Pancreatic cancer is a highly lethal disease that is difficult to diagnose and treat. The advances of proteomics technology, especially quantitative proteomics, have stimulated a great interest to apply this technology for pancreatic cancer study. A variety of tissue proteomics approaches have been applied to investigate pancreatic cancer and the associated diseases. These studies were carried out with various goals, aiming to better understand the molecular mechanisms underlying pancreatic tumorigenesis, to improve therapeutic treatment and to identify cancer associated protein signatures, signaling events as well as interactions between cancer cells and tumor microenvironment. Here, we provide an overview on the tissue proteomics studies of pancreatic cancer reported in the past few years in light of discovery and technology development.
Proteomics; pancreatic cancer; mass spectrometry; biomarker; chronic pancreatitis; tissues; pancreas; formalin-fixed paraffin embedded (FFPE) tissue
Id3 promotes B cells homing to the aorta and atheroprotection in Apoe−/− mice. We sought to determine the impact of loss of Id3 in the Ldlr−/− mouse model of diet-induced atherosclerosis and identify novel Id3 targets in the vessel wall.
Methods and Results
Ex vivo optical imaging confirmed that Id3−/− Ldlr−/− mice have significantly fewer aortic B cells than Id3+/+ Ldlr−/− mice. Following 8 and 16 weeks of Western diet, Id3−/− Ldlr−/− mice developed significantly more atherosclerosis than Id3+/+ Ldlr−/− mice, with Id3+/−
Ldlr−/− mice demonstrating an intermediate phenotype. There were no differences in serum lipid levels between genotypes. Immunostaining demonstrated that aortas from Id3−/− Ldlr−/− mice had greater intimal macrophage density and CCL20 and VCAM-1 expression compared with Id3+/+ Ldlr−/− mice. Real time PCR demonstrated increased VCAM-1 mRNA levels in the aortas of Id3−/−
Ldlr−/− mice. Primary VSMCs from Id3−/− mice expressed greater amounts of VCAM-1 protein compared with control. Gain and loss of function studies in primary VSMCs identified a role for Id3 in repressing VCAM-1 promoter activation. ChIP demonstrated interaction of E12 with the VCAM-1 promoter which is inhibited by Id3.
Id3 is an atheroprotective transcription regulator with targets in both B cells and vessel wall cells leading to reduced macrophages accumulation and reduced atherosclerosis formation.
Pancreatic intraductal papillary mucinous neoplasms (IPMN) are now identified with increasing frequency. The detection of carcinoma in IPMN is difficult and suffers from high false-positive and false-negative rates, often resulting in inappropriate treatment decisions. Improved detection of malignancy using novel biomarkers may therefore improve diagnostic accuracy. One such promising novel biomarker is Plectin-1 (Plec-1).
Using immunohistochemistry, Plec-1 expression was assayed in benign (low and moderate dysplasia, n=6) as well as malignant IPMN (high-grade dysplasia and invasive carcinoma, n=31) and lymph node metastases from carcinoma arising in IPMN (n=12). Furthermore, cyst fluids from benign (n=3) and malignant IPMN (n=4) were evaluated for Plec-1 expression.
Results and discussion
Twenty-six of 31 malignant IPMN and all 12 lymph node metastases were Plec-1 positive. In contrast, only one of six benign IPMN expressed Plec-1. The specificity of Plec-1 in distinguishing malignant IPMN from benign IPMN was 83% and its sensitivity 84%. Furthermore, all (four out of four) cyst fluids from malignant IPMN, but none of the three benign IPMN, were Plec-1 positive. These data support Plec-1 as an excellent biomarker for the early detection of carcinoma arising in IPMN.
Plectin-1; Biomarker; Malignant IPMN; Benign IPMN
To examine perceptions of cervical cancer risk in elevated-risk Appalachians.
Appalachian women (n=571) completed interviews examining self-regulation model factors relevant to perceived risk of cervical cancer.
Women with good/very good knowledge of cervical cancer, greater worry, and history of sexually transmitted infection had higher odds of rating their perceived risk as somewhat/much higher than did other women. Former smokers, compared to never smokers, had lower risk perceptions.
Self-regulation model factors are important to understanding perceptions of cervical cancer risk in underserved women. The relationship of smoking and worry to perceived risk may be a target for intervention.
cervical cancer; risk factors; risk perception
B cells are abundant in the adventitia of normal and diseased vessels. Yet, the molecular and cellular mechanisms mediating homing of B cells to the vessel wall and B cell effects on atherosclerosis are poorly understood. Inhibitor of Differentiation-3 (Id3), is important for atheroprotection in mice and polymorphism in the human ID3 gene has been implicated as a potential risk marker of atherosclerosis in humans. Yet the role of Id3 in B cell regulation of atherosclerosis is unknown.
To determine if Id3 regulates B cell homing to the aorta and atheroprotection, and identify molecular and cellular mechanisms mediating this effect.
Methods and Results
Loss of Id3 in Apoe−/− mice resulted in early and increased atherosclerosis. Flow cytometry revealed a defect in Id3−/− Apoe−/− mice in the number of B cells in the aorta, but not the spleen, lymph nodes and circulation. Similarly, B cells transferred from Id3−/− Apoe−/− mice into B cell deficient micereconstituted spleen, lymph node and blood similarly to B cells from Id3+/+ Apoe−/− mice, but aortic reconstitution and B cell-mediated inhibition of diet-induced atherosclerosis was significantly impaired. In addition to retarding initiation of atherosclerosis, B cells homed to regions of existing atherosclerosis, reduced macrophage content in plaque and attenuated progression of disease. The chemokine receptor, CCR6, was identified as an important Id3 target mediating aortic homing and atheroprotection.
Together, these results are the first to identify the Id3-CCR6 pathway in B cells and demonstrate its role in aortic B cell homing and B cell mediated protection from early atherosclerosis.
Atherosclerosis; B lymphocytes; Transcription factors; Helix-loop-helix; Homing
Pancreatic ductal adenocarcinoma (PDAC) is highly malignant disease that is the fourth leading cause of cancer-related death in the US. Gene therapy using AAV vectors to selectively deliver genes to PDAC cells is an attractive treatment option for pancreatic cancer. However, most AAV serotypes display a broad spectrum of tissue tropism and none of the existing serotypes specifically target PDAC cells. This study tests the hypothesis that AAV2 can be genetically re-engineered to specifically target PDAC cells by modifying the capsid surface to display a peptide that has previously been shown to bind plectin-1. Toward this end, a Plectin-1 Targeting Peptide (PTP) was inserted into the loop IV region of the AAV2 capsid, and the resulting capsid (AAV-PTP) was used in a series of in vitro and in vivo experiments. In vitro, AAV-PTP was found to target all five human PDAC cell lines tested (PANC-1, MIA PaCa-2, HPAC, MPanc-96, and BxPC-3) preferentially over two non-neoplastic human pancreatic cell lines (human pancreatic ductal epithelial and human pancreatic stellate cells). In vivo, mice bearing subcutaneous tumor xenografts were generated using the PANC-1 cell line. Once tumors reached a size of ∼1–2 mm in diameter, the mice were injected intravenously with luciferase reporter vectors packaged in the either AAV-PTP or wild type AAV2 capsids. Luciferase expression was then monitored by bioluminescence imaging on days 3, 7, and 14 after vector injection. The results indicate that the AAV-PTP capsid displays a 37-fold preference for PANC-1 tumor xenographs over liver and other tissues; whereas the wild type AAV2 capsid displays a complementary preference for liver over tumors and other tissues. Together, these results establish proof-of-principle for the ability of PTP-modified AAV capsids to selectively target gene delivery to PDAC cells in vivo, which opens promising new avenues for the early detection, diagnosis, and treatment of pancreatic cancer.
AAV; pancreatic cancer; gene therapy; targeted gene delivery; capsid modification; phage display
Molecular imaging allows clinicians to visualize disease specific molecules, thereby providing relevant information in the diagnosis and treatment of patients. With advances in genomics and proteomics and underlying mechanisms of disease pathology, the number of targets identified has significantly outpaced the number of developed molecular imaging probes. There has been a concerted effort to bridge this gap with multidisciplinary efforts in chemistry, proteomics, physics, material science, and biology; all essential to progress in molecular imaging probe development. In this review, we will discuss target selection, screening techniques and probe optimization with the aim of developing clinically relevant molecularly targeted imaging agents.
molecular imaging; probe discovery; screening; target
Managing drug-resistant Mycobacterium tuberculosis requires drug susceptibility testing, yet conventional drug susceptibility testing is slow, and molecular testing does not yield results for all antituberculous drugs. We addressed these challenges by utilizing real-time PCR of mycobacteriophage D29 DNA to evaluate the drug resistance of clinical M. tuberculosis isolates. Mycobacteriophages infect and replicate in viable bacterial cells faster than bacterial cells replicate and have been used for detection and drug resistance testing for M. tuberculosis either by using reporter cells or phages with engineered reporter constructs. Our primary protocol involved culturing M. tuberculosis isolates for 48 h with and without drugs at critical concentrations, followed by incubation with 103 PFU/ml of D29 mycobacteriophage for 24 h and then real-time PCR. Many drugs could be incubated instantly with M. tuberculosis and phage for 24 h alone. The change in phage DNA real-time PCR cycle threshold (CT) between control M. tuberculosis and M. tuberculosis treated with drugs was calculated and correlated with conventional agar proportion drug susceptibility results. Specifically, 9 susceptible clinical isolates, 22 multidrug-resistant (MDR), and 1 extensively drug-resistant (XDR) M. tuberculosis strains were used and CT control-CT drug cutoffs of between +0.3 and −6.0 yielded 422/429 (98%) accurate results for isoniazid, rifampin, streptomycin, ethambutol, amikacin, kanamycin, capreomycin, ofloxacin, moxifloxacin, ethionamide, para-aminosalicylic acid, cycloserine, and linezolid. Moreover, the ΔCT values correlated with isolate MIC for most agents. This D29 quantitative PCR assay offers a rapid, accurate, 1- to 3-day phenotypic drug susceptibility test for first- and second-line drugs and may suggest an approximate MIC.
Despite a growing literature on the psychosocial impact of the threat of cancer recurrence, underserved populations, such as those from the Appalachian region, have been understudied. To examine worry and perceived risk in cancer survivors, cancer patients at an ambulatory oncology clinic in a university hospital were surveyed. Appalachians had significantly higher worry than non-Appalachians. Cancer type and lower need for cognition were associated with greater worry. Those with missing perceived risk data were generally older, less educated, and lower in monitoring, blunting, and health literacy. Additional resources are needed to assist Appalachians and those with cancers with poor prognoses to cope with worry associated with cancer recurrence. More attention to prevention of cancer is critical to improve quality of life in underserved populations where risk of cancer is greater.
Appalachian region; cancer; health disparities; oncology; perceived risk; psychosocial factors
Challenges to the identification of hereditary cancer in primary care may be more pronounced in rural Appalachia, a medically underserved region.
To examine primary care physicians’ identification of hereditary cancers.
A cross-sectional survey was mailed to family physicians in the midwestern and southeastern United States, stratified by rural/non-rural and Appalachian/non-Appalachian practice location (N=176). Identification of hereditary breast-ovarian cancer (BRCA1/2), hereditary non-polyposis colon cancer (HNPCC), and other hereditary cancers was assessed.
Less than half of physicians (45%) reported having patients with cancer genetic testing. Most (70%) correctly identified the BRCA1/2-relevant scenario; 49% correctly identified the HNPCC-relevant scenario. Factor analysis of psychosocial variables revealed 2 factors: Confidence (knowledge, comfort, confidence) and Importance (responsible, important, effective, need) of identifying hereditary cancer. Greater confidence was associated with use of 3 generation pedigree in taking family history. Greater knowledge and access to genetic services were associated with use of genetic testing. More recent graduation year, greater knowledge, and greater confidence were associated with identifying the BRCA1/2-relevant scenario. Greater knowledge and confidence were associated with identifying the HNPCC-relevant scenario.
Although rural Appalachian physicians do not differ in ability to identify high risk individuals, access barriers may exist for genetic testing. Interventions are needed to boost physician confidence in identifying hereditary cancer and to improve availability and awareness of availability of genetic services.
hereditary cancer; physicians; primary care; psychosocial factors; Appalachian region
Prostate cancer is the most commonly diagnosed non-skin malignancy in the United States and presents with a wide range of aggressiveness from extremely slow-growing to highly aggressive. There is a clinical need to determine the metastatic potential of the primary tumor to design the most appropriate treatment plan ranging from watchful waiting to more aggressive, invasive surgical treatments. In this study we have developed a nanoparticle based imaging agent that targets SPARC (Secreted Protein Acidic Rich in Cysteine), a molecular marker of prostate cancer metastatic potential. Previous studies by this group used phage display to identify a peptide with high binding affinity and specificity for SPARC. In this study, the SPARC-targeted peptide sequence was used to design a biomaterial with improved pharmacokinetic properties by attaching it to a biocompatible nanoparticle that is also coupled to a fluorophore for in vivo imaging. Prostate cancer cell lines with varying degrees of SPARC expression were used to show the ability of the targeted nanoparticle to bind specifically to SPARC in vitro and in vivo including the clinically relevant bone and lung metastases. We show that in vivo imaging information correlates with the metastatic potential of the prostate tumor. This prognostic information could enable doctors to stratify patients and design personalized treatment strategies.
We are in great need of specific biomarkers to detect pancreatic cancer (PDAC) at an early stage, ideally before invasion. Plectin-1 (Plec1) was recently identified as one such biomarker. However, its suitability as a specific biomarker for human pancreatic cancer, and its usability as an imaging target remain to be assessed.
Specimens of human PDAC, chronic pancreatitis and normal pancreata were evaluated by IHC and Western blot analysis. To validate Plec1 as an imaging target, Plec1-targeting peptides (tPTP) were used as a contrast agent for single photon emission computed tomography in an orthotopic and liver metastasis murine model of PDAC.
Plec1 expression was noted to be positive in all PDACs but negative in benign tissues. Plec1 expression increases during pancreatic carcinogenesis. It was found to be misexpressed in only 0–3.85% of early PDAC precursor lesions (PanINs-I/II) but in 60% of PanIN III lesions. Plec1 expression was further noted to be retained in all metastatic foci assayed and clearly highlighted these metastatic deposits in lymph nodes, liver and peritoneum. In vivo imaging using tPTP specifically highlighted the primary and metastatic tumors. Biodistribution studies performed after imaging demonstrate that the primary pancreatic tumors and liver metastasis retained 1.9–2.9 fold of tPTP over normal pancreas and 1.7-fold over normal liver.
Plec1 is the first biomarker to identify primary and metastatic PDAC by imaging and may also detect preinvasive PanIN III lesions. Strategies designed to image Plec1 could therefore improve detection and staging.
Plectin; biomarker; imaging biomarker; pancreatic cancer; PanIN
Patients receiving complementary and alternative medicine (CAM) therapies often report shifts in well-being that go beyond resolution of the original presenting symptoms. We undertook a research program to develop and evaluate a patient-centered outcome measure to assess the multidimensional impacts of CAM therapies, utilizing a novel mixed methods approach that relied upon techniques from the fields of anthropology and psychometrics. This tool would have broad applicability, both for CAM practitioners to measure shifts in patients' states following treatments, and conventional clinical trial researchers needing validated outcome measures. The US Food and Drug Administration has highlighted the importance of valid and reliable measurement of patient-reported outcomes in the evaluation of conventional medical products. Here we describe Phase I of our research program, the iterative process of content identification, item development and refinement, and response format selection. Cognitive interviews and psychometric evaluation are reported separately.
From a database of patient interviews (n = 177) from six diverse CAM studies, 150 interviews were identified for secondary analysis in which individuals spontaneously discussed unexpected changes associated with CAM. Using ATLAS.ti, we identified common themes and language to inform questionnaire item content and wording. Respondents' language was often richly textured, but item development required a stripping down of language to extract essential meaning and minimize potential comprehension barriers across populations. Through an evocative card sort interview process, we identified those items most widely applicable and covering standard psychometric domains. We developed, pilot-tested, and refined the format, yielding a questionnaire for cognitive interviews and psychometric evaluation.
The resulting questionnaire contained 18 items, in visual analog scale format, in which each line was anchored by the positive and negative extremes relevant to the experiential domain. Because of frequent informant allusions to response set shifts from before to after CAM therapies, we chose a retrospective pretest format. Items cover physical, emotional, cognitive, social, spiritual, and whole person domains.
This paper reports the success of a novel approach to the development of outcome instruments, in which items are extracted from patients' words instead of being distilled from pre-existing theory. The resulting instrument, focused on measuring shifts in patients' perceptions of health and well-being along pre-specified axes, is undergoing continued testing, and is available for use by cooperating investigators.
Complementary and alternative medicine (CAM); patient-reported outcomes (PROs); patient-centered care; non-specific outcomes; questionnaire development; retrospective pre-test; well-being
Available measures of patient-reported outcomes for complementary and alternative medicine (CAM) inadequately capture the range of patient-reported treatment effects. The Self-Assessment of Change questionnaire was developed to measure multi-dimensional shifts in well-being for CAM users. With content derived from patient narratives, items were subsequently focused through interviews on a new cohort of participants. Here we present the development of the final version in which the content and format is refined through cognitive interviews.
We conducted cognitive interviews across five iterations of questionnaire refinement with a culturally diverse sample of 28 CAM users. In each iteration, participant critiques were used to revise the questionnaire, which was then re-tested in subsequent rounds of cognitive interviews. Following all five iterations, transcripts of cognitive interviews were systematically coded and analyzed to examine participants' understanding of the format and content of the final questionnaire. Based on this data, we established summary descriptions and selected exemplar quotations for each word pair on the final questionnaire.
The final version of the Self-Assessment of Change questionnaire (SAC) includes 16 word pairs, nine of which remained unchanged from the original draft. Participants consistently said that these stable word pairs represented opposite ends of the same domain of experience and the meanings of these terms were stable across the participant pool. Five pairs underwent revision and two word pairs were added. Four word pairs were eliminated for redundancy or because participants did not agree on the meaning of the terms. Cognitive interviews indicate that participants understood the format of the questionnaire and considered each word pair to represent opposite poles of a shared domain of experience.
We have placed lay language and direct experience at the center of questionnaire revision and refinement. In so doing, we provide an innovative model for the development of truly patient-centered outcome measures. Although this instrument was designed and tested in a CAM-specific population, it may be useful in assessing multi-dimensional shifts in well-being across a broader patient population.
Complementary and alternative medicine (CAM); patient-reported outcomes (PROs); cognitive interviewing; patient-centered care; non-specific outcomes; questionnaire development; retrospective pre-test; well-being
The sequencing of the human genome holds out the hope for personalized medicine, but it is clear that analysis of DNA or RNA content alone is not sufficient to understand most disease processes. Proteomic strategies that allow unbiased identification of proteins and their post-transcriptional and -translation modifications are an essential complement to genomic strategies. However, the enormity of the proteome and limitations in proteomic methods make it difficult to determine the targets that are particularly relevant to human disease. Methods are therefore needed that allow rational identification of targets based on function and relevance to disease. Screening methodologies such as phage display, SELEX, and small-molecule combinatorial chemistry have been widely used to discover specific ligands for cells or tissues of interest, such as tumors. Those ligands can be used in turn as affinity probes to identify their cognate molecular targets when they are not known in advance. Here we report an easy, robust and generally applicable approach in which phage particles bearing cell- or tissue-specific peptides serve directly as the affinity probes for their molecular targets. For proof of principle, the method successfully identified molecular binding partners, three of them novel, for 15 peptides specific for pancreatic cancer.
Quantification of microvascular network structure is important in a myriad of emerging research fields including microvessel remodeling in response to ischemia and drug therapy, tumor angiogenesis, and retinopathy. To mitigate analyst-specific variation in measurements and to ensure that measurements represent actual changes in vessel network structure and morphology, a reliable and automatic tool for quantifying microvascular network architecture is needed. Moreover, an analysis tool capable of acquiring and processing large data sets will facilitate advanced computational analysis and simulation of microvascular growth and remodeling processes and enable more high throughput discovery. To this end, we have produced an automatic and rapid vessel detection and quantification system using a MATLAB graphical user interface (GUI) that vastly reduces time spent on analysis and greatly increases repeatability. Analysis yields numerical measures of vessel volume fraction, vessel length density, fractal dimension (a measure of tortuosity), and radii of murine vascular networks. Because our GUI is open sourced to all, it can be easily modified to measure parameters such as percent coverage of non-endothelial cells, number of loops in a vascular bed, amount of perfusion and two-dimensional branch angle. Importantly, the GUI is compatible with standard fluorescent staining and imaging protocols, but also has utility analyzing brightfield vascular images, obtained, for example, in dorsal skinfold chambers. A manually measured image can be typically completed in 20 minutes to 1 hour. In stark comparison, using our GUI, image analysis time is reduced to around 1 minute. This drastic reduction in analysis time coupled with increased repeatability makes this tool valuable for all vessel research especially those requiring rapid and reproducible results, such as anti-angiogenic drug screening.
Imaging has become a crucial tool in oncology throughout the course of disease detection and management and is an integral part of clinical trials. Anatomic and functional imaging led the way, providing valuable information used in the diagnosis of disease, including data regarding the size and location of the tumor and on physiologic processes such as blood flow and perfusion. As understanding of cancer pathogenesis has advanced through the identification of genetic, biochemical, and cellular alterations in evolving tumors, emphasis has been made on developing methods to detect and serially monitor such alterations. This class of approaches is referred to as molecular imaging. Molecular imaging offers the potential for increasingly sensitive and specific visualization and quantification of biological processes at the cellular and molecular level. These approaches have become established as essential tools for cancer research, early cancer detection and staging and monitoring and predicting response to targeted therapies. Here, we will discuss recent advances in the development of molecular imaging agents and their implementation in basic cancer research as well as in more rationalized approaches to cancer care.
Molecular Imaging; Tumor; Cancer; Targeted Molecular Imaging; Therapeutic Response; PET; MRI; SPECT
Background and Purpose
This study utilized middle cerebral artery occlusion (MCAO) with tissue plasminogen activator (tPA) to assess inhibition of the NOX2 isoform of NADPH oxidase on brain injury and functional recovery in aged rats.
Effects of NOX2 on the degree of brain injury and functional recovery following MCAO and tPA reperfusion was assessed in young adult and aged rats. Rats received apocynin (NOX2 inhibitor; 5 mg/kg) or saline 30 min prior to MCAO. At 24 h following MCAO, blood-brain barrier permeability (BBB), stroke infarct volume, edema formation, and oxidative damage were measured.
Apocynin treatment in aged rats increased mortality rate and failed to improve functional outcome, total infarct volume, edema formation, and BBB permeability. Aged rats displayed increased BBB permeability to sucrose in the contralateral hemisphere following MCAO and diminished antioxidant capacity in the brain as compared to young adult rats.
We conclude that inhibition of NOX2 in the aged rat exacerbates stroke injury and diminishes functional outcome. These results suggest age is an important factor in stroke damage and more rigorous examination of apocynin as a therapeutic agent for treatment of stroke must be done.
neurovascular unit; apocynin; MCAO; blood brain barrier; NADPH oxidase
Age is a primary risk factor in stroke that is often overlooked in animal studies. We contend that using aged animals yields insight into aspects of stroke injury and recovery that are masked, or not elicited, in younger animals. In this study, we examined effects of co-administration of a plasminogen activator inhibitor type 1 derived peptide, EEIIMD, with tissue plasminogen activator (tPA) on infarct volume and functional outcome in aged rats following a transient middle cerebral artery occlusion. Results of our study showed aged (18–20 months) rats treated with EEIIMD along with tPA had reduced cortical infarction volume. However, aged rats showed no improvement in total infarction volume, edema formation, or functional outcome as compared to aged rats administered only tPA. Young adult rats (3–4 months) treated with EEIIMD showed significant improvement in cortical and total infarction volumes, edema formation, and functional outcome. Striatal infarction volume was unaffected by EEIIMD treatment in both young adult and aged rats. These findings emphasize that physiological differences exist between young adult and aged rats and suggest that taking aging processes into account when assessing stroke may improve our ability to discern which therapeutics can be translated from bench to bedside.
cerebral ischemia; tissue plasminogen activator; cortex; striatum; edema; stroke
Visual masking deficit in schizophrenia has been suggested to be a potential vulnerability marker for schizophrenia. An important characteristic of a vulnerability marker is stability over time, but relatively little is known about the longitudinal course of masking performance of schizophrenia patients. In this study, we examined the stability of visual masking performance in recent-onset schizophrenia patients over an 18-month period. We administered both forward and backward masking trials with multiple stimulus onset asynchronies for four masking conditions at three time points (baseline, 6-month, and 18-month). Recent-onset schizophrenia patients showed stable masking performance for both forward and backward conditions over a period of 18 months. Furthermore, the stable performance was observed across all four masking conditions. The findings of this study provide further support for the view that visual masking deficits reflect a possible vulnerability marker for schizophrenia.
visual masking; stability; vulnerability; recent-onset schizophrenia; longitudinal study
In vivo imaging reveals how proteins and cells function as part of complex regulatory networks in intact organisms, and thereby contributes to a systems-level understanding of biological processes. However, the development of novel in vivo imaging probes remains challenging. Most probes are directed against a limited number of pre-specified protein targets; cell-based screens for imaging probes have shown promise, but raise concerns over whether in vitro surrogate cell models recapitulate in vivo phenotypes. Here, we rapidly profile the in vitro binding of nanoparticle imaging probes in multiple samples of defined target vs. background cell types, using primary cell isolates. This approach selects for nanoparticles that show desired targeting effects across all tested members of a class of cells, and decreases the likelihood that an idiosyncratic cell line will unduly skew screening results. To adjust for multiple hypothesis testing, we use permutation methods to identify nanoparticles that best differentiate between the target and background cell classes. (This approach is conceptually analogous to one used for high-dimensionality datasets of genome-wide gene expression, e.g. to identify gene expression signatures that discriminate subclasses of cancer.) We apply this approach to the identification of nanoparticle imaging probes that bind endothelial cells, and validate our in vitro findings in human arterial samples, and by in vivo intravital microscopy in mice. Overall, this work presents a generalizable approach to the unbiased discovery of in vivo imaging probes, and may guide the further development of novel endothelial imaging probes.
To iteratively develope and validate an 18F labeled small molecule VCAM-1 affinity ligand and demonstrate the feasibility of imaging VCAM-1 expression by PET-CT in murine arteries.
Hybrid PET-CT imaging may allow simultaneous assessment of atherosclerotic lesion morphology (CT) and biology through the development of novel tracers (PET), thus facilitating early risk assessment in individual patients.
A cyclic, a linear, and an oligomer affinity peptide, internalized into endothelial cells by VCAM-1–mediated binding, were initially derivatized with DOTA to determine their binding profiles and pharmacokinetics. The lead compound was then 18F labeled and tested in apoE−/− mice as well as models of MI and heart transplant rejection.
The tetrameric peptide had the highest affinity and specificity for VCAM-1 (97% inhibition with soluble VCAM-1). In vivo PET-CT imaging using 18F-4V showed 0.31±0.02 SUV in murine atheroma (ex vivo %IDGT 5.9±1.5). 18F-4V uptake colocalized with atherosclerotic plaques on Oil Red O staining, and correlated to mRNA levels of VCAM-1 measured by quantitative RT-PCR (R=0.79, p=0.03). Mice treated with atorvastatin had significantly lower lesional uptake (p<0.05). Furthermore, 18F-4V imaging in myocardial ischemia and in transplanted hearts showed good correlation with ex vivo measurement of VCAM-1 mRNA.
18F-4V allows noninvasive PET-CT imaging of VCAM-1 in inflammatory atherosclerosis, has the dynamic range to quantify treatment effects and correlates with inflammatory gene expression.
atherosclerosis; molecular imaging; inflammation; VCAM-1; PET-CT
Early detection and diagnosis of prostate cancer (PCA) is key to designing effective treatment strategies. Microarrays have resulted in the discovery of Hepsin (HPN) as a biomarker for detection of PCA. In this study we explore the development of HPN imaging probes for detection of prostate cancer. We used phage display to isolate HPN binding peptides with 190 ± 2.2 nM affinity in monomeric form and high specificity. The identified peptides were able to detect human prostate cancer on tissue microarrays and in cell based assays. HPN targeted imaging agents were synthesized by conjugating multiple peptides to fluorescent nanoparticles to further improve avidity through multivalency and to improve pharmacokinetics. When injected into mouse xenograft models, HPN-targeted nanoparticles bound specifically to HPN-expressing LNCaP xenografts compared to non-HPN expressing PC3 xenografts. HPN imaging may provide a new method for detection of PCA.
Prostate cancer; early detection; molecular imaging
Fluorogenic imaging agents emitting in the near infrared are becoming important research tools for disease interrogation in vivo. Often pathophysiological states such as cancer and cystic fibrosis are associated with disruptions in acid/base homeostasis. The development of optical sensors for pH imaging would facilitate the investigation of these diseased conditions. In this report, the design and synthesis of a ratiometric near infrared emitting probe for pH quantification is detailed. The pH-responsive probe is prepared by covalent attachment of pH-sensitive and pH-insensitive fluorophores to a bacteriophage particle scaffold. The pH responsive cyanine dye, HCyC-646, used to construct the probe has a fluorogenic pKa of 6.2, which is optimized for visualization of acidic pH often associated with tumor hypoxia and other diseased states. Incorporation of pH insensitive reference dyes enables the ratiometric determination of pH independent of the probe concentration. With the pH-responsive construct measurement of intracellular pH and accurate determination of pH through optically diffuse biological tissue is demonstrated.