The 'gold standard' for oncogenic HPV detection is the demonstration of transcriptionally active high-risk HPV in tumor tissue. However, detection of E6/E7 mRNA by quantitative reverse transcription polymerase chain reaction (qRT-PCR) requires RNA extraction which destroys the tumor tissue context critical for morphological correlation and has been difficult to be adopted in routine clinical practice. Our recently developed RNA in situ hybridization technology, RNAscope, permits direct visualization of RNA in formalin-fixed, paraffin-embedded (FFPE) tissue with single molecule sensitivity and single cell resolution, which enables highly sensitive and specific in situ analysis of any RNA biomarker in routine clinical specimens. The RNAscope HPV assay was designed to detect the E6/E7 mRNA of seven high-risk HPV genotypes (HPV16, 18, 31, 33, 35, 52, and 58) using a pool of genotype-specific probes. It has demonstrated excellent sensitivity and specificity against the current 'gold standard' method of detecting E6/E7 mRNA by qRT-PCR. HPV status determined by RNAscope is strongly prognostic of clinical outcome in oropharyngeal cancer patients.
21 Related JoVE Articles!
Profiling of Estrogen-regulated MicroRNAs in Breast Cancer Cells
Institutions: University of Houston.
Estrogen plays vital roles in mammary gland development and breast cancer progression. It mediates its function by binding to and activating the estrogen receptors (ERs), ERα, and ERβ. ERα is frequently upregulated in breast cancer and drives the proliferation of breast cancer cells. The ERs function as transcription factors and regulate gene expression. Whereas ERα's regulation of protein-coding genes is well established, its regulation of noncoding microRNA (miRNA) is less explored. miRNAs play a major role in the post-transcriptional regulation of genes, inhibiting their translation or degrading their mRNA. miRNAs can function as oncogenes or tumor suppressors and are also promising biomarkers. Among the miRNA assays available, microarray and quantitative real-time polymerase chain reaction (qPCR) have been extensively used to detect and quantify miRNA levels. To identify miRNAs regulated by estrogen signaling in breast cancer, their expression in ERα-positive breast cancer cell lines were compared before and after estrogen-activation using both the µParaflo-microfluidic microarrays and Dual Labeled Probes-low density arrays. Results were validated using specific qPCR assays, applying both Cyanine dye-based and Dual Labeled Probes-based chemistry. Furthermore, a time-point assay was used to identify regulations over time. Advantages of the miRNA assay approach used in this study is that it enables a fast screening of mature miRNA regulations in numerous samples, even with limited sample amounts. The layout, including the specific conditions for cell culture and estrogen treatment, biological and technical replicates, and large-scale screening followed by in-depth confirmations using separate techniques, ensures a robust detection of miRNA regulations, and eliminates false positives and other artifacts. However, mutated or unknown miRNAs, or regulations at the primary and precursor transcript level, will not be detected. The method presented here represents a thorough investigation of estrogen-mediated miRNA regulation.
Medicine, Issue 84, breast cancer, microRNA, estrogen, estrogen receptor, microarray, qPCR
Initiation of Metastatic Breast Carcinoma by Targeting of the Ductal Epithelium with Adenovirus-Cre: A Novel Transgenic Mouse Model of Breast Cancer
Institutions: Wistar Institute, University of Pennsylvania, Geisel School of Medicine at Dartmouth, University of Pennsylvania, University of Pennsylvania, University of Pennsylvania.
Breast cancer is a heterogeneous disease involving complex cellular interactions between the developing tumor and immune system, eventually resulting in exponential tumor growth and metastasis to distal tissues and the collapse of anti-tumor immunity. Many useful animal models exist to study breast cancer, but none completely recapitulate the disease progression that occurs in humans. In order to gain a better understanding of the cellular interactions that result in the formation of latent metastasis and decreased survival, we have generated an inducible transgenic mouse model of YFP-expressing ductal carcinoma that develops after sexual maturity in immune-competent mice and is driven by consistent, endocrine-independent oncogene expression. Activation of YFP, ablation of p53, and expression of an oncogenic form of K-ras was achieved by the delivery of an adenovirus expressing Cre-recombinase into the mammary duct of sexually mature, virgin female mice. Tumors begin to appear 6 weeks after the initiation of oncogenic events. After tumors become apparent, they progress slowly for approximately two weeks before they begin to grow exponentially. After 7-8 weeks post-adenovirus injection, vasculature is observed connecting the tumor mass to distal lymph nodes, with eventual lymphovascular invasion of YFP+ tumor cells to the distal axillary lymph nodes. Infiltrating leukocyte populations are similar to those found in human breast carcinomas, including the presence of αβ and γδ T cells, macrophages and MDSCs. This unique model will facilitate the study of cellular and immunological mechanisms involved in latent metastasis and dormancy in addition to being useful for designing novel immunotherapeutic interventions to treat invasive breast cancer.
Medicine, Issue 85, Transgenic mice, breast cancer, metastasis, intraductal injection, latent mutations, adenovirus-Cre
Optimization and Utilization of Agrobacterium-mediated Transient Protein Production in Nicotiana
Institutions: Fraunhofer USA Center for Molecular Biotechnology.
-mediated transient protein production in plants is a promising approach to produce vaccine antigens and therapeutic proteins within a short period of time. However, this technology is only just beginning to be applied to large-scale production as many technological obstacles to scale up are now being overcome. Here, we demonstrate a simple and reproducible method for industrial-scale transient protein production based on vacuum infiltration of Nicotiana
plants with Agrobacteria
carrying launch vectors. Optimization of Agrobacterium
cultivation in AB medium allows direct dilution of the bacterial culture in Milli-Q water, simplifying the infiltration process. Among three tested species of Nicotiana
, N. excelsiana
× N. excelsior
) was selected as the most promising host due to the ease of infiltration, high level of reporter protein production, and about two-fold higher biomass production under controlled environmental conditions. Induction of Agrobacterium
harboring pBID4-GFP (Tobacco mosaic virus
-based) using chemicals such as acetosyringone and monosaccharide had no effect on the protein production level. Infiltrating plant under 50 to 100 mbar for 30 or 60 sec resulted in about 95% infiltration of plant leaf tissues. Infiltration with Agrobacterium
laboratory strain GV3101 showed the highest protein production compared to Agrobacteria
laboratory strains LBA4404 and C58C1 and wild-type Agrobacteria
strains at6, at10, at77 and A4. Co-expression of a viral RNA silencing suppressor, p23 or p19, in N. benthamiana
resulted in earlier accumulation and increased production (15-25%) of target protein (influenza virus hemagglutinin).
Plant Biology, Issue 86, Agroinfiltration, Nicotiana benthamiana, transient protein production, plant-based expression, viral vector, Agrobacteria
Adaptation of Semiautomated Circulating Tumor Cell (CTC) Assays for Clinical and Preclinical Research Applications
Institutions: London Health Sciences Centre, Western University, London Health Sciences Centre, Lawson Health Research Institute, Western University.
The majority of cancer-related deaths occur subsequent to the development of metastatic disease. This highly lethal disease stage is associated with the presence of circulating tumor cells (CTCs). These rare cells have been demonstrated to be of clinical significance in metastatic breast, prostate, and colorectal cancers. The current gold standard in clinical CTC detection and enumeration is the FDA-cleared CellSearch system (CSS). This manuscript outlines the standard protocol utilized by this platform as well as two additional adapted protocols that describe the detailed process of user-defined marker optimization for protein characterization of patient CTCs and a comparable protocol for CTC capture in very low volumes of blood, using standard CSS reagents, for studying in vivo
preclinical mouse models of metastasis. In addition, differences in CTC quality between healthy donor blood spiked with cells from tissue culture versus patient blood samples are highlighted. Finally, several commonly discrepant items that can lead to CTC misclassification errors are outlined. Taken together, these protocols will provide a useful resource for users of this platform interested in preclinical and clinical research pertaining to metastasis and CTCs.
Medicine, Issue 84, Metastasis, circulating tumor cells (CTCs), CellSearch system, user defined marker characterization, in vivo, preclinical mouse model, clinical research
Electrochemotherapy of Tumours
Institutions: Institute of Oncology Ljubljana, University of Ljubljana.
Electrochemotherapy is a combined use of certain chemotherapeutic drugs and electric pulses applied to the treated tumour nodule. Local application of electric pulses to the tumour increases drug delivery into cells, specifically at the site of electric pulse application. Drug uptake by delivery of electric pulses is increased for only those chemotherapeutic drugs whose transport through the plasma membrane is impeded. Among many drugs that have been tested so far, bleomycin and cisplatin found their way from preclinical testing to clinical use. Clinical data collected within a number of clinical studies indicate that approximately 80% of the treated cutaneous and subcutaneous tumour nodules of different malignancies are in an objective response, from these, approximately 70% in complete response after a single application of electrochemotherapy. Usually only one treatment is needed, however, electrochemotherapy can be repeated several times every few weeks with equal effectiveness each time. The treatment results in an effective eradication of the treated nodules, with a good cosmetic effect without tissue scarring.
Medicine, Issue 22, electrochemotherapy, electroporation, cisplatin, bleomycin, malignant tumours, cutaneous lesions
Two Methods for Establishing Primary Human Endometrial Stromal Cells from Hysterectomy Specimens
Institutions: University of Virginia, University of Virginia.
Many efforts have been devoted to establish in vitro
cell culture systems. These systems are designed to model a vast number of in vivo
processes. Cell culture systems arising from human endometrial samples are no exception. Applications range from normal cyclic physiological processes to endometrial pathologies such as gynecological cancers, infectious diseases, and reproductive deficiencies. Here, we provide two methods for establishing primary endometrial stromal cells from surgically resected endometrial hysterectomy specimens. The first method is referred to as “the scraping method” and incorporates mechanical scraping using surgical or razor blades whereas the second method is termed “the trypsin method.” This latter method uses the enzymatic activity of trypsin to promote the separation of cells and primary cell outgrowth. We illustrate step-by-step methodology through digital images and microscopy. We also provide examples for validating endometrial stromal cell lines via quantitative real time polymerase chain reactions (qPCR) and immunofluorescence (IF).
Medicine, Issue 87, uterus, endometrium, endometrial stroma, (primary) cell culture, surgical blade, trypsin, tissue procurement, spontaneous decidualization
Analysis of Cell Migration within a Three-dimensional Collagen Matrix
Institutions: Witten/Herdecke University.
The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including embryonic development, wound healing, and immune responses. However, cell migration is also a key mechanism in cancer enabling these cancer cells to detach from the primary tumor to start metastatic spreading. Within the past years various cell migration assays have been developed to analyze the migratory behavior of different cell types. Because the locomotory behavior of cells markedly differs between a two-dimensional (2D) and three-dimensional (3D) environment it can be assumed that the analysis of the migration of cells that are embedded within a 3D environment would yield in more significant cell migration data. The advantage of the described 3D collagen matrix migration assay is that cells are embedded within a physiological 3D network of collagen fibers representing the major component of the extracellular matrix. Due to time-lapse video microscopy real cell migration is measured allowing the determination of several migration parameters as well as their alterations in response to pro-migratory factors or inhibitors. Various cell types could be analyzed using this technique, including lymphocytes/leukocytes, stem cells, and tumor cells. Likewise, also cell clusters or spheroids could be embedded within the collagen matrix concomitant with analysis of the emigration of single cells from the cell cluster/ spheroid into the collagen lattice. We conclude that the 3D collagen matrix migration assay is a versatile method to analyze the migration of cells within a physiological-like 3D environment.
Bioengineering, Issue 92, cell migration, 3D collagen matrix, cell tracking
An Ex vivo Model to Study Hormone Action in the Human Breast
Institutions: Ecole polytechnique fédérale de Lausanne.
The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro
culture, primary mammary epithelial cells tend to lose hormone receptor expression. Widely used hormone receptor positive breast cancer cell lines are of limited relevance to the in vivo
situation. Here, we describe an ex vivo
model to study hormone action in the human breast. Fresh human breast tissue specimens from surgical discard material such as reduction mammoplasties or mammectomies are mechanically and enzymatically digested to obtain tissue fragments containing ducts and lobules and multiple stromal cell types. These tissue microstructures kept in basal medium without growth factors preserve their intercellular contacts, the tissue architecture, and remain hormone responsive for several days. They are readily processed for RNA and protein extraction, histological analysis or stored in freezing medium. Fluorescence activated cell sorting (FACS) can be used to enrich for specific cell populations. This protocol provides a straightforward, standard approach for translational studies with highly complex, varied human specimens.
Medicine, Issue 95, Hormone signaling, breast cancer, reduction mammoplasty, breast tissue microstructures, ex vivo model, estrogen, progesterone, mammary epithelial cells, tissue digestion, paracrine signaling, microenvironment, tissue architecture
Validation of Nanobody and Antibody Based In Vivo Tumor Xenograft NIRF-imaging Experiments in Mice Using Ex Vivo Flow Cytometry and Microscopy
Institutions: University Medical Center, Hamburg, University Medical Center, Hamburg, University Medical Center, Hamburg, University Medical Center, Hamburg.
This protocol outlines the steps required to perform ex vivo
validation of in vivo
near-infrared fluorescence (NIRF) xenograft imaging experiments in mice using fluorophore labelled nanobodies and conventional antibodies.
First we describe how to generate subcutaneous tumors in mice, using antigen-negative cell lines as negative controls and antigen-positive cells as positive controls in the same mice for intraindividual comparison. We outline how to administer intravenously near-infrared fluorophore labelled (AlexaFluor680) antigen-specific nanobodies and conventional antibodies. In vivo
imaging was performed with a small-animal NIRF-Imaging system. After the in vivo
imaging experiments the mice were sacrificed. We then describe how to prepare the tumors for parallel ex vivo
analyses by flow cytometry and fluorescence microscopy to validate in vivo
The use of the near-infrared fluorophore labelled nanobodies allows for non-invasive same day imaging in vivo
. Our protocols describe the ex vivo
quantification of the specific labeling efficiency of tumor cells by flow cytometry and analysis of the distribution of the antibody constructs within the tumors by fluorescence microscopy. Using near-infrared fluorophore labelled probes allows for non-invasive, economical in vivo
imaging with the unique ability to exploit the same probe without further secondary labelling for ex vivo
validation experiments using flow cytometry and fluorescence microscopy.
Medicine, Issue 98, Nanobody, antibody, VHH, fluorescence imaging, molecular imaging, xenograft, animal model
Polymalic Acid-based Nano Biopolymers for Targeting of Multiple Tumor Markers: An Opportunity for Personalized Medicine?
Institutions: Cedars-Sinai Medical Center.
Tumors with similar grade and morphology often respond differently to the same treatment because of variations in molecular profiling. To account for this diversity, personalized medicine is developed for silencing malignancy associated genes. Nano drugs fit these needs by targeting tumor and delivering antisense oligonucleotides for silencing of genes. As drugs for the treatment are often administered repeatedly, absence of toxicity and negligible immune response are desirable. In the example presented here, a nano medicine is synthesized from the biodegradable, non-toxic and non-immunogenic platform polymalic acid by controlled chemical ligation of antisense oligonucleotides and tumor targeting molecules. The synthesis and treatment is exemplified for human Her2-positive breast cancer using an experimental mouse model. The case can be translated towards synthesis and treatment of other tumors.
Chemistry, Issue 88, Cancer treatment, personalized medicine, polymalic acid, nanodrug, biopolymer, targeting, host compatibility, biodegradability
Measuring Intracellular Ca2+ Changes in Human Sperm using Four Techniques: Conventional Fluorometry, Stopped Flow Fluorometry, Flow Cytometry and Single Cell Imaging
Institutions: Instituto de Biotecnología-Universidad Nacional Autónoma de México, Edison State College.
Spermatozoa are male reproductive cells especially designed to reach, recognize and fuse with the egg. To perform these tasks, sperm cells must be prepared to face a constantly changing environment and to overcome several physical barriers. Being in essence transcriptionally and translationally silent, these motile cells rely profoundly on diverse signaling mechanisms to orient themselves and swim in a directed fashion, and to contend with challenging environmental conditions during their journey to find the egg. In particular, Ca2+
-mediated signaling is pivotal for several sperm functions: activation of motility, capacitation (a complex process that prepares sperm for the acrosome reaction) and the acrosome reaction (an exocytotic event that allows sperm-egg fusion). The use of fluorescent dyes to track intracellular fluctuations of this ion is of remarkable importance due to their ease of application, sensitivity, and versatility of detection. Using one single dye-loading protocol we utilize four different fluorometric techniques to monitor sperm Ca2+
dynamics. Each technique provides distinct information that enables spatial and/or temporal resolution, generating data both at single cell and cell population levels.
Cellular Biology, Issue 75, Medicine, Molecular Biology, Genetics, Biophysics, Anatomy, Physiology, Spermatozoa, Ion Channels, Cell Physiological Processes, Calcium Signaling, Reproductive Physiological Processes, fluorometry, Flow cytometry, stopped flow fluorometry, single-cell imaging, human sperm, sperm physiology, intracellular Ca2+, Ca2+ signaling, Ca2+ imaging, fluorescent dyes, imaging
Identification of protein complexes with quantitative proteomics in S. cerevisiae
Institutions: University of British Columbia - UBC, University of British Columbia - UBC.
Lipids are the building blocks of cellular membranes that function as barriers and in compartmentalization of cellular processes, and recently, as important intracellular signalling molecules. However, unlike proteins, lipids are small hydrophobic molecules that traffic primarily by poorly described nonvesicular routes, which are hypothesized to occur at membrane contact sites (MCSs). MCSs are regions where the endoplasmic reticulum (ER) makes direct physical contact with a partnering organelle, e.g., plasma membrane (PM). The ER portion of ER-PM MCSs is enriched in lipid-synthesizing enzymes, suggesting that lipid synthesis is directed to these sites and implying that MCSs are important for lipid traffic. Yeast is an ideal model to study ER-PM MCSs because of their abundance, with over 1000 contacts per cell, and their conserved nature in all eukaryotes. Uncovering the proteins that constitute MCSs is critical to understanding how lipids traffic is accomplished in cells, and how they act as signaling molecules. We have found that an ER called Scs2p localize to ER-PM MCSs and is important for their formation. We are focused on uncovering the molecular partners of Scs2p. Identification of protein complexes traditionally relies on first resolving purified protein samples by gel electrophoresis, followed by in-gel digestion of protein bands and analysis of peptides by mass spectrometry. This often limits the study to a small subset of proteins. Also, protein complexes are exposed to denaturing or non-physiological conditions during the procedure. To circumvent these problems, we have implemented a large-scale quantitative proteomics technique to extract unbiased and quantified data. We use stable isotope labeling with amino acids in cell culture (SILAC) to incorporate staple isotope nuclei in proteins in an untagged control strain. Equal volumes of tagged culture and untagged, SILAC-labeled culture are mixed together and lysed by grinding in liquid nitrogen. We then carry out an affinity purification procedure to pull down protein complexes. Finally, we precipitate the protein sample, which is ready for analysis by high-performance liquid chromatography/ tandem mass spectrometry. Most importantly, proteins in the control strain are labeled by the heavy isotope and will produce a mass/ charge shift that can be quantified against the unlabeled proteins in the bait strain. Therefore, contaminants, or unspecific binding can be easily eliminated. By using this approach, we have identified several novel proteins that localize to ER-PM MCSs. Here we present a detailed description of our approach.
Biochemistry, Issue 25, Quantitative proteomics, Stable isotope, Amino acid labeling, SILAC, Isotope-coded affinity tag, Isotope labeling, Quantitation, Saccharomyces cerevisiae, ER polarization
Right Hemihepatectomy by Suprahilar Intrahepatic Transection of the Right Hemipedicle using a Vascular Stapler
Institutions: Tübingen University Hospital.
Successful hepatic resection requires profound anatomical knowledge and delicate surgical technique. Hemihepatectomies are mostly performed after preparing the extrahepatic hilar structures within the hepatoduodenal ligament, even in benign tumours or liver metastasis.1-5
. Regional extrahepatic lymphadenectomy is an oncological standard in hilar cholangiocarcinoma, intrahepatic cholangio-cellular carcinoma and hepatocellular carcinoma, whereas lymph node metastases in the hepatic hilus in patients with liver metastasis are rarely occult. Major disadvantages of these procedures are the complex preparation of the hilus with the risk of injuring contralateral structures and the possibility of bleeding from portal vein side-branches or impaired perfusion of bile ducts. We developed a technique of right hemihepatectomy or resection of the left lateral segments with intrahepatic transection of the pedicle that leaves the hepatoduodenal ligament completely untouched. 6
However, if intraoperative visualization or palpation of the ligament is suspicious for tumor infiltration or lymph node metastasis, the hilus should be explored and a lymphadenectomy performed.
Medicine, Issue 35, Liver resection, liver tumour, intrahepatic hilus stapling, right hemipedicle
Brain Imaging Investigation of the Neural Correlates of Emotion Regulation
Institutions: University of Illinois, Urbana-Champaign, University of Alberta, Edmonton, University of Alberta, Edmonton, University of Alberta, Edmonton, University of Alberta, Edmonton, University of Illinois, Urbana-Champaign, University of Illinois, Urbana-Champaign.
The ability to control/regulate emotions is an important coping mechanism in the face of emotionally stressful situations. Although significant progress has been made in understanding conscious/deliberate emotion regulation (ER), less is known about non-conscious/automatic ER and the associated neural correlates. This is in part due to the problems inherent in the unitary concepts of automatic and conscious processing1
. Here, we present a protocol that allows investigation of the neural correlates of both deliberate and automatic ER using functional magnetic resonance imaging (fMRI). This protocol allows new avenues of inquiry into various aspects of ER. For instance, the experimental design allows manipulation of the goal to regulate emotion (conscious vs. non-conscious), as well as the intensity of the emotional challenge (high vs. low). Moreover, it allows investigation of both immediate (emotion perception) and long-term effects (emotional memory) of ER strategies on emotion processing. Therefore, this protocol may contribute to better understanding of the neural mechanisms of emotion regulation in healthy behaviour, and to gaining insight into possible causes of deficits in depression and anxiety disorders in which emotion dys
regulation is often among the core debilitating features.
Neuroscience, Issue 54, Emotion Suppression, Automatic Emotion Control, Deliberate Emotion Control, Goal Induction, Neuroimaging
Long-term Culture of Human Breast Cancer Specimens and Their Analysis Using Optical Projection Tomography
Institutions: University of Edinburgh, MRC Technology.
Breast cancer is a leading cause of mortality in the Western world. It is well established that the spread of breast cancer, first locally and later distally, is a major factor in patient prognosis. Experimental systems of breast cancer rely on cell lines usually derived from primary tumours or pleural effusions. Two major obstacles hinder this research: (i) some known sub-types of breast cancers (notably poor prognosis luminal B tumours) are not represented within current line collections; (ii) the influence of the tumour microenvironment is not usually taken into account.
We demonstrate a technique to culture primary breast cancer specimens of all sub-types. This is achieved by using three-dimensional (3D) culture system in which small pieces of tumour are embedded in soft rat collagen I cushions. Within 2-3 weeks, the tumour cells spread into the collagen and form various structures similar to those observed in human tumours1. Viable adipocytes, epithelial cells and fibroblasts within the original core were evident on histology. Malignant epithelial cells with squamoid morphology were demonstrated invading into the surrounding collagen. Nuclear pleomorphism was evident within these cells, along with mitotic figures and apoptotic bodies.
We have employed Optical Projection Tomography (OPT), a 3D imaging technology, in order to quantify the extent of tumour spread in culture. We have used OPT to measure the bulk volume of the tumour culture, a parameter routinely measured during the neo-adjuvant treatment of breast cancer patients to assess response to drug therapy.
Here, we present an opportunity to culture human breast tumours without sub-type bias and quantify the spread of those ex vivo
. This method could be used in the future to quantify drug sensitivity in original tumour. This may provide a more predictive model than currently used cell lines.
Medicine, Issue 53, Breast cancer, Optical Projection Tomography, Imaging, Three-dimensional, computer assisted, Tumour microenvironment
Imaging of Estrogen Receptor-α in Rat Pial Arterioles using a Digital Immunofluorescent Microscope
Institutions: Uniformed Services University of the Health Sciences.
Many of estrogen's effects on vascular reactivity are mediated through interaction with estrogen receptors 1, 2, 3
. Although two sub-types exist (estrogen receptor -α and β),estrogen receptor-α has been identified in both the smooth muscle and in endothelial cells of pial arterial segments using fluorescent staining combined with confocal laser scanning microscopy 4
. Furthermore, ER-α is located in the nuclei and in the cytoplasm of rat basilar arteries 5
. The receptors are abundant and fluoresce brightly, but clear visualization of discrete groups of receptors is difficult likely due to the numbers located in many cell layers of pial vessel segments. Additionally, many reports using immunohistochemical techniques paired with confocal microscopy poorly detail the requirements critical for reproduction of experiments 6
. Our purpose for this article is to describe a simple technique to optimize the staining and visualization of ER-α using cross-sectional slices of pial arterioles obtain from female rat brains. We first perfuse rats with Evans blue dye to easily identify surface pial arteries which we isolate under a dissecting microscope. Use of a cryostat to slice 8 μm cross sections of the arteries allows us to obtain thin vessel sections so that different vessel planes are more clearly visualized. Cutting across the vessel rather than use of a small vessel segment has the advantage of easier viewing of the endothelial and smooth muscle layers. In addition, use of a digital immunofluorescent microscope with extended depth software produces clear images of ten to twelve different vessel planes and is less costly than use of a confocal laser scanning microscope.
Molecular Biology, Issue 57, digital immunofluorescent microscopy, brain, estrogen receptor-α, cerebral microvasculature, rat, immunohistochemistry
Heterogeneity Mapping of Protein Expression in Tumors using Quantitative Immunofluorescence
Institutions: University of Edinburgh, HistoRx Inc..
Morphologic heterogeneity within an individual tumor is well-recognized by histopathologists in surgical practice. While this often takes the form of areas of distinct differentiation into recognized histological subtypes, or different pathological grade, often there are more subtle differences in phenotype which defy accurate classification (Figure 1). Ultimately, since morphology is dictated by the underlying molecular phenotype, areas with visible differences are likely to be accompanied by differences in the expression of proteins which orchestrate cellular function and behavior, and therefore, appearance. The significance of visible and invisible (molecular) heterogeneity for prognosis is unknown, but recent evidence suggests that, at least at the genetic level, heterogeneity exists in the primary tumor1,2
, and some of these sub-clones give rise to metastatic (and therefore lethal) disease.
Moreover, some proteins are measured as biomarkers because they are the targets of therapy (for instance ER and HER2 for tamoxifen and trastuzumab (Herceptin), respectively). If these proteins show variable expression within a tumor then therapeutic responses may also be variable. The widely used histopathologic scoring schemes for immunohistochemistry either ignore, or numerically homogenize the quantification of protein expression. Similarly, in destructive techniques, where the tumor samples are homogenized (such as gene expression profiling), quantitative information can be elucidated, but spatial information is lost. Genetic heterogeneity mapping approaches in pancreatic cancer have relied either on generation of a single cell suspension3
, or on macrodissection4
. A recent study has used quantum dots in order to map morphologic and molecular heterogeneity in prostate cancer tissue5
, providing proof of principle that morphology and molecular mapping is feasible, but falling short of quantifying the heterogeneity. Since immunohistochemistry is, at best, only semi-quantitative and subject to intra- and inter-observer bias, more sensitive and quantitative methodologies are required in order to accurately map and quantify tissue heterogeneity in situ
We have developed and applied an experimental and statistical methodology in order to systematically quantify the heterogeneity of protein expression in whole tissue sections of tumors, based on the Automated QUantitative Analysis (AQUA) system6
. Tissue sections are labeled with specific antibodies directed against cytokeratins and targets of interest, coupled to fluorophore-labeled secondary antibodies. Slides are imaged using a whole-slide fluorescence scanner. Images are subdivided into hundreds to thousands of tiles, and each tile is then assigned an AQUA score which is a measure of protein concentration within the epithelial (tumor) component of the tissue. Heatmaps are generated to represent tissue expression of the proteins and a heterogeneity score assigned, using a statistical measure of heterogeneity originally used in ecology, based on the Simpson's biodiversity index7
To date there have been no attempts to systematically map and quantify this variability in tandem with protein expression, in histological preparations. Here, we illustrate the first use of the method applied to ER and HER2 biomarker expression in ovarian cancer. Using this method paves the way for analyzing heterogeneity as an independent variable in studies of biomarker expression in translational studies, in order to establish the significance of heterogeneity in prognosis and prediction of responses to therapy.
Medicine, Issue 56, quantitative immunofluorescence, heterogeneity, cancer, biomarker, targeted therapy, immunohistochemistry, proteomics, histopathology
Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance
Institutions: University of Central Florida.
AB toxins consist of an enzymatic A subunit and a cell-binding B subunit1
. These toxins are secreted into the extracellular milieu, but they act upon targets within the eukaryotic cytosol. Some AB toxins travel by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) before entering the cytosol2-4
. In the ER, the catalytic A chain dissociates from the rest of the toxin and moves through a protein-conducting channel to reach its cytosolic target5
. The translocated, cytosolic A chain is difficult to detect because toxin trafficking to the ER is an extremely inefficient process: most internalized toxin is routed to the lysosomes for degradation, so only a small fraction of surface-bound toxin reaches the Golgi apparatus and ER6-12
To monitor toxin translocation from the ER to the cytosol in cultured cells, we combined a subcellular fractionation protocol with the highly sensitive detection method of surface plasmon resonance (SPR)13-15
. The plasma membrane of toxin-treated cells is selectively permeabilized with digitonin, allowing collection of a cytosolic fraction which is subsequently perfused over an SPR sensor coated with an anti-toxin A chain antibody. The antibody-coated sensor can capture and detect pg/mL quantities of cytosolic toxin. With this protocol, it is possible to follow the kinetics of toxin entry into the cytosol and to characterize inhibitory effects on the translocation event. The concentration of cytosolic toxin can also be calculated from a standard curve generated with known quantities of A chain standards that have been perfused over the sensor. Our method represents a rapid, sensitive, and quantitative detection system that does not require radiolabeling or other modifications to the target toxin.
Immunology, Issue 59, Surface plasmon resonance, AB toxin, translocation, endoplasmic reticulum, cell culture, cholera toxin, pertussis toxin
Mitochondria-associated ER Membranes (MAMs) and Glycosphingolipid Enriched Microdomains (GEMs): Isolation from Mouse Brain
Institutions: St Jude Children's Research Hospital.
Intracellular organelles are highly dynamic structures with varying shape and composition, which are subjected to cell-specific intrinsic and extrinsic cues. Their membranes are often juxtaposed at defined contact sites, which become hubs for the exchange of signaling molecules and membrane components1,2,3,4
. The inter-organellar membrane microdomains that are formed between the endoplasmic reticulum (ER) and the mitochondria at the opening of the IP3-sensitive Ca2+
channel are known as the mitochondria associated-ER membranes or MAMs4,5,6
. The protein/lipid composition and biochemical properties of these membrane contact sites have been extensively studied particularly in relation to their role in regulating intracellular Ca2+4,5,6
. The ER serves as the primary store of intracellular Ca2+
, and in this capacity regulates a myriad of cellular processes downstream of Ca2+
signaling, including post-translational protein folding and protein maturation7. Mitochondria, on the other hand, maintain Ca2+
homeostasis, by buffering cytosolic Ca2+
concentration thereby preventing the initiation of apoptotic pathways downstream of Ca2+
. The dynamic nature of the MAMs makes them ideal sites to dissect basic cellular mechanisms, including Ca2+
signaling and regulation of mitochondrial Ca2+
concentration, lipid biosynthesis and transport, energy metabolism and cell survival 4,9,10,11,12
. Several protocols have been described for the purification of these microdomains from liver tissue and cultured cells13,14
Taking previously published methods into account, we have adapted a protocol for the isolation of mitochondria and MAMs from the adult mouse brain. To this procedure we have added an extra purification step, namely a Triton X100 extraction, which enables the isolation of the glycosphingolipid enriched microdomain (GEM) fraction of the MAMs. These GEM preparations share several protein components with caveolae and lipid rafts, derived from the plasma membrane or other intracellular membranes, and are proposed to function as gathering points for the clustering of receptor proteins and for protein–protein interactions4,15
Neuroscience, Issue 73, Genetics, Cellular Biology, Molecular Biology, Biochemistry, Membrane Microdomains, Endoplasmic Reticulum, Mitochondria, Intracellular Membranes, Glycosphingolipids, Gangliosides, Endoplasmic Reticulum Stress, Cell Biology, Neurosciences, MAMs, GEMs, Mitochondria, ER, membrane microdomains, subcellular fractionation, lipids, brain, mouse, isolation, animal model
Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading (TED)
Institutions: University of Wuerzburg, Max Planck Institute of Neurobiology, Martinsried, Ludwig-Maximilians University of Munich.
Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent Ca2+
indictors have become popular. Here we demonstrate TED (= targeted-esterase induced dye loading), a method to improve the release of Ca2+
indicator dyes in the ER lumen of different cell types. To date, TED was used in cell lines, glial cells, and neurons in vitro
. TED bases on efficient, recombinant targeting of a high carboxylesterase activity to the ER lumen using vector-constructs that express Carboxylesterases (CES). The latest TED vectors contain a core element of CES2 fused to a red fluorescent protein, thus enabling simultaneous two-color imaging. The dynamics of free calcium in the ER are imaged in one color, while the corresponding ER structure appears in red. At the beginning of the procedure, cells are transduced with a lentivirus. Subsequently, the infected cells are seeded on coverslips to finally enable live cell imaging. Then, living cells are incubated with the acetoxymethyl ester (AM-ester) form of low-affinity Ca2+
indicators, for instance Fluo5N-AM, Mag-Fluo4-AM, or Mag-Fura2-AM. The esterase activity in the ER cleaves off hydrophobic side chains from the AM form of the Ca2+
indicator and a hydrophilic fluorescent dye/Ca2+
complex is formed and trapped in the ER lumen. After dye loading, the cells are analyzed at an inverted confocal laser scanning microscope. Cells are continuously perfused with Ringer-like solutions and the ER calcium dynamics are directly visualized by time-lapse imaging. Calcium release from the ER is identified by a decrease in fluorescence intensity in regions of interest, whereas the refilling of the ER calcium store produces an increase in fluorescence intensity. Finally, the change in fluorescent intensity over time is determined by calculation of ΔF/F0
Cellular Biology, Issue 75, Neurobiology, Neuroscience, Molecular Biology, Biochemistry, Biomedical Engineering, Bioengineering, Virology, Medicine, Anatomy, Physiology, Surgery, Endoplasmic Reticulum, ER, Calcium Signaling, calcium store, calcium imaging, calcium indicator, metabotropic signaling, Ca2+, neurons, cells, mouse, animal model, cell culture, targeted esterase induced dye loading, imaging
A Method for Selecting Structure-switching Aptamers Applied to a Colorimetric Gold Nanoparticle Assay
Institutions: Wright-Patterson Air Force Base, The Henry M. Jackson Foundation, UES, Inc..
Small molecules provide rich targets for biosensing applications due to their physiological implications as biomarkers of various aspects of human health and performance. Nucleic acid aptamers have been increasingly applied as recognition elements on biosensor platforms, but selecting aptamers toward small molecule targets requires special design considerations. This work describes modification and critical steps of a method designed to select structure-switching aptamers to small molecule targets. Binding sequences from a DNA library hybridized to complementary DNA capture probes on magnetic beads are separated from nonbinders via a target-induced change in conformation. This method is advantageous because sequences binding the support matrix (beads) will not be further amplified, and it does not require immobilization of the target molecule. However, the melting temperature of the capture probe and library is kept at or slightly above RT, such that sequences that dehybridize based on thermodynamics will also be present in the supernatant solution. This effectively limits the partitioning efficiency (ability to separate target binding sequences from nonbinders), and therefore many selection rounds will be required to remove background sequences. The reported method differs from previous structure-switching aptamer selections due to implementation of negative selection steps, simplified enrichment monitoring, and extension of the length of the capture probe following selection enrichment to provide enhanced stringency. The selected structure-switching aptamers are advantageous in a gold nanoparticle assay platform that reports the presence of a target molecule by the conformational change of the aptamer. The gold nanoparticle assay was applied because it provides a simple, rapid colorimetric readout that is beneficial in a clinical or deployed environment. Design and optimization considerations are presented for the assay as proof-of-principle work in buffer to provide a foundation for further extension of the work toward small molecule biosensing in physiological fluids.
Molecular Biology, Issue 96, Aptamer, structure-switching, SELEX, small molecule, cortisol, next generation sequencing, gold nanoparticle, assay