to antibody 93F3 in the absence of 1,3-diketone hapten derivatives have also been developed. With using these phage-displayed peptides, ligand-bound states of the antibody were distinguished from each other. A docking model of one of the peptides bound to the antibody 93F3-diketone complex was created using a sequential divide-and-conquer peptide docking strategy; the model suggests that the peptide interacts with both the antibody and the ligand through a delicate hydrogen bonding network.

Population pharmacokinetic data analysis of three phase I studies of matuzumab, a humanised anti-EGFR monoclonal antibody in clinical cancer development

A population pharmacokinetic model based on data from three phase I studies was to be developed including a covariate analysis to describe the concentration–time profiles of matuzumab, a novel humanised monoclonal antibody. Matuzumab was administered as multiple 1 h i.v. infusions with 11 different dosing regimens ranging from 400 to 2000 mg, q1w–q3w. For analysis, 90 patients with 1256 serum concentration–time data were simultaneously fitted using the software NONMEM™. Data were best described using a two-compartment model with the parameters central (V₁) and peripheral distribution volume (V₂), intercompartmental (Q) and linear (CLL) clearance and an additional nonlinear elimination pathway (K_m, V_max). Structural parameters were in agreement with immunoglobulin characteristics. In total, interindividual variability on V_max, CLL, V₁ and V₂ and interoccasion variability on CLL was 22–62% CV. A covariate analysis identified weight having an influence on V₁ (+0.44% per kg) and CLL (+0.87% per kg). All parameters were estimated with good precision (RSE<39%). A robust population pharmacokinetic model for matuzumab was developed, including a nonlinear pharmacokinetic process. In addition, relevant and plausible covariates were identified and incorporated into the model. When correlated to efficacy, this model could serve as a tool to guide dose selection for this ‘targeted’ cancer therapy.

Identification and characterization of a novel peptide ligand of Tie2 for targeting gene therapy

Tyrosine kinase with immunoglobulin and epidermal growth factor homology domain-2 (Tie2) has been considered as a rational target for gene therapy in solid tumors. In order to identify a novel peptide ligand of Tie2 for targeted gene therapy, we screened a phage display peptide library and identified a candidate peptide ligand NSLSNASEFRAPY (designated GA5). Binding assays and Scatchard analysis revealed that GA5 could specifically bind to Tie2 with a dissociation constant of 2.1x10(-8)M. In addition, we showed that GA5 was internalized into tumor cells highly expressing Tie2. In the biodistribution assay, (125)I-GA5 was mainly accumulated in SPC-A1 xenograft tumors that express Tie2. In gene delivery studies, GA5-conjugated polyethylenimine vector could achieve greater transgene transduction than non-targeted vectors both in vitro and in vivo. Tumor growth inhibition was observed in SPC-A1 xenograft-bearing mice that received eight intratumoral injections of GA5-polyethylenimine/p53 complexes in 3 weeks. The difference in tumor volume between the experiment and control groups was significant (P<0.05). Our results showed that GA5 is a potentially efficient targeting element for cancer gene or molecular therapy.

Bio-nanocapsules for In vivo Pinpoint Drug Delivery

To maximize the beneficial effects and minimize the side effect of drugs, DDS (drug delivery system) has been attracted many researchers in the recent drug development. Especially, the in vivo pinpoint delivery system for drugs is very important and key technology for developing the next generations of anti-cancer drugs and gene therapies. Bio-nanocapsule (BNC) is recombinant yeast-derived hepatitis B virus surface antigen particle, which has been used as a recombinant hepatitis B vaccine for the last 20 years in the world. BNC can incorporate various materials (chemical compounds, proteins, genes, siRNA, etc) by the fusion with liposome, and deliver them to the organs and tissues in vivo specifically by the action of bio-recognition molecules on the BNC's surface. The transfection efficiency is significantly higher than that of liposome, because BNC harbors the complete set of hepatitis B virus infection machinery. Recently, we succeeded in the in vivo retargeting of BNC by displaying either antibody or homing peptide, less than 10 amino acid residues for in vivo targeting. BNC is a hybrid of liposome and virus, and very flexible system for in vivo retargeting. BNC might be very promising carriers in the next generation of DDS.

Targeting of human renal tumor-derived endothelial cells with peptides obtained by phage display

The phenotypic and molecular diversity of tumor-associated vasculature provides a basis for the development of targeted diagnostics and therapeutics. In the present study, we have developed a peptide-based targeting of human tumor endothelial cells (TEC) derived from renal carcinomas. We used a murine model of human tumor angiogenesis, in which TEC injected subcutaneously in severe combined immunodeficiency (SCID) mice organized in vascular structures connected with the mouse circulation, to screen in vivo a phage display library of random peptides. Using this approach, we identified cyclic peptides showing specific binding to TEC and not to normal human endothelial cells or to murine tumor endothelial cells. In particular, the peptide CVGNDNSSC (BB1) bound to TEC in vitro and in vivo. Using BB1 peptide conjugated with the ribosome-inactivating toxin saporin, we targeted TEC in vivo. Injection of BB1-saporin but not saporin alone or control modified BB-1ala saporin induced a selective cell apoptosis and disruption of the TEC vessel network. No increase in cell apoptosis was found in other murine organs. In conclusion, the identification of peptide sequences able to bind selectively human tumor-derived endothelial cells may represent a tool to deliver antiangiogenic or antitumor agents within the neoplastic vessels.

Evidence-based principles and practices in pathology: selected problem areas

Contrary to the intuitive impression of most pathologists, there are still many areas in laboratory medicine where evidence-based medicine (EBM) principles are not applied. These include aspects of both anatomic and clinical pathology. Some non-EBM practices are perpetuated by clinical "consumers" of laboratory services, because of inadequate education, habit, or over-reliance on empirical factors. Other faulty procedures are pathologist-driven, with similar underpinnings. This overview considers several exemplary problem areas representing non-EBM practices in the hospital laboratory. Such examples include ideas and techniques centering on metastatic malignancies, "targeted" oncological therapy, analysis of surgical margins in the excision of neoplasms, general laboratory testing and data utilization, evaluation of selected coagulation defects, administration of blood products, and analysis of hepatic iron-overload syndromes. The concepts illustrating departures from EBM are discussed for each of those topics.