Ceramide as an endothelial cell surface receptor and a lung-specific lipid vascular target for circulating ligands.

The vascular endothelium from individual organs is functionally specialized, and it displays a unique set of accessible molecular targets. These serve as endothelial cell receptors to affinity ligands. To date, all identified vascular receptors have been proteins. Here, we show that an endothelial lung-homing peptide (CGSPGWVRC) interacts with C16-ceramide, a bioactive sphingolipid that mediates several biological functions. Upon binding to cell surfaces, CGSPGWVRC triggers ceramide-rich platform formation, activates acid sphingomyelinase and ceramide production, without the associated downstream apoptotic signaling. We also show that the lung selectivity of CGSPGWVRC homing peptide is dependent on ceramide production in vivo. Finally, we demonstrate two potential applications for this lipid vascular targeting system: i) as a bioinorganic hydrogel for pulmonary imaging and ii) as a ligand-directed lung immunization tool against COVID-19. Thus, C16-ceramide is a unique example of a lipid-based receptor system in the lung vascular endothelium targeted in vivo by circulating ligands such as CGSPGWVRC.

Towards a transcriptome-based theranostic platform for unfavorable breast cancer phenotypes.

Inflammatory breast carcinoma (IBC) is one of the most lethal forms of human breast cancer, and effective treatment for IBC is an unmet clinical need in contemporary oncology. Tumor-targeted theranostic approaches are emerging in precision medicine, but only a few specific biomarkers are available. Here we report up-regulation of the 78-kDa glucose-regulated protein (GRP78) in two independent discovery and validation sets of specimens derived from IBC patients, suggesting translational promise for clinical applications. We show that a GRP78-binding motif displayed on either bacteriophage or adeno-associated virus/phage (AAVP) particles or loop-grafted onto a human antibody fragment specifically targets orthotopic IBC and other aggressive breast cancer models in vivo. To evaluate the theranostic value, we used GRP78-targeting AAVP particles to deliver the human Herpes simplex virus thymidine kinase type-1 (HSVtk) transgene, obtaining simultaneous in vivo diagnosis through PET imaging and tumor treatment by selective activation of the prodrug ganciclovir at tumor sites. Translation of this AAVP system is expected simultaneously to image, monitor, and treat the IBC phenotype and possibly other aggressive (e.g., invasive and/or metastatic) subtypes of breast cancer, based on the inducible cell-surface expression of the stress-response chaperone GRP78, and possibily other cell-surface receptors in human tumors.

Targeted molecular-genetic imaging and ligand-directed therapy in aggressive variant prostate cancer.

Aggressive variant prostate cancers (AVPC) are a clinically defined group of tumors of heterogeneous morphologies, characterized by poor patient survival and for which limited diagnostic and treatment options are currently available. We show that the cell surface 78-kDa glucose-regulated protein (GRP78), a receptor that binds to phage-display-selected ligands, such as the SNTRVAP motif, is a candidate target in AVPC. We report the presence and accessibility of this receptor in clinical specimens from index patients. We also demonstrate that human AVPC cells displaying GRP78 on their surface could be effectively targeted both in vitro and in vivo by SNTRVAP, which also enabled specific delivery of siRNA species to tumor xenografts in mice. Finally, we evaluated ligand-directed strategies based on SNTRVAP-displaying adeno-associated virus/phage (AAVP) particles in mice bearing MDA-PCa-118b, a patient-derived xenograft (PDX) of castration-resistant prostate cancer bone metastasis that we exploited as a model of AVPC. For theranostic (a merging of the terms therapeutic and diagnostic) studies, GRP78-targeting AAVP particles served to deliver the human Herpes simplex virus thymidine kinase type-1 (HSVtk) gene, which has a dual function as a molecular-genetic sensor/reporter and a cell suicide-inducing transgene. We observed specific and simultaneous PET imaging and treatment of tumors in this preclinical model of AVPC. Our findings demonstrate the feasibility of GPR78-targeting, ligand-directed theranostics for translational applications in AVPC.

Integrated nanotechnology platform for tumor-targeted multimodal imaging and therapeutic cargo release.

A major challenge of targeted molecular imaging and drug delivery in cancer is establishing a functional combination of ligand-directed cargo with a triggered release system. Here we develop a hydrogel-based nanotechnology platform that integrates tumor targeting, photon-to-heat conversion, and triggered drug delivery within a single nanostructure to enable multimodal imaging and controlled release of therapeutic cargo. In proof-of-concept experiments, we show a broad range of ligand peptide-based applications with phage particles, heat-sensitive liposomes, or mesoporous silica nanoparticles that self-assemble into a hydrogel for tumor-targeted drug delivery. Because nanoparticles pack densely within the nanocarrier, their surface plasmon resonance shifts to near-infrared, thereby enabling a laser-mediated photothermal mechanism of cargo release. We demonstrate both noninvasive imaging and targeted drug delivery in preclinical mouse models of breast and prostate cancer. Finally, we applied mathematical modeling to predict and confirm tumor targeting and drug delivery. These results are meaningful steps toward the design and initial translation of an enabling nanotechnology platform with potential for broad clinical applications.

Targeting the interleukin-11 receptor α in metastatic prostate cancer: A first-in-man study.

BACKGROUND: Receptors in tumor blood vessels are attractive targets for ligand-directed drug discovery and development. The authors have worked systematically to map human endothelial receptors ("vascular zip codes") within tumors through direct peptide library selection in cancer patients. Previously, they selected a ligand-binding motif to the interleukin-11 receptor alpha (IL-11Rα) in the human vasculature. METHODS: The authors generated a ligand-directed, peptidomimetic drug (bone metastasis-targeting peptidomimetic-11 [BMTP-11]) for IL-11Rα-based human tumor vascular targeting. Preclinical studies (efficacy/toxicity) included evaluating BMTP-11 in prostate cancer xenograft models, drug localization, targeted apoptotic effects, pharmacokinetic/pharmacodynamic analyses, and dose-range determination, including formal (good laboratory practice) toxicity across rodent and nonhuman primate species. The initial BMTP-11 clinical development also is reported based on a single-institution, open-label, first-in-class, first-in-man trial (National Clinical Trials number NCT00872157) in patients with metastatic, castrate-resistant prostate cancer. RESULTS: BMTP-11 was preclinically promising and, thus, was chosen for clinical development in patients. Limited numbers of patients who had castrate-resistant prostate cancer with osteoblastic bone metastases were enrolled into a phase 0 trial with biology-driven endpoints. The authors demonstrated biopsy-verified localization of BMTP-11 to tumors in the bone marrow and drug-induced apoptosis in all patients. Moreover, the maximum tolerated dose was identified on a weekly schedule (20-30 mg/m(2) ). Finally, a renal dose-limiting toxicity was determined, namely, dose-dependent, reversible nephrotoxicity with proteinuria and casts involving increased serum creatinine. CONCLUSIONS: These biologic endpoints establish BMTP-11 as a targeted drug candidate in metastatic, castrate-resistant prostate cancer. Within a larger discovery context, the current findings indicate that functional tumor vascular ligand-receptor targeting systems may be identified through direct combinatorial selection of peptide libraries in cancer patients.

Targeting IL11 Receptor in Leukemia and Lymphoma: A Functional Ligand-Directed Study and Hematopathology Analysis of Patient-Derived Specimens.

PURPOSE: The IL11 receptor (IL11R) is an established molecular target in primary tumors of bone, such as osteosarcoma, and in secondary bone metastases from solid tumors, such as prostate cancer. However, its potential role in management of hematopoietic malignancies has not yet been determined. Here, we evaluated the IL11R as a candidate therapeutic target in human leukemia and lymphoma. EXPERIMENTAL DESIGN AND RESULTS: First, we show that the IL11R protein is expressed in a variety of human leukemia- and lymphoma-derived cell lines and in a large panel of bone marrow samples from leukemia and lymphoma patients, whereas expression is absent from nonmalignant control bone marrow. Moreover, a targeted peptidomimetic prototype (termed BMTP-11), specifically bound to leukemia and lymphoma cell membranes, induced ligand-receptor internalization mediated by the IL11R, and resulted in a specific dose-dependent cell death induction in these cells. Finally, a pilot drug lead-optimization program yielded a new myristoylated BMTP-11 analogue with an apparent improved antileukemia cell profile. CONCLUSIONS: These results indicate (i) that the IL11R is a suitable cell surface target for ligand-directed applications in human leukemia and lymphoma and (ii) that BMTP-11 and its derivatives have translational potential against this group of malignant diseases.

Selection and identification of ligand peptides targeting a model of castrate-resistant osteogenic prostate cancer and their receptors.

We performed combinatorial peptide library screening in vivo on a novel human prostate cancer xenograft that is androgen-independent and induces a robust osteoblastic reaction in bonelike matrix and soft tissue. We found two peptides, PKRGFQD and SNTRVAP, which were enriched in the tumors, targeted the cell surface of androgen-independent prostate cancer cells in vitro, and homed to androgen receptor-null prostate cancer in vivo. Purification of tumor homogenates by affinity chromatography on these peptides and subsequent mass spectrometry revealed a receptor for the peptide PKRGFQD, α-2-macroglobulin, and for SNTRVAP, 78-kDa glucose-regulated protein (GRP78). These results indicate that GRP78 and α-2-macroglobulin are highly active in osteoblastic, androgen-independent prostate cancer in vivo. These previously unidentified ligand-receptor systems should be considered for targeted drug development against human metastatic androgen-independent prostate cancer.

Semi-quantitative Multispectral Optoacoustic Tomography (MSOT) for volumetric PK imaging of gastric emptying.

A common side effect of medication is gastrointestinal intolerance. Symptoms can include reduced appetite, diarrhea, constipation, GI inflammation, nausea and vomiting. Such effects often have a dramatic impact on compliance with a treatment regimen. Therefore, characterization of GI tolerance is an important step when establishing a novel therapeutic approach. In this study, Multispectral Optoacoustic Tomography (MSOT) is used to monitor gastrointestinal motility by in vivo whole body imaging in mice. MSOT combines high spatial and temporal resolution based on ultrasound detection with strong optical contrast in the near infrared. Animals were given Indocyanine Green (ICG) by oral gavage and imaged by MSOT to observe the fate of ICG in the gastrointestinal tract. Exponential decay of ICG signal was observed in the stomach in good correlation with ex vivo validation. We discuss how kinetic imaging in MSOT allows visualization of parameters unavailable to other imaging methods, both in 2D and 3D.

A macrophage uptaking near-infrared chemical probe CDnir7 for in vivo imaging of inflammation.

Visualization of macrophages in live animals has been of great interest for a better understanding of inflammation. We developed a near infrared (NIR) probe that can selectively detect macrophages and visualize inflammation in vivo using the IVIS spectrum, Fluorescence Molecular Tomography (FMT) and Multi-Spectral Optoacoustic Tomography (MSOT).

Mechanism of action and initial evaluation of a membrane active all-D-enantiomer antimicrobial peptidomimetic.

Development of therapy against infections caused by antibiotic-resistant pathogens is a major unmet need in contemporary medicine. In previous work, our group chemically modified an antimicrobial peptidomimetic motif for targeted applications against cancer and obesity. Here, we show that the modified motif per se is resistant to proteolytic degradation and is a candidate antiinfective agent. We also show that the susceptibility of microorganisms to the drug is independent of bacterial growth phase. Moreover, this peptidomimetic selectively interferes with the integrity and function of the microbial surface lipid bilayer, data indicative that bacterial death results from membrane disruption followed by dissipation of membrane potential. Finally, we demonstrate two potential translational applications: use against biofilms and synergy with antibiotics in use. In summary, we introduce the mechanism of action and the initial evaluation of a prototype drug and a platform for the development of D-enantiomer antimicrobial peptidomimetics that target bacterial membranes of certain gram-negative problem pathogens with promising translational applications.

Multispectral opto-acoustic tomography (MSOT) of the brain and glioblastoma characterization.

Brain research depends strongly on imaging for assessing function and disease in vivo. We examine herein multispectral opto-acoustic tomography (MSOT), a novel technology for high-resolution molecular imaging deep inside tissues. MSOT illuminates tissue with light pulses at multiple wavelengths and detects the acoustic waves generated by the thermoelastic expansion of the environment surrounding absorbing molecules. Using spectral unmixing analysis of the data collected, MSOT can then differentiate the spectral signatures of oxygenated and deoxygenated hemoglobin and of photo-absorbing agents and quantify their concentration. By being able to detect absorbing molecules up to centimeters deep in the tissue it represents an ideal modality for small animal brain imaging, simultaneously providing anatomical, hemodynamic, functional, and molecular information. In this work we examine the capacity of MSOT in cross-sectional brain imaging of mice. We find unprecedented optical imaging performance in cross-sectional visualization of anatomical and physiological parameters of the mouse brain. For example, the potential of MSOT to characterize ischemic brain areas was demonstrated through the use of a carbon dioxide challenge. In addition, indocyanine green (ICG) was injected intravenously, and the kinetics of uptake and clearance in the vasculature of the brain was visualized in real-time. We further found that multiparameter, multispectral imaging of the growth of U87 tumor cells injected into the brain could be visualized through the intact mouse head, for example through visualization of deoxygenated hemoglobin in the growing tumor. We also demonstrate how MSOT offers several compelling features for brain research and allows time-dependent detection and quantification of brain parameters that are not available using other imaging methods without invasive procedures.

A peptidomimetic targeting white fat causes weight loss and improved insulin resistance in obese monkeys.

Obesity, defined as body mass index greater than 30, is a leading cause of morbidity and mortality and a financial burden worldwide. Despite significant efforts in the past decade, very few drugs have been successfully developed for the treatment of obese patients. Biological differences between rodents and primates are a major hurdle for translation of anti-obesity strategies either discovered or developed in rodents into effective human therapeutics. Here, we evaluate the ligand-directed peptidomimetic CKGGRAKDC-GG-(D)(KLAKLAK)(2) (henceforth termed adipotide) in obese Old World monkeys. Treatment with adipotide induced targeted apoptosis within blood vessels of white adipose tissue and resulted in rapid weight loss and improved insulin resistance in obese monkeys. Magnetic resonance imaging and dual-energy x-ray absorptiometry confirmed a marked reduction in white adipose tissue. At experimentally determined optimal doses, monkeys from three different species displayed predictable and reversible changes in renal proximal tubule function. Together, these data in primates establish adipotide as a prototype in a new class of candidate drugs that may be useful for treating obesity in humans.

Enhanced relative biological effectiveness of proton radiotherapy in tumor cells with internalized gold nanoparticles.

The development and use of sensitizing agents to improve the effectiveness of radiotherapy have long been sought to improve our ability to treat cancer. In this letter, we have studied the relative biological effectiveness of proton beam radiotherapy on prostate tumor cells with and without internalized gold nanoparticles. The effectiveness of proton radiotherapy for the killing of prostate tumor cells was increased by approximately 15%-20% for those cells containing internalized gold nanoparticles.

In vivo anti-tumor effect of expressing p14ARF-TAT using a FGF2-targeted cationic lipid vector.

PURPOSE: To develop an efficient and safe strategy to introduce a therapeutic gene into target cells in vivo for cancer therapy. The overall efficiency is based on proper selection of the delivery vector and expressed protein. METHODS: A plasmid coding for a specific cytotoxic fusion peptide, p14ARF-TAT, was evaluated in a xenograft mouse tumor model. The expressed peptide consisted of three domains, a secretory signal, a membrane permeability segment and a cytotoxic fragment. Gene expression was verified in U87-MG cells by Western blot and cytotoxicity confirmed with CyQuant assay. To improve the delivery, a FGF2 targeting peptide, MQLPLATC, was incorporated into the vector, which was evaluated using a luciferase-expressing plasmid. RESULTS: The luciferase activity in vitro was two-fold higher with the targeted formulations, and cytotoxicity was three-fold higher with expression of the p14ARF-TAT protein. A murine xenograph model of human glioma (U87-MG cells) tumors was used to address in vivo activity. FGF2-targeted lipoplexes demonstrated increased tumor volume reduction as compared to non-targeted formulations. RT-PCR and Western blot of tumor homogenizes indicated p14ARF-TAT expression in tumors along with other tissues. CONCLUSION: p14ARF-TAT was cytotoxic and is a promising approach when combined with an efficient targeting.

Systemic combinatorial peptide selection yields a non-canonical iron-mimicry mechanism for targeting tumors in a mouse model of human glioblastoma.

The management of CNS tumors is limited by the blood-brain barrier (BBB), a vascular interface that restricts the passage of most molecules from the blood into the brain. Here we show that phage particles targeted with certain ligand motifs selected in vivo from a combinatorial peptide library can cross the BBB under normal and pathological conditions. Specifically, we demonstrated that phage clones displaying an iron-mimic peptide were able to target a protein complex of transferrin and transferrin receptor (TfR) through a non-canonical allosteric binding mechanism and that this functional protein complex mediated transport of the corresponding viral particles into the normal mouse brain. We also showed that, in an orthotopic mouse model of human glioblastoma, a combination of TfR overexpression plus extended vascular permeability and ligand retention resulted in remarkable brain tumor targeting of chimeric adeno-associated virus/phage particles displaying the iron-mimic peptide and carrying a gene of interest. As a proof of concept, we delivered the HSV thymidine kinase gene for molecular-genetic imaging and targeted therapy of intracranial xenografted tumors. Finally, we established that these experimental findings might be clinically relevant by determining through human tissue microarrays that many primary astrocytic tumors strongly express TfR. Together, our combinatorial selection system and results may provide a translational avenue for the targeted detection and treatment of brain tumors.

An integrated approach for the rational design of nanovectors for biomedical imaging and therapy.

The use of nanoparticles for the early detection, cure, and imaging of diseases has been proved already to have a colossal potential in different biomedical fields, such as oncology and cardiology. A broad spectrum of nanoparticles are currently under development, exhibiting differences in (i) size, ranging from few tens of nanometers to few microns; (ii) shape, from the classical spherical beads to discoidal, hemispherical, cylindrical, and conical; (iii) surface functionalization, with a wide range of electrostatic charges and biomolecule conjugations. Clearly, the library of nanoparticles generated by combining all possible sizes, shapes, and surface physicochemical properties is enormous. With such a complex scenario, an integrated approach is here proposed and described for the rational design of nanoparticle systems (nanovectors) for the intravascular delivery of therapeutic and imaging contrast agents. The proposed integrated approach combines multiscale/multiphysics mathematical models with in vitro assays and in vivo intravital microscopy (IVM) experiments and aims at identifying the optimal combination of size, shape, and surface properties that maximize the nanovectors localization within the diseased microvasculature.

On the synergistic effects of ligand-mediated and phage-intrinsic properties during in vivo selection.

Phage display has been used as a powerful tool in the discovery and characterization of ligand-receptor complexes that can be utilized for therapeutic applications as well as to elucidate disease mechanisms. While the basic properties of phage itself have been well described, the behavior of phage in an in vivo setting is not as well understood due to the complexity of the system. Here, we take a dual approach in describing the biophysical mechanisms and properties that contribute to the efficacy of in vivo phage targeting. We begin by considering the interaction between phage and target by applying a kinetic model of ligand-receptor complexation and internalization. The multivalent display of peptides on the pIII capsid of phage is also discussed as an augmenting factor in the binding affinity of phage-displayed peptides to cellular targets accessible in a microenvironment of interest. Lastly, we examine the physical properties of the total phage particle that facilitate improved delivery and targeting in vivo compared to free peptides.

Ligand-directed cancer gene therapy to angiogenic vasculature.

Gene therapy strategies in cancer have remained an active area of preclinical and clinical research. One of the current limitations to successful trials is the relative transduction efficiency to produce a therapeutic effect. While intratumoral injections are the mainstay of many treatment regimens to date, this approach is hindered by hydrostatic pressures within the tumor and is not always applicable to all tumor subtypes. Vascular-targeting strategies introduce an alternative method to deliver vectors with higher local concentrations and minimization of systemic toxicity. Moreover, therapeutic targeting of angiogenic vasculature often leads to enhanced bystander effects, improving efficacy. While identification of functional and systemically accessible molecular targets is challenging, approaches, such as in vivo phage display and phage-based viral delivery vectors, provide a platform upon which vascular targeting of vectors may become a viable and translational approach.

Development of peptide-targeted lipoplexes to CXCR4-expressing rat glioma cells and rat proliferating endothelial cells.

A peptide analog, 4-fluorobenzoyl-RR-(L-3-(2-naphthyl)alanine)-CYEK-(L-citrulline)-PYR-(L-citrulline)-CR, covalently linked to a phospholipid, was used for targeting a lipid-based gene delivery vehicle to CXCR4(+)-cells. Characterization of transfection activity was done in vitro using a transformed rat glioma cell line (RG2) that expresses CXCR4. The substitution of the targeting lipid at increasing mole percentages in the place of helper lipids yielded a progressive increase in reporter gene expression, reaching a maximum of 2.5 times the control value at 20 mol% of ligand. The substitution of helper lipids with cysteine-derivatized phospholipid analog or phosphatidylethanolamine resulted in a progressive decrease in transfection activity, with complete inactivation of the complex occurring at 20 mol%. A DNA dose-response with 10 mol% of lipopeptide reduced the effective DNA dose at least fivefold with regard to the number of transfected cells and >20-fold with regard to the amount of gene expression. Gene transfer to rat endothelial cells was studied in the context of an arterial organ culture. Mesenteric arteries were cannulated and maintained in culture for up to 4 days. CXCR4 cell-surface expression on endothelial cells was induced after overnight incubation with vascular endothelial growth factor (VEGF). Gene transfer studies showed that only the peptide-targeted lipoplexes transfected the endothelium, and only after CXCR4 had been induced with VEGF. These results demonstrate that non-viral transfection complexes can be targeted to cells expressing CXCR4, and that gene transfer is dependent upon cell surface receptor expression levels.