This work was supported by the National Institutes of Health (NIMHD-G12MD007581) through the RCMI-Center for Environmental Health at Jackson State University and the U.S. Department of Defense, Idea Award 11-1-0205.

NOTE: This protocol is described in McArdle et al.11. A timeline is provided in Figure 1.
1. Preparation of the culture plate
<ol>
	<li>Wash the 35-mm culture dish containing a 10-mm glass-bottom well with 1 mL of 1 M hydrochloric acid (HCl) for 15 min to lower the hydrophobicity of the glass-bottom.</li>
	<li>Wash the culture plate twice with 1 mL of phosphate buffer saline (PBS) to get rid of all the HCl.</li>
	<li>Wash the culture plate twice with 1 mL of 70% ethanol.</li>
	<li>Rinse the culture plate with 1 mL of the cell specific culture medium (here, use &#945;-MEM supplemented with 10% heat inactivated FBS and 1% non-essential amino acids). 
	Note: The treated culture plate containing the culture medium can be stored in the CO2 incubator with a humidifier at 37 &#176;C until the next day.</li>
	<li>Grow the cells (MSCs and MCF-7 co-culture) in the treated glass-bottom well of the 35-mm culture dish to 100% confluency. Co-culture 35,000 MSC cells and 75,000 of MCF7 cells for 24 h.</li>
</ol>
2. Preparation of the collagen gel
<ol>
	<li>Store the micropipette tips used for pipetting the collagen gel in the freezer to prevent the polymerization of the collagen upon contact. 
	Note: This is the most critical step.</li>
	<li>Determine a volume of rat tail collagen I to be used based on the concentration of the collagen stock. Prepare 100 &#181;L of collagen gel for this assay. 
	Note: High concentration of rat tail collagen I stock works better. Determine the volume of 10x Dulbecco&#39;s Modified Eagle&#39;s Medium to be used to dilute the collagen accordingly.</li>
	<li>Combine on ice rat tail collagen I (3.8 &#181;g/mL stock), 10x Dulbecco&#39;s Modified Eagle&#39;s Medium and 1x cell culture medium supplemented with 2% fetal bovine serum and the appropriate chemoattractant to a final concentration of collagen of 2.4 mg/mL.</li>
	<li>Add to the mixture 4.5% of sodium bicarbonate solution to neutralize the collagen gel. 
	Note: The volume of sodium bicarbonate solution added may vary based on the exact pH of the other reagents. It is best to test the mixture with pH strips to ensure neutral solution, or use a pH indicator in the culture medium.</li>
	<li>Lay 80 &#181;L of the collagen mixture over the cells within the glass-bottom well of the culture dish.</li>
	<li>Allow the collagen gel to polymerize for 30 min in a CO2 incubator with a humidifier at 37 &#176;C.</li>
	<li>Cover the collagen gel with 2 mL of cell medium with reduced serum (2%) and incubate the cells at 37 &#176;C in a CO2 incubator with a humidifier for 24, 48, or 72 h. 
	Caution: The plate should be handled with care to prevent the collagen gel from detaching from the glass bottom.</li>
</ol>
3. Example of preparation of collagen gel using a rat tail collagen stock of 3.8 &#181;g /mL
<ol>
	<li>On ice, combine 114.5 &#181;L of rat tail collagen, 16.6 &#181;L of 10x DMEM, and 33.1 &#181;L of culture medium containing the chemoattractant.</li>
	<li>Neutralize the collagen mixture with 14.0 &#181;L of sodium bicarbonate.</li>
	<li>Continue as in step 2.5.</li>
</ol>
4. Imaging of the cells
<ol>
	<li>Gently remove the media from the dish.</li>
	<li>Gently rinse the gel with 1 mL of PBS.</li>
	<li>Fix the cells with 1 mL of 4% paraformaldehyde for 15 min.</li>
	<li>Wash the cells twice with 1 mL of PBS.</li>
	<li>Stain the cells with DAPI solution (100 ng/mL) for 20 min at room temperature.</li>
	<li>Image the cells using a confocal microscope at different locations and taking 400 &#181;m z-stack images of each location in 16 &#181;m steps. The microscope used has a disk scanning unit that enables confocal imaging using a white light, arc excitation source. Use a 20X lens utilized with numerical aperture of 0.75.</li>
	<li>Reconstitute images .
	<ol>
		<li>Open images for a given gel (approximately 25 images) and create an image stack by clicking image &#8594; stacks &#8594;&#160;images to stack. The first image corresponded to the bottom of the gel (z = 0 &#181;m), the second image corresponded to the first step in the z direction (z = 16 &#181;m), the third image corresponded to the second step in the z direction (z = 32 &#181;m). Assess each nucleus at each image depth and designate the depth at which the nucleus was in sharpest focus as the invasion depth for that particular cell.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Friedl, P., Brocker, E. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biology+of+cell+locomotion+within+three-dimensional+extracellular+matric.">The biology of cell locomotion within three-dimensional extracellular matric.</a> Cell Mol Life Sci. 57, 41-64 (2000).</li><li>Bissell, M. J., Rizki, A., Mian, I. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+architecture:+the+ultimate+regulator+of+breast+epithelial+function.">Tissue architecture: the ultimate regulator of breast epithelial function.</a> Curr Opin Cell Biol. 15, 753-762 (2003).</li><li>Friedl, P., Wolf, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumour-cell+invasion+and+migration:+diversity+and+escape+mechanisms.">Tumour-cell invasion and migration: diversity and escape mechanisms.</a> Nat Rev Cancer. 3, 362-374 (2003).</li><li>Yarrow, J. C., Perlman, Z. E., Westwood, N. J., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+cell+migration+assay+using+scratch+wound+healing,+a+comparison+of+image-based+readout+methods.">A high-throughput cell migration assay using scratch wound healing, a comparison of image-based readout methods.</a> BMC Biotechnol. 4, 21 (2004).</li><li>Wolf, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compensation+mechanism+in+tumor+cell+migration:+mesenchymal-amoeboid+transition+after+blocking+of+pericellular+proteolysis.">Compensation mechanism in tumor cell migration: mesenchymal-amoeboid transition after blocking of pericellular proteolysis.</a> J Cell Biol. 160, 267-277 (2003).</li><li>Sahai, E., Marshall, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differing+modes+of+tumour+cell+invasion+have+distinct+requirements+for+Rho/ROCK+signalling+and+extracellular+proteolysis.">Differing modes of tumour cell invasion have distinct requirements for Rho/ROCK signalling and extracellular proteolysis.</a> Nat Cell Biol. 5, 711-719 (2003).</li><li>Kam, Y., Guess, C., Estrada, L., Weidow, B., Quaranta, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+circular+invasion+assay+mimics+in+vivo+invasive+behavior+of+cancer+cell+lines+and+distinguishes+single-cell+motility+in+vitro.">A novel circular invasion assay mimics in vivo invasive behavior of cancer cell lines and distinguishes single-cell motility in vitro.</a> BMC Cancer. 8, 198 (2008).</li><li>Staton, C. A., Reed, M. W., Brown, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+analysis+of+current+in+vitro+and+in+vivo+angiogenesis+assays.">A critical analysis of current in vitro and in vivo angiogenesis assays.</a> Int J Exp Pathol. 90, 195-221 (2009).</li><li>Poujade, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collective+migration+of+an+epithelial+monolayer+in+response+to+a+model+wound.">Collective migration of an epithelial monolayer in response to a model wound.</a> Proc Natl Acad Sci USA. 104, 15988-15993 (2007).</li><li>Noubissi, F. K., Harkness, T., Alexander, C. M., Ogle, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis-induced+cancer+cell+fusion:+a+mechanism+of+breast+cancer+metastasis.">Apoptosis-induced cancer cell fusion: a mechanism of breast cancer metastasis.</a> FASEB J. 29, 4036-4045 (2015).</li><li>McArdle, T. J., Ogle, B. M., Noubissi, F. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+In+Vitro+Inverted+Vertical+Invasion+Assay+to+Avoid+Manipulation+of+Rare+or+Sensitive+Cell+Types.">An In Vitro Inverted Vertical Invasion Assay to Avoid Manipulation of Rare or Sensitive Cell Types.</a> J Cancer. 7, 2333-2340 (2016).</li><li>Noubissi, F. K., Ogle, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+Cell+Fusion:+Mechanisms+Slowly+Unravel.">Cancer Cell Fusion: Mechanisms Slowly Unravel.</a> Int J Mol Sci. 17, (2016).</li><li>Meyvantsson, I., Beebe, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+culture+models+in+microfluidic+systems.">Cell culture models in microfluidic systems.</a> Annu Rev Anal Chem. 1, 423-449 (2008).</li><li>Hooper, S., Marshall, J. F., Sahai, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+cell+migration+in+three+dimensions.">Tumor cell migration in three dimensions.</a> Methods In Enzymol. 406, 625-643 (2006).</li><li>Yang, C., Tibbitt, M. W., Basta, L., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+memory+and+dosing+influence+stem+cell+fate.">Mechanical memory and dosing influence stem cell fate.</a> Nat Materials. 13, 645-652 (2014).</li></ol>

The authors have declared that no competing interest exists.

Here, we describe a simple inverted vertical invasion assay which is convenient for a variety of cell types including cells that are rare and/or dependent on their microenvironment. In this 3D invasion assay, cells remain in their original microenvironment and are covered by the collagen gel containing a chemoattractant. The cells then migrate and invade in the collagen. In this assay, the cells can be stained and easily monitored within the gel. The simplicity and reproducibility of this assay makes it a convenient tool...

Cell motility is a normal developmental and physiological process of cells. However, changes in the pattern and the ability of cells to migrate and invade are associated with pathological conditions including inflammatory diseases and cancer metastasis1,2,3. Metastasis is arguably the most poorly understood aspect in cancer. To metastasize, cancer cells must degrade the extra cellular matrix (ECM), invade the local tissue and intravasate. Once in circulation, the cancer cells will disseminate to the distant site, extravasate and form secondary tumors. Therefore, the ability of cells to degrade the ECM, to migrate, and to invade is related to their metastatic potential. Different approaches have been developed to analyze and quantify the migration and invasion capabilities of cells. The most used approaches include the wound healing assay, time-lapse microscopy, and the Boyden chamber assay. The wound healing assay4 and time lapse microscopy are simple and convenient assays that would give preliminary insight into cell migration. However, both are 2D assays that do not reflect the 3D environment in which cells exist in vivo. Studies have shown that cells respond differently to a 3D environment compared to a 2D one5,6. Moreover, wound healing assays are difficult to reproduce and to yield quantitative results7,8,9. The Cell Exclusion Zone assay, which is a 3D modification of the wound healing assay, is a more physiologically relevant assay but it is not suitable for cells low in number such as hybrid cells resulting from cell fusion events10,11.
The Boyden chamber assay is a 3-dimensional assay that provides relevant microenvironments for cellular studies. However, it requires cells to be removed from their original microenvironment and to be deposited into the upper chamber of the Boyden assay system to migrate and invade downwards toward the chemoattractant containing medium. This 3D approach is not appropriate in analyzing the migration and invasion capability of cells vulnerable to their microenvironment and/or limited in number10,11,12. A newer approach to analyze cell migration and invasion is the microfluidic gradient chamber assay13. Although suitable and reliable in migration and invasion studies, this assay is more expensive and could be technically challenging for a typical laboratory. We describe here a simple inverted vertical invasion assay that is compatible with many cell types including cells sensitive to their microenvironment and/or restricted in number. This assay was adapted from the protocol proposed by Hooper et al.14. In this assay, the cells remain in their original microenvironment and their migration and invasion is monitored as they move upwards in the collagen gel containing a chemoattractant11. This assay is reproducible and has been optimized and validated in the 35-mm culture dish. It could be adapted to different assay conditions including different cell culture sizes, different matrices or strength of adhesion, and different chemoattractants. This assay could serve as an in vitro platform for initial screening in the drug discovery process.

<table><tbody><tr><td>MatTek P35G-1.5-10C</td><td>MatTek Corporation, Ashland, MA</td><td>P35G-1.5-10-C</td><td>mattek glass bottom dishes</td></tr><tr><td>Rat tail collagen I</td><td>Corning, Corning, NY, USA</td><td>354236</td><td>Collagen gel</td></tr><tr><td>Hydrochloric acid</td><td>Sigma-Aldrich, St. Louis, MO 63178 USA</td><td>H1758</td><td>HCl</td></tr><tr><td>Phosphate buffered saline</td><td>Thermo Fisher Scientific Inc., Whaltham, MA, USA</td><td>10010023</td><td>PBS</td></tr><tr><td>10X Dulbecco&#039;s Modified Eagle&#039;s Medium</td><td>Sigma-Aldrich, St. Louis, MO 63178 USA</td><td>D2429</td><td>10X DMEM</td></tr><tr><td>Sodium bicarbonate</td><td>Sigma-Aldrich, St. Louis, MO 63178 USA</td><td>S5761</td><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;</td></tr><tr><td>Confocal Fluorescent microscope</td><td>Olympus America, Center Valley, PA, USA</td><td>Olympus IX81</td><td>Confocal&amp;nbsp; microscope</td></tr><tr><td>Defined Fetal Bovine Serum</td><td>GE Healthcare Life Sciences HyClone Laboratories, Utah, USA</td><td>SH30070.03</td><td>FBS</td></tr><tr><td>Ti:Sapphire multi-photon laser scanning microscope</td><td>Prarie Technologies, Sioux Falls, SD, USA</td><td>40x NA 0.8 objective</td><td>MPLSM</td></tr><tr><td>Imaris software</td><td>Bitplane Inc. Zurich, CH</td><td>Imaris 7.5.2</td><td>Imaris software</td></tr><tr><td>DAPI</td><td>Sigma-Aldrich, St. Louis, MO 63178, USA</td><td>D9542</td><td>DAPI</td></tr><tr><td>Paraformaldehyde</td><td>Thermo Fisher Scientific Inc., Whaltham, MA, USA</td><td>50980487</td><td>PFA</td></tr><tr><td>&amp;alpha;-minimum essential medium</td><td>Sigma-Aldrich, St. Louis, MO 63178, USA</td><td>M0894</td><td></td></tr><tr><td>MDA-MB-231</td><td>ATCC; Manassas, VA, USA</td><td>HBT-22</td><td></td></tr><tr><td>MSC</td><td>Trivedi and Hematti, 2007</td><td></td><td></td></tr><tr><td>20X lens UPLAPO</td><td>Olympus America, Center Valley, PA, USA</td><td>36-064</td><td>Olympus UPLSAPO 20X Objective</td></tr></tbody></table>

moving upwards: a simple and flexible in vitro three-dimensional invasion assay protocol

Although 3D invasion assays have been developed, the challenge remains to study cells without affecting the integrity of their microenvironment. Traditional 3D assays such as the Boyden Chamber require that cells are displaced from the original culture location and moved to a new environment. Not only does this disrupt the cellular processes that are intrinsic to the microenvironment, but it often results in a loss of cells. These problems are especially challenging when dealing with cells that are either rare, or extremely sensitive to their microenvironment. Here, we describe the development of a 3D invasion assay that avoids both concerns. In this assay, cells are plated within a small well and an ECM matrix containing a chemoattractant is laid atop the cells. This requires no cell displacement, and allows the cells to invade upwards into the matrix. In this assay, cell invasion as well as cell morphology can be assessed within the collagen gel. Using this assay, we characterize the invasive capacity of rare and sensitive cells; the hybrid cells resulting from fusion between breast cancer cells MCF7 and mesenchymal/multipotent stem/stroma cells (MSCs).

We have used a 35-mm culture dish with a glass bottom and rat tail collagen I to develop and optimize an in vitro 3D invasion assay protocol. Using this assay, we showed that breast cancer cells MCF7 and MSC cells could invade into the collagen gel to an average distance of 0.04 &#177; 1.8 &#181;m, and 41.3 &#177; 76.0 &#181;m respectively after 48 h when IGF1 (18.6 ng/mL) was used as chemoattractant (Figure 2). More importantly, we showed that fusio...

Watch this Scientific Journal Video about Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol at JoVE.com

Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

This protocol describes an inverted vertical invasion assay that could be used to quantify the migration and invasion capabilities of cells in a three-dimensional setting while preserving the cell microenvironment. This assay is suitable for rare and/or sensitive cells.

Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

Although 3D invasion assays have been developed, the challenge remains to study cells without affecting the integrity of their microenvironment. ...

moving-upwards-simple-flexible-vitro-three-dimensional-invasion-assay

Research

JoVE Journal

Cancer Research

6.0K Views.  University of Minnesota - Twin Cities. Dit protocol beschrijft een omgekeerde verticale invasie-bepaling die kan worden gebruikt om het kwantificeren van de mogelijkheden voor migratie en invasie van cellen in een driedimensionale omgeving met behoud van de cel-communicatie. Deze test is geschikt voor zeldzame en/of gevoelige cellen.

Video: Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

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.

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 ...

Medicine

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 ...

Fully Human Tumor-based Matrix in Three-dimensional Spheroid Invasion Assay

Two-dimensional cell culture-based assays are commonly used in in vitro cancer research. However, they lack several basic elements that form the tumor microenvironment. To obtain more reliable in vitro results, several three-dimensional (3D) cell culture assays have been introduced. These assays allow cancer cells to interact with the extracellular matrix. This interaction affects cell behavior, such as proliferation and invasion, as well as cell morphology. Additionally, this interaction could induce or suppress the expression of several pro- and anti-tumorigenic molecules. Spheroid invasion assay was developed to provide a suitable 3D in vitro method to study cancer cell invasion. Currently, animal-derived matrices, such as mouse sarcoma-derived matrix (MSDM) and rat tail type I collagen, are mainly used in the spheroid invasion assays. Taking into consideration the differences between the human tumor microenvironment and animal-derived matrices, a human myoma-derived matrix (HMDM) was developed from benign uterus leiomyoma tissue. It has been shown that HMDM induces migration and invasion of carcinoma cells better than MSDM. This protocol provided a simple, reproducible, and reliable 3D human tumor-based spheroid invasion assay using the HMDM/fibrin matrix. It also includes detailed instructions on imaging and analysis. The spheroids grow in a U-shaped ultra-low attachment plate within the HMDM/fibrin matrix and invade through it. The invasion is daily imaged, measured, and analyzed using ilastik and Fiji ImageJ software. The assay platform was demonstrated using human laryngeal primary and metastatic squamous cell carcinoma cell lines. However, the protocol is suitable also for other solid cancer cell lines.

Tumor microenvironment is an essential part of cancer growth and invasion. To mimic carcinoma progression, a biologically relevant human matrix is needed. This protocol introduces an improvement for the in vitro three-dimensional spheroid invasion assay by applying a human leiomyoma-based matrix. The protocol also introduces a computer-based cell invasion analysis.

Two-dimensional cell culture-based assays are commonly used in in vitro cancer research. However, they lack several basic elements that form the tumor ...

An In vitro FluoroBlok Tumor Invasion Assay

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to both secrete proteases that break down the basement membrane as well as migrate in order to be invasive. BD BioCoat Tumor Invasion System provides cells with conditions that allow assessment of their invasive property in vitro1,2. It consists of a BD Falcon FluoroBlok 24-Multiwell Insert Plate with an 8.0 micron pore size PET membrane that has been uniformly coated with BD Matrigel Matrix. This uniform layer of BD Matrigel Matrix serves as a reconstituted basement membrane in vitro providing a true barrier to non-invasive cells while presenting an appropriate protein structure to study invasion. The coating process occludes the pores of the membrane, blocking non-invasive cells from migrating through the membrane. In contrast, invasive cells are able to detach themselves from and migrate through the coated membrane. Quantitation of cell invasion can be achieved by either pre- or post-cell invasion labeling with a fluorescent dye such as DiIC12(3) or calcein AM, respectively, and measuring the fluorescence of invading cells. Since the BD FluoroBlok membrane effectively blocks the passage of light from 490-700 nm at &gt;99% efficiency, fluorescently-labeled cells that have not invaded are not detected by a bottom-reading fluorescence plate reader. However, cells that have invaded to the underside of the membrane are no longer shielded from the light source and are detected with the respective plate reader. This video demonstrates an endpoint cell invasion assay, using calcein AM to detect invaded cells.

An In vitro FluoroBlok Tumor Invasion Assay

This video demonstrates how to measure cell invasion through cell culture inserts using a fluorescence-based methodology.

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to ...

Biology

In Vitro Assays to Evaluate the Migration, Invasion, and Proliferation of Immortalized Human First-trimester Trophoblast Cell Lines

Cell movement is a critical property of trophoblasts during placental development and early pregnancy. The significance of proper trophoblast migration and invasion is demonstrated by pregnancy disorders such as pre-eclampsia and intrauterine growth restriction, which are associated with inadequate trophoblast invasion of the maternal vasculature. Unfortunately, our understanding of the mechanisms by which the placenta develops from migrating trophoblasts is limited. In vitro analysis of cell migration via the scratch assay is a useful tool in identifying factors that regulate trophoblast migratory capacity. However, this assay alone does not define the cellular changes that can result in altered cell migration. This protocol describes three different in vitro assays that are used collectively to evaluate trophoblast cell movement: the scratch assay, the invasion assay, and the proliferation assay. The protocols described here may also be modified for use in other cell lines to quantify cell movement in response to stimuli. These methods allow investigators to identify individual factors that contribute to the cell movement and provide a thorough examination of potential mechanisms underlying apparent changes in cell migration.

Here, we present a highly accessible protocol for evaluating the cell movement in human trophoblast cells using three in vitro assays: the scratch assay, the transwell invasion assay, and the cell proliferation assay.

Cell movement is a critical property of trophoblasts during placental development and early pregnancy. The significance of proper trophoblast migration ...

Developmental Biology

Quantification of Breast Cancer Cell Invasiveness Using a Three-dimensional (3D) Model

It is now well known that the cellular and tissue microenvironment are critical regulators influencing tumor initiation and progression. Moreover, the extracellular matrix (ECM) has been demonstrated to be a critical regulator of cell behavior in culture and homeostasis in vivo. The current approach of culturing cells on two-dimensional (2D), plastic surfaces results in the disturbance and loss of complex interactions between cells and their microenvironment. Through the use of three-dimensional (3D) culture assays, the conditions for cell-microenvironment interaction are established resembling the in vivo microenvironment. This article provides a detailed methodology to grow breast cancer cells in a 3D basement membrane protein matrix, exemplifying the potential of 3D culture in the assessment of cell invasion into the surrounding environment. In addition, we discuss how these 3D assays have the potential to examine the loss of signaling molecules that regulate epithelial morphology by immunostaining procedures. These studies aid to identify important mechanistic details into the processes regulating invasion, required for the spread of breast cancer.

Quantification of Breast Cancer Cell Invasiveness Using a Three-dimensional 3D Model

This article provides detailed methodologies for the use of three-dimensional (3D) assays to quantify breast cancer cell invasion. Specifically, we discuss the procedures required to set up such assays, quantification, and data analysis, as well as methods to examine the loss of membrane integrity that occurs when cells invade.

It is now well known that the cellular and tissue microenvironment are critical regulators influencing tumor initiation and progression. Moreover, the ...

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 ...

3D Models in Cancer Biology: Invasion Dynamics in Heterospheroids

Alternative Strategy to Analyze In Vitro Cell Invasion of 3D Cultures

Spheroid culture is a 3D model that provides an improved replication of the in vivo microenvironment compared to traditional two-dimensional (2D) cultures. Invasion is a cellular outcome of utmost interest in cancer biology. In this protocol, we have devised an alternative strategy for evaluating cancer cell invasion in vitro, employing heterospheroids comprised of oral squamous cell carcinoma (OSCC), cancer-associated fibroblasts (CAF), and monocytes. These heterospheroids aim to mimic the tumor microenvironment (TME), including two relevant non-neoplastic cell types alongside the cancer cells. Each cell type was labeled with vital fluorescent markers emitting in distinct wavelengths before spheroid formation. Once formed, heterospheroids were seeded onto a layer of human leiomyoma-derived extracellular matrix in the upper compartment of a microporous membrane. Invasion was assessed in the z-axis using confocal microscopy. Digital images were obtained in the corresponding fluorescent channels at 10 &#181;m intervals, covering a depth of 90 &#181;m in the z-axis. Analysis was performed using freeware image software by calculating the integrated fluorescence intensity in each image and fluorescence channel. This approach enables a more dynamic analysis of cell invasion patterns in a multilayered context, as well as the examination of spatial co-localization of different cell types during invasion.

Invasion is a major biological phenomenon in the development and progression of cancer. This process is influenced by non-neoplastic cells and components of the tumor microenvironment. The purpose of this study is to describe an alternative method for analyzing tumor cell invasion in vitro using three-dimensional (3D) cultures.

Spheroid culture is a 3D model that provides an improved replication of the in vivo microenvironment compared to traditional two-dimensional (2D) ...

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 ...

A Cancer Cell Spheroid Assay to Assess Invasion in a 3D Setting

The invasive nature of cancer cell lines is thought to correlate with their metastatic potential. Most traditional assays, however, do not examine these invasive features in a three-dimensional environment and the resulting data suffer from reduced biological applicability. Here an approach is presented to visualize the invasive ability of cell lines in a physiologically relevant setting. The cancer cell spheroid invasion assay first utilizes gravity to generate spheroids within drops of media that hang from the lid of a cell culture dish. Next, these spheroids are embedded in a 3D matrix consisting of a mixture of basement membrane materials and type I collagen. Cancer cell egression from the spheroids into the surrounding matrix is then monitored over time. The method described here can be modified to examine invasion after coculture of different cell types, inclusion of drugs/inhibitors, or alterations in extracellular matrix (ECM) constituents.

This method evaluates cancer cell invasion from spheroids into a surrounding 3D matrix. Spheroids are generated via the hanging drop culture method and then embedded in a matrix comprised of basement membrane materials and type I collagen. Invasion out of the spheroids is subsequently monitored.

The invasive nature of cancer cell lines is thought to correlate with their metastatic potential.  Most traditional assays, however, do not examine these ...

Moving Upwards: A Simple and Flexible In Vitro Three-dimensional Invasion Assay Protocol

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