In Vivo Targeting of Hydrogen Peroxide by Activatable Cell-Penetrating Peptides

A hydrogen peroxide (H₂O₂)-activated cell-penetrating peptide was developed through incorporation of a boronic acid-containing cleavable linker between polycationic cell-penetrating peptide and polyanionic fragments. Fluorescence labeling of the two ends of the molecule enabled monitoring its reaction with H₂O₂ through release of the highly adhesive cell-penetrating peptide and disruption of fluorescence resonance energy transfer. The H₂O₂ sensor selectively reacts with endogenous H₂O₂ in cell culture to monitor the oxidative burst of promyelocytes and in vivo to image lung inflammation. Targeting H₂O₂ has potential applications in imaging and therapy of diseases related to oxidative stress

Introduction: the significance of continuing debates

This comprehensive text encourages trainee and practising teachers to engage with and reflect on key issues, concepts and debates in geography education

New Dioxaborolane Chemistry Enables [¹⁸F]-Positron-Emitting, Fluorescent [¹⁸F]-Multimodality Biomolecule Generation from the Solid Phase

New protecting group chemistry is used to greatly simplify imaging probe production. Temperature and organic solvent-sensitive biomolecules are covalently attached to a biotin-bearing dioxaborolane, which facilitates antibody immobilization on a streptavidin-agarose solid-phase support. Treatment with aqueous fluoride triggers fluoride-labeled antibody release from the solid phase, separated from unlabeled antibody, and creates [¹⁸F]-trifluoroborate-antibody for positron emission tomography and near-infrared fluorescent (PET/NIRF) multimodality imaging. This dioxaborolane-fluoride reaction is bioorthogonal, does not inhibit antigen binding, and increases [¹⁸F]-specific activity relative to solution-based radiosyntheses. Two applications are investigated: an anti-epithelial cell adhesion molecule (EpCAM) monoclonal antibody (mAb) that labels prostate tumors and Cetuximab, an anti-epidermal growth factor receptor (EGFR) mAb (FDA approved) that labels lung adenocarcinoma tumors. Colocalized, tumor-specific NIRF and PET imaging confirm utility of the new technology. The described chemistry should allow labeling of many commercial systems, diabodies, nanoparticles, and small molecules for dual modality imaging of many diseases

Fluorescent Ligand for Human Progesterone Receptor Imaging in Live Cells

We employed molecular modeling to design and then synthesize fluorescent ligands for the human progesterone receptor. Boron dipyrromethene (BODIPY) or tetramethylrhodamine were conjugated to the progesterone receptor antagonist RU486 (Mifepristone) through an extended hydrophilic linker. The fluorescent ligands demonstrated comparable bioactivity to the parent antagonist in live cells and triggered nuclear translocation of the receptor in a specific manner. The BODIPY labeled ligand was applied to investigate the dependency of progesterone receptor nuclear translocation on partner proteins and to show that functional heat shock protein 90 but not immunophilin FKBP52 activity is essential. A tissue distribution study indicated that the fluorescent ligand preferentially accumulates in tissues that express high levels of the receptor <i>in vivo</i>. The design and properties of the BODIPY-labeled RU486 make it a potential candidate for <i>in vivo</i> imaging of PR by positron emission tomography through incorporation of ¹⁸F into the BODIPY core

Distribution of Tumor Size for each Contrast Group.

<p>Distribution of Tumor Size for each Contrast Group.</p

Tumor Detection at 3 Tesla with an Activatable Cell Penetrating Peptide Dendrimer (ACPPD-Gd), a T1 Magnetic Resonance (MR) Molecular Imaging Agent

<div><p>Purpose</p><p>The ability to detect small malignant lesions with magnetic resonance imaging (MRI) is limited by inadequate accumulations of Gd with standard chelate agents. To date, no T1-targeted agents have proven superiority to Gd chelates in their ability to detect small tumors at clinically relevant field strengths. Activatable cell-penetrating peptides and their Gd-loaded dendrimeric form (ACPPD-Gd) have been shown to selectively accumulate in tumors. In this study we compared the performance of ACPPD-Gd vs. untargeted Gd chelates to detect small tumors in rodent models using a clinical 3T-MR system.</p><p>Materials and Methods</p><p>This study was approved by the Institutional-Animal Care-and-Use Committee. 2 of 4 inguinal breast fat pads of 16 albino-C57BL/6 mice were inoculated with tumor Py8119 cells and the other 2 with saline at random. MRI at 3T was performed at 4, 9, and 14 days after inoculation on 8 mice 24-hours after injection of 0.036mmol Gd/kg (ACPPD-Gd), and before and 2–3 minutes after 0.1 mmol/kg gadobutrol on the other 8 mice. T1-weighted (T1w) tumor signal normalized to muscle, was compared among the non-contrast, gadobutrol, and ACPPD-Gd groups using ANOVA. Experienced and trainee readers blinded to experimental conditions assessed for the presence of tumor in each of the 4 breast regions. Receiver operator characteristic (ROC) curves and area-under-curve (AUC) values were constructed and analyzed.</p><p>Results</p><p>Tumors ≥1mm³ were iso-intense to muscle without contrast on T1w sequences. They enhanced diffusely and homogeneously by 57±20% (p<0.001) 24 hours after ACPPD-Gd and by 25±13% (p<0.001) immediately after gadobutrol. The nearly 2-fold difference was similar for small tumors (1-5mm³) (45±19% vs. 19±18%, p = 0.03). ACPPD-Gd tended to improve tumor detection by an experienced reader (AUC 0.98 vs 0.91) and significantly more for a trainee (0.93 vs. 0.82, p = 0.02) compared to gadobutrol. This improvement was more pronounced when obvious tumors (>5mm³) were removed from the ROC analysis for both the experienced observer (0.96 vs. 0.86) and more so for the trainee (0.86 vs. 0.69, p = 0.04).</p><p>Conclusion</p><p>ACPPD-Gd enhances MMP-expressing tumors of any size at 3T 24 hours after administration, improving their detection by blinded observers when compared to non-contrast and contrast groups given commercial Gd-chelates and imaged during the equilibrium phase.</p></div

Effect of cumulative ACPPD-Gd injections on Liver Enhancement.

<p>Mean liver enhancement ± SD as measured on T1w coronal scans normalized to muscle just prior to tumor inoculation and before any ACPPD-Gd administration (day 0) and 24 hours following ACPPD-Gd on days 4, 9, and 14. Note that liver enhancement of approximately 25% greater than baseline liver signal remained similar after each injection.</p

Photoswitching Mechanism of Cyanine Dyes

Photoswitching Mechanism of Cyanine Dye

ROC curves.

<p>The ROC curves are plotted for the experienced (top row) and trainee (bottom row) for all 288 breasts (left column) that were normal (n = 181) or tumor bearing (107) and the breasts with small tumors (<5mm³) (n = 58) and the associated normal breasts within the same animals (right column). Note that the AUC improved for both observers after ACPPD-Gd but the improvement was more significant for the trainee.</p

An Optimized Triple Modality Reporter for Quantitative <i>In Vivo</i> Tumor Imaging and Therapy Evaluation

<div><p>We present an optimized triple modality reporter construct combining a far-red fluorescent protein (E2-Crimson), enhanced firefly luciferase enzyme (Luc2), and truncated wild type herpes simplex virus I thymidine kinase (wttk) that allows for sensitive, long-term tracking of tumor growth <i>in vivo</i> by fluorescence, bioluminescence, and positron emission tomography. Two human cancer cell lines (MDA-MB-231 breast cancer and HT-1080 fibrosarcoma cancer) were successfully transduced to express this triple modality reporter. Fluorescence and bioluminescence imaging of the triple modality reporter were used to accurately quantify the therapeutic responses of MDA-MB-231 tumors to the chemotherapeutic agent monomethyl auristatin E <i>in vivo</i> in athymic nude mice. Positive correlation was observed between the fluorescence and bioluminescence signals, and these signals were also positively correlated with the <i>ex vivo</i> tumor weights. This is the first reported use of both fluorescence and bioluminescence signals from a multi-modality reporter construct to measure drug efficacy <i>in vivo</i>.</p></div