Name: a real-time electrical impedance based technique to measure invasion of endothelial cell monolayer by cancer cells
Uploaded: 2011-04-01T13:00:00
Duration: 8 min 51 s
Description: Watch this Scientific Journal Video about A Real-time Electrical Impedance Based Technique to Measure Invasion of Endothelial Cell Monolayer by Cancer Cells at JoVE.com

This work was generously supported by funds from Children's Cancer Foundation (Baltimore, MD), Brandon Carrington Lee Foundation (Silver Spring, MD), DOD (W81XWH-10-1-0137) and NIH (R01CA108641). 
We would like to thank Dr. Anton Wellstein and members of his laboratory for sharing their experience and helping us to optimize presented methods.

1. Preparation
<ol>
	<li>All steps should be performed under sterile conditions in a tissue culture hood.</li>
 <li>The xCELLigence station is placed in a 37&deg;C incubator in the presence of 5% CO2. </li>
 <li>Use low passage HUVEC cells, preferably no more than passage 6. Also, make sure that the cells are no more than 75% confluent at time of harvest. </li>
 <li>HUVEC cells are grown in EGM-2 media reconstituted with EGM-2 bullet kit (Lonza Biosciences) containing growth factors, supplements and 5% fetal bovine serum. </li>
 <li>All traces of trypsin should be removed from cell suspensions by spinning cells at 200xg, washing once with PBS, and resuspending them to indicated cell densities. </li>
 <li>Coat xCELLigence E-plate 16 with 0.1% gelatin for 1 hour at 37&deg;C or overnight at 4&deg;C. Wash plate with PBS and add 100&#x03BC;L reconstituted EGM-2 media. Perform a blank reading on the xCELLigence system to measure background impedance in the absence of cells. </li>
 
</ol>
2. Generating HUVEC monolayer 

<ol>
	<li>Harvest a sub-confluent flask of HUVEC cells by trypsinization. Resuspend cells in reconstituted EGM-2 media to a final density of 2.5 x 105 cells/ml. </li>
 <li>To each well of a background calibrated E-plate containing 100&#x03BC;L EGM-2 media, add 100&mu;L of the HUVEC cell suspension (2.5 x 104 HUVEC cells).</li>
 <li>Immediately install E-Plate in the xCELLigence instrument.</li>
 <li>Program xCELLigence software to perform impedance readings at 10 minute intervals. </li>
 <li>Let the endothelial cells grow for 18-21 hours until they form a monolayer, as evidenced by a flattening of cell index (Figure 2).</li>
</ol>

3. Addition of invading cells and data normalization.
<ol>
	<li>Once a stable HUVEC monolayer has formed, harvest tumor cells by trypsinization and resuspend to a final density of 1 x 105 cells/ml in media used to grow tumor cells (such as RPMI or DMEM media containing 10% FBS)</li>
 <li>Pause impedance readings on the xCELLigence software and remove E-Plate from the station. </li>
 <li>Remove EGM-2 media by aspiration. Add 100&#x03BC;L of tumor cell suspension containing 1 x 104 cells. Generally, a 1:2.5 ratio of tumor cells : endothelial cells seeded, works best for the assay. However, the ratio can be optimized for individual cell lines. </li>
 <li>Place the E-plate on the xCELLigence system in the incubator and continue impedance readings at 10 minute intervals. </li>
 <li>Invasion can be monitored in real-time over the next 6-12 hours as a drop in cell index due to the retraction of endothelial junctions and penetration by invading tumor cells. </li>
 <li>Normalize results to the time of addition of invading tumor cells. The xCELLigence software permits normalization to any time point and results can be directly viewed in the software window.</li>
</ol>
4. Representative Results: 
An example of HUVEC monolayer invasion by metastatic and non-metastatic cells is shown in Figure 3. K7M2 is a metastatic osteosarcoma cell line. These cells express high levels of the cytoskeletal linker protein ezrin, which accounts for the invasive properties of this cell line13,14. When HUVEC cells are challenged with K7M2 cells, there is a drop in electrical resistance within 6 hours. This drop in electrical resistance represents the invasion of HUVEC monolayer by the invading tumor cells. The K12 cell-line, on the other hand, expresses much lower levels of ezrin and is consequently less metastatic13. Challenging the HUVEC monolayer with K12 cells results in a less steep drop in resistance as the cells are unable to adhere to or invade through the HUVEC monolayer (Figure 3). 

<img src="/files/ftp_upload/2792/2792fig1.jpg" alt="Figure 1"/> 
Figure 1. Schematic diagram of work flow process for invasion of endothelial cells by tumor cells. HUVEC cells are plated on gelatin coated E-plates and allowed to form a confluent monolayer. Malignant cells are added once a monolayer has formed and invasion is monitored in real-time as the cell index changes due to invasion of the endothelial monolayer.

<img src="/files/ftp_upload/2792/2792fig2.jpg" alt="Figure 2"/> 
Figure 2. HUVEC monolayer formation. Changes in cell index as HUVEC cells attach to and spread on gelatin-coated gold electrodes. The formation of a confluent monolayer is represented by a stabilization of cell index after 18 hours. 

<img src="/files/ftp_upload/2792/2792fig3.jpg" alt="Figure 3"/> 
Figure 3. Invasion of HUVEC cells by K7M2 and K12 osteosarcoma cells. A steep decrease in cell-index occurs within a few hours of the introduction of highly metastatic K7M2 cells. K12 cells, on the other hand, are less metastatic and are unable to penetrate the endothelial monolayer as efficiently as K7M2 cells. This is represented by a less steep decrease in cell index when the HUVEC monolayer is challenged with K12 cells. Control represents impedance of HUVEC monolayer in the absence of cancer cells. Experiments were performed in triplicate.

<ol>
	<li>Klein, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer.+The+metastasis+cascade.">Cancer. The metastasis cascade.</a> Science. 321, 1785-1787 (2008).</li><li>Chiang, A. C., Massague, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+basis+of+metastasis.">Molecular basis of metastasis.</a> N Engl J Med. 359, 2814-2823 (2008).</li><li>Orr, F. W., Wang, H. H., Lafrenie, R. M., Scherbarth, S., Nance, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+between+cancer+cells+and+the+endothelium+in+metastasis.">Interactions between cancer cells and the endothelium in metastasis.</a> J Pathol. 190, 310-329 (2000).</li><li>Bacac, M., Stamenkovic, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metastatic+cancer+cell.">Metastatic cancer cell.</a> Annu Rev Pathol. 3, 221-247 (2008).</li><li>Christofori, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+signals+from+the+invasive+front.">New signals from the invasive front.</a> Nature. 441, 444-450 (2006).</li><li>Kramer, R. H., Nicolson, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+of+tumor+cells+with+vascular+endothelial+cell+monolayers:+a+model+for+metastatic+invasion.">Interactions of tumor cells with vascular endothelial cell monolayers: a model for metastatic invasion.</a> Proc Natl Acad Sci U S A. 76, 5704-5708 (1979).</li><li>Giaever, I., Keese, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+fibroblast+behavior+in+tissue+culture+with+an+applied+electric+field.">Monitoring fibroblast behavior in tissue culture with an applied electric field.</a> Proc Natl Acad Sci U S A. 81, 3761-3764 (1984).</li><li>Giaever, I., Keese, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromotion+of+mammalian+cells+measured+electrically.">Micromotion of mammalian cells measured electrically.</a> Proc Natl Acad Sci U S A. 88, 7896-7900 (1991).</li><li>Tiruppathi, C., Malik, A. B., Del Vecchio, P. J., Keese, C. R., Giaever, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+method+for+detection+of+endothelial+cell+shape+change+in+real+time:+assessment+of+endothelial+barrier+function.">Electrical method for detection of endothelial cell shape change in real time: assessment of endothelial barrier function.</a> Proc Natl Acad Sci U S A. 89, 7919-7923 (1992).</li><li>Whipple, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial-to-mesenchymal+transition+promotes+tubulin+Detyrosination+and+Microtentacles+that+enhance+endothelial+engagement.">Epithelial-to-mesenchymal transition promotes tubulin Detyrosination and Microtentacles that enhance endothelial engagement.</a> Cancer Res. 70, 8127-8137 (2010).</li><li>Boyd, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cell-microelectronic+sensing+technique+for+profiling+cytotoxicity+of+chemicals.">A cell-microelectronic sensing technique for profiling cytotoxicity of chemicals.</a> Anal Chim Acta. 615, 80-87 (2008).</li><li>Khanna, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+membrane-cytoskeleton+linker+ezrin+is+necessary+for+osteosarcoma+metastasis.">The membrane-cytoskeleton linker ezrin is necessary for osteosarcoma metastasis.</a> Nat Med. 10, 182-186 (2004).</li><li>Ren, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+actin-cytoskeleton+linker+protein+ezrin+is+regulated+during+osteosarcoma+metastasis+by+PKC.">The actin-cytoskeleton linker protein ezrin is regulated during osteosarcoma metastasis by PKC.</a> Oncogene. 28, 792-802 (2009).</li></ol>

The publication cost for this manuscript was kindly provided by Roche Applied Science.

The real-time HUVEC invasion assay is a simple, yet powerful method for monitoring invasion. It provides results in real-time, which is a significant advantage over other traditional techniques that rely on end-point analysis. The assay can be modified to test drugs, antibodies, ligands and proteins as inhibitors or stimulators of metastasis. The effect of different agents on endothelial/cancer cell cross-talk can be assessed as well. When introducing exogenous agents, such as growth factors and drugs in the culture media, it is important to ensure that they do not affect the integrity of the HUVEC monolayer. Disruption of the HUVEC monolayer can be tested by introducing the exogenous agent in the absence of invading cells, and ensuring that there is no change in cell index. Thus, appropriate controls should be included as part of the experimental design.
Different cell-lines demonstrate different cell-index curves as they form a confluent monolayer. The shape of the curve, as well as the maximum cell-index attained, is cell-type specific. HUVEC cells show a characteristic transient flattening of cell index 4-6 hours after seeding, followed by another stabilization at a higher cell index after 16-18 hours. Hence, it is important to let the cells form a confluent monolayer for at least 18 hours before the addition of tumor cells.
Since the cell index is dependent on the ionic environment at the electrode/cell interphase, various factors such as cell-morphology and quality of cell-cell adhesions influence the cell-index, in addition to the area of well bottom covered. Thus, the decrease in cell index, which occurs upon tumor cell invasion, is a function of several factors, which include the retraction of endothelial junctions and subsequent tumor cell invasion. 
The xCELLigence instrument is manufactured in three different configurations: real time cell analyzer (RTCA) SP, RTCA MP and RTCA DP. The RTCA SP instrument holds one 96-well E-plate whereas the RTCA MP instrument can hold up to six 96-well E-plates simultaneously. This allows for high-throughput screening of drugs and compounds. The experiments in this article are performed using the RTCA DP instrument, which can hold three 16-well E-plates. Each E-plate holding station can be independently operated, which allows multiple users to run experiments simultaneously. The RTCA DP instrument can also be used to study migration using CIM-plates. These are 16-well plates with upper and lower chambers separated by a polyethylene terephtalate (PET) membrane with a median pore size of 8um. The electronic sensors are located on the underside of the porous membrane of the upper chamber. The lower chamber serves as a reservoir for chemoattractant for cells in the upper chamber. However, a major advantage of the HUVEC invasion assay over the CIM-plates is that the tumor cell invasion in the former is not restricted by the pore size, as endothelial cell invasion depends on cross-talk between the tumor and endothelial cells. 
The HUVEC invasion assay can also be performed on ECIS Z instrument, manufactured by Applied Biophysics (Troy, NY). The ECIS Z instrument utilizes a technology similar to the xCELLigence instrument, with differences in the array and electrode configurations. We have successfully performed HUVEC invasion assays using the 8-well ECIS arrays. It is important to note that the well-bottom surface area is larger in the ECIS arrays, which requires a larger number of endothelial and tumor cells to be plated: 2.5 x 105and 1 x 105 cells respectively.

<table border="1">
	<tbody>
 <tr>
 	<th>Name of the reagent</th>
 <th>Company</th>
 <th>Catalogue number</th>
 <th>Comments (optional)</th>
 </tr> 
 <tr>
 	<td>xCELLigence RTCA DP station</td>
 <td>Roche	</td>
 <td>05469759001</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 	<td>RTCA control unit</td>
 <td>Roche</td>
 <td>05454417001</td>
 <td>Notebook with preinstalled RTCA software</td>
 </tr>
 <tr>
 	<td>E-Plate 16</td>
 <td>Roche</td>
 <td>05469830001</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 	<td>HUVEC cells</td>
 <td>Lonza</td>
 <td>CC-2517</td>
 <td></td>
 </tr>
 <tr>
 	<td>EGM-2 media</td>
 <td>Lonza</td>
 <td>CC-3156</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 	<td>EGM-2 bullet kit</td>
 <td>Lonza</td>
 <td>CC-4176</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 	<td>0.1% Gelatin in 
sterile H2O
</td>
 <td>Millipore</td>
 <td>MCPROTO045</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

a real-time electrical impedance based technique to measure invasion of endothelial cell monolayer by cancer cells

Metastatic dissemination of malignant cells requires degradation of basement membrane, attachment of tumor cells to vascular endothelium, retraction of endothelial junctions and finally invasion and migration of tumor cells through the endothelial layer to enter the bloodstream as a means of transport to distant sites in the host1-3. Once in the circulatory system, cancer cells adhere to capillary walls and extravasate to the surrounding tissue to form metastatic tumors4,5. The various components of tumor cell-endothelial cell interaction can be replicated in vitro by challenging a monolayer of human umbilical vein endothelial cells (HUVEC) with cancer cells. Studies performed with electron and phase-contrast microscopy suggest that the in vitro sequence of events fairly represent the in vivo metastatic process6. Here, we describe an electrical-impedance based technique that monitors and quantifies in real-time the invasion of endothelial cells by malignant tumor cells.
Giaever and Keese first described a technique for measuring fluctuations in impedance when a population of cells grow on the surface of electrodes7,8. The xCELLigence instrument, manufactured by Roche, utilizes a similar technique to measure changes in electrical impedance as cells attach and spread in a culture dish covered with a gold microelectrode array that covers approximately 80% of the area on the bottom of a well. As cells attach and spread on the electrode surface, it leads to an increase in electrical impedance9-12. The impedance is displayed as a dimensionless parameter termed cell-index, which is directly proportional to the total area of tissue-culture well that is covered by cells. Hence, the cell-index can be used to monitor cell adhesion, spreading, morphology and cell density.
The invasion assay described in this article is based on changes in electrical impedance at the electrode/cell interphase, as a population of malignant cells invade through a HUVEC monolayer (Figure 1). The disruption of endothelial junctions, retraction of endothelial monolayer and replacement by tumor cells lead to large changes in impedance. These changes directly correlate with the invasive capacity of tumor cells, i.e., invasion by highly aggressive cells lead to large changes in cell impedance and vice versa. This technique provides a two-fold advantage over existing methods of measuring invasion, such as boyden chamber and matrigel assays: 1) the endothelial cell-tumor cell interaction more closely mimics the in vivo process, and 2) the data is obtained in real-time and is more easily quantifiable, as opposed to end-point analysis for other methods.

Watch this Scientific Journal Video about A Real-time Electrical Impedance Based Technique to Measure Invasion of Endothelial Cell Monolayer by Cancer Cells at JoVE.com

A Real-time Electrical Impedance Based Technique to Measure Invasion of Endothelial Cell Monolayer by Cancer Cells

This article describes an in vitro technique for monitoring cancer cells invading through a monolayer of endothelial cells. The data is acquired in real-time as a function of changes in impedance on the surface of electrodes at the well bottom.

Metastatic dissemination of malignant cells requires degradation of basement membrane, attachment of tumor cells to vascular endothelium, retraction of ...

a-real-time-electrical-impedance-based-technique-to-measure-invasion

Research

JoVE Journal

Medicine

Evaluation of Nanoparticle Uptake in Tumors in Real Time Using Intravital Imaging

Current technologies for tumor imaging, such as ultrasound, MRI, PET and CT, are unable to yield high-resolution images for the assessment of nanoparticle uptake in tumors at the microscopic level1,2,3, highlighting the utility of a suitable xenograft model in which to perform detailed uptake analyses. Here, we use high-resolution intravital imaging to evaluate nanoparticle uptake in human tumor xenografts in a modified, shell-less chicken embryo model. The chicken embryo model is particularly well-suited for these in vivo analyses because it supports the growth of human tumors, is relatively inexpensive and does not require anesthetization or surgery 4,5. Tumor cells form fully vascularized xenografts within 7 days when implanted into the chorioallantoic membrane (CAM) 6. The resulting tumors are visualized by non-invasive real-time, high-resolution imaging that can be maintained for up to 72 hours with little impact on either the host or tumor systems. Nanoparticles with a wide range of sizes and formulations administered distal to the tumor can be visualized and quantified as they flow through the bloodstream, extravasate from leaky tumor vasculature, and accumulate at the tumor site. We describe here the analysis of nanoparticles derived from Cowpea mosaic virus (CPMV) decorated with near-infrared fluorescent dyes and/or polyethylene glycol polymers (PEG) 7, 8, 9,10,11. Upon intravenous administration, these viral nanoparticles are rapidly internalized by endothelial cells, resulting in global labeling of the vasculature both outside and within the tumor7,12. PEGylation of the viral nanoparticles increases their plasma half-life, extends their time in the circulation, and ultimately enhances their accumulation in tumors via the enhanced permeability and retention (EPR) effect 7, 10,11. The rate and extent of accumulation of nanoparticles in a tumor is measured over time using image analysis software. This technique provides a method to both visualize and quantify nanoparticle dynamics in human tumors.

We present a novel approach to quantify nanoparticle localization in the vasculature of human xenografted tumors using dynamic, real-time intravital imaging in an avian embryo model.

Current technologies for tumor imaging, such as ultrasound, MRI, PET and CT, are unable to yield high-resolution images for the assessment of nanoparticle ...

Multi-photon Imaging of Tumor Cell Invasion in an Orthotopic Mouse Model of Oral Squamous Cell Carcinoma

Loco-regional invasion of head and neck cancer is linked to metastatic risk and presents a difficult challenge in designing and implementing patient management strategies. Orthotopic mouse models of oral cancer have been developed to facilitate the study of factors that impact invasion and serve as model system for evaluating anti-tumor therapeutics. In these systems, visualization of disseminated tumor cells within oral cavity tissues has typically been conducted by either conventional histology or with in vivo bioluminescent methods. A primary drawback of these techniques is the inherent inability to accurately visualize and quantify early tumor cell invasion arising from the primary site in three dimensions. Here we describe a protocol that combines an established model for squamous cell carcinoma of the tongue (SCOT) with two-photon imaging to allow multi-vectorial visualization of lingual tumor spread. The OSC-19 head and neck tumor cell line was stably engineered to express the F-actin binding peptide LifeAct fused to the mCherry fluorescent protein (LifeAct-mCherry). Fox1nu/nu mice injected with these cells reliably form tumors that allow the tongue to be visualized by ex-vivo application of two-photon microscopy. This technique allows for the orthotopic visualization of the tumor mass and locally invading cells in excised tongues without disruption of the regional tumor microenvironment. In addition, this system allows for the quantification of tumor cell invasion by calculating distances that invaded cells move from the primary tumor site. Overall this procedure provides an enhanced model system for analyzing factors that contribute to SCOT invasion and therapeutic treatments tailored to prevent local invasion and distant metastatic spread. This method also has the potential to be ultimately combined with other imaging modalities in an in vivo setting.

A comprehensive overview of the techniques involved in generating a mouse model of oral cancer and quantitative monitoring of tumor invasion within the tongue through multi-photon microscopy of labeled cells is presented. This system can serve as a useful platform for the molecular assessment and drug efficacy of anti-invasive compounds.

Loco-regional invasion of head and neck cancer is linked to metastatic risk and presents a difficult challenge in designing and implementing patient ...

Spheroid Assay to Measure TGF-&#946;-induced Invasion

TGF-&beta; has opposing roles in breast cancer progression by acting as a tumor suppressor in the initial phase, but stimulating invasion and metastasis at later stage1,2. Moreover, TGF-&beta; is frequently overexpressed in breast cancer and its expression correlates with poor prognosis and metastasis 3,4. The mechanisms by which TGF-&beta; induces invasion are not well understood.
TGF-&beta; elicits its cellular responses via TGF-&beta; type II (T&beta;RII) and type I (T&beta;RI) receptors. Upon TGF-&beta;-induced heteromeric complex formation, T&beta;RII phosphorylates the T&beta;RI. The activated T&beta;RI initiates its intracellular canonical signaling pathway by phosphorylating receptor Smads (R-Smads), i.e. Smad2 and Smad3. These activated R-Smads form heteromeric complexes with Smad4, which accumulate in the nucleus and regulate the transcription of target genes5. In addition to the previously described Smad pathway, receptor activation results in activation of several other non-Smad signaling pathways, for example Mitogen Activated Protein Kinase (MAPK) pathways6.
To study the role of TGF-&beta; in different stages of breast cancer, we made use of the MCF10A cell system. This system consists of spontaneously immortalized MCF10A1 (M1) breast epithelial cells7, the H-RAS transformed M1-derivative MCF10AneoT (M2), which produces premalignant lesions in mice8, and the M2-derivative MCF10CA1a (M4), which was established from M2 xenografts and forms high grade carcinomas with the ability to metastasize to the lung9. This MCF10A series offers the possibility to study the responses of cells with different grades of malignancy that are not biased by a different genetic background.
For the analysis of TGF-&beta;-induced invasion, we generated homotypic MCF10A spheroid cell cultures embedded in a 3D collagen matrix in vitro (Fig 1). Such models closely resemble human tumors in vivo by establishing a gradient of oxygen and nutrients, resulting in active and invasive cells on the outside and quiescent or even necrotic cells in the inside of the spheroid10. Spheroid based assays have also been shown to better recapitulate drug resistance than monolayer cultures11. This MCF10 3D model system allowed us to investigate the impact of TGF-&beta; signaling on the invasive properties of breast cells in different stages of malignancy.

Spheroid Assay to Measure TGF-&amp;#946;-induced Invasion

An assay to quantitatively measure Transforming Growth Factor (TGF)-&#x03B2;-induced invasion in 3-dimensional collagen gels is described. This assay takes advantage of the MCF10A series of cell lines, which represent different stages of breast cancer development. This method can be adopted to be used with other cell lines and might be used to investigate other potential activators or inhibitors of invasion.

TGF-&beta; has opposing roles in breast cancer progression by acting as a tumor suppressor in the initial phase, but stimulating invasion and metastasis ...

Modeling and Imaging 3-Dimensional Collective Cell Invasion

A defining characteristic of cancer malignancy is invasion and metastasis 1. In some cancers (e.g. glioma 2), local invasion into surrounding healthy tissue is the root cause of disease and death. For other cancers (e.g. breast, lung, etc.), it is the process of metastasis, in which tumor cells move from a primary tumor mass, colonize distal sites and ultimately contribute to organ failure, that eventually leads to morbidity and mortality 3. It has been estimated that invasion and metastasis are responsible for 90&#37; of cancer deaths 4. As a result, there has been intense interest in identifying the molecular processes and critical protein mediators of invasion and metastasis for the purposes of improving diagnosis and treatment 5.
A challenge for cancer scientists is to develop invasion assays that sufficiently resemble the in vivo situation to enable accurate disease modeling 6. Two-dimensional cell motility assays are only informative about one aspect of invasion and do not take into account extracellular matrix (ECM) protein remodeling which is also a critical element. Recently, research has refined our understanding of tumor cell invasion and revealed that individual cells may move by elongated or rounded modes 7. In addition, there has been greater appreciation of the contribution of collective invasion, in which cells invade in strands, sheets and clusters, particularly in highly differentiated tumors that maintain epithelial characteristics, to the spread of cancer 8.
We present a refined method 9 for examining the contributions of candidate proteins to collective invasion 10. In particular, by engineering separate pools of cells to express different fluorescent proteins, it is possible to molecularly dissect the activities and proteins required in leading cells versus those required in following cells. The use of RNAi provides the molecular tool to experimentally disassemble the processes involved in individual cell invasion as well as in different positions of collective invasion. In this procedure, mixtures of fluorescently-labeled cells are plated on the bottom of a Transwell insert previously filled with Matrigel ECM protein, then allowed to invade "upwards" through the filter and into the Matrigel. Reconstruction of z-series image stacks, obtained by confocal imaging, into three-dimensional representations allows for visualization of collectively invading strands and analysis of the representation of fluorescently-labeled cells in leading versus following positions.

Models of tumor cell invasion into three-dimensional extracellular matrix better reflect the in vivo situation than two-dimensional motility assays. Using matrix invasion assays combined with confocal imaging of fluorescently-labeled cells, detailed information on invasion modes and the distinct contributions of leading versus following cells can be obtained.

A defining characteristic of cancer malignancy is invasion and metastasis 1. In some cancers (e.g. glioma 2), local invasion into surrounding healthy ...

MicroRNA Detection in Prostate Tumors by Quantitative Real-time PCR (qPCR)

MicroRNAs (miRNAs) are single-stranded, 18&#x2013;24 nucleotide long, non-coding RNA molecules. They are involved in virtually every cellular process including development1, apoptosis2, and cell cycle regulation3. MiRNAs are estimated to regulate the expression of 30% to 90% of human genes4 by binding to their target messenger RNAs (mRNAs)5. Widespread dysregulation of miRNAs has been reported in various diseases and cancer subtypes6. Due to their prevalence and unique structure, these small molecules are likely to be the next generation of biomarkers, therapeutic agents and/or targets.
Methods used to investigate miRNA expression include SYBR green I dye- based as well as Taqman-probe based qPCR. If miRNAs are to be effectively used in the clinical setting, it is imperative that their detection in fresh and/or archived clinical samples be accurate, reproducible, and specific. qPCR has been widely used for validating expression of miRNAs in whole genome analyses such as microarray studies7. The samples used in this protocol were from patients who underwent radical prostatectomy for clinically localized prostate cancer; however other tissues and cell lines can be substituted in. Prostate specimens were snap-frozen in liquid nitrogen after resection. Clinical variables and follow-up information for each patient were collected for subsequent analysis8.
Quantification of miRNA levels in prostate tumor samples. The main steps in qPCR analysis of tumors are: Total RNA extraction, cDNA synthesis, and detection of qPCR products using miRNA-specific primers. Total RNA, which includes mRNA, miRNA, and other small RNAs were extracted from specimens using TRIzol reagent. Qiagen's miScript System was used to synthesize cDNA and perform qPCR (Figure 1). Endogenous miRNAs are not polyadenylated, therefore during the reverse transcription process, a poly(A) polymerase polyadenylates the miRNA. The miRNA is used as a template to synthesize cDNA using oligo-dT and Reverse Transcriptase. A universal tag sequence on the 5' end of oligo-dT primers facilitates the amplification of cDNA in the PCR step. PCR product amplification is detected by the level of fluorescence emitted by SYBR Green, a dye which intercalates into double stranded DNA. Specific miRNA primers, along with a Universal Primer that binds to the universal tag sequence will amplify specific miRNA sequences. 
The miScript Primer Assays are available for over a thousand human-specific miRNAs, and hundreds of murine-specific miRNAs. Relative quantification method was used here to quantify the expression of miRNAs. To correct for variability amongst different samples, expression levels of a target miRNA is normalized to the expression levels of a reference gene. The choice of a gene on which to normalize the expression of targets is critical in relative quantification method of analysis. Examples of reference genes typically used in this capacity are the small RNAs RNU6B, RNU44, and RNU48 as they are considered to be stably expressed across most samples. In this protocol, RNU6B is used as the reference gene.

MicroRNA Detection in Prostate Tumors by Quantitative Real-time PCR qPCR

Quantitative Real Time polymerase chain reaction (qPCR) is a rapid and sensitive method to investigate the expression levels of various microRNA (miRNA) molecules in tumor samples. Using this method expression of hundreds of different miRNA molecules can be amplified, quantified, and analyzed from the same cDNA template.

MicroRNAs (miRNAs) are single-stranded, 18&#x2013;24 nucleotide long, non-coding RNA molecules. They are involved in virtually every cellular process ...

A Multiplexed Luciferase-based Screening Platform for Interrogating Cancer-associated Signal Transduction in Cultured Cells

Genome-scale interrogation of gene function using RNA interference (RNAi) holds tremendous promise for the rapid identification of chemically tractable cancer cell vulnerabilities. Limiting the potential of this technology is the inability to rapidly delineate the mechanistic basis of phenotypic outcomes and thus inform the development of molecularly targeted therapeutic strategies. We outline here methods to deconstruct cellular phenotypes induced by RNAi-mediated gene targeting using multiplexed reporter systems that allow monitoring of key cancer cell-associated processes. This high-content screening methodology is versatile and can be readily adapted for the screening of other types of large molecular libraries.

Achieving a systems level understanding of cellular processes is a goal of modern-day cell biology. We describe here strategies for multiplexing luciferase reporters of various cellular function end-points to interrogate gene function using genome-scale RNAi libraries.

Genome-scale interrogation of gene function using RNA interference (RNAi)  holds tremendous promise for the rapid identification of chemically tractable  ...

Cerebrospinal Fluid MicroRNA Profiling Using Quantitative Real Time PCR

MicroRNAs (miRNAs) constitute a potent layer of gene regulation by guiding RISC to target sites located on mRNAs and, consequently, by modulating their translational repression. Changes in miRNA expression have been shown to be involved in the development of all major complex diseases. Furthermore, recent findings showed that miRNAs can be secreted to the extracellular environment and enter the bloodstream and other body fluids where they can circulate with high stability. The function of such circulating miRNAs remains largely elusive, but systematic high throughput approaches, such as miRNA profiling arrays, have lead to the identification of miRNA signatures in several pathological conditions, including neurodegenerative disorders and several types of cancers. In this context, the identification of miRNA expression profile in the cerebrospinal fluid, as reported in our recent study, makes miRNAs attractive candidates for biomarker analysis.
There are several tools available for profiling microRNAs, such as microarrays, quantitative real-time PCR (qPCR), and deep sequencing. Here, we describe a sensitive method to profile microRNAs in cerebrospinal fluids by quantitative real-time PCR. We used the Exiqon microRNA ready-to-use PCR human panels I and II V2.R, which allows detection of 742 unique human microRNAs. We performed the arrays in triplicate runs and we processed and analyzed data using the GenEx Professional 5 software.
Using this protocol, we have successfully profiled microRNAs in various types of cell lines and primary cells, CSF, plasma, and formalin-fixed paraffin-embedded tissues.

We describe a protocol of real time PCR to profile microRNAs in the cerebrospinal fluid (CSF). With the exception of RNA extraction protocols, the procedure can be extended to RNA extracted from other body fluids, cultured cells, or tissue specimens.

MicroRNAs (miRNAs) constitute a potent layer of gene regulation by guiding RISC to target sites located on mRNAs and, consequently, by modulating their ...

A Modified In vitro Invasion Assay to Determine the Potential Role of Hormones, Cytokines and/or Growth Factors in Mediating Cancer Cell Invasion

Blood serum serves as a chemoattractant towards which cancer cells migrate and invade, facilitating their intravasation into microvessels. However, the actual molecules towards which the cells migrate remain elusive. This modified invasion assay has been developed to identify targets which drive cell migration and invasion. This technique compares the invasion index under three conditions to determine whether a specific hormone, growth factor, or cytokine plays a role in mediating the invasive potential of a cancer cell. These conditions include i) normal fetal bovine serum (FBS), ii) charcoal-stripped FBS (CS-FBS), which removes hormones, growth factors, and cytokines and iii) CS-FBS + molecule (denoted &#8220;X&#8221;). A significant change in cell invasion with CS-FBS as compared to FBS, indicates the involvement of hormones, cytokines or growth factors in mediating the change. Individual molecules can then be added back to CS-FBS to assay their ability to reverse or rescue the invasion phenotype. Furthermore, two or more factors can be combined to evaluate the additive or synergistic effects of multiple molecules in driving or inhibiting invasion. Overall, this method enables the investigator to determine whether hormones, cytokines, and/or growth factors play a role in cell invasion by serving as chemoattractants or inhibitors of invasion for a particular type of cancer cell or a specific mutant. By identifying specific chemoattractants and inhibitors, this modified invasion assay may help to elucidate signaling pathways that direct cancer cell invasion.

A Modified In vitro Invasion Assay to Determine the Potential Role of Hormones, Cytokines and/or Growth Factors in Mediating Cancer Cell Invasion

This video article describes a modified in vitro method to examine the role of hormones, cytokines and/or growth factors in driving cancer cell invasion.

Blood serum serves as a chemoattractant towards which cancer cells migrate and invade, facilitating their intravasation into microvessels. However, the ...

Assessment of Ovarian Cancer Spheroid Attachment and Invasion of Mesothelial Cells in Real Time

Ovarian cancers metastasize by shedding into the peritoneal fluid and dispersing to distal sites within the peritoneum. Monolayer cultures do not accurately model the behaviors of cancer cells within a nonadherent environment, as cancer cells inherently aggregate into multicellular structures which contribute to the metastatic process by attaching to and invading the peritoneal lining to form secondary tumors. To model this important stage of ovarian cancer metastasis, multicellular aggregates, or spheroids, can be generated from established ovarian cancer cell lines maintained under nonadherent conditions. To mimic the peritoneal microenvironment encountered by tumor cells in vivo, a spheroid-mesothelial co-culture model was established in which preformed spheroids are plated on top of a human mesothelial cell monolayer, formed over an extracellular matrix barrier. Methods were then developed using a real-time cell analyzer to conduct quantitative real time measurements of the invasive capacity of different ovarian cancer cell lines grown as spheroids. This approach allows for the continuous measurement of invasion over long periods of time, which has several advantages over traditional endpoint assays and more laborious real time microscopy image analyses. In short, this method enables a rapid, determination of factors which regulate the interactions between ovarian cancer spheroid cells invading through mesothelial and matrix barriers over time.

Ovarian cancer cell invasion into the mesothelial lining of the peritoneum is a dynamic process over time. Utilizing a real time analyzer, the invasive capacity of ovarian cancer cells in a spheroid-mesothelial cell co-culture model can be quantified over prolonged time periods, providing insights into factors regulating the metastatic process.

Ovarian cancers metastasize by shedding into the peritoneal fluid and dispersing to distal sites within the peritoneum. Monolayer cultures do not ...

Three-Dimensional (3D) Tumor Spheroid Invasion Assay

Invasion of surrounding normal tissues is generally considered to be a key hallmark of malignant (as opposed to benign) tumors. For some cancers in particular (e.g., brain tumors such as glioblastoma multiforme and squamous cell carcinoma of the head and neck &#8211; SCCHN) it is a cause of severe morbidity and can be life-threatening even in the absence of distant metastases. In addition, cancers which have relapsed following treatment unfortunately often present with a more aggressive phenotype. Therefore, there is an opportunity to target the process of invasion to provide novel therapies that could be complementary to standard anti-proliferative agents. Until now, this strategy has been hampered by the lack of robust, reproducible assays suitable for a detailed analysis of invasion and for drug screening. Here we provide a simple micro-plate method (based on uniform, self-assembling 3D tumor spheroids) which has great potential for such studies. We exemplify the assay platform using a human glioblastoma cell line and also an SCCHN model where the development of resistance against targeted epidermal growth factor receptor (EGFR) inhibitors is associated with enhanced matrix-invasive potential. We also provide two alternative methods of semi-automated quantification: one using an imaging cytometer and a second which simply requires standard microscopy and image capture with digital image analysis.

Three-Dimensional 3D Tumor Spheroid Invasion Assay

Invasion of surrounding normal tissues is a defining characteristic of malignant tumors. We provide here a simple, semi-automated micro-plate assay of invasion into a natural 3D biomatrix that has been exemplified with a number of models of advanced human cancers.

Invasion of surrounding normal tissues is generally considered to be a key hallmark of malignant (as opposed to benign) tumors. For some cancers in ...