Publications by authors named "Christopher H Contag"

213 Publications

A protease-activated, near-infrared fluorescent probe for early endoscopic detection of premalignant gastrointestinal lesions.

Proc Natl Acad Sci U S A 2021 Jan;118(1)

Department of Radiology, Bio-X Program and Molecular Imaging Program, Stanford University School of Medicine, Stanford, CA 94305;

Fluorescence imaging is currently being actively developed for surgical guidance; however, it remains underutilized for diagnostic and endoscopic surveillance of incipient colorectal cancer in high-risk patients. Here we demonstrate the utility and potential for clinical translation of a fluorescently labeled cathepsin-activated chemical probe to highlight gastrointestinal lesions. This probe stays optically dark until it is activated by proteases produced by tumor-associated macrophages and accumulates within the lesions, enabling their detection using an endoscope outfitted with a fluorescence detector. We evaluated the probe in multiple murine models and a human-scale porcine model of gastrointestinal carcinogenesis. The probe provides fluorescence-guided surveillance of gastrointestinal lesions and augments histopathological analysis by highlighting areas of dysplasia as small as 400 µm, which were visibly discernible with significant tumor-to-background ratios, even in tissues with a background of severe inflammation and ulceration. Given these results, we anticipate that this probe will enable sensitive fluorescence-guided biopsies, even in the presence of highly inflamed colorectal tissue, which will improve early diagnosis to prevent gastrointestinal cancers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.2008072118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7817203PMC
January 2021

Ceria-based nanotheranostic agent for rheumatoid arthritis.

Theranostics 2020 25;10(26):11863-11880. Epub 2020 Oct 25.

Department of Biomedical Engineering and the Institute for Quantitative Health Science & Engineering.

Rheumatoid arthritis (RA) is an autoimmune disease that affects 1-2% of the human population worldwide, and effective therapies with targeted delivery for local immune suppression have not been described. We address this problem by developing a novel theranostic nanoparticle for RA and assessed its therapeutic and targeting effects under image-guidance. Albumin-cerium oxide nanoparticles were synthesized by the biomineralization process and further conjugated with near-infrared, indocyanine green (ICG) dye. Enzymatic-like properties and reactive oxygen species (ROS) scavenging activities, as well as the ability to reprogram macrophages, were determined on a monocyte cell line in culture. The therapeutic effect and systemic targeting potential were evaluated in collagen-induced arthritis (CIA) mouse model using optical/optoacoustic tomographic imaging. Small nanotheranostics with narrow size distribution and high colloidal stability were fabricated and displayed high ROS scavenging and enzymatic-like activity, as well as advanced efficacy in a converting pro-inflammatory macrophage phenotype into anti-inflammatory phenotype. When administrated into affected animals, these nanoparticles accumulated in inflamed joints and revealed a therapeutic effect similar to the gold-standard therapy for RA, methotrexate. The inflammation-targeting, inherent contrast and therapeutic activity of this new albumin-cerium oxide nanoparticle may make it a relevant agent for assessing severity in RA, and other inflammatory diseases, and controlling inflammation with image-guidance. The design of these nanotheranostics will enable potential clinical translation as systemic therapy for RA.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7150/thno.49069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7667692PMC
October 2020

Mind Over Magnets - How Magnetic Particle Imaging is Changing the Way We Think About the Future of Neuroscience.

Neuroscience 2020 Nov 13. Epub 2020 Nov 13.

Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, USA.

Magnetic particle imaging (MPI) is an emerging imaging technique, which has the potential to provide the sensitivity, specificity and temporal resolution necessary for novel imaging advances in neurological applications. MPI relies on the detection of superparamagnetic iron-oxide nanoparticles, which allows for visualization and quantification of iron or iron-labeled cells throughout a subject. The combination of these qualities can be used to image many neurological conditions including cancer, inflammatory processes, vascular-related issues and could even focus on cell therapies and theranostics to treat these problems. This review will provide a basic introduction to MPI, discuss the current use of this technology to image neurological conditions, and touch on future applications including the potential for clinical translation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroscience.2020.10.036DOI Listing
November 2020

Biodegradable fluorescent nanoparticles for endoscopic detection of colorectal carcinogenesis.

Adv Funct Mater 2019 Dec 10;29(51). Epub 2019 Oct 10.

Molecular Imaging Program at Stanford University (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA 94305, USA.

Early and comprehensive endoscopic detection of colonic dysplasia - the most clinically significant precursor lesion to colorectal adenocarcinoma - provides an opportunity for timely, minimally-invasive intervention to prevent malignant transformation. Here, the development and evaluation of biodegradable near-infrared fluorescent silica nanoparticles (FSN) is described that have the potential to improve adenoma detection during fluorescence-assisted white-light colonoscopic surveillance in rodent and human-scale models of colorectal carcinogenesis. FSNs are biodegradable (t of 2.7 weeks), well-tolerated, and enable detection and delineation of adenomas as small as 0.5 mm with high tumor-to-background ratios. Furthermore, in the human-scale, porcine model, the clinical feasibility and benefit of using FSN-guided detection of colorectal adenomas using video-rate fluorescence-assisted white-light endoscopy is demonstrated. Since nanoparticles of similar size (., 100-150-nm) or composition (., silica, silica/gold hybrid) have already been successfully translated to the clinic, and, clinical fluorescent/white light endoscopy systems are becoming more readily available, there is a viable path towards clinical translation of the proposed strategy for early colorectal cancer detection and prevention in high-risk patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adfm.201904992DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7546531PMC
December 2019

Molecular Imaging of Infective Endocarditis With 6''-[F]Fluoromaltotriose Positron Emission Tomography-Computed Tomography.

Circulation 2020 May 26;141(21):1729-1731. Epub 2020 May 26.

Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Bio-X Program (M.W., G.G., E.C., M.N., T.H., M.T.G., J.C.W., S.S.G.), Stanford University School of Medicine, CA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCULATIONAHA.119.043924DOI Listing
May 2020

Magnetic Particle Imaging of Macrophages Associated with Cancer: Filling the Voids Left by Iron-Based Magnetic Resonance Imaging.

Mol Imaging Biol 2020 08;22(4):958-968

Robarts Research Institute and Department of Medical Biophysics, Western University, London, Ontario, Canada.

Purpose: Magnetic particle imaging (MPI) is an emerging molecular imaging technique that directly detects iron nanoparticles distributed in living subjects. Compared with imaging iron with magnetic resonance imaging (MRI), MPI signal can be measured to determine iron content in specific regions. In this paper, the detection of iron-labeled macrophages associated with cancer by MRI and MPI was compared.

Procedures: Imaging was performed on 4T1 tumor-bearing mice 16-21 days post-cancer cell implantation, 24 h after intravenous injection of Ferucarbotran, a superparamagnetic iron oxide (SPIO) or Ferumoxytol, an ultra-small SPIO. Images of living mice were acquired on a 3T clinical MRI (General Electric, n = 6) or MPI (Magnetic Insight, n = 10) system. After imaging, tumors and lungs were removed, imaged by MPI and examined by histology.

Results: MRI signal voids were observed within all tumors. In vivo, MPI signals were observed in the tumors of 4 of 5 mice after the administration of each contrast agent and in all excised tumors. Signal voids visualized by MRI were more apparent in tumors of mice injected with Ferumoxytol than those that received Ferucarbotran; this was consistent with iron content measured by MPI. Signal voids relating to macrophage uptake of iron were not detected in lungs by MRI, since air also appears hypointense. In vivo, MPI could not differentiate between iron in the lungs vs the high signal from iron in the liver. However, once the lungs were excised, MPI signal was detectable and quantifiable. Histologic examination confirmed iron within macrophages present in the tumors.

Conclusions: MPI provides quantitative information on in vivo iron labeling of macrophages that is not attainable with MRI. The optimal iron nanoparticle for MPI in general is still under investigation; however, for MPI imaging of macrophages labeled in vivo by intravenous administration, Ferumoxytol nanoparticles were superior to Ferucarbotran.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-020-01473-0DOI Listing
August 2020

Software-Based Phase Control, Video-Rate Imaging, and Real-Time Mosaicing With a Lissajous-Scanned Confocal Microscope.

IEEE Trans Med Imaging 2020 04 27;39(4):1127-1137. Epub 2019 Sep 27.

We present software-based methods for automatic phase control and for mosaicing high-speed, Lissajous-scanned images. To achieve imaging speeds fast enough for mosaicing, we first increase the image update rate tenfold from 3 to 30 Hz, then vertically interpolate each sparse image in real-time to eliminate fixed pattern noise. We validate our methods by imaging fluorescent beads and automatically maintaining phase control over the course of one hour. We then image fixed mouse brain tissues at varying update rates and compare the resulting mosaics. Using reconstructed image data as feedback for phase control eliminates the need for phase sensors and feedback controllers, enabling long-term imaging experiments without additional hardware. Mosaicing subsampled images results in video-rate imaging speeds, nearly fully recovered spatial resolution, and millimeter-scale fields of view.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1109/TMI.2019.2942552DOI Listing
April 2020

Microvesicle-Mediated Delivery of Minicircle DNA Results in Effective Gene-Directed Enzyme Prodrug Cancer Therapy.

Mol Cancer Ther 2019 12 26;18(12):2331-2342. Epub 2019 Aug 26.

Department of Pediatrics, Stanford University, Stanford, California.

An emerging approach for cancer treatment employs the use of extracellular vesicles, specifically exosomes and microvesicles, as delivery vehicles. We previously demonstrated that microvesicles can functionally deliver plasmid DNA to cells and showed that plasmid size and sequence, in part, determine the delivery efficiency. In this study, delivery vehicles comprised of microvesicles loaded with engineered minicircle (MC) DNA that encodes prodrug converting enzymes developed as a cancer therapy in mammary carcinoma models. We demonstrated that MCs can be loaded into shed microvesicles with greater efficiency than their parental plasmid counterparts and that microvesicle-mediated MC delivery led to significantly higher and more prolonged transgene expression in recipient cells than microvesicles loaded with the parental plasmid. Microvesicles loaded with MCs encoding a thymidine kinase (TK)/nitroreductase (NTR) fusion protein produced prolonged TK-NTR expression in mammary carcinoma cells. delivery of TK-NTR and administration of prodrugs led to the effective killing of both targeted cells and surrounding tumor cells via TK-NTR-mediated conversion of codelivered prodrugs into active cytotoxic agents. evaluation of the bystander effect in mouse models demonstrated that for effective therapy, at least 1% of tumor cells need to be delivered with TK-NTR-encoding MCs. These results suggest that MC delivery via microvesicles can mediate gene transfer to an extent that enables effective prodrug conversion and tumor cell death such that it comprises a promising approach to cancer therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1158/1535-7163.MCT-19-0299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6891168PMC
December 2019

Tunable structured illumination light sheet microscopy for background rejection and imaging depth in minimally processed tissues.

J Biomed Opt 2019 04;24(4):1-6

Stanford University, Edward L. Ginzton Laboratory, Stanford, California, United States.

We demonstrate improved optical sectioning in light sheet fluorescence microscopy using tunable structured illumination (SI) frequencies to optimize image quality in scattering specimens. The SI patterns are generated coherently using a one-dimensional spatial light modulator for maximum pattern contrast, and the pattern spatial frequency is adjustable up to half the incoherent cutoff frequency of our detection objective. At this frequency, we demonstrate background reductions of 2 orders of magnitude.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1117/1.JBO.24.4.046501DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454294PMC
April 2019

Detection of Premalignant Gastrointestinal Lesions Using Surface-Enhanced Resonance Raman Scattering-Nanoparticle Endoscopy.

ACS Nano 2019 02 4;13(2):1354-1364. Epub 2019 Feb 4.

Department of Radiology , Memorial Sloan Kettering Cancer Center , New York , New York 10065 , United States.

Cancers of the gastrointestinal (GI) tract are among the most frequent and most lethal cancers worldwide. An important reason for this high mortality is that early disease is typically asymptomatic, and patients often present with advanced, incurable disease. Even in high-risk patients who routinely undergo endoscopic screening, lesions can be missed due to their small size or subtle appearance. Thus, current imaging approaches lack the sensitivity and specificity to accurately detect incipient GI tract cancers. Here we report our finding that a single dose of a high-sensitivity surface-enhanced resonance Raman scattering nanoparticle (SERRS-NP) enables reliable detection of precancerous GI lesions in animal models that closely mimic disease development in humans. Some of these animal models have not been used previously to evaluate imaging probes for early cancer detection. The studies were performed using a commercial Raman imaging system, a newly developed mouse Raman endoscope, and finally a clinically applicable Raman endoscope for larger animal studies. We show that this SERRS-NP-based approach enables robust detection of small, premalignant lesions in animal models that faithfully recapitulate human esophageal, gastric, and colorectal tumorigenesis. This method holds promise for much earlier detection of GI cancers than currently possible and could lead therefore to marked reduction of morbidity and mortality of these tumor types.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.8b06808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428194PMC
February 2019

A Dual-Modality Hybrid Imaging System Harnesses Radioluminescence and Sound to Reveal Molecular Pathology of Atherosclerotic Plaques.

Sci Rep 2018 06 12;8(1):8992. Epub 2018 Jun 12.

Division of Medical Physics, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, USA.

Atherosclerosis is a progressive inflammatory condition caused by an unstable lesion, called thin-cap fibro atheromata (TCFA) that underlies coronary artery disease (CAD)-one of the leading causes of death worldwide. Therefore, early clinical diagnosis and effective risk stratification is important for CAD management as well as preventing progression to catastrophic events. However, early detection could be difficult due to their small size, motion, obscuring F-FDG uptake by adjacent myocardium, and complex morphological/biological features. To overcome these limitations, we developed a catheter-based Circumferential-Intravascular-Radioluminescence-Photoacoustic-Imaging (CIRPI) system that can detect vulnerable plaques in coronary arteries and characterizes them with respect to pathology and biology. Our CIRPI system combined two imaging modalities: Circumferential Radioluminescence Imaging (CRI) and PhotoAcoustic Tomography (PAT) within a novel optical probe. The probe's CaF:Eu based scintillating imaging window provides a 360° view of human (n = 7) and murine carotid (n = 10) arterial plaques by converting β-particles into visible photons during F-FDG decay. A 60× and 63× higher radioluminescent signals were detected from the human and murine plaque inflammations, respectively, compared to the control. The system's photoacoustic imaging provided a comprehensive analysis of the plaque compositions and its morphologic information. These results were further verified with IVIS-200, immunohistochemical analysis, and autoradiography.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-26696-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5997702PMC
June 2018

Functional DNA Delivery Enabled by Lipid-Modified Charge-Altering Releasable Transporters (CARTs).

Biomacromolecules 2018 07 11;19(7):2812-2824. Epub 2018 May 11.

Safe and effective DNA delivery systems are required to enable or enhance clinical strategies and research involving gene therapy and DNA vaccinations. To address this delivery problem, a series of charge-altering releasable transporters (CARTs) with varied lipid content were prepared and evaluated for plasmid DNA (pDNA) delivery into cultured cells. These lipid-modified CART co-oligomers were synthesized in only two steps via sequential organocatalytic ring-opening polymerization of lipid-containing cyclic carbonate monomers and morpholinone monomers. Lipid variations of the CARTs substantially impacted the delivery efficiency of pDNA, with oleyl- and linoleyl-based CARTs showing enhanced performance relative to the commercial transfection agent Lipofectamine 2000 (L2000). The best-performing oleyl CART was carried forward to study stable luciferase transfection with a Sleeping Beauty ( SB) transposon system. The oleyl CART outperformed the L2000 positive control with respect to stable transfection efficiency. CART-pDNA complexes represent a new DNA delivery system for research and clinical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.biomac.8b00401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6542359PMC
July 2018

Magnetic particle imaging of islet transplantation in the liver and under the kidney capsule in mouse models.

Quant Imaging Med Surg 2018 Mar;8(2):114-122

Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.

Background: Islet transplantation (Tx) represents the most promising therapy to restore normoglycemia in type 1 diabetes (T1D) patients to date. As significant islet loss has been observed after the procedure, there is an urgent need for developing strategies for monitoring transplanted islet grafts. In this report we describe for the first time the application of magnetic particle imaging (MPI) for monitoring transplanted islets in the liver and under the kidney capsule in experimental animals.

Methods: Pancreatic islets isolated from Papio hamadryas were labeled with superparamagnetic iron oxides (SPIOs) and used for either islet phantoms or Tx in the liver or under the kidney capsule of NOD scid mice. MPI was used to image and quantify islet phantoms and islet transplanted experimental animals post-mortem at 1 and 14 days after Tx. Magnetic resonance imaging (MRI) was used to confirm the presence of labeled islets in the liver and under the kidney capsule 1 day after Tx.

Results: MPI of labeled islet phantoms confirmed linear correlation between the number of islets and the MPI signal (R=0.988). Post-mortem MPI performed on day 1 after Tx showed high signal contrast in the liver and under the kidney capsule. Quantitation of the signal supports islet loss over time, which is normally observed 2 weeks after Tx. No MPI signal was observed in control animals. MRI confirmed the presence of labeled islets/islet clusters in liver parenchyma and under the kidney capsule one day after Tx.

Conclusions: Here we demonstrate that MPI can be used for quantitative detection of labeled pancreatic islets in the liver and under the kidney capsule of experimental animals. We believe that MPI, a modality with no depth attenuation and zero background tissue signal could be a suitable method for imaging transplanted islet grafts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.21037/qims.2018.02.06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5891680PMC
March 2018

Automated Cell Segmentation for Quantitative Phase Microscopy.

IEEE Trans Med Imaging 2018 04;37(4):929-940

Automated cell segmentation and tracking is essential for dynamic studies of cellular morphology, movement, and interactions as well as other cellular behaviors. However, accurate, automated, and easy-to-use cell segmentation remains a challenge, especially in cases of high cell densities, where discrete boundaries are not easily discernable. Here, we present a fully automated segmentation algorithm that iteratively segments cells based on the observed distribution of optical cell volumes measured by quantitative phase microscopy. By fitting these distributions to known probability density functions, we are able to converge on volumetric thresholds that enable valid segmentation cuts. Since each threshold is determined from the observed data itself, virtually no input is needed from the user. We demonstrate the effectiveness of this approach over time using six cell types that display a range of morphologies, and evaluate these cultures over a range of confluencies. Facile dynamic measures of cell mobility and function revealed unique cellular behaviors that relate to tissue origins, state of differentiation, and real-time signaling. These will improve our understanding of multicellular communication and organization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1109/TMI.2017.2775604DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5907807PMC
April 2018

Intracellular biomass flocculation as a key mechanism of rapid bacterial killing by cationic, amphipathic antimicrobial peptides and peptoids.

Sci Rep 2017 12 1;7(1):16718. Epub 2017 Dec 1.

Department of Bioengineering, Stanford University, Stanford, California, United States.

Many organisms rely on antimicrobial peptides (AMPs) as a first line of defense against pathogens. In general, most AMPs are thought to kill bacteria by binding to and disrupting cell membranes. However, certain AMPs instead appear to inhibit biomacromolecule synthesis, while causing less membrane damage. Despite an unclear understanding of mechanism(s), there is considerable interest in mimicking AMPs with stable, synthetic molecules. Antimicrobial N-substituted glycine (peptoid) oligomers ("ampetoids") are structural, functional and mechanistic analogs of helical, cationic AMPs, which offer broad-spectrum antibacterial activity and better therapeutic potential than peptides. Here, we show through quantitative studies of membrane permeabilization, electron microscopy, and soft X-ray tomography that both AMPs and ampetoids trigger extensive and rapid non-specific aggregation of intracellular biomacromolecules that correlates with microbial death. We present data demonstrating that ampetoids are "fast killers", which rapidly aggregate bacterial ribosomes in vitro and in vivo. We suggest intracellular biomass flocculation is a key mechanism of killing for cationic, amphipathic AMPs, which may explain why most AMPs require micromolar concentrations for activity, show significant selectivity for killing bacteria over mammalian cells, and finally, why development of resistance to AMPs is less prevalent than developed resistance to conventional antibiotics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-017-16180-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711933PMC
December 2017

Local estrogen axis in the human bone microenvironment regulates estrogen receptor-positive breast cancer cells.

Breast Cancer Res 2017 Nov 15;19(1):121. Epub 2017 Nov 15.

Department of Pediatrics, Stanford University School of Medicine, 150E Clark Center, 318 Campus Drive, Stanford, CA, 94305-5427, USA.

Background: Approximately 70% of all breast cancers express the estrogen receptor, and are regulated by estrogen. While the ovaries are the primary source of estrogen in premenopausal women, most breast cancer is diagnosed following menopause, when systemic levels of this hormone decline. Estrogen production from androgen precursors is catalyzed by the aromatase enzyme. Although aromatase expression and local estrogen production in breast adipose tissue have been implicated in the development of primary breast cancer, the source of estrogen involved in the regulation of estrogen receptor-positive (ER+) metastatic breast cancer progression is less clear.

Methods: Bone is the most common distant site of breast cancer metastasis, particularly for ER+ breast cancers. We employed a co-culture model using trabecular  bone tissues obtained from total hip replacement (THR) surgery specimens to study ER+ and estrogen receptor-negative (ER-) breast cancer cells within the human bone microenvironment. Luciferase-expressing ER+ (MCF-7, T-47D, ZR-75) and ER- (SK-BR-3, MDA-MB-231, MCF-10A) breast cancer cells were cultured directly on bone tissue fragments or in bone tissue-conditioned media, and monitored over time with bioluminescence imaging (BLI). Bone tissue-conditioned media were generated in the presence vs. absence of aromatase inhibitors, and testosterone. Bone tissue fragments were analyzed for aromatase expression by immunohistochemistry.

Results: ER+ breast cancer cells were preferentially sustained in co-cultures with bone tissues and bone tissue-conditioned media relative to ER- cells. Bone fragments analyzed by immunohistochemistry revealed expression of the aromatase enzyme. Bone tissue-conditioned media generated in the presence of testosterone had increased estrogen levels and heightened capacity to stimulate ER+ breast cancer cell proliferation. Pretreatment of cultured bone tissues with aromatase inhibitors, which inhibited estrogen production, reduced the capacity of conditioned media to stimulate ER+ cell proliferation.

Conclusions: These results suggest that a local estrogen signaling axis regulates ER+ breast cancer cell viability and proliferation within the bone metastatic niche, and that aromatase inhibitors modulate this axis. Although endocrine therapies are highly effective in the treatment of ER+ breast cancer, resistance to these treatments reduces their efficacy. Characterization of estrogen signaling networks within the bone microenvironment will identify new strategies for combating metastatic progression and endocrine resistance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13058-017-0910-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5688761PMC
November 2017

The tyrosine kinase inhibitor imatinib mesylate suppresses uric acid crystal-induced acute gouty arthritis in mice.

PLoS One 2017 5;12(10):e0185704. Epub 2017 Oct 5.

Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.

Gouty arthritis is caused by the deposition of monosodium urate (MSU) crystals in joints. Despite many treatment options for gout, there is a substantial need for alternative treatments for patients unresponsive to current therapies. Tyrosine kinase inhibitors have demonstrated therapeutic benefit in experimental models of antibody-dependent arthritis and in rheumatoid arthritis in humans, but to date, the potential effects of such inhibitors on gouty arthritis has not been evaluated. Here we demonstrate that treatment with the tyrosine kinase inhibitor imatinib mesylate (imatinib) can suppress inflammation induced by injection of MSU crystals into subcutaneous air pouches or into the ankle joint of wild type mice. Moreover, imatinib treatment also largely abolished the lower levels of inflammation which developed in IL-1R1-/- or KitW-sh/W-sh mice, indicating that this drug can inhibit IL-1-independent pathways, as well as mast cell-independent pathways, contributing to pathology in this model. Imatinib treatment not only prevented ankle swelling and synovial inflammation when administered before MSU crystals but also diminished these features when administrated after the injection of MSU crystals, a therapeutic protocol more closely mimicking the clinical situation in which treatment occurs after the development of an acute gout flare. Finally, we also assessed the efficiency of local intra-articular injections of imatinib-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles in this model of acute gout. Treatment with low doses of this long-acting imatinib:PLGA formulation was able to reduce ankle swelling in a therapeutic protocol. Altogether, these results raise the possibility that tyrosine kinase inhibitors might have utility in the treatment of acute gout in humans.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185704PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628843PMC
October 2017

Cell Labeling with Magneto-Endosymbionts and the Dissection of the Subcellular Location, Fate, and Host Cell Interactions.

Mol Imaging Biol 2018 02;20(1):55-64

Bell Biosystems, San Francisco, CA, USA.

Purpose: The purposes of this study are to characterize magneto-endosymbiont (ME) labeling of mammalian cells and to discern the subcellular fate of these living contrast agents. MEs are novel magnetic resonance imaging (MRI) contrast agents that are being used for cell tracking studies. Understanding the fate of MEs in host cells is valuable for designing in vivo cell tracking experiments.

Procedures: The ME's surface epitopes, contrast-producing paramagnetic magnetosomal iron, and genome were studied using immunocytochemistry (ICC), Fe and MRI contrast measurements, and quantitative polymerase chain reaction (qPCR), respectively. These assays, coupled with other common assays, enabled validation of ME cell labeling and dissection of ME subcellular processing.

Results: The assays mentioned above provide qualitative and quantitative assessments of cell labeling, the subcellular localization and the fate of MEs. ICC results, with an ME-specific antibody, qualitatively shows homogenous labeling with MEs. The ferrozine assay shows that MEs have an average of 7 fg Fe/ME, ∼30 % of which contributes to MRI contrast and ME-labeled MDA-MB-231 (MDA-231) cells generally have 2.4 pg Fe/cell, implying ∼350 MEs/cell. Adjusting the concentration of Fe in the ME growth media reduces the concentration of non-MRI contrast-producing Fe. Results from the qPCR assay, which quantifies ME genomes in labeled cells, shows that processing of MEs begins within 24 h in MDA-231 cells. ICC results suggest this intracellular digestion of MEs occurs by the lysosomal degradation pathway. MEs coated with listeriolysin O (LLO) are able to escape the primary phagosome, but subsequently co-localize with LC3, an autophagy-associated molecule, and are processed for digestion. In embryos, where autophagy is transiently suppressed, MEs show an increased capacity for survival and even replication. Finally, transmission electron microscopy (TEM) of ME-labeled MDA-231 cells confirms that the magnetosomes (the MRI contrast-producing particles) remain intact and enable in vivo cell tracking.

Conclusions: MEs are used to label mammalian cells for the purpose of cell tracking in vivo, with MRI. Various assays described herein (ICC, ferrozine, and qPCR) allow qualitative and quantitative assessments of labeling efficiency and provide a detailed understanding of subcellular processing of MEs. In some cell types, MEs are digested, but the MRI-producing particles remain. Coating with LLO allows MEs to escape the primary phagosome, enhances retention slightly, and confirms that MEs are ultimately processed by autophagy. Numerous intracellular bacteria and all endosymbiotically derived organelles have evolved molecular mechanisms to avoid intracellular clearance, and identification of the specific processes involved in ME clearance provides a framework on which to develop MEs with enhanced retention in mammalian cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-017-1094-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5736464PMC
February 2018

Characterization of Magneto-Endosymbionts as MRI Cell Labeling and Tracking Agents.

Mol Imaging Biol 2018 02;20(1):65-73

Radiology Department and Molecular Imaging Program (MIPS), Stanford University, Stanford, CA, USA.

Purpose: Magneto-endosymbionts (MEs) show promise as living magnetic resonance imaging (MRI) contrast agents for in vivo cell tracking. Here we characterize the biomedical imaging properties of ME contrast agents, in vitro and in vivo.

Procedures: By adapting and engineering magnetotactic bacteria to the intracellular niche, we are creating magneto-endosymbionts (MEs) that offer advantages relative to passive iron-based contrast agents (superparamagnetic iron oxides, SPIOs) for cell tracking. This work presents a biomedical imaging characterization of MEs including: MRI transverse relaxivity (r ) for MEs and ME-labeled cells (compared to a commercially available iron oxide nanoparticle); microscopic validation of labeling efficiency and subcellular locations; and in vivo imaging of a MDA-MB-231BR (231BR) human breast cancer cells in a mouse brain.

Results: At 7T, r relaxivity of bare MEs was higher (250 s mM) than that of conventional SPIO (178 s mM). Optimized in vitro loading of MEs into 231BR cells yielded 1-4 pg iron/cell (compared to 5-10 pg iron/cell for conventional SPIO). r relaxivity dropped by a factor of ~3 upon loading into cells, and was on the same order of magnitude for ME-loaded cells compared to SPIO-loaded cells. In vivo, ME-labeled cells exhibited strong MR contrast, allowing as few as 100 cells to be detected in mice using an optimized 3D SPGR gradient-echo sequence.

Conclusions: Our results demonstrate the potential of magneto-endosymbionts as living MR contrast agents. They have r relaxivity values comparable to traditional iron oxide nanoparticle contrast agents, and provide strong MR contrast when loaded into cells and implanted in tissue.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-017-1093-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5730509PMC
February 2018

Specific Imaging of Bacterial Infection Using 6″-F-Fluoromaltotriose: A Second-Generation PET Tracer Targeting the Maltodextrin Transporter in Bacteria.

J Nucl Med 2017 10 10;58(10):1679-1684. Epub 2017 May 10.

Department of Radiology, Stanford University School of Medicine, Stanford, California

6″-F-fluoromaltotriose is a PET tracer that can potentially be used to image and localize most bacterial infections, much like F-FDG has been used to image and localize most cancers. However, unlike F-FDG, 6″-F-fluoromaltotriose is not taken up by inflammatory lesions and appears to be specific to bacterial infections by targeting the maltodextrin transporter that is expressed in gram-positive and gram-negative strains of bacteria. 6″-F-fluoromaltotriose was synthesized with high radiochemical purity and evaluated in several clinically relevant bacterial strains in cultures and in living mice. 6″-F-fluoromaltotriose was taken up in both gram-positive and gram-negative bacterial strains. 6″-F-fluoromaltotriose was also able to detect in a clinically relevant mouse model of wound infection. The utility of 6″-F-fluoromaltotriose to help monitor antibiotic therapies was also evaluated in rats. 6″-F-fluoromaltotriose is a promising new tracer that has significant diagnostic utility, with the potential to change the clinical management of patients with infectious diseases of bacterial origin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2967/jnumed.117.191452DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632736PMC
October 2017

Regulatory Aspects of Optical Methods and Exogenous Targets for Cancer Detection.

Cancer Res 2017 05 20;77(9):2197-2206. Epub 2017 Apr 20.

Department of Otolaryngology, Stanford University, Stanford, California.

Considerable advances in cancer-specific optical imaging have improved the precision of tumor resection. In comparison to traditional imaging modalities, this technology is unique in its ability to provide real-time feedback to the operating surgeon. Given the significant clinical implications of optical imaging, there is an urgent need to standardize surgical navigation tools and contrast agents to facilitate swift regulatory approval. Because fluorescence-enhanced surgery requires a combination of both device and drug, each may be developed in conjunction, or separately, which are important considerations in the approval process. This report is the result of a one-day meeting held on May 4, 2016 with officials from the National Cancer Institute, the FDA, members of the American Society of Image-Guided Surgery, and members of the World Molecular Imaging Society, which discussed consensus methods for FDA-directed human testing and approval of investigational optical imaging devices as well as contrast agents for surgical applications. The goal of this workshop was to discuss FDA approval requirements and the expectations for approval of these novel drugs and devices, packaged separately or in combination, within the context of optical surgical navigation. In addition, the workshop acted to provide clarity to the research community on data collection and trial design. Reported here are the specific discussion items and recommendations from this critical and timely meeting. .
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1158/0008-5472.CAN-16-3217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5567809PMC
May 2017

Neutrophil myeloperoxidase diminishes the toxic effects and mortality induced by lipopolysaccharide.

J Exp Med 2017 05 6;214(5):1249-1258. Epub 2017 Apr 6.

Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305

Neutrophils have crucial antimicrobial functions but are also thought to contribute to tissue injury upon exposure to bacterial products, such as lipopolysaccharide (LPS). To study the role of neutrophils in LPS-induced endotoxemia, we developed a new mouse model, mice, in which injection of diphtheria toxin induces selective neutrophil ablation. Using this model, we found, surprisingly, that neutrophils serve to protect the host from LPS-induced lethal inflammation. This protective role was observed in conventional and germ-free animal facilities, indicating that it does not depend on a particular microbiological environment. Blockade or genetic deletion of myeloperoxidase (MPO), a key neutrophil enzyme, significantly increased mortality after LPS challenge, and adoptive transfer experiments confirmed that neutrophil-derived MPO contributes importantly to protection from endotoxemia. Our findings imply that, in addition to their well-established antimicrobial properties, neutrophils can contribute to optimal host protection by limiting the extent of endotoxin-induced inflammation in an MPO-dependent manner.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1084/jem.20161238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413333PMC
May 2017

Imaging of Tumor-Associated Macrophages in a Transgenic Mouse Model of Orthotopic Ovarian Cancer.

Mol Imaging Biol 2017 10;19(5):694-702

Departments of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, 94305, USA.

Purpose: Tumor-associated macrophages (TAMs) are often associated with a poor prognosis in cancer. To gain a better understanding of cellular recruitment and dynamics of TAM biology during cancer progression, we established a novel transgenic mouse model for in vivo imaging of luciferase-expressing macrophages.

Procedures: B6.129P2-Lyz2/J mice, which express Cre recombinase under the control of the lysozyme M promoter (LysM) were crossed to Cre-lox Luc reporter mice (RLG), to produce LysM-LG mice whose macrophages express luciferase. Cell-type-specific luciferase expression in these mice was verified by flow cytometry, and via in vivo bioluminescence imaging under conditions where macrophages were either stimulated with lipopolysaccharide or depleted with clodronate liposomes. The distribution of activated macrophages was longitudinally imaged in two immunocompetent LysM-LG mouse models with either B16 melanoma or ID8 ovarian cancer cells.

Results: In vivo imaging of LysM-LG mice showed luciferase activity was generated by macrophages. Clodronate liposome-mediated depletion of macrophages lowered overall bioluminescence while lipopolysaccharide injection increased macrophage bioluminescence in both the B16 and ID8 models. Tracking macrophages weekly in tumor-bearing animals after intraperitoneal (i.p.) or intraovarian (i.o.) injection resulted in distinct, dynamic patterns of macrophage activity. Animals with metastatic ovarian cancer after i.p. injection exhibited significantly higher peritoneal macrophage activity compared to animals after i.o. injection.

Conclusion: The LysM-LG model allows tracking of macrophage recruitment and activation during disease initiation and progression in a noninvasive manner. This model provides a tool to visualize and monitor the benefit of pharmacological interventions targeting macrophages in preclinical models.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-017-1061-2DOI Listing
October 2017

Targeted Nanomeetings within a Larger Delivery Congress.

Mol Imaging Biol 2017 06;19(3):323-324

Institute of Quantitative Health Science and Engineering, Department of Biomedical Engineering, and Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-017-1067-9DOI Listing
June 2017

Charge-altering releasable transporters (CARTs) for the delivery and release of mRNA in living animals.

Proc Natl Acad Sci U S A 2017 01 9;114(4):E448-E456. Epub 2017 Jan 9.

Department of Chemistry, Stanford University, Stanford, CA 94305;

Functional delivery of mRNA to tissues in the body is key to implementing fundamentally new and potentially transformative strategies for vaccination, protein replacement therapy, and genome editing, collectively affecting approaches for the prevention, detection, and treatment of disease. Broadly applicable tools for the efficient delivery of mRNA into cultured cells would advance many areas of research, and effective and safe in vivo mRNA delivery could fundamentally transform clinical practice. Here we report the step-economical synthesis and evaluation of a tunable and effective class of synthetic biodegradable materials: charge-altering releasable transporters (CARTs) for mRNA delivery into cells. CARTs are structurally unique and operate through an unprecedented mechanism, serving initially as oligo(α-amino ester) cations that complex, protect, and deliver mRNA and then change physical properties through a degradative, charge-neutralizing intramolecular rearrangement, leading to intracellular release of functional mRNA and highly efficient protein translation. With demonstrated utility in both cultured cells and animals, this mRNA delivery technology should be broadly applicable to numerous research and therapeutic applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1614193114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5278438PMC
January 2017

A Clinical Wide-Field Fluorescence Endoscopic Device for Molecular Imaging Demonstrating Cathepsin Protease Activity in Colon Cancer.

Mol Imaging Biol 2016 12;18(6):820-829

Department of Radiology, Stanford University, James H. Clark Center for Biomedical Engineering & Sciences, Stanford, CA, 94305, USA.

Purpose: Early and effective detection of cancers of the gastrointestinal tract will require novel molecular probes and advances in instrumentation that can reveal functional changes in dysplastic and malignant tissues. Here, we describe adaptation of a wide-field clinical fiberscope to perform wide-field fluorescence imaging while preserving its white-light capability for the purpose of providing wide-field fluorescence imaging capability to point-of-care microscopes.

Procedures: We developed and used a fluorescent fiberscope to detect signals from a quenched probe, BMV109, that becomes fluorescent when cleaved by, and covalently bound to, active cathepsin proteases. Cathepsins are expressed in inflammation- and tumor-associated macrophages as well as directly from tumor cells and are a promising target for cancer imaging. The fiberscope has a 1-mm outer diameter enabling validation via endoscopic exams in mice, and therefore we evaluated topically applied BMV109 for the ability to detect colon polyps in an azoxymethane-induced colon tumor model in mice.

Results: This wide-field endoscopic imaging device revealed consistent and clear fluorescence signals from BMV109 that specifically localized to the polypoid regions as opposed to the normal adjacent colon tissue (p < 0.004) in the murine colon carcinoma model.

Conclusions: The sensitivity of detection of BMV109 with the fluorescence fiberscope suggested utility of these tools for early detection at hard-to-reach sites. The fiberscope was designed to be used in conjunction with miniature, endoscope-compatible fluorescence microscopes for dual wide-field and microscopic cancer detection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-016-0956-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5564400PMC
December 2016

World Molecular Imaging Congress 2016: Imaging Biology-Improving Therapy.

Mol Imaging Biol 2016 06;18(3):313-4

Department of Pediatrics, Stanford University, Stanford, CA, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-016-0958-5DOI Listing
June 2016

A role of the adaptive immune system in glucose homeostasis.

BMJ Open Diabetes Res Care 2016 15;4(1):e000136. Epub 2016 Feb 15.

Departments of Pediatrics, Radiology, Microbiology & Immunology , Stanford University , Stanford, California , USA.

Objective: The immune system, including the adaptive immune response, has recently been recognized as having a significant role in diet-induced insulin resistance. In this study, we aimed to determine if the adaptive immune system also functions in maintaining physiological glucose homeostasis in the absence of diet-induced disease.

Research Design And Methods: SCID mice and immunocompetent control animals were phenotypically assessed for variations in metabolic parameters and cytokine profiles. Additionally, the glucose tolerance of SCID and immunocompetent control animals was assessed following introduction of a high-fat diet.

Results: SCID mice on a normal chow diet were significantly insulin resistant relative to control animals despite having less fat mass. This was associated with a significant increase in the innate immunity-stimulating cytokines granulocyte colony-stimulating factor, monocyte chemoattractant protein 1 (MCP1), and MCP3. Additionally, the SCID mouse phenotype was exacerbated in response to a high-fat diet as evidenced by the further significant progression of glucose intolerance.

Conclusions: These results support the notion that the adaptive immune system plays a fundamental biological role in glucose homeostasis, and that the absence of functional B and T cells results in disruption in the concentrations of various cytokines associated with macrophage proliferation and recruitment. Additionally, the absence of functional B and T cells is not protective against diet-induced pathology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/bmjdrc-2015-000136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4800071PMC
March 2016

Signaling by Extracellular Vesicles Advances Cancer Hallmarks.

Trends Cancer 2016 02 22;2(2):84-94. Epub 2016 Jan 22.

Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Radiology, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

Mammalian cells secrete various extracellular vesicles (EVs; exosomes, microvesicles, and apoptotic bodies) that differ in biogenesis, composition, and function. Each vesicle type can originate from normal or cancerous cells, transfer molecular cargo to both neighboring and distant cells, and modulate cellular behaviors involved in eubiology and pathology, such as tumor development. Here, we review evidence for the role of EVs in the establishment and maintenance of cancer hallmarks, including sustaining proliferative signaling, evading growth suppression, resisting cell death, reprogramming energy metabolism, acquiring genomic instability, and remodeling the tumor microenvironment. We also discuss how EVs are implicated in the induction of angiogenesis, control of cellular invasion, initiation of premetastatic niches, maintenance of inflammation, and evasion of immune surveillance. The deeper understanding of the biology of EVs and their contribution to the development and progression of tumors is leading to new opportunities in the diagnosis and treatment of cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.trecan.2015.12.005DOI Listing
February 2016